Patent GB-1444625-A (GB)
Title: Continuous casting of metals to form composite strands
IPC: B22D11/11
Filed: 1973-07-26
Abstract: 1444625 Continuous composite casting; making porous metal plates CONCAST AG 26 July 1973 [27 July 1972] 35709/73 Headings B3A and B3F Porous bodies 20, e.g. of carbon with a metal coating or of carbonized balsa wood, having a specific gravity less than unity, are introduced into molten metal such as Al, Cu, iron or steel 10 before it commences to solidify in a continuous casting mould 2, and pressure at least equal to the buoyancy acting on the bodies 20 in the metal is applied (e.g. by a feed 23, Fig. 1, or transverse walls 60, Fig. 2, of a container 45 formed by three axially-movable walls 46, 47 (48) of steel wire grid or Al sheet, and a fixed plate wall (49). The resulting strand, with a proportion of about 60% porous spheres encast, if the metal is Al, has a specific gravity slightly more than unity. In Fig. 1 a refractory container 3 closes the top of an oscillated copper mould 2 and is fed from a tundish 13 and also provided with oil lubrication and an induction heater 36 so that the solidification can be retarded and the porous bodies 20 pre-heated. They may be 4-6 mm. spheres of specific gravity less than 0À1 and fed through a blanket of inert gas from a line 26. The tundish stopper rod is controlled by a mechanism 34 of a control 30 for maintaining the level in the container 3. Combustion products are sucked out of the container 3 and it has an inlet for inert gas. The speed of rotation of the screw feed 23 is related to the speed of the withdrawal rolls 5 by an electrical connection 35 to maintain the proportion of porous bodies 20 in the casting. In Fig. 2, the two wide walls 46, 47 and one narrow wall (48) advanced into the mould 2 by rollers 50, 51, (52) may be steel wire grids which become embedded with the proous bodies 20 in a cast Al slab or may be Al sheet which deoxidizes steel which is cast. The walls 60 which push down the porous bodies 20 are fixed at intervals on the wall 47 and are located by supports 61 on the wall 46. The three grid walls may be spaced from sides of a refractory container 40 (which may be omitted) and the mould 2, as shown, so that bodies 20 contained by the walls are spaced from three sides of the casting. The molten metal enters through a side opening (41) in the container 40. Making plates.-Two cast slabs may be subsequently welded together at their fourth (narrow) sides where the bodies are visible. However both narrow sides may be so open and a number of slabs may be welded together and have a specific gravity less than 1 to be floatable on water. In another embodiment, Fig. 4 (not shown), the vertical mould is provided by two pairs of endless moving bands and the tundish spout and screwfeed extend through a block (82) which closes the top of the mould space. A level controller like that of Fig. 1 maintains the metal level above the parts of the belts cooled by sprays and features of Fig. 2 may be used. Arrangements for horizontal or upward casting of a round bar, Fig. 5 (not shown), have the screwfeed mounted on a vertical inlet of a horizontal refractory container (87) extending from an open-topped feeding vessel for molten iron. To prevent entry of the porous bodies (20) into the feed vessel, the container (87) may include a perforated barrier at its metal inlet portion or, preferably, the latter may incline down to the vessel outlet. The mould has a graphite lining wherein the iron is moved round by an electromagnetic coil (102) to distribute the porous spheres. The strand withdrawl for horizontal casting is intermittent and synchronized with the screwfeed. A container with an extended outlet may be used in an upward casting installation. The casting direction may be arcuate. The strand may be tubular.