1990-02-01

Determination of Aluminum Vacuum Brazing Furnace Conditions by Post-Mortem Examination of Brazed Assemblies 900409

The effects of temperature, pressure, and atmosphere composition were examined to determine how each influenced vacuum brazed aluminum radiator tube-to-header joints. Brazing at 1 x 10-5 Torr (1.3 x 10-3 Pa), while varying the braze temperature from 1070°F (577°C) to 1125°F (607°C), showed that acceptable joints were produced in the 1080°F (582°C) to 1110°F (590°C) range. Below 1080°F (582°C), insufficient melting caused poor filleting. Above 1110°F (590°C) severe tube core dissolution occurred. Increasing the pressure (constant temperature) by introducing air into the furnace caused extremely poor fillets above 2.0 x 10-4 Torr (3 x 10-2 Pa). Acceptable fillets were formed in N2 saturated with 10,000 ppm of H2O at 9 x 10-4 Torr (0.12 Pa). XPS analyses of the air generated oxides showed that they were 700 A thick or less, and composed of MgO and Al2O3. Techniques were developed which allow the operating temperature and pressure of the furnace to be estimated from brazed radiators.

SAE MOBILUS

Subscribers can view annotate, and download all of SAE's content. Learn More »

Access SAE MOBILUS »

Members save up to 43% off list price.
Login to see discount.
Special Offer: Purchase more aerospace standards and aerospace material specifications and save! AeroPaks off a customized subscription plan that lets you pay for just the documents that you need, when you need them.
X