【摘要】 通过成分分析、硬度测量、金相组织检验和裂纹断口扫描电镜观察,分析了某汽包环焊缝裂纹性质与原因。结果显示,裂纹断口上可观察到疲劳台阶;裂纹尖端可观察到Z字形扩展路径;裂纹断面上未观察到结晶裂纹和腐蚀裂纹特征形貌。根据这些特征与汽包结构特点,可以判断该裂纹为热应力导致的低周疲劳(LCF)裂纹。该裂纹产生的原因,一是BHW35钢焊缝金属低周疲劳寿命低于母材;二是该裂纹处焊缝金属晶粒粗大,塑性储备不高。根据该设备损伤情况,建议该机组尽量避免调峰运行;运行中保持参数平稳;机组启停时,严格控制汽包内外壁温差和周向温差。更多还原

【Abstract】 Properties and reasons of crack in the boiler drum girth welding were analyzed through chemical composition analysis,hardnessmeasure,metallurgical structure examination and crack fracture observation by scanning electron microscope(SEM).The results showed thatfatigue steps were observed in fracture surface,zig propagation path was presented in crack tip,no solidification crack configuration andcorrosion crack feature was discovered in the piece.According to those features and drum structure characteristic,the crack was confirmedas low cycle fatigue(LCF) crack caused by thermal stress.The reasons of crack,one was that the LCF life of BHW35 welding metal waslower than the base metal,another was that coarse metallurgical structure of welding metal which led low ductility.Based on fatigue damagestatus of the drum,some operation suggests are put forward,which include avoiding peak load operation as soon as possible,keeping steadyparameter during operating,and controlling temperature difference along thickness and circumference direction when unit starts and shutsdown.更多还原