JP3129078B2 - Bottom hole tapping type flotation melting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method in which a conductive material to be melted is placed in an alternating magnetic field and induction-heated by electromagnetic induction, and a magnetic field having a predetermined distribution is generated to float the material to be melted by electromagnetic force. A flotation melting apparatus capable of obtaining a high-purity material by applying a force to melt in a floating state, in particular, a solid piece of a material to be melted is supplied continuously or intermittently from an upper part and provided at a lower part of a crucible. The present invention relates to a flotation and melting apparatus of a prepared hole tapping system for taking out molten metal continuously or intermittently from a tapping pipe section.

[0002]

2. Description of the Related Art In a levitation melting apparatus, a material to be melted is placed in an alternating magnetic field generated so as to have a predetermined distribution, and eddy current flowing through the material to be melted by electromagnetic induction is used for induction heating and electromagnetic force. And a buoyancy force, and simultaneously melt the material in a state where it does not come into contact with other objects such as a floating crucible to obtain a product having a predetermined material and dimensions. It has a high melting point and a high melting point because it has features such as extremely low contamination of foreign matter because it does not come into contact with other objects during melting, the ability to melt even materials with a high melting point, and a small heat conduction loss. It is used for dissolving materials requiring purity, for example, titanium and silicon.

There are various methods for taking out the product melted by the flotation melting apparatus. There is a method in which a tap is provided at the bottom of a crucible and the molten metal is taken out from the tap continuously or intermittently (Japanese Patent Laid-Open No. 5-15950). No.). According to this publication,
While melting the material in the crucible while controlling the current of the induction coil to be almost constant, a small piece of solid material is supplied continuously or intermittently from the top of the crucible, and the molten metal according to the supply amount is continuously supplied from the tap. Alternatively, it is intermittently discharged and taken out, and injected into the next step such as pouring into a mold.

FIG. 3 is a schematic perspective view showing an example of a flotation and melting apparatus of a conventional prepared hole tapping type, in which a part of the front half is omitted so that the molten metal inside can be seen. In this figure, the crucible 1A has a bottomed cylindrical shape, is provided with slits equally spaced in the circumferential direction, and has an insulating plate 12A inserted therein.Each portion divided by the slit is a segment 11A. is called.

[0005] The bottom of the crucible 1A is provided with a tap hole 14A for taking out the molten metal to the outside. An induction coil 2A is provided outside the crucible 1A, and the induction coil 2A is supplied with current by an AC power supply 3A. The crucible 1A is internally provided with a cooling pipe (not shown), and cooling water is supplied from the outside to be cooled strongly. The molten metal 5 is melted in the crucible 1A as shown and is in a floating state. The levitation force necessary for the molten metal 5 to float is due to the eddy current generated in the molten metal 5 by the alternating current flowing through the induction coil 2A and the electromagnetic force accompanying the eddy current. The electromagnetic force is generated by the eddy current near the lower surface of the molten metal 5 and also generated by the eddy current flowing on the side surface in such a direction that the radius of the molten metal 5 is reduced so that the molten metal 5 does not spread laterally. Such a force is called a lateral drawing force.

The AC power supply 3A is a high-frequency power supply of several kHz or several tens of kHz, rectifies commercial AC power by a rectifier and converts it into DC, and obtains high-frequency power from the inverter. When a high-frequency current flows through the induction coil 2, an eddy current is generated in the crucible 1A and the molten metal 5 by electromagnetic induction, and the above-described levitation force and lateral drawing force are generated by the electromagnetic force acting between the currents.

[0007] The molten metal 5 is enlarged by continuously feeding small solid pieces from the upper portion of the crucible 1A by a charging device (not shown), and the molten metal 5 flows out from the lower molten hole 14A and flows out. The melt can be obtained continuously or intermittently by appropriately controlling the charging and discharging of the small pieces. FIG. 4 is a schematic perspective view showing a flotation and melting apparatus of a conventional prepared hole tapping system different from that of FIG. 3, in which the same components as those in FIG. And replace with B or omit the subscript to omit redundant description.
The difference between this figure and FIG. 3 is that the tapping pipe section is located at the bottom of the crucible 1B.
13B is provided, and a tapping control coil 20 is provided outside thereof. Hot water supply control coil 20 is supplied with current from AC power supply 30. When the molten metal 5 flows out, the molten metal 5 is caused to flow out of the molten metal hole 14. At this time, no current is supplied to the molten metal control coil 20 or a current having the same frequency as that of the AC power supply 3 is supplied in the opposite direction to the molten metal 5. Reduce the buoyancy of A current of a predetermined frequency is supplied to the tapping control coil 20 to cut the molten metal through the tap hole 14A in order to stop the tapping from the tapping state, thereby generating a strong lateral drawing force in the molten metal and cutting the molten metal. The same current is supplied when the tap is not in the tapping state.
When the molten metal 5 is supplied, the electromagnetic force on the lower surface of the molten metal 5 becomes large, and an action of keeping the molten metal 5 stable in a state where the molten metal is not discharged can be performed. The tapping pipe section 13B is integrally formed with the crucible 1B as shown in the figure, and similarly to the relation between the crucible 1B and the induction coil 2B, the tapping control coil 20 is thermally cut off from tapping, and its inductance is reduced. I'm making it smaller. Hot water pipe section 13
B can be a separate component besides having an integral structure with the crucible 1B as shown. In the case of an integrated structure, the entrance and exit of the cooling pipe passing through the inside of the crucible 1B can be provided in the tapping pipe section 13B so that the arrangement of the induction coil 2 and the tapping control coil 20 is not obstructed by the entrance and exit of the cooling pipe. .

FIG. 5 is a computer drawing of the eddy current flowing in the crucible 1B and the electromagnetic force generated in the molten metal 5 when a current flows through the induction coil 2 and the tapping control coil 20 in the flotation and melting apparatus of the prepared hole tapping type shown in FIG. It is an eddy current and electromagnetic force distribution map obtained by magnetic field calculation. In this figure, the straight line on the left is the axis of symmetry, and the crucible and the coil have a rotationally symmetric structure as is clear from FIG. When current flows through the induction coil 2 and the tapping control coil 20, an eddy current representing the size of the crucible 1B including the tapping pipe section 13B flows on the outer diameter side of the crucible 1B, and the eddy current on the outer diameter side also flows on the inner diameter side. An eddy current indicated by a circle, which is a sum equal to the sum of? □ and と indicate that the current directions are opposite to each other.

An electromagnetic force is generated by the interaction between the current flowing through the crucible 1B and the coils 2 and 20 through which the eddy current flows also in the molten metal 5, which is indicated by an arrow in the figure. This electromagnetic force is a vector product of the eddy current at the position and the magnetic flux density, and the length of the arrow is drawn so as to be proportional to the magnitude of the electromagnetic force at the position. The hole in the molten metal 5 is for calculation and the actual molten metal 5 is clogged to the inside. Due to the well-known skin effect, most of the current flowing in the molten metal 5 flows near the surface, so that the electromagnetic force is also generated only near the surface. There is a saving effect.

The electromagnetic force generated in the molten metal 5 has leftward and upward components in the figure as shown in the figure. The leftward component is mainly on the side surface of the molten metal 5, and the upward component is large near the lower surface. The leftward component is the aforementioned lateral drawing force, and the upward component is the levitation force.

[0011]

By the way, when the molten metal 5 is not in the tapping state, the molten metal 5 is in a floating state, but it is indispensable to secure the floating force of the lower surface thereof in order to keep the molten metal 5 in a stable floating state. If the crucible and the induction coil have the same configuration, the levitation force can be increased by increasing the current in the induction coil 2. However, this not only increases the current consumption of the molten metal 5 but also increases the lateral drawing force, thereby increasing the molten metal. 5 becomes unstable. Therefore, it is important for the stable operation of the levitation melting apparatus to increase the levitation force without increasing the lateral drawing force so much.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a flotation and melting apparatus of a prepared hole tapping type in which the levitation force for floating the molten metal becomes larger without increasing the current. To provide.

[0013]

According to the present invention, in order to solve the above problems, segments made of a good conductive metal are laminated in the circumferential direction via an insulating plate to form a bottomed cylindrical shape. Supply current to a crucible with a tapping tube for discharging molten metal at the bottom, an induction coil provided on the outside diameter side of the crucible, a tapping control coil provided on the outside diameter side of the tapping tube, an induction coil and a tapping control coil 20 In the flotation / melting apparatus of the prepared hole tapping type provided with two AC power supplies, the inside diameter of the tapping tube portion is increased except for the joint between the bottom of the crucible and the tapping tube portion.

[0014]

In the structure of the present invention, if the inside diameter of the tapping tube is increased except for the joint between the bottom of the crucible and the tapping tube, a projecting portion projecting toward the inside diameter is formed at the joint. The eddy current on the inner surface of the crucible, which is generated by the current flowing through the induction coil, concentrates on the protrusion, so that the levitation force of the molten metal generated as a result of the interaction between the eddy current on this portion and the eddy current flowing on the lower surface of the molten metal. Increase.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
FIG. 1 is a schematic perspective view of a flotation / melting apparatus of a pilot hole tapping type according to a first embodiment of the present invention, in which the same components as those in FIG. Components that have been omitted are denoted by reference numerals with the suffix B omitted, and redundant description is omitted. The difference between FIG. 1 and FIG. 4 is that the outlet hole 15 is formed by increasing the inner diameter of the tapping tube section 13 and only the tapping hole 14 at the junction between the tapping pipe section 13 and the crucible 1 is the conventional tapping hole of FIG. The point is that it is configured to keep the same small inner diameter as the tap hole 14B.

By adopting such a structure, a portion projecting toward the inner diameter side is formed at a portion surrounding the tap hole 14 of the connecting portion.
16 are formed. The magnetic flux generated by the current flowing through the induction coil 2 and the tapping control coil 20 flows from the outlet hole 15 to the tapping hole.
The creep crucible 1 penetrates into the crucible 1 through the hole 14. At this time, since the inside diameter of the tap hole 14 is small, this partial magnetic flux is narrowed to increase the magnetic flux density. growing. As a result of the increase of the eddy current in this portion, the levitation force generated by the interaction with the eddy current flowing on the lower surface of the molten metal 5 increases.

FIG. 2 is a computer drawing of an eddy current flowing through the crucible 1 and an electromagnetic force generated in the molten metal 5 when a current flows through the induction coil 2 and the tapping control coil 20 in the flotation and melting apparatus of the prepared hole tapping type shown in FIG. FIG. 6 is an eddy current and electromagnetic force distribution diagram obtained by magnetic field calculation, and the conditions such as the configuration, shape, dimensions, and current of the tapping pipe portion 13 are the same as those in FIG.

When FIG. 2 is compared with FIG. 5, the current on the outer diameter side of the crucible 1 is almost the same in both figures, but the inner surface of the tapping tube 13 and the protrusion 16 at the tap hole 14 and the outlet hole 15 are not shown. Eddy currents are very different. In other words, while the eddy current on the inner surface of the tapping tube portion 13B in FIG. 5 is uniform and the size thereof is about the size of a circle, the magnitude of the eddy current on the inner surface of the tapping tube portion 13 in FIG. Is a small circle, and it can be seen that the eddy current is concentrated on the protrusion 16 instead. It can be seen that the electromagnetic force on the lower surface of the molten metal 5 is partially twice as large in FIG. 2 as compared with that in FIG. Thus, the protrusion
Eddy currents are concentrated in this part by forming 16,
As a result, the effect of increasing the buoyancy of molten metal 5 is obtained.

The diameter of the tap hole 14 is as follows.
Although it is necessary to have a size that does not interfere with tapping out of the molten metal, it is preferable that the size is as small as possible in order to secure the buoyancy of the molten metal 5 as described above. The larger the diameter of the outlet hole 15 is, the better the increase of the buoyancy described above is.
When the above-described configuration in which the inlet and outlet of the cooling pipe is provided in 13 is adopted, the thickness dimension naturally has a lower limit, so in order to increase the diameter of the outflow hole 15, the outer diameter of the tapping pipe section 13 and the Accordingly, it is necessary to increase the diameter of the tapping control coil 20. This leads to an increase in the weight and power loss of the tapping pipe section 13 and the tapping control coil 20. Therefore, the diameter of the outflow hole 15 is determined in consideration of these factors. If the levitation force is increased by increasing the diameter of the outflow hole 15 and the levitation force becomes more
It is possible to increase the diameter of 14 and increase the amount of hot water. Therefore, the optimum diameter of the outflow hole 15, that is, the diameter of the tapping pipe section 13 and the tapping control coil 20 is determined in consideration of this point.

[0020]

According to the present invention, as described above, the inner diameter of the tapping tube portion is increased, and the projecting portion projecting toward the inner diameter side is formed at the joint between the main body of the crucible and the tapping tube portion.
The eddy current flows intensively in the protruding portion, and the floating force of the molten metal increases due to the interaction between the eddy current in this portion and the eddy current flowing on the lower surface of the molten metal, so that the molten metal 5 is in a stable floating state when not in the molten state. Therefore, there is an effect that the stable operation of the flotation and melting apparatus of the prepared hole tapping system can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a flotation melting apparatus of a pilot hole tapping type showing an embodiment of the present invention.

FIG. 2 is an eddy current of the flotation / melting apparatus of the downhole tapping type shown in FIG.
Electromagnetic force distribution diagram

FIG. 3 is a schematic perspective view showing an example of a conventional flotation / melting apparatus of a prepared hole tapping type.

FIG. 4 is a schematic perspective view showing an example of a flotation melting apparatus of a conventional prepared hole tapping system different from FIG.

5 is an eddy current of the flotation / melting device of the downhole tapping type shown in FIG. 4,
Electromagnetic force distribution diagram

[Explanation of symbols]

1, 1A, 1B… Crucible 11… Segment 12…
Insulating plate 13, 13B ... tapping pipe section 14, 14A, 14B ... tapping hole 15 ...
Outflow hole 16… Projecting part 2, 2A… Induction coil 3, 3A, 30… AC power supply 20… Tap control coil 5… Molten metal

(56) References JP-A-5-15950 (JP, A) JP-A-5-3075 (JP, A) JP-A-2-52094 (JP, U) (58) Fields surveyed (Int .Cl. ⁷ , DB name) H05B 6/32 F27B 14/00 F27D 11/06

Claims (1)

(57) [Claims] 1. A crucible having a tapping pipe for discharging a molten metal at the bottom of a crucible having segments formed of a good conductive metal laminated circumferentially via an insulating plate to form a bottomed cylinder. A crucible in a flotation and melting apparatus of a prepared hole tapping type including an induction coil provided, a tapping control coil provided on the outer diameter side of the tapping pipe section, and two AC power supplies for supplying current to the induction coil and the tapping control coil. A flotation and melting apparatus of a prepared hole tapping type characterized in that the inside diameter of the tapping pipe section is enlarged except for the joint between the bottom and the tapping pipe section.