Method for producing a metal part

Abstract

The invention relates to methods of casting metal parts in sand molds, with the particularity that it is not necessary to use sleeves surrounding the feed risers which are arranged outside the part to offset the shrinkage occurring during the solidification of the molten metals. The operations of placing the sleeves which must be arranged around the risers are eliminated with the method object of the invention, the actual sleeves being made when the sand mold is produced.

1 . A method of producing a metal part ( 1 ) by casting a molten metal into a sand mold ( 2 ), characterized in that it comprises:
 a) placing a model ( 4 ) in a casting box ( 3 ) for shaping a cavity ( 5 ) which will define the shape of the metal part ( 1 ) and at least one riser ( 11 ),   b) pouring a molding sand ( 6 ) into the casting box ( 3 ) after step a) for shaping the sand mold ( 2 ),   c) pouring an insulating or exothermic mixture ( 7 ) into the casting box ( 3 ) after step a) to delay the solidification of a molten metal,   d) extracting the model ( 4 ) for shaping the mentioned cavity ( 5 ),   e) casting a molten metal into the mentioned cavity ( 5 ),   f) extracting the part ( 1 ) produced after the solidification of the molten metal,   wherein the insulating or exothermic mixture ( 7 ) is arranged in contact with the model ( 4 ) in some areas ( 41 ,  42 ) in which it is required that the molten metal cast in step e) remains in the liquid state for a longer time period than the rest of the molten metal that is going to shape the part ( 1 ), such that once the model ( 4 ) is removed in step d), the insulating or exothermic mixture ( 7 ) delays the solidification of the molten metal cast in step e) in the areas ( 41 ,  42 ) in which the mentioned mixture ( 7 ) has been arranged.   
     
     
         2 . The method of producing a metal part ( 1 ) according to  claim 1 , further comprising, after step a), placing an auxiliary part ( 8 ) around the area ( 41 ), such that after step b) the mentioned auxiliary part ( 8 ) is removed, a gap ( 9 ) being shaped between the molding sand ( 6 ) and the model ( 4 ), into which the insulating or exothermic mixture ( 7 ) of step c) is poured. 
     
     
         3 . The method of producing a metal part ( 1 ) according to  claim 2 , wherein the auxiliary part ( 8 ) is a bush with a circular section. 
     
     
         4 . The method of producing a metal part ( 1 ) according to  claim 1 , wherein the insulating or exothermic mixture ( 7 ) is a non-fibrous mixture. 
     
     
         5 . The method of producing a metal part ( 1 ) according to  claim 1 , wherein the insulating or exothermic mixture ( 7 ) is in contact with the molten metal in an area ( 41 ) forming the riser ( 11 ) to supply heat or insulation. 
     
     
         6 . The method of producing a metal part ( 1 ) according to  claim 1 , further comprising arranging the insulating or exothermic mixture ( 7 ) in contact with a portion of the molten metal in an area with difficult access ( 42 ) of the part ( 1 ) which requires a heat supply or insulation. 
     
     
         7 . The method of producing a metal part according to  claim 1 , wherein the molding sand ( 6 ) and the insulating or exothermic mixture ( 7 ) shaping the sand mold ( 2 ) are located in independent tanks ( 12 ) feeding a mixer ( 13 ) in which they are mixed with agglomerating resins so that they access the casting box ( 3 ) by gravity. 
     
     
         8 . The method of producing a metal part ( 1 ) according to  claim 2 , wherein the insulating or exothermic mixture ( 7 ) is a non-fibrous mixture. 
     
     
         9 . The method of producing a metal part ( 1 ) according to  claim 3 , wherein the insulating or exothermic mixture ( 7 ) is a non-fibrous mixture. 
     
     
         10 . The method of producing a metal part ( 1 ) according to  claim 2 , wherein the insulating or exothermic mixture ( 7 ) is in contact with the molten metal in an area ( 41 ) forming the riser ( 11 ) to supply heat or insulation. 
     
     
         11 . The method of producing a metal part ( 1 ) according to  claim 3 , wherein the insulating or exothermic mixture ( 7 ) is in contact with the molten metal in an area ( 41 ) forming the riser ( 11 ) to supply heat or insulation. 
     
     
         12 . The method of producing a metal part ( 1 ) according to  claim 4 , wherein the insulating or exothermic mixture ( 7 ) is in contact with the molten metal in an area ( 41 ) forming the riser ( 11 ) to supply heat or insulation. 
     
     
         13 . The method of producing a metal part ( 1 ) according to  claim 9 , wherein the insulating or exothermic mixture ( 7 ) is in contact with the molten metal in an area ( 41 ) forming the riser ( 11 ) to supply heat or insulation. 
     
     
         14 . The method of producing a metal part ( 1 ) according to  claim 2 , further comprising arranging the insulating or exothermic mixture ( 7 ) in contact with a portion of the molten metal in an area with difficult access ( 42 ) of the part ( 1 ) which requires a heat supply or insulation. 
     
     
         15 . The method of producing a metal part ( 1 ) according to  claim 3 , further comprising arranging the insulating or exothermic mixture ( 7 ) in contact with a portion of the molten metal in an area with difficult access ( 42 ) of the part ( 1 ) which requires a heat supply or insulation. 
     
     
         16 . The method of producing a metal part ( 1 ) according to  claim 4 , further comprising arranging the insulating or exothermic mixture ( 7 ) in contact with a portion of the molten metal in an area with difficult access ( 42 ) of the part ( 1 ) which requires a heat supply or insulation. 
     
     
         17 . The method of producing a metal part ( 1 ) according to  claim 13 , further comprising arranging the insulating or exothermic mixture ( 7 ) in contact with a portion of the molten metal in an area with difficult access ( 42 ) of the part ( 1 ) which requires a heat supply or insulation. 
     
     
         18 . The method of producing a metal part according to  claim 2 , wherein the molding sand ( 6 ) and the insulating or exothermic mixture ( 7 ) shaping the sand mold ( 2 ) are located in independent tanks ( 12 ) feeding a mixer ( 13 ) in which they are mixed with agglomerating resins so that they access the casting box ( 3 ) by gravity. 
     
     
         19 . The method of producing a metal part according to  claim 3 , wherein the molding sand ( 6 ) and the insulating or exothermic mixture ( 7 ) shaping the sand mold ( 2 ) are located in independent tanks ( 12 ) feeding a mixer ( 13 ) in which they are mixed with agglomerating resins so that they access the casting box ( 3 ) by gravity. 
     
     
         20 . The method of producing a metal part according to  claim 17 , wherein the molding sand ( 6 ) and the insulating or exothermic mixture ( 7 ) shaping the sand mold ( 2 ) are located in independent tanks ( 12 ) feeding a mixer ( 13 ) in which they are mixed with agglomerating resins so that they access the casting box ( 3 ) by gravity.