Precipitation Hardening Stainless Steel Control Phase Change Process And Organizational Performance Relationship Research

PH15-7Mo is a kind of control phase transformation precipitation hardening stainless steel which possesses concurrently austenite stainless steel and the martensitic stainless steel merit, may adjust its performance through the heat treatment in the very wide range. For example, the solution treatment makes plastic forming processing and welding more easily, control phase transformation together with precipitation hardening processing may obtain high strength. Therefore, studying on and establishing the relationship between the processing craft and the microstructure has great significance.The effects of solution treatment, hot rolling and subsequent hot treatment on microstructure has been studied. The main results are:(1) It is shown that 30min is the optimum solution treatment time of PH15-7Mo stainless steel at the conditions of this dissertation. Under such condition, the microstructure is uniform and the 5 ferrite content is close to 10% with the lowest hardness of about 142 HBS1/30/ which is beneficial to the next plastic forming processing.(2) For sample hot rolled at 850℃with the thickness reduction of 80% after solution treatment, there were Fe-Cr-Mo phase present in it through backscattered electron image and energy spectrum analysis. The Fe-Cr-Mo phase redissolved at 900℃showed that it is a kind of low-temperature phase.(3) The heat treatment temperature has remarkable effect on the recrystallization of PH15-7Mo with the thickness reduction of 80%. For samples hot rolled with the thickness reduction of 80% after solution treatment, recrystallization took place completely in austenite matrix when heat preservation at 900℃. However ferrite maintained deformation state untill 1000℃and grew obviously at 1100℃.(4) For sample hot rolled at 850℃with the thickness reduction of 80% after solution treatment, the ferrite grains were refined as well as the content reduced of the ferrite grains with drawing velocity rises during zone annealing at 1100℃.(5) For sample hot rolled at 850℃with the thickness reduction of 80% and 65% after solution treatment, the critical drawing velocitys for formation of columnar ferrite grains were 3μm/s and 5μm/s respectively.