JP3056657B2 - Continuous casting method of molten metal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a method for continuously casting molten metal using a square fixed mold for casting steel, stainless steel, alloy, aluminum or the like, and disposing an electromagnetic coil outside the mold. The present invention relates to a continuous casting method of molten metal in which a molten metal in a mold is provided with a pinch force to promote feeding of a lubricant.

[0002]

2. Description of the Related Art Conventionally, for example, in a continuous casting process of steel, a lubricant added to a molten steel surface and melted is
The interaction between the mold vibrating under the predetermined conditions and the solidified shell drawn at a constant speed is caused by the interaction or natural fall of the mold, and is consumed.The lubricity of this lubricant is determined by the operability of continuous casting, It is known that it greatly affects the quality of cast slabs, particularly the surface properties.

[0003] The consumption of the lubricant is considered to be an important factor governing the lubrication between the mold and the solidified shell, and various measures have been proposed to increase this. For example, JP-A-52-32824 discloses, for example,
As shown in FIG. 5, an electromagnetic coil 3 is disposed outside a stationary mold 1 formed of a copper plate 1a via a back plate 2 so as to surround the same, and an immersion nozzle 4 is arranged in the mold. While the molten metal s is being injected into the mold from the immersion nozzle, power is supplied to the electromagnetic coil 3 from the power supply 5 to apply an electromagnetic force to the meniscus portion of the molten metal s in the mold, and the meniscus portion sf is molded. 1 to form a recessed portion 6, thereby facilitating the feeding of the lubricant (powder) p to enhance the lubricity, and thereby solidifying the slab sc
It is disclosed to improve the surface properties of the steel.

In the continuous casting method disclosed herein, when a square fixed mold is used, and when a mold plate forming the mold is made of a material having the same electric resistivity, When an electromagnetic force is applied to the molten metal in the mold by energizing an electromagnetic coil disposed outside the mold, eddy currents flowing through the molten metal concentrate on the corners of the mold.

In this case, since the electromagnetic force acting on the molten metal in the mold is proportional to the magnetic flux density × eddy current, the electromagnetic force is excessively concentrated at the corners of the mold, and the uniform electromagnetic force is applied in the circumferential direction of the mold. There is a problem that a force cannot be generated and a cast piece having sufficiently uniform surface properties cannot be obtained.

[0006]

In the present invention, an electromagnetic coil is disposed outside a rectangular mold for injecting and solidifying molten metal, and the molten metal is cast while applying an electromagnetic force to the molten metal in the mold. It is an object of the present invention to provide a continuous casting method for molten metal capable of casting a slab having sufficiently uniform surface properties by suppressing the concentration of electromagnetic force at a corner of a mold and making the electromagnetic force uniform.

[0007]

Means for Solving the Problems The first invention of the present invention is:
In the continuous casting method of molten metal in which a molten metal is injected and solidified by placing an electromagnetic coil on the outside of a rectangular fixed mold to be solidified and applying an electromagnetic force to the molten metal in the mold, the corner of the mold and its corner The near portion is made of a material having a lower electric resistivity than the material forming the other portions, and the concentration of the electromagnetic force at the corner of the mold is reduced to generate a uniform electromagnetic force. A continuous casting method for molten metal. The second invention is characterized in that, in the first invention, the region made of a material having a low electric resistivity is within a range of 50 mm or less from the corner of the mold, and the third invention is, in the first invention, The electrical resistivity of the material constituting the corner portion of the mold and the vicinity thereof is 0.1 to 0.7 times the electrical resistivity of the material constituting the other portions.

A fourth invention is a continuous casting of molten metal in which an electromagnetic coil is arranged outside a rectangular fixed mold for injecting and solidifying molten metal and casting is performed while applying an electromagnetic force to the molten metal in the mold. In the method, a magnetic shielding material is arranged between the mold and the electromagnetic coil at the corner of the mold and in the vicinity thereof, and the magnetic flux density at the corner of the square mold is attenuated to reduce the concentration of the electromagnetic force, thereby achieving a uniform electromagnetic force. A method for continuously casting molten metal, characterized in that it is generated. A fifth invention is characterized in that, in the fourth invention, the magnetic shield material provided between the mold and the electromagnetic coil at the corner of the mold and in the vicinity thereof is a magnetic material or a conductor.

A sixth invention is a continuous casting of molten metal in which an electromagnetic coil is arranged outside a rectangular fixed mold for injecting and solidifying a molten metal and casting is performed while applying an electromagnetic force to the molten metal in the mold. In the method, the thickness of the mold plate at the corner portion of the mold and the vicinity thereof is made thicker than the thickness of the mold plate constituting the other portions, so that the concentration of the electromagnetic force at the corner portion of the mold is alleviated and the uniform electromagnetic force is reduced. A method for continuous casting of molten metal, characterized in that: A seventh invention is characterized in that, in the sixth invention, the region where the thickness of the mold plate is increased is within 50 mm from the corner of the mold, and the eighth invention is characterized in that in the sixth invention, The thickness of the corner portion where the thickness is increased and the region in the vicinity thereof is 1.1 to 3.0 times the thickness of the mold plate in the other region.

A ninth invention is a continuous casting of molten metal in which an electromagnetic coil is arranged outside a rectangular fixed mold for injecting and solidifying molten metal, and casting is performed while applying an electromagnetic force to the molten metal in the mold. In the method, a conductive shielding material is disposed above the meniscus of the molten metal in the mold at and near the corner of the mold to reduce the eddy current at the corner of the mold and to concentrate the electromagnetic force at the corner of the mold. This is a method for continuous casting of molten metal, characterized in that a uniform electromagnetic force is generated by alleviating the problem.

[0011]

According to the present invention, there is provided a continuous casting method for a molten metal in which an electromagnetic coil is disposed outside a rectangular fixed mold for injecting and solidifying the molten metal, and casting is performed while applying an electromagnetic force to the molten metal in the mold. In, the concentration of electromagnetic force in the corner of the mold and its vicinity is suppressed, a uniform electromagnetic force can be generated, the electromagnetic force in the circumferential direction of the mold is made uniform, and a slab having a uniform surface property is obtained. Can be cast.

The present inventors dispose an electromagnetic coil outside a rectangular fixed mold for injecting and solidifying molten metal, and perform continuous casting of molten metal by applying an electromagnetic force to the molten metal in the mold. When the mold plates are all made of the same material with the same thickness through various experiments on the method, there is a phenomenon of concentration of electromagnetic force at the corner of the mold, and the electromagnetic force can be generated uniformly in the circumferential direction of the mold. It was found that it was not possible to obtain good cast slabs with uniform surface properties. Therefore,
The present invention has been completed with the idea of reducing the concentration of electromagnetic force at the corners of the mold.

In the present invention, as means for reducing the concentration of the electromagnetic force at the corner of the mold, the electric resistance of the mold plate forming the corner of the mold is reduced. Increase the thickness of the mold plate forming the mold corners. A magnetic shield is provided between the coil and the mold plate forming the corner of the mold. A conductive shield is placed above the molten metal at the corner of the mold. Such a method is effective.

In the case of using the method described above, the corner portion and the region in the vicinity thereof are made of a material having a low electric resistivity, so that the attenuation of the magnetic flux density at the corner portion is made relatively large, and the corner portion is formed into the corner portion. Alleviate the electromagnetic force concentration. At this time, the region made of a material having a low electric resistivity is
It is desirable that the distance be within 50 mm from the corner of the mold. Above that, the magnetic flux density is excessively attenuated at the corners, which rather promotes non-uniformity of the electromagnetic force distribution.

When the mold is made of a plurality of materials,
Since these are electrically connected, if the difference in electrical resistivity is too large, a large amount of electric charge is induced on the joint surface, and a spark is generated. In order to avoid such a problem and to obtain a sufficient effect of uniformizing the magnetic flux, 50
It is desirable that the electric resistivity in the region of mm be selected in the range of 0.1 to 0.7 times the electric resistivity in the other region.
Note that, in this case, the electric resistivity may be made to gradually decrease toward the corner within a range of 50 mm from the corner.

In the case of using the method described above, by increasing the thickness of the mold plate at the corner of the mold, the attenuation of the magnetic flux density at the corner can be increased. Since the electromagnetic force acting on the molten metal in the mold is proportional to the magnetic flux density × eddy current, the concentration of the electromagnetic force on the corners can be reduced. In a region 50 mm or more away from the mold, the electromagnetic force is not concentrated by the corner, so the region where the thickness of the mold is increased is within 50 mm from the corner of the mold.

The magnetic flux density in the mold is determined by the thickness t of the mold plate.
, Exp (−kt) times the magnetic flux density outside the mold (k
Therefore, if the thickness of the mold plate at the corner portion is too large as compared with the other regions, the attenuation of the magnetic flux density at the corner portion becomes excessive, and the electromagnetic force distribution becomes rather uneven. Therefore, it is desirable that the thickness of the mold plate in the corner portion be selected in a range of 1.1 to 3.0 times the thickness of the mold plate in the other region.

In the case of using the method, it is necessary to dispose a magnetic shield only at the corner of the mold to weaken one or both of the eddy current and the magnetic flux density. When a magnetic shield is provided between the electromagnetic coil corresponding to the corner of the mold and the mold, the magnetic flux density at the corner can be reduced. Here, a magnetic material or a conductor is used as the magnetic shield material.

In the case of using the above method, an eddy current flows through the conductive shield by applying a conductive shield by a conductor above the meniscus of the molten metal in the mold. The generated eddy current can be suppressed.

The present invention is applicable as a continuous casting method using a fixed mold for casting stainless steel, alloys, aluminum and the like in addition to steel.

[0021]

【Example】

(Embodiment 1) An embodiment in which the present invention is applied to a continuous casting method of molten steel will be described below together with an example of an apparatus. In this embodiment, as shown in FIG. 1, in a continuous casting apparatus using a square fixed mold as shown in FIG. 5, a corner 1c of a copper plate 1a forming a mold 1 is made of a material having a low electric resistivity. The other portion 1b is formed of a material having a higher electric resistivity than the material forming the corner portion 1c. Here, the amount of attenuation of the magnetic flux density at the corners of the mold is relatively increased to reduce the concentration of electromagnetic force at the corners.

(Example 1-1) A region from the corner of the copper plate 1a to 40 mm from the corner was formed of pure copper having an electric resistivity of 1.8 × 10 ⁻⁸ Ωm, and the other portions were formed of an electric resistivity of 7.1 ×. 1
Continuous casting was performed using a mold formed of a copper alloy of 0 ^-8 Ωm. As a result, in the obtained slab, the effect of making the oscillation mark shallow in both the corner portion and the long side portion was obtained. While the depth of the oscillation mark when no electromagnetic force was applied was 250 μm, in this example, the depth of the oscillation mark was 80 μm on average, indicating a considerable improvement effect.

(Comparative Example) A copper plate 1a was formed with an electric resistivity of 7.1 ×
Continuous casting was performed using a mold composed of a single piece of copper alloy of 10 ⁻⁸ Ωm. As a result, in the obtained slab, the oscillation mark disappeared at the corner part and the vicinity thereof, and although the surface properties at this part were satisfactory, the oscillation was disturbed at other parts, especially at the long side part. Marks, hot wrinkles, and entrainment of lubricant were observed, and the effect of improving surface properties was not uniform in the circumferential direction. This is due to the concentration of electromagnetic force at the corners, from the corner to the periphery,
This is because flow has occurred.

(Embodiment 2) This embodiment is similar to the embodiment shown in FIG.
As shown in (b), in a continuous casting apparatus as shown in FIG. 5, a corner 1c of a copper plate 1a forming a mold 1 is formed.
Is a thick portion, and the other portion 1b has a constant thickness smaller than the thickness of the corner portion. Here, the corner portions of the copper plate 1a and the thick portion 1c _t, by increasing the attenuation of the magnetic flux density at the mold corners and so as to alleviate the electromagnetic force concentration on the corner portion.

(Example 2-1) A copper plate 1a was formed of a copper alloy having an electric resistivity of 7.1 × 10 ^-8 Ωm, and its thickness in a region 35 mm from a corner was obtained as shown in FIG. , the thick portion 1c _t corners 1c increased gradually up to 50mm toward the corner, using the template set to 25mm the thickness of the other portions 1b, was continuously cast.
As a result, in the obtained slab, the effect of making the oscillation mark shallow in both the corner portion and the long side portion was obtained.
While the depth of the oscillation mark when no electromagnetic force was applied was 250 μm, in this example, the depth of the oscillation mark was 100 μm on average, indicating a considerable improvement effect.

(Comparative Example) Continuous casting was performed using a mold in which a copper plate 1a was formed of a copper alloy having a thickness of 25 mm and an electrical resistivity of 7.1 × 10 ⁻⁸ Ωm. As a result, the resulting slab is
Oscillation marks disappear at the corners and in the vicinity of the corners, and although the surface properties in this area are satisfactory, in other parts, especially on the long side, turbulent oscillation marks, hot water wrinkles, and entrainment of lubricant may occur. As a result, the effect of improving the surface properties was not uniform in the circumferential direction. This is because the electromagnetic force is concentrated on the corner portion and the flow is generated from the corner toward the periphery.

(Embodiment 3) In this embodiment, as shown in FIG. 3, in a continuous casting apparatus as shown in FIG. 5, a back plate 2 at a corner 1c of a copper plate 1a forming a square mold 1 is formed. A magnetic shield 7 made of a ferromagnetic material is provided between the electromagnetic coils 3. Here, the magnetic shield 7
Thus, the amount of attenuation of the magnetic flux density at the corner of the mold is increased, so that the concentration of electromagnetic force on the corner is reduced.

(Example 3-1) A copper plate 1a was formed of a copper alloy having an electric resistivity of 7.1 × 10 ⁻⁸ Ωm, and as shown in FIG. 3, along a corner shape between a corner portion 1c and an electromagnetic coil. An L-shaped magnetic shield was provided. This magnetic shield is made of steel and has a thickness of 10 mm, a length of 40 mm from the corner to the tip, and a height of 800 mm, and is 5 mm from the outer surface of the copper plate a.
It is located at a remote location.

Continuous casting was performed using the mold having the above-described structure. As a result, when the surface properties of the obtained slab were measured, the effect of making the oscillation mark shallower in both the corner portion and the long side portion was obtained. The oscillation mark depth when no electromagnetic force is applied is 280
In this example, the average depth of the oscillation marks was 70 μm, whereas the depth of the oscillation marks was 70 μm.

(Comparative Example) Continuous casting was performed using a mold in which a copper plate 1a was formed of a copper alloy having a thickness of 25 mm and an electrical resistivity of 7.1 × 10 ⁻⁸ Ωm. As a result, the resulting slab is
Oscillation marks disappear at the corners and in the vicinity of the corners, and although the surface properties in this area are satisfactory, in other parts, especially on the long side, turbulent oscillation marks, hot water wrinkles, and entrainment of lubricant may occur. As a result, the effect of improving the surface properties was not uniform in the circumferential direction. This is because the electromagnetic force is concentrated on the corner portion and the flow is generated from the corner toward the periphery.

(Embodiment 4) In this embodiment, as shown in FIG. 4, in a continuous casting apparatus using a square fixed mold as shown in FIG. 5, a conductive material is formed above the corner meniscus of the molten metal in the mold. In this case, a sex shield 8 is provided. Here, the eddy current flowing in the conductive shield 8 suppresses the eddy current generated at the corner of the mold, so as to reduce the concentration of the electromagnetic force on the corner.

(Example 4-1) At a position 15 mm above the corner meniscus of the molten metal in the mold, a thickness 15 mm, 40 mm
Continuous casting was performed using a mold in which a conductive shield made of pure copper having a square shape of mm × 40 mm was arranged. As a result, when the surface properties of the obtained slab were measured, an effect of improving the uniform surface properties in the circumferential direction of the slab cross section was observed, and the average depth of the oscillation marks was 90 μm.

(Comparative Example) Continuous casting was performed using a continuous casting apparatus without a magnetic shield and a conductive shield. As a result, in the obtained slab, the oscillation mark disappeared at the corner portion and the vicinity thereof, and although the surface properties at this portion were satisfactory, the oscillation was disturbed at other portions, especially at the long side portion. Marks, hot wrinkles, and entrainment of lubricant were observed, and the effect of improving surface properties was not uniform in the circumferential direction. This is because the electromagnetic force is concentrated on the corner portion and the flow is generated from the corner toward the periphery.

Casting conditions (common to Examples 1-4 and Comparative Examples) Cast slab Steel type: carbon steel Size: 1500 mm in width, cavity thickness 250 mm Mold height: 800 mm Mold plate center part thickness: 25 mm Back plate (SUS304) Thickness: 40mm Electromagnetic coil Size: Inner dimensions 1700mm × 450mm Magnetic flux density: 1200 gauss Casting speed: 2m / min Applied oscillation to mold: Frequency 120cpm, Stroke ± 5mm

[0035]

According to the present invention, there is provided a continuous casting method for a molten metal in which an electromagnetic coil is arranged outside a rectangular mold for injecting and solidifying a molten metal and casting is performed while applying an electromagnetic force to the molten metal in the mold. , The concentration of electromagnetic force at the corner of the mold and its vicinity can be suppressed, the uniform electromagnetic force can be generated in the circumferential direction of the mold, the electromagnetic force in the circumferential direction of the mold can be uniform, Can be cast.

[Brief description of the drawings]

FIG. 1 is a schematic plan cross-sectional explanatory view showing Embodiment 1 of a mold structure of a continuous casting apparatus for implementing the present invention.

FIGS. 2 (a) and 2 (b) are plan sectional schematic explanatory views showing Embodiment 2 of a mold structure of a continuous casting apparatus embodying the present invention.

FIG. 3 is a schematic plan cross-sectional explanatory view showing Embodiment 3 of a mold structure of a continuous casting apparatus for implementing the present invention.

FIG. 4 is a schematic plan cross-sectional explanatory view showing Embodiment 4 of a mold structure of a continuous casting apparatus for implementing the present invention.

5A is a schematic longitudinal sectional view showing an example of a continuous casting apparatus for molten steel to which the present invention is applied, and FIG. 5B is a schematic plan sectional view of FIG.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 mold 1a copper plate 1b copper plate other than corner portion 1c _t thick portion 2 back plate 3 electromagnetic coil 4 immersion nozzle 5 power supply 6 molten metal surface depression 7 magnetic shield 8 conductive shield s molten steel sf molten steel surface sc cast piece p lubricant (powder)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI B22D 27/02 B22D 27/02 W (72) Inventor Takehiko Fuji 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology (56) References JP-A-3-99753 (JP, A) JP-A-4-13443 (JP, A) JP-A-4-13442 (JP, A) JP-A-6-182496 (JP, A A) JP-A-8-33959 (JP, A) JP-A-58-41661 (JP, A) JP-A-52-32824 (JP, A) JP-A-64-33339 (JP, U)

Claims (9)

(57) [Claims] 1. A method for continuously casting molten metal in which an electromagnetic coil is arranged outside a rectangular fixed mold for injecting and solidifying molten metal and casting is performed while applying an electromagnetic force to the molten metal in the mold. The corner portion and its vicinity are made of a material having a lower electric resistivity than the material constituting the other portions, and the concentration of the electromagnetic force at the mold corner portion is reduced to generate a uniform electromagnetic force. A continuous casting method for molten metal, characterized by the following. 2. The continuous casting method for molten metal according to claim 1, wherein the region made of a material having a low electric resistivity is set within a range of 50 mm or less from a corner of the mold. 3. An electric resistivity of a material constituting a corner portion of the mold and its vicinity is 0.1 to 0.7 times an electric resistivity of a material constituting the other portion. The method for continuously casting molten metal according to claim 1. 4. A continuous casting method for molten metal in which an electromagnetic coil is arranged outside a rectangular fixed mold for injecting and solidifying molten metal and casting is performed while applying an electromagnetic force to the molten metal in the mold. A magnetic shielding material is placed between the mold and the electromagnetic coil at the corners and near the corners to attenuate the magnetic flux density at the corners of the square mold, reduce the concentration of electromagnetic force, and generate uniform electromagnetic force A continuous casting method for molten metal, characterized by the following. 5. The continuous casting method for molten metal according to claim 4, wherein the magnetic shield material provided between the mold and the electromagnetic coil at the corner of the mold and in the vicinity thereof is a magnetic material or a conductor. . 6. A continuous casting method for a molten metal in which an electromagnetic coil is arranged outside a rectangular fixed mold for injecting and solidifying the molten metal and casting is performed while applying an electromagnetic force to the molten metal in the mold. The thickness of the mold plate at the corners and its vicinity is made larger than the thickness of the mold plate constituting the other parts to reduce the concentration of electromagnetic force at the corners of the mold to generate uniform electromagnetic force. A continuous casting method for molten metal, characterized by the following. 7. The continuous casting method for molten metal according to claim 6, wherein the region where the thickness of the mold plate is increased is within 50 mm from the corner of the mold. 8. The method according to claim 6, wherein the thickness of the corner portion which increases the thickness of the mold plate and the region in the vicinity thereof are 1.1 to 3.0 times the thickness of the mold plate in the other region. Continuous casting method of molten metal. 9. A continuous casting method for molten metal in which an electromagnetic coil is arranged outside a rectangular fixed mold into which molten metal is injected and solidified, and casting is performed while applying an electromagnetic force to the molten metal in the mold. A conductive shielding material is arranged above the meniscus of the molten metal in the mold at the corners of the mold and in the vicinity thereof, to reduce the eddy current at the mold corners, and to reduce the concentration of electromagnetic force at the mold corners. A method for continuously casting molten metal, which generates a uniform electromagnetic force.