缓冷工艺对钢板探伤检验合格率的影响

Influence of slow cooling process on pass of steel plate flaw detection

某厂生产的某批次钢板探伤检验发现大面积分层缺陷,通过对缺陷位置进行取样分析,对比同一炉次钢板的加热、轧制、缓冷工艺,找出了导致探伤检验不合格的根本原因。连铸坯料内部MnS偏析严重,轧后冷却速度不合适导致贝氏体组织的形成,诱发微裂纹;而钢板矫直后缓冷不及时,内应力大释放不充分,导致内部微裂纹扩大,造成探伤检验不合格。通过优化影响钢板冷却的相关工艺后,厚度不大于30mm的钢板探伤检验合格率达99.32%。

Large area lamination defects were found on one batch of steel plates during flaw detecting in a plant.Sample analysis of the defect position was conducted and the heating,rolling and slow cooling processes of the steel plates from the same furnace were compared.The root cause of steel plate flaw detection disqualification was figured out.Serious MnS segregation in continuous casting slabs and unsuitable cooling speed after rolling leaded to formation of bainite and then induced microcracks.Slow cooling was not timely and internal stress releasing was not sufficient.The internal stress made the microcracks expand,which caused flaw detection unqualified.By optimizing the related process,the pass rate of steel plate flaw detection with gauge of less than 30 mm came up to 99.32 %.