Induction heating furnace and bottom tapping mechanism thereof

Details Induction heating furnace and bottom tapping mechanism thereof Induction heating furnace and bottom tapping mechanism thereof

2002-02-01

2003-01-14

Hoang, Tu Ba (Department: 3742)

Industrial electric heating furnaces

Induction furnace device

For charging or discharging

C373S156000

Reexamination Certificate

active

06507598

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an induction heating furnace for melting metals through induction heating and a bottom tapping mechanism thereof.
2. Description of the Related Art
In the case of producing a high purity metal or a metal alloy of desired components by melting a high reactive metal, attention has focused on an induction heating furnace which is capable of ensuring an uniform temperature over the entirety of a molten metal by induction heating and agitation to prevent variations in quality, and also suppressing the mixing of impurities into the molten metal to a low level, to prevent reduction in quality.
A conventional induction heating furnace has a side wall extending so obliquely as to increase an aperture from a bottom having a tapping portion to a certain point and then rising up vertically therefrom to an upper edge with the aperture kept at a constant diameter, as disclosed by, for example, Japanese Laid-open Patent No. Hei 4(1992)-327342. The side wall is formed by a plurality of longitudinally split, conductive segments arrayed circumferentially and insulated from each other. At the outer periphery of the side wall, an induction coil is arranged so that a metal at the inside of the side wall can be heated by induction heating. The tapping portion is provided with a mold to which a tapping passageway is communicated vertically. With the induction heating furnace thus constructed, the metal is melted by induction heating and then the molten metal flows into the tapping passageway of the mold, so as to be taken out with being solidified.
Also, Japanese Laid-open Patent No. Hei 8(1996)-145571 discloses an induction heating furnace including a side wall rising up vertically from a flat bottom having a tapping portion to an upper end, with an aperture kept at a constant diameter; and a bottom lid for closing the tapping portion. This induction heating furnace is so designed that when metal is melted by induction heating, the bottom lid can be melted to open the tapping portion, so as to take out the molten metal.
With the former arrangement in which the mold is provided at the tapping portion, a solidified layer in the tapping passageway in the mold and a solidified layer on the side wall become connected with each other. Due to this, taking out the metal from the mold requires a very large drawing force, thus causing difficulties in taking it out. Also, with the latter arrangement in which the tapping portion is closed with the bottom lid, once the bottom lid is melted to open the tapping portion, the tapping portion cannot be closed until all molten metal has completely been taken out. Due to this, switching between the melting of the metal and taking out the molten metal cannot be made smoothly. In short, the conventional type arrangements have a first problem that the melting of the metal and the task of taking out the molten metal cannot be made with ease and the switching operation between the melting of metal and taking out the molten metal cannot be made smoothly.
Further, where the side wall rises up with the aperture kept at a constant diameter, as in the above-described arrangement, when metallic vapor evaporates from the molten metal surface or the components of the gas produced in the molten metal dissipates from the molten metal surface, the evaporating direction of the metallic vapor or the rising direction of the gas become parallel to a wall surface of the side wall. Thus, the conventional arrangements have the second problem that the metal easily adheres to the side wall, thus requiring labor in the cleaning of the side wall, while the gas readily contacts the side wall to increase the flow resistance of the exhaust gas, which hinders the gas from being fully eliminated and causes a reduction of quality.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an induction heating furnace capable of solving at least one of the first and second problems described above, and a bottom tapping mechanism thereof.
According to a feature of the present invention, the above and other objects are accomplished by a novel induction heating furnace which comprises an accommodating vessel having a bottom, a tapping portion formed at the bottom, and a side wall formed by a plurality of longitudinally split, conductive segments arrayed circumferentially and insulated from each other for accommodating a to-be-melted material therein while cooling it; a coil arranged at an outer periphery of the tapping portion and the side wall for subjecting the to-be-melted material in the accommodating vessel to induction heating; a power source for supplying power to the coil; and a power source control for controlling the power source so that the tapping portion can be selectively switched between open and closed states by the melting and solidification of the to-be-melted material.
This construction can provide the following results. When the to-be-melted material accommodated in the accommodating vessel is subjected to induction heating, the to-be-melted material is melted while the molten material at the part contacting the side wall and a bottom wall of the accommodating vessel and the wall surface of the tapping portion is cooled and solidified. Thus, the power source control controlling the induction heating by the power source enables the tapping portion to be closed by the solidified material when the to-be-melted material is melted, and to be opened by melting the solidified material when the melted material is taken out. This enables the melting and removal of the material to be facilitated and also enables the switching operation between melting and takeout to be made with ease.
The induction heating furnace according to the invention may comprise an accommodating vessel having a bottom, a top edge portion and a side wall extending so obliquely as to increase in radius from the bottom to the top edge portion and formed by a plurality of longitudinally split, conductive segments arrayed circumferentially and insulated from each other; a coil arranged at an outer periphery of the side wall for subjecting a to-be-melted material accommodated in the accommodating vessel to induction heating; and a power source for supplying AC power to the coil.
This construction can provide the following results. When AC power is supplied to the coil from the power source, an alternating magnetic field is generated by the coil, whereby the to-be-melted material accommodated in the accommodating vessel is subjected to induction heating and is melted. When the to-be-melted material is thus melted material, the to-be-melted material evaporates at the molten material surface, and also components of gas produced in the molten material are discharged therefrom. At that time, the rise of the evaporated material and of the vaporized gas is not obstructed by the side wall, because the side wall of the accommodating vessel extends so obliquely as to increase in radius from the bottom to the top edge portion. Thus, almost no evaporated material contacts the side wall above the molten material surface, so that the drawbacks caused by the to-be-melted material adhering to the side wall are reduced. In addition, since almost no gas contacts the side wall, the flow resistance of the exhaust gas can be reduced and the gas can be fully eliminated.
Also, the induction heating furnace according to the present invention may comprise an accommodating vessel having a bottom, a top edge portion, a tapping portion formed at the bottom, and a side wall extending so obliquely as to increase in radius from the bottom to the top edge portion and formed by a plurality of longitudinally split, conductive segments arrayed circumferentially and insulated from each other; a coil arranged at an outer periphery of the tapping portion and the side wall for subjecting a to-be-heated material in the accommodating vessel to induction heating; a power source for supplying AC power to the coil; and a power source control for contro

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