JPS57198257A - Heat exchanger core made of aluminum - Google Patents

Abstract

PURPOSE:To obtain heat exchanger cores of a long life in the stage of brazing liquid flow pipes using a noncorrosive flux and cooling fins in a furnace, by forming Zn diffusion layers that prevent pitting on the outside surfaces of the liquid flow pipes. CONSTITUTION:Liquid flow pipes 2 of an Al material A1050 and cooling fins 3 of core and skin materials of the same A3003, A4045 are used. Zn-diffusion layers 5 of >=50mu diffusion depth and 2.5-10% concns. of surface Zn are carried out by plating or the like on the outside surfaces of the pipes 2. Many of the pipes 2 and the fins 3 are alternately superposed, seat plates 4, 4' are provided at both ends and these are tentatively assembled. These are subjected to a flux treatment wherein they are immersed in an aq. flux soln. of KAlF4-K3AlF6, after which they are heated in a furnace, whereby all the elements are brazed to each other. Then, the layers 5 act as sacrifice electrodes and since the corrosion of the core materials takes place after the entire part of the layers 5 is sacrificially corroded, a longer life is provided. If the diffusion depth of the layers 5 is insufficient, defective brazing, etc. will result, and said layers are too thin for the sacrifice corrosion layers. If the concn. of Zn is below the lower limit, there is a problem in corrosion resistance on account of electrolytic corrosion during brazing and in excess of the upper limit, corrosion resistance is not improved.