GB1338061A - Electroslag refining process - Google Patents

Abstract

1338061 Casting processes and moulds BRITISH IRON & STEEL RESEARCH ASSOCIATION 15 Oct 1971 [15 Oct 1970] 48931/70 Heading B3F An electroslag refining process for casting ingots with a change of cross-section along their length uses a mould comprising upper and lower sections 4, 5, the diameter of the lower section 4 being greater than that of the upper section 5, and the upper section 5 depending into the lower section 4 with a space between opposing walls of each section. When casting an ingot for a roll, a mould including a cooled base-plate 3 surmounted by three cooled mould sections 2, 4, 5 is employed and the process commenced by fusing a consumable electrode 9 into a molten slag bath 8 in the lowest mould section 2. When the molten metal level 10 reaches the centre mould section 4 additional slag is added to the slag bath 8 to maintain a constant depth of molten slag. The additional slag is supplied as powder retained in the centre mould section 4 by a tube 7 of material destroyed by the molten slag, or as a liquid through an aperture in the mould wall (not shown). An annular electrode 13 or a circular array of rods (not shown) is/are fused down with electrode 9 into the centre mould section 4. As the molten metal reaches a level B-B in the centre mould section 4 fusing down of electrodes 9, 13 is stopped and the upper mould section 5 is lowered into the slag bath 8 to displace excess slag into the space between the upper and centre mould sections, where it can be frozen by a chill plate (not shown). To complete the ingot the electrode 9 is fused down into the upper mould section 5. In an alternative embodiment, the lower section 2 of a similar 3-section mould is provided with a baseplate movable between the top and bottom of the lower section. At start-up of the process the base-plate is located at the top of the lower section and an electrode fused into a slag bath in the mould centre section 4. As refining proceeds the base-plate is lowered so that molten metal runs into the lower section 2 of the mould. A further modification involves the use of a preformed electrode with a centre-section of increased diameter compared with its upper and lower sections, which is fused down into a 3- section mould.