The influence of technological parameters on the formation of a wall bead during multi-pass welding in shielding gases
High-quality welding in vital metal structures, such as bridges, machinery, pipes, etc., imposes strict limitations on the power supply per unit length. In the case of multi-pass welding, the buildup of heat transfer to the base metal in the area, where the filler metal and the edge fuse together, increases the possibility of faulty fusion. To control the quality of welding, analytical relationships between the primary and secondary welding parameters and the base metal penetration depth under the flawless wall bead formation are required. The method of mathematical planning of the full factorial experiment was used to derive analytical dependences of the wall bead cross-section area and the total thermal efficiency of the welding process on the groove angle, electrode position in the grooving, and the welding speed. The most significant parameters affecting the formation of the wall bead without faulty fusion are determined. For a given welding current, voltage, and electrode diameter, the input data include the position of the electrode in the grooving and the welding speed. The study showed that shifting the electrode to the edge increases the heat transfer to the base metal and, consequently, increases the efficiency and quality of the welding process. Increasing the welding speed to a certain value increases the penetration depth due to the decrease of a liquid layer thickness under the arc and, therefore, improves the efficiency of the welding process and the weld quality.