Effect of large strain warm rolling and subsequent annealing on the microstructure and mechanical properties of austenitic stainless steels

Abstract

The microstructural evolution of 304L and 316L steels during warm plate rolling to a strain of 3 and subsequent annealing as well as the structural effect on the mechanical properties were investigated. The warm rolled microstructures consisted of flattened wavy austenitic grains with transverse grain sizes of about 220 and 160 nm in 304L and 316L steels, respectively. The formation of the wavy austenite structures was facilitated by high density of microshear bands. The subsequent annealing was accompanied by the development of static recrystallization and grain growth. The 304L steel specimens were characterized by a lower stability against recrystallization and grain growth as compared to the 316L ones. The grain coarsening during annealing was accompanied by gradual softening. The hardness decreased by 50% in both steels after annealing at 800°C. The grain coarsening was accompanied by strength degradation, although the tensile strength above 900 and 1000 MPa remained in the 304L and 316L steel specimens, respectively, after annealing at 700°C.