Keywords: similar and dissimilar steel welds, residual stresses, thermo physical and mechanical properties, carbon and stainless steels, finite element analysis.

Residual stresses that developed in and around the welds can be detrimental to the integrity and the service behaviour of the welded part. Tensile residual stresses are generally detrimental, increasing the susceptibility of a weld to fatigue damage, stress corrosion cracking and fracture during service. Moreover, welding of dissimilar steels produces different residual stresses in welds as compared with welding of similar steels. Therefore, a good estimation of residual stresses in dissimilar steel welds is required to assure the sound design and safety of the structure. However, accurate prediction of welding residual stresses is very difficult because of the complexity of welding process which includes localized heating, temperature dependence of material properties and moving heat source, etc. Accordingly, simulation tools based on finite element (FE) method are very useful to predict welding residual stresses.

In this paper, three-dimensional thermal elastic-plastic FE analyses have been performed to investigate the characteristics of residual stresses in dissimilar steel welds between carbon (SM490) and stainless steels (SUS304). Moreover, residual stresses in similar steel weds are examined for the comparison. Some of the key findings are as follows:

1. In dissimilar steel welds, the maximum longitudinal tensile residual stress is imposed at the weld, and the SM490 carbon steel has higher tensile residual stresses than those of the SUS304 stainless steel. The high yield stress of the SM490 when compared to the SUS304 could have caused the higher tensile residual stresses.
2. In similar steel welds of the materials, the longitudinal tensile residual stresses in the weld and its vicinity are increased with increasing yield stress of the base metal welded. In general, welds undergo yielding in the process of cooling after welding; then tensile residual stresses over yield stress of the weld remain there. Hence, residual stresses in welds increase with increasing yield stress of the steel welded.

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