JPH06190431A - Method and device for cooling thick steel plate - Google Patents

Abstract

PURPOSE:To improve rolling efficiency by setting water pressure at a specified pressure using all of headers at the time of cooling and setting it at a specified pressure using the headers on the side of rolling roll at the time of descaling. CONSTITUTION:Just above and just under the pass line of thick steel plate in front and in the rear of rolling rolls 6, the high-pressure water jetting nozzles 1a, 1b whose jetting directions are taken as the opposite sides of rolling rolls and their headers 3, 3' are arranged on the side of rolling rolls 6. Further, water jetting nozzles 2a, 2b whose jetting directions are taken as the side of rolling rolls 6 and their headers 4, 4' on the opposite side of rolling rolls 6. Pressure controlling means are provided in the water supply systems for these headers 3, 3', 4, 4', the pressure is set at >=30kg/cm<2> using all of the headers 3-4' at the time of cooling and set at >=150kg/cm<2> using the headers 3, 3' on the side of the rolling rolls 6 at the time of descaling. In this way, the waiting time for temp. decrease at transporting thickness is shortened by water-cooling.

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 thick steel plates.

[0002]

Controlled rolling (hereinafter referred to as C
R) The rolling method has been widely used. The CR rolling is characterized in that the rolling temperature during rolling can be controlled accurately and the final rolling finish temperature can be set directly above the Ar ₃ temperature to make the structure finer and improve the strength and toughness.

In the conventional CR rolling method, as shown in FIG. 2, the rolling is temporarily stopped at a transfer thickness of a certain thickness (for example, 2t) with respect to the product sheet thickness t, and then air cooling is performed to obtain a temperature T at that time.
After cooling from ₁ to a predetermined temperature T ₂ , rolling is performed again,
The final finishing temperature at the time of final rolling to obtain a predetermined plate thickness t is A
The r ₃ temperature is directly above.

[0004]

In the CR rolling, unlike the ordinary rolling, the rolling work is temporarily stopped during the rolling and the rolling work is cooled until the temperature of the rolled material changes from T ₁ to T _2. However, there is a problem in that the rolling efficiency is reduced. To solve this problem, as shown in FIG. 2, which is conventionally performed in CR rolling,
This can be solved by repeatedly rolling the material to be rolled for a predetermined number of passes and water cooling as shown in FIG. 3 without waiting for the temperature to be intensively cooled by air in a specific pass during rolling. However, the cooling device for the thick steel plate close to the rolling mill has the following problems.

As a cooling device around the rolling mill, Japanese Patent Laid-Open No. 61-61
-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 is as long as the rear of the installation position. Similarly, when the cooling capacity is small, the cooling machine length becomes longer, and the steel sheet transfer time becomes longer. However, there is a problem that the rolling efficiency cannot be improved for a long time. On the other hand, when a cooling device is installed close to the rolling mill, the "warpage" of the steel sheet during rolling is sometimes large, and a structure in consideration of equipment protection such as a cooling header is required. Further, since the installation space is small, there is a problem that a compact and highly cooling facility is required while maintaining the descaling function.

Further, there is high water pressure descaling as a method of 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 in the cooling water and the surface temperature of the material to be rolled. It is blown away by the momentum by. This jetting is to minimize the jetted water amount and increase the collision force in order to suppress the temperature decrease of the steel sheet. The injection direction of the high-pressure water in this case is directed to the entry side of the material to be rolled. Further, in the system in which a shutoff valve is incorporated in the high-pressure water supply main, low-pressure water flows for nozzle protection as a valve response and a water hammer countermeasure, and it is impossible to prevent supercooling of the front tail part. There is.

[0007]

The gist of the present invention is as follows. (1) When cooling the thick steel plate in the rolling roll approaching part of the rolling mill, the injection direction is set to the rolling roll side and the injection direction to the anti-rolling roll side on the front surface and the rear surface of the rolling roll immediately above and below the thick steel plate pass line, respectively. The high-pressure water jet nozzle and its header are arranged, and further, on the side opposite to the rolling rolls, the water jet nozzle whose jetting direction is the rolling roll side and its header are arranged.
A pressure control means is provided in the water supply system of these headers, the pressure is set to 30 kg / cm ² or more by using all of the headers during cooling, and the pressure is 150 kg / cm ² by using the header on the rolling roll side during descaling. A method for cooling a thick steel plate, which is set as described above.

(2) In the cooling device for cooling the thick steel plate in the rolling roll approaching part of the rolling mill, the injection direction is set to the rolling roll side just above and directly below the thick steel plate pass line on each of the front surface and the rear surface of the rolling roll. A high-pressure water jet nozzle on the side opposite to the rolling roll and its header are arranged, and a water jet nozzle on the side opposite the rolling roll and its header are arranged, and the water supply system for these headers is arranged. A pressure control means is provided at the pressure control means, 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 set to 15 kg at the time of descaling by using the header on the rolling roll side.
A means for setting at least 0 kg / cm ² is provided, and the pitch of the water injection nozzles of the header on the side opposite to the rolling roll is the nozzle lap rate (nozzle injection width / nozzle mounting pitch at the portion where the injection water collides with the thick steel plate). ) Was made into 2. The cooling device of the thick steel plate characterized by the above-mentioned. (3) The apparatus for cooling a thick steel plate according to (2), wherein the high-pressure water jet nozzle of the rolling roll side header is a nozzle having an on-off valve built in immediately before the nozzle jet hole.

[0009]

In the past, while the temperature waiting at the transfer thickness during CR rolling was performed by air cooling to operate at low efficiency, the cooling time was shortened and high efficiency was achieved by using the cooling device close to this rolling mill. Operation is now possible. The cooling system close to this rolling mill uses headers for both descaling and cooling from the rolling mill side, and a high-hydraulic spray exclusively for cooling is used on the outside of the rolling mill. It has become possible to cool down and shorten the kickout length. Furthermore, equipment protection measures have been taken to deal with "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. During descaling, the injection pressure was adjusted according to the scale condition to enable operation without waste. Further, during cooling, the temperature waiting time in CR rolling is eliminated, and cooling can be performed under the required conditions so that the rolling finish temperature is directly above Ar ₃ . By placing a high-pressure water injection nozzle with a built-in on-off valve immediately in front of the nozzle injection hole, it is possible to perform high-speed injection and stop, and by setting the injection width narrower than the strip width of the rolled material,
Prevents overcooling of the edge and saves the amount of water sprayed. By matching the injection start and end timings with the tracking of the steel sheet and inside the tip and tail of the steel sheet, it is possible to prevent supercooling of the tip and tail 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 is possible to prevent the cooling water injected from the nozzle from flowing to the tail end side after colliding with the steel plate. As a result, the problem of supercooling in the longitudinal direction of the steel sheet from the tip to the tail end is solved, and there is an excellent effect that cooling can be performed uniformly over the entire length.

In the case of cooling by spraying high-pressure water, the cooling capacity of the spray impingement portion is the highest. When the nozzle lap ratio is set to 2, collision portions are generated twice in the steel plate width direction, so that the muscle coldness due to the nozzle lap ratio difference can be eliminated in the width direction.

[0013]

[Examples] The rolling conditions of control rolling of thick plates will be disclosed as examples. Slab dimensions (thickness 211 mm, width 177
0mm, length 4890mm) product dimensions (thickness 23.5mm,
When rolling with a width of 2679 mm and a length of 29010 mm, C
As the R condition, a transfer thickness of 41 mm and a rolling temperature of 890 ° C. or less are 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 according to this rolling schedule. Air cooling is performed for 268 seconds at the 12th pass plate thickness of 41 mm. Next, FIG. 3 shows the temperature transition when the cooling device of the present invention is used. However, FIG. 3 shows the temperature transition up to the twelfth pass, and cooling was performed by the cooling device close to the rolling mill in the previous passes. It is clear that it has been cooled to a predetermined temperature within 12 passes up to the CR start 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]

Among these results, the injection pressure of the "descaling / cooling headers 3, 3 '" on the rolling mill side is 150 kg / which is the maximum pressure of the Desuke pump during descaling.
Injection is performed at cm ² , and the injection pressure is adjusted during cooling other than descaling. Injection pressure "cooling-only Header 4,4 '' anti-rolling mill side to be used for cooling are injected at 30kg / cm ^2. This makes it possible to cool to the target CR start temperature when the plate thickness is predetermined.

In this embodiment, FIG. 1 is a longitudinal sectional view of a cooling device installed in a finish rolling mill 5, in which a thick steel plate is carried in from the right hand of the drawing and reverse rolling is performed by finish rolling rolls 6 and 7 in the drawing. After being rolled to a predetermined size, it is conveyed to the left side of the drawing. In this rolling, the thick steel plates are cooled by water jets from the descaling / cooling headers 3 and 3'and the cooling headers 4 and 4 ', which are installed in pairs vertically. At this time, the roll side of the rolling mill is the descaling / cooling headers 3 and 3 ', and the jetting direction is the direction opposite to the rolling mill. On the side opposite to the rolling mill, cooling headers 4 and 4'are provided, and the jetting direction is the rolling mill direction. As a result, the cooling water sprayed from the nozzle portions 1a and 1b can be prevented from flowing toward the tail end side by the cooling water sprayed from the nozzles 2a and 2b after colliding with the steel plate, and the steel plate longitudinal direction from the tip to the tail end can be prevented. The problem of supercooling has been resolved, and cooling is possible evenly over the entire length. In addition, in order to prevent the spray water from scattering,
It is jetted toward the top guide 13 and the hood for preventing scattering. Injection nozzle 1 installed at the tip of each header
Reference numerals a, 1b, 2a and 2b are high-pressure water injection nozzles with a built-in on-off valve immediately before the nozzle injection holes. The upper header is installed in the rolling mill top guide 13 as a measure against warpage during rolling of the thick steel plate.

FIG. 4 is a system diagram of the cooling water supply, which is shown as one of the embodiments, and includes a descaling / cooling combined header 3,
3'is connected to the descaling pump 8 and a pressure gauge 9, a pressure adjusting valve 10 and a high speed on / off valve 11 are arranged in the middle of the piping. The cooling headers 4 and 4'are connected to a cooling high-pressure pump 12, and a pressure gauge 9 ', a pressure adjusting 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.

FIGS. 5A, 5B and 5C show the collision pattern (a) and (b) of the conventional cooling nozzles 2a and 2b and the temperature change image (c), and "A" is the nozzle. It shows a position where there is a non-lapped part of the collision part, and it only passes once through the nozzle collision part with high cooling capacity, and the temperature drop is small. On the other hand, the "B portion" indicates a position where the lap portion of the nozzle collision portion is present, and the temperature drops largely because the nozzle collision portion having high cooling capacity is passed twice. A temperature difference as shown in the image of temperature drop occurs, and muscle coldness due to the nozzle lap occurs in the width direction of the steel sheet.

FIGS. 6 (a), 6 (b) and 6 (c) show the collision pattern (a) and (b) and the temperature change image (c) of the cooling nozzles 2a and 2b of the present invention. The positions "C part" and "D part" have the same temperature drop because they pass twice through the nozzle collision part having the same cooling ability. As shown in the temperature change image, there is no temperature difference, and the problem of muscle coldness caused by nozzle laps in the width direction of the steel sheet can be solved.

[0022]

As described above, water cooling during rolling has the excellent effect of achieving stable operation and shortening of kickout and protection of the cooling device for the purpose of improving the rolling efficiency. . Further, since the descaling header has both the descaling function and the cooling function, it becomes a compact device, and since the pressure adjusting function is incorporated, it has an excellent effect that it can operate under each optimum condition.

Further, a high-pressure water injection nozzle with a built-in on-off valve is installed immediately in front of the nozzle injection hole to improve responsiveness, prevent supercooling of the edge portion by controlling the injection width, save cooling water, and track thick steel plate. It was possible to prevent the supercooling of the tip and tail of the steel sheet by controlling the injection timing according to the above. By using a plurality of headers and setting the jetting direction of the last-stage header to the rolling mill side, the cooling water jetted from the nozzle portion was prevented from colliding with the steel sheet and flowing to the tail end side. This solves the problem of supercooling in the longitudinal direction of the steel sheet from the tip to the tail, and has an excellent effect that cooling can be performed uniformly over the entire length.

Although the cooling water supply system in the embodiment uses separate pumps for descaling and cooling,
It is obvious that the same effect can be obtained by using a high-pressure pump that can share the supply source. When the nozzle lap ratio of the high-pressure water spray is set to 2, the collision portion is generated twice in the steel plate width direction, so that there is an excellent effect that muscle coldness due to the nozzle lap ratio difference in the width direction can be eliminated.

[Brief description of drawings]

FIG. 1 shows a vertical cross-sectional view of a cooling device adjacent 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 among all 14 passes).

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

FIG. 5 shows an impact pattern and a temperature change image of a cooling-only nozzle according to a conventional method.

FIG. 6 shows an impact pattern and a temperature change image of the cooling nozzle of the present invention.

[Explanation of symbols]

 1a, 1b Injection nozzle 2a, 2b Cooling dedicated nozzle 3,3 'Descaling / cooling header 4,4' Cooling dedicated header 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

Front page continued (72) Inventor Masakazu Abe, Oita City, Oita Prefecture, 1st Nishinosu, Nippon Steel Co., Ltd., Oita Steel Works, Nippon Steel Co., Ltd. Company Oita Works

Claims (3)

[Claims] 1. When cooling a thick steel plate at a rolling roll approaching portion of a rolling mill, the injection direction is opposite to the rolling roll side just above and just below the thick steel plate pass line on each of the front surface and the rear surface of the rolling roll. Side high-pressure water jet nozzle and its header are arranged, and further, on the side opposite to the rolling roll, the water jet nozzle whose jetting direction is the rolling roll side and its header are arranged, and pressure control is applied to the water supply system of these headers. A means is provided so that 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 in a rolling roll approaching portion of a rolling mill, wherein the injection direction is reversed to the rolling roll side just above and just below the thick steel plate pass line on each of the front surface and the rear surface of the rolling roll. The high-pressure water jet nozzle on the rolling roll side and its header are arranged, and the water jet nozzle and its header on the side opposite to the rolling roll are set to the water supply system of these headers. 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 set at 150 kg by using the header on the rolling roll side at the time of descaling.
A means for setting at least kg / cm ² is provided, and the pitch of the water jet nozzle of the header on the side opposite to the rolling roll is the nozzle lap ratio (nozzle jet width / nozzle mounting pitch at the portion where the jet water collides with the thick steel plate). ) Was made into 2. The cooling device of the thick steel plate characterized by the above-mentioned. 3. The cooling apparatus for a thick steel plate according to claim 2, wherein the high-pressure water jet nozzle of the rolling roll side header is a nozzle having an on-off valve built in immediately before the nozzle jet hole.