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Arc welding with external gas as the arc medium and protecting the arc and spot welder area is referred to as gas shielded arc spot welding. Using CO2 gas as protection, the burning arc is used to melt the upper and lower two metal components on the two lap sheets. The welding gun and welding parts are not moving during the welding process. Due to the melting of the welding wire, a rivet shape is formed on the surface of the upper plate. This welding method is realized by arc spot welding by completely melting one plate into another plate.
The plate of CO2 gas arc spot welding is generally not more than 5mm, and the thicker plate can also be directly arc spot welding, but before welding, the upper plate should be drilled or punched, and the arc directly heats the lower plate through the hole to form the weld. This welding method is also called plug welding. CO2 gas shielded arc spot welding is different from resistance spot welding. Resistance spot welding uses electrodes to press two thin metal plates. At this time, the electrodes are connected to the power supply, and the current generates resistance heat on the contact surfaces of the two thin metal plates, so that the contact points flowing through the current on the contact surfaces melt and form welding spots.
The characteristics of the welding process of CO2 gas arc spot welding are that the two metal plates to be welded should be close, no gap between them, the welding current should be large, the arc burning time should be short, and the no-load voltage of the welding machine should be higher, generally more than 70V, to protect the reliability of frequent arc starting in the spot welding process.
Solid core welding wire is one of the most commonly used welding wire in CO2 gas shielded welding. It is made of hot rolled wire after drawing process. In order to prevent the rust of the welding wire, special treatment must be carried out on the surface of the welding wire (except stainless steel wire).
Using solid core wire CO2 gas shielded arc welding, gas protection is that 100% of CO2 gas, welding spatter is big, in the process of welding soot is big also, lower impact toughness after weld, basic can meet the requirements of mechanical properties, protective gas price is the cheapest, compared with Ar and He, gas is more economical, thus got the most common use.
But in the actual production, mostly using φ(CO2)80%+φ(O2)20%(volume fraction for gas welding, which is stronger than the use of pure CO2 gas oxidation, welding arc heat will be higher, can greatly improve the welding speed and weld penetration depth.