Uncovering the precision of vacuum brazing operations

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Brazing process in vacuum environment

How does vacuum brazing process work? Let’s go deep into the microscopic world and unveil its mystery.

In a vacuum environment with almost no air, it is like entering a super pure “sterile room”. Without the interference of gases such as oxygen, the metal surface will not be oxidized, which lays the foundation for high-quality welding. In this vacuum space, we put the metal parts and brazing materials to be welded. Brazing materials are like a special “glue” with a lower melting point than the metal to be welded. When we heat them, the brazing materials first melt and become liquid. Driven by capillary action, liquid brazing materials are like active small water droplets, quickly and evenly filling the tiny gaps between metal parts. Just like filling the gaps between bricks with cement when building a house, brazing materials fill and fill the gaps between metal parts, making them tightly combined. As the temperature decreases, the brazing materials gradually cool and solidify, forming a strong metallurgical bond with the metal parts, just like cement solidifies and tightly bonds bricks together, thus realizing the connection of metal parts, making the originally separated metal parts a closely coordinated whole.

Precision operation of vacuum brazing

The process of vacuum brazing is rigorous and delicate. Each step is like a key gear in a precision instrument, working closely together to ensure the reliability of welding quality.

Before formal welding, the surface treatment of the workpiece is crucial. The staff needs to carefully clean the oil, oxides and impurities on the surface of the workpiece. If these tiny pollutants are not removed, they may become “troublemakers” in the welding process and hinder the good combination of the brazing material and the workpiece. Common cleaning methods include mechanical grinding, which uses grinding tools to grind away impurities on the surface to make the surface flat and smooth; and chemical cleaning, which uses chemical solutions to react with impurities to dissolve and remove them. For example, in the welding of electronic components, special cleaning agents are used to remove the oxide layer on the surface of the components to ensure the reliability of welding. After the processing is completed, the workpiece and the brazing material are carefully assembled, just like building blocks, each part must be placed in the correct position to prepare for subsequent welding.

Everything is ready, and the workpiece is carefully placed in the vacuum furnace. The vacuum furnace is like a super pure chamber that can provide an ideal vacuum environment for welding. After the workpiece is placed, vacuuming begins. The vacuum pump acts like a diligent cleaner, quickly extracting the air and other gases in the furnace. As the gas gradually decreases, the vacuum degree in the furnace continues to increase, which is the key prerequisite for achieving high-quality welding. Generally speaking, for most vacuum brazing processes, the vacuum degree needs to be controlled between 10-3 Pa and 10-5 Pa. In such a high vacuum environment, the metal surface will not be oxidized, creating excellent conditions for welding.

Next is the heating link, which is the core part of the entire process, like the climax of a wonderful performance. Through the heating system, the temperature in the vacuum furnace gradually increases. The heating process needs to be precisely controlled, and the heating rate should not be too fast or too slow. If the heating rate is too fast, the workpiece may be heated unevenly, thermal stress may be generated, and even the workpiece may be deformed or damaged; if the heating rate is too slow, the welding time will be extended and the production efficiency will be reduced. When the temperature rises to the melting point of the brazing material, the brazing material begins to melt and quickly fills the gap between the workpieces, just like water flowing into the gap of a sponge, tightly connecting the workpieces together. Then enter the insulation stage, keep the temperature stable for a certain period of time, let the brazing material and the workpiece fully interact and form a strong metallurgical bond. There are also strict requirements for the length of the insulation time. If the insulation time is too short, the brazing material and the workpiece will not be fully combined, which will affect the welding strength; if the insulation time is too long, it will not only waste energy and time, but also may cause the brazing material to melt excessively, causing adverse effects on the workpiece.

After completing the heating and insulation, it enters the cooling stage. The cooling process also needs to be strictly controlled, usually by natural cooling or filling with inert gas (such as argon) to assist cooling. Natural cooling is like letting a cup of hot water cool down naturally, the speed is relatively slow, but it can avoid thermal stress caused by rapid cooling; filling with inert gas cooling can speed up the cooling speed, while protecting the welded joint from oxidation during the cooling process. The cooling speed should be moderate. Too fast cooling speed will cause internal stress in the welded joint, reducing the strength and toughness of the joint; too slow cooling speed will affect production efficiency.

The last is the quality inspection link, which is a strict inspection of the entire welding process. There are many ways to inspect quality, including appearance inspection, which uses the naked eye or a magnifying glass to observe whether the surface of the welded joint is smooth, and whether there are cracks, pores and other defects; non-destructive testing, such as ultrasonic testing, uses the propagation characteristics of ultrasonic waves in different media to detect whether there are defects inside the joint; and radiographic testing, which uses the radiation to penetrate the welded joint and judge whether there are defects inside based on the degree of radiation attenuation. Only products that pass strict quality inspections can enter the next production link or be put into use, ensuring that the quality and performance of the final product meet high standards.

Vacuum Brazing Furnace