405不锈钢高温组织转变研究

通过热膨胀法以及Thermo-Calc热力学计算软件对SA240-405不锈钢铁素体向奥氏体转变的温度进行了测量和计算。进一步结合淬火与回火热处理,分析了405不锈钢在高温下组织随温度与时间的变化关系。研究结果表明,405不锈钢铁素体向奥氏体开始转变的温度为795~832℃,转变终了温度为910~925℃。温度高于1 050℃,随温度升高,奥氏体逐渐向铁素体转变,淬火后的马氏体含量降低。在950及980℃淬火,得到的组织为马氏体与铁素体的双相组织,淬火时间为30~60 min得到的硬度较高;进一步延长淬火时间,硬度逐渐降低。在730℃回火后得到的组织为铁素体与回火马氏体,无明显残余奥氏体,回火后组织的硬度随时间延长逐渐降低。

Study of microstructure evolution for 405 stainless steel under high temperature

The phase transformation temperature of ferrite to austenite for SA 240-405 stainless steel was measured by applying thermodiatometry method and calculated using the Thermo -Calc software .Meanwhile , the effect of temperature and soaking time on the microstructure evaluation was studied by different quenching and tempering treatment . The results demonstrated that the transformation of the ferrite to austenite of this steel started between 795-832℃, and finished during 910-925 ℃.When the specimens annealed at temperature higher than 1 050 ℃, austenite would transform into ferrite gradually , consequently the content of as-quenched martensite decreased with the increasing temperature .Moreover , when the specimens quenched between 950 ℃ and 980 ℃, the microstructure of duplex phases composed of ferrite and martensite was obtained .The relatively high HRB values could be obtained when the quenching time was kept for 30-60 minutes, and then the hardness would gradually decrease with increasing quenching time .Tempering at 730 ℃resulted in ferrite and tempered martensite , and no obvious residual austenite was observed .Meanwhile the hardness gradually decreased with the increasing tempering time .