Effect of preheat on residual stress distributions in arc-welded mild steel plates

Residual stress distribution in the longitudinal and transverse directions on a 6-mm-thick arc-welded mild steel plate was experimentally examined with and without initial preheat. Stress measurements were completed by monitoring strain changes on mounted strain gauges resulting from successive milling of the welded plate specimens. Machining stresses were also compensated for by carrying out measurements of strain changes due to milling operation of a stress-free unwelded annealed mild steel plate. High tensile residual stresses exist close to the weld line in both longitudinal and transverse stresses. Maximum longitudinal residual stress values existing close to the weld line are reduced (between 50 and 75%) due to the effect of initial metal preheat of 200 degrees C of the welded steel plate.