JP3595533B2 - Continuous casting mold - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a continuous casting apparatus having an electromagnetic coil, and more particularly to a mold capable of stably applying an electromagnetic force to a molten metal in a mold and obtaining a high-quality cast piece for a long time.
[0002]
[Prior art]
In the continuous casting technology of molten metal, a technology that uses electromagnetic force during casting has been developed to achieve the stabilization of the molten metal surface, the smoothness of the continuously cast slab surface, and the increase in casting speed. Japanese Patent Application Laid-Open No. 52-32824 discloses that, as shown in FIG. 14, an alternating current is supplied to an energizing coil 35 which is disposed so as to surround the mold 31 and is insulated with a refractory material, and It discloses that the meniscus portion 32 is curved to promote the inflow of the powder 34 and to reduce the contact pressure between the mold and the slab during the initial solidification to improve the surface properties. However, an induced current is induced in the cooling copper plate constituting the mold by the AC magnetic field applied by the electromagnetic coil, and the magnetic field to be applied to the molten metal in the mold is attenuated by the surface effect.
[0003]
In order to suppress the attenuation of the magnetic field in the mold in this technology using electromagnetic force and further improve the electromagnetic effect, Japanese Patent Application Laid-Open No. H05-15949 discloses a metal-made internal water cooling structure as shown in FIG. A continuous casting apparatus for metal comprising a mold 31 and an electromagnetic coil 35 that passes around the mold and passes a high-frequency current, wherein the mold 31 a) extends in the casting direction on its upper part and extends to the upper end of the mold. Has a segment portion 37 of an internal-coolable structure divided by a plurality of slits 36 that do not reach, or b) an internal-coolable segment divided by a plurality of slits 36 extending in the casting direction and reaching the upper end of the mold. 37, and a plurality of girders connecting the segment portions, and a continuous casting apparatus in which the electromagnetic coil 35 is arranged so as to orbit around the segment portions, It is shown.
[0004]
However, the mold provided with such a slit cannot be reinforced by a back plate or the like and has low rigidity. Therefore, the mold is likely to be thermally deformed, and is applicable to a mold for casting a large section such as a slab. It was difficult. In order to solve these points, Japanese Unexamined Patent Publication No. 2000-246397 discloses that, as shown in FIG. 12, electromagnetic force is applied to a metal near a meniscus initial solidification portion of a molten metal in a continuous casting mold in a direction perpendicular to the mold wall. In a continuous casting apparatus for molten metal for applying a force, an electromagnetic coil 35 for supplying an alternating current to the outer peripheral surface of the mold 31, a pair of first cooling copper plates 39, and a non-magnetic stainless steel combined with the copper plates. A plurality of divided cooling units including a first back plate 41, a pair of second cooling copper plates 40, a second back plate 42 made of non-magnetic stainless steel combined with the copper plates, and an insulator 46 Wherein each of the first cooling copper plate and the second cooling copper plate has at least one groove on a surface opposite to a casting surface, and each of the first and second cooling copper plates has a groove. With the back plate, the surfaces of the first and second cooling copper plates having the grooves are hermetically fixed, whereby the grooves form the cooling passages 43, and the first cooling copper plate and the second cooling copper plate are formed. The copper plate is electrically insulated through an insulator 46, and the first back plate and the second back plate are insulated and fastened in a state of being electrically insulated from each other. Is disclosed.
[0005]
[Problems to be solved by the invention]
In the mold of the continuous casting apparatus disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2000-246397, the loss of electromagnetic force can be reduced, and the processing accuracy and the assembly accuracy can be secured by dividing the entire length of each side of the mold as a unit. There is an advantage.
[0006]
However, as shown in FIG. 11, which is a schematic cross-sectional view in which a corner portion of a mold in which a cooling copper plate is combined is enlarged, an insulator 46 that electrically insulates the cooling copper plate has only a mating surface 48. Molten metal penetrates into the gap created by repeated use of the mold due to wear of the mating surface, splash of molten metal during casting adheres near the corner of the mold wall, etc. In addition, it is inevitable that the insulating property is reduced near the mating surface of the cooling copper plate or the hack plate of the mold and near the corner of the mold. When the insulation property decreases, an induced current flows through the cooling copper plate, and the magnetic field strength decreases. Therefore, there is a problem that the electromagnetic force applied to the molten metal also decreases.
[0007]
The present invention relates to a continuous casting mold for continuous casting of molten metal having an electromagnetic coil, in order to ensure stable insulation of the mold even during long-term use of the mold and to obtain a high-quality slab for a long time. To provide.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following configuration as a gist.
[0009]
(1) In a continuous casting apparatus having an electromagnetic coil, a pair of first cooling copper plates of a continuous casting mold is sandwiched between a pair of second cooling copper plates, and a pair of first cooling copper plates combined with the first cooling copper plate. A first back plate and a pair of second back plates combined with the second cooling copper plate are electrically insulated from each other via an insulator, and the first cooling copper plate and the second cooling copper plate are insulated from each other. The mating surface with the copper plate is electrically insulated from each other via an insulator of the mating surface, and the pair of first cooling copper plates is formed so as to be sandwiched between the pair of second cooling copper plates. An insulator near the corner is installed on the casting surface of the first cooling copper plate and / or the casting surface of the second cooling copper plate in a range of more than 0 to 50 mm or less from the corner portion on the casting surface side. A continuous casting mold , characterized in that:
[0010]
(2) In the mating surface of the first cooling copper plate and the second cooling copper plate, an insulator of the mating surface is disposed on one or both of the first cooling copper plate and the second cooling copper plate. (1) The casting mold for continuous casting according to (1).
[0011]
(3) The insulator on the mating surface and the insulator near the corner portion are an electrically insulating ceramic plate and / or an electrically insulating ceramic formed by thermal spraying (1) or (2) The continuous casting mold according to (2).
[0012]
(4) an insulating material of the mating surface, the corner near the insulator is alumina-based ceramics and / or, according to any one of to, characterized in that a zirconia-based ceramics (1) - (3) Continuous casting equipment .
[0013]
(5) The insulator according to any one of (1) to (4), wherein the insulator near the corner portion is an alumina-based ceramic, and the insulator on the mating surface is a zirconia-based ceramic . Continuous casting mold .
[0014]
(6) The continuous casting mold according to (1) or (2) , wherein the insulator on the mating surface is one or more of a mica plate, a ceramic fiber molded body, and PTFE .
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings of the embodiments. FIG. 1 is a perspective view showing the concept of assembling the continuous casting mold of the present invention, and FIG. 2 is a schematic horizontal sectional view of the continuous casting mold of the present invention thus assembled. 1 and 2, a continuous casting mold according to the present invention includes a first pair of opposed cooling copper plates 1 and 1 (usually, on the short side of the mold) and a second cooling copper plate facing the sandwiched sandwich. 2, 2 (usually, the long side of the mold) constitutes a mold wall surface. Further, on the back surface of these cooled copper plates, that is, the surface of the cooled copper plate opposite to the side in contact with molten steel, the first cooled copper plate A pair of back plates 7, 7 are provided in combination with the first cooling plate 1 to support the same, and second back plates 8, 8 are provided in combination with the second cooling copper plates 2, 2 to support the same. Further, the mating surface 12 between the first cooling copper plate and the second cooling copper plate sandwiched between the first cooling copper plate and the second cooling copper plate is electrically insulated by an insulator, and the back plates 7, 7 and the back plate 8 sandwiching the same , 8 are electrically insulated and fastened.
[0016]
The back plate is preferably made of non-magnetic stainless steel, has a gap 13 between the back plate 7 and the back plate 8 combined therewith, and is electrically insulated by fastening bolts 14 and fastened and fixed. Is done. That is, the insulating washer 10 and the insulating sleeve 11 are interposed between the head and the shaft of the fastening bolt 14 and the outer surface of the back plate 8 and the inner surface of the bolt hole. Fixed, thereby forming a mold.
[0017]
The gap 13 is preferably about 1 to 5 mm in order to prevent deformation of the mold during casting and short-circuiting due to adhered matter.
[0018]
A coil 9 for passing an alternating current for applying an alternating magnetic field to the molten metal in the mold at the time of casting is provided on the outer periphery of the mold configured as described above. Note that in the present invention, an insulator refers to an object that is electrically insulated.
[0019]
As described above, the mating surface 12 of the first cooling copper plate 1 and the second cooling copper plate 2 interposed therebetween is provided with an insulator of the mating surface. And cooling copper plate 2 on one or both surfaces. That is, FIGS. 3 to 5 are schematic horizontal cross-sectional views in which the vicinity of the corner portion (A portion in FIG. 2) of the continuous casting mold of the present invention shown in FIG. 2 is enlarged. In the example shown in FIG. 3, the insulators 3 and 4 of the mating surfaces are provided on the mating surfaces 12 of both the first cooling copper plate 1 and the second cooling copper plate 2 interposed therebetween.
[0020]
FIGS. 6 (a) to 6 (c) and FIGS. 7 (a) to 7 (c) show corner portions of the continuous casting mold of the present invention shown in FIG. It is a horizontal cross-sectional schematic diagram in which the vicinity is enlarged. As shown in these figures, the insulator 3 or 4 of the mating surface may be arranged on the surface of either the cooling copper plate 1 or the cooling copper plate 2.
[0021]
In the mold of the present invention, as described above, in addition to interposing an insulator on the mating surface 12 of the cooling copper plate, a corner of a surface 17 (hereinafter, referred to as a casting surface) of the cooling copper plate that comes into contact with the molten metal. Place an insulator near the part. That is, in the mold of FIG. 3, the insulator 5 near the corner is provided on the casting surface of the first cooling copper plate 1. In the example shown in FIG. 4, an insulator 6 near the corner is provided on the casting surface of the second cooling copper plate 2. Further, in the example shown in FIG. 5, insulators 5, 6 near the corners are provided on the casting surfaces of the first and second cooling copper plates, respectively.
[0022]
6 (a) to 6 (c) and FIGS. 7 (a) to 7 (c) show, as described above, the mating surface with one of the mating surfaces 12 of the cooling copper plate. 3 shows the state of installation of the insulators 5 or 6 near the corners arranged on the casting surface of the cooling copper plate when the insulators 3 or 4 are provided.
[0023]
That is, FIGS. 6A to 6C show that the mating surface insulator 3 is provided on the mating surface of the first cooling copper plate 1, and FIG. 6A shows the first cooling copper plate 1. 6B shows the insulating material 5 near the corner on the casting surface of the copper plate 1, FIG. 6B shows the insulating material 6 near the corner on the casting surface of the second cooling copper plate 2, and FIG. And insulators 5 and 6 near the corners are provided on the casting surfaces of the second cooling copper plates 1 and 2, respectively. In the case of a continuous casting mold of a type in which the short side is moved (variable width type), it is preferable to make it as shown in FIG.
[0024]
The length of the contact portion between the insulator and the molten metal in the vicinity of the corner located near the corner of the casting surface, that is, the width W of the insulator, should be increased in order to ensure electrical insulation over a wide range. However, since many insulators generally have a lower thermal conductivity than a copper plate, it is necessary to consider the effect on solidification by providing the insulator on the casting surface of a cooled copper plate.
[0025]
In order to study this, as shown in the examples, the inventors constructed a water-cooled mold having a size of 1500 mm x 250 mm and a height of 800 mm from a copper plate having a thickness of 20 mm, and the back surface thereof. And a stainless steel back plate having a thickness of 50 mm was arranged thereon to form a mold as shown in FIG. As shown in FIG. 4, a zirconia-based ceramic is sprayed on the mating surface of the first cooling copper plate 1 to form an insulator having a thickness of 0.5 mm, a width of 20 mm, and a height of 800 mm. 3 was formed and electrically insulated.
[0026]
On the other hand, an alumina plate having a thickness of 1 mm × (width 20 mm (matching surface) + width W (mm) (insulator near the corner of the casting surface) × height 200 mm) is provided on the mating surface of the second cooling copper plate 2. The four sheets were vertically adhered to form insulators 4 and 6 having a total height of 800 mm and were electrically insulated, where W is the width of the insulator near the corner of the casting surface, and this width Was varied, but an alumina plate was prepared as an integrated width including the width of the mating surface and the width of the insulator near the corner, and bonded to a cooling copper plate.
[0027]
Using the thus-configured mold of the present invention, molten steel of S45C as molten metal is supplied to the mold, continuous casting is performed, the shell thickness of the corner at the lower end of the mold is measured by sulfur printing, and the solidification of the corner is performed. Delay rate = Minimum shell thickness (mm) at the lower end of the mold / Maximum shell thickness (mm) at the lower end of the mold × 100 (%). This was plotted against the width W (mm) of the insulator near the corner to obtain the relationship shown in FIG. As can be seen from FIG. 9, when the contact length of the insulator with the molten steel, that is, the width of the insulator exceeds 50 mm, the solidification delay rate at the corners increases, and the solidification shell exceeds the strength limit of 50%, which is considered to be the limit. . For this reason, the contact length of the insulator with the molten steel, that is, the width of the insulator disposed near the corner portion is set to 50 mm or less. For this reason, the insulator near the corner is placed within a range of 50 mm or less from the corner of the first and second cooling copper plates.
[0028]
The thickness t (mm) of the insulator is preferably about 0.5 to 1.00 mm from the same thermal viewpoint.
[0029]
As shown in FIG. 8, it is desirable that the insulator near the corner be provided over the entire height of the cooling copper plate of the mold in the vertical direction, similarly to the insulator on the mating surface.
[0030]
As a result, it is possible to prevent the adhesion of the deposits over a wide range due to the fluctuation of the molten metal level and the insulation from being deteriorated due to wear of the mating surface near the lower end. FIG. 8A shows an example in which the insulator 15 of the alumina plate is provided at the entire height near the corner of the first water-cooled copper plate 1, and FIG. 8B shows the spraying of alumina near the corner of the cooled copper plate 1. This is an example in which an insulator 16 is provided. 8A and 8B, a mating surface insulator is provided on the surface of the first cooling copper plate, and FIG. 8A shows an alumina plate insulator 15 'and FIG. 8B. Is an example in which an insulator 16 'for spraying alumina is provided.
[0031]
The insulating material near the mating surface and the corner may be an electrically insulating material having heat resistance, but an electrically insulating ceramic which has corrosion resistance to molten metal and also has excellent wear resistance. preferable. As such a ceramic, an alumina-based ceramic is preferable. In addition, in a portion that is not always in contact with the molten metal, for example, in an upper portion of the mold, a zirconia-based ceramic that withstands a rapid increase in temperature and has insulating properties is desirable.
[0032]
Therefore, the insulator on the mating surface may be a zirconia-based ceramic, and the insulator near the corner portion on the side (casting surface) in contact with the molten steel (a cast surface) may be an alumina-based ceramic insulator. Thereby, thermal shock to the alumina-based ceramic due to a large temperature difference between the molten steel and the cooled copper plate can be reduced.
[0033]
The insulator on the mating surface is formed by molding ceramic fibers such as mica plate, alumina, and zirconia into a plate of 0.1 to 1 mm in order to achieve both heat resistance and assembly accuracy. Teflon (registered trademark) ( PTFE: Polytetra Fluoroethylene ) and the like are preferred.
[0034]
The method of providing an insulator near the mating surface and the corner of the cooling copper plate is to bond an insulator, for example, a ceramic plate with an adhesive (ceramics or the like), a heat-resistant inorganic adhesive, or the like, or to use a ceramic powder. A method of forming a thermal sprayed layer on the surface of a copper plate by a thermal spraying method in which melt spraying is performed together with plasma or gas can be appropriately employed.
[0035]
As shown in the examples of FIGS. 3 to 5, 6 (a), 6 (c), 7 (b), and 7 (c), the mating surface and the corner portion are formed on the same cooling copper plate. In the case where an insulator is provided both in the vicinity and in the vicinity, it is needless to say that providing the insulator in the vicinity of the mating surface and the corner portion as a continuous and integral body is preferable in reducing the boundary between the insulators.
[0036]
It is also preferable that the insulator near the corner portion and the insulator on the mating surface be made of the same insulating material and provided by the same method. For example, an insulator provided on the mating surface of the first cooling copper plate and the second cooling copper plate and near the corner of the first cooling copper plate and / or near the corner of the second cooling copper plate is a single alumina plate. It is also preferable to provide an insulator by bonding them, or to form a sprayed layer in which the insulator is formed by thermal spraying once.
[0037]
The insulator near the corner and the insulator on the mating surface may be made of different insulating materials, and may be provided by different methods or may be provided by the same method. Similarly, the insulator near the corner and the insulator on the mating surface may be made of the same insulating material, and may be provided by different methods or may be provided by the same method.
[0038]
In the mold of the present invention, the method of cooling the cooling copper plate may be such that a cooling water passage is provided between the copper plate and the back plate as disclosed in JP-A-2000-246397, or a through-hole is formed in the copper plate. A well-known method, such as providing a cooling water passage by drilling a hole, can be employed.
[0039]
【Example】
A water-cooled mold with an internal size of 1500 mm x 250 mm and a height of 800 mm is made of a 20 mm thick copper plate, and a 50 mm thick non-magnetic stainless steel back plate is arranged on the back of the mold. Then, an electromagnetic coil was installed on the outer periphery of the mold. As shown in FIG. 4, zirconia ceramics are sprayed on the mating surface of the first cooling copper plate 1 to form an insulator 3 having a thickness of 0.5 mm × a width of 20 mm × a height of 800 mm, as shown in FIG. did.
[0040]
In addition, a thickness of 1 mm × (a width of 20 mm at the mating surface + a width (W) of 5 mm at the vicinity of the corner portion) × height near the mating surface of the second cooling copper plate 2 and near the corner of the second cooling copper plate 2. Four 200 mm-thick alumina plates were attached in the height direction to form insulators 4 and 6 having a total height of 800 mm. The alumina plate was attached as an integral plate having a width obtained by adding the width of the mating surface and the width near the corner.
[0041]
Using the thus-configured mold of the present invention, molten steel of S45C as a molten metal was supplied to the mold, and continuous casting was performed while supplying an alternating current of 100 Hz to the electromagnetic coil 9.
[0042]
For comparison, the same casting was performed using a mold in the vicinity of the corner portion where no insulator was provided.
[0043]
After completion of casting, the coil was energized, the magnetic field strength was measured at the center of the coil in the vertical direction, and at the center of the mold width and thickness, and the magnetic field strength at each time point and the magnetic field strength in the initial state were measured. The relative magnetic field strength was investigated. The result is shown in FIG.
[0044]
As can be seen from FIG. 10, when the conventional mold was used, the relative magnetic field strength decreased with the elapse of the casting time, whereas when the mold of the present invention was used, the casting time was reduced to 100 hours. Even if it exceeds, there is no decrease in the relative magnetic field, and it can be seen that the insulating property is sufficiently secured as in the initial stage.
[0045]
【The invention's effect】
The continuous casting mold of the present invention, when continuously casting the molten metal by applying an electromagnetic force, wear of the mating surface due to repeated use of the mold, adhesion of the molten metal splash near the corner of the mold, etc. of the mold It is possible to prevent the lowering of the insulation near the mating surface of the cooling copper plate and the corner of the mold, and to stably secure the insulation of the mold even during long-term use of the mold, and to obtain a high quality slab for a long time. .
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of assembling a continuous casting mold according to the present invention.
FIG. 2 is a schematic horizontal sectional view of the continuous casting mold of the present invention.
FIG. 3 is a schematic partial horizontal cross-sectional view showing the arrangement of insulators in the vicinity of a corner (part A) of the continuous casting mold of the present invention.
FIG. 4 is a partial horizontal cross-sectional schematic view showing another arrangement state of the insulator near the corner portion (A portion) of the continuous casting mold of the present invention.
FIG. 5 is a partial horizontal cross-sectional schematic view showing another arrangement state of the insulator near the corner portion (A portion) of the continuous casting mold of the present invention.
6A and 6B are partial horizontal cross-sectional schematic views showing the arrangement of insulators near corners (part A) of the continuous casting mold of the present invention. FIG. (b) shows a situation where an insulator is placed on the other copper plate near the corner, and (c) shows a situation where insulators are placed on both copper plates near the corner.
FIGS. 7A and 7B are partial horizontal cross-sectional schematic views showing the arrangement of insulators near corners (A) of the continuous casting mold of the present invention. FIG. (b) shows a situation where an insulator is placed on the other copper plate near the corner, and (c) shows a situation where insulators are placed on both copper plates near the corner.
FIG. 8 is a partial vertical cross-sectional schematic view showing an arrangement state of an insulator near a corner of the continuous casting mold of the present invention, and FIG. 8A is an arrangement state of an insulator near the corner by attaching an alumina plate; (B) shows the arrangement of insulators in the vicinity of the corners formed by spraying alumina.
FIG. 9 is a diagram showing the relationship between the width of the insulator near the corner and the rate of solidification delay in the corner of the continuous casting mold of the present invention.
FIG. 10 is a diagram showing the relationship between casting time and relative magnetic field strength in the continuous casting mold of the present invention.
FIG. 11 is a partial horizontal cross-sectional schematic view showing the state of attachment of deposits to a mold wall in a conventional mold.
FIG. 12 is a horizontal sectional view of a conventional continuous casting mold.
FIG. 13 is a horizontal sectional view of a conventional continuous casting mold.
FIG. 14 is a conceptual diagram showing a continuous casting technique for applying an electromagnetic force.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... 1st cooling copper plate 2 ... 2nd cooling copper plate 3 ... Insulator of the joining surface of 1st cooling copper plate 4 ... Insulator of the joining surface of 2nd cooling copper plate 5 ... Corner part of 1st cooling copper plate Insulator 6 near the insulator 7 near the corner of the second cooling copper plate 7 First back plate 8 Second back plate 9 Electromagnetic coil 10 Insulation washer 11 Insulation sleeve 12 Matching the cooling copper plate Surface 13 Gap 14 Fastening bolts 15 and 15 'Ceramic plates 16 and 16' Ceramic sprayed layer 17 Casting surface 31 Mold 32 Melted metal 33 Meniscus 34 Powder 35 Current coil 36 Slit 37 Segment 38 immersion nozzle 39 first cooling copper plate 40 second cooling copper plate 41 first back plate 42 second back plate 43 cooling water passage 44 fastening bolt 45 insulation tightening Bolt 46 ... insulator 47 ... sealing material 48 ... mating face 49 ... the casting surface

Claims (6)

In a continuous casting apparatus having an electromagnetic coil, a pair of first cooling copper sheets of a continuous casting mold are sandwiched between a pair of second cooling copper sheets, and a pair of first bags combined with the first cooling copper sheets. A plate and a pair of second back plates combined with the second cooling copper plate are electrically insulated from each other via an insulator, and the first cooling copper plate and the second cooling copper plate The mating surfaces are electrically insulated from each other via insulators of the mating surfaces, and are formed by forming the pair of first cooling copper plates between the pair of second cooling copper plates. An insulator near the corner is provided on a casting surface in a range from more than 0 to 50 mm or less from the surface side corner along the casting surface of the first cooling copper sheet and / or the second cooling copper sheet . A continuous casting mold, characterized in that: In the mating surface of the first cooling copper plate and the second cooling copper plate, an insulator of the mating surface is arranged on one or both of the first cooling copper plate and the second cooling copper plate. The continuous casting mold according to claim 1, wherein: 3. The insulator according to claim 1, wherein the insulator on the mating surface and the insulator near the corner portion are an electrically insulating ceramic plate and / or an electrically insulating ceramic formed by thermal spraying. 4. Continuous casting mold. The mold for continuous casting according to any one of claims 1 to 3, wherein the insulator on the mating surface and the insulator near the corner portion are alumina-based ceramics and / or zirconia-based ceramics. . The continuous casting mold according to any one of claims 1 to 4, wherein the insulator near the corner portion is an alumina-based ceramic, and the insulator on the mating surface is zirconia-based ceramics. 3. The continuous casting mold according to claim 1, wherein the insulator on the mating surface is at least one of a mica plate, a ceramic fiber molded body, and PTFE . 4.

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