ALUMINIUM ALLOY EXTRUDED MATERIAL WITH SUPERIOR MACHINABILITY AND PRODUCTION METHOD THEREFOR

摘要

Provided is an Al-Mg-Si based aluminium alloy extruded material with a smooth surface without hindering productivity and without seizing. In the present invention, an aluminium alloy billet comprising Si: 2.0 to 6.0 mass%, Mg: 0.3 to 1.2 mass%, Ti: 0.01 to 0.2 mass%, a Fe content limited to at most 0.2 mass% and the remainder comprising Al and inevitable impurities is subjected to homogenization maintained for 4 to 15 hours at 500 to 550 °C; forced to cool to a temperature of at most 250 °C at an average cooling rate of at least 50 °C/hour; heated to 450 to 500 °C; and subjected to hot extrusion at an extrusion rate of 3 to 10 m/min. The extruded material is forced to cool at an average cooling rate of at least 50 °C/second and subjected to an ageing treatment. This enables production of an extruded material with a surface having a ten-point average roughness Rz of at most 80 μm.