控制相变沉淀硬化不锈钢处理工艺与组织性能关系研究

【作者】 李峰；

【导师】 陈光；

【作者基本信息】 南京理工大学 ， 材料学， 2008， 硕士

【摘要】 PH15-7Mo钢具有广泛用途,属于控制相变沉淀硬化不锈钢,兼具奥氏体不锈钢和马氏体不锈钢的优点,可以通过热处理在很大范围内调整其性能。如固溶处理可以获得好的工艺性能,易于塑性成形加工和焊接;控制相变与沉淀硬化处理可以获得好的使用性能,具有高强度。因此,研究并建立处理工艺与其组织性能的关系具有重要意义。本文通过实验研究了固溶处理、热轧变形及随后的淬火、退火以及区域退火等处理工艺对PH15-7Mo钢组织性能的影响,得到如下主要结论:(1)PH15-7Mo不锈钢在1050℃固溶处理,存在一个最佳保温时问。在本实验条件下,该最佳保温时间为30min,此时,不锈钢中δ-铁素体含量接近理想值,约为10%,且组织最均匀,硬度最低,为142HBS1/30/,有利于下一步的塑性加工。(2)借助背散射电子像及能谱分析发现,经固溶处理后在850℃轧制80%变形量的试样中有Fe-Cr-Mo相析出,在随后的900℃保温淬火后该析出相溶解,表明其为低温析出沉淀相。(3)热处理温度对热轧变形量80%的PH15-7Mo钢再结晶有显著影响:900℃奥氏体基体完全再结晶;超过1000℃铁素体开始再结晶,到1100℃时才出现较明显长大。(4)对850℃热轧预变形量80%的PH15-7Mo钢进行热区温度为1100℃的区域退火,发现随着热区移动速率的加快,试样升温速率增大,在高温区保温时间缩短,铁素体晶粒细化,含量减少。(5)固溶处理后经850℃热轧预变形量为80%和65%的PH15-7Mo钢在热区温度为1100℃的区域退火中形成柱状铁素体的临界热区移动速率分别是3μm/s和5μm/s。更多还原

【Abstract】 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.更多还原