Welding is the process of connecting metal parts using a variety of fused alloys (solder).
The melting point of the solder is lower than that of the welded material, so that the component will be welded through the contact between the molecules on its surface without being melted. Welding can be divided into soft welding and hard welding, soft welding temperature below 450 ℃, hard welding higher than 450 ℃. Hard welding is usually used in silver, gold, steel, copper and other metals, its welding point is much stronger than soft welding, shear strength for soft welding 20~30 times.
The term welding is usually used for both of these thermal connections, as both cases are written to the molten solder in a slender gap of two clean and close solid metal surfaces to be installed. Welding ensures the continuity of the metal. On the one hand, the two metals are linked to each other by bolted or physical adhesion, manifested as a strong metal whole, but the joints are discontinuous, and sometimes the surface of the metal, if there is an oxide insulating film, they even have physical contact with the wrong. Another defect in the comparison between mechanical joints and welding is the continued oxidation of the contact surface, which leads to the addition of resistors. In addition, vibrations and other mechanical shocks can also loosen the joints. Welding eliminates these problems, the welding site does not occur relative movement, contact surface will not oxidize, continuous conductive methods can be adhered to. Welding is the fusion process between the two metals, solder in the melting state, will dissolve some of the metal in contact with it, and the welded metal surface is often a thin layer of solder insoluble oxide film, flux is used to remove this layer of oxide film.
