HIGH-STRENGTH ALUMINUM ALLOY MATERIAL FOR WHEEL RIM AND PROCESS FOR PREPARING THE SAME

摘要

An aluminum alloy material comprising 3.0 to 4.0 % by weight of Mg, 0.5 to 1.0 % of Mn, and 0.05 to 0.3 % by weight of Zr with the balance consisting of Al and unavoidable impurities, the volume fraction of a subgrain structure after finish annealing being 50 to 90 vol %. It may further contain at least one of 0.01 to 0.5 % by weight of Cu and 0.05 to 0.5 % by weight of Cr. An alloy ingot having this composition is soaked in the temperature range of from 430 to 480 °C and subjected to controlled hot rolling with the final rolling temperature being 150 to 250 °C to prepare the above aluminum alloy material. After the hot rolling, the aluminum alloy material is cold-rolled with a reduction ratio of not less than 20 % to a predetermined sheet thickness and then subjected to finish annealing. This provides a high-strength aluminum alloy material for wheel rims having a high fatigue strength and excellent moldability and corrosion resistance.