MANUFACTURE OF ALUMINUM ALLOY FOR EXTRUDED HEAT-EXCHANGER TUBE WITH FINE CROSS-SECTIONAL STRUCTURE AND EXTRUDED HEAT-EXCHANGER TUBE WITH FINE CROSS-SECTIONAL STRUCTURE

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)°C/hr heating rate and to homogenizing treatment at 500 to 610°C for 0.5 to 8 hr. Subsequently, cooling is applied at (200 to 500)°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 ≤30 μm by which the surface condition and quality of the extruded material can be improved.;COPYRIGHT: (C)1999,JPO