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Growth order system manner of the oxide film at the time of heat treatment of the aluminum or aluminum alloy material and growth of the oxide film in the time of heat treatment order are controlled the aluminum or aluminum alloy material and its manufacturing method
Growth order system manner of the oxide film at the time of heat treatment of the aluminum or aluminum alloy material and growth of the oxide film in the time of heat treatment order are controlled the aluminum or aluminum alloy material and its manufacturing method
PURPOSE:To remarkably inhibit the growth of an oxide film even if an Al or Al-alloy material is subjected to subsequent heating treatment at high temp. by previously allowing fluorine to exist in a surface oxide film. CONSTITUTION:An Al or Al-alloy material is treated with an F- ion-containing solution in which the proportion of F is regulated to =about 100ppm and also pH is regulated to =about 5, by which F is allowed to exist desirably by =about 0.01atomic% in the surface oxide film of the above Al or Al-alloy alloy material. Further, it is desirable that F in the above oxide film forms a complex compound together with the oxide film. By the above method, at the time, e.g., of joining fins and tubes composed of the Al-alloy material by means of brazing to assemble a heat exchanger, remarkable growth of the oxide film on the surface of the Al-alloy material can be prevented at the time of the above brazing operation. Accordingly, a superior heat exchanger having high joining strength between fins and tubes can be provided.
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