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 . Aluminum alloy castings produced by die casting using an aluminum alloy, the aluminum alloy 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;   an Mn/Fe ratio is 1.5 or more;   an amount of Cu is controlled to 0.5% by weight or less;   amounts of Zn, Ni and Sn as unavoidable impurities are controlled to 0.05% by weight or less;   amounts of Pb and Bi as unavoidable impurities are controlled to 0.005% by weight or less;   the remainder of the aluminum alloy is aluminum and unavoidable impurities; wherein   each of the aluminum alloy castings comprise:   a radiator fin of an electrical heat-generating part; wherein the radiator fin has a plurality of thin-walled fins integrally formed on both top and bottom surfaces of a plate-like substrate; and   a circular mounting hole extends through a flat portion of the plate-like substrate having no thin-walled fin formed on the flat portion; wherein the electrical heat-generating part has a cylindrical profile and is fixed in the circular mounting hole by press-fitting.   
     
     
         2 . The aluminum alloy castings according to  claim 1 , wherein the aluminum alloy further comprises at least one impurity selected from the group consisting of Ti, B, Zr, Sr, Ca, Na and Sb. 
     
     
         3 . The aluminum alloy castings according to  claim 1 , wherein an upper limit of the Mn/Fe is 5.0 or less. 
     
     
         4 . The aluminum alloy castings according to  claim 1 , wherein a portion of the plate-like substrate having the plurality of thin-walled fins having a minimum plate thickness of 0.5 to 1.5 mm. 
     
     
         5 . The aluminum alloy castings according to  claim 1 , wherein the electrical heat-generating part is a diode. 
     
     
         6 . A production process for producing the aluminum alloy castings according to  claim 1 , comprising:
 a decompression step, in which a mold is closed and an 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.   
     
     
         7 . A producing process for producing the aluminum alloy castings according to  claim 1 , comprising:
 a venting step, in which a 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 air 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.   
     
     
         8 . Aluminum alloy castings produced by die casting using an aluminum alloy, the aluminum alloy 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;   an Mn/Fe ratio is 1.5 or more;   an amount of Cu is controlled to 0.5% by weight or less;   amounts of Zn, Ni and Sn as unavoidable impurities are controlled to 0.05% by weight or less;   amounts of Pb and Bi as unavoidable impurities are controlled to 0.005% by weight or less;   the remainder of the aluminum alloy is aluminum and unavoidable impurities; wherein   each of the aluminum alloy castings comprise:   a radiator fin of an electrical heat-generating part; wherein the radiator fin has a plurality of thin-walled fins integrally formed on both top and bottom surfaces of a plate-like substrate; and   a circuit mounting hole extend through a flat portion of the plate-like substrate having no thin-walled fin formed on the flat portion, wherein the electrical heat-generating part has a cylindrical profile and is fixed in the circular mounting hole by caulking.   
     
     
         9 . The aluminum alloy castings according to  claim 8 , wherein the aluminum alloy further comprises at least one impurity selected from the group consisting of Ti, B, Zr, Sr, Ca, Na and Sb. 
     
     
         10 . The aluminum alloy castings according to  claim 8 , wherein an upper limit of the Mn/Fe is 5.0 or less. 
     
     
         11 . The aluminum alloy castings according to  claim 8 , wherein a portion of the plate-like substrate has the plurality of thin-walled fins having a minimum plate thickness of 0.5 to 1.5 mm. 
     
     
         12 . The aluminum alloy castings according to  claim 8 , wherein the electrical heat-generating part is a diode. 
     
     
         13 . A production process for producing the aluminum alloy castings according to  claim 8 , comprising:
 a decompression step, in which a mold is closed and an 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.   
     
     
         14 . A producing process for producing the aluminum alloy castings according to  claim 8 , comprising:
 a venting step, in which a 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 air 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.