某电站锅炉水冷壁补焊层裂纹原因分析

Causal Analysis of Cracks in Repair-welded Layer of Boiler Water-cooled Wall of an Actual Plant

针对某电站锅炉水冷壁管补焊层裂纹的问题,通过宏观检查、无损探伤、成分分析、金相组织、硬度检验、力学性能检验和微区能谱分析等方法来查找原因,结果表明在焊缝金属中C质量分数较高,造成晶界处的S、P元素富集,形成低熔点共晶体,而这主要是由于在补焊过程中管样表面涂层未打磨干净所导致的,同时焊接热应力较高,最终在焊后沿晶界处产生焊接裂纹。

This study mainly focused on seeking the causes of cracks in the repair-welded layer of a boiler′s water-cooled wall in an actual power plant.The observations and tests employed in the study were macroscopic inspection,non-destructive testing,composition analysis,metallographic analysis,hardness testing,and micro-area energy spectroscopy.It was found high mass fraction of C element in the welded seam metal,resulting in enriching of S and P elements at the grain boundary and the formation of low-melting-point eutectics.This could be attributed to the incomplete polishing of tube surface coating prior to the repair welding process.The low-melting-point eutectics and the high welding thermal stress together led to welding cracks along the grain boundary.