JPH0336618B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for cutting slabs to double the width, and in particular, to a red-hot slab that has been continuously cast to double the width and cut in the width direction, using a day scroll. The present invention relates to a method for cutting slabs to double the width thereof by adding grooves to reduce the thickness in the longitudinal direction of the slab, ensuring an extremely thin remaining thickness of the slab, and making it possible to cut at high speed and reduce yield loss.

[Conventional technology]

A conventional technique for cutting slabs to double the width will be explained with reference to FIG. FIG. 9 is a schematic perspective view showing continuous slab casting. Mold 1 from Tandaitsu etc.
The molten steel 12 cast into the mold 10 is rapidly cooled by the cooling water of the mold, gradually forming a solidified shell from the outer layer in contact with the mold 10, and is pulled out by pinch rolls leaving the unsolidified molten steel inside the mold. Get out. mold 10
The slab pulled out from the mold 10 is guided to guide rolls 14 from directly below the mold 10, and is cooled by secondary cooling water injected from between the guide rolls 14, and is drawn out as a completely solidified red-hot slab 2. .

After the drawn slab 2 passes through a drawing straightening roll, it is generally cut by a gas cutting machine 16 into lengths of approximately 10 m in length in the width direction of the slab. The red-hot slab 2 cut into regular lengths is sent to the next rolling process. The production capacity of such a continuous casting machine is determined by the cross section of the slab 2 and the casting speed depending on the machine characteristics, and the casting speed is determined by the amount of molten steel cast per unit time. Therefore, the productivity of a continuous casting machine is determined by the thickness and width of the slab 2, so when the thickness is constant, it depends on the width of the slab. As a result, production capacity is significantly reduced when casting narrow width maintenance.

Therefore, in order to increase the production capacity of the slab 2, the width of the slab 2 is usually doubled, and the glowing slab 2 is cut to a standard length of about 10 m. A method of cutting to double size is used. Conventionally, a gas cutting method has been commonly used as this width cutting method. This method can be used either online or offline, but the cutting width reaches approximately 10 to 25 mm, resulting in a deterioration of the slab yield.In addition, cutting slag adheres to the bottom of the gas cut, and countermeasures are required. Therefore, the commonly used methods of width-doubling cutting are the rolling shearing method using a day scroll, and the rolling shearing method using a day scroll 1 to cut the slab 2 into grooves as shown in Fig. 2. There is a combination method in which processing is performed and then the reduced thickness portion of the slab 2, that is, the groove portion 3 is gas cut.

The former rolling shearing method includes a method of increasing the rolling reduction and cutting in one pass at once, and a method of cutting in multiple passes. The method of cutting in one pass is shown in Fig. 1, but the slab 2 cut by the day scroll 1 is severely bent, and as shown in Fig. 3, the amount of curvature δ is 10 m.
Since the slabs are cut to lengths that can reach 0.5 m, they cannot be used in actual equipment. Even in the method of cutting in several passes, bending of the cut slab occurs.
Therefore, a new orthodontic device is required. Furthermore, as shown in cross section in FIGS. 3 and 4, there is a problem in that sharp protrusions 4 are generated at the cut portion, resulting in scratches on the product. Therefore, the latter method, which combines groove processing using a day scroll and gas cutting, is currently being used.

When reducing slab thickness by day scroll,
In consideration of high-speed cutting and reduction of cutting loss, that is, improvement of yield in width-doubling cutting work, it is preferable that the remaining thickness of the slab be as small as possible. The remaining thickness of the groove 3 is limited to about 20% of the original thickness of the slab in the one-pass reduction method, and this limit is targeted at the thickness cut by the biting side of the groove. That is,
When the reduction in one pass approaches the critical residual thickness of about 80%, a phenomenon occurs in which even if the biting side A is cut, the opposite biting side B is not cut, as shown in FIG. Therefore, in conventional grooving of slabs, the critical thickness at which the biting side does not cut is called the critical residual thickness. This amount of residual thickness has a significant effect on high-speed cutting and reduction of cutting loss in the above-mentioned width cutting work. For example, when cutting a slab slab at a temperature of about 800°C using gas cutting, it is difficult to cut a slab slab with a residual thickness of 30 mm. Maximum speed is 6m/
However, when the remaining thickness becomes 50 mm, the maximum cutting speed becomes 3 m/min. Further, the cutting loss is approximately twice as large when the remaining thickness is 50 mm as the cutting width is larger than when the remaining thickness is 30 mm.

[Problem to be solved by the invention]

The purpose of the present invention is to overcome the drawbacks and problems of the above-mentioned conventional techniques in cutting slabs to a double width, and to reduce the amount of remaining thickness to the limit when processing grooves to reduce the thickness of slabs. The purpose of the present invention is to provide a method for cutting the width at scale.

[Means and actions for solving the problem]

The gist of the present invention is as follows. That is, the step of cutting a red-hot slab continuously cast to double the width and cutting in the width direction using a day scroll to reduce the thickness of the slab in the longitudinal direction of the slab, and the process of cutting the remaining thickness of the grooved slab into the subsequent process. In the width-doubling cutting method of the slab, which comprises the step of finally cutting the slab with a cutting machine, the thickness reduction step cuts the biting portion of the slab into the slab with one or more passes of a day scroll. A step of pre-reducing the slab to less than 15% to 80% of the original thickness, and applying a day scroll to the pre-reduced slab.
This is a method for cutting a slab to double width, the method comprising: applying a large reduction of 80 to 90% of the original thickness of the slab in each pass;

The present invention is shown in Fig. 6 A, B, C, Fig. 7 A, B,
C, D and their steps will be explained based on the embodiment shown in FIGS. 8A, B, and C, which are perspective views.

In the first method, a cast slab 2 having a length l and a thickness d as shown in FIG. 6A is first subjected to preliminary reduction at the biting portion 2A as shown in FIG. 6B.

This pre-reduction is a step taken because, as mentioned above, in the thickness reduction method using one-pass reduction, the remaining thickness is limited to about 20% of the original thickness of the slab.

This preliminary reduction is performed by repeating one pass or multiple passes at the biting part 2A when the slab is processed into a groove to reduce its thickness using a day scroll, and
Applying a reduction of less than ~80%, at least the original thickness of the slab
This is a preliminary process for leaving a critical residual thickness of 20% in the biting portion 2A.

The reason why this preliminary reduction is limited to less than 15% to 80% of the original thickness of the slab is because if the reduction in one pass exceeds 80%, the biting part 2A will be cut. This is because it is necessary to maintain a residual thickness of more than 15% to prevent cutting, and the reason for setting it to 15% or more is that under the following large pressure of 80 to 95%,
This is to avoid cutting and separation of the biting portion 2A.
This preliminary reduction can be done in one pass, but it is better to do it in multiple passes.

Next, as shown in FIG. 6C, the slab that has undergone preliminary reduction is rolled over the entire slab 2 from the biting part 2A by a day scroll to a thickness of 80 to 95% of the original thickness of the slab.
A large pressure is applied in one pass. 80% due to this one pass
With the above reduction, the bite side 2A usually cuts, but since the bite side 2A has been pre-reduced in advance before this large reduction, the bite side 2A has a cutting rate of 80%.
This large pressure allows machining to leave a critical residual thickness over not only the biting portion 2A but also the entire slab 2.

Furthermore, FIG. 6C shows an example in which the remaining thickness of the biting part 2A is increased, the amount of reduction across the rear end is increased, and the remaining thickness is made smaller than that of the biting part 2A. By increasing the thickness, cutting of the biting portion 2A is sufficiently prevented. Further, by applying this preliminary reduction to the biting portion 2A, biting becomes easy when applying a large reduction of 80 to 95% in one pass.

The thin slab remaining after this thickness-reducing groove processing is easily cut by a subsequent cutting machine.

Next, the method of FIG. 2 will be explained with reference to FIG. 7 and FIG. 8 which is shown in a perspective view.

In this method, as shown in FIG. 7A, a slab 2 having a length l and a thickness d is first rolled down at its biting part 2A, as shown in FIGS. 7B and 8A, and then rolled down. As shown in FIG. 7C and FIG. 8B, the reduction is also applied when returning after the reduction in FIG. 7B, that is, when chewing back. As described above, by applying pressure reduction also during chewing, compared to the first method, reduction can be applied both during chewing and during chewing back.
A larger reduction can be applied to the bite portion 2A in a shorter time than in the first method. By repeating this for one pass or multiple passes, a preliminary reduction of 15 to less than 80% of the original thickness of the slab is applied to the biting portion 2A.

After this preliminary reduction, as shown in FIG. 7D and FIG. 8C, the slab 2 is advanced and, as in the first method, the day scroll 1 is used to reduce the original thickness of the slab from 80 to
Apply a large pressure reduction of 95%. The reason why the biting part 2A does not break even when this large pressure reduction is applied is the same as the first method shown in FIG. In this manner, a groove portion 3 is formed that leaves a critical residual thickness that will not be cut not only in the biting portion 2A but also over the entire slab 2. These thin slab residual thicknesses are easily final cut by a subsequent cutter. The first part shown in Figure 6 A, B, and C earlier
This method is the second method shown in FIGS. 8A, B, and C, and is a case in which there is no step (B) of blowing back and rolling down, and simply pushing back without rolling down.

Preliminary rolling of the biting portion 2A performed initially in the first and second methods is preferably performed in multiple passes rather than in one pass. This is clear from the following experimental results by the inventor. That is, Fig. 6,
In Fig. 7, for the thickness d of slab 2 = 215 mm,
If the remaining thickness is 30 to 50 mm, depending on the pass reduction, the biting side will be cut or the non-biting side will not be cut.
In addition, when the residual thickness was 50 mm or more, neither the bite side nor the non-bite side was cut. On the other hand, in the case of multiple passes, for the same slab thickness of 215 mm, even if the remaining thickness was 5 to 10 mm, the slab was not cut, so the pre-reduction by biting or the preliminary reduction by biting back depends on the rolling reduction rate, but as described above. Multiple passes are desirable, such as If the biting side is cut, the slab will warp as described above, so it is most important in the grooving process to leave the minimum thickness within the uncut range, that is, the critical residual thickness. In the groove machining process according to the present invention, by applying a large reduction of 80 to 95% that corresponds to the limit remaining thickness, it is possible to easily obtain the limit remaining thickness that does not cut the biting side, and the subsequent cutting machine This has the effect of making final cutting extremely easy.

〔Effect of the invention〕

As is clear from the above embodiments, the present invention involves applying a thickness-reducing groove to a red-hot slab that has been continuously cast to double the width and cut in the width direction using a day scroll.
In the width-doubling cutting method for slabs in which the remaining thickness of the grooved slab is finally cut by a subsequent cutting machine, the thickness reduction groove processing process has been improved from the conventional method, and the biting part is first cut into the day scroll. A pre-reduction is applied in one pass or multiple passes to reduce the original thickness of the slab to less than 15-80%, and then a large reduction of 80-95% is applied to the pre-reduced slab in one pass with a day scroll. By using the addition method, we were able to achieve the following effects.

(a) The slab was able to secure the thinnest limit thickness reduction without cutting the biting side, making the final cutting work extremely easy.

(b) Not only did the bending of the slab as in the conventional method not occur, but the final cutting speed could be greatly improved.

(c) Cutting loss has been reduced and protrusions on the cut cross section, as in the case of the conventional method, no longer occur, so the yield of slabs and cutting can be significantly improved.

[Brief explanation of drawings]

Figure 1 is a plan view showing the bending of a slab cut by the conventional method of cutting slabs to double the width using a day scroll, and Figure 2 is a cross-sectional view showing the method of cutting slabs to double the width using a day scroll. , Figure 3 is a schematic perspective view showing the bending of the slab that occurs when cutting the slab to double the width using only a day scroll, with a length of about 10 m shortened.
Figure 4 is a cross-sectional view showing the protrusions that occur on the cut section of slab when cutting the slab to double the width using only the day scroll;
The figure is a plan view showing a slab that has been cut on the biting side and not cut on the opposite side; Figures 6A, B, and C show the method of cutting a slab with a length l of approximately 10 m to double width according to the present invention. FIG. 7 is a schematic front sectional view showing the steps of an example; FIG. 7 is a schematic front sectional view showing steps of another embodiment of the present invention; FIGS. It is a schematic perspective view showing the steps of the second method indicated by A, B, C, and D, where A shows the time when the biting part is rolled down, B shows the time when the biting part is finished being rolled down, and C shows the time when the biting part is finished being rolled down.
% state at the end of large pressure reduction. FIG. 9 is a schematic perspective view showing the state of gas cutting after continuous casting of a slab slab and the state immediately before width-multiplying cutting with a day scroll. 1... Day scroll, 2... Slab, 3... Groove, 4... Protrusion, 10... Mold, 12... Molten steel,
14...Guide roll, 16...Gas cutting machine, A
...Bite side, B...Anti-bite side.

Claims (1)

[Claims] 1. Process of cutting a red-hot slab continuously cast to double the width and cutting in the width direction to reduce the thickness of the slab in the longitudinal direction of the slab using a day scroll, and subsequent cutting of the remaining thickness of the grooved slab. In the width-doubling cutting method of the slab, which comprises the step of final cutting with a machine, the thickness-reducing groove machining step involves cutting the biting part of the slab into the slab base using a day scroll pass or multiple passes. A step of pre-reducing the thickness to less than 15-80%, and a step of subjecting the pre-reduced slab to a large reduction of 80-95% of the original thickness of the slab in one pass of a day scroll. Features a method of cutting slabs to double the width.