In manufacturing of the steel bridge, fillet welded T-joint is widely used and angular distortion is often generated. So, reduction or control of angular distortion without additional processes to welding is strongly demanded because it takes great time and effort to correct the angular distortion. In this study, the effectiveness of welding with trailing reverse-side flame line heating for preventing angular distortion was investigated through the welding experiment and numerical simulation in submerged arc welding of fillet T-joint with three different thick flange plate. First, the heat source models for numerical analysis of both submerged arc welding and flame line heating were constructed based on the comparison with the measured temperature histories and angular distortion. And then, these heat source models were used in combination with various kinds of distance between two heat sources to make clear the appropriate distance condition for smallest angular distortion was 150 mm, and it doesn't depend on thickness of flange plate. It was also confirmed that the experimental angular distortions were in good agreement with those calculated. With a focus on the influence of thickness of flange plate, the reduction of angular distortion by welding with trailing reverse-side flame line heating becomes smaller with increasing thickness of flange plate. However, angular distortion could be adequately prevented under the appropriate flame line heating condition in either thickness of flange plate because the welding-induced angular distortion also becomes smaller with increasing thickness of flange plate. Thus, it was concluded that welding with trailing reverse-side flame line heating could be useful for preventing angular distortion of fillet T-joint, which is a component of steel bridge, enough not to correct it after welding.
Lap joints of an upper Al alloy (1.0-mm-thick A5052) and lower Zn-coated steel (1.2-mm-thick GA steel) were welded by a novel spot welding process for dissimilar metal lap joints using a new tool with the tip made of spherical ceramics, i.e., "Friction Anchor Welding." As a result, the Al atoms in the Al alloy diffused into the Zn-Fe layer on the GA steel, and the layer transformed into an altered layer which was mainly composed of Al-Fe intermetallic compounds. Because of this altered layer, a steel projection could not extend straight when the rotating tool was plunged through the Al alloy into the GA steel. Consequently, the height of the steel projection was small and exhibited a rugged shape while the steel projection was formed in the Al alloy. Furthermore, large amounts of Al-Fe intermetallic compounds existed near the steel projection. Additionally, Zn atoms in the Zn-Fe layer on the GA steel penetrated into the Al alloy and cracks occurred due to the Al-Zn eutectic melt. Thus, the tensile shear strength reached only about 2.7 kN/point, compared to that of the weld between A5052 and SPCC, which reached about 3.6 kN/point.