JPH07148555A - Device for continuously casting molten metal - Google Patents

Abstract

PURPOSE:To improve and stabilize the quality of a cast slab by arranging an electromagnetic coil at the upper part of a mold to impress AC current and further arranging a coil generating the static magnetic field having the max. value at the lower part of the discharging hole of a pouring nozzle in the mold to impress DC current. CONSTITUTION:The electromagnetic coil 2 for giving the electromagnetic force (pinch force) to molten steel (s) in the mold 1 is arranged and an electric source device 5 for impressing AC current to this electromagnetic coil 2 is arranged, too. The pouring nozzle 3 for pouring the molten steel (s) into the mold is arranged in the center part of the mold 1. The coil 4 generating the static magnetic field for restraining the interference of the pouring natural flow is arranged at the lower part of the mold 1 so as to surround the copper plates Cp of the mold 1. The electric source device 6 for impressing DC current is arranged in this coil 4. By this method, the interference of the natural flow is effectively restrained and further, the entrapment of inclusion can be restrained and the operationability of the continuous casting is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting apparatus for molten metal, in which an electromagnetic coil for applying a pinch force to the molten metal in the casting mold is provided on the upper portion of the casting mold, and in particular, a slab-shaped slab is continuously cast. As in the case, it has a rectangular mold and is more suitable for use in a continuous casting apparatus for molten metal in which the discharge port of the injection nozzle faces the short side of the mold.

[0002]

2. Description of the Related Art Conventionally, for example, in the field of continuous casting of molten steel, it has been known that the flow of molten steel in a mold greatly affects the operability of continuous casting and the quality of slabs. That is, the flow of the molten steel injected from the injection nozzle into the mold brings the slag-based or deoxidized oxide-based inclusions intervening in the molten steel deep into the lower part of the strand pool. The deeper the depth, the more easily inclusions are captured by the solidified shell, causing slab defects. Therefore, it is desirable that the depth of penetration of the downward flow of the molten steel be as shallow as possible.

On the other hand, on the molten steel surface, when the molten steel flow velocity at the meniscus is high as in the case of high speed casting, the powder on the molten steel surface is caught in the molten steel, and in addition to the inclusions in the molten steel, Since the level fluctuation of the molten steel surface becomes large and stable formation of solidified shells is not possible, the quality of the slab and the operability of casting are unavoidable.

Further, when the flow velocity at the meniscus is slow as in the case of low speed casting, deckle is formed on the surface of the molten steel, which hinders the casting operation, and inclusions and bubbles are trapped in the solidified shell to clean it. Therefore, stable solidified shells cannot be generated, so that the operability of casting is deteriorated and the quality of the slab is unavoidable.

From such a point of view, it is necessary to control the flow pattern of the molten steel injected into the mold from the injection nozzle to be in a preferable state and constant in both the high speed casting and the low speed casting.

In order to meet such a demand, for example, in Japanese Patent Publication No. 57-21408, an electromagnetic coil is used to apply an electromagnetic force (pinch force) to the initial solidification portion of the injected molten steel in a mold, and the molten steel surface The method of raising the upper surface shape of the above in a convex shape, controlling the meniscus, optimizing the inflow of the lubricating powder, and reducing the oscillation mark is disclosed.

For example, when the principle of this method is applied to a mold a containing molten steel s (stationary state) as shown in FIG. 3, the alternating magnetic field produced by the current applied to the electromagnetic coil b is
The top surface shape of the molten steel surface is made convex, and a stirring flow wa, wb is generated inside the molten steel s.

In the case of a normal continuous casting mold in which molten steel s is continuously injected into the mold a and is not stirred by an alternating magnetic field, natural injection flows wc and wd by the injection nozzle c are generated as shown in FIG.

Therefore, this Japanese Patent Publication No. 57-21408
When the method disclosed in the publication is carried out in an ordinary continuous casting mold, as shown in FIG. 5, the stirring flows wa and wb due to the alternating magnetic field and the natural flows wc and wd due to the injection simultaneously occur and interfere with each other. On the short side of the mold where the discharge ports ca and cb of the nozzle c face, the molten steel surface remarkably oscillates to cause a wave phenomenon, and inclusions are also involved. In particular, the solidified shell is not generated on the short side of the mold. It is inevitable that the slab quality becomes stable and the casting operability deteriorates, and the slab quality also deteriorates.

[0010]

SUMMARY OF THE INVENTION According to the present invention, when an electromagnetic coil for imparting a pinch force to molten metal is arranged in a mold of a continuous casting apparatus for molten metal, a natural flow of injection by an injection nozzle and an electromagnetic coil are provided. (EN) A continuous casting apparatus capable of stably generating solidified shells by suppressing the interference of electromagnetic force induced flow (stirring flow) due to, suppressing the ripple phenomenon of the molten metal near the molten metal surface in the mold.

[0011]

According to a first aspect of the present invention, an electromagnetic coil for applying a pinch force to the molten metal in the mold is arranged above the mold into which the molten metal is injected, and an alternating current is applied to the electromagnetic coil. In a continuous casting apparatus for molten metal equipped with a power supply device for applying a coil, a coil for generating a static magnetic field having a maximum value is arranged in the mold below the discharge port of an injection nozzle for injecting the molten metal into the mold. A continuous casting device for molten metal, characterized in that a power supply device for applying a direct current is additionally provided.

According to a second aspect of the present invention, in the electromagnetic coil for producing the static magnetic field according to the first aspect, a line connecting an intersection of the horizontal center line and the inner surface of the mold and the center of the discharge port of the injection nozzle and the center line of the injection nozzle. Angle θ ₀ and the angle θ formed by the ejection port center line of the injection nozzle and the ejection direction line from the ejection port center
Is a continuous casting apparatus for molten metal, which is arranged so as to satisfy the relationship of 0 ° ≦ θ ≦ θ ₀ .

[0013]

According to the present invention, a pinching force is applied to the molten metal on the upper part of the mold of a continuous casting machine by an alternating magnetic field to obtain the pinching force effect, and at the same time, interference between the stirring flow generated at this time and the natural flow generated by the injection is prevented. , Effectively suppressed by the action of the DC magnetic field by the coil arranged at an appropriate position below the injection nozzle,
Further, inclusion of inclusions can be suppressed, the operability of continuous casting can be improved, and the quality of the obtained slab can be improved and stabilized.

The present invention uses an injection nozzle which has a rectangular mold and in which the discharge port is inclined downward toward the short side of the mold, as in the case of continuous casting of slab-shaped slabs. It is more suitable for continuous casting equipment.
The present invention has a remarkable effect when applied to a continuous casting apparatus for molten steel, but the effect can be expected even when applied to a continuous casting apparatus for copper, aluminum, various alloys and the like.

[0015]

EXAMPLE An example in which the present invention is applied to a continuous casting apparatus for molten steel will be described below with reference to FIG. Figure 1
In FIG. 1, 1 is a mold, and an electromagnetic coil 2 for applying an electromagnetic force (pinch force) to the molten steel in the mold is arranged on the upper part of the mold, and the molten steel s is added to the mold at the center of the mold 1. An injection nozzle 3 for injecting is provided. This injection nozzle 3
Is a lower end closed type, and a pair of discharge ports 3 are inclined downward at about 45 ° toward the short side of the mold 1 at the lower end.
a and 3b are provided.

In the lower part of the mold 1, injected molten steel s
The agitated flow w generated when the injection coil natural flows wc and wd are controlled and a pinch force is applied to the molten steel s by the electromagnetic coil
A coil 4 that creates a static magnetic field for suppressing the interference between a and wb and the injection natural flow is arranged so as to surround the copper plate Cp of the mold 1.

In the figure, 5 is an electromagnetic coil 2 provided on the upper part of the mold.
Is an alternating current power source, 6 is a direct current power source for the coil 4 provided at the bottom of the mold, 7 is a lubricating powder, and the arrow 8 indicates the direction of the magnetic flux by the coil 4.

The coil 4 has an intersection point p between the horizontal center line d and the inner surface 1o of the mold, and a discharge port center 3c of the injection nozzle.
An angle θ ₀ formed by the line e connecting the two and the center line f of the injection nozzle,
The ejection port center 3c of the injection nozzle and the angle θ formed by the ejection direction line g from the ejection port center are arranged so as to satisfy the relationship of 0 ° ≦ θ ≦ θ ₀ (1). That is, the distance between the intersections of the discharge port center 3c of the injection nozzle, the center line f thereof, and the horizontal center line d of the coil is set apart by Ho.

Θ ₀ is expressed by the following equation. θ ₀ = tan ⁻¹ {L / (2Ho)} (2) where L is the distance between the opposing mold inner surfaces 1o, and Ho
Is the distance between the intersection of the discharge port center 3c of the injection nozzle, its center line f, and the horizontal center line d of the coil.

In the present invention, as described above, in the mold in which the electromagnetic coil 2 for imparting the pinch force is arranged on the upper part of the mold 1, the coil 4 is provided below the molten steel injection nozzle 3,
Injecting natural flow wc generated when injecting molten steel by the injecting nozzle 3
, Wd to control the electromagnetic coil 2 disposed above the mold 1.
The main purpose is to effectively suppress the interference with the molten steel stirring flows wa and wb caused by the above. To achieve this purpose, the position of the coil 4 arranged at the lower part of the mold 1 is set to the discharge nozzle of the injection nozzle 3. It is necessary to be below the outlets 3a and 3b, and it is preferable to satisfy the arrangement condition represented by the above formula in order to more reliably obtain the effect.

If this arrangement condition is not satisfied, the natural pouring flow w that occurs during molten steel injection in the mold 1 during continuous casting.
c, wd cannot be effectively controlled, and the stirring flow wa, of molten steel generated in the mold 1 by the electromagnetic coil 2 disposed above the mold 1
The effect of suppressing the interference with wb is small. As a result, the solidification of the molten steel in the mold 1 causes a ripple phenomenon of the molten steel in the initial stage of the formation, the formation of the solidified shell becomes unstable, and the operability of casting is improved. And the quality of the slab deteriorates.

[0022]

[Experimental example] This experimental example is a case where the present invention is applied to the continuous casting apparatus for molten steel of the present invention having the structure shown in FIG. 1, and the width L is 1120 mm and the thickness is 254 mm.
This is a case where a slab is continuously cast using a mold 1 having a cross section (horizontal cross section) and a vertical portion of 2.4 m. Here, the molten steel surface level was set to be 100 mm lower than the upper end of the mold, and the casting speed was set to 1.6 m / min.

In this experimental example, a coil 2 for imparting a pinch force that raises the molten steel surface in the mold in a convex shape is provided on the upper part of the mold 1 with the position 100 mm above the upper end of the mold as the upper end and the position 350 mm above the upper end of the mold as the lower end. Then, an alternating magnetic field of 100 Hertz having a magnetic flux density of 1200 Gauss was applied at the center of the mold thickness direction and at the upper end of the coil.

The injection nozzle 3 for injecting the molten steel s into the mold 1 has two holes of the lower end closed type discharge ports 3a and 3b, and each discharge port is inclined 45 ° downward toward the short side of the mold. The center of the discharge port 3c is 3 from the top of the mold 1.
It was fixed at the position of 00 mm.

The coil 4 for controlling the natural pouring flow wc, wd generated in the mold 1 at the time of pouring the molten steel is provided below the discharge ports 3a, 3b of the injection nozzle 3 with the horizontal center d of the coil 4 from the upper end of the mold 1. 600mm position (Ho
(Equal to 300 mm), the static magnetic field in the mold thickness direction generated by the coil 4 has a uniform distribution in the mold width direction, and the magnetic flux density is 3000 gauss at the maximum at the coil center 4c. Continuous casting was performed while applying a static magnetic field.

As a result, the electromagnetic coil 2 is provided only on the upper part of the mold 1.
When the molten steel s is cast by applying a pinch force to the molten steel s, the ripples of the molten steel s due to the interference between the stirring flows wa and wb and the natural injection flows wc and wd which are generated especially in the upper portion of the molten steel surface of the mold 1. The phenomenon is remarkably reduced, and molten steel in the mold
In the initial stage of solidified shell formation, the maximum amplitude in the vertical direction due to the ripple phenomenon of molten steel decreased from the conventional value of about 20 mm to 5 mm (see Fig. 2). Along with this, the unevenness of the surface of the slab was reduced to about 100 μm as in the vicinity of the central portion in the mold direction, and a homogeneous and good slab could be obtained.

[0027]

INDUSTRIAL APPLICABILITY According to the present invention, a pinching force is applied to the molten metal on the upper part of the mold of a continuous casting apparatus by an alternating magnetic field to obtain this pinching force effect, and the stirring flow generated at this time and the natural flow generated by injection interfere with each other. Is effectively suppressed by the action of a static magnetic field by a coil arranged at an appropriate position below the injection nozzle, and inclusion of inclusions can be suppressed, improving the operability of continuous casting and obtaining the quality of the obtained slab. Can be improved and stabilized.

[Brief description of drawings]

1A is a cross-sectional schematic explanatory view showing an embodiment of the present invention, FIG. 1B is a schematic plan explanatory view of FIG. 1A, and FIG.
Aa-Ab arrow cross-section outline explanatory drawing in.

FIG. 2 (a) is a cross-sectional schematic explanatory view showing a generation state of a molten steel flow generated in a mold in an experimental example of the present invention, and FIG. 2 (b) is a plan schematic explanatory view of (a).

FIG. 3 (a) is a schematic cross-sectional explanatory view showing a situation of molten steel stirring flow generation in a mold in which a coil for applying a pinch force (electromagnetic force) is arranged above the mold, and FIG. 3 (b) is a plan view of (a). Explanatory drawing.

FIG. 4A is a schematic cross-sectional explanatory view showing a state of occurrence of a natural flow of injection that occurs during molten steel injection in a normal mold in which a coil is not arranged in the mold, and FIG. 4B is a schematic plan view of FIG.

FIG. 5 (a) is a cross-sectional schematic explanatory view showing a state of occurrence of interference between a molten steel stirring flow and a natural injection flow in a mold in which a coil for imparting a pinch force is arranged on the upper part of the mold. FIG. 3A is a schematic plan view of FIG.

[Explanation of symbols]

 1 Mold 1o Mold inner surface (short side) 2 Electromagnetic coil 3 Injection nozzle 3a, 3b Discharge port 3c Discharge port center 4 Coil 4c Coil center 5 AC power supply (for electromagnetic coil) 6 DC power supply (for coil) 7 Lubrication powder 8 Direction of magnetic flux Cp Mold copper plate d Horizontal center line of coil e Line connecting mold inner surface and discharge port center f Injection nozzle center line g Discharge direction center line L Mold inner surface distance (length of long side) s Molten steel sc Solidified shell a mold b electromagnetic coil c injection nozzle ca, cb discharge port wa, wb agitated flow wc, wb natural injection flow

Claims (2)

[Claims] 1. An electromagnetic coil for imparting a pinch force to the molten metal in the mold is provided above the mold into which the molten metal is injected,
A coil for generating a static magnetic field having a maximum value in a mold below a discharge port of an injection nozzle for injecting molten metal into a mold in a continuous casting device for molten metal equipped with a power supply device for applying an alternating current to this electromagnetic coil And a power supply device for applying a direct current to the coil are provided together, a continuous casting device for molten metal. 2. A coil for generating a static magnetic field according to claim 1, wherein an angle θ ₀ between a center line of the injection nozzle and a line connecting an intersection of the horizontal center line with the inner surface of the mold and the discharge port center of the injection nozzle. And the relationship between the discharge outlet centerline of the injection nozzle and the angle θ formed by the discharge direction line from the discharge outlet center is arranged so as to satisfy 0 ° ≦ θ ≦ θ _0. Continuous metal casting equipment.