Sand casting a diesel piston with an as-cast, reentrant combustion bowl

Abstract

A diesel engine piston and a method of making the piston. The method involves casting the piston with complex geometries, including undercut features. The casting uses an aggregate disposable mold that can be removed from the as-cast part. In one form, the complex geometry includes an undercut combustion bowl formed in the piston dome, while in another, it may include an internal cooling passage. The undercut bowl and internal passages may be produced using the aggregate disposable mold.

1 . A method of making a diesel piston comprising:
 providing a pattern for the piston, the pattern including a dome and a reentrant bowl;   forming a piston mold around the pattern, the mold comprising an aggregate material and a binder;   removing the pattern from the piston mold;   introducing molten metal into the piston mold;   contacting the piston mold with a solvent for the binder and removing the binder and the aggregate;   cooling the molten metal; and   solidifying the molten metal to form the piston with the dome and the reentrant bowl without need for post-casting processing.   
     
     
         2 . The method of  claim 1  wherein the binder is water soluble, and wherein the solvent is water. 
     
     
         3 . The method of  claim 1  wherein cooling the molten metal and solidifying the molten metal are controlled separately. 
     
     
         4 . The method of  claim 3  wherein cooling the molten metal and solidifying the molten metal are controlled separately by applying the solvent to one area of the piston before other areas or by applying different amounts of solvent to different areas of the piston. 
     
     
         5 . The method of  claim 1  wherein the aggregate material is silica sand, zircon sand, chromite sand, ceramic micro spheres, or combinations thereof. 
     
     
         6 . The method of  claim 1  wherein cooling the molten metal comprises contacting a shell of solidified metal around the molten metal with the solvent. 
     
     
         7 . The method of  claim 1  further comprising:
 providing a mold for an internal cooling passage, the mold for the internal cooling passage comprising a second aggregate material and a second binder; 
 placing the mold for the internal cooling passage in the piston mold before introducing the molten metal into the piston mold; and 
 contacting the mold for the internal cooling passage with a solvent for the second binder and removing the second binder and the second aggregate. 
 
     
     
         8 . The method of  claim 6  wherein the second aggregate material and the second binder are the same as the aggregate material and the binder for the piston mold. 
     
     
         9 . The method of  claim 1  wherein contacting the piston mold with a solvent for the binder comprises spraying the piston mold with the solvent. 
     
     
         10 . A method of making a diesel piston comprising:
 providing a pattern for the piston, the pattern including a dome and a reentrant bowl;   forming a piston mold around the pattern, the mold comprising an aggregate material and a water-soluble binder;   removing the pattern from the piston mold;   introducing molten metal into the piston mold;   contacting the piston mold with water and removing the binder and the aggregate;   cooling the molten metal; and   solidifying the molten metal to form the piston with the dome and the reentrant bowl without need for post-casting processing.   
     
     
         11 . The method of  claim 10  wherein cooling the molten metal and solidifying the molten metal are controlled separately. 
     
     
         12 . The method of  claim 11  wherein cooling the molten metal and solidifying the molten metal are controlled separately by applying water to one area of the piston before other areas or by applying different amounts of water to different areas of the piston. 
     
     
         13 . The method of  claim 10  wherein the aggregate material is silica sand, zircon sand, chromite sand, ceramic micro spheres, or combinations thereof. 
     
     
         14 . The method of  claim 10  wherein cooling the molten metal comprises contacting a shell of solidified metal around the molten metal with water. 
     
     
         15 . The method of  claim 10  further comprising:
 providing a mold for an internal cooling passage, the mold for the internal cooling passage comprising a second aggregate material and a second binder; 
 placing the mold for the internal cooling passage in the piston mold before introducing the molten metal into the piston mold; and 
 contacting the mold for the internal cooling passage with a solvent for the second binder and removing the second binder and the second aggregate. 
 
     
     
         16 . The method of  claim 15  wherein the second aggregate material and the second binder are the same as the aggregate material and the binder for the piston mold. 
     
     
         17 . The method of  claim 10  wherein contacting the piston mold with water comprises spraying the piston mold with water.