Aluminum alloy for high pressure die-casting, subordinate frame for automobile, and high pressure die-casting method

Abstract

An aluminum alloy for die-casting capable of being used in high pressure die-casting method, and capable of providing a product having a sufficiently high strength and elongation without T6 treatment after casting and endurable under a corrosive atmosphere. Such aluminum alloy is used as a material of a subordinate frame for an automobile. The aluminum alloy contains from 8.0 to 9.0 mass % of Si, from 0.35 to 0.45 mass % of Mg, from 0.3 to 0.4 mass % of Mn, from 0.002 to 0.008 mass % of Be, less than 0.20 mass % of Fe, not more than 0.2 mass % of Cu, not more than 0.1 mass % of Zn, not more than 0.1 mass % of Ni, not more than 0.1 mass % of Sn, and remainders of Al and inevitable impurities. High pressure die casting is performed with this alloy by a die-casting machine provided with a seal ring disposed over a plunger tip, liquidized gaskets, a sealing rubber and a pin seal plate those being capable of providing high seal-ability and high vacuum in a mold cavity.

What is claimed is:  
     
         1 . An aluminum alloy for high pressure die-casting containing from 8.0 to 9.0 mass % of Si, from 0.35 to 0.45 mass % of Mg, from 0.3 to 0.4 mass % of Mn, from 0.002 to 0.008 mass % of Be, less than 0.20 mass % of Fe, not more than 0.2 mass % of Cu, not more than 0.1 mass % of Zn, not more than 0.1 mass % of Ni, not more than 0.1 mass % of Sn, and remainders of Al and inevitable impurities.  
     
     
         2 . A subordinate frame for an automobile produced through high pressure die-casting method, the subordinate frame being made from an aluminum alloy containing from 8.0 to 9.0 mass % of Si, from 0.35 to 0.45 mass % of Mg, from 0.3 to 0.4 mass % of Mn, from 0.002 to 0.008 mass % of Be, less than 0.20 mass % of Fe, not more than 0.2 mass % of Cu, not more than 0.1 mass % of Zn, not more than 0.1 mass % of Ni, not more than 0.1 mass % of Sn, and remainders of Al and inevitable impurities.  
     
     
         3 . A high pressure die-casting method including the steps of: 
 using an aluminum alloy containing from 8.0 to 9.0 mass % of Si, from 0.35 to 0.45 mass % of Mg, from 0.3 to 0.4 mass % of Mn, from 0.002 to 0.008 mass % of Be, less than 0.20 mass % of Fe, not more than 0.2 mass % of Cu, not more than 0.1 mass % of Zn, not more than 0.1 mass % of Ni, not more than 0.1 mass % of Sn, and remainders of Al and inevitable impurities;    injecting the aluminum alloy into a mold cavity; and    evacuating the mold cavity by means of highly vacuum gas vent means to a level not more than 10 kPa during the injection step.