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Si-Mn-Mo-V钢渗碳后直接淬火的钎尾,渗碳层中存在大量马氏体微裂纹,即使在等温淬火后这种微裂纹很难消除,影响使用性能;但是在渗碳淬火后等温淬火前,经一次高温回火,渗碳层马氏体微裂纹可基本消除。另外,马氏体微裂纹形成的临界含碳量为0,75%。据此,改进了钎尾热处理工艺:渗碳层含碳量不应大于0.8%,气体渗碳油冷后经550～650℃×1h回火,然后再加热至钎尾心部Ac3以上20～30℃保温20min,于260℃等温淬火并二次回火。
There is a large amount of martensite micro-cracks in the brazing tips and carburized layers of the Si-Mn-Mo-V steel after carburizing. Even if the micro-cracks are hardly eliminated after the isothermal quenching, the performance will be affected. However, Quenching before quenching, after a high temperature tempering, martensitic carburized layer of micro-cracks can be basically eliminated. In addition, the critical carbon content of martensitic microcracks is 0,75%. Accordingly, the brazing tail heat treatment process is improved: the carbon content of the carburized layer should not be more than 0.8%, the carburizing oil is cooled after the carburizing oil is cooled and tempered at 550-650 ° C for 1h and then heated to above Ac3 of the brazing tip for 20 ~ 30 ℃ insulation 20min, at 260 ℃ isothermal quenching and secondary tempering.