Liquid Metal Directional Casting Process

Abstract

Processes for directionally casting liquid metal to form an articles can include compressing a seal intermediate a mold chill plate and a mold assembly, wherein the seal circumscribes a shell mold in the mold assembly; filling the shell mold in the mold assembly with molten metal; immersing the mold assembly into a liquid metal cooling bath from a bottom portion to a top portion of the mold assembly; and transmitting heat from the mold assembly to the liquid metal cooling bath to solidify the molten metal from the bottom portion to the top portion of the mold assembly.

1 . A process for directionally casting an article, the process comprising:
 compressing a seal member intermediate a mold chill plate and a mold assembly, wherein the seal member circumscribes a shell mold in the mold assembly;   filling the shell mold in the mold assembly with molten metal;   immersing the mold assembly into a liquid metal cooling bath at a controlled rate from a first position to a second position of the mold assembly; and   transmitting heat from the mold assembly to the liquid metal cooling bath to directionally solidify the molten metal as the molten metal assembly is immersed from the first position to the second position of the mold assembly.   
   
   
       2 . The process of  claim 1 , wherein the seal member is formed of a metal or a ceramic. 
   
   
       3 . The process of  claim 1 , wherein the mold assembly is a cluster mold assembly comprising a plurality of the shell molds; and wherein the seal member is disposed about each one of the shell molds in the cluster mold assembly. 
   
   
       4 . The process of  claim 1 , wherein the seal member is selected to have a melting temperature higher than an operating temperature at which the seal member is exposed. 
   
   
       5 . The process of  claim 1 , wherein the seal member has a shape comprising an essentially circular shape, an essentially elliptical shape, or an essentially polygonal shape. 
   
   
       6 . The process of  claim 1 , wherein compressing the seal member comprises seating the seal member in a channel formed on a bottom surface of the mold assembly, wherein the seal member has a diameter greater than a height dimension of the channel. 
   
   
       7 . The process of  claim 1 , wherein the article is an airfoil, bucket, blade, or vane. 
   
   
       8 . A process for sealing a shell mold in a mold assembly, the process comprising:
 forming a channel in a bottom surface of the mold assembly, wherein the channel circumscribes the shell mold;   placing a first ring in the channel; and   securing the mold assembly to a mold chill plate and compressing the first ring against the mold chill plate and the mold assembly.   
   
   
       9 . The process of  claim 8 , further comprising forming an boss in the mold chill plate having a shape complementary to the channel of the mold assembly, wherein the channel is dimensioned to accommodate the boss and the first ring. 
   
   
       10 . The process of  claim 9 , wherein the first ring abuts an interior sidewall of the boss. 
   
   
       11 . The process of  claim 9 , wherein the first ring abuts an exterior sidewall of the boss. 
   
   
       12 . The process of  claim 9 , further comprising an additional ring, wherein the first ring abuts an interior sidewall of the boss and the additional ring abuts an exterior sidewall of the boss. 
   
   
       13 . The process of  claim 8 , wherein the mold assembly is a cluster mold assembly comprising a plurality of shell molds, wherein the first ring circumscribes the shell molds. 
   
   
       14 . The process of  claim 13 , further comprising at least one additional ring, wherein the first ring circumscribes a selected one of the plurality of shell molds, and the at least one additional ring circumscribes a selected other one of the plurality of shell molds. 
   
   
       15 . The process of  claim 8 , wherein the first ring is formed of a ceramic material or a metal material. 
   
   
       16 . The process of  claim 15 , wherein the ceramic material comprises alumina, alumina-silica, alumina-boria-silica, or combinations thereof. 
   
   
       17 . The process of  claim 15 , wherein the metal material comprises aluminum, copper, or combinations thereof. 
   
   
       18 . The process of  claim 8 , further comprising coating the first ring with a paste prior to securing the mold assembly to the mold chill plate. 
   
   
       19 . A process for directionally casting an article, the process comprising:
 securing a mold assembly to a chill plate, wherein the mold assembly comprises an opening for receiving molten metal, at least one shell mold in fluid communication with the opening, and a skirt laterally extending from the at least one shell mold, wherein the skirt comprises a channel disposed in a bottom surface and configured to surround at least one shell mold, the channel further comprising a ring formed of a compressible material disposed therein, wherein the chill plate comprises a boss having a shape complementary to the channel of the mold assembly;   heating the mold assembly;   filling at least one shell mold in the mold assembly with molten metal;   lowering the chill plate and the mold assembly into a liquid metal cooling bath at a controlled rate from a first position to a second position of the mold assembly; and   transmitting heat from the mold assembly to the liquid metal cooling bath to solidify the molten metal as the mold assembly transitions from the first position to the second position.   
   
   
       20 . The process of  claim 19 , wherein the ring is dimensioned to prevent fluid from the liquid metal cooling bath from entering the at least one shell mold and to prevent egress of the molten metal from the shell mold.