淬火温度对渗碳淬火组织及变形的影响

Effect of Quenching Temperature on Microstructure and Deformation of Carburizing and Quenching

以12Cr2Ni4合金渗碳钢为试验材料,以C形畸变试样为试验工具,采用金相显微镜分析渗碳层的金相组织,进行了780、820℃淬火对渗层组织及变形影响的工艺试验。金相显微组织检验的结果表明:淬火温度对渗层碳化物的形态、数量、大小以及分布没有影响; 820℃淬火对心部组织有优化作用; 820℃淬火使"马氏体+残余奥氏体"的评级不合格;由于试样尺寸小、淬火转移时间长,820℃淬火的畸变量并没有增大;预处理正火和成分偏析共同导致的畸变量大幅增加40%以上。结论:12Cr2Ni4合金渗碳钢的淬火温度不能升高到820℃,预备热处理采用调质、严格控制成分的均匀性,对控制渗碳淬火畸变有重要作用。

The metallographic structure of carburizing layer was analyzed by metallographic microscope using 12Cr2Ni4 alloy carburized steel as test material and C-shaped distorted specimen as test tool. Th e process test about the effect of quenching temperature at 780 ℃ and 820℃ on microstructure and deforma- tion of carburizing layer was carried out. The results tested on microstructure of carburizing layer showed that the quenching temperature did not effect on morphology, quantity, size and distribution of carbide in carburizing layer. There was the optimizing effect on microstructure in core, which made the rating of mat- ensite and retained austenite unqualify. The distortion of quenching at 820℃ did not increase because of small size and long-time transfer of specimen. The combined effect of normalizing pre-heat treatment and composition segregation made distortion increase more than 40%. The conclusion is that the quenching temperature of 12Cr2Ni4 alloy carburized steel can not rise to 820℃, and there is important effect on con- trolling carburizing and quenching distortion when pre-heat treatment is quenching and temping and the uniformitv of composition is strictly controlled.