Welding is a processing method in which two pieces of metal are locally heated or heated and pressurized simultaneously. We often use the welding method in which workers hold the mask in one hand and the welding tongs and welding rod connected to the wire in the other hand is called manual arc welding, which uses the high temperature generated by arc discharge to melt the welding rod and weldment to join them.
Manual arc welding is not widely used in automobile manufacturing. Spot welding is widely used in automobile body manufacturing. Spot welding is suitable for welding thin steel plates. During operation, two electrodes apply pressure to the two steel plates to bond them together, and at the same time, the bonding point (circular with a diameter of 5-6 barrels) is heated and melted to be firmly joined. When two body parts are welded, their edges are welded at a point every 50-100 to make the two parts form a discontinuous multi-point connection. To weld the entire car body, usually thousands of welding points are required. The strength requirements of the solder joints are very high. Each solder joint can withstand a tensile force of 5kN, even if the steel plate is torn, the solder joints cannot be separated.
The common gas welding in the repair shop is to burn acetylene and use oxygen to support combustion to generate a high-temperature flame, so that the welding rod and the weldment are melted and joined. You can also use this high-temperature flame to cut the metal, which is called gas cutting. The application of gas welding and gas cutting is more flexible, but the heat-affected zone of gas welding is larger, which causes deformation and metallographic structure changes of weldments, and performance declines. Therefore, gas welding is rarely used in automobile manufacturing.
