The oxide film on the metal surface during vacuum brazing furnace brazing affects the wettability of the liquid filler metal to the base metal. During the vacuum brazing furnace brazing process, if the oxide film on the surface of the base metal cannot be effectively removed, it is difficult to form high-quality brazing joints. Different brazing methods adopt different measures for removing oxide film and preventing oxidation. The general brazing method is to remove the oxide film through the chemical action of the brazing flux or the reduction effect of the reducing atmosphere.

Although vacuum brazing does not have the chemical effect of brazing flux or the reducing effect of reducing atmosphere, the vacuum of the vacuum brazing furnace can reduce the oxygen partial pressure in the brazing area, remove the oxide film on the surface of the weldment, and protect the weldment from oxidation. In this way, high-strength, bright and dense joints can be obtained by brazing in the vacuum atmosphere of the vacuum brazing furnace.

The mechanism of removing metal oxide film during vacuum brazing includes the following aspects:

The oxide film can decompose on its own at high temperatures and high temperatures. When vacuum brazing in a vacuum brazing furnace, the decomposition pressure of the oxide is greater than that of the oxygen in the vacuum system, resulting in the oxidation force on the surface of the part. It can be seen that only a few types of metal oxides can decompose on their own under brazing conditions. Most metal oxides cannot decompose. Therefore, the self decomposition of oxides is not the main factor for removing the oxide film during vacuum brazing.