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Tips on controlling and influencing vacuum degree in vacuum brazing

Vacuum brazing is a brazing process performed in a vacuum environment. It is widely used in aviation, aerospace, nuclear energy and electronics, and is particularly outstanding in high-precision and high-demand applications. The core is to provide a low-pressure environment to avoid oxidation and improve the wettability and diffusivity of the brazing material, so as to obtain high-quality joints. The control of vacuum degree is a key link in the entire process, which directly affects the welding quality, joint strength and performance of the brazing material.

Introduction to vacuum brazing process
Vacuum brazing does not involve melting the parent material, but relies on the flow and diffusion of the brazing material in a vacuum environment to form the joint. Its advantages include avoiding oxidation, reducing impurity contamination, and being able to handle the connection of different materials. It is particularly suitable for high-reliability fields such as aerospace. The low-pressure environment significantly improves the sealing and strength of the joint by reducing oxygen and water vapor in the air. Typical range and unit of vacuum degree According to research, the typical vacuum degree range of vacuum brazing is 10-4 to 10-6 Torr (about 0.013 to 0.00013 Pa), and the specific value depends on the material and application requirements. For example, brazing of single crystal diamond usually requires high vacuum (10-4 to 10-3 Pa) or inert gas protection, while some metals such as titanium and aluminum may require lower pressure to prevent oxidation. The unit of vacuum is often Torr or Pa, and millibar (mbar) is also common in industry, where 1 Torr ≈ 133.322 Pa, 1 mbar = 100 Pa.

Staged vacuum control, the entire brazing process is divided into three stages:
Pre-vacuuming: quickly reduce the gas pressure to below 10-3 Pa to remove residual gas in the furnace.
Brazing vacuum: maintain a high vacuum (such as 10-2 Pa or lower) to ensure brazing material wetting and diffusibility.
Cooling vacuum: control the vacuum to avoid uneven cooling, reduce the impact of residual gas on the joint, and maintain high strength and high temperature resistance.
The vacuum environment effectively prevents oxygen, water vapor and other harmful gases in the air from reacting with the brazing material and the base material. Oxides will reduce the wettability of the brazing material, resulting in a decrease in joint strength, and high vacuum (such as 10-5 Torr) can significantly reduce this risk.
At low vacuum, the fluidity and wettability of the brazing material are improved. For example, a vacuum below 10-3 Pa ensures that the brazing material can better penetrate the joint surface and form a uniform connection.

Importance of vacuum control
The control of vacuum in vacuum brazing is critical to the quality of the weld and may affect the strength and durability of the joint. Appropriate vacuum (such as 10-4 to 10-6 Torr, about 0.013 to 0.00013 Pa) can reduce oxidation, improve brazing wettability, and reduce porosity.
The control methods of vacuum include selecting a suitable vacuum pump system, using vacuum sensors, and performing leak detection, depending on the material and application requirements. The effects of vacuum on joint quality include enhanced strength, improved density, and improved heat resistance, but too high or too low vacuum can bring challenges.
Accurate control of vacuum is critical in vacuum brazing and directly affects the quality and reliability of the joint. By optimizing the vacuum pump system, vacuum sensors, and leak detection management, the strength, density, and heat resistance of the joint can be effectively improved. As technology advances, vacuum control technology will develop further and provide stronger support for high-end applications such as aircraft engines.