EP0657236B1

EP0657236B1 - Molten metal pouring pot with induction heater

Info

Publication number: EP0657236B1
Application number: EP94119315A
Authority: EP
Inventors: Yasuyuki C/O Fuji Electric Co. Ltd. Ikeda
Original assignee: Fuji Electric Co Ltd
Current assignee: Fuji Electric Co Ltd
Priority date: 1993-12-10
Filing date: 1994-12-07
Publication date: 2000-05-10
Anticipated expiration: 2014-12-07
Also published as: CN1056326C; DE69424380D1; JP3094761B2; CN1109807A; TW272953B; MY111808A; JPH07155934A; EP0657236A1; DE69424380T2

Description

BACKGROUND OF THE INVENTION

(Field of the Invention)

The present invention relates to a molten metal pouring pot used when molten metal of conductive metal such as cast iron received from a melting furnace or the like into the molten metal pouring pot is poured into molds or the like, and particularly to a molten metal pouring pot with an induction heater.

(Description of the Related Art)

A molten metal pouring pot is directed to a vessel for storing, carrying and pouring high-temperature molten metal. The housing of the molten metal pouring pot is constituted by a structural steel plate in order to support the weight of the molten metal, and the inner surface thereof is covered with a refractory material so as to be proof against the heat of the molten metal. A molten metal outlet is formed at a place near an upper portion of the molten metal pouring pot so as to facilitate pouring of the molten metal into molds.
The metal which is molten in a melting furnace is put into a molten metal pouring pot, and then carried by a carrying means such as a crane, a hoist or the like to a place where molds are prepared. At that place, the molten metal is poured into a plurality of molds out of the molten metal pouring pot. Generally, about 10 to 40 molds are be filled at one time with molten metal stored in one molten metal pouring pot. It takes 10 to 30 minutes from reception of molten metal into a molten metal pouring pot from a melting furnace till completion of pouring of the molten metal into molds. Meanwhile the temperature of the molten metal goes on dropping so that sometimes it becomes lower than the lowest temperature required for casting to thereby result in defective cast goods. In order to prevent defective goods from being produced, the work of pouring of the molten metal is brought into an end when the temperature of the molten metal becomes lower than the lowest temperature required for casting, even if the molten metal still remains in the molten metal pouring pot. The molten metal remaining in the molten metal pouring pot must be returned into the melting furnace to raise the temperature, and then put into the molten metal pouring pot again so as to be poured into molds. This is a vain work.
In order to eliminate such a vain work of returning temperature-dropped molten metal into a melting furnace again, there is a case where such temperature drop of molten metal is estimated in advance so that the molten metal is heated excessively. In this case, however, a wasteful energy is required for heating molten metal excessively.
In order to solve such a problem that a vain work is carried out and a wasteful energy is required, there is a conventional molten metal pouring pot with an induction heater for compensating for the temperature drop of molten metal. Fig. 7 is a front view of a conventional example 1, and Fig. 8 is a front view of a conventional example 2. Fig. 7 shows an ordinary molten metal pouring pot 71, and Fig. 8 shows a ladle-type molten metal pouring pot 81. In Fig. 7, the molten metal pouring pot 71 has a hanger ear 74 and a housing 72 the inner surface of which is covered with a refractory material 73. Molten metal 1 is stored in the molten metal pouring pot 71 and comes out from a molten metal outlet 75 when the molten metal pouring pot 71 is tilted. A groove-type induction heater 76 is provided in a bottom portion of the molten metal pouring pot 71 to thereby compensate for the temperature drop of the molten metal 1. In Fig. 8, the molten metal pouring pot 81 has a hanger ear 84 and a housing 82 the inner surface of which is covered with a refractory material 83. Molten metal 1 is stored in the molten metal pouring pot 81 and comes out from a molten metal outlet 85 when the molten metal pouring pot 81 is tilted. A crucible-like induction heater 86 is provided in a bottom portion of the molten metal pouring pot 71 to thereby compensate for the temperature drop of the molten metal 1.
In both the conventional examples mentioned above, it is indeed possible to compensate for the temperature drop of molten metal, but it is necessary to provide an induction heater for every molten metal pouring pot, and it is a troublesome work to combine the induction heater with the molten metal pouring pot. In addition, a refractory material of the induction heater is always exposed to a high temperature so that, in fact, it is necessary to repair the refractory material once a day, and every time repair is performed it is necessary to remove and attach electric wiring and cooling pipes from and to the induction heater.
From GB 2226261 A there is known an apparatus for pouring molten metal comprising a tiltable molten metal pouring pot and an induction heater wherein said induction heater is pivotally mounted to the margin of the open end of said pouring pot so as to be opposite through a gap to any molten metal stored in said molten metal pouring pot.
It is an object of the present invention to provide a molten metal pouring pot of a type as indicated in the preamble portion of claim 1, having the improvement that it is not necessary to provide an induction heater for every molten metal pouring pot thereby eliminating the need to combine an induction heater with each molten metal pouring pot.
The above object is achieved by the assembly defined in claim 1.
In a molten metal pouring pot with an induction heater according to the invention, a planar induction coil of the induction heater which is independently separated from the molten metal pouring pot is disposed so as to be opposite through a gap to molten metal stored in the molten metal pouring pot through a gap, and the molten metal pouring pot and the induction heater are shaped and disposed so that the inner circumference of the molten metal pouring pot and the outer circumference of the induction heater do not interfere with each other when the molten metal pouring pot is tilted.
According to a preferred embodiment, the housing of the molten metal pouring pot is constituted by a non-magnetic material.
Further, a yoke may be disposed on the back surface of the induction coil of the induction heater.
Still further, the induction heater may be driven by a commercial frequency.
Still further, the induction heater may have an elevator movable in the vertical direction.
Since the induction heater is independently separated from the molten metal pouring pot, it is not necessary to provide an induction heater for every molten metal pouring pot, and it is not required to combine the induction heater with the molten metal pouring pot. In addition, since the planar induction heater is disposed so as to be opposite through a gap to the molten metal of the molten metal pouring pot, the molten metal is heated so that the temperature drop thereof can be compensated for, and at the same time the refractory material of the induction heater has a long life. Since the inner circumference of the molten metal pouring pot and the outer circumference of the induction heater do not interfere with each other when the molten metal pouring pot is tilted, it is possible to proceed the tilting without any fear that the induction heater hits the molten metal pouring pot even if the molten metal pouring pot is tilted so as to further pour the molten metal into molds.
Also, if the housing of the molten metal pouring pot is constituted by a nonmagnetic material, the interlinkage of magnetic flux with the molten metal is not prevented, and the housing is not heated.
Further, the yoke may increase the magnetic flux density, and facilitates the interlinkage of the magnetic flux with the molten metal.
If the induction heater is driven by a commercial frequency it has a superior electrical efficiency.
If the height from the molten metal to the induction heater is smaller than the height from the molten metal to the upper edge of the molten metal pouring pot, the molten metal pouring pot can be moved horizontally to a place under the induction heater which has been raised once by the elevator.
Since the center of tilting is disposed near the molten metal outlet, the surface of the molten metal, the position of which depends on the molten metal outlet, is always constant near the center of tilting even if continuous pouring decreases the molten metal. Accordingly, even if the height of the center of tilting and the height of the induction heater are kept constant relative to the floor, induction heating is continued properly while the gap between the molten metal and the induction heater is always kept constant. In addition, since the molten metal pouring pot has its tilting center in the neighborhood of the molten metal outlet, the trace of the flow of the molten metal dropping from the molten metal outlet naturally and quietly is rarely changed. Accordingly, even if continuous pouring decreases the molten metal, the positions of molds and so on relative to the floor can be left constant without adjustment.
The above and other objects and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a front view showing a molten metal pouring pot with an induction heater according to a first embodiment;
Fig. 2 is a front view showing a molten metal pouring pot with an induction heater according to a second embodiment;
Fig. 3 is a longitudinal sectional view showing an induction heater in Fig. 1 or 2;
Fig. 4 is a plan view partially illustrating the section taken on line A-A in Fig. 3;
Fig. 5 is a distribution diagram of magnetic flux in Fig. 2;
Fig. 6 is a plan view of an induction coil according to a third embodiment;
Fig. 7 is a front view of one conventional molten metal pouring pot with an induction heater; and
Fig. 8 is a front view of a conventional molten metal pouring pot with an induction heater.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Fig. 1 is a front view showing a molten metal pouring pot with an induction heater according to a first embodiment. Parts referenced by the same numeral in the conventional examples and the drawings have almost the same function, and will not always be described repeatedly.
In Fig. 1, the inner surface of a housing 13 of a normal molten metal pouring pot 12 having a handle 11 for a hanger ear is covered with a refractory material 14. The molten metal pouring pot 12 stores molten metal 1, and pours the molten metal 1 from a molten metal outlet 15 when it is tilted. In order to compensate for the temperature drop of the molten metal 1, a planar induction coil 32 of an induction heater 31 which is independently separate from the molten metal pouring pot 12 is disposed so as to be opposite through a gap to the molten metal 1 stored in the molten metal pouring pot 12. The molten metal pouring pot 12 and the induction heater 31 are shaped and located so that the inner circumference of the molten metal pouring pot 12 and the outer circumference of the induction heater 31 do not interfere with each other when the molten metal pouring pot 12 is tilted.
The housing 13 of the molten metal pouring pot 12 is constituted by a nonmagnetic material, and a yoke 33 is disposed on the back surface of the induction coil 32 of the induction heater 31. The induction heater 31 is driven by a commercial frequency (50 or 60 Hz). Preferably, the induction heater 31 has an elevator 34 movable in the vertical direction. The molten metal pouring pot 12 is moved by a crane or the like while a not-shown hanger ear hangs the handle 11. The molten metal pouring pot 12 is then put on a fixed roller conveyor 16a, and tilted by a tiltable roller conveyor 16b. The center of tilting is located on a pin 17 near the molten metal outlet 15, and the pin 17 of the molten metal pouring pot 12 which has moved there is fitted into a fixed hook 18.
Fig. 2 is a front view showing a molten metal pouring pot with an induction heater according to a second embodiment;
The molten metal pouring pot shown in Fig. 2 has the same structure as that in Fig. 1, except for the molten metal pouring pot is a ladle-type molten metal pouring pot 22. The molten metal pouring pot 22 is constituted by a handle 11, a nonmagnetic housing 23, a refractory material 14, a molten metal outlet 15, roller conveyors 16a and 16b, a pin 17 near the molten metal outlet 15, and a hook 18. A planar induction coil 32 of an induction heater 31 is disposed so as to be opposite to molten metal 1. The molten metal pouring pot 22 and the induction heater 31 are shaped and located so that the inner circumference of the molten metal pouring pot 22 and the outer circumference of the induction heater 31 do not interfere with each other when the molten metal pouring pot 22 is tilted. This embodiment of Fig. 2 is similar to that of Fig. 1 in the point that the induction heater 31 has a yoke 33 and an elevator 34 and it is driven by a commercial frequency.
According to both the embodiments mentioned above, since the induction heater 31 is independently separated from the molten metal pouring pot 12 or 22, it is not necessary to provide such an induction heater 31 for every molten metal pouring pot, and it is not required to perform a work to combine the induction heater 31 with the molten metal pouring pot 12 or 22. In addition, since the planar induction heater 31 is disposed so as to be opposite through a gap to the molten metal 1 of the molten metal pouring pot 12 or 22, the molten metal 1 is heated so that the temperature drop thereof can be compensated for, and at the same time the refractory material 14 of the induction heater 31 has a long life. Since the inner circumference of the molten metal pouring pot 12 or 22 and the outer circumference of the induction heater 31 do not interfere with each other when the molten metal pouring pot 12 or 22 is tilted, it is possible to proceed the tilting without any fear that the induction heater 31 hits the molten metal pouring pot even if the molten metal pouring pot 12 or 22 is tilted to continue the pouring of the molten metal 1 into molds 19.
Since the housing 13 or 23 of the molten metal pouring pot 12 or 22 is constituted by a nonmagnetic material, magnetic flux is not prevented from interlinking with the molten metal 1, and the housing 13 and 23 is not heated. The yoke 33 increases magnetic flux density, and facilitates interlinkage of the magnetic flux with the molten metal 1. The induction heater 31 driven by a commercial frequency has a superior electrical efficiency. When the height from the molten metal 1 to the induction heater 31 is smaller than the height from the molten metal 1 to the upper edge of the molten metal pouring pot 12 or 22, the molten metal pouring pot 12 or 22 can be moved horizontally to a place under the induction heater 31 which has been raised once by the elevator 34. Since the center of tilting is disposed near the molten metal outlet 15, the surface of the molten metal 1 the position of which depends on the molten metal outlet 15 is always constant near the center of tilting even if continuous pouring decreases the molten metal 1. Accordingly, even if the height of the center of tilting and the height of the induction heater 31 are kept constant to the floor, induction heating is properly continued as the gap between the molten metal 1 and the induction heater 31 is always kept constant. In addition, since the molten metal pouring pot 12 or 22 is tilted centering the neighborhood of the molten metal outlet 15, the trace of the flow of the molten metal dropping from the molten metal outlet 15 naturally and quietly is rarely changed. Accordingly, even if continuous pouring decreases the molten metal, the positions of the molds 19 and so on relative to the floor can be left constant without adjustment.
The structure of the induction heater 31 will be described in detail with reference to Figs. 3 and 4. Fig. 3 is a longitudinal sectional view showing an induction heater in Fig. 1 or 2 and Fig. 4 is a plan view partially illustrating the section taken on line A-A in Fig. 3.
In the inductor heater 31, the induction coil 32 has two planar stages of spirals, and the radial yoke 33 is disposed on the back surface (upper surface) thereof and in the horizontal direction. An insulator 35 and an adiabator 36 are successively laid on the surfaces of the induction coil 32 and the yoke 33. A refractory castable 37 is given to the surfaces and outer circumferences of the yoke 33 and the adiabator 36, and an outer frame 38 covers the front surface, the outer circumferential surface and the back surface of the castable 37 other than part of the center portion of the surface. The insulator 35 is suspended by a suspension hook 39 elongated downward from the back of the outer frame 38, and the castable 37 is hung by a locking metal fitting 40. Legs 41 for the elevator 34 are fixed to the back of the outer frame 38. A terminal 42 of the water-cooled induction coil 32 is extracted from the back of the outer frame 38. A cooling pipe 43 is brought into contact with the outer frame 38 so that cooling water is supplied from the outside to cool the induction heater 31.
Fig. 5 is a distribution diagram showing magnetic flux in Fig. 2. In Fig. 5, the illustration of the magnetic flux in the center portion is omitted in the drawing because the density of the magnetic flux is so high at that place. The interlinkage of the magnetic flux with the molten metal 1 can be sen clearly. It was confirmed by experiment that electrical efficiency is better at a commercial frequency of 50 or 60 Hz than at an intermediate frequency in a range of from 150 Hz to 10 kHz.
Fig. 6 is a plan view showing an induction coil according to a third embodiment.
An induction coil 60 shown in Fig. 6 is shaped into a planar square, and the planar spiral induction coil 32 may be replaced by the planar square induction coil 60.
In the inventive assembly, the induction heater is independently separated from the molten metal pouring pot. Accordingly, there is an effect that is not necessary to provide an induction heater for every molten metal pouring pot, and it is not required to combine the induction heater with the molten metal pouring pot. In addition, since the planar induction heater is disposed so as to be opposite through a gap to molten metal of the molten metal pouring pot, there is an effect that the molten metal is heated so that the temperature drop thereof can be compensated for, and at the same time the refractory material of the induction heater has a long life.
Also, since a housing of the molten metal pouring pot may be constituted by a nonmagnetic material, there is an effect that magnetic flux is not prevented from interlinking with the molten metal, and the housing is not heated.
Further, there may be an effect that a yoke increases magnetic flux density, and facilitates the interlinkage of magnetic flux with the molten metal. Still further, there may be obtained an effect that the induction heater driven by a commercial frequency has a superior electrical efficiency.
Still further, there may be an effect that when the height from the molten metal to the induction heater is smaller than the height from the molten metal to the upper edge of the molten metal pouring pot, the molten metal pouring pot can be moved horizontally to a place under the induction heater which has been raised once by an elevator.
Still further, according to the invention, since the center of tilting is disposed near a molten metal outlet, there is an effect that the surface of the molten metal the position of which depends on the molten metal outlet is always constant near the center of tilting, so that even if the height of the center of tilting and the height of the induction heater are kept constant to the floor, induction heating is continued as the gap between the molten metal and the induction heater is always kept constant and proper. In addition, since the molten metal pouring pot has its tilting center in the neighborhood of the molten metal outlet, there is an effect that the trace of the flow of the molten metal dropping from the molten metal outlet naturally and quietly is rarely changed, so that even if continuous pouring decreases the molten metal, the positions of molds and so on relative to the floor can be left constant without adjustment.
The foregoing description of preferred embodiments of the invention has been presented for purposes of illustration and description. It is not indented to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiment was chosen and described and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.

Claims

An assembly comprising a tiltable molten metal pouring pot (12, 22) and an induction heater (31); wherein said heater (31) has a planar coil (32) juxtaposed to the surface of molten metal contained in said pouring pot,
characterised in that
said induction heater is independently separated from said molten metal pouring pot and said induction heater is shaped and disposed so that the inner circumference of said molten metal pouring pot and the outer circumference of said induction heater do not interfere with each other when said molten metal pouring pot is tilted, wherein the center of tilting of said molten metal pouring pot is located near to a molten metal outlet (15) of said pouring pot.
An assembly according to Claim 1, characterized in that a housing of said molten metal pouring pot is constituted by a nonmagnetic material.
An assembly according to Claim 1, characterized in that a yoke is disposed on the back surface of said induction coil of said induction heater.
An assembly according to Claim 1, characterized in that said induction heater is driven by a commercial frequency.
An assembly according to Claim 1, characterized in that said induction heater has an elevator movable in the vertical direction.