Effect of TIG Remelting Distance and Current on Fatigue Performance of Q690D Steel GMAW Cross Joints

The fillet weld of the gas metal arc welding (GMAW) cross joint of Q690D low alloy high strength steel was remelted by non-melting inert gas shielded arc welding (TIG). The effects of the remelting distance (distance from the center of the heat source to the weld toe, 2, 1, 0, −1 mm) and the remelting current (150, 170, 190, 210 A) on the shape of the weld toe after remelting and the fatigue performance of the joints were studied. The results show that under the remelting current of 150 A, when the remelting distance was 0, the remelted weld completely covered the original weld toe, the curvature radius of the weld toe was large, and the transition between the base metal and the weld was smooth. When the remelting distances were 2 mm and 1 mm, the original weld toe could not be remelted. When the remelting distance was −1 mm, a depression was formed in the remelted weld. Under the remelting distance of 0, the curvature radius of the weld toe after remelting under different currents was larger than that of the original weld toe, and the transition angle was lower than that of the original weld toe. With the increase of the remelting current, the curvature radius first decreased, then increased, and then decreased, while the transition angle first increased and then decreased. The curvature radius was the largest and the transition angle was the smallest at the remelting current of 150 A. Under the remelting currents of 170, 190, 210 A, the fatigue crack source positions of the remelted joints changed from the original weld toe to the remelted weld and the remelted fusion zone. No fatigue cracking occurred in the joint under the remelting current of 150 A. The fatigue life of the joint after remelting was higher than that of the original joint. With the increase of the remelting current, the fatigue life of the remelted joint first decreased, then increased, and then decreased again, and was the highest at the remelting current of 150 A.