| 摘要 |
PROBLEM TO BE SOLVED: To inexpensively provide a differential gear case having sufficient rigidity, sufficient abrasion resistance, sufficient high-temperature strength and low thermal expansion properties. SOLUTION: An aluminum alloy has a composition comprising 12.0-14.0 mass% Si, 3.5-4.5 mass% Cu, 0.3-0.5 mass% Mg, 0.2-0.3 mass% Mn, 0.1-0.2 mass% Ti, 0.003-0.015 mass% P and the balance Al with unavoidable impurities. The method for manufacturing the differential gear case comprises the steps of: melting the above aluminum alloy; degasifying the molten metal until an amount of gas in the molten metal in a holding furnace becomes 0.1 cc/100 g of Al or less; then supplying the molten metal into a die at a casting temperature of 680 to 730°C; liquid-forging the molten metal with a molding pressure of 50 to 100 MPa; solution-treating the obtained liquid-forged product at 500 to 520°C; and then aging it at 160 to 190°C for 1 to 10 hours. Thus, heat-treated aluminum alloy has a structure in which primary Si crystals have the maximum particle diameter of 20μm or smaller and eutectic Si crystals have the maximum length of 10μm or shorter. COPYRIGHT: (C)2007,JPO&INPIT
|
