Dependence of Magnetic Permeability on Residual Stresses in Welded Steels

The aim of this paper was to further broaden current knowledge of magnetic properties' dependence on welded steels' stress state. For this reason, commercial micro-alloyed steel was welded using tungsten inert gas as the welding technique. Magnetic stress calibration curve (MASC) was a useful laboratory tool for evaluating the material's residual stress distribution with the aid of magnetic permeability values. X-ray and neutron diffraction techniques were used for determining surface and bulk residual stress values, respectively. The overall measurement results have shown that the residual stress determined by the magnetic method was in good agreement with the diffraction results. In order to investigate the potential utilization of the magnetic method in evaluating residual stresses, the magnetic calibration curves of various ferromagnetic steels' grade were examined. The normalization of these curves revealed the existence of a unique curve, which suggested the existence of a universal relationship between the intrinsic magnetic properties and the internal elastic mechanical characteristics of steels. Further experimental investigations are required to validate the preliminary results and to verify the presence of a unique normalized magnetic stress calibration curve.