What Is Vacuum Brazing? Process,Benefits,& More

Vacuum brazing furnace flux
Flux is also called flux. In metallurgy, it is a substance that uses chemical methods to clean the surface of the metal to be welded to facilitate soldering, brazing, or positioning welding. Different fluxes are used to weld different metals. According to the classification of deoxidizer and alloying agent added to the flux, it can be divided into neutral flux, active flux and alloy flux. Flux is stable at room temperature, highly reducing at high temperatures, and can be used to clean residual contaminants from brazed surfaces. Flux can be applied in a variety of forms, including flux paste, liquid, powder, or pre-made brazing paste that mixes flux with filler metal powder.
Flux can also be applied using a flux-coated soldering rod or flux core. When brazing, flux flows into the joint and is displaced by the molten filler metal entering the joint.
After the cycle is complete, excess flux should be removed as flux left in the joint can cause corrosion, prevent joint inspection, and interfere with further surface finishing operations. Phosphorus-containing brazing alloys can self-flux when joining copper to copper.
Fluxes are often selected based on their performance on specific base metals. To be effective, the flux must be chemically compatible with the base and filler metals used. Autofluxing phosphorus filled alloys can produce brittle phosphides if used on iron or nickel. In general, longer brazing cycles should use less active flux than shorter brazing cycles.
Vacuum brazing furnace solder filling
A variety of alloys are used as filler metals for brazing, depending on the intended use or method of application. Generally speaking, brazing alloys are composed of 3 or more metals to form an alloy with the desired properties. Filler metal for a specific application is selected based on its ability to: wet the base metal, withstand the required service conditions, and melt at lower or specific temperatures than the base metal.
Brazing alloys are typically available in rods, strips, powders, pastes, pastes, wires, and preforms (such as stamped washers). Depending on the application, the filler material can be pre-placed in the desired location or applied during the heating cycle. For hand brazing, wire and rod forms are typically used because they are easiest to apply when heated. In the case of furnace brazing, the alloy is usually pre-positioned because the process is usually highly automated. Some of the more common filler metals used are:
Aluminum silicon alloy
copper
copper silver
Copper zinc (brass)
Copper and tin (bronze)
gold silver nickel alloy
For silver, amorphous brazing foils of nickel, iron, copper, silicon, boron, phosphorus, etc. are used.
Vacuum brazing furnace classification
Vacuum brazing furnaces can be classified into many categories based on their structure, function, and application scope.
Classified by use:
High-temperature vacuum brazing furnace: capable of brazing under high-temperature conditions, suitable for brazing of high-temperature alloys, ceramics and other materials.
Low-temperature vacuum brazing furnace: capable of brazing at lower temperatures, suitable for applications that are sensitive to material temperature.
Classification by working method:
Manually operated vacuum brazing furnace: The operator manually controls the heating temperature, vacuum degree and brazing process.
Automated vacuum brazing furnace: Using an automatic control system, it can realize automatic control of heating temperature, vacuum degree and brazing process, improving production efficiency and consistency.
Classification by furnace type:
Vertical vacuum brazing furnace: The layout of the furnace is a vertical structure, which is suitable for certain specific workpiece shapes or space constraints.
Horizontal vacuum brazing furnace: The layout of the furnace is a horizontal structure, which is suitable for brazing certain large or long workpieces.
Classification by vacuum degree:
High vacuum brazing furnace: It can realize brazing under high vacuum conditions and is suitable for application scenarios that require high purity of materials and no gas pollution.
Low vacuum brazing furnace: low vacuum requirements, usually used for general brazing processes.

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