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采用金相显微镜、扫描电镜、洛氏硬度计、冲击试验,观察和分析了7Cr17MoV马氏体不锈钢在990~1110℃淬火+180~220℃回火的组织和性能变化。结果表明:淬火组织为残留奥氏体和碳化物分布于马氏体基体上。随淬火温度的升高,残留奥氏体含量和马氏体过饱和度增加,针状马氏体组织变粗,1080℃淬火硬度升高到最大值62.5HRC。冲击试验结果表明:随回火温度逐渐升高,试样硬度有部分下降,但韧性显著提高,200~220℃时韧性最佳,达到19 J/cm~2。综合硬度和韧性考虑,最佳热处理工艺为1080℃淬火+200~220℃回火。盐雾试验表明:1080℃淬火+200℃回火后腐蚀率小于4%,符合使用要求。
The microstructure and properties of 7Cr17MoV martensitic stainless steel were quenched at 990 ~ 1110 ℃ and tempered at 180 ~ 220 ℃ by using optical microscope, scanning electron microscope, Rockwell hardness tester and impact test. The results show that the quenched microstructure is the distribution of retained austenite and carbides on the martensite matrix. With the increase of quenching temperature, retained austenite content and martensite supersaturation increased, acicular martensite structure coarsening, quenching hardness at 1080 ℃ increased to a maximum of 62.5HRC. The results of impact test show that with the tempering temperature gradually increasing, the hardness of the sample partially decreases, but the toughness increases remarkably. The toughness is the best at 200-220 ℃, reaching 19 J / cm ~ 2. Comprehensive hardness and toughness considerations, the best heat treatment process for quenching 1080 ℃ +200 ~ 220 ℃ tempering. Salt spray test shows that the corrosion rate after tempering at 1080 ℃ and tempering at 200 ℃ is less than 4%, which meets the requirements of use.