JP4114701B2 - Hot-rolled steel strip cooling device, its cooling method, and hot-rolled steel strip manufacturing method - Google Patents

Description

  The present invention relates to a cooling device for cooling a hot-rolled high-temperature steel strip, a cooling method thereof, and a method of manufacturing a hot-rolled steel strip.

  Generally, a hot-rolled steel strip is obtained by heating a slab to a predetermined temperature in a heating furnace, rolling the heated slab to a predetermined thickness with a roughing mill to form a rough bar, and then forming the rough bar with a plurality of stands. In a continuous hot finish rolling mill, the steel strip has a predetermined thickness. And after cooling this hot-rolled steel strip in the cooling stand on a run-out table, it manufactures by winding up with a winder.

In such an on-line cooling device that transports the rolled high-temperature steel strip on a line and continuously cools it before it is wound up by a winder, firstly, the plate-passability of the steel strip is taken into consideration. There must be.
For example, in order to cool the upper surface of the steel strip, a circular laminar cooling nozzle is provided in a straight line at the upper portion of the steel strip transporting roll (also called a roller table) and across the width of the steel strip. A plurality of laminar cooling water is poured from the cooling nozzle. The run-out table is a collection of a plurality of the transport rolls.

  At this time, even if the steel strip is pushed by the cooling water pressure, the steel strip pass line is directly above the transport roll and the transport roll so that the steel strip pass line is not pushed downward from the line connecting the upper contacts of the transport roll. A laminar cooling nozzle having the same total length as the axial length is arranged. Further, a spray nozzle is disposed between the transport rolls, and cooling water is sprayed upward from here to cool the lower surface of the steel strip.

Therefore, in such a cooling mode, the cooling of the upper and lower surfaces of the steel strip is not strictly symmetrical, and the cooling of the steel strip is intermittent cooling particularly on the upper surface side, and rapid cooling (for example, with a plate thickness of 3 mm) A cooling rate of 200 ° C./s or more) is almost impossible.
On the other hand, in recent years, a hot-rolled steel strip with a fine crystal grain size has been demanded for its excellent workability and high strength even at low Cep, and rapid cooling (strong cooling) is required for that purpose. ing. Thus, when performing rapid cooling with respect to a hot-rolled steel strip, the conventional cooling device has the following problems.

That is, since the cooling start positions where the cooling water is applied do not coincide on the upper and lower surfaces of the steel strip, there is a possibility that the material may become non-uniform. Further, after cooling, cooling water stays on the upper surface of the steel strip, causing overcooling on the upper surface side. This supercooling is not uniform in the longitudinal direction, and the cooling stop temperature in this direction varies.
Further, in the width direction, the cooling water flows out from the end of the steel strip to both sides of the line, so that the end is likely to be overcooled compared to the central portion of the steel strip, and the temperature stop time varies. As a result, the material was not uniform.

  [Patent Document 1] proposes a method of discharging the coolant on the upper surface of the steel strip by injecting a fluid in an oblique direction across the steel strip. [Patent Document 2] proposes a draining method in which cooling water is dammed up using a constraining roll (also called a pinch roll) as a draining roll. [Patent Document 3] proposes a method of effectively cooling the upper and lower water amount ratio of the cooling water at the tip of the steel strip by increasing the amount of water on the lower surface.

  In [Patent Document 4], a plurality of roller tables are arranged on a frame provided in the feeding direction of the steel strip, and a cooling water guide is provided between these roller tables. In order to hold the guide and the steel strip surface at a predetermined interval, a device is disclosed in which a guide roll is provided on the guide and pressed against the steel strip.

[Patent Document 5] discloses an immediate cooling device that cools a steel strip immediately after being unloaded from a rolling mill. On the other hand, as a device for obtaining a stable plate, [Patent Document 6] discloses a technique for providing a driving force to a steel strip by providing another drive roll that is rotationally driven above a table roll. .
JP 09-141322 A JP-A-10-166023 Japanese Patent Laid-Open No. 06-328117 Japanese Patent Publication No.59-050420 Japanese Examined Patent Publication No. 04-011608 Japanese Utility Model Publication No.57-082407

  However, according to the cooling water discharge method of [Patent Document 1], if strong cooling is performed, a large amount of cooling water stays on the steel strip and there is almost no draining effect. In the draining method of [Patent Document 2], the steel strip tip from the rolling mill to the winder is transported in a free state. Pass in restraint state.

  Therefore, providing the restraining roll on the roller table hinders the stable passage plate, and it has been difficult to apply the restraining roll to the runout cooling device. In addition, if it is attempted to strongly cool the vicinity of the vibrating steel strip tip without restraint, the vibration at the tip is further deteriorated and a stable plate cannot be secured. The generation of wrinkles was unavoidable due to the contact between the restraining roll and the steel strip.

  In the cooling method of increasing the amount of water on the bottom surface of the cooling water ratio at the tip of the steel strip in [Patent Document 3], if the cooling water amount ratio is changed, the cooling on the top and bottom surfaces becomes unbalanced, and particularly rapid cooling is required. However, it is inevitable that the material is uneven. And since lower surface cooling becomes weak, it was difficult to implement | achieve strong cooling required for material.

In particular, when cooling a steel strip with a thickness of 2 mm or less, called a thin object, the tip of the steel strip vibrates up and down due to the cooling water pressure, or the steel strip is folded in the latter half of the run-out table, and a stable plate cannot be made. It is also possible that the threading plate will become impossible.
[Patent Document 4] In order to keep the cooling water guide and the steel strip surface at a predetermined distance, in the apparatus in which a guide roll is provided on the guide and pressed against the steel strip, the tip of the steel strip is conveyed while undulating and vibrating. Therefore, it is difficult to make the cooling water guide and the steel strip surface uniform. In the case of a thin steel strip, when the tip comes into contact with the transport roll, a trouble is likely to occur that the plate is blocked and the steel strip is clogged.

  Normally, steel strips are often not flat, such as ear waves and medium stretches. To target such poorly shaped steel strips, they cannot be pressed with a guide roll. The work man-hours become large.

  In the latest cooling device that cools the steel strip immediately after it is unloaded from the rolling mill of [Patent Document 5], a sensor for detecting the steel strip temperature and thickness during rolling, which is an important item in quality control of the steel strip. Can not be provided. Therefore, an air cooling zone must be provided at the rear of the final finish rolling mill, and a thermometer and thickness meter must be installed in this air cooling zone, but the steel strip tip is free and vibrates up and down, so cooling from the steel strip tip Difficult to start with.

  In the technique of providing a driving roll to the steel strip by providing a driving roll above the table roll of [Patent Document 6], the tip of the steel strip is a roll unless the upper drive roll is arranged densely like the bottom table roll. There is a risk of rushing in between or breaking from the middle. Once the tip of the steel strip collides with the upper roll or the lower roll, vertical vibrations occur due to the reaction, and it is difficult to make a stable plate, especially with thin steel strips. Moreover, if the rolls are densely arranged on both the upper and lower surfaces of the steel strip, the space for arranging the cooling nozzles is reduced and strong cooling cannot be performed.

  The first invention has been made in consideration of the above circumstances, and the object of the invention is to provide a steel strip that is not subjected to tension in the run-out table from the final finish rolling mill to the winder. An object of the present invention is to provide a hot-rolled steel strip cooling device that stably and strongly cools, and a cooling method therefor.

  The second invention has been made in consideration of the above-mentioned circumstances, and the object is to rapidly cool the steel strip from the final finish rolling mill to the winder. An object of the present invention is to provide a cooling device for a hot-rolled steel strip that allows the leading end of the strip to pass through stably and ensure cooling efficiency, and a cooling method therefor.

The third invention has been made in consideration of the above circumstances, and its purpose is as follows:
A method for manufacturing a hot-rolled steel strip, comprising a cooling process for cooling a hot-rolled steel plate using any one of the cooling apparatus for a hot-rolled steel strip according to the first and second inventions and the cooling method therefor. It is something to try.

The first invention has been made to solve such a problem. On the runout where the steel strip is conveyed, a lower surface cooling box is installed between the conveying rolls, and an upper surface which can be moved up and down to a position facing the box. A cooling box is installed and cooling water is jetted symmetrically with respect to the steel strip, and the steel strip is passed through almost the center where these cooling water flows merge, and at least the outlet side has the same peripheral speed as the transport roll. Thus, the draining roll that rotates synchronously is installed so as to freely move up and down, and at the same time as the steel strip tip passes, the draining roll is lowered while rotating, and at the same time, the upper surface cooling box is also lowered to cool the steel strip.
Furthermore, simultaneously with the passage of the tip of the steel strip, the top and bottom surfaces of the tip are pinched with a draining roll and a transport roll, and cooling water is sprayed from the top and bottom surfaces of the steel strip together with this pinch under predetermined conditions to cool the steel strip. A cooling device for a hot-rolled steel strip and a cooling method therefor.

The second invention is made to solve such a problem, and is a runout in which a steel strip is conveyed on a conveying means composed of a plurality of rotating conveying rolls behind the final finishing rolling mill, and the steel is directly above the conveying rolls. The entrainment roll is continuously installed from the finishing mill exit side with a gap more than the strip thickness, and the entrainment roll is rotated at almost the same peripheral speed as the transport roll, at a peripheral speed higher than the transport speed of the steel strip. Rotate and push the steel strip backwards.
Furthermore, guides for passing plates are provided between the conveying rolls and between the accompanying rolls, and a steel strip is passed between these guides. A cooling nozzle is provided on the opposite side of the steel strip with respect to the guide, and cooling is performed by injecting cooling water from above and below the steel strip. Such a cooling device is provided in the runout in front of the winder behind the final finisher.

  Furthermore, at least one pinch roll pair that pinches the steel strip is provided in the middle or immediately after the passage of the cooling device, and at the same time as the leading edge of the steel strip reaches the pinch roll pair, the upstream steel strip Apply tension to the plate to stabilize the plate. Further, the rolling contact of the pinch roll pair is released sequentially as soon as it reaches the downstream pinch roll pair or the winder.

  3rd invention is equipped with the cooling process which cools a hot-rolled steel strip using either the cooling apparatus of the hot-rolled steel strip by the above 1st and 2nd invention, and its cooling method, Hot-rolled steel Manufacture of obi.

The present invention has the following effects.
(1) Cooling can be performed under uniform cooling conditions from the front end to the rear end of the steel strip. Especially, the cooling stop temperature is constant in the longitudinal direction and the width direction, the variation in material is reduced, uniform and free of defects. Since a steel strip is obtained, the quality is stable. Along with this, the cutting margin at the tip is reduced and the yield is high.
(2) Even if the steel strip passes through the cooling device in a state of no tension, since the running of the steel strip is stable, there are few troubles of clogging and operation stop.

(3) Even when the steel strip threading until the steel strip tip is taken up by the winder is unstable, the plate-passability in the cooling device is stable and uniform cooling is possible. The coil yield is consistently high. In particular, it is possible to perform stable cooling and complete cooling for a thin steel strip having a thickness of 2 mm or less.
(4) The length of the tip of the steel strip that is transported and cooled without tension can be short, and cooling can be performed in substantially the same manner as the central portion of the steel strip, so the portion where the material varies is shortened. Since the running of the steel strip during cooling is stable, troubles such as clogging and operation stop can be reduced.

The first invention will be described below with reference to the drawings.
FIG. 1 schematically shows a production facility for a hot-rolled steel strip in the first embodiment, and FIG. 2 schematically shows a first cooling device.
The rough bar 1 rolled by the roughing mill is transported on a transporting roll as a transporting means and continuously rolled to a predetermined thickness by seven continuous finishing rolling mills 2, and then behind the final finishing rolling mill 2E. To the runout table 3. A cooling device (cooling means) is disposed in almost the most part of the run-out table 3, and after being cooled here, it is wound up by a winder 4 to form a hot rolled coil.

The narrower the distance between the transport rolls 11 constituting the run-out table, the better the stability of the plate. However, if it is too narrow, there is no space for placing the cooling device, the cooling length is long, and the cooling efficiency is deteriorated. Therefore, it is desirable that the distance between the transport rolls 11 is a roll diameter +100 mm to a pitch of about three times the roll diameter.
As the cooling device, a first cooling device 5 is disposed on the upstream side of the run-out table 3, and a second cooling device 6 is disposed on the downstream side.
The first cooling device 5 is provided from a position about 10 m behind the final finish rolling mill 2E to a position about 25 m, and is configured as described later.

The second cooling device 6 is installed on the downstream side of the first cooling device 5 over about 70 m, and is a plurality of circular tube laminars arranged at a predetermined pitch on the upper side of the runout table 3. It consists of a nozzle 7 and a plurality of commercially available spray nozzles 8 arranged between the transport rolls 11 constituting the steel strip transport means on the lower surface side.
Furthermore, a steel strip thermometer 9 and a γ-ray thickness gauge 10 are installed between the final finish rolling mill 2E and the first cooling device 5.

The first and second cooling devices 5 and 6 arranged along the run-out table 3 perform rapid cooling processing immediately after rolling with the first cooling device 5 for the steel types that require strong cooling, and then predetermined The cooling process can be performed by the second cooling device 6 at the rear so as to be wound at the winding temperature of.
Moreover, about the steel strip which does not require strong cooling, the operation | movement of the rapid cooling of the 1st cooling device 5 is stopped, and the cooling process only with the 2nd cooling device 6 which is a conventional slow cooling is made. It is possible to make steel strips as materials.
As shown in FIG. 2, in the arrangement space of the first cooling device 5, conveyance rolls 11 constituting conveyance means having a diameter of about 350 mm are arranged at a pitch of about 800 mm in the longitudinal direction, and these conveyance rolls 11 are made of steel. Located on the lower side of the band.

A lower surface cooling box 12 having a length of about 430 mm and a width of about 1860 mm is provided between the transport rolls 11 and serves as a lower surface cooling means. A total of 12 lower surface cooling boxes 12 are arranged along the longitudinal direction of the apparatus, and the first cooling apparatus 5 is provided over a total length of about 5160 mm. And the distance of this lower surface cooling box 12 end surface and the steel strip 13 lower surface cooled is set to about 50 mm.
On the other hand, on the upper surface side of the steel strip 13 in the first cooling device 5, there is an upper surface cooling box 14 that constitutes an upper surface cooling means that is set at a position facing the lower surface cooling box 12 and having exactly the same length and width dimensions. The same number as the lower surface cooling boxes 12 is arranged.

The upper surface cooling box 14 is supported by a frame 18, and a draining roll 16 serving as a draining means is attached to the outgoing side of the upper surface cooling box 14 of the frame. This water draining roll 16 is for removing the cooling water staying on the upper surface of the steel strip, which causes overcooling of the steel strip when cooling the hot-rolled steel strip as will be described later. It is an effective means for homogenization of.
An air cylinder 15 is connected to the frame 18, and an upper cooling block 20 is constituted by these.

The height of the upper cooling box 14 is set so that the distance between the upper surface of the steel strip 13 and the end surface of the upper cooling box 14 is equal to the distance between the end surface of the lower cooling box 12 and the lower surface of the steel strip 13 by the action of the air cylinder 15. Can be adjusted.
When the first cooling device 5 is not cooled and the air cylinder 15 is operated at the timing when the end of the steel strip passes, the upper cooling box 14 and the draining roll 16 are moved to a position approximately 500 mm above the line. They are raised and retracted from the steel strip 13. During normal cooling action on the steel strip 13, the distance between the upper and lower double-sided cooling boxes 14, 12 is set to be the plate thickness of the steel strip 13 + 100 mm.

The draining roll 16 is a roll that is rotationally driven with a diameter of 200 mm at a position facing the transport roll 11, and its rotation is controlled to be the same as the peripheral speed of the lower transport roll 11.
In this embodiment, the upper surface cooling box 14 and the draining roll 16 are set to move at the same time. However, in order to increase the cooling responsiveness, the upper part on the upstream side is interlocked with the passage of the tip of the steel strip 13. It is desirable to operate sequentially from the cooling block 20 to start the lowering of the respective draining rolls 16 and the upper cooling box 14, and for this purpose, the upper cooling box 14 and the draining roll 16 may be able to move up and down independently of each other.

Steel plates having a plate thickness of 1.6 mm are used for the end faces of the upper and lower cooling boxes 14 and 12 facing the steel strips 13. The steel plate is provided with nozzle holes having a predetermined diameter in a staggered manner at predetermined intervals. The cooling water supplied from these nozzle holes forms a columnar laminar flow, and the positions of the upper and lower cooling boxes 14 and 12 are aligned so that at least the collision point on the upstream side is symmetrical in the vertical direction.
Further, in order to stabilize the plate passing property, a so-called squirrel guide 17 is provided between the lower surface cooling box 12 and the transport roll 11 for the lower surface of the steel strip 13 and between the upper surface cooling boxes 14 for the upper surface of the steel strip 13. In particular, the steel strip 13 is devised so that the tip of the steel strip 13 is not caught in each gap.

In addition, the surface of the slat-like guide 17 that may come into contact with the steel strip 13 is covered with an organic resin film, and is devised so that wrinkles do not occur in the steel strip even when it comes into contact with the steel strip. The material of this organic resin film is softer than the steel strip so that no flaws occur in the steel strip, and is heat resistant so that the strength is maintained even if the temperature rises due to the radiant heat received when the hot steel strip passes. Material is preferred.
In the case where the cooling water is not injected from the first cooling device 5, it is effective to inject the cooling water in a range that does not reach the steel strip so that this surface does not reach a high temperature. Desirably, the draining roll 16 is also coated with the same resin material on the surface of the roll so as to suppress the generation of wrinkles.

Next, a cooling process for the hot-rolled steel strip 13 will be described.
At the same time that the tip of the hot-rolled steel strip 13 carried out from the final finish rolling mill 2E passes through the first cooling device 5, the upper cooling block 20 at the corresponding position is operated, and the upper surface cooling box 14 and the draining roll 16 are operated. Is lowered. Then, cooling water is jetted from the lowered upper surface cooling box 14 and the lower surface cooling box 12 at a position corresponding to this box.
The setting of such a process is that if cooling water is injected from the upper and lower surface cooling boxes 14 and 12 before the end of the steel strip passes, the cooling water becomes resistance to passage with respect to the end of the steel strip and obstructs the plateability of the tip. It is because there is a possibility of doing.

After the end of the steel strip 13 has passed once, the pass line of the steel strip 13 depends on the balance between the pressure of the cooling water injected from the upper surface cooling box 14 and the pressure of the cooling water injected from the lower surface cooling box 12. Kept constant. Therefore, even if no tension is applied to the steel strip 13, the plateability of the steel strip 13 is stabilized, and uniform strong cooling of the steel strip 13 is performed.
The steel strip 13 tip enters the first cooling device 5 and the cooling water is jetted from the upper and lower cooling boxes 14 and 12 corresponding to the tip, but at this time, the upper cooling box 14 is kept in the raised position. Good. And even if the upper surface cooling box 14 and the draining roll 16 are lowered at the stage where the plate-passability is stabilized, the plate-passability of the steel strip portion that has already passed and the steel strip portion that is about to pass through will not be adversely affected. .

However, when the draining roll 16 is descending, the peripheral speed of the transport roll 11 and the draining roll 16 is preferably slightly higher than the rolling speed to prevent sagging of the steel strip between the rolling mill and the cooling device. Can be ensured.
And if these rotations are controlled so that fixed tension | tensile_strength works on the steel strip 13 in the state which the draining roll 16 descend | falls completely and the steel strip 13 was pinched with the draining roll 16 and the conveyance roll 11, a hot-rolled steel strip It is possible to provide a function of securing a stable plate, and is effective in preventing wrinkles due to slippage between the draining roll 16 and the steel strip 13.

The relationship between the pinch timing for the steel strip 13 and the cooling conditions for the upper and lower surfaces of the steel strip is as follows.
That is, simultaneously with the passage of the tip of the steel strip 13, a step of pinching the top and bottom surfaces of the tip with the draining roll 16 and the transport roll 11, and simultaneously with this pinching step, cooling water is injected from the top and bottom surfaces of the steel strip 13 under predetermined conditions. And a step of cooling the steel strip.
Alternatively, simultaneously with the passage of the tip of the steel strip 13, the step of pinching the top and bottom surfaces of the tip with the draining roll 16 and the transport roll 11, and the fluid pressure applied to the top surface of the steel strip 13 and the fluid pressure applied to the bottom surface together with this pinching step And cooling the steel strip by injecting cooling water so as to be substantially equal to each other.

Alternatively, simultaneously with the passage of the tip of the steel strip 13, the draining roll 16 is lowered and brought into contact with the tip, and the steel strip is pinched at the same peripheral speed as the lower conveying roll 11, together with this pinching step. And a step of cooling the steel strip by injecting cooling water so that the fluid pressure applied to the upper surface and the fluid pressure applied to the lower surface are substantially equal.
The distance between the upper and lower surface cooling boxes 14 and 12 constituting the first cooling device 5 and the steel strip 13 is set to 50 mm here, for the following reason.
That is, if the distance between the cooling means and the steel strip is further increased, the momentum of the cooling water is absorbed by the fluid (cooling water) existing between the steel strip and the cooling means, and weakens. On the contrary, if the distance between the cooling means and the steel strip is made closer, the momentum of the cooling water increases, so that the steel strip balances the surface pressure received from the cooling water injected from the upper surface and the surface pressure received from the lower surface. The effect of correcting and centering the vibration of the steel strip and the offset running through the position works.

Usually, the above-mentioned centering effect can be expected if the pressure at which the fluid acts on the steel strip is about 0.01 to 0.2 Kg / cm 2 G. At this time, the laminar cooling water reaches the steel strip, and in order to cool the steel strip, the distance between the cooling means and the steel strip cannot be so great.
This distance is preferably 30 to 100 mm when the diameter of the laminar nozzle outlet is about 2 to 5 mm. For example, if it is 100 mm or more, the momentum of the cooling water flow weakens and strong cooling becomes impossible. On the other hand, if it is too close to 30 mm or less, there is no place for the cooling water and it becomes difficult to obtain a good water flow. Therefore, rapid cooling becomes impossible, or the flow of cooling water is greatly different between the central portion and the end portion of the steel strip, resulting in uneven cooling.

The above conditions vary depending on the configuration of the cooling means, and are not limited to the above. However, the force that the fluid acts on the steel strip is about 0.01 to 0.2 Kg / cm 2 G, and the steel strip What is necessary is just to determine various injection conditions of the cooling water which makes the cooling of the width direction uniform.
Further, in order to stabilize the plate-passability, another set of draining rolls 16 that can be lifted and lowered on the entry side of the first cooling device 5 is provided on the entry side of the first cooling device 5. It may be possible to ensure the stability of the threading plate. However, since the conveying speed of the steel strip is fast, the entry side draining roll 16 has a larger contribution to the stability of the plate passing rather than the effect of preventing leakage of the cooling water.

In the above equipment, a steel strip having a finished sheet width of 1500 mm and a finished sheet thickness of 3 mm is accelerated at a threading speed of 650 mpm and an acceleration rate of 9 mpm / s, accelerated to a maximum of 1200 mpm, decelerated, and the steel band rear end is moved at 650 mpm. I missed my butt.
At the time of acceleration of the steel strip, the coiling temperature was controlled to be constant by increasing the amount of water in the first cooling device 5 and the second cooling device 6. At that time, the steel strip passed through the cooling devices 5 and 6 stably from the front end to the rear end, and predetermined cooling was performed. Moreover, there was no leakage of cooling water before and after each of the cooling devices 5 and 6, and there was no generation of soot.
As a result, it was possible to stably produce a hot-rolled steel strip having a crystal grain size that was almost constant from the front end to the rear end. The fluctuation of the winding temperature was within 15 ° C. from the front end to the rear end, and stable cooling was realized. When the cooling rate of the steel strip 13 is estimated from the actually measured values of each thermometer, the first cooling device 5 realizes rapid cooling at 500 ° C./s.

By adopting the cooling device 5 and the cooling method in the first invention as described above, rapid cooling can be performed symmetrically in the vertical direction, and stable production of the hot-rolled steel strip 13 having a fine grain size can be achieved by this online cooling. Is possible.
As a result, it is possible to prevent overcooling without cooling water remaining on the steel strip 13 on the downstream side of the cooling device 5, the cooling stop temperature is constant in the width direction and the longitudinal direction of the steel strip 13, The cooling conditions on the bottom surface are exactly the same, and not only bending during cooling and the occurrence of residual stress after cooling are reduced, but the steel grains 13 have a uniform crystal grain size in the longitudinal direction, width direction, and thickness direction. A stable production of the hot-rolled steel strip 13 is obtained.
In addition, even in a state where the tension before the tip of the steel strip 13 is wound by the winder is not applied, the cooling water can be injected under the same cooling conditions as the central portion of the steel strip 13 where the tension is applied. Uniform in the vertical direction and uniform in the longitudinal direction, the product yield is high, and the quality of the steel strip 13 is stabilized.

(Comparative example)
As a comparative example, a hot-rolled steel strip with a finishing plate thickness of 3 mm is rolled with the same rolling equipment as in the first embodiment, and then the maximum is within the range that does not interfere with the stable plate with the second cooling device 6 described above. A case where the flow rate is cooled will be described.
A steel strip having a finished sheet thickness of 3 mm was accelerated at a threading speed of 650 mpm and an acceleration rate of 9 mpm / s, accelerated to a maximum of 1200 mpm, then decelerated, and the rear end of the steel band was pulled through at 650 mpm. At this time, rapid cooling was performed in which cooling was performed with the maximum amount of cooling water within a range in which stable plate passage was possible with only the second cooling device 6.
The cooling rate was 70 ° C./s, and there was a large variation in the crystal grain size especially on the upper and lower surfaces of the steel strip, and there was variation from the front end to the rear end. As a result, in this steel strip, 70 m of the front end portion and the rear end portion were cut off because a predetermined material could not be obtained, and the yield was lowered.

The second invention will be described below with reference to the drawings.
FIG. 3 (A) schematically shows a production facility for hot-rolled steel strip in the second embodiment, and FIG. 3 (B) shows details of a cooling device (cooling means) in this production facility. Show.
This embodiment is a condition for cooling a hot-rolled steel strip having a thickness of 3 mm, a cooling device is disposed at a position away from the final finish rolling mill, and the strip guide and the entry side / exit side pinch rolls Applies if the pair does not exist.
That is, the rough bar 1 rolled by the roughing mill A is transported on the transport table, continuously rolled to a predetermined thickness by the seven continuous finish rolling mills 2, and then the runout behind the final finish rolling mill 2E. Guided to table 3. A cooling device (cooling means) 50 is disposed almost at the center of the run-out table 3, where the steel strip 13 is cooled and then wound by the rear winder 6 to form a hot rolled coil.

If it demonstrates, the conveyance means in the said run-out table 3 consists of the some conveyance roll 11 with a diameter of 300 mm, and is arrange | positioned continuously by roll pitch being 350 mm.
The cooling device 50 is arranged from a position 5 m to a position 20 m from the final finish rolling mill 2 </ b> E in the run-out table 3. Sensors such as a thickness meter and a finishing thermometer (not shown) are arranged on the entrance side of the cooling device 50.
In the cooling device 50, a plurality of transport rolls 11 are arranged at a pitch of 517 mm. On each transport roll 11, an accompanying roll 51 that can be driven in the vertical direction is disposed in parallel with the transport roll 11.

These accompanying rolls 51 are means necessary for stably passing the tip of the steel strip, and structurally serve as the above-described draining roll. Basically, the accompanying roll 51 is rotationally driven in the same direction as the transport roll 11 and at the same peripheral speed.
And the clearance gap with the conveyance roll 11 which opposes the accompanying roll 51 is set to plate | board thickness + about 5 mm of the hot-rolled steel strip 13 passed. In consideration of the plate-passability, the thickness of the steel strip 13 is suitably within +30 mm.

In order to prevent the steel strip from wrinkling due to the contact between the transport roll 11 and the accompanying roll 51 and the hot-rolled steel strip 13, the peripheral speed of these rolls 11 and 51 is 0 to 20% faster than the transport speed of the steel strip 13. It is preferable to set the speed.
And, in order to further improve the plate-passability, it is set at a speed 5 to 20% faster than the conveying speed of the steel strip 13 so that a pulling force is applied forward at the tip of the steel strip 13. It is more preferable in order to make the passage plate more stable.

In the state where tension is applied after the steel strip tip reaches the winder, the peripheral speed of these rolls may be changed to be approximately equal to the steel strip conveyance speed from the viewpoint of preventing wrinkles. As used herein, “substantially equal circumference” means a range including a speed deviation that is unavoidable mechanically, and usually means a speed error of about ± 5%.
The length of the cooling device 50 itself is about 15 m, and therefore 30 accompanying rolls 51 and 30 transport rolls 11 are provided. The accompanying roll 51 can be raised and lowered, and can be retracted upward before the steel strip 13 is conveyed.

The cooling device 50 includes a cooling device 50a located on the lower surface side of the steel strip 13 to be passed and a cooling device 50b located on the upper surface side.
In the lower surface side cooling device 50a, a flat plate-like guide plate (passage plate guide body) 52 is installed between the transport rolls 11, and a plurality of spray nozzles 53 are arranged below the guide. The passage guide 52 is provided with a hole through which cooling water sprayed from the spray nozzle 53 passes.
In the upper surface cooling device 50b, a flat plate guide (passage plate guide body) 52 is installed between the accompanying rolls 51, and a spray nozzle 53 having the same structure is provided above the guide. The passage guide 52 is provided with a hole through which cooling water sprayed from the spray nozzle 53 passes.

In addition, if the position of the steel strip 13 to be conveyed and each spray nozzle 53 is separated more than necessary, the momentum of the cooling water is absorbed by the fluid existing between the steel strip 13 and the spray nozzle 53 and weakens.
If the optimum amount approaches, the momentum of the cooling water increases, and the steel strip 13 passes through a position where the surface pressure due to the cooling water ejected from the upper surface and the surface pressure due to the cooling water ejected from the lower surface are balanced. Therefore, vibration of the steel strip 13 is suppressed and the steel strip 13 that is offset in the vertical direction is centered.

The through-plate guide 52 may be a slat-like shape or a lattice shape, or may be a type in which a hole is provided only in a portion necessary for passing cooling water through a flat plate.
Below, the cooling process which cools the steel strip 13 rolled with the continuous finish rolling mill 3 with the cooling device 50 is demonstrated.
At the latest, before the tip of the hot-rolled steel strip 13 is unloaded from the continuous finish rolling mill 2E, cooling water is injected from the upper and lower spray nozzles 53 constituting the cooling device 50. At this time, the injection pressure and the flow rate are adjusted so that the injection conditions acting on the upper surface and the lower surface of the steel strip 13 of the spray nozzle 53 are the same.

As a result, the fluid pressure acting on the upper and lower surfaces of the steel strip 13 to be passed becomes the same, and the steel strip 13 does not vibrate up and down, and of course, the centering effect can be obtained without shifting in one direction. Is stable.
And all the accompanying roll 51 and the conveyance roll 11 are rotationally driven, and waiting for carrying in of the steel strip 13 is waited. As described above, the rotation direction of the rolls 51 and 11 is a direction in which both the rolls 51 and 11 lead the steel strip 13 from the rolling mill 2 to the winder 4, and the peripheral speed is the plate passing speed of the steel strip 13. It is adjusted so that it is the same as or slightly faster than that.

When the steel strip 13 having a thickness of 3 mm exiting from the final finish rolling mill 2E had a thickness of 3 mm, the transport speed of the transport roll 11 was 650 mpm. The finishing temperature of the steel strip 13 at this time was 890 ° C.
In the cooling device 50, the clearance between the transport roll 11 and the accompanying roll 51 is set to 8 mm, and the two rolls 11 and 51 are rotationally driven so that the peripheral speed is 680 mpm.
The steel strip 13 carried into the cooling device 50 may collide with the accompanying roll 51 or the transport roll 11 at the tip thereof, but since both of these rolls 51 and 11 are rotating, the tip of the steel strip 13 is smooth. Slip into the gap between the accompanying roll 51 and the transport roll 11. Moreover, the pass line of the steel strip 13 is kept constant by the pressure of the cooling water from the upper surface side and the lower surface side by the upper and lower spray nozzles 53.

Based on the above-mentioned condition setting, even if it is the thin steel strip 13 having a plate thickness of about 3 mm, a stable plate is realized from the tip, and uniform strong cooling is performed.
The temperature of the steel strip 13 at the position exiting the cooling device 50 was 700 ° C. Then, although the steel strip 13 front-end | tip is plate-passed on the conveyance roll 11 arrange | positioned downstream, the steel strip 13 in a plate passing through the inside of the cooling device 50 does not vibrate or offset. There is no variation in the temperature of the steel strip in the threading plate, and even after the end of the steel strip 13 is taken up by the winder 4, the plate passing and cooling is continued stably.

Thus, in the run-out table 3 provided with the cooling device 50, the same thermal history can be realized from the front end to the central portion of the steel strip 13 having a plate thickness of about 3 mm, and thereafter and to the end portion. Overall, the material variation is small, and the strength and elongation are uniform.
In addition, although the spray nozzle 53 was used as a nozzle which cools the upper and lower surfaces of the steel strip 13, a columnar circular tube laminar system or a jet system may be used. The conditions for obtaining the centering effect by the fluid pressure acting on the upper surface and the lower surface of the steel strip 13 differ depending on each cooling method, and may be determined according to the cooling method.

As described above, the accompanying roll 51 has the function of a draining roll that prevents the injected cooling water from flowing out to the upstream side or the downstream side, and can realize cooling with good controllability.
That is, for example, when cooling water flows out from the cooling device 50 in the front-rear direction, local supercooling is caused to the steel strip 13. Moreover, since the cooling water flows in the width direction and falls from the end portion on the steel strip 13 side, the cooling water becomes uneven in the width direction. By providing the accompanying roll 51 having the function of a draining roll, the occurrence of such a problem is prevented.

FIG. 4 (A) schematically shows a hot-rolled steel strip manufacturing facility in the third embodiment, and FIG. 4 (B) shows details of the cooling device (cooling means) in this manufacturing facility. Show.
This embodiment is a condition for cooling a hot-rolled steel strip having a thickness of 1.6 mm, a so-called thin hot-rolled steel strip, which is poorer than the second embodiment and away from the final finish rolling mill. This is applied to the case where the cooling device is disposed at the position and the strip guide and the pair of pinch rolls are provided on the entry side and the exit side. The thin hot-rolled steel strip is generally a steel strip having a thickness of 2 mm or less.

That is, after the rough bar 1 rolled by the rough rolling mill A is transported on the transport roll and continuously rolled to a predetermined thickness by the seven continuous finish rolling mills 2, the rear of the final finish rolling mill 2E. Guided to the run-out table 3.
A cooling device (cooling means) 50A is arranged at substantially the center of the run-out table 3. Here, after the steel strip 13 is cooled, it is wound up by the rear winder 4 to form a hot rolled coil.

On the run-out table 3, conveyance rolls 11 having a diameter of 300 mm are continuously arranged as conveyance means at a roll pitch of 350 mm. 50 A of said cooling devices are arrange | positioned ranging from the position of 5 m to the position of 20 m from the final finish rolling mill 2E.
Pinch roll pairs 55A and 55B for pinching the steel strip 13 are provided at a position immediately before the entry side of the cooling device 50A and a position immediately after the exit side. The steel strip 13 is pinched between the pair of pinch rolls 55A and 55B, and tension is applied to the steel strip 13 at the same time as the steel strip passes through the pair of pinch rolls. The inter-roll gap between the pair of pinch rolls 55A and 55B is set to a plate thickness of the steel strip 13 of −0.1 mm, and is driven to rotate in the same direction.

As shown only in FIG. 4 (B), a pair of upper and lower strip guides 56a is provided on the rolling mill 2 side of the entry side pinch roll pair 55A. The strip guides 56a are widely spaced from each other on the rolling mill 2 side, narrow on the pinch roll pair 55A side so as to face the roll-to-roll contact portion, and are inclined with respect to each other. From this, the tip of the steel strip 13 guided from the rolling mill 2 can be guided smoothly and reliably between the pinch roll pair 55A.
These pinch roll pairs 55A and 55B have a function of controlling the tension on the steel strip 13 and a function of adjusting the left and right pressing force so that the steel strip 13 after the pinch does not meander from side to side.

In this embodiment, the pinch roll pair 55B is arranged immediately after the cooling device 50A. However, the present invention is not limited to this, and the steel strip is sent by arranging the pinch roll pair in the cooling device 50A. It is also effective to sequentially pinch and cool the plate while ensuring plate-passability.
In the cooling device 50A, a plurality of transport rolls 11 are arranged at a pitch of 517 mm. On each transport roll 11, an accompanying roll 51 that can be driven in the vertical direction is arranged in parallel with the transport roll 11.

These accompanying rolls 51 are rotationally driven in the same direction as the transport roll 11 and at the same peripheral speed. The gap between the transport rolls 11 facing each of the accompanying rolls 51 is set to the plate thickness of the steel strip 13 to be passed through + about 5 mm.
The total length of the cooling device 50A itself is about 15 m, and therefore 30 accompanying rolls 51 and 30 transport rolls 11 are provided. The accompanying roll 51 can be raised and lowered, and can be retracted upward before the steel strip 13 is conveyed.

The cooling device 50A includes a cooling device 50a located on the lower surface side of the steel strip 13 to be passed and a cooling device 50b located on the upper surface side. Both the lower surface side cooling device 50a and the upper surface side cooling device 50b have the same configuration as that described above with reference to FIG. 3B, and here, the same reference numerals are given and new descriptions are omitted.
Below, the cooling process which cools the steel strip 13 rolled with the continuous finish rolling mill 2 with 50 A of cooling devices is demonstrated.
At the latest, before the tip of the hot-rolled steel strip 13 is unloaded from the continuous finish rolling mill 2, cooling water is injected from the upper and lower spray nozzles 53 constituting the cooling device 50A. At this time, the injection pressure and the flow rate are adjusted so that the injection conditions acting on the upper surface and the lower surface of the steel strip 13 of the spray nozzle 53 are the same.

As a result, the fluid pressure acting on the upper and lower surfaces of the steel strip 13 to be passed becomes the same, and the steel strip 13 does not vibrate up and down, and of course, the centering effect can be obtained without shifting in one direction. Is stable.
And all the accompanying roll 51 and the conveyance roll 11 are rotationally driven, and waiting for carrying in of the steel strip 13 is waited. The direction of rotation of these rolls 51 and 11 is the direction in which any of the rolls 8 and 7 leads the steel strip 13 from the rolling mill 2 to the winder 4 and the peripheral speed is the same as the sheet feeding speed of the steel strip 13 or The fact that it has been adjusted to be slightly faster than that is no different here.

When the thickness of the steel strip 13 from the final finish rolling mill 2E was 1.6 mm, the steel strip 13 was passed at a conveyance speed of 650 mpm. The finishing temperature of the steel strip 13 at this time was 840 ° C.
In the cooling device 50A, the gap between the transport roll 11 and the accompanying roll 51 is set to 7 mm, and the rollers 7 and 8 are rotationally driven so that the peripheral speed of both the rolls 7 and 8 is 680 mpm.
The steel strip 13 passed through from the final finish rolling mill 2E is guided by strip guides 56a and 56a, and the tip thereof is smooth and surely sandwiched between the pair of pinch rolls 55A on the entry side.

Tension is applied to the steel strip 13 at the moment when the steel strip 13 is pinched by the entrance side pinch roll pair 55A. Once the tip of the steel strip 13 is once bitten into the pinch roll pair 55A, the plate passes stably thereafter.
Thereafter, the steel strip 13 is guided between the first (first) accompanying roll 51 and the transport roll 11. At this time, even if the tip of the steel strip 13 may collide with the accompanying roll 51, the accompanying roll 51 is rotating and the steel strip 13 is restrained from moving up and down by the pair of pinch rolls 11A. Therefore, it smoothly slides into the gap between the accompanying roll 51 and the transport roll 11 and does not fold or stick.

In the cooling device 50A, the pass line is made constant by the pressure of the cooling water from the upper surface side and the lower surface side by the upper and lower spray nozzles 53, and the steel plate 13 is stably passed and cooled.
The temperature of the steel strip 13 at the position exiting the cooling device 50A was 400 ° C. After that, the tip end of the steel strip 13 is pinched again by the outgoing side pinch roll pair 55B, and tension is applied.
The steel strip 13 is passed through the downstream transport roll 11 until the tip of the steel strip 13 is taken up by the winder 4, and during that time, the steel strip 13 passing through the cooling device 50 </ b> A vibrates or deflects. There is nothing. There is no variation in the temperature of the steel strip 13 when leaving the cooling device 50A, and the plate passing and cooling are stably continued even after the end of the steel strip 13 is wound up.

The pinch roll pair 55A is set so that the tip of the steel strip 13 passes through and reaches the downstream side pinch roll pair 55A to be pinched or wound around the winder 4 in sequence.
As described above, in the run-out table 3 provided with the cooling device 50A, the same thermal history can be realized from the front end to the central portion of the thin steel strip 13 having a plate thickness of about 1.6 mm, and thereafter and the end portion. The variation of the material of the entire coil as a product is small, and the strength and elongation are uniform.

By providing the pinch roll pair 55A on the entrance side of the cooling device 50A, the tip of the steel strip 13 can be reliably guided to the gap between the first entraining roll 51 and the transport roll 11, and further the final finish rolling mill Tension is applied so that the steel strip 13 is not folded or accordion-shaped between 2E and the cooling device 50A.
Since the pinch roll pair 55B is provided on the exit side of the cooling device 50A, even if the steel strip tip vibrates before the steel strip 13 coming out of the cooling device 50A reaches the winder 4, the effect thereof Does not reach the steel strip 13 in the cooling device 50A.
And after the steel strip 13 is once clamped by the pinch roll pair 55B, tension is applied to the steel strip in the cooling device 50A, so that stable cooling can be performed.

FIG. 5 (A) schematically shows a production facility for hot-rolled steel strip in the fourth embodiment, and FIG. 5 (B) shows a cooling device (cooling) from the final finish rolling mill used in this production facility. Means) The entire region is shown enlarged.
In this embodiment, a cooling device is disposed immediately after the final finish rolling mill under conditions for cooling a hot-rolled steel strip having a thickness of 1.2 mm, which has poor plate-passability as compared with the second embodiment described above. Applicable if

That is, after the rough bar 1 rolled by the rough rolling mill A is transported on the transport roll and continuously rolled to a predetermined thickness by the seven continuous finish rolling mills 2, the rear of the final finish rolling mill 2E. Guided to the run-out table 3.
A cooling device (cooling means) 50B is disposed almost at the center of the run-out table 3, and after the steel strip 13 is cooled, it is taken up by the rear winder 4 to form a hot rolled coil.

In the run-out table 3, a conveying roll 11 having a diameter of 300 mm is continuously arranged as a conveying means from the final finish rolling mill 2 </ b> E exit side to the winder 4 via the cooling device 50 </ b> B. Sensors such as a thickness gauge and a finishing thermometer (not shown) are arranged on the entrance side of the cooling device 50B.
On the run-out table 3, the accompanying roll 51 that rotates in the direction in which the peripheral speed is the same as that of the transport roll 11 and feeds the steel strip 13 from the rolling mill 2 to the winder 4 is 20 m from the final finish rolling mill 2E. It is arranged continuously over.

A pinch roll pair 55 is provided at a position adjacent to the rearmost accompanying roll 11. This pair of pinch rolls 55 is supported by a mechanism that moves up and down in the vertical direction, and is brought into rolling contact with the steel strip 13 to be conveyed and applies tension to the steel strip.
In the cooling device 50B, the transport rolls 11 are arranged at intervals of 500 mm. On each conveyance roll 11, an accompanying roll 51 that can be driven in the vertical direction is arranged in parallel with the conveyance roll 11.

These accompanying rolls 51 are rotationally driven in the same direction as the transport roll 11 and at the same peripheral speed. The gap between each of the accompanying rolls 51 and the conveying roll 11 that is opposed is set to the plate thickness of the steel strip 13 to be passed through and about 5 mm.
The length from the final finish rolling mill 2E exit side to the cooling device 50B exit side is about 20 m, and therefore 40 accompanying rolls 51 are installed. Since these accompanying rolls 51 can be raised and lowered, they can be retracted upward before the steel strip 13 is conveyed.

Between the final finish rolling mill 2E and the first (first) accompanying roll 51, and between the accompanying rolls 51 after that until the final end of the cooling device 50B, a sheet guide (passing plate guide body) is provided. ) 52a is provided.
Further, between the final finish rolling mill 2E and the first (first) transporting roll 11 and between the transporting rolls 11 after that until the final end of the cooling device 50B, a threading guide (for threading) Guide body) 52b is provided.

Therefore, the guides 52a and 52b are arranged on the upper surface side and the lower surface side with respect to the steel strip 13 to be passed. The distance between the guides 52a and 52b is set to be narrow to some extent so that the tip of the steel strip 13 to be passed through does not turn up or bend backward.
The cooling device 50B will be described. The cooling device 50a is disposed from the position of the exit side 5m of the final finish rolling mill 2E to the position of 20m, and located on the lower surface side of the steel strip 13 to be passed through, And a cooling device 50b located on the upper surface side.

In the lower surface side cooling device 50 a, a spray nozzle 53 is disposed as a cooling nozzle below the lower plate guide 52 b between the transport rolls 11. The passage guide 52b is provided with a hole through which the cooling water sprayed from the spray nozzle 53 passes.
On the other hand, the upper surface cooling device 50b is provided with a spray nozzle 53 having the same structure above a through plate guide 52a installed between the accompanying rolls 51. The passage guide 52a is provided with a hole through which cooling water sprayed from the spray nozzle 53 passes.

In addition, if the position of the steel strip 13 to be conveyed and each spray nozzle 53 is separated more than necessary, the momentum of the cooling water is absorbed by the fluid existing between the steel strip 13 and the spray nozzle 53 and weakens.
However, since the momentum of the cooling water increases when approaching the optimum amount, the steel strip 13 passes through a position where the surface pressure due to the cooling water ejected from the upper surface and the surface pressure due to the cooling water ejected from the lower surface are balanced. . Therefore, vibration of the steel strip 13 is suppressed, and the steel strip 13 offset in the vertical direction is centered.

Below, the cooling process which cools the steel strip 13 rolled with the continuous finish rolling mill 2 with the cooling device 50B is demonstrated.
At the latest, before the tip of the hot-rolled steel strip 13 is unloaded from the final finish rolling mill 2E, cooling water is injected from the upper and lower spray nozzles 53 constituting the cooling device 50B. At this time, the injection pressure and the flow rate are adjusted so that the injection conditions acting on the upper surface and the lower surface of the steel strip 13 of the spray nozzle 53 are the same.

Accordingly, the fluid pressure acting on the upper surface and the lower surface of the steel strip 13 to be passed becomes the same, and the steel strip 13 does not vibrate up and down, and it is not necessary to be displaced in one direction, and a centering effect is obtained and the passing plate is obtained. Stabilize.
And all the accompanying roll 51 and the conveyance roll 11 are rotationally driven, and waiting for carrying in of the steel strip 13 is waited. The direction of rotation of these rolls 51 and 11 is the direction in which any of the rolls 51 and 11 leads the steel strip 13 from the rolling mill 2 to the winder 4 and the peripheral speed is the same as the sheet feeding speed of the steel strip 13 or It is adjusted to be slightly faster than that.

The pair of pinch rolls 55 arranged on the exit side of the cooling device 50B is adjusted so that the roll interval is the same as the plate thickness of the steel strip 13 so as to make rolling contact with the tip of the steel strip carried out of the cooling device 50B. Has been.
Between the final finish rolling mill 2E and the pair of pinch rolls 55, the steel strip 13 has a free end and no tension. Therefore, the steel strip 13 may vibrate freely and may be loosened. . Therefore, the conveyance speed is set to 720 mpm so that the rotation speed of the pair of pinch rolls 11 is a lead rate of about 10% (a leading rate of the roll peripheral speed with respect to the conveyance speed of the steel strip).

  When the steel strip 13 having a thickness of 1.2 mm exiting from the final finish rolling mill 2E has a thickness of 1.2 mm, the transport speed is set to 650 mpm and the steel strip 13 is carried into the cooling device 50B from the tip of the steel strip. The finishing temperature of the steel strip 13 at this time was 890 ° C.

In this cooling device 50B, the gap between the transport roll 11 and the accompanying roll 51 is set to 6 mm. Then, both the transport roll 11 and the accompanying roll 51 are driven to rotate at a peripheral speed of 680 mpm so that the read rate is 5%.
The steel strip 13 carried into the cooling device 50B may collide with the accompanying roll 51 or the transport roll 11 at the tip thereof, but since both the accompanying roll 51 and the transport roll 11 are rotating, the tip of the steel strip 13 is rotated. Smoothly slides into the gap between the accompanying roll 51 and the transport roll 11.

  The vertical vibration of the steel strip 13 is regulated by the upper and lower section plate guides 52a and 52b provided between the accompanying rolls 51 and the conveying rolls 11 extending from the final finish rolling mill 2E to the final end of the cooling device 50B. Moreover, the pass line of the steel strip 13 is constant due to the pressure of the cooling water between the upper and lower surfaces of the upper and lower spray nozzles 53.

  From these various conditions, even if it is the thin steel strip 13 with a plate thickness of 1.2 mm, a stable plate is realized from the tip of the steel strip 13, and uniform strong cooling is performed. When the tip of the steel strip 13 comes out of the cooling device 50B and reaches the pair of pinch rolls 55 and is pinched here, tension is generated in the steel strip on the upstream side, and the pass line becomes more stable.

  Note that the temperature of the steel strip 13 near the pinch roll pair 55 after exiting the cooling device 50B was 700 ° C. The steel strip 13 is transported by the transport roller 11 on the lower surface side until the tip of the steel strip 13 is taken up by the winder 4 from the pair of pinch rolls 55, and the steel strip 13 in the plate passing through the cooling device 50B vibrates or is offset There is no. Cooling of the steel strip 13 is performed stably, and there is no variation in the temperature of the steel strip when it leaves the cooling device 50B.

At the timing when the tip of the steel strip 13 reaches the winder 4, the rolls of the pinch roll pair 55 are separated from each other, and the steel strip 13 is released. Along with the winding action of the winder 4, a new tension is generated on the steel strip 13, and the sheet passing and cooling are continued and stabilized.
To summarize the above, the hot-rolled steel strip is transported in a state in which cooling water is jetted under a predetermined jetting condition, and the tip of the hot-rolled steel strip is immediately after the entrance side and / or the exit side of the cooling device and / or during the cooling. At the same time, the pinch roll pair pinches, and at the same time as the steel strip tip reaches the tension applying means such as the downstream pinch roll pair or the winder 4, the hot rolled steel strip is sequentially moved from the upstream pinch roll pair. Will be released.

In this way, by configuring the run-out table 3 provided with the cooling device 50B, the same thermal history can be realized from the tip of the steel strip 13 to the central portion, and thereafter and the terminal portion, and the entire coil as a product can be realized. The material variation is small, and the strength and elongation are uniform.
In addition, although the spray nozzle 53 was used as a nozzle which cools the upper and lower surfaces of the steel strip 13, it is not limited to this, A columnar pipe laminar system, a jet system, etc. may be used. And the conditions for obtaining the centering effect by the fluid pressure acting on the upper surface and the lower surface of the steel strip 13 differ depending on each cooling method, and may be determined according to the cooling method.

In the second to fourth embodiments described above, the gap between the entraining roll 51 and the transport roll 11 is set to the plate thickness of the steel strip 13 + about 5 mm based on the following reason. .
That is, if the distance between the accompanying roll 51 and the transporting roll 11 is equal to or less than the thickness of the steel strip 13, the accompanying roll 51 is loaded. In order to perform stable plate passing, detailed rotational speed control for the accompanying roll 51 is necessary, and if the pressing force of both bearings supporting the accompanying roll 51 is not balanced, the steel strip 13 meanders thereafter. There is a risk.

Therefore, making the accompanying roll 51 a pinch roll with respect to the steel strip 13 requires a rather complicated function both in terms of equipment and function. On the other hand, if the interval is widened to the steel strip thickness +30 mm or more, the vertical vibration becomes intense when the tip of the steel strip 13 passes, and the stable plate is damaged.
Therefore, the gap between the accompanying roll 51 and the transport roll 11 exceeds the plate thickness of the steel strip 13 and is set to a plate thickness +30 mm or less. Desirably, a conclusion that the thickness of the steel strip 13 + about 5 mm is good is obtained.

  By adopting the hot rolled steel strip cooling devices 50, 50A, 50B and the cooling method in the second invention as described above, the steel strip 13 immediately after rolling can be stably and rapidly cooled. In particular, even in a state where the tension before the steel strip 13 tip is wound on the winder 4 is not applied, cooling is performed under the same cooling conditions as the central portion of the steel strip 13 where the tension is applied. Are exactly the same.

The generation of bending and the generation of residual stress after cooling are suppressed, and the crystal grain sizes are aligned in the longitudinal direction, the width direction, and the thickness direction. A hot-rolled steel strip 13 having a uniform material, a high product yield, and a stable quality can be provided.
Even if cooling is performed, the steel strip 13 does not fold or become an accordion, and the pass line of the steel strip becomes constant due to the upper and lower fluid pressures, which leads to prevention of wrinkles.

(Comparative example)
Eight comparative examples described below were carried out using the same manufacturing equipment as those of the second to fourth embodiments described above.
In Comparative Example 1, the entraining roll and the plate guide of the second embodiment are not provided, and instead of these, a steel nozzle having a thickness of 3 mm is cooled in a state where a spray nozzle is provided at the same position and cooling water is injected. This is a case where it is sent to the apparatus and cooled from the steel strip tip.
In Comparative Example 2, the accompanying roll of the second embodiment was provided, but the plate guide was not provided. Instead, a spray nozzle was provided at the same position, and cooling water was injected, and the plate thickness was 3 mm. This is a case where the steel strip is sent to a cooling device and cooled from the tip of the steel strip.

Comparative Example 3 has the same device configuration as that of the second embodiment, but here is a case where a hot-rolled steel strip having a thickness of 1.6 mm is sent to a cooling device and cooled from the tip of the steel strip.
Comparative Example 4 is a case where there is no strip guide provided on the entrance side of the cooling device in the third embodiment. Comparative Example 5 is a case where there is no entry-side pinch roll pair in the third embodiment. Similarly, Comparative Example 6 is a case where there is no pair of outlet pinch rolls in the third embodiment.

Comparative Example 7 is a case where there is no accompanying roll in the range from the rolling mill to 5 m in the fourth embodiment, and Comparative Example 8 is also in the range from 5 m to the rolling mill in the fourth embodiment. This is the case where there is no plate guide.
The above results are summarized in Table 1.

In Comparative Example 1, since there is no means for restraining the steel strip from the upper surface side from the final finish rolling mill exit side to the cooling device entrance side, the steel strip having a medium rigidity with a plate thickness of 3 mm Even so, the tip of the steel strip in the threading plate vibrates greatly in the vertical direction due to the collision with the transport roll. The steel strip tip cannot be caught between the first cooling nozzle and the transport roll in the cooling device, and the steel strip collides with the cooling nozzle, resulting in nozzle breakage.
The cooling water leaking from the gap between the accompanying roll and the steel strip is preferably blown off from one side edge of the steel strip immediately after the accompanying roll, for example, by high-pressure spray water sprayed from a draining spray.

As a result, there is almost no cooling water remaining on the steel strip behind the entrained roll, and supercooling due to accumulated water is eliminated, and the cooling end temperature of each part of the steel strip becomes constant. When the material was investigated in detail in the longitudinal direction of the steel strip, it was found that a steel strip having a uniform grain size could be obtained stably.
In Comparative Example 2, there is no thread guide even if the tip is bitten by the first accompanying roll, so there is a possibility that the steel strip tip may squeeze between the accompanying roll and the cooling nozzle. Can not.

In Comparative Example 3, since the accompanying roll and the passing plate guide exist, stable passing and cooling can be performed if the steel strip tip enters between the first accompanying roll and the conveying roll. Compared to this form, the plate thickness was thin, so the rigidity was small, the vibration of the steel strip was large, and accordion-like clogging occurred when the tip reached the cooling device.
In Comparative Example 4, a pair of pinch rolls for pinching the steel strip was provided on the entry / exit side of the cooling device of Comparative Example 3. However, since there is no strip guide, the tip of the steel strip may not be caught in the gap between the pair of pinch rolls. At that time, accordion-like clogging occurred when the tip reached the cooling device.

In Comparative Example 5, the strip guide is provided on the entry side of the cooling device of Comparative Example 3, but since there is no pair of pinch rolls on the entry side, the tip is conveyed from the finish rolling mill to the cooling device in a free state. . As a result, the slack of the steel strip generated between the rolling mill and the cooling device grew like an accordion, and clogging occurred.
In Comparative Example 6, a strip guide was provided on the entry side of the cooling device and a pinch roll pair was provided on the exit side. However, since there was no pinch roll pair on the entry side, the tip was free from the finish rolling mill to the cooling device. Be transported. As a result, the slack of the steel strip generated between the rolling mill and the cooling device grew like an accordion, and clogging occurred.

In Comparative Example 7, a strip guide and a pinch roll pair were provided on the inlet side of the cooling device, but there was no pair of pinch rolls on the outlet side. Therefore, slack occurred between the finishing mill and the cooling device, and in the cooling device. Finally, it grew like an accordion and clogging occurred.
This slack is eliminated to some extent by setting the rotation speed of the pinch roll pair with the lead rate, but it cannot be removed by either one of the pinch roll pairs, or it takes time until it can be removed, and cooling is stable during that time Does not vibrate, vibrates, or has frequent wrinkles due to contact with the guide.
Comparative Example 8 is a case where there is no accompanying roll in the portion of 5 m after the rolling mill in the fourth embodiment, and Comparative Example 9 is a case where there is no plate guide, both of which have a plate thickness of 1.2 mm The tip of the steel strip was clogged and stable threading was not possible.

  As described above, as described in the first to fourth embodiments, the cooling devices 5, 50, 50 </ b> A, 50 </ b> B for the hot-rolled steel sheet 13 in the first invention and the second invention and any one of the cooling methods are used. In addition, by providing a cooling step for cooling the hot-rolled steel sheet 13 and manufacturing the hot-rolled steel sheet 13, it is possible to efficiently eliminate the cooling water from the upper surface 13 of the steel strip, thereby preventing overcooling and bending during cooling. In addition to reducing the occurrence of residual stress after cooling and cooling, it is possible to stably produce a uniform hot-rolled steel strip 13 having crystal grain sizes aligned in the longitudinal direction, width direction, and thickness direction of the steel strip 13.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of the rolling equipment which shows 1st Embodiment in 1st invention. The schematic block diagram of the cooling device of the embodiment. The schematic block diagram of the rolling equipment and the cooling device which shows 2nd Embodiment in 2nd invention. The schematic block diagram of the rolling installation and cooling device which shows 3rd Embodiment in the same invention. The schematic block diagram of the rolling installation and cooling device which shows 4th Embodiment in the same invention.

Explanation of symbols

  2E ... Final finish rolling mill, 13 ... Hot rolled steel strip, 11 ... Transport roll (transport means), 12 ... Lower surface cooling box (lower surface cooling means), 14 ... Upper surface cooling box (upper surface cooling means), 16 ... Draining roll ( Draining means), 3 ... runout table, 5 ... first cooling device, 6 ... second cooling device, 51 ... entraining roll, 52 ... passing plate guide (passing plate guide body), 53 ... spray nozzle (cooling nozzle) ), 55A, 55B, 55 ... pair of pinch rolls, 56a, 56b ... strip guides.

Claims (11)

A rough bar rolled by a roughing mill is rolled to a predetermined thickness by a finishing mill and wound by a winder to be provided behind the final finish rolling mill in a hot rolled steel strip manufacturing facility. Conveying means comprising a plurality of conveying rolls arranged at intervals and conveying the hot-rolled steel strip;
At least one upper surface cooling means that is disposed on the upper surface side of the conveying means and that cools the upper surface of the hot-rolled steel strip by injecting cooling water;
It is arranged on the lower surface side through the upper surface cooling means and the hot-rolled steel strip to be conveyed, and comprises at least one lower surface cooling means for injecting and cooling cooling water to the lower surface of the hot-rolled steel strip,
The upper surface cooling means is movable up and down, and includes draining means at least on the exit side and at a position facing the transport roll ,
The upper surface cooling means and the lower surface cooling means are arranged at positions facing each other through a hot-rolled steel strip, and the distance between the upper surface cooling means and the upper surface of the hot-rolled steel strip is set to the distance between the lower surface cooling means and the hot-rolled steel strip. A cooling device for a hot-rolled steel strip, characterized by being adjustable so as to be equal to the distance to the bottom surface of the strip.   The apparatus for cooling a hot-rolled steel strip according to claim 1, wherein the draining means comprises a draining roll. The distance between the upper surface cooling means and the lower surface cooling means and the hot-rolled steel strip is 30 to 100 mm, respectively, and the hot-rolled steel strip cooling device according to any one of claims 1 and 2 . At the rear of the final finish rolling mill in a hot rolled steel strip manufacturing facility, a rough bar rolled by a rough rolling mill is rolled to a predetermined thickness by a finish rolling mill and wound by a winder . passage of the tip and simultaneously, a step of pinching the steel strip at the top and bottom surfaces of the tip and draining roll and the transport roll, with the pinch process, and the fluid pressure is substantially equal according to the fluid pressure and the lower surface according to the upper surface of the steel strip And a step of cooling the steel strip by injecting cooling water as described above. In the step of pinching the steel strip, simultaneously with the passage of the tip of the steel strip, the draining roll is lowered and brought into contact with the tip, and the steel strip is pinched at the same peripheral speed with the lower transfer roll. The method for cooling a hot-rolled steel strip according to claim 4, It is installed in a hot-rolled steel strip manufacturing facility where a rough bar rolled by a rough rolling mill is rolled to a predetermined thickness by a finish rolling mill and wound by a winding machine, and the steel strip that has been hot rolled by the finish rolling mill is conveyed. In a cooling device for a hot-rolled steel strip comprising transport means comprising a plurality of transport rollers, and a cooling means for cooling the steel strip,
At a position facing the transporting roll through the steel strip to be transported, the steel strip rotates at a substantially equal peripheral speed with a gap exceeding the thickness of the steel strip and within a thickness of +30 mm , or the steel strip transport speed. A cooling device for a hot-rolled steel strip, wherein an accompanying roll rotating at the above peripheral speed is arranged. Between each said conveyance roll and each said accompanying roll, the guide body for passing plates is each provided ,
The cooling means is a plurality of cooling nozzles for injecting cooling water are provided at predetermined intervals, the cooling nozzle is disposed at a position facing through the through plate guide member and the steel strip Rukoto The apparatus for cooling a hot-rolled steel strip according to claim 6 . A pair of pinch rolls provided at a position immediately before the cooling means entering side, pinching the steel strip and leading to the cooling means,
Provided inlet side immediately before the position of the pinch roll pairs, a steel strip is conveyed to claim 6 or claim 7, characterized by comprising a strip guide for guiding in the gap of the pinch roll pairs The hot-rolled steel strip cooling apparatus as described. The position immediately after cooling the middle or exit side of the cooling means, the cooling of the hot rolled strip of the mounting serial to any one of claims 6 to 8, characterized in that the pinch roll pair is provided to pinch the steel strip apparatus. A method for cooling a hot-rolled steel strip produced by rolling a rough bar rolled by a rough rolling mill to a predetermined thickness by a finish rolling mill, cooling by a cooling device and then winding by a winder,
The hot-rolled steel strip is transported in a state where it is jetted from the cooling means under predetermined jetting conditions, and the tip of the hot-rolled steel strip is placed at the position on the entry side and / or exit side of the cooling means and / or in the middle of the cooling. Pinching and releasing the hot-rolled steel strip sequentially from the upstream pinch roll at the same time that the steel strip tip reaches the tension applying means such as the downstream pinch roll or winder Steel strip cooling method. A heating process for heating the slab;
A rough rolling step of rough rolling the slab heated in the heating step;
A finish rolling step for finish rolling the rough bar roughly rolled in the rough rolling step;
The steel strip finish-rolled by the finish rolling step is any one of the cooling devices of claims 1 to 3 , 6 to 9 , or the cooling of claims 4, 5 and 10 . A cooling step for cooling by any of the methods;
A winding step of winding the steel strip cooled in the cooling step;
A method for producing a hot-rolled steel strip, comprising:

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