Investigating the effect of number of weld passes on the residual stress state of steel plates by micro magnetic method

Variations of surface residual stresses with subsequent weld passes were investigated in the API 5L X70 steel plates by Magnetic Barkhausen Noise (MBN) method. The plates were welded by applying different number of passes under fully clamped condition. After each weld pass, MBN signal and hardness distributions on the front and back surfaces of the plates were measured. A specific calibration procedure and set-up was used for conversion of MBN signals into elastic stress values. The results were analyzed by considering microstructure investigations and hardness measurements, and then, they were compared with the results of X-ray diffraction measurements. MBN measurement after appropriate calibration seems to be a good candidate for rapid nondestructive monitoring the variation of surface residual stresses in the welded components. Moreover, it might provide critical data for computer simulation and weld process design leading to a higher performance and longer life in service by controlling residual stress state.