Method of manufacturing precision cast parts for vehicle exhaust systems

Abstract

A method of manufacturing precision cast parts for vehicle exhaust systems includes fabricating a model of a product to be manufactured using a substance selected from the group consisting of a wax and a plastic, forming a first coating layer on a surface of the model using a first slurry, forming a second coating layer on the surface of the model coated with the first coating layer using a second slurry, drying the first and second coating layers to form a mold and heating the mold to remove the model, pre-heating the mold, placing the mold in a ceramic box with a top portion open, and filling an inner part of the ceramic box with ceramic balls, and producing a product by injecting a molten metal into the mold to cast the product.

What is claimed is: 
     
         1 . A method of manufacturing precision cast parts for vehicle exhaust systems, comprising:
 fabricating a model of a product to be manufactured using a substance selected from the group consisting of a wax and a plastic;   forming a first coating layer on a surface of the model using a first slurry;   forming a second coating layer on the surface of the model coated with the first coating layer using a second slurry;   drying the first and second coating layers to form a mold and heating the mold to remove the model;   pre-heating the mold, placing the mold in a ceramic box with a top portion open, and filling an inner part of the ceramic box with ceramic balls; and   producing a product by injecting a molten metal into the mold to cast the product.   
     
     
         2 . The method of  claim 1 , further comprising heating the ceramic balls to a temperature of 500 to 700° C. to remove foreign substances from surfaces of the ceramic balls prior to the cast preparation. 
     
     
         3 . The method of  claim 1 , wherein the cast preparation comprises pre-heating the mold to 500 to 1,200° C. 
     
     
         4 . The method of  claim 1 , wherein the step of producing a product comprises casting the product in a vacuum state to prevent oxidation of the molten metal. 
     
     
         5 . The method of  claim 1 , wherein the ceramic balls are formed of alumina (Al 2 O 3 ) and comprise first and second ceramic balls having different diameters, wherein the first ceramic balls have a greater diameter than the second ceramic balls. 
     
     
         6 . The method of  claim 1 , wherein the ceramic box is formed of Inconel. 
     
     
         7 . The method of  claim 1 , wherein the first slurry is formed by mixing zircon powder and colloidal silica. 
     
     
         8 . The method of  claim 1 , wherein the second slurry is formed by mixing aluminosilicate, colloidal silica, and sand.