MIL-HDBK-660B
5.7 Brazing flanges on aluminum waveguide. The basic equipment and methods required for brazing aluminum flanges on aluminum waveguide are described below.
5.7.1 Torch tips (numbers 1 to 5). The use of various size torch tips are determined by the thickness and size of the area to be brazed. The tips vary according to the size of their openings. The No. 3 tip is suggested for waveguide brazing.
5.7.2 Brazing rod. The main requirement for a good brazing alloy is that it melts at a low temperature to provide a practicable brazing range. Specifically recommended is BAlSi-4 as specified in AWS-A5.8 or Alcoa No. 716, or equal brazing rod, .0625 inch (1.5875 mm) thick - brazing range 512°C to 595°C (970°F to 1085°F).
5.7.3 Brazing. Place the guide upright with the prepared end to be soldered on the bottom. Insert the waveguide through the flange so that .031 inch (0.79 mm) of guide extends beyond the face of the flange, preventing the solder from entering the guide. A suitable jig, such as four bolts threaded into the flange (see figure 36), can be used to keep the flange from its flat surface. After the parts to be brazed are properly damped or supported, apply the flux to the areas to be brazed and to several inches of the brazing rod. Use a No. 3 torch tip and adjust for "reducing" flame (oxygen starved flux). Apply heat to the parts to be brazed, keeping the torch in constant motion at all times for an even distribution of heat for proper fusion. When the flux dissolves into a liquid and becomes transparent, apply the
brazing rod to the area to be brazed. The rod applied at one point only will flow around and seal the joint if the heat is properly distributed (see figure 39). Do not allow the flame to concentrate on one spot as it may burn the flux or melt
the bare metal. Once the filled metal has started to flow into the joint, the heat should not be increased. After the
joint has cooled, all traces of the flux should be removed to prevent corrosion of the parts.
5.8 Dip brazing of aluminum waveguide.
5.8.1 Brazing flux. A recommended dip brazing flux is Aluminum Brazing Salt Pack Type "D", produced by Park
Chemical Co., or equivalent.
5.8.1.2 Preparation of parts.
5.8.1.2.1 Cleaning. The cleaning directions given in 5.4 are to be used.
5.8.1.2.2 Chemical dipping. Parts should be dipped and rinsed as follows:
a. Immerse parts in a nitric hydrofluoric acid solution maintained at room temperature for 30 to 60 seconds.
The solution should be prepared as follows:
Quantity |
Composition |
1 gallon half pint 9 gallons |
58-62 percent HNO3(39'5'Be') 48 percent HF (1 15 specific gravity) water (room temperature) |
b. Rinse in two cascade cold-water rinse tanks with running water and constant overflow. Fresh water supply to tank two with overflow to tank one. Rinse for 30 seconds min. in tank one and then tank two in that order. Do not rinse in hot water.
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