Evaluation of the Hot Ductility of a C–Mn Steel Produced from Scrap Recycling

The use of scrap for the production of steel has been related to a high incidence of transverse cracking during continuous casting. This phenomenon is linked to the high contents on residual elements and impurities present in recycled steels. In order to understand the embrittlement mechanisms that can take place at high temperatures, the hot ductility of a C‐Mn steel with residual contents of Cu and Sn was analyzed. The steel was evaluated in two as-received conditions, i.e. as-cast and as-rolled, and samples were subjected to different reheating and in-situ melting cycles prior to tensile tests. Testing temperatures ranged from 650 to 1 100°C and strain rate was 5 · 10 � 3 s � 1 . Results show that the width and depth of ductility troughs depend on both the reheating cycle and the as-received condition of the material. According to the fractographical analysis, a reheating of the samples at 1 100°C leads to a combined intergranular and interdendritic fracture while samples reheated at 1 330°C exhibit mainly intergranular features at temperatures in the ductility trough. The interdendritic brittleness for samples reheated at the low temperature is related to the microsegretation taking place during solidification as it can be demonstrated with samples in-situ melted. On the other hand, intergranular brittleness is related to the segregation of impurities and residuals to grain boundaries. The recovery of the ductility in the high temperature range is associated to the appearance of D-REX. The differences observed between the as-cast and as-rolled as-received condition of the steel are associated to differences in the austenite grain size and its effect on dynamic recrystallization.