T91与TP347H异种钢焊接蒸汽管道蠕变失效分析

Creep failure analysis on welded steam pipeline of T91-TP347H dissimilar steel

建立了T91与TP347H异种钢焊接接头的有限元模型,模拟其实际服役过程,分析了接头的内外表面和两侧焊缝界面的最大主应力、等效应力、应力三轴度的变化规律。结果表明,蒸汽侧T91钢焊缝区域弱化严重,孔洞更易形核,应力较为集中,孔洞易扩展,属于较高应力三轴度区域,孔洞密度较高,是危险区域。T91钢侧随着服役时间的延长出现了应力松弛,所以失效的原因并非是应力集中区域应力水平的增加,而是长时间服役导致的材料性能劣化。

The finite element model of dissimilar welded joints of T91-TP347H steel was established to simulate the actual service process, and the variation law of maximum principal stress, equivalent stress and stress triaxiality on the inner and outer surface of the joint and both sides of the welding were analyzed. The results showed that the T91-weld area on the steam side was seriously weakened, the holes were more likely to nucleate, the stress was more concentrated, and the holes were easy to expand. It belonged to the area of higher stress triaxiality, and the hole density was higher, which was a dangerous area. Stress relaxation appeared on the T91 side as the service time increased, so the cause of the failure was not the increase in the stress level in the stress concentration area, but the deterioration of the material performance caused by the long service.