Aluminum alloy for die castings and production process of aluminum alloy castings

Abstract

The present invention provides an aluminum alloy for die castings that has superior castability and corrosion resistance. The amounts of Mn, Fe and Cu contained in the aluminum alloy components for die castings were determined to have a considerable effect on the corrosion resistance of the aluminum alloy. Therefore, the aluminum alloy for die castings of the present invention contains 9.0 to 12.0% by weight of Si, 0.20 to 0.80% by weight of Mg, and 0.7 to 1.1% by weight of Mn+Fe, the Mn/Fe ratio is 1.5 or more, the amount of Cu as impurity is controlled to 0.5% by weight or less, and the remainder is composed of aluminum and unavoidable impurities.

1 . An aluminum alloy for die castings comprising 9.0 to 12.0% by weight of Si, 0.20 to 0.80% by weight of Mg, and 0.7 to 1.1% by weight of Mn+Fe; wherein, 
 the Mn/Fe ratio is 1.5 or more, and    the amount of Cu as impurity is controlled to 0.5% by weight or less, and the remainder is composed of aluminum and unavoidable impurities.    
   
   
       2 . An aluminum alloy for die castings according to  claim 1 , wherein one or more types of Ti, B, Zr, Sr, Ca, Na or Sb is contained as impurity.  
   
   
       3 . An aluminum alloy for die castings according to  claim 1 , wherein the upper limit of the Mn/Fe ratio is 5.0 or less.  
   
   
       4 . A production process for producing aluminum alloy castings using the aluminum alloy for die castings according to  claim 1  comprising: 
 a decompression step, in which the mold is closed and the inside of the mold is decompressed to at least a predetermined pressure that is lower than atmospheric pressure, and    a melt filling step, in which a melt of the aluminum alloy is filled into the mold after the decompression step.    
   
   
       5 . A production process for producing aluminum alloy castings using the aluminum alloy for die castings according to  claim 1  comprising: 
 a venting step, in which the mold is closed and air inside the mold is vented,    an atmospheric adjustment step, in which oxygen is supplied to the mold after the venting step to replace the inside of the mold with an oxygen atmosphere, and    a melt filling step, in which a melt of the aluminum alloy is filled into the mold after the atmospheric adjustment step.    
   
   
       6 . Aluminum alloy castings produced using the aluminum alloy for die castings according to  claim 1 , the castings having thin-walled fins in which the plate thickness of the portion having the minimum plate thickness is 0.5 to 1.5 mm.  
   
   
       7 . Aluminum alloy castings produced using the aluminum alloy for die castings according to  claim 1 , the castings having a coupling that is coupled to another part by press-fitting or caulking.