Subsurface chills to improve railcar knuckle formation

Abstract

A method for manufacturing a railcar coupler knuckle includes, before casting, positioning an external chill within a cope mold portion and a drag mold portion offset from and adjacent internal walls of a pulling face and a throat of the cope and drag mold portions, thus producing a casting with reduced micro-shrinkage in at least the throat, a high-stress section of the casting. Use of subsurface chills produces an improved surface with fewer inclusions when compared to an equivalent surface produced in a process without use of a subsurface chill. The external chill may be a cone chill of a larger size to improve cooling and solidification at and below the surface. The external chill may also be a cylindrical and/or oblong chill with a tapered design that may correspond to the internal walls of the cope and drag mold portions between the pulling face and the throat.

1 . (canceled) 
     
     
         2 . An assembly for casting a railcar coupler knuckle, comprising:
 a mold portion, the mold portion having internal walls defining at least in part perimeter boundaries of a coupler knuckle mold cavity including a front face portion, a nose portion, a pulling face portion, a heel portion, a throat portion, a tail portion, a lock shelf portion, and a locking face portion;   at least one internal core placed to shape inside portions of the railcar coupler knuckle; and   an external chill positioned within the mold portion, the external chill positioned between the front face portion and the tail portion of the mold portion and adjacent to the throat portion and the C-10 pin hole, the external chill offset from and adjacent the internal walls of the pulling face and the throat of the mold portion, wherein a wall of sand exists between the external chill and the internal walls of the coupler knuckle mold cavity;   wherein a coupler knuckle is formable of metal from the mold portion that includes the chill, the coupler knuckle including an improved surface with reduced subsurface micro-shrinkage at a location of at least the throat of the coupler knuckle as compared to an equivalent surface cast in a process using a surface chill.   
     
     
         3 . The assembly of  claim 2 , wherein the improved surface extends substantially between the pulling face and a lock shelf of the coupler knuckle. 
     
     
         4 . The assembly of  claim 2 , wherein the chill is cone shaped. 
     
     
         5 . The assembly of  claim 4 , wherein the cone shaped chill is truncated cones including dimensions of a major diameter of more than 2.0″, a minor diameter of more than 1.50″ and a height of more than 1.85″. 
     
     
         6 . The assembly of  claim 2 , wherein the chill is comprised of one or more materials selected from the group consisting of: cast steel, cast gray iron, graphite, silicon carbide and a combination thereof. 
     
     
         7 . The assembly of  claim 2 , wherein the chill has a volume of at least ten cubic inches. 
     
     
         8 . The assembly of  claim 2 , wherein the chill has a maximum cross-section of about four square inches. 
     
     
         9 . The assembly of  claim 2 , wherein the chill has a mass of at least 3 pounds. 
     
     
         10 . The assembly of  claim 2 , further comprising at least two internal cores, a first internal core placed to define within the coupler knuckle a finger cavity and a second internal core placed to define within the coupler knuckle a pivot pin cavity and a kidney cavity. 
     
     
         11 . The assembly of  claim 2 , further comprising at least two internal cores, a first internal core placed to define within the coupler knuckle a finger cavity and pivot pin cavity and a second internal core placed to define within the coupler knuckle a kidney cavity. 
     
     
         12 . An assembly for creating a mold for casting a railcar coupler knuckle, comprising:
 a pattern plate;   a pattern half attachable to the pattern plate with which to form a mold portion, the pattern half having exterior walls defining in the mold portion at least in part perimeter boundaries of a coupler knuckle mold cavity including a front face portion, a nose portion, a pulling face portion, a heel portion, a throat portion, a tail portion, a lock shelf portion, and a locking face portion; and   an external chill releasably attached to the pattern plate positioned between the front face portion and the tail portion of the pattern and adjacent to the throat portion and the C-10 pin hole, the chill offset adjacent a throat region of respective pattern halves, the chill releasably attached to the pattern plate such that after the pattern is removed from the mold portion, the chill remains in the mold portion with a thin wall of sand between the chill and an internal wall of the mold portion.   
     
     
         13 . The assembly of  claim 12 , wherein the chill is releasably attached to the pattern plates with one or more vertical pins. 
     
     
         14 . The assembly of  claim 12 , wherein the chill includes a larger cross-sectional area on a side that is mounted to the pattern plate than the cross-sectional area taken at any other height. 
     
     
         15 . The assembly of  claim 12 , wherein the chill is cone shaped. 
     
     
         16 . The assembly of  claim 15 , wherein the cone shaped chill is a truncated cone including dimensions of a major diameter of more than 2.0″, a minor diameter of more than 1.50″ and a height of more than 1.85″. 
     
     
         17 . The assembly of  claim 12 , wherein the chill is comprised of one or more materials selected from the group consisting of: cast steel, cast gray iron, graphite, silicon carbide and a combination thereof. 
     
     
         18 . The assembly of  claim 12 , wherein the chill has a volume of at least ten cubic inches. 
     
     
         19 . The assembly of  claim 12 , wherein the chill has a maximum cross-section of about four square inches. 
     
     
         20 . The assembly of  claim 12 , wherein the chill has a mass of at least 3 pounds. 
     
     
         21 . An assembly for casting a railcar coupler knuckle, comprising:
 a mold portion, the mold portion having internal walls defining at least in part perimeter boundaries of a coupler knuckle mold cavity including a front face portion, a nose portion, a pulling face portion, a heel portion, a throat portion, a tail portion, a lock shelf portion, and a locking face portion; and   at least one ingate;   at least one riser preceding and engaged with the at least one ingate; and   at least one internal core placed to shape inside portions of the railcar coupler knuckle;   an external chill positioned within the mold portion, the external chill positioned between the front face portion and the tail portion of the mold portion and adjacent to the throat portion and the C-10 pin hole, the external chill offset from and adjacent the internal walls of the pulling face and the throat of the mold portion, wherein a wall of sand exists between the external chill and the internal walls of the coupler knuckle mold cavity.