Welding characteristics of galvanized steel
Galvanized steel is generally coated with a layer of zinc on the outside of low carbon steel, and the zinc layer is generally 20um thick. The melting point of zinc is 419°C and the boiling point is around 908°C. During welding, zinc melts into a liquid and floats on the surface of the molten pool or at the root of the weld. Zinc has a large solid solubility in iron. The zinc liquid will etch the weld metal deeply along the grain boundaries, and the low melting point zinc will form "liquid metal embrittlement."
At the same time, zinc and iron can form intermetallic brittle compounds. These brittle phases reduce the plasticity of the weld metal and cause cracks under the action of tensile stress.
If fillet welds are welded, especially the fillet welds of T-shaped joints, they are most likely to produce penetration cracks. When welding galvanized steel, the zinc layer on the groove surface and edges will oxidize, melt, evaporate and even volatilize
white smoke and steam under the action of arc heat, which can easily cause weld porosity.
.jpg)
