Effect of Sn and Cu residual elements on the static recrystallisation behaviour in a C–Mn steel

As the steel industry moves toward more sustainable practices, increasing amounts of steel scrap are used as feedstock, particularly in Electric Arc Furnace (EAF) production. However, the presence of residual elements in scrap, such as tin (Sn) and copper (Cu), influence microstructural evolution during thermomechanical processing. In this study, the effects of Sn and Cu on the static recrystallisation of a low-alloy C–Mn steel were examined. Double-hit compression tests were performed using the Gleeble-HDS-V40 thermo-mechanical simulator to determine the recrystallised fraction for steels containing up to 0.2 wt.% Sn and 0.9 wt.% Cu. All compositions had a prior austenite grain size of 50 μm. Tests were conducted at a range of strains, temperatures, and interpass times, resulting in partial and full recrystallisation. Sn caused a significant reduction in austenite recrystallisation, reaching ∼55% reduction at 0.1 wt.% before the effect plateaued, consistent with a pronounced solute drag effect. In comparison, Cu had a much weaker influence, with a maximum reduction of ∼25% at 0.9 wt.%. This contrast is reflected in the calculated solute retardation parameter (SRP) values: Sn exhibited a high SRP of 48 (between Mo and Ti), whereas Cu showed a markedly lower value of 6. The influence of Sn and Cu on the recrystallised austenite grain size was examined using Electron Backscatter Diffraction (EBSD) on quenched fully recrystallised samples. The results indicated that for Sn the grain refinement rate was 35 μm per 0.1 wt.% Sn addition, while the corresponding value was much lower for Cu (0.39 μm per 0.1 wt.%).