JP4990517B2 - Continuous casting mold - Google Patents

Description

  The present invention relates to a continuous casting mold provided with an electromagnetic stirring device for electromagnetically stirring molten steel in a mold.

  The molten steel refined in the converter or vacuum processing furnace contains a large amount of dissolved oxygen, and excess oxygen is deoxidized by aluminum, which is a strong deoxidizing element. However, aluminum produces alumina inclusions by deoxidation and aggregates and forms coarse alumina clusters. This alumina cluster causes surface flaws during the production of the steel sheet and greatly deteriorates the surface quality of the thin steel sheet. In particular, low carbon steel, which is a material for thin steel sheets with low carbon concentration and high dissolved oxygen after refining, has a large amount of alumina clusters, a high rate of surface flaws, and measures to reduce alumina inclusions are a major issue. It has become. On the other hand, a method of electromagnetically stirring the molten steel in the mold is known to agglomerate and float the alumina inclusions in the mold, reduce the inclusions in the molten steel, and obtain a slab with excellent surface quality. . In Patent Document 1, a cooling wall is stretched on the molten steel side outer surface of the cooling box, a water supply chamber for supplying cooling water to the cooling water groove provided on the cooling wall, and cooling water from the cooling groove is drained. In the continuous casting apparatus in which the cooling box is provided with a draining chamber for storing and a storage chamber for storing the electromagnetic stirring device, the storage chamber is provided above the cooling box, and the drainage chamber is provided below the storage chamber. A continuous casting mold has been proposed in which a frame in contact with the cooling wall of the cooling box is provided with a drain groove having one end communicating with the cooling groove and the other end communicating with the drain chamber.

Patent Document 2 discloses a technique for easily removing only a copper plate fixing plate and a copper plate inside a mold equipped with an electromagnetic stirring device into a cassette type. By adopting this cassette mold, the time for replacing the copper plate can be greatly reduced, spare parts for the cooling box are not required, and the equipment cost can be greatly reduced.
Japanese Utility Model Publication No.59-49172 JP 2005-052840 A

  However, when the cassette type mold disclosed in Patent Document 2 is equipped with an electromagnetic stirrer, an induced current flows through the joint surface between the copper plate fixing plate and the cooling box due to the influence of the moving magnetic field. In addition, there is a problem in that the induced current is concentrated in unspecified local areas due to variations in the fastening force of the fastening bolts between the copper plate fixing plate and the cooling box and unevenness of the joint surface, and local heat is generated. Moreover, if it occurs at a site where the cooling is difficult, this local heat generation exceeds 200 ° C., and the sealing member attached to the joint surface between the copper plate fixing plate and the cooling box is melted down, resulting in failure of the electromagnetic stirring device. Lead to accidents.

  In view of the above problems, the present invention accommodates an electromagnetic stirrer in a cooling box, stretches a cooling wall composed of a copper plate fixing plate and a copper plate on the molten steel side of the cooling box, and lowers the cooling box In a continuous casting mold with a water supply header that supplies cooling water to the cooling wall and a drain header that drains the cooling water after water supply, induced current flowing through the joint surface between the copper plate fixing plate and the cooling box is prevented. An object of the present invention is to suppress local heat generation at the joint surface, suppress damage to the seal member, and prevent failure of the electromagnetic stirring device.

In order to solve the above problems, a continuous casting mold according to the present invention houses an electromagnetic stirrer in a cooling box, and stretches a cooling wall composed of a copper plate fixing plate and a copper plate on the molten steel side of the cooling box, In a continuous casting mold provided with a water supply header for supplying cooling water to a cooling wall and a drainage header for discharging cooling water after water supply at the lower part of the cooling box, between the upper surface of the copper plate and the upper surface of the copper plate fixing plate Before the insulator is attached to the joint surface between the copper plate fixing plate and the cooling box, the insulator is attached to the joint surface coated with an insulating seal adhesive, and the joint surface between the copper plate fixing plate and the cooling box is fastened. by bolts to mounting an insulating washer that, except for the engagement portion, is attached an insulator under the neck of the bolt, a distance from the copper plate upper surface and the distance h1 from the copper plate fixed plate top surface to the molten steel top surface to the molten steel top surface 2 and there is the copper plate so that h1> h2, characterized in that it is stretched in the copper plate fixed plate.

  The insulating paper desirably has a performance of 5.0 kV / mm or more in terms of dielectric breakdown voltage (test method: ASTM D-149).

  Moreover, it is preferable that the insulator attached to the joint surface between the copper plate fixing plate and the cooling box is an insulating paper having a thickness of 0.01 mm or more and 0.2 mm or less.

  In a mold with an electromagnetic stirrer attached to a conventional cassette mold, the induced current is concentrated in unspecified local areas due to variations in the fastening force of the fastening bolts between the copper plate fixing plate and the cooling box or the unevenness of the joint surface. However, there was a problem that caused local heat generation. Also, if it occurs in a part where cooling is difficult, this local heat generation exceeds 200 ° C., and the sealing member attached to the joint surface between the copper plate fixing plate and the cooling box is melted down, causing a failure of the electromagnetic stirring device, etc. Leading to an accident. According to the present invention, it is possible to prevent an induced current in the joint surface between the copper plate fixing plate and the cooling box and to prevent the electromagnetic stirrer from being damaged.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  1 is an overall view of a mold of an embodiment of a continuous casting mold according to the present invention, FIG. 2 is a view taken along the line AA in FIG. 1, FIG. 3 is a detailed view of a portion B in FIG. It is a figure which shows the insulator mounting part of a plate.

  In the mold according to the present invention, a copper plate fixing plate 10 is stretched on the molten steel 22 side of the front plate 8 of the cooling box 1 with bolts 6, 7, 9, and a copper plate 11 is stretched on the copper plate fixing plate 10. Yes. The front plate 8 is welded and fixed to the long-side cooling box 1 and is configured as one member of the cooling box 1, and an electromagnetic stirring device including a coil 2 and a core 3 is accommodated in the cooling box 1. Yes.

  An opening 16 is provided in the front plate 8 so that the tip of the core 3 constituting the electromagnetic stirring device approaches the molten steel 22, and the tip of the core 3 is disposed through the opening 16.

  The front end proximity portion of the core 3 of the copper plate fixing plate 10 has a concave portion 15 formed in the copper plate fixing plate 10. By providing the concave portion 15, the front end of the core 3 can be brought close to the molten steel 22.

  In the present invention, in order to provide the electromagnetic stirring device on the upper part of the mold, the drainage header 4 of the mold cooling water, which is conventionally provided on the upper part of the mold, is provided at the lower part of the cooling box, and at one end of the copper plate fixing plate 10. However, the mold cooling water is drained from the copper plate cooling slit 13 by providing the drain hole 12 communicating with the copper plate cooling slit 13 and the drain header 4 at the other end. The mold cooling water is supplied from the water supply header 5 through the water absorption holes 17.

  In the mold of the present invention, the upper surface of the front plate 8 and the upper surface of the copper plate fixing plate 10 are set to coincide with each other, and the upper surface of the copper plate fixing plate 10 is set to a height h1 from the molten steel upper surface 14. Further, the copper plate 11 stretched on the copper plate fixing plate 10 has a height h <b> 2 from the molten steel upper surface 14. In general, in a casting mold for continuous casting, a copper plate 11 is stretched to increase the cooling effect by passing cooling water for the purpose of cooling and solidifying molten steel injected into the mold. The copper plate 11 is generally stretched over the entire front plate. Further, the copper plate fixing plate 10 to which the copper plate 11 is fastened is fastened by bolts to the front plate 8 of the cooling box 1 that houses the electromagnetic stirring device.

  As a method for attaching the copper plate fixing plate 10, either a flange portion for attaching the bolt is provided, or a bolt portion is attached from the back of the cooling box to eliminate the flange portion. When a bolt is installed in a cooling box in a mold equipped with an electromagnetic stirrer, it is necessary to remove the magnetic stirrer in the cooling box for maintenance, open the space, remove the bolt, and maintenance time is required. . When a bolt is provided with a flange portion, a space corresponding to the thickness of the flange is required on the upper surface of the cooling box. In the present invention, in consideration of maintenance, the distance from the upper surface of the copper plate fixing plate 10 to the molten steel upper surface 14 is h1, and the space for mounting the mounting bolt 9 is secured. The copper plate 11 stretched on the front surface is stretched on the copper plate fixing plate 10 so as to be h2 from the molten steel upper surface 14.

  Moreover, in this invention, in order to make the distance h1 from the molten steel upper surface 14 to the upper surface of the copper plate fixing plate 10 as low as possible, the mounting bolt 9 for fixing the copper plate fixing plate 10 and the front plate 8 was attached from the molten steel surface side. Is.

  In the mounting portion shown in FIG. 3 (detailed portion B in FIG. 1), when the cassette type mold is equipped with an electromagnetic stirring device, the copper plate fixing plate 10 and the front plate 8 of the cooling box 1 are joined by the influence of the moving magnetic field. An induced current flows through the surface. And the influence of the fastening force 9 of the fastening bolt 9 between the copper plate fixing plate 10 and the front plate 8 of the cooling box 1 and the unevenness of the joint surface causes the induced current to concentrate in unspecified local areas, and generate local heat. There was a problem that occurred. When this heat generation occurs at a site where cooling is difficult, the local heat generation exceeds 200 ° C., and the sealing member 21 attached to the joint surface between the copper plate fixing plate 10 and the front plate 8 of the cooling box 1 is melted. This can lead to accidents such as causing a failure of the electromagnetic stirring device.

  Since local heat is generated when the induced current flows locally on the joint surface between the copper plate fixing plate 10 and the front plate 8 of the cooling box 1, electric current is generated on the joint surface around the electromagnetic stirrer where the induced current easily occurs. Insulating current is cut off by installing an insulator capable of static insulation. In the embodiment shown in FIG. 3, an insulator 19b having a thickness of 0.05 mm and a dielectric breakdown voltage of 20 kV / mm is attached to the joint surface between the copper plate fixing plate 10 and the front plate 8 of the cooling box 1. In addition, since an induced current flows through the mounting bolt 9 of the copper plate fixing plate 10, it is necessary to block the induced current around the mounting bolt 9. Therefore, an insulating washer 19 a is attached to the seating surface of the mounting bolt 9. The insulating washer 19a is a glass base laminated insulating plate manufactured by impregnating a mat-like glass fiber with a resin admixture and heating and pressing, and has a penetration breakdown voltage of 20 to 30 kV / mm. Further, the copper plate fixing plate mounting bolt 9 is provided with an insulator 18 below the neck of the bolt except for the threaded portion. In the embodiment shown in FIG. 3, three sheets of insulating paper having a thickness of 0.25 mm and a dielectric breakdown voltage of 20 kV / mm are mounted.

  In order to improve the affixing operation of the insulator, a liquid insulating sealant is applied on the joint surface between the copper plate fixing plate 10 and the front plate 8 of the cooling box 1 for the purpose of bonding the insulator 19b, and then the insulator 19b is affixed. It is desirable to attach. In the embodiment shown in FIG. 3, a silicone adhesive sealant having a dielectric breakdown voltage of 23 kV / mm is used as the liquid insulating sealant. Further, the copper plate fixing plate mounting bolt 9 is provided with an insulator 18 under the bolt neck except for the screwing portion. In order to improve the attaching operation of the insulator, in the embodiment shown in FIG. A Kapton film insulating tape coated with a silicone-based adhesive having a thickness of 0.012 mm and a breakdown voltage of 5 kV / mm is wound twice.

  Since local heat is generated when the induced current flows locally on the joint surface between the copper plate fixing plate 10 and the front plate 8 of the cooling box 1, electric current is generated on the joint surface around the electromagnetic stirrer where the induced current easily occurs. Insulating current is cut off by installing an insulator capable of static insulation. As the insulation performance of the insulator, it was confirmed by experiments that local heat generation can be prevented if the insulation breakdown voltage (test method: ASTM D-149) has an insulation performance of 5 kV / mm or more.

  In FIG. 3, when the insulator 19b capable of electrical insulation is attached to the joint surface between the copper plate fixing plate 10 and the front plate 8 of the cooling box 1, the insulator is used when the insulator is attached to the entire joint surface. The effect of the thickness is small. However, as shown in FIG. 4, at least the upper surface of the copper plate fixing plate 10 from the upper surface of the copper plate 11, which is difficult to be cooled by cooling water, among the joint surfaces of the front plate 8 between the copper plate fixing plate 10 and the cooling box 1. In the case where the insulator 19b is mounted on the joint surface between them, it is desirable that the thickness of the insulator 19b be 0.2 mm or less so that the thickness of the insulator 19b does not affect the attachment accuracy of the joint surface. The lower limit of the thickness of the insulator is not a problem as long as it satisfies the above insulation performance, but is preferably 0.01 mm or more in consideration of mechanical strength.

  In a mold with an electromagnetic stirrer attached to a conventional cassette mold, induced current is concentrated in unspecified local areas due to variations in the fastening force of the fastening bolts between the copper plate fixing plate and the cooling box or unevenness of the joint surface. However, there was a problem that caused local heat generation. Also, if it occurs in a part where cooling is difficult, this local heat generation exceeds 200 ° C., and the sealing member attached to the joint surface between the copper plate fixing plate and the cooling box is melted down, causing a failure of the electromagnetic stirring device, etc. Leading to an accident. According to the present invention, it is possible to prevent an induced current in the joint surface between the copper plate fixing plate and the cooling box and to prevent the electromagnetic stirrer from being damaged.

1 is an overall view of an embodiment of a continuous casting mold according to the present invention. It is an AA arrow line view of FIG. It is the B section detailed drawing of FIG. It is a figure which shows the insulator mounting part of a copper plate fixing plate.

Explanation of symbols

1: Cooling box 2: Coil 3: Core 4: Drain header for mold cooling 5: Water supply header for mold cooling 6, 7: Bolt for fixing copper plate fixing plate 8: Front plate 9: Bolt for fixing copper plate fixing plate 10: Copper plate Fixed plate 11: Copper plate 12: Drain hole 13: Copper plate cooling slit 14: Molten steel upper surface 15: Copper plate fixed plate recess 16: Front plate opening 17: Water supply hole 18: Insulator 19a: Insulating washer 19b: Insulator 20: Flat Washer + spring washer 21: seal member 22: molten steel h1: distance from the upper surface of the copper plate fixing plate to the molten steel surface h2: distance from the upper surface of the copper plate to the molten steel surface

Claims (3)

A water supply header that houses an electromagnetic stirrer in the cooling box, stretches a cooling wall composed of a copper plate fixing plate and a copper plate on the molten steel side of the cooling box, and supplies cooling water to the cooling wall below the cooling box; In a continuous casting mold provided with a drain header for draining cooling water after water supply,
The insulator is attached to the joining surface to which an insulating seal adhesive is applied before attaching the insulator to the joining surface of the copper plate fixing plate and the cooling box between the upper surface of the copper plate and the upper surface of the copper plate fixing plate,
An insulating washer is attached to the bolt that fastens the joining surface of the copper plate fixing plate and the cooling box, and an insulator is attached below the neck of the bolt, except for the threaded portion .
The copper plate is stretched over the copper plate fixing plate such that a distance h1 from the upper surface of the copper plate fixing plate to the upper surface of the molten steel and a distance h2 from the upper surface of the copper plate to the upper surface of the molten steel satisfy h1> h2. Continuous casting mold. The mold for continuous casting according to claim 1, wherein the insulator has a performance of 5.0 kV / mm or more at a dielectric breakdown voltage (test method: ASTM D-149) . 3. The continuous casting mold according to claim 1 , wherein the insulator to be attached to the joining surface of the copper plate fixing plate and the cooling box is an insulating paper having a thickness of 0.01 mm or more and 0.2 mm or less. .

Images