JP3159615B2 - Continuous casting machine for 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 fixed mold for casting steel, stainless steel, alloy, aluminum, etc., wherein an electromagnetic coil is disposed outside the mold. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting apparatus for molten metal that applies a pinch force to a molten metal in a mold to promote feeding of a lubricant and improve lubricity of the molten metal in the mold.

[0002]

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

[0003] The consumption of the lubricating powder 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, Japanese Patent Application Laid-Open No. 52-32824 discloses that a continuous casting mold is provided with an electromagnetic coil so as to surround the continuous casting mold and apply an electromagnetic force of 30 to 1000 Gauss to a meniscus portion of the molten metal in the mold. It is also disclosed that the meniscus portion is curved in the vicinity of the mold to enhance the lubrication by facilitating the feeding of the lubricating powder and to improve the surface properties of the solidified slab.

[0004] Separately, for the purpose of improving the internal quality of a slab, it has been proposed to apply a moving magnetic field to a molten metal and perform electromagnetic stirring. For example, JP-A-56-1
No. 48459, 148460 discloses that a moving magnetic field generates a circumferential flow of a mold in molten steel.

[0005] When such electromagnetic stirring is intended,
A frequency at which a sufficiently large electromagnetic force is generated in the circumferential direction of the mold and the attenuation of the electromagnetic force at the mold is small, that is, 1.5 to 10
Low frequencies on the order of Hz were used. When such a low frequency is used, the electromagnetic force in the thickness direction of the mold is small and the pinch force hardly acts, so the lubricating powder is not sufficiently fed between the mold and the molten metal, and the surface properties of the slab There is a problem that can not be improved.

[0006]

In the present invention, the frequency level of the moving magnetic field is increased, the electromagnetic force in the thickness direction of the mold is increased, and a sufficient pinch force is applied to the molten metal in the mold. Another object of the present invention is to provide a continuous casting apparatus for molten metal capable of improving the surface properties of a slab by promoting the feeding of lubricating powder between a mold and a molten metal.

[0007]

Means for Solving the Problems The first invention of the present invention is:
It has a mold for injecting and solidifying molten metal, and an electromagnetic coil arranged outside the mold and for applying a moving magnetic field in the horizontal direction, and performs casting while applying an electromagnetic force to the molten metal in the mold. In a continuous casting apparatus for metal, a slit having a width penetrating the inner surface of the mold and preventing intrusion of molten metal is continuously formed in a copper plate or a copper plate and a back plate constituting a mold on a surface facing the electromagnetic coil in a thickness direction of the mold. A continuous casting apparatus for molten metal, characterized in that at least one or more are provided and a frequency of an alternating current applied to the electromagnetic coil is 10 to 1000 Hz. A second invention is the continuous casting apparatus for molten metal according to the first invention, wherein the layer composed of the slit is a low electric conductive layer having a resistance of 1 to 10Ω. It is.

[0008]

In the present invention, 10 to 1 in the horizontal direction of the mold.
The moving magnetic field is generated in the 000Hz, the molten metal in the mold, it is possible to impart a large pinching force, mold lubricant can effectively fed between the molten metal to improve the lubricating properties In addition, the surface properties of the slab can be improved.

Through various experiments, the present inventors have found that in order to apply a large pinching force to molten metal, it is effective to generate a moving magnetic field having a frequency of 10 to 1000 Hz in the horizontal direction of the mold. It has been found that as a simple means for applying a moving magnetic field at the level of 1000 Hz to the molten metal, it is effective to provide a low electric conductive layer continuous in the thickness direction of the mold. The present invention has been completed based on these findings.

FIG. 1 shows characteristics of electromagnetic force and frequency in the circumferential direction of the mold and in the thickness direction of the mold. From this figure, it can be seen that in a mold having no low electric conductive layer, the electromagnetic force in the sliding direction is maximum at 2 Hz, and when the frequency is higher, the attenuation by the mold is large and the electromagnetic force is small.

On the other hand, in the mold provided with the low electric conductive layer, the circumferential electromagnetic force becomes maximum at a frequency of 15 Hz, and the thickness direction electromagnetic force shows a larger characteristic as the frequency becomes higher.
However, if the frequency is 1000 Hz or more, heat generation of the electromagnetic coil becomes a problem.

As the low electric conductive layer in the present invention, a slit, a ceramic layer having an electric resistance of 1 to 10 Ω, a metal (including metal oxide) layer or a mixed layer thereof is effective. A material having an electric resistance necessary to obtain a necessary frequency is selected according to casting conditions (including the type of lubricant and the supply amount).

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.

[0014]

【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 FIG. 2, reference numeral 1 denotes a mold, which is formed of copper plates 1a and 1b. An immersion nozzle 2 for injecting molten steel s from a tundish (not shown) is provided at the center of the mold 1. Then, molten steel s is supplied from the immersion nozzle 2 into the mold, and continuous casting is performed while maintaining the molten steel surface at a predetermined level to obtain a slab c.

An electromagnetic coil 4 is disposed outside the copper plate 1a forming the long side of the mold 1 via a back plate 3, and generates a moving magnetic field in the horizontal direction of the mold 1 by using By pinching the vicinity of the molten metal surface of the molten steel s in the mold, the molten steel surface sf in the mold 1 is raised toward the center, and a molten metal surface depression 6 is formed between the inner surface of the mold 1 and the molten steel surface. Promote the delivery of

In order to reduce the loss in the mold because a large electromagnetic force is required, in this example,
As shown in FIG. 3B, the copper plate 1 on the side where the electromagnetic coil 4 is disposed
In FIG. 3A, three horizontal slits 5a, 5b, 5c penetrating at both ends of the copper plate 1a are formed as a low electric conductive layer so as to block an eddy current generated by a moving magnetic field of the electromagnetic coil 4. Here, since this slit is formed in the copper plate 1a that forms the long side of the mold 1, the width a of this slit is set within a range that can prevent intrusion of molten steel. In the drawing, reference numeral 7 denotes a coolant passage formed between the copper plate 1a and the back plate 3 for cooling the mold.

The slit 5 is used as a low electric conductive layer.
Although a, 5b, and 5c are provided, the present invention is not limited to this. The slit may be filled with ceramics, metals (including oxides) having a higher electric resistance value than the copper plate, or these copper plates 1 may be filled. A material having a higher electric resistance may be bonded to a copper plate.

(Embodiment 2) In this embodiment, the present invention is applied to a continuous casting method using a steel continuous casting apparatus having a configuration as shown in FIG. In this embodiment, a mold 1 having a width of 1600 mm, a height of 750 mm, and a cavity thickness of 230 mm is used for a copper plate 1a, 1 having a thickness of 25 mm.
b and a back plate 3 made of stainless steel (SUS304) having a thickness of 50 mm, and a copper plate 1a forming the long side of the mold is formed with a horizontal slit 5a having a width of 0.5 mm at a position 150 mm from the upper end. A linear motor (electromagnetic coil) excited by three-phase alternating current outside 1a
4 is arranged to apply a moving magnetic field. In this example, the frequency of the current flowing through the linear motor is set to 1 to 1.
Continuous casting was performed at 200 Hz.

FIG. 4 shows the results of measuring the surface roughness of the slab c obtained in this example. In this figure, the vertical axis is normalized by the surface roughness of the slab when casting is performed without applying a moving magnetic field, and the smaller the value is, the better the surface properties are.

In the frequency range of 1 to 10 Hz, the surface roughness of the slab is not much different from that when no electromagnetic force is applied, but this is because the pinch force acting on the molten steel is small and the lubricant p (powder) is fed. This is because the effect is not remarkable. On the other hand, when the frequency is 10 Hz or more, the effect of improving the surface properties of the slab by the action of the pinch force is seen, and the frequency is 200 Hz.
Has improved the surface roughness of the slab to 30%.

For comparison, a similar experiment was conducted using a mold 1 in which no slit was provided in the copper plate 1a.
No improvement in the surface properties of the slab was observed. This is because the electromagnetic force was attenuated by the mold, and the pinch force hardly acted on the molten steel s.

Casting conditions Cast slab: Slab slab having a cross section (horizontal cross section) of 1600 mm in width and 230 mm in thickness Material: carbon steel Casting speed: 2 m / min Molten steel surface level: 100 mm downward from upper end of mold

[0023]

According to the present invention, in the horizontal direction of the mold, 1
The moving magnetic field is generated in 0～1000Hz, the molten metal in the mold, a large pinching force can be imparted to the lubricant can be effectively fed between the mold and the molten metal, the lubricating properties And the surface properties of the slab can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a relationship between a frequency of a moving magnetic field and an electromagnetic force acting on molten steel in a mold.

FIG. 2 is a schematic vertical sectional view showing an example of a continuous casting apparatus for molten steel to which the present invention is applied.

FIG. 3 (a) is a schematic plan sectional view showing an example of a mold structure of a continuous casting apparatus embodying the present invention. (B) The figure is an AA solid view outline explanatory drawing of (a) figure.

FIG. 4 is an explanatory diagram showing a relationship between a frequency of a moving magnetic field generated by an electromagnetic coil and a surface roughness index of a slab obtained in an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 1a, 1b Copper plate 2 Immersion nozzle 3 Back plate 4 Electromagnetic coil (linear motor) 5a, 5b, 5c Slit (low electric conduction layer) 6 Depressed part of metal surface 7 Refrigerant passage s Molten steel sf Molten steel surface p Lubricant (powder) )

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takehiko Fuji 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (56) References JP-A-58-205651 (JP, A) JP-A-7-148554 (JP, A) JP-A-7-148553 (JP, A) JP-A-4-319056 (JP, A) JP-A-4-100658 (JP, A) JP-A-62-230459 (JP-A-62-230459) JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/115 B22D 11/04 311 B22D 11/04 313 B22D 11/07

Claims (2)

(57) [Claims] 1. A mold for injecting and solidifying a molten metal,
An electromagnetic coil disposed outside the mold to apply a moving magnetic field in the horizontal direction, wherein the molten metal continuous casting apparatus performs casting while applying an electromagnetic force to the molten metal in the mold, a copper plate or a copper plate and the back plate constituting the mold opposite faces, only through the mold inner surface
One with a slit width intrusion can be prevented in the molten metal continuously in the thickness direction of the mold provided at least one,
The frequency of the alternating current applied to the electromagnetic coil is set to 10 to 100.
A continuous casting apparatus for molten metal, which is set to 0 Hz. 2. The method according to claim 1, wherein the layer comprising the slit comprises a low electric conductive layer of 1 to 10 Ω.
Continuous casting apparatus for molten metal.