JPH07148553A - Continuous casting mold for molten metal - Google Patents

Abstract

PURPOSE:To restrain the induction current loss in a mold body and to always give the optimum current by arranging a low electric conductive layer continued in the thickness direction in copper plates and/or back plates constituting the long sides of the mold in magnetic field acting zone. CONSTITUTION:The mold having rectangular cross sectional surfaces is composed of copper plates 2 for long sides and short sides directly contacting with molten steel and the back plates 3 made of SUS, etc., provided with cooling water flow passages 4 arranged at the outside so as to surround the copper plates. The copper plate 2 for long side is formed of the copper-made main body and the lamination of members composed of a material having low electric conductivity and insulating material of mica, etc. Further, electromagnetic coils 1 are arranged along the back plates 3 for long sides, and movable magnetic field is generated by impressing the electromagnetic force, and the thrust is given in the unidirection in the molten steel to generate the circular stirring flow in the horizontal direction. By this method, the induction current loss is restrained and the electromagnetic force having wider frequency range than the conventional method can be used, and the stable circulating stirring flow is given to the molten metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting mold for molten metal, and more particularly to a casting mold capable of obtaining good quality slab by swirling and stirring molten steel by a moving magnetic field.

[0002]

2. Description of the Related Art For example, when continuously casting a steel slab,
A moving magnetic field generating coil is arranged along the long side of the rectangular casting mold, an alternating current is caused to flow through the coil, the moving magnetic field generated thereby is applied to the molten steel, and a swirling stirring flow is formed in the molten steel cross-sectional direction. As a result, the technique of preventing segregation of molten steel and casting a slab with few defects, so-called electromagnetic stirring, is well known. As a representative document, "Material processing using electromagnetic force" (129th and 130th Nishiyama Memorial Technology Course, April 1989) explains electromagnetic induction and skin effect of alternating magnetic field and stirring technology and effects. Has been done. In addition, as an example of a mold structure, Japanese Patent Publication No. Sho 58-49172 discloses an "electromagnetic stirrer for continuous casting".

Generally, a continuous casting mold comprises a copper plate having a thickness of several tens of mm on the inside and a cooling water passage on the outside thereof, and a back plate having a thickness of several tens of mm for suppressing deformation of the copper plate. Therefore, in the electromagnetic stirring as described above, since the copper plate and the back plate are relatively good in terms of electrical conductivity, the induced current easily flows straight in both metals, and the induced current loss occurs. Conventionally, a low-frequency current of several Hz at most, which is unavoidably strong, is used, and it is designed to minimize the loss. In addition, it is considered that when the frequency is increased, the induced current concentrates on the surface side due to the skin effect, which is one of the reasons why the high frequency is not adopted.

[0004]

However, in swirling stirring by the electromagnetic force of molten steel, when a frequency in the commercial frequency range or a high frequency range is used, a stable stirring flow is more easily obtained than a low frequency. From this point, it is more effective to use electromagnetic stirring if it is possible to select a high frequency range that is optimal for each frequency depending on the shape, size, and steel type to be cast, in other words, to increase the degree of freedom of the selected frequency. Sex will be increased.

The present invention has been made in view of the above points, and it is possible to reduce the induced current loss in the mold body as much as possible, thereby expanding the frequency use range and always providing an optimum current. It is an object of the present invention to provide a continuous casting mold that enables

[0006]

The gist of the present invention is as follows. (1) In a continuous casting mold in which a moving magnetic field generated by a coil installed along the long side of the mold is applied to the molten metal to swirl and stir the molten metal in the horizontal direction, at least the long side of the mold in the magnetic field working region. Copper plate and /
Alternatively, a continuous casting mold for a molten metal, characterized in that a copper plate and / or at least one low electric conductivity layer continuous in the thickness direction of the back plate is provided in the back plate. (2) The mold according to (1), wherein the low electric conductivity layer is made of a solid insulator having a low electric conductivity such as mica or ceramic or a metal having an electric conductivity lower than that of at least a copper plate. (3) The mold according to (1), wherein the low electric conductivity layer is a slit formed in the copper plate and / or the back plate.

[0007]

[Function] At least in the magnetic field working area of the long side of the mold, there is a continuous (penetrating) portion with a small electrical conductivity in the thickness direction of the long side, so the induced current from the coil is blocked at this location. There is no current flowing straight out, which reduces induced current loss in the mold as much as possible,
Even if the frequency is increased, a thrust similar to that of the low frequency is obtained, and stable swirling stirring is achieved.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan sectional view showing an example of a mold for continuous casting of a steel slab according to the present invention, and FIG. 2 is a perspective view showing a part of the mold body in FIG. As shown,
Rectangular cross-section molds are long-side / short-side copper plates that directly contact molten steel 2
And a back plate 3 made of SUS or the like having a cooling water flow path 4 arranged outside the copper plate so as to surround the copper plate.
Composed of. Further, the electromagnetic coil 1 is arranged along the back plate 3 on the long side, and a moving magnetic field is generated by application of an electromagnetic force by the coil 1, and a thrust force is applied in one direction in the molten steel to horizontally move the molten steel. A swirling stir flow occurs.

In the above, the copper plate 2 constituting the long side of the mold
As shown in FIG. 2, a body 5 made of a metal having a high electric conductivity, for example, copper or a copper alloy, and a material 6 having a low electric conductivity, for example, a member 6 made of an insulator such as mica or ceramic are laminated. To form. The member 6 having a low electric conductivity may have at least one layer (three layers are provided at regular intervals in the figure), but the formation range thereof needs to be within the range of the magnetic field of the electromagnetic coil 1. Is.

Further, not only when the member 6 having a low electric conductivity is provided only on the long side of the mold, it is more effective to reduce the loss of the mold by interposing the member 6 on the short side together with the long side. . Further, in the illustrated example, the layer of the member 6 having a low electric conductivity is formed only on the copper plate side, but this member 6 is also provided on the back plate 3 side, or in some cases, the copper plate side. Back plate 3
It is also possible to provide only on the side.

3 and 4 show another specific example of the long side portion of the mold according to the present invention. Instead of the solid insulating member of FIG. 2, the slit layer 7 is penetrated (continuously) at least in the thickness direction of the copper plate. It has a structure in which three layers are formed. In the case of the slit layer 7, the strength of the mold copper plate itself is taken into consideration, and the slit copper layer 7 is not continuous over the entire length in the longitudinal direction but has a partial structure as shown in the drawing, but it may be formed intermittently in the longitudinal direction if necessary. This also applies to the case of FIG.
Further, the slit type of FIG. 3 may also be provided on the short side of the mold as in FIG. 2 and can also be formed on the back plate 3 side, but in this case, it does not communicate or interfere with the cooling water flow path 4. However, in the case of a slit, it is desirable not to provide a slit on the back plate side.

The mold copper plate 2 and the back plate 3 may be joined together by a mechanical fixing method such as bolts and nuts as shown in FIG. 3, or by a diffusion joining method suitable for joining dissimilar metals. . In addition, in FIG. 2 and FIG.
Although the solid member 6 and the slit 7 are horizontal, they may be provided with an inclination in the mold thickness direction or the longitudinal direction. Further, the thickness and gap of the solid member 6 and the slit 7 are within a range that can be manufactured or formed, at least 0.2.
It may be about mm or more, and the upper limit is about 1 mm.

FIG. 5 shows an electromagnetic relationship between the electromagnetic coil 1, the long side 2 of the mold (including 3) and the molten steel 8. When a magnetic field 9 is applied from the coil toward the mold, the mold 2 or 3 is shown.
A vertical induction current 10 flows in the inner and molten steel 8, and a unidirectional thrust 11 is generated in the molten steel, which gives a swirling flow to the molten steel 8. Here, if there is a large amount of current flowing in the mold portion, there will be a corresponding loss, but if an insulator or slit is formed in the mold to block this current as in the present invention, this loss can be reduced as much as possible. become.

(Operation example) width 1500 mm, height 800 mm,
The long side of the mold with a cavity thickness of 250 mm, the copper plate thickness 25
mm, SUS304 stainless steel back plate thickness 50
Composed in mm. At this time, the copper mold plate is divided into 7 parts in the horizontal direction (6 0.5 mm from the top to 50 mm to 200 mm in height).
A thick slit was formed). As a result of casting molten steel under the application of a moving magnetic field using a mold using such a mold long side, as a result, the thrust at the ¼ width part position from the end to the long side on the inner surface of the mold It is shown in FIG. 6 in comparison with the template.

As can be seen from FIG. 6, in the mold of the present invention having six slits, it was possible to obtain a thrust at 20 Hz which was about 20% higher than the thrust obtained at 3 Hz by the mold having 0 slits. .

[0016]

As described above, according to the continuous casting mold of the present invention, it is possible to suppress the induced current loss in the mold body as much as possible, which allows the use of electromagnetic force in a wider frequency range than ever before. As a result, a stable swirling stirring flow can be imparted to the molten metal.

[Brief description of drawings]

FIG. 1 is a plan sectional view of a continuous casting mold according to the present invention.

FIG. 2 is a perspective view showing a structural example of a long side which constitutes the mold of the present invention.

FIG. 3 is a perspective view showing another structural example of the long side that constitutes the mold of the present invention.

FIG. 4 is a sectional view of a slit portion of FIG.

FIG. 5 is an explanatory plan view showing the relationship between the electromagnetic coil, the mold and the molten steel in an electromagnetic manner.

FIG. 6 is a graph showing the results according to the operation example of the present invention together with the comparative example.

[Explanation of symbols]

 1 Electromagnetic Coil 2 Mold Length / Short Side 3 Back Plate 4 Cooling Water Flow Path 5 Copper Plate 6 Solid Insulation Member 7 Slit Layer 8 Molten Steel 9 Magnetic Field 10 Induced Current 11 Thrust

Claims (3)

[Claims] 1. A continuous casting mold in which a moving magnetic field generated by a coil installed along the long side of the mold is applied to the molten metal to swirl and stir the molten metal in a horizontal direction, at least the mold in the magnetic field working region. A continuous casting mold for molten metal, characterized in that at least one low electrical conductive layer continuous in the thickness direction of the copper plate and / or the back plate is provided in the copper plate and / or the back plate constituting the long side. 2. The mold according to claim 1, wherein the low electric conductivity layer is made of a solid insulator having a low electric conductivity such as mica or ceramics, or a metal having an electric conductivity lower than that of at least a copper plate. 3. The mold according to claim 1, wherein the low electric conductive layer is a slit formed in the copper plate and / or the back plate.