中厚板Q355B边部横裂原因探讨

Causes Analysis and Discussion on Edge Transversal Cracksof Medium Steel Plate Q355B

某钢厂生产厚度规格为60 mm的Q355B中厚板出现边部横裂。金相检验未在裂纹周围发现明显氧化质点和脱碳现象,但表层至板厚1/4部位出现了大量WF+B组织,且距表层约1~3 mm部位组织呈现沿轧制方向的流变形态。分析结果表明:轧制喷水过程钢板边部聚集大量残留水,导致产生异常组织和表面裂纹,可通过强化冷却过程层流水的管控加以改善。

Edge transversal cracks occur on Q355B medium steel plate of 60 mm thickness produced by a steel mill.The metallographic examination result shows no obvious oxidization particle and decarbonization phenomenon existing around the cracks,but a large amount of WF+B exists in the plate from surface to 1/4 thickness position,and the microstructure from surface to the position of 1~3 mm below surface presents rheological morphology along rolling direction.The analysis reveals that it is the large amount of residual water accumulation at plate edge that results in the abnormal microstructure and surface cracks during water spraying in the mill,which can be improved by enhancing the water flow control during cooling.