Patent GB-686033-A (GB)
Title: Continuous casting process and apparatus
IPC: B22D11/20
Filed: 1950-06-05
Abstract: 686,033. Continuous casting-machines. BABCOCK & WILCOX CO. June 5, 1950 [July 9, 1949], No. 13988/50. Class 83 (i). [Also in Group XL (b)] Ferrous metal is continuously cast in a vertical open-ended mould made of a metal of lower melting-point, by pouring molten metal at a substantially uniform rate from the lip of a storage vessel into the top of the mould where an oxygen consuming atmosphere is maintained, cooling the exterior of the mould by a high velocity turbulent flow of cooling liquid and by mechanically withdrawing the solidified casting at a cyclically changing rate. A vessel 10 containing molten metal is mounted on a frame 14 adapted to be tilted on trunnions 13 by a cable 20 passing over a drum 18 driven by a motor 27. In order that the rate of pouring shall be constant, the rate of tilt of the vessel 10 is controlled by a pin cam 22 driven at a uniform angular velocity by a synchronous motor 23. One shaft 32 of a differential comparator 33 is driven at the speed of the drum 18 while the other shaft 35 is driven through pulleys 37, 38 from a chain 36 riding on the contour of the cam 22. Any difference in movement of the shafts 32, 35 causes a rotation of the output shaft 42 of the comparator which acts through a control unit 24 and rheostat to alter the speed of the drum 18 and consequently the rate of tilt of the vessel. From the vessel 10, the molten metal enters the receiving chamber 44a of a tundish, passes through a port 46 into the discharge chamber 44b, which is heated by a burner 43, and thence by way of a pouring lip 48 into the mould 60. The tundish may be tilted about trunnions 50 by a screw 57 and may be adjusted by other screws in two directions in the horizontal plane. The mould comprises an open-ended tube 60 of oval cross-section, preferably of brass or copper mounted in a top plate 90 and surrounded by a metal skirt 93 leaving an annular passage 61 through which cooling water is passed as a high velocity turbulent stream from a chamber 91 and pipes 92. An oxygen consuming atmosphere is maintained above the metal in the mould as described in Specification 656,386. Below the mould, the casting is cooled by water jets from nozzles 75 and then passes between spaced pairs of pinch rolls 71 driven by a variable speed motor 70 which is operated so that the level of the molten metal alternately rises and falls. While the surface of the metal is at the lower level, the upper part of the mould is cooled and so acts as a chill when the level rises again, thus causing a more rapid growth of a solid skin. The cyclic operation of the pinch rolls may be effected by time control or by time control for only one part of the cycle, the other part being under the control of a level detector, or by level-detector control for each part of the cycle or by time control for each part with a detector control used as a safety device at either or both levels. The detector comprises an X-ray tube 62 from which rays pass through the mould into an ionization chamber 64 having means for measuring the conductivity thereof, changes in which are used to influence the control device of the motor 70. When the withdrawal of the casting is stopped, it may be stopped suddenly by means of a brake 74 so that the inertia of the molten centre tends to bulge out the solid skin into contact with the mould from which it had shrunk, and so increase the rate of cooling.