某公司循环油蒸汽发生器上部最外侧换热管的中间贴胀部位发生断裂。采用宏观观察、垢物成分分析、金相检验、硬度测试及扫描电镜分析等方法,分析了该换热管断裂的原因。结果表明:该换热管断裂的主要原因是碱应力腐蚀;在断裂前,换热管外壁已形成了碱脆裂纹,在轴向拉应力的作用下,碱脆裂纹快速扩展,最终导致换热管发生断裂。

Cracking occurred at the middle expansion part of the outermost heat exchange tube on the upper part of the circulating oil steam generator of a company. The reasons for the cracking of the heat exchange tube were analyzed by means of macroscopic observation, analysis of scale composition, metallographic examination, hardness test and scanning electron microscope analysis. The results show that the cracking of the heat exchange tube was mainly caused by alkali stress corrosion. Alkali embrittlement cracks had been formed on the outer wall of the heat exchange tube before the fracture. Under the axial tensile stress, the alkali embrittlement cracks expanded rapidly, and finally led to the cracking of the heat exchange tube.