X52管线钢焊缝金属裂纹分析

Analysis of cracks in weld metal for X52 pipeline steel

采用化学成分分析、宏观金相分析、金相组织分析、扫描电镜和能谱分析方法,分析了某X52管线钢焊接接头中裂纹产生原因。结果表明:焊缝中的裂纹为横向裂纹,位于盖面焊缝处;钢管、焊缝金属和焊材的化学成分符合相应标准要求,裂纹附近的显微组织未见异常;裂纹断面呈沿晶开裂,断面上S元素含量较高,为焊接热裂纹;焊接过程中S元素在晶界偏析形成低熔点共晶是裂纹产生的主要原因。

The reasons for the cracks in the welded joint of X52 pipeline steel were investigated by performing chemical composition analysis,macro-metallographic analysis,metallographic structure analysis,scanning electron microscopy(SEM)and energy spectrum analysis.The following observations can be made from the results:The cracks in the weld are transverse ones located at the cap weld;the chemical compositions of the steel pipe,weld metal,and weld material meet the requirements of related standards;no abnormality is observed in the microstructure near the cracks;the crack surface appears to be intergranular cracking,with a high content of the S element on the surface.The welding cracks are welding hot cracks;the segregation of the S element on the grain boundary during the welding causes the formation of a eutectic with a low melting point,which is the major reason for the cracks.