What is brazing? Brazing is a metal-joining process in which two or more materials are joined when a filler metal (with a melting point lower than those of the materials themselves) is drawn into the joint between them by capillary action.
Brazing has many advantages over other metal-joining techniques, particularly welding. Since the base metals never melt, brazing allows much tighter control over tolerances and produces a cleaner connection, normally without the need for secondary finishing. Because components are heated uniformly, brazing consequently results in less thermal distortion than welding. Brazing also provides the ability to easily join dissimilar metals and non-metals and is ideally suited to cost-effective joining of complex and multi-part assemblies.
Vacuum brazing is carried out in the absence of air, using a specialized furnace, which delivers significant advantages:
- Extremely clean, flux-free joints of high integrity and superior strength
- Improved temperature uniformity
- Lower residual stresses due to slow heating and cooling cycle
- Significantly improved thermal and mechanical properties of the material
- Heat treating or age hardening in the same furnace cycle
- Easily adapted for mass production
In order to obtain high-quality brazed joints, parts must be closely fitted and the base metals must be clean and free of oxides, normally accomplished by either chemical or mechanical (abrasive) cleaning. In the case of mechanical cleaning, proper surface roughness must be maintained as the capillary action of the filler material occurs much more readily on a rough surface than a smooth surface.
Temperature and time are also important factors that contribute to the quality of brazed joints. As the temperature of the braze alloy is increased, the alloying and wetting action of the filler metal increases as well. In general, the brazing temperature selected must be above the melting point of the filler metal, though there are several other factors that influence temperature selection.
Typically, the preferred process will have the lowest possible braze temperature to minimize heat effects on the assembly, keep filler metal/base metal interactions to a minimum and maximize the life of fixtures. Most production braze processes are optimized to minimize brazing time and the associated costs.
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Vacuum Brazing Furnaces
Ipsen manufactures vacuum brazing furnaces for many different materials including:
Examples of vacuum aluminum brazed parts include:
- Heat Exchangers
- Oil Coolers
Industries that often use this processing technology are: