JPH11226611A - Equipment for manufacturing steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a steel plate at high yield without greatly changing existing equipment by using a slab of a larger unit weight and reducing scale loss and crop loss with a reversing type hot rolling mill. SOLUTION: A coiler 7 for preventing interference of the material 1 to be rolled in rolling with before and behind equipment is provided on both or either front side and rear side of the reversing type hot rolling mill 3. A hot cutting machine 8 for cutting the material to be rolled corresponding to the length of products of the equipment with which the length of the products in the subsequent processes is determined is provided on the outlet side of the hot rolling mill 3 and the material to be rolled is cut into a prescribed size before the material is cooled down to rooms temp. with the hot cutting machine 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slab heated to a predetermined temperature, which is rolled by one or a plurality of reverse type hot rolling mills, and optionally subjected to accelerated cooling and shape correction to obtain a predetermined size. The present invention relates to a thick steel plate manufacturing facility for manufacturing thick steel plates at a high yield.

[0002]

2. Description of the Related Art A slab heated to a predetermined temperature in a heating furnace is rolled by one or a plurality of reverse hot rolling mills. After cooling to room temperature,
It is manufactured by cutting to predetermined dimensions.

[0003] In the production of such thick steel plates, improvement in production yield is required. The major factors that lower the production yield of thick steel plates are scale loss due to oxide scale generated when the slab, which is the material, is heated in a heating furnace, and crop loss because the thick plate shape after rolling does not become rectangular. can give.

It is said that the thickness of the scale generated when the slab is heated in the heating furnace increases as the slab heating time increases. Therefore, in order to reduce the generation of scale, it is effective to shorten the in-situ time of the slab in the heating furnace. However, the slab must be heated evenly to the center in the thickness direction in the heating furnace. In particular, in the case of a thick slab, a long heating time is required, so that the furnace time is reduced. Has a limit. Therefore, it is not possible to prevent the generation of scale by shortening the furnace time.

As a technique for improving the planar shape of a thick steel plate in order to reduce crop loss, for example, Japanese Patent Publication No.
Japanese Patent Publication No. 17961 and Japanese Patent Publication No. Sho 59-34405 disclose a method of giving a change in thickness to a material to be rolled by controlling the roll opening during rolling. However, such a method has a limitation in reducing the crop loss at the front and rear ends of the steel sheet because the shape of the change in thickness changes due to a slight shift in roll opening control during rolling.

[0006] When the single weight of the slab as the material is increased, the scale loss is reduced by reducing the surface area of the formed scale with respect to the volume of the slab, and the crop loss is reduced by reducing the ratio of the rolling unsteady portion. It becomes possible. However, increasing the slab single weight causes the following problems.

That is, when the slab single weight is increased, the rolling end length of the thick steel plate is inevitably increased. On the inlet and outlet sides of the rolling mill, for example, descaling equipment, accelerated cooling equipment,
Since various facilities such as a shape straightening machine are arranged, if the end length of the rolling becomes large, work by the devices arranged before and after the above-mentioned rolling mill will be hindered. Therefore, there is a limit to the rolling end length of a thick steel plate.

[0008] In addition, since a hot-rolled steel plate is generally cooled to near room temperature in a cooling floor and then cut into predetermined product dimensions, the thickness of the hot-rolled steel plate is reduced to a size that enters the cooling floor. The rolling end length of the steel sheet cannot be increased. In order to avoid such a restriction on the rolling end length,
It is necessary to change the arrangement of the existing rolling equipment consisting of the rolling mill and the devices before and after the rolling mill, which requires enormous costs and long-term construction. It cannot be implemented.

[0009] Another problem caused by the lengthening of the elongation is that the rolling time is increased and the rolling temperature is reduced accordingly. FIG. 2 is a graph showing the relationship between the sheet thickness and the rolling time when the slab length is doubled. In FIG. 2, the solid line shows the rolling time when the reference slab length is used, and the broken line shows the rolling time when it is twice the reference slab length. As shown in the drawing, when the slab length is twice the reference slab length, the rolling time becomes twice or more.

Particularly problematic is the time from rolling down of the material to be rolled by the rolling rolls to the next rolling. If this time is long, the slab is air-cooled during that time to reduce the temperature. Invite. When this temperature drop is remarkable, the deformation resistance of the slab increases, so that rolling may not be possible.

As means for preventing such a decrease in slab temperature during rolling, Japanese Unexamined Patent Publication No. Hei 7-314007 (hereinafter referred to as prior art 1) discloses one of two reverse rolling mills. A technology is disclosed in which a heat retaining coiler is provided on the inlet side of a reverse rolling mill, and the slab is retained by the heat retaining coiler to prevent a decrease in slab temperature and an uneven shape.

Japanese Patent Application Laid-Open No. Sho 59-30406 (hereinafter referred to as "prior art 2") discloses a technique for improving the yield by increasing the single weight of a slab after rolling a slab to a required thickness of a thick steel plate. A technique of cutting a predetermined length and rolling the remaining material to a target thickness of a thin steel plate is disclosed. Japanese Patent Application Laid-Open No. 60-68102 (hereinafter referred to as Prior Art 3) discloses a slab. Rough rolling to an intermediate thickness, cutting to a predetermined length, keeping it in a heat insulating cover, and finish rolling to a predetermined size in order to roll steel plates of different width and thickness from one material Is disclosed.

[0013]

In the case of the prior art 1, since it is premised that the steel sheet after finish rolling is wound up and processed into a coil shape, the steel sheet after finish rolling is sheet-shaped. In the case of a thick steel plate treated by the method described above, the problem of the accommodation length of the cooling floor described above cannot be avoided. In the case of thick steel plates, high-grade steel sheets with excellent strength and toughness are often obtained by immediately accelerating and cooling the rolled steel sheets. In this case, the steel sheets after finish rolling are immediately wound up. It cannot solve the problem that the space before and after the rolling mill is restricted.

In the case of Prior Art 2, since a product is to be obtained in the middle of rolling, in a general rolling schedule, the crown thickness of the product is reduced and the thickness of the finished plate is reduced to ensure flatness. Under the current situation where the amount of reduction is restricted as the number of passes increases, the number of passes increases near the finished plate thickness of the thick steel plate. Therefore, compared to the case of rolling a thin steel plate alone,
As the efficiency is reduced, the finishing temperature of the thin steel plate is lowered, and rolling may not be possible.

In the case of the prior art 3, since the crop is generated by finish rolling after cutting at an intermediate thickness, the effect of reducing the crop is small. Further, in each of the prior arts 2 and 3, the cutting is performed at an intermediate stage of the rolling, but there is a problem that the dimension before cutting is restricted to a length that does not interfere with the preceding and following facilities.

Accordingly, an object of the present invention is to solve the above-mentioned problems, to use a large slab having a single unit weight, to reduce scale loss and crop loss and to produce a high yield steel plate without greatly changing existing equipment. An object of the present invention is to provide a manufacturing equipment for a thick steel plate that can be manufactured.

[0017]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, in order to improve the yield, it has become possible to use a slab having a large single weight as a material. In order to prevent a decrease in the temperature of the steel sheet during rolling, without preventing the treatment by the equipment before and after the hot rolling mill, furthermore, the length of the steel sheet after rolling may be set to a length that can be accommodated in the cooling floor. I understand.

The present invention has been made based on the above findings, and a steel plate manufacturing facility of the present invention comprises at least a heating furnace, a descaling device, a reverse hot rolling mill, and a cooling floor, In the steel plate manufacturing facility arranged in the above order, the rolling material being rolled interferes with the preceding and following facilities on both or one of the front side and the rear side of the reverse hot rolling mill. A coiler for preventing rolling is provided, and a hot roll for cutting a material to be rolled in accordance with the product length of equipment whose product length is controlled in a subsequent process is provided on the exit side of the hot rolling mill. A cutting machine is provided, and is characterized in that the material to be rolled is cut into predetermined dimensions by the hot cutting machine before being cooled to room temperature.

The reason why the coiler is provided on the front side and / or the rear side of the rolling mill is that the material to be rolled is wound into a coil during rolling, thereby avoiding interference with the preceding and following equipment. In addition, in order to prevent the temperature drop, in order to further enhance the effect of preventing the temperature drop,
It is desirable to use a heat retaining coiler that has been subjected to a treatment such as surrounding the coiler with a heat insulating material.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a steel plate manufacturing facility according to the present invention will be described with reference to the drawings. FIG. 1 is a layout diagram showing an embodiment of the equipment of the present invention. As shown in the drawing, the heating furnace 1, the descaling device 2, the reverse hot rolling mill 3, the accelerated cooling device 4, the shape corrector 5, and the cooling floor 6 are arranged along the rolling line in this order. , Same as conventional equipment. Note that a heat treatment apparatus may be provided in the above facility.

The slab A, which is a raw material, is heated to a predetermined temperature in a heating furnace 1 and is descaled in a descaling device 2 while moving along a rolling line, and a predetermined thickness in a reverse hot rolling mill 3. Rolled. The steel plate rolled to a predetermined thickness in this way is:
Next, it is accelerated and cooled in the accelerated cooling device 4, the shape is corrected in the shape corrector 5, and cooled to room temperature in the cooling floor 6, and then sent to the refining process.

In the equipment of the present invention, the heat retaining coilers 7, 7 are provided on the front side and the rear side of the reverse hot rolling mill 3.
7 'is provided on the outlet side of the hot rolling mill 3, in front of a facility where the product length is controlled in the subsequent steps, for example, in front of the cooling floor 6 and on the rear side of the hot rolling mill 3. Between the hot coiler 7 ′ and the accelerated cooling device 4, there is provided a hot cutting machine 8 for cutting the material to be rolled according to the product length. Although the heat retaining coilers 7, 7 'are excellent in the effect of preventing the temperature of the material to be rolled from decreasing, a simple coiler may be provided when the temperature of the material to be rolled is not a problem.

The slab A is rolled by the reverse hot rolling mill 3, wound up by the heat retaining coilers 7, 7 ', then unwound, and reduced by the hot rolling mill 3 a plurality of times, so that the slab A is rolled. The steel sheet is rolled into a thick steel plate A 'having a predetermined thickness while maintaining a substantially uniform temperature without lowering the temperature. The steel plate A 'thus rolled is then
After being cut to a length that can be accommodated in the cooling floor 6 by the hot cutting machine 8, it is sent to the accelerated cooling device 4.

In the present invention, the steel plate rolled by the reverse hot rolling mill 3 is once wound by the heat retaining coilers 7, 7 'arranged on the front and rear sides of the rolling mill 3 as described above. Therefore, the temperature is prevented from lowering, and the pressure elongation is not increased. Therefore, interference with equipment provided before and after the rolling mill 3 is prevented. The heat retaining coilers 7, 7 'are provided on both front and rear sides of the hot rolling mill 3,
If the temperature effect can be prevented depending on the target product range, it may be provided on one of the front surface and the rear surface of the rolling mill, where the material to be rolled may interfere with other equipment.

Since the thick steel plate A 'rolled by the rolling mill 3 as described above is cut by the hot cutting machine 8 and then sent to a post-process, there is no problem in the processing in the post-process. There is no. The hot cutting machine 8 includes the hot rolling mill 3 described above.
In addition to being installed between the cooling device 4 and the acceleration cooling device 4, if possible due to the arrangement of the equipment, the device is installed between the acceleration cooling device 4 and the shape correction device 5 or between the shape correction device 5 and the cooling floor 6. There is no problem. In addition, as the hot cutting machine 8, a traveling cutting machine may be used in addition to a rolling cut shear type cutting machine that temporarily stops and cuts a traveling thick steel plate.

[0026]

[Example] Thickness 220mm, width 1900mm, length 3000
The slab of mm was reverse-rolled by the equipment of the present invention into a thick steel plate 5.5 mm thick, 4000 mm wide and 57000 mm long. Table 1 shows the results.

[0027]

[Table 1]

In Table 1, Nos. 1 to 3 are examples of the present invention, and No. 1 is a method in which a material to be rolled is kept warm by a heat retaining coiler provided on the front side and the rear side of the rolling mill. This is an example in which this is cut between a mill and a cooling floor, and in this case, the rolling finish temperature is 11
2 ° C higher, enough finish temperature can be secured,
There was no restriction on the length of the equipment, and the pressure extension could be expanded sufficiently.

No. 2 is an example in which the material to be rolled is kept warm by a heat retaining coiler provided on the rear side of the rolling mill and cut between the rolling mill and the cooling floor. In addition, the length extension occurring on the rear side of the rolling mill was eliminated, so that the elongation of the pressure could be expanded, and the finishing temperature of the rolling was 55 ° C. higher than in the case where the heat was not kept, so that the finishing temperature could be secured.

No. 3 is an example in which the material to be rolled is kept warm by a heat retaining coiler provided on the front side of the rolling mill and cut between the rolling mill and the cooling floor. In addition, the length restriction generated on the front side of the rolling mill was eliminated, the pressure extension could be expanded, and the rolling finish temperature was 55 ° C. higher than in the case where the heat was not kept, so that the finish temperature could be secured.

Nos. 4 to 6 are comparative examples, and No. 4 is
The material to be rolled was kept warm by the heat retaining coilers provided on the front side and the rear side of the rolling mill, but it was an example in which cutting was not performed between the rolling mill and the cooling floor, and the finishing temperature could be secured. However, the rolled steel plate could not be accommodated in the cooling floor. No. 5 is an example of cutting between the rolling mill and the cooling floor without keeping the heat on either side of the front and back of the rolling mill. No. 6 was not keeping heat on either side of the front and back of the rolling mill. In addition, this is an example in which cutting was not performed between the rolling mill and the cooling floor, and in each case, the temperature was significantly lowered during rolling, and smooth rolling could not be performed.

[0032]

As described above, according to the present invention, a long and thick steel plate having a high yield can be obtained by using a slab having a large single weight, reducing scale loss and crop loss without largely changing existing equipment. Which is industrially useful.

[Brief description of the drawings]

FIG. 1 is a layout view showing an embodiment of the equipment of the present invention.

FIG. 2 is a graph showing a relationship between a sheet thickness and a rolling time when a slab length is doubled.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Descaling device 3 Hot rolling mill 4 Accelerated cooling device 5 Shape correction machine 6 Cooling floor 7 Heat retaining coiler 8 Hot cutting machine

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B21C 47/00 B21C 47/00 A (72) Inventor Shogo Tomita 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Steel Pipe Co., Ltd. (72) Inventor Masamasa Kamada 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (1)

[Claims] 1. At least a heating furnace, a descaling device, a reverse hot rolling mill and a cooling floor,
In the steel plate manufacturing facility arranged in the above order,
A coiler is provided on both or either the front side or the rear side of the reverse hot rolling mill to prevent the material to be rolled from interfering with the front and rear facilities,
And, on the outlet side of the hot rolling mill, a hot cutting machine for cutting the material to be rolled in accordance with the product length of the equipment whose product length is controlled in the subsequent process is provided, and the material to be rolled is provided. ,
A steel plate manufacturing facility characterized in that the steel plate is cut to a predetermined size by the hot cutting machine before being cooled to room temperature.