The reasons for the generation of air holes in the weld bead are as follows: (1) Rust, oil, or other impurities on the surface of the welding wire and the groove of the metal being welded. (2) Artificially elongated arcs, the welding area is not fully protected. (3) Improper selection of welding parameters or welding materials. (4) The purity of the shielding gas is insufficient. (5) The gas heater does not work properly.