JP3186817B2 - Twin-roll continuous casting method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to continuous casting of a thin slab having a thickness of several mm suitable for directly performing cold rolling without going through hot rolling from a casting state by a twin roll continuous casting method. The invention relates to a method and an apparatus for its implementation.

[0002]

2. Description of the Related Art It is extremely important to cast a slab having good surface properties, since a thin plate slab has a relatively small workability to a final product and the surface properties of the slab strongly influence the surface quality of the product. It 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 weirs pressed against both end surfaces thereof, and molten metal in a pool (melt pool) formed in the mold. Is cooled by contacting the outer peripheral surface of each cooling roll to form a pair of solidified shells, and the solidified shells that have moved downward due to the rotation of the two cooling rolls are united near the nearest position (kissing point) of the cooling rolls to be thin. It is delivered downward as a strip of slab.

[0003] In order to improve the surface properties of the slab, it is necessary to prevent scum (oxide) floating on the pool surface from being entrained, and to eliminate the effects of ripples on the pool surface to remove the scum and the outer peripheral surface of the cooling roll. It is necessary to stabilize the contact line with the device. As a method thereof, it has been proposed to separate the surface of the pool and the outer peripheral surface of the cooling roll by a limiting plate provided by bringing the tip into contact with the outer peripheral surface of the cooling roll and contacting both side edges with the side weir. (Japanese Patent Laid-Open No. 58-14)
No. 8056). In addition to the effect of eliminating the effects of scum entrainment and waving on the surface of the molten metal, this limiting plate makes the position where the molten metal starts to contact the outer peripheral surface of the cooling roll uniform in the axial direction of the cooling roll, and uniform solidification in the slab width direction Has the effect of improving the properties.

[0004] In order to stably obtain the above-mentioned action, the tip of the limiting plate must be brought into close contact with the outer peripheral surface of the cooling roll so that molten metal does not enter between the limiting plate and the outer peripheral surface of the cooling roll. Although it is necessary, there are actually the following problems. (1) With the progress of casting, the pressing surface of the side weir is cut off by the end face of the cooling roll and retreats, and the side weir advances by that amount. A gap is formed apart from the outer peripheral surface, and the molten metal leaks from the gap and enters the space between the limiting plate and the outer peripheral surface of the cooling roll.

(2) In the preparation stage of casting, it is difficult to always keep the side weir and the limiting plate in close contact with high accuracy, and a gap may be formed between the side weir and the limiting plate. The molten metal penetrates into the space between the limiting plate and the outer peripheral surface of the cooling roll from this gap and solidifies, and this solidified product damages the tip of the limiting plate or gets caught between the cooling rolls to deteriorate the slab properties. .

In addition, when the pouring temperature is relatively low due to the composition of the molten metal, or when the molten metal has good thermal conductivity and tends to solidify,
The molten metal is cooled at the tip of the limiting plate to form a solidified material, which is combined with the solidified shell and caught between the cooling rolls to expand the cooling roll interval. (Lag zone), which causes slab breakage.

[0007] Japanese Patent Application Laid-Open No. Sho 60-166146 proposes to preheat side weirs. However, according to an experiment conducted by the present inventors, simply preheating the side weirs could not completely prevent the formation of solids on the surface of the side weirs. Inevitable.

As described above, the function of the limiting plate cannot be sufficiently exhibited by the above-mentioned conventional method, and a cast slab having good surface properties cannot be stably obtained.

[0009]

The object of the present invention is to ensure the close contact between the limiting plate and the side weirs and the outer peripheral surface of the cooling roll, to prevent the formation of unnecessary solidified products, and to fully exert the function of the limiting plate. Accordingly, an object of the present invention is to provide a twin-roll continuous casting method capable of stably casting a thin plate slab having good surface properties and an apparatus for performing the method.

[0010]

In order to achieve the above object, a twin-roll continuous casting method of the present invention is characterized in that a side weir is pressed against both end faces of a pair of cooling rolls arranged horizontally and parallel to each other. When a molten metal is poured into the formed continuous casting mold to form a pool, the restriction plate provided by contacting the tip with the outer peripheral surface of the cooling roll and contacting both side edges with the side dam is used to form the pool. In a twin-roll type continuous sheet casting method for separating a surface from an outer peripheral surface of a cooling roll, a limiting plate having both shrinkable side edges is used.

[0011] A twin-roll type continuous sheet casting apparatus for carrying out the method of the present invention has a continuous casting mold formed by pressing a side weir against both end faces of a pair of cooling rolls arranged horizontally and parallel to each other. A limiting plate provided with the tip in contact with the outer peripheral surface of the cooling roll and the side edges in contact with both side edges; when the molten metal is poured into the mold to form a pool, the pool is set by the limiting plate; In the twin-roll type continuous continuous sheet casting apparatus in which the surface of the cooling plate is separated from the outer peripheral surface of the cooling roll, both side edges of the limiting plate are made shrinkable.

[0012]

According to the present invention, even when the side weir pressing surface is scraped by the end face of the cooling roll with the progress of casting and retreats, and the side weir is displaced forward, both edges of the shrinkable limit plates absorb the displacement. As a result, the restricting plate does not bend due to the side dam pressing force, and the close contact between the distal end of the restricting plate and the outer peripheral surface of the cooling roll can always be stably maintained.

This prevents the occurrence of a gap between the tip of the limiting plate and the outer peripheral surface of the cooling roll, and eliminates the conventional adverse effects caused by the intrusion of molten metal into the space between the limiting plate and the outer peripheral surface of the cooling roll. When the pouring temperature is relatively low due to the composition of the molten metal, or when the molten metal has good thermal conductivity and is easy to solidify, for example, like a copper alloy, the tip of the limiting plate is heated by a resistance heating element embedded in the vicinity thereof. Prevents the formation of coagulated material at the tip of the limiting plate, and heats the pressing part of the side weir against the end face of the cooling roll with a resistance heating element embedded inside it so that the side weir and the cooling roll come in contact with the corner part. Coagulation can be prevented.

The higher the heating temperature at the end of the limiting plate, the greater the effect of preventing the formation of solidified material at the end, but if the temperature is too high, the temperature of the outer peripheral surface of the roll becomes excessively high and the formation of solidified shell becomes unstable. . Usually, it is desirable that the temperature be equal to or lower than the solidus temperature of the molten metal. The higher the heating temperature of the pressing surface of the side weir against the cooling roll end surface, the more effective. However, if it is too high, the temperature near the end surface of the roll outer peripheral surface becomes too high and the slab side edges become unsolidified. Normally, it is also desirable that the temperature be equal to or lower than the solidus temperature of the molten metal.

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

[0016]

1 and 2 show a plan view and a front view, respectively, of a main part of a twin-roll type continuous sheet casting apparatus according to the present invention. Side weirs 3 are pressed against both end surfaces 1A of a pair of internal water-cooled cooling rolls 1 arranged horizontally and parallel to each other to form a continuous casting mold. The cooling roll 1 is formed integrally with the rotating shaft 2 and rotates in the direction of arrow 11.

The limiting plate 4 has a central portion 5 formed of boron nitride (B
N), both side edges 6 are made of shrinkable fibrous alumina refractory, and are held by the holding arm 7 at the center portion 5 so that the tip 4A is in close contact with the outer peripheral surface 1B of the cooling roll. . As an assembling procedure, after the limiting plate 4 is installed as shown in the figure, the side weir 3 is pressed against the cooling roll end face 1A to be in close contact therewith. In this state, the contractible side edge 6 of the restricting plate 4 also comes into close contact with the side weir 4.

As shown in FIG. 2, a molten metal is injected from a tundish (not shown) through a pouring nozzle 8 into a mold formed by the cooling roll 1 and the side weir 3, thereby forming a pool 9. The solidified shells formed on the outer peripheral surfaces 1B of the two cooling rolls 1 are combined into a thin plate slab 10, which is sent downward (arrow 12) by the rotation of the cooling rolls 1. The molten metal surface 9A of the pool 9 is isolated from the outer peripheral surface 1B of the cooling roll by the restriction plate 4.

As the casting progresses, the portion of the side weir 3 that is pressed against the cooling roll end face 1A wears and retreats, and the side weir 3 is displaced forward by that much, and the distance between the side weirs 3 is reduced. This displacement (regression reduction) is absorbed by the compressive displacement of the fibrous alumina-based refractory compressible side edge 6 of the limiting plate 4, so that the BN central portion 5, which constitutes most of the limiting plate 4, bends. Without limiting, the limiting plate tip 4A and the outer peripheral surface 1B of the cooling roll 1
Is always secured.

As shown in FIG. 3, a resistance heating wire 13 is buried in the vicinity of the tip 4A of the limiting plate 4, and the tip 4A can be heated to a required temperature by energizing the wire. As shown in FIG. 4, a resistance heating element 15 is embedded at a position along the circumference of the cooling roll of the side weir 3, and a portion for pressing the side weir 3 against the cooling roll end face 1A is required by supplying electricity to the heating element. It can be heated to any temperature.

In this embodiment, the limiting member 4 in which the fibrous alumina-based refractory 6 is fixed to both ends of the BN central portion 5 with a refractory adhesive such as alumina bond is installed, and then the side dam 3
After the BN plate 5 is installed and the side weir 3 is arranged, the restricting plate 4 is formed by filling the gap between both ends of the BN plate 5 and the side weir 3 with the refractory material 6. You may.

The limiting plate 4 constructed as in the present embodiment is used.
After installing the side weir 3 and the limiting plate 4, the side weir 3
When the gap between them is larger than a certain degree, this gap can be further filled with a shrinkable refractory. Using the apparatus of the present invention, a thin plate slab was cast under the following casting conditions. Casting condition Cooling roll: Size: diameter 400 mm, width 350 mm Material: copper Cooling method: internal water cooling Operating condition: Casting speed: 20 to 50 m / min (= cooling roll rotation speed) Cooling roll / metal contact arc length: about 170 mm Pool depth: approx. 150 mm (distance from the kissing point to the surface) Cast metal: SUS304 stainless steel Limiting plate configuration: central part: BN plate Side edge: fibrous alumina refractory Width 10 mm, allowable displacement 0.5 mm (One side) Resistance heating wire for tip heating: Mo wire (diameter: 1 mm) embedded (cast under both conditions with and without heating of the limiting plate) Side weir configuration: Main body: BN refractory 17 in steel frame 16 Holding Resistance heating element: Alumina graphite embedded Power supplied from copper water-cooled electrode 14 (Casted under both conditions with and without heating of side dam) Limitation When the side weir was not heated, a slight tendency of solidification was observed, but by performing the heating, a very good thin sheet slab having a surface property of about 1 to 3 mm in thickness and about 350 mm in width was obtained. Was done.

When a casting test was conducted by changing the heating temperature in the range of about 500 to 1450 ° C., the solidus temperature of the molten metal (SUS 304) (about 1
(425 ° C.) or lower, it was found that it is desirable to heat to as high temperature as possible. When the side weir was heated to a temperature higher than the solidus temperature, the side edge of the slab became unsolidified and the side edge shape was poor.
The effect of reducing the coagulated material was observed even at about 500 ° C., and the effect became remarkable at about 900 ° C. or higher.

For comparison, a conventional limiting plate consisting only of a BN plate was used, and casting was performed without heating both the limiting plate and the side weir. The adhesion with the side weir was maintained during installation before casting. In addition to the difficulty, the molten metal penetrated from the tip of the limiting plate to the outer peripheral surface of the cooling roll during casting, and casting defects (hot bands) were generated.

[0025]

As described above, according to the present invention,
Since it is possible to secure the close contact between the limit plate and the side weirs and the outer peripheral surface of the cooling roll, it is possible to produce a thin surface slab with good surface properties without causing scum on the pool surface and roughening of the slab surface due to undulation of the pool surface. Casting can be performed stably.

Further, by heating the tip of the limiting plate and the pressing surface of the side weir below the solidus temperature of the molten metal, it is possible to prevent undesired solidified products from being formed and completely prevent casting defects caused by the solidified products. be able to. This aspect of the present invention is particularly effective when applied to a molten metal having a low pouring temperature or a composition having a good thermal conductivity and easy to solidify.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a twin-roll continuous casting apparatus according to the present invention.

FIG. 2 is a front view of the apparatus of FIG. 1;

FIGS. 3A and 3B are a plan view and a side view showing an example of the limiting plate of the present invention.

FIG. 4 shows an example of a side weir of the present invention (a).
It is a front view and (b) a top view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... A pair of cooling rolls 1A ... End surface of cooling roll 1 1B ... Outer peripheral surface of cooling roll 1 2 ... Rotating shaft of cooling roll 1 3 ... Side weir 4 ... Limiting plate 4A ... End of limiting plate 4 5 ... Limiting plate 4 Central part 6 ... Side edge of limiting plate 4 7 ... Arm holding limiting plate 4 8 ... Pouring nozzle 9 ... Molten metal (pool) 9A ... Fluid surface of pool 9 10 ... Sheet cast piece 11 ... Cooling roll 1 Rotational direction 12 ... Sending direction of slab 10 13 ... Resistance heating wire (Mo wire) 14 ... Copper water cooling electrode 15 ... Resistance heating element (alumina graphite) 16 ... Steel metal frame of side weir 3 17 ... Fire resistance of side weir 3 Goods (BN)

──────────────────────────────────────────────────の Continuation of the front page (72) Inventor Ryuichi Hori 1 Kimitsu, Kimitsu City, Chiba Prefecture Inside the Nippon Steel Corporation Kimitsu Works (56) References JP-A-2-295643 (JP, A) JP-A-61-224051 (JP, A) JP-A-58-144806 (JP, A) JP-A-3-114632 (JP, A) JP-A-4-4955 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) B22D 11/06 330

Claims (9)

(57) [Claims] When a molten metal is poured into a continuous casting mold formed by pressing a side weir against both end surfaces of a pair of cooling rolls arranged horizontally and parallel to each other, a pool is formed. In a twin-roll type thin plate continuous casting method for separating a surface of the pool and an outer peripheral surface of the cooling roll by a limiting plate provided by bringing a tip into contact with an outer peripheral surface and contacting both side edges with the side weir, A twin-roll type continuous casting method for a thin plate, comprising using the above-mentioned limiting plate having both side edges of shrinkability. 2. Heating the tip of the limiting plate with a resistance heating element embedded in the vicinity thereof, and heating the pressing surface of the side weir against the end face of the cooling roll with the resistance heating element embedded therein. The method for continuously casting a twin-roll thin sheet according to claim 1, wherein: 3. The twin-roll continuous thin plate casting method according to claim 2, wherein the heating temperature of the limiting plate and the side weir is set to be equal to or lower than the solidus temperature of the molten metal. 4. The width of a contractible side edge of the limiting plate is about 10 m.
4. The method according to claim 1, wherein m is set to m.
Item 2. The twin-roll type continuous sheet casting method according to the item [1]. 5. The method according to claim 1, wherein the shrinkable side edge is made of a fibrous alumina refractory. 6. A continuous casting mold formed by pressing a side weir against both end faces of a pair of cooling rolls arranged horizontally and in parallel with each other, and a tip is brought into contact with an outer peripheral surface of the cooling roll and is contacted with the side weir. A limiting plate provided with both side edges in contact with each other is provided. When a molten metal is poured into the mold to form a pool, the surface of the pool and the outer peripheral surface of the cooling roll are separated by the limiting plate. A twin-roll type continuous sheet casting apparatus, wherein both side edges of the limiting plate are made shrinkable. 7. The apparatus according to claim 7, wherein the limiting plate includes a resistance heating element embedded near a tip thereof, and the side weir includes a resistance heating element embedded in a portion pressed against an end face of the cooling roll. 7. The twin-roll thin-sheet continuous casting apparatus according to claim 6. 8. The width of a contractible side edge of the limiting plate is about 10 m.
8. The twin-roll thin-sheet continuous casting apparatus according to claim 6, wherein m is m. 9. The twin-roll type continuous sheet casting apparatus according to claim 6, wherein the shrinkable side edge is made of a fibrous alumina-based refractory.