Vacuum brazing and normal brazing

Both belong to the soldering process, the principle of vacuum brazing and common brazing similar, use the function of capillary force is made in the parent metal surface wetting liquid filler metals, spread out and dissolve each other, realize the connection between parts such as diffusion, caulking, the difference is in the whole vacuum brazing welding process is in a vacuum atmosphere (general vacuum degree higher than 2 x 10 ^ – 3 pa, drainage limit vacuum in 10 pa ^ – 4 orders of magnitude) under complete, i.e., the use of fixture clamping parts together, around the joint plus hard solder, and then in a vacuum furnace heating melt solder diaspora in the gap. Compared with common brazing, vacuum brazing has another specific difference: different forms of surface oxide film removal.

In the process of brazing, whether vacuum brazing or other brazing, the oxide film on the metal surface will affect the wettability of liquid filler metal to the base metal, thus affecting the quality of brazing joint. General brazing in the chemistry of soldering flux or in reducing atmosphere reduction to remove oxide film, but not vacuum brazing flux reduction with reducing atmosphere, using the vacuum low pressure to remove the oxide film on the surface of the weldment and protect welding parts from oxidation, and avoid carbonization, decarburization and tainted phenomenon, improve the strength of welded joint. The low pressure can also discharge the volatile gas released by the metal at brazing temperature, so that the properties of the fund can be improved and bright and compact joints can be obtained.

In addition, since brazing agent is not used in vacuum atmosphere, there will be no pores, inclusions and other defects, which can improve the corrosion resistance of the matrix metal and save the process of cleaning residual flux required by general welding. In vacuum furnace, vacuum brazing can braze more than one adjacent brazing joint at a time, and brazing several components in the same furnace can greatly improve welding efficiency and complete the process synchronously with the heat treatment process. In addition to these, vacuum brazing can be welded by many base metals, including aluminum alloy, titanium alloy, refractory metal, ceramic glass, graphite, diamond, composite materials, etc.

Therefore, vacuum brazing has been popularized in aerospace, atomic energy, electrical instruments, petrochemical, automobile and many other fields.

learn more : Vacuum Sintering Furnace