Problems that may occur during welding of galvanized sheets

【Summary Description】 Atmosphere protection welding Galvanized sheets produce smoke and white floats during welding. If you want to completely eliminate, it is necessary to use a protective atmosphere welding. For example with CO2 shielded welding. Application of Gas Shielded Arc Welding TIG welding can obtain excellent welding quality of the weld, its disadvantage is that the welding energy is limited, not suitable for welding thick parts, especially the strong thermal conductivity of the metal. In order to overcome this shortcoming, the year produced the molten metal extremely inert gas shielded arc welding (MIG), this method uses the metal welding wire as the electrode, the arc is generated between the welding wire and the workpiece, the welding wire is continuously fed and melted into the weld. Therefore, the welding current used in this method can be greatly improved and is suitable for welding medium and thick plates. Because argon is scarce and welding costs are high, TIG and MIG welding are mainly used to weld non-ferrous metals (aluminum, magnesium and their alloys), rare metals (molybdenum, titanium, nickel and their alloys) and stainless steel. In order to reduce the cost of gas shielded welding, people successfully replaced argon with CO2 gas in, and invented carbon dioxide gas shielded welding (). It is an arc welding method with CO2 gas as a protective medium, with welding wire as an electrode, and welding in an automatic or semi-automatic manner. CO2 welding has low cost, high productivity and wide application range. However, due to the arc atmosphere has a strong oxidizing, easy to make alloy elements burning, will cause pores and welding process is easy to produce metal splash, it must be used to contain deoxidizer welding wire and special welding power supply. At present, CO2 arc welding is mainly used for welding ferrous metals such as low carbon steel and low alloy steel, but it is not suitable for stainless steel, high alloy steel and non-ferrous metals. In the early stage of gas shielded arc welding, a single gas was mainly used, such as argon (Ar), helium (He) and CO2 gas. Later, it was found that after adding a certain amount of another or two gases to one gas, satisfactory results could be obtained in refining the droplet, reducing spatter, improving the stability of the arc, improving the melting depth and increasing the temperature of the arc. Commonly used mixed gases are:(1)Ar + He. It is widely used in the welding of large thickness aluminum plate and high thermal conductivity materials, as well as the high-speed mechanized welding of stainless steel. (2)Ar + H2. Using the reduction of mixed gas to weld nickel and its alloys can eliminate the pores in nickel welds. (3)Ar + O2 mixed gas (O2 content is 1%). Especially suitable for stainless steel MIG welding, can overcome the phenomenon of cathode drift when using argon alone. (4)Ar + CO2 or Ar + CO2 + O2. Suitable for welding low carbon steel and low alloy steel, the weld formation, joint quality and arc stability and droplet transfer are very satisfactory.

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