某660 MW高压加热器的筒体接管角焊缝在焊接过程中发生开裂并扩展至筒体母材。对其进行了宏观检验、硬度测试、金相检验、扫描电镜及能谱分析，以分析开裂原因。结果表明：接管与筒体角焊缝根部成形不良，存在夹渣、气孔等焊接缺陷；在焊接应力、结构拘束应力的作用下，焊接缺陷处产生应力集中，裂纹从此处萌生并扩展开裂。采用了与筒体返修开口尺寸匹配的整体锻件返修方案，强度计算满足设计要求，并一次返修合格。

The fillet welding seam of the 660 MW high-pressure heater nozzle cracked and the cracks extended to the base material of the cylinder in the process of welding. The weld seam was examined by macrographic examination, hardness testing, metallographic examination, scanning electron microscope and energy spectrum analysis to analyze the cracking reasons. The results show that:the formation was bad at the fillet weld root of the nozzle and cylinder, and there were welding defects such as slag, porosity and so on; under the action of welding stress and structural restraint stress, stress concentration generated on the position of welding defects, which led to crack initiation and propagation. The integral forging scheme which matched with the repairing gap of the cylinder was adopted, and the forging strength calculation could meet the design requirements and the repair had been successfully done at the first try.