Classification of CO2 gas shielded welding 3of 3
There are five kinds of CO2 gas shielded welding, such as hybrid gas shielded welding, gas electric vertical welding, CO2 gas shielded arc spot welding, solid cored wire CO2 gas shielded welding and flux cored wire CO2 gas shielded welding.
Flux cored wire CO2 gas shielded welding
Flux cored wire is composed of steel belt and flux. The flux is placed on a special steel belt, which is cored and drawn by the coiling machine. The welding process that can be shielded by gas is called flux cored wire welding, and the CO2 gas welding that can be shielded by flux cored wire is called flux cored wire CO2 gas welding. In the welding process, flux-cored wire produces gas and slag under the action of high temperature of the arc, which plays the role of gas protection and slag protection. Without additional gas protection, it is called self-protecting flux-cored wire. This welding method is called self-protecting flux-cored wire welding.
Principle of CO2 gas shielded flux cored wire welding
The difference between this welding method and CO2 gas shielded welding is that flux cored wire is used instead of solid cored wire for welding, as shown in Figure 1-27.
Flux cored wire is made of thin steel plate rolled into a round steel tube or special-shaped steel tube, filled with a certain amount of powder, after drawing the wire, the role of powder in the welding process is the same as the electrode coating. Therefore, the welding process of flux cored wire gas shielded welding is double protection and gas slag combined protection, which can obtain higher welding quality. Figure 1-28 shows the cross section of a flux-cored welding wire.
Characteristics of CO2 gas shielded flux cored wire welding
advantage：
- High melting coefficient. Since the welding current only flows through the metal skin of flux cored wire, its current density is very high, resulting in a large amount of resistance heat, making it melt faster than solid cored wire of the same diameter. Under normal circumstances, flux cored wire cladding rate of 75%~88%, production efficiency is 1.5-2 times of solid cored wire, is 5~8 times of manual electrode.
- Welding depth is large. Because the current only flows through the metal skin of flux cored wire, the current density is large, so that the weld depth increases. The results show that when the actual thickness of fillet weld increases, the joint strength does not change with the change of the appearance size of the weld. Therefore, the size of the weld foot can be reduced, and the weld metal can be saved by 50%~60%.
- Good technology. Because of the arc stabilizer and slagging agent in the core, the arc is stable, the droplet is uniform, the splash is small, the slag is easy to be removed, and the weld bead is beautiful. Good weld surface forming is beneficial to improve the dynamic load performance of the welding structure.
- Low welding cost. The total cost of flux cored CO2 gas shielded welding is only 45.1% of manual arc welding, and slightly lower than solid cored CO2 gas shielded welding.
- Adaptable. Different types of flux cored wires can be obtained by changing the composition of flux cored wires to meet different needs. In short, flux cored CO2 gas shielded welding is a kind of high efficiency, energy saving, economic, good technology, high welding quality welding process.
disadvantage:
Compared with solid cored CO2 gas shielded welding, flux cored CO2 gas shielded welding has the following disadvantages:
- The smoke is big. There is a lot of smoke during welding.
- Welding slag. There are more welding slag than solid cored wire CO2 gas shielded welding, so attention should be paid to slag removal during multi-layer welding to prevent slag inclusion defects. But the amount of slag is much less than that of manual arc welding, so the slag cleaning workload is not large.
- Flux cored wire can be used for welding stainless steel, low alloy high strength steel and surfacing. At present, flux-cored welding wire is widely used in heavy machinery, construction machinery bridge, petroleum, chemical industry, nuclear power plant equipment, large power generation equipment and oil production platform and other manufacturing industries, and has achieved good results.