马氏体/奥氏体异种钢焊接接头Ⅳ型蠕变失效数值模拟

Numerical Simulation on the Type Ⅳ Creep Failure of Dissimilar Welded Joint between T91 and HR3C Heat-resistant Steels

采用有限元法建立马氏体与奥氏体(T91/HR3C)异种钢焊接接头蠕变数值模型,模拟温度为600℃、内压为42.26 MPa条件下T91/HR3C接头的蠕变最大主应力、von Mises等效应力和应力三轴度。结果表明,最大主应力峰值位于接头内表面HR3C/焊缝和焊缝/T91界面以及离外表面2.96 mm处焊缝/T91界面附近区域;von Mises等效应力峰值均位于焊缝/T91界面区域;内表面应力三轴度峰值位于焊缝/T91界面附近,而离内表面1.29 mm处和离外表面2.96 mm处的应力三轴度峰值位于T91钢侧细晶热影响区内,两部位的孔洞容易连接形成Ⅳ型蠕变裂纹。采用应力三轴度分析T91/HR3C接头T91侧细晶热影响区内蠕变孔洞扩张及裂纹扩展特性更为准确,与加速试验结果比较一致。

Creep finite element method（FEM） model of dissimilar welded joint between martensitic heat-resistant steel （T91） and austenitic（HR3C） is established. The maximum principal stress, von Mises equivalent stress and stress triaxiality is simulated at 600℃ and in the inner pressure of 42.26 MPa. The results show that the peaks of the maximum principal stresses are in the interface of weld/T91 and HR3C/weld in inner surface, and in the vicinity of weld/T91 interface in the distance of 2.96 mm away from outer surface. The creep cavities are ease to form in the weld/T91 interface in inner surface and in the place of 2.96 mm away from outer surface. In tttm, in the weld/T91 interface of 1.29 mm away from inner surface, outer surface and 2.96 mm away from outer surface. The higher yon Mises equivalent stress is in the weld/T91 interface of inner surface, and cavities are ease to expand. In turn, in the weld/T91 interface of 1.29 mm away from inner surface, outer surface and 2.96 mm away from outer surface. The stress triaxiality in the weld/T91 interface of inner surface is quit high, creep cavities are ease to link into interracial creep cracks. And that, the stress triaxiality in the fine grain heat affected zone（HAZ） of 1.29 mm away from inner surface and 2.96 mm way from outer surface are also quit high, accordingly, creep cavities are ease to take the form of type IV creep crack, Therefore, using stress triaxiality to describing creep cavity expansion and crack development of the weld/T91 interface and fine grain HAZ is more reasonable for dissimilar welded joint between T91 and HR3C, and the numerical simulating results are good in agreement with those of experiment.