JPH11156502A - Equipment and method for controlling molten steel flow in mold, in continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the flow control of both a FC system which applies a static magnetic field of direct current between facing mold long sides of an upper surface and a lower surface of the molten steel in the mold so as to control a molten steel stream, and a MEMS system which applies a transfer magnetic field of alternating current while the field is sequentially switched so as to carry out the molten steel agitation in a mold long side direction by one continuous casting facility. SOLUTION: In accordance with the pouring condition, the AC/DC current to be applied to division magnetic poles 3a and the magnetization direction of each magnetic pole of the division magnetic poles 3a are switched by using the plural division magnetic poles 3a; which are facing each other on the back side of a mold long side wall; from which many magnetic poles are parallely protruded at upper and lower positions and arranged like a comb; and which are connected in a U shape with a yoke at the top and bottom of its rear part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus and method for controlling molten steel flow in a mold, and more particularly to an apparatus and method for controlling the flow of molten steel by generating a magnetic field in a mold of a continuous casting facility.

[0002]

2. Description of the Related Art In a continuous casting facility, molten steel is injected into a mold from an immersion nozzle to perform casting. In this casting, non-metallic inclusions and air bubbles are usually present in the molten steel to be injected. Due to the flow of molten steel in the mold,
The non-metallic inclusions and bubbles may be trapped and caught in the solidifying shell, causing a defect at the stage of the rolled product.
Further, due to the flow of the molten steel, the powder of the powder layer serving as a seal layer with the outside air may be caught in the molten steel, which may cause a defect.

In order to avoid such problems caused by the flow of the molten steel in the mold, the flow of the molten steel in the mold is controlled. FIG. 2 is an explanatory view showing an example of a conventional flow control of molten steel in a mold, and FIG. 2A is a cross-sectional view in the direction of a long side of the mold showing a flow of a molten steel in a mold and a magnetic field. FIG. 2B is a cross-sectional view taken along the line AA of FIG. 2A.

The molten steel jetted from the discharge port 6a of the immersion nozzle 6 forms a molten steel flow 12 as shown in the figure.
The flow rate of this molten steel flow necessarily increases with higher throughput casting. This causes fluctuations in the molten metal level, causes the powder to be entrained from the powder layer 10, and further hinders the floating of nonmetallic inclusions in the molten steel. To solve this, as shown in the cross-sectional view of FIG.
A static magnetic field is generated by the electromagnet 7, and the force in the direction F shown in FIG. 2A is applied by Lorentz action to suppress the flow of molten steel. The FC electromagnet 7 has the structure shown in FIG. 4 and generates a static magnetic field in the direction of the arrow in FIG. 4 by applying a direct current. This static magnetic field is a static magnetic field corresponding to the direction of the arrow shown in the sectional view of FIG.

As described above, a static magnetic field of DC is applied between the upper and lower sides of the molten steel in the mold to oppose each other, thereby damping the flow of the molten steel, and suppressing the fluctuation of the molten steel surface on the upper side. The flow control method of molten steel that prevents entrainment of powder and adjusts the flow of molten steel on the lower side to promote the floating of nonmetallic inclusions is called FC method. Regarding this FC system,
It is disclosed in Japanese Patent Application Laid-Open No. 4-319052.

On the other hand, at the time of casting with low throughput,
There is a problem that the flow of molten steel in the mold becomes too small. Hereinafter, another flow control of molten steel in a mold suitable for solving this problem will be described with reference to FIG. FIG. 3 (a)
FIG. 3 is a cross-sectional view of a flow of molten steel in a mold and a magnetic field in a long side direction of the mold. FIG. 3B is a plan view thereof. FIG. 3C is a partial cross-sectional view taken along the line BB of FIG.

As shown in FIG. 3C, non-metallic inclusions and air bubbles in the molten steel 11 are trapped between the dendrite trees 13 grown on the inner shell surface of the mold 5 (long side 5b of the mold). become. The trapped non-metallic inclusions and air bubbles between the dendrite trees 13 flow out and float,
To improve the quality under the surface layer, the F shown in FIG.
A directional force is generated to cause molten steel to rotate and flow in a plane direction as shown by the arrow.

FIG. 5 shows details of the MEMS electromagnet 8 applied for rotating and flowing the molten steel on a plane. M
The EMS type electromagnet 8 is composed of a number of divided magnetic poles in which a number of magnetic poles are vertically projected in the horizontal direction and arranged in a comb shape, and the upper and lower portions on the rear side are joined in a U-shape with a yoke. . Then, by applying an alternating current to the coils wound around the respective polarized magnetic poles, the directions of adjacent different magnetic poles are sequentially switched, and the magnetic field is sequentially moved as shown by arrows. Thus, the molten steel is caused to rotate and flow.

[0009] The rotation and flow of molten steel and stirring are called electromagnetic stirring, and this method is called a MEMS method. According to the present MEMS system, in addition to improving the quality under the shell surface layer, the shell solidification thickness and the surface temperature can be made uniform, and the surface quality can be improved.

[0010]

As described above, the use of the FC system and the MEMS system has been effective. However, when attempting to cast multiple steel types and multiple sizes of continuous cast material with one continuous casting facility, the range of throughput becomes extremely large, and the required quality differs for each steel type. Therefore, in one continuous casting facility, the flow control of molten steel by FC method is optimal for one casting, and MEM is used for another casting.
In some cases, the flow control of molten steel in the S method is optimal.

However, due to the required capacity of each of the above electromagnets, the space on the side wall surface of the mold is almost full just by mounting either of them, and it is not possible to mount both types of electromagnets at the same time. Therefore, when introducing the equipment, the FC method and the MEMS method are compared and examined based on the quality required for the multiple steel types and multiple sizes of the continuous casting material cast in the continuous casting equipment. At present, they are selectively installed.

[0012] For this reason, quality problems remain. An object of the present invention is to provide a molten steel flow control apparatus and method in a mold that does not cause such a quality problem even when casting multiple steel types and multiple sizes of continuous cast material in one continuous casting facility. And

[0013]

Means for Solving the Problems The present inventors have developed MEMS.
By changing the wiring of the magnetized coils of each of the many protruding magnetic poles of the electromagnet of the system to have the same magnetization direction, and applying direct current, the MEMS electromagnet can be made equivalent to the FC electromagnet. However, they have found that the MEMS system and the FC system can be arbitrarily switched by switching the AC / DC power supply and changing the wiring of the magnetized coil of each of a large number of projecting magnetic poles.

Here, since the MEMS electromagnet is divided, the effective area of the core is smaller than that of the FC electromagnet. In the FC system, the whole magnetic flux density is reduced as it is, and the relative performance is reduced. The decline cannot be avoided. However, by increasing the number of turns of the magnetization coil of each magnetic pole and increasing the applied current,
It has been confirmed that this problem can be easily solved and no problem occurs.

In view of the above, the present invention provides a flow control device for molten steel in a mold in continuous casting, in which a large number of magnetic poles project vertically and parallel to the back side of each long side wall of the mold for continuous casting. A plurality of split magnetic poles arranged in a comb shape, the upper and lower portions of the rear side of the magnetic poles are connected in a U-shape with a yoke, and the magnetic pole directions of the respective magnetic poles can be freely switched. This problem has been solved by using a wiring switch provided for each divided magnetic pole and an AC / DC switching device capable of freely switching between AC and DC on the primary side of the wiring switch.

Further, the lower magnetic pole facing the plurality of divided magnetic poles is a single pole for forming a DC magnetic field in the facing direction, and a non-magnetic material is disposed in place of the yoke, so that the FC system and the ME system can be used.
We have found out that it can be used as a flow control device for molten steel in a mold that combines the MS method. A large number of magnetic poles are arranged in a comb shape so as to protrude vertically in parallel in the horizontal direction and face the rear side of each of the mold long side walls, and the upper and lower sides of the magnetic pole rear side are joined in a U-shape with a yoke. Using a plurality of divided magnetic poles, according to the casting conditions, alternating current and DC applied to the divided magnetic poles, and switching the wiring of the magnetized coil of each magnetic pole of the divided magnetic poles, the upper and lower sides of the molten steel in the mold, respectively Flexible switching between FC method, in which a static DC magnetic field is applied between opposing mold long sides to dampen molten steel flow, and MEMS method, in which an alternating moving magnetic field is applied while sequentially switching in the mold long side direction to stir molten steel, This problem was solved by a method of controlling molten steel flow in a mold in continuous casting.

Further, in the method for controlling molten steel flow in a mold in the continuous casting, a direct-current static magnetic field is applied to a lower divided magnetic pole facing the plurality of divided magnetic poles to apply the FC method, and the opposed lower magnetic pole is applied. It has been found that a MEMS system in which an alternating moving magnetic field is applied while sequentially switching in the direction of the long side of the mold can be applied to the divided magnetic poles other than the divided magnetic poles.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of a molten steel flow control device in a mold according to the present invention. The electromagnet 3 is provided on the long side of the mold 5. In the figure, only one side is shown and the other side is omitted. The electromagnet 3 is a lower split magnetic pole
3a and the upper divided magnetic pole 3a are joined by a yoke 3b to form a U-shaped electromagnet. Here, only the upper and lower pairs are shown, but the present invention is not limited to this, and more divided magnetic poles may be provided in parallel.

In the divided magnetic pole 3a of the present invention, a coil is independently wired for each of the divided protruding magnetic poles, and is wired to the wiring switch 4 respectively. The wiring switch 4 can freely switch the wiring of the coil for each protruding magnetic pole, and freely set the wiring such as aligning the directions of all the magnetic poles or inverting every other magnetic pole. be able to.

Each wiring switch 4 is connected to the AC / DC switching device 2 so that AC and DC electricity can be freely switched and input. AC / DC switching device 2
May be configured to freely switch between two power supplies of AC and DC, or may be configured to input AC commercial power and rectify to generate DC.

The AC / DC switching device 2 is connected to a required power supply 1. By adopting the molten steel flow control device in the mold having such a configuration, the FC system and the MEMS system can be freely switched. First, the case of using the FC system will be described with reference to FIG. FIG.
(A) is a diagram illustrating the magnetization direction of each magnetic pole when the electromagnet 3 is of the FC system. The magnetic pole arrays of the upper divided magnetic poles 3a are all N poles, and the magnetic pole arrays of the lower divided magnetic poles 3a are all S poles. In this case, the power supply is DC, and a static magnetic field Φ is formed.

By applying this electromagnet, FIG.
As shown in (b), the same control as the flow control of molten steel of the FC system described in FIG. 2 is performed. Next, a case where the MEMS system is used will be described with reference to FIG. FIG.
(A) is a figure explaining the magnetization direction of each magnetic pole when the electromagnet 3 is a MEMS system. The configuration of each of the magnetic poles is exactly the same as the configuration described in FIG. 5, and need not be described again here. in this case,
The current is alternating current, and a moving magnetic field is formed by sequentially switching the magnetic poles.

By applying the MEMS electromagnet, the molten steel is stirred as shown in FIG. 7B, and the same control as the flow control of the MEMS molten steel described with reference to FIG. 3 is performed. . As described above, according to the present invention, the flow control apparatus for molten steel in one mold
It became possible to freely switch between the C system and the MEMS system.

FIG. 8 is an explanatory diagram showing another embodiment of the present invention. FIG. 8A shows an FC / MEMS electromagnet 14 to which the FC system and the MEMS system are applied simultaneously.
In the FC / MEMS electromagnet 14, the upper side is a divided magnetic pole 3a having a MEMS type magnetic pole arrangement, and the lower side is F
It is a C-type single magnetic pole 3d. Then, an alternating current is applied to the upper magnetic pole, and a direct current is applied to the lower magnetic pole. In the case of this method, a non-magnetic material 3c is inserted between the upper and lower magnetic poles, and magnetically insulates them to form an efficient magnetic field.

In this manner, a horizontal swirling flow of the molten steel is formed on the upper surface of the mold, and the flow of the molten steel discharged from the discharge port of the immersion nozzle can be braked on the lower surface, which is excellent in quality assurance. The effect can be obtained. Structurally, on the contrary, the upper side may be the FC system and the lower side may be the MEMS system, but the above is superior from the viewpoint of quality effect.

In FIG. 8A, the lower magnetic pole is a single magnetic pole. This is because the magnetic pole is superior in terms of the efficiency of the magnetic field, and as shown in FIG. It goes without saying that the FC system may be used by using the divided magnetic poles.

[0027]

EXAMPLES Table 1 shows a comparison between the power supply capacity and the magnetic flux density in each of the conventional system and the present invention. A comparison is made between the FC method applied to hot materials and the MEMS method applied to thick plate materials.

[0028]

[Table 1]

As described above, in the case of the MEMS system, it can be said that there is no substantial difference between the conventional system and the present invention. F
In the case of the C system, the magnetic flux density could be made equal to or higher than that of the conventional system by increasing the power supply capacity in the present invention. Next, for each of the conventional example and the present invention,
Table 2 shows the results of comparison using various evaluation indices. In Table 2, the results of the present invention are shown with the result of each index being 100 in the conventional example.

[0030]

[Table 2]

In each index, the results when the present invention is applied are improved by about 10% as compared with the results of the conventional example. This is considered to be because in the present invention, it has become possible to employ an optimal molten steel flow control method for a multi-steel type and a multi-size continuous cast material.

[0032]

According to the present invention, it is possible to adopt the optimum molten steel flow control method for multiple steel types and multiple sizes of continuous cast material in one continuous casting facility, thereby improving the quality under the shell surface layer. I was able to. Further, the shell solidification thickness and the surface temperature are made uniform, which can greatly contribute to the improvement of the surface quality of the continuous cast material.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a molten steel flow control device in a mold of the present invention.

FIG. 2 is an explanatory view of flow control of molten steel in a mold by a conventional FC method, and FIG. 2 (a) is a cross-sectional view in the long side direction of the mold showing a flow of a molten steel in a mold and a magnetic field. (B)
FIG. 2A is a cross-sectional view taken along the line AA in FIG.

FIG. 3 is an explanatory view of the flow control of molten steel in a mold by the conventional MEMS method, and FIG. 3 (a) is a cross-sectional view in the direction of the long side of the mold showing the flow of molten steel in the mold and the magnetic field.
(B) is a plan view. (C) is BB in FIG.
It is the fragmentary sectional view cut in the direction.

FIG. 4 is a perspective view showing a structure of a conventional FC electromagnet.

FIG. 5 is a perspective view showing the structure of a conventional MEMS electromagnet.

6A and 6B are explanatory diagrams in a case where the molten steel flow control in the mold of the FC system is performed by the molten steel flow control device in the mold of the present invention, and FIG. 6A is an explanatory diagram illustrating a state of magnetic poles of an electromagnet. (B) is explanatory drawing which shows typically the flow of the molten steel in a mold, and a magnetic field.

FIG. 7 is a MEM with the molten steel flow control device in the mold of the present invention.
It is explanatory drawing at the time of performing molten steel flow control in a mold of S system, (a) is explanatory drawing which shows the mode of the magnetic pole of an electromagnet. (B) is explanatory drawing which shows typically the flow of the molten steel in a mold, and a magnetic field.

FIG. 8 shows another embodiment of the present invention, FC system and MEMS.
It is explanatory drawing of the molten steel flow control in a mold which performs a method simultaneously, (a) is explanatory drawing which shows the mode of the magnetic pole of an electromagnet. (B) is explanatory drawing which shows typically the flow of the molten steel in a mold, and a magnetic field.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power supply 2 AC / DC switching device 3 Electromagnet 3a Split magnetic pole 3b Yoke 3c Non-magnetic material 3d Single magnetic pole 4 Wiring switch 5 Mold 5a Mold short side 5b Mold long side 6 Immersion nozzle 6a Discharge port 7 FC electromagnet 8 MEMS electromagnet 10 Powder layer 11 Molten steel 12 Molten steel flow 13 Dendrite tree 14 FC / MEMS electromagnet

Claims (4)

[Claims] 1. A plurality of magnetic poles are arranged in a comb shape so as to protrude horizontally and vertically in parallel with each other on a long side wall of a long side wall of a mold for continuous casting. A plurality of divided magnetic poles coupled in a U-shape, a wiring switch provided for each of the divided magnetic poles so that the magnetic pole direction of each of the divided magnetic poles can be freely switched, and a primary switch of the wiring switch. A flow control device for molten steel in a mold in continuous casting, comprising an AC / DC switching device capable of freely switching between AC and DC on the side. 2. The magnetic head according to claim 1, wherein the lower magnetic pole facing the plurality of divided magnetic poles is a single pole for forming a DC magnetic field in the facing direction, and a nonmagnetic material is arranged in place of the yoke. Of molten steel flow in mold in continuous casting of steel. 3. A plurality of magnetic poles are arranged in a comb shape so as to protrude vertically in parallel in a horizontal direction and face the back side of each of the long side walls of the mold. Using a plurality of split magnetic poles coupled to, according to the casting conditions, alternating current and DC applied to the split magnetic pole, switching the wiring of the magnetized coil of each magnetic pole of the split magnetic pole,
FC that applies a static DC magnetic field between the opposing long sides of the molten steel in the mold and damps the flow of molten steel
A method for controlling the flow of molten steel in a mold in continuous casting, wherein the method can be freely switched between a method and a MEMS method in which an alternating moving magnetic field is applied while sequentially switching in the direction of the long side of the mold to stir molten steel. 4. An FC method is applied by applying a DC static magnetic field to a lower divided magnetic pole opposed to the plurality of divided magnetic poles, and the divided magnetic poles other than the opposed lower divided magnetic pole are applied to a mold long side direction. 4. The flow control method of molten steel in a mold in continuous casting according to claim 3, wherein a MEMS method of applying an alternating moving magnetic field while sequentially switching the applied moving magnetic field is applied.