Patent GB-1457263-A (GB)
Title: Continuous casting of ingots
IPC: B22D11/14
Filed: 1973-12-17
Abstract: 1457263 Continuous casting; making girders URAL ORDENA TRUDOV KRAS ZNAMENI POLITEKHN INST IM KIROVA 17 Dec 1973 58391/73 Headings B3A and B3F Molten metal 2 is fed up into a curved mould 3 (by gas pressure in a tundish 1 or by an induction pump in an interconnection 4, both 1 and 4 being preheated) to contact a dummy bar head 10, Fig. 2, having a channel 14 through which air escapes (and attached by grippers 11, 12 to a withdrawing device 13), then the pressure of metal is increased to urge the forming strand shell 16 against the mould surface and then reduced; a hole is then made (by a tool inserted through the channel 14) in the shell formed on the end of the dummy head 10 and neutral gas is fed therethrough to form a gas cushion; a length of shell is then withdrawn upwardly into a secondary cooling device (water-cooled guide bars and rolls 8) leaving the tail and in the mould 3; further molten metal is then fed in to form a succeeding length of shell 16 (joined to the lower end of the previous length) in the same manner as before, i.e. with a period of increase of metal pressure, during which time the first shell length is moved back slightly to compensate for contraction of the fresh length; This cycle may be repeated to provide a series of such attached tubular lengths and, in any case, with each withdrawal of a length from the mould, a previously withdrawn hollow length is straightened and reduced, e.g. by rolls 9, possibly to an intermediate profile before a second reduction to an I-profile, Fig. 7, in which case there may be induction heaters at the top of the secondary cooling zone. The pressing of the skin 16 against the mould wall is said to result in a fine-grained product. During the pause between withdrawals, the metal pressure may be changed repeatedly, the height of the metal varying between Hmax and Hmin, i.e. over a range of 0À5-2 m., such that the level of the metal in the mould varies at a rate of 0À5 to 1À5 m./sec. The mould cooling may be varied. 1-3 sees. before strand-length withdrawal, a cooling agent, e.g. a liquid metal, at 100-400‹ C., may be fed to the mould 3 so that the consequent expansion of the latter facilitates withdrawal. Subsequent use of a cooler agent gives extra pressure by the mould walls on the solidified skin. For composite products having layers of different metals, a hollow length of strand is cast as before and the molten metal drained out before a second metal is put in the tundish 1 and supplied to the strand interior up to a required level so that a lining layer is cast under the pressure of a gas cushion 17. This may be repeated with a third metal and in each case the level of molten metal may be raised and lowered as before. The length of shell formed is withdrawn and reduced as before. Before feeding in the later metals, the shell is heated by feeding in a coolant at 200-400‹ C. to the mould and by heating the shell by induction heating in the secondary cooling zone. After holding the later metal, a lower temperature coolant is substituted and there is contraction of the primary shell on to inner layers for tighter fit and cohesion.