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Continuous casting methods and apparatus are described wherein a defect in the cast surfaces consisting of longitudinal bands of sinkage, sometimes called "sinks", which are spaced relatively far inwardly from the edges of wide, relatively thin slab or strip, usually being spaced inwardly away from

Continuous casting methods and apparatus are described wherein a defect in the cast surfaces consisting of longitudinal bands of sinkage, sometimes called "sinks", which are spaced relatively far inwardly from the edges of wide, relatively thin slab or strip, usually being spaced inwardly away from the edges by a distance of 3 to 7 times (sometimes up to 9 times) the thickness of the cast slab, is practically eliminated by means of a coating or covering of non-wettable refractory ceramic material of low heat conductivity applied to the inner faces of the edge-dam blocks for reducing heat flow out of the edges of the slab or strip being cast. Numerous such blocks are strung onto a flexible metal band or cable to constitute each of the two edge dams which define the edges of the mold space. Alternative methods for reducing heat flow from the edges of the slab or strip being cast are disclosed--notably the breaking of thermal contact by means of jiggling by rocking individual edge-dam blocks back and forth; also the use of sintered edge-dam blocks, and the heating of the edge-dam blocks along the casting region. One or more of these alternative methods may be used in conjunction with the coating of refractory material on the inner faces of the edge-dam blocks for further reducing or controlling the flow of heat out of the margins of the metal being cast into the edge-dam blocks.

대표청구항 ▼

1. In the method for continuously casting metal product directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between opposed moving mold surfaces and laterally defined by first and second traveling edge dams consisting of flexible stri

1. In the method for continuously casting metal product directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between opposed moving mold surfaces and laterally defined by first and second traveling edge dams consisting of flexible strings of dam blocks, the improvement comprising: reducing the rate of heat transfer from the freezing metal to the edge-dam blocks to a value of less than 80 percent of the said rate against either adjacent mold surface. 2. The method of claim 1 wherein the heat transfer reducing step comprises, prior to casting the metal product: applying an intermediate layer of refractory metal to those faces of the said edge-dam blocks normally contacted by molten metal; and applying a coating of molten insulative refractory ceramic to the intermediate layer, said insulative refractory ceramic being non-wetting with respect to the metal being cast. 3. The method as claimed in claim 2, in which: the said insulative refractory ceramic is zirconia. 4. The method for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between opposed moving mold surfaces and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the method comprising: reducing the rate of heat transfer from the freezing metal to the edge-dam blocks to a value of less than 80 percent of the said rate against either adjacent mold surface. 5. The method as claimed in claim 4 for casting a relatively wide slab metal product directly from molten metal, said slab having a width-to-thickness ratio of at least about twenty-five for avoiding longitudinal bands of sinkage located in the slab product at a distance of three to seven times the slab product thickness inwardly from the traveling edge dams for avoiding such sinkage deformation of the relatively wide slab product. 6. The method as claimed in claim 4, in which: the reduction in heat transfer is achieved by means of, prior to casting the metal product: applying an adherent intermediate layer of refractory metal to those faces of the said edge-dam blocks which will normally be contacted by molten metal, and applying an adherent coating of molten insulative refractory ceramic to the refractory metal on the said edge-dam blocks on the faces which will normally be contacted by molten metal, the said insulative refractory ceramic being non-wetting with respect to the metal being cast. 7. The method as claimed in claim 6, in which: the said insulative refractory ceramic is zirconia. 8. The method of continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between opposed moving mold surfaces and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the method comprising: reducing the rate of heat transfer from the freezing metal to the said edge-dam blocks to a value of less than 80 percent of the said rate against uncoated edge-dam blocks consisting of similar base material similarly placed. 9. The method as claimed in claim 8, in which: the reduction in heat transfer is achieved by means of, prior to casting the metal product: applying an adherent intermediate layer of refractory metal to those faces of the said edge-dam blocks which will normally be contacted by molten metal, and applying an adherent coating of molten insulative refractory ceramic to the refractory metal on the said edge-dam blocks on the faces which will normally be contacted by molten metal, the said insulative refractory ceramic being non-wetting with respect to the metal being cast. 10. The method for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between opposed moving mold surfaces and laterally defined by first and second travelling edge dams consisting of flexible strings of blocks mainly metallic the method comprising, prior to casting the metal product: applying an adherent intermediate layer of refractory metal to those faces of the said edge-dam blocks which will normally be contacted by molten metal, and applying an adherent layer of molten insulative refractory ceramic to the refractory metal on those faces of the dam blocks which will normally be contacted by molten metal, said insulative refractory ceramic being non-wetting with respect to the metal being cast, followed by: causing the said edge-dam blocks to be jiggled or vibrated while in contact with the freezing product, whereby: the rate of heat transfer during casting is reduced to a value of less than 80% of said rate against untreated edge dam blocks of similar base material similarly placed. 11. The method for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between opposed moving mold surfaces and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the method comprising, prior to casting the metal product: applying an adherent intermediate layer of refractory metal to those faces of the said edge-dam blocks which will normally be contacted by molten metal, and applying an adherent layer of molten insulative refractory ceramic to the refractory metal on those faces of the said edge-dam blocks which would normally be contacted by molten metal, the said insulative refractory ceramic being non-wetting with respect to the metal being cast, followed by: hardening the remaining faces of the said edge-dam blocks by the process of nitriding, without any masking of previously coated surface, whereby: the rate of heat transfer during casting is reduced to a value of less than 80% of said rate against untreated edge-dam blocks of similar base material similarly placed, while the said edge-dam blocks are rendered long wearing at minimal cost. 12. The method for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between opposed moving mold surfaces and laterally defined by first and second travelling edge dams consisting of flexible strings of blocks mainly metallic, the method comprising: heating the said edge-dam blocks to a temperature of at least 50 percent of the freezing point of the metal being cast, as measured on the Fahrenheit scale, but to not less than 450 degrees Fahrenheit, whereby: the rate of heat transfer during casting is reduced to a value of less than 80% of said rate against untreated edge-dam blocks of similar base material similarly placed. 13. The method for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between opposed moving mold surfaces and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the method comprising: causing the said edge-dam blocks to wobble in relation to the freezing metal product for breaking close thermal contact between each block and the freshly frozen metal, whereby: the rate of heat transfer during casting from the metal into the blocks is reduced to a value of less than 80% of the value occurring with similar blocks similarly placed without such wobbling. 14. The method for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between the mold surfaces of two opposed, cooled moving endless flexible casting belts passing over backup rollers and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the method comprising: reducing the rate of heat transfer from the freezing metal to the said edge-dam blocks to a value of less than 80 percent of the said rate against either adjacent flexible casting belt. 15. The method as claimed in claim 14, in which: the reduction in heat transfer is achieved by means of, prior to casting the metal product: applying an adherent intermediate layer of refractory metal to those faces of the said edge-dam blocks which will normally be contacted by molten metal, and applying an adherent coating of molten insulative refractory ceramic to the refractory metal on the said edge-dam blocks on the faces which will normally be contacted by molten metal, the said refractory insulative ceramic being non-wetting with respect to the metal being cast. 16. The method as claimed in claim 15, in which: the said insulative refractory ceramic is zirconia. 17. The method for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between the mold surfaces of two opposed, cooled moving endless flexible casting belts passing over backup rollers and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the method comprising: reducing the rate of heat transfer from the freezing metal to the edge-dam blocks to a value of less than 80 percent of the said rate against uncoated edge-dam blocks consisting of similar base material similarly placed. 18. The method as claimed in claim 17, in which: the reduction in heat transfer is achieved by means of, prior to casting the metal product: applying an adherent intermediate layer of refractory metal to those faces of the said edge-dam blocks which will normally be contacted by molten metal, and applying an adherent coating of molten insulative refractory ceramic to the refractory metal on the said edge-dam blcoks on the faces which will normally be contacted by molten metal, the said refractory insulative ceramic being non-wetting with respect to the metal being cast. 19. The method for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between the mold surfaces of two opposed, cooled moving endless flexible casting belts passing over backup rollers and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the method comprising, prior to casting the metal product: applying an adherent intermediate layer of refractory metal to those faces of the said edge-dam blocks which will normally be contacted by molten metal, and applying an adherent layer of molten insulative refractory ceramic to the refractory metal on those faces of the said edge-dam blocks which will normally be contacted by molten metal, the said insulative refractory ceramic being non-wetting with respect to the metal being cast, followed by: causing the said edge-dam blocks to be jiggled or vibrated while in contact with the adjacent freezing product, whereby: the rate of heat transfer during casting is reduced to a value less than 80% of said rate against untreated edge-dam blocks of similar base material similarly placed. 20. The method for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between the mold surfaces of two opposed, cooled moving endless flexible casting belts passing over backup rollers and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the method comprising, prior to casting the metal product: applying adherent intermediate layer of refractory metal to those faces of the said edge-dam blocks on the faces which will normally be contacted by molten metal, and applying an adherent layer of molten insulative refractory ceramic to the refractory metal on those faces of the said edge-dam blocks which will normally be contacted by molten metal, the said insulative refractory ceramic being non-wetting with respect to the metal being cast, followed by: hardening the remaining faces of the said edge-dam blocks by the process of nitriding, without any masking of previously coated surface, whereby: the rate of heat transfer during casting is reduced to a value of less than 80% of said rate against untreated edge-dam blocks of similar base material similarly placed, while the said blocks are rendered long wearing at minimal cost. 21. The method for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between the mold surfaces of two opposed, cooled moving endless flexible casting belts passing over backup rollers and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the method comprising: heating the said edge-dam blocks to a temperature of at least 50 percent of the freezing point of the metal being cast, as measured on the Fahrenheit scale, but to a temperature of not less than 450 degrees Fahrenheit, whereby: the rate of heat transfer during casting is reduced to a value of less than 80% of said rate against untreated edge-dam blocks of similar base material similarly placed. 22. The method for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between the mold surfaces of two opposed, cooled moving endless flexible casting belts passing over backup rollers and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the method comprising: causing the said blocks to oscillate in relation to the freezing metal product for breaking close thermal contact between each block and the freshly frozen metal, whereby: the rate of heat transfer during casting from the metal into the blocks is reduced to a value less than 80% of the rate of heat transfer from the metal into similar blocks similarly placed without oscillating. 23. The apparatus for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the apparatus comprising: an adherent intermediate layer of refractory metal on those faces of the said edge-dam blocks which will normally be contacted by molten metal, and an outer adherent layer of molten insulative refractory ceramic on the layer of refractory metal on those faces of the said edge-dam blocks which will normally be contacted by molten metal, the thermal conductance of the said layer being no more than 3000 British thermal units per square foot per hour per degree Fahrenheit, the said insulative refractory ceramic being non-wetting with respect to the metal being cast, whereby: the rate of heat transfer during casting is reduced to a value of less than 80% of said rate against untreated edge-dam blocks of similar base material similarly placed. 24. The apparatus as claimed in claim 23, in which: the said insulative refractory ceramic is zirconia. 25. Apparatus for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between opposed moving mold surfaces and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the apparatus comprising: an intermediate layer of refractory metal which is adhered to those faces of the dam blocks which will normally be in contact with molten metal, and an outer adherent coating of insulative refractory ceramic on the layer of refractory metal on those surfaces which will normally be contacted by molten metal, said insulative refractory ceramic thickness being at least 0.003 inch (0.08 mm), the said insulative refractory ceramic being non-wetting in relation to the metal being cast, whereby: the rate of heat transfer during casting is reduced to a value of less than 80% of said rate against untreated edge-dam blocks of similar base material similarly placed. 26. The apparatus as claimed in claim 25, in which: the said insulative refractory ceramic is zirconia. 27. The apparatus as claimed in claims 23, 24, 25, or 26 in which: at least one edge of the constituent material of the said dam blocks adjacent to their working faces is chamfered to relieve its sharpness, whereby: the said layer of insulative refractory ceramic is protected from chipping. 28. Apparatus for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between opposed moving mold surfaces and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the apparatus comprising: means to effect slight movement of some of the said blocks in relation to the freezing metal product, whereby: the rate of heat transfer during casting is reduced. 29. Apparatus for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between the mold surfaces of two opposed, cooled moving endless flexible casting belts passing over backup rollers and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the apparatus comprising: an adherent intermediate layer of refractory metal on those faces of the said edge-dam blocks which will normally be contacted by molten metal, and an outer adherent layer of molten insulative refractory ceramic on the layer of refractory metal on those faces of the dam blocks which will normally be contacted by molten metal, the thermal conductance of said layer being no more than 3000 British thermal units per square foot per hour per degree Fahrenheit, the said insulative refractory ceramic being non-wetting in relation to the metal being cast, whereby: the rate of heat transfer during casting is reduced to a value of less than 80% of said rate against untreated edge-dam blocks of similar base material similarly placed. 30. The apparatus as claimed in claim 29, in which: the said insulative refractory ceramic is zirconia. 31. Apparatus for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between the mold surfaces of two opposed, cooled moving endless flexible casting belts passing over backup rollers and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the apparatus comprising: an intermediate layer of refractory metal adhered to those faces of the dam blocks which will normally be in contact with molten metal, and an outer adherent coating of insulative refractory ceramic on the layer of refractory metal on those surfaces of the edge-dam blocks which will normally be contacted by molten metal, said insulative refractory ceramic thickness being at least 0.003 inch (0.08 mm), the said insulative refractory ceramic being non-wetting in relation to the metal being cast, whereby: the rate of heat transfer during casting is reduced to a value of less than 80% of said rate against untreated edge-dam blocks of similar base material similarly placed. 32. The apparatus as claimed in claim 31, in which: the said insulative refractory ceramic is zirconia. 33. Apparatus for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between the mold surfaces of two opposed, cooled moving endless flexible casting belts passing over backup rollers and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the apparatus comprising: an adherent intermediate layer of refractory metal on those faces of the said edge-dam blocks which will normally be contacted by molten metal, and an outer adherent coating of insulative refractory ceramic on the layer of refractory metal on those faces of the dam blocks which will normally be contacted by molten metal, the said insulative refractory ceramic being non-wetting with respect to the metal being cast, together with: the said backup rollers in such capacity as to effect slight movement of the said dam blocks in relation to the freezing metal product, by the close moving proximity of the said blocks past the said rollers, whereby: the rate of heat transfer during casting is reduced to a value of less than 80% of said rate against untreated edge-dam blocks of similar base material similarly placed. 34. The apparatus as claimed in claim 33, in which: the said insulative refractory ceramic is zirconia. 35. The apparatus as in claims 29, 30, 31, 32, 33, or 34 in which: at least one edge of the constituent material of the said dam blocks adjacent to their working faces is chamfered to relieve it of its sharpness, whereby: the said insulative refractory ceramic is protected from shipping. 36. Apparatus for continuously casting metal product of a thickness between 1/4 inch (6 mm) and 3 inches (75 mm) and of a width at least four times its thickness, directly from molten metal, wherein the molten metal is introduced into a moving mold, said moving mold being defined between the mold surfaces of two opposed, cooled moving endless flexible casting belts passing over backup rollers and laterally defined by first and second traveling edge dams consisting of flexible strings of blocks mainly metallic, the apparatus comprising: slightly tapered conical collars on and concentric to the said backup rollers at points opposite the said edge dams, the collars being arranged so as to cause the said dam blocks to oscillate in slight rotation as they pass between the said backup rollers, whereby: the rate of heat transfer during casting is reduced.