制氢转化炉炉管下法兰失效分析

Analysis of Failure of Lower Flanges in Tubes of Hydrogen-Transformation Furnace

工程停修后制氢转化炉炉管下法兰开工试车时发生开裂泄漏。就此,对下法兰进行了裂纹宏观分析、化学成分分析、金相分析、断口形貌观察及腐蚀产物分析。结果表明,下法兰焊缝、热影响区及母材均发生了一定程度的敏化。下法兰的开裂属于敏化状态下的连多硫酸应力腐蚀开裂,这种开裂,除工作条件、环境因素外,还与材料不符合标准有关,建议选用双相不锈钢或耐热不锈钢加以避免。

Macro analysis, chemical composition analysis, metallo-graphic analysis , analysis of fracture morphology, and analysis of corrosion products were conducted with respect to the breakage and leaking of the lower flanges in tubes of hydrogen-transformationfurnace subjected to maintenance. It was found that the solderingjoint, heat-affected zone, and matrix material were all liableto sensitizing to a certain degree, and the lower flanges were dominated by sensitized stress corrosion cracking in the presence of polythionic acid. Aside from working and environment conditions,such a kind of stress corrosion cracking was also attributed to the use of incorrectly selected materials. Therefore, it was suggestedto select bi-phase stainless steel or thermal-resistant stainlesssteel so as to eliminate the cracking and get rid of failure of the lower flanges.