Steel, in a variety of forms, is an essential material in today's world. It plays a key role in areas ranging from construction, to transport, to domestic goods. But there is more to steel than meets the eye. As engineering and manufacturing techniques grow ever more sophisticated, our expectations of the steel we use grow increasingly varied, specialised and demanding.
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In a car panel, for example, strength is vital for safety. At the same time, reduced weight is important from an environmental and fuel-consumption viewpoint. The aesthetic properties of the steel, its flexibility and its ease of shaping or welding may all be important requirements as well. If the steel is for use in construction, pipelines, or power plants, a different set of properties may be required. For steel producers, it is vital to understand how the physical properties of steel can be affected during the manufacturing process and produce widely varying characteristics in the finished metal.
Extending this understanding, in order to pave the way for steel production of more consistent and predictable quality, to reduce wastage, and to facilitate the future development of improved grades of steel, was the aim of MEPMO, a European Union (EU)-funded project bringing together two steel producers, three research institutes and one university.
Part of the research programme of the Research Fund for Coal and Steel (RFCS) the MEPMO team set about this challenge by building on earlier RFCS projects and looking closely at the microscopic structure of steel - the level at which the metal's final properties are determined.
Examined at this level, the microstructure of steel can be seen to be divided into polygons, called 'grains'. In modern steels this microstructure is highly complex and the grains are further subdivided into even smaller units. For steel producers, this is where the key lies. The microstructure defines the properties of the steel - and reheating or deforming the steel, as happens during processing, changes this microstructure.
The objective of the MEPMO team was both to increase our understanding of the relationship between microstructures and the mechanical properties of the finished steel, and to identify improved ways of modelling these relationships in order to predict the nature of the steel that would be produced from a given production method. This would enable the reliable and consistent production of different types of steel to meet required sets of specific physical characteristics.
While previous European RFCS projects had made some progress in this area, existing models were not adequate to deal with more recently developed grades of steel with much more complex microstructures. MEPMO successfully applied the advances achieved by earlier projects to the modelling of these more complex microstructures. It also investigated different modelling approaches and compared them in terms of ease of application and accuracy of the predictions. This resulted in the production of a suite of models, any one of which can be selected by users according to the level of detail required.
Already in use in plants run by the project's two industrial partners, ThyssenKrupp Steel and Corus UK (now Tata Steel) the models developed by MEPMO have helped to minimise the quality control tests that need to be carried out, thus reducing time and cost requirements, they have also improved product reliability and cut wastage, and they have speeded up the research process to produce new grades of steel.
The MEPMO results have also enabled research institutes to progress further in improving the consistency of mechanical properties in complex steels and to develop new steel grades in collaboration with industry.
MEPMO's researchers acknowledge that the journey is far from over. As the world advances, so will the demand for more and more sophisticated steels to meet the stringent and specialised demands of society. But by delving deeper than ever before into the microstructures of a material most of the world sees as simple sheets of metal, MEPMO has enabled a major step forward both for the industry and for its customers.