PRODUCTION OF ALUMINUM HEAT EXCHANGER HAVING EXCELLENT PITTING RESISTANCE

摘要

PURPOSE:To obtain the heat exchanger having excellent pitting resistance by applying a flux prepd. by mixing Zn powder and the fluoride of K and Al with a synthetic resin binder to a specific thickness on the surface of an Al (alloy) tubular material and diffusing the Zn powder at the time of a heating treatment for brazing. CONSTITUTION:A corrugated alloy fin material consisting of a brazing sheet formed by cladding an Al-Si alloy brazing filler metal on one or both surfaces of an Al alloy core material is combined with the Al (alloy) tubular material which is extrusion molded to a straight pipe shape or is bent. The synthetic resin binder of an acrylic acid or the like is mixed with the flux essentially consisting of the Zn powder and the fluoride of the K and Al, such as K3AlF6 and the mixture is applied to 10 to 300mum thickness on the surface of the Al (alloy) tubular material. The fluoride of the K and Al in the flux extremely accelerates the diffusion of the Zn powder to the surface part of the tubular material at the time of the heating treatment for brazing and the Zn penetrates deeply into the surface part of the tubular material. The Al heat exchanger exhibits the excellent pitting resistance over a long period of time even in severe corrosive environment.