Aluminum alloy for microporous hollow material which has excellent extrudability and grain boundary corrosion resistance, and method for producing same

Abstract

As an aluminum alloy for a microporous hollow material, an aluminum alloy is provided which contains Cu, which is an element having poor grain boundary corrosion resistance, in a reduced amount, can have a nobly kept spontaneous potential, contains a transition metal that does not adversely affect extrudability of the material, and has excellent corrosion resistance and extrudability. An aluminum alloy having a chemical composition comprising, in mass%, 0.05 to 0.20% of Fe, 0.10% or less of Si, 0.15 to 0.32% of Cu, 0.08 to 0.15% of Mn, 0.05% or less of Zr, 0.06 to 0.15% of Ti, 0.03% or less of Cr, and a remainder made up by Al and unavoidable impurities, wherein the amount of a gas in an alloy billet is 0.25 cc / 100 g or less; and a method for producing an aluminum alloy, comprising producing a DC cast billet having the above-mentioned chemical composition by a melt treatment employing proper casting conditions so that the content of a gas in the DC cast billet can be reduced to 0.25 cc / 100 g or less, and then subjecting the DC cast billet to a soaking treatment, wherein the soaking treatment comprises heating the DC cast billet to 550 to 590 DEG C at a rate of 80 DEG C / hour or less, then holding the heated DC cast billet at that temperature for 0.5 to 6 hours, and then holding the resultant product at a temperature falling within the range from 450 to 350 DEG C for 0.5 to 1 hour or cooling the resultant product to 200 DEG C or lower at a cooling rate of 50 DEG C / hour.

Description

technical field [0001] The present invention relates to an aluminum alloy excellent in extrudability and intergranular corrosion resistance used in extruded micropore hollow flat tubes constituting aluminum heat exchangers such as condensers, evaporators, and intercoolers, and its manufacture method. Background technique [0002] Typically, aluminum heat exchangers such as figure 1 The illustrated condenser for an automobile air conditioner consists of flat tubes 1 ( figure 2 (a)) The corrugated fins 2 that exchange heat with the air, the header 3 as the container part, and the inlet and outlet parts 4 are composed, and there is a brazing part (solder) between any parts that are connected to each other, and a non-corrosive flux is used. For brazing joints ( figure 2 (b)). [0003] Aluminum heat exchangers require high durability, and of course extruded flat tubes as components also require corrosion resistance, strength, brazability, extrudability, and the like. [00...

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Problems solved by technology

[0007] However, in such a method of coating the surface of the flat tube with Zn metal, the Zn concentration of the Zn diffusion layer increases, and the Zn diffusion layer portion including the junction with the heat sink is consumed early instead, resulting in a decrease in the performance of the heat exchanger. technical issues

[0008] Although many such aluminum alloys for extruded flat tubes requiring extrudability and intergranular corrosion resistance have been proposed, no satisfactory solution has been realized so far.

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