JPH06277809A - Dummy bar for continuous casting and method for executing rolling reduction to cast slab in continuous caster - Google Patents

Abstract

PURPOSE:To enable rolling reduction to a cast slab in a continuous caster without needing the reconstruction of the continuous casting equipment itself by improving a dummy bar, in a dummy bar for continuous casting and the method for executing the rolling reduction to the cast slab in the continuous caster by using the dummy bar. CONSTITUTION:In the dummy bar 10 used in the continuous caster containing the rolling reduction means for reducing the thickness of the cast slab 21 drawn from a continuous casting mold to the prescribed thickness, a dummy bar head 11 which can be deformed without substantially disturbing the rolling reduction of the cast slab at the time of executing the rolling reduction and can transmit the force needed to the drawing to the starting end of solidification of the cast slab, is fitted attachably/detachably to/from the dummy bar body 12 having the thickness of the prescribed thickness or lower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting dummy bar and a method for rolling down a slab in a continuous casting machine using the dummy bar.

[0002]

2. Description of the Related Art In recent years, in continuous casting of metal, in order to adjust the thickness of the slab and reduce segregation, a technique has been developed in which the slab is pressed in the thickness direction in a continuous casting machine. Conventionally, since the dummy bar is generally configured to be a rigid body in the thickness direction of the cast piece, when applying the reduction in the thickness direction of the cast piece in the continuous casting machine as described above, the dummy bar is used as a reduction means at the initial stage of casting. Until this passes, the thickness of this reduction means is kept larger than the thickness of the dummy bar, and after the dummy bar has passed through the reduction means, it is narrowed down to a thickness corresponding to the predetermined reduction margin, and the subsequent slab is reduced to the predetermined thickness. Has been done.

Typically, the rolling-down means is composed of a pulling roll having a variable opening and a guide roll having a fixed opening. Since the thickness of the slab and the thickness of the dummy bar are often different, the roll opening of the drawing roll can be adjusted according to the thickness of the dummy bar and the slab according to the progress of the slab. However, with respect to the guide rolls arranged adjacent to the drawing rolls, it is general that both the dummy bar and the cast slabs are fixed to an opening degree that allows the progress without constraint. Therefore, the conventional rolling-down method cannot be applied as it is. Further, although it is technically possible to modify the equipment so that the conventional reduction method can be applied, it cannot be practically adopted because the modification cost becomes huge.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems, and an improved dummy bar capable of rolling down a cast piece in a continuous casting machine without the need for modifying the continuous casting equipment itself, and a dummy bar thereof. It is an object of the present invention to provide a method for reducing a cast piece in a continuous casting machine used.

[0005]

According to the present invention, the above object is to provide a dummy bar used in a continuous casting machine including a reduction means for reducing the thickness of a cast piece drawn from a continuous casting mold to a predetermined thickness, A dummy bar head having a thickness equal to or less than the predetermined thickness is a dummy bar head that is deformable without substantially hindering the rolling of the slab during the rolling down and can transmit the force required for the drawing to the solidification start end of the slab. It is achieved by a dummy bar for continuous casting, which is detachably attached to the dummy bar.

Further, the method for reducing a cast piece in a continuous casting machine of the present invention using the above dummy bar is a method for performing a reduction in a continuous casting machine for reducing the thickness of a cast piece drawn from a continuous casting mold to a predetermined thickness. A dummy bar head that can be deformed without substantially hindering the rolling of the slab during rolling and that can transmit the force required for the drawing to the solidification start end of the slab is attached to and detached from the main body of the dummy bar having a thickness not more than the predetermined thickness It is characterized in that the dummy bar head and the solidification start end of the slab are continuously pressed down to the predetermined thickness by using a dummy bar which is mounted so as to be possible.

[0007]

First, by setting the dummy bar body to a thickness of the cast piece on the delivery side of the continuous casting machine or less, the cast piece can be drawn out without being affected by the thickness reduction in the machine. Since the opening of the draw roll can be changed according to the progress of the slab as described above, the opening is set to match the thickness of the dummy bar when passing through the dummy bar, and to the opening that corresponds to the predetermined amount of reduction when passing through the slab. To do.

The dummy bar head forming the connecting portion between the dummy bar and the cast piece should be deformed so as not to hinder the reduction of the solidification start end (generally, the lower end of the cast piece) which is directly connected to the cast piece, especially the dummy bar head, during the reduction. To do. This can be easily realized, for example, by providing a cavity having a size capable of sufficiently absorbing the reduction margin inside the dummy bar head. Desirably, on the dummy bar main body side of the dummy bar head, from the main body thickness to the cast piece thickness (specifically, cast piece thickness-α: where α =
[Lower end width of mold]-[clearance for seal material between slab mold walls]), a space is provided inside the head at that portion, and the head is pressed by the pressing force when passing through the thickness reducing means. Is prepared to have a strength capable of reducing the thickness.

Further, since the solidification start end of the slab is low in temperature and has a high rigidity, a cavity is formed in this part of the slab so that this part can be easily pressed when the thickness is reduced. It is desirable to provide a hollow protrusion. The molten metal injected into the mold at the start of casting surrounds the hollow protrusion at the tip of the dummy bar head and solidifies, leaving a cavity inside the solidification start end of the slab.

The slab side of the dummy bar head is shaped so that the engaging portion is formed by solidification of the slab so that the drawing force can be transmitted to the slab. It is necessary to separate the dummy bar from the slab that has gone out of the continuous casting machine through the thickness reduction.
Therefore, the dummy bar head is detachably attached to the dummy bar body. The dummy bar head removed from the dummy bar body is in a state of being fixed to the solidification start end of the slab by solidification of the slab. The slab and the dummy bar are finally separated by separating the slab end portion including the dummy bar head fixing portion from the slab body. The adhered material between the cut slab end and the dummy bar head is discarded. That is, in the dummy bar of the present invention, the head portion is made disposable, and a new dummy bar head is mounted on the dummy bar main body for each casting.

The dummy bar of the present invention and the method for rolling down a slab using the same are particularly effective when applied to a case where the thickness of a slab is greatly reduced by narrowing down multi-stage guide rolls. As a method of significantly reducing the thickness of the slab,
In addition to this, a single-stage or a relatively small number of reduction devices can be used, but in that case, the temperature drop of the slab inevitably increases and the energy efficiency decreases.

As described above, according to the present invention, when the thickness of the cast piece is reduced in the continuous casting machine, the thickness of the piece connected to the solidification start end of the cast piece when the dummy bar at the start of casting passes through the reduction means. By easily deforming the directionally deformable dummy bar head part, the thickness reduction device itself can pass through the entire dummy bar without any particular change, and it is possible to continuously perform a predetermined amount of reduction on the succeeding slab body. Become.

Hereinafter, the present invention will be described in more detail by way of examples with reference to the accompanying drawings.

[0014]

EXAMPLE The present invention was applied to a so-called near net shape continuous casting machine. One problem with near net shape continuous casting machines is the injection of molten metal into thin wall molds. For example, when the thickness of the mold cavity is reduced to the same as the thickness of the thin cast piece, if the discharge portion of the immersion nozzle is reduced accordingly, various problems such as nozzle clogging will occur. In order to avoid this, the thickness of the mold cavity was increased to some extent, and in order to obtain a predetermined cast piece thickness in the continuous casting machine, the cast piece thickness was reduced by narrowing down the guide rolls in the machine. The shape of the dummy bar used is shown in FIG. The figure is a vertical cross-sectional view along the thickness direction of the cast slab.

The dummy bar 10 of the present invention has a dummy bar head 11 directly connected to the lower end (solidification start end) of a cast piece 21.
Is mounted on the dummy bar body 12. A portion of the dummy bar head 11 on the dummy bar body 12 side has a thickness Td equivalent to that of the body 12. The dummy bar head 11 and the dummy bar main body 12 are used by being engaged with each other at the key-shaped ends at the mounting portion A, and can be easily removed after use.

The cast bar 1 side portion of the dummy bar head 11 is
The inside is hollow S so that it can be easily crushed when the thickness of the cast piece is reduced. The upper portion S1 of the cavity S bites into the inside of the solidified slab and forms a cavity inside the solidification start end of the slab. As a result, it is possible to easily reduce the solidification start end of the slab, which has a relatively low temperature and a high rigidity when the thickness is reduced. A steel material having a T-shaped cross section is welded to the upper surface of the dummy bar head 11, and is fixedly engaged with the surrounding solidified slab portion so that the slab withdrawal force can be transmitted.

The cast slab 1 drawn out by using the dummy bar 10 is pressed down from the thickness T1 at the time of solidification to a predetermined thickness T when passing through a pressing means (not shown) such as a guide roll. The thickness Td of the dummy bar body 12 is set to be smaller than the predetermined thickness T, and does not interfere with the thickness reduction. The size P of the opening of the upper cavity S1
Is slightly larger than the difference (reduction margin) between the thickness T1 of the cast slab 1 as it is solidified and the predetermined thickness T after reduction, so that the opening P can be reduced at a predetermined reduction margin without being completely closed. There is.

The portion of the dummy bar head 11 on the cast piece 21 side is tapered so that the thickness continuously increases from the dummy bar body 12 side (thickness Td) toward the cast piece 21 side (thickness T1). The thickness of the shoulder 11B that is most overhanged is equal to the thickness T1 of the cast slab 21. With such a shape, the thickness reduction gradually starts in the range of the tapered portion (internal cavity S), and the subsequent thickness reduction of the cast piece itself can be smoothly performed.

FIG. 2 schematically shows the progress of the thickness reduction in the region from the dummy bar head 11 to the end of the cast slab 21 when passing through the roll for performing the thickness reduction. The slab is pulled out in the direction of the arrow in the figure and proceeds in the order of (a) to (d) in the figure. The roll 22 is, for example, a guide roll whose opening is fixed. At the position of FIG. 2A, the leading roll 22 approaches the tapered hollow portion of the dummy bar head 11. No reduction has yet occurred at this point.

At the position of FIG. 2 (d), the leading roll 22 starts to roll down the tapered hollow portion of the dummy bar head 11. When reaching the position of FIG. 2 (c), the dummy bar head 11 is pressed down to the shoulder 11B and crushed. Upper cavity S1
The opening P of is not completely closed. At the position of FIG. 2 (d), the upper cavity S1 is also crushed and remains as a slight gap, and the substantial thickness reduction of the cast slab 21 starts.

FIG. 3 shows an arrangement example when twin belt type continuous casting is performed using the dummy bar of the present invention. The immersion nozzle 26 extending downward from the tundish 25 is inserted in the mold cavity 24 between the mold walls constituted by the pair of circulating cooling belts 23, and the lower part is closed by the dummy bar head 11 of the present invention. Then, the molten metal 27 is injected and casting is started. Dummy bar head 11 and cooling belt 23
The clearance between and is sealed with a sealing material 28 such as asbestos. In addition, inside the cooling belt 23, the iron wire mesh 2 is used to prevent the splash at the start of the molten metal injection and to have a cooling function.
9 are arranged.

The lower part 12A of the dummy bar main body 12 has a chain structure which can be freely bent in the thickness direction of the slab 21, so that it can be advanced along the curvilinear arrangement of the drawing rolls or the guide rolls 22 without restriction. Has become. In the present example, since it is not possible to change the opening degree of the guide roll online in the existing continuous casting machine, casting was performed using the dummy bar of the present invention. Since the dummy bar head was made disposable, it was necessary to discard the used dummy bar head after each casting and prepare a new dummy bar head and mount it on the dummy bar body instead, but the casting itself could be performed without any problems. Further, since no large-scale facility modification such as slab progress monitoring in the continuous casting machine was necessary, the existing continuous casting facility could be used as it was.

In the present embodiment, the member 11A having a T-shaped cross section is used by welding in order to engage the dummy bar head 11 and the slab 1 so as to be able to transmit the drawing force. It is not limited to this. For example, as shown in FIG. 4, if the portion of the upper cavity S1 is tapered so as to expand in the direction opposite to that of FIG.
It is possible to obtain a pulling force transmission action without using. In addition to this, in consideration of the fact that the dummy bar head 11 is disposable, various dummy bar head shapes can be used within a range that does not require too much work cost.

[0024]

As described above, according to the dummy bar or the cast piece rolling-down method of the present invention, it is possible to inexpensively manufacture the dummy bar head and to replace it, without the need for modifying the continuous casting equipment itself. The slab can be rolled in a continuous casting machine.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view in the thickness direction of a slab showing an example of a dummy bar according to the present invention.

FIG. 2 is a longitudinal sectional view in the thickness direction of a slab showing the progress of thickness reduction in continuous casting using the dummy bar according to the present invention shown in FIG.

3 is a vertical sectional view in the thickness direction of a slab showing an example in which the dummy bar according to the present invention shown in FIG. 1 is applied to twin belt type continuous casting.

FIG. 4 is a sectional view in the thickness direction of the cast slab showing another embodiment of the head portion of the dummy bar according to the present invention shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Dummy bar 11 of this invention 11 ... Dummy bar head 11A ... T-shaped member for engagement with the slab 1 11B ... Shoulder of the dummy bar head 11 (maximum overhanging part) 12 ... Dummy bar main body 12A ... Flexible part of the dummy bar main body S ... Dummy bar head 11 Cavity portion S1 ... Upper portion of cavity S (portion into the slab 21) P ... Size of opening of cavity S1 T1 ... Thickness of slab 1 as cast T ... Thickness of slab 1 after rolling Td ... Thickness of dummy bar main body 21 ... Slab 22 ... Drawing roll or guide roll 23 ... Cooling belt 24 ... Mold cavity 25 ... Tundish 26 ... Immersion nozzle 27 ... Molten metal 28 ... Seal material (asbestos) 29 ... Splash prevention and cooling Wire mesh

Claims (4)

[Claims] 1. A dummy bar for use in a continuous casting machine, comprising a reduction means for reducing the thickness of a slab drawn from a continuous casting mold to a predetermined thickness, wherein the reduction of the slab is not substantially prevented during the reduction. A dummy bar head for continuous casting, characterized in that a dummy bar head that is deformable and capable of transmitting the force required for drawing to the solidification start end of the slab is removably attached to the dummy bar body having a thickness of the predetermined thickness or less. . 2. The dummy bar head includes a cavity capable of absorbing a reduction margin of the cast slab.
The dummy bar shown. 3. A method of performing a reduction in a continuous casting machine for reducing the thickness of a cast piece drawn out from a continuous casting mold to a predetermined thickness, which is deformable without substantially hindering the reduction of the cast piece during the reduction. And a dummy bar head capable of transmitting the force required for drawing to the solidification start end of the slab is detachably attached to the dummy bar main body having a thickness of the predetermined thickness or less, using the dummy bar head and the slab. The method for continuously reducing the cast piece in a continuous casting machine, which comprises continuously reducing the solidification start end of the product to the predetermined thickness. 4. The dummy bar head includes a cavity capable of absorbing a reduction margin of the cast slab.
The method described.