Technical field
[0001]
　The present invention relates to a cooling apparatus and cooling method of hot rolled steel sheet to finish rolling at a hot finish rolling mill comprising a plurality stand, it relates to a cooling technology for material control when particular production of high performance steel.
BACKGROUND
[0002]
　In the manufacture of hot-rolled steel sheet, heating the cast slab produced by such a continuous casting machine (slab) in a heating furnace, and the rough rolling mill rough rolling steel (coarse bar), then under finish rolling in the finishing mill the predetermined thickness of the steel sheet, and hot-rolled steel sheet was further cooled steel sheet at a predetermined cooling pattern. The finishing mill, a plurality of rolling stands are arranged in series, rough rolled steel is finish rolled by sequentially passing through a plurality of rolling stands.
[0003]
　In the manufacture of hot-rolled steel sheet by quenching the steel sheet immediately after finish rolling, the grain size of the steel sheet grains and grain refining, are known to be able to produce a superior hot-rolled steel sheet mechanical properties. That is, for example Ar 3 ends the finish rolling at lower than the transformation point, and start cooling within 0.1-0.2 seconds after rolling, Ar 3 by rapid cooling to a temperature below the transformation point, finish after rolling is achieved suppressed to grain refining crystal growth of the hot-rolled steel sheet, the material properties of the deep drawability and the like of the final product can be improved. Rapid cooling immediately after the finish rolling can be carried out by water cooling for injecting water into the steel plate immediately after finishing the finish rolling.
[0004]
　Cooling between rolling stands in the finishing mill which has been conventionally carried out, the heating furnace due, improvements and the temperature distribution in the steel sheet by the width direction uneven expansion due like rolling roll, the temperature rise due to working heat generation increase in finish rolling is what is done for prevention, was to cool about 20 ° C. at a temperature of the steel strip as it passes through the rolling stand. And in this degree of cooling, to suppress the growth of crystal grain size cooling capacity was insufficient. Further, in order to start cooling immediately after rolling, it is necessary to install the cooling device as much as possible located close to the rolling stand.
[0005]
　Patent Document 1, the finish rolling stands, the steel plate cooling device provided with a full cone spray nozzle or the like for ejecting the cooling water is provided, subjected to rapid cooling immediately after rolling of a steel plate cooling device between the preceding finish rolling stand, in the steel plate cooling device between the trailing to finish rolling stand Ar 3 performs rapid cooling temperature range including transformation, the temperature range that passes through the roll stand finishing sandwiched between two steel plates cooler Ar 3 transformation point + 20 ° C. Ar from 3 be a temperature range up transformation point is disclosed.
[0006]
　Patent Document 2, a cooling device between the finish rolling stands provided, by opening the rolling rolls of the downstream side of the finishing rolling stand of the cooling device, that after the rapid cooling immediately after rolling is not performed soft reduction There has been disclosed.
[0007]
　Patent Document 3, the steel plate cooling apparatus disposed on the exit side of the finishing rolling stand is disclosed. The cooling device includes a cooling box interior becomes reservoir of cooling water, within the cooling box, spray nozzles for injecting cooling water are arranged.
[0008]
　Patent Document 4, finishing the rolling mill outlet side of placing a cooling apparatus comprising a plurality of cooling boxes, when continuously cooling the steel strip traveling on the hot run table, over the steel strip entire length, each cooling box the water flow rate at the time of use 2500L / min · m 2 and more constant values, is possible to cool the steel strip is disclosed using and more than 80% of the total cooling box having a cooling device at the maximum cooling of the steel strip ing.
[0009]
　Patent Document 5, in hot rolling, carried out between stand cooling of the finishing mill, rolling after cooling is carried out at a reduction ratio of degree of grain size which is reduced is not coarsened again, downstream of the stand It has been described to a draining station that does not perform substantial rolling.
[0010]
　Patent Document 6, as a cooling device for cooling the lower surface of the steel sheet during hot rolling, the box header is provided between the lower apron exit side and the looper roll inlet side of the outlet side lower work rolls, the upper surface of the box header cooling water jetting for drilled hole fitted with a nozzle plate of a large number arranged the apron serves cooling device is disclosed.
[0011]
　Patent Document 7 includes the lower step side of the finishing mill (exit side), a plurality of nozzles for injecting cooling water against the steel plate top surface, and a plurality of nozzles for injecting cooling water against the steel plate bottom surface placing the cooling device, the maximum impact pressure P in the steel plate top surface of the cooling water injected from the upper surface side nozzles C1 and (kPa), the minimum collision pressure P C2 and (kPa), S ( when the kPa), (P C1 -P C2 ) / P S has been disclosed that satisfy ≧ 1.4.
[0012]
　Patent Document 8, the exit side nearest position of the finishing mill, the upper surface cooling box for cooling by jetting cooling water against the strip upper surface, is cooled by injecting cooling water against the strip lower surface and a lower surface cooling box, cooling apparatus is disclosed for injecting cooling water from these top cooling box and the lower surface cooling boxes vertically symmetrically with respect to the steel strip.
[0013]
　Patent Document 9, the outlet side of the roll stand, provided adjacent to the upper side of the guide strip, and the spray bar above spraying cooling water onto the upper surface of the strip (s spray nozzles), the strip the provided adjacent to the lower side of the guide, the cooling device including a spray bar below (multiple spray nozzles) for spraying cooling water to the lower surface of the strip is disclosed.
CITATION
Patent Document
[0014]
Patent Document 1: JP 2009-241115 Patent Publication
Patent Document 2: JP 2009-241113 Patent Publication
Patent Document 3: JP 2009-241114 Patent Publication
Patent Document 4: JP 2005-279736 Patent Publication
Patent Document 5: JP 2003-305502 JP
Patent Document 6: JP-A 4-200816 Patent Publication
Patent Document 7: JP 2014-50878 JP
Patent Document 8: JP 2001-246412 JP
Patent Document 9: JP-T 2010-516473 Patent Publication
Summary of the Invention
Problems that the Invention is to Solve
[0015]
　To suppress coarsening of crystal grain size, immediately after possible rolling, and, it is desirable to strongly cooled close as possible to the steel sheet, on the other hand, the cooling device, so as not to collide with the steel plate after rolling It must be placed. Further, on the delivery side of the rolling stand, typically, is provided guide, when replacing the rolling rolls, it is necessary to retreat to a position away guide from rolling roll. At this time, close to the guide, when the cooling device as a separate body is disposed, and a problem that it is troublesome to work retracting the cooling device, located remotely cooling device from the rolling mill and steel sheet there is a problem that forced. Further, on the opposite side to the guide of the steel plate must be installed a cooling device of the rolling rolls, the structure of the cooling device becomes a problem. Also, when installing the final stage of the rolling mill finishing the cooling device, after finishing mill of a plate thickness measuring apparatus and a plate temperature measuring device is required, in order to carry out proper management of the thickness and the plate temperature lengthening the cooling captain undesirable.
[0016]
　However, there is no description of the specific mounting structure of even cooling apparatus to any of Patent Documents 1-5. Further, Patent Document 6 is intended to refer to a cooling device of only the lower of the steel sheet also has separately from the cooling device and the lower apron. Further, in the disclosed cooling apparatus in Patent Document 7, although the nozzles are disposed along the guide, and is separate from the still nozzle and the guide. Further, since this arrangement can not be installed a cooling device of the rolling rolls, there is a concern that the rolling roll is deformed by the heat received from the steel sheet, the shape of the steel sheet is deteriorated.
[0017]
　In this regard, in the cooling apparatus disclosed in Patent Document 8, the cooling boxes of the upper and lower surfaces are provided continuously to the guide at the exit side nearest position of the finishing mill. However, this guide length, the rolling roll has a (work roll) over several times the diameter, the time until cooling start is increased, grain refining effect will be reduced. Further, the finish rolling after the sheet thickness measuring apparatus to be typically placed in up to the end of cooling from no place to install or plate temperature measuring device, accuracy of plate thickness, it is difficult to manage the material. Further, the cooling device disclosed in Patent Document 9, there is interference in the case of moving the guide during roll change, it is difficult to the cooling device is close enough to the rolling mill. Since the addition the distance between the spray nozzle and the strip varies in the rolling direction, the cooling water sprayed from the spray nozzle, impact surface becomes uneven in the rolling direction of the strip, again resulting in non-uniform cooling. Also in other cooling apparatus of Patent Document 1 to 7, when the steel sheet after finish rolling is inclined not considered, it may also occur problems of cooling nonuniformity.
[0018]
　The present invention has been made in view of the foregoing, immediately after hot finish rolling (including immediately after rolling by the rolling stand.) Steel plate was cooled from as close as possible to, the finish of the hot-rolled steel sheet after rolling while achieving grain refining by suppressing the growth of crystal, that the hot-rolled steel sheet was uniformly cooled, and to provide a cooling apparatus and cooling method for hot-rolled steel sheet can be simplified labor during rolling roll replacement for the purpose.
Means for Solving the Problems
[0019]
　To solve the above problems, the present invention is injected at hot finish rolling mill comprising a plurality of rolling stands, a cooling water toward one or both of the upper and lower surfaces of the hot-rolled steel sheet immediately after being rolled by the rolling stand a plurality of nozzles, the nozzle, of the guide provided above and below the exit side of the rolling stand, provided adjacent to the downstream side in or the guide one or both of the guide, the upper and lower guide with respect to the steel plate design position of the hot-rolled steel sheet is set between the nozzle ejection distance along the jet central axis between the injection port of the nozzle to the steel sheet design position, the rolling direction of the nozzle a cooling device for changing the position, the injection angle of the nozzle of the largest position the nozzle firing distance is found from the ejection angle of the nozzle of the smallest position the nozzle firing distance Fence, in accordance with the nozzle firing distance increases, the injection angle of the nozzle is characterized by comprising the same or smaller.
[0020]
　The steel sheet design position may be set to (be. Described below defined) tangent plane at the top vertex of the lower rolling roll of the rolling stand (work roll). Alternatively, the steel sheet design position may be set to 1/2 angle of the plane of the angle between the upper and lower guide.
[0021]
　The nozzle firing distance is the smallest position, the located on the most upstream side of the cooling device, the nozzle firing distance is the largest position may be on the most downstream side of the cooling device. Alternatively, the nozzle firing distance is the largest position, located on the most upstream side of the cooling device, the smallest position the nozzle firing distance may be in a most downstream side of the cooling device.
[0022]
　The nozzle may be provided inside of the cooling box. Injection port of the nozzle of the cooling box, located on the steel plate design position side of the surface and the back side of the same surface or the surface (the center side of the cooling box), the opposite end the jet port of the nozzle it may protrude into the cooling box from the inner surface position of the cooling box inside.
[0023]
　Injection port of the nozzle may be arranged in the guide plane formed on the same plane. Alternatively, the injection port of the nozzle may be arranged on the opposite side of the steel plate design position from a plane formed the guide.
[0024]
　Wherein the nozzle is a full cone nozzle, impingement region in the hot-rolled steel sheet of the cooling water injected from the nozzle may satisfy the following equation (1).
[Number 1]

However,
L: nozzle firing distance (m)
alpha: nozzle spray angle (degrees)
i, j: any column of the nozzles provided in the rolling direction (i columns, j columns)
[0025]
　Wherein the nozzle is oblong spray nozzles, impingement area of the hot-rolled steel sheet of the cooling water injected from the nozzle may satisfy the following formula (2).
[Number 2]

However,
L: nozzle firing distance (m)
beta: nozzle length directions injection angle (degrees)
gamma: nozzle minor axis injection angle (degrees)
i, j: Any of the nozzles provided in the rolling direction column (i row, j column)
[0026]
　Water flow rate of the cooling water from the nozzle may not satisfy the following formula (3).
Wa 0.5 × Ma / (t × V) ≧ 0.08 · · · (3)
However,
Wa: water density of the cooling water from the nozzle (m 3 / m 2 · min)
Ma: in said cooling device cooling range length of the rolling direction (m)
t: plate thickness of the hot-rolled steel sheet (mm) V:
sheet passing speed of the hot-rolled steel sheet (m / s)
[0027]
　Downstream of the measuring device performs measurement of the hot-rolled steel sheet exit side of the rolling stand at the most downstream side of the hot finish rolling mill, jet cooling water toward one or both of the upper and lower surfaces of the hot-rolled steel sheet to place multiple cooling zone with a cooling nozzle, the water density of the cooling water from the cooling nozzle 2m 3 / m 2 at · min or more, may not satisfy the following formula (4).
Wb 0.5 × Mb / (t × V) ≧ 0.55 · · · (4)
However,
wb: the water density of the cooling water from the cooling nozzles (m 3 / m 2 ·
min) Mb: the cooling zone cooling range length of the rolling direction in (m)
t: plate thickness of the hot-rolled steel sheet (mm) V:
sheet passing speed of the hot-rolled steel sheet (m / s)
[0028]
　Wherein said cooling device between rolling stands arranged, the cooling device opens the rolling rolls of the rolling stand downstream of, the rolling rolls (working rolls) roll gap plus 7mm to aim thickness values ​​of It follows and, in the exit side of the rolling stand at the most downstream side of the hot finishing rolling mill, may be arranged draining device for removing the plate clean water leaked from rolling stands of the most downstream side.
[0029]
　Said cooling device on the outlet side of the rolling stand at the most downstream side of the hot finish rolling mill disposed on the downstream side of the cooling device, by placing the draining device for removing the plate clean water leaked from the cooling device it may be.
[0030]
　Wherein the plurality of nozzles, a row is disposed in the width direction, constitutes a plurality of nozzle groups aligned in the rolling direction in accordance a predetermined number of the column in the rolling direction, the number of the plurality of nozzle groups, with a maximum , the same number of columns in the rolling direction of the nozzle provided in the rolling direction, the pipe, each cooling water is supplied to each nozzle group is connected, wherein each each pipe three-way valve and flow control valve is it may be provided.
[0031]
　Further, the present invention according to another aspect, a cooling method using the cooling device, in the delivery side of the rolling stand of the hot finish rolling mill, to one or both of the upper and lower surfaces of the hot rolled steel sheet, said from the nozzle, characterized by injecting the cooling water.
[0032]
　Further, the present invention according to another aspect, a cooling method using the cooling device, in the delivery side of the rolling stand of the hot finish rolling mill, to one or both of the upper and lower surfaces of the hot rolled steel sheet, said upon injecting the cooling water from the nozzle, by adjusting the number of the rolling direction of the nozzle group for ejecting a cooling water to the hot-rolled steel sheet according to the sheet passing speed of the hot-rolled steel sheet, when the through plate speed increases the, to turn the far side from the side close to the rolling stand, increasing the number of the nozzle groups for ejecting cooling water to the hot-rolled steel sheet, when the through plate speed is decelerated, the far side from the rolling stand in order from, characterized in that the cooling water flows closes the injection into the hot-rolled steel sheet from the nozzles of the nozzle group to the drainage side.
Effect of the invention
[0033]
　According to the present invention, by providing a plurality of nozzles adjacent to the downstream side of the existing guide in or the guide which is installed on the exit side of the rolling stand, the hot-rolled steel sheet immediately after passing through the rolling stand in contrast, it is possible to cool the close. Thus, finish by suppressing the growth of crystal grain size of the hot-rolled steel sheet after the rolling can be achieved grain refinement, it is possible to manufacture a high-quality steel sheet at a low cost. Also, if the nozzle firing distance is changed by the position of the rolling direction of the nozzle, in the present invention, the injection angle of the nozzle of the largest position nozzle firing distance is smaller than the injection angle of the nozzle of the smallest position nozzle firing distance, according nozzle firing distance increases, since the injection angle of the nozzle is the same or smaller, and a uniform impact surface in the rolling direction, can the cooling capacity uniformly, it is possible to uniformly cool the resulting hot-rolled steel sheet. Moreover, in the cooling apparatus of the present invention, it can take no time to save work when exchanging the rolling rolls.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034]
FIG. 1 is a schematic diagram showing the configuration of a cooling system hot rolling facility provided with a according to an embodiment of the present invention.
Is a side view schematically showing the output-side configuration of the finishing rolling stand provided with a cooling device according to [2] The present embodiment.
3 is a diagram showing an outline of a configuration of a cooling device according to the present embodiment.
[Figure 4] is a view for explaining the accumulation of water in the cooling box during standby, (a) shows the case where the cooling box is not divided, (b) if the cooling box is divided into a plurality of sections It is shown.
5 is a diagram illustrating a spray angle of the nozzle in accordance with the nozzle firing distance.
6 is an explanatory view showing an injection angle from the full cone nozzle (spread angle of the nozzle jet).
[Figure 7] is an explanatory view showing a (spread angle of the nozzle jet) injection angle from the oval spray nozzles, showing the (a) shows the injection angle of the major axis, (b) the ejection angle of the minor axis direction .
[8] finish rolling stand passing plate angle of hot-rolled steel sheet immediately after (steel design position) is an explanatory view showing a case is 0 degrees.
Is an explanatory view showing the case [9] passing plate angle (steel design position) of the hot-rolled steel sheet after finish rolling stand is 1/2 of the upper and lower guide angle theta.
Is a side view showing an outline of FIG. 10 of the outlet side of the rolling stand finishing provided with a cooling device according to another embodiment configurations.
11 is a side view schematically showing the output-side configuration of the rolling stand finishing provided with a cooling device according to another embodiment.
Is a side view showing an outline of FIG. 12 of the outlet side of the rolling stand finishing provided with a cooling device according to another embodiment configurations.
13 is a diagram schematically showing the configuration of a cooling apparatus according to another embodiment.
14 is a side view schematically showing the output-side configuration of the rolling stand finishing provided with a cooling device according to another embodiment.
15 is a diagram showing a schematic configuration of another according to the embodiment the cooling device hot rolling facility provided with.
DESCRIPTION OF THE INVENTION
[0035]
　Hereinafter, the embodiments of the present invention will be described with reference to FIG. In the specification and drawings, in the elements having substantially the same function and structure are a repeated explanation thereof by referring to the figures.
[0036]
　First, a description will be given hot rolling mill system having a cooling device according to the present embodiment. Figure 1 is an explanatory diagram showing an outline of a hot rolling mill 1 of the configuration.
[0037]
　In the hot rolling facility 1, continuously rolling the slab 5 which heated, wind the hot-rolled steel sheet 10 which has been thinned to the thickness of about 1 ~ 20 mm. As shown in FIG. 1, the hot rolling facility 1 includes a heating furnace 11 for heating the slab 5, the width direction rolling mill 12 for rolling the slab 5 heated by the heating furnace 11 in the width direction, the rolling in the width direction by rolling a slab 5, which is the vertical direction and the roughing mill 13 to a coarse bar 6, a finish rolling mill 14 the crude bar 6 further continuously to a predetermined thickness to a hot finish rolling, the finishing mill It includes a cooling unit 15 for cooling the hot rolled steel sheet 10 which is hot finish rolling to a predetermined temperature by 14, and a winding device 16 for winding the hot-rolled steel sheet 10 which has been cooled in the cooling section 15 into a coil . Incidentally, hot rolling facilities 1 above a typical system configuration, hot rolling mill to which the present invention is applied is not limited to this.
[0038]
　A heating furnace 11, various burner for heating the slab 5 is provided. In the heating furnace 11, the process of heating the slab 5 which has been carried in from outside to a predetermined temperature is performed. When the heating treatment in the heating furnace 11 is completed, the slab 5 is conveyed into the heating furnace 11 outside, the process proceeds to the rolling process according to the width direction mill 12 and rough rolling mill 13.
[0039]
　The roughing mill 13, a cylindrical rolling rolls are disposed over a plurality of stands. The rolling roll, there is a backup roll to suppress or control the deflection of the work roll and the work rolls for sandwiching a material to be rolled directly. In rough rolling mill 13, the slab 5 being fed and passed through the gap between these rolling rolls (work rolls), is rolled to thickness a thickness of about 30 ~ 60 mm, it is conveyed to the subsequent finish rolling mill 14 that.
[0040]
　A finishing mill 14, a plurality groups, the rolling stands F1 ~ F7 of example 7 group are arranged in series, each with a rolling roll. The rolling rolls, there is a backup roll to suppress or control the deflection of the work roll and the work rolls for sandwiching a material to be rolled directly, special cases it may sandwich the intermediate rolls between them. In relation to the cooling device of the present invention, a rolling roll, primarily refers to the work roll, is sometimes used as a generic term that rarely including backup roll. In the finishing mill 14, these rolling roll is passed through a coarse bar 6 after rough rolling gap (work roll), which was slowly rolled, the thickness of about 1 ~ 20 mm (e.g., about several mm plate thickness) until the rolling. Finish rolled hot rolled steel sheet 10 is delivered to the cooling section 15 is conveyed by the conveying rolls (not shown).
[0041]
　The cooling unit 15, and below the hot-rolled steel sheet 10 being conveyed, the cooling nozzle for injecting cooling water toward the hot-rolled steel sheet 10 are arranged side by side a plurality in the rolling direction. These cooling nozzles, for example, slit laminar nozzle or pipe laminar nozzles, spray nozzles are used.
[0042]
　Winding device 16 winds the hot-rolled steel sheet 10 which has been cooled to a predetermined temperature by the cooling unit 15. Hot-rolled steel sheet 10 coiled by the take-up device 16 is conveyed to the hot rolling mill 1 outside.
[0043]
　In the present invention, the cooling unit 15 separately from the cooling device 21 for strongly cooling the hot-rolled steel sheet 10 immediately after the finish rolling is provided on the exit side of the rolling stand. The exit side of the rolling stand, a position on the downstream side of the plurality ordered rolling stands F1 ~ F7 during or between the final rolling stands F7,, preferably, hot-rolled steel sheet 10 after being fully finish rolling to cool the cooling device 21 is provided on the exit side of the subsequent rolling stands close to the final rolling stand F7 of the finishing rolling mill 14. In this embodiment, are the two positions, the cooling device 21 is disposed between the have a finishing mill 14 rolling stands F1 ~ 7 groups F7, for example between the F5 and F6, and F6 and F7 . Here, the strong cooling, for example, cooling rate is 50 ° C. / s or higher, the steel sheet temperature and cooling to decrease 30 ° C. or higher by passing through a cooling apparatus 21 at one location.
[0044]
　Figure 2 shows a schematic of the output-side configuration of the roll stand provided with a cooling device 21 of the present embodiment. The distance between the upper and lower guide 33 (the vertical distance) becomes larger toward the downstream side from the rolling direction upstream side. Thus the upper and lower guide 33 is disposed, it is the tip of the hot-rolled steel sheet 10 even with butter in the vertical, so as not to collide with the equipment in which the hot-rolled steel sheet 10 is provided on its upper and lower . Then, the distal end portion of the upper and lower guide 33, the cooling device 21 is provided according to the present embodiment. Guide 33 is sometimes referred to stripper guide, it referred to simply guide the present invention.
[0045]
　Cooling apparatus 21, as shown in FIG. 3 includes a cooling box 22 consisting of a closed container, a plurality of nozzles 23 provided in the cooling box 22, a pipe 24 for supplying cooling water to the cooling box 22 ing. Cooling box 22 is provided by integrating the tip facing away from the rolling roll (work roll) 31 of the upper and lower respective guide 33, as shown in FIG. Cooling box 22, as hot-rolled steel sheet 10 is cooled immediately after passing through the rolling stands, as close as possible to the rolling stand, and is preferably be placed as close as possible to the hot-rolled steel sheet 10 (steel design position), FIG. as shown in 2, it is provided immediately after the roll cooling water header 32. Incidentally, the steel sheet design position of the hot-rolled steel sheet 10 is set at the time of designing of the cooling device 21, the hot-rolled steel sheet 10 is a position where the Tsuban, between the upper and lower guide 33, for example, the constant of the hot-rolled steel sheet 10 It is determined in light of the passing plate angle of the time state. It will be described in detail later determination method of this steel plate design position.
[0046]
　Inside the cooling box 22, a plurality of nozzles 23 for injecting cooling water toward the hot-rolled steel sheet 10 is provided. The nozzle 23, used is a full cone nozzle or oblong spray nozzles, so that its injection surface is a guide 33 and substantially coplanar, each of the plurality of nozzles 23 in the width direction and the rolling direction of the cooling box 22 is provided It is. Note that the ejection surface, a surface constituted by a plurality of nozzles jets 23a, in the case of the cooling box 22 is provided on top of the steel plate design position provided lower surface, the lower portion of the steel plate design position in the case of the cooling box 22 is a surface to be the top surface.
[0047]
　As shown in FIG. 3, the injection port 23a of the nozzle 23 is than flush with the surface or the surface of the steel plate design position side of the cooling box 22 located on the inner side (center side of the cooling box 22) it may be. On the surface of the steel sheet design position side of the cooling box 22 to place the nozzle 23. At that time, it does not protrude the injection port 23a of the nozzle 23 from the surface of the steel sheet design position side, located on the inner side than the same surface or the surface. That is, the injection port 23a of the nozzle 23 is arranged or is arranged flush with the surface of the steel plate design position, or recessed from the surface. In such a case, finish rolling, when the tip and tail of the hot-rolled steel sheet 10 passes through the roll stand, even the tip and tail collides swings up and down in the cooling box 22, the hot-rolled steel sheet 10 is a nozzle 23 It does not conflict, it is possible to prevent damage to the nozzle 23.
[0048]
　Further, opposite end portions 23b and the injection port 23a in the nozzle 23, than the inner of the inner surface positions of the cooling box 22 and projects into the interior of the cooling box 22. In such a case, when not injecting cooling water from the nozzle 23 is also cooled by the cooling water nozzles 23 remains in the interior of the cooling box 22, it is possible to prevent damage to the nozzle 23. In addition, in the case of ON / OFF of ejection of the cooling water from the nozzle 23, because of the water remaining in the interior of the cooling box 22, from the state of stopping the jetting of the cooling water until the start of injection of the cooling water it is possible to shorten the response time. Also, the water supply in order to stop the injection of the cooling water from the nozzle 23 can reduce the amount of cooling water falls on the hot-rolled steel sheet 10 from the stop, i.e., injection substantially stopped in the cooling water it is also possible to shorten the response time to be.
[0049]
　Internal cooling box 22, as shown in FIG. 3, is divided into a plurality of compartments 22a in the rolling direction. Each compartment 22a, the cooling water pipe 24 is provided to be supplied, each pipe 24, respectively and a three way valve 25 and flow control valve 26 is provided. The three-way valve 25 includes a water supply header 27 for supplying cooling water to the cooling box 22, is provided between the drainage header 28 or the drainage area to discharge the cooling water. In Figure 3, the interior of the cooling box 22, but is divided so that one section 22a for each of the two rows nozzle 23 in the rolling direction, in one compartment 22a for each nozzle 23 of one row in the rolling direction may be divided so that, also, may be divided so that one section 22a in the rolling direction every three or more rows of nozzles 23. Thus compartment 22a is partitioned into a predetermined number of nozzles 23 constitute a nozzle group according to the present invention. The internal cooling box 22 is not divided into a plurality of compartments 22a, it may be one of the compartments 22a.
[0050]
　By providing a three-way valve 25 in the pipe 24 is always adapted to the cooling water is filled in the interior of the pipe 24. Therefore, when cooling the hot rolled steel sheet 10, short time from the issued instruction to open the three-way valve 25 to the cooling water is supplied into the cooling box 22, a good response. The three-way valve 25, for example, an electromagnetic valve is used. Further, the three-way valve 25 is preferably disposed slightly lower height than the upper end of the nozzle 23. Although not shown in FIG. 3, thereby, the tip of the pipe 24 becomes slightly lower height than the upper end of the nozzle 23, always in the cooling water is filled in the interior of the pipe 24.
[0051]
　In the cooling box 22 is divided into a plurality of compartments 22a in the rolling direction, by providing the piping 24 to the respective compartments 22a, to adjust the flow rate of the cooling water in each compartment 22a, a wide range of sheet passing speed of the hot rolled steel sheet 10 it is possible to control the cooling capacity in response to Do changes. Moreover, the amount that can be residual water remaining in the cooling box 22 while waiting is increased, it is possible to increase the response speed of the injection start of the cooling water. When in a direction along the guide 33 to install the cooling box 22, for example, cooling box 22 provided at the tip of the upper guide 33 is inclined as shown in FIG. If all of the nozzles 23 are arranged in one space The tilted in the cooling box 22 without being divided, as shown in FIG. 4 (a), when not injecting cooling water, the lowest position only up to a position lower than the upper end of the nozzle 23 can not be allowed to dwell water. From this state, in order to inject cooling water from all of the nozzles 23, such response time to supply water to a position higher than the upper end of the highest position the nozzle. However, by dividing the inside of the cooling box 22 to the rolling direction, as shown in FIG. 4 (b), each section 22a, that allowed to dwell water to a position lower than the upper end of each lower nozzle 23 can. Thus, at the start injection, the supply of less cooling water is injected from all the nozzles 23 is started, thereby improving the responsiveness. If split so that one section 22a for each row of nozzles 23 in the rolling direction, it is possible to keep the water was retained until slightly lower position than the upper end of all the nozzles 23, the response at the time of injection a can most quickly.
[0052]
　Here, from the tip of the nozzle 23 (injection port 23a), as shown in FIG. 5, the injection center axis of until steel design position of the hot-rolled steel sheet 10 a distance along the (one-dot chain line in the drawing), a nozzle jet It is defined as a distance L. Then, the cooling box 22 is tilted as described above, nozzle firing distance L is different in the rolling direction of the cooling box 22. That is, the nozzle injection distance L as a distance from the rolling stand is increased, the smallest position nozzle firing distance L is on the most upstream side of the cooling device 21, the largest position nozzle firing distance L is the most downstream side of the cooling device 21 It is in. Therefore, when equal injection angle of all the nozzles 23, who injected from a position away from the hot-rolled steel sheet 10, the spread of jet impingement portion when striking the hot-rolled steel sheet 10 increases, the same amount of cooling water injection If it, cooling capacity is lowered. Further, the overlap of the jet impingement portion occurs, resulting in non-uniform cooling. Therefore, as shown in FIG. 5, far from the rolling stands, that is, as the nozzle injection distance L becomes longer, to reduce the injection angle of the nozzle 23. In this embodiment, the upper guide 33 of steel plate design position cooling box 22 are disposed inclined from the rolling direction, but to reduce the injection angle of the nozzle 23 in the upper nozzle 23 at the lower portion the injection angle may be reduced.
[0053]
　In the present invention, the nozzles 23 adjacent to the rolling direction, nozzle firing distance L is the largest position the injection angle of the nozzle 23 (Figure In 5 downstream) nozzle firing distance L is the smallest position (FIG. 5 in need not be smaller than the injection angle of the nozzle 23 on the upstream side). That is, in the present invention, (1) the spraying angle of the nozzle firing distance L is the largest position nozzle 23 is smaller than the ejection angle of the nozzle firing distance L is the smallest position nozzle 23, and, (2) rolling spraying angle of the nozzle jet distance L is smaller than the side nozzles 23 to the nozzle 23 adjacent the direction, not simultaneously satisfy the two conditions of not less than the injection angle of the nozzle firing distance L is larger side of the nozzle 23 lever, the nozzles 23 adjacent to the rolling direction may be the same injection angle to each other.
[0054]
　In terms of nozzle firing distance L has small injection angle of the nozzle 23 in accordance with increases further, the difference between the collision area of ​​the nozzle jet at an arbitrary position in the rolling direction, i.e. the difference between the minimum collision area and the maximum collision area 10% by below, a reduction in the cooling capacity when the distance is enlarged collision area changes between the tip and the hot-rolled steel sheet 10 of the nozzle 23 and more suppressed, the cooling capacity of the rolling direction each position more constant can do. As a result, it is possible to cool the hot-rolled steel sheet 10 more uniformly.
[0055]
　Specifically, when the nozzle 23 is full cone nozzle, as the collision area in the hot-rolled steel sheet 10 of the injected cooling water from the collision area (nozzle 23 of the nozzle jet satisfies the following formula (1), the nozzles 23 . injection angle α is set Incidentally, the injection angle α of the nozzle 23 as shown in FIG. 6, a spread angle of the nozzle jet (diameter D).
[Equation 3]

However,
L: nozzle firing distance (m)
alpha: nozzle spray angle (degrees)
i, j: any column of nozzles provided in the rolling direction (i columns, j columns)
[0056]
　If the nozzle 23 is oblong spray nozzles, the collision area of the nozzle jet so as to satisfy the following formula (2), the major axis direction injection angle β to the minor axis direction injection angle γ of the nozzle 23 is set. Incidentally, the longer diameter injection angle β of the nozzle 23 as shown in FIG. 7 (a), a spread angle of the major axis D1 of the nozzle jet, minor spraying angle γ of the nozzle 23 as shown in FIG. 7 (b), it is a spread angle of the minor diameter D2 of the nozzle jet.
[Expression 4]

However,
L: nozzle firing distance (m)
beta: nozzle length directions injection angle (degrees)
gamma: nozzle minor axis injection angle (degrees)
i, j: any column of nozzles provided in the rolling direction (i row, j column)
[0057]
　By tilting the moving direction of the hot-rolled steel sheet 10 immediately after the rolling stand finishing the looper 34, the hot-rolled steel sheet 10 from 0 (zero) degrees is the rolling direction as shown in FIG. 8, formed of upper and lower guide 33 it can be passed a plate in an angle theta. That is, the angle of the steel plate design position of the finish rolling stand hot-rolled steel sheet 10 immediately is between 0 degree angle theta. This is the depending angle guide 33 theta, be any angle through plate angle of finish rolling stand hot-rolled steel sheet 10 immediately after the difference between the collision area of ​​the nozzle jet at an arbitrary position in the rolling direction, that is, the maximum collision making the difference between the minimum collision area as below 10% is not easy.
[0058]
　However, in a steady state except such as during and end at the beginning of rolling, the sheet passing the hot rolled steel sheet 10 immediately after the finish rolling stand angle is often substantially constant angle. Therefore, when designing a cooling apparatus 21, the hot-rolled steel sheet 10 has chosen a strip passing angle of the steady state, predetermining the strip passing angle underlying the design. Position of the hot-rolled steel sheet 10 which is determined in this way is a steel designed position in the present invention. When the hot-rolled steel sheet 10 is in a predetermined sheet passing angle, that is, such as when the hot rolled steel sheet 10 is in the passing plate angle in the steady state, that the difference between the 10% or less it is possible. In this way, when in the strip passing angle hot rolled steel sheet 10 has been previously determined, that is, in a case of passing plate angle of the steady state, the difference in the can 10% or less, the result, it is possible to cool the hot-rolled steel sheet 10 more uniformly.
[0059]
　Here, in the actual operation, passing plate angle of the steady state of the finish rolling stand hot-rolled steel sheet 10 immediately from 0 ° shown in FIG. 8, the angle θ of the upper and lower guides 33 as shown in FIG. 9 in many cases an angle of up to 1/2 angle. Therefore, in this embodiment, so as to satisfy the above formula (1) or formula (2), the particular angle at which strip passing angular position of the hot-rolled steel sheet 10 has a medium of 0 ~ theta / 2 degrees, at design time It is a predetermined sheet passing angle. Then, the steel plate design position of the hot-rolled steel sheet 10 as shown in FIG. 8 is 0 °, i.e. it may be set to the tangent plane at the lower side of the rolling roll top vertex of (work roll) 31 of the rolling stand. Note that the tangent plane is a plane in contact with the rolling rolls including a line connecting the upper vertices of the rolling roll (work roll) 31 of the lower rolling stand adjacent, and the rolling stand adjacent cooling device 21 is two when in the rolling stand refers to the two roll stands, when the cooling device 21 is in the delivery side of the rolling stand F7 final refers to rolling stands F6, F7. Further, the steel plate design position after rolling stands finish as shown in FIG. 9 may be set above and below the guide half face of the angle θ of. With this design a cooling device 21, the angle theta (preferably the upper and lower guide 33 from 0 degrees through plate angle of hot-rolled steel sheet 10 immediately after the finish rolling stand is rolling direction, half of the angle theta when a particular angle with the medium up to angle), the collision area in the hot-rolled steel sheet 10 of the injected cooling water from the nozzle 23 can be cooled so as to satisfy the formula (1) or the formula (2) .
[0060]
　In other words, the collision area of ​​the hot-rolled steel sheet 10 of the injected cooling water from the nozzle 23 through plate angle immediately after finish rolling stand that satisfies the formula (1) or the formula (2) is a rolling direction 0 (preferably, 1/2 angle of the angle theta) the angle theta of the upper and lower guide 33 from time if there is a cooling device present in up, the cooling device using, finish hot rolled steel sheet after rolling stand 10 inclination angle of the can if the even and strip passing in "above formula (1) or the formula (2) passing plate angle such as to satisfy the" more uniformly cooled.
[0061]
　Cooling apparatus according to the present invention, the finish immediately after rolling stand, there if hot-rolled steel sheet 10 is assumed to Tsuban by passing plate angle, the collision area in the hot-rolled steel sheet 10 of the injected cooling water from the nozzle 23 is the formula ( 1) or through plate angle immediately after rolling stand finishing satisfies the above equation (2) can be regarded as a cooling device is in the 0 degree is a rolling direction of the angle θ of the upper and lower guide 33. Furthermore, in other words, the steel plate design position immediately after finish rolling stand (passing plate angle), the collision area in the hot-rolled steel sheet 10 of the injected cooling water from the nozzle 23 is above formula (1) or the formula (2) angle satisfying (where the angle is. 0 degree is the rolling direction in the angle θ of the upper and lower guide 33) can be regarded as an arbitrary angle in the.
[0062]
　In this embodiment, water density Wa of the cooling water from the nozzle 23 is preferably satisfies the following formula (3). Equation (3) shows the required cooling capacity when lowering certain level with a temperature of hot-rolled steel sheet 10. That is, in the left-hand side of equation (3) is a molecule (Wa 0.5 is × Ma), a (cooling capacity indicator per unit time per unit area corresponding to the heat flux) × (cooling range length), all It shows the cooling capacity. Further, a denominator (t × V) is the volume of a unit width of the hot rolled steel sheet passing per unit time (the material), it is equivalent to the amount of heat required to lower 1 ℃ hot-rolled steel sheet. As a result of inventors studied intensively, if the left-hand side of equation (3) is a constant value 0.08 or more was found to be able to properly control the crystal grain. The cooling range length Ma are, for example, 1m or more 3m or less. In this case, Ar 3 from transformation temperature Ar 3 of the cooling of 40 ° C. or more up to the transformation temperature -30 ° C. can be performed immediately after the rolling, thereby sufficiently preventing the coarsening of crystal grains, the grain refining It can be performed.
Wa 0.5 × Ma / (t × V) ≧ 0.08 · · · (3)
However,
Wa: water density of the cooling water from the nozzle 23 (m 3 / m 2 ·
min) Ma: Cooling Range Length
(m) t: plate thickness of the hot rolled steel sheet 10
(mm) V: sheet passing speed of the hot rolled steel sheet 10 (m / s)
[0063]
　The above equation relates to (3), JP 2009-241115, water density W of the cooling water (l / m 2 · min) W 0.663 satisfies × M ≧ 260, the cooling range length M is disclosed that satisfies the following 1.8 m. However, this JP disclosed in 2009-241115 discloses, in the conditions of water flow rate of cooling water, there is no sheet passing speed conditions of the plate thickness and the hot rolled steel sheet of the hot-rolled steel sheet is insufficient.
[0064]
　Further, the angle θ of the upper and lower guide 33, for example in the range below 8 degrees 30 degrees. The angle theta, for example, may be within the following 30 degrees or 10 degrees 25 degrees 8 degrees.
[0065]
　Although excluded in this embodiment, in the present invention, the strip passing angle of hot-rolled steel sheet 10 immediately after the rolling stand finishing that is predetermined when designing the cooling system, the following angle θ of the upper and lower guides 33 if, it may exceed the half angle of the angle θ of the upper and lower guide 33.
[0066]
　Further, in the above formula (1) or the formula (2), i and j are any column (i columns, j columns) of the nozzles 23 provided in the rolling direction is set to. This is the formula (1) or the formula (2) is, for all nozzle columns (L · tan [alpha) 2 to calculate the ratio between the maximum value and the minimum value (maximum value denominator) is 0. which means that it is 90 or more. More, the above equation (1) When a nozzle injection angle α is constant in the difference of the collision area of the nozzle jet at an arbitrary position in the rolling direction to be less than 10%, for all nozzle arrays, the nozzle It means that the ratio between the maximum value and the minimum value of the injection distance L (maximum denominator) is (in 0.95 rounded to two decimal places) or the square root of 0.90. That is, in order to satisfy the above formula (1), the difference between the maximum value and the minimum value of the nozzle firing distance L should be within 5% of its maximum value. Similarly, in the above formula (2), a nozzle diameter direction injection angle β is constant, and, if the nozzle minor axis injection angle γ is constant, the difference between the maximum value and the minimum value of the nozzle firing distance L , it is required to be within 5% of its maximum value.
[0067]
　The nozzle used in this cooling system 21, the same types of nozzles (e.g., full cone nozzle, oval blow nozzles) to be preferable.
[0068]
　By the above cooling device 21, hot-rolled steel sheet 10 which is hot rolled through the rolling stand, in a state where the strain immediately after leaving the rolling rolls 31 remaining, cooled by cooling water sprayed from the cooling box 22 It is. This cooling, for example with the 30 ° C. or higher strength cooled between one position of the stand, thereby, for example, Ar 3 shorten up transformation point time, and comminuted by suppressing the expansion of the crystal grain size, the hot-rolled steel sheet it can improve the quality of the 10 material of.
[0069]
　When passing plate speed of hot-rolled steel sheet 10 is slow, out of the nozzle 23 in the cooling box 22, for injecting cooling water from nozzles 23 closer to the roll stand. This control is performed by the three-way valve, in accordance with the sheet passing speed which is set in advance, by giving priority to the side close to the rolling stand, the cooling water is supplied to the compartment 22a of the nozzle 23 for injecting cooling water, the other, the three-way valve 25 provided in the compartment 22a of the nozzle 23 far from the rolling stand to open toward the drainage header 28 or the drainage area. When the strip passing speed is desired to be improved for increased cooling capability, the three-way valve 25 which has been open to the drain header 28, sequentially from the side close to the rolling stand to the far side, toward the cooling box 22 open to increase the partition 22a for injecting cooling water into the hot-rolled steel sheet 10. Also Until compartment 22a of the nozzle 23 did not injecting cooling water, since the inlet of in the cooling box 22 of the nozzle 23 intrudes into the cooling box 22, until slightly below the upper end of the nozzle 23 water has accumulated, also is always water is filled in the pipe 24, it is possible to inject cooling water from the rapidly nozzle 23 switching the three-way valve 25. When passing plate speed is decelerated, in order from the far side of the compartment 22a from rolling stand, it switches the three-way valve 25 to the drainage side.
[0070]
　As described above, the upper and lower guide 33 provided on the delivery side of the rolling stand provided with a cooling box 22, by the ejection surface of the nozzle 23 in the cooling box 22 and the guide 33 and substantially flush, immediately after rolling after that can cool the hot-rolled steel sheet 10 from the close position, the hot-rolled steel sheet 10 is not caught by the nozzle 23. Further, the guide by 33 to provide a cooling box 22, than the conventional cooling device has been provided as a separate body to avoid the position of the guide 33, it is possible to start cooling from nearby rolling stand. Accordingly, even between space is limited stand, to secure a large rolling direction length of the cooling box 22, it is possible to increase the cooling capacity.
[0071]
　Further, when replacing the rolling rolls 31 of the rolling stand, it is necessary to retract the guide 33 in the rolling direction downstream side, in the case of the cooling box 22 and the guide 33 are separated structure, it collides with the retraction time of the guide 33 lest, it must be separately moved cooling box 22. According to the present invention, since the guide 33 is cooled box 22 is provided, without laborious to retreat the work during rolling roll 31 exchange, it is carried out in the same manner as when the cooling box 22 is not installed it can.
[0072]
　Sheet passing speed in the hot rolling, generally fluctuates due productivity and the like desired. If the change in strip passing speed is high, the steel sheet temperature constant by changing accordingly also the cooling capacity, it is necessary to make uniform the quality in the longitudinal direction. In this case, the injection of water is at low pressures, considering that the cooling ability jet shape is deteriorated is not uniform, with adjustment by only the flow control valve 26, the substantial control range of the cooling water is considered narrow. As in this embodiment, if divided in the cooling box 22, in addition to the control range of the flow rate adjusting valve 26, by performing the water control by divided sections 22a, it is possible to widen the control range. Also, if the on-off valve, the response speed for the cooling water flows from a state in which the supply of cooling water is stopped is delayed, by providing a three-way valve 25 as in this embodiment, by simply switching the direction of injection, a large it is possible to quickly switch in water. Note that the large amount of water, for example, ~ 10 m 2 3 / m 2 a / min.
[0073]
　In the above embodiment, a plurality of nozzles 23 in the cooling box 22, the injection surface was provided so as to guide 33 and substantially coplanar, the ejection surface is not on the guide 33 and coplanar it may be. Ejecting surface of the nozzle 23 as shown in FIG. 10 may be curved toward the downstream side from the rolling direction upstream side. Even such a case can enjoy the same advantages as the above embodiment, the injection angle of the nozzle 23 is made smaller toward the downstream side from the rolling direction upstream side, and a uniform cooling capacity, hot rolled steel sheet it can be uniformly cooled. Also, as in the embodiment of FIG. 10, the injection surface of the upper plurality of nozzles 23 is equal to or guide 33 flush, or may be above the surface. In this case, the injection surface of the lower side of the plurality of nozzles 23 may be left in the same plane as the guide 33.
[0074]
　Further, a plurality of nozzles 23 in the upper side of the cooling box 22 as shown in FIG. 11, the ejection face may be provided so as to be above the guide 33. Although not shown, a plurality of nozzles 23 in the cooling box 22 and the lower ejection face may be provided such that the guide 33 downward. The jetting surface of the plurality of nozzles 23 as the guide 33 is above plane formed, may be disposed on the opposite side of the steel plate design position of the hot-rolled steel sheet 10.
[0075]
　Further, in the above embodiment, farther from the roll stand, although the nozzle firing distance from a plurality of nozzles 23 was larger, nozzle firing distance in the cooling box 22 of the lower side as shown in FIG. 11 is smaller it may be. That is, nozzle firing distance is the largest position may be on the most upstream side of the cooling device 21. Although not shown, nozzle firing distance also in the upper cooling box 22 can be reduced. Farther from the rolling stand, in any case when small and when nozzle firing distance larger, (1) the injection angle of the nozzle firing distance L is the largest position nozzle 23 is the smallest position nozzle firing distance L of less than the injection angle of the nozzle 23, and, (2) spraying angle of the nozzle jet distance L with respect to the nozzle 23 adjacent to the rolling direction is smaller than the side of the nozzle 23 of nozzle firing distance L is larger side nozzles 23 if satisfied two conditions that not less than the injection angle simultaneously, a collision area of ​​the cooling water in the hot-rolled steel sheet 10 can be uniform in the rolling direction, it is possible to receive the same effect as the above-described embodiment it can.
[0076]
　Further, in the above embodiment, a plurality of nozzles 23 were provided in the cooling box 22, is omitted cooling box 22 as shown in FIG. 12, a plurality of nozzles 23 is provided on the guide 33 it may be. Further in this case, every predetermined number of nozzles 23 as shown in FIG. 13 may be constructed of one nozzle group in the two nozzles 23 in the illustrated example. Each nozzle group, the above-described embodiment as well as the three-way valve 25 and the flow regulating valve 26 is connected to a pipe 24 provided further pipe 24 is connected to a water supply header 27 and the water discharge header 28. Then, such a case also, it is possible to receive the same effect as the above embodiment.
[0077]
　A plurality of nozzles 23, among the guide 33 as shown in FIG. 12, or a position adjacent to the downstream side of the guide 33 as shown in FIGS. 8-11, may be provided only in either one of . On the other hand, a plurality of nozzles 23 may be provided at both positions adjacent to the downstream side in the guide 33 of the guide 33 as shown in FIG. 14. In this case, a case where there is a nozzle 23 for injecting cooling water toward the both upper and lower surfaces of the hot rolled steel sheet 10, only a plurality of nozzles 23 for injecting cooling water toward one side, in the guides 33 guide downstream of 33 may be provided on both the adjacent positions. Further, a plurality of nozzles 23 for injecting cooling water toward the both upper and lower surfaces of the hot rolled steel sheet 10 may be both provided at both positions adjacent to the downstream side of the guide 33 in the guide 33. The present invention is provided in both a position adjacent to the downstream side in the guide 33 and the guide 33, it is intended to include those embodiments.
[0078]
　In the above embodiment, a cooling device 21, between the rolling stand F5 and F6, and an example is shown provided at two positions between the rolling stands F6 and F7, the performance of the hot-rolled steel sheet 10 the desired may be only one place between the mill stands F6 and F7. Alternatively, it may be provided only one place in the final exit side of the rolling stand F7 of. In this case (corresponding to the measuring device 50 in FIG. 15.) Measuring device for measuring the dimensions of the hot rolled steel sheet 10 which is provided on the downstream side of the finishing mill 14, temperature, etc. is not affected by water as such, it is preferred to provide a draining system on the downstream side of the cooling device 21.
[0079]
　Further, in the above embodiments, the case of arranging the cooling device 21 to the rolling stand, may be opened rolling rolls 31 of the rolling stand downstream of the cooling device 21. For example, when placing the cooling device 21 between the roll stand F6 and F7, to open the rolling rolls 31 of the rolling stand F7. In this case, since there is no soft reduction after the rapid cooling immediately after rolling, it is possible to improve the mechanical properties of hot-rolled steel sheet 10 by rapid cooling immediately after without finish rolling the adverse effect of soft reduction occurs .
[0080]
　Further, in order to free the rolling roll 31 as described above, preferably not more than the addition of 7mm the roll gap of the rolling rolls 31 to aim thickness value. In such a case, it is possible to limit the amount of plate clean water leaking from the rolling stand. Further, preferably provided with draining device on the outlet side of the rolling stand F7 of the most downstream side (final) (not shown). Usually, the delivery side of the rolling stand F7 of the most downstream side (final), the measuring device is provided for measuring the dimensions and temperature of the hot-rolled steel sheet 10. In such a case, when providing a draining device on the outlet side of the rolling stand F7, even though it does not perform reduction by rolling stand F7, in order to adversely affect the downstream side of the measuring device of the finishing rolling mill 14 is eliminated is there. In the case where the final downstream of the rolling stand F7 of a cooling device 21 of the present invention, the position of the measuring device, the downstream side of the cooling apparatus 21 of the present invention.
[0081]
　In the above embodiment, the downstream side of the measuring device 50 for measuring the delivery side of the final rolling stand F7 of the finishing mill 14 as shown in FIG. 15, the dimensions and temperature of the hot-rolled steel sheet 10, a hot-rolled the upper surface of the steel plate 10 may be provided with a cooling zone 60 for cooling. Cooling zone 60 is provided, for example, on the upstream side of the cooling unit 15. Further, the cooling zone 60, for example a cooling nozzle for ejecting a coolant toward the upper surface of the hot-rolled steel sheet 10 (not shown) are arranged side by side a plurality in the rolling direction. As these cooling nozzles, for example, slit laminar nozzle or pipe laminar nozzles, spray nozzles are used.
[0082]
　Water flow rate of the cooling water from the cooling nozzle of the cooling zone 60 2m 3 / m 2 at-minutes or more, preferably satisfies the following formula (4). 2m 3 / m 2 less than, Equation (4), in a manner similar to the above-mentioned equation (3) shows the required cooling capacity when lowering certain level with a temperature of hot-rolled steel sheet 10. That is, in the left-hand side of equation (4), a molecule (Wb 0.5 is × Mb), a (cooling capacity indicator per unit time per unit area corresponding to the heat flux) × (cooling range length), all It shows the cooling capacity. Further, a denominator (t × V) is the volume of a unit width of the hot rolled steel sheet passing per unit time (the material), it is equivalent to the amount of heat required to lower 1 ℃ hot-rolled steel sheet. As a result of inventors studied intensively, if the left-hand side of equation (4) is a predetermined value less than 0.55 was found to be able to properly control the crystal grain. In this case, for example, by cooling the hot-rolled steel sheet 10 immediately after the rolling at a cooling device 21 provided on the delivery side of the rolling stand F7, to prevent coarsening of crystal grains, the hot-rolled steel sheet 10 further cooling zone 60 by cooling, it aims to grain refinement, it is possible to perform the intensity adjustment.
Wb 0.5 × Mb / (t × V) ≧ 0.55 · · · (4)
However,
wb: water density of the cooling water from the cooling nozzles (m 3 / m 2 ·
min) Mb: the cooling zone 60 cooling range length
(m) t: plate thickness of the hot rolled steel sheet 10
(mm) V: sheet passing speed of the hot rolled steel sheet 10 (m / s)
[0083]
　In the example shown, the cooling zone 60 was provided on the upper surface side of the hot-rolled steel sheet 10 may be provided on the lower surface side, or be provided on both sides of the upper and lower side good. If not installed Should measuring device 50, the cooling zone 60 may be disposed downstream of the cooling device 21 of the present invention.
[0084]
　Having described the preferred embodiments of the present invention, the present invention is not limited to such an example. Those skilled in the art within the scope of the technical idea described in the claims, it is clear that could conceive various modifications, the technical scope of the present invention as for their It is understood to belong ones.
[0085]
　For example, in the above embodiment, and that a plurality of nozzles 23 is omitted or cooling box 22 with a cooling box 22, provided adjacent to the downstream side in the upper and lower sides of the guide 33 and / or the guide 33 but it was, may be provided adjacent to the downstream side in and / or the guide 33 of the upper and lower either one of only the guide 33. In the above embodiment, a plurality of nozzles 23 is omitted or cooling boxes 22 with upper and lower sides of the cooling box 22, the above formula (1) or was not satisfy the equation (2), of the upper and lower one or the other cooling box 22 a plurality of nozzles 23 or that omitting the cooling box 22 with may be meet the above expression (1) or formula (2).
[0086]
　In the above embodiment, the distance between the upper and lower guide 33 is increased toward the downstream side from the rolling direction upstream side, is provided further downstream the rolling direction (horizontal direction) in the guide of the guide 33 it may be provided. Also, such a horizontal direction of the guide, the cooling device may be provided for cooling the hot rolled steel sheet 10. Further, on the downstream side of the cooling apparatus 21 of the present invention may guide no separate cooling devices are provided.
Example 1
[0087]
　Thickness 3 mm, hot-rolled steel sheet width 1200 mm, and hot finish rolling at a strip running speed 400 ~ 600mpm, the delivery side of the rolling stand F6 in FIG. 1, it was placed a cooling device 21 according to this embodiment. Cooling length was 1.2 m, the nozzle rows and five columns. Water flow rate of the cooling water from the nozzle of the upper surface side 7m 3 / m 2 to · minutes, water density of the cooling water from the lower surface side of the nozzle is 10 m 3 / m 2 was · min. The inclination angle of the upper guide 12 degrees, the inclination angle of the lower guide is 0 degree, namely the upper and lower guides of the angle θ is 12 °, the strip passing angle rolling stands F6 hot-rolled steel sheet 10 immediately by looper 34 It was 6 degrees is theta / 2 angle (see FIG. 9). The type of nozzle was full cone nozzle. The spread angle of the position and the nozzle jet of each nozzle (ejection angle of the nozzle) shown in Table 1. Incidentally, in Table 1, is indicative to evaluate also (the difference be less than 10% of the maximum collision area and the minimum collision area of the nozzle jet), the collision area of the reference + 10% difference in the (1) (in the table, the spread angle + 10%) spread angle and spread angle (in the table, the spread angle -10%) from the collision area of the reference becomes -10% difference also together referred.
[0088]
　Then, as shown in Table 2, (in the table, the top surface spread angle) spread angle of the nozzle jets of the upper surface side, (in the table, the lower surface spread angle) spread angle of the lower surface side of the nozzle jets and varying the heat to confirm the temperature variation in the width direction of the rolled steel sheet. Incidentally, in Table 2, it is also collectively denoted width direction maximum temperature drop due to cooling.
[0089]
　In Examples 1-3, the spread angle of the top and bottom surfaces of the nozzle jet, respectively, are smaller on the downstream side from the rolling direction upstream side. Further examples 2 and 3 in top and bottom surfaces of the nozzle both in the equation (1) is satisfied. In this case, 18 ° C. The temperature variation in the width direction, 11 ° C., and 13 ° C., was reduced to 20 ° C. or less. Then, by this way uniformly cool the hot-rolled steel sheet can be produced an excellent hot-rolled steel sheet mechanical properties. Incidentally, the underlined portion of Example 1 in Table 2 does not satisfy the above formula (1), the effect of uniform cooling in comparison with Examples 2-3 was small.
[0090]
　On the other hand, as shown in Comparative Examples 1-3, the spread angle of the nozzle jets of the upstream and downstream, when the same in the rolling direction, the temperature variation 25 ° C. in the width direction, 27 ° C., was as large as 26 ° C. . Therefore, in Comparative Examples 1 to 3, deviations occurred in the mechanical properties of hot-rolled steel sheet.
[0091]
[Table 1]

[0092]
[Table 2]

Example 2
[0093]
　Thickness 3 mm, hot-rolled steel sheet width 1200 mm, and hot finish rolling at a strip running speed 400 ~ 600mpm, the delivery side of the rolling stand F6 in FIG. 1, it was placed a cooling device 21 according to this embodiment. Cooling length was 1.2 m, the nozzle rows and five columns. Water flow rate of the cooling water from the nozzle of the upper surface side 7m 3 / m 2 to · minutes, water density of the cooling water from the lower surface side of the nozzle is 10 m 3 / m 2 was · min. The inclination angle of the upper guide 12 degrees, the inclination angle of the lower guide is 0 degree, the passage plate angle of the rolling stand F6 hot-rolled steel sheet 10 immediately by looper 34 and 0 degrees is the rolling direction (see FIG. 8) . The type of nozzle was full cone nozzle. The spread angle (spray angle of the nozzles) of the position and the nozzle jet of the nozzle shown in Table 3. Incidentally, in Table 3, as an index to evaluate also (the difference be less than 10% of the maximum collision area and the minimum collision area of the nozzle jet), the collision area of the reference + 10% difference in the (1) (in the table, the spread angle + 10%) spread angle and spread angle (in the table, the spread angle -10%) from the collision area of the reference becomes -10% difference also together referred.
[0094]
　Then, as shown in Table 4, (in the table, the top surface spread angle) spread angle of the nozzle jets of the upper surface side, (in the table, the lower surface spread angle) spread angle of the lower surface side of the nozzle jets and varying the heat to confirm the temperature variation in the width direction of the rolled steel sheet. Incidentally, in Table 4, it is also collectively denoted width direction maximum temperature drop due to cooling.
[0095]
　In Example 4, the spread angle of the nozzle jets of the upper surface side, the same or decreases downstream from the rolling direction upstream side, in the further embodiment 5, the nozzle of the upper surface side satisfies the above formula (1). In this case, 18 ° C. The temperature variation in the width direction, and 11 ° C., was reduced to 20 ° C. or less. Then, by this way uniformly cool the hot-rolled steel sheet can be produced an excellent hot-rolled steel sheet mechanical properties. Incidentally, the underlined portion of Example 4 in Table 4 are not satisfy equations (1), the effect of uniform cooling in comparison with Example 5 was small.
[0096]
　On the other hand, as shown in Comparative Examples 4 and 5, when the spread angle of the nozzle jets of the upstream side and the downstream side in the same in the rolling direction, the temperature variation 27 ° C. in the width direction, was as large as 29 ° C.. Therefore, in Comparative Examples 4 and 5, the deviation occurs in the mechanical properties of hot-rolled steel sheet.
[0097]
[table 3]

[0098]
[Table 4]

Example 3
[0099]
　Thickness 3 mm, hot-rolled steel sheet width 1200 mm, and hot finish rolling at a strip running speed 400 ~ 600mpm, the delivery side of the rolling stand F6 in FIG. 1, it was placed a cooling device 21 according to this embodiment. Cooling length was 1.2 m, the nozzle rows and five columns. Water flow rate of the cooling water from the nozzle of the upper surface side 7m 3 / m 2 to · minutes, water density of the cooling water from the lower surface side of the nozzle is 10 m 3 / m 2 was · min. The inclination angle of the upper guide 12 degrees, the inclination angle of the lower guide is 0 degree, namely the upper and lower guides of the angle θ is 12 °, the strip passing angle rolling stands F6 hot-rolled steel sheet 10 immediately by looper 34 It was 6 degrees is theta / 2 angle (see FIG. 9). The type of nozzle was oval spray nozzle. The spread angle of the major axis and the minor axis of a position and the nozzle jet of each nozzle (ejection angle of the nozzle) shown in Table 5. Incidentally, in Table 5, as an index to evaluate also (the difference be less than 10% of the maximum collision area and the minimum collision area of the nozzle jet), the collision area of the reference + 10% difference in the (2) (in the table, the spread angle + 10%) spread angle and spread angle (in the table, the spread angle -10%) from the collision area of the reference becomes -10% difference also together referred.
[0100]
　Then, as shown in Table 6, (in the table, the major axis divergence angle and short 径広 rising angle) spread angle of the nozzle jets of the upper surface side and, in the spread angle (Table of the lower surface side of the nozzle jet diameter divergence angle and minor axis spread angle) and was allowed to vary, to confirm the temperature variation in the width direction of the hot-rolled steel sheet. Incidentally, in Table 6, it is also collectively denoted width direction maximum temperature drop due to cooling.
[0101]
　In Example 6, the major axis divergence angle and short 径広 rising angle of the nozzle jets of the upper surface, each major axis divergence angles and short 径広 rising angle of the lower surface side of the nozzle jet, is the same or smaller on the downstream side from the rolling direction upstream side there. In such a case, it could reduce the temperature fluctuation in the width direction in 17 ° C.. Then, by this way uniformly cool the hot-rolled steel sheet can be produced an excellent hot-rolled steel sheet mechanical properties. However, it underlined in Example 6 in Table 6 do not satisfy the above expression (2).
[0102]
　Further, the major axis divergence angle of the major axis divergence angles and short 径広 rising angle, the lower surface nozzle jet of the upper surface of the nozzle jet of Example 7, compared to the most downstream side (1200 mm) the most upstream side (0 mm) and minor axis spread angle is small, respectively. Further, the major axis divergence angle and short 径広 rising angle of the nozzle jets of the upper surface side, respectively major axis divergence angle and short 径広 rising angle of the nozzle jets of the lower surface side, is smaller on the downstream side from the rolling direction upstream side, further, the upper surface both sides and the lower surface side satisfies the above expression (2) to. In such a case, it could be sufficiently small and 12 ° C. The temperature variation in the width direction.
[0103]
[table 5]

[0104]
[Table 6]

Example 4
[0105]
　Thickness 3 mm, hot-rolled steel sheet width 1200 mm, and hot finish rolling at a strip running speed 400 ~ 600mpm, the delivery side of the rolling stand F6 in FIG. 1, it was placed a cooling device 21 according to this embodiment. Cooling length was 1.2 m, the nozzle rows and five columns. Water flow rate of the cooling water from the nozzle of the upper surface side 7m 3 / m 2 to · minutes, water density of the cooling water from the lower surface side of the nozzle is 10 m 3 / m 2 was · min. The inclination angle of the upper guide 12 degrees, the inclination angle of the lower guide is 0 degree, the passage plate angle of the rolling stand F6 hot-rolled steel sheet 10 immediately by looper 34 and 0 degrees is the rolling direction (see FIG. 8) . The type of nozzle was oval spray nozzle. The spread angle of the major axis and the minor axis of a position and the nozzle jet of each nozzle (ejection angle of the nozzle) shown in Table 7. In Table 7 are indicative to evaluate also (the difference be less than 10% of the maximum collision area and the minimum collision area of the nozzle jet), the collision area of the reference + 10% difference in the (2) (in the table, the spread angle + 10%) spread angle and spread angle (in the table, the spread angle -10%) from the collision area of the reference becomes -10% difference also together referred.
[0106]
　Then, as shown in Table 8, (in the table, the major axis divergence angle and short 径広 rising angle) spread angle of the nozzle jets of the upper surface side and, in the spread angle (Table of the lower surface side of the nozzle jet diameter divergence angle and minor axis spread angle) and was allowed to vary, to confirm the temperature variation in the width direction of the hot-rolled steel sheet. Incidentally, in Table 8, it is also collectively denoted width direction maximum temperature drop due to cooling.
[0107]
　In Example 8, each major axis divergence angles and short 径広 rising angle of the nozzle jet surface side becomes smaller in the downstream side from the rolling direction upstream side, further the upper surface nozzle (major axis side) satisfies the above expression (2) ing. In such a case, it could reduce the temperature fluctuation in the width direction in 16 ° C.. Then, by this way uniformly cool the hot-rolled steel sheet can be produced an excellent hot-rolled steel sheet mechanical properties. However, it underlined in Example 8 in Table 8 do not satisfy the above expression (2).
[0108]
　In Example 9, the major axis divergence angle and short 径広 rising angle of the nozzle jets of the upper surface side as compared to the most downstream side (1200 mm) the most upstream side (0 mm) is small, respectively. Further, each of the major axis divergence angle and short 径広 rising angle of the nozzle jets of the upper surface side is adapted the same or smaller on the downstream side from the rolling direction upstream side, further, satisfies both the upper surface and the lower surface side of the above equation (2) there. In such a case, the temperature variation in the width direction can 11 ° C. and sufficiently small, uniform cooling effect as compared with Examples 8 was large.
[0109]
[Table 7]

[0110]
[Table 8]

Example 5
[0111]
　The hot-rolled steel sheet conditions shown in Table 9 in the plate width 1200 mm, hot finish rolling, the delivery side of the rolling stand F6 in FIG. 1, it was placed a cooling device 21 according to this embodiment. Water flow rate of the cooling length-upper and lower surfaces are both assumed in Table 9, the nozzle array is 5 columns. The inclination angle of the upper guide 12 degrees, the inclination angle of the lower guide is 0 degree, namely the upper and lower guides of the angle θ is 12 °, the strip passing angle rolling stands F6 hot-rolled steel sheet 10 immediately by looper 34 0 degrees and the. The type of nozzle was full cone nozzle. Spread angle position and the nozzle jet of each nozzle (ejection angle of the nozzle) are as shown in Table 3. The angular spread as in Example 4 in Table 4 was set. Table 9 shows the results. According indicator of equation (3) (left side 0.08 or more expressions (3)), if the condition satisfying the formula (3) as shown in Examples 10-18, the temperature drop of the steel sheet Ar 3 transformation temperature from a higher temperature Ar 3 were able to obtain a 40 ° C. or higher temperature drop that can be cooled to a transformation temperature -30 ° C. or less. However, in a state which does not satisfy the condition of Equation (3) as shown in Comparative Examples 6-9, the temperature drop is at 40 ° C. or less, there is not sufficient cooling to obtain the effect of the desired metal structure refinement It was.
[0112]
[Table 9]

Example 6
[0113]
　Thickness 3 mm, hot-rolled steel sheet width 1200 mm, and hot finish rolling at a strip running speed 400 ~ 600mpm, the delivery side of the rolling stand F6 in FIG. 1, it was placed a cooling device 21 according to this embodiment. Cooling length was 1.2 m, the nozzle rows and five columns. Water flow rate of the cooling water from the nozzle of the upper surface side 7m 3 / m 2 to · minutes, water density of the cooling water from the lower surface side of the nozzle is 10 m 3 / m 2 was · min. The inclination angle of the upper guide 12 degrees, the inclination angle of the lower guide is 0 degree, the passage plate angle of the rolling stand F6 hot-rolled steel sheet 10 immediately by looper 34 and 0 degrees is the rolling direction (see FIG. 8) . The type of nozzle was full cone nozzle. Spread angle position and the nozzle jet of each nozzle (ejection angle of the nozzle) are as shown in Table 3.
[0114]
　Then, as shown in Example 4 in Table 4, setting (in the table, the top surface spread angle) spread angle of the nozzle jets of the upper surface side, (in the table, the lower surface spread angle) spread angle of the lower surface side of the nozzle jet and did. To F7 outlet side of the stand, a draining device is installed, F7 was changing the gap of the stand from the plate thickness + 3mm up to + 15mm, will be a lot runoff water more than the thickness + 7mm, F7 draining water of the stand delivery side Otherwise more than 1.5 times that of less thickness + 7 mm, the downstream side of the draining device, portions that can not thickness measurements or plate temperature measurement has been found to occur.
Example 7
[0115]
　Thickness 3 mm, hot-rolled steel sheet width 1200 mm, and hot finish rolling at a strip running speed 400 ~ 600mpm, the delivery side of the rolling stand F7 of Figure 1, it was placed a cooling device 21 according to this embodiment. Cooling length was 1.2 m, the nozzle rows and five columns. Water flow rate of the cooling water from the nozzle of the upper surface side 7m 3 / m 2 to · minutes, water density of the cooling water from the lower surface side of the nozzle is 10 m 3 / m 2 was · min. The inclination angle of the upper guide 12 degrees, the inclination angle of the lower guide is 0 degree. Since the rear of the rolling stand F7 looper 34 is not installed, passing plate angle of the rolling stand F7 hot-rolled steel sheet 10 immediately becomes zero degree is rolling direction. The type of nozzle was full cone nozzle. Spread angle position and the nozzle jet of each nozzle (ejection angle of the nozzle) are as shown in Table 3.
[0116]
　Then, as shown in Example 4 in Table 4, setting (in the table, the top surface spread angle) spread angle of the nozzle jets of the upper surface side, (in the table, the lower surface spread angle) spread angle of the lower surface side of the nozzle jet and did. The delivery side of the rolling stand F7, draining device is installed, it rolled draining water stand F7 delivery side, by opening the rolling roll rolling stand F7 is installed a cooling device 21 on the outlet side of the rolling stand F6 draining device as compared with the case of example 6 was to function as, was set to twice or more, at the downstream side of the draining device was found not to affect the thickness measurement and the plate temperature measurement.
Example 8
[0117]
　Thickness 3 mm, hot-rolled steel sheet width 1200 mm, and hot finish rolling at a strip running speed 400 ~ 600mpm, the delivery side of the rolling stand F7 of Figure 1, it was placed a cooling device 21 according to this embodiment. Cooling length was 1.2 m, the nozzle rows and five columns. Water flow rate of the cooling water from the nozzle of the upper surface side 7m 3 / m 2 to · minutes, water density of the cooling water from the lower surface side of the nozzle is 10 m 3 / m 2 was · min. The inclination angle of the upper guide 12 degrees, the inclination angle of the lower guide is 0 degree. Since the rear of the rolling stand F7 looper 34 is not installed, passing plate angle of the rolling stand F7 hot-rolled steel sheet 10 immediately becomes zero degree is rolling direction. The type of nozzle was full cone nozzle. Spread angle position and the nozzle jet of each nozzle (ejection angle of the nozzle) are as shown in Table 3.
[0118]
　Further, in the present embodiment further a cooling zone 60 shown in FIG. 15, the upstream side of the cooling section 15, and and placed on the upper surface side of the hot-rolled steel sheet 10. Cooling range length of the cooling zone 60 (equipment length) was 15 m. Water flow rate of the cooling water from the cooling nozzle of the cooling zone 60 3m 3 / m 2 was · min. Cooling zone 60 in the present embodiment satisfies the above expression (4).
[0119]
　When performing the cooling of hot-rolled steel sheet 10 and the cooling device 21 according to the cooling zone 60 as in this embodiment, the hot-rolled steel sheet as compared with the case of Example 7 without the cooling zone 60 provided with a cooling device 21 We were able to further promote the miniaturization of the 10 metallographic.
Industrial Applicability
[0120]
　The present invention is applied as a cooling device and a cooling method for grain refinement of the crystal grain size of the hot-rolled steel sheet after finish rolling in the hot rolling process, for example, high tensile steel (high tension) or ultra-low carbon steel ( IF steel: Interstitial atom free steel) is suitable in improving the quality effects of high-quality steel, such as.
DESCRIPTION OF SYMBOLS
[0121]
1 hot rolling mill
5 slab
6 crude bar
10 hot-rolled steel sheet
11 heating furnace
12 widthwise rolling mill
13 rough rolling mill
14 finishing mill
15 cooling unit
16 the winding device
21 cooling unit
22 cooling boxes
22a compartments
23 nozzle
23a injection port
23b end
24 pipe
25 three-way valve
26 flow regulating valve
27 water supply header
28 drainage header
31 rolling rolls (working
rolls) 32 roll cooling water header
33 guide
34 looper
50 measuring device
60 cooling zone
F1, F2, F3, F4, F5, F6, F7 rolling stand (finish rolling stand)

The scope of the claims
[Requested item 1]
In the hot finish rolling mill comprising a plurality of rolling stands having a plurality of nozzles for injecting cooling water toward one or both of the upper and lower surfaces of the hot-rolled steel sheet immediately after being rolled in the rolling stand,
said nozzle of the guide provided above and below the exit side of the rolling stand, provided adjacent to the downstream side in or the guide one or both of the guide,
the hot-rolled to be set between the upper and lower guide with respect to the steel plate design position of the steel plate, nozzle firing distance along the jet central axis between the injection port of the nozzle to the steel sheet design position, a cooling device for changing the position of the rolling direction of the nozzle,
the injection angle of the nozzle of the nozzle firing distance highest position is smaller than the injection angle of said nozzle of said nozzle firing distance is the smallest position,
the nozzle firing distance is large Runishitagai, injection angle of the nozzle is characterized by comprising the same or smaller, the cooling device of hot-rolled steel sheet.
[Requested item 2]
The steel sheet design position is characterized in that it is set to the tangent plane at the top vertex of the lower rolling roll of the rolling stand, cooling device for a hot-rolled steel sheet according to claim 1.
[Requested item 3]
The steel sheet design position is characterized in that it is set to 1/2 angle of the plane of the angle between the upper and lower guide, the cooling device for a hot-rolled steel sheet according to claim 1.
[Requested item 4]
The nozzle firing distance is the smallest position, the located on the most upstream side of the cooling device,
the nozzle firing distance is the largest position of claims 1 to 3, characterized in that on the most downstream side of the cooling device cooling device for a hot-rolled steel sheet according to any one.
[Requested item 5]
The nozzle firing distance is the largest position, the located on the most upstream side of the cooling device,
the nozzle firing distance is the smallest position, according to claim 1, characterized in that the most downstream side of the cooling device cooling device for a hot-rolled steel sheet according to any one.
[Requested item 6]
The nozzle is characterized in that provided inside the cooling box, cooling device for a hot-rolled steel sheet according to any one of claims 1 to 5.
[Requested item 7]
Injection port of the nozzle of the cooling box, located on the steel plate design position side of the surface and the back side of the same surface or the surface (the center side of the cooling box),
the opposite end the jet port of the nozzle , characterized in that it projects into the cooling box from the inner surface position of the cooling box inside, the cooling device for a hot-rolled steel sheet according to claim 6.
[Requested item 8]
Injection port of the nozzle is characterized in that the guide is arranged in a plane formed on the same plane, a cooling device for a hot-rolled steel sheet according to any one of claims 1 to 6.
[Requested item 9]
Injection port of the nozzle is characterized in that the guide is arranged on the opposite side of the steel plate design position from a plane formed, the cooling device for a hot-rolled steel sheet according to any one of claims 1 to 6, .
[Requested item 10]
Wherein the nozzle is a full cone nozzle,
impingement region in the hot-rolled steel sheet of the cooling water injected from said nozzle is characterized by satisfying the following formula (1), in any one of claims 1 to 9 cooling device for a hot-rolled steel sheet according.
[Number 1]

However,
L: nozzle firing distance (m)
alpha: nozzle spray angle (degrees)
i, j: any column of the nozzles provided in the rolling direction (i columns, j columns)
[Requested item 11]
Wherein the nozzle is oblong spray nozzles,
impingement area of the hot-rolled steel sheet of the cooling water injected from said nozzle is characterized by satisfying the following formula (2), any one of claims 1 to 9, cooling device for a hot-rolled steel sheet according to.
[Number 2]

However,
L: nozzle firing distance (m)
beta: nozzle length directions injection angle (degrees)
gamma: nozzle minor axis injection angle (degrees)
i, j: Any of the nozzles provided in the rolling direction column (i row, j column)
[Requested item 12]
Water flow rate of the cooling water from the nozzle is characterized by satisfying the following formula (3), a cooling device for a hot-rolled steel sheet according to any one of claims 1 to 11.
Wa 0.5 × Ma / (t × V) ≧ 0.08 · · · (3)
However,
Wa: water density of the cooling water from the nozzle (m 3 / m 2 · min)
Ma: in said cooling device cooling range length of the rolling direction (m)
t: plate thickness of the hot-rolled steel sheet (mm) V:
sheet passing speed of the hot-rolled steel sheet (m / s)
[Requested item 13]
Downstream of the measuring device performs measurement of the hot-rolled steel sheet exit side of the rolling stand at the most downstream side of the hot finish rolling mill, jet cooling water toward one or both of the upper and lower surfaces of the hot-rolled steel sheet to place multiple cooling zone with a cooling nozzle, the water density of the cooling water from the cooling nozzle 2m 3 / m 2 at-minutes or more, and satisfies the following formula (4), claim cooling device for a hot-rolled steel sheet according to any one of 1 to 12.
Wb 0.5 × Mb / (t × V) ≧ 0.55 · · · (4)
However,
wb: the water density of the cooling water from the cooling nozzles (m 3 / m 2 ·
min) Mb: the cooling zone cooling range length of the rolling direction in (m)
t: plate thickness of the hot-rolled steel sheet (mm) V:
sheet passing speed of the hot-rolled steel sheet (m / s)
[Requested item 14]
Wherein said cooling device between rolling stands arranged,
than said cooling device opens the rolling rolls of the rolling stands downstream, and following the addition of 7mm the roll gap of the rolling rolls to aim thickness values,
heat in the delivery side of the rolling stands downstream side between the finishing rolling mill, characterized by placing a drainage device for removing the plate clean water leaked from rolling stands of the most downstream side, of the claims 1 to 13, cooling device for a hot-rolled steel sheet according to any one.
[Requested item 15]
Said cooling device on the outlet side of the rolling stand at the most downstream side of the hot finish rolling mill disposed,
downstream of the cooling device, placing the draining device for removing the plate clean water leaked from the cooling device wherein the cooling device for a hot-rolled steel sheet according to any one of claims 1 to 13.
[Requested item 16]
Wherein the plurality of nozzles, a row is disposed in the width direction, constitutes a plurality of nozzle groups aligned in the rolling direction in accordance a predetermined number of the column in the rolling direction,
the number of the plurality of nozzle groups, with a maximum , the same number of columns in the rolling direction of the nozzle provided in the rolling direction,
the pipe, each cooling water is supplied to each nozzle group is connected,
wherein each each pipe three-way valve and flow control valve is and it is provided, the cooling device for a hot-rolled steel sheet according to any one of claims 1 to 15.
[Requested item 17]
A cooling method using a cooling device for a hot-rolled steel sheet according to any one of claims 1 to 16,
in the delivery side of the rolling stand of the hot finish rolling mill, one of the upper and lower surfaces of the hot rolled steel sheet or for both, from the nozzle, characterized by injecting cooling water, the cooling method of hot rolled steel sheet.
[Requested item 18]
A cooling method using a cooling device for a hot-rolled steel sheet according to claim 16,
in the delivery side of the rolling stand of the hot finish rolling mill, to one or both of the upper and lower surfaces of the hot-rolled steel sheet, the nozzle from upon injecting cooling water,
adjust the number of the rolling direction of the nozzle group for ejecting a cooling water to the hot-rolled steel sheet according to the sheet passing speed of the hot-rolled steel sheet,
when the through plate speed increases is to sequentially farther from the side close to the rolling stand, increasing the number of the nozzle groups for ejecting cooling water to the hot-rolled steel sheet,
when the through plate speed is decelerated, the far side from the rolling stand in turn, characterized in that the cooling water flows closes the injection into the hot-rolled steel sheet from the nozzles of the nozzle group to the drainage side, the cooling method of hot rolled steel sheet.