T91/TP347HFG异种钢焊接接头裂纹原因分析

火电厂高温过热器用T91+TP347HFG异种钢焊接接头运行时,发生开裂泄露.分别从未开裂和开裂部分的焊接接头处取样,采用金相显微镜、扫描电镜、显微硬度计等对焊接接头试样进行检测和对比研究,分析其开裂原因.结果表明:焊接和焊后热处理工艺不当导致T91侧热影响区位置在整个焊接接头区域脆性较大,并有淬硬倾向比较大的组织出现;同时由于焊接规范参数较大而导致焊接热影响区较宽,在一定应力下的作用导致裂纹从此处萌生和扩展,最终导致该异种钢焊接接头开裂失效.

Crack Analysis of T91/TP347 HFG Dissimilar Steel Welding Joint

T91/TP347HFG dissimilar steel welding joints of superheater in a heat-engine plant cracked during service. The samples obtained from the normal and cracked welding joints were examined by the metallographic microscopy, scanning electron microscopy, and micro hardness testing to make comparison and analyze the cracking reason. The results showed that the improper process of welding and postweld heat treatment led to the formation of quenched structure and made the heat-affected zone at the T91 side have greater brittleness. At the same time, a larger range of welding parameter made the heat-affected-zone wider, from which the cracks initiated and propagated under certain stress. Eventually, the dissimilar steel welded joints cracked and failed.