MANUFACTURE OF MEDIUM-STRENGTH AL-MG-SI ALLOY EXTRUDED MATERIAL EXCELLENT IN AIR HARDENING PROPERTY

摘要

PROBLEM TO BE SOLVED: To provide an Al-Mg-Si alloy capabel of air hardening and showing the excellent mechanical property after aging by applying the homogenization, extrusion and aging to the cast ingot of the prescribed composition under the prescribed condition. ;SOLUTION: A cast ingot having the composition consisting of, by weight, 0.8-1.0% Mg, 0.6-0.75% Si, 0.3-0.4% Cu, 0.05-0.12% Cr, 0.05-0.3% Fe, 0.01-0.05% Ti, 0.001-0.01% B, and the balance Al, is manufactured by the DC casting method. The cast ingot in heated, and kept for 2-10 hours at 520-560°C, an homogenized through cooling to regulate the area ratio of the α phase to be 15-80%. The cast ingot is heated to 450-500°C immediately before the extrusion, and extruded to that the surface temperature of an extruded material is 500-560°C immediately after the extrusion, and force-cooled to the room temperature at the cooling speed of 80-250°C/min. at the outlet of an extruder to regulate the mean grain size of the recrystallization to be within 2 mm, then is aged by heating the extruded material for 2-15 hours at 160-200°C within 100 hours after cooling.;COPYRIGHT: (C)1998,JPO