Method or restoring ingot mold stools and closed-bottom ingot mold

Abstract

A method of repairing large castings, such as ingot molds and mold stools, by employing an aluminothermic reduction reaction without using containment perimeters and without preheating the casting. The resultant repaired article has a metallurgically bonded plug in the hole or eroded surface with a thick abrasion-resistant slag covering over the deposited metal.

We claim: 
     
       1. A method of repairing an erosion cavity in ingot mold stools and the bottoms of closed-bottom metal molds .Iadd.and other large castings .Iaddend.comprising: placing in said cavity an exothermic reaction mixture consisting essentially of a fuel powder and a metallic oxide, the amount of said mixture having a volume no greater than one and a half times the volume of the cavity;   igniting said mixture to form a superheated melt comprising a metal phase and a slag phase, such that said melt is contained entirely within said cavity,   maintaining said melt in said cavity for a time sufficient to allow said melt to separate so that said metal phase is at the bottom and the slag phase thereover,   permitting said melt to solidify with the metal phase securely bonded to the bottom of the cavity and said slag phase securely attached to said metal phase, and permitting said slag phase to remain in said erosion cavity during subsequent use of said mold or mold stool to thereby provide extra protection from erosion and extend the life of the repaired stool or mold.   
     
     
       2. A method in accordance with claim 1, wherein said fuel powder is aluminum. 
     
     
       3. A method in accordance with claim 2, wherein said aluminum powder has a size consisting of -100 mesh and +400 mesh. 
     
     
       4. A method in accordance with claim 1, wherein said metallic oxide is Fe 2  O 3 . 
     
     
       5. A method in accordance with claim 4, wherein said Fe 2  O 3  is at least as fine as -35 mesh. 
     
     
       6. A method in accordance with claim 1, wherein said exothermic reaction mixture comprises a substantially stoichiometric mixture of Fe 2  O 3  and aluminum powders. 
     
     
       7. A method in accordance with claim 1, wherein said mold is cast iron. 
     
     
       8. A method in accordance with claim 1 in which a portion of said mixture is placed in said cavity and ignited to form a first melt comprising a metal phase and a slag phase, and thereafter the remaining portion of said mixture is placed in said cavity and ignited to form a second melt comprising a metal phase and a slag phase. 
     
     
       9. A method in accordance with claim 8 in which said first melt is solidified before said remaining portion of said mixture is placed in said cavity. 
     
     
       10. A method in accordance with claim 8 in which said first melt is still molten when said remaining portion of said mixture is placed in said cavity. 
     
     
       11. A method in accordance with claim 8 in which mixture is divided into more than two portions each of which are individually placed in said cavity and ignited. 
     
     
       12. A method of repairing an erosion cavity in the bottom of a closed-bottom ingot mold comprising: placing in the bottom of said mold an exothermic reaction mixture consisting essentially of a fuel powder and a metallic oxide, the amount of said mixture having a volume greater than 1.5 times the cavity volume but less than 5 times the cavity volume,   igniting said mixture to form a superheated melt comprising a metal phase and a slag phase,   maintaining said melt at the bottom of said mold for a time sufficient to allow said melt to separate into a metal phase and a slag phase, said metal phase separating to the bottom and being entirely contained within said cavity, while said slag phase covers the entire bottom of the mold,   permitting said melt to solidify with the metal phase securely bonded to the bottom of the cavity and said slag phase securely attached to the metal phase to provide a slag surface over the entire bottom of the mold, and permitting said slag phase to remain in on said mold bottom during subsequent use of said mold to thereby provide extra protection from erosion and extend the life of the repaired mold.   
     
     
       13. A method in accordance with claim 12, wherein said fuel powder is aluminum. 
     
     
       14. A method in accordance with claim 13, wherein said aluminum powder has a size consisting of -100 mesh and +400 mesh. 
     
     
       15. A method in accordance with claim 12, wherein said metallic oxide is Fe 2  O 3 . 
     
     
       16. A method in accordance with claim 15, wherein said Fe 2  O 3  is at least as fine as -35 mesh. 
     
     
       17. A method in accordance with claim 12, wherein said exothermic reaction mixture comprises a substantially stoichiometric mixture of Fe 2  O 3  and aluminum powders. 
     
     
       18. A method in accordance with claim 12, wherein said mold is cast iron. 
     
     
       19. A method in accordance with claim 12 in which said slag phase is no thicker than about 2 inches.