Improvement of steel hot-rolling by the use of lubrication and hss rolls

Project Information

Grant agreement ID: BRPR950133

Project closed

Start date 1 April 1996

End date 31 December 2000

Funded under

• Specific research and technological development programme in the field of industrial and materials technologies, 1994-1998

Total cost

No data

EU contribution

No data

Coordinated by

Cockerill Sambre SA
Belgium

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Deliverables

A Metallurgical Rolling Force Model used for the “on-line” calculation of the friction coefficient in each stand of the mill

The MRF model (Metallurgical Rolling Force model) allows the computation of the evolution of the friction coefficient during a rolling campaign. The model uses the slice method to calculate the pressure distribution and is based on the von Karman’s theory. The normal pressure inside the roll gap is divided into two components: the steel deformation resistance and the friction. After each rolled strip, the roll force and power are automatically calculated and their evolutions are related to the evolution of the friction coefficient. With the MRF model it has also been possible to evaluate the efficiency of work roll lubrication and the relationship between friction on rolled-in-scale defects. The MRF model allows the classification of the work rolls used in a plant. The "on-line" use of the model allows to follow in real time the state of the work rolls (degradation) that can be related to the surface defects detected on the hot strip (rolled in scale). The new model can be easily applied on all types of rolling mills. Some extra work is needed for integration in the mill computer.

The use of an on-line inspection system (viewing units) for the control of the work roll surface degradation

To have a better understanding of the onset and the evolution of the degradation of the work roll surface during a rolling campaign, CRM has developed a work roll surface inspection system, based on a CCD camera. The inspection system consists of two major parts: a sensing head (300x500x75mm) located in the stand in front of the work roll, containing a stroboscopic light source, a CCD camera and a lens with a motorised focus adjustment, and an acquisition and control cabinet installed in the gauges control room. The principle of the inspection system is to illuminate the roll surface by means of stroboscopic light source and simultaneously acquire a CCD image. The work roll surface is monitored during rolling on an area of 6mm x 8mm. To control the system a special acquisition programme has been developed in C language (working under Windows NT). This programme gives to the operator the possibility to select the acquisition rate and to tune the quality of the image. It is also possible to correct the image by changing its contrast and brightness by software. External synchronisation signals were added to the acquisition unit (e.g. rolling speed, work roll position and presence of the strip). With these additional signals, it is possible to synchronise the acquisition of the CCD images with the rolling sequence and to monitor a specific spot of the work roll surface. The acquired image is presented on the screen of an industrial computer. The CCD images can be stored on the hard disk at regular time intervals or at specific moments of the rolling sequence (one image after each strip) to analyse the work roll deterioration. This gives the possibility to investigate the evolution of the work roll surface deterioration in relationship with the number of rolled strips and the processing parameters.