Thermal insulation molten metal

Abstract

There is disclosed a material and method for preventing heat loss from molten metal, one side of this material being impregnated with heat insulating refractory or exothermic material. The impregnated side has a porosity of less than about 50 AFS units and contains a binder.

We claim as our invention: 
     
       1. A material for minimizing heat loss from the exposed surfaces of molten metal comprising a preformed and self-supporting fibrous mat in sheet form which may be handled without disintegrating and which may be cut to size prior to the application of said preformed and self-supporting mat to the exposed surfaces of molten metal having an inner metal facing surface and an outer exposed surface, with only the metal facing surface of said mat being impregnated with a material selected from the group consisting of heat insulating refractory materials and exothermic materials, and containing a binding agent to bind said material to the fibers of the metal facing surface of said preformed and self-supporting fibrous mat, said impregnated metal facing surface having an average porosity of less than about 50 AFS. 
     
     
       2. A material for minimizing heat loss from the exposed surfaces of molten metal according to claim 1 which is impregnated on the metal facing surface of said fibrous mat with a heat insulating refractory material selected from the class consisting of finely divided sand, silica flour, silimanite, grog, zirconia, burned dolomite, refractory silicates, alumina, magnesia, sircon flour and chromote flour. 
     
     
       3. A material for minimizing heat loss from the exposed surfaces of molten metal according to claim 2 wherein at least 50 percent by weight of the finely divided material passes a 200 BSS mesh. 
     
     
       4. A material for minimizing heat loss from the exposed surfaces of molten metal according to claim 1 wherein the metal facing surface of said mat is impregnated with an exothermic material consisting essentially of finely divided oxidisable material and an oxidising agent therefor. 
     
     
       5. A material for minimizing heat loss from the exposed surfaces of molten metal according to claim 4 wherein the finely divided oxidisable material is selected from the class consisting of particulate aluminum, calcium silicide and ball mill dusts, at least 5 percent by weight of which passes a 200 BSS sieve. 
     
     
       6. A material for minimizing heat loss from the exposed surfaces of molten metal according to claim 4 wherein the oxidising agent is selected from the class consisting of alkali metal and ammonium nitrates, chlorates and perchlorates, iron oxide and manganese dioxide. 
     
     
       7. A material for minimizing heat loss from the exposed surfaces of molten metal according to claim 1 wherein the fibre of said fibrous mat is a refractory fibre selected from the class consisting of aluminum silicate, calcium silicate and metal fibres. 
     
     
       8. A material for minimizing heat loss from the exposed surfaces of molten metal according to claim 1 wherein the fibre of said fibrous mat is an organic fibre selected from the class consisting of cotton, jute and acrylonitrile fibres. 
     
     
       9. A material for minimizing heat loss from the exposed surfaces of molten metal according to claim 1 wherein the binding agent is selected from the class consisting of natural and synthetic gums and resins, alkali metal silicates, sulphite lye, colloidal silica and aluminum phosphates. 
     
     
       10. A material for minimizing loss from the exposed surfaces of molten metal according to claim 1 wherein the total thickness of said fibrous mat is between about 6 and about 150 mm thick, and wherein the impregnation of the metal facing surface extends to a depth of between about 1 and about 50 mm. 
     
     
       11. A material for minimizing heat loss from the exposed surfaces of molten metal according to claim 1 wherein the total thickness of said fibrous mat is between about 12 and about 50 mm thick, and wherein the impregnation of the metal facing surface extends to a depth of between about 6 and about 25 mm. 
     
     
       12. A material for minimizing heat loss from the exposed surfaces of molten metal according to claim 1 which is faced with a layer, on the impregnated metal facing surface of said mat, selected from the class consisting of heat insulating refractory materials and exothermic materials. 
     
     
       13. A material for minimizing heat loss from the exposed surfaces of molten metal according to claim 12 wherein said facing layer is less than about 25 mm thick and has a density of between about 0.2 and about 1.5 mm/cc. 
     
     
       14. A material for minimizing heat loss from the exposed surfaces of molten metal according to claim 12 wherein said fibrous mat is reinforced by a metal mesh of grid. 
     
     
       15. A process for minimizing heat loss from the exposed surfaces of molten metal which comprises applying to said exposed metal surfaces a fibrous mat having only one of its surfaces impregnated with a material selected from the group consisting of heat insulating refractory materials and exothermic materials, and a binding agent to bind said impregnating material to the fibers of the impregnated surface of said mat, so that the impregnated surface of said fibrous mat is adjacent to and covers the exposed metal surfaces, said impregnated surface having an average porosity of less than about 50 AFS. 
     
     
       16. The process of claim 15 wherein the impregnated surface of the fibrous mat applied to the exposed surfaces of molten metal is impregnated with a heat insulating refractory material selected from the class consisting of finely divided sand, silica flour, sillimanite, grog, zirconia, burned dolomite, refractory silicates, alumina, magnesia, sircon flour and chromote flour. 
     
     
       17. The process of claim 15 wherein the impregnated surface of the fibrous mat applied to the exposed surfaces of molten metal is impregnated with an exothermic material consisting essentially of finely divided oxidisable material and an oxidising agent therefor. 
     
     
       18. The process of claim 15 wherein the fibre of the fibrous mat applied to the exposed surfaces of molten metal is a refractory fibre selected from the class consisting of aluminum silicate, calcium silicate and metal fibres. 
     
     
       19. The process of claim 15 wherein the fibre of the fibrous mat applied to the exposed surfaces of molten metal is an organic fibre selected from the class consisting of cotton, jute, and acrylonitrile fibres. 
     
     
       20. The process of claim 15 wherein the binding agent used to bind the impregnating material to the fibers of the impregnated surface of the fibrous mat applied to the exposed surfaces of molten metal is selected from the class consisting of natural and synthetic gums and resins, alkali metal silicates, sulphite lye, colloidal silica and aluminum phosphates. 
     
     
       21. The process of claim 15 wherein the total thickness of the fibrous mat applied to the exposed surfaces of molten metal is between about 6 and about 150 mm, and wherein the impregnation of the impregnated surface extends to a depth of between about 1 and about 50 mm. 
     
     
       22. The combination comprising an exposed surface of molten metal and a material for minimizing heat loss from said exposed molten metal surfaces which comprises a preformed fibrous mat in sheet form having an inner metal facing surface which is adjacent to and covers said exposed molten metal surfaces and an outer exposed surface, with only the metal facing surface of said mat being impregnated with a material selected from the group consisting of heat insulating refractory materials and exothermic materials, and containing a binding agent to bind said material to the fibers of the metal facing surface of said fibrous mat, said impregnated metal facing surface having an average porosity of less than about 50 AFS. .Iadd. 23. In a shaped heat article for forming a molten-metal contacting lining for metallurgical moulds or the like which comprises a refractory composite consisting essentially of an inorganic fibrous refractory material and a granular refractory filler material, an exothermic mixture of a fuel and an oxidising agent, and a binder, the improvement wherein said fibrous refractory material is a material selected from aluminosilicate fibres and said shaped article has a density of about 0.2 to 1.5 grams per cubic centimeter. .Iaddend..Iadd. 24. A shaped heat insulating article according to claim 23 comprising a fluoride catalyst for the exothermic mixture. .Iaddend..Iadd. 25. A shaped heat insulating article according to claim 24 wherein the fluoride catalyst is cryolite. .Iaddend..Iadd. 26. The article defined in claim 23, wherein said granular material is one or more materials selected from the group consisting essentially of alumina, magnesia, chromite and zirconia. .Iaddend. .Iadd. 27. The article defined in claim 23, wherein the fuel is one or more materials selected from the group consisting essentially of aluminum and magnesium powders. .Iaddend..Iadd. 28. The article defined in claim 27, wherein the oxidising agent is one or more materials selected from the group consisting essentially of iron oxide or manganese dioxide. .Iaddend..Iadd. 29. In a shaped heat insulating article for forming a molten-metal contacting lining for metallurgical moulds or the like which comprises a refractory composite consisting essentially of an inorganic fibrous refractory material and a granular refractory filler material, an exotheric mixture of a fuel and an oxidising agent, and a binder, the improvement wherein said fibrous refractory material is a material selected from aluminosilicate fibres and said shaped article has a density of about 0.48 grams per cubic centimeter. .Iaddend. .Iadd. 30. In a shaped heat insulating article for forming a molten-metal contacting lining for metallurgical moulds or the like which comprises a refractory composite consisting essentially of an inorganic fibrous refractory material and a granular refractory filler material, an exothermic mixture of a fuel and an oxidising agent, and a binder, the improvement wherein said fibrous refractory material is a material selected from aluminosilicate fibres and said shaped article has a density of up to 0.5 grams per cubic centimeter.