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Vacuum Brazing Furnace

Vacuum Furnace Brazing Process

Basic principles of vacuum brazing

Brazing refers to a welding method in which the solder is melted by heating (above 450°C, but lower than the melting temperature of the base metal), and the capillary action of the liquid solder is used to fill the solder joint and mutually diffuse with the base metal to achieve the connection. In order to improve the production efficiency of brazing, it is necessary to clearly understand the basic knowledge of brazing.

The basic steps of vacuum brazing mainly include:

Very good fit and good clearance

Clean metal surfaces

Proper clamping

Apply the appropriate flux/atmosphere to the part

Appropriate heating method

Post weld cleaning

Vacuum brazing: Using a filler metal (called brazing material or solder) with a lower melting point than the base material (material to be brazed), at a temperature lower than the melting point of the base material and higher than the melting point of the brazing material, the liquid brazing material is used to A welding method that wets and spreads the surface of the base metal and fills the gaps between the base metal, and dissolves and diffuses with the base metal to achieve the connection between parts.

Vacuum brazing application characteristics

⑴The brazing heating temperature is low, the joints are smooth and flat, the structure and mechanical properties change little, the deformation is small, and the workpiece size is accurate.

⑵ It can weld dissimilar metals and dissimilar materials, and there is no strict limit on the thickness difference of the workpiece.

Vacuum Brazed Diamond Grinding Wheel

⑶ Some brazing methods can weld multiple welding parts and multiple joints at the same time, with high productivity.

⑷The brazing equipment is simple and the production investment cost is low.

⑸The joint strength is low, the heat resistance is poor, and the cleaning requirements before welding are strict, and the solder price is relatively expensive.

Vacuum brazing applications

Brazing is not suitable for the welding of general steel structures and heavy-load and dynamically loaded parts. It is mainly used to manufacture precision instruments, electrical components, dissimilar metal components and complex thin plate structures, such as sandwich components, honeycomb structures, etc. It is also commonly used to braze various types of different wires and carbide cutting tools. During vacuum brazing, the contact surfaces of the workpieces to be brazed are cleaned and then assembled in the form of overlap. The solder is placed near the joint gap or directly into the joint gap. When the workpiece and the solder are heated together to a temperature slightly higher than the melting temperature of the solder, the solder will melt and infiltrate the surface of the weldment. The liquid solder will flow and spread along the joint with the help of capillary action. As a result, the metal to be brazed and the brazing filler metal dissolve and penetrate each other to form an alloy layer. After condensation, a brazing joint is formed.

Vacuum brazing is widely used in machinery, motors, instruments, radio and other departments. Carbide cutting tools, drilling bits, bicycle frames, heat exchangers, conduits and various containers, etc.; in the manufacturing of microwave waveguides, electron tubes and electronic vacuum devices, vacuum brazing is even the only possible connection method.

Characteristics of vacuum brazing

First, the joint has a smooth surface, good air tightness, stable shape and size, little change in the structure and performance of the weldment, and can connect the same or different metals and some non-metals. During vacuum brazing, the workpiece can also be heated as a whole to weld many welds at one time, which improves productivity. However, the strength of brazed joints is low, and lap joints are often used to increase the joint strength by increasing the overlap length; in addition, the preparation work before brazing is required to be high.

The second is that the solder melts but the weldment does not melt. In order to make the brazing part firmly connected and enhance the adhesion of the brazing material, flux should be used during brazing to remove oxides on the surface of the brazing material and the weldment. Brazing materials (such as copper-based, silver-based, aluminum-based, nickel-based, etc.) have high strength and can connect parts that bear loads. They are widely used, such as carbide cutting tools and bicycle frames. Soft solder (such as tin, lead, bismuth, etc.) has low welding strength and is mainly used for welding parts that do not bear load but require good sealing, such as containers, instrument components, etc.

Brazing uses an alloy with a lower melting point than the base metal as the filler metal. When heated, the filler metal melts, fills and remains in the joint gap by wetting and capillary action, while the base metal is in a solid state, relying on the liquid filler metal and solid parent material. The mutual diffusion between materials forms a brazed joint. Vacuum brazing has little impact on the physical and chemical properties of the base metal, has small welding stress and deformation, can weld dissimilar metals with large differences in performance, can complete multiple welds at the same time, has beautiful and neat joint appearances, simple equipment, and low production investment. However, the strength of the brazed joint is low and the heat resistance is poor.