JPH044950A - Electromagnetic stirring device for twin directional drawing type horizontal continuous caster - Google Patents

Abstract

PURPOSE:To stably execute horizontal continuous casting by setting an electromagnetic stirring device arranged as surrounding a mold at lower part of a feed nozzle in a horizontal continuous caster to both side parts and lower part of the mold and connecting only with a yoke set at upper face of the feed nozzle side. CONSTITUTION:The electromagnetic stirring device 18 surrounding the mold 6 just below the feed nozzle 8 in the twin directional drawing type horizontal continuous caster is composed of the yoke 20, coils 22 and part, which forms magnetic poles 24 by conducting electric current to the coils 22, and at three faces of both side faces and bottom face surrounding the mold 6, the coils 22 are set, but at the upper face of mold 6 just below the feed nozzle 8, only the yoke 20 is set and the coil 22 is not set. As magnetic fluxes at upper and lower sides are uniformized and there is no leakage of the magnetic flux, the magnetic flux acting effectively to molten steel is increased and there is effect that flowing velocity of the molten steel 2 passed through the mold 6 is made to fast. By this method, as the flowing velocity at the pouring part of molten steel just below the feed nozzle can be increased, separating point of right and left cast billets is easily controlled to the position just below the feed nozzle, and the stable operation of horizontal continuous casting can be executed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an electromagnetic stirring device for a bidirectional drawing type horizontal continuous casting machine, and is particularly effective in controlling when the slab separation point deviates from the center. Regarding a certain electromagnetic stirring device, it is used in the field of continuous casting of steel etc.

[Conventional technology]

It is well known that in conventional vertical or curved continuous casting machines, electromagnetic stirring devices are installed in the secondary cooling zone below the mold and at the solidification end of the slab, and are effective in improving the quality of the slab. be.

The principle is that when a rotating or moving magnetic field is applied close to the slab, a current is induced in the unsolidified portion inside the slab. When a current flows perpendicular to a magnetic field, a force perpendicular to the current acts according to Faraday's law, and this thrust stirs the unsolidified molten steel.

The electromagnetic stirring device may be either a moving magnetic field type or a rotating magnetic field type.

The electromagnetic stirring device is effective when applied not only to the above-mentioned vertical or curved regular continuous casting machines, but also to molds for bi-directional drawing type horizontal continuous casting machines, and the present inventors have previously proposed the same in Japanese Patent Application No. 63-153.
749 (Japanese Unexamined Patent Publication No. 1-202341), by using a static magnetic field and an electromagnetic stirring device in combination, the temperature non-uniformity of the initially solidified shell in the mold in the cross section of the mold is suppressed, the separation point is fixed, and accidents such as breakouts are prevented. This has the effect of eliminating this problem and contributing to the establishment of casting stability.

For molds for bi-directional drawing type horizontal continuous casting machines, it is also effective to use an electromagnetic stirring device alone, but the electromagnetic stirring device used conventionally can be Since the mold 6 was arranged so as to surround it from four sides, there were various problems, especially when it was installed on the upper surface directly below the feed nozzle 8.

Hereinafter, with reference to FIG. 4, an overview of the operation of the bidirectional drawing type horizontal continuous casting machine and the relationship with the electromagnetic stirring device 18 will be explained.

Below a container 4, such as a ladle or a tundish, which accommodates molten steel 2, a mold 6 is installed horizontally with its end facing in the horizontal direction. Container 4 and mold 6 are feed nozzle 8
This ensures communication so that melt #42 does not leak. Mold 6. The container 4 is vibrated left and right by a vibrating device 1o, and the slab 12 in which the molten steel 2 has solidified is punched left and right by pinch rolls 1 and 4.

In horizontal continuous casting, in which slabs are drawn horizontally from both ends of the mold, it is necessary to satisfy the contradictory demands of forming a strong solidified shell without breakouts and also allowing the solidified shell to break stably at a fixed position. be. However, left and right slabs 1
The most difficult technique of the horizontal continuous casting method was to control the separation point 16 of t4 to the center of the mold 6 directly below the feed nozzle 8, but by installing an electromagnetic stirring device in the mold 6,
By generating a swirling flow in the melt @2 in the center of the mold 6, a highly satisfactory level was achieved.

However, as shown in FIGS. 4 and 5, the conventional electromagnetic stirring device for providing swirling flow is installed so as to surround the four sides of the mold 6 (top, bottom, left and right), so the mounting position of the feed nozzle 8 The electromagnetic stirrer must be installed through the upper part of the mold 6, which increases the length of the expensive feed nozzle, making it difficult to manufacture due to its mechanical strength and shortening the life of the feed nozzle. As a result of installing the stirring device, the height of the tundish inevitably increases, resulting in an increase in static iron pressure, which poses a problem that is disadvantageous in casting. Therefore, we considered installing an electromagnetic stirring device to avoid the vicinity of the feed nozzle, but it was not possible to stir the molten steel injection section, and there was also a problem in controlling the original separation point of the left and right slabs directly below the feed nozzle. It turns out that there is.

It has been found that the above-mentioned problems are particularly noticeable when multiple strands are simultaneously cast.

In order to solve this problem, the present inventors proposed an electromagnetic stirring device as shown in FIGS. 2 and 3 in Japanese Patent Application No. 1-254039. Its gist is as follows. In other words, "In an electromagnetic stirring device installed surrounding a mold below a feed nozzle of a horizontal continuous casting machine, the electromagnetic stirring device is arranged on three sides of the mold, excluding the top surface on the feed nozzle side, on both sides and the bottom. An electromagnetic stirring device used in casting using a bidirectional drawing type horizontal continuous casting machine.

This invention has solved the problems of the conventional four-way enclosed type electromagnetic stirring device, and has achieved the following effects. That is, (a) it can be applied without changing the configurations of the tundish, feed nozzle, and mold.

(σ) Compared to the conventional four-way encircling type electromagnetic stirring device, the structure is simple because there is no need for the feed nozzle to penetrate through the center.

(c) The feed nozzle does not need to be long, and a normal feed nozzle can be used, so there is no increase in manufacturing costs or shortening of life.

(d) There are no operational problems caused by an increase in static iron pressure as in the conventional case.

(f) From the above results, it became easier to stir the molten steel pouring part in horizontal casting.

This invention can of course be applied to a single strand mold, but can also be effectively applied to multiple strands, and has achieved some effects such as making it possible to simultaneously manufacture 14 strands, but it also has the following advantages: There remained some problems.

[Problem to be solved by the invention]

The following problems remain as a result of using the electromagnetic stirring device disclosed in the above-mentioned Japanese Patent Application No. 1-254039, which is disposed in three directions on both sides and the bottom of the mold, except for the top surface on the feed nozzle side. found.

(a) It has a U-shape that surrounds it in three directions, and the upper part is empty, so the magnetic resistance is large.

(b) Therefore, most of the magnetic flux flows through the lower yoke, which has low magnetic resistance. As a result, it is necessary to increase the cross-sectional area of the lower yoke, which increases the overall external dimensions.

(c) The direction and distribution of the upper leakage magnetic flux Φ6 are uneven.

The purpose of the present invention is to solve the above-mentioned problems of the U-type electromagnetic stirring device, to control the deviation of the slab separation point by the bidirectional drawing type horizontal continuous caster, and to enable stable operation of simultaneous casting of multiple strands. The purpose of the present invention is to provide an electromagnetic stirring device.

[Means to solve the problem]

The gist of the present invention is as follows.

That is, in an electromagnetic stirring device provided surrounding a mold below a feed nozzle of a horizontal continuous casting machine, the electromagnetic stirring device is arranged on three sides of the mold, on both sides and the bottom, and on the upper surface on the feed nozzle side. This is an electromagnetic stirring device for a bidirectional drawing-type horizontal continuous casting machine, characterized in that it is connected only by a disposed yoke.

An embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a schematic cross-sectional view showing only the electromagnetic stirring device 18 of the present invention surrounding the mold 6 directly below the feed nozzle 8 of a bidirectional drawing type horizontal continuous casting machine. It consists of a coil 22 and a part that forms a magnetic pole 24 by energizing the coil 22. The coil 22 is provided on three sides surrounding the mold 6, on both sides and on the bottom surface, 6 has only a yoke 20 and no coil 22.

The electromagnetic stirring device 18 of the present invention will be explained by comparing its structure with the electromagnetic stirring device disclosed in Japanese Patent Application No. 1-254039 shown in FIGS. 2 and 3. That is, Figure 2, Figure 3 @
As shown in FIG. 2, there is nothing on the upper surface of the mold 6 directly below the feed nozzle 8 to connect the yokes 20 on both sides and the bottom of the mold 6.

In contrast, in the present invention, as shown in FIG. 1, the coil 22 is not provided on the top surface, but the yoke 20 that surrounds both side surfaces and the bottom surface also extends to the top surface and surrounds the mold 6.

In the conventional device shown in FIG. 2, as described above, since the upper part is a space, the magnetic resistance is increased, and most of the magnetic flux flows to the lower yoke, which has a lower magnetic resistance. As shown,
If we divide the upper and lower parts into two and compare them, we can see that the leakage magnetic flux in the upper part is Φ
9 is much smaller than the magnetic flux Φ8 passing through the lower yoke. That is, Φ4 (ΦYO......()) Therefore, the cross-sectional area of the lower yoke 20 had to be increased.Furthermore, the conventional device shown in FIG. , there was a problem that leakage magnetic flux occurred due to the space at the top, which disturbed the direction and distribution of the magnetic flux from both sides and the bottom that acted on the molten W! 2 passing through the mold 6, making it uneven. .

On the other hand, in the electromagnetic stirring device of the present invention shown in FIG.
Since there is also a yoke 20 at the top, leakage magnetic flux at the top disappears, and the magnetic flux at the top Φ. and the lower magnetic flux Φゎ are almost equal.

That is, Φ. = Φ0・・・・・・・・・・・・(2) In this case, in Figures 1 and 2, Φ4+Φ8 = Φ0+Φ9・・・(3
), Φ8 would have to be extremely large as shown in equation (1), and the cross-sectional area of the yoke would become large, resulting in a dog-like external shape of the entire electromagnetic stirring device.However, in the present invention, (2 )
As shown in the equation, since there is no leakage magnetic flux that equalizes the upper and lower magnetic fluxes, the magnetic flux that effectively acts on the molten steel increases, which has the effect of increasing the flow velocity of the molten steel 2 passing through the mold 6.

Although this embodiment describes a three-phase two-pole rotating magnetic field type electromagnetic stirring device used for high-speed casting in a bidirectional drawing type horizontal continuous caster, the technology of the present invention can also be applied to other types of electromagnetic stirring devices. Thoughts are applicable to everything.

〔Effect of the invention〕

The electromagnetic stirring device for a horizontal continuous casting machine according to the present invention is similar to the electromagnetic stirring device disclosed earlier and shown in FIG. In order to solve the problem of having to increase the cross-sectional area, we designed a structure where only the yoke was used at the top, and the yoke was extended from both sides and the bottom, resulting in the following effects: .

(a) Since the leakage magnetic flux in the upper part is eliminated, the direction and distribution of magnetic flux between the upper part and the lower part become uniform.

(o) As a result of (a), the upper and lower magnetic fluxes are almost equal.

(c) The cross-sectional area of the yoke is smaller than that of Japanese Patent Application No. 1-254039, and the external dimensions of the entire device can be reduced by about 30% without impairing the conventional capabilities.

(d) Since the leakage magnetic flux in the upper part was eliminated, the magnetic flux in the upper part was equalized and increased, making it possible to increase the flow rate of the heated steel in the mold directly under the feed nozzle by about 10%.

(E) Since there is only a yoke directly under the feed nozzle and no coil, there is no need to make the foot nozzle particularly long compared to the conventional four-way enclosed type, and it is relatively easy to manufacture in terms of mechanical strength, and the tundish is also particularly There's no need to make it expensive.

(F) Since the flow velocity of the molten steel injection part directly below the feed nozzle can be increased, it is easy to control the separation point of the left and right slabs to be directly below the foot nozzle, and stable operation of horizontal continuous casting has become possible.

[Brief Description of the Drawings] Fig. 1 is a schematic sectional view showing an embodiment of an electromagnetic stirring device for a bidirectional drawing horizontal continuous caster according to the present invention, and Fig. 2 is a
A schematic sectional view showing an embodiment of the electromagnetic stirring device previously disclosed in No. 254039, and FIG.
54039 is a transverse cross-sectional view in the longitudinal direction of the slab showing the mounting arrangement of the electromagnetic stirring device disclosed in No. 54039, and FIG.
A sectional view similar to Figure 3 showing a conventional electromagnetic stirring device that surrounds the mold before 254039 from the top, bottom, and both sides, Figures 5 (A) and (B) are shown in Figure 4. FIG. 2 is a cross-sectional view showing a molten steel flow and a slab during casting by a bidirectional drawing type horizontal continuous caster equipped with a conventional electromagnetic stirrer;
) is a vertical cross-sectional view in the length direction of the slab, and (B) is a cross-sectional view in the length direction of the slab directly below the foot nozzle. 2... Molten steel 4... Tundish 6... Mold 8... Feed nozzle 10... Oscillation device 12... Slab 14
... Pinch roll 18 ... Electromagnetic stirring device 22 ... Coil 16 ... Separation point 20 ... Yoke 24 ... Magnetic pole $/1 trouble

Claims (1)

[Claims] (1) In an electromagnetic stirring device provided surrounding a mold below a feed nozzle of a horizontal continuous casting machine, the electromagnetic stirring device is provided on three sides of the mold, on both sides and at the bottom, and on the upper surface on the side of the feed nozzle. An electromagnetic stirring device for a bidirectional drawing-type horizontal continuous casting machine, characterized in that it is connected only by a yoke provided in the yoke.