Feasibility study on tandem narrow gap GMAW of 65 mm thick steel plate

In this work, a tandem narrow gap gas metal arc welding(GMAW) system was developed to improve the efficiency in welding of thicker materials, which are mostly used in shipbuilding and nuclear power plant. A special welding torch was desgined, where the two wires are fed through the bent contact tip to point to each side of narrow gap groove. Effect of wire distance and bent angle of contact tip on weld bead shape is studied. The experimental results show that defect free weld bead can be obtained when the wire distance is 5 mm and bent angle of contact tip is 10°. Finally, tandem narrow gap GMAW of 65 mm thick low carbon steel was successfully carried out with one pass per layer. The obtained weld cross-section photo indicates that there is no defect of lack of side fusion or slag inclusion.