JPH09276992A - Light rolling reduction device at end stage of solidification in rotary continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light rolling reduction device for continuously executing the rolling reduction without restricting the rotation of a cast slab drawn while rotating in order to apply the light rolling reduction at the end stage of the solidification to the cast billet at the rotary continuous casting process. SOLUTION: In the rotary continuous casting apparatus of molten metal for continuously drawing while rotating the cast billet 15 with a rotary mold 2, one stage or multi-stage type of the rotary reduction device 9 is arranged between a secondary cooling zone 7 in the continuous casting process and one extractor unit having a rotation driving device 12 of the cast slab 15. Further, the rolling reduction device 9 is provided with plural inclining angle changable rolls and further, a driving device for supplying rotating force and feeding force to the cast slab in at least one stage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to prevent the segregation of impurity elements found in the center of rotary continuous casting slabs, that is, in the case of steel slabs, to segregate sulfur, phosphorus, manganese, etc. The present invention relates to a light-rolling device at the end of coagulation.

[0002]

2. Description of the Related Art In the steelmaking process, a continuous casting process in which molten metal is continuously cooled and solidified in a mold to produce a slab is adopted in most steelmaking plants from the viewpoint of stable productivity and quality. As for the quality of the slab, it is desired that the slab has good surface properties and is free from internal defects.

As a measure for improving the surface quality,
The rotary continuous casting method is Andre L. Gueussier, et.al .: Spec
ific aspects of rotary continuous casting ``, Iron
andSteel Engineer, January (1982), p.53. The distribution of carbon in the cross section of the slab obtained by this method is shown in FIG. 9, and it can be seen that there is a positive segregation portion in the center of the cross section corresponding to the final solidification position. Impurities such as sulfur and manganese are concentrated and segregated in the center segregation part of such steel, and the center segregation part is likely to be cracked during the use process of the product or the wire drawing process of the wire rod. Coveted.

FIG. 7 is a diagram showing the concentration distribution of carbon and sulfur in the thickness direction of a rectangular slab produced by continuous casting of a fixed mold. It can be seen that even in the case of a slab having a rectangular cross section, a positive segregation zone of carbon or sulfur is present in the central portion, as in the case of a round cross section slab manufactured by rotary continuous casting. As a measure for reducing the center segregation of a rectangular cross-section slab, Japanese Examined Patent Publication No. 59-1682 discloses that the liquid phase of the slab is reduced by one or more pairs of reduction rolls in the drawing process following the secondary cooling zone in the continuous casting process of molten metal. Disclosed is a continuous casting method characterized by continuously rolling down between the wire crater tip and the solid phase wire crater tip in a steady drawing process at a rolling reduction rate of 1.5% or less per pair of rolls. Has been done.

FIG. 6 is an explanatory view of a continuous casting apparatus showing an embodiment thereof, in which a cast piece 15 drawn out from a fixed mold 25 is drawn out via a pinch roll 26 by a drawing-out portion which also serves as a rolling down device 27, and a curved die is used. In casting, as a group of rolls of a pulling-out portion which also serves as the rolling down device 27, rolling is applied to the cast slab 15 by hydraulic pressure or the like, and necessary power is applied by an electric motor to drive it. FIG. 5 is a model diagram of the crater tip of the cast slab 15. The cast slab 15 in the range between the liquidus crater tip 21 and the solidus crater tip 22 is drawn by a pulling roll reduction device 27, one each. As a result of continuously applying a rolling reduction of 0.5 to 4 mm per roll in the steady drawing process, it was not possible to recognize the occurrence of center segregation or center porosity in any of the cases. That is, in continuous casting, it is possible to prevent the occurrence of a central segregation zone by subjecting the slab to a light reduction at the end of solidification under appropriate conditions.

If this final solidification light reduction method is applied to a slab by the above-mentioned continuous rotation casting, an ideal slab with good surface properties and few internal defects can be manufactured. However, since the slab in the rotary continuous casting process is rotating at a speed of about 100 rpm, the conventional reduction device shown in FIG. 6 has a problem that the reduction roll restrains the rotation of the slab and casting cannot be performed. .

Japanese Unexamined Patent Publication (Kokai) No. 4-41048 discloses a continuous casting apparatus for round cast pieces shown in FIG. That is, the slab 15 that has been solidified by being drawn from the fixed mold 25 is uniformly heated by the heater 28 that is arranged along the drawing path. Then, apply appropriate reduction with the rotary mill 29,
After the diameter is reduced to a diameter corresponding to the reduction degree, the round cast piece 30 having a desired diameter and length is cut by a cutting machine disposed on the rear side of these. Therefore, it is possible to manufacture round slabs of various diameters from one mold. In this case, however, it is unclear whether or not this device can be directly applied to the final stage of solidification because the slab that has been solidified is rolled. In addition, since it is a fixed mold, the slab itself must not rotate, so a rotary mill with a complicated structure must be adopted as a rolling mill, and it cannot be applied to a light reduction device due to high cost and facility reliability. .

[0008]

As described above, in order to produce a slab having good surface properties and less center segregation, light rolling at the final stage of solidification is applied to a slab being rotated in a rotary continuous casting process. It was difficult to manufacture a slab with a small center segregation because there was no suitable device to perform it. In order to apply a final solidification light reduction to a slab in a rotary continuous casting process, it is an urgent issue to develop a light reduction device that continuously reduces the rotation of the slab that is being drawn while it is being rotated. It was

[0009]

The means for solving the above-mentioned problems is, in the invention of claim 1, a rotary continuous casting apparatus for molten metal which continuously withdraws a slab while rotating the slab. It is a final stage solidification light reduction device of rotary continuous casting, characterized in that one or more stages of reduction device are arranged between an extractor unit having a secondary cooling zone and a slab rotation drive device.

According to a second aspect of the present invention, the rolling reduction device has a plurality of tilt rolls with variable tilt angles.

According to the invention of claim 3, at least one stage of the reduction device has a drive device for supplying a rotational force and a feeding force to the slab.
Is a light rolling reduction device in the last stage of solidification of the rotary continuous casting in the above means.

The operation of the present invention will be described in more detail below. In rotary continuous casting of molten metal in which a slab is continuously drawn while rotating, there is no application example of a light reduction device at the final stage of solidification. The inventor has studied the arrangement method of the equipment from various angles in consideration of the characteristics unique to the rotary continuous casting method.
As a result, the inventor, as shown in FIG. 1, arranges a single-stage or multiple-stage reduction device between the secondary cooling zone of the continuous casting device and the extractor unit having the slab rotation drive device. I found out. That is, the slab 15 withdrawn from the rotary mold 4 is rotated by being applied with a rotating force and a withdrawing force by the extractor unit, and is rotated by the primary cooling zone 5.
And, after passing through the secondary cooling zone 7 to be cooled and solidified, it is cut by the cutting device 13 to be a billet or a bloom.
As shown in FIG. 5, the slab is solidified from the outside, and the solidified portion 16 is drawn to the outside, then the solid-liquid coexisting region 18, and the central portion is drawn out in the state of molten steel 14. After passing through the secondary cooling zone 7, the slab is centered. Since the part solidifies, at that time, the slab 15 in the range between the liquidus crater tip 21 and the solidus crater 22 is reduced by the rolling down device 9
To continuously roll down a predetermined amount. After that, the slab 15 that has solidified to the center and secured sufficient strength is sent at a predetermined speed while applying a rotational driving force by the extractor unit, and immediately after that, the slab 15 that has completely solidified is cut by the cutting device 13 for a predetermined length. Cut it into billets or blooms.

Further, it is desirable that the rolling-down device is composed of a plurality of inclined roll-type rolling-down rolls 23 whose tilt angles are variable as shown in FIG. 2 and guide shoes 24 if necessary. The reason why the inclined roll is used as the pressing roll is that, when the slab is pressed, the slab can be continuously rolled down by following the rotation and the feeding of the slab. The inclination angle of the roll is made variable in order to adjust the inclination angle to an optimum value according to the reduction rate to achieve matching between rotation and feed. Further, as shown in FIG. 3, the guide shoe prevents the deformed shape of the cross section due to the reduction of the cast piece from changing from a circle to a polygon,
It is used to prevent harmful cracking due to rolling, and may be omitted if there is no concern that cracking will occur depending on rolling conditions.

More preferably, in the reduction device 9 shown in FIG. 1, at least one reduction device has a roll driving device like an inclined rolling mill. This simplifies the mechanism for supplying the turning force and the feeding force to the slab by substituting the function of the extractor unit by the reduction device having the driving device, and thereby the rotation and the feeding of the slab and the driving device are prevented. This is to facilitate speed matching.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the invention. That is, the molten steel 14 in the ladle 1 is cast into the rotary mold 4 through the tundish 2 and the nozzle 3 and is pressed against the rotary mold 4 due to centrifugal force, and due to the rapeseed oil lubrication, a solidified shell with few surface defects. A cast slab 15 having is formed. Then, the slab is cooled by the primary cooling zone 5 and the secondary cooling zone 7 to increase the shell thickness, and immediately before the completion of solidification, the single or a plurality of reduction devices 9 are used for the tip of the liquidus crater and the solid phase property shown in FIG. It is pressed down between the tips of the craters. At that time, as shown in FIG. 3, the cross section of the slab deforms from the broken line to the solid line, and the cross-sectional area of the unsolidified portion 17 of the slab decreases, so that the solidification at the center of the slab at the final solidification position occurs. Compensate for shrinkage and prevent center segregation. The solidified slab is cut by the cutting device 13 into billets or blooms having a predetermined size. The rotation and the feeding of the slab are given a driving force by the extractor unit 11 or the rolling down device 9.

The reduction device is composed of an inclined roll 23 and a guide shoe 24 as shown in FIG. The number of rolls and the presence or absence of guide shoes may be appropriately selected depending on the rolling conditions. In addition, the inclination angle of the reduction roll must be controlled to an optimum value from the reduction rate, the rotation speed of the slab, and the feed rate.

[0017]

EXAMPLE Using the rotary continuous casting machine of FIG. 1 with one stage of each of the three types of reduction devices shown by b, c and d of FIG. 2, S45
By adjusting the feed rate of the C slab, the crater end position was pressed down so that the cross-section reduction rate was about 1.5%. As a result, as shown in FIG. 4, it became possible to prevent solidification segregation of carbon in the central portion. The center segregation of other components such as phosphorus and manganese was also improved.

Further, the same casting was performed by installing a plurality of reduction devices in five stages. However, even if the casting speed is changed, the crater end position can be reduced by adjusting the reduction position, and as shown in FIG. The center segregation was greatly reduced. Further, the same study was carried out for other steel types and metals, but the center segregation was alleviated in all cases.

[0019]

As described above, between the secondary cooling zone of the rotary continuous casting device and the extractor unit having the rotary drive device for the cast slab, one or a plurality of reduction devices, particularly a plurality of inclination angles. By arranging a reduction device having a variable tilt roll, it is possible to prevent the center segregation of the slab without hindering the withdrawal and rotation of the slab from the rotary continuous casting, thus improving the internal quality of the slab. It can be remarkably improved, and based on this, there is a remarkable effect in improving the fatigue strength of the final product such as a slab, a bar, and a wire.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a rotary continuous casting device to which a rolling reduction device of the present invention is applied.

FIG. 2 is an explanatory view of a rolling down device of the present invention, (a) is a side view showing a relationship between a cast piece and a rolling down roll, (b), (c), (d).
FIG. 3 is a view of this from the entrance side, (b) shows a case of two rolls, (c) shows a case of three rolls, and (d) shows a case of four rolls.

FIG. 3 is a diagram for explaining the operation of the rolling-down device according to the present invention.

FIG. 4 is an explanatory diagram showing an effect of one embodiment of the present invention.

FIG. 5 is a model diagram of a tip portion of a crater.

FIG. 6 is an explanatory diagram of a continuous casting device to which a conventional rolling down device is applied.

FIG. 7 is an explanatory diagram showing segregation of a slab produced by conventional continuous casting.

FIG. 8 is an explanatory diagram showing a conventional technique.

FIG. 9 is an explanatory diagram showing a graph of carbon segregation in a cross section of a billet in the prior art.

[Explanation of symbols]

 1 Ladle 2 Tundish 3 Nozzle 4 Rotating Mold 5 Primary Cooling Zone 6 Guide Roll 7 Secondary Cooling Zone 8 Guide Roll 9 Rolling Down Device 10 Pinch Roll 11 Extractor Unit 12 Drive Unit 13 Cutting Device 14 Molten Steel 15 Cast Piece 16 Solidification of Cast Piece Part 17 Unsolidified part of slab 18 Solid-liquid coexistence region 19 Cross-sectional profile of slab on inlet side of rolling mill 20 Cross-sectional profile of slab on outgoing side of rolling mill 21 Liquid-phase crater tip 22 Solid-phase crater tip 23 Rolling roll 24 Guide shoe 25 Fixed mold 26 Pinch roll 27 Rolling down device 28 Heater 29 Rotary mill 30 Round cast slab

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[Procedure amendment]

[Submission date] April 17, 1996

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

[Fig. 2]

Claims (3)

[Claims] 1. A single or a plurality of stages of reduction between a secondary cooling zone of a rotary continuous casting apparatus for molten metal that continuously draws a cast slab and an extractor unit having a rotary drive device for the slab. A device for arranging the equipment, which is a light-rolling device for the final stage of solidification in rotary continuous casting. 2. The final solidification stage light-rolling apparatus for rotary continuous casting according to claim 1, wherein the rolling-down apparatus has a plurality of tilt rolls with variable tilt angles. 3. The final stage of solidification in rotary continuous casting according to claim 1 or 2, wherein at least one stage of the reduction device has a drive device for supplying rotational force and feed force to the slab. Light reduction device.