Immersion Casting

Abstract

A method of immersion casting objects from molten metal, by crystallizing the metal outwardly from a heat-absorbing forming element such that upon removal from the molten metal bath, the solidified object has an internal surface defined by the shape of the forming element, and an outer surface that features random crystallization and a high degree of texture. The method can be facilitated by the interaction of the forming element and molten metal with molten salt provided as a layer on the molten metal. When the object is cast from a high purity metal such as aluminum or copper, the exposed crystal structure is especially random and highly reflective and can be enhanced by electro-chemical brightening.

1 . A method of manufacturing a shaped metal object, comprising:
 providing a molten metal bath contained in a heated crucible;   immersing a cooling element into the metal bath whereby the molten metal crystallizes radially outwardly from the cooling element, forming a solid, shaped metal object around the cooling element;   withdrawing the shaped metal object and cooling element from the crucible, whereby the shaped metal object has a randomly crystallized outer surface; and   withdrawing the cooling element from the shaped metal object.   
     
     
         2 . The method of  claim 1 , wherein
 a supernatant layer of molten salt is present over the molten metal;   the cooling element is immersed into the layer of salt whereby a layer of salt solidifies at an interface on the cooling element; and   upon further immersion of the cooling element into the molten metal, solidified salt at interface with the molten metal is initially converted to molten form while the salt at the interface with the cooling element remains solid.   
     
     
         3 . The method of  claim 2 , wherein
 the solid salt at the interface with the cooling element shrinks toward and thereby adheres to the cooling element; and   the solidified molten metal at the interface with the molten salt shrinks toward the cooling element and thereby adheres to the molten salt.   
     
     
         4 . The method of  claim 3 , wherein
 after withdrawal of the metal object and cooling element from the crucible the salt exists as a solid layer between the cooling element and a solid raw vessel;   the salt layer is fractured or dissolved; and   the cooling element slides out of the metal object.   
     
     
         5 . A method of manufacturing a shaped metal object, comprising:
 providing a molten metal bath;   providing a preform with a shape corresponding to the shape of the metal object;   immersing the preform into the metal bath;   maintaining the immersed preform at a temperature lower than the temperature of the molten metal, whereby the molten metal crystallizes outwardly from the preform with increasing thickness of solid metal in a raw shape complimentary to the preform;   withdrawing the raw shaped solid metal and preform from the molten metal bath together, whereby the withdrawn raw shaped solid metal exhibits a randomly crystallized outer surface;   separating the raw shaped metal solid from the preform; and   treating the randomly crystallized outer surface with a brightening agent to produce a finished shaped metal object.   
     
     
         6 . The method of  claim 5 , wherein the preform is cylindrical. 
     
     
         7 . The method of  claim 5 , wherein the preform is a plate. 
     
     
         8 . The method of  claim 5 , wherein
 an interface agent is provided between the immersed preform and the molten metal, which interface agent adheres to both the preform and metal surrounding the preform such that the raw shaped solid metal and preform can be withdrawn from the molten metal bath together; and   the raw shaped metal solid and preform are separated by disturbing the interface agent.   
     
     
         9 . The method of  claim 8 , wherein
 the withdrawn preform and adhered solid metal are cooled before being separated; and   the cooling reduces the adhesion of the interface agent such that the preform can be'separated from the metal solid.   
     
     
         10 . The method of  claim 8 , wherein the interface agent is provided as a layer of salt on the molten metal bath. 
     
     
         11 . The method of  claim 5 , including supplying a flow of cooling fluid within the preform while the preform is immersed in the molten metal. 
     
     
         12 . The method of  claim 5 , including displacing the preform into and out of the molten bath at a predetermined variable rate. 
     
     
         13 . A method of manufacturing a shaped metal object, comprising:
 selecting a crucible having a working chamber;   depositing a metal material into the crucible, which metal material has a relatively low melt temperature and a relatively high density;   introducing a salt into the crucible, which salt has a relatively lower density than the density of the metal;   heating the crucible to liquefy the metal and a supernatant layer of salt;   passing a forward portion of a preform into the heated crucible, through the layer of salt into the molten metal, whereby the salt adheres to the forward portion of the preform before the forward portion of the preform enters the molten metal;   connecting the preform to a heat sink whereby the molten metal around the salt on the preform cools below the melt temperature of the metal, and the metal crystallizes radially outwardly from the preform with a solid metal thickness around the preform that is dependent on the length of time the preform is in the molten metal;   lifting the preform with adhered solidified metal and salt out of the crucible;   removing the preform from the solidified metal, leaving a raw metal object with a randomly textured outer surface.   
     
     
         14 . The method of  claim 13 , wherein the preform is solid and the heat sink is a solid body integral with and extending transversely to the preform above the crucible. 
     
     
         15 . The method of  claim 13 , wherein the metal is one of aluminum or tin, the salt is sodium chloride, and the preform is copper. 
     
     
         16 . The method of  claim 13 , wherein the salt comprises at least one or combination of sodium chloride and barium chloride. 
     
     
         17 . The method of  claim 13 , wherein the metal is silver, the salt is silicon oxide and the rod is iron. 
     
     
         18 . The method of  claim 13 , wherein the preform is graphite. 
     
     
         19 . The method of  claim 13 , including cleaning and brightening the textured outer surface of the raw vessel. 
     
     
         20 . The method of  claim 19 , wherein the textures outer surface is electrochemically brightened. 
     
     
         21 . The method of  claim 20 , wherein the electrochemically brightened surface is sealed with a nickel salt bath. 
     
     
         22 . The method of  claim 13 , wherein the salt has a relatively higher melt temperature than the melt temperature of the metal and all the salt on the immersed rod solidifies as the molten metal cools outwardly. 
     
     
         23 . The method of  claim 13 , wherein the salt has an interface with the molten metal and the salt at the interface remains molten as the molten metal solidifies outwardly.