针对18Ni马氏体发动机壳体磁粉探伤时发生线状磁痕显示,通过金相观察、能谱分析、相变点计算等检测分析手段,对其产生的原因进行了分析。结果表明:发动机壳体材料存在合金元素Ti、Mo、Ni偏析,从而导致马氏体相变点M_s、M_f降低,固溶处理后基体内存在较多残余奥氏体。由于奥氏体组织(顺磁)与马氏体组织(铁磁)在物理磁特性上存在着显著的不一致性,从而形成线状磁痕显示。通过时效处理,可以有效降低残余奥氏体,减轻磁痕显示。

The cause of the linear magnetic mark of 18Ni martensite motor shell was analyzed by means of metallographic observation, energy spectrum analysis and phase change point calculation. The results show that the alloy elements Ti, Mo and Ni segregation exist in the engine shell material, resulting in the reduction of M_s and M_f at the martensite phase transition point. Because of the significant inconsistencies in the physical magnetic properties of austenite (paramagnetic) and martensite (ferromagnetic), linear magnetic traces are formed. The residual austenite can be effectively reduced and the magnetic mark can be reduced by aging treatment.