JPH0732108A - Method for producing wide and thin slab and continuous casting equipment therefor - Google Patents

Abstract

(57) [Summary] [Structure] Center free roll 21, left free roll 22 and right free roll 2
3, the center free roll 21 has the same diameter as the conventional one (for example, 100 mm), and the left and right free rolls 2
2,23 is 1.5 times larger than the conventional diameter (eg 300m
m). [Effect] The contact arc length between the slab and the roll is increased to suppress the longitudinal extension, surface cracks can be prevented, and a high quality thin slab can be obtained with a simple structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing wide and thin slabs and continuous casting equipment.

[0002]

2. Description of the Related Art A continuous casting facility for pouring molten metal into a water-cooled mold from a tundish to form a solidified shell on the surface and solidifying it to the center in the process of pulling it downward to obtain a slab is the mainstay of steelmaking plants. Equipment. The slab is cast into a cross section such as a circle, a square, or a rectangle, assuming the shape of the final product. If the final product is a plate (thin plate, thick plate), a slab slab with a rectangular cross section is suitable, but this slab slab is thin and wide because it is rolled down to a specified thickness by a rolling mill. It is desirable that it is a cast piece.

Conventionally, a belt type wall surface moving molding method, a Schlehmann-Jimmark method, etc. have been proposed as a continuous casting method for thin slabs, but they are not satisfactory because there are problems to be solved respectively. (For details, see JP-A-2-
(Refer to the prior art section of 207953 publication)

Therefore, as a means for obtaining a thin cast piece, a method of reducing the cast piece before it is completely solidified is effective. This is a method of rolling the roller in a roller apron zone where an unsolidified portion exists inside the slab.

[0005]

FIG. 9 is a drawing of a conventional unrolled slab by means of flat rolls, and a slab 102 containing an unsolidified portion 101 therein is shown by a pair of flat rolls 103, 103. It is pressed down.

Further, when the casting side 102 is pressed down, it not only swells in the width direction but also in the longitudinal direction (width-perpendicular direction, casting direction).
Also bulges out. In FIG. 9, the short side portions 104, 104 are sufficiently solidified, and are plastically deformed in the longitudinal direction and extended. On the other hand, since molten steel that has not solidified exists inside the long side portions 105, 105, the strain caused by the reduction is absorbed by the molten steel flowing upward, and as a result, even if it is reduced, the strain is extended in the longitudinal direction. I won't let you down. Therefore, as shown in FIG. 10 (operation diagram of FIG. 9), shear tensile strain may occur at the boundary portion, and so-called surface crack 110 may occur. Such internal cracks 108 and surface cracks 110 significantly deteriorate the quality of the cast slab 102, and a technique for preventing them from occurring is required.

[0007]

In order to meet the above-mentioned requirements, the present invention is a slab that is extracted from a water-cooled mold and has an unsolidified part inside, which is thinned by pressing a free roll against its long side. In the manufacturing method described above, the short side portions at both ends of the long side portion of the cast slab are pressed with a larger amount of reduction than other portions.

Therefore, for example, a free roll as a reduction roll is composed of a center free roll and left / right free rolls divided into three, and these left / right free rolls are at least 1.5 times as large as the center free roll. In addition, by combining the center free roll and the left and right free roll pass lines, a continuous casting facility for wide and thin slabs is constructed.

Alternatively, the free roll is composed of a center free roll and three left and right free rolls.
A continuous casting facility for wide and thin slabs is constructed by making the right free roll a taper roll whose outer diameter increases as it moves away from the center free roll.

[0010]

The short side portions at both ends of the slab extracted from the water-cooled mold and having an unsolidified portion inside are pressed by a large-diameter roll or taper roll with a larger amount of reduction than other portions. By increasing the reduction amount, the elongation of the slab in the longitudinal direction is suppressed and the elongation in the width direction is promoted. As a method of increasing the reduction amount, there are a method of increasing the roll diameter and a method of increasing the reduction rate with a taper roll.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of the reference numerals.
FIG. 1 is a conceptual diagram of a continuous casting facility according to the present invention. The continuous casting facility 1 includes a water-cooled mold (mold) 2, a reduction zone 3,
The static control zones 4, 5 and the pinch rolls 6, 6 are arranged in an arc from top to bottom. FIG. 2 is a view taken in the direction of arrow 2 in FIG. 1. In the reduction zone 3, a drive roll set 10 divided into three and a free roll 20 divided into three are arranged at a certain roll pitch.

FIG. 3 is a view taken in the direction of arrow 3-3 in FIG. 2. The drive roll set 10 has a center drive roll 11, a left drive roll 12 and a right drive roll 13 coaxially connected to each other and is driven by a motor (not shown). It is driven via the shaft 14. Above center
The left and right drive rolls 11, 12, 13 have the same outer diameter.
4 is a view taken in the direction of arrow 4-4 in FIG. 2. The free roll set 20 is composed of a center free roll 21, a left free roll 22 and a right free roll 23, which are independently rotatably supported by a bearing block 24. Has been done. The outer diameter of the center free roll 21 is 100 mm, for example,
Outer diameter of both left and right free rolls 22 and 23 is 300m
The feature is that the left and right free rolls 22 and 23 are significantly larger in diameter than the conventional rolls (100 mm). However, as shown in FIG. 4, the roll center axes are displaced so that the pass lines of the rolls 21, 22, and 23 are uniform.

In FIG. 2, reference numeral 8 is a spray nozzle, and cooling water is sprayed from the nozzle 8 onto the slab 9 to promote cooling of the slab 9. Large diameter left and right freeroll 22,2
Since there are almost no gaps around 3, the spray nozzle 8 is arranged on the side of the center free roll 21 having a small diameter.
Since the sprayed cooling water is dammed by the center free roll 21, it flows right and left on the roll 21 and falls from the bearing block 24. The bearing blocks 24 are arranged in a staggered manner so that the falling water meanders so that the falling water does not have cooling streaks on the surface of the slab 9.

The operation of the free roll having the above structure will be described below. FIG. 5 is a rolling reduction action diagram of the free roll of the present invention. When the slab 9 is rolled down by the free rolls 21 to 23, the illustrated contact arc length is geometrically determined from the rolling reduction amount and the roll diameter. FIG. 6 is a graph showing the relationship between the free roll of the present invention and the contact arc length. The larger the roll diameter, the larger the contact arc length. For example, if the reduction amount is 3 mm, 1
The contact arc length of the 00 mm center free roll 21 is about 17
mm, 300 mm left / right center freeroll 2
The contact arc length of 2,23 is about 30 mm.

The larger the contact arc length, the greater the restraining force of the slab in the longitudinal direction (casting direction). That is, in the device of this embodiment in which the left and right free rolls have a diameter of 300 mm, the short side portion of the end of the cast slab 9 is not extended so much in the longitudinal direction as compared with the conventional device in which the left and right free rolls have a diameter of 100 mm. To that extent, it will be extended in the width direction. As a result, the slab 9
The shearing force between the long side portion and the short side portion is sufficiently reduced, and the occurrence of surface cracks can be prevented.

In the above embodiment, the ratio of the diameter of the left / right free rolls 22 and 23 to the diameter of the center free roll 21 was set to 3/1 (three times). It has been found that the expected effect can be obtained when the ratio is 1.5 times or more. In addition, left and right freeroll 22,
The barrel length (barrel length) of 23 does not need to be so large, but is at least ⅕ or more of the width of the cast slab 9. Further, as described with reference to FIG. 2, the pitch between the large-diameter left free rolls 22, 22 is set so small that the rolls do not come into contact with each other. The same applies between the right free rolls 23, 23. The reason why the roll pitch is not expanded is to prevent bulging (a trouble that the solidified shell is cracked by the static iron pressure of molten steel). As a result, the spray nozzle 8 cannot be disposed between the large-diameter left free rolls 22 and 22 and between the large free rolls 23 and 23. Therefore, in order to provide the spray nozzle 8, the diameter of the center free roll is reduced.

FIG. 7 is a diagram of a free roll according to another embodiment of the present invention. This free roll set 30 includes a center free roll 31 having a small diameter and left / right tapered free rolls 3.
It consists of 2, 33. When this free roll set 30 is adopted, since the left and right taper free rolls 32 and 33 have a larger diameter than the center roll 31, the contact arc length increases and the longitudinal restraining force increases as described with reference to FIG. To do.
Moreover, the taper does not prevent the slab 9 from bulging in the width direction. Therefore, the short side portion of the slab end does not extend so much in the longitudinal direction but in the width direction. As a result, the slab 9
The shearing force between the long side portion and the short side portion is sufficiently reduced, and the occurrence of surface cracks can be prevented.

In FIG. 7, θ is a taper free roll 3
The taper angle θ is 2, 33, and this taper angle θ varies depending on the ratio of the thickness of the slab in the water-cooled mold and the thickness of the slab after the reduction. For example, when the slab 9 having a thickness of 100 mm is reduced to 70 mm. A taper angle θ of 30 ° is sufficient. Also,
When the lengths of the taper free rolls 32 and 33 are L and the maximum width of the slab 9 is W, (W / 20) ≦ L ≦ (W / 1
The lengths of the taper free rolls 32 and 33 may be determined so as to satisfy 0). This is because if it is less than W / 20, a sufficient width-expanding effect (expanding the slab in the width direction by rolling down) cannot be obtained, and if it exceeds W / 10, it becomes difficult to obtain good flatness.

FIG. 8 is a plan view of a water-cooled mold suitable for another embodiment of the present invention, which is characterized in that the opening 36 of the water-cooled mold 35 is not oblong but substantially oval. The casting mold 35 forms a slab having a cross section in which the short side portion is curved and bulged, and the curved short side portion is tapered free roll 3 as shown in FIG.
2, 33 positively reduces the width and effectively squeezes the width, and at the same time, suppresses the elongation of the slab in the longitudinal direction. The bulging shape of the short side portion may be an arc, a triangle, or the like, as long as it is a shape that promotes width-out.

The method of the present invention is characterized in that the short side portion of the slab is pressed with a larger amount of reduction than other parts. However, in order to increase the amount of reduction, a large volume (volume) can be obtained with a large-diameter roll.
A typical example is a method of rolling down a large volume in a large diameter portion while increasing the rolling reduction rate with a taper roll.
However, for example, by interposing one small-diameter roll between two large-diameter rolls arranged in the casting direction, and substantially increasing the number of reduction rolls compared to the other parts, the amount of reduction per unit length in the longitudinal direction is reduced. May be increased, and the method of increasing the reduction amount is not limited to the above representative example.

[0021]

As described above, according to the method of the present invention, the short side portions of both ends of the slab having an unsolidified portion are pressed with a large diameter roll or taper roll with a larger amount of reduction than other portions,
By suppressing the expansion of the slab in the longitudinal direction by increasing the amount of reduction,
The present invention promotes widthwise extension and prevents the occurrence of surface cracks. The present invention enables stable production of high quality thin cast pieces.

Further, in a continuous casting facility for rolling down the short side of the slab with a large-diameter roll, the contact arc length between the slab and the roll is increased to suppress the lengthwise extension, which is a simple structure. A high quality thin slab can be obtained.

Further, in a continuous casting facility in which the short side of the slab is rolled down with a taper roll, the slab can be laid out along the taper angle, increasing the width extension and suppressing the longitudinal extension. It is possible to obtain a quality thin slab.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a continuous casting facility according to the present invention.

FIG. 2 is a view on arrow 2 of FIG.

FIG. 3 is a view on arrow 3-3 in FIG.

FIG. 4 is a view on arrow 4-4 of FIG.

FIG. 5 is a drawing showing the rolling action of the free roll of the present invention.

FIG. 6 is a graph showing the relationship between the free roll of the present invention and the contact arc length.

FIG. 7 is a diagram of a free roll according to another embodiment of the present invention.

FIG. 8 is a plan view of a water-cooled mold suitable for another embodiment of the present invention.

FIG. 9 is a drawing process chart of a conventional flat roll for rolling down an unsolidified slab

FIG. 10 is an operation diagram of FIG.

[Explanation of symbols]

1 ... Continuous casting equipment, 2 ... Water-cooled mold, 9 ... Slab, 20, 3
0 ... Free roll set, 21, 31 ... Center free roll, 22, 23 ... Left / right free roll (large diameter roll), 32, 33 ... Left / right free roll (taper roll), 101 ... Unsolidified part, 104 ... Short side of slab, 10
5 ... long side.

Claims (3)

[Claims] 1. A method for producing a slab, which is extracted from a water-cooled mold and has an unsolidified portion inside by pressing a free roll against the long side of the slab to reduce the thickness of the slab. A method for producing a wide thin slab, comprising pressing a short side portion with a larger amount of reduction than other portions. 2. In a continuous casting facility for thinning a slab extracted from a water-cooled mold and having a non-solidified portion inside by pressing a free roll on its long side portion, the free roll is a center free roll and left and right. The left and right free rolls are divided into three parts, the left and right free rolls are at least 1.5 times as large as the center free roll, and the center free roll and the left and right free rolls have the same pass line. A continuous casting facility that features wide and thin slabs. 3. A continuous casting facility for thinning a slab, which is extracted from a water-cooled mold and has an unsolidified portion inside, by pressing a free roll against the long side of the slab to thin the slab. A continuous casting facility for wide thin slabs, which consists of three separate free rolls, and these left and right free rolls are tapered rolls whose outer diameter increases with distance from the center free roll.