METHOD FOR MANUFACTURING HEAT TREATMENT TYPE ALUMINUM ALLOY MATERIAL FOR COLD WORKING SUPERIOR IN MACHINABILITY

摘要

PROBLEM TO BE SOLVED: To provide an aluminum alloy material for cold working, which inhibits the proceeding of natural aging, and has superior machinability and appearance even after being cold-worked.;SOLUTION: The aluminum alloy material includes 0.4-1.3 mass% Si, 0.4-1.3 mass% Mg, 0.1-0.5 mass% Cu, 0.1-0.5 mass% Fe and 0.04-0.4 mass% Cr, while controlling a mass ratio of Mg/Si to 0.6 to 1.4. The manufacturing method comprises adding the holding step of heating it within 24 hours to 80 to 150°C at a heating rate of 10°C/minute or higher, holding it at the temperature for 5 to 600 seconds, and then cooling it to ordinary temperature at a cooling rate of 10°C/minute or higher, between the steps of solution-heating the alloy material and cold working it. The addition of the holding step inhibits the proceeding of the natural aging, and the age hardening after cold working inhibits the degradation of dimensional accuracy and also enhances cold workability. The mass ratio of Mg/Si controlled to 0.6 to 1.4 crystallizes and/or precipitates hard Si particles in addition to Mg₂Si particles, makes them work as starting points of chip parting, and improves the machinability.;COPYRIGHT: (C)2005,JPO&NCIPI