JPH09277006A - Method for continuously casting molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a continuously cast slab having only a little internal defect and surface defect by using an electromagnetic brake device and controlling valocity distribution of molten metal flow in an immersion nozzle. SOLUTION: The difference Δh of the molten metal heights is detected with thermocouples 11a, 11b embedded in the mold walls 4a, 4b. The detected signals are inputted to an input device 13 and treated with an arithmetic device 14 and the electromagnetic brake 5a is shifted in the vertical direction to the pouring direction of the molten metal through a control device 15. In the electromagnetic brake 5a, the molten metal flowing velocities 6a, 6b in the immersion nozzle are adjusted with an electromagnet generated by an impressed current and the spouting flows 7a, 7b of the immersion nozzle are uniformized to execute the restraint of drift flow in the mold. By this method, the drift flow of the molten metal in the mold can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting method for molten metal, which can prevent molten metal from drifting in a mold by controlling the molten metal flow in a dipping nozzle.

[0002]

2. Description of the Related Art When a molten metal in a tundish is poured into a mold in a continuous casting process, the molten metal flow fluctuates depending on the throttle opening of a sliding nozzle installed between the immersion nozzle and the tundish and the casting speed. When the oxide inclusions adhere to the inner wall of the immersion nozzle, the symmetry of the velocity distribution of the molten metal flowing inside the immersion nozzle deteriorates, and the velocity of the molten metal discharged from the immersion nozzle increases. The distribution also has poor symmetry. As a result, a so-called drift phenomenon occurs in the mold, in which the symmetry of the molten metal flow with respect to the long side and the short side of the mold is impaired.

When this drift occurs, the molten metal discharged from the nozzle reaches a deep portion inside the mold and non-metallic inclusions in the molten metal reach a deep portion inside the mold, as compared with the case where there is no drift, and most of the molten metal is hot water. Although it floats to the surface, the remaining part is trapped inside the slab and induces product defects.

Conventionally, as a means for controlling the drift of molten metal in a mold, Japanese Patent Laid-Open No. 62-252650 discloses that the drift is detected from temperature information by thermocouples embedded on both short sides of the mold, and the drift is detected in the mold. A method of solving the problem by using an electromagnetic stirring device provided is disclosed. In addition, JP-A-3-294053
Japanese Unexamined Patent Publication (Kokai) discloses a method in which a plurality of eddy current sensors provided on the molten metal surface detect uneven flow and the electromagnetic brake device provided in the mold eliminates the drift.

[0005]

As described above, Japanese Patent Application Laid-Open No. 62-252650 uses an electromagnetic stirring device in a mold, and Japanese Patent Application Laid-Open No. 3-294053 discloses:
Although a method of preventing the drift of the molten metal in the mold by using the electromagnetic brake device in the mold is disclosed, the controllability is poor and the efficiency is poor because the action volume of the electromagnetic force is large. An object of the present invention is to control the velocity distribution of the molten metal flow in the immersion nozzle by using an electromagnetic brake device to prevent uneven flow of the molten metal flow in the mold, and to achieve continuous casting with excellent internal quality and surface quality. It is an object of the present invention to provide a continuous casting method capable of producing a piece.

[0006]

The present invention is intended to solve the above problems, and the gist thereof is as follows. (1) In the continuous casting method for molten metal, a drift of molten metal flow in the mold is detected by a thermocouple embedded in the mold or a level meter installed between the immersion nozzle and the mold, and the molten metal in the tundish is melted. By controlling the velocity distribution of the molten metal flow in the immersion nozzle using an electromagnetic brake device installed on the outer periphery of the immersion nozzle for injecting metal into the mold, it is possible to prevent drift of the molten metal in the mold. This is a continuous casting method for molten metal. And (2) the electromagnetic brake device described in the preceding paragraph (1),
A continuous casting method for molten metal, having a structure capable of moving in a direction perpendicular to a direction of injecting molten metal, and (3) an electromagnetic brake according to (1) or (2) above. The device is characterized by using an electromagnetic brake device composed of a plurality of electromagnetic coils installed in a direction perpendicular to a direction of injecting molten metal, and having a structure capable of passing different currents to the respective electromagnetic coils. A molten metal continuous casting method, (4) the immersion nozzle according to (1) above has a rectangular rectangular cross-section, and the ratio of the length of the long side to the length of the short side is 3 or more and 20 or less. The method for continuous casting of molten metal is characterized in that the immersion nozzle is used. Further, (5) the electromagnetic brake device according to any one of (1), (2), and (3) above has an axial direction of a spiral coil formed by alternately stacking flat conductors and insulators. It is a continuous casting method for molten metal, characterized by using a bitter coil having a structure for cooling the electromagnetic coil by penetrating a plurality of water passages for passing cooling water.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS. In the continuous casting of the molten metal shown in FIGS. 1 to 3, the molten metal 1 is poured into the mold 4 from the tundish 2 through the immersion nozzle 3. When fluctuations occur in the molten metal flow in the immersion nozzle 3, or when oxide inclusions adhere to the inner wall of the immersion nozzle, the molten metal flow rates 6a and 6b inside the immersion nozzle, the molten metal discharged from the immersion nozzle There is a difference in the flow velocities 7a, 7b of As a result, a difference occurs between the molten metal flow rates 8a and 8b to the lower part of the mold and the molten metal flow rates 9a and 9b to the upper part of the mold, and further, the molten metal swells 10a and 10b on the free surface of the molten metal.
Also causes a difference Δh.

At this time, in FIG.
It is detected by thermocouples 11a and 11b embedded in a and 4b. The detected signal is input to the input device 1 such as an A / D converter.
3, processed by the arithmetic unit 14, and controlled by the control unit 15.
Through the electromagnetic brake device 5a as shown in FIGS.
Is moved in a direction perpendicular to the pouring direction of the molten metal.
In the electromagnetic brake device 5a, the molten metal flow rates 6a and 6b in the immersion nozzle are adjusted by the electromagnetic force generated by the applied current to make the immersion nozzle discharge flows 7a and 7b uniform and suppress uneven flow in the mold. .

Further, in FIG. 3, the difference Δh between the rises 10a and 10b of the molten metal on the free surface of the molten metal is detected by the in-mold molten metal level gauges 12a and 12b.
The detected signal is input to the input device 13 such as an A / D converter, processed by the arithmetic device 14, and passed through the control device 16 to the electromagnetic brake device 5b installed in the immersion nozzle as shown in FIG. The current applied to 5c is controlled independently. In these electromagnetic brake devices 5b and 5c, the molten metal flow rates 6a and 6b in the immersion nozzle are adjusted by the electromagnetic force generated by the applied current, and the immersion nozzle discharge flow 7
A and 7b are made uniform to suppress uneven flow in the mold.

The immersion nozzle 3 used here is shown in FIG.
As shown in FIGS. 6 to 6, it is desirable that the cross-sectional shape is a rectangular shape in which the ratio of the long side portion to the short side portion is 3 or more and 20 or less. When the length ratio is 3 or less, the distance between the magnetic poles of the electromagnetic brake increases, and the braking effect decreases. Further, if the length ratio is 20 or more, the length of the molten metal flow path in the dipping nozzle in the short side direction becomes short, and there is a concern that clogging may occur due to the adhesion of oxide inclusions such as alumina.

Furthermore, it is desirable to use a bitter coil for the electromagnetic brake device 5 (5a, 5b, 5c) installed on the outer periphery of the immersion nozzle 3. What is Bitter Coil? M.Garn
ier has a coil structure disclosed in 1990 at IISC Nagoya, and has a flat conductor 17, an insulator 18, shown in FIG.
It has a structure formed of a cooling water hole 19 and a bolt hole 20, and allows the cooling water to flow through the conductor 17 and the insulator 18 in the axial direction of the coil. Regarding the structure of this bitter coil, Proceeding of The 6th IISC, 1990, Nagoya, ISI
J Vol.4 P233, Fig-1 and text. Compared to a water-cooled coil that uses a normal water-cooled tube, the bitter coil has less pressure loss in the cooling water flow path and can supply a large amount of cooling water, making it suitable for applying a large current and enabling the coil to be made compact. is there.

[0012]

Embodiments of the present invention will be described below. Example 1 In order to examine the effect of the present invention, a width 138
Using a curved slab continuous casting machine (radius 10.5 m) with a cross section of 0 mm and a thickness of 250 mm, drawing speed 1.0 m / m
Casting of medium carbon aluminum killed steel was carried out at in. The immersion nozzle has a rectangular flat cross section with a width of 800 mm and a thickness of 150 mm, and the electromagnetic brake device has a structure movable in a direction perpendicular to the molten metal injection direction shown in FIGS. And Two sets of eddy current type level sensors installed at a position 100 mm from the short side of the mold were used to detect the drift of the molten steel flow in the mold.

FIG. 8 shows an example of comparison of differences Δh in molten metal height. When the immersion nozzle of the method of the present invention having a rectangular cross section is used, the difference Δh in the height of the molten metal surface is clearly smaller than that in the conventional method which does not use the electromagnetic brake in the immersion nozzle. This shows that the effect of preventing drift is great.

[Embodiment 2] In order to study the effect of the present invention, a drawing speed of 1.0 m / min was used with a curved slab continuous casting machine (radius 10.5 m) having a width of 1380 mm and a thickness of 250 mm. Casting of medium carbon aluminum killed steel was carried out. The immersion nozzle has a rectangular flat cross section with a width of 800 mm and a thickness of 150 mm, and the electromagnetic brake device is composed of two sets of electromagnetic coils installed in the direction perpendicular to the direction of molten metal injection shown in FIG. And the magnetic field strength was 2T. Two sets of eddy current type level sensors installed at a position 100 mm from the short side of the mold were used to detect the drift of the molten steel flow in the mold.

FIG. 9 shows an example of comparison of differences Δh in molten metal height. When the immersion nozzle of the method of the present invention having a rectangular cross section is used, the difference Δh in the height of the molten metal surface is clearly smaller than that in the conventional method which does not use the electromagnetic brake in the immersion nozzle. This shows that the effect of preventing drift is great.

[0016]

By adopting the continuous casting method of the present invention, by controlling the flow of the molten metal in the immersion nozzle for injecting the molten metal in the tundish into the mold in the continuous casting process of molten metal, Since the drift of the molten metal in the mold can be prevented, it is possible to manufacture a continuous cast slab having extremely few internal defects and surface defects.

[Brief description of drawings]

FIG. 1 is a schematic view showing the arrangement of a tundish, an immersion nozzle, a mold and an electromagnetic coil in a continuous casting process of molten metal.

FIG. 2 is a diagram schematically showing a configuration of a drift metal preventing device for molten metal in a mold (when there is one electromagnetic coil) according to the method of the present invention and a molten metal flow state in the mold.

FIG. 3 is a diagram schematically showing the configuration of a molten metal drift preventive device in a mold (when there are two electromagnetic coils) according to the method of the present invention and the molten metal flow state in the mold.

FIG. 4 is a conceptual diagram showing the relationship between the immersion nozzle and the electromagnetic brake in the case of Example 1, showing the position of the electromagnetic coil when suppressing the flow velocity of molten steel on the right side inside the immersion nozzle,
(A) is a perspective view and (b) is a top view.

FIG. 5 is a conceptual diagram showing the relationship between the immersion nozzle and the electromagnetic brake in the case of Example 1, showing the position of the electromagnetic coil when suppressing the flow velocity of the molten steel on the left side of the immersion nozzle,
(A) is a perspective view and (b) is a top view.

6A and 6B are conceptual diagrams showing an arrangement of an immersion nozzle and an electromagnetic brake in the case of installing two electromagnetic coils in the case of Example 2, where FIG. 6A is a perspective view and FIG. 6B is a top view.

FIG. 7 is a conceptual diagram of a bitter coil used in the present invention,
(A) is a structural explanatory view, (b) shows a single substance of an electric conductor and an insulator.

FIG. 8 is a diagram showing a comparison of the difference Δh between the conventional method and the method of the present invention in the rise height of the molten metal surface in the case of Example 1.

FIG. 9 is a diagram showing a comparison of the difference Δh between the conventional method and the method of the present invention in the rise height of the molten metal surface in the case of Example 2;

[Explanation of symbols]

 1 Molten Metal 2 Tundish 3 Immersion Nozzle 4 Mold 4,4a, 4b Mold 5,5a, 5b, 5c Electromagnetic Coil 6a, 6b Nozzle Molten Steel Flow 7a, 7b Nozzle Discharge Flow 8a, 8b Mold Downflow 9a, 9b Mold Rise Flow 10a, 10b Hot metal surface rise 11a, 11b Thermocouple in mold 12a, 12b Level gauge in mold 13 Input device 14 Computing device 15 Electromagnetic brake control device 16 Electromagnetic brake control device 17 Conductor 18 Insulator 19 Cooling water hole 20 Volt Hole Δh Difference in molten metal height

Claims (5)

[Claims] 1. In a continuous casting method of molten metal, a drift of molten metal flow in the mold is detected by a thermocouple embedded in the mold or a plurality of level meters installed between the dipping nozzle and the mold, and the inside of the tundish is detected. Prevents drift of molten metal in the mold by controlling the velocity distribution of the molten metal flow in the immersion nozzle using an electromagnetic brake device that is installed around the outer periphery of the immersion nozzle that injects the molten metal into the mold. A method for continuously casting molten metal, comprising: 2. The electromagnetic brake device according to claim 1,
A continuous casting method for molten metal, which has a structure capable of moving in a direction perpendicular to the direction of injection of the molten metal. 3. An electromagnetic brake device comprising a plurality of electromagnetic coils installed in a direction perpendicular to a direction of injecting molten metal, and having a structure capable of supplying different currents to the respective electromagnetic coils. The continuous casting method for molten metal according to claim 1 or 2, characterized by using. 4. The immersion nozzle is characterized in that the planar cross-sectional shape of the immersion nozzle is rectangular and the ratio of the length of the long side to the length of the short side is 3 or more and 20 or less. The method for continuous casting of molten metal according to. 5. An electromagnetic brake device comprising: an axial direction of a spiral coil formed by alternately stacking flat conductors and insulators;
By passing through multiple water passages for passing cooling water,
The molten metal continuous casting method according to claim 1, wherein a bitter coil having a structure for cooling the electromagnetic coil is used.