Industrial electric heating furnaces – Arc furnace device – Charging or discharging
Patent
1997-06-05
1998-09-22
Hoang, Tu B.
Industrial electric heating furnaces
Arc furnace device
Charging or discharging
373 81, 373 84, 373115, 373143, 266 15, 266 45, 266242, F27D 300
Patent
active
058125876
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the supply of molten metal from a holding furnace to a casting launder and in particular to an apparatus and process which enables the supply of molten metal to continue while the holding furnace is being recharged. The invention also relates to a process for refilling the holding furnace of the invention and the batch operation of the apparatus.
2. Description of the Related Art
During the casting of molten metals such as aluminium, a holding furnace is tilted to maintain a constant level in the casting launder. The level in the launder is usually automatically controlled by sensing the launder metal level and tilting the furnace by adjusting the flow of hydraulic fluid to the furnace tilting cylinder(s).
In conventional arrangements where the holding furnace is filled by pouring, a charging port shaped like an angled funnel is often used to direct the molt metal poured from a spout on the transport crucible through the furnace wall above the maximum metal level. Where the furnace is filled by siphoning, the siphon pipe is usually suspended from an overhead hoist with the delivery leg of the pipe passing through a hole in the wall of the furnace above the maximum metal level. Where a charging port is employed, it is usually located to suit the delivery point of the transport crucible and to avoid furnace equipment such as burners and access doors. This type of conventional charging arrangement will not normally permit the furnace to be tilted during a charging operation. While the furnace is continually tilting about the tilt axis during the casting operation, it is technologically difficult and would require complex equipment to be able to charge fresh molten metal to the holding furnace during a casting operation.
Consequently, once the holding furnace is emptied, it is returned to its upright position and refilled by either pouring or as has been suggested, siphoning molten metal from the potline crucible which supplies molten metal.
To provide a casting operation with a continuous supply of molten metal, it is necessary to have two holding furnaces arranged to feed into a common launder system. While this results in a duplication of supply apparatus, and increased capital cost, it allows one furnace to supply the casting operation, while the other furnace is being filled.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of supplying molten metal and an apparatus for the supply of molten metal which enables intermittent charging while maintaining a constant supply of molten metal to the casting process.
Accordingly, the invention provides a method of supplying molten metal including the steps of providing a holding furnace for molten metal pivotable about a pivot axis, tilting said holding furnace about the pivot axis for the supply of molten metal to a casting process from an outlet in the holding furnace via a launder, intermittently charging a controlled flow of molten metal to an inlet well communicating with a metal chamber in the holding furnace and positioned on the holding furnace on or adjacent to the pivot axis of the holding furnace, the inlet well being axially displaced along the pivot axis from the outlet of the holding furnace and controlling the tilting of the holding furnace to maintain the level of molten metal in the launder at a predetermined level.
By maintaining the level of molten metal in the launder at a predetermined level, a constant supply of molten metal can be maintained to the casting process.
Preferably the tilting of the holding furnace is controlled by monitoring the level of molten metal in the launder and adjusting the tilt angle of the holding furnace to maintain a predetermined level of molten metal in the casting launder.
In a preferred form of the invention, the molten metal is charged into the inlet well of the holding furnace from a crucible. The level of molten metal in the crucible is preferably above the level of molten metal in the inlet
REFERENCES:
patent: 3747912 (1973-07-01), Wernii
patent: 3898365 (1975-08-01), Antoine et al.
patent: 4433421 (1984-02-01), Wooding
patent: 5559827 (1996-09-01), Shimada et al.
Comalco Aluminium Limited
Hoang Tu B.
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