JP2986928B2 - Continuous forging method of slab strand in continuous casting. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In a slab strand obtained by continuous casting, center segregation and center porosity, which cause quality deterioration, are inevitably generated, and in order to prevent or reduce this, a process of drawing a slab strand is performed. In the vicinity of the solidification completion point of the strand is subjected to forging, but when such a forging method is applied to continuous casting of a large strand such as a slab, since the width dimension is large, internal cracking due to bulging occurs. Outbreaks are inevitable. An object of the present invention is to effectively avoid defects such as internal cracks, which are a concern when applying forging to a wide slab strand such as a slab.

[0002]

2. Description of the Related Art In the vicinity of the completion of the solidification point of a slab strand drawn from a continuous casting mold, forging is performed by an anvil sandwiching the strand on both sides, and the internal quality of the slab strand is improved by the forging. Regarding this, many proposals have already been found, for example, in JP-A-63-183765.

[0003] When such a forging process is applied to a large slab or the like, there is the following problem unlike forging for a bloom or the like. In other words, because the width of a plate such as a slab is large, a large rolling force is required, and when a device having a large capacity corresponding to this is applied to an existing continuous casting machine, there are cases where it cannot be installed due to space restrictions. In addition, since the slab has a large width dimension as described above, bulging tends to occur in the process of drawing the casting, but it is not possible to reliably support the slab strand especially in the area where the forging device is installed. In addition, slabs of various widths are cast even in the same slab, and internal forging due to bulging is likely to occur. In order to cope with such operations, forging processing is performed. Where the anvil needs to have a variable width structure, the device with such a structure has a problem in strength because of excessive load at high temperature, and it is practically Installation was difficult. JP-A-61-238449, JP-A-62-124057 and JP-A-62-124058 each disclose a method for preventing the occurrence of bulging of a slab in continuous casting. If such a technique is applied only to the forging of a slab strand, internal cracking may occur at the initial stage of forging, and even in the technique disclosed in Japanese Patent Application Laid-Open No. 2-121760, a large-sized slab may be formed. When performing forging work on such a wide cast slab, an excessive rolling force is required during the rolling work, and it is difficult to apply existing equipment, and at present, there is no effective means. Was.

[0004]

In the case of forging a large slab strand such as a slab,
It is an object of the present invention to propose a method capable of realizing effective forging work without requiring an excessive rolling force.

[0005]

According to the present invention, a solidified shell is crimped by applying a reduction by an anvil in the thickness direction of a slab strand in the vicinity of a solidification completion point of the slab strand drawn from a continuous casting mold. In doing so, there is provided a continuous forging method for a slab strand in continuous casting, wherein forging is performed a plurality of times in the width direction of the slab strand. In the present invention, it is particularly advantageous that the thickness of the slab strand in the width direction is changed by the continuous casting mold or the roller apron on the exit side of the continuous casting mold.

[0006]

The self-supporting effect of a relatively narrow material such as bloom has a self-supporting effect, that is, since the width of the unsolidified portion that causes bulging is small, the bending span is small and the solidified shell of the slab strand is small. Since stiffness can provide sufficient support, the occurrence of bulging is extremely small, and in the present invention as well, the sectional shape is made as close as possible to a bloom. As a specific method, forging of a slab strand is performed a plurality of times in the width direction of the strand. Here, forging in the longitudinal direction of the slab strand is also considered,
In this case, there is an advantage that the forging device can be downsized. However, when such a processing method is applied, an internal crack may be generated when the solidified shell of the slab strand does not crimp under the initial pressure. Therefore, in the present invention, the rolling is performed a plurality of times in the width direction of the slab strand. Also in this case, there is a possibility that internal cracks occur depending on the rolling conditions, but in such a case, the width direction of the slab strand is measured by a continuous casting mold or a roller apron on the exit side of the continuous casting mold. Can be dealt with by changing the thickness.

[0007] By performing the forging process a plurality of times in the width direction of the slab strand, the solidified shell is partially pressed and the width dimension against bulging is reduced, so that the same support effect as bloom can be expected. In addition, at the time of continuous casting or at the roller apron on the delivery side of the continuous casting, by reducing both end regions in the width direction of the slab strand where a large rolling force is required to be thinner than other regions, the rolling force is reduced. It is possible to use a single type of anvil even when machining slab strands having different widths, especially if the thickness reduction region of the slab strand is appropriately adjusted, so that the width of the anvil can be varied. No mechanism is needed at all.

FIG. 1 shows a schematic diagram of a continuous casting equipment suitable for use in the practice of the present invention. In the figure, reference numeral 1 denotes a continuous casting mold, 2 denotes a slab strand drawn from the casting mold 1, and 3 denotes a roller. The roller apron 3 is provided with a rolling roll having a variable roll interval. Also 4
a, 4b is a continuous forged device disposed solidification completion point proximity of the slab strand 2, a set A ₁ of the anvil in the forging device 4a, also forging apparatus anvil and 4b set A ₂
An example is shown of a two-division system in which forging is performed on the central region in the width direction of the slab strand by the device 4a and then forging is performed on the unprocessed region by 4b.

To apply forging to a slab-like slab strand using the equipment having the above configuration, first, as shown in FIG. 2, a forging device 4a is used to forge the slab strand 1 in the width direction. Is subjected to partial reduction. In this case, the rolling region is a central portion as shown in the figure in the case of one location, and the rolling width is set to a range which is about half of the entire width and does not cause bulging in order to reduce the rolling force in half with forging in the next stage. Here, in the case of a wide slab, a very high self-support effect can be expected by applying a plurality of rows of anvils to the first-stage reduction. The forging amount can take the following values to prevent internal cracking and improve center segregation. Next, in the forging device 4b that performs the second-stage reduction, the remaining region of the unsolidified portion is reduced as shown in FIG. The rolling width by the anvil can be limited to the area excluding the rolling area at the first stage, but if there is enough rolling force, the entire area in the width direction of the slab strand 1 from the viewpoint of maintaining flatness after processing It is preferred that In addition, by performing such processing in the second stage, even if the width of the slab strand 1 is variously changed, it is not necessary to change the width of the anvil each time, and the equipment itself is not necessary. This has the advantage of being simpler and of reducing operational effort. In addition, in the above-mentioned FIG. 1, the case where the forging process of the slab strand is divided into two has been described. By reducing the width of the width end area as shown in FIG. 4, the rolling force can be reduced. As a method of thinning, the casting may be performed in such a shape with a continuous casting mold, or the aggressive reduction or bulging by the roll may be advanced by appropriately adjusting the roll interval of the reduction roll of the roller apron. It may have a cross-sectional shape, or it may be used in combination. In the case where the slab strand is glad to cause internal cracks under the first-stage pressure, the slab strand may be thinned by using a mold or a roller apron as described above as long as the slab strand is prevented.

[0010]

[Example] A slab strand with a thickness of 250 mm and a width of 2000 mm
(Low or medium carbon steel) in the same area as the case where the surface temperature of the slab strand is 900 ° C. and the entire width is forged with a reduction of 60 mm while continuously casting (low or medium carbon steel). 1
In the case where the forging process was performed by the two-stage division as shown in Table 2, the internal quality of each of the obtained cast pieces was comparatively investigated. In the case of forging by two-stage division,
It is cast in advance in a cross-sectional shape as shown in FIG. 5 and the first-stage reduction is performed by reducing the width of the central portion of the slab strand 1000 mm in the widthwise central area 1000 mm by a reduction amount of 60 mm. Forging processing was performed with a 60 mm reduction amount mainly on the unpressed lower part.
As a result, both had good internal quality, but in the former case, the rolling force required for forging was normal.
According to the forging process according to the present invention, 5000 tons are required, 1800 tons for the first stage and 2,200 tons for the second stage, and it has been confirmed that the rolling force required for the process can be reduced. In addition, if the equipment cost is set to 100 by index in the case of the conventional method,
According to the present invention, it can be reduced to about 85.

[0011]

As described above, according to the present invention, it is possible to reduce the rolling force per operation in the forging process of a wide slab strand such as a slab, and it is possible to reduce the size of the equipment. It can be easily applied to other facilities. Further, according to the present invention, bulging or the like can be avoided as much as possible, so that internal cracks during forging can be prevented, and the product quality can be effectively improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of equipment suitable for use in carrying out the present invention.

FIG. 2 is a cross-sectional view of a slab strand during forging.

FIG. 3 is a cross-sectional view of a slab strand during forging processing.

FIG. 4 is a cross-sectional view of a slab strand in the casting mold or roller apron region.

FIG. 5 is a cross-sectional view of a slab strand cast in an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Continuous casting mold 2 Slab strand 3 Roller apron 4 Forging device

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B22D 11/128 350

Claims (2)

(57) [Claims] In a region near the solidification completion point of a slab strand drawn from a continuous casting mold, a pressure is applied by an anvil in the thickness direction of the slab strand to press a solidified shell. A continuous forging method for a slab strand in continuous casting, wherein a plurality of forging operations are performed in a width direction. 2. The method according to claim 1, wherein the thickness of the slab strand in the width direction is changed by a continuous casting mold or a roller apron at an outlet side of the continuous casting mold.