Final Report Summary - STACAST (New Quality and Design Standards for Aluminium Alloys Cast Products)
Executive Summary:
Four main issues constitute the starting point of StaCast project:
- the strategic role of Aluminium Alloys for the future of EU Foundry Industry
- the need of reliably identifying defects in Al Alloys cast products
- the need of correctly evaluating mechanical potential of Al foundry Alloys
- the need of engineering rules for the mechanical design of Al alloys castings
The set of activities of the StaCast project has been organised according to consistent work-plan, articulated into 6 WPs, to focus the standardisation needs (WP1), to support the development of new CEN Technical Reports (WP2 and WP3), to elaborate new guidelines for using such CEN Technical Reports in mechanical design (WP4), to disseminate the knowledge on and promote the use of new CEN Technical Reports and Guidelines (WP5), to integrate and manage the overall Project (WP6).
The work has been performed in perfect coherency with this plan, along the 18 month of Project duration, leading to the achievement of the following main results
1) a complete survey, carried out involving about 60 EU Aluminium alloys foundries (representing the 12.5% of the EU Aluminium casting production), showed the potential existing in this field;
2) a new CEN Technical Report for the Classification of Casting Defects and Imperfections has been developed, in coordination with CEN Technical Committee 132 (Aluminium and its alloys), and submitted, as draft, to the CEN Formal Enquiry Process;
3) a new CEN Technical Report for the Evaluation of Mechanical Potential of Al-Si foundry alloys has been developed, in coordination with CEN Technical Committee 132 (Aluminium and its alloys), and submitted, as draft, to the CEN Formal Enquiry Process;
4) a technical document, introducing and developing rules and guidelines, in order to correctly make use of the two new CEN Technical Reports (i.e. to take into account the way in which defects and imperfections in cast products are limiting the mechanical potential of Al-Si foundry alloys) in the design stage of Al alloys cast components has been elaborated.
5) a coordinated set of dissemination activities (i.e. the Project website, 8 seminars & conference presentations, 10 press releases and technical papers, 4 scientific papers, the "StaCast" book) has been done, making available the results of the project to the Aluminium alloys foundries and related companies.
These results have direct impacts and use in the EU Aluminium foundry field. In fact
1) the survey carried out among EU Aluminium alloys foundries evidenced the key-issues of the field, as well as the level of knowledge and use of existing CEN Standards and the needs for new ones; all these information have been shared with and transmitted to CEN-related Technical Committee (i.e. TC 132 – Aluminium and its alloys); the evidenced standardisation needs have been taking into account for the elaboration of results 2) and 3).
2) the new CEN Technical Report for the Classification of Casting Defects and Imperfections, once approved, will help EU Aluminium alloys foundries at promptly performing corrective actions to reduce/eliminate defects, and will constitute a useful “communication tool” among all the actors of the design and manufacturing chain of Al alloys cast components.
3) the new CEN Technical Report on Mechanical Potential of Al-Si foundry alloys will offer the clear information of which properties can be expected by these alloys, cast in reference dies with state-of-the-art knowledge on die design, process management and alloy treatments correctly applied to minimize defects and imperfections.
4) the rules and guidelines for mechanical design of Aluminium cast products will encourage the correct use of the two new CEN Technical Reports in the design stage of Al alloys cast components, offering relevant information to mechanical designers.
5) the dissemination activities (starting from the StaCast website: about 50.000 contacts recorded) performed put into evidence the potential of these new Technical Reports and Guidelines for Aluminium alloys foundries and related companies in the design & supply chain.
Project Context and Objectives:
Producing sound castings is really strategic for the EU industry, as well as having proper and dedicated engineering tools for the optimised design of cast components. To reach this target, in the opinion of StaCast proposers, four main issues have to be put into evidence:
- the strategic role of Aluminium Alloys for the future of EU Foundry Industry
- the need of reliably identifying defects in Al Alloys cast products
- the need of correctly evaluating mechanical potential of Al foundry Alloys
- the need of engineering rules for the mechanical design of Al alloys castings
Such issues are strongly related to the four main StaCast objectives:
1. to evaluate, by means of a properly carried out survey among EU Aluminium alloys foundries, the vast potential existing in this field, and put into evidence the main needs for these industries in terms of new and advanced CEN Technical Reports, particularly in the fields of Defects classification and Mechanical Design, which are mutually inter-related.
2. to elaborate a new CEN Technical Report for the Classification of Casting Defects, which will help EU Aluminium alloys foundries at promptly performing corrective actions to reduce/eliminate defects; such CEN Technical Report will be also a useful “communication tool” among all the actors of the design and manufacturing chain.
3. to elaborate a new CEN Technical Report, in order to correctly evaluate the effective mechanical potential of Al foundry alloys.
4. to prepare dedicated rules and guidelines, in order to correctly make use of the two new CEN Technical Reports in the design stage of Al alloys cast components
In addition, a fifth and relevant objective is constituted by a coordinated set of dissemination activities (technical and scientific publications, conference presentations, public meetings, the "StaCast" book), to make available the results of the project to the Aluminium alloys foundries and related companies.
Project Results:
The main S&T results/foreground of StaCast Project are referred to
1. Survey carried out among EU Aluminium alloys foundries;
2. New CEN Technical Report for the Classification of Casting Defects and Imperfections;
3. New CEN Technical Report on Mechanical Potential of Al-Si foundry alloys;
4. Rules and guidelines for mechanical design of Aluminium cast products;
5. Dissemination activities.
Full details are given in the annexed files: Annex_1_to_final_report.pdf Annex_2_to_final_report.pdf Annex_3_to_final_report.pdf Annex_4_to_final_report.pdf Annex_5_to_final_report.pdf.
In the next sections, the more relevant information on these results/foregrounds are collected.
1. Survey carried out among EU Aluminium alloys foundries
1.1 Questionnaire
First of all, StaCast Project has been aimed at individuating by means of properly elaborated questionnaires (distributed using the mailing lists of each of the Partners) and of dedicated surveys (elaborated by some of the University Partners) the specific standardization needs for what concerns Al alloys castings.
This activity is the direct consequence of the StaCast Project motivation, which is based on four key-issues.
1) The vast potential of Aluminium Alloys EU Foundry Industry strongly needs a coordinated set of Support Actions, in which a central role MUST be played by the elaboration of new and advanced Standards, particularly in the fields of Defects classification and Mechanical Design, which are mutually inter-related.
2) The use of a new EU Standard for the Classification of Casting Defects, which will help EU Aluminium alloys foundries at promptly performing corrective actions to reduce/eliminate defects, is becoming strategic. Such Standard will be also a useful “communication tool” among all the actors of the design and manufacturing chain.
3) The development of a new Standard on mechanical properties is strongly needed too, in order to correctly evaluate the effective mechanical potential of Al foundry alloys.
4) The design and manufacturing of Al alloys cast components NEED the availability of dedicated rules and guidelines, in order to correctly make use of the two new standards deriving from issues 2) and 3).
The four issues above need, first of all, to be confirmed by a dedicated survey to be carried out on an EU basis. This is the background which led to the set up of the Questionnaire, and to the related answers elaboration.
The Questionnaire has been developed with the aim of involving, with their peculiarities, all the players in the Al alloy foundry scenario: foundries, suppliers and providers (materials, equipments, technologies, dies, engineering services), end-users of castings and Universities & Research Centres. For this reason, a different set of questions has been defined for foundries (Full Questionnaire) and for other companies and institutions ("Short" Questionnaire).
The Full Questionnaire (Figure 1) consists of 6 Sections:
1) Company Information and Profile, collecting the main contacts data and identifying the type of Company (SME: < 250 employees; turnover < 50 million Euro/year or IND: > 250 employees; turnover > 50 million Euro/year).
2) General Data on Production: annual production (five classes, in terms of ton/year have been suggested), main production process (High Pressure Die Casting, i.e. HPDC and/or Gravity Casting and/or Low Pressure Die Casting), type(s) of used alloy(s) (according to CEN standards, or others), type(s) of final application of castings (Automotive, Mechanical Engineering, Electronics, Architecture and Design, Other), Castings Category (Thin walls components, Safety components, Housings & Covers, Engine blocks, Other).
3) CEN Standards currently used, selected from a list containing EN 1559-1 (Founding - Technical conditions of delivery - Part 1: General), EN 1559-4 (Founding - Technical conditions of delivery - Part 4: Additional requirements for aluminium alloy castings), EN 1676 (Al and Al alloys - Alloyed aluminium ingots for remelting – Specifications), EN 1706 (Aluminium and aluminium alloys - Castings - Chemical composition and mechanical properties), EN 1780-1 (Aluminium and aluminium alloys - Part 1: Numerical designation system), EN 1780-2 (Aluminium and aluminium alloys - Part 2: Chemical symbol based designation system), EN 1780-3 (Aluminium and aluminium alloys - Part 3: Writing rules for chemical composition), EN 12258-1 (Aluminium and aluminium alloys - Terms and definitions - Part 1: General terms), EN 12258-2 (Aluminium and aluminium alloys - Terms and definitions - Part 2: Chemical analysis), EN 12681 (Founding - Radiographic examination), EN 14361 (Aluminium and aluminium alloys - Chemical analysis - Sampling from metal melts).
4) Need for new European Standards, with specific reference to
- New CEN Standard about Classification of casting defects (very high/high/medium/low/any),
- New CEN Standard about mechanical properties of Al-based casting alloys (very high/high/medium/ low/any),
- New CEN Standard about mechanical properties of Al-based castings (very high/high/medium/low/any),
- New CEN Standard and/or Guidelines on Al-based cast products design (very high/high/medium/low/any).
5) Techniques usually employed with Defects Analysis, taking into account:
- if the control method (considering Visual control, X Ray inspection, Leak tightness, Density, Liquid penetrant, Ultrasonic testing, Destructive testing: machining, sawing, metallography, fractography) is applied on 100% of castings or on a statistical basis,
- the main categories of defects (achieved by grouping the defects reported in Deliverable D1.1: Gas/Air porosity, Inclusions, Shrinkage, Cracks, Filling-related defects, Metal-die interactions).
6) Frequency of detection, for each of the defect categories mentioned in Section 5).
The "Short" Questionnaire consists, for obvious reasons, only of Section 1) and of Section 4).
The Questionnaire resulted from several preliminary discussion and meetings/contacts inside and among all Partners, and from separate meetings with industrial experts.
Once the final version has been elaborated, the questionnaire (as well as its Italian and German translations) has been implemented in StaCast website, using a format aimed at making as easy as possible the answering by industrial companies.
To facilitate the filling of the Questionnaire, when specific questions are asked on defects, some information files are available (explaining, for instance, the main characteristics of a given defect or giving the abstract of each of the mentioned CEN Standards).
Once the Questionnaire has been implemented, all the Partners activated their contacts (mailing lists, web-pages, magazines, etc.), to diffuse the information about the initiative, and particularly to promote the filling of Questionnaire to EU Companies involved in Al alloys foundry activities.
Apart from Partners, two EU Associations have been involved for communication and promotion:
- CAEF (European Association of Foundries);
- CEMAFON (European Association of Foundry Suppliers).
The overall number of Questionnaires correctly filled was 82, split as follows: 58 Foundries, 11 Providers of Materials and Services, 2 Die-Makers, 3 End-Users, 8 Universities and RTD Centres.
To understand the reliability and the validity of the information coming from the Questionnaire and of their elaboration, it is necessary a short overview of the industrial field to which StaCast is addressed. The relevant figures about the situation of EU Al alloys foundries are the following [sources: ASSOFOND, Report on EU & Italian Foundry in 2011, Assofond, Milano (2012); EAA Annual reports, Bruxelles (2012), in http://www.alueurope.eu/; CAEF, Annual reports, Bruxelles (2011), in http://www.caef.org/; Organisation of the European Aluminium Recycling Industry, http://www.oea-alurecycling.org/en/recycling/eckdaten.php]:
- there are roughly more than 2000 Aluminium alloys foundries in Europe;
- they are basically SMEs, with an average number of employees around 50 (but most part of them has less than 20 employees);
- the end users of cast products are the transport industry (60%), mechanics (7%), electro-mechanics (9%), civil engineering (20%), with a growing trend in automotive and transport, motivated by the reduction achievable in fuel consumption and emission;
- the production, due to the well-known effects of crisis, has been strongly reduced in 2008 and 2009, with a partial recovery in 2010 and 2011.
The Questionnaire has been answered by almost 3% of EU Al alloys foundries (i.e. by 58 on ~2000), which is reasonably good considering that
- the amount of foundries reached by StaCast communication is certainly below 2000;
- the most part of such foundries are SMEs, i.e. without personnel specifically devoted to process and quality control, data elaboration, or with knowledge of the three languages used for the Questionnaire.
The Questionnaire has been answered by 58 foundries, with the majority of SMEs (53.4%), while large industries (IND) correspond to 46.6%. This result has a clear explanation in the sense that large industries (even if they represent, numerically, a small part of the EU foundries) are certainly well organised in terms of availability of data and of personnel able of implementing data themselves into StaCast website. It seems reasonable to assume that SMEs which have filled the Questionnaire represent, generally speaking, the "top class" of SMEs involved in EU Al alloys casting.
1.2 Products, Processes, Alloys
From Questionnaire answers, it has been seen that the most part of foundries are performing the HPDC process (69.0%), while gravity and low pressure die casting are used by 31%. It can be observed that this partition is well in agreement with the actual share of EU Al alloy castings productions: a percentage ranging from 60% to 70% of the total production is usually estimated for HPDC. The partition between SMEs and IND, for gravity/LPDC and HPDC is substantially similar.
For what concerns the production data, there is a relatively homogeneous distribution of the foundries among the 5 categories individuated. Almost half of the foundries, being SMEs, has a year production lower than 3000 tons (24.1% less than 1000 tons/year, 20.7% from 1000 to 3000 tons/year). On the other side, a significant part of foundries (25.9%), essentially IND, has a production higher than 10.000 tons/year.
From the production data, it is possible a preliminary estimation of the representativeness of the companies which answered the Questionnaire, with respect to the amount of castings manufactured. In fact, considering average production data for the first four classes of production (less than 1000 tons/year, from 1001 to 3000 tons/year, from 3001 to 5000 tons/year, from 5001 to 10.000 tons/year) and a conservative value of 15.000 tons/year for the fifth class (more than 10.000 tons/year), the overall production of the "StaCast" foundries can be estimated in terms of almost 375.000 tons/year, roughly representing the 12.5% of the annual EU production. This estimation gives a further and good support in terms of reliability of the survey performed.
The alloy which has the widest diffusion is EN AB 46000 (Al-Si9-Cu3(Fe)), which is used by the 58.6% of foundries, followed by EN AB 43400 (Al-Si10-Mg(Fe)), used in 37.9% of the foundries. Four of the five most used alloys (EN AB46000, EN AB43400, EN AB47100, EN AB46100) are typical HPDC alloys, in agreement with the fact that this is the casting process more adopted in Al alloys foundry. Alloys which are not included in the actual CEN 1706 standard are very few, and mentioned only by 36.2% of foundries.
84.5% of the "StaCast" foundries are manufacturing castings for automotive applications (with a similar percentage for SMEs and IND), followed by Mechanical Engineering (34.5%), Electronics (25.8%) and Architecture and Design (10.3%). In the "Other" category, mainly applications for mechanics and engineering have been mentioned.
Among the various categories suggested, "StaCast" foundries are mainly producing Housing and Covers (29.3%), followed by Thin wall components (20.7%), Safety components (19.0%) and Engine blocks (6.9%). By comparing SMEs and IND, it can be seen that Engine blocks are almost exclusively produced by IND, which are also predominant in the production of safety components (in both cases, they are critical castings, requiring high reliability in manufacturing and in quality control procedures). For Housing and covers there is a substantial balance between IND and SMEs, which, on the other side, are predominant in Thin wall components manufacturing.
1.3 Knowledge and use of CEN Standards on Al alloys
The knowledge about, adoption and use of the more important CEN standards on Al alloys), with reference to all the issues associated to foundry production can be considered satisfactory. In fact, as expected, the EN 1706 and EN 1676 Standards (referred to Al casting alloys composition, properties, characteristics, etc) are in the top positions (the are adopted and used, respectively, by 90.3% and 48.4% of SMEs, and by 77.8% and 48.1% of IND). Such values can be considered as a good proof of diffusion of EN Standards on alloys.
It is still low, on the other side, the level of knowledge, adoption and use of Standards on Technical conditions of delivery of castings (EN 1559-1 and EN 1559-4) and on General terms and definitions of Al alloys (EN 12258-1 and EN 12258-2). These Standards are adopted and used by an overall percentage of foundries ranging from 22.2% to 33.3% of the foundries.
Some specific standards on Sampling from Metal Melts (EN 14361) and on Radiographic Inspection (EN 12681), which are crucial for quality assurance in Al alloys cast products, are adopted and used only by 19% and 25.9% of foundries.
On all these topics, the difference of approach between IND and SMEs seems not so dramatic.
It is worth mentioning, however, that still a relevant amount of strong and focussed dissemination activities needs to be performed, in order to improve the Standard "penetration" in European foundries manufacturing Al alloys castings, especially for what concerns quality assurance.
1.4 Need for new CEN Technical Reports/Standards
The Questionnaire specifically asked to indicate the need for the development of new standards, deriving from the topics of StaCast:
- New CEN Standard on Classification of casting defects
- New CEN Standard on Mechanical Properties of Al-based casting alloys
- New CEN Standard on Mechanical Properties of Al-based castings
- New CEN Standard and/or Guideline on Al-based cast products design
If only foundries are taken into account, the interest and need for
• a new CEN Standard on Mechanical Properties of Al-based casting alloys can be considered as "Medium" (average score: 52/100),
• a new CEN Standard and/or Guideline on Al-based cast products design can be considered as "Medium-High" (average score: 58/100),
• a new CEN Standard on Mechanical Properties of Al-based castings can be considered as "Medium-High" (average score: 59/100),
• a new CEN Standard on Classification of casting defects can be considered as "Medium-High" (average score: 61/100).
1.5 Frequency, measurement and quantification of defects
For all categories of defects, it has been asked to foundries to specify if they are also measured or quantified (and not only simply detected). From the answers achieved, it appears clear that quantification is performed (for the majority of foundries) when Gas/Air Porosity (70.9%) or Shrinkage (56.4%) are considered. For these defects, detection is mainly carried out by X-Rays inspection (in the range from 70% to 80% of cases, as shown in previous Paragraphs), which, by means of modern data elaboration systems, can be associated to quantitative evaluations. Furthermore, these kinds of defects, in some cases can be accepted in the castings, if they are within a previously identified threshold (in this sense, and according to the definition of EN 12258-1, they can be considered as "imperfections" instead of "defects").
Metal-Die interaction, Filling-related and Cracks defects are basically located on the surface of castings, and basically individuated by visual inspection, which defines if the casting is or not acceptable. In these cases, defect measurement/quantification is less strategic (carried out, respectively, by 41.8%, 49.1% and 47.3%) of the "StaCast" foundries.
Inclusions can be detected mainly by metallography, i.e. on a statistical basis; the need of measure/quantify them is probably associated to specific requirements of the castings, and thus carried out only by 47.3% of foundries.
A quantitative description of the frequency of defects (as estimated by foundries) has been achieved. The "ranking" among the various categories of defects is
• Gas/Air porosity (52%): with significant frequency,
• Metal/Die interaction (47%): in some cases, but not frequently,
• Shrinkage (44%): in some cases, but not frequently,
• Filling-related (36%): slightly more than occasionally,
• Crack (33%): occasionally,
• Inclusions (26%): less than occasionally.
The ranking seems in good agreement with the common perception concerning casting defects: Gas/Air porosity, Metal-Die interaction and Shrinkage are "physiological" phenomena associated to foundry, while Filling-related and Crack defects are probably most associated to incorrect design of dies and casting systems; inclusions are probably the less-investigated casting defect.
The ranking among defects, in terms of frequency, does not change if SMEs foundries and IND foundries are considered. In general, higher frequency (typically +5%) can be seen for defects in IND foundry production. This aspect can be probably associated to a high level of quality requirements and defect detection systems for IND foundries, with respect to SME foundries.
It is also evident that the defects genesis is strongly associated to the specific casting process adopted. For this reason, it is useful to compare the situation, in terms of defects frequency, of HPDC foundries with that of gravity/LPDC foundries. The "ranking" among the various categories is quite different if different processes are considered. In fact, for HPDC, the relevancy of Metal/Die interaction defects and of Gas/Air porosity defects is significantly high, with respect to the overall data. The relevancy of Shrinkage defects becomes significantly high, with respect to the overall data, for gravity/LPDC processes. Metal-Die interaction defects, which are criticism for HPDC, are almost negligible for gravity/LPDC.
2. New CEN Technical Report for the Classification of Casting Defects and Imperfections
StaCast Project is aimed at improving Standards and Technical documents regarding Quality and Design of Aluminium Alloys Cast Products. In the first part of its activities, StaCast performed a very detailed survey (see above), to individuate the most relevant Standardisation needs for EU companies involved as foundry or as supplier in supply chain of Al alloys cast products. More than 80 companies and institutions contributed to this survey, described in Deliverable D1.1 of StaCast. In detail, the need for New CEN Standard documents (and/or Technical Reports) about Classification of casting defects has been considered as "High".
Starting from more diffused approaches for defects classification of cast components proposed in literature or currently adopted by foundries, and taking advantage from a previous 2-years survey carried out by the Italian Association of Metallurgy, with the involvement of about 50 Al-alloys foundries, StaCast suggested a new classification approach, based on a 3-levels defects individuation:
I) morphology/location of defects (internal, external, geometrical);
II) metallurgical origin of defects (e.g. gaseous porosity, solidification shrinkage, etc.);
III) specific type of defects (the same metallurgical phenomenon may generate various defects).
This classification of defects is of hybrid type and multi-level, and is referred to metallurgically-based defects of high pressure die casting and permanent mold casting products. Defects directly related to handling, finishing, machining operations following ejection from the die are excluded from the classification, even if they could be possible causes for product rejection.
On the basis of the above described activities, StaCast activated official contacts with CEN Technical Committee 132 – Aluminium and its alloys, in view of the development of a specific CEN Document on Defects Classification for Al alloys cast products.
The following activities have been performed in the frame of these contacts:
• A Consultation paper on StaCast project for CEN/TC 132 was prepared by Dr. Krupka (CEN TC 132) in early August 2013.
• The Consultation paper had, as attachments, the draft StaCast proposal on "Defects classification in Aluminium alloys casting" (corresponding to Deliverable D2.2 of StaCast).
• The Consultation was processed by CEN Internal Balloting portal, and it was verified (September 16th 2013) that CEN/TC 132 Members agreed to include the StaCast proposal on "Defects classification in Aluminium alloys casting" into the CEN/TC 132 working programme.
• A dedicated Task Force/Working Group of TC 132 has been set up, including members of StaCast Consortium, to process the StaCast proposal on "Defects classification in Aluminium alloys casting", and to finalise it as CEN Technical Report (TR) or CEN Technical Specifications (TS).
• The CEN/TC 132 Task Force had an official meeting in Milan (hosted by Italian Association of Metallurgy), on November 13th-14th 2013, to process the StaCast drafts for TR (or TS).
• During the meeting, it was decided to deliver Technical Report (instead of Technical Specification), with the final title "Aluminium and aluminium alloys — Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products" and the scope:
This European Technical Report specifies the classification of the defects and imperfections may be present in cast products manufactured by high pressure, low pressure and gravity die casting of Aluminium alloys.
During the meeting, the time scheduling and the action list to achieve the official approval from CEN TC 132 of the StaCast Technical Report on Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products was defined.
In detail, it has to be pointed out that the draft Technical Report on Defects and Imperfections is the official outcome of the concerted action performed by CEN TC 132 and StaCast project, being draft of the CEN Technical Report on "Aluminium and aluminium alloys — Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products".
This draft followed the consolidated procedure for approval of CEN Technical Reports: Internal Enquiry (deadline: 10th January 2014); Informal Internal Consultation (deadline: 1st March 2014); Official TC 132 Consultation (deadline: 25th June 2014). The timing is in agreement with CEN rules for Technical Reports approval.
The development of the process of approval of the draft of the CEN Technical Report on "Aluminium and aluminium alloys — Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products" has been followed in the frame of StaCast WP4 (implementing the up-graded CEN TR into the design guidelines) and WP5 (dissemination of the contents of the up-graded CEN TR), up to March 31st 2014.
After March 31st 2014, the Partners of StaCast will continue, on a voluntary basis, to monitor the evolution of the CEN Technical Report on "Aluminium and aluminium alloys — Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products", and to support CEN TC 132 with all the needed information.
3. New CEN Technical Report on Mechanical Potential of Al-Si foundry alloys
StaCast Project is aimed at improving Standards and Technical documents regarding Quality and Design of Aluminium Alloys Cast Products. In the first part of its activities, StaCast performed a very detailed survey, to individuate the most relevant Standardisation needs for EU companies involved as foundry or as supplier in supply chain of Al alloys cast products. More than 80 companies and institutions contributed to this survey, described in StaCast survey. In detail, the need for New CEN Standard documents (and/or Technical Reports) about Mechanical Properties of Aluminium casting alloys has been considered as "Medium-High".
The reasons for this interest are clear, and are already explained in current standards on Al casting alloys (and summarised in Deliverable D3.1 of StaCast). EN 1706 Standard (Aluminium and aluminium alloys - Castings – Chemical composition and mechanical properties) put into evidence that
- for high pressure die cast alloys, "the mechanical properties are very dependent on injection parameters and the properties given are for guidance only"; the values given "are not typical values, but are the minimum values that may be expected from separately pressure die cast test pieces of 20,0 mm2 cross sectional area with a typical wall thickness of 2,0 mm"; however, "Pressure die cast test pieces are normally not produced" and "To test the entire casting with loads reflecting the intended service conditions is more meaningful";
- for other processes (low pressure die casting and gravity die casting) "the exact design of test pieces shall be agreed between supplier and purchaser" and "the use of existing rules or standards is recommended until a suitable European Standard is published"; furthermore, "Separately cast test pieces have a valuable function as a check on melt quality; however, the values obtained from castings may differ from the minimum values specified in the tables because of variations in structure arising from differences in section thickness and soundness".
Nowadays, the evaluation of mechanical properties in Aluminium alloys cast products has become a relevant issue, which is not fully covered by existing International Standards or Technical Reports or Technical Specifications. The advanced design and engineering tools currently available to optimise casting process allow a radical change in this approach. The real mechanical potential of Al-based cast alloys (in terms of Ultimate Tensile Strength, Yield Strength and Elongation), which can be exploited by Al-Si alloys, cast by high pressure, low pressure and gravity (permanent mould) processes, needs to be clearly identified. This mechanical potential can be accurately evaluated by means of properly designed reference dies (in the case of high pressure die casting) or by using already available (but not included in actual EN Standards) reference dies (in the case of low pressure die casting and gravity die casting).
On the basis of the above described activities, StaCast activated official contacts with CEN Technical Committee 132 – Aluminium and its alloys, in view of the development of a specific CEN Document on Mechanical Potential of Al-Si foundry alloys.
The following activities have been performed in the frame of these contacts:
• A Consultation paper on StaCast project for CEN/TC 132 was prepared by Dr. Krupka (CEN TC 132) in early August 2013.
• The Consultation paper had, as attachments, the draft StaCast proposal on "Mechanical properties of Aluminium casting alloys" (corresponding to Deliverable D3.2 of StaCast).
• The Consultation was processed by CEN Internal Balloting portal, and it was verified (September 16th 2013) that CEN/TC 132 Members agreed to include the StaCast proposal on "Mechanical properties of Aluminium casting alloys" into the CEN/TC 132 working programme.
• A dedicated Task Force/Working Group of TC 132 has been set up, including members of StaCast Consortium, to process the StaCast proposal on " Mechanical properties of Aluminium casting alloys", and to finalise it as CEN Technical Report (TR) or CEN Technical Specifications (TS).
• The CEN/TC 132 Task Force had an official meeting in Milan (hosted by Italian Association of Metallurgy), on November 13th-14th 2013, to process the StaCast drafts for TR (or TS).
• During the meeting, it was decided to deliver Technical Report (instead of Technical Specification), with the final title "Aluminium and aluminium alloys — Mechanical potential of Al-Si alloys for high Pressure, low pressure and gravity die casting" and the scope:
This Technical Report presents the mechanical potential (in terms of Ultimate Tensile Strength, Yield Strength and Elongation) which can be exploited by Al-Si alloys, cast by high pressure, low pressure and gravity (permanent mould) processes. These properties are measured on test specimens produced by using optimized reference dies and process parameters, properly defined for exploiting the mechanical potential of cast alloys.
• During the meeting, the time scheduling and the action list to achieve the official approval from CEN TC 132 of the StaCast Technical Report on Mechanical potential of Al-Si alloys for high Pressure, low pressure and gravity die casting was defined.
In detail, it has to be pointed out that the draft Technical Report on Mechanical Potential of Al-Si foundry alloys constitutes the official outcome of the concerted action performed by CEN TC 132 and StaCast project, being draft of the CEN Technical Report on "Aluminium and aluminium alloys — Mechanical potential of Al-Si alloys for high Pressure, low pressure and gravity die casting ". This draft is following the consolidated procedure for approval of CEN Technical Reports: Internal Enquiry (deadline: 10th January 2014); Informal Internal Consultation (deadline: 1st March 2014); Official TC 132 Consultation (deadline: 25th June 2014). The timing is in agreement with CEN rules for Technical Reports approval.
The development of the process of approval of the draft of the CEN Technical Report on "Aluminium and aluminium alloys — Mechanical potential of Al-Si alloys for high Pressure, low pressure and gravity die casting " has been followed in the frame of StaCast WP4 (implementing the up-graded CEN TR into the design guidelines) and WP5 (dissemination of the contents of the up-graded CEN TR), up to March 31st 2014.
After March 31st 2014, the Partners of StaCast will continue, on a voluntary basis, to monitor the evolution of the CEN Technical Report on " Aluminium and aluminium alloys — Mechanical potential of Al-Si alloys for high Pressure, low pressure and gravity die casting ", and to support CEN TC 132 with all the needed information.
4. Rules and guidelines for mechanical design of Aluminium cast products
4.1 Introduction
StaCast intended to elaborate an operative support to mechanical designers, involved in the field of Al alloy components. The availability of two new CEN Technical Reports on defects & imperfections in castings (resulting from WP2) and mechanical potential of Al-Si foundry alloys (resulting from WP3) makes necessary the development of a new approach in the design stage. Such a new approach has to take into account
- the “mechanical potential” of Al foundry alloys (draft CEN Technical Report: Fpr TR 16748 (00132378), "Aluminium and Aluminium alloys - Mechanical Potential of Al-Si alloys for High Pressure, Low Pressure and Gravity Die Casting",
- the critical role played in castings by the different types of defects, classified in the new CEN Technical Report Fpr TR 16749 (001323789), "Aluminium and aluminium alloys - Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products",
- the need of considering, for cast products, the interaction existing among microstructure, defects and mechanical behaviour, leading to a “distribution of mechanical properties”.
4.2 Quality and Defects & Imperfections in Al-Si alloys castings
A great contribution to the use of Al-Si alloys comes from improvements in casting processes, which allow to increase the production, to reduce the cycle time and to manufacture complex-shaped castings with thin wall thickness. Among the recent casting techniques, the gravity die casting and the high-pressure die-casting are largely used by the automotive sector since fulfils the above advantages.
A limit to large diffusion of these technologies, but in general of the foundry techniques, remains the final quality of castings. Unlike forging or other thermo-mechanical processes, the properties of shape Al alloy castings are almost entirely dependent upon the filling and solidification conditions, which should be considered during the design chain. For instance, from a stress-engineering viewpoint, thickening up a section of a component will lead to increased load-bearing capacity at that location. During casting, a thicker region will solidify more slowly and, for Al alloys, coarser microstructures will result in lower mechanical strength. Problems with feeding and shrinkage defects may also arise in thicker sections.
While the combination of high speed casting and high cooling rate can give the possibility of thin walled castings and high production rate, the associated turbulence remains a great source of inner and surface casting defects, which have deleterious effects on mechanical properties.
In gravity and high-pressure die-casting if a number of parameters is not adequately determined and adjusted, the quality of the die cast part results rather poor. Macrosegregation of eutectic, primary intermetallic and α-Al crystals, porosity, oxide bifilms and confluence welds are addressed as typical casting defects.
New technical evolutions of the traditional foundry processes, such as vacuum technique, pore-free and semi-solid processes, have been developed to minimise the defects’ content, leading to the production of high integrity thin walled castings. However, the diffusion of these new technologies still remains limited due to the high investment costs.
When designing and developing die cast components and process parameters, a great number of optimisation goals must be taken into consideration, e.g. dimensional accuracy, distortions of the component, casting defects. A useful approach in the development of die casting optimisation is the correct definition of the casting problems and their importance towards quality. Considering HPDC, casting defects are mentioned by foundrymen at first. Therefore, in case of a single optimisation goal, such as minimizing casting defects, an interactive optimisation cycle should be adopted to combine the changes of the die design, including the runner system and overflows, and the variations of injection parameters, such as the plunger speeds, the commutation point between the first and second phase. This is done in order to improve the final integrity of castings.
If more optimisation goals are defined, different “good solutions” can be obtained. This however does not mean that the selected solution will be the best. With reference to the defined optimisation goals, it only represents the best compromise. On the other hand it cannot be completely concluded that there is not any solution that would fulfil the optimisations goals in full.
From another point of view, the variation of the casting parameters (including die thermal management) allows a more easy change of the casting quality, if compared to the expensive and time consuming machining operations of the die. Moreover, when speaking about traditional HPDC, it is common opinion that a certain amount of defects will be always entrapped within the die cast part, even if not optically revealed after subsequent machining. By means of the casting parameters’ adjustments, foundrymen try to restrict and isolate the major part of defects into casting regions that will not be mechanically stressed during normal working. Further, thin-walled castings, like those produced by HPDC, are more affected by the presence of defects since a single macrodefect can cover a significant fraction of the cross-section area.
4.3 Quality and Defects & Imperfections
Quality is maximised when Defects and Imperfections are minimised. The definition of Defects and Imperfections, according to the draft of CEN Technical Report elaborated by StaCast project, is the following:
• Defect: A quality characteristic is lower with respect to the level or state foreseen (usually specified); it does not allow the product to carry out the function requested [EN 12258-1: 2001, 7.1.2];
• Imperfection: A quality characteristic is for a some extent lower with respect to the level or state foreseen; this does not mean necessarily that the product is not suitable for use: an imperfection must be evaluated by means of a proper scale, based on the related specifications, to decide if the product has a quality level making it suitable for the use [EN 12258-1: 2001, 7.1.1].
Defects and Imperfections can be classified according to the scheme already described in Deliverable D2.3 of StaCast Project. In order to understand the physical, chemical and/or metallurgical phenomena generating Defects and Imperfections, the key-information is contained in the second level of the Classification. In fact, D&I are generated by those phenomena, which can be active both in the surface or internally in the castings (first level) and can produce various specific kinds of D&I.
Obviously, the relevance of each family of defects and imperfections is different for each kind of castings, and is associated to an extremely high number of processing conditions and parameters. Anyway, with specific reference to HPDC processes, it has been already specified in Deliverable D1.1 of StaCast project that there is the following ranking:
• Metal/Die interaction (57%): significant frequency,
• Gas/Air porosity (54%): significant frequency,
• Shrinkage (37%): slightly more than occasionally,
• Filling-related (35%): slightly more than occasionally,
• Crack (33%): occasionally,
• Inclusions (24%): less than occasionally.
4.4 Processing parameters, defects & imperfections, mechanical properties
Quality of castings can be defined as being a measure of excellence or a state of being free from defects, imperfections and significant variations, where high quality is brought about by the strict and consistent adherence to measurable and verifiable standards to achieve uniformity of output that satisfies specific customer or user requirements. The casting quality in engineering applications refers to reaching a suitable compromise drawn from among numerous factors which would produce minimum risk and maximum performance in conjunction with cost efficiency.
During the design stage of a component, the combined knowledge of the alloy expected strength, microstructure and presence of defects is required. The knowledge of the expected strength of the alloys gives a view of the mechanical properties which can be achieved in optimized casting conditions. The way in which microstructure (which varies according to local solidification time in different regions of the cast components) influences mechanical behaviour constitutes another relevant issue. Lastly, the understanding of the way in which the expected strength of foundry alloys is limited by the negative effects of various kinds and amount of defects induced during the casting process is also fundamental. Often the formation of defects is sensitive to small variations in the casting conditions and the causes cannot be only connected to the process profile adopted, even if this variable results the main source of defects. Such a combined knowledge is matter of interest and interaction between foundry-men and mechanical designers.
However, the final mechanical behaviour of Al alloy die-castings is mainly controlled by defects size and amount; only when the presence of defects is avoided, microstructure becomes the controlling factor. This is because defect-containing regions in a tensile sample reduce load-bearing area and produce a concentration of strain. Particularly, castings with thin sections, such as those produced by high-pressure die-casting, are vulnerable to the effect of defects, since a single macro-defect could cover a significant fraction of the cross-sectional area.
Correlations between defects, process parameters and mechanical properties of Al-Si alloy castings can be described in terms of:
- Influence of casting defects on microstructural and tensile properties,
- Influence of process parameters on microstructural and tensile properties.
4.5 Some Guidelines for Design of Aluminium Alloy Castings
A number of researchers has investigated the influence of casting defects on the mechanical properties both of gravity cast and high-pressure die-cast Al alloys. However, the works of Gokhale et al. and Timelli et al. evidenced how the mechanical properties decrease monotonically with increasing the area fraction of defects revealed on the fracture surfaces of die cast aluminium specimens. The common conclusion was that even high integrity castings contain defects and thus it is important to predict their effect on final mechanical properties.
Several approaches have been suggested and they are based on through-process modelling for prediction of the structural behaviour of magnesium and aluminium alloys components subjected to static and dynamic loads.
Generally, two different routes based on constitutive models or stochastic approaches are used. Cáceres and Lee reported that the theoretical approach based on the Ghosh constitutive model can accurately predict the experimental tensile properties of cast Al alloys, even though they used a simple determinist approach. In the model, based upon the tensile instability, the tensile strength and deformation of material with internal discontinuities significantly depend upon the fraction of internal discontinuity, the strain rate sensitivity and strain-hardening ability.
On the other side, the effect of structural defects on mechanical properties can be characterized by Weibull statistics, more specifically, by the two-parameter Weibull modulus. In these studies, the Weibull modulus appeared to be a useful measure of the reliability of the casting process. Since then, the two-parameter Weibull modulus has been extensively used to characterize the tensile properties, especially the tensile strength. Recently, the use of three-parameter Weibull statistics has been explored to illustrate its superior analytical potential over the traditional two-parameter approach. The three-parameter Weibull analysis provides new information. In particular, minimum values of strength, below which the material is extremely unlikely to fail, are found.
Both the constitutive and stochastic approaches can be adopted as useful guidelines for designing Al alloy castings.
5. Dissemination activities
5.1 StaCast Website
The structure of the StaCast website has been presented in Deliverable D5.2. After one-and-half year of Project, some aspects are certainly worth mentioning. The website has been organised with a proper counter, which evidenced that at the end of the Project the total number of contacts was more than 50.000. During the last month of the Project, the average number of weekly contacts has been higher than 1.000. It can be stated that the StaCast website has been a really powerful tool for the information about the project and for the dissemination of its main outcomes. In fact, the website contains a specific page dedicated to Deliverables, on which all the public results of the project are (or are going to be) downloadable. The StaCast website has been also a very useful instrument for internal dissemination and exchange of results, as well as for making available all the dissemination-related materials: ppt presentations used in public meetings and seminars, papers and articles related to the Project, photos from events, etc.
It has been decided by Partners to keep operative the StaCast website also after the end of the Project, at least for a period of 3 years, to continue its dissemination actions.
5.2 Public Meetings, Seminars and Courses
There have been several initiatives publically present the project, show the outcomes, collecting information and opinions from Industry and Academy.
The StaCast Project Public Meeting, which was kept in Milano on September 26th 2013, with the aim of
- presenting the results of the StaCast Survey on EU foundries,
- illustrating structure and contents of the two Drafts of CEN Technical Reports on Defects & Imperfections and on Mechanical Potential,
- collecting contributions, comments and suggestions from industrial experts, to support the finalization of these two Drafts as Deliverables D2.3 and D3.3.
35 persons participated to the meeting, mainly from Italy, with a share of 80% in terms of industrial experts.
Other public meetings and seminars have been participated by StaCast Partners, to present the development of the Project as well as its main outcomes. They can be mentioned:
- the Course on "Aluminium Alloys" (Milano, 25 June 2013),
- the Course on "Heat Treatments" (Milano, 17-18 September 2013),
- the Course on "Energy efficiency to reduce costs in HPDC (Rovigo, 1 October 2013),
- the International CAE Conference (Verona, 21-22 October 2013),
- the 24th Italian National Conference on "Heat Treatments" (Piacenza, 17-18 October 2013)
- the Course on "Thermal Behaviour of Dies" (Bergamo, 31 October 2013),
- the International Barbara Kolloquium (Aalen, 3 December 2013),
- the Course on "Quality of Diecastings" (Bergamo, 27 March 2014).
5.3 Technical Publications & Book, Scientific Papers, Press Releases
The approach, activities and outcomes of StaCast Project have been presented and disseminated by means of various types of publications:
- Press releases and project descriptions,
- Technical papers,
- one Technical book,
- Scientific papers.
Press releases and project general descriptions have been published on the magazines "Aluminium and Alloys" (text in English and Italian, printed 8 times every year, 5.000 copies for each issue), "High Pressure Diecasting and Foundry Technologies" (text in English and Italian, printed 4 times every year, 5.000 copies for each issue), "Assomet news" (text in Italian, printed monthly). The first two magazines are also published on-line by Edimet SpA: http://www.aluplanet.com/ita/RivisteOnLine_Login.asp.
During the Project, various Technical Papers have been elaborated on subjects referred to defects & imperfections classification and to mechanical potential of Al foundry alloys. Such Technical Papers have been published on "Industria Fusoria" (text in Italian, printed 6 times every year, 2.000 copies for each issue) and on the already mentioned magazines "Aluminium and Alloys" and "High Pressure Diecasting and Foundry Technologies".
The high quality level of the approach adopted by the StaCast Project is witnessed by the elaboration (and forecast publication) of four Scientific Papers, addressed to the "Intermational Journal of Metalcasting" (2 papers, one accepted , the other under evaluation) and to the 71st World Foundry Congress (1 paper accepted) and to the 14th International Conference on Aluminium Alloys (1 paper accepted).
The International Journal of Metalcasting (IJMC) is published by the American Foundry Society and is dedicated to leading the transfer of research and technology for the global metalcasting industry. The editorial peer review board represents three international metalcasting groups: academia (metalcasting professors), science and research (personnel from national labs, research and scientific institutions), and industry (leading technical personnel from metalcasting facilities). IJMC is also indexed in Thomson Reuters Journal Impact Factor.
The 71st World Foundry Congress Twill take place in Bilbao (Spain), from May 19th-21st 2014. The different activities gathered within the Congress and the International Foundry Exhibition will represent an extraordinary opportunity to exchange technical knowledge. The preliminary programme forecasts about 200 papers, and more than 400 participants are expected.
The 14th International Conference on Aluminium Alloys will be held in Trondheim (Norway). It will cover all aspects of aluminium alloy technology, ranging from alloy design and process development, via advanced characterisation and computer modelling of solid microstructures and related properties, to design, properties and performance of finished products. Accepted papers will be published in Materials Science Forum, indexed in the major academic databases, including EI Compendex, Thomson ISI and with full text online at http://www.scientific.net. The number of accepted papers can be estimated to be around 80, and about 200 participants are expected.
Apart from the above described publications, the StaCast Partners decided to elaborate a unique document collecting the main information and outcomes from the Project. This document is constituted by a 200 pages book, entitled "Aluminium alloy castings: the EU StaCast guide to defects classification, mechanical potential and design issues". The StaCast book is constituted by four Chapters, substantially based on four of the main Deliverables of the Project: D1.1 D2.1 D3.1 and D4.1. The book has an A5 format, so that it can be easily handled also in a foundry environment. It has been provided with an official ISBN number, which is 978-88-98990-00-9.
The Chapters of the book will also made available on the StaCast website, to promote and further disseminate the outcomes of the Project.
5.4 Interaction with CEN
A key-dissemination activity of the StaCast Project is constituted by the interaction which has been established with the European Committee for Standardization (CEN), and particularly with Technical Committee on Aluminium and its alloys (TC 132). Three specific initiatives are worth mentioning:
- the official CEN TC132 – StaCast meeting, which was held in Milano, on November 2013, to discuss and preliminarily elaborate the drafts of the 2 CEN Technical Reports on defects & imperfections and on mechanical potential; the official launch of the approval procedure for the 2 drafts will be opened in June 2014 (Plenary Meeting of CEN TC132 in Madrid) and will be concluded in September 2014;
- the final StaCast meeting, which was held in Brussels, on March 2014, at CEN-CENELEC building, with the target of officially present to CEN the outcomes of the Project; during the meeting, an overview of CEN-CENELEC activities and of their links with R&D EU Projects has been presented by A. Gulacsi (Unit Manager of CEN-CENELEC Research Integration Unit);
- the preliminary agreement between StaCast and CEN-CENELEC Research Integration Unit, in order to include StaCast into the list of "Success stories" (a list of current EU projects where a standardization partner is active, and mentioned as 'Best Practices' documents); this will subsequently result into the elaboration of a dedicated CEN-CENELEC brochure.
5.5 Cross-cutting Initiatives
The activity of StaCast had a duration of 18 months. During this period, StaCast developed some cross-cutting initiatives, in the field of Aluminium alloys foundry, aimed at consolidation current and future activities on standardisation. In particular, from October 2012 StaCast interacted with MUSIC project (MUlti-layers control&cognitive System to drive metal and plastic production line for Injected Components, FP7- FoF-ICT-2011.7.1 PROJECT n. 314145, http://music.eucoord.com/home/body.pe). MUSIC is a highly interdisciplinary project (4 years duration: 2012-2016), particularly addressed ad developing new tools for the optimisation of Aluminium alloys products, manufactured by means of high pressure diecasting. Three of StaCast Partners (GTA, DTG and ASSO) are also Partners of MUSIC Consortium. The general relationship between the two projects has been approved by the Steering Committees of both StaCast and MUSIC.
The main outcomes of StaCast Project have been already valorised in the frame of MUSIC project.
Potential Impact:
The final results of StaCast Project have direct impacts and use.
1. Survey carried out among EU Aluminium alloys foundries
The survey carried out among EU Aluminium alloys foundries evidenced the key-issues of the field, as well as the level of knowledge and use of existing CEN Standards and the needs for new ones; all these information have been shared with and transmitted to CEN-related Technical Committee (i.e. TC 132 – Aluminium and its alloys).
The reliability and representativeness of the information collected are certainly good: a sufficient number of foundries (58) answered, well representing
- the two Countries leading the EU production in the field of Al alloys casting (33 German foundries, 25 Italian foundries),
- the overall EU production of Al alloys castings (10% of EU production has been conservatively estimated for the foundries answering the Questionnaire),
- the most diffused casting processes: 69% of the foundries are using HPDC (i.e. the process estimated to be used for the 60-70% of EU production of Al alloys castings), the other gravity and LPDC,
- the average size of EU Al Alloys foundries, with 32 SMEs (which are the majority in EU Al alloys casting production) and 26 large industries.
A relevant consideration coming from answers elaboration is that EU Standards, and particularly those referred to the more technical issues on defect detection and quality control (radiographic inspection, EN 12681, and control of melt composition, EN 14361) as well as to technical conditions of delivery of castings (EN 1559) need to be better disseminated.
The need of new EN Standards and guidelines identified by StaCast (Defect classification, Mechanical properties of Al casting alloys, Mechanical properties of Al castings, Rules for design of cast products) seems relevant. The evidenced standardisation needs have been taking into account for the elaboration of results 2) and 3).
From the elaboration carried out, a sort of "mapping" of defect knowledge, detection and control has been achieved. In particular, it is worth mentioning that a new EN Standard on Defect classification for Al alloys cast product should contain a clear definition of defects characteristics and of the principles and experimental techniques and tools for their detection.
The defect frequency maps for SME and IND are substantially similar, with a higher value (+5%, almost constant for each class of defect) for IND, in comparison to SME. The defect frequency maps for HPDC and gravity/LPDC processes are highly different. The relevancy of Metal/Die interaction defects and of Gas/Air porosity defects is significantly higher for HPDC process, while Shrinkage defects becomes the main criticism for gravity/LPDC processes. The availability of a new EN Standard on defect classification for Al alloys cast products will help each foundry in setting up its own defects map. Such a "Foundry-level" defects map, continuously upgraded, will constitute a strategic tool for process control and for quality and competitiveness increase.
The information tool (Questionnaire + Website implementation + Data Elaboration approach) developed by StaCast has a relevant potential for a continuous up-grade and monitoring of the field.
The file "Annex_1_to_final_report.pdf" collects all detailed information on this StaCast result.
2. New CEN Technical Report for the Classification of Casting Defects and Imperfections
The new CEN Technical Report for the Classification of Casting Defects and Imperfections, once approved, will help EU Aluminium alloys foundries at promptly performing corrective actions to reduce/eliminate defects, and will constitute a useful “communication tool” among all the actors of the design and manufacturing chain of Al alloys cast components.
StaCast suggested a new classification approach, based on a 3-levels defects individuation:
I) morphology/location of defects (internal, external, geometrical);
II) metallurgical origin of defects (e.g. gaseous porosity, solidification shrinkage, etc.);
III) specific type of defects (the same metallurgical phenomenon may generate various defects).
This classification of defects is of hybrid type and multi-level, and is referred to metallurgically-based defects of high pressure die casting and permanent mold casting products. Defects directly related to handling, finishing, machining operations following ejection from the die are excluded from the classification, even if they could be possible causes for product rejection.
On the basis of the above described activities, StaCast activated official contacts with CEN Technical Committee 132 – Aluminium and its alloys, in view of the development of a specific CEN Document on Defects Classification for Al alloys cast products.
After these contacts, it was decided to deliver the draft Technical Report, with the title "Aluminium and aluminium alloys — Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products" and the scope:
This European Technical Report specifies the classification of the defects and imperfections may be present in cast products manufactured by high pressure, low pressure and gravity die casting of Aluminium alloys.
The file "Annex_2_to_final_report.pdf" collects all detailed information on this StaCast result.
3. New CEN Technical Report on Mechanical Potential of Al-Si foundry alloys
The new CEN Technical Report on Mechanical Potential of Al-Si foundry alloys will offer the clear information of which properties can be expected by these alloys, cast in reference dies with state-of-the-art knowledge on die design, process management and alloy treatments correctly applied to minimize defects and imperfections.
Nowadays, the evaluation of mechanical properties in Aluminium alloys cast products has become a relevant issue, which is not fully covered by existing International Standards or Technical Reports or Technical Specifications. The advanced design and engineering tools currently available to optimise casting process allow a radical change in this approach. The real mechanical potential of Al-based cast alloys (in terms of Ultimate Tensile Strength, Yield Strength and Elongation), which can be exploited by Al-Si alloys, cast by high pressure, low pressure and gravity (permanent mould) processes, needs to be clearly identified. This mechanical potential can be accurately evaluated by means of properly designed reference dies (in the case of high pressure die casting) or by using already available (but not included in actual EN Standards) reference dies (in the case of low pressure die casting and gravity die casting), as proposed by StaCast project.
On the basis of the above described activities, StaCast activated official contacts with CEN Technical Committee 132 – Aluminium and its alloys, in view of the development of a specific CEN Document on Mechanical Potential of Al-Si foundry alloys.
After these contacts, it was decided to deliver a draft Technical Report, with the title "Aluminium and aluminium alloys — Mechanical potential of Al-Si alloys for high Pressure, low pressure and gravity die casting" and the scope:
This Technical Report presents the mechanical potential (in terms of Ultimate Tensile Strength, Yield Strength and Elongation) which can be exploited by Al-Si alloys, cast by high pressure, low pressure and gravity (permanent mould) processes. These properties are measured on test specimens produced by using optimized reference dies and process parameters, properly defined for exploiting the mechanical potential of cast alloys.
The file "Annex_3_to_final_report.pdf" collects all detailed information on this StaCast result.
4. Rules and guidelines for mechanical design of Aluminium cast products
The rules and guidelines for mechanical design of Aluminium cast products will encourage the correct use of the two new CEN Technical Reports in the design stage of Al alloys cast components, offering relevant information to mechanical designers.
StaCast intended to elaborate an operative support to mechanical designers, involved in the field of Al alloy components. The availability of two new CEN Technical Reports on defects & imperfections in castings (result n. 2) and mechanical potential of Al-Si foundry alloys (result n. 3) makes necessary the development of a new approach in the design stage. Such a new approach has to take into account
- the “mechanical potential” of Al foundry alloys (draft CEN Technical Report: Fpr TR 16748 (00132378), "Aluminium and Aluminium alloys - Mechanical Potential of Al-Si alloys for High Pressure, Low Pressure and Gravity Die Casting",
- the critical role played in castings by the different types of defects, classified in the new CEN Technical Report Fpr TR 16749 (001323789), "Aluminium and aluminium alloys - Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products",
- the need of considering, for cast products, the interaction existing among microstructure, defects and mechanical behaviour, leading to a “distribution of mechanical properties”.
The file "Annex_4_to_final_report.pdf" collects all detailed information on this StaCast result.
5. Dissemination activities
The dissemination activities (starting from the StaCast website: about 50.000 contacts recorded) performed put into evidence the potential of these new Technical Reports and Guidelines for Aluminium alloys foundries and related companies in the design & supply chain. A coordinated set of dissemination activities (i.e. the Project website, 8 seminars & conference presentations, 10 press releases and technical papers, 4 scientific papers, the "StaCast" book) has been done, making available the results of the project to the Aluminium alloys foundries and related companies.
The file "Annex_5_to_final_report.pdf" collects all detailed information on this StaCast result.
More generally to understand the impact of the StaCast Project on EU industrial context, it has to be considered that
- there are more than 2000 Aluminium alloys foundries in Europe;
- they are basically SMEs, with an average number of employees around 50,
- the end users of cast products are the transport industry (60%), mechanics (7%), electro-mechanics (9%), civil engineering (20%), with a growing trend in automotive and transport, motivated by the reduction achievable in fuel consumption and emission;
- foundry processes make use, in the majority of cases, of re-cycled (the so-called “secondary”) alloys, with a relevant saving in terms of energy and natural resources.
For EU foundries, the possibility to survive through the present economical crisis is strongly associated to competitiveness, efficiency, innovation. A key-role will be certainly played, in the next few years, by the availability of CEN Standards & Technical Reports and design tools (such as those developed by StaCast).
In fact, Al foundries are highly limited by “no-quality costs”. The new CEN Technical Report on defects classification will directly impact on the reduction in no-quality costs, promoting process efficiency, which will be an advantage for all the other players involved.
In the opinion of StaCast Consortium, having a clear picture of defects in casting and a realistic vision of the mechanical potential of foundry alloys will make EU foundry more competitive, thanks to the increased knowledge about their products which will be encouraged by the two new CEN Technical Reports. These documents, specifically focussed on quality, will help foundries in reducing no-quality costs, expanding the margins of their competitiveness. Each action and result in terms of scrap reduction immediately causes reduction in the energy consumption.
In this sense, even if technical and organisational activities aimed at decreasing no-quality costs in foundries have been carried out recently (but only with “local spot” actions as specific patents, lay-out solutions, changes in process flow), the new CEN Technical Report on defects classification represent a real “structural” action to improve quality of foundry products.
List of Websites:
The StaCast public website is: www.stacast-projecy.org
The relevant contact details are the following:
Partner n.1:
Università degli Studi di Padova
Dipartimento di Tecnica e Gestione dei sistemi industriali (DTG)
Str. S. Nicola, 3 36100 Vicenza, ITALY
Website: www.gest.unipd.it
Contact person for the StaCast Project: Prof. F. Bonollo (bonollo@gest.unipd.it)
Partner n.2:
HOCHSCHULE AALEN - TECHNIK UND WIRTSCHAFT
Beethovenstraße 1 - 73430 Aalen, GERMANY
Website: www.htw-aalen.de/gta
Contact person for the StaCast Project: Prof. L. Kallien (Lothar.Kallien@htw-aalen.de)
Partner n.3:
NORGES TEKNISK-NATURVITENSKAPELIGE UNIVERSITET - NTNU
Hogskoleringen, 1 - NO-7491 Trondheim, NORWAY
Website: www.ntnu.no
Contact person for the StaCast Project: Prof. L. Arnberg (arnberg@ntnu.no)
Partner n.4:
Associazione Italiana di Metallurgia (AIM)
Piazzale Morandi, 2 - 20121 Milano, ITALY
Website: www.aimnet.it
Contact person for the StaCast Project: Dr. F. Bassani (secretariat@aimnet.it)
Partner n.5:
ASSOMET servizi srl
Via dei Missaglia, 97 - 20142 Milano, ITALY
Website: www.assomet.it
Contact person for the StaCast Project: Mr. C. De Cani (assomet@assomet.it)
Partner n.6:
The Federation of Aluminium Consumers in Europe (FACE)
Rond Point Schuman 6, Box 5 - B-1040 Brussels, BELGIUM
Website: www.facealuminium.com
Contact person for the StaCast Project: Dr. M. Conserva (face@facealuminium.com)
Four main issues constitute the starting point of StaCast project:
- the strategic role of Aluminium Alloys for the future of EU Foundry Industry
- the need of reliably identifying defects in Al Alloys cast products
- the need of correctly evaluating mechanical potential of Al foundry Alloys
- the need of engineering rules for the mechanical design of Al alloys castings
The set of activities of the StaCast project has been organised according to consistent work-plan, articulated into 6 WPs, to focus the standardisation needs (WP1), to support the development of new CEN Technical Reports (WP2 and WP3), to elaborate new guidelines for using such CEN Technical Reports in mechanical design (WP4), to disseminate the knowledge on and promote the use of new CEN Technical Reports and Guidelines (WP5), to integrate and manage the overall Project (WP6).
The work has been performed in perfect coherency with this plan, along the 18 month of Project duration, leading to the achievement of the following main results
1) a complete survey, carried out involving about 60 EU Aluminium alloys foundries (representing the 12.5% of the EU Aluminium casting production), showed the potential existing in this field;
2) a new CEN Technical Report for the Classification of Casting Defects and Imperfections has been developed, in coordination with CEN Technical Committee 132 (Aluminium and its alloys), and submitted, as draft, to the CEN Formal Enquiry Process;
3) a new CEN Technical Report for the Evaluation of Mechanical Potential of Al-Si foundry alloys has been developed, in coordination with CEN Technical Committee 132 (Aluminium and its alloys), and submitted, as draft, to the CEN Formal Enquiry Process;
4) a technical document, introducing and developing rules and guidelines, in order to correctly make use of the two new CEN Technical Reports (i.e. to take into account the way in which defects and imperfections in cast products are limiting the mechanical potential of Al-Si foundry alloys) in the design stage of Al alloys cast components has been elaborated.
5) a coordinated set of dissemination activities (i.e. the Project website, 8 seminars & conference presentations, 10 press releases and technical papers, 4 scientific papers, the "StaCast" book) has been done, making available the results of the project to the Aluminium alloys foundries and related companies.
These results have direct impacts and use in the EU Aluminium foundry field. In fact
1) the survey carried out among EU Aluminium alloys foundries evidenced the key-issues of the field, as well as the level of knowledge and use of existing CEN Standards and the needs for new ones; all these information have been shared with and transmitted to CEN-related Technical Committee (i.e. TC 132 – Aluminium and its alloys); the evidenced standardisation needs have been taking into account for the elaboration of results 2) and 3).
2) the new CEN Technical Report for the Classification of Casting Defects and Imperfections, once approved, will help EU Aluminium alloys foundries at promptly performing corrective actions to reduce/eliminate defects, and will constitute a useful “communication tool” among all the actors of the design and manufacturing chain of Al alloys cast components.
3) the new CEN Technical Report on Mechanical Potential of Al-Si foundry alloys will offer the clear information of which properties can be expected by these alloys, cast in reference dies with state-of-the-art knowledge on die design, process management and alloy treatments correctly applied to minimize defects and imperfections.
4) the rules and guidelines for mechanical design of Aluminium cast products will encourage the correct use of the two new CEN Technical Reports in the design stage of Al alloys cast components, offering relevant information to mechanical designers.
5) the dissemination activities (starting from the StaCast website: about 50.000 contacts recorded) performed put into evidence the potential of these new Technical Reports and Guidelines for Aluminium alloys foundries and related companies in the design & supply chain.
Project Context and Objectives:
Producing sound castings is really strategic for the EU industry, as well as having proper and dedicated engineering tools for the optimised design of cast components. To reach this target, in the opinion of StaCast proposers, four main issues have to be put into evidence:
- the strategic role of Aluminium Alloys for the future of EU Foundry Industry
- the need of reliably identifying defects in Al Alloys cast products
- the need of correctly evaluating mechanical potential of Al foundry Alloys
- the need of engineering rules for the mechanical design of Al alloys castings
Such issues are strongly related to the four main StaCast objectives:
1. to evaluate, by means of a properly carried out survey among EU Aluminium alloys foundries, the vast potential existing in this field, and put into evidence the main needs for these industries in terms of new and advanced CEN Technical Reports, particularly in the fields of Defects classification and Mechanical Design, which are mutually inter-related.
2. to elaborate a new CEN Technical Report for the Classification of Casting Defects, which will help EU Aluminium alloys foundries at promptly performing corrective actions to reduce/eliminate defects; such CEN Technical Report will be also a useful “communication tool” among all the actors of the design and manufacturing chain.
3. to elaborate a new CEN Technical Report, in order to correctly evaluate the effective mechanical potential of Al foundry alloys.
4. to prepare dedicated rules and guidelines, in order to correctly make use of the two new CEN Technical Reports in the design stage of Al alloys cast components
In addition, a fifth and relevant objective is constituted by a coordinated set of dissemination activities (technical and scientific publications, conference presentations, public meetings, the "StaCast" book), to make available the results of the project to the Aluminium alloys foundries and related companies.
Project Results:
The main S&T results/foreground of StaCast Project are referred to
1. Survey carried out among EU Aluminium alloys foundries;
2. New CEN Technical Report for the Classification of Casting Defects and Imperfections;
3. New CEN Technical Report on Mechanical Potential of Al-Si foundry alloys;
4. Rules and guidelines for mechanical design of Aluminium cast products;
5. Dissemination activities.
Full details are given in the annexed files: Annex_1_to_final_report.pdf Annex_2_to_final_report.pdf Annex_3_to_final_report.pdf Annex_4_to_final_report.pdf Annex_5_to_final_report.pdf.
In the next sections, the more relevant information on these results/foregrounds are collected.
1. Survey carried out among EU Aluminium alloys foundries
1.1 Questionnaire
First of all, StaCast Project has been aimed at individuating by means of properly elaborated questionnaires (distributed using the mailing lists of each of the Partners) and of dedicated surveys (elaborated by some of the University Partners) the specific standardization needs for what concerns Al alloys castings.
This activity is the direct consequence of the StaCast Project motivation, which is based on four key-issues.
1) The vast potential of Aluminium Alloys EU Foundry Industry strongly needs a coordinated set of Support Actions, in which a central role MUST be played by the elaboration of new and advanced Standards, particularly in the fields of Defects classification and Mechanical Design, which are mutually inter-related.
2) The use of a new EU Standard for the Classification of Casting Defects, which will help EU Aluminium alloys foundries at promptly performing corrective actions to reduce/eliminate defects, is becoming strategic. Such Standard will be also a useful “communication tool” among all the actors of the design and manufacturing chain.
3) The development of a new Standard on mechanical properties is strongly needed too, in order to correctly evaluate the effective mechanical potential of Al foundry alloys.
4) The design and manufacturing of Al alloys cast components NEED the availability of dedicated rules and guidelines, in order to correctly make use of the two new standards deriving from issues 2) and 3).
The four issues above need, first of all, to be confirmed by a dedicated survey to be carried out on an EU basis. This is the background which led to the set up of the Questionnaire, and to the related answers elaboration.
The Questionnaire has been developed with the aim of involving, with their peculiarities, all the players in the Al alloy foundry scenario: foundries, suppliers and providers (materials, equipments, technologies, dies, engineering services), end-users of castings and Universities & Research Centres. For this reason, a different set of questions has been defined for foundries (Full Questionnaire) and for other companies and institutions ("Short" Questionnaire).
The Full Questionnaire (Figure 1) consists of 6 Sections:
1) Company Information and Profile, collecting the main contacts data and identifying the type of Company (SME: < 250 employees; turnover < 50 million Euro/year or IND: > 250 employees; turnover > 50 million Euro/year).
2) General Data on Production: annual production (five classes, in terms of ton/year have been suggested), main production process (High Pressure Die Casting, i.e. HPDC and/or Gravity Casting and/or Low Pressure Die Casting), type(s) of used alloy(s) (according to CEN standards, or others), type(s) of final application of castings (Automotive, Mechanical Engineering, Electronics, Architecture and Design, Other), Castings Category (Thin walls components, Safety components, Housings & Covers, Engine blocks, Other).
3) CEN Standards currently used, selected from a list containing EN 1559-1 (Founding - Technical conditions of delivery - Part 1: General), EN 1559-4 (Founding - Technical conditions of delivery - Part 4: Additional requirements for aluminium alloy castings), EN 1676 (Al and Al alloys - Alloyed aluminium ingots for remelting – Specifications), EN 1706 (Aluminium and aluminium alloys - Castings - Chemical composition and mechanical properties), EN 1780-1 (Aluminium and aluminium alloys - Part 1: Numerical designation system), EN 1780-2 (Aluminium and aluminium alloys - Part 2: Chemical symbol based designation system), EN 1780-3 (Aluminium and aluminium alloys - Part 3: Writing rules for chemical composition), EN 12258-1 (Aluminium and aluminium alloys - Terms and definitions - Part 1: General terms), EN 12258-2 (Aluminium and aluminium alloys - Terms and definitions - Part 2: Chemical analysis), EN 12681 (Founding - Radiographic examination), EN 14361 (Aluminium and aluminium alloys - Chemical analysis - Sampling from metal melts).
4) Need for new European Standards, with specific reference to
- New CEN Standard about Classification of casting defects (very high/high/medium/low/any),
- New CEN Standard about mechanical properties of Al-based casting alloys (very high/high/medium/ low/any),
- New CEN Standard about mechanical properties of Al-based castings (very high/high/medium/low/any),
- New CEN Standard and/or Guidelines on Al-based cast products design (very high/high/medium/low/any).
5) Techniques usually employed with Defects Analysis, taking into account:
- if the control method (considering Visual control, X Ray inspection, Leak tightness, Density, Liquid penetrant, Ultrasonic testing, Destructive testing: machining, sawing, metallography, fractography) is applied on 100% of castings or on a statistical basis,
- the main categories of defects (achieved by grouping the defects reported in Deliverable D1.1: Gas/Air porosity, Inclusions, Shrinkage, Cracks, Filling-related defects, Metal-die interactions).
6) Frequency of detection, for each of the defect categories mentioned in Section 5).
The "Short" Questionnaire consists, for obvious reasons, only of Section 1) and of Section 4).
The Questionnaire resulted from several preliminary discussion and meetings/contacts inside and among all Partners, and from separate meetings with industrial experts.
Once the final version has been elaborated, the questionnaire (as well as its Italian and German translations) has been implemented in StaCast website, using a format aimed at making as easy as possible the answering by industrial companies.
To facilitate the filling of the Questionnaire, when specific questions are asked on defects, some information files are available (explaining, for instance, the main characteristics of a given defect or giving the abstract of each of the mentioned CEN Standards).
Once the Questionnaire has been implemented, all the Partners activated their contacts (mailing lists, web-pages, magazines, etc.), to diffuse the information about the initiative, and particularly to promote the filling of Questionnaire to EU Companies involved in Al alloys foundry activities.
Apart from Partners, two EU Associations have been involved for communication and promotion:
- CAEF (European Association of Foundries);
- CEMAFON (European Association of Foundry Suppliers).
The overall number of Questionnaires correctly filled was 82, split as follows: 58 Foundries, 11 Providers of Materials and Services, 2 Die-Makers, 3 End-Users, 8 Universities and RTD Centres.
To understand the reliability and the validity of the information coming from the Questionnaire and of their elaboration, it is necessary a short overview of the industrial field to which StaCast is addressed. The relevant figures about the situation of EU Al alloys foundries are the following [sources: ASSOFOND, Report on EU & Italian Foundry in 2011, Assofond, Milano (2012); EAA Annual reports, Bruxelles (2012), in http://www.alueurope.eu/; CAEF, Annual reports, Bruxelles (2011), in http://www.caef.org/; Organisation of the European Aluminium Recycling Industry, http://www.oea-alurecycling.org/en/recycling/eckdaten.php]:
- there are roughly more than 2000 Aluminium alloys foundries in Europe;
- they are basically SMEs, with an average number of employees around 50 (but most part of them has less than 20 employees);
- the end users of cast products are the transport industry (60%), mechanics (7%), electro-mechanics (9%), civil engineering (20%), with a growing trend in automotive and transport, motivated by the reduction achievable in fuel consumption and emission;
- the production, due to the well-known effects of crisis, has been strongly reduced in 2008 and 2009, with a partial recovery in 2010 and 2011.
The Questionnaire has been answered by almost 3% of EU Al alloys foundries (i.e. by 58 on ~2000), which is reasonably good considering that
- the amount of foundries reached by StaCast communication is certainly below 2000;
- the most part of such foundries are SMEs, i.e. without personnel specifically devoted to process and quality control, data elaboration, or with knowledge of the three languages used for the Questionnaire.
The Questionnaire has been answered by 58 foundries, with the majority of SMEs (53.4%), while large industries (IND) correspond to 46.6%. This result has a clear explanation in the sense that large industries (even if they represent, numerically, a small part of the EU foundries) are certainly well organised in terms of availability of data and of personnel able of implementing data themselves into StaCast website. It seems reasonable to assume that SMEs which have filled the Questionnaire represent, generally speaking, the "top class" of SMEs involved in EU Al alloys casting.
1.2 Products, Processes, Alloys
From Questionnaire answers, it has been seen that the most part of foundries are performing the HPDC process (69.0%), while gravity and low pressure die casting are used by 31%. It can be observed that this partition is well in agreement with the actual share of EU Al alloy castings productions: a percentage ranging from 60% to 70% of the total production is usually estimated for HPDC. The partition between SMEs and IND, for gravity/LPDC and HPDC is substantially similar.
For what concerns the production data, there is a relatively homogeneous distribution of the foundries among the 5 categories individuated. Almost half of the foundries, being SMEs, has a year production lower than 3000 tons (24.1% less than 1000 tons/year, 20.7% from 1000 to 3000 tons/year). On the other side, a significant part of foundries (25.9%), essentially IND, has a production higher than 10.000 tons/year.
From the production data, it is possible a preliminary estimation of the representativeness of the companies which answered the Questionnaire, with respect to the amount of castings manufactured. In fact, considering average production data for the first four classes of production (less than 1000 tons/year, from 1001 to 3000 tons/year, from 3001 to 5000 tons/year, from 5001 to 10.000 tons/year) and a conservative value of 15.000 tons/year for the fifth class (more than 10.000 tons/year), the overall production of the "StaCast" foundries can be estimated in terms of almost 375.000 tons/year, roughly representing the 12.5% of the annual EU production. This estimation gives a further and good support in terms of reliability of the survey performed.
The alloy which has the widest diffusion is EN AB 46000 (Al-Si9-Cu3(Fe)), which is used by the 58.6% of foundries, followed by EN AB 43400 (Al-Si10-Mg(Fe)), used in 37.9% of the foundries. Four of the five most used alloys (EN AB46000, EN AB43400, EN AB47100, EN AB46100) are typical HPDC alloys, in agreement with the fact that this is the casting process more adopted in Al alloys foundry. Alloys which are not included in the actual CEN 1706 standard are very few, and mentioned only by 36.2% of foundries.
84.5% of the "StaCast" foundries are manufacturing castings for automotive applications (with a similar percentage for SMEs and IND), followed by Mechanical Engineering (34.5%), Electronics (25.8%) and Architecture and Design (10.3%). In the "Other" category, mainly applications for mechanics and engineering have been mentioned.
Among the various categories suggested, "StaCast" foundries are mainly producing Housing and Covers (29.3%), followed by Thin wall components (20.7%), Safety components (19.0%) and Engine blocks (6.9%). By comparing SMEs and IND, it can be seen that Engine blocks are almost exclusively produced by IND, which are also predominant in the production of safety components (in both cases, they are critical castings, requiring high reliability in manufacturing and in quality control procedures). For Housing and covers there is a substantial balance between IND and SMEs, which, on the other side, are predominant in Thin wall components manufacturing.
1.3 Knowledge and use of CEN Standards on Al alloys
The knowledge about, adoption and use of the more important CEN standards on Al alloys), with reference to all the issues associated to foundry production can be considered satisfactory. In fact, as expected, the EN 1706 and EN 1676 Standards (referred to Al casting alloys composition, properties, characteristics, etc) are in the top positions (the are adopted and used, respectively, by 90.3% and 48.4% of SMEs, and by 77.8% and 48.1% of IND). Such values can be considered as a good proof of diffusion of EN Standards on alloys.
It is still low, on the other side, the level of knowledge, adoption and use of Standards on Technical conditions of delivery of castings (EN 1559-1 and EN 1559-4) and on General terms and definitions of Al alloys (EN 12258-1 and EN 12258-2). These Standards are adopted and used by an overall percentage of foundries ranging from 22.2% to 33.3% of the foundries.
Some specific standards on Sampling from Metal Melts (EN 14361) and on Radiographic Inspection (EN 12681), which are crucial for quality assurance in Al alloys cast products, are adopted and used only by 19% and 25.9% of foundries.
On all these topics, the difference of approach between IND and SMEs seems not so dramatic.
It is worth mentioning, however, that still a relevant amount of strong and focussed dissemination activities needs to be performed, in order to improve the Standard "penetration" in European foundries manufacturing Al alloys castings, especially for what concerns quality assurance.
1.4 Need for new CEN Technical Reports/Standards
The Questionnaire specifically asked to indicate the need for the development of new standards, deriving from the topics of StaCast:
- New CEN Standard on Classification of casting defects
- New CEN Standard on Mechanical Properties of Al-based casting alloys
- New CEN Standard on Mechanical Properties of Al-based castings
- New CEN Standard and/or Guideline on Al-based cast products design
If only foundries are taken into account, the interest and need for
• a new CEN Standard on Mechanical Properties of Al-based casting alloys can be considered as "Medium" (average score: 52/100),
• a new CEN Standard and/or Guideline on Al-based cast products design can be considered as "Medium-High" (average score: 58/100),
• a new CEN Standard on Mechanical Properties of Al-based castings can be considered as "Medium-High" (average score: 59/100),
• a new CEN Standard on Classification of casting defects can be considered as "Medium-High" (average score: 61/100).
1.5 Frequency, measurement and quantification of defects
For all categories of defects, it has been asked to foundries to specify if they are also measured or quantified (and not only simply detected). From the answers achieved, it appears clear that quantification is performed (for the majority of foundries) when Gas/Air Porosity (70.9%) or Shrinkage (56.4%) are considered. For these defects, detection is mainly carried out by X-Rays inspection (in the range from 70% to 80% of cases, as shown in previous Paragraphs), which, by means of modern data elaboration systems, can be associated to quantitative evaluations. Furthermore, these kinds of defects, in some cases can be accepted in the castings, if they are within a previously identified threshold (in this sense, and according to the definition of EN 12258-1, they can be considered as "imperfections" instead of "defects").
Metal-Die interaction, Filling-related and Cracks defects are basically located on the surface of castings, and basically individuated by visual inspection, which defines if the casting is or not acceptable. In these cases, defect measurement/quantification is less strategic (carried out, respectively, by 41.8%, 49.1% and 47.3%) of the "StaCast" foundries.
Inclusions can be detected mainly by metallography, i.e. on a statistical basis; the need of measure/quantify them is probably associated to specific requirements of the castings, and thus carried out only by 47.3% of foundries.
A quantitative description of the frequency of defects (as estimated by foundries) has been achieved. The "ranking" among the various categories of defects is
• Gas/Air porosity (52%): with significant frequency,
• Metal/Die interaction (47%): in some cases, but not frequently,
• Shrinkage (44%): in some cases, but not frequently,
• Filling-related (36%): slightly more than occasionally,
• Crack (33%): occasionally,
• Inclusions (26%): less than occasionally.
The ranking seems in good agreement with the common perception concerning casting defects: Gas/Air porosity, Metal-Die interaction and Shrinkage are "physiological" phenomena associated to foundry, while Filling-related and Crack defects are probably most associated to incorrect design of dies and casting systems; inclusions are probably the less-investigated casting defect.
The ranking among defects, in terms of frequency, does not change if SMEs foundries and IND foundries are considered. In general, higher frequency (typically +5%) can be seen for defects in IND foundry production. This aspect can be probably associated to a high level of quality requirements and defect detection systems for IND foundries, with respect to SME foundries.
It is also evident that the defects genesis is strongly associated to the specific casting process adopted. For this reason, it is useful to compare the situation, in terms of defects frequency, of HPDC foundries with that of gravity/LPDC foundries. The "ranking" among the various categories is quite different if different processes are considered. In fact, for HPDC, the relevancy of Metal/Die interaction defects and of Gas/Air porosity defects is significantly high, with respect to the overall data. The relevancy of Shrinkage defects becomes significantly high, with respect to the overall data, for gravity/LPDC processes. Metal-Die interaction defects, which are criticism for HPDC, are almost negligible for gravity/LPDC.
2. New CEN Technical Report for the Classification of Casting Defects and Imperfections
StaCast Project is aimed at improving Standards and Technical documents regarding Quality and Design of Aluminium Alloys Cast Products. In the first part of its activities, StaCast performed a very detailed survey (see above), to individuate the most relevant Standardisation needs for EU companies involved as foundry or as supplier in supply chain of Al alloys cast products. More than 80 companies and institutions contributed to this survey, described in Deliverable D1.1 of StaCast. In detail, the need for New CEN Standard documents (and/or Technical Reports) about Classification of casting defects has been considered as "High".
Starting from more diffused approaches for defects classification of cast components proposed in literature or currently adopted by foundries, and taking advantage from a previous 2-years survey carried out by the Italian Association of Metallurgy, with the involvement of about 50 Al-alloys foundries, StaCast suggested a new classification approach, based on a 3-levels defects individuation:
I) morphology/location of defects (internal, external, geometrical);
II) metallurgical origin of defects (e.g. gaseous porosity, solidification shrinkage, etc.);
III) specific type of defects (the same metallurgical phenomenon may generate various defects).
This classification of defects is of hybrid type and multi-level, and is referred to metallurgically-based defects of high pressure die casting and permanent mold casting products. Defects directly related to handling, finishing, machining operations following ejection from the die are excluded from the classification, even if they could be possible causes for product rejection.
On the basis of the above described activities, StaCast activated official contacts with CEN Technical Committee 132 – Aluminium and its alloys, in view of the development of a specific CEN Document on Defects Classification for Al alloys cast products.
The following activities have been performed in the frame of these contacts:
• A Consultation paper on StaCast project for CEN/TC 132 was prepared by Dr. Krupka (CEN TC 132) in early August 2013.
• The Consultation paper had, as attachments, the draft StaCast proposal on "Defects classification in Aluminium alloys casting" (corresponding to Deliverable D2.2 of StaCast).
• The Consultation was processed by CEN Internal Balloting portal, and it was verified (September 16th 2013) that CEN/TC 132 Members agreed to include the StaCast proposal on "Defects classification in Aluminium alloys casting" into the CEN/TC 132 working programme.
• A dedicated Task Force/Working Group of TC 132 has been set up, including members of StaCast Consortium, to process the StaCast proposal on "Defects classification in Aluminium alloys casting", and to finalise it as CEN Technical Report (TR) or CEN Technical Specifications (TS).
• The CEN/TC 132 Task Force had an official meeting in Milan (hosted by Italian Association of Metallurgy), on November 13th-14th 2013, to process the StaCast drafts for TR (or TS).
• During the meeting, it was decided to deliver Technical Report (instead of Technical Specification), with the final title "Aluminium and aluminium alloys — Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products" and the scope:
This European Technical Report specifies the classification of the defects and imperfections may be present in cast products manufactured by high pressure, low pressure and gravity die casting of Aluminium alloys.
During the meeting, the time scheduling and the action list to achieve the official approval from CEN TC 132 of the StaCast Technical Report on Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products was defined.
In detail, it has to be pointed out that the draft Technical Report on Defects and Imperfections is the official outcome of the concerted action performed by CEN TC 132 and StaCast project, being draft of the CEN Technical Report on "Aluminium and aluminium alloys — Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products".
This draft followed the consolidated procedure for approval of CEN Technical Reports: Internal Enquiry (deadline: 10th January 2014); Informal Internal Consultation (deadline: 1st March 2014); Official TC 132 Consultation (deadline: 25th June 2014). The timing is in agreement with CEN rules for Technical Reports approval.
The development of the process of approval of the draft of the CEN Technical Report on "Aluminium and aluminium alloys — Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products" has been followed in the frame of StaCast WP4 (implementing the up-graded CEN TR into the design guidelines) and WP5 (dissemination of the contents of the up-graded CEN TR), up to March 31st 2014.
After March 31st 2014, the Partners of StaCast will continue, on a voluntary basis, to monitor the evolution of the CEN Technical Report on "Aluminium and aluminium alloys — Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products", and to support CEN TC 132 with all the needed information.
3. New CEN Technical Report on Mechanical Potential of Al-Si foundry alloys
StaCast Project is aimed at improving Standards and Technical documents regarding Quality and Design of Aluminium Alloys Cast Products. In the first part of its activities, StaCast performed a very detailed survey, to individuate the most relevant Standardisation needs for EU companies involved as foundry or as supplier in supply chain of Al alloys cast products. More than 80 companies and institutions contributed to this survey, described in StaCast survey. In detail, the need for New CEN Standard documents (and/or Technical Reports) about Mechanical Properties of Aluminium casting alloys has been considered as "Medium-High".
The reasons for this interest are clear, and are already explained in current standards on Al casting alloys (and summarised in Deliverable D3.1 of StaCast). EN 1706 Standard (Aluminium and aluminium alloys - Castings – Chemical composition and mechanical properties) put into evidence that
- for high pressure die cast alloys, "the mechanical properties are very dependent on injection parameters and the properties given are for guidance only"; the values given "are not typical values, but are the minimum values that may be expected from separately pressure die cast test pieces of 20,0 mm2 cross sectional area with a typical wall thickness of 2,0 mm"; however, "Pressure die cast test pieces are normally not produced" and "To test the entire casting with loads reflecting the intended service conditions is more meaningful";
- for other processes (low pressure die casting and gravity die casting) "the exact design of test pieces shall be agreed between supplier and purchaser" and "the use of existing rules or standards is recommended until a suitable European Standard is published"; furthermore, "Separately cast test pieces have a valuable function as a check on melt quality; however, the values obtained from castings may differ from the minimum values specified in the tables because of variations in structure arising from differences in section thickness and soundness".
Nowadays, the evaluation of mechanical properties in Aluminium alloys cast products has become a relevant issue, which is not fully covered by existing International Standards or Technical Reports or Technical Specifications. The advanced design and engineering tools currently available to optimise casting process allow a radical change in this approach. The real mechanical potential of Al-based cast alloys (in terms of Ultimate Tensile Strength, Yield Strength and Elongation), which can be exploited by Al-Si alloys, cast by high pressure, low pressure and gravity (permanent mould) processes, needs to be clearly identified. This mechanical potential can be accurately evaluated by means of properly designed reference dies (in the case of high pressure die casting) or by using already available (but not included in actual EN Standards) reference dies (in the case of low pressure die casting and gravity die casting).
On the basis of the above described activities, StaCast activated official contacts with CEN Technical Committee 132 – Aluminium and its alloys, in view of the development of a specific CEN Document on Mechanical Potential of Al-Si foundry alloys.
The following activities have been performed in the frame of these contacts:
• A Consultation paper on StaCast project for CEN/TC 132 was prepared by Dr. Krupka (CEN TC 132) in early August 2013.
• The Consultation paper had, as attachments, the draft StaCast proposal on "Mechanical properties of Aluminium casting alloys" (corresponding to Deliverable D3.2 of StaCast).
• The Consultation was processed by CEN Internal Balloting portal, and it was verified (September 16th 2013) that CEN/TC 132 Members agreed to include the StaCast proposal on "Mechanical properties of Aluminium casting alloys" into the CEN/TC 132 working programme.
• A dedicated Task Force/Working Group of TC 132 has been set up, including members of StaCast Consortium, to process the StaCast proposal on " Mechanical properties of Aluminium casting alloys", and to finalise it as CEN Technical Report (TR) or CEN Technical Specifications (TS).
• The CEN/TC 132 Task Force had an official meeting in Milan (hosted by Italian Association of Metallurgy), on November 13th-14th 2013, to process the StaCast drafts for TR (or TS).
• During the meeting, it was decided to deliver Technical Report (instead of Technical Specification), with the final title "Aluminium and aluminium alloys — Mechanical potential of Al-Si alloys for high Pressure, low pressure and gravity die casting" and the scope:
This Technical Report presents the mechanical potential (in terms of Ultimate Tensile Strength, Yield Strength and Elongation) which can be exploited by Al-Si alloys, cast by high pressure, low pressure and gravity (permanent mould) processes. These properties are measured on test specimens produced by using optimized reference dies and process parameters, properly defined for exploiting the mechanical potential of cast alloys.
• During the meeting, the time scheduling and the action list to achieve the official approval from CEN TC 132 of the StaCast Technical Report on Mechanical potential of Al-Si alloys for high Pressure, low pressure and gravity die casting was defined.
In detail, it has to be pointed out that the draft Technical Report on Mechanical Potential of Al-Si foundry alloys constitutes the official outcome of the concerted action performed by CEN TC 132 and StaCast project, being draft of the CEN Technical Report on "Aluminium and aluminium alloys — Mechanical potential of Al-Si alloys for high Pressure, low pressure and gravity die casting ". This draft is following the consolidated procedure for approval of CEN Technical Reports: Internal Enquiry (deadline: 10th January 2014); Informal Internal Consultation (deadline: 1st March 2014); Official TC 132 Consultation (deadline: 25th June 2014). The timing is in agreement with CEN rules for Technical Reports approval.
The development of the process of approval of the draft of the CEN Technical Report on "Aluminium and aluminium alloys — Mechanical potential of Al-Si alloys for high Pressure, low pressure and gravity die casting " has been followed in the frame of StaCast WP4 (implementing the up-graded CEN TR into the design guidelines) and WP5 (dissemination of the contents of the up-graded CEN TR), up to March 31st 2014.
After March 31st 2014, the Partners of StaCast will continue, on a voluntary basis, to monitor the evolution of the CEN Technical Report on " Aluminium and aluminium alloys — Mechanical potential of Al-Si alloys for high Pressure, low pressure and gravity die casting ", and to support CEN TC 132 with all the needed information.
4. Rules and guidelines for mechanical design of Aluminium cast products
4.1 Introduction
StaCast intended to elaborate an operative support to mechanical designers, involved in the field of Al alloy components. The availability of two new CEN Technical Reports on defects & imperfections in castings (resulting from WP2) and mechanical potential of Al-Si foundry alloys (resulting from WP3) makes necessary the development of a new approach in the design stage. Such a new approach has to take into account
- the “mechanical potential” of Al foundry alloys (draft CEN Technical Report: Fpr TR 16748 (00132378), "Aluminium and Aluminium alloys - Mechanical Potential of Al-Si alloys for High Pressure, Low Pressure and Gravity Die Casting",
- the critical role played in castings by the different types of defects, classified in the new CEN Technical Report Fpr TR 16749 (001323789), "Aluminium and aluminium alloys - Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products",
- the need of considering, for cast products, the interaction existing among microstructure, defects and mechanical behaviour, leading to a “distribution of mechanical properties”.
4.2 Quality and Defects & Imperfections in Al-Si alloys castings
A great contribution to the use of Al-Si alloys comes from improvements in casting processes, which allow to increase the production, to reduce the cycle time and to manufacture complex-shaped castings with thin wall thickness. Among the recent casting techniques, the gravity die casting and the high-pressure die-casting are largely used by the automotive sector since fulfils the above advantages.
A limit to large diffusion of these technologies, but in general of the foundry techniques, remains the final quality of castings. Unlike forging or other thermo-mechanical processes, the properties of shape Al alloy castings are almost entirely dependent upon the filling and solidification conditions, which should be considered during the design chain. For instance, from a stress-engineering viewpoint, thickening up a section of a component will lead to increased load-bearing capacity at that location. During casting, a thicker region will solidify more slowly and, for Al alloys, coarser microstructures will result in lower mechanical strength. Problems with feeding and shrinkage defects may also arise in thicker sections.
While the combination of high speed casting and high cooling rate can give the possibility of thin walled castings and high production rate, the associated turbulence remains a great source of inner and surface casting defects, which have deleterious effects on mechanical properties.
In gravity and high-pressure die-casting if a number of parameters is not adequately determined and adjusted, the quality of the die cast part results rather poor. Macrosegregation of eutectic, primary intermetallic and α-Al crystals, porosity, oxide bifilms and confluence welds are addressed as typical casting defects.
New technical evolutions of the traditional foundry processes, such as vacuum technique, pore-free and semi-solid processes, have been developed to minimise the defects’ content, leading to the production of high integrity thin walled castings. However, the diffusion of these new technologies still remains limited due to the high investment costs.
When designing and developing die cast components and process parameters, a great number of optimisation goals must be taken into consideration, e.g. dimensional accuracy, distortions of the component, casting defects. A useful approach in the development of die casting optimisation is the correct definition of the casting problems and their importance towards quality. Considering HPDC, casting defects are mentioned by foundrymen at first. Therefore, in case of a single optimisation goal, such as minimizing casting defects, an interactive optimisation cycle should be adopted to combine the changes of the die design, including the runner system and overflows, and the variations of injection parameters, such as the plunger speeds, the commutation point between the first and second phase. This is done in order to improve the final integrity of castings.
If more optimisation goals are defined, different “good solutions” can be obtained. This however does not mean that the selected solution will be the best. With reference to the defined optimisation goals, it only represents the best compromise. On the other hand it cannot be completely concluded that there is not any solution that would fulfil the optimisations goals in full.
From another point of view, the variation of the casting parameters (including die thermal management) allows a more easy change of the casting quality, if compared to the expensive and time consuming machining operations of the die. Moreover, when speaking about traditional HPDC, it is common opinion that a certain amount of defects will be always entrapped within the die cast part, even if not optically revealed after subsequent machining. By means of the casting parameters’ adjustments, foundrymen try to restrict and isolate the major part of defects into casting regions that will not be mechanically stressed during normal working. Further, thin-walled castings, like those produced by HPDC, are more affected by the presence of defects since a single macrodefect can cover a significant fraction of the cross-section area.
4.3 Quality and Defects & Imperfections
Quality is maximised when Defects and Imperfections are minimised. The definition of Defects and Imperfections, according to the draft of CEN Technical Report elaborated by StaCast project, is the following:
• Defect: A quality characteristic is lower with respect to the level or state foreseen (usually specified); it does not allow the product to carry out the function requested [EN 12258-1: 2001, 7.1.2];
• Imperfection: A quality characteristic is for a some extent lower with respect to the level or state foreseen; this does not mean necessarily that the product is not suitable for use: an imperfection must be evaluated by means of a proper scale, based on the related specifications, to decide if the product has a quality level making it suitable for the use [EN 12258-1: 2001, 7.1.1].
Defects and Imperfections can be classified according to the scheme already described in Deliverable D2.3 of StaCast Project. In order to understand the physical, chemical and/or metallurgical phenomena generating Defects and Imperfections, the key-information is contained in the second level of the Classification. In fact, D&I are generated by those phenomena, which can be active both in the surface or internally in the castings (first level) and can produce various specific kinds of D&I.
Obviously, the relevance of each family of defects and imperfections is different for each kind of castings, and is associated to an extremely high number of processing conditions and parameters. Anyway, with specific reference to HPDC processes, it has been already specified in Deliverable D1.1 of StaCast project that there is the following ranking:
• Metal/Die interaction (57%): significant frequency,
• Gas/Air porosity (54%): significant frequency,
• Shrinkage (37%): slightly more than occasionally,
• Filling-related (35%): slightly more than occasionally,
• Crack (33%): occasionally,
• Inclusions (24%): less than occasionally.
4.4 Processing parameters, defects & imperfections, mechanical properties
Quality of castings can be defined as being a measure of excellence or a state of being free from defects, imperfections and significant variations, where high quality is brought about by the strict and consistent adherence to measurable and verifiable standards to achieve uniformity of output that satisfies specific customer or user requirements. The casting quality in engineering applications refers to reaching a suitable compromise drawn from among numerous factors which would produce minimum risk and maximum performance in conjunction with cost efficiency.
During the design stage of a component, the combined knowledge of the alloy expected strength, microstructure and presence of defects is required. The knowledge of the expected strength of the alloys gives a view of the mechanical properties which can be achieved in optimized casting conditions. The way in which microstructure (which varies according to local solidification time in different regions of the cast components) influences mechanical behaviour constitutes another relevant issue. Lastly, the understanding of the way in which the expected strength of foundry alloys is limited by the negative effects of various kinds and amount of defects induced during the casting process is also fundamental. Often the formation of defects is sensitive to small variations in the casting conditions and the causes cannot be only connected to the process profile adopted, even if this variable results the main source of defects. Such a combined knowledge is matter of interest and interaction between foundry-men and mechanical designers.
However, the final mechanical behaviour of Al alloy die-castings is mainly controlled by defects size and amount; only when the presence of defects is avoided, microstructure becomes the controlling factor. This is because defect-containing regions in a tensile sample reduce load-bearing area and produce a concentration of strain. Particularly, castings with thin sections, such as those produced by high-pressure die-casting, are vulnerable to the effect of defects, since a single macro-defect could cover a significant fraction of the cross-sectional area.
Correlations between defects, process parameters and mechanical properties of Al-Si alloy castings can be described in terms of:
- Influence of casting defects on microstructural and tensile properties,
- Influence of process parameters on microstructural and tensile properties.
4.5 Some Guidelines for Design of Aluminium Alloy Castings
A number of researchers has investigated the influence of casting defects on the mechanical properties both of gravity cast and high-pressure die-cast Al alloys. However, the works of Gokhale et al. and Timelli et al. evidenced how the mechanical properties decrease monotonically with increasing the area fraction of defects revealed on the fracture surfaces of die cast aluminium specimens. The common conclusion was that even high integrity castings contain defects and thus it is important to predict their effect on final mechanical properties.
Several approaches have been suggested and they are based on through-process modelling for prediction of the structural behaviour of magnesium and aluminium alloys components subjected to static and dynamic loads.
Generally, two different routes based on constitutive models or stochastic approaches are used. Cáceres and Lee reported that the theoretical approach based on the Ghosh constitutive model can accurately predict the experimental tensile properties of cast Al alloys, even though they used a simple determinist approach. In the model, based upon the tensile instability, the tensile strength and deformation of material with internal discontinuities significantly depend upon the fraction of internal discontinuity, the strain rate sensitivity and strain-hardening ability.
On the other side, the effect of structural defects on mechanical properties can be characterized by Weibull statistics, more specifically, by the two-parameter Weibull modulus. In these studies, the Weibull modulus appeared to be a useful measure of the reliability of the casting process. Since then, the two-parameter Weibull modulus has been extensively used to characterize the tensile properties, especially the tensile strength. Recently, the use of three-parameter Weibull statistics has been explored to illustrate its superior analytical potential over the traditional two-parameter approach. The three-parameter Weibull analysis provides new information. In particular, minimum values of strength, below which the material is extremely unlikely to fail, are found.
Both the constitutive and stochastic approaches can be adopted as useful guidelines for designing Al alloy castings.
5. Dissemination activities
5.1 StaCast Website
The structure of the StaCast website has been presented in Deliverable D5.2. After one-and-half year of Project, some aspects are certainly worth mentioning. The website has been organised with a proper counter, which evidenced that at the end of the Project the total number of contacts was more than 50.000. During the last month of the Project, the average number of weekly contacts has been higher than 1.000. It can be stated that the StaCast website has been a really powerful tool for the information about the project and for the dissemination of its main outcomes. In fact, the website contains a specific page dedicated to Deliverables, on which all the public results of the project are (or are going to be) downloadable. The StaCast website has been also a very useful instrument for internal dissemination and exchange of results, as well as for making available all the dissemination-related materials: ppt presentations used in public meetings and seminars, papers and articles related to the Project, photos from events, etc.
It has been decided by Partners to keep operative the StaCast website also after the end of the Project, at least for a period of 3 years, to continue its dissemination actions.
5.2 Public Meetings, Seminars and Courses
There have been several initiatives publically present the project, show the outcomes, collecting information and opinions from Industry and Academy.
The StaCast Project Public Meeting, which was kept in Milano on September 26th 2013, with the aim of
- presenting the results of the StaCast Survey on EU foundries,
- illustrating structure and contents of the two Drafts of CEN Technical Reports on Defects & Imperfections and on Mechanical Potential,
- collecting contributions, comments and suggestions from industrial experts, to support the finalization of these two Drafts as Deliverables D2.3 and D3.3.
35 persons participated to the meeting, mainly from Italy, with a share of 80% in terms of industrial experts.
Other public meetings and seminars have been participated by StaCast Partners, to present the development of the Project as well as its main outcomes. They can be mentioned:
- the Course on "Aluminium Alloys" (Milano, 25 June 2013),
- the Course on "Heat Treatments" (Milano, 17-18 September 2013),
- the Course on "Energy efficiency to reduce costs in HPDC (Rovigo, 1 October 2013),
- the International CAE Conference (Verona, 21-22 October 2013),
- the 24th Italian National Conference on "Heat Treatments" (Piacenza, 17-18 October 2013)
- the Course on "Thermal Behaviour of Dies" (Bergamo, 31 October 2013),
- the International Barbara Kolloquium (Aalen, 3 December 2013),
- the Course on "Quality of Diecastings" (Bergamo, 27 March 2014).
5.3 Technical Publications & Book, Scientific Papers, Press Releases
The approach, activities and outcomes of StaCast Project have been presented and disseminated by means of various types of publications:
- Press releases and project descriptions,
- Technical papers,
- one Technical book,
- Scientific papers.
Press releases and project general descriptions have been published on the magazines "Aluminium and Alloys" (text in English and Italian, printed 8 times every year, 5.000 copies for each issue), "High Pressure Diecasting and Foundry Technologies" (text in English and Italian, printed 4 times every year, 5.000 copies for each issue), "Assomet news" (text in Italian, printed monthly). The first two magazines are also published on-line by Edimet SpA: http://www.aluplanet.com/ita/RivisteOnLine_Login.asp.
During the Project, various Technical Papers have been elaborated on subjects referred to defects & imperfections classification and to mechanical potential of Al foundry alloys. Such Technical Papers have been published on "Industria Fusoria" (text in Italian, printed 6 times every year, 2.000 copies for each issue) and on the already mentioned magazines "Aluminium and Alloys" and "High Pressure Diecasting and Foundry Technologies".
The high quality level of the approach adopted by the StaCast Project is witnessed by the elaboration (and forecast publication) of four Scientific Papers, addressed to the "Intermational Journal of Metalcasting" (2 papers, one accepted , the other under evaluation) and to the 71st World Foundry Congress (1 paper accepted) and to the 14th International Conference on Aluminium Alloys (1 paper accepted).
The International Journal of Metalcasting (IJMC) is published by the American Foundry Society and is dedicated to leading the transfer of research and technology for the global metalcasting industry. The editorial peer review board represents three international metalcasting groups: academia (metalcasting professors), science and research (personnel from national labs, research and scientific institutions), and industry (leading technical personnel from metalcasting facilities). IJMC is also indexed in Thomson Reuters Journal Impact Factor.
The 71st World Foundry Congress Twill take place in Bilbao (Spain), from May 19th-21st 2014. The different activities gathered within the Congress and the International Foundry Exhibition will represent an extraordinary opportunity to exchange technical knowledge. The preliminary programme forecasts about 200 papers, and more than 400 participants are expected.
The 14th International Conference on Aluminium Alloys will be held in Trondheim (Norway). It will cover all aspects of aluminium alloy technology, ranging from alloy design and process development, via advanced characterisation and computer modelling of solid microstructures and related properties, to design, properties and performance of finished products. Accepted papers will be published in Materials Science Forum, indexed in the major academic databases, including EI Compendex, Thomson ISI and with full text online at http://www.scientific.net. The number of accepted papers can be estimated to be around 80, and about 200 participants are expected.
Apart from the above described publications, the StaCast Partners decided to elaborate a unique document collecting the main information and outcomes from the Project. This document is constituted by a 200 pages book, entitled "Aluminium alloy castings: the EU StaCast guide to defects classification, mechanical potential and design issues". The StaCast book is constituted by four Chapters, substantially based on four of the main Deliverables of the Project: D1.1 D2.1 D3.1 and D4.1. The book has an A5 format, so that it can be easily handled also in a foundry environment. It has been provided with an official ISBN number, which is 978-88-98990-00-9.
The Chapters of the book will also made available on the StaCast website, to promote and further disseminate the outcomes of the Project.
5.4 Interaction with CEN
A key-dissemination activity of the StaCast Project is constituted by the interaction which has been established with the European Committee for Standardization (CEN), and particularly with Technical Committee on Aluminium and its alloys (TC 132). Three specific initiatives are worth mentioning:
- the official CEN TC132 – StaCast meeting, which was held in Milano, on November 2013, to discuss and preliminarily elaborate the drafts of the 2 CEN Technical Reports on defects & imperfections and on mechanical potential; the official launch of the approval procedure for the 2 drafts will be opened in June 2014 (Plenary Meeting of CEN TC132 in Madrid) and will be concluded in September 2014;
- the final StaCast meeting, which was held in Brussels, on March 2014, at CEN-CENELEC building, with the target of officially present to CEN the outcomes of the Project; during the meeting, an overview of CEN-CENELEC activities and of their links with R&D EU Projects has been presented by A. Gulacsi (Unit Manager of CEN-CENELEC Research Integration Unit);
- the preliminary agreement between StaCast and CEN-CENELEC Research Integration Unit, in order to include StaCast into the list of "Success stories" (a list of current EU projects where a standardization partner is active, and mentioned as 'Best Practices' documents); this will subsequently result into the elaboration of a dedicated CEN-CENELEC brochure.
5.5 Cross-cutting Initiatives
The activity of StaCast had a duration of 18 months. During this period, StaCast developed some cross-cutting initiatives, in the field of Aluminium alloys foundry, aimed at consolidation current and future activities on standardisation. In particular, from October 2012 StaCast interacted with MUSIC project (MUlti-layers control&cognitive System to drive metal and plastic production line for Injected Components, FP7- FoF-ICT-2011.7.1 PROJECT n. 314145, http://music.eucoord.com/home/body.pe). MUSIC is a highly interdisciplinary project (4 years duration: 2012-2016), particularly addressed ad developing new tools for the optimisation of Aluminium alloys products, manufactured by means of high pressure diecasting. Three of StaCast Partners (GTA, DTG and ASSO) are also Partners of MUSIC Consortium. The general relationship between the two projects has been approved by the Steering Committees of both StaCast and MUSIC.
The main outcomes of StaCast Project have been already valorised in the frame of MUSIC project.
Potential Impact:
The final results of StaCast Project have direct impacts and use.
1. Survey carried out among EU Aluminium alloys foundries
The survey carried out among EU Aluminium alloys foundries evidenced the key-issues of the field, as well as the level of knowledge and use of existing CEN Standards and the needs for new ones; all these information have been shared with and transmitted to CEN-related Technical Committee (i.e. TC 132 – Aluminium and its alloys).
The reliability and representativeness of the information collected are certainly good: a sufficient number of foundries (58) answered, well representing
- the two Countries leading the EU production in the field of Al alloys casting (33 German foundries, 25 Italian foundries),
- the overall EU production of Al alloys castings (10% of EU production has been conservatively estimated for the foundries answering the Questionnaire),
- the most diffused casting processes: 69% of the foundries are using HPDC (i.e. the process estimated to be used for the 60-70% of EU production of Al alloys castings), the other gravity and LPDC,
- the average size of EU Al Alloys foundries, with 32 SMEs (which are the majority in EU Al alloys casting production) and 26 large industries.
A relevant consideration coming from answers elaboration is that EU Standards, and particularly those referred to the more technical issues on defect detection and quality control (radiographic inspection, EN 12681, and control of melt composition, EN 14361) as well as to technical conditions of delivery of castings (EN 1559) need to be better disseminated.
The need of new EN Standards and guidelines identified by StaCast (Defect classification, Mechanical properties of Al casting alloys, Mechanical properties of Al castings, Rules for design of cast products) seems relevant. The evidenced standardisation needs have been taking into account for the elaboration of results 2) and 3).
From the elaboration carried out, a sort of "mapping" of defect knowledge, detection and control has been achieved. In particular, it is worth mentioning that a new EN Standard on Defect classification for Al alloys cast product should contain a clear definition of defects characteristics and of the principles and experimental techniques and tools for their detection.
The defect frequency maps for SME and IND are substantially similar, with a higher value (+5%, almost constant for each class of defect) for IND, in comparison to SME. The defect frequency maps for HPDC and gravity/LPDC processes are highly different. The relevancy of Metal/Die interaction defects and of Gas/Air porosity defects is significantly higher for HPDC process, while Shrinkage defects becomes the main criticism for gravity/LPDC processes. The availability of a new EN Standard on defect classification for Al alloys cast products will help each foundry in setting up its own defects map. Such a "Foundry-level" defects map, continuously upgraded, will constitute a strategic tool for process control and for quality and competitiveness increase.
The information tool (Questionnaire + Website implementation + Data Elaboration approach) developed by StaCast has a relevant potential for a continuous up-grade and monitoring of the field.
The file "Annex_1_to_final_report.pdf" collects all detailed information on this StaCast result.
2. New CEN Technical Report for the Classification of Casting Defects and Imperfections
The new CEN Technical Report for the Classification of Casting Defects and Imperfections, once approved, will help EU Aluminium alloys foundries at promptly performing corrective actions to reduce/eliminate defects, and will constitute a useful “communication tool” among all the actors of the design and manufacturing chain of Al alloys cast components.
StaCast suggested a new classification approach, based on a 3-levels defects individuation:
I) morphology/location of defects (internal, external, geometrical);
II) metallurgical origin of defects (e.g. gaseous porosity, solidification shrinkage, etc.);
III) specific type of defects (the same metallurgical phenomenon may generate various defects).
This classification of defects is of hybrid type and multi-level, and is referred to metallurgically-based defects of high pressure die casting and permanent mold casting products. Defects directly related to handling, finishing, machining operations following ejection from the die are excluded from the classification, even if they could be possible causes for product rejection.
On the basis of the above described activities, StaCast activated official contacts with CEN Technical Committee 132 – Aluminium and its alloys, in view of the development of a specific CEN Document on Defects Classification for Al alloys cast products.
After these contacts, it was decided to deliver the draft Technical Report, with the title "Aluminium and aluminium alloys — Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products" and the scope:
This European Technical Report specifies the classification of the defects and imperfections may be present in cast products manufactured by high pressure, low pressure and gravity die casting of Aluminium alloys.
The file "Annex_2_to_final_report.pdf" collects all detailed information on this StaCast result.
3. New CEN Technical Report on Mechanical Potential of Al-Si foundry alloys
The new CEN Technical Report on Mechanical Potential of Al-Si foundry alloys will offer the clear information of which properties can be expected by these alloys, cast in reference dies with state-of-the-art knowledge on die design, process management and alloy treatments correctly applied to minimize defects and imperfections.
Nowadays, the evaluation of mechanical properties in Aluminium alloys cast products has become a relevant issue, which is not fully covered by existing International Standards or Technical Reports or Technical Specifications. The advanced design and engineering tools currently available to optimise casting process allow a radical change in this approach. The real mechanical potential of Al-based cast alloys (in terms of Ultimate Tensile Strength, Yield Strength and Elongation), which can be exploited by Al-Si alloys, cast by high pressure, low pressure and gravity (permanent mould) processes, needs to be clearly identified. This mechanical potential can be accurately evaluated by means of properly designed reference dies (in the case of high pressure die casting) or by using already available (but not included in actual EN Standards) reference dies (in the case of low pressure die casting and gravity die casting), as proposed by StaCast project.
On the basis of the above described activities, StaCast activated official contacts with CEN Technical Committee 132 – Aluminium and its alloys, in view of the development of a specific CEN Document on Mechanical Potential of Al-Si foundry alloys.
After these contacts, it was decided to deliver a draft Technical Report, with the title "Aluminium and aluminium alloys — Mechanical potential of Al-Si alloys for high Pressure, low pressure and gravity die casting" and the scope:
This Technical Report presents the mechanical potential (in terms of Ultimate Tensile Strength, Yield Strength and Elongation) which can be exploited by Al-Si alloys, cast by high pressure, low pressure and gravity (permanent mould) processes. These properties are measured on test specimens produced by using optimized reference dies and process parameters, properly defined for exploiting the mechanical potential of cast alloys.
The file "Annex_3_to_final_report.pdf" collects all detailed information on this StaCast result.
4. Rules and guidelines for mechanical design of Aluminium cast products
The rules and guidelines for mechanical design of Aluminium cast products will encourage the correct use of the two new CEN Technical Reports in the design stage of Al alloys cast components, offering relevant information to mechanical designers.
StaCast intended to elaborate an operative support to mechanical designers, involved in the field of Al alloy components. The availability of two new CEN Technical Reports on defects & imperfections in castings (result n. 2) and mechanical potential of Al-Si foundry alloys (result n. 3) makes necessary the development of a new approach in the design stage. Such a new approach has to take into account
- the “mechanical potential” of Al foundry alloys (draft CEN Technical Report: Fpr TR 16748 (00132378), "Aluminium and Aluminium alloys - Mechanical Potential of Al-Si alloys for High Pressure, Low Pressure and Gravity Die Casting",
- the critical role played in castings by the different types of defects, classified in the new CEN Technical Report Fpr TR 16749 (001323789), "Aluminium and aluminium alloys - Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products",
- the need of considering, for cast products, the interaction existing among microstructure, defects and mechanical behaviour, leading to a “distribution of mechanical properties”.
The file "Annex_4_to_final_report.pdf" collects all detailed information on this StaCast result.
5. Dissemination activities
The dissemination activities (starting from the StaCast website: about 50.000 contacts recorded) performed put into evidence the potential of these new Technical Reports and Guidelines for Aluminium alloys foundries and related companies in the design & supply chain. A coordinated set of dissemination activities (i.e. the Project website, 8 seminars & conference presentations, 10 press releases and technical papers, 4 scientific papers, the "StaCast" book) has been done, making available the results of the project to the Aluminium alloys foundries and related companies.
The file "Annex_5_to_final_report.pdf" collects all detailed information on this StaCast result.
More generally to understand the impact of the StaCast Project on EU industrial context, it has to be considered that
- there are more than 2000 Aluminium alloys foundries in Europe;
- they are basically SMEs, with an average number of employees around 50,
- the end users of cast products are the transport industry (60%), mechanics (7%), electro-mechanics (9%), civil engineering (20%), with a growing trend in automotive and transport, motivated by the reduction achievable in fuel consumption and emission;
- foundry processes make use, in the majority of cases, of re-cycled (the so-called “secondary”) alloys, with a relevant saving in terms of energy and natural resources.
For EU foundries, the possibility to survive through the present economical crisis is strongly associated to competitiveness, efficiency, innovation. A key-role will be certainly played, in the next few years, by the availability of CEN Standards & Technical Reports and design tools (such as those developed by StaCast).
In fact, Al foundries are highly limited by “no-quality costs”. The new CEN Technical Report on defects classification will directly impact on the reduction in no-quality costs, promoting process efficiency, which will be an advantage for all the other players involved.
In the opinion of StaCast Consortium, having a clear picture of defects in casting and a realistic vision of the mechanical potential of foundry alloys will make EU foundry more competitive, thanks to the increased knowledge about their products which will be encouraged by the two new CEN Technical Reports. These documents, specifically focussed on quality, will help foundries in reducing no-quality costs, expanding the margins of their competitiveness. Each action and result in terms of scrap reduction immediately causes reduction in the energy consumption.
In this sense, even if technical and organisational activities aimed at decreasing no-quality costs in foundries have been carried out recently (but only with “local spot” actions as specific patents, lay-out solutions, changes in process flow), the new CEN Technical Report on defects classification represent a real “structural” action to improve quality of foundry products.
List of Websites:
The StaCast public website is: www.stacast-projecy.org
The relevant contact details are the following:
Partner n.1:
Università degli Studi di Padova
Dipartimento di Tecnica e Gestione dei sistemi industriali (DTG)
Str. S. Nicola, 3 36100 Vicenza, ITALY
Website: www.gest.unipd.it
Contact person for the StaCast Project: Prof. F. Bonollo (bonollo@gest.unipd.it)
Partner n.2:
HOCHSCHULE AALEN - TECHNIK UND WIRTSCHAFT
Beethovenstraße 1 - 73430 Aalen, GERMANY
Website: www.htw-aalen.de/gta
Contact person for the StaCast Project: Prof. L. Kallien (Lothar.Kallien@htw-aalen.de)
Partner n.3:
NORGES TEKNISK-NATURVITENSKAPELIGE UNIVERSITET - NTNU
Hogskoleringen, 1 - NO-7491 Trondheim, NORWAY
Website: www.ntnu.no
Contact person for the StaCast Project: Prof. L. Arnberg (arnberg@ntnu.no)
Partner n.4:
Associazione Italiana di Metallurgia (AIM)
Piazzale Morandi, 2 - 20121 Milano, ITALY
Website: www.aimnet.it
Contact person for the StaCast Project: Dr. F. Bassani (secretariat@aimnet.it)
Partner n.5:
ASSOMET servizi srl
Via dei Missaglia, 97 - 20142 Milano, ITALY
Website: www.assomet.it
Contact person for the StaCast Project: Mr. C. De Cani (assomet@assomet.it)
Partner n.6:
The Federation of Aluminium Consumers in Europe (FACE)
Rond Point Schuman 6, Box 5 - B-1040 Brussels, BELGIUM
Website: www.facealuminium.com
Contact person for the StaCast Project: Dr. M. Conserva (face@facealuminium.com)
