发电厂304不锈钢热电偶套管开裂原因  

Causes of cracking of 304 stainless steel thermocouple casing in power plant

作　　者：谌磊 陈成 胡杰 胥洋 李睿 黄隆瑶 CHEN Lei;CHEN Cheng;HU Jie;XU Yang;LI Rui;HUANG Longyao(China Construction Machinery Test Center,Changsha 410013,China)

机构地区：[1]国家建筑城建机械质量监督检验中心,长沙410013

出　　处：《理化检验（物理分册）》2024年第8期53-58,共6页Physical Testing and Chemical Analysis(Part A:Physical Testing)

摘　　要：某发电厂304不锈钢热电偶套管发生开裂现象,采用宏观观察、壁厚测量、化学成分分析、金相检验、硬度测试、扫描电镜和能谱分析、浸水试验等方法对套管开裂原因进行分析。结果表明:套管的表面质量差,在Cl^(‒)和S^(2‒)的作用下,套管产生应力腐蚀裂纹;空气中的冷凝水沿着微裂纹进入套管内,冷凝水被绝缘材料(主要成分为MgO)吸收,导致套管绝缘层体积膨胀,加速了套管的应力腐蚀开裂。The 304 stainless steel thermocouple casing of a power plant cracked.The causes of casing cracking were analyzed by macroscopic observation,wall thickness measurement,chemical composition analysis,metallographic examination,hardness test,scanning electron microscope and energy spectrum analysis,immersion test and other methods.The results show that the surface quality of the casing was poor.Under the action of Cl^(‒)and S^(2‒),the casing produced stress corrosion cracks.The condensed water in the air entered the casing along the micro-cracks,and the condensed water was absorbed by the insulating material(mainly composed of MgO),resulting in the volume expansion of the casing insulation layer and accelerating the stress corrosion cracking of the casing.

关 键 词：304不锈钢 热电偶套管 应力腐蚀开裂 壁厚测量 腐蚀产物 

分 类 号：TG142.71[一般工业技术—材料科学与工程] TG115.2[金属学及工艺—金属材料]