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Vacuum Heat Treatment Furnace

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Vacuum Brazing Furnace

Basic knowledge of brazing joints

Types of brazing joints
Generally speaking, the difference between a satisfactory brazed joint pattern and a satisfactory one is the amount of overlap required to obtain a satisfactory joint. A strong soldered joint has a larger surface area wetted by the solder. However, too much overlap is detrimental to the joint because the solder cannot cover the entire surface after flowing to the joint.

The strength of brazed joints
The strength of a brazed joint depends primarily on two factors: the wetted surface area of the joint and the width of the gap in which the solder flows. For vacuum furnace brazing, a gap width of 0.003–0.008 inches (0.08–2.0 mm) works best. The clearance of a brazed joint depends on the manufacturing tolerances of the parts being brazed and the clamping (preloading) of the components being brazed.

Clamping of components
When vacuum brazing, the component assembly must be properly clamped to ensure correct joint clearance, joint alignment, runner alignment and overall assembly tolerances.
The material of the clamp must be chosen carefully because different materials have different coefficients of expansion. Fixtures are also designed to be part-specific, must be carefully considered and in some cases must employ proprietary technology, as they are an integral part of the manufacturing process.

Parts cleaning
In addition to proper joint design and fixtures, vacuum brazing requires proper cleaning of component components prior to assembly and then careful handling to avoid further contamination prior to the brazing process. All oil and particles must be removed from the surface of the base metal and solder metal. Assemblers must be careful not to rub oil from their own skin onto the cleaned surface when stacking components. Typical cleaning methods include steam degreasing, hydrocarbon scrubbing, water flushing, acid soaking and vacuum degreasing.

In conclusion
What is most important in vacuum aluminum brazing? High vacuum levels, precise temperature control and excellent temperature uniformity are all important process parameters that need to be guaranteed by optimized vacuum furnace design and control. Successful factors in component brazing also include proper joint design (joint surface area and joint clearance), cleanliness of the components, and proper clamping of the component components.