Final Report Summary - FECOPROGEN (FeCo based magnetic alloys with high strength and minimized iron losses, for new high speed aerospace generator) Executive Summary:The equiatomic Fe-Co alloy (with 2%V) – as the AFK502R grade of Aperam Alloys Imphy – is produced to fulfil every requirement in power electrical engineering at low-medium frequency asking firstly and strongly for lightening or volume reduction. Such advantage is allowed by the the high magnetic saturation together with its rather high permeability. BUT a very fast ordering transformation acting below 700°C brings brittleness in the strip: then at the end of hot rolling the Fe-Co tapes has to be intensively water-quenched to prevent brittleness and in order to bear cold transformation. Through cold rolling the laminations are then sold to customers in the as-rolled and ductile state, with a good ability to be stamped into pieces BEFORE static annealing which involves recrystallization and then restores the soft magnetic properties. Such a process is called “semi-process” (strips sold in the as-rolled state). After static annealing the pieces (or stacks of them) become very brittle and can’t bear any stamping, punching etc. The box static annealing allows only low or medium yield mechanical strength (<500MPa), low or medium magnetic losses, and induces out of shape deformation during the final annealingFacing this lack of high yield stress (>500MPa) and/or this absence of fully process grade (delivered as annealed and electrically insulated) and/or this out of shape during the final annealing, the FeCoProGen project aims to develop an original metallurgical path, starting from industrially annealed hot bands (usual AFK502 grade) through a very dedicated and well-controlled continuous annealing (called HSP for High Strength Processing) in place of the final static annealing, and able to prevent from ordering base embrittlement together with the availability to get precise high strength AND improved compromises between mechanical and magnetic properties. Peculiarly the project target consists in decreasing the magnetic losses down to less than 200W/kg at 2T/400Hz for a required yield strength (YS) of at least 800MPa in every measurement direction of the rolling plane, called Min(YS). The 2 years of project have shown that :- a reduced lamination thickness has to be favoured (for example 0,2mm), that a double stage process (one intermediate annealing between the cold rolling) can be at least as interesting - in terms of compromise between magnetic losses and yield stress – as the single stage process delivering High Strength (HSP). 250W/kg at 2T/400Hz could be obtained with a minimum isotropic yield stress of 800MPa, in case of 0,2mm thick laminations.- downstream industrial processes (after final annealing) may lead to drastic and damaging effects on magnetic properties and have to be well controlled.- multiply product, made of glued thin HSP laminations, have been done successfully, without high magnetic damage (15% on losses), with a medium ability to stamping, allowing a potential reduction of stacking factor and production cost with nearly the technical characteristics of thin HSP laminations. Project Context and Objectives:Summary description of the project context and the main objectivesPrior art: The equiatomic Fe-Co alloy (with 2%V) – as the AFK502R grade of Aperam Alloys Imphy – is known for a long time for its high magnetic saturation Js (allowing very high power density of generator or electromagnetic actuator in on-board application such as aerospace generators...) together with its rather high permeability. BUT a very fast ordering transformation acting below 700°C brings brittleness in the strip: then at the end of hot rolling the Fe-Co tapes has to be intensively water-quenched to prevent brittleness and in order to bear cold transformation. Through cold rolling the laminations are then sold to customers in the as-rolled and ductile state, with a good ability to be stamped into pieces BEFORE static annealing (recrystallization in order to restore soft magnetic properties). Such a process is called “semi-process” (strips sold in the as-rolled state). After static annealing the pieces (or stacks of them) become very brittle (no problem in the piece state), providing low or medium yield mechanical strength, low or medium magnetic losses.Problem to be solved : Such usual Fe-Co processing is unable to provide high strength OR to provide annealed and ductile (then able for stamping) state of metal (known as “fully process” state in electrical steel) OR to provide no deformation of complex piece shape during a subsequent final annealing (in order to further minimise magnetic losses). Main objectives: The FeCoProGen project aims to develop an original metallurgical path, starting from industrially annealed hot bands (usual AFK502 grade) through a very dedicated and well-controlled continuous annealing (called HSP for High Strength Processing) in place of the final static annealing, and able to prevent from ordering base embrittlement together with the availability to get precise high strength AND improved compromises between mechanical and magnetic properties. Peculiarly the project target consists in decreasing the magnetic losses down to roughly 180W/kg at 2T/400Hz for a required yield strength (YS) of at least 800MPa in every measurement direction of the rolling plane, called Min(YS). Project Results:Description of the work performed since the beginning of the project and the main results achieved so farIn the second period the double stage High Strength Processing HSP has been studied intensively, exploiting the enhanced number of possibilities (process parameters: speed and temperature annealing, cold rolling ratii) allowing a marked modification of texture heredity. In the 2nd part of period2, resources have been concentrated on double stage metallurgical ways for a final gauge of 0,2mm, the most promising thickness (compromise) for the product considering the needs for low magnetic losses, stamp-ability, reduced production cost, good stacking factor. In such thickness, a few attempts have been made with 0,35mm and 0,5mm intermediate thicknesses: it shows that the compromise losses-Min(YS) is at least as interesting as the one reached with single stage process but these results are based on very few trials; nevertheless the first productions for end-user demonstrators have been selected from these first successful attempts in double stage. In the second period the study of an other potential way to improve the compromise “losses-Min(YS)” – said the supplementary recovery annealing - has shown that such process added to HSP introduce either ordering and then loss of yield stress, or a non-neglecting prolongation of crystallization which reduces more the yield stress YS than it reduces the magnetic losses. As a conclusion about recovery after HSP, in every case the compromise losses-Min(YS) is damaged. In the second period the study of an other potential way to improve the compromise “losses-Min(YS)” – said the gluing of HSP thin laminations into bimetal - has shown that some technical glues can fulfil the requirements for adhesion (as well at RT as 250°C), rigidity, shearing and stamping ability of bimetal, reduced damage (15%) in magnetic losses of the bimetal compared to the state before gluing. If the end-user can’t bear the drawback of 0,2mm thick lamination (stamping ability, stacking factor...) the 2x0,2mm (for example) may be a good solution (but more expensive) to overcome such disadvantages and to take benefit of the HSP products. Potential Impact:Description of the expected final results and their potential impacts and use (including socio-economic impact and the wider societal implications of the project so far)FeCoProGen has stopped the 31st of October, 2015. In November 2015 the production of double stage HSP laminations, 0,2mm thick for the demonstrators of generator were finished, including several process steps after the last continuous annealing (as a difference from materials produced in small quantities for every tasks and WPs of FeCoProGen): coating insulation, planishing and cutting into pieces on industrials tools. This 1st production for demonstrator has been sent to the end-user to answer to 2 important objectives related to the validation of the best final lamination thickness:• Checking, on the end-user plant, if the new HSP grade, 0,2mm in thickness is easy to stamp and cut. To establish the evolution of the stacking factor compared to 0,35 or 0,4mm thick laminations.• Made attempt to cut and stamp the glued 2x0,2mm new HSP products on the end-user plant. Hundreds of rectangular pieces have been firstly glued by a subcontractor of Aperam, before providing to the end-user for stamping rotor piecesMoreover new productions of AFK502FP for generators/demonstrator (and their testing by end-user) are running since 2015 in Imphy/Aperam, starting from a single stage process.In 2016, as an extension of FeCoProGen the research&development about the HSP products do not stop: it is now concentrated on double stage HSP in order to complete the FeCoProGen studies; - Basically Fully Processed HSP allow to reach a yield stress between 600 and 1100MPa with reduced magnetic losses. The yield stress could be decreased between 200 and 600MPa after further final box annealing. Any application of electrical engineering may consequently be addressed with this new product, offering both designed yield stress, geometry stability through further final annealing (important for aerospace transformer), easy shaping and ability for stamping. This new product is aimed to progressively increase the market share of Aperam in the field of magnetic cores for aerospace electrical engineering (generators, transformers, inductance, EHA and EMA).- The world market of Fe-Co lamination for electrical engineering is evaluated between 300 and 500t/year with 70-80% belonging to the American company Cartech. APERAM and its german competitor share the remaining market. APERAM produces about 30-50t/year of Fe-Co laminations. The industrial development and commercialisation of such new Fully Processed grade should allow European manufacturer of aero-generator to propose lighter devices (at equivalent delivered power) than those proposed by American competitors. The target of Aperam is to increase by 100 – 200% its world market share of Fe-Co laminations, with a targeted production of about 100t/year.List of Websites:www.aperam.com/alloys-imphy/
