1. Manual arc welding: This is a common welding method, manual arc welding equipment is simple, flexible and convenient operation, suitable for welding in any space position, especially suitable for welding short weld. But the production efficiency is low, the labor intensity is high, and the welding quality has a great relationship with the welder's technical level and mental state.
2. Automatic or semi-automatic submerged arc welding (arc welding): submerged arc welding is an arc welding method in which the arc burns under the flux layer. The welding wire feeding and the movement of welding direction are controlled by a special organization, which is called submerged arc automatic arc welding; The welding wire feeding is controlled by a special organization, and the movement of welding direction is operated by workers, which is called submerged arc semi-automatic arc welding.
The welding wire of submerged arc welding is not coated with flux, but the welding end is covered by the granular flux automatically flowing down by the flux leakage head. The arc is completely buried in the flux. The heat of the arc is concentrated and the penetration is large. It is suitable for thick plate welding and has high productivity. Due to the automatic or semi-automatic operation, the welding process is stable and the chemical composition of the weld is uniform, so the quality of the weld is good and the deformation of the weldment is small. At the same time, high welding speed also reduces the range of heat affected zone. But the assembly precision (such as gap) of submerged arc welding is higher than that of manual welding.
3. Gas shielded welding: gas shielded welding is the use of carbon dioxide gas or other inert gas as a protective medium of arc welding method. It directly depends on the protective gas to create a local protective layer around the arc, so as to prevent the invasion of harmful gas and ensure the stability of the welding process. There is no slag in the weld melting zone of gas shielded welding, and the welder can clearly see the welding process; Because the shielding gas is ejected, it is helpful to the transfer of the droplet; Because of the heat concentration, fast welding speed and deep penetration of the weldment, the formed weld has higher strength, better plasticity and corrosion resistance than manual arc welding, which is suitable for all position welding. But it is not suitable for welding in windy place.
4. Resistance welding: resistance welding is to use the heat generated by the current through the surface resistance of the contact point of the weldment to melt the metal, and then weld it by pressing. Resistance welding is only applicable to the welding of plate stack thickness not more than 12mm. For cold-formed thin-walled steel members, resistance welding can be used to join members with wall thickness less than 3.5mm.
Different welding methods bring different welding effect, which can be selected according to the specific situation. Only proper operation and attention to certain details can better ensure the welding quality and the quality of steel structure.
