What should be paid attention to when welding galvanized steel pipe

What should be paid attention to when welding galvanized steel pipe

1. The premise must be polished

The galvanized layer of the weld must be polished away, otherwise air bubbles, trachoma, false welding, etc. will occur. It will also make the weld brittle and reduce the rigidity.

2. The welding characteristics of galvanized steel

Galvanized steel is generally coated into a layer of zinc on the outside of low-carbon steel, and the galvanized layer is generally 20um thick. At the same time, zinc and iron can form brittle compounds between metals. These brittle phases reduce the plasticity of the weld metal and cause cracks under tensile stress. If the fillet welds are welded, especially the fillet welds of the T-shaped joints, penetration cracks are most likely to occur. When welding galvanized steel, the zinc layer on the groove surface and the edge will oxidize, melt, evaporate and even volatilize white smoke and steam under the action of the arc heat, which can easily cause weld pores. Secondly, due to the evaporation of zinc, a large amount of white smoke is emitted, which is irritating and harmful to the human body. Therefore, the galvanized layer of the weld must be polished.

3. Welding process control

The pre-welding preparation of galvanized steel is the same as that of general low-carbon steel. It should be noted that the groove size and the nearby galvanized layer must be carefully handled.