JP2001314946A - Continuous casting method of thin casting piece and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent entrainment of scum floating on a surface of molten metal in a pouring basin portion onto a shell in a pair of drum type continuous casting. SOLUTION: In a method casting a thin casting piece c while supplying molten metal r from a pouring nozzle 5 to a pouring basin portion 3 formed by a pair of cooling drums 1 and 1, non-oxidizable gas is blown to a surface of molten metal in the pouring basin portion 3 in which gas nozzles 7a and 7a provided on an upper portion of the cooling drums 1 and 1 point to a pouring molten metal nozzle 5 from a side of a meniscus m at a peripheral surface of the cooling drums. Consequently, entrainment of the scum onto a shell can be prevented as the scrums is moved toward a center portion of the pouring basin portion 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a thin and wide cast slab having a thickness of about 1 to 10 mm by continuous casting, and more particularly to a treatment of scum floating on a molten metal surface in a pool. Things.

[0002] As a method for producing a thin wide slab (hereinafter referred to as a thin slab) by continuous casting, a twin-drum continuous casting method comprises a pair of cooling drums rotating in opposite directions to each other,
The molten metal is supplied to a pool formed by a pair of side weirs pressed against both end surfaces of the cooling drum, and the molten metal forms a solidified shell on the peripheral surface of the rotating cooling drum. The thin slab is pressed into a thin slab at the closest portion between the thin slabs, and the thin slab is coiled downstream.

Slag is mixed into the molten metal supplied to the pool, and metal oxides are generated on the surface of the molten metal by oxidation. These slag and metal oxide are scummed on the molten metal in the pool. Then, it floats and is caught from the meniscus to the drum peripheral surface and the slab surface. As a result, the cooling of the portion is delayed or uneven, so that the thin slab is cracked, has an uneven structure, or has an uneven pickling, and further has an uneven structure.

[0004] As a method of preventing scum from being generated on the molten metal surface of the molten metal pool, the pool is covered with a seal chamber, and a non-oxidizing gas such as an inert gas is supplied into the sealed chamber to form a scum on the molten metal pool. A method for preventing oxidation is known, for example, from JP-A-3-198951. However, even if the melt surface is sealed by such a method, generation of scum cannot be sufficiently prevented.

On the other hand, as a method of preventing the flow of the scum to the meniscus, a pair of scum weirs extending in the drum width direction are provided between the pouring nozzle and the cooling drum in the hot water pool by immersing the scum in the molten metal. A method of preventing the flow of the scum to the cooling drum by using the method described in, for example, Japanese Patent Application Laid-Open No. 3-66450. However, even if the scum weir is provided, it cannot cope with scum generated near the meniscus between the scum weir and the cooling drum.

It is a particular problem that the scum is entangled unevenly in the width direction of the slab. However, if the amount of scum is large, the scum is likely to be unevenly entangled. Since the amount of scum generated increases as the casting time elapses, there is a problem that when casting is performed for a long time to improve production efficiency, the amount of scum generated increases and the scum is likely to be unevenly involved.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for producing thin cast slabs by continuous casting, in which a scum floating near a meniscus of a pool is brought close to the center of the pool to form a scum drum. An object of the present invention is to prevent entrapment on a peripheral surface or a slab surface.

[0008]

According to the present invention, there is provided a thin cast slab continuous casting method according to the present invention. (1) A molten metal is poured from a pouring nozzle into a pool formed by a pair of cooling drums and a pair of side dams. In the method of casting a thin slab while supplying the non-oxidizing gas, the non-oxidizing gas is blown onto the molten metal surface of the pool in a direction closer to the meniscus of the peripheral surfaces of the pair of cooling drums toward the center of the pool. It is characterized by the following.

[0009] The thin cast slab continuous casting apparatus according to the present invention which solves the above-mentioned problems is: (2) an apparatus in which a pouring nozzle is provided in a hot-water pool formed by a pair of cooling drums and a pair of side weirs. A gas nozzle directed above the cooling drum from the meniscus portion of the peripheral surface of the cooling drum toward the center of the pool.

(3) In a device in which a pair of cooling drums and a pair of side dams are provided with a pair of scum dams extending in a drum width direction at a hot water pool formed by the pair of side dams, the device is provided above the pair of cooling drums. Gas nozzles directed from the meniscus portion of the peripheral surface of the cooling drum to the side weir are provided separately in two directions in the drum width direction,

(4) Further, in an apparatus in which a pair of scum weirs extending in the drum width direction are provided in a hot-water pool formed by a pair of cooling drums and a pair of side weirs, A gas nozzle directed from the cooling drum to the center of the pool is provided,

(5) A pouring nozzle having a plurality of molten metal discharge holes in a drum width direction is provided in a hot water pool formed by a pair of cooling drums and a pair of side weirs. In a device provided with a pair of scum weirs extending in the drum axis direction between cooling drums, a scum flow hole is provided at a portion of the pair of scum weirs opposed to between the molten metal discharge holes, and the pair of cooling drums is provided. And a gas nozzle directed from the meniscus portion of the peripheral surface of the cooling drum toward the scum flow hole.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an outline of a twin-drum continuous casting apparatus common to all the embodiments of the present invention. A pair of side dams are provided on both end surfaces of a pair of cooling drums 1, 1 rotating in opposite directions. 2 and 2 (indicated by phantom lines) are pressed to form a pool 3 and the pool 3
The molten metal r is supplied from the tundish 4 through the pouring nozzle 5. The upper portion of the pool 3 is covered with a seal chamber 6 in order to prevent scum from being generated by oxidation of the molten metal r, and a non-oxidizing gas such as argon or nitrogen is supplied into the seal chamber 6.

The molten metal r in the pool 3 is cooled on the peripheral surfaces of the pair of rotating cooling drums 1 and 1 to form a pair of solidified shells g and g. The thin cast c is sent out downward as a thin slab c. The thin slab c is wound in a coil shape by a winding machine (not shown) arranged on the downstream side.

FIGS. 2 and 3 show an embodiment in which the first and second aspects of the present invention are applied to the twin-drum continuous casting apparatus shown in FIG. 1. One of the members common to FIG. The parts are not shown and their description is omitted. In the figure, 7a, 7a are provided in the drum width direction above the pair of cooling drums 1, 1,
A gas nozzle which blows a non-oxidizing gas such as argon or nitrogen onto the molten metal surface in a direction toward the pool center O slightly before the meniscus m on the drum peripheral surface, and the nozzle is supported by a seal chamber (not shown).

The type of the gas nozzle 7a may be any type such as a slit type and a round hole type. Examples of the slit type include a width of 1.0 to 1.5 mm,
Length: 20mm, hole pitch: 25mm, distance from the surface of the metal;
60-70 mm, and as an example of a round hole type,
Nozzle diameter: 0.5 to 1.0 mm, hole pitch: 5 mm, distance from molten metal surface: 80 mm. The height of the gas nozzle 7a and the gas ejection angle can be adjusted according to the height of the molten metal surface, etc., and the gas flow rate is 20 to 20 for both the slit type and the round hole type.
30 mps.

A method of moving the scum floating near the meniscus m to the center of the pool by using the twin-drum continuous casting apparatus shown in FIGS. 2 and 3 will be described. Slag is mixed into the molten metal r supplied to the pool 3 through the pouring nozzle 5, and the molten metal supplied to the pool 3 is oxidized to form metal oxides by oxidization, forming scum scum and scum. Part 3
Floating on the surface of the molten metal.

According to the first and second embodiments of the present invention, the gas nozzles 7a, 7a are directed toward the pool center O from the meniscus m side of the drum peripheral surface, and the surface of the molten metal such as argon, nitrogen, etc. When the non-oxidizing gas is blown, the scum s floating near the meniscus m flows from the meniscus m toward the pool O and can be removed from the vicinity of the meniscus m. At this time, in order to more reliably eliminate the scum and prevent surface defects of the cast slab due to waving at the meniscus m, the lower end of the gas ejected from the gas nozzles 7a, 7a is 10 mm to 50 mm shorter than the meniscus m. So that the angle α at the lower end of the gas is 4
5 ° or less is desirable.

FIGS. 4 and 5 show an embodiment in which claim 3 of the present invention is applied to the twin-drum continuous casting apparatus shown in FIG. 1. Some of the members common to FIG. Illustration and description thereof are omitted. In the figure, reference numerals 8 and 8 denote a pair of scum dams for blocking the flow of the molten metal discharged from the pouring nozzle 5 to prevent the flow of the scum s to the meniscus m. I have. 7b, 7
b is a gas nozzle attached to the back side of the scum weirs 8, 8 and spraying a non-oxidizing gas such as argon or nitrogen to the molten metal in the basin toward the side weir 2 slightly before the meniscus m on the peripheral surface of the drum. And the gas nozzles 7b, 7
b indicates that the gas ejection direction is 2 at the center of the drum width direction.
The gas nozzle 7b has the same structure as described above.

A method for moving the scum floating near the meniscus to the center of the pool by the twin-drum continuous casting apparatus shown in FIGS. 4 and 5 will be described. The molten metal r supplied to the pool 3 through the pouring nozzle 5 is cooled by the cooling drum 1,
It flows towards 1, but most of that flow is blocked by the scum weirs 8,8. However, a part of the molten metal flows below the scum weirs 8 and 8 and flows to the back side of the scum weirs 8 and 8, and the scum floats on the back side of the scum weirs 8 and 8 because the molten metal surface is oxidized. .

According to the embodiment of the present invention, when a non-oxidizing gas such as argon or nitrogen is blown from the gas nozzles 7b, 7b to the molten metal surface of the pool 3, the gas is blown out from the gas nozzles 7b, 7b. The generated gas is blown obliquely onto the scum weirs 8, 8 from the portion of the drum peripheral surface near the meniscus m to the molten metal surface. As a result, the scum s floating near the meniscus m flows along the scum weirs 8 and 8 and is brought near the side weirs 2 and 2 and can be removed from the vicinity of the meniscus m.

FIG. 6 is a perspective view showing an embodiment in which the fourth aspect of the present invention is applied to the twin-drum continuous casting apparatus shown in FIG. 1. A part of members common to FIG. The description is omitted. On the left and right sides (only the left side in FIG. 6 is shown) of the pair of scum weirs 8, 8 disposed in the pool 3, non-oxidized gas such as nitrogen gas or argon gas is applied to the molten surface of the pool 3. Gas nozzle 7c for spraying a neutral gas,
7c is disposed with the same inclination as the scum weirs 8,8. The structure of the gas nozzles 7c, 7c is the same as described above,
The gas ejection direction from the gas nozzle 7c is directed from the cooling drum 1 side to the pool center O.

A method of bringing the scum floating near the meniscus to the center of the pool using the twin-drum continuous casting apparatus shown in FIG. 6 will be described. Nozzles 7c, 7c during casting
When the non-oxidizing gas is ejected from the cooling drums 1 and 1 toward the pool center O from the cooling drums 1, the scum s floating on the molten metal surfaces on the left and right sides of the scum weirs 8 and 8 is discharged from the cooling drums 1 and 1 side. The scum flows x toward the pool center O to form a scum flow x. Due to the scum flow x, the scum s in the vicinity of the meniscus m flows to the pool center O, and the meniscus m
It can be excluded from the vicinity.

FIGS. 7 and 8 show an embodiment in which claim 5 of the present invention is applied to the twin-drum continuous casting apparatus shown in FIG. 1. Some of the members common to FIG. The illustration and description thereof are omitted, and only one side is shown with the center of the hot water pool as a boundary. The pouring nozzle 5a is formed to have a wide width in order to equalize the shell thickness in the drum width direction, and has three horizontally elongated molten metal discharge holes 9 on one side on the side of the lower part of the nozzle body facing the cooling drum 1. (Total 6
) Are provided. The reason why the molten metal discharge holes 9 are formed into a plurality of divided structures is to secure the strength of the nozzle. As a result, the nozzle support members 10 are formed between the molten metal discharge holes.

The pool 3 is provided with a pair of scum weirs 8a for blocking the flow of scum floating on the molten metal surface to the drum side. The scum weir 8a is provided at a position facing the nozzle support member 10 of the scum weir 8a. The cutout hole 11 serving as a scum escape path is provided with its upper end above the surface of the molten metal.

In the seal chamber 6 which covers the upper part of the water pool 3, four gas nozzles 7d for ejecting non-oxidizing gas from the drum side toward the notch holes 11 are provided in the figure, and the gas from the nozzles is provided. By the blowing, the scum s near the meniscus m can flow toward the pouring nozzle 5a through the notch hole 11. The structure of the gas nozzle 7d is the same as described above.

A method of moving the scum s near the meniscus m to the center of the pool 3 will be described with reference to the embodiment shown in FIG. 7 and FIG. Pouring nozzle 5a
Of the three melt flows a discharged from the scum dam 8a, the melt flow b is generated near the meniscus m. As a result, scum-like scum is generated between the plurality of melt flows b.

According to the embodiment of the present invention, the molten metal flows b are formed on both the left and right sides of the scum scum, and the scum is formed at the scum weir 8a adjacent to the scum s. Since the cutout hole 11 serving as an escape path is formed, the scum scum stagnates toward the cutout hole 11 by the molten metal flow b. At the same time, when a non-oxidizing gas is blown from the gas nozzle 7d toward the stagnation scum s, the scum s flows through the notch hole 11 toward the pouring nozzle 5a and can be removed from the vicinity of the meniscus m. .

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A twin-drum continuous casting apparatus shown in FIG. 1 using a cooling drum having a diameter of 1200 mm and a width of 1300 mm is used, and in Example 1 of the present invention corresponding to claims 1 and 2, FIGS. In the second embodiment of the present invention corresponding to claim 3, the embodiment shown in FIGS. 4 and 5 is adopted, and in the third embodiment of the present invention corresponding to claim 4, the embodiment shown in FIG. In the present invention example 4 corresponding to the above, the form shown in FIGS. 7 and 8 was used, and thin cast pieces were cast respectively. In the comparative example, a conventional scum weir was used, but scum gas blowing was not performed. FIG. 9 shows the index of occurrence of surface defects in the present invention examples 1 to 4 in which the surface cracks and uneven glossiness of the products were integrated, with the comparative example as 100.

[0030]

According to the present invention, the scum floating near the meniscus of the basin can be blown toward the center of the basin and removed from the vicinity of the meniscus, so that the peripheral surface of the scum and the surface of the slab can be removed. Entrainment can be prevented. Thus, accumulation of scum particularly in long-time casting can be eliminated.

[Brief description of the drawings]

FIG. 1 is a side view (partially sectional view) showing an outline of a twin-drum continuous casting apparatus.

FIG. 2 is a side sectional view illustrating an embodiment according to claims 1 and 2;

FIG. 3 is a plan view of FIG. 2;

FIG. 4 is a side sectional view illustrating an embodiment according to claim 3;

FIG. 5 is a plan view of FIG. 4;

FIG. 6 is a perspective view illustrating an embodiment according to claim 4;

FIG. 7 is a side sectional view illustrating an embodiment according to claim 5;

FIG. 8 is a plan view of FIG. 7;

FIG. 9 is a view showing a surface defect occurrence index of a thin slab in comparison with the present invention and a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cooling drum 2 ... Side weir 3 ... Hot water pool part 4 ... Tundish 5 ... Pouring nozzle 5a ... Pouring nozzle 6 ... Seal chamber 7a-7d ... Gas nozzle 8 ... Scum weir 8a ... Scum weir 9 ... Horizontal molten metal discharge Hole 10: Support member 11: Notch hole of scum dam r: Melt g: Solidified shell c: Thin slab m: Meniscus kp: Drum kiss point s: Scum x: Scum flow a, b: Melt flow O: Hot water pool center

Continued on the front page (72) Inventor Mamoru Yamada 3434 Shimada, Hikari-shi, Yamaguchi Prefecture Nippon Steel Corporation Hikari Works (72) Inventor Tomohide Takeuchi 3434 Shimada, Hikari-shi, Yamaguchi Prefecture Nippon Steel Corporation F term in the Kokko Works (reference) 4E004 DA13 SA08 SB07 SB10

Claims (5)

[Claims] 1. A method of casting a thin slab while supplying molten metal from a pouring nozzle to a pool formed by a pair of cooling drums and a pair of side weirs, the method comprising: A thin slab continuous casting method, characterized in that a non-oxidizing gas is blown from a portion of the peripheral surface of the cooling drum near the meniscus toward the center of the pool. 2. An apparatus in which a pouring nozzle is provided in a hot water pool formed by a pair of cooling drums and a pair of side dams, wherein a pouring nozzle is provided above the pair of cooling drums from a portion near a meniscus of a peripheral surface of the cooling drum. A thin slab continuous casting apparatus, wherein a gas nozzle directed to the center of the pool is provided. 3. An apparatus in which a pair of cooling drums and a pair of side dams are provided with a pair of scum dams extending in a drum width direction in a water pool formed by the pair of side dams. A gas nozzle directed from the meniscus portion of the peripheral surface toward the side weir in the width direction of the drum 2
A thin cast slab continuous casting apparatus characterized by being provided in different directions. 4. A device in which a pair of cooling drums and a pair of side dams are provided with a pair of scum dams extending in a drum width direction in a hot-water pool formed by the pair of side dams. A thin nozzle continuous casting apparatus, wherein a gas nozzle directed to the center of the pool is provided. 5. A pouring nozzle having a plurality of molten metal discharge holes in a drum width direction is provided in a hot water pool formed by a pair of cooling drums and a pair of side weirs. In an apparatus provided with a pair of scum weirs extending in the drum axis direction, a scum flow hole is provided at a portion of the pair of scum weirs that faces between the molten metal discharge holes, and is provided above the pair of cooling drums. A thin slab continuous casting apparatus, wherein a gas nozzle is provided from a portion of the peripheral surface of the cooling drum near the meniscus to the scum flow hole.