Q345R钢板分层缺陷原因分析

对Q345R钢板分层缺陷原因进行了研究。结果表明:分层缺陷钢板的夹杂物超标,且在钢板厚度方向存在明显的偏析线。分层处有明显的点列状孔洞分布,这是引起裂纹扩展的主要原因。钢板的基体组织为珠光体+铁素体,分层处组织为马氏体+少量贝氏体+少量铁素体。裂纹起源处的夹杂物为MnS和Al_2O_3且以MnS为主,沿着带状组织和夹层分布。分层处的断口形貌为解理断裂,呈片层状或羽毛状,断口有明显的分层现象。分层处的贝氏体、马氏体组织使材料脆性增加,在与MnS夹杂物的共同作用下,形成应力集中而产生裂纹。

Cause analysis of lamination defect of Q345R plate

The causes of forming lamination defect of Q345R plate were analyzed.The results showed that the over standard inclusions were obvioused in plate,and the segregation lines in plate thickness direction were found.The points and column shape holes distribution in lamination position were obvioused too,which was the main cause of crack propagation.The basic microstructure type of the plate was ferrite+pearlite,with martensite and a small amount of bainite were found in the lamination position.The cracks originated from MnS and Al2O3 inclusions,priority to with MnS,which distributed along the banded structure lamination defect.Cleavage fracture shaped lamellar or plume with obvious stratification was found in the lamination position.With the interaction effect of the increase of bainite and martensite and MnS inclusions,the stress concentration was caused and resulted in crack generation.