| 摘要 |
PROBLEM TO BE SOLVED: To manufacture an Al alloy capable of stably manufacturing an extruded material for extruded heat-exchanger tube excellent in corrosion resistance and having a cross section of fine structure by providing a specific composition which consists of Si, Cu, Ti, Fe, Zn, Zr, and the balance Al with inevitable impurities and in which the value of Fe/Si is regulated to a specific value or above. SOLUTION: This Al alloy has a composition consisting of, by weight, <=0.15% Si, 0.35-0.55% Cu, 0.003-0.010% Ti, 0.15-0.35% Fe, <0.03% Zn, 0.02-<0.05% Zr, and the balance Al with inevitable impurities and satisfying Fe/Si >=2.5. A semi-continuously cast billet of the above composition is subjected to temp. raise at (50 to 300) deg.C/hr heating rate and to homogenizing treatment at 500 to 610 deg.C for 0.5 to 8 hr. Subsequently, cooling is applied at (200 to 500) deg.C/hr cooling rate to finely precipitate an intermetallic compound containing Zr and Fe. After preheating, the billet is extruded and controlled so that the size of recrystallized grains after extrusion becomes <=30μm by which the surface condition and quality of the extruded material can be improved.
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