WO2007026905A1

WO2007026905A1 - Hot rolling facility of steel plate and hot rolling method

Info

Publication number: WO2007026905A1
Application number: PCT/JP2006/317394
Authority: WO
Inventors: Naoki Nakata; Takashi Kuroki; Akio Fujibayashi; Shogo Tomita
Original assignee: Jfe Steel Corporation
Priority date: 2005-08-30
Filing date: 2006-08-29
Publication date: 2007-03-08
Also published as: JP2007061838A; EP1935521B1; EP1935521A1; CN101253011A; JP4586682B2; CN101253011B; EP1935521A4; KR100973692B1; KR20080034966A

Abstract

Hot rolling facility and method of steel plate excellent in facility cost and maintainability of facility and having good cooling capacity which can produce a steel plate having excellent characteristics efficiently by controlling the temperature of a rolling material properly. At a position where the inlet side and the outlet side of a mill (12) are close to each other, a cooling facility (20), for supplying cooling water to the upper and lower surfaces of the steel plate (10) that is being passed, is arranged. The cooling facility (20) is provided with an upper header (21) having an upper nozzle (22) for ejecting rod-shaped cooling water (23) toward the upper surface of the steel plate (10) at an inclination angle θU=30°-60° at such a position that the stagnant cooling water (24) supplied to the upper surface of the steel plate (10) is dammed by a work roll (12a), and provided with a lower header (31) having a lower nozzle (32) for ejecting rod-shaped cooling water (33) toward the lower surface of the steel plate (10) at an angle of elevation θL=45°-90° between the work roll (12a) and a table roller (13a) adjacent thereto.

Description

Item 窨

Steel sheet hot rolling equipment and hot rolling method

The present invention relates to a steel plate and steel sheet hot rolling equipment (hot rolling mi 11) and a hot rolling method. Background art

In recent years, in the process of manufacturing a steel sheet by hot rolling, the temperature of the rolling material is controlled to manufacture a steel sheet having excellent characteristics.

For example, the temperature of the rolled material; ^ Controlled rolling in which finish rolling is performed in the non-recrystallization temperature range (non-: recrystallization temperature range)

By applying (Controlled Rolling; CR), steel sheets with excellent performance are built.

In addition, by supplying cooling water to the steel sheet immediately after it exits the roll bite of the hot rolling mill, the surface temperature of the steel sheet is lowered to reduce the scale formation, thereby reducing the scale formation. (Thin seal steel sheet) is being considered.

The following techniques are used for controlling the temperature of such rolled material.

For example, as a technique for cooling a steel sheet by supplying cooling water during hot finish rolling of a thin steel sheet, there is a technique described in Japanese Patent Application Laid-Open No. 2000-0 3 6 1 3 15. This is because it can be used for the production of fine-grained steel sheets by injecting film-like cooling water from the slit nozzles of the headers installed between the finishing stands to obtain a high cooling rate. Has been.

Further, as a technique for cooling the hot steel sheet by supplying cooling water, there is a technique described in Japanese Patent Application Laid-Open No. 6 2 -260 0 2. This is to raise and lower the nozzle unit that injects cooling water in opposition, and a laminar nozzle is installed separately. It is said that a wide range of cooling rates can be secured by using with a spray nozzle.

However, the technology described in the above-mentioned Japanese Patent Application Laid-Open No. 2002-36 1 3 15 and Japanese Patent Application Laid-Open No. 6-260 00 22 is not limited to equipment cost, equipment maintenance and cooling performance. There are the following problems.

First, in the technology described in Japanese Patent Application Laid-Open No. 2002 2-36 1 3 1 5, the cooling water supplied to the upper surface of the steel sheet stays on the steel sheet for a while, but this staying state changes to change the cooling region of the steel sheet. There is a problem that high temperature control accuracy cannot be obtained. Also, since the header has a built-in flow adjuster, the equipment is large, so there is a limit to installing it close to the rolling mill, which is not suitable for the production of thin-scale steel sheets.

In the technique described in Japanese Patent Application Laid-Open No. 62-260022, the slit nozzle unit must be brought close to the steel plate. It may cause damage to the slit nozzle unit by colliding with the steel plate, or the steel plate may become unable to move, causing the production line to stop or the yield to decrease. Therefore, it may be possible to operate the elevating mechanism to retract the slit nozzle unit upward when the tip or tail passes, but in this case the cooling of the leading and trailing ends is insufficient, and the target material Cannot be obtained. In addition, there is a problem that the equipment cost for installing the elevator cage is high. In addition, since there is an elevating mechanism, it is difficult to install the nozzle unit close to the rolling mill, so it is not suitable for the production of thin-scale steel sheets.

Furthermore, in the techniques described in Japanese Laid-Open Patent Publication Nos. 2002 2-36 1 3 15 and 6-226002 2, it is assumed that a slit nozzle is used. If the outlet is not always kept clean, the cooling water will not form a film. For example, as shown in FIG. 6, when the foreign matter 60 adheres to the soot outlet of the slit nozzle 52 and becomes clogged, the cooling water film 53 is broken. In addition, in order to keep cooling water in the injection area (in the cooling area), it must be injected at a high pressure. However, if the film-like cooling water 53 is sprayed at a high pressure, the balance of the injection pressure will deteriorate. Cooling water film 5 3 There was a problem that was easy to break. Cooling water film 5 3 Force S If not formed well; Cooling 'Water leaks in the upstream and downstream direction of the injection area, and it stays on the steel plate 10 to partially cool the steel plate 10 and uneven temperature There is a problem that occurs. There is also a technology to eliminate the cooling water staying on the upper surface of the steel plate 10 by side spraying, etc., but if the amount of cooling water is large, it cannot be completely eliminated, and there is still a problem that temperature deviation is generated. .

The present invention has been made in view of the above circumstances, and when performing hot rolling of a steel sheet, the equipment cost is excellent in equipment maintainability and has a good cooling capacity. It is an object of the present invention to provide a hot rolling facility for a steel sheet and a hot rolling method for a steel sheet that can efficiently produce a steel sheet having excellent characteristics by appropriately controlling the temperature of the steel sheet. Disclosure of the invention

In order to solve the above problems, the present invention has the following features.

[1] A cooling facility for supplying cooling water to the upper surface of the steel sheet while passing the steel sheet is disposed at a position close to the rolling mill on the entry side and / or exit side of the rolling mill for hot rolling the steel sheet, The cooling equipment includes a header having a nozzle that radiates rod-like water flow with respect to the upper surface of the steel sheet at an angle of depression of 30 ° to 60 ° toward the rolling mill. A hot rolling facility for a steel plate, characterized in that the cooling water after being supplied to the steel plate is provided at a position where it is blocked by a work roll of a rolling mill. In addition, the rod-shaped cooling water (also referred to as columnar flow cooling water) in this effort refers to cooling water sprayed from a circular (including elliptical or polygonal) nozzle nozzle outlet. . Further, the rod-shaped cooling water of the present invention is not a spray-like jet, but the cross-section of the water flow is maintained in a substantially circular shape until it collides with the steel plate from the nozzle outlet, thereby cooling the continuous and straight water flow. Say water. '.

[2] The cooling equipment further includes a nozzle that sprays rod-shaped cooling water on the lower surface of the steel sheet toward the rolling mill at an angle of elevation of 45 ° to 90 °. To the rolling mill work roll and it! The hot-rolling equipment for steel sheets described in [1] above, which is provided between a table roll and ⁵ rolls.

[3] Using the hot-rolling equipment for steel sheets described in [1] or [2] above, spraying the cooling water so that the cooling water after being supplied to the steel sheet reaches the work roll of the rolling mill. A method for hot rolling a steel sheet, comprising rolling.

[4] Using the hot-rolling equipment for steel sheets described in [1] or [2] above, while the steel sheet is not rolled, the roll gap of the work roll is set to 2 mm or less and cooling water is supplied. A method of hot rolling a steel sheet characterized by spraying.

In the present invention, when hot rolling a steel sheet, it has excellent equipment cost and equipment maintainability, and has a good cooling capacity. The steel plate which has a characteristic can be manufactured efficiently. Brief Description of Drawings

FIG. 1 is a layout diagram of a “hot rolling facility for steel sheets” according to an embodiment of the present invention.

FIG. 2 is a layout diagram of another steel plate hot rolling facility according to an embodiment of the present invention. FIG. 3 is a detailed view of a cooling facility in one embodiment of this effort.

FIG. 4 is a detailed view of the cooling facility in one embodiment of the present invention.

FIG. 5 is a diagram showing an example of a nozzle arrangement of a header in an embodiment of the present invention. FIG. 6 is an explanatory diagram of the prior art.

(Explanation of symbols)

1 0: Steel plate, 1 1: reheating furnace, 1 2: Hot rolling mill, 1 2 a: Work roll nore, 1 3: Table roller, 2 0 cooling equipment, 2 1 : Upper header, 2 2: Upper nozzle, 2 3 cooling water, 2 4: Remaining cooling water, 2 5: Cooling water, 3 1 Lower header, 3 2: Lower nozzle, 3 3: Rod cooling water 3 4: Cooling water after supply BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 and FIG. 2 are diagrams showing a hot rolling facility in an embodiment of the present invention. Fig. 1 shows a hot rolling mill for steel plates or a hot roughing mill for steel sheets, and Fig. 2 shows a hot finishing rolling facility for thin steel plates ( Finishing mill).

In FIG. 1, a heating furnace 11 that heats a slab to a predetermined temperature, and a rolling mill that rolls the slab 10 extracted from the heating furnace 11 into a steel plate 10 having a predetermined thickness (here, Lever rolling mill) 1 2 and slab (steel plate) 1 0 while passing slab (steel plate) 10 through the adjacent positions on the entry side (upstream side) and exit side (downstream side) of rolling mill 1 2 A cooling facility 20 for supplying cooling water to the lower surface is arranged. In the figure, 1 3 is a tape / reroller.

In FIG. 2, a heating furnace 11 for heating the slab to a predetermined temperature, and a rough rolling machine (not shown) for roughly rolling the slab 10 extracted from the heating furnace 11 into a steel plate 10 having a predetermined thickness. And a finishing mill (here, a tandem mill) 1 2 for rolling the steel sheet 10 roughly rolled to a predetermined thickness by a roughing mill to a predetermined finishing thickness. A cooling facility 20 for supplying cooling water to the upper and lower surfaces of the steel plate 10 while allowing the steel plate 10 to pass therethrough is disposed at a position close to the exit side (downstream side). In the figure, 13 is a tape / reroller.

Then, as shown in FIG. 3, the cooling facility 20 is configured so that the bar-shaped cooling water 23 is directed toward the work roll 12 a side of the rolling mill 12 2 with respect to the upper surface of the steel plate 10, and the depression angle 30 ° to 6 Nozzle for injection at 0 (circular tube nozzle) 2 2 Residual cooling water 2 2 after feeding the upper header 2 1.ヮロール Roll 1 2. Prepared at a position where it can be dammed by a, and rod-shaped cooling water 3 3 against the lower surface of the steel plate 1 0 toward the work roll 1 2 a side of the mill 1 2 Elevation angle 0 _L = 4 5 ° to 90 ° Lower nozzle (circular tube nozzle) 3 1 with lower nozzle 3 1, work roll 1 2 a of rolling mill 1 2 a and table roller 1 3 a adjacent to it And prepare for.

FIG. 5 shows an arrangement example of the circular tube nozzles 2 2 attached to the upper header 21. Circular tube nozzles 2 2 are arranged in multiple rows in the conveying direction of steel plate 10 In the width direction, the cooling water can be supplied to the entire width of the passing steel plate 10. Further, the circular nozzle 3 2 attached to the lower header 3 1 is also arranged in the same manner.

The reason for arranging multiple rows in the transport direction is that a single row of nozzles weakens the ability to dam the stagnant cooling water between the cooling water that collides with the steel sheet and the cooling water. Therefore, it is preferable to arrange three or more rows in the transport direction. More preferably, 5 or more rows are arranged. Further, in the plate width direction, the cooling water is supplied to the entire width of the passing steel plate 10. In addition, one upper header is provided here, but two or more headers and circular tube nozzles 22 may be arranged.

By the way, in this embodiment, the cooling water sprayed from the upper nozzle 22 is a rod-shaped cooling water. This is because the power to dam is large. · Also, when film-like cooling water is sprayed at an angle, the water film near the steel sheet becomes thinner and more prone to spilling as the distance from the steel sheet to the nozzle increases.

In addition, the vertical angle 0 u of the rod-shaped cooling water 2 3 sprayed from the upper nozzle 22 is set to 30 ° to 60 ° because the vertical angle θ υ force S 3 0 ° is smaller than the rod-shaped cooling water 2 3 This is because the vertical velocity component becomes smaller and the collision with the steel plate 10 becomes weaker and the cooling capacity is reduced. When the depression angle 0 u is larger than 60 °, the conveying direction velocity component of the rod-shaped cooling water 23 is reduced. This is because it is not sufficient, and the ability to dam the stagnant cooling water 24 is weak, and the stagnant cooling water 24 leaks outside in the transport direction, making the cooling region unstable. Further preferred dip angle is from 40 ° to 50 °. It is.

Also, the elevation angle Θ _L of the rod-shaped cooling water 3 3 sprayed from the lower nozzle 3 2 is set to 45 ° to 90 °. The elevation angle is less than 45 °. As the directional velocity component becomes smaller, the collision with the steel plate becomes weaker, the cooling capacity decreases, and the distance between the crawl 1 2 a and the table roller 1 3 a must be increased. If the elevation angle 0 _L is larger than 90 °, the cooling water is scattered around the rolling mill 12, which is not preferable in terms of operability and facility maintenance. The cooling facility 20 supplies cooling water from the upper header 21 toward the upper surface of the steel plate 10 so that the water density on the steel plate surface is 4 m ³ / m ² min or more, and toward the lower surface of the steel plate 10. Cooling water is also supplied from the lower header 31 so that the water density on the steel plate surface is 4 m ³ / m ² mi ιι or more.

Here, the reason why the water density is set to 4 m ³ / m ² min or more will be described. The staying cooling water 24 shown in FIG. 3 is formed by being blocked by the rod-shaped cooling water 23 to be supplied. At this time, if the water density is small, it cannot be dammed itself, and if the water density is larger than a certain quantity, the amount of the accumulated cooling water 24 that can be dammed increases, and the cooling water discharged from the end of the plate width Retained cooling water 24 is kept constant as the amount of cooling water supplied is balanced.

In the case of thick steel plates, the typical plate width is 2 to 5 m. If cooling is performed with a water density of 4 m ³ Zm ² ni in or more, the accumulated cooling water can be kept constant at these plate widths, and rolling A desired temperature drop can be obtained while passing the steel plate 10.

The higher the water density is over 4 m ³ / m ² min, the more control rolled material that eliminates the waiting for cooling. For example, if the water density is small, the waiting time for cooling can be solved only with a rolled material with a thin plate thickness, but if the water content density is increased, the waiting time for cooling can be eliminated even with a rolled material with a somewhat thick plate thickness. However, the effect of shortening the cooling waiting time for increasing the water volume gradually decreases as the water density increases, so the water density takes into account the effect of shortening the cooling waiting time and the equipment cost. Therefore, it is preferable to determine. A more preferable water density is 4 to 10 m ³ / m ² ni in.

„It is preferable that the jet speed of the rod-shaped cooling water 23 from the upper nozzle 22 is 8 m / s or more. The upper limit of the number of rows is the size of the steel sheet to be cooled, the transport speed, the target temperature drop, etc. In addition, if the injection speed exceeds 30 m / s, the pressure loss increases, and the problem of increased wear on the inner surface of the nozzle arises. For this reason, the injection speed is preferably 30 m / s or less. In order to prevent the nozzle from clogging and to ensure the spraying speed of the cooling water, the inner diameter of the nozzle only needs to be in the range of 3 to 8 mm. Further, in order to prevent the cooling water from flowing out from the gap between the rod-shaped cooling waters, the interval between adjacent nozzles on the imaginary line drawn in the plate width direction should be within 10 times the nozzle inner diameter.

Furthermore, when supplying film-like cooling water with unstable water flow to the steel plate 10, the header needs to be close to the steel plate 10, whereas when supplying rod-like cooling water 23 to the steel plate, The upper header 21 can be arranged at a position away from the pass line. Therefore, in order to prevent the upper nozzles 2 2 _a and 2 2 b from being damaged due to warpage of the steel plate 10, the position of the tip of the upper nozzle 22 should be separated from the pass line. However, if it is too far away, the cooling water will disperse and become rod-shaped and will not function to block the cooling water, so the distance between the tip of the upper nozzle 22 and the pass line should be 50 O mm to l 80 O mm. preferable.

When hot rolling of the steel sheet is performed using the hot rolling equipment configured as described above, the retained cooling water 24 after being supplied to the upper surface of the steel sheet 10 and the lower surface of the steel sheet 10 after being supplied Rolling is carried out while spraying rod-shaped cooling water 2 3 and 3 3 so that the cooling water 3 4 reaches the workpiece hole 1 2 a of the compressor 1 2.

Thus, in this embodiment, the rod-shaped cooling water 2 3 is jetted toward the work roll 1 2 a side with respect to the upper surface of the steel plate 10 at an inclination angle of 0 u = 30 ° to 60 °, and the steel plate 1 Since the staying cooling water 24 after being supplied to the upper surface of 0 reaches the work roll 12 a, the staying cooling water 24 is between the work roll 12 a and the rod-like cooling water 23. And a stable cooling area is formed. As a result, the problem that the stagnant cooling water 24 moves freely on the steel plate 10 and cools the steel plate 10 non-uniformly and the temperature unevenness occurs is solved, and the steel plate 10 is cooled uniformly. be able to.

Here, the cooling region is sandwiched between the position where the rod-shaped cooling water from the circular tube nozzle in the row farthest from the rolling roll (outermost row) collides with the steel plate 10 and the rolling nozzle in the upper header. It is a territory. By forming the cooling region in this way, the distance from the roll byte of the work roll 12 a to the cooling start position (position where cooling with cooling water starts) is zero.

In addition, since the position of the tip of the upper nozzle 2 2 can be separated from the pass line to some extent, even when a steel plate with a tip or tail is warped, the steel plate 1 0 collides with the upper header 2 1 and the upper header 2 1 2 If 1 is damaged or the steel plate 10 cannot move, causing the production line to stop or the yield to decrease. Therefore, since it is not necessary to provide an elevating device to avoid the steel plate 10 from colliding with the upper header 21, the equipment cost can be reduced.

Furthermore, since the lifting device is not provided, the upper header 21 can be installed close to the rolling mill 12. As a result, by supplying cooling water to the steel plate 10 immediately after exiting the roll tool of the rolling mill 12, the surface temperature of the steel plate 10 can be lowered and the amount of scale generation can be suppressed. It is also suitable for the manufacture of Scalender steel plates.

'' Moreover, the cooling water 2 4 and 3 4 after being supplied to the steel plate 10 hits the surface of the work roll 1 2 a and has the effect of cooling the work roll 1 2 a. It is no longer necessary to prepare, and equipment costs can be reduced.

Furthermore, even when the work holes 1 2 a, such as between the rolling passes or between the preceding rolled material and the subsequent rolled material, are not spraying the steel plate 10, if the cooling water 2 3, 3 3 is sprayed, Since the cooling water 2 5 flows as shown in FIG. 4, a large amount of cooling water can be supplied to the upper and lower work rolls 1 2 a. As a result, the growth of the thermal crown is suppressed and dimensional control with high accuracy becomes possible. At this time, if there is a margin in setting the roll gap, for example, if there is a gap of 45 seconds or more between the preceding rolled material and the succeeding rolled material, the roll gap of the work roll 1 2 a is increased. It is only necessary to narrow down to about 2 mm and inject cooling water 2 3 and 3 3. This is because the cooling water 25 can be prevented from scattering through the roll gear and the cooling water 25 is supplied to the work roll 12 a in a wider range in the outer peripheral direction. Of course, when roll cooling between the rolling passes as described above is not required, spraying of the cooling water 2 3 and 3 3 may be stopped. Thus, in this embodiment, when hot rolling a steel sheet, the equipment cost is excellent in equipment maintainability and has a good cooling capacity, and the temperature of the rolled material is appropriately controlled based on the equipment cost. By doing so, it is possible to efficiently manufacture a steel sheet having excellent characteristics.

In this embodiment, in FIG. 1, an upper header 2 1 and a lower header 3 1 are provided on the entrance side and the exit side of the rolling mill 12, respectively, and in FIG. 2, the exit side of the rolling mill 12 is provided. However, the present invention is not limited to this. If the installation space is limited or the effect to be obtained may be limited, for example, it may be installed only on either the entry side or the exit side of the rolling mill 12 or Only the upper header 2 1 may be installed without providing the header 3 1. However, both the upper header 2 1 and the lower header 3 1 should be installed so that the cooling capacity is about the same in the upper and lower sides in order to suppress the occurrence of warping when the rolling material stagnates into the rolling mill 1 2. Is desirable. Example 1

As Example 1 of the present invention, controlled rolling in a hot rolling line for thick steel plates was performed. Here, after rolling the plate thickness to 28 mm, controlled rolling was performed at a predetermined rolling temperature in the final three passes.

At that time, as Example 1 of the present invention, the hot rolling equipment (FIG. 1) shown in the above-described embodiment was used, and it was installed on the entry side and the exit side of the rolling mill 12 in 4 passes before performing the controlled rolling. Bar cooling water is sprayed from the column cooling equipment 20 and rolled while cooling the steel plate 10 so that the temperature of the steel plate 10 becomes a predetermined temperature when the four passes are completed. Control rolling was performed in a pass.

The vertical angle 0 u of the upper nozzle 2 2 was 45 °, and the elevation angle 0 _L of the lower nozzle 3 2 was 60 °.

The inner diameter of the upper nozzle 2 2 and the lower nozzle 3 2 was 6 mm, and the injection speed of the rod-shaped cooling water was 8 mZ s.

On the other hand, as Comparative Example 1, controlled rolling was performed using a hot rolling facility that does not have a cooling facility for cooling the steel sheet during rolling. Plate thickness at relatively high temperature 28 mm The steel sheet rolled in step 3 was subjected to 30 s air-cooling standby before being controlled to a predetermined temperature, and then subjected to controlled rolling in the final three passes.

Further, as Comparative Example 2, instead of the cooling facility 20 of the present invention example 1, a hot rolling facility equipped with the cooling facility described in the above-mentioned Japanese Patent Application Laid-Open No. Sho 62-2660 2 is used. Control rolling was performed in the same manner as Example 1 of the present invention. That is, in 4 passes before performing the controlled rolling, film-like cooling water is injected from the slit nozzle, and rolling is performed while cooling the steel plate so that the temperature of the steel plate becomes a predetermined temperature when the 4 passes are completed. After that, controlled rolling was performed in the final three passes. The header was installed at a bank where the distance from the work roll roll bite to the cooling open position (the position where cooling with cooling water started) was 4 m, and the header was cooled while passing the steel plate.

The results are shown in Table 1. In Table 1, X is indicated when productivity and quality are reduced, and ○ is indicated when it is not.

table 1

As shown in Table 1, in Comparative Example 1, an air cooling waiting machine of 30 s was performed before controlled rolling, so the rolling pitch was 2 10 s. In Comparative Example 2, the equipment cost was high because a lifting mechanism had to be provided. And it was sporadic that the steel plate with the bent tip collided with the nozzle unit and damaged the equipment. The steel plate that damaged the equipment was deformed and could not become a product, resulting in a 10% drop in yield. Although control rolling could be performed without air-cooling standby for 30 s, the conveyance distance of the steel plate in 4 passes before performing control rolling. The transfer time increased by the longer separation, and the overall rolling pitch was 24 4 s shorter than Comparative Example 1 and 1 86 6 s.

In addition, both Comparative Examples 1 and 2 required a cooling device for cooling the rolling rolls, which required equipment costs.

On the other hand, in the present invention example 1, the stagnant cooling water 24 is dammed between the work rolls 12a and the rod-shaped cooling water 23, and a stable cooling region is formed. The problem that the cooling water 24 arbitrarily moves on the steel plate 10 to cool the steel plate 10 non-uniformly and the temperature unevenness occurs is solved, and the steel plate 10 can be cooled uniformly. ...

In addition, even when the steel plate with a bent tip or tail is cooled, the steel plate 10 collides with the upper header 21 and damages the upper header 21 or the steel plate 10 cannot move. There has never been an event that caused a stoppage or a decrease in yield. Therefore, it was not necessary to install a lifting device to avoid the steel plate 10 from colliding with the upper header 21, and the equipment cost could be reduced.

And it was possible to perform controlled rolling without waiting for 30 s of air cooling, and the steel plate conveyance distance in the four passes before performing controlled rolling was about the same as in Comparative Example 1, so the rolling pitch was Compared with Comparative Example 2, it was 1680 s shorter by 6 s.

Moreover, since the cooling water 2 4 and 3 4 after being supplied to the steel plate 10 hits the surface of the work roll 1 2 a to cool the work roll 1 2 a, there is a separate cooling device for roll cooling. There was no need to prepare, and the equipment cost was reduced. Example 2

As Example 2 of the present invention, rough rolling was performed on a thin steel sheet in a hot rolling line. Here, the slab was rolled to a sheet thickness of 42 mm using a roughing mill.

At that time, as the example 2 of the present invention, the hot rolling equipment (FIG. 1) shown in the above-described embodiment is used, and the three passes in the rough rolling are provided on the inlet side and the outlet side of the rolling mill 12. The cooling equipment 2 was rolled while cooling the steel sheet 10 by injecting bar-shaped cooling water from the side. The vertical angle of the upper nozzle 2 2 was 45 °, and the elevation angle S of the lower nozzle 3 2 was 60 °. The inner diameter of the upper nozzle 22 and the lower nozzle 32 was 6 mna, and the spray speed of the rod-shaped cooling water was 8 mZ s.

On the other hand, as Comparative Example 3, rough rolling was performed using a hot rolling facility that does not have a cooling facility for cooling the steel plate during rolling. When the slab was heated at a relatively high temperature, the end temperature of the rough rolling became high. Therefore, in order to suppress the occurrence of scale flaws, an air cooling standby of 15 s was performed on the entrance side of the finishing mill.

Further, as Comparative Example 4, instead of the cooling facility 20 of the present invention example 2, using a hot rolling facility equipped with the cooling facility described in the above-mentioned JP-A-62-260200, Rough rolling was performed in the same manner as Example 2 of the present invention. That is, in the three passes of rough rolling, rolling was performed while film-like cooling water was jetted from a slit nozzle to cool the steel sheet. The vedder is installed in a place where the distance from the work roll roll bite to the cooling start position (cooling water, where cooling starts) is 4 m, and cooling is performed while passing the steel plate. went.

The results are shown in Table 2. In Table 2, “X” is assigned to the case where the productivity and quality are reduced, and “Yes” is the case where it is not.

Table 2

As shown in Table 2, in Comparative Example 3, when the slab was heated at a relatively high temperature, it was air-cooled for 15 s at the entrance of the finishing mill. Therefore, the rolling pitch is 10 5 s, and the rolling efficiency is decreasing.

Moreover, in Comparative Example 4, the equipment cost was high because a lifting mechanism had to be provided. Then, the steel plate with the bent tip collides with the nozzle unit and Can be broken. The steel plate that damaged the equipment was deformed and could not become a product, resulting in a 10% drop in yield. Although it was not necessary to wait for 15 s of air cooling at the finishing mill entry side, the conveyance time increased by the increase in the conveyance distance to the cooling facility, and the overall rolling pitch was It was 9 3 s shorter than 1 2 s.

In addition, both Comparative Examples 3 and 4 required a cooling device for cooling the rolling rolls, which required equipment costs.

On the other hand, in the present invention example 2, the stagnant cooling water 24 is dammed between the work rolls 12a and the rod-like cooling water 23, and a stable cooling region is formed. The problem that the cooling water 24 arbitrarily moves on the steel plate 10 to cool the steel plate 10 non-uniformly and the temperature unevenness occurs is solved, and the steel plate 10 can be cooled uniformly. As a result, it was possible to appropriately suppress the occurrence of skewering without causing material variations.

In addition, even when a steel plate with a bent tip or tail is cooled, steel plate 10 collides with upper header 21 and damages upper header 21 or steel plate 10 cannot move. There has never been a loss of line or a drop in yield. Therefore, it was not necessary to install a lifting device to avoid the steel plate 10 from colliding with the upper header 21, and the equipment cost could be reduced.

And there was no need to wait for 15 s of air cooling at the finishing mill entry side; because the steel plate transport distance when cooled by the cooling equipment 20 is also similar to Comparative Example 3, The rolling pitch was 90 s shorter than Comparative Example 4 by 3 s.

Moreover, since the cooling water 2 4 and 3 4 after being supplied to the steel plate 10 hits the surface of the work roll 1 2 a, there is also an effect of cooling the work roll 1 2 a. There was no need to prepare, and the equipment cost could be reduced. Example 3

As Example 3 of the present invention, finish rolling was performed on a thin steel sheet in a hot rolling line. Here, it was rolled to a finishing plate thickness of 3 mm by a 7-mill finish rolling mill of F1 to F7.

At that time, as Example 3 of the present invention, using the hot finish rolling equipment (FIG. 2) shown in the above-described embodiment, the cooling provided on the exit side of the rolling mill 12 in 4 stands F 4 to F 7 Rolling was performed while cooling the steel plate 10 by injecting rod-shaped cooling water from the equipment 20. The vertical angle of the upper nozzle 2 2 is 45 °, and the elevation angle Θ _L of the lower nozzle 3 2 is 60. It was. The inner diameter of the upper nozzle 22 and the lower nozzle 32 was 6 mm, and the jet speed of the rod-shaped cooling water was 8 m / s.

On the other hand, as Comparative Example 5, in place of the cooling facility 20 of the present Example 3, the heat provided with the cooling facility described in the above-mentioned special 2 0 0 2-3 6 1 3 15 Finish rolling was performed in the same manner as in Example 3 of the present invention using a cold rolling facility. That is, in 4 stands of F4 to F7, rolling was performed while film-like cooling water was sprayed from slit nozzles to cool the steel sheet. The header was installed in a place where the distance from the mouthpiece / revite of the workpiece hole to the cooling start position (position where cooling with cooling water starts) was 2 m.

Further, as Comparative Example 6, instead of the cooling facility 20 of Example 3 of the present invention, using a hot rolling facility equipped with the cooling facility described in the above-mentioned JP-A-62-260200, Finish rolling was performed in the same manner as Example 3 of the present invention. That is, rolling was performed while cooling the steel sheet by spraying film-like cooling water from the slit nozzles in four stands of F4 to F7. The header was installed in a place where the distance from the work roll roll bite to the cooling start position (position where cooling with cooling water starts) was 2 m.

The results are shown in Table 3. In Table 3, X is indicated when productivity and quality are reduced, and ○ is indicated when it is not. Table 3

* Distance from work roll roll bite to cooling start position As shown in Table 3, in Comparative Example 5, the staying state of the cooling water staying on the upper surface of the steel sheet changes and the cooling area of the steel sheet fluctuates. Unevenness became large. As a result, variations in the material (strength) of the product such as tensile strength increased (difference between maximum strength and minimum strength: 3 kg / nnn ² or more), and high-quality steel sheets could not be manufactured.

In Comparative Example 6, the equipment cost was high because a lifting mechanism had to be provided. And it was sporadic that the steel plate with the warped tip collided with the nozzle unit and damaged the equipment. The steel plate that damaged the equipment was deformed and could not become a product, resulting in a 10% drop in yield.

In both Comparative Examples 5 and 6, since the header was installed at a distance of 2 m from the work roll, it was not possible to suppress the generation of scale on the steel sheet immediately after exiting the roll tool, making it possible to produce a thin scale steel sheet. could not.

In addition, both Comparative Examples 5 and 6 required a cooling device for cooling the rolling rolls, which required equipment costs.

On the other hand, in the invention example 3, the stagnant cooling water 24 is dammed between the work rolls 12a and the rod-like cooling water 23, and a stable cooling region is formed. Cooling water 2 4 moves on the steel plate 10 on its own and cools the steel plate 10 non-uniformly, which eliminates the problem of uneven temperature, and makes it possible to cool the steel plate 10 uniformly. Came. As a result, there was little variation in materials such as tensile strength (difference between maximum strength and minimum strength: 1 kg / wake ² or less). High quality steel sheets could be manufactured.

In addition, even when a steel plate with a bent tip or tail is cooled, the steel plate 10 collides with the upper header 21 and damages the upper header 21 or the steel plate 10 cannot move. It has never been possible to stop the process or reduce the yield. Therefore, it is not necessary to provide a lifting device to avoid the steel plate 10 from colliding with the upper header 21, and the equipment cost can be reduced.

In addition, the cooling water was supplied to the steel plate 10 immediately after exiting the roll byte of the rolling mill 12 and the surface temperature of the steel plate 10 could be lowered, thereby suppressing the generation of scale and reducing the thin scale. Steel sheet could be manufactured.

Moreover, since the cooling water 2 4 and 3 4 after being supplied to the steel plate 10 hits the surface of the work roll 1 2 a and has an effect of cooling the work roll 1 2 a, a cooling device for cooling the roll is provided separately. There was no need, and the equipment cost could be reduced.

Claims

The scope of the claims

1. A cooling facility for supplying cooling water to the upper surface of the steel sheet while passing the steel sheet is disposed at a position close to the rolling mill on the entry side and / or the exit side of the rolling mill that hot-rolls the steel sheet. The cooling equipment has an angle of depression of 30 ° to 60 ° with rod-shaped cooling water facing the rolling mill side with respect to the upper surface of the steel plate. A steel plate hot rolling facility equipped with a header having a nozzle for spraying at a position where cooling water after being supplied to the steel plate is blocked by a work roll of a rolling mill.

2. The cooling equipment further has an elevation angle of 45 with the rod-shaped cooling water directed toward the rolling mill with respect to the lower surface of the steel plate. ~ 9 0. 2. The hot rolling facility for steel sheets according to claim 1, wherein a header having a nozzle sprayed at is provided between a work roll of a rolling mill and a table roller adjacent thereto.

3. A steel plate that is rolled while spraying the cooling water so that the cooling water supplied to the steel plate reaches the first crawl of the rolling mill using the hot rolling facility for the steel plate according to claim 1 or 2. Hot rolling method.

4. Using the hot rolling equipment described in claim 1 or 2, hot rolling of a steel sheet in which cooling water is injected with a roll gap of 1 crawl within 2 mm while the steel sheet is not rolled. Method.