Brazing process for stainless steel heat exchangers
OwnerKam Dianatkhahinventor
Life of this patent
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Abstract
An improved brazing process increases the strength and longevity of joints between stainless steel tubes and aluminum fins. The process is especially useful in joining tubes and fins of HVAC secondary heat exchangers and high chrome steels and aluminum. The process is comprised of first plating stainless steel tubes with nickel before applying a brazing flux containing potassium fluoroaluminate complexes such as a NOCOLOK® flux. Subsequently, aluminum fins are pressed to the tubes and flux. The entirety is then brazed in a controlled atmosphere brazing oven. The aluminum becomes metallurgically bonded to the flux, nickel coating, and other constituents of the tubes.
Claims13
A process for making heat exchangers from steel and aluminum comprising:
- (a) plating Ni in a layer upon an outer surface of at least one steel tube;
- (b) selecting a brazing flux comprising Al, K, and F wherein the amount of F is between 30 and 60 percent by weight;
- (c) applying the brazing flux to at least one surface of either the nickel side of the at least one steel tube or the aluminum;
- (d) mating the steel and the aluminum;
- (e) heating the mated steel and aluminum in an oven until a metallurgical bond forms between the flux, nickel and aluminum.
At least one steel heat exchanger tube with aluminum fins wherein the aluminum fins are joined to the steel by the process of:
- (a) plating Ni in a layer upon an outer surface of the at least one steel tube;
- (b) selecting a brazing flux comprising Al, K, and F wherein the amount of F is between 30 and 60 percent by weight;
- (c) applying the brazing flux to at least one surface of either the nickel side of the at least one steel tube or the aluminum;
- (d) mating the at least one steel tube and the aluminum;
- (e) heating the at least one steel tube and aluminum in an oven until a metallurgical bond forms between the flux, nickel and aluminum.
Dependencies are inferred from the claim text.