[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a continuous casting facility and a method for operating the same, which improve the quality of a cast slab to be manufactured and realize stable operation.
More specifically, the present invention relates to a continuous casting apparatus for providing a stopper for opening and closing the outlet of molten steel on the bottom surface of a tundish and providing a rotating blade to the stopper to generate a rotating flow in the molten steel and a method of operating the same.
[0002]
[Prior art]
In a continuous casting facility, molten steel injected from a ladle into a tundish is injected into a mold via a stopper installed in the tundish to adjust the injection amount of molten steel, and continuously produces a slab.
Conventionally, various proposals have been made for a continuous casting facility in which a rotary blade is provided on the stopper to rotate molten steel.
[0003]
For example, Japanese Unexamined Patent Publication No. Hei 5-318068 discloses that in a casting facility having a small throughput, in order to perform stable injection amount control, a molten steel rotation flow in a horizontal direction perpendicular to the molten steel injection direction is formed. It is generated and controlled by acting as a brake on the flow of molten steel.
In this conventional technique, in a continuous casting facility using an operating end called a stopper for operation at a low injection amount, a stirring blade is provided on the stopper and rotated, and by changing the rotation speed of the stopper, the tundish to the mold is changed. This is a continuous casting method in which stable control is achieved easily and inexpensively even at a low injection amount by changing the suppressing force of the injection amount of molten steel.
However, the continuous casting method disclosed in Japanese Patent Application Laid-Open No. Hei 5-318068, although provided with a stirring blade in the stopper and rotated, aims at controlling the level of molten metal in the lower container of the stopper in the low injection region. The object of the invention is to improve the quality of a cast slab, and the invention is an invention having completely different objects, functions and effects.
[0004]
Japanese Patent Application Laid-Open No. 2002-11565 discloses that a molten steel in a tundish is provided with an ascending flow by rotating a stopper with a stirring blade around a stopper axis so that a molten steel flow flowing out to a nozzle is not swirled. A stopper is disclosed which prevents slag entrainment and has a floating effect of impurities due to an upward flow.
The main purpose of this prior art is to prevent the molten steel from rotating around the tundish nozzle, thereby preventing the slag from being entrained.The stopper is provided with stirring blades and is rotated. It is not necessary to make the ascending flow in the floating effect of the object.Also, with the aim of improving the quality in the mold and suppressing the clogging of the immersion nozzle, stable operation by turning the molten steel aggressively after the tundish nozzle. The present invention is completely different from the present invention in terms of the problems and the functions and effects.
[0005]
Further, conventionally, for the purpose of improving the quality of a cast slab to be manufactured, an electromagnetic stirring device in a mold for stirring molten steel in a mold by using an electromagnetic force, an electromagnetic brake technology, and the like have been applied.
This device using electromagnetic force involves a large amount of capital investment and requires a large amount of space around the mold, and has the disadvantage that it cannot be easily introduced in a balance between quality and capital investment. Also, there is no effect on the molten steel in the tundish and no effect of reducing clogging between the tundish nozzle and the immersion nozzle.
Furthermore, as a measure for improving the quality of cast slabs, Japanese Patent Application Laid-Open No. 2002-239690 discloses a method in which a refractory having a screw structure is incorporated in an immersion nozzle to generate a swirling flow in the immersion nozzle.
However, in the method disclosed in Japanese Patent Application Laid-Open No. 2002-239690, the structure inside the immersion nozzle becomes complicated, so that the immersion nozzle body becomes expensive. In addition, the risk of clogging of molten steel inside the immersion nozzle is higher than that of conventional products, and strict calculation of the screw structure in the immersion nozzle based on the steel type, molten steel injection amount, etc. There is a drawback that it is necessary to manufacture a product, and there is no effect on the molten steel in the tundish and the effect of reducing clogging in the tundish nozzle as in the case of the equipment using electromagnetic force.
[0006]
[Patent Document 1] JP-A-5-318068 [Patent Document 2] JP-A-2002-11565 [Patent Document 3] JP-A-2002-239690
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems of the prior art, and provides a stopper for opening and closing the molten steel outlet on the bottom surface of the tundish, and provides a rotating blade to the stopper to generate a rotating flow in the molten steel. An object of the present invention is to provide a continuous casting facility and a method of operating the same, which can improve the quality of a cast slab to be manufactured and realize a stable operation thereof.
[0008]
[Means for Solving the Problems]
The present invention has been made to solve the above-described problem, and a slab is manufactured by injecting a rotating flow of molten steel generated by rotation of a stopper into a mold while turning the inside of an immersion nozzle. The present invention provides a continuous casting facility and a method for operating the same, which are capable of realizing improved quality and stable operation of the apparatus, the gist of which is as described below in the claims.
[0009]
(1) A continuous casting facility for providing a stopper for opening and closing the outlet of molten steel on the bottom surface of a tundish and providing a rotating blade to the stopper to generate a rotating flow in the molten steel. A continuous casting facility characterized by injecting a rotating flow into a mold while swirling in an immersion nozzle.
(2) The method for operating a continuous casting facility according to (1), wherein the stopper is set based on a molten steel type, a molten steel injection amount or a casting speed, a molten steel temperature in a tundish, and a molten steel weight in the tundish. Determine the rotation speed of
A method of operating a continuous casting facility, wherein a rotation drive device is controlled so as to reach the determined rotation speed of the stopper.
(3) The method for operating a continuous casting facility according to (1), wherein the direction of rotation of the stopper is clockwise as viewed from above the ground in the continuous casting facility installed in the northern hemisphere, and the continuous casting is installed in the southern hemisphere. A method of operating a continuous casting facility, wherein the facility is counterclockwise as viewed from above.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described in detail with reference to FIGS.
The following embodiments are mere examples embodying the present invention, and do not limit the technical scope of the present invention.
FIG. 1 is a conceptual diagram illustrating a continuous casting facility and a control device thereof according to the present invention.
In FIG. 1, 1 is a ladle, 2 is a ladle molten steel discharge operation end, 3 is a tundish, 4 is a tundish stopper, 5 is a rotary blade, 6 is a tundish stopper rotation drive device, 7 is a stopper rotation control device, and 8 is a stopper rotation control device. Molten steel in a tundish, 9 denotes a tundish nozzle, 10 denotes a submerged nozzle, 11 denotes a mold, 12 denotes molten steel in a mold, and 13 denotes a swirling molten steel flow.
In FIG. 1, a tundish stopper 4 is rotated by a tundish stopper rotation driving device 6, and a swirling flow is given to molten steel by a rotating blade 5 formed on the tundish stopper 4.
As a result, the molten steel 8 in the tundish turns and the floating of inclusions is promoted, the temperature distribution of the molten steel in the tundish is made uniform, and the effect of reducing nozzle clogging due to precipitation of molten steel components in the tundish nozzle portion 9 is exhibited. You.
[0011]
This swirling molten steel flow is discharged as a swirling molten steel flow 13 into the casting mold 11 via the immersion nozzle 10, and the molten steel 12 in the casting mold is also stirred. As a result, the effects of uniforming the discharge flow distribution of the immersion nozzle, promoting the floating of inclusions of the molten steel in the mold, and uniforming the temperature distribution of the molten steel in the mold are exhibited. The stabilization of the operation and the control of the level of the molten steel in the mold can be realized by reducing the clogging and stabilizing the discharge flow.
The tundish stopper rotation drive device may be installed above the stopper, or may be indirectly driven by a chain or the like while avoiding the vicinity of the stopper support device from the viewpoint of heat protection.
[0012]
The structure of the rotor blades is such that the molten steel has resistance in the rotation direction, the mounting position is the lower part of the tundish stopper 4, and the number of rotor blades is not limited as long as a stirring force can be obtained. As described above, the rotation direction is preferably clockwise in the northern hemisphere and counterclockwise in the southern hemisphere when the ground is viewed from above, in order to promote the generation of the molten steel flow.
The rotation speed of the stopper that generates the molten steel flow has a variable range of 30 rpm to 300 rpm, and within the variable range, the type of molten steel, molten steel injection amount (= throughput amount) or casting speed, molten steel temperature in the tundish, and In accordance with the weight of the molten steel in the tundish, an optimum rotation speed is given from a table of past actual values and used.
Further, when the stopper is fully closed, it is necessary to stop the rotation to protect the stopper and the nozzle refractory. To check the fully closed position, an interlock that stops the rotation of the motor is determined based on the torque limit of the motor, the motor current value, or the load value of the load cell that detects the pressing load of the stopper incorporated in the stopper support device. Is preferably provided. Further, when a stopper position detector is provided, an interlock for stopping rotation according to the position signal may be provided.
[0013]
When there is an existing electromagnetic stirrer or when a new electromagnetic stirrer is introduced, by using the present invention together, it is possible to further improve the quality together with the floating effect of the inclusions of the molten steel in the tundish. In addition, from the viewpoint of power saving, even if the thrust of the electromagnetic stirrer is reduced and used, an effect equal to or more than that of the case where the electromagnetic stirrer is fully operated alone can be expected.
Furthermore, in recent years, a tundish molten steel plasma heating device may be introduced to maintain or heat the molten steel temperature in the tundish, but by using the present invention, local heating by this heating device is reduced, and the temperature is reduced. The effect of making the distribution uniform can also be expected.
[0014]
FIG. 2 is a flowchart illustrating an embodiment of a method for operating a continuous casting facility according to the present invention.
The continuous casting facility to which the present invention is directed is a facility for providing a stopper for opening and closing the outlet of molten steel on the bottom surface of the tundish, and providing a rotating blade for the stopper to generate a rotating flow in the molten steel, as exemplified below. The rotation speed of the stopper is controlled by the control flow.
[0015]
First, the molten steel type, molten steel injection amount or casting speed, molten steel temperature in the tundish, and molten steel weight in the tundish are measured, and the rotation speed of the stopper is determined based on the measured values.
The inventors have proposed a stopper for improving the quality of cast slabs and achieving stable operation by controlling the type of molten steel, the amount of molten steel injected or casting speed, the temperature of molten steel in the tundish, and the weight of molten steel in the tundish. It has been found that it is important to control the number of revolutions.
As a method of calculating the number of rotations of the stopper, for example, it is preferable to prepare a table in a range of an appropriate number of rotations according to the above-mentioned operation factor based on past actual values, and set a value in this table.
Next, the rotation driving device is controlled so that the determined rotation speed of the stopper is obtained,
For example, it is preferable to recalculate the optimal rotation speed at that time again at regular time intervals.
According to this operation method, the following actions and effects are exhibited in the tundish and the mold.
[0016]
<In the tundish>
-It is possible to promote the floating of impure inclusions of molten steel in the tundish.
-It is possible to promote uniform temperature distribution of the molten steel in the tundish.
-Clogging of the tundish nozzle can be reduced.
<In the mold>
-Clogging of the immersion nozzle can be reduced.
-It is possible to promote uniform temperature distribution of molten steel in the mold.
-The floating of the impurity inclusions in the molten steel in the mold can be promoted.
・ Stable control of molten steel level in the mold by stabilizing the discharge flow from the immersion nozzle.
In addition, it is preferable that the direction of rotation of the stopper be clockwise when viewed from above the ground in a continuous casting facility installed in the northern hemisphere, and counterclockwise when viewed from above in the continuous casting facility installed in the southern hemisphere.
This is because the rotation direction of the molten steel is reversed between the northern hemisphere and the southern hemisphere due to the shift of the rotation axis of the earth, so that the stirring effect of the molten steel can be enhanced by adjusting the rotation direction of the stopper to the rotation direction of the molten steel. .
[0017]
【The invention's effect】
According to the present invention, it is possible to improve the quality of a slab to be manufactured and realize stable operation by injecting a rotational flow of molten steel generated by rotation of a stopper into a mold while rotating the immersion nozzle. It is possible to provide a continuous casting facility that can be used and a method of operating the same, and has a remarkable industrially useful effect.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram illustrating a continuous casting facility and a control device thereof according to the present invention.
FIG. 2 is a flowchart illustrating an embodiment of a method for operating a continuous casting facility according to the present invention.
[Explanation of symbols]
1: Ladle,
2: Ladle molten steel discharge operation end,
3: Tundish,
4: Tundish stopper,
5: Rotor wing,
6: Tundish stopper rotation drive device,
7: stopper rotation control device,
8: molten steel in tundish,
9: Tundish nozzle,
10: immersion nozzle,
11: mold,
12: molten steel in mold,
13: Swirling molten steel flow
