高温过热器T91/TP347H异种钢焊接接头断裂失效分析

Fracture Failure Analysis of a Welding Joint of T91/TP347H Dissimilar Steels for the High Temperature Superheater

某电厂超临界火电锅炉的高温过热器管在服役约4×10~4 h后,T91/TP347H异种钢焊接接头T91钢管侧出现环向断裂事故。通过宏观检查、结构分析、化学成分分析、金相检验及硬度测试等方法,对该焊接接头断裂失效的原因进行了分析。结果表明:焊接接头的T91钢管侧内壁车削后的厚度小于钢管的最小需要壁厚,该处钢管过量车削后的结构造成的工质流动变化引起了局部超温,材料加速老化,钢管强度下降;T91钢管侧热影响区由于强度不足而发生胀粗,产生蠕变裂纹,裂纹在轴向应力的作用下不断扩展,最终引起钢管环向断裂。

The welding joint of T91/TP347 Hdissimilar steels fractured circumferentially on the side of T91 steel pipe after the high temperature superheater of one supercritical thermal power boiler serviced for 4×104 hours.Macroscopic inspection,structure analysis,chemical composition analysis,metallographic examination and hardness testing were carried out to analyze the fracture failure reasons for the welded joint.The results show that：the thickness of the T91 steel pipe was less than the required minimum thickness after the inner wall being over turned;the change of the fluid flow caused by the structure of the turned steel pipe led to the local overtemperature,accelerating ageing and decreasing the strength;due to the insufficient strength of the heat affected zone in the side of T91 steel pipe,the pipe swelled and creeping cracks occurred;the creeping cracks continuously expanded under the effect of axial stress,and eventually caused the circumferential fracture of the steel pipe.