what is vacuum brazing?
Vacuum Brazing is a process that creates high quality joints under temperatures from about 800°C to 1150°C in a vacuum atmosphere. This also allows for the joining of different materials like for example ceramic to steel.
Basically, brazing is a process that combines elements with the use of a brazing material. Prepared elements with applied brazing material are placed in a vacuum furnace and heated up to brazing temperature (from 800 to 1150°C) which is higher than the liquidus temperature. At this temperature, the parts are held for a short time (10 min) and then are slowly cooled to solidus temperature. This also allows for the joining of different materials like for example ceramic to steel.
During the process, the appropriate level of vacuum needs to be kept. Brazing in a vacuum furnace can also take place in a protective atmosphere, most often an argon atmosphere.
A typical vacuum brazing treatment takes place as follows:
- Cleaning the parts to be brazed
- Assembly of braze (foil, thread, paste, powder, galvanic layer) and products
- Setting up the part on the furnace frame
- Furnace process (steered by microprocessor)
- Unpacking and visual inspection
- Testing / final check
The following aspects play an important role:
- cleaning the parts to be brazed
- the availability of clean assembly rooms
- the use of high vacuum furnaces
- the process variables
- the loading tools
- the testing facilities
fields of application
The most important properties of vacuum brazed connections are as follows:
- Very strong and reproducible joints. Equal to or even stronger than the basic material.
- By using precious brazing material, corrosion resistant joints are created.
- Joints can be exposed to relatively high temperatures. (< 800 ºC)
- Clean process. Products remain metallically blank.
- Brazing without flux agents. Therefore, no undesirable surface reactions.
- Very clean, hygienic gap free joint. Important for the food or medical industry.
- Vacuum tight/leak proof joints.
- Possibility of joining various materials with each other (e.g.: metal-ceramics).
- Brazing and hardening possible in a single process.
- Parts can undergo practically all hardening processes after a brazing treatment.
- High level of construction freedom; thick/thin is possible, large surfaces can be joined.
- More than one joint can be created in a single process. The creation of complex products is possible
- High level of dimensional stability possible, no or practically no distortions.
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