Hot Deformation Behavior of 301L Stainless Steel and Dissolution Behavior of δ-Ferrite During Heat Treatment

The hot deformation behavior of 301 L stainless steel is investigated at 1000-1250 & DEG;C and 0.1-50 s(-1). Deformation characteristics are studied through compressive stress-strain curves and constitutive equations. According to the dynamic material model and a series of diffusion annealing experiments, the hot processing map of 301 L stainless steel is established to determine the suitable processing domain. The results show that the stable domain is located in 1085-1240 & DEG;C and high strain rate range of 4.5-50 s(-1), and the strain rate is the main factor affecting the machinability. Based on the hot compression tests, & delta;-ferrite gradually forms a network structure with the increase of temperature; however, it can be inhibited at high strain rate. Therefore, it is necessary to reduce the temperature and increase the strain rate in the actual processing of the machinable area. It is found that diffusion annealing can reduce the content of & delta;-ferrite from 12% to 0.67%, and the dissolution of & delta;-ferrite is controlled by the diffusion of Cr and Ni, especially noticeable at the interface between & gamma; and & delta; phase. Finally, the optimum diffusion annealing process parameter is determined at 1300 & DEG;C and 10 min.