Sustainable metallurgy for scrap-based steelmaking processes

Secondary steel manufacturing involves complex and energy-intensive processes that rely on precise control of alloy composition and microstructure manipulation, mainly in downstream stages. While the current approach has been successful, largely due to a good understanding of solid-state processing, it heavily depends on energy-intensive primary metal to maintain low concentrations of key elements known to be detrimental. If carbon neutrality is to be achieved by 2050, an urgent transition to more sustainable metals manufacturing and increased utilization of low-carbon, higher impurity recycled metal is needed. However, producing alloys from diverse scrap sources, whether increased or lower-grade, leads to the accumulation of tramp elements. Even trace amounts of elements like Cu, Sn, and Zn can segregate in semi-solid regions, resulting in grain boundary decohesion and the formation of damaging defects and secondary phases, including non-metallic inclusions (NMIs). The segregation of these harmful tramp elements at grain boundaries at high temperature presents a significant challenge in steelmaking and processing. To date, there has been no quantification of high-temperature (800 °C - 1100 °C) segregation or reliable tolerance values, and existing technical solutions are primarily based on empirical approaches.

The project will employ a ground-breaking artificial intelligence-enhanced multi-modal X-ray imaging technique, developed within the group, to study and quantify the dynamic evolution of micro- and macro-segregation of tramp elements in steel. The research will commence by investigating copper (Cu) segregation mechanisms in the liquid phase and examining the relationship between solidification segregation and solid-state diffusion. Experimental methodologies will be devised to replicate the conditions of ingot and continuous casting, followed by homogenization before hot working. This knowledge will be applied to develop strategies to mitigate the detrimental effects of these segregations. Focus will primarily be on copper (Cu), the most challenging impurity, with the potential to extend to other tramp elements such as tin (Sn) and zinc (Zn) as progress allows.

The project will be part of two extensive collaborative EPSRC projects involving the Materials and Engineering departments at Oxford, Loughborough University, and STFC. The project will also be linked to others ongoing collaborations in the field of sustainable metals, including academic collaborators at Kassel University and the Max-Planck Institute (Germany), Diamond Light Source and the European Synchrotron Research Facility (ESRF, France).

The project and successful applicant may be eligible for partial or full funding from an industry partner.