Residual stress in machined duplex stainless steel welds developed through automatic process

As design engineering components have become less conservative, there has been an increase interest in the effect of residual stresses on mechanical properties. The demand for high quality focuses attention on product’s surface integrity such as residual stresses in the weld’s machined surface due to their effect on product’s performance, longevity and reliability (e.g. joining process of pipes which usually includes welding and surface machining). Both processes (welding and machining) induce residual stresses which end-up with the occurrence of stress corrosion cracking. It is therefore necessary to quantify the material’s integrity properties of the weld bead as a function of the machining conditions. The aim of this research is focus on the analysis of the residual stresses developed as a consequence of a welding process and subsequent machining of the weld bead conducted on duplex stainless steel. Two main variables were studied: i) heat input as a welding variable and ii) chips cross-sectional area as a machining variable.
The residual stress was measured in all samples after the welding process and after the machining of the weld bead. These measurements were conducted using the Hole-Drilling strain-gage technique. Results showed that higher values of compressive residual stresses were generated when developing chips with a cross-sectional area of 0.3 mm2, and that the tensile residual stresses increased in the weld bead when machining the weld beads with constant chip cross-sectional area of 0.6 mm2.