热采锅炉炉管接头失效分析

Failure Analysis of Furnace Tube Joint in Thermal Recovery Boiler

某热采锅炉投入使用不到一年,其炉管焊接接头就发生失效,通过宏观观察、化学成分和微观组织分析、断口形貌扫描电镜观察以及焊接接头硬度分布测试,对早期失效原因进行了分析。结果表明:接头反面成型出现焊瘤,近缝区出现魏氏体过热组织,裂纹沿熔合区或过热区扩展,打底焊缝和盖面焊缝组织不均匀,打底焊位置接头的硬度分布不均匀性明显高于盖面焊缝。打底焊采用的热输入太大是炉管早期失效的根本原因。

Several furnace tube joints in a thermal recovery boiler failed shortly after being put into use. Failure analysis was carried out using microscopy, SEM and chemical composition analysis instrument together with testing the distribution of hardness in welded joints. The results show that there are overlaps on back bead and overheated structure such as Widmanstaten structure in the zone near the weld, and cracks propagate along the fusion zone or overheated zone. The distribution of hardness across backing bead is non-uniform comparing with that across other beads. Therefore, it can be concluded that it is the too big heat input applied to the back bead that induces the failure of the tube joints.