First, the surface of the joint is smooth, airtight, stable in shape and size, and the structure and performance of the weldment does not change much, and the same or different metals and some non-metals can be connected. When brazing, heating the workpiece as a whole can also be used to weld many welds at one time, which improves productivity. However, the strength of brazed joints is low, and lap joints are often used to increase the strength of the joint by increasing the length of the lap; in addition, the preparation work before brazing requires higher.
The second is that the solder melts but the weldment does not melt. In order to make the brazing part firmly connected and enhance the adhesion of the brazing material, flux should be used during brazing to remove the oxides on the surface of the brazing material and the weldment. Brazing materials (such as copper-based, silver-based, aluminum-based, nickel-based, etc.) have high strength and can be connected to load-bearing parts. They are widely used, such as cemented carbide tools and bicycle frames. Soft solder (such as tin, lead, bismuth, etc.) has low welding strength and is mainly used for welding parts that do not bear load but require good sealing, such as containers, instrument components, etc.
Brazing uses an alloy with a melting point lower than the base material as the brazing filler metal. The brazing filler metal melts when heated, and fills and remains in the joint gap by wetting and capillary action, while the base material is in a solid state, relying on liquid filler metal and solid base material. The interdiffusion between materials forms a brazed joint. Brazing has little effect on the physical and chemical properties of the base metal, welding stress and deformation are small, and it can weld dissimilar metals with large differences in performance. It can complete multiple welds at the same time. The appearance of the joints is beautiful and neat, the equipment is simple, and the production investment is small. However, the strength of the brazed joint is low and the heat resistance is poor.
