桥壳钢边部裂纹缺陷原因分析

桥壳钢边部出现线状裂纹缺陷，钢板开裂发生在距离边部 20mm范围之内。通过金相显微检验对裂纹产生的原因进行分析，检验结果表明：钢板传动侧与操作侧边部表层均观察到厚度约 150μm的贝氏体组织，钢板板宽方向的其他部位表层组织与试样正常组织相同，均为铁素体＋珠光体。由此可知，钢板边部冷速过快导致贝氏体组织出现，贝氏体塑性较铁素体＋珠光体差，在钢板卷取过程中导致开裂的发生。

Analysis of the cracking defects on the edge of axle housing steel

Linear crack defects appeared on the edge of the axle housing steel，and the distance between the crack and the edge was less than 20 mm. The causes of cracks were analyzed by metallographic microscopic examination. The result showed that the bainite structure with a thickness of about 150 μm was observed on the surface of the transmission side and the operation side of the steel plate，and the microstructure of other places along the width direction of the steel plate were the same as the normal structure of the sample，which were ferrite and pearlite. So that the rapid cooling speed at the edge of the steel plate led the appearance of bainite structure，the plasticity of bainite was worse than that of ferrite and pearlite，which caused the occurrence of cracking during the coiling process of the steel sheet.