Solidification microstructure of aggregate molded shaped castings

Abstract

A shaped metal casting made in an aggregate mold comprises fine solidification microstructure that is finer than the solidification microstructure of an analogous metal casting made from conventional molding processes. The solidification microstructure may be up to five times finer than the solidification microstructure of a conventionally prepared casting. In preferred embodiments, as a result of directional solidification, the fine solidification microstructure is substantially continuous from a distal end of the casting to a proximal end of the casting, and exhibits greatly enhanced soundness. Because of the control of the uniformity of freezing of the casting, its properties are substantially uniform.

1 . A shaped metal casting formed in a mold comprising an aggregate by an ablation casting process, the casting comprising a fine solidification microstructure that is finer than the microstructure of a casting having a similar metal of a similar weight or section thickness that is produced by a conventional aggregate molded casting process, wherein the fine microstructure comprises one or more of grains, dendrites, eutectic phases or combinations thereof. 
   
   
       2 . The shaped metal casting according to  claim 1 , wherein the fine solidification microstructure is about five times finer than the microstructure of a casting of a similar metal that is produced by a conventional aggregate casting process. 
   
   
       3 . The shaped metal casting according to  claim 1 , wherein the casting comprises about 100% fine solidification microstructure. 
   
   
       4 . The shaped metal casting according to  claim 1 , wherein the fine solidification microstructure is continuous from a distal end of the casting to a proximal end thereof. 
   
   
       5 . The shaped metal casting according to  claim 1 , wherein the fine solidification microstructure is substantially continuous from a distal end of the casting to a proximal end thereof. 
   
   
       6 . The shaped metal casting according to  claim 1 , wherein the casting is substantially free of porosity. 
   
   
       7 . The shaped metal casting according to  claim 1 , further comprising a dual solidification microstructure region comprising (i) a coarse solidification microstructure portion, and (ii) a fine solidification microstructure portion interspersed within the coarse solidification microstructure portion. 
   
   
       8 . The shaped metal casting according to  claim 7 , wherein the dual solidification microstructure region is substantially continuous from a distal end of the casting to a proximal end thereof. 
   
   
       9 . A metal casting formed in a mold comprising an aggregate via a rapid cooling process and exhibiting a cast microstructure, the microstructure comprising: a first region located adjacent a surface of the metal casting, the first region comprising a coarse solidification microstructure; and a second region located internal to the first region, the second region comprising a fine solidification microstructure. 
   
   
       10 . The metal casting according to  claim 9 , wherein the second region is substantially continuous from a distal end of the casting to a proximal end thereof. 
   
   
       11 . The metal casting according to  claim 9 , wherein the fine solidification microstructure of the second region is finer than a fine solidification microstructure of a casting of a similar metal having a similar weight or section thickness that is formed by a conventional aggregate casting process. 
   
   
       12 . The metal casting according to  claim 9 , wherein the second region comprises dendrites having a dendrite arm spacing of about 20 micrometers or less. 
   
   
       13 . The metal casting of  claim 9 , wherein the second region comprises dendrites having a dendrite arm spacing of about 5 to about 15 micrometers. 
   
   
       14 . The metal casting of  claim 9 , wherein the first region comprises dendrites having a dendrite arm spacing of about 20 to about 200 micrometers. 
   
   
       15 . The metal casting of  claim 9 , wherein the casting is substantially free of at least one of (i) shrinkage porosity, and (ii) damaging iron-rich platelets. 
   
   
       16 . The metal casting of  claim 9 , wherein the first region comprises approximately 100% course solidification microstructure, and the second region comprises approximately 100% fine solidification microstructure. 
   
   
       17 . The metal casting of  claim 16  further comprising a third region located between the first and second regions, wherein the third region comprises a dual solidification microstructure comprising (i) one or more coarse solidification microstructure portions, and (ii) one or more fine solidification microstructure portions. 
   
   
       18 . The metal casting of  claim 17 , wherein the one or more coarse solidification microstructure portions of the dual solidification microstructure region comprises dendrites having a dendrite arm spacing of about 20 to about 200 micrometers and the one or more fine solidification microstructure portions of the dual solidification microstructure region comprises dendrites having a dendrite arm spacing of about 15 micrometers or less. 
   
   
       19 . The metal casting of  claim 17  wherein the third region is substantially continuous throughout a shape of the metal casting. 
   
   
       20 . A metal casting formed from a eutectic-containing alloy, the casting comprising a dual solidification microstructure region, wherein the dual solidification microstructure region comprises (i) one or more fine dendrite portions; and (ii) one or more fine eutectic portions. 
   
   
       21 . The metal casting of  claim 20  further comprising a coarse solidification microstructure region located between the dual solidification microstructure region and a surface of the metal casting. 
   
   
       22 . The metal casting of  claim 21  further comprising a fine solidification microstructure region located adjacent the dual solidification microstructure region. 
   
   
       23 . The metal casting of  claim 20 , wherein the one or more fine dendrite portions has a dendrite arm spacing of about 5 to about 30 micrometers, and the one or more fine eutectic portions has a dendrite arm spacing of 1 micrometer or less. 
   
   
       24 . The metal casting of  claim 20 , wherein the casting is substantially free of shrinkage porosity. 
   
   
       25 . The metal casting of  claim 20 , wherein the casting is substantially free of damaging iron-rich platelets. 
   
   
       26 . A shaped metal casting made in a mold comprising an aggregate, the casting comprising a dual solidification microstructure region, wherein the dual solidification microstructure region comprises: at least one coarse solidification microstructure portion having a dendrite arm spacing in the range of about 50 to about 200 micrometers; and at least one fine solidification microstructure portion having a dendrite arm spacing of less than about 15 micrometers. 
   
   
       27 . The metal casting of  claim 26 , wherein the at least one fine solidification microstructure region is substantially continuous from a distal end of the metal casting to a proximal end thereof. 
   
   
       28 . The metal casting of  claim 26 , wherein the at least one fine solidification microstructure region comprises a first fine solidification microstructure region located adjacent a distal end of the metal casting and a second fine solidification microstructure region located adjacent a proximal end thereof. 
   
   
       29 . The metal casting of  claim 26 , further comprising a substantially continuous fine solidification microstructure region internal to and distinct from the dual solidification microstructure region. 
   
   
       30 . The metal casting of  claim 26 , wherein the at least one fine solidification microstructure portion has a dendrite arm spacing in the range of about 5 to 15 micrometers. 
   
   
       31 . The metal casting of  claim 26 , wherein the casting is substantially free of at least one of (i) shrinkage porosity, and (ii) damaging iron-rich platelets.