ALUMINUM ALLOY BRAZING SHEET FOR VACUUM BRAZING AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To provide an aluminum alloy brazing sheet for vacuum brazing, having extremely excellent corrosion resistance by allowing a Zn-concentrated surface layer formed by diffusion of Zn in the surface of a core material to exhibit a sacrificial anode effect even after Zn in a brazing filler metal is evaporated at the time of vacuum brazing. SOLUTION: The aluminum alloy brazing sheet for vacuum brazing has a core material composed of aluminum or aluminum alloy material and an Al-Si-Mg or Al-Si-Mg-Bi alloy brazing filler metal laminated on one side or both sides of the core material. The core material has a Zn concentrated surface layer of >=0.3 wt.% Zn concentration in >=100μm thickness, from the interface between the brazing filler metal on one side and the core material toward the central side of plate thickness of the core material. This Zn concentrated surface layer can be formed by laying the brazing filler metal composed of Al-Si-Mg or Al-Si-Mg-Bi alloy having 2.5-7.0 wt.% Zn concentration on the core material to clad the core material with the brazing filler metal and then performing heating at 430-460 deg.C for 180-240 min to allow Zn from the brazing filler metal into the core material.