JPH05212501A - Thin plate continuous casting method and apparatus - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a twin-roll continuous casting method and apparatus for continuously casting thin-plate slabs by twin-roll continuous casting, which casts thin-plate slabs with good surface properties by using an electromagnetic sealing method. With the goal. [Structure] An open / close type cold crucible whose four walls are composed of conductive segments is placed on the mold to form a molten pool container, and the horizontal lower ends of the pair of opposing walls are located directly above the outer peripheral surface of the cooling roll. In addition, the cold crucible is held so that the other pair of opposing wall parts are positioned as side dams near the end surface of the cooling roll, and the molten metal pool in the container is generated by the electromagnetic field generated by the induction coil provided on the outer periphery of the cold crucible. The dome shape is maintained so that the molten metal pool and the cold crucible wall are controlled by controlling the electromagnetic field so that the molten metal and the cold crucible wall are in non-contact state except for soft contact near the horizontal lower end. Configure to maintain.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention continuously casts a thin plate slab having a thickness of several mm suitable for direct cold rolling from a cast state without hot rolling by a twin roll continuous casting method. A method and an apparatus for its implementation.

[0002]

2. Description of the Related Art Thin plate slabs have a relatively low workability up to the final product, and the surface quality of the slab strongly affects the surface quality of the product, so it is extremely important to cast a slab with good surface properties. Is. In the twin roll continuous casting method, a molten metal is poured into a continuous casting mold composed of a pair of cooling rolls and side dams arranged on both end faces of the cooling roll, and the molten metal in a pool (molten pool) formed in the mold Are cooled by coming into contact with the outer peripheral surface of each cooling roll to form a pair of solidified shells, and the solidified shells that have moved downward by the rotation of both cooling rolls coalesce near the closest position (kissing point) of the cooling rolls and become thin. It is delivered downward as a strip-shaped cast piece.

In order to improve the surface quality of the cast slab, it is necessary to prevent the scum floating on the pool surface from being caught, and to eliminate the influence of the corrugation of the pool molten metal surface, thereby making contact lines between the molten metal surface and the outer peripheral surface of the cooling roll. Need to be stabilized. As a method, in order to apply a large molten metal static pressure to the solidified shell, a container for the molten metal pool is additionally provided on the mold formed by the cooling roll and the side weir, and under-surface solidification that forms a deep molten metal pool. The law is being developed. This is effective for the above problem, but another problem that the container leaks from the contact portion between the roll and the roll, or if the container is pressed against the roll to prevent this leak, the container wears. Occurs.

As a countermeasure, an electromagnetic sealing method has been proposed in which the molten metal pool is held by electromagnetic force. But,
In the above-mentioned conventional electromagnetic sealing method, since a refractory material is used as a container for the molten metal pool, there is a problem that the molten metal is contaminated or the refractory material is worn (Japanese Patent Laid-Open No. 63-80945), or the current-carrying pipe and the molten metal. Since a high potential difference causes a spark when they contact with each other, it is necessary to use a refractory for insulation, and there is the same problem as described above (Japanese Patent Laid-Open No. 63-80944).

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks of the conventional electromagnetic sealing method, and provides a twin roll continuous casting method for casting a thin plate slab having good surface properties, and an apparatus for carrying out the method. The purpose is to do.

[0006]

In order to achieve the above object, the thin plate continuous casting method of the present invention is a continuous casting mold in which side dams are arranged at both end faces of a pair of cooling rolls arranged horizontally and in parallel. In the thin plate continuous casting method which comprises, a plurality of conductive segments are arranged with an insulating zone sandwiched between them, and an upper and lower open type cold crucible that constitutes the four-sided wall portion is arranged on the mold, and from above the mold inside. The cold crucible is used as a container for maintaining the molten metal pool, and the horizontal lower ends of a pair of opposing wall portions are located directly above the outer peripheral surface of the cooling roll and the other pair of opposing wall portions serve as the side weirs. The molten metal pool in the container is held by an electromagnetic field generated by an induction coil which is held near the end surface of the cooling roll and is arranged on the outer periphery of the cold crucible. By holding the molten metal surface in a dome shape and controlling the electromagnetic field of the induction coil, the molten metal pool and the cold crucible wall portion make soft contact with substantially no electrical conduction near the horizontal lower end. Other than that, it is characterized by maintaining the shape of the molten metal dome so as to be in a non-contact state.

The thin plate continuous casting apparatus for carrying out the method of the present invention is a thin plate continuous casting apparatus in which a side dam is arranged on both end surfaces of a pair of cooling rolls arranged horizontally and in parallel to form a continuous casting mold. Arranged on the mold as a container for maintaining a molten metal pool extending upward from the inside of the mold, a plurality of conductive segments are arranged across an insulating zone to form a four-sided open cold Crucible, the cold crucible, so that the horizontal lower ends of the pair of opposing wall portions are located directly above the cooling roll outer peripheral surface and the other pair of opposing wall portions are located near the cooling roll end surface as the side dams. Cold crucible holding means for holding, electromagnetic for holding the molten metal pool in the container in a dome shape by the electromagnetic force induced inside the pool In order to generate, the induction coil arranged on the outer periphery of the cold crucible, the metal melt pool and the cold crucible wall portion are in non-contact except that they make a soft contact with substantially no electrical conduction near the horizontal lower end. An electromagnetic field control device for controlling the electromagnetic field of the induction coil is provided so as to maintain the shape of the molten metal dome.

[0008]

In the present invention, as a container for maintaining the molten metal pool extending from the inside of the mold to the upper part, a plurality of conductive segments are arranged with an insulating zone in between to form a four-sided open type cold cold box. By providing the crucible inside the induction coil, the structure was such that the coil and the molten metal did not come into direct contact with each other, and sparks due to a high potential difference were prevented.

The arrangement of the cold crucible and the cooling roll is such that the horizontal lower ends of the pair of opposing walls of the cold crucible are located directly above the outer peripheral surface of the cooling roll and the other pair of opposing walls serve as the side dams. After placing the cooling roll close to the end face (that is, the cold crucible and the cooling roll are not in contact with each other), the electromagnetic field generated by the induction coil arranged on the outer circumference of the cold crucible causes the inside of the container (cold crucible) to move. By inducing electromagnetic force inside the molten metal pool to hold the molten metal in a dome shape and controlling the electromagnetic field of the induction coil, the molten metal pool and the cold crucible wall part are located near the horizontal lower end. Maintain the dome shape on the surface of the molten metal so that it is in a non-contact state except that it makes a soft contact with virtually no electrical conduction. . Here, “soft contact” means that electrical conduction between the molten pool and the cold crucible wall surface is not substantially observed, but the bottom edge of the surface dome is mechanically held by the cold crucible wall surface and The contact state is such that solidified shells do not form.

The molten metal in the vicinity of the molten metal surface is subjected to electromagnetic force and self-magnetic force even in a small gap between the horizontal lower end and the outer peripheral surface of the cooling roll, which is held just above the outer peripheral surface of the cooling roll below the soft contact position with the cold crucible wall surface. It is retained without leaking due to the surface tension of. Further, the cold crucible wall portion, which is held in the immediate vicinity of the end surface of the cooling roll and acts as a side dam, is held in a non-contact state by the electromagnetic force and does not leak.

As a result, the scum of the molten metal surface is not entrained, and the influence of the waviness of the molten metal surface is eliminated by the soft contact portion, and the contact line between the molten metal surface and the outer peripheral surface of the cooling roll can be stabilized. Further, as described above, since it is not necessary to use a refractory material in the present invention, its wear or contamination of the molten metal does not occur. Hereinafter, the present invention will be described in more detail by way of examples with reference to the accompanying drawings.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1, FIG. 2 and FIG. 3 show the external appearance of the main part of a thin plate continuous casting apparatus according to the present invention as seen obliquely from above, the direction of the end surface of a cooling roll and one cooling roll side.
A vertically open cold crucible 1 is arranged above the mold space between a pair of cooling rolls 2 arranged horizontally and in parallel, and is used as a container for maintaining a molten metal pool 3 extending upward from the inside of the mold. ..

The induction coil 4 is a cold crucible 1
Are arranged around the outer periphery of the. The induction coil 4 is
Although the cold crucible wall portion 1A located above the outer peripheral surface 2A of the cooling roll 2 is substantially horizontal,
A portion of the side dam 2B is bent downward by a few turns so that the electromagnetic field effectively acts on the deepest part of the molten metal pool 3 on the side dam 1B side.

As shown in FIG. 4, due to the electromagnetic field generated by the induction coil 4, the cold crucible walls 1A, 1
An electromagnetic force F in the direction of pushing away from B is induced in the molten metal pool 3, and the metal molten metal pool 3 in the container 1 is held with its molten metal surface 3A in a dome shape. The induction coil 4 preferably has an output suitable for supplementarily heating the molten metal pool 3.

Molten metal is supplied from the tundish 11 through the injection nozzle 12 to form a molten metal pool 3 extending from the mold space between the chill rolls 2 into the cold crucible 1 above it. The molten metal in the pool 3 is cooled at the portion in contact with the outer peripheral surface 2A of each cooling roll 2 to form a pair of solidified shells 10 ', which are united at the closest position (kissing point) 2X of the cooling roll 2 to obtain a thickness. It is delivered downward as a strip-shaped thin plate slab 10 of several mm.

FIG. 5 shows a state in which parts of the four wall portions 1A and 1B constituting the cold crucible 1 are cut along a horizontal plane. The walls 1A and 1B are formed by arranging a plurality of conductive segments 1P with the insulating band 1Q interposed therebetween. Each conductive segment 1P is made of copper or copper alloy,
A cooling water passage 1R is provided inside. The insulating zone 1Q may be made of a refractory insulating material or may be a void.

In the cold crucible 1, the horizontal lower ends 1e of the pair of opposing wall portions 1A are located immediately above the outer peripheral surface 2A of the cooling roll 2 (FIG. 6), and the other pair of opposing wall portions 1B serve as side weirs. It is held by a holding means (not shown) so as to be positioned immediately near the end face 2B (FIG. 7).
Distance d between the outer peripheral surface 2A of the cooling roll and the lower end 1e of the wall 1A
Is set within a range where hot water leakage at this portion can be prevented by electromagnetic force. Usually, this distance d is within several mm, preferably within 1 mm, and most preferably within 0.5 mm.

The electromagnetic field of the induction coil 4 is controlled by a control device (not shown) so that the molten metal pool 3 and the cold crucible walls 1A and 1B have substantially no electrical conduction in the region 3B near the horizontal lower end 1e. The shape of the molten metal surface dome 3A is maintained so as to be in a non-contact state except for soft contact. A specific example will be described below. The casting conditions are as follows. (A) Casting machine-Roll diameter: 400 mm-Roll width: 350 mm-Roll material: Copper (b) Pool container conditions-Cold crucible Roll radial width: 350 mm Height: 1 mm from the top of the roll: 200 mm from the upper position Side height S: Roll closest position ・ Induction coil 10 turns In the cold crucible height, evenly spaced from the upper end to the lower end (equally spaced from the top of the cold crucible to the closest roll position) (c) Operating condition・ Casting speed: 20 to 100 m / min ・ Deepest pool depth: 150 to 160 from the roll top end
mm ・ Input to coil: 1 kHz frequency Adjust so that the magnetic flux density at the uppermost end of the roll is 0.17 Tesla. (d) Cast alloy Fe-50 wt% Cu alloy Casting under these conditions and leakage of molten metal Without
A slab with good surface properties was obtained.

[0019]

According to the present invention, a cold crucible held in a non-contact state with a cooling roll is used as a container for the molten metal pool, and the electromagnetic force generated by an induction coil arranged on the outer periphery of the cold crucible softens the cold crucible and the molten metal pool. By maintaining non-contact in areas other than the contact area, it is possible to prevent the occurrence of sparks due to direct contact between the molten metal and the coil, and to prevent contamination of molten metal and refractory materials that cannot be avoided by conventional methods that require the use of refractory materials. It is possible to stably cast a thin plate slab having good surface properties without causing any wear and without causing scum on the pool hot water surface and roughening the surface of the slab due to waviness of the pool hot water surface.

[Brief description of drawings]

FIG. 1 is a perspective view of a thin plate continuous casting apparatus of the present invention as seen obliquely from above.

FIG. 2 is a front view of the device of FIG. 1 viewed from the end surface side of a cooling roll.

FIG. 3 is a side view of the apparatus shown in FIG. 1 viewed from one cooling roll side.

FIG. 4 is a vertical cross-sectional view of the vicinity of the central portion of the cooling roll body length of the apparatus of FIG.

5 is a partial cross-sectional view of a cold crucible wall used in the device of FIG.

6 is a cross-sectional view showing the profile of the molten metal pool surface near the lower end of the cold crucible wall portion held just above the outer peripheral surface of the cooling roll of the apparatus of FIG. 1;

7 is a cross-sectional view showing the relationship between a cold crucible wall surface that is held near the end surface of the cooling roll of the apparatus of FIG. 1 and functions as a side weir, and the molten metal pool molten metal surface.

[Explanation of symbols]

1 ... Cold crucible (molten metal container) 1A ... Cold crucible wall portion located directly above the outer peripheral surface 2A of the cooling roll 2 1B ... Cold crucible wall portion located immediately adjacent to the end surface 2B of the cooling roll 2 1P ... Wall of the cold crucible 1 Conductive segments 1Q forming parts 1A and 1B ... Insulation zones of walls 1A and 1B of cold crucible 1R ... Cooling water flow path 1e ... Lower ends of cold crucible wall 1A ... Pairs of cooling rolls 2A ... Outer periphery of cooling roll 2 Surface 2B ... End surface of cooling roll 2 ... Molten pool 3A ... Molten pool 3 molten surface 3B ... Region where the molten metal surface 3A makes soft contact with the vicinity of the lower end 1e of the cold crucible wall 1A 4 ... Induction coil 10 ... Strip-shaped thin plate casting Piece 10 '... Solidified shell 11 ... Tundish 12 ... Injection nozzle

Claims (2)

[Claims] 1. A thin plate continuous casting method in which side weirs are arranged on both end surfaces of a pair of cooling rolls arranged horizontally and in parallel to form a continuous casting mold, wherein a plurality of conductive segments are arranged with an insulating zone interposed therebetween. The upper and lower open type cold crucibles constituting the four wall parts are arranged on the mold and used as a container for maintaining the molten metal pool extending from the inside of the mold to the upper side. The horizontal lower end of the section was positioned directly above the outer peripheral surface of the cooling roll, and the other pair of opposing wall parts were held so as to be positioned near the end surface of the cooling roll as the side dams, and were arranged on the outer periphery of the cold crucible. The electromagnetic field generated by the induction coil controls the electromagnetic field of the induction coil by holding the molten metal pool in the container with its molten metal surface in a dome shape. According to, the molten metal pool and the cold crucible wall portion maintain a molten metal dome shape so as to be in a non-contact state except for a soft contact with substantially no electrical conduction near the horizontal lower end. A method for continuously casting thin plates. 2. A thin plate continuous casting apparatus in which a side weir is arranged on both end faces of a pair of cooling rolls arranged horizontally and in parallel to form a continuous casting mold, in which a molten metal pool extending from the inside of the mold to an upper part is maintained. An upper and lower open type cold crucible in which a plurality of conductive segments are arranged on both sides of an insulating zone to form a wall on four sides as a container for Cold crucible holding means for holding so that the horizontal lower end is located directly above the outer peripheral surface of the cooling roll and the other pair of opposing wall parts are located near the end surface of the cooling roll as the side weirs, the molten metal in the container In order to generate an electromagnetic field that holds the pool surface in a dome shape by the electromagnetic force induced inside the pool, the outside of the cold crucible is generated. The induction coil, which is arranged around the circumference, and the molten metal pool and the cold crucible wall portion maintain a molten metal dome shape which is in a non-contact state except for a soft contact with substantially no electrical conduction near the horizontal lower end. Thus, a thin plate continuous casting apparatus comprising an electromagnetic field control device for controlling the electromagnetic field of the induction coil.