JP2968140B2 - Cooling method and cooling device for thick steel plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for cooling a thick steel plate.

[0002]

2. Description of the Related Art Controlled rolling (hereinafter referred to as C) is a method for producing a steel sheet having excellent strength and toughness.
R) The rolling method has been widely used. This CR rolling is characterized in that the rolling temperature during rolling is accurately controlled, and the final rolling finish temperature is made to be just above the Ar ₃ temperature, whereby the structure can be refined and the strength and toughness can be improved.

In this CR rolling method, as shown in FIG. 2, rolling is once stopped at a transfer thickness of a certain thickness (for example, 2t) with respect to a product sheet thickness t, and then the temperature T at that time is reduced by air cooling.
After cooling from ₁ to a predetermined temperature T _2, performs rolling again,
The final finishing temperature at the time of final rolling at a predetermined thickness t is A
The temperature should be just above r ₃ .

[0004]

[Problems that the Invention is to Solve] Unlike normal rolling in such a CR rolling, rolling once stops rolling operation in the middle, rolling operation because rolling material temperature is cooled from T ₁ until T ₂ Has a problem that the rolling efficiency is reduced. As shown in FIG. 2, as conventionally performed in CR rolling,
The problem can be solved by repeatedly rolling and water-cooling the material to be rolled for a predetermined pass as shown in FIG. 3 without performing intensive air-cooling temperature waiting in a specific pass during rolling. However, the following problems exist in a cooling device for a thick steel plate close to a rolling mill.

A cooling device around a rolling mill is disclosed in
-26729. At this installation position, the distance between the rolling mill and the cooling device is as long as 20 m, and the kickout length after rolling becomes longer up to the rear of the installation position. Similarly, when the cooling capacity is small, the cooling machine length becomes longer, and the transport time of the steel sheet becomes longer. However, there is a problem that the rolling efficiency cannot be improved for a long time. Conversely, when a cooling device is installed near a rolling mill, the "warp" of the steel sheet during rolling is sometimes large, and a structure such as a cooling header or the like in which equipment protection is taken into consideration is required. Furthermore, since the installation space is narrow, there is a problem that a facility that is compact and has a high cooling capacity is required while maintaining the descaling function.

There is a high water pressure descaling method for injecting high pressure water from a nozzle in a rolling mill. In general high water pressure descaling, high-pressure water is injected from the injection nozzle of the descaling header to the material to be rolled, and the surface scale of the material to be rolled is floated by the difference between the cooling water and the surface temperature of the material to be rolled. Is blown away by momentum. The purpose of this injection is to minimize the amount of water injected to suppress the temperature drop of the steel sheet and increase the collision force. In this case, the injection direction of the high-pressure water is directed to the entry side of the material to be rolled. In addition, in the system that incorporates a shut-off valve in the high-pressure water supply main pipe, low-pressure water flows to protect the nozzle as a measure against valve responsiveness and water hammer, making it impossible to prevent overcooling of the front tail. There is.

[0007]

The gist of the present invention is as follows. (1) When cooling a thick steel plate in a portion near a rolling roll of a rolling mill, the injection direction is set to the rolling roll side and directly above and below the thick steel sheet pass line on the front and rear surfaces of the rolling roll, respectively. A high-pressure water injection nozzle and its header are arranged, and further, on the anti-rolling roll side, a water injection nozzle and its header with an injection direction of the rolling roll side are arranged,
A pressure control means is provided in a water supply system of these headers, and the pressure is set to 30 kg / cm ² or more by using all of the headers at the time of cooling, and the pressure is set to 150 kg / cm ² by using the header on the rolling roll side at the time of descaling. A method for cooling a thick steel plate, wherein the method is set as described above.

(2) In a cooling device for cooling a thick steel plate at a portion close to a rolling roll of a rolling mill, the injection direction is set to the rolling roll side immediately above and immediately below a thick steel plate pass line on the front surface and the rear surface of the rolling roll, respectively. A high-pressure water injection nozzle and its header on the anti-roll side are provided, and a water injection nozzle and its header on the anti-roll side are provided on the anti-roll side. The pressure control means is provided at the time of cooling, and the pressure is set to 30 kg / cm ² or more by using the entire header at the time of cooling.
In addition to providing means for setting the pressure to 0 kg / cm ² or more, the pitch of the water jet nozzle of the header on the side of the anti-roll roll is determined by the nozzle wrap ratio (nozzle jet width / nozzle mounting pitch at the portion where the jet water collides with the thick steel plate). 2.) A cooling device for a thick steel plate, wherein (3) The thick steel plate cooling device according to the above (2), wherein the high-pressure water injection nozzle of the roll-side header is a nozzle having an on-off valve immediately before the nozzle injection hole.

[0009]

In the past, low-efficiency operation was performed by air-cooling while waiting for the temperature at the transfer thickness during CR rolling. However, by using a cooling device close to this rolling mill, the cooling time was shortened and high efficiency was achieved. Operation became possible. The cooling device close to this rolling mill employs a descaling and cooling header from the rolling mill side, and a high water pressure spray for cooling the outside of the rolling mill. Cooling and kick-out length were made possible. In addition, equipment protection measures are taken to cope with the "warpage" of the rolled material.

This cooling method and apparatus have a descaling function and a cooling function, and the injection pressure can be adjusted. At the time of descaling, the injection pressure was adjusted according to the scale state, enabling operation without waste. Further, at the time of cooling, the temperature waiting time in CR rolling is eliminated, and cooling can be performed under necessary conditions so that the finished rolling temperature is just above Ar ₃ . By arranging a high-pressure water injection nozzle with a built-in on-off valve just before the nozzle injection hole, high-speed injection / stop is possible.By setting the injection width narrower than the strip width of the rolled material,
This prevents overcooling of the edge and saves the amount of water jet. By setting the injection start and end timings in accordance with the tracking of the steel sheet and inside the front and rear ends of the steel sheet, it is possible to prevent overcooling of the front and rear ends of the steel sheet.

Further, by using a plurality of headers and setting the injection direction of the inlet side to the rolling mill side, it was possible to prevent the cooling water injected from the nozzle from flowing to the tail end side after collision with the steel sheet. As a result, the problem of overcooling in the longitudinal direction of the steel sheet from the front end to the tail end is solved, and an excellent effect that uniform cooling can be performed over the entire length is obtained.

In the case of cooling by spraying high-pressure water, the cooling capacity of the spray collision portion is the highest. When the nozzle wrap ratio is set to 2, the collision portion occurs twice in the width direction of the steel sheet, so that there is an excellent effect that the streaking due to the difference in the nozzle wrap ratio in the width direction can be eliminated.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The rolling state of the control rolling of a thick plate will be disclosed as an embodiment. Slab dimensions (thickness 211mm, width 177)
0mm, length 4890mm) to product dimensions (thickness 23.5mm,
In rolling of 2679 mm width and 29010 mm length), C
As the R condition, a rolling thickness of 890 ° C. or less at a transfer thickness of 41 mm is regulated. Table 2 shows the rolling pass schedule of this CR rolled material. FIG. 2 shows the temperature transition during rolling when water cooling is not performed in this rolling schedule. Air cooling is performed for 268 seconds at a plate thickness of 41 mm in the 12th pass. Next, FIG. 3 shows a temperature transition when the cooling device of the present invention is used. However, FIG. 3 shows the temperature transition up to the twelfth pass, which was cooled by a cooling device close to the rolling mill in the previous pass. It is clear that the cooling is performed to the predetermined temperature by 12 passes to the CR starting temperature. Tables 1 and 3 show the main specifications and cooling results of the cooling device of FIG. 1 used for the main rolling.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

According to the results, the injection pressure of the "descaling / cooling header 3, 3 '" on the rolling mill side was 150 kg / desc.
Injection is performed in cm ² and the injection pressure is adjusted during cooling other than descaling. The injection pressure of the "header for cooling 4, 4 '" on the side of the anti-rolling mill used for cooling is injected at 30 kg / cm ² . This makes it possible to cool to a target CR start temperature at a predetermined plate thickness.

FIG. 1 is a longitudinal sectional view of a cooling device installed in a finishing mill 5 in the present embodiment. A steel plate is loaded from the right side of the drawing and reverse-rolled by finishing rolling rolls 6 and 7 in the drawing. After being rolled to a predetermined size, it is transported to the left of the drawing. In this rolling, the steel plate is cooled by water jetted from the descaling / cooling headers 3 and 3 'and the cooling-dedicated headers 4 and 4' which are installed in a vertical pair. At this time, the roll side of the rolling mill is the header 3 and 3 'for both descaling and cooling, and the injection direction is the direction opposite to the rolling mill. On the non-rolling mill side, cooling headers 4 and 4 'are used, and the injection direction is the rolling mill direction. Thereby, the cooling water injected from the nozzle portions 1a and 1b can be prevented from flowing toward the tail end side by the cooling water injected from the nozzles 2a and 2b after the collision with the steel plate, and the cooling water in the longitudinal direction of the steel plate from the tip to the tail end can be prevented. The problem of overcooling has been resolved, and cooling can be performed uniformly over the entire length. Also, the jet direction of the lower nozzle is to prevent the jet water from scattering.
It is sprayed in the direction of the top guide 13 and the hood for scattering prevention. Injection nozzle 1 installed at the tip of each header
Reference numerals a, 1b, 2a, and 2b denote high-pressure water injection nozzles with built-in on-off valves immediately before the nozzle injection holes. The upper header is provided in a rolling mill top guide 13 as a measure against warpage during rolling of a thick steel plate.

FIG. 4 is a system diagram of the supply of cooling water, which is shown as one of the embodiments, and includes headers 3 for both descaling and cooling.
3 'is connected to a descaling pump 8 and has a pressure gauge 9, a pressure regulating valve 10, and a high-speed on / off valve 11 arranged in the middle of the piping. The headers 4 and 4 'dedicated to cooling are connected to a high-pressure pump 12 dedicated to cooling, and a pressure gauge 9', a pressure regulating valve 10 'and a high-speed on / off valve 11' are arranged in the same way as the piping. The injection nozzle installed at the tip of each header is a high-pressure water injection nozzle with a built-in on-off valve immediately before the nozzle injection hole.

5 (a), 5 (b) and 5 (c) show the collision pattern (a) and (b) and the temperature change image (c) of the conventional cooling nozzles 2a and 2b, respectively. It indicates the position of the non-lapping portion of the collision portion, and only passes once through the nozzle collision portion having high cooling capacity, and the temperature drop is small. On the other hand, “part B” indicates a position where the lap portion of the nozzle collision portion is present, and the temperature drops greatly because it passes twice through the nozzle collision portion having high cooling ability. The temperature difference as shown in the image of the temperature drop occurs, and the streaking due to the nozzle wrap occurs in the width direction of the steel sheet.

FIGS. 6 (a), 6 (b) and 6 (c) show the collision portion patterns (a) and (b) of the cooling nozzles 2a and 2b and the temperature change image (c) of the present invention. The positions “part C” and “part D” have the same temperature drop because they pass twice through the nozzle collision part having the same cooling capacity. As shown in the image of the temperature change, there is no occurrence of a temperature difference, and the problem of the occurrence of streaking due to nozzle wrap in the width direction of the steel sheet can be solved.

[0022]

As described above, water cooling during rolling has an excellent effect of achieving a stable operation while achieving a reduction in kickout and protection of the cooling device for the purpose, thereby improving the rolling efficiency. . In addition, since the descaling header combines the descaling function and the cooling function, the apparatus is compact, and since the pressure adjusting function is incorporated, it is possible to operate the apparatus under optimum conditions.

Further, by installing a high-pressure water injection nozzle with a built-in on-off valve immediately before the nozzle injection hole, the responsiveness is improved. By controlling the injection width, supercooling of the edge portion is prevented, cooling water is saved, and tracking of thick steel plate is performed. By controlling the injection timing in accordance with the above, it was possible to prevent overcooling of the steel plate tip and tail end. By using a plurality of headers and setting the injection direction of the last stage header to the rolling mill side, it was possible to prevent the cooling water injected from the nozzle portion from flowing toward the tail end after colliding with the steel plate. This solves the problem of overcooling in the longitudinal direction of the steel plate from the tip to the tail end, and has an excellent effect that cooling can be performed uniformly over the entire length.

The cooling water supply system in the embodiment uses separate pumps for descaling and cooling.
Obviously, a similar effect can be obtained even with a high-pressure pump that can share a supply source. By setting the nozzle wrap ratio of the high-pressure water spray to 2, the collision portion occurs twice in the width direction of the steel sheet, so that there is an excellent effect that the streaking due to the nozzle wrap ratio difference in the width direction can be eliminated.

[Brief description of the drawings]

FIG. 1 shows a longitudinal section of a cooling device close to a rolling mill.

FIG. 2 shows a temperature transition during rolling when a proximity cooling device is not used.

FIG. 3 shows a temperature transition during rolling when a proximity cooling device is used (however, a temperature transition up to the 12th pass out of a total of 14 passes).

FIG. 4 shows a system diagram of cooling water supply.

FIG. 5 shows a collision portion pattern and a temperature change image of a conventional cooling-dedicated nozzle.

FIG. 6 shows a collision portion pattern and a temperature change image of the cooling-dedicated nozzle of the present invention.

[Explanation of symbols]

 1a, 1b Injection nozzle 2a, 2b Nozzle dedicated to cooling 3, 3 'Header dedicated to both descaling and cooling 4, 4' Header dedicated to cooling 5 Finishing mill 6 Rolling roll 7 Backup roll 8 Descaling pump 9, 9 'Pressure gauge 10, 10 'Pressure regulating valve 11, 11' High-speed on / off valve 12 High pressure pump 13 Rolling mill top guide

Continuing from the front page (72) Inventor Masakazu Abe 1 Nishinosu, Oji, Oita City, Oita Prefecture Nippon Steel Corporation Inside the Oita Works (72) Inventor Hiroki Miyawaki 1 Nishinosu, Oita, Oita City, Oita Prefecture Nippon Steel Corporation (56) References JP-A-6-190426 (JP, A) JP-A-6-142750 (JP, A) JP-A 64-11012 (JP, A) JP-A-59-76616 ( JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B21B 45/02 320 B21B 45/08

Claims (3)

(57) [Claims] When a thick steel plate is cooled in a portion close to a rolling roll of a rolling mill, an injection direction is set to an anti-roll roll on a rolling roll side immediately above and immediately below a thick steel plate pass line on a front surface and a rear surface of the rolling roll, respectively. The high-pressure water injection nozzle and its header are arranged on the side, and the water injection nozzle and its header are set on the anti-roll side, and the pressure is controlled in the water supply system of these headers. Means are provided so that when cooling, the entire header is used and the pressure is 30
Set kg / cm ² or more, descaling at the time, the cooling method of steel plate characterized by setting the pressure used header of the rolling roll side to 150 kg / cm ² or more. 2. A cooling device for cooling a thick steel plate at a rolling roll approaching portion of a rolling mill, wherein a jet direction is opposite to a rolling roll side immediately above and immediately below a thick steel sheet pass line on a front surface and a rear surface of the rolling roll, respectively. A high-pressure water jet nozzle and its header on the rolling roll side are provided, and a water jet nozzle and its header on the anti-roll roll side and the jetting direction are on the rolling roll side are further provided. A pressure control means is provided, and the pressure is set to 30 kg / cm ² or more by using the entire header at the time of cooling, and the pressure is adjusted to 150 kg by using the header on the rolling roll side at the time of descaling.
In addition to providing means for setting the pressure to kg / cm ² or more, the pitch of the water injection nozzle of the header on the side of the anti-roll roll is determined by the nozzle wrap ratio (nozzle injection width / nozzle installation pitch at the portion where the jet water collides with the thick steel plate). 2.) A cooling device for a thick steel plate, wherein 3. The cooling apparatus for a steel plate according to claim 2, wherein the high-pressure water injection nozzle of the roll-side header is a nozzle having a built-in opening / closing valve immediately before the nozzle injection hole.