Tooling design and application

As with the approach to an assembly’s detail construction, the design and application of tooling demands very different approaches between Salt Bath brazing and Vacuum brazing. Stable, flat, low mass fixturing is a key concept irrespective of the process. If your fixtures are too massive preheat times, braze time, and cooling times are increased. If they are not stable enough, flexing during the process will cause greater difficulties in straightening. Your parts will only be as flat after braze as your fixtures are before braze.

INCONEL® alloys make the best fixture material, holding up best to thermal cycling and the chloride environment of the salt bath process, but are the most expensive. The next best alloy choice is 316L CRES (X2crNiMo17-12-2).

Generally, fixturing used in the vacuum brazing process is more complex and expensive as details need to be loaded during the thermal cycle to maintain intimate contact and avoid any gaps.

Salt bath brazing is generally a more forgiving process and less expensive in terms of fixturing. On many assemblies tack welding can be used to hold many details in position during the brazing, external filler can be applied in the form of wire, foils and pastes to adjust fillet sizes and fill detail gaps within the process limitations.

Each process has its own strengths and weaknesses. Some part types are best brazed using the vacuum process and other best brazed using the salt bath process. Many fall into a class that can be successfully brazed using either process.

If you find yourself unsure of the best approach to your application contact us and we will be glad to offer our experience.