蒸汽过热炉集气管管帽失效原因分析

Analysis of failure of manifold head of steam superheater

对取自蒸汽过热炉辐射室集气管出口管线管帽失效部位的材料进行了腐蚀部位宏观形貌检查、化学成分、夹杂物、金相组织、氧化物、扫描电镜观察及能谱分析,认为封头是在高温蒸汽的冲刷腐蚀和高温氧化腐蚀的联合作用下破坏的。材料的成分符合标准要求,夹杂为沉淀强化第二相,金相组织中含晶粒度为10.5级的细晶粒条带,在晶界析出了铬的化合物,铬未完全溶入奥氏体中。结合使用工况、热处理条件,认为管帽固溶处理温度偏低、时间过短、铬未完全固溶、晶粒过于细小是材料在高温下强度过低、抗氧化能力较低的主要原因,应提高管帽固溶处理温度,同时也可对进出口管线端头的设计进行适当改进。

The material taken from the failed part of manifold outlet pipeline head of steam superheater＇ s radiant chamber was examined by macrotopography, ehemieal composition analysis, impurity analysis, metallographic analysis, oxides analysis, sweep, electronie microscope （SEM） and energy dispersion spectrum （EDS）, It was confirmed that the failure was. eaused by the combination effect of high-temperature steam ero- sion and high-temperature oxidation corrosion. The＇ compositions of the material met the specifications and im- purities were second precipitations. There were＇ grain ribbons in the metallurgical structure with 10.5 grade grain size. Chromium compound was educed at grain boundary and chromium was not completely dissolved into austenite. In the heat treatment, the solution tneatment temperature of pipeline head was too low and time was too short, which resulted in incomplete solution and small grain sizes. As the result, the material strength and anti-oxidation performance were too low at superheated conditions. Therefore, the solution treatment temperature should be raised and design of heads on the inlet and outlet pipelines should be improved.