JPH07241656A - Slab heating device in continuous casting machine - Google Patents

Abstract

PURPOSE:To provide a means for preventing corner crack in a bending deforming zone, in a vertical bend type continuous casting machine for high speed casting. CONSTITUTION:In the vertical bend type continuous casting machine, a heating means 2 for heating the reference surface of the side surfaces of a cast slab is set at the outer side of the side surface in the width direction in the bend deforming zone 10 of applying the bend-deformation to bend the cast slab. A heating means 2 for heating the other side reference surface is set on the straightening zone 20 of straightening the curved cast slab. Adjusting mechanisms each for adjusting the setting position of the means 2 by shifting heating means 2 in the width direction of the cast slab are arranged respectively. Further, the heating means 2 set in the bend deforming zone 10 adopts the type of an induction heating device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slab heating device in a vertical bending type continuous casting machine.

[0002]

2. Description of the Related Art In a continuous casting machine, in order to flatten a slab that has normally passed through a curved portion, a straightening band is used to correct the shape. In this straightening strip, tensile stress acts on the surface of the slab opposite to the reference surface (which becomes the lower surface after casting), so that cracking occurs when ductility is low. Generally, the ductility of steel depends on the temperature, and it is known that there is an embrittlement region at 750 to 900 ° C. When a cast product is produced by a continuous casting machine, the corner portion of the cast product is more easily cooled than the other parts, and enters the embrittlement zone before the other parts. Therefore, when the slab enters the straightening zone in this state, cracks called corner cracks occur.

The following techniques have been proposed as measures for preventing corner cracks in this straightening zone. The first technique is to control the secondary cooling spray, which is a method of adjusting the amount of water in the secondary cooling spray and the spraying range of the spray water to the slab. The simplest method is to reduce the amount of water in the secondary cooling spray so that it does not enter the embrittlement area, including the slab corners, but this reduces productivity, so it cannot always be used. It doesn't. Therefore, for example, JP-A-58-1
In the technique described in Japanese Patent No. 63559, cooling of the slab corner portion is alleviated by cooling both ends of the slab in the width direction without cooling.

The second technique is a method using a cover. In the technique described in Japanese Patent Laid-Open No. 50-110933,
Both ends of the slab in the width direction are covered with covers to prevent spray water from hitting. Further, there is also a method of attaching a heat insulating material to the inside of the cover to keep the corner portion of the slab warm.

The third technique is a method of heating the corner portion of the slab. In the technique described in Japanese Utility Model Laid-Open No. 57-97667, a burner is installed in the gap between the guide rolls of the straightening belt,
The corners of the slab are being heated. 57-116
In the technique described in Japanese Patent No. 364, the induction coil inserted from the gap between the guide rolls of the straightening strip is arranged near the corner of the slab for induction heating.

FIG. 4 is a diagram showing these prior art heating devices. In the figure, 1 is a slab, 5 is a roll, 7 is a bracket, and 8 is a guide rail. Bracket 7
Is installed by being inserted into the gap of the roll 5, and a burner or an induction coil is attached to the tip thereof. These heating means heat the corner portion of the slab from the thickness direction of the slab.

[0007]

It is well known that the continuous casting machine is structurally divided into several molds, which are commonly used such as a vertical mold, a vertical bending mold, and a bending mold. . Among them, the vertical and vertical bending type continuous casting machines are installed for the purpose of obtaining clean steel because non-metallic inclusions are not trapped in the solidification interface and easily float. Among them, the vertical type continuous casting machine has a large vertical dimension,
Moreover, since the hydrostatic pressure of the molten steel in the unsolidified portion also becomes large, it is difficult to increase the capacity of the equipment. Therefore, in order to obtain clean steel with a large capacity, a vertical bending type continuous casting machine is used.

The vertical bending type continuous casting machine is characterized by a bending deformation band for shifting the cast piece from the vertical portion to the bending portion, as compared with the bending type. Here, bending deformation is applied to the slab, and the slab is pulled out along the guide roll of the curved portion while drawing an arc.

In recent years, in order to improve productivity, a high-speed casting technique with an increased drawing speed has been developed. However, as the drawing speed increases, the thickness of the solidified shell of the slab decreases and breakout easily occurs. Therefore, cooling is strengthened to ensure a sufficient thickness of the solidified shell. As a result, in the bending deformation zone, the corner portion of the cast piece is excessively cooled and is often already in the embrittlement region, which causes a problem that cracking is likely to occur.

Therefore, if the corner crack preventing technique conventionally used for straightening strips is applied to a vertical bending type continuous casting machine for high speed casting, the following problems arise. First, even if the method of controlling the secondary cooling spray, cooling the both ends of the slab in the width direction without cooling it, or applying the cover to this bending deformation zone, Excessive cooling of the corners is inevitable. Even in this case,
The corner portion of the slab is 100 to 100 mm from the center in the width direction of the slab.
The temperature drops to 150 ° C. When the slab is strongly cooled by this method, the central portion in the width direction does not enter the embrittlement region (100
Even at around 0 ° C., the corner portion is cooled to the embrittlement region (900 or less), and the corner crack cannot be prevented. Therefore, strong cooling of the slab cannot be performed, cooling must be weakened, and there is a problem that breakout or the like is likely to occur.

Next, applying the technique of heating the corner portion in the straightening band to the bending deformation band is a problem because it is difficult to install the heating means in a continuous casting machine intended for high speed casting. This is because the thickness of the solidified shell of the slab decreases due to high-speed casting, and internal cracking of the slab easily occurs, so that the roll pitch is reduced.

As a result of the reduction of the roll pitch, it becomes difficult to insert the burner or the induction heating device through the gap between the rolls. In addition, since the roll diameter also decreases as the roll pitch decreases, the size of the part surrounded by the surface of the roll and the surface of the slab becomes smaller, making it difficult to install a burner or induction heating device in this part. There is. In particular, in the bending deformation zone, the solidified shell is thin and breakout is likely to occur, and it is essential to reduce the roll pitch and the roll diameter, so that it is difficult to apply the conventional technique.

The present invention provides means for preventing a corner crack in a bending deformation zone and a straightening zone in a vertical bending type continuous casting machine for high speed casting.

[0014]

According to a first aspect of the present invention, in a vertical bending type continuous casting machine, (a) a bending deformation zone for applying bending deformation to bend a slab is a reference of a side surface of the slab. The heating means for heating the surface side portion is provided outside the side surface of the slab in the width direction, and (b) the straightening band for correcting the curved slab has a portion on the side opposite to the reference surface on the side surface of the slab. A heating device for continuously cast slabs is provided, in which heating means for heating the slab are installed, and (c) an adjusting mechanism for moving the heating means in the width direction of the slab and adjusting the installation position. Second
According to the first invention, in the first invention, the heating means installed in the bending deformation zone is a heating device for continuously cast slab, which is an induction heating device.

[0015]

In the first aspect of the invention, first, in the bending deformation zone,
By heating the portion of the side surface of the slab on the reference surface side (the one that becomes the lower surface after casting), the corner portion on the reference surface side also rises in temperature due to heat conduction from the side surface. As a result, the corner portion on the reference surface side becomes higher in temperature than the embrittlement region and the ductility is recovered. Tensile stress acts on the reference surface side of the slab, but cracks do not occur because the ductility is also restored at the corners.

On the side opposite to the reference surface of the cast slab, there is a possibility that the slab remains in the embrittlement zone because it is not heated, but since compressive stress acts on this side, cracking does not occur. In addition, it is desirable that the heating means be installed from a position slightly before the bending deformation zone so that the temperature of the corner portion rises before the cast piece enters the bending deformation zone.

Next, in the straightening zone, tensile stress acts on the side opposite to the reference surface of the slab, but here again, the temperature rises due to heat conduction from the heated side surface, and ductility is increased. Since it has recovered, it does not crack. Here again, it is desirable to install the heating means from a position slightly before the correction band.

Finally, since the heating means can be moved in the width direction of the slab by the adjusting mechanism for adjusting the installation position, the heating means and the side surface of the slab can be changed by following the width change of the slab. It is possible to always keep the distance properly. As a result, the temperature rise of the corner portion of the slab is stably obtained, and the corner crack is prevented.

In the second aspect of the invention, in addition to the above, since the heating means for the bending deformation zone is an induction heating device, the roll and the like are not damaged by the flame of the burner, and the guide roll is a small diameter roll. But it can be applied.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a view showing the arrangement of a heating apparatus of the present invention in a continuous casting machine. In the figure, 1 is a slab, 2 is heating means, 5 is a guide roll, 9 is a mold, 10 is a bending deformation zone, 20 is a straightening zone, and 91 is a meniscus (molten steel free surface).
Are shown respectively. The heating unit 2 is installed at a position slightly before the bending deformation band and the straightening band so that the corner portion is sufficiently heated before the slab reaches the bending deformation band 10 and the straightening band 20. It is installed from the position. Although not shown in this figure, the heating means 2 is provided with an adjusting mechanism for following the width change of the slab 1.

FIG. 2 is a diagram showing an embodiment in which an induction heating device is used as the heating means for the bending deformation zone. In the figure, 2 is a heating means, 3 is an adjusting mechanism, 4 is a power supply cable, 5 is a guide roll, 6 is a split bearing, 21 is an induction heating device, and other reference numerals are the same as in FIG.

In order to prevent breakout, the bending deformation zone has a guide roller 5 having a reduced diameter by employing a split bearing 6, and the roll pitch of the guide roller is also reduced. Even in such a slab supporting device using a small-diameter guide roll, the induction heating device 21 is used as the heating means 2, and the slab corner portion is heated by facing it to the side surface of the slab 1. It became possible to do.

The induction heating device 21 is composed of an induction coil having one turn, and its specification is that the operating frequency is 2.
It has a frequency of 5 kHz and a capacity of 300 kW. Desirable casting conditions for this induction heating device are cast piece thicknesses 220, 25.
0, 300 mm, slab width 1600-2100 mm, casting speed 1.2-2.0 m / min.

FIG. 3 is a diagram showing the temperature transition of the slab corner portion when the heating device of the present invention is used. In the figure, the horizontal axis indicates the distance L from the meniscus, the vertical axis indicates the temperature T of the slab corner, A indicates the installation position of the heating means for the bending deformation zone, and B indicates the installation position of the heating means for the straightening zone. By using the heating device of the present invention (Example: solid line in the figure), the temperature T of the slab corner portion is increased by 100 ° C. or more as compared with the case where this is not used (Comparative example: broken line in the diagram). ing. As a result, it was confirmed that it was effective in preventing corner cracking.

In the embodiment, an air cylinder is used as a drive device for the adjusting mechanism 3, but this may be a hydraulic cylinder, an electric screw, or the like that moves linearly, other than the air cylinder. Further, in the embodiment, the heating means of the straightening band is also installed on the outer side in the width direction from the side surface of the slab and heats the corner portion from the side surface of the slab, but the roll diameter of the guide roll of the straightening band Is large as in the prior art, the heating means may be inserted through the gap between the guide rolls.

In the above embodiments, the induction heating device was used as the heating means 2 for both the bending deformation band and the correction band, but a burner or the like may be used for these. However, if the combustion adjustment of the burner is not always taken care of, there is a risk of the burner flame hitting the split rolls, split bearings, etc., so it is desirable to use an induction heating device. Especially for the bending deformation zone, use of a small-diameter roll is inevitable for high-speed casting, and as a result, the flame of the burner easily hits the roll and the like, so an induction heating device is preferable.

[0027]

In the vertical bending type continuous casting machine, the bending deformation zone and the straightening zone are provided with heating means, so that the ductility of the corner portion is recovered and cracking can be prevented. Further, since the heating means of the bending deformation zone is a method of heating from the side surface of the slab and is installed on the outside in the width direction of the slab, the gap between the guide rolls is small and continuous using a small diameter roll for high speed casting. It can also be applied to a casting machine.

[Brief description of drawings]

FIG. 1 is a diagram showing an arrangement of a heating device of the present invention in a continuous casting machine.

FIG. 2 is a diagram showing an embodiment in which an induction heating device is used as a heating means.

FIG. 3 is a view showing a temperature transition on the surface of a slab when the heating device of the present invention is used.

FIG. 4 is a diagram showing a conventional heating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cast piece 2 Heating means 3 Adjusting mechanism 10 Bending deformation zone 20 Straightening zone

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Kubota 1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Ken Matsuzaki 1-2-1 Marunouchi, Chiyoda-ku, Tokyo This Steel Pipe Co., Ltd. (72) Inventor Hiromi Nakamura Marunouchi 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Japan Steel Pipe Co., Ltd. (72) Inventor Mikio Suzuki 1-21-2 Marunouchi, Chiyoda-ku, Tokyo Japan Steel Pipe Incorporated (72) Inventor Yuichi Yamaoka 1-2, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Tube Ltd. (72) Inventor Taizo Sera 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd. In-house (72) Inventor Minoru Takada 1-2 1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (2)

[Claims] 1. A vertical bending type continuous casting machine,
(A) In the bending deformation zone that applies bending deformation to bend the slab, a heating means for heating a portion of the side surface of the slab on the reference surface side is installed outside the side surface of the slab in the width direction. ) In the straightening band for straightening the curved slab, a heating means for heating the side surface of the slab opposite to the reference surface is installed,
(C) A cast piece heating device in a continuous casting machine, each of which is provided with an adjusting mechanism for adjusting the installation position by moving these heating means in the width direction of the cast piece. 2. The slab heating device in a continuous casting machine according to claim 1, wherein the heating means installed in the bending deformation zone is an induction heating device.