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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。
Aiming at the cracking of specimen surface after tensile deformation of the wear-resistant steel NM400 finished board, the fracture surface, surface cracks and the microstructure of the specimen were observed and analyzed by means of metallographic microscope and scanning electron microscope. The results show that the crack on the surface of the sample during NM400 stretching is caused by microcracks cracking along the crystal and may form after the rolling. The steel plate is cooled and cut on the cooling bed. The inclusions distributed along the grain boundaries weaken the grain boundaries. Under the action of internal stress, grain boundary inclusions act as the source of cracks. The resulting cracks in the subsequent quenching and heating process appears high temperature oxidation and slight decarburization characteristics.