12Cr1MoVG集箱三通焊缝横向开裂原因分析及预防措施

Cause Analysis and Preventive Measures for Tee Weld Horizontal Cracking of 12Cr1MoVG Header

为了解决某锅炉12Cr1MoVG集箱厚壁三通焊缝频繁出现横向开裂的问题,通过对开裂焊缝母材壁厚范围和部件结构特点进行分析,并采用宏观检验、化学成分分析、金相组织及断口微观分析等方法,对开裂原因进行了分析,并提出了开裂预防措施。结果表明,三通焊缝开裂主要原因是焊接过程中焊接工艺执行不当,焊缝中形成晶粒粗大区域并形成热裂纹,运行中在循环应力作用下不断扩展并最终导致开裂。建议在机组施工中采取调整三通结构、严格执行焊接工艺及热处理工艺等措施预防焊缝开裂。

In order to solve the problem of frequent horizontal cracking in the thick wall tee weld of 12Cr1MoVG header,the causes of cracking are explored by analyzing the wall thickness range of the cracked weld base metal and the structural characteristics of the components,and by means of macro inspection,chemical composition analysis,metallographic structure and fracture microanalysis,and the preventive measures for cracking are put forward.The results show that the main cause of tee weld cracking is the improper execution of welding process,the formation of coarse grain areas and thermal cracks in the weld,and the continuous expansion of the thermal cracks under the action of cyclic stress during operation,which eventually leads to cracking.It is suggested to take measures such as adjusting the tee structure,strictly executing the welding process and heat treatment process in the unit construction to prevent weld cracking.