First, the principle and advantages and disadvantages of brazing

The principle of brazing

Brazing is to use a metal material with a lower melting point than the base material as a brazing material, and the weldment (base metal) and the brazing material are heated to a temperature higher than the melting point of the brazing material but lower than the melting point of the base material, and the mother is wetted with the liquid brazing material. The method of joining the weldments by filling the joint gap and interdiffusing with the base material.

2. Advantages and disadvantages of brazing

Compared with fusion welding, brazing has the following characteristics:

1) During brazing, the solder melts and the weldment does not melt. The soldering temperature varies from room temperature to a range close to the melting of the base material depending on the solder selected. In order to prevent changes in the microstructure and properties of the base metal, it is possible to select a brazing material having a low melting point for brazing, and there is no such room for welding.

2) During brazing, the weldment is usually heated as a whole or uniformly heated around the brazing joint. Therefore, the relative deformation of the weldment and the residual stress of the brazed joint are much smaller than that of the fusion weld, and it is easy to ensure the precise size of the weldment.

3) The brazing joint is mainly solidified by filling the gap with liquid brazing material. As long as the brazing material, flux and brazing method are properly selected, multiple brazing seams or large quantities of welding consumables can be brazed simultaneously or continuously. , high productivity. The brazing process is rarely affected by the openness and accessibility of the weldment structure.

4) Since the brazing reaction is carried out only at the interface of several micrometers to several tens of micrometers of the base metal, it does not generally involve the deep structure of the base metal, so it is particularly advantageous for dissimilar metals, even between metals and nonmetals, and between nonmetals and The connection between non-metals is not possible with fusion welding methods.

5) The strength and heat resistance of the brazing joint are lower than that of the parent metal. In order to compensate for the lack of strength, it is often used to increase the overlap area to solve the problem. Therefore, the brazed joint uses a lap joint to increase the weight of the structure and consume more materials.