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神头二电厂过热器异种钢接头高温运行约 4× 10 4 h后 ,沿耐热钢HAZ发生了裂纹 .经手弧焊修补 ,运行一段时间后再次出现裂纹 .本文通过断口及金相分析表明 ,接头前期失效为蠕变失效 ,这可由耐热钢HAZ珠光体球化 ,碳化物聚集和碳迁移说明 ;接头后期失效为应力腐蚀失效 ,这可由存在的应力和含有Cl-的水蒸气共同作用导致 .另外 ,接头焊接缺陷引起应力集中 ,也加速了SCC的产生 .改进焊接工艺 ,采用镍基焊丝TIG焊的过渡接头可有效提高其蠕变强度和服役寿命 .
After the high temperature operation of the superheater dissimilar steel joint of Shentou No.2 power plant operated for about 4 × 10 4 h, cracks occurred along the HAZ of the heat-resisting steel. After hand arc welding repaired, cracks appeared again after operating for some time. According to the fracture and metallographic analysis, Failure of the pre-joint failure as creep failure is illustrated by HAZ pearlite spheroidization, carbide agglomeration and carbon migration of heat-resistant steels; late failure of the joint is stress corrosion failure caused by the combined effect of the existing stresses and water vapor containing Cl- In addition, the weld defects caused by stress concentration, but also accelerated the generation of SCC to improve the welding process, the use of nickel-based TIG welding transition joints can effectively improve its creep strength and service life.