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某钢厂生产的GCr15轴承钢用于生产铁路轴承滚子,在对轴承滚子进行磁粉探伤检验时,发现个别滚子表面有聚磁现象。对该轴承钢聚磁件进行低倍检验、金相检验、电镜扫描及能谱分析,结果表明,轴承钢淬火金相组织存在隐晶马氏体区和结晶马氏体区,这是由于钢锭结晶时产生树枝状偏析造成碳和铬在成分上的不均匀所致,在加热淬火时此微区为欠热区,存在较多的未溶碳化物颗粒、较细的奥氏体晶粒和较多隐晶马氏体区,从而保留较多的残余奥氏体,产生聚磁现象。
GCr15 bearing steel produced by a steel mill is used for the production of railway bearing rollers. When testing the bearing rollers for magnetic particle inspection, it is found that the surface of individual rollers has a phenomenon of poly-magnetic phenomenon. The microstructure of bearing steel was examined by low magnification, metallographic examination, scanning electron microscopy and energy spectrum analysis. The results showed that there existed cryptocrystalline martensite and crystallized martensite in the quenched microstructure of bearing steel, The dendritic segregation during crystallization results in the nonuniformity of carbon and chromium in the composition. In the case of heating and quenching, the micro-zone is under-heated, and there are many undissolved carbide particles, finer austenite grains and More cryptocrystalline martensite, so as to retain more retained austenite, poly phenomenon.