ASSURE 2 - Advanced Steel Shaping Using Reduced Energy

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Steel continues to be the most used material in the world by value and play an essential role in all aspects of society, from construction to transport, energy generation to food production. The UK steel industry is undergoing significant changes with changes in ownership. The long-term sustainability of UK steel making requires lower energy production and the development of high value steel products. Energy constitutes a significant portion of the cost of steel production, between 20% to 40% and, whilst the amount of energy required to produce a tonne of steel has reduced by 50% in the past 30 years through changes in steel making technologies, further improvements are necessary. Heating and reheating steel is responsible for significant energy consumption in the steel supply chain. Therefore the introduction of new processing routes to minimise or eliminate reheating stages will have a dramatic effect on energy use, and, if this is coupled with reduced hot deformation by casting to near net shape, further energy reductions can be realised.This project is concerned with establishing the process and chemistry windows for production of conventional and advanced high strength strip (AHSS) steel grades using belt casting technology. Belt casting is a near net shape casting process, producing strip that needs minimal hot deformation to achieve the required product thickness. It is a significantly lower energy production route compared to traditional continuous casting to large sections with subsequent hot rolling, for example energy consumption could be reduced by > 3 GJ/tonne steel produced (based on savings of approx. 2 GJ/tonne from reduced hot rolling and approx. 1.25 GJ/tonne from near net shape casting). In addition belt casting allows the production of AHSS steel grades that cannot currently be manufactured using conventional processing: TWIP (twinning induced plasticity) and TRIP (transformation induced plasticity) grades have high work hardening rates meaning they cannot be rolled in current hot rolling strip mills; and low density (high Al) steels have very large grain sizes (millimeters) that result in poor processability (e.g. hot tearing during continuous casting). These steels are extremely attractive commercially, given their vastly superior properties (TWIP and TRIP steels are 2x as strong, with 3x the ductility of conventional steels, and high Al steels have a combination of good strength and lower density), which can contribute to light weighting in the automotive and construction industries.During the ASSURE feasibility project facilities were established at WMG to allow simulation belt cast microstructures, including dynamic direct observation of the solidifying steel at different cooling rates. It was shown that the microstructures are altered by the higher cooling rate of belt casting, compared to conventional slab casting, and that further beneficial modifications (e.g. reduction in grain size in high Al steels) can be achieved by composition control. In this project (ASSURE2), quantitative relationships between composition, process parameters and microstructure (and hence final product properties) will be established, taking into account the higher cooling rates of belt casting and the reduced hot deformation after casting to final thickness compared to conventional processing. Novel new concepts, such as atmospheric control for composition modification and / or solidification temperature reduction and electromagnetic fields for microstructure refinement will also be considered. The collaboration with Professor Guthrie at McGill University in Canada, the leading expert on belt casting technology and computational modelling of liquid metal processes, will provide significant added value to the scientific studies, with the subcontract to use their pilot plant facilities, at MetSim, allowing us to consider the scale up from laboratory scientific studies to industrially relevant processing.