Magnetic Barkhausen measurements for determining residual stress distribution in welded electrical steels

In the present research work the determination of residual stress distribution in welded non-oriented electrical steel samples is discussed. Tungsten Inert Gas and Electron Beam Welding were used as the welding methods. The residual stresses induced by welding estimated by the magnetic, non-destructive method of Barkhausen noise and were compared with the values resulting from the semi-destructive method of X-ray diffraction Bragg-Brentano (XRD-BB). In order to evaluate accuracy and reliability of the magnetic methods applied, the steel samples were subjected in both compressive and tensile stress and the magnetic noise values were correlated to residual stress values through an appropriate calibration curve. Furthermore, the fluctuations of the residual stresses in the welding zones of the welded samples were discussed on the basis of the experimental evidence and the microstructural changes occurring during welding. It was found that the residual stress determined by MBN method was in good agreement with the XRD-BB results. However, the residual stress determined by magnetic permeability method was not in good agreement with the XRD-BB results. In contrast to the XRD-BB method, the magnetic techniques required a precise calibration procedure in all zones with noticeably different microstructure.