JPH0914863A - High-frequency melting apparatus - Google Patents

Abstract

PURPOSE: To enhance the utilization efficiency of applied power and to save the power consumption by enclosing a high frequency coil by a ferromagnetic material having high permeability, a high melting point and high resistance except the inner surface of the coil, and forcibly cooling the material. CONSTITUTION: A ferromagnetic material 3 is formed of a cylindrical part 3a disposed at the outside of a high frequency coil 2, first extended parts 3b extended from both the ends to the inside along both end faces of the coil 2, and second extended parts 3c extended from the ends to opposite sides. The parts 3c are so set at the interval to the same height as that of the coil 2 as not to cover the inner surface of the coil 2. That is, the ends of the parts 3b are extended to the opposite side, and the parts 3c are formed to enclose the coil 2. The any part of the material 3 has a refrigerant passage and is forcibly cooled by refrigerant such as water or oil passing the channel. Thus, the magnetic flux amount and density inside the opened coil are increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency melting apparatus for melting various metals such as silicon and titanium by high frequency induction heating.

[0002]

2. Description of the Related Art In recent years, in order to obtain a directional solidified rod of silicon used as a material for solar cells, a continuous casting method of silicon by high-frequency induction heating melting has been developed, and research toward its practical use has been continued. ing.

As shown in FIG. 6, the continuous casting method of silicon by high-frequency induction heating melting uses a bottomless crucible 1 divided in the circumferential direction and a high-frequency coil 2 arranged outside the crucible to form a bottomless crucible. The raw material silicon in the form of agglomerates that is put into the crucible 1 is melted by high-frequency induction heating, and the melted silicon 4 is gradually drawn downward from the bottomless crucible 1 to solidify it, whereby the silicon rod 5 is continuously manufactured. In addition to high efficiency, this method has a distinctive feature that the amount of impurity contamination from the bottomless crucible 1 is small because the molten silicon 4 is held in a non-contact state with the bottomless crucible 1.

[0004]

However, high-frequency induction heating melting consumes a large amount of electric power, unlike the case of simple induction heating. The continuous casting method of silicon by high-frequency induction heating melting is no exception to this, and since a large current needs to be supplied to the high-frequency coil 2, the power cost increases, and this raises the casting cost. It has become one of the major obstacles above.

In the continuous casting method for silicon by high-frequency induction heating melting, the minimum required energy is basically constant unless the amount of molten metal formed changes, and in the end, how effectively the input power is used for melting silicon is used. The point is whether to do it. This high-frequency induction heating melting is also used in the gas atomizing method, which is one of the methods for producing titanium powder, and the FZ method, which is one of the methods for producing silicon single crystals, but effective utilization of input power is still important. Has become one of the challenges.

An object of the present invention is to provide a high-frequency melting apparatus for improving the utilization efficiency of input power and reducing the power consumption.

[0007]

The high-frequency induction melting apparatus of the present invention is a high-frequency induction heating melting apparatus for inductively heating and melting a metal material supplied to the inside of a high-frequency coil by the high-frequency coil. The ferromagnetic material with a high melting point and high resistance surrounds the inner surface of the coil, leaving the inner surface of the coil to be forcibly cooled.

[0008]

[Function] When a high-frequency coil is surrounded by a ferromagnetic material having a high magnetic permeability, a high melting point, and a high resistance while leaving the inner surface of the coil, a magnetic path is formed in the ferromagnetic material, and the magnetic flux amount and the magnetic flux density are increased inside the opened coil. Increase. As a result, strong magnetic lines of force act on the metal material inside the coil, and the dissolution efficiency of the metal material increases. Also, leakage of magnetic flux is prevented.

Further, even a ferromagnetic material cannot be directly applied to high frequency induction heating melting. This is because a high magnetic permeability is required to increase the dissolution efficiency, but the higher the magnetic permeability, the lower the Neel temperature tends to be, so the magnetic permeability decreases due to the high temperature, and the magnetic properties cannot be obtained. Occurs. In the present invention, however, this problem does not occur because the ferromagnetic material is forcibly cooled by using a coolant such as water or oil.

Although a magnetic shield itself for eliminating leakage magnetic flux is well known, a general magnetic shield is a non-magnetic material such as an aluminum plate or a copper plate and does not form a magnetic path even when used for high frequency induction heating melting, so that the melting efficiency is rather increased. Lower. In addition, it is difficult to actually use because the temperature becomes high due to heat generation by its own eddy current.

As the ferromagnetic material, a composite ferrite having a high magnetic permeability, a high melting point and a high resistance and having particularly high levels thereof is desirable. Table 1 shows the magnetic properties of typical composite ferrites.

It is desirable that the magnetic permeability of the composite ferrite is high in order to improve the melting efficiency. Specifically, the initial relative magnetic permeability is 1
× 10 ² or more is desirable. It is desirable that the resistivity be high in order to suppress own eddy current loss, specifically 1 ×
10 ⁵ Ω · cm or more is desirable. Examples of composite ferrites that satisfy these requirements include MgZn and CuZn.

As a cooling structure for a ferromagnetic material, a cooling medium flow path is typically formed in the ferromagnetic material, but the cooling structure is not limited to this.

The shape of the ferromagnetic material is preferably such that the inner surface of the high frequency coil is left and the coil is surrounded as wide as possible. Specifically, the cylindrical portion located outside the high frequency coil and both end portions of the cylindrical portion are preferable. It is preferable that the first extension part extends inwardly from the first extension part and the second extension part extends from each tip of the first extension part to the opposite side.

[0015]

[Table 1] μ _i initial relative permeability, I _s saturation magnetization, H _c coercive force δ domain wall width, T _c nail temperature, ρ resistivity

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a side view of a silicon continuous casting apparatus showing one embodiment of the present invention. This casting apparatus comprises a bottomless crucible 1, a high-frequency coil 2 arranged outside the crucible 1, and a ferromagnetic body 3 surrounding the high-frequency coil 2. The bottomless crucible 1 is made of water-cooled copper and is divided into a plurality of pieces in the circumferential direction while leaving a part in the axial direction. The high frequency coil 2 is a water-cooled copper coil having several turns.

The ferromagnetic material 3 important in the present invention includes a cylindrical portion 3a located outside the high-frequency coil 2 and a first extending portion extending inward from both end portions along both end surfaces of the high-frequency coil 2. 3b, 3b and second extending portions 3c, 3c extending from the respective tips of the first extending portions 3b, 3b to the opposite side. The intervals between the second extending portions 3c and 3c are set to be the same as the height of the high frequency coil 2 so as not to cover the inner surface of the high frequency coil 2.

FIG. 2 is a side view of a silicon continuous casting apparatus showing another embodiment of the present invention. The casting apparatus of FIG. 1 is different in that the ferromagnetic body 3 does not have the second extending portions 3c and 3c. That is, in the casting apparatus of FIG. 2, the ferromagnetic material 3 covers only the outer surface and both end surfaces of the high frequency coil 2 and completely opens the inside of the coil, whereas the casting apparatus of FIG.
The tip portions of the extending portions 3b, 3b extend to the opposite side to form the second extending portions 3c, 3c, and surround the high frequency coil more widely than in the case of FIG.

As the material of the ferromagnetic material 3, composite ferrite is used in any casting apparatus. Further, every part of the ferromagnetic body 3 has a flow path for a refrigerant, and is forcibly cooled by a refrigerant such as water or oil passing through the flow path.

In any of the casting apparatuses, by feeding the raw material silicon into the bottomless crucible 1 and supplying a high frequency current to the high frequency coil 2, an eddy current is generated in the raw material silicon in the crucible via the bottomless crucible 1. Occurs and the silicon melts. The molten silicon 4 is gradually pulled out from the bottomless crucible 1 downward and solidified to become a silicon rod 5. An example of the magnetic potential distribution at this time is shown in FIG. 3 in comparison with the case of a conventional device without a ferromagnetic material.

In the case of a conventional casting machine without the ferromagnetic material 3,
Since magnetic lines of force spread outside the high-frequency coil 2, the magnetic flux density inside the high-frequency coil 2 is small. In the device of FIG. 1 and the device of FIG. 2 in which the high-frequency coil 2 is surrounded by the ferromagnetic material 3, a magnetic path is formed in the ferromagnetic material 3, and the magnetic flux is squeezed and the formation of the magnetic flux is promoted. Inside the coil 2, both the amount of magnetic flux and the magnetic flux density increase. As a result, strong magnetic lines of force act on the bottomless crucible 1 and the silicon inside thereof, and the silicon melting efficiency is improved.

This effect is obtained by connecting the high frequency coil 2 to the ferromagnetic material 3.
The device of FIG.

In each of the devices shown in FIGS. 1 and 2, the ferromagnetic material 3 is MnZn (μ _i = 3 × 10 ³ ), MgMn, N.
Using iZn, induction frequency 20 kHz, coil current density
Table 2 shows the eddy current loss generated in the bottomless crucible and the silicon in the crucible when performing continuous casting of silicon under the induction heating melting condition of 5.0 × 10 ⁶ AT / m ² . For comparison, the eddy current loss is also shown when a ferromagnetic material is not used. In addition, Table 3 shows the power consumption of the coil required to form the same amount of molten silicon for each.

As can be seen from Tables 2 and 3, by enclosing the high frequency coil with a ferromagnetic material, the eddy current force generated in silicon in the bottomless crucible increases when the input power is the same, and as a result, When the amount of dissolution is the same, power consumption is low. Since this effect mainly corresponds to the magnitude of magnetic permeability, when the material of the ferromagnetic material is MgMn rather than NiZn, and when it is MnZn rather than MgMn, and the shape of the ferromagnetic material is The case of FIG. 1 is larger than that of FIG.

FIG. 4 shows changes in eddy current loss when the relative permeability of the ferromagnetic material is changed for the cases where the shape of the ferromagnetic material is as shown in FIG. 1 and FIG. The eddy current loss increases as the relative permeability increases, and a particularly large eddy current loss is obtained at 1 × 10 ² or more. In addition, eddy current loss larger than that of the magnetic body shown in FIG. 2 is obtained in the magnetic body shown in FIG. 1 as a whole.

[0027]

[Table 2] (Unit: kW)

[0028]

[Table 3] (Unit: kW)

5 (a) and 5 (b) are device configuration diagrams showing still another embodiment of the present invention. In the example of FIG. 5A, the present invention is applied to gas atomization for producing titanium powder. When the titanium rod 6 is induction-heated and melted by the high-frequency coil 2 and the melted titanium is made into fine droplets by the gas flow, the high-frequency coil 2 is surrounded by the ferromagnetic material 3 while leaving the inner surface side of the titanium rod 6 melted. It can improve efficiency and save power consumption.

The example of FIG. 5B is one in which the present invention is applied to the FZ method for producing a silicon single crystal. When the polycrystalline silicon rod 5 is induction-heated and melted by the high-frequency coil 2 to be single-crystallized, the high-frequency coil 2 is surrounded by the ferromagnetic material 3 while leaving the inner surface side thereof, so that the silicon melting efficiency is increased and the consumption is increased. Power can be saved.

[0031]

As described above, in the high frequency melting apparatus of the present invention, the high frequency coil is surrounded by a ferromagnetic material except for the inner surface of the high frequency coil, and the ferromagnetic material is cooled to obtain a high magnetic permeability. By making it possible to use ferromagnetic materials,
It effectively utilizes the input power and exerts a great effect on saving power consumption.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of the apparatus configuration when the melting apparatus of the present invention is applied to continuous casting of silicon.

FIG. 2 is a schematic view showing another apparatus configuration when the melting apparatus of the present invention is applied to continuous casting of silicon.

FIG. 3 is a schematic diagram showing an example of magnetic potential distribution in the melting apparatus of the present invention in comparison with the case of a conventional apparatus.

FIG. 4 is a graph showing the influence of the shape and magnetic permeability of a ferromagnetic material on the dissolution efficiency.

FIG. 5 shows the melting apparatus of the present invention using a gas atomizing method and F
It is a schematic diagram which shows the example of a device structure when applied to Z method.

FIG. 6 is a device configuration diagram of a silicon casting device using a conventional melting device.

[Explanation of symbols]

 1 Bottomless crucible 2 High frequency coil 3 Ferromagnetic material 4 Melted silicon 5 Silicon rod 6 Titanium rod

Claims (2)

[Claims] 1. A high-frequency induction heating melting apparatus for inductively heating and melting a metal material supplied to the inside of a high-frequency coil, wherein the high-frequency coil is made of a ferromagnetic material having high magnetic permeability, high melting point and high resistance. A high-frequency melting apparatus which is characterized in that it surrounds an inner surface and forcibly cools a ferromagnetic material. 2. The ferromagnetic body includes a tubular portion located outside the high frequency coil, a first extending portion extending inward from both end portions of the tubular portion, and a tip end of each of the first extending portions facing each other. The high-frequency melting apparatus according to claim 1, comprising a second extending portion extending to