Thermal Deformation Behavior of Bismuth-Containing Stainless Steel

In the process of thermoplastic processing, bismuth stainless steel is prone to cracking, leading to a high reject rate and even failure in production. To solve this problem and provide a feasible process for the actual production, the true stress-strain -strain curves of the material were obtained by hot compression experiments. Because the thermal simulation system cannot automatically consider the temperature and stress variation of the specimen because of the heat of plastic deformation and the friction between the specimen and the tool, experimental errors were carefully corrected. A kind of exponential function is found to be suitable for describing the modified stress-strain -strain relationship of the invested steel. Based on the dynamic material model and Murty criterion, the thermal processing diagram of the free-cutting austenitic stainless steel was established, and the stable and unstable regions of the hot working of the free-cutting austenitic stainless steel were given. Rolling tests showed that under the condition of the selected stable zone, no crack occurred in the section of the rolled piece. Microscopic analyses showed that the microstructure distribution of rolled parts by the noninstability zone process is relatively uniform, and there were fewer spherical and fusiform inclusions.