ISSN   1004-0595

CN  62-1224/O4

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固溶处理对新型全奥氏体高锰低温钢微观组织、力学性能及摩擦性能的影响

Effect of Solution Treatment on Wear Resistance of a New Type of Austenitic High Manganese Low Temperature Steel

  • 摘要: 针对新型奥氏体高锰低温钢在LNG (Liquefied natural gas)储罐应用中的磨损问题,本文中研究了不同固溶处理温度对微观组织、力学性能和耐磨性能影响以及三者之间的关联性. 将25Mn高锰钢分别在950、1 000、1 050以及1100 ℃下固溶处理0.5 h,并采用光学显微镜、白光干涉仪、扫描电子显微镜及能谱仪对试样的微观组织、磨损轮廓和磨痕形貌进行了表征. 结果表明:随着固溶处理温度的升高,高锰钢的表面硬度逐渐下降,1 100℃固溶处理后钢材硬度降到最低,约为261 HV. 另外,钢材的抗拉强度随固溶温度升高先增大后减小,其中在1 000 ℃下展现出最优的抗拉强度、屈服强度及应变硬化速率. 在摩擦性能测试结果中可以看出,高锰钢表面平均摩擦系数随着固溶处理温度先增大后减小再增大,在1 000 ℃时因发生氧化摩擦而降到最低,约为0.39,磨损率为0.49‰,表现了最优的耐磨性能. 这主要是由于1 000 ℃热处理后的高锰钢磨痕表面密布颗粒均匀的碳化物,导致磨损后的硬度增大近50.6%,磨损机理从颗粒磨损与疲劳磨损结合转变为黏着磨损为主,颗粒磨损为辅.

     

    Abstract: In response to the wear issue of a new type of austenitic high manganese low-temperature steel in LNG storage tanks, this paper investigated the effects of different solution treatment temperatures on microstructure, mechanical properties, and wear resistance, as well as the correlation between the three. 25 Mn high manganese steel was solid-solution treated at 950, 1 000, 1 050 and 1 100 ℃ for 0.5 hours, and the microstructure, wear profile, and wear scar morphology of the sample were characterized using optical microscopy, white light interferometer, scanning electron microscopy, and energy dispersive spectroscopy. The results showed that with the increase of solution treatment temperature, the alloy compound gradually dissolved into the crystal, leading to the diameter of the crystal gradually becoming larger. When the solution temperature was 1 100 ℃, the crystal diameter was the largest, 87.9 μm. Due to the dissolution of carbides and the increase of grain size, the surface hardness of high manganese steel gradually decreased with the increase of solution temperature. After solution treatment at 1 100 ℃, the hardness of the steel decreased to the lowest, about 261 HV. In addition, the tensile strength of steel first increased and then decreased with the increase of solution temperature, with the optimal tensile strength, yield strength, and strain hardening rate exhibited at 1 000 ℃. It was speculated that the reason may be related to the dissolution of grain carbides and the increase of crystal diameter. Carbides would generate stress concentration during the stretching process, leading to a decrease in tensile performance. As the carbides dissolved, the stress concentration effect decreased, so the tensile performance gradually enhanced. At the same time, the alloy compounds in the metal were also dissolving, leading to the increase of the crystal diameter and the weakening of the fine grain strengthening ability of the steel, so the tensile properties began to decline again. In the friction performance test results, it could be seen that the average friction coefficient on the surface of high manganese steel first increased, then decreased, and then increased with the solution treatment temperature. At 1 000 ℃, it decreased to the lowest point due to oxidation friction, about 0.39, and the wear rate was 0.49 ‰, demonstrating the optimal wear resistance. EDS analysis was conducted on the worn surface and debris at 1 000 ℃, and the results showed that oxygen elements were uniformly distributed on the worn surface. The main components of the debris were Si, Al, and O elements. This indicated that during the friction process, the steel undergone an oxidation reaction, forming an oxide layer film, resulting in a decrease in the friction coefficient. At the same time, it could be seen from the microscope that the wear scar surface of high manganese steel after heat treatment at 1000 ℃ was densely covered with uniform carbides, which leaded to the hardness increase of nearly 50.6% after wear. Similar conclusions could be obtained from the work hardening ability. Therefore, after solution treatment at 1 000 ℃, the steel's hardness increased rapidly due to its excellent work hardening ability, so the wear amount was the lowest. Due to the increase in solid solution temperature, the crystal diameter increased, reducing the plasticity of the friction surface, leading to a transformation of the wear mechanism. The friction and wear mechanism shifted from the combination of particle wear and fatigue wear to adhesive wear, with particle wear as the auxiliary.

     

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