Microstructural evolution of 405 stainless steel under high temperature

The ferrite-to-austenite phase transformation temperature of SA240-405 stainless steel was measured using the thermodilatometry method and calculated using Thermo-Calc. In addition, the effect of temperature and the soaking time on the microstructural evolution was investigated for various quenching and tempering treatments. The results indicated that the ferrite-to-austenite transformation of this steel started between 795℃ and 832 ℃ and finished between 910 ℃ and 925℃. When the specimens were annealed above 1050℃, the austenite gradually transformed into ferrite; consequently, the content of as-quenched martensite decreased with increasing temperature. Moreover, when the specimens were quenched between 950 ℃ and 980℃, a microstructure of duplex phases comprising ferrite and martensite was obtained. Relatively high B-scale of Rockwell hardness（ HRB ） values were observed for quenching times of 30-60 minutes; then, the hardness gradually decreased with increasing quenching time. Tempering at 730 ℃ resulted in ferrite and tempered martensite, and no obvious residual austenite was observed. In addition, the hardness gradually decreased with increasing tempering time.

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1050℃，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30～60min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。

690合金管在不同法向载荷下的切向微动磨损性能研究

目的通过690合金管/405不锈钢块(线接触)的切向微动试验,探究690合金管在不同法向载荷作用下的切向微动磨损机制和损伤演变规律。方法采用自制的多功能复合微动磨损试验机,研究法向载荷(10、20、40 N)对690合金传热管/405不锈钢抗振条的切向微动磨损性能的影响。通过分析摩擦系数和耗散能,获得试验过程中的动力学信息,再通过光学显微镜、扫描电镜对磨痕进行微观分析,获得其磨损机制以及损伤演变规律。结果当位移幅值为100、200μm,法向载荷为10、20、40 N时,690合金管/405不锈钢块的微动运行状态处于完全滑移区。随着法向载荷的增加,摩擦耗散能和摩擦力增大,690合金管的损伤加剧,产生的磨屑增加,磨痕表面的剥落坑被磨屑覆盖而减少,摩擦系数呈下降趋势。沿微动方向,690合金表面的磨损区域内O、Fe、Ni和Cr的含量呈锯齿变化;沿接触方向,690合金管的磨损深度也呈现锯齿状,这都是690合金管和405不锈钢块均为非理想平面所致。结论总体而言,随着法向载荷的增加,690合金管和405不锈钢块的磨损体积增加,690合金管主要的磨损机制为剥层和磨粒磨损。

690合金传热管在不同摩擦副条件下的微动磨损性能研究

采用MFF-3000电磁振动微动疲劳与磨损试验机,研究两种抗振条材料(退火405不锈钢和淬火回火06Cr13)对690合金传热管的微动磨损性能的影响,试验采用块/管线接触方式,即线接触.试验结束后,采用OM、SEM、EDX和EPMA和三维光学显微镜对磨痕微观形貌和成分等进行分析,对比分析两种摩擦副的微动摩擦行为.结果表明:当配副材料为405不锈钢时,690合金的磨损相对严重;工况相同时,06Cr13的磨损比405不锈钢严重,且405不锈钢的磨屑尺寸较小,06Cr13磨痕表面存在大量的剥层裂纹.随着温度增加,磨屑增加,氧化程度加剧,磨损加剧,主要的磨损机制为磨粒磨损和剥层.