JP2626861B2 - Flow control device for molten steel in continuous casting mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling the flow of molten steel in a continuous casting mold.

[0002]

2. Description of the Related Art In continuous casting, the flow of molten steel in a continuous casting mold is an important factor influencing slab quality. Therefore, it is a common practice to electromagnetically stir the unsolidified portion of a slab to reduce segregation inside the slab and obtain a good slab.

For example, in Japanese Patent Publication No. Sho 64-10305, two electromagnetic stirrers are installed facing each other in the vicinity of a meniscus on at least one long side of a mold, and the mold is provided by an electromagnetic stirrer installed on the long side. It is disclosed that a flow toward the center in the width direction is imparted to the inner molten steel, and the depth of penetration of the molten steel flow from the immersion nozzle into the molten steel in the mold is reduced, thereby producing a slab of good quality.

In Japanese Patent Application Laid-Open No. 64-2771, a moving magnetic field is applied in accordance with the strength of molten steel discharge flow from the left and right discharge ports of an immersion nozzle to realize an appropriate magnitude of level change in the molten metal. It is disclosed to prevent surface defects due to mold powder wrapping and cast slab surface cracks due to abnormal metal surface fluctuations.

[0005]

The present invention further provides a flow control device for molten steel in a continuous casting mold that controls the meniscus flow rate in the mold to obtain a slab having excellent surface properties.

[0006]

The present invention SUMMARY OF THE INVENTION is the segmented electromagnetic coil center meniscus near the electromagnetic coils casting direction into two or more divisions in a continuous casting mold spokes direction and electromagnetic carp
Provided at a position where the reel body can inhibit the discharge downflow from the immersion nozzle, an alternating current and direct current by both applied, cast
In the continuous casting mold, a control unit capable of simultaneously controlling the moving magnetic field in the direction parallel to the mold long side and the static magnetic field in the direction perpendicular to the mold long side is connected to the coil. It is a flow control device for molten steel.

[0007]

The present invention will be described in detail below together with the operation. FIG. 2 is a perspective view showing a main part of a continuous casting mold according to the present invention, partially cut away.

The mold comprises long-side mold copper plates 1-1 and 1-2 and short-side mold copper plates 1-3 and 1-4. The lower part of the immersion nozzle 2 attached to the tundish provided above is inserted. I have. The discharge holes provided at the lower part of the immersion nozzle 2 are opened one by one on both sides of the immersion nozzle 2 so as to face in the short side direction of the mold, but are not particularly limited.

Molten steel 3 is injected into the mold from the tundish through the immersion nozzle 2, and the discharge flow 5 discharged from the immersion nozzle 2 is directed toward the short side mold copper plate 1-3 and hits the short side. , And the molten steel flow directed upward becomes a discharge reverse flow 8 to form a meniscus flow 6. On the other hand, the molten steel flow directed downward becomes the downward flow 7.

[0010] As shown in FIG. 1, the present invention provides two outsides of long sides 1-1 and 1-2 of the mold in the width direction of the mold.
Electromagnetic coils 7-1 and 7-2 that are divided into sections or more are provided. The coil has a three-phase structure of U, V, and W. By applying AC and DC simultaneously as a power source, a moving magnetic field is applied in a direction parallel to the long side of the mold , and the moving magnetic field is perpendicular to the long side of the mold.
Static magnetic field can be applied simultaneously in various directions. The switching current control in the magnetic field direction is performed by the control unit 10.

According to the experiments of the present inventors, the immersion nozzle 2
Controlling the meniscus flow rate formed by the discharge flow 5 within a certain range while securing the collision strength of the molten steel 3 poured from the slag and suppressing the descending flow 7 is extremely effective in improving the surface properties of the slab. Was obtained. That is, the present invention is provided such that the centers of the electromagnetic coils 7-1 and 7-2 in the casting direction are located near the meniscus.

In order to wash out the surface layer of the solidified shell 4 and remove inclusions and segregation, a certain flow rate of molten steel is required. Further, in order to remove inclusions and the like flowing downward together with the downward flow 7 discharged together with the discharge flow 5, it is necessary to suppress the downward flow 7. Further, control of the meniscus flow 6 is necessary to prevent inclusions from being captured by the meniscus.

The present inventors have set the meniscus flow rate to 10 cm.
/ Sec to 60 cm / sec, it has been found that the surface defects of the slab are reduced. However, it was found that this could not suppress defects caused by inclusions and the like flowing down the downflow 7. Therefore, the present inventors have intensively studied and have simultaneously controlled the meniscus flow velocity and the descending flow velocity like the descending flow 7a.

The meniscus flow velocity is measured by, for example, inserting a thermo-alloy cylinder into a molten steel flow and measuring the resistance F caused by the flow with a strain gauge. The strain and the resistance can be determined in advance by drawing a calibration curve using a weight and using a regression equation.

The controller 10 shown in FIG. 1A can simultaneously control the directions and strengths of the moving magnetic field and the static magnetic field for each of the electromagnetic coils 7-1, 7-2,. FIG. 1B shows the operation of each coil.

[0016]

EXAMPLE Continuous casting was performed using the stirring pattern shown in FIG. 3 under the molding conditions and electromagnetic stirring conditions shown in Table 1, and the incidence of surface defects was investigated. Table 2 shows the coil specifications and capabilities in this case.

FIG. 3 shows various modes of the stirring pattern of the molten steel, and FIGS. 3 (a) to 3 (e) show the stirring patterns of the embodiment of the present invention. FIG.

[0018]

[Table 1]

[0019]

[Table 2]

FIG. 4 (a) shows the rate of occurrence of surface defects in the conventional example when only electromagnetic stirring is performed. 10-60cm / s
Although ec is about 5% at the maximum, it is not complete yet. According to the example of the present invention, as shown in FIG. 4B, the rate of occurrence of surface defects was 1% or less in the range of the meniscus flow rate of 10 to 60 cm / sec. The downward flow suppressing effect of the present invention is as shown in FIG.

[0021]

According to the molten steel flow control device of the present invention, the alternating current and the direct current are applied to the electromagnetic coil provided near the meniscus to control the meniscus flow rate of the molten steel in the continuous casting mold. In addition, the downward flow can be simultaneously controlled to prevent inclusions and the like from being caught in the solidified shell, and a cast piece having excellent surface properties can be obtained.

[Brief description of the drawings]

FIGS. 1A and 1B show a main part of the present invention. FIG. 1A is a perspective view showing the arrangement of electromagnetic coils, and FIG. 1B is a drawing showing the operation of each coil.

FIG. 2 is a partially cutaway perspective view of a main part of a continuous casting mold according to the present invention.

FIG. 3 shows various aspects of a stirring pattern of molten steel,
(A), (b) is a drawing which shows the stirring pattern of the Example of this invention.

FIGS. 4A and 4B show the relationship between the meniscus flow velocity and the incidence rate of surface defects. FIG. 4A shows a conventional example, and FIG. 4B shows an example of the present invention.

[Explanation of symbols]

 1-1, 1-2 Long-side mold copper plate 1-3, 1-4 Short-side mold copper plate 2 Immersion nozzle 3 Molten metal (molten steel) 4 Solidified shell 5 Molten discharge flow 6 Meniscus flow 7 Downflow (conventional example) 7a Downflow (Example of the present invention) 8 Ascending flow 7-1, 7-2 Stirring coil 10 Control unit

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Fukuda 1 Kimitsu, Kimitsu City, Chiba Prefecture Nippon Steel Corporation Kimitsu Works (56) References JP-A-57-75268 (JP, A) 1-228645 (JP, A) JP 3-33055 (JP, B2)

Claims (1)

(57) [Claims] An electromagnetic coil divided into two or more sections in the width direction of a continuous casting mold is such that the center of the electromagnetic coil in the casting direction is near the meniscus, and the main body of the electromagnetic coil is from an immersion nozzle.
It is provided at a position where discharge downward flow can be suppressed, and by applying both AC and DC currents, it is possible to
In the same direction, and in the direction perpendicular to the long side of the mold.
3. A flow controller for molten steel in a continuous casting mold, wherein a control unit capable of simultaneously controlling a static magnetic field is connected to the coil.