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)