ASSURE - Advanced Steel Shaping Using Reduced Energy

Steel is the most used material in the world by value and second most used by weight (after concrete), it is also one of the most recyclable materials. In 2013 about 12 million tonnes of steel were manufactured in the UK, the majority at large integrated works such as the Tata Steel plants at Port Talbot and Scunthorpe. Energy constitutes a significant portion of the cost of steel production, from 20% to 40% depending on the plant. Whilst the amount of energy required to produce a tonne of steel has been reduced by 50% in the past 30 years, through improvements in steel making technologies, further improvements are necessary to allow the industry to remain competitive. Heating and reheating steel is responsible for most 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 requirements by casting to near net shape, further energy reductions can be realised.
This project is concerned with establishing laboratory facilities for simulating the microstructures produced in steels during belt casting, or similar near net shape casting technologies. Belt casting has high productivity and therefore could be installed in large integrated steel works, such as those in the UK where conventional continuous casting to large sections is currently used. The introduction of this new technology would reduce energy consumption by > 3 GJ/tonne steel produced (based on savings of approximately 2 GJ/tonne from reduced hot rolling and approximately 1.25 GJ/tonne from near net shape casting). Reductions in CO2 emissions, due to the reduced energy use, is also significant; considering that 12 million metric tonnes of steel were produced in the UK in 2013, this project could result in a reduction in UK CO2 emissions of >0.4%.
The major success criteria from this feasibility study will be to establish experimental simulation techniques that can accurately reproduce the solidification structures (micro-segregation levels, grain structure, surface characteristics) of belt cast material, where cooling rates of approximately 60 C/s can occur. This will be achieved using laboratory facilities for solidification studies (a Gleeble 3500 and a confocal scanning laser microscope) already present at the universities of Warwick and Birmingham, with additional equipment being acquired at Warwick (Gleeble HDS-V40) to allow uni-directional cooling during solidification and direct feed of the hot steel into deformation. This latter capability will generate a unique facility in the UK and allow further research to optimise processing conditions and steel chemistries to generate enhanced properties in advanced high strength steels (AHSS). Further success will be demonstrated by initial trials to determine casting process windows (cooling rates and composition limits) for producing an AHSS grade.

This project aims to assess the potential for eliminating energy intensive re-heating for hot rolling and instead directly produce strip steels using high productivity belt casting. This requires high, asymmetric cooling rates during solidification affecting the steel structure, but enables the production of novel more highly alloyed steel grades with potentially new microstructures and ways to control them.

Energy and C footprint
The elimination of re-heating will result in a reduction of 2-2.4 GJ and 110-132 kg of CO2 per tonne of steel. Considering that 12 million metric tonnes of steel was produced in the UK in 2013 this will have a substantial impact nationally (full elimination of reheating would give approximately 0.3% reduction in the national CO2 emissions) and, if the technology is licenced and exported a further global impact.

Energy Savings and Technical Benefits to UK Steel Industry and Society
The chief industrial beneficiaries are the automotive-steel producers, including Tata Steel UK Limited; the industrial collaborator of this research. Tata Steel employs 19,000 people directly in the UK and produces steel products in several UK sites using continuous casting, with automotive grade and electrical steel in sheet steels being key products produced at Tata Steel's UK Strip plant in Port Talbot and Cogent-Orb Steel in Newport respectively. In addition to the energy and CO2 saving noted above, through the use of direct strip rather than continuous casting, the former technique would allow steels more highly alloyed with Al, Mn and Si, such as AHSS (Advanced High Strength Steels), to be produced. These high value grades are not currently produced and success in this project would increase the range of steel grades offered by the UK manufacturers. It should be noted that the ability to manufacture these value added steels will increase sales of conventional steel grades, as customers often choose suppliers that can provide complete order coverage. This will provide Tata Steel with a competitive advantage in the international market. The use of mini-mill steel production using twin roll casting by competitors allows low cost (due to low energy use) manufacture, however the increased capacity of belt casting, and hence suitability for UK production, will give market advantage. The approach of this project would also allow new alloy grades to be designed that optimise the direct casting process parameters to yield unique microstructure and property combinations.

Light Weighting of Steel Products - Benefits to UK's Automotive Industry
A secondary beneficiary of this project will be the automotive industry, which will have access to a UK-source for light weight AHSS products. The automotive sector in the UK comprises over 3000 separate companies employing over 180,000 people. The UK has the sector's 4th highest output in Europe and the 12th highest globally. The use of new AHSS in automotive parts is vital to the competitive advantage of UK car manufacturers since the EU has defined legislation to meet the requirements of the Kyoto protocol and beyond.

Educational Impact
Within the project we are training a RF and an EPSRC case student. We expect to involve MSc and undergraduate students in the research area through offering related projects (three during the 18 month feasibility project) with the equipment capability legacy contributing to a much larger number of projects, and therefore educational awareness of cutting edge steel research, after the feasibility study is complete. In addition exposure of younger students to the research area will be achieved via links with the WMG Academy, which offers places to 640 students aged 14-19 years from the Coventry, Warwickshire and Solihull areas and is coordinated with over 40 employers located in the midland.
(http://www2.warwick.ac.uk/fac/sci/wmg/about/capitalprojects/wmgacademy/).