This article involves a metal surface treatment method, especially in the aluminum alloy vacuum brazing process, which effectively promotes the removal of oxide films and improves the quality of the weld.
Background technology: Aluminum alloy vacuum brazing is brazing-free. Compared with aluminum alloy brazing technologies such as traditional salt bath brazing, aluminum alloy vacuum brazing technology has the advantages of environmental protection, high efficiency, good welding quality, and complex welding structure. It is a brazing technology that has been widely used in recent years. However, due to the unique physical and chemical properties of aluminum alloys, its brazing performance is poor and a series of defects will occur.
In order to achieve the above purpose, this article adopts the following technical solutions: including surface treatment, rust prevention, cleaning, assembly molding and welding; surface treatment is to perform overall sandblasting treatment on the welding surface that is not attached to the brazing workpiece, so that uniform pits are formed on the welding surface. ; Among them, the distance between the nozzle and the surface to be welded is 100~350mm, the injection pressure is 5000~20000Pa, and the particle size of the sand is 20~80 mesh of quartz sand.
The preferred technical solution in this article is: the distance between the nozzle and the surface to be welded is 150~300mm, the injection pressure is 5000~15000Pa, and the quartz sand particle size is 30~60 mesh.
Compared with the existing technology, this paper uses the current mature sandblasting technology to sandblast the surface to be welded of the aluminum alloy that is not attached to the brazing workpiece, forming small pits with uniform thickness, irregular surface microstructure, and dense pits on the surface to be welded. . Therefore, since the expansion direction of the surface to be welded is inconsistent after heating, the oxide film is more likely to be completely broken; in addition, the surface to be welded is rough, and a certain gap will be formed between the surface to be welded and the surface to be welded, which is not only conducive to the release of gas generated by brazing Discharge also helps the broken oxide film to be floated and discharged by the brazing material, thereby forming a perfect brazing seam. This completely overcomes the problem that the surface to be welded is still relatively smooth after the traditional chemical method removes the film. The gap between the surface to be welded and the contact surface is too small, the oxide film and gas cannot be completely discharged, and the brazing material cannot completely wet the base metal, resulting in a weld seam. Defects of unstable quality.