GB760154A - Continuous metal casting process - Google Patents

Abstract

760,154. Continuous - casting machines. AMERICAN SMELTING & REFINING CO. April 27, 1954 [July 21, 1953], No. 12242/54. Class 83 (1). A continuous-casting process, particularly for copper and copper-base alloys, comprises casting into an open-ended mould having an uncooled section whose inside surface-temperature is maintained above the melting-point of the metal, and an adjacent chill-zone whose temperature is maintained below the freezing-point of the metal, the melt being introduced into the end containing the uncooled zone at a rate which, in relation to the withdrawal rate, is sufficient to maintain molten and non-turbulent metal in the uncooled zone in the vicinity of a plane between the zones, and in which plane the metal remains entirely molten. The metal is maintained stationary with respect to the mould in the chill-zone until a shell of strength to permit withdrawal without rupture is formed by heat withdrawal laterally through the surface of the chill-zone, thereafter a predetermined length of cast-metal is withdrawn from the other end of the mould, the withdrawal is stopped before shell formation takes place on a major portion of the outer surface of the moltenmetal moving beyond said plane into the chillzone during withdrawal, and the shell freezing and casting withdrawal steps are repeated until a casting of desired length is obtained, whereby a major proportion of the shell of the thuswithdrawn metal is formed within the mould while stationary with respect thereto, thereby enhancing the surface characteristics of the casting. The stationary period is preferably such that no molten-metal exists in the casting below the boundary between the two zones at a distance which exceeds the largest horizontal dimension of the mould-cavity. A mould 2, Fig. 1, threadedly-connected to a holding- furnace 12, comprises an uncooled-section 9 and a chill-section 10, the casting being intermittently withdrawn by rolls 11, at least one of which is driven and may be braked. In a modification, Fig. 2, particularly for casting large shapes, the metal falls freely into a graphite-mould 2 from a launder 25 supplied by a tilting-furnace 24 arranged to deliver at a rate which, in relation to the withdrawal-rate, maintains non-turbulent conditions in the pool above the line 32, below which the metal is frozen. A layer 34 of powdered material, e.g. graphite, magnesia, charcoal, coal or coke-breeze is maintained on the molten-metal surface, or alterna. tively an inert or reducing gas such as N, CO, may be used. To prevent oxidation of the outside-wall of the uncooled section of the mould, it is surrounded by a wall 35 and the annular space 36 filled with the protective material. Alternatively the section may contain a ceramic or replaceable graphite insert protecting the inner or both inner and outer surfaces. The uncooled section, the launder and the space in the furnace may be protected by an inert or reducing gas. Heat may also be applied to the uncooled-section. The chill section may be of metal, e.g. copper. In a further modification a mould having a number of cavities is used, particularly for small shapes. The intermittent withdrawal may be effected by reciprocating the mould, which moves with the continuously-lowered casting during the periods in which the metal is stationary with respect to the mould, and then is moved upwardly to effect withdrawal.