Effect of copper element on hot behavior of 304L stainless steel

Hot-deformation behavior of the 304L stainless steel containing copper was investigated with compression experiments at temperatures ranging from 1173 K to 1423 K under strain rates of 0.01-20 s(-1) up to the true strain of 0.69. The adiabatic heating analysis indicated that the addition of copper to 304L resulted in a temperature rise, which was found to be sensitive to the strain rate. By calculating the constitutive equation, the hot-deformation activation energy of the non-Cu-containing steel was found to be 409 kJ/mol, but it reduced to 376 kJ/mol when 2.42 % copper was added to the steel, which implied that the addition of copper to stainless steel was not conducive to the occurrence of dynamic recrystallization. Furthermore, the true stress-strain curves indicated that the dynamic-recrystallization temperature and strain rate of the 2.42 % Cu-304L steel decreased. The processing maps showed that the unstable region increased and the hot-working area became narrower. The instability region was dominated by the adiabatic-shear zone and local-flow instability. Moreover, the morphological changes of delta-ferrite into coarse columnar crystals made the steel more prone to cracking.