锅炉过热器管道爆管原因分析

Cause analysis of pipe explosion of boiler superheater

某公司自备电厂锅炉的过热器管道发生爆管。对送检的爆管及爆管附近管段进行宏观检验,化学成分、硬度检验,金相检验,结果表明,爆管的开裂性质为长时高温运行,且爆管在炸裂前出现了超温的情况,在高温下钢的强度急剧下降,管子发生大量的塑性变形,管径胀粗,管壁减薄,随后发生断裂而胀破。相邻管段的组织为块状铁素体及碳化物颗粒,仅有少量的贝氏体区域痕迹,碳化物聚集长大,大部分碳化物呈颗粒状分布在晶界及晶内。金相试验结果表明材质球化等级为4级,已经进入寿命的末期阶段。

The pipe explosion of superheater pipeline for a boiler in one self-owned power plant occurred.The exploded pipes and adjacent sections were analyzed by macroscopic inspection,chemical composition,hardness test and metallographic inspection.The results showed that the cracking was due to the long-term high temperature operation of pipes.In addition,the exploded pipes were subjected to overtemperature before explosion.The strength of steel was reduced sharply at high temperature,leading to significant plastic deformation of the pipes.Due to the expansion of the diameter and the thinning of the wall,the rupture and bursting of pipes occurred.The adjacent pipe sections were composed of massive ferrite and carbide particles with only a few traces of bainite range.After the aggregation and growth of carbides,most of them were granularly distributed at grain boundaries and within grains.The metallographic test results showed that the spheroidization grade of the material was 4,and the material had already entered the last stage of life.