1, gas welding (OFW), which uses the flame produced by the mixed combustion of combustible gas and combustion-supporting gas as the heat source to melt the weldment and welding material and realize atomic bonding.
The combustion-supporting gas is mainly oxygen, and the combustible gas is mainly acetylene and liquefied petroleum gas. The welding materials used mainly include combustible gas, combustion-supporting gas, welding wire and gas welding flux. It is characterized by simple equipment and no need of electricity.
2, arc welding, arc as a heat source, using the physical phenomenon of air discharge, electric energy is converted into heat energy and mechanical energy needed for welding, so as to achieve the purpose of connecting metals. The main methods are covered electrode arc welding, submerged arc welding and gas shielded welding, among which covered electrode arc welding is the most widely used welding method in industrial production.
Extended data
Matters needing attention in welding
1, the length of the arc
The arc length is related to the type and thickness of covered electrode coating. However, short arcs, especially low hydrogen covered electrode, should be used as much as possible. Long arcs may cause blowholes. Short arc can prevent harmful gases such as O2 and N2 in the atmosphere from invading the weld metal and forming undesirable impurities such as oxides, which will affect the welding quality.
2. Welding speed
Suitable welding speed depends on covered electrode diameter, coating type, welding current, heat capacity of welding object, structure beginning and other conditions, so it is impossible to make standard provisions.
Keeping proper welding speed, slag can cover the molten pool well. Make all kinds of impurities and gases in the molten pool have enough floating time to avoid slag inclusion and porosity in the weld. When welding, if the rod feeding speed is too fast, the shrinkage stress will increase when the welding part cools, which will cause the weld to crack.
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