JPH07270083A - Electromagnetic agitator for molten metal pouring ladle - Google Patents

Abstract

PURPOSE:To increase an agitating force of molten metal and to prevent an increase in overheat and inductance of a core due to an eddy current by decreasing a leakage magnetic flux generated from a horizontal part of a pole end side of the metal side and increasing a magnetic flux density in the metal when an end of an electromagnetic agitator at the molten metal side pole is formed in a stair state of predetermined number of stages and approached to the metal. CONSTITUTION:An end 5 of a protrusion 12 of a core 1 of an electromagnetic agitator disposed on an outer periphery of a ladle 6 at the ladle 6 side is formed in a stair state, approached to molten metal 9. A coil 2a is so disposed as to be disposed along a gradient of the end 5. Water-cooled copper plates 3a, 3a' are brought into close contact with both upper and lower end faces of the protrusion 12 of the core 1, or a plurality of auxiliary coils are provided on a back surface side of a main coil.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic stirrer for a metal and alloy melting apparatus for preventing local solidification of molten metal held in a ladle and nonuniform concentration of components. More specifically, the present invention relates to an improvement for increasing the stirring force of molten metal of an electromagnetic stirring device provided in a ladle having an inverted trapezoidal cross section.

[0002]

2. Description of the Related Art In a relatively large melting apparatus, when a molten metal or alloy melted in a melting furnace is cast into a mold, a ladle is used as an intermediate container for carrying the molten metal in the melting furnace to the mold and casting it. To do. In the ladle, the outer wall, which is the outer skin, is usually made of steel sheet, and the inner wall part that contacts the molten metal is usually lined with refractory bricks to have an adiabatic structure so that the molten metal held does not cool and solidify. ing. Since the molten metal in the melting furnace is accompanied by convection due to the thermal energy provided by the heating source, and in the case of electromagnetic induction heating such as high-frequency induction heating melting furnace, it is accompanied by the stirring action by eddy current, so the alloy components of the molten metal are always It is evenly distributed. However, the ladle is for accommodating the molten metal in the melting furnace, carrying it to the mold and casting it, and does not have a special stirring means, so when the temperature of the molten metal discharged from the melting furnace is low or the molten metal in the ladle is When the holding time is long, the molten metal locally cools and solidifies, or non-uniformity due to difference in mass of alloy components in the molten metal, that is, concentration distribution occurs. In order to prevent the above-mentioned local solidification and the occurrence of concentration distribution, various means for stirring the molten metal in the ladle have been taken. An electromagnetic stirrer, which is one of these means, applies an alternating current to a coil wound around an iron core arranged on the outer periphery of a ladle to generate an alternating magnetic field that penetrates into the molten metal, ) Stir the melt.

Generally, the cross-sectional shape of a ladle is determined by its internal volume, that is, the amount of molten metal to be contained, and there are a cylindrical shape, a substantially elliptical shape and an inverted trapezoidal shape according to the present invention. Figure 6
FIG. 6A is a partially cutaway sectional view showing an electromagnetic stirrer arranged on the outer periphery of a ladle, which is an example of a conventional technique, and FIG.
It is a partially broken plan view of the electromagnetic stirring device with the ladle of (A) removed. In the figure, reference numeral 6 is an inverted trapezoidal ladle, and when an electromagnetic stirrer is used, a refractory 8 having a predetermined thickness is preferably provided on the inside of an outer skin 7 made of a non-magnetic material. The molten metal 9 is held in the. Ladle 6 above
On the outer peripheral side of the annular portion 11, a plurality of thin magnetic metal layers are laminated, and the annular portion 11 is radially inwardly projected from the inner diameter side end portion of the annular portion with a predetermined equal interval in the circumferential direction. Iron core 1a having a plurality of protrusions 12a, and the iron core 1a
And the coil 2c wound around each of the protrusions 12a of
The iron core 1a is arranged in a fixed state on a support frame (not shown). In the present invention, the structure of the iron core and the coil of the electromagnetic stirrer is an important requirement, so description of other conventional members of the electromagnetic stirrer that are not directly related to the present invention will be omitted. Side wall 7a of ladle 6 having an inverted trapezoidal cross section
The protrusion 12 of the iron core 1a with a predetermined space on the outer peripheral side.
The coil 2c wound around a is arranged, but since the inner diameter side tip surface 12i of the protrusion 12a of the iron core 1a is formed vertically, the inner diameter side tip surface 12i and the molten metal outer edge portion 9a are arranged in the horizontal direction. The distance is larger toward the bottom.

FIG. 7 is a schematic diagram showing the distribution of magnetic flux from the magnetic poles of a permanent magnet (Source: Illustrated Dictionary of Electrical and Electronic Terms, p20
4, Practical Publishing). A plurality of magnetic fluxes Mf indicated by arrows are distributed parabolicly from the central axis of the magnet M to the left and right (up and down in the figure) as the distance from the magnetic pole tip surface Pf increases, and the magnetic flux density is the distance from the magnetic pole tip surface Pf to the front. It increases sharply and decreases sharply. In FIG. 6, the tip end surface 12i on the inner diameter side of the iron core 1a which is a magnetic body serves as a magnetic pole (hereinafter referred to as a magnetic pole),
The magnetic flux generated from the magnetic poles has the same direction (opposite signs)
Since there is no opposing magnetic pole, the protrusion 12 is the same as that shown in FIG.
Radially dispersed with reference to the central axis C of a. Ladle 6
Since the side wall 7a of the molten metal is inclined so as to narrow downward, the distance between the magnetic pole and the molten metal is larger in the lower portion of the molten metal than in the upper portion of the molten metal. The magnetic flux density is smaller than the upper part. The magnitude of the stirring force of the molten metal when an alternating current is passed through the electromagnetic coil and the generated alternating magnetic field stirs the molten metal is expressed by the following equation (1). F∝Bg ² (1) where F: electromagnetic stirring force of the molten metal Bg: magnetic flux density According to the formula (1), the electromagnetic stirring force in the molten metal is proportional to the square of the magnetic flux density in the molten metal. As described above, the stirring force is insufficient in the lower part of the molten metal which is separated from the magnetic pole. Therefore, in order to increase the stirring power, it is necessary to increase the magnetic flux density in the molten metal.

As a method for this, as the electromagnetic stirring device, 1) use a large electromagnetic coil, 2) increase the value of the current flowing in the electromagnetic coil, 3) decrease the distance between the tip surface of the iron core and the molten metal. Measures such as yes are possible. The measures of 1) above are not efficient or economical because they lead to the enlargement of the device, and 2) above.
Since the above-mentioned measures 1) and 2) are unrealistic, if a large current is forcibly applied to a coil having a predetermined capacity, it will cause heat generation or a short circuit, resulting in an accident. As a countermeasure against 3), there is an iron core structure of an electromagnetic stirrer disclosed in Japanese Patent No. 819953 (Japanese Patent Application No. 62-12976: registered July 12, 1991), which is a prior art. FIG. 8 is a partially broken cross-sectional view showing the iron core structure of the above-described prior art electromagnetic stirrer. Reference numeral 16 is a crucible having an inverted trapezoidal cross section, and an electromagnetic stirrer is arranged on the outer peripheral side of the crucible 16 with a predetermined interval. Inclined side wall 17a of the crucible 16
The magnetic pole tips 22i on the crucible 16 side of the iron core 21 are formed in three steps in a stepwise manner so as to be parallel to each other on average. The crucible in the above-mentioned prior art is for melting a solid charge of a metal or an alloy itself, and is different from the ladle as the intermediate container in the present invention, but both are substantially in the point of containing the molten metal. Are similar. The efficiency of the magnetic force for stirring is increased by making the magnetic pole tip 22i of the iron core 21 stepwise so as to reduce the distance to the magnetic pole even in the lower part of the molten metal.

[0006]

However, when the magnetic pole tip on the molten metal side is made closer to the molten metal by forming the magnetic pole tip on the molten metal side in a stepwise manner as described above, each of the stepped magnetic pole tip portions has a relatively large surface area. A horizontal horizontal surface 22f (see FIG. 8) is formed, and a magnetic flux generated from this surface, that is, a leakage magnetic flux is generated to reduce the magnetic flux reaching the molten metal.
There have been drawbacks such as overheating of the iron core and increase of inductance due to eddy currents. An object of the present invention is to prevent overheating of the iron core, keep the inductance small, reduce the leakage current to further increase the magnetic flux density reaching the molten metal, and increase the stirring force.

[0007]

The structure of the present invention for solving the above problems is as follows. An annular or semi-circular annular protrusion formed by laminating a plurality of thin silicon steel plates and protruding inward at predetermined equal intervals in the circumferential direction thereof. 1) A stair with a large number of steps at the magnetic pole tip on the molten metal side. 2) the coil is wound parallel to an imaginary line connecting the upper ends of the projecting portions of the staircase-shaped iron core and inclined, and the inner diameter side end of the coil is positioned substantially along the imaginary line. ) A water-cooled copper plate is brought into close contact with both upper and lower end surfaces of the protrusion, 4) a plurality of auxiliary coils are provided on the back side of the coil of the protrusion (on the side of the annular portion of the iron core), and 5) on the annular portion of the iron core. The above problem was solved by closely contacting a copper water-cooled shield plate with the curved surface on the inner diameter side of.

[0008]

The operation of the above-described structure of the present invention is as follows. 1) Reduce the distance between the magnetic pole tip of the electromagnetic stirrer and the molten metal, make the winding direction of the coil the same as the inclination of the magnetic pole tip, and reduce the exposed amount of the iron core around the magnetic pole, The magnetic flux density to be reached is increased and the leakage magnetic flux is reduced to prevent the core from overheating and the inductance from increasing. 2) A water-cooled copper plate is used to cool from the upper end surface and the lower end surface of the protrusion of the iron core to prevent the iron core from overheating. 3) The auxiliary coil provided on the back side of the coil enhances the performance of the power supply device and the compatibility of the coil characteristics and facilitates the setting of optimum conditions. 4) A copper water-cooled shield plate is provided on the inner diameter side surface of the annular portion of the iron core to reduce the inductance.

[0009]

【Example】

Example 1: FIG. 1 (A) is a partially broken sectional view of a ladle in which an electromagnetic stirring device according to the present invention is arranged, and FIG. 1 (B) is shown in FIG.
It is a partially broken partial top view which removed the ladle of (A).
In the drawings referred to in the following description, the same members as those shown in FIGS. 6 and 8 are designated by the same reference numerals, and the duplicated description will be omitted. Iron core 1 with multiple silicon steel sheets laminated
Has a circular annular portion 11 and projecting portions 12 provided on the inner diameter side of the annular portion 11 at predetermined equal intervals. The tip portion 5 of the protruding portion 12 on the molten metal 9 side is formed in a stepped shape of a plurality of steps from 5 steps to 10 steps (5 steps in this example), and is an annular portion which is integrally continuous with the protruding portion 12. A back surface (outer peripheral surface) 13 which is an end portion on the outer diameter side of 11 is vertically aligned with a flat curved surface.

In FIG. 1A, which is a sectional view, a ladle 6 is provided.
The virtual line I connecting the side wall 7a of the core and the upper end 5b of each step of the tip 5 of the iron core 1 is parallel. Therefore, the molten metal outer edge 9a is also parallel, and the molten metal outer edge 9a is the magnetic pole. The distance between the tip 5 of the protrusion 12 (of the iron core) and the tip 5 is substantially equal from the upper end to the lower end of the magnetic pole. As a result, FIG.
The distance A'-P between the outer edge of the molten metal and the tip of the magnetic pole according to the present invention shown in FIG. 1A is smaller than the distance AP between the outer periphery of the molten metal and the tip of the magnetic pole shown in FIG. Becomes
The dispersion of magnetic flux was reduced, and the magnetic flux density at the outer edge of the molten metal was increased by 10 to 15%. In this way, the magnetic flux density in the molten metal is increased by 10 to 15% as compared with the conventional case, and as a result, the stirring force of the molten metal according to the formula (1) is increased by 20 to 30%. In this case, since the number of steps is increased from 5 to 10 as compared with the above-described three-step staircase according to the registered design, the surface area of the horizontal portion 5d of each step is small and the leakage magnetic flux can be reduced. did it.

Embodiment 2 In the structure according to Embodiment 1, the magnetic flux density in the molten metal is made larger than that of the conventional one in that the distance between the magnetic pole and the molten metal is made smaller, while the distance from the coil to the magnetic pole tip is increased. As a magnetic flux is generated from a portion other than the magnetic pole tip surface, insufficient points remain for increasing leakage magnetic flux, heat generation of the iron core, and increasing inductance. In order to further improve this point, the winding direction of the coil is parallel to the imaginary line connecting the upper ends of the magnetic pole tips, and the molten metal side tip of the coil is brought closer to the stepped magnetic pole tip to expose the core closer to the molten metal than the coil. The area was reduced. FIG. 2 is a partially cutaway sectional view in which the electromagnetic stirrer in which the coil winding position is changed as described above is arranged on the outer periphery of the ladle. By this means, most of the iron core on the tip 5 side of the stepped magnetic pole on the molten metal side is covered with the inclined coil 2a, and it becomes difficult to generate magnetic flux that is not perpendicular to the winding direction of the coil 2a. That is, the leakage magnetic flux from the horizontal surface of the stepped magnetic pole is less likely to occur. In this case, the exposed amount of the iron core is 0 when the horizontal distance H between the imaginary line I connecting the upper ends of the staircase-shaped magnetic poles and the molten metal side end surface is 0.
It can be set to a preferable value by setting it in a range of up to 20 mm. When the end surface of the coil on the melt side is closer to the melt than the imaginary line I, the distance between the melt and the magnetic pole becomes large, and the magnetic flux density in the melt decreases. Further, when the horizontal distance H is larger than 20 mm, the iron core is overheated and the inductance is significantly increased.

With the configuration shown in this figure, the leakage flux is greatly reduced as compared with the prior art shown in FIG. 8, so that the inductance of the coil is reduced by 15 to 30%. When a coil with a large capacity is used, the length of the iron core in the radial direction becomes large, and even if the coil is inclined as described above, the amount of heat generated by the iron core tends to become large. When there is a risk of overheating, the water-cooled copper plates 3a, 3a 'made of water-cooled copper or copper alloy are brought into close contact with the upper and lower end surfaces of the iron core to prevent overheating, as shown in FIG.
FIG. 3 is a plan view of a water-cooled copper plate brought into close contact with the lower end surface of the iron core as an example. The water-cooled copper plate 3a is composed of a copper plate 32 brazed with copper pipes 33 having a rectangular cross section on three sides, and is cooled by water flowing in the copper pipes 33.

Embodiment 3: In each of the above-mentioned embodiments, the magnetic stirrer in which the coils are arranged on all the projecting portions of the iron core has been described. However, in order to further enhance the stirring effect of the electromagnetic stirrer according to the present invention, only half a circumference is provided. An example of arranging the coil in is shown below. FIG. 4 is a schematic plan layout view of a semi-annular iron core in which a coil is wound around a projecting portion of the iron core. In this case, the annular portion 11 of the iron core 1c is formed in a semicircle of approximately 180 °, and the protrusion 1
2 are also formed in the range of the annular part 11 at equal intervals. In this semi-annular electromagnetic stirrer, magnetic flux generated by the magnetic stirrer is effective because the magnetic force from the opposing magnetic poles with opposite directions (the same sign) does not occur as in the electromagnetic stirrer with coils all around. A large stirring force can be obtained by acting on the molten metal. In FIG. 4, the iron core 1c formed in a semi-annular shape is shown, but the iron core is formed in the entire circumference (annular shape), and only the protruding portion in the range of a half circumference is formed among the protruding portions provided in the entire circumference at a predetermined interval. The same effect can be obtained by winding the coil around.

Example 4: An agitator using electromagnetic force is normally operated by a low frequency inverter (0.5 to 9.9 Hz), and the voltage and current from this power supply unit, the number of turns, the outer shape and the wire diameter are used. In some cases, the combination with the characteristics of the coil is not optimal. As a means for eliminating the mismatch of the above combinations, the coils shown in the first to third embodiments are used as the main coil, and an auxiliary coil is provided separately from the main coil. FIG. 5A is a partially cutaway sectional view showing an embodiment of this configuration.
5B is a partially cutaway plan view with the ladle of FIG. 5A removed. Reference numeral 2a ′ is a main coil, and the main coil 2
A plurality of (two in the figure) auxiliary coils 2b and 2b are provided in the vicinity of the outer surface of the a'on the side opposite to the ladle 6. The winding direction of the auxiliary coil 2b is parallel to the winding direction of the main coil. A copper water-cooled shield plate 3b is attached to the inner diameter side surface 13a of the annular portion 11 of the iron core 1. As for the winding method of the plurality of auxiliary coils 2b, when winding is performed with the same number of turns and the same outer dimensions, it is preferable that the auxiliary coil 2b is wound widely in the circumferential direction of the annular core and narrowly in the radial direction. Further, it is preferable that the distance between the adjacent auxiliary coils is smaller. By adjusting the number of turns of the above auxiliary coil, the matching between the performance on the power supply side and the characteristics of the main coil and auxiliary coil can be obtained in a wide range, and the degree of freedom (flexibility) in the design of the electromagnetic stirring device is improved. it can. Also, the copper water-cooled shield plate reduces the leakage magnetic flux from the iron core, thereby making it possible to further reduce the inductance by several% as compared with the above-mentioned embodiments.

[0015]

The magnetic stirrer poles of the electromagnetic stirrer arranged on the outer periphery of the ladle are formed stepwise so as to approach the molten metal, and the coils are arranged along the inclination of the magnetic pole tip, and the upper and lower ends of the iron core are arranged. A water-cooled copper plate was brought into close contact with the surface or an auxiliary coil was provided on the back side of the coil to increase the magnetic flux density in the molten metal and increase the stirring force of the molten metal without increasing the inductance and overheating the iron core.

[Brief description of drawings]

FIG. 1A is a partially cutaway sectional view of a ladle in which an electromagnetic stirring device according to the present invention is arranged, and FIG. 1B is a partially cutaway plan view of the ladle shown in FIG. 1A.

FIG. 2 is a partially cutaway sectional view in which an electromagnetic stirrer in which the winding position of a coil is changed is arranged on the outer circumference of a ladle.

FIG. 3 is a plan view of a water-cooled copper plate used for the lower end surface of the protrusion.

FIG. 4 is a schematic plan layout view in which an iron core structure of a semicircular electromagnetic stirring device is arranged on the outer periphery of a ladle.

5A is a partially cutaway sectional view of an iron core structure provided with an auxiliary coil arranged on the outer periphery of a ladle, and FIG. 5B is a sectional view of FIG.
It is a partially broken plan view with the ladle of FIG.

FIG. 6 (A) is a partially cutaway cross-sectional view in which the iron core structure of the electromagnetic stirring device according to the prior art is arranged on the outer periphery of the ladle,
(B) is a partially cutaway plan view of the state in which the ladle of (A) is removed.

FIG. 7 is a schematic diagram showing a distribution of magnetic flux from a magnetic pole portion of a permanent magnet.

FIG. 8 is a partially cutaway cross-sectional view in which the iron core structure of the electromagnetic stirrer according to the prior art is arranged on the outer circumference of the ladle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Iron core 2a, 2c Coil 2a 'Main coil 2b Auxiliary coil 3a, 3a' Water-cooled copper plate 3b Copper water-cooled shield plate 5 Tip part 6 Ladle 7 Outer skin 8 Refractory material 9 Molten metal 9a Molten metal outer edge part 11 Annular part 12 Projection part 13 Back surface 13a Inner diameter side surface C Central axis I Virtual line

Claims (6)

[Claims] 1. A molten metal or alloy melted in a melting furnace is cast into a mold, so that the cross section for accommodating the molten metal from the melting furnace to the mold is arranged close to the outer peripheral side of an inverted trapezoidal ladle. In order to prevent solidification and inhomogeneity of the components of the molten metal contained in the pan, a plurality of magnetic thin plates that generate an alternating magnetic field and stir the molten metal are layered together and kept in a circular shape and at equal intervals in the circumferential direction. In an electromagnetic stirrer comprising an iron core provided with a protruding portion radially inward from the inner diameter side of the annular portion, and a coil in which an insulated wire is wound around the protruding portion, the inner diameter side end portion of the protruding portion is in the vertical direction. 5 to 10 steps, and an imaginary line connecting the upper ends of the steps is formed parallel to the outer surface of the ladle, and the inner end of the protruding portion and the inside of the ladle are formed. The horizontal distance from the outer edge of the molten metal is small, and the magnetic flux density generated in the molten metal is large. Rot and, together with the stirring force of molten metal is increased, leakage magnetic stirrer ladle for pouring, characterized in that to prevent overheating and inductance increase in the magnetic flux is small has been the core. 2. The electromagnetic stirrer for a pouring ladle according to claim 1, wherein the insulated wire is wound such that an end surface of the coil on the ladle side and an end surface on the opposite side thereof are parallel to the virtual line. . 3. The electromagnetic stirrer for a pouring ladle according to claim 1, wherein a water-cooled copper plate is closely attached to the upper end surface and the lower end surface of the iron core. 4. The coil according to any one of claims 1 to 3, wherein the coil is wound only on the protruding portion in a range of a half circumference of the protruding portion provided on the inner diameter side of the annular portion of the iron core. An electromagnetic stirring device for a ladle for pouring as described in one item. 5. The iron core has a substantially semi-circular shape formed in a range of approximately 180 ° in the circumferential direction, and the projecting portion has approximately 1
The electromagnetic stirring device for a pouring ladle according to any one of claims 1 to 3, which is provided in a range of 80 °. 6. A plurality of auxiliary coils each having an insulated electric wire wound in parallel with the winding direction of the insulated electric wire of the coil, in the vicinity of the annular portion side of the coil wound around the protruding portion, The electromagnetic stirrer for a pouring ladle according to any one of claims 1 to 5, wherein a copper water-cooled shield plate is arranged on the inner diameter side surface of the annular portion of the iron core.