What is the impact and correlation of vacuum degree of vacuum brazing furnace

In order to ensure sufficient brazing permeability, reasonable alloying reaction, avoid the occurrence of brazing defects in vacuum brazing furnace, and obtain good brazing joints, it is necessary to choose brazing parameters reasonably. The process parameters of vacuum brazing furnace vacuum brazing include vacuum degree, heating speed of vacuum brazing furnace, stable temperature and time, brazing temperature of vacuum brazing furnace, brazing time, cooling method, and outlet temperature of vacuum brazing furnace.

(1) In order to prevent oxidation and discoloration of brazed components and furnace components (heating elements, radiation screens, etc.), and to prevent hot gas from directly passing through mechanical pumps, the vacuum brazing furnace cavity should be pre pumped to a certain degree of vacuum before the vacuum brazing furnace heats up. This vacuum degree is called the cold vacuum degree. The cold vacuum degree is mainly selected based on the properties of the brazing matrix material.

(2) Hot vacuum degree: The so-called hot vacuum degree refers to the pressure inside the vacuum brazing furnace from the beginning of heating to the beginning of cooling. When the vacuum brazing furnace begins to heat up, the parts and tools are all gassing out. When using paste solder. The volatilization of the adhesive agent can affect the pressure inside the vacuum brazing furnace to varying degrees, but generally does not affect the normal operation of the heating cycle. Moreover, the volatile matter of the adhesive is harmless to the brazing operation.

When the brazing material is about to melt, it is required to restore the pressure in the vacuum brazing furnace to the cold state vacuum degree. Use the method of appropriately extending the stabilization time until the vacuum degree meets the requirements, and then continue to apply brazing.

If the brazing material contains elements with high evaporation pressure, inert gas should be introduced into the vacuum brazing furnace when heated to a temperature below the melting point of the brazing material. To prevent a large amount of alloy elements from volatilizing and polluting the vacuum brazing furnace. The purity of inert gases should comply with regulations.

The pressure of inert gases is selected based on the volatilization characteristic curve of the metal. Inert gas slightly higher than the equilibrium pressure of metal volatilization should be introduced into the vacuum brazing furnace.