BRAZING SHEET FOR FLUX-FREE BRAZING, METHOD FOR FLUX-FREE BRAZING AND METHOD FOR MANUFACTURING HEAT EXCHANGER

摘要

A brazing sheet for flux-free brazing has an outermost surface brazing filler metal layer, consisting of an Al—Si-based alloy containing 2 to 13% Si in mass %, and an intermediate brazing filler metal layer, consisting of an Al—Si—Mg-based alloy containing 4 to 13% Si and 0.1 to 5.0% Mg in mass %, which are cladded on one or both sides of a core material. In the outermost surface brazing filler metal layer, the number of Si particles having a circle equivalent diameter of 1.75 μm or more is 10% or more of the number having a circle equivalent diameter of 0.8 μm or more, as observed in the direction of the surface layer. The intermediate brazing filler metal layer contains less than 3000 per 10000 μm² of Si particles having a circle equivalent diameter of 0.25 μm or more, as observed in a cross section of the brazing filler metal layer.