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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Problems in brazing of Aluminum
Q. My name is Carlos Ospino and I an a student researching for information for a school project. My major is in Engineering. I am looking for information on a compound used for brazing aluminum condenser/radiators in a very low temperature (about 700 °F) oven. It is a paste type of compound like a tooth paste and it is applied to the parts with a gun like device. I have tried all literature possible on this subject but I have not found the right information. I appreciate any input. Thank you.
Carlos Ospinocounty college - Elizabeth, New Jersey
2006
A. Search for 'aluminum solder paste.' This contains both flux and filler metal powder. The American Welding Society considers 800 °F the divider between soldering and brazing processes.
Aluminum brazing is usually performed in the range 990-1140 °F, or more precisely, 70-90 °F below the alloy melting point.
Heatbath has a page on 'ALUMINUM SALT BATH BRAZING.' The molten salt heats and fluxes the aluminum. Aluminum radiators are usually made of Al 3003 clad with a thin layer of a lower melting, Al-7.5%Si alloy, so no additional filler is needed. I believe most are fluxed and then furnace brazed under a protective nitrogen atmosphere. SECO/WARWICK has lots of information on Controlled Atmosphere furnace Brazing (CAB): http://www.secowarwick.com/aluminumbrazing.html
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2006
SOLDER-IT HAS ALUMINUM SOLDER PASTE
richard bell- Marietta, Georgia
March 13, 2010
Q. AWS C3.7 and MIL-B-7883 [on DLA] state that the dip temperature can not exceed the solidus of the braze alloy (in this case 6061 Aluminum) 1080 °F. The filler metal solidus is also 1080 °F . If they are both at their solidus how is it possible that they braze without moving towards the liquidus of either?
Tim jarret- needham Massachusetts US
October 4, 2012
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