Influence of the cooling strategy on the intergranular crack formation during continuous casting of TRIP steels produced from low-grade scrap

The ongoing transformation of the steel industry towards green steelmaking calls for new technologies to be implemented in steel plants. Thin Slab Casting and Rolling processes, such as the Arvedi ESP process, are proven technologies for the reduction of energy and direct CO2 emissions during the continuous casting and hot rolling of steel by an accelerated process speed compared to conventional continuous casting. However, the increasing use of scrap-based EAF processes leads to a higher intake of tramp elements such as Cu and Sn to the steelmaking process, leading to decreased slab quality and surface crack formation. In the present study, a conventional TRIP980 and a Cu- and Sn-contaminated TRIP980 steel are investigated towards their susceptibility to surface crack formation under conventional continuous casting conditions and under accelerated cooling conditions similar to Arvedi ESP by experimentally simulating different casting conditions on directly cast samples and a three-point bending test at high temperatures. Results show the tremendous negative effect of tramp elements on the hot ductility of steels, especially in the temperature region between 900 – 1000 °C under continuous casting conditions. On the contrary, accelerated cooling leads to a higher tolerance for tramp elements, leading to a significant lower number of surface cracks. However, a deformation temperature of 1000 °C provokes an increase of surface crack sensitivity in both processes.