Flux-free aluminum brazing sheet

Abstract

The invention provides an aluminum brazing sheet for fluxless brazing, which is used for brazing in a non-oxidizing atmosphere without using a flux and without a reduced pressure. Al-Si-Mg-Bi series solder coatings containing 0.01 to 2.0% of Mg, 1.5 to 14.0% of Si, and 0.05 to 1.5% of Bi by mass% is located on the outermost surface by covering one or both sides of the core material. The Mg-Bi-based compound contained in the Al-Si-Mg-Bi-based solder has an equivalent circle diameter of 0.01 [mu] m or more and less than 5. There are more than 10 Mg-Bi compounds with a diameter of 0 [mu] m in thefield of view per 10,000 [mu] m2; The field of view of 10,000 m2 is less than two. When the particles of Bi element contained in the brazing material are viewed from the surface layer surface beforebrazing, the particles of Bi element having a diameter of 5.0 [mu] m or more in terms of equivalent circle diameter per 10,000 [mu] m2 Field of view is less than 5.

Description

technical field

[0001] The present invention relates to an aluminum brazing sheet for fluxless brazing that is joined by fluxless. Background technique

[0002] With regard to heat exchangers for automobiles made of aluminum such as radiators, the aluminum material has become thinner and stronger in line with the previous miniaturization and weight reduction. In the manufacturing process of aluminum heat exchangers, brazing is performed to join the joints, but in the current mainstream brazing method using fluoride-based fluxes, the fluxes are not activated because they react with Mg in the material In addition, poor brazing is likely to occur, so the utilization of Mg-added high-strength components is limited. Therefore, a brazing method for joining Mg-added aluminum alloys without using flux is desired.

[0003] In flux-free soldering using Al-Si-Mg solder, the Al oxide film (Al 2 o 3 ) undergo reductive decomposition to join. In closed surface joints, etc., the joint...

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