2006 Volume 24 Issue 4 Pages 312-323
A newly developed low-transformation-temperature welding wire, of which transformation start temperature is lower than that of conventional welding wires for 490-MPa class structural steels, was applied to fabrication of fillet welded T-joints. The welding angular distortion and the temperature profile of the weld metal were continuously measured during the welding process. The angular distortion of the fabricated T-joint was reduced when the weld metal reached the martensitic transformation start temperature. The residual angular distortion was less with the low-transformation-temperature welding wire than that with the conventional wire. It was also determined that the transformation start temperature of the weld metal rose from 205°C to 380°C resulting from dilution of chemical composition from the base metal. The welding distortion of T-joints was calculated by a numerical simulation with consideration of the effect of phase transformation under weld thermal cycles. Material properties used in the numerical simulation such as continuous cooling transformation diagrams and dilatometric curves were determined by actual measurement with specimens extracted from the weld metals of the fabricated joints. The welding distortion was reproduced with high accuracy in the numerical simulation. Results of numerical simulation also determined that there was a direct correspondence between the transformation expansion of the weld metal and the angular distortion.
