1. Preheating should keep the temperature unchanged during the whole welding process to facilitate the overflow of diffusible hydrogen and slow cooling after welding.
2. Since gas shielded welding is a short-circuit transition form, the arc combustion is discontinuous, that is, the welding arc is instantly extinguished. It occurs about 60-100 times per second. But the wire feed is continuous. This process characteristic of gas shielded welding makes it have a high deposition rate and high production efficiency. However, unfused and dispersed slag inclusions are also prone to occur. Because of the orientation of the defects, it is possible that radiographic inspection will fail to detect these defects in the weld. The lack of fusion in gas shielded welding is mainly caused by the large swing spacing during swing welding, and the insufficient infiltration of the solid metal on both sides of the groove by the liquid metal in the molten pool. Welders should observe carefully during actual operation. Usually, when the liquid metal has slight ripples at both ends of the groove and the liquid surface is depressed downward, it means that the infiltration is sufficient, and the liquid metal is protruding, indicating that the infiltration is insufficient.
3. During multi-layer welding, the weld bead should be cleaned up.
