Vacuum brazing process

Claim 2

The process of vacuum brazing aluminum parts comprising A. assembling a part to be joined in the desired relationship and in contact with a vacuum brazing sheet comprising an aluminum alloy core, clad to said core a brazing alloy consisting essentially of about 5 to 15 percent by weight silicon, about 0.5 to 5 percent by weight magnesium, 0.8 percent by weight maximum iron, 0.25 percent by weight maximum copper, 0.20 percent by weight maximum zinc, 0.20 percent by weight maximum manganese, 0.1 percent by weight maximum other elements each and the balance aluminum and clad to said brazing alloy a magnesium-free aluminum alloy, said magnesium-free alloy having a melting point at least 1100*F.; B. subjecting the assembled parts to a pressure less than 10 2 Torr of mercury (absolute) and heating the part and the brazing sheet to brazing temperature to melt said brazing alloy and to cause said brazing alloy to dissolve said magnesium-free cladding and thereby allow the magnesium in said brazing alloy to vaporize; C. maintaining said brazing temperature until said brazing alloy has flowed into contact with said part in contact with the brazing sheet so as to form a fillet therewith; and D. cooling the assembly to solidify the brazing alloy.

Claim 3

A PROCESS FOR VACUUM BRAZING ALUMINUM PARTS COMPRISING: A. ASSEMBLING AN ALUMINUM PART TO BE JOINED IN THE DESIRED RELATIONSHIP AND IN CONTACT WITH AN ALUMINUM BRAZING SHEET HAVING A BRAZING ALLOY CLADDING, B. PLACING SAID ASSEMBLED MEMBERS IN A CHAMBER CAPABLE OF SUSTAINING A VACUUM AND IN CLOSE PROXIMITY TO SAID ASSEMBLED MEMBERS A MAGNESIUM SOURCE COMPRISING A METAL BASE CONTAINING AT LEAST 0.8 PERCENT BY WEIGHT MAGNESIUM, SAID METAL BASE SELECTED FROM THE GROUP CONSISTING OF ALUMINUM ALLOYS AND MAGNESIUM OR MAGNESIUM ALLOYS, AND HAVING BONDED TO THE SURFACE OF SAID METAL BASE A MAGNESIUM-FREE ALUMINUM ALLOY HAVING A MELTING POINT OF AT LEAST 50*F. HIGHER THAN SAID METAL BASE, C. SUBJECTING THE ASSEMBLED MEMBERS AND SAID MAGNESIUM SOURCE TO A PRESSURE LESS THAN 10**-2 TORR OF MERCURY (ABSOLUTE), D. HEATING THE ASSEMBLED MEMBERS AND SAID MAGNESIUM SOURCE TO BRAZING TEMPERATURE SO AS TO MELT SAID BRAZING ALLOY ON THE BRAZING SHEET AND TO CAUSE SAID METAL BASE TO K DISSOLVE THE MAGNESIUM FREE CLADDING ON THE SURFACE THEREOF AND THEREBY ALLOW THE MAGNESIUM IN SAID METAL BASE TO VAPORIZE, E. MAINTAINING SAID BRAZING TEMPERATURE UNTIL SAID BRAZING ALLOY HAS FLOWED INTO CONTACT WITH SAID ALUMINUM PART IN CONTACT WITH THE BRAZING SHEET SO AS TO FORM A FILLET THEREWITH, AND F. COOLING THE ASSEMBLY TO SOLIDIFY THE BRAZING ALLOY.

Claim 4

A PROCESS FOR VACUUM BRAZING ALUMINUM PARTS COMPRISING: A. ASSEMBLING AN ALUMINUM PART TO BE JOINED IN THE DESIRED RELATIONSHIP AND IN CONTACT WITH AN ALUMINUM BRAZING SHEET HAVING A BRAZING ALLOY CLADDING, B. PLACING SAID ASSEMBLED MEMBERS IN A CHAMBER CAPABLE OF SUSTAINING A VACUUM AND IN CLOSE PROXIMITY TO SAID ASSEMBLED MEMBERS A MAGNESIUM SOURCE COMPRISING A METAL BASE CONTAINING AT LEAST 0.8 PERCENT BY WEIGHT MAGNESIUM, SAID METAL BASE SELECTED FROM THE GROUP CONSISTING OF ALUMINUM ALLOYS AND MAGNESIUM OR MAGNESIUM ALLOYS, AND HAVING BONDED TO THE SURFACE OF SAID METAL BASE A MAGNESIUM-FREE ALUMINUM ALLOY HAVING A MELTING POINT OF AT LEAST 50*F. HIGHER THAN SAID METAL BASE, C. SUBJECTING THE ASSEMBLED MEMBERS AND SAID MAGNESIUM SOURCE TO A PRESSURE LESS THAN 10**-2 TORR OF MERCURY (ABSOLUTE), D. HEATING THE ASSEMBLED MEMBERS AND SAID MAGNESIUM SOURCE TO BRAZING TEMPERATURE SO AS TO MELT SAID BRAZING ALLOY ON THE BRAZING SHEET AND TO CAUSE SAID METAL BASE TO K DISSOLVE THE MAGNESIUM FREE CLADDING ON THE SURFACE THEREOF AND THEREBY ALLOW THE MAGNESIUM IN SAID METAL BASE TO VAPORIZE, E. MAINTAINING SAID BRAZING TEMPERATURE UNTIL SAID BRAZING ALLOY HAS FLOWED INTO CONTACT WITH SAID ALUMINUM PART IN CONTACT WITH THE BRAZING SHEET SO AS TO FORM A FILLET THEREWITH, AND F. COOLING THE ASSEMBLY TO SOLIDIFY THE BRAZING ALLOY.

Claim 5

The method of claim 1 wherein said pressure is less than 5 X 10 5 Torr.

Claim 6

The method of claim 2 wherein said pressure is maintained less than 1 X 10 5 Torr.

Claim 7

The method of claim 2 wherein said assembly and magnesium source is subjected to temperatures between about 1100* and 1150*F.

Claim 8

The method of claim 1 wherein the thickness of said magnesium-free aluminum alloy ranges from about 0.00001 to about 0.25 inch.