Weak zone shift in welded joints for low cycle fatigue

LI Yifei; CAI Zhipeng; TANG Zhinan; PAN Jiluan; LIU Xia; SUN Lingen

doi:10.16511/j.cnki.qhdxxb.2015.22.003

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Journal of Tsinghua University(Science and Technology) ›› 2015, Vol. 55 ›› Issue (10) : 1056-1060,1066. DOI: 10.16511/j.cnki.qhdxxb.2015.22.003

MECHANICAL ENGINEERING

Weak zone shift in welded joints for low cycle fatigue

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Abstract

Weak zones in welded joints due to low cycle fatigue can affect the safety of welded steam turbine rotors. This study analyzes the low cycle fatigue strength of welded 25Cr2Ni2MoV refractory steel steam turbine rotor joints. The strains in the weak zones of the welded joints are modeled statistically. The reason for the weak zone shift is studied using hardness tests and finite element analyses. The experimental results show that cracks develop in the weld and in tempered regions of the heat affected zone. The weak zone shifts from the weld to tempered regions with decreasing strain. With large strains, the plastic strain concentrates in the weld while with low strains, the weld stays in the elastic range. The large hardness gradient in the tempered region with sandwich construction increases the strain concentration.

Key words

welded rotor / low cycle fatigue / NiCrMoV refractory steel / weak zone shift / strain concentration

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LI Yifei, CAI Zhipeng, TANG Zhinan, PAN Jiluan, LIU Xia, SUN Lingen. Weak zone shift in welded joints for low cycle fatigue[J]. Journal of Tsinghua University(Science and Technology). 2015, 55(10): 1056-1060,1066 https://doi.org/10.16511/j.cnki.qhdxxb.2015.22.003

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