JP2854479B2 - Continuous casting machine for slab and thin slab continuous casting method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slab continuous casting machine and a thin slab continuous casting method using the same.

[0002]

2. Description of the Related Art Thin slab slabs usually have a thickness of 50 to 100 mm.
Since the width is as thin as 800 to 2700 mm, when casting with a mold with a general rectangular cross section, the thickness of the refractory of the immersion nozzle for pouring from the tundish into the mold becomes thinner and the life is shortened? Alternatively, there is a problem that the design of the immersion nozzle itself becomes impossible.

In order to solve such a problem, there has been proposed a mold structure (conventional example I) in which the cross section of the mold is drum-shaped and the cross section of the discharge side is rectangular, and the width of the portion where the immersion nozzle enters is widened. According to the conventional example I, the width of the central portion in the mold is widened, so that the thickness of the refractory can be ensured to some extent. However, there is another disadvantage in that the quality of the slab is reduced. That is, since the outgoing cross-sectional area is smaller than the ingoing cross-sectional area of the mold, the slab receives stress in the mold, and internal cracks or breakouts are liable to occur in the slab.

As another prior art, Japanese Patent Laid-Open No. 3-32 is disclosed.
No. 455 has proposed a continuous casting machine (conventional example II). This conventional example II is a continuous casting mold as shown in FIG.
Guide rollers 52, 54 for unsolidified slab reduction are provided immediately below 51. As shown in FIG. 5, a long-side copper plate 62 attached to the inside of the long-side frame 54 in the mold 51 is located in the center area of the inner wall. In the guide roller group, as shown in FIG. 6 (a), the upstream side 52 of the guide roller group has a concave shape in the center region of the roll drum as compared with the end portion. Using a deformed roll 63 provided with a roll crown having a shape similar to that of the inner wall of the side wall, the crown amount is sequentially reduced on the downstream side 54 until it becomes zero, and a straight roll 64 is used on the most downstream side as shown in FIG. It was what was.

[0005] In this conventional example II, first, a slab is cast into a shape in which the center thickness of the slab is thicker than the end thickness in a continuous casting mold, and the thickness of the slab central portion becomes equal to the end thickness in the process of solidification. The method of gradually reducing the pressure is used. This casting method will be described in detail with reference to FIG. Figure (a)
Is the cross-sectional shape of the slab in or immediately below the mold, and the center thickness To is greater than the end thickness Ti. FIG. 13B shows a cross-sectional shape of the slab in the upstream side guide roller group 52, and the central portion of the slab has an initial thickness T0 to T.
The pressure has been reduced to 0 '. FIG. 4C shows the cross-sectional shape of the slab after the completion of the rolling. The center portion is also lowered to the slab thickness T1 equal to the thickness of the end portion to obtain the final slab shape.

[0006]

However, in the conventional example II, since a rolling action is applied to the slab shell in the slab shell support area immediately below the mold, there is a problem that cracks occur in the agar-like portion immediately after solidification. is there. This crack (internal crack) does not stick even if the entire slab solidifies,
There is a drawback that it remains as a crack and becomes a defective slab.

In view of such circumstances, the present invention is capable of casting a thin slab having a small final slab thickness while securing the thickness of the refractory of the immersion nozzle, and furthermore, a continuous slab that can obtain good slab quality. An object is to provide a casting machine and a continuous casting method.

[0008]

The continuous casting machine for slabs of the present invention is a continuous casting machine for slabs comprising a mold for thin slabs and a group of guide rolls arranged along a pass line. The long side copper plate is formed in a concave shape in which the center portion is recessed with respect to both ends thereof, and the guide roll group is a guide segment band from directly below the mold to the middle of the pass line, and a slab from the middle of the pass line. And a lightly reduced segment zone up to the position beyond the solidification completion point of
The guide roll in the guide segment band is a drum-shaped roll conforming to the shape of the drum-shaped slab on the mold exit side, and the roll cavity is substantially the same as the slab thickness on the mold exit side over the entire guide segment band. The guide roll in the light reduction segment band is a straight roll, and the roll cavity is set so as to gradually decrease from the thickness at the center of the slab to the thickness at both ends of the slab. It is characterized by having.

In the continuous thin slab casting method of the present invention, using the continuous casting machine, a slab slab cast into a drum-shaped cross section by a mold is pressed down by a drum-shaped roll in a guide segment band starting immediately below the mold. It is characterized in that the drum-shaped slabs are successively pressed down by straight rolls in the lightly-depressed segment band and finished in a rectangular cross section.

[0010]

According to the continuous casting machine of the present invention, since the central portion of the long side copper plate of the mold is concave, the width of the central portion in the mold is wide and the thickness of the refractory of the immersion nozzle can be secured. The slab cast in the mold has a drum-shaped cross section, but finally, the thickness of the slab is reduced by a straight roll to make the thickness of the slab the same at both ends and at the center. Casting is possible.

According to the continuous casting method of the present invention, the slab shell support area directly below the mold is guided only by the drum-shaped roll of the guide roll segment band, and is not reduced. Cracks do not occur in the agar-like portion of the slab, and the quality of the surface layer of the slab is improved. Then, the drum-shaped slab is reduced by the straight roll for the first time after reaching the light reduction segment zone. In this case, the unsolidified portion of the slab core is squeezed to the upstream side, so that the center segregation is improved, and the slab core is improved. The quality is improved.

[0012]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 2 shows a curved continuous casting machine. In the figure, reference numeral 1 denotes a mold, and a guide roller group is disposed along a pass line from immediately below the mold. It consists of a guide segment zone 2 extending halfway along the line and a lightly reduced segment zone 3 following it.

The lightly reduced segment zone 3 starts 5 to 10 m ahead of the solidification completion point SP of the slab S and continues to several meters behind the solidification completion point SP. The guide segment band 2 upstream of the lightly reduced segment band is a slab shell support area whose main purpose is to hold the slab shell. The position of the solidification completion point SP is determined by controlling the amount of cooling water for the slab S drawn from the mold 1.

As shown in FIG. 1A, the mold 1 has a configuration in which it is surrounded by two long-side copper plates 11 and two short-side copper plates 12 in a rectangular shape. And attached to the short side frame. The long side copper plate
Numeral 11 denotes a concave surface having a concave central portion with respect to both ends, and the same is applied to the entrance side and the exit side. Therefore, the copper plate surface interval Y at the center in the mold is wider than the copper plate surface interval X at both ends. It is optional whether or not the long side copper plate 11 is tapered from the entry side to the exit side. As described above, since the copper plate surface interval at the central portion in the mold 1 is wide, the thickness of the refractory of the immersion nozzle that supplies molten steel into the mold can be increased.

The guide segment band 2 is constructed by forming a pair of two drum-shaped rolls 21 as shown in FIG. 1B and arranging a large number of sets along a pass line. The hourglass roll 21 has the same curvature as the curvature of the concave shape of the long-side copper plate 11 and has a narrow center portion and thick end portions. Therefore, the shape matches the drum-shaped slab shape on the mold exit side.

Since the guide segment strip 2 only supports the slab shell without rolling down the slab, the roll cavity between the pair of opposed rolls 21, 21 is equal to or the same as the slab thickness on the mold exit side. The cavity is adapted to the cooling shrinkage of the slab, and is the same throughout the entire guide segment band 2.

The above-mentioned lightly-depressed segment band 3 is constituted by forming a pair of straight rolls 31 as shown in FIG. 1C and arranging a large number of sets along a pass line. The roll cavities are tapered so as to gradually decrease from the start end to the end of the lightly-depressed segment band 3, and the end roll cavities correspond to the finished thickness of both ends of the slab. In addition, a drive roll for pulling out the slab S is appropriately arranged in the lightly reduced segment band 3.

Next, a thin slab casting method according to the above embodiment will be described with reference to FIG. The slab S cast by the mold 1 comes out in a drum shape along the concave shape of the long side copper plate 11 (see FIG. 1A). At this time, the thickness Y of the central portion of the slab coincides with the copper plate surface interval Y of the central portion of the mold (see FIG. 1A). Subsequently, the slab S is pulled out while supporting the slab shell by the guide segment strip 2, but at this time, it is only guided without reducing. Therefore, the shape of the slab S is a drum shape as it comes out of the mold 1 as shown in FIG. Of course, as the shell is pulled out, the shell solidifies, so the shell thickness increases. At this stage, an agar-like portion immediately after solidification is also formed,
Because it is not rolled down, this part does not crack,
Therefore, the quality of the slab surface layer is improved.

Subsequently, when entering the light reduction segment zone 3, the pressure is gradually reduced by the straight rolls.
1) and the thickness y1, y of the slab S as shown in FIG.
2 gradually decreases and becomes closer to a rectangle. Finally, as shown in FIG. 3D, the slab is finished into a rectangular thin slab cast piece S. The thickness X-α of the finished slab S is a value obtained by subtracting the slab shrinkage α from the copper plate surface spacing X at both ends of the mold 1 (see FIG. 1A). In this lightly reduced segment band, the unsolidified portion of the slab core Sc is squeezed up to the upstream side, so that the center segregation is improved and the quality of the slab core is improved.

[0020]

According to the present invention, it is possible to ensure the thickness of the refractory of the immersion nozzle while casting a thin slab having a small slab thickness, and to cast the surface layer and the core. A cast piece with good flake quality is obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view (A) of a mold 1 in a continuous casting machine for slabs of the present invention, an explanatory view (B) of an hourglass roll 21, and an explanatory view (C) and (D) of a straight roll 31.

FIG. 2 is a side view of the continuous casting machine for slabs of the present invention,
A, A, B, C, and D arrows indicate the positions of the arrows (A), (B), (C), and (D) in FIG. 1.

FIG. 3 is an explanatory view of the thin slab continuous casting method of the present invention.

FIG. 4 is a schematic side view of a continuous casting machine of Conventional Example II.

FIG. 5 is a plan view of a mold 51 of Conventional Example II.

FIG. 6 is a plan view of guide rolls 63 and 64 of Conventional Example II.

FIG. 7 is an explanatory view of a casting method according to Conventional Example II.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Mold 2 Guide segment band 3 Lightly reduced segment band 11 Long side copper plate 21 Hourglass roll 31 Straight roll

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) B22D 11/128 350 B22D 11/128 B22D 11/128 340 B22D 11/04 311

Claims (2)

(57) [Claims] 1. A continuous slab casting machine comprising a thin slab mold and a group of guide rolls arranged along a pass line, wherein a long side copper plate of the mold has a central portion with respect to both ends. The guide roll group is formed in a concave concave shape, and the guide roll group is a guide segment band from just below the mold to the middle of the pass line, and a light reduction segment band from the middle of the pass line to a position beyond the solidification completion point of the slab. The guide roll in the guide segment zone,
A drum-shaped roll conforming to the shape of a drum-shaped slab on the mold exit side, and the roll cavity is substantially the same as the slab thickness on the mold exit side over the entire guide segment zone, and the guide roll in the lightly-depressed segment zone is provided. Is a straight roll, and the roll cavity is set so that the thickness gradually decreases from the thickness at the center of the slab toward the thickness at both ends of the slab. Casting machine. 2. A slab slab cast in a drum-shaped cross-section by a mold is guided by a drum-shaped roll by a drum-shaped roll in a guide segment band starting immediately below the mold, and is drawn out.
2. The thin slab continuous casting method using a continuous casting machine according to claim 1, wherein the drum-shaped cast slabs are sequentially reduced by straight rolls in the lightly reduced segment band to finish the rectangular slabs.