采用渗透检测、金相检验、断口分析和力学性能测试等方法对锅炉给水预热器管箱高温段环焊缝开裂原因进行分析。结果表明：焊后热处理不符合要求，使环焊缝及热影响区形成马氏体；设备在服役过程中，马氏体分解产生析出相，使晶界蠕变能力降低，在高温运行环境下，环焊缝产生再热裂纹并发生沿晶开裂。

Penetrant test, metallographic examination, fracture analysis and mechanical properties test were used to analyze the causes of girth weld cracking in high temperature section of boiler feed water preheater tube box. The results show that the post-weld heat treatment did not meet the requirements, and martensite was formed in the girth weld and heat affected zone. During the service of the equipment, martensite decomposed to produce precipitated phase, which reduced the creep ability of the grain boundary. Under the high temperature operation environment, the girth weld produced reheat cracks and intergranular cracks.