Wear-resistant aluminum alloy for casting engine blocks with linerless cylinders

Abstract

An aluminum-silicon alloy composition is disclosed which meets the manufacturing and performance conditions for linerless cylinder engine block casting using low-cost casting processes such as silica-sand molds. The alloy of the invention comprises in weight percent: 13%-14% Si; 2.3%-2.7% Cu; 0.1%-0.4% Fe; 0.1%-0.45% Mn; 0.1%-0.30% Mg; 0.1%-0.6% Zn; 0.05%-0.11 % Ti; 0.4%-0.8% Ni; 0.01%-0.09% Sr; and and the rest being aluminum plus any remainders. This alloy has very good machining characteristics, giving a significantly improved surface finish in the cylinder bores. The manufacturing cost of engine blocks is reduced in about 40% as compared with using current commercial alloys of the prior art requiring iron liners. Any primary Si present is substantially uniformly dispersed, and copper does not segregate during solidification and cooling.

1 . An abrasion resistant aluminum alloy comprising (in weight percent):
 13%-14% Si;   2.3%-2.7% Cu;   0.1%-0.4% Fe;   0.1%-0.45% Mn;   0.1%-0.30% Mg;   0.1%-0.6% Zn;   0.05%-0.11% Ti;   0.4%-0.8% Ni;   0.01%-0.09% Sr; and   the balance being predominately aluminum plus any remainders.   
   
   
       2 . In a method for producing a complex aluminum engine linerless cylinder block casting, the improvement comprising use of an Al—Si alloy to form such casting having a composition according to  claim 1 . 
   
   
       3 . The method according to  claim 2 , comprises forming said casting in a silica sand mold with silica sand cores and wherein said casting after solidification has a microstructure where any primary Si present is substantially uniformly dispersed. 
   
   
       4 . The method according to  claim 3 , wherein said molten alloy is poured in said silica sand mold at a temperature between about 760° C. to about 780° C. 
   
   
       5 . An abrasion resistant aluminum alloy comprising (in weight percent):
 13%-14% Si;   2.3%-2.7% Cu;   0.1%-0.4% Fe;   0.1%-0.45% Mn;   0.1%-0.30% Mg;   0.1%-0.6% Zn;   0.05%-0.11% Ti;   0.4%-0.8% Ni;   0.01%-0.09% Sr; and   the balance being essentially aluminum.   
   
   
       6 . A method for producing a casting of an Al—Si alloy having a composition according to  claim 5 , for manufacturing an aluminum alloy engine block with cylinder bores having a surface with improved wear resistance made of the same aluminum alloy so as to withstand the operation of said engine block without cylinder liners; said method comprising: providing a silica sand mold with silica sand cores and chill means for causing said alloy to solidify in a controlled direction and solidification rate, such that said casting after solidification has a microstructure wherein any primary Si present is substantially uniformly dispersed; introducing said alloy as a molten metal into said mold to form said engine block casting. 
   
   
       7 . The method according to  claim 6 , wherein said chilling means is a metallic mass having a weight such that the ratio of chill weight to casting weight is in the range between 1 to 5. 
   
   
       8 . The method according to  claim 6 , wherein said cooling rate is in the range from about 0.3 to 3.0° C./s. 
   
   
       9 . The method according to  claim 7 , wherein said cooling rate is in the range from about 0.3 to 3.0° C./s. 
   
   
       10 . The method according to  claim 6 , wherein said molten alloy is poured in said silica sand mold at a temperature from about 760° C. to about 780° C. 
   
   
       11 . The method according to  claim 7 , wherein said molten alloy is poured in said silica sand mold at a temperature between about 760° C. to about 780° C. 
   
   
       12 . The method according to  claim 8 , wherein said molten alloy is poured in said silica sand mold at a temperature between about 760° C. to about 780° C. 
   
   
       13 . The method according to  claim 9 , wherein said molten alloy is poured in said silica sand mold at a temperature between about 760° C. to about 780° C. 
   
   
       14 . The method according to  claim 6 , wherein said molten alloy is poured in said silica sand mold at a temperature between about 755° C. and about 765° C. 
   
   
       15 . The method according to  claim 9 , wherein said molten alloy is poured in said silica sand mold at a temperature between about 755° C. and about 765° C. 
   
   
       16 . A cast article made from an aluminum-silicon alloy having improved wear resistance characteristics suitable for manufacturing engine blocks with cylinder bores having a surface with improved wear resistance made of the same aluminum alloy so as to withstand the operation of said engine block without cylinder liners; said cast article having the following composition by weight:
 13%-14% Si;   2.3%-2.7% Cu;   0.1%-0.4% Fe;   0.1%-0.45% Mn;   0.1%-0.30% Mg;   0.1%-0.6% Zn;   0.05%-0.11% Ti;   0.4%-0.8% Ni;   0.01%-0.09% Sr; and   the balance being essentially aluminum.