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针对耐磨钢NM400成品板拉伸变形后试样表面出现开裂现象,利用金相显微镜、扫描电镜等手段对试样断口、表面裂纹及其组织进行观察分析。结果表明:NM400拉伸过程中试样表面裂纹是由沿晶开裂的微裂纹引起的,可能形成于轧制结束后钢板在冷床上冷却和切割两个工序。沿晶界分布的夹杂物弱化了晶界,在内应力的作用下,晶界夹杂物充当了裂纹源。形成的裂纹在后续淬火加热过程中出现高温氧化和轻微脱碳特征。

Analysis on Cracking of the Tensile Specimen Surface of NM400 Sear-Resistant Steel

To the problem of cracking of the tensile specimen surface of NM400 wear-resistant steel after tensile deformation, the fracture, surface cracks and microstructure were investigated by optical microscopy, electron scanning microscopy and energy spectroscopy. The results show that the surface cracking resulted from the process between rolling and quenching, which may be the cooling process on the cooling bed after rolling or flame cutting process. Some inclusions distributed at grain boundary weakening the boundary, and under the effect of internal stress, the inclusions became cracking source. During the subsequent process of quenching, the crack appears the high temperature oxidation and slight decarburization.