JP7523802B2 - Molten metal stirring device and continuous casting system - Google Patents

Description

The present invention relates to a molten metal stirring device and a continuous casting system, more specifically to a molten metal stirring device for stirring molten metal, and a continuous casting system equipped with the molten metal stirring device and capable of continuously forming cast products.

Conventionally, there is known a molten metal stirring device that uses electromagnetic force to stir molten non-ferrous metals such as aluminum and copper (hereinafter simply referred to as "molten metal" or "molten metal"). For example, Patent Document 1 describes a stirring device that generates a moving magnetic field by passing a three-phase alternating current through multiple coils wound around a ring-shaped iron core, and stirs the molten metal inside the iron core. In addition, linear motor-type molten metal stirring devices are also widely used.

All of these molten metal stirring devices generate a moving magnetic field by passing a three-phase alternating current through multiple coils wound around an iron core, and stir the molten metal using electromagnetic forces acting on the molten metal due to eddy currents generated within the molten metal.

Japanese Unexamined Patent Publication No. 2-182358

However, to ensure sufficient stirring force, it is necessary to generate a magnetic field of sufficient strength in the space containing the molten metal to be stirred.

One way to generate a strong magnetic field is to pass a large current through a coil. However, as the current through the coil increases, the power consumption increases, which increases the running costs of the mixing device. In addition, powerful cooling equipment such as a water-cooling system is required, which increases not only manufacturing costs but also maintenance costs.

Another method for generating a strong magnetic field is to increase the number of turns in the coil. However, the inductance of the coil increases in proportion to the square of the number of turns. This causes the flow of AC current to be impeded, making it difficult to obtain a strong magnetic field. In addition, it is known that the stirring force is proportional to the frequency of the AC current, but if the inductance increases as the number of turns in the coil increases, it becomes difficult to increase the frequency of the AC current.

The present invention was made based on the above technical recognition, and aims to provide a molten metal stirring device and continuous casting system that can obtain a large stirring force while consuming low power.

The molten metal stirring device according to the present invention is
A molten metal stirring device for stirring a molten metal,
A magnetic field device having first to third magnetic field generating units,
Each of the first to third magnetic field generating units is
A first annular core;
a second annular core having a central axis coaxial with the first annular core and spaced apart from the first annular core;
a first yoke connecting the first annular core and the second annular core;
a second yoke arranged to face the first yoke across the central axis and connecting the first annular core and the second annular core;
a first coil wound around the first annular core;
a second coil wound around the first annular core so as to be located on the opposite side of the first coil;
a third coil wound around the second annular core; and
a fourth coil wound around the second annular core so as to be located on the opposite side of the third coil,
each of the first coil and the second coil is wound so as to generate a first magnetic field directed toward one of the first yoke and the second yoke when a current flows therethrough, and each of the third coil and the fourth coil is wound so as to generate a second magnetic field directed toward the one of the yokes when a current flows therethrough;
The first to third magnetic field generating units are characterized in that the first and second yokes of each unit are disposed at intervals from each other.

In addition, in the molten metal stirring device,
The first and second annular iron cores of the first to third magnetic field generating units may be configured so that a thickness in a first direction along the central axis is smaller than a thickness in a second direction perpendicular to the first direction.

In addition, in the molten metal stirring device,
The first and second annular iron cores of the first to third magnetic field generating units may have a planar shape corresponding to the shape of a mold.

In addition, in the molten metal stirring device,
The first and second annular iron cores of the first to third magnetic field generating units may each have a circular planar shape.

In addition, in the molten metal stirring device,
The first to third magnetic field generating units may be arranged such that the first and second yokes of the first to third magnetic field generating units are positioned at equal intervals on a circumference around the central axis.

In addition, in the molten metal stirring device,
The first annular iron core of the first magnetic field generating unit, the first annular iron core of the second magnetic field generating unit, the first annular iron core of the third magnetic field generating unit, the second annular iron core of the first magnetic field generating unit, the second annular iron core of the second magnetic field generating unit, and the second annular iron core of the third magnetic field generating unit may be arranged in this order along the direction of the central axis.

In addition, in the molten metal stirring device,
the first coil, the second coil, the third coil, and the fourth coil of the first magnetic field generating unit are connected in series to form a first series coil;
the first coil, the second coil, the third coil, and the fourth coil of the second magnetic field generating unit are connected in series to form a second series coil;
the first coil, the second coil, the third coil, and the fourth coil of the third magnetic field generating unit are connected in series to form a third series coil;
The first series coil, the second series coil and the third series coil are star-connected.

In addition, in the molten metal stirring device,
The motor may further include an AC power supply that causes an R-phase current to flow through the first series coil, an S-phase current to flow through the second series coil, and a T-phase current to flow through the third series coil.

In addition, in the molten metal stirring device,
The first yoke and the second yoke of the first magnetic field generating unit, the first yoke and the second yoke of the second magnetic field generating unit, and the first yoke and the second yoke of the third magnetic field generating unit may be arranged so that a portion of the projection of each yoke onto the central axis overlaps with each other.

In addition, in the molten metal stirring device,
The magnetic field device further includes a case for housing the magnetic field device.
The case is
An outer cylinder portion;
an inner cylindrical portion coaxial with the outer cylindrical portion;
a bottom plate that closes a gap on one side between the outer cylinder portion and the inner cylinder portion;
a cover plate that closes the gap on the other side between the outer cylinder portion and the inner cylinder portion,
The magnetic field device may be housed in the case such that the inner cylindrical portion is inserted into the first and second annular iron cores of the first to third magnetic field generating units.

In addition, in the molten metal stirring device,
The outer cylinder portion may be provided with an air intake port for taking air into the inside of the case, and an air exhaust port for exhausting air inside the case to the outside.

In addition, in the molten metal stirring device,
The air intake and the air exhaust may be disposed on opposite sides of the magnetic field device.

In addition, in the molten metal stirring device,
A blower may be connected to the air intake to provide forced air cooling for the magnetic field device.

In addition, in the molten metal stirring device,
The first and second yokes of the first to third magnetic field generating units may have protrusions protruding toward the central axis.

The continuous casting system according to the present invention comprises:
A mold that receives liquid molten metal from an inlet and discharges a solid casting from an outlet by cooling;
The molten metal stirring device is provided so as to surround at least a portion of the mold;
The present invention is characterized by comprising:

The present invention provides a molten metal stirring device and continuous casting system that can generate a large stirring force while consuming low power.

FIG. 2 is a front view of the molten metal stirring device according to the embodiment. FIG. 2 is a partial cross-sectional view of a side surface of the molten metal stirring device according to the embodiment. FIG. 2 is a plan view of a first annular core around which two coils are wound. FIG. 2 is a plan view of a second toroidal core around which two coils are wound. FIG. 13 is a plan view of a third toroidal core around which two coils are wound. FIG. 13 is a plan view of a fourth annular core around which two coils are wound. FIG. 13 is a plan view of a fifth annular core around which two coils are wound. FIG. 13 is a plan view of a sixth annular core around which two coils are wound. FIG. 2 is a front view of the magnetic field device of the molten metal stirring apparatus according to the present embodiment. 5 is a cross-sectional view taken along line II in FIG. 4. 5 is a cross-sectional view taken along line II-II in FIG. 4. FIG. 2 is a wiring diagram of a plurality of coils included in the magnetic field device according to the present embodiment. FIG. 2 is a front view of a magnetic field generating unit for explaining generation of a magnetic field in the magnetic field device according to the present embodiment. FIG. 2 is a side view of a magnetic field generating unit for explaining generation of a magnetic field in the magnetic field device according to the present embodiment. FIG. 11 is a cross-sectional view of a magnetic field device having a yoke according to a modified example. 1 is a cross-sectional view of a continuous casting system according to an embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings.

<Molten metal stirring device 1>
A schematic configuration of a molten metal stirring apparatus 1 according to an embodiment will be described. Fig. 1 shows a front view of the molten metal stirring apparatus 1, and Fig. 2 shows a partial cross-sectional view of the side of the molten metal stirring apparatus 1. Note that Fig. 1 does not show the coil wound around the annular iron core 21 of the magnetic field device 2. Fig. 2 also does not show the coil wound around the annular iron cores 21 to 26 of the magnetic field device 2, the yoke, and the mounting base 8.

The molten metal stirring device 1 is configured to stir the molten metal by utilizing the electromagnetic force acting on the molten metal due to the moving magnetic field generated by the magnetic field device 2.

As shown in FIG. 1, the molten metal stirring device 1 includes a magnetic field device 2, a case 3, an air intake 4, an air exhaust 5, a terminal box 6, an AC power source 7, and a mounting base 8.

The magnetic field device 2 is configured to generate a moving magnetic field for stirring the molten metal. This magnetic field device 2 is housed in the case 3. When the molten metal stirring device 1 is in operation, the magnetic field device 2 is cooled by cooling air taken in from the air intake 4.

As shown in FIG. 2, the magnetic field device 2 has a number of annular iron cores 21-26 arranged at intervals. The annular iron cores 21-26 are arranged so that their central axes CL are coaxial. Note that in this embodiment, the annular iron cores 21-26 are arranged at equal intervals, but they may also be arranged at unequal intervals.

The annular cores 21-26 are made of a ferromagnetic material, for example, silicon steel plate or carbon steel plate. From the viewpoint of reducing iron loss, silicon steel plate is advantageous. However, as described below, according to this embodiment, the eddy currents generated in the annular cores 21-26 during operation can be reduced more than in the past, so it is possible to use carbon steel plate, which is more cost-effective. Using carbon steel plate also makes it possible to reduce the weight of the magnetic field device 2.

From the viewpoint of reducing magnetic flux leakage, it is preferable that the annular cores 21 to 26 are closed. However, it is not excluded that a gap is provided in part of the annular core, and an iron core with a gap is also included in the annular core referred to in this application.

The annular cores 21-26 may be thin. As shown in FIG. 2, the annular cores 21-26 may have a thickness t1 in a first direction along the central axis CL that is smaller than a thickness t2 in a second direction perpendicular to the first direction. This can further improve the cooling efficiency of the magnetic field device 2 and further reduce iron loss. Note that it is preferable to set the thicknesses of the annular core in the first and second directions based on the magnetic saturation value of the annular core so as to ensure the desired magnetomotive force.

The annular cores 21-26 have a planar shape that corresponds to the shape of the mold (casting). Since the molten metal stirring device 1 of this embodiment is installed in a mold for casting billets, the planar shape of the annular cores 21-26 is circular. When casting a slab, the planar shape of the annular cores 21-26 may be square. In this case, the annular cores 21-26 will be square rings rather than circular rings.

As shown in Figures 3A to 3F, two coils are wound around each of the annular cores 21 to 26 at symmetrical positions with respect to the central axis CL. That is, coils 41a and 41b are wound around the annular core 21, coils 42a and 42b are wound around the annular core 22, coils 43a and 43b are wound around the annular core 23, coils 44a and 44b are wound around the annular core 24, coils 45a and 45b are wound around the annular core 25, and coils 46a and 46b are wound around the annular core 26. In this embodiment, the number of turns of each coil is the same so that the strength of the magnetic field generated by each coil is approximately equal. Note that insulating paper for insulation may be interposed between the coils and the annular core.

Coils 41a and 41b are wound around annular core 21 in a mutually forward direction, and coils 44a and 44b are wound around annular core 24 in a mutually forward direction. Coils 41a and 41b (coils 44a and 44b) are connected in series so that current flows in opposite directions (see FIG. 7). As a result, when current flows through the first series coil, magnetic fields in opposite directions are generated.

In addition, coils 41a and 41b may be wound around annular core 21 in opposite directions, and coils 44a and 44b may be wound around annular core 24 in opposite directions. In this case, coils 41a and 41b (coils 44a and 44b) are connected in series so that current flows in the forward direction.

Similarly, coils 42a and 42b are wound in a forward direction relative to each other around the annular core 22, and coils 45a and 45b are wound in a forward direction relative to each other around the annular core 25. Coils 43a and 43b are wound in a forward direction relative to each other around the annular core 23, and coils 46a and 46b are wound in a forward direction relative to each other around the annular core 26.

There are no particular limitations on how the coils are wound or connected, as long as they generate magnetic fields in opposite directions in each annular core.

The annular cores 21 to 26 are divided into three pairs, and each pair of the annular cores is connected by two yokes. This yoke is provided between the two coils wound around the annular cores, and functions as a magnetic pole when the coils are energized, as described below. Each yoke is made of, for example, iron, pure iron (SUY), stainless steel material, or an alloy such as permendur.

More specifically, as shown in Figures 4, 5A, and 5B, annular core 21 and annular core 24 are connected by yoke 31a and yoke 31b. Similarly, annular core 22 and annular core 25 are connected by yoke 32a and yoke 32b, and annular core 23 and annular core 26 are connected by yoke 33a and yoke 33b.

Each yoke is roughly U-shaped in side view and has a connection portion that connects to the annular core and a linking portion that connects the connection portions together. In more detail, as shown in Figures 5A and 5B, yoke 31a has connection portion 31a1 that connects to annular core 21, connection portion 31a2 that connects to annular core 24, and linking portion 31a3 that links connection portion 31a1 and connection portion 31a2. Yoke 31b has connection portion 31b1 that connects to annular core 21, connection portion 31b2 that connects to annular core 24, and linking portion 31b3 that links connection portion 31b1 and connection portion 31b2.

Similarly, yoke 32a has a connection portion 32a1 that connects to annular core 22, a connection portion 32a2 that connects to annular core 25, and a linking portion 32a3 that links connection portion 32a1 and connection portion 32a2. Yoke 32b has a connection portion 32b1 that connects to annular core 22, a connection portion 32b2 that connects to annular core 25, and a linking portion 32b3 that links connection portion 32b1 and connection portion 32b2.

Similarly, yoke 33a has a connection portion 33a1 that connects to annular core 23, a connection portion 33a2 that connects to annular core 26, and a linking portion 33a3 that links connection portion 33a1 and connection portion 33a2. Yoke 33b has a connection portion 33b1 that connects to annular core 23, a connection portion 33b2 that connects to annular core 26, and a linking portion 33b3 that links connection portion 33b1 and connection portion 33b2.

The shape of each yoke is not limited to a U-shape. For example, each annular core may have a protrusion on its inner circumferential surface that faces the center, and the yoke may connect the protrusions of the two annular cores. Also, the connecting portion of each yoke may be formed in an arc shape that bulges toward the central axis CL.

As shown in FIG. 4, the six yokes (yokes 31a, 31b, 32a, 32b, 33a, 33b) are arranged so as not to overlap. When the annular cores 21-26 are circular as in this embodiment, the six yokes are positioned at equal intervals (60° intervals) on a circumference around the central axis CL of the annular cores 21-26.

As described above, the annular cores 21 to 26 are divided into three groups (i.e., annular cores 21 and 24, annular cores 22 and 25, and annular cores 23 and 26), and the annular cores of each group are connected by two yokes. The annular cores 21 and 24 and the yokes 31a and 31b form the first magnetic field generating section. The annular cores 22 and 25 and the yokes 32a and 32b form the second magnetic field generating section. The annular cores 23 and 26 and the yokes 33a and 33b form the third magnetic field generating section. The operation of the magnetic field generating section will be explained later with reference to Figures 7 and 8.

In the magnetic field device 2 of this embodiment, the annular core 21 of the first magnetic field generating unit, the annular core 22 of the second magnetic field generating unit, the annular core 23 of the third magnetic field generating unit, the annular core 24 of the first magnetic field generating unit, the annular core 25 of the second magnetic field generating unit, and the annular core 26 of the third magnetic field generating unit are arranged in this order along the direction of the central axis CL of the annular cores 21 to 26. In other words, the magnetic field device 2 is configured so that the first to third magnetic field generating units are combined with each other.

Next, we will explain the connection relationship between the coils wound around the annular cores 21 to 26.

As shown in FIG. 6, coils 41a, 41b, 44a, and 44b are connected in series to form a first series coil. Similarly, coils 42a, 42b, 45a, and 45b are connected in series to form a second series coil. Coils 43a, 43b, 46a, and 46b are connected in series to form a third series coil. The first series coil, the second series coil, and the third series coil are star-connected. The first series coil is electrically connected to the R phase of the AC power supply 7, the second series coil is electrically connected to the S phase of the AC power supply 7, and the third series coil is electrically connected to the T phase of the AC power supply 7.

The connection between the coils is not limited to the above, and other connection configurations are possible as long as the repulsive magnetic fields (H1, H2, H3) described below are generated.

Next, we will explain the case 3 that houses the magnetic field device 2.

As shown in Fig. 1 and Fig. 2, the case 3 has an outer cylinder 3a, an inner cylinder 3b coaxial with the outer cylinder 3a, a bottom plate 3c, and a cover plate 3d. The material of the case 3 is not particularly limited, but may be, for example, a fireproof material, stainless steel, or other metal.

The bottom plate 3c closes the gap on one side (the right side in FIG. 2) between the outer tube portion 3a and the inner tube portion 3b. The cover plate 3d closes the gap on the other side (the left side in FIG. 2) between the outer tube portion 3a and the inner tube portion 3b. For example, the bottom plate 3c is welded to the outer tube portion 3a and the inner tube portion 3b, and the cover plate 3d is detachably attached to the outer tube portion 3a and the inner tube portion 3b by fastening means such as screws or bolts.

The magnetic field device 2 is housed in the case 3 so that the inner cylinder portion 3b is inserted through the annular iron cores 21-26. A spacer (not shown) made of an insulating material is interposed between the annular iron cores 21-26 and the inner cylinder portion 3b so that the annular iron cores 21-26 are kept at a predetermined distance from the inner cylinder portion 3b. A stud bolt (not shown) is then provided so as to pass through the spacer along the direction of the central axis CL of the magnetic field device 2. Both ends of this stud bolt are fixed to the bottom plate 3c and cover plate 3d of the case 3, thereby fixing the magnetic field device 2 within the case 3.

In addition, spacers may be interposed between the annular cores to keep the distance between them constant.

The air intake 4 is provided to take in air into the case 3 to cool the magnetic field device 2. The air exhaust 5 is provided to exhaust the air inside the case 3 to the outside. In this embodiment, the air intake 4 is configured as a connection flange for an air duct for supplying cold air. Therefore, it is possible to connect a blower (not shown) to the air intake 4 and forcibly cool the magnetic field device 2 with air.

As shown in FIG. 1, the air intake 4 and air exhaust 5 are provided on the circumferential surface (outer cylinder portion 3a) of the case 3. This allows the cooling air taken into the case 3 to pass between the annular iron cores 21-26 and be exhausted from the air exhaust 5, thereby improving the cooling efficiency of the magnetic field device 2. Note that the air intake 4 and air exhaust 5 may be provided in a straight line as shown in FIG. 1.

The terminal box 6 is provided in the case 3 and houses a terminal post (not shown). The terminal post is electrically connected to the coil of the magnetic field device 2. The terminal box 6 has a wiring inlet 6a for introducing wiring that connects the terminal post to the AC power source 7.

The AC power supply 7 is a three-phase AC power supply that outputs a constant current, constant frequency three-phase AC current. In more detail, the AC power supply 7 passes an R-phase current through the first series coil, an S-phase current through the second series coil, and a T-phase current through the third series coil.

The AC power supply 7 may be configured to vary the output current and frequency to adjust the stirring power and stirring speed.

The mounting base 8 is a support base on which the case 3 containing the magnetic field device 2 is placed.

In this embodiment, the magnetic field device 2 is installed horizontally (i.e., the central axis CL of the annular cores 21-26 is horizontal). However, the magnetic field device 2 may be installed vertically (i.e., the central axis CL is vertical).

<Operation of magnetic field device 2>
Next, the operation of the magnetic field device 2 will be described. As described above, the magnetic field device 2 is configured to have three magnetic field generating units. In other words, if two annular iron cores connected by two yokes are considered as one unit, the magnetic field device 2 has three magnetic field generating units (a first magnetic field generating unit, a second magnetic field generating unit, and a third magnetic field generating unit).

In more detail, the first magnetic field generating unit has annular core 21, annular core 24, yoke 31a, and yoke 31b. The second magnetic field generating unit has annular core 22, annular core 25, yoke 32a, and yoke 32b. The third magnetic field generating unit has annular core 23, annular core 26, yoke 33a, and yoke 33b. The first to third magnetic field generating units are arranged such that the six yokes (yokes 31a, 31b, 32a, 32b, 33a, 33b) are spaced apart from one another, as shown in FIG. 4.

The magnetic field generated by the first magnetic field generating unit will be described with reference to Figures 7 and 8. Note that the coil is omitted in Figure 8.

When the current output from the AC power source 7 flows through the coils 41a and 41b, magnetic fields H1 and H2 are generated in the annular iron core 21. That is, magnetic field H1 is generated when a current flows through coil 41a, and magnetic field H2 is generated when a current flows through coil 41b. Magnetic fields H1 and H2 are in opposite directions and are approximately equal in magnitude.

The magnetic fields H1 and H2 thus generated flow through the annular core 21 toward the yoke 31b, collide and repel at the portion where the connection portion 31b1 is provided, and then flow through the connection portion 31b1 to the coupling portion 31b3. The same is true for the annular core 24. That is, the two magnetic fields generated in the annular core 24 by the current flowing through the coils 44a and 44b collide and repel at the portion where the connection portion 31b2 of the yoke 31b is provided, and then flow through the connection portion 31b2 to the coupling portion 31b3.

The two repulsive magnetic fields that flow from the annular core 21 and the annular core 24 into the connecting portion 31b3 collide and repel each other near the center of the connecting portion 31b3, as shown in FIG. 8, and are radiated as a magnetic field H3 toward the connecting portion 31a3 of the yoke 31a.

In this way, the magnetic field generating unit generates a strong magnetic field through two stages of magnetic field repulsion: the repulsion of the magnetic field at each annular iron core and the repulsion of the magnetic field at the connection part of one of the yokes, and radiates it toward the other yoke.

As with the first magnetic field generating unit, when the current output from the AC power source 7 flows through the coil in the second and third magnetic field generating units, a strong magnetic field is formed through two stages of repulsion and is radiated from the connection part of one yoke to the connection part of the other yoke.

When the molten metal stirring device 1 is in operation, three-phase AC current flows through the coils of the first to third magnetic field generating units. That is, R-phase current of the AC power source 7 flows through the first series coil of the first magnetic field generating unit, S-phase current flows through the second series coil of the second magnetic field generating unit, and T-phase current of the AC power source 7 flows through the third series coil of the third magnetic field generating unit. This generates a strong moving magnetic field within the annular iron cores 21 to 26. This moving magnetic field can stir the molten metal inside the magnetic field device 2 with sufficient force.

<Action and effect>
As described above, in the molten metal stirring device 1 of this embodiment, the magnetic field device 2 has the first to third magnetic field generating units, and each magnetic field generating unit has an annular iron core and a coil. Since the annular iron core and the coil are divided in this manner, the thermal and electrical loads on each annular iron core and each coil are reduced.

More specifically, the surface area of the magnetic field device 2 is increased because the magnetic field device 2 is made up of multiple annular iron cores 21-26 arranged coaxially at intervals. This allows for a significant improvement in heat dissipation characteristics compared to the conventional device. As a result, in conventional molten metal stirring devices, it was essential to cool the magnetic field device by water cooling, but in this embodiment, it is possible to cool the magnetic field device by air cooling. In the case of a water-cooled system, the maintenance costs are enormous, such as pre-treatment of the cooling water, such as softening treatment, and regular removal of algae to prevent clogging of the pipes. In this embodiment, such maintenance costs can be reduced. In addition, the molten metal stirring device 1 can be made smaller.

In addition, by making the annular cores 21-26 thinner, the cooling efficiency can be further improved. As mentioned above, by making the thickness t1 of the annular cores 21-26 smaller than the thickness t2, the cooling efficiency of the magnetic field device 2 can be further improved and iron loss can be further reduced.

In addition, the air intake 4 and air exhaust 5 are arranged on the outer tube portion 3a of the case 3 so that they sandwich the magnetic field device 2, allowing the cooling air to pass between the annular iron cores, thereby allowing the magnetic field device 2 to be cooled with high efficiency.

In addition, because each of the annular cores 21-26 is thinner than the annular cores of conventional magnetic field devices, it is possible to reduce eddy currents that occur in each of the annular cores 21-26 when current is passed through the coil. For this reason, general-purpose carbon steel plates can be used as the material for the annular cores 21-26, rather than laminated thin silicon steel plates with low iron loss. This allows the cost of the magnetic field device 2 (design costs, material costs, and manufacturing costs) to be reduced, and the weight of the molten metal stirring device 1 to be reduced.

Furthermore, in the molten metal stirring device 1 of this embodiment, a strong moving magnetic field is generated by a repulsive magnetic field in the magnetic field generating section having two annular iron cores and two yokes. This makes it possible to generate a strong magnetic field without passing a large current through the coil.

Here, the configurations of the first to third magnetic field generating units of the magnetic field device 2 are summarized as follows.
Each magnetic field generating unit has two coaxially arranged annular iron cores, two coils are wound around each annular iron core, and the two annular iron cores are connected by two yokes. That is, each magnetic field generating unit includes a first annular iron core (21, 22, 23), a second annular iron core (24, 25, 26) that is coaxial with the first annular iron core and is arranged at a distance from the first annular iron core and has a central axis CL, a first yoke (31a, 32a, 33a) that extends along the central axis CL and connects the first annular iron core to the second annular iron core, a second yoke (31b, 32b, 33b) that extends along the central axis CL so as to face the first yoke across the central axis CL and connects the first annular iron core to the second annular iron core, and a coil that connects the first yoke and the second annular iron core. The coil has a first coil (41a, 42a, 43a) wound around a first annular core between the yokes, a second coil (41b, 42b, 43b) wound around the first annular core so as to be located on the opposite side of the first coil across the first and second yokes, a third coil (44a, 45a, 46a) wound around the second annular core between the first and second yokes, and a fourth coil (44b, 45b, 46b) wound around the second annular core so as to be located on the opposite side of the third coil across the first and second yokes.

The first to third magnetic field generating units are arranged so that the first and second yokes (31a, 32a, 33a, 31b, 32b, 33b) of each magnetic field generating unit do not overlap with each other. In other words, the first to third magnetic field generating units are arranged so that the first and second yokes of each magnetic field generating unit are positioned at intervals from each other around the central axis CL of the annular iron cores 21 to 26. In this embodiment, the first to third magnetic field generating units are arranged at positions rotated at 60° intervals around the central axis CL of the annular iron cores 21 to 26.

In this embodiment, as shown in FIG. 5A, each yoke has a length L that overlaps in the direction of the central axis CL. That is, the yokes 31a and 31b of the first magnetic field generating unit, the yokes 32a and 32b of the second magnetic field generating unit, and the yokes 33a and 33b of the third magnetic field generating unit are arranged so that a portion of the projection of each yoke onto the central axis CL overlaps with each other. In this way, the six yokes are arranged so as not to be dispersed as much as possible in the direction of the central axis CL, so that a uniform stirring force can be generated around the central axis CL.

As described above, in the magnetic field device 2 of this embodiment, the first annular iron core of the first magnetic field generating unit, the first annular iron core of the second magnetic field generating unit, the first annular iron core of the third magnetic field generating unit, the second annular iron core of the first magnetic field generating unit, the second annular iron core of the second magnetic field generating unit, and the second annular iron core of the third magnetic field generating unit are arranged in this order along the direction of the central axis CL of the annular iron cores. This increases the overlap of the projections of each yoke onto the central axis CL, making it easier to generate a uniform stirring force around the central axis CL.

In addition, the magnetic field device is not limited to the above form, and may be configured by arranging the first to third magnetic field generating units in series. In this case, the first annular iron core of the first magnetic field generating unit, the second annular iron core of the first magnetic field generating unit, the first annular iron core of the second magnetic field generating unit, the second annular iron core of the second magnetic field generating unit, the first annular iron core of the third magnetic field generating unit, and the second annular iron core of the third magnetic field generating unit are arranged in this order along the direction of the central axis CL of the annular iron cores. How the annular iron cores 21 to 26 are connected by the yoke can be selected arbitrarily depending on the required stirring characteristics, etc.

The first coil and the second coil of each magnetic field generating unit are wound and connected so as to generate a first magnetic field (H1) toward one of the first and second yokes (yoke 31b in FIG. 7) on the first annular core when a current flows, and the third coil and the fourth coil are wound and connected so as to generate a second magnetic field (H2) toward the one of the yokes when a current flows.

The first and second yokes of each magnetic field generating unit become magnetic poles when electricity is passed through the coil. By passing three-phase alternating current through the first to third magnetic field generating units, a moving magnetic field is generated between the magnetic poles of each magnetic field generating unit.

In each of the magnetic field generating sections, the magnetic field H1 generated by the current flowing through the first coil of the first annular iron core and the magnetic field H2 generated by the current flowing through the second coil collide and repel each other where the yoke is provided. The repulsive magnetic field flows into the yoke. Similarly, in the second annular iron core, the magnetic field generated by the third coil and the magnetic field generated by the fourth coil collide and the repulsive magnetic field flows into the yoke. The repulsive magnetic fields flowing in from both ends of the yoke further collide and repel each other in the center of the yoke, and are radiated toward the opposing yoke. In this way, a strong magnetic field can be obtained by going through two stages of repulsion. As a result, the magnetic flux concentrated in the yoke (magnetic pole) is two to three times greater than that of conventional magnetic field devices.

As described above, according to this embodiment, a strong magnetic field can be generated without passing a large current, and a large stirring force can be obtained. Therefore, it is possible to provide a molten metal stirring device that has a large stirring force while consuming low power.

In order to facilitate the radiation of the repulsive magnetic field from the yoke, a protrusion 34 may be provided on each yoke, as shown in FIG. 9. This protrusion 34 is provided so as to protrude toward the central axis CL of the annular cores 21 to 26.

<Continuous casting system 100>
Next, a continuous casting system 100 using the molten metal stirring device 1 will be described with reference to Fig. 10. Fig. 10 shows a cross section of the continuous casting system 100. Note that the yoke and coil are omitted in Fig. 10.

The continuous casting system 100 is configured to continuously mold a casting (product) P by flowing molten metal M into a mold 70. More specifically, the continuous casting system 100 is configured to receive a supply of molten metal M of a conductive material in a liquid phase, and to extract a casting P in a solid phase by cooling the molten metal.

The molten metal M is, for example, molten aluminum. Note that the molten metal may be molten metal of other metals (Cu, Zn, Si, etc.), or may be molten metal of an alloy consisting of at least two of Al, Cu, Zn, and Si, or molten metal of a magnesium alloy.

As shown in FIG. 10, the continuous casting system 100 according to this embodiment includes a mold 70 and a molten metal stirring device 1.

The mold 70 is supplied with molten metal M in a liquid phase from the inlet side (right side of FIG. 10), and discharges a solid-phase casting P from the outlet side (left side of FIG. 10) upon cooling. The mold 70 in this embodiment is cylindrical. The cylindrical mold 70 is positioned so that its central axis is coaxial with the central axis CL of the magnetic field device 2. Note that when the casting is a slab, a rectangular mold is used.

The mold 70 is made of a refractory material. If it is made of graphite, a casting with a smoother surface can be obtained because graphite is a soft material.

The mold 70 has a water jacket (not shown) for cooling the molten metal M that flows into the mold 70. Cooling water is circulated within the water jacket, and the outer periphery of the mold 70 is cooled by this cooling water. This causes the molten metal M to be cooled rapidly. The water jacket can be of any of a variety of known structures.

The molten metal stirring device 1 is arranged to surround at least a portion of the mold 70. The mold 70 is arranged to be inserted into the inner cylinder portion 3b of the case 3.

By supplying three-phase AC current from the AC power source 7 to the magnetic field device 2, a moving magnetic field is generated within the mold 70. This moving magnetic field generates eddy currents in the unsolidified molten metal, which stirs the molten metal.

According to the above-mentioned continuous casting system 100, the molten metal M in the mold 70 is thoroughly stirred by the strong moving magnetic field generated by the magnetic field device 2 of the molten metal stirring device 1. As a result, a high-quality casting product P can be obtained.

The stirring force can be adjusted by adjusting the magnitude and frequency of the AC current output from the AC power source 7.

Furthermore, as described above, the yokes of the first to third magnetic field generating units of the magnetic field device 2 have a length L that overlaps in the direction of the central axis CL, so that a uniform stirring force is generated around the central axis CL and acts on the molten metal M in the mold 70. As a result, the molten metal M can be effectively stirred, and a high-quality casting can be produced.

Based on the above description, a person skilled in the art may be able to conceive of additional effects and various modifications of the present invention, but the aspects of the present invention are not limited to the above-described embodiment. Various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and intent of the present invention derived from the contents defined in the claims and their equivalents.

1 Molten metal stirring device 2 Magnetic field device 21 to 26 Annular iron core 31a to 33a, 31b to 33b Yoke 31a1 to 33a1, 31a2 to 33a2, 31b1 to 33b1, 31b2 to 33b2 Connection part 31a3 to 33a3, 31b3 to 33b3 Connection part 34 Protrusion part 41a to 46a, 41b to 46b Coil 3 Case 3a Outer cylinder part 3b Inner cylinder part 3c Bottom plate 3d Cover plate 4 Air intake port 5 Air exhaust port 6 Terminal box 6a Wiring inlet 7 AC power source 8 Mounting base 70 Mold 100 Continuous casting system CL Center axis L Length P Casting

Claims (15)

A molten metal stirring device for stirring a molten metal,
A magnetic field device having first to third magnetic field generating units,
Each of the first to third magnetic field generating units is
A first annular core;
a second annular core having a central axis coaxial with the first annular core and spaced apart from the first annular core;
a first yoke connecting the first annular core and the second annular core;
a second yoke arranged to face the first yoke across the central axis and connecting the first annular core and the second annular core;
a first coil wound around the first annular core;
a second coil wound around the first annular core so as to be located on the opposite side of the first coil;
a third coil wound around the second annular core; and
a fourth coil wound around the second annular core so as to be located on the opposite side of the third coil,
each of the first coil and the second coil is wound so as to generate a first magnetic field directed toward one of the first yoke and the second yoke when a current flows therethrough, and each of the third coil and the fourth coil is wound so as to generate a second magnetic field directed toward the one of the yokes when a current flows therethrough;
A molten metal stirring device, characterized in that the first to third magnetic field generating units are arranged such that the first and second yokes are positioned at intervals from each other. The molten metal stirring device according to claim 1, characterized in that the first and second annular iron cores of the first to third magnetic field generating units have a thickness in a first direction along the central axis that is smaller than the thickness in a second direction perpendicular to the first direction. The molten metal stirring device according to claim 1 or 2, characterized in that the first and second annular iron cores of the first to third magnetic field generating units have a planar shape corresponding to the shape of the mold. The molten metal stirring device according to claim 3, characterized in that the planar shape of the first and second annular iron cores of the first to third magnetic field generating units is circular. The molten metal stirring device according to claim 4, characterized in that the first to third magnetic field generating units are arranged such that the first and second yokes of the first to third magnetic field generating units are positioned at equal intervals on a circumference around the central axis. The molten metal stirring device according to any one of claims 1 to 5, characterized in that the first annular iron core of the first magnetic field generating unit, the first annular iron core of the second magnetic field generating unit, the first annular iron core of the third magnetic field generating unit, the second annular iron core of the first magnetic field generating unit, the second annular iron core of the second magnetic field generating unit, and the second annular iron core of the third magnetic field generating unit are arranged in this order along the direction of the central axis. the first coil, the second coil, the third coil, and the fourth coil of the first magnetic field generating unit are connected in series to form a first series coil;
the first coil, the second coil, the third coil, and the fourth coil of the second magnetic field generating unit are connected in series to form a second series coil;
the first coil, the second coil, the third coil, and the fourth coil of the third magnetic field generating unit are connected in series to form a third series coil;
7. The molten metal stirring device according to claim 1, wherein the first series coil, the second series coil and the third series coil are star-connected. The molten metal stirring device according to claim 7, further comprising an AC power source that passes an R-phase current through the first series coil, an S-phase current through the second series coil, and a T-phase current through the third series coil. The molten metal stirring device according to any one of claims 1 to 8, wherein the first yoke and the second yoke of the first magnetic field generating unit, the first yoke and the second yoke of the second magnetic field generating unit, and the first yoke and the second yoke of the third magnetic field generating unit are arranged such that a portion of the projection of each yoke onto the central axis overlaps with each other. The magnetic field device further includes a case for housing the magnetic field device.
The case is
An outer cylinder portion;
an inner cylindrical portion coaxial with the outer cylindrical portion;
a bottom plate that closes a gap on one side between the outer cylinder portion and the inner cylinder portion;
a cover plate that closes the gap on the other side between the outer cylinder portion and the inner cylinder portion,
The molten metal stirring device according to any one of claims 1 to 9, characterized in that the magnetic field device is housed in the case so that the inner cylindrical portion is inserted into the first and second annular iron cores of the first to third magnetic field generating units. The molten metal stirring device according to claim 10, characterized in that the outer cylinder is provided with an air intake for taking in air into the case and an air exhaust port for exhausting the air in the case to the outside. The molten metal stirring device according to claim 11, characterized in that the air intake and the air exhaust are arranged on either side of the magnetic field device. The molten metal stirring device according to claim 11 or 12, characterized in that a blower is connected to the air intake, and the magnetic field device is forced air-cooled. The molten metal stirring device according to any one of claims 1 to 13 , characterized in that the first and second yokes of the first to third magnetic field generating units have protrusions protruding toward the central axis. A mold that receives liquid molten metal from an inlet and discharges a solid casting from an outlet by cooling;
The molten metal stirring device according to any one of claims 1 to 14, which is provided so as to surround at least a part of the mold;
A continuous casting system comprising:

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