Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1990-11-19
1992-09-15
Batten, Jr., J. Reed
Metal founding
Process
Shaping liquid metal against a forming surface
164509, B22D 2310, B22D 2702
Patent
active
051469766
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is related to the electro-slag refining process.
Briefly stated, the electro-slag refining process comprises providing a pool of electrically conductive molten slag in a metallic bath into which is fed a consumable electrode through which a current is fed into the slag pool to keep it molten. Metal melts from the electrode and falls in drops to the bottom of the bath during which process it is refined, with dross and impurities floating to the top of the pool. Usually all of the refined metal is derived from the electrode, but this is not essential and in other embodiments bar stock or the like may be fed into the slag in addition to the electrode.
If the bottom of the bath incorporates a cooled exit passage (the combination of an electro-slag bath and structure defining such a passage is called a "mould" hereinafter) from which a solidified plug may be extracted, the rates of electrode feed and plug extraction and the amperage may be adjusted and controlled to provide for the continuous casting of an ingot of the refined metal. The emerging ingot has a cross-sectional shape determined by that of the passage.
Similarly, if a hot core body substantially but not completely plugging the passage is moved through the mould at an appropriate velocity, refined metal entering the passage with the core body may fuse to it to become a surface layer thereon conforming to the passage shape.
The invention utilises both versions of the process described above either to make an ingot, suitable for use, for example, as a mill roll, from raw stock metal, or to apply a surface layer to a core body, which may be a worn mill roll to be thus reclaimed.
DESCRIPTION OF THE PRIOR ART
Australian patent specification 466334 (The British Iron and Steel Research Association) discloses both the production of a tubular ingot and the surface cladding of a roll shaped arbor by the electro-slag process. In the latter instance the relative movement of the arbor and the mould is effected by raising the mould about the arbor. There is no suggestion of any movement of the consumable electrodes relative to the mould except for their raising and lowering to maintain current flow through the flux. The arbor may be rotated about its own axis as cladding proceeds. A coil encircles the mould which is said to be activated "to promote stirring of the flux and molten metal pool" in the mould but there are no further details or paramaters of that coil. Because in electro-slag apparatus the heating current tends to take the shortest path from the electrode(s) to the mould it is thought, with electrode(s) disposed as shown in this prior art specification, that the degree of stirring that would be required to produce substantially uniform temperatures throughout the bath, would be impracticable to obtain.
Australian patent specification 535772 (Nippon Steel Corporation) also discloses the cladding of a cylindrical core body by the electro-slag process. This specification also discloses apparatus in which the mould rises about the core body. The core body is rotated about its own axis, allegedly to obtain "a uniform circumferential temperature-distribution in the slag". The mould is preferably rotated in synchronism with the core body "to reduce friction between the mould and the workpiece".
Thus both of the prior art specifications (which are the most pertinent known to the applicant) teach the desirability of uniform temperature distribution in the slag and both disclose apparatus in which the mould is raised to create the relative movement of mould and the emergent product.
In practice it is necessary to set or adjust several parameters simultaneously to obtain a fully formed ingot or a fully formed and correctly bonded surface layer. Those parameters include the speed of relative movement between the mould and the product, the magnitude of the electric current, the temperature of the core body, the feed-in speed of the electrode(s), the level of the liquid metalflux interface in the mould and the depth o
REFERENCES:
patent: 3834443 (1974-09-01), Ujiie
patent: 3835914 (1974-09-01), Ujiie
patent: 3835916 (1974-09-01), Ujiie
patent: 4280550 (1981-07-01), Roberts
Batten, Jr. J. Reed
The Broken Hill Proprietary Company Limited
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