JP5613997B2 - Hot-rolled steel sheet cooling device, hot-rolled steel sheet manufacturing apparatus and manufacturing method - Google Patents

Description

  The present invention relates to a hot-rolled steel sheet cooling apparatus, a hot-rolled steel sheet manufacturing apparatus, and a manufacturing method. The present invention particularly relates to a hot-rolled steel sheet cooling apparatus and a hot-rolled steel sheet manufacturing apparatus that are suitably used when manufacturing a hot-rolled steel sheet having ultrafine crystal grains, and a hot-rolled steel sheet having ultrafine crystal grains. It relates to a manufacturing method.

  Steel materials used for automobiles, structural materials, etc. are required to have excellent mechanical properties such as strength, workability, and toughness. It is effective to reduce the size. Therefore, many manufacturing methods for obtaining a hot rolled steel sheet having fine crystal grains have been sought. Further, if the crystal grains are refined, it is possible to produce a high-strength hot-rolled steel sheet having excellent mechanical properties even if the addition amount of the alloy element is reduced.

  As a method of refining crystal grains of hot-rolled steel sheet, particularly in the latter stage of hot finish rolling, high-pressure rolling is performed to refine austenite grains and accumulate rolling strain in the grains, after cooling (or after transformation) And the like, and the like. And, from the viewpoint of suppressing recrystallization and recovery of austenite grains and promoting ferrite transformation, it is effective to cool the steel sheet to a predetermined temperature or lower (for example, 720 ° C. or lower) in a short time after rolling. . In other words, in order to manufacture hot rolled steel sheets with fine crystal grains, it is effective to install a cooling device that can cool faster than before, followed by hot finish rolling, and rapidly cool the rolled steel sheet. It is.

For example, Patent Literature 1 discloses a material control method and apparatus for hot-rolled material as a technique for rapidly cooling a steel plate immediately after rolling on the exit side of the rolling mill to obtain a steel plate having excellent characteristics. In Patent Document 1, in order to rapidly cool the material immediately after rolling, the water cooling nozzle of the latest rapid cooling device is attached to the roll bite so as to be inclined, and the hot rolling in which cooling water is injected at an injection pressure of 50 to 200 kg / cm ^2. A material control method for a material is disclosed. Moreover, as a technique aiming at providing the hot rolling equipment and hot rolling method of a steel plate excellent in equipment cost and equipment maintainability, for example, Patent Document 2 discloses a rod-shaped cooling water on the rolling mill side. A hot-rolling equipment for steel sheets provided with a header having nozzles facing and spraying at an inclination angle of 30 ° to 60 ° is disclosed. Moreover, as a technique which enables manufacture of the hot-rolled steel plate which has a fine crystal grain, for example, in patent document 3, the steel plate which consists of carbon steel or low alloy steel containing C: 0.01-0.3 mass%, or A method of producing a hot-rolled steel sheet by hot rolling a slab in multiple passes, characterized in that the final rolling pass is completed at a temperature of Ar ₃ points or higher and then cooled to 720 ° C. or lower within 0.4 seconds. The manufacturing method of the ultra-fine grain hot-rolled steel sheet is disclosed.

JP 60-243226 A JP 2007-61838 A Japanese Patent Laid-Open No. 2005-213595

However, the techniques disclosed in the above patent documents have the following problems.
(1) When a large amount of cooling water is sprayed toward the steel plate in order to rapidly cool the steel plate immediately after rolling, it is considered that a large amount of cooling water stays particularly on the upper surface of the steel plate. If a large amount of cooling water stays in the vicinity of the exit of the roll bite, it becomes difficult to rapidly cool the steel plate and to cool the steel plate uniformly, and ultrafine crystal grains (for example, crystal grains having an average grain size of 3 μm or less) It is difficult to produce a hot-rolled steel sheet (hereinafter sometimes referred to as “ultrafine grained steel”) having the same. Therefore, in order to produce ultrafine-grained steel, it is particularly important to improve the drainage on the upper surface of the steel plate. However, the technique disclosed in Patent Document 1 does not take measures to improve drainage. Moreover, the technique currently disclosed by patent document 2 is a technique in which a cooling water is actively retained on the upper surface of a steel plate. Patent Document 3 does not disclose a detailed configuration of a cooling device that can cool a steel plate to 720 ° C. within 0.4 seconds from the end of the final rolling pass. Therefore, even if the techniques disclosed in Patent Documents 1 to 3 are simply used, it is difficult to rapidly cool the steel sheet, and it is difficult to produce ultrafine-grained steel.
(2) The rapid cooling required when producing ultrafine-grained steel has a cooling rate of at least 400 ° C./s or more as shown in Patent Document 3, for example, and nucleate boiling cooling the steel sheet Is required. In the rapid cooling required when producing ultrafine-grained steel, it is necessary to make the cooling water collide with the steel plate surface at a predetermined pressure or higher, whereas in the technique disclosed in Patent Document 2, It merely defines the injection angle of the rod-shaped cooling water supplied to the steel plate. Further, in Patent Document 2, the cooling water sprayed onto the steel sheet flows to the exit of the roll bite, so that it can be cooled immediately after the roll bite part. However, the cooling water flowing on the steel plate after the collision can be sufficiently quenched. In addition, the cooling of this portion hardly contributes to the formation of ultrafine crystal grains.
(3) The area of the collision surface which collides with the surface of a steel plate is small compared with the cooling water sprayed from the flat spray nozzle. Therefore, when trying to rapidly cool the steel sheet using the technique disclosed in Patent Document 2, uneven cooling tends to occur between a portion where the cooling water collides with the steel plate surface and a portion where the cooling water does not collide.
(4) When a flat spray nozzle is simply applied to the techniques disclosed in Patent Document 1 and Patent Document 2, the high-pressure jet water sprayed from each flat spray nozzle adjacent in the width direction of the steel sheet Cooling water interference or the like occurs at the boundary part (the part where the two collision areas overlap), and cooling unevenness occurs in the width direction of the steel sheet.
That is, the technique disclosed in the above patent document has a problem that it is difficult to produce ultrafine-grained steel. Moreover, there also existed a problem that it was difficult to cool a steel plate uniformly.

  Accordingly, the present invention provides a hot-rolled steel sheet cooling device and a hot-rolled steel sheet manufacturing apparatus capable of manufacturing a hot-rolled steel sheet having ultrafine crystal grains, and a method for producing a hot-rolled steel sheet having ultrafine crystal grains. It is an issue to provide.

The present inventors conducted research on the production of ultrafine-grained steel and obtained the following knowledge.
1) As shown in FIG. 14, after rolling in a temperature range of Ar ₃ points or more and completing cooling to 720 ° C. within 0.2 seconds, the crystal grains can be further refined. .
2) Ar cooling at 100 ° C. from 820 ° C. to 720 ° C. at ₃ or more points, for example, is to be completed within 0.2 seconds after rolling, it is necessary to perform rapid cooling at a cooling rate of 600 ° C./s . When the steel plate is cooled at a cooling rate of 600 ° C./s, the time required for lowering the temperature of the steel plate by 100 ° C. is 0.167 seconds. Therefore, in order to finish the cooling within 0.2 seconds, it is necessary to start the cooling within 0.033 seconds after rolling. For example, when the steel plate is moved at a speed of 10 m / s, the moving distance in 0.033 seconds is 0.33 m. Therefore, the rapid cooling after rolling starts within a distance corresponding to the radius of the work roll of the final stand in the hot rolling mill row, and it is necessary to rapidly cool almost continuously in the final stand in the hot rolling mill row.
3) There is a correlation between the pressure at which the cooling water jetted onto the steel plate collides with the steel plate and the cooling rate of the steel plate (see FIG. 12), and by increasing the pressure at which the cooling water strikes the steel plate, It becomes possible to increase the cooling rate. Therefore, in order to perform rapid cooling at a cooling rate of 600 ° C./s or more, it is necessary to inject high-pressure jet water toward the steel plate, and it is necessary to cool the steel plate by nucleate boiling.
4) In order to secure the collision pressure of high-pressure jet water on the steel plate surface, which is required for rapidly cooling the steel plate at a cooling rate of 600 ° C./s or more, the amount of cooling water staying on the steel plate surface is reduced. It is effective. Therefore, it is important to improve drainage in order to produce ultrafine-grained steel.
5) Even when producing ultrafine-grained steel, it is important to cool the steel plate uniformly. If drainage from the steel sheet surface is hindered, the level of cooling water staying on the steel sheet surface may increase, which may increase cooling non-uniformity. Therefore, it is important to improve drainage from the aspect of uniform cooling.
6) In order to improve facility maintainability, it is particularly effective to reduce the amount of water reaching the drive unit of the equipment. In order to reduce this amount of water, it is effective to specify the direction of the flow of cooling water on the steel sheet surface.

  The present invention has been completed based on the above findings, and the gist thereof is as follows.

  The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated embodiments. In the following, the angle formed by the axial direction of the flat spray nozzle and the vertical direction may be referred to as “vertical in-plane inclination angle”.

The first aspect of the present invention is arranged on the downstream side of the final stand (11g) in the hot finish rolling mill row (11) and can inject high-pressure jet water toward the steel plate (1) transported through the pass line. A hot-rolled steel sheet cooling device (20) provided with a header (21, 22) provided with a plurality of flat spray nozzles (21a, 21a, ..., 22a, 22a, ...) in a section from within a radius corresponding position of the roll to the housing posts outlet side of the final stand, toward the steel sheet is continuously injectable constructed from a flat spray nozzle a high-pressure jet water to the conveyance direction of the steel sheet, the flat spray nozzles This is the angle between the longitudinal direction of the jet collision zone formed by the jetted high-pressure jet water colliding with the surface to be cooled and the plate width direction of the steel plate. A twist angle beta is beta ≠ 0, a high-pressure jet water ejected from the flat spray nozzles are arranged on the upstream side of the delivery of at least the steel sheet intersects the vertical plane toward the upstream side in the conveying direction of the steel plate is injected in a direction, at least, a flat spray nozzle for injecting a high-pressure jet water in a direction intersecting a vertical plane toward the upstream side in the transport direction of the steel sheet is the angle between the conveying direction of the axial and the steel sheet horizontal plane A cooling apparatus for hot-rolled steel sheets, characterized in that the inner inclination angle θ2 is θ2 ≠ 0 .

  Here, the “downstream side” refers to the downstream side in the conveying direction of the steel plate (1). The “high pressure jet water” refers to jet water having a pressure capable of nucleate boiling cooling the steel plate (1). Further, “the position corresponding to the radius of the work roll of the final stand” means, as shown in FIG. 3, a portion (more specifically, a portion where the rolled steel plate (1) and the work roll (11 gw, 11 gw) of the final stand are in contact with each other. Are the bottom dead center of the work roll (11 gwu) that contacts the upper surface of the steel plate (1) and the top dead center of the work roll (11 gwd) that contacts the lower surface of the steel plate (1). It may be referred to as a “bite portion”.) From the downstream side in the conveying direction of the steel plate (1) by the radius of the work roll (11gw, 11gw) of the final stand. “From within the position equivalent to the radius of the work roll of the final stand” means between the position equivalent to the radius of the work roll of the final stand and the roll bite part (on the side of the roll bite from the position equivalent to the radius of the work roll of the final stand) ) Is supplied to the surface of the steel plate (1) existing in the high pressure jet water jetted from the nozzles (21a, 21a,..., 22a, 22a,...). The strict start point of the section in which the high-pressure jet water is continuously jetted is the point closest to the upstream side of the portion where the high-pressure jet water directly collides with the steel plate within the position corresponding to the radius of the work roll, that is, the roll bite portion. When the nozzle for injecting high-pressure jet water is installed closest to the work roll of the final stand, the point where the tangent line drawn from the center of the nozzle injection hole to the surface of the work roll reaches the surface of the steel plate This corresponds to the strict start point of the section where jet water is continuously injected. The “housing post exit side of the final stand” refers to the outer surface of the housing post (11gh) of the final stand (the outer surface on the downstream side in the steel plate conveyance direction). Moreover, "it is comprised so that high pressure jet water can be continuously sprayed in the conveyance direction of a steel plate from a nozzle" means a plurality of nozzles (21a, 21a arranged at predetermined intervals in the conveyance direction of a steel plate (1). ,..., 22a, 22a,...), The high pressure jet water can be continuously jetted from the steel plate (1) to the surface. “Torsion angle” refers to the longitudinal direction of a belt-like or oval jet collision zone formed by a high-pressure jet injected from a flat spray nozzle colliding with the surface to be cooled (the jet collision zone is long). In the case of a circle, this is the angle between the major axis direction) and the sheet width direction of the steel sheet. Further, “giving a torsion angle” means that a flat spray nozzle is arranged so that the longitudinal direction of the jet collision area and the plate width direction of the steel sheet are non-parallel. In addition, “the tilt angle in the horizontal plane is given” means that when the top view or the bottom view of the steel sheet that is quenched by the high-pressure jet water sprayed from the flat spray nozzle is described, the transport direction of the steel sheet and the flat spray It means that the flat spray nozzle is arranged so that the axial direction of the nozzle is not parallel.

  In the first aspect of the present invention, it is preferable that a nozzle twist angle is not given to at least a part of the flat spray nozzle.

  Here, “nozzle torsion angle” means, for example, that the header is arranged in parallel and horizontally in the width direction, is cylindrical, and the center axis of the cylinder and the center axis of the flat spray nozzle are arranged in the same plane. In this case, when viewed from the front in the axial direction of the flat spray nozzle, it means an angle formed by the long axis of the oval portion of the flat spray nozzle and the axis of the header (see FIG. 8C). The shape and arrangement of the header are not limited to this. Further, “no nozzle twist angle is given” means that the nozzle twist angle is set to zero.

  Further, in the first aspect of the present invention, when a horizontal plane inclination angle is given to each flat spray nozzle adjacent to the steel plate conveyance direction, the horizontal plane inclination angle is given and adjacent to the steel plate conveyance direction. The flat spray nozzle to be used is a first flat spray nozzle and a second flat spray nozzle, the inclination angle in the horizontal plane given to the first flat spray nozzle is α [rad] (0 <| α | <π), and the second flat spray It is preferable that α · β <0, where β [rad] (0 <| β | <π) is the inclination angle in the horizontal plane applied to the nozzle.

  Here, “α · β <0” means, for example, the inclination in the horizontal plane of the first flat spray nozzle so that high-pressure jet water is jetted toward one end in the width direction of the steel sheet (for example, the working side of the final stand). When the angle is determined, the inclination angle in the horizontal plane of the second flat spray nozzle is determined so that the high-pressure jet water is sprayed toward the other end in the steel sheet width direction (for example, the drive side of the final stand). That means.

  In the first aspect of the present invention, the high-pressure jet water is preferably jetted toward at least the upper surface of the steel plate.

  In the first aspect of the present invention, the average value of the steel plate surface collision pressure of the high-pressure jet water in the section is preferably 3.5 kPa or more.

  Here, the “average value of the steel plate surface collision pressure of the high-pressure jet water” refers to the steel plate surface along a line segment in the steel plate conveyance direction at an arbitrary position in the steel plate width direction, for example, the central portion in the width direction. The collision pressure of high-pressure jet water is measured or calculated and averaged over a predetermined area. In order to uniformly cool the steel plate in the plate width direction, it is desirable to make the average value in the steel plate conveyance direction equal in all regions in the steel plate width direction. Even when considering a surface having a width corresponding to at least the nozzle pitch, it should be equal to the steel plate surface collision pressure obtained on the line segment. Therefore, in obtaining the average value in the steel plate conveyance direction, the average collision pressure on the steel plate surface handled by one nozzle may be obtained for each nozzle row arranged in the steel plate conveyance direction and averaged in the steel plate conveyance direction. In the present invention, for example, as shown in FIG. 13, when the nozzle pitch in the steel plate width direction is A and the nozzle pitch in the steel plate conveyance direction, that is, the header interval is B, the parallelogram whose area is represented by A × B. The average value of the pressure of the cooling water that collided with the steel sheet, which is derived by dividing the force of the cooling water that collided with the region (collision force) by the area A × B of the parallelogram, It can be set as the average value of the steel plate surface collision pressure in the steel plate conveyance direction.

  Further, in the first aspect of the present invention, a space capable of discharging cooling water is secured between both end faces in the steel plate width direction of the cooling device (20) and both end faces in the steel plate width direction of the final stand (11g). It is preferable.

  Here, the “steel plate width direction both end surfaces of the cooling device (20)” refers to the outer surfaces of the cooling device (20) on both ends in the width direction of the steel plate (1). Moreover, the “steel plate width direction both end surfaces of the final stand (11g)” refers to the inner surfaces of the housing posts (11gh) of the final stand on both ends in the width direction of the steel plate (1).

  Further, in the first aspect of the present invention, a plurality of headers (21, 31, 22, 32) are provided, and at least a part of the headers are in the conveying direction of the steel plate (1) and the width direction of the steel plate (1). It is preferable that the cooling water can be collectively supplied to the nozzles (31a, 31a, ..., 32a, 32a, ...) arranged in a plurality of rows.

  In the first aspect of the present invention, at least a part of the header is configured to be able to collectively supply cooling water to nozzles arranged in a plurality of rows in each of the conveying direction of the steel sheet and the width direction of the steel sheet. A plurality of headers (21, 31) are arranged on the upper surface side of the steel plate, and among the headers provided on the upper surface side of the steel plate, at least the header (31) arranged on the most upstream side in the conveying direction of the steel plate is It is preferable that the header is configured so that the cooling water can be collectively supplied to the nozzles (31a, 31a,...) Arranged in a plurality of rows in each of the conveying direction and the width direction of the steel plate.

  In the first aspect of the present invention, at least a part of the header is configured to be able to collectively supply cooling water to nozzles arranged in a plurality of rows in each of the conveying direction of the steel sheet and the width direction of the steel sheet. A plurality of headers (22, 32) are disposed on the lower surface side of the steel sheet, and among the headers provided on the lower surface side of the steel sheet, at least the header (32) disposed on the most upstream side in the conveying direction of the steel sheet is It is preferable that the header is configured so that the cooling water can be collectively supplied to the nozzles (32a, 32a,...) Arranged in a plurality of rows in each of the conveying direction and the width direction of the steel plate.

  According to a second aspect of the present invention, there is provided a final stand (11g) in the hot finish rolling mill row (11) and a hot-rolled steel sheet cooling device (20) according to the first aspect of the present invention. It is a manufacturing apparatus (10) of a hot-rolled steel sheet, which is provided in order in the conveying direction of 1).

  The third aspect of the present invention is rolled at the final stand (11g) in the hot finish rolling mill (11) using the hot-rolled steel sheet manufacturing apparatus (10) according to the second aspect of the present invention. It is a manufacturing method of a hot-rolled steel plate characterized by including the process of processing the obtained steel plate (1).

  In the present invention, since the steel sheet is continuously cooled by the high-pressure jet water in the section from the position corresponding to the work roll radius of the final stand to the roll post side of the final stand to the housing post exit side of the final stand, the austenite structure It is possible to rapidly cool the rolled steel sheet while suppressing the recovery of heat. Furthermore, in the present invention, the flat spray nozzle is provided with a torsion angle, a vertical in-plane inclination angle, and a horizontal in-plane inclination angle. Uniform cooling can be improved. By improving drainage, it becomes easy to rapidly cool the steel sheet. Therefore, according to the present invention, a hot-rolled steel sheet cooling apparatus and a hot-rolled steel sheet manufacturing apparatus capable of manufacturing a hot-rolled steel sheet having ultrafine crystal grains, and a hot-rolled steel sheet having ultrafine crystal grains are provided. A manufacturing method can be provided.

It is a figure which shows typically a part of manufacturing apparatus of the hot-rolled steel plate concerning this invention. It is a figure which expands and shows the part by which the cooling device of the hot-rolled steel plate of this invention is arrange | positioned from FIG. It is a figure explaining the radius equivalent position of the work roll of the last stand, and the housing post exit side of the last stand. It is a figure explaining vertical in-plane inclination angle theta. It is a figure which shows the form of the high pressure jet water injected from the flat spray nozzle row | line | column to which only perpendicular | vertical in-plane inclination | tilt angle (theta) 1 was provided. It is a figure which shows the form of the high pressure jet water injected from the flat spray nozzle row | line | column to which the perpendicular | vertical in-plane inclination | tilt angle (theta) 1 and the horizontal plane inclination | tilt angle (theta) 2 were provided. It is a figure explaining torsion angle (beta). It is a figure explaining nozzle twist angle (theta) 3. It is a figure which shows three-dimensional arrangement | positioning with a flat spray nozzle and the jet collision area | region formed in the steel plate surface. It is a figure which shows the collision area shape example by the high pressure jet water injected from the 3 flat spray nozzle row | line | column adjacent to the conveyance direction of the steel plate to which the inclination angle in a horizontal surface was provided in different directions. It is a figure which shows typically a part of manufacturing apparatus of the hot-rolled steel plate of this invention concerning other embodiment. It is a figure which shows the relationship between the steel plate conveyance direction average value of the steel plate surface collision pressure of high pressure jet water, and the average cooling rate of a steel plate. It is a figure explaining the steel plate conveyance direction average value of the steel plate surface collision pressure of high pressure jet water. It is a figure which shows the relationship between the required time for cooling to 720 degreeC, and the ferrite particle size obtained.

  Embodiments of the present invention will be described below.

  FIG. 1 is a diagram schematically showing a part of a hot-rolled steel sheet cooling apparatus 20 according to the present invention and a hot-rolled steel sheet manufacturing apparatus 10 according to the present invention provided with the cooling apparatus 20. In FIG. 1, the steel sheet 1 is conveyed from the left (upstream side) to the right (downstream side) of the drawing, and the vertical direction of the drawing is the vertical direction. Hereinafter, the upstream side / downstream side direction may be described as the conveying direction, and the direction of the plate width of the steel plate to be passed through may be described as the steel plate width direction. For ease of viewing, repeated reference numerals may be omitted in the drawings.

  As shown in FIG. 1, a hot-rolled steel sheet manufacturing apparatus 10 of the present invention (hereinafter sometimes simply referred to as “manufacturing apparatus 10”) includes a hot finish rolling mill row 11 and a hot-rolled steel sheet of the present invention. A cooling device 20 (hereinafter, simply referred to as “cooling device 20”), a transport roll 12 and a pinch roll 13 are provided. Although illustration and explanation are omitted, a heating furnace, a rough rolling mill row, and the like are arranged on the upstream side of the hot finish rolling mill row 11, and the conditions of the steel sheet rolled by the hot finish rolling mill row 11 are adjusted. ing. On the other hand, on the downstream side of the pinch roll 13, other cooling devices, winders and the like are arranged, and various facilities for shipping the steel plate as a coil are arranged.

  A hot-rolled steel sheet is generally manufactured as follows. That is, the rough bar extracted from the heating furnace and rolled to a predetermined thickness by a roughing mill is continuously rolled to a predetermined thickness by the hot finish rolling mill row 11 while the temperature is controlled. Thereafter, it is rapidly cooled by the cooling device 20. Here, the cooling device 20 includes the work rolls 11gw and 11gw of the final stand from the inside of the housing post 11gh of the final stand of the hot finish rolling mill row 11 (see FIG. 2). 11 gw may be referred to as “work roll 11 gwu”, and the work roll 11 gw in contact with the lower surface of the steel plate 1 may be referred to as “work roll 11 gwd”). And the steel plate which passed the pinch roll 13 is cooled to predetermined winding temperature by another cooling device after that, and is wound up in a coil form with the winder.

  As described above, the manufacturing apparatus 10 includes the hot finish rolling mill row 11. In this embodiment, seven rolling mills (11a, 11b, 11c,..., 11g) are arranged in parallel along the transport direction. Each of the rolling mills 11a, 11b,..., 11g is a rolling mill that constitutes a so-called stand, and can satisfy conditions such as thickness, mechanical properties, and surface quality required for the final product. Thus, the rolling reduction is set.

  FIG. 2 is an enlarged view showing a portion where the cooling device 20 is arranged. FIG. 2 shows a state of the cooling device 20 that rapidly cools the upper surface and the lower surface of the steel plate immediately after passing through the roll bite portion of the final stand 11g, and the dotted line in FIG. 2 represents high-pressure jet water. FIG. 3 is a view for explaining the position corresponding to the radius of the work roll of the final stand and the exit side of the housing post 11gh of the final stand 11g. 3 is the upstream side in the conveyance direction of the steel sheet (hereinafter, simply referred to as “upstream side”), and the right side of the plane of FIG. 3 is the downstream side in the conveyance direction of the steel sheet (hereinafter, simply “downstream side”). ”). Hereinafter, the cooling device 20 will be described in detail with reference to FIGS. 2 and 3.

  As shown in FIGS. 2 and 3, the cooling device 20 is disposed on the downstream side of the final stand 11 g in the hot finish rolling mill row 11. The cooling device 20 includes a plurality of flat spray nozzles 21 a, 21 a,... (Hereinafter, simply referred to as “nozzle 21 a”, etc.) that inject high-pressure jet water toward the upper surface of the steel plate 1. .., And flat spray nozzles 22a, 22a,... (Hereinafter, simply referred to as “nozzle 22a” or the like) that inject high-pressure jet water toward the lower surface of the steel plate 1. Are provided with a plurality of headers 22, 22,... Connected in the width direction of the steel plate 1. In the cooling device 20, the headers 21, 21,... And the headers 22, 22,... Are arranged in a plurality of rows in the conveying direction of the steel plate 1, and the nozzles 21a and 22a are arranged inside the housing post of the final stand 11g. In addition, it is continuously arranged downstream of the housing post of the final stand 11g. The nozzles 21a, 21a,..., And the nozzles 22a, 22a,... Are provided with torsion angles and inclination angles in the horizontal plane, and the nozzles 21a, 21a,. Further, a vertical in-plane inclination angle is given to 22a,. The nozzles 21 a, 21 a and the nozzles 22 a, 22 a adjacent to each other in the conveying direction of the steel plate 1 are provided with inclination angles in the horizontal plane in different directions, and a plurality of nozzles provided in the width direction of the steel plate 1. The direction and magnitude of the in-horizontal inclination angle given to 21a, 21a,... And the in-horizontal inclination angle given to a plurality of nozzles 22a, 22a,. The direction and size are the same. The headers 21, 21,... Are configured to be able to supply cooling water to the plurality of nozzles 21a, 21a,..., And the headers 22, 22 are configured to be able to supply cooling water to the plurality of nozzles 22a, 22a,. Yes. Between the nozzles 21a, 21a,... And the upper surface of the steel plate 1, upper surface guides 23, 23 for preventing the nozzles 21a, 21a,... And the steel plate 1 from colliding are provided, and the nozzles 22a, 22a,. 1 are provided with lower surface guides 24, 24 for preventing collision between the nozzles 22a, 22a,... The cooling device 20 includes headers 21, 21... Provided close to the work roll 11 gwu of the final stand 11 g and the upper surface guide 23, and is provided close to the work roll 11 gwd of the final stand 11 g. The headers 22, 22,... And the lower surface guide 24 are integrally formed. Therefore, for example, when exchanging the work rolls 11gw and 11gw of the final stand, the headers 21, 21,... Are moved together with the upper surface guide 23 provided close to the work roll 11gwu of the final stand, The headers 22, 22,... Can be moved together with the lower surface guide 24 provided close to the work roll 11 gwd, so that a space where the chock on the drive side (the back side of the paper in FIG. 2) escapes to the operation side can be obtained. It becomes possible to perform vacant and roll exchange work.

  As shown in FIGS. 2 and 3, when the steel sheet 1 is rapidly cooled using the cooling device 20, the collision area of the high-pressure jet injected from the nozzle 21a installed on the most upstream side is the workpiece of the final stand 11g. The collision area of the high-pressure jet, which reaches the region on the roll bite portion side from the roll radius equivalent position and is injected from the nozzle 22a installed on the most upstream side, rolls more than the work roll radius equivalent position of the final stand 11g. Reach the byte side area. Further, as shown in FIGS. 2 and 3, the nozzles 21a, 21a,..., And the nozzles 22a, 22a,... Provided in the cooling device 20 are continuously arranged along the conveying direction of the steel plate. Therefore, by using the cooling device 20, high-pressure jet water is continuously applied to the upper surface and the lower surface of the steel plate 1 in the section from the position corresponding to the work roll radius of the final stand 11g to the exit side of the housing post 11gh of the final stand. Can be injected. By injecting high-pressure jet water onto the upper and lower surfaces of the steel plate 1, even if stagnant water is present on the surface of the steel plate 1, the high-pressure jet water jetted from the nozzle 21a and the nozzle 22a forms a boiling film on the steel plate surface. Since it can penetrate, it becomes possible to cool the steel plate 1 by nucleate boiling (rapid cooling). That is, by setting the cooling device 20 in such a form, it is possible to cool the upper and lower surfaces of the steel plate 1 that has passed through the roll bite portion faster, stronger, and continuously. Therefore, according to the present invention, it is possible to provide a cooling device 20 capable of producing ultrafine-grained steel.

  FIG. 4 is a diagram for explaining the vertical in-plane inclination angle θ1. As described above, the vertical in-plane inclination angle θ1 is given to the nozzle 21a and the nozzle 22a arranged on the upstream side. By adopting such a form, it becomes easy to form a collision area of a high-pressure jet on the surface of the steel plate located within the position corresponding to the radius of the work roll of the final stand 11g, so that it is possible to manufacture ultrafine-grained steel. It becomes easy.

  FIG. 5 is a diagram showing a simplified form of the high-pressure jet water ejected from the flat spray nozzle array to which only the vertical in-plane inclination angle θ1 is given. The vertical direction of the paper surface of FIG. 5 is the steel plate width direction, and the horizontal direction of the paper surface of FIG. 5 is the conveying direction of the steel plate. As shown in FIG. 5, when a steel plate is cooled using high-pressure jet water sprayed from a flat spray nozzle array to which only a vertical in-plane inclination angle θ1 is applied, it is sprayed from flat spray nozzles adjacent in the width direction of the steel plate. The interference of the cooling water occurs at the boundary portion of the high pressure jet collision area. Therefore, even if the steel plate is cooled using a cooling device including a flat spray nozzle array to which only the vertical in-plane inclination angle θ1 is provided, it is difficult to uniformly cool the steel plate. Therefore, in addition to the vertical in-plane tilt angle θ1, the nozzles 21a, 21a,... And the nozzles 22a, 22a,. .

  FIG. 6 is a diagram for explaining the in-plane inclination angle θ2. The vertical direction of the paper surface of FIG. 6 is the steel plate width direction, and the horizontal direction of the paper surface of FIG. 6 is the conveyance direction of the steel plate. Hereinafter, the lower side in FIG. 6 is referred to as the working side of the final stand, and the upper side in FIG. 6 is referred to as the driving side of the final stand. The flat spray nozzle shown in FIG. 6 is given a vertical in-plane inclination angle θ1 shown in FIG. 4, and further, an in-horizontal inclination angle θ2 is given to the lower side of the page, that is, to the working side of the final stand. Yes. By ejecting the high-pressure jet water from the flat spray nozzle installed in such a form, it becomes easy to discharge the water on the steel sheet surface to the working side of the final stand.

FIG. 7 is a diagram illustrating the twist angle β. The torsion angle is an angle formed by the major axis of the jet collision area of the high-pressure jet and the sheet width direction of the steel sheet. As shown in FIG. 6, high-pressure jet water is jetted from the flat spray nozzle array provided with the vertical in-plane inclination angle θ1 and the horizontal in-plane inclination angle θ2 toward the steel plate, and has a twist angle β defined in FIG. When the collision areas of adjacent high-pressure jets are overlapped in the width direction of the steel sheet, it becomes possible to reduce cooling unevenness in the width direction of the steel sheet. When high-pressure jet water is sprayed from the flat spray nozzle with a tilt angle θ2 in the horizontal plane toward the steel plate, a flow of water from the drive side of the final stand to the work side can be formed on the steel plate surface. It becomes easy to drain to the working side of the stand. That is, it is possible to improve drainage by giving a flat spray nozzle a tilt angle within a horizontal plane. By improving the drainage, it becomes possible to reduce the level of the cooling water staying on the surface of the steel sheet, so that it is easy to rapidly cool the steel sheet. Therefore, according to the present invention, the flat spray nozzle to which a vertical in-plane inclination angle is applied in order to inject high-pressure jet water within a distance corresponding to the radius of the work roll of the final stand is further provided with an in-horizontal inclination angle. Since it becomes easy to rapidly cool the surface of the steel sheet existing within the distance corresponding to the radius of the work roll of the final stand, it becomes possible to produce ultrafine-grained steel.
In FIG. 6, the flat spray nozzle provided with the horizontal plane tilt angle on the working side of the final stand is illustrated, but the high pressure jet from the flat spray nozzle provided with the horizontal plane tilt angle on the final stand drive side toward the steel plate. When water is sprayed, a flow of water from the working side of the final stand to the driving side can be formed on the surface of the steel plate, so that it is easy to drain to the driving side of the final stand.

  Thus, it becomes possible to improve drainage by further giving a horizontal plane inclination angle to the flat spray nozzle to which the vertical in-plane inclination angle is given. The high-pressure jet water sprayed from the flat spray nozzle to which the inclination angle in the horizontal plane is given has a velocity component in the steel plate width direction. Therefore, the cooling water after the high-pressure jet water collides with the surface to be cooled of the steel plate also continues to have a velocity component in the steel plate width direction, and drainage in the steel plate width direction is promoted. In the cooling device of the present invention, since the same horizontal plane inclination angle is given to the plurality of flat spray nozzles arranged at predetermined intervals in the steel plate width direction, drainage in the steel plate width direction is promoted for each header. The

  FIG. 8 is a diagram illustrating the nozzle twist angle θ3. FIG. 8A is a view of a header including a plurality of flat spray nozzles provided with a vertical in-plane inclination angle θ1 and a horizontal in-plane inclination angle θ2 from the upstream side in the steel plate conveyance direction, and FIG. 8B. FIG. 8A is a diagram in which the header in FIG. 8A is rotated so that the vertical in-plane inclination angle θ1 = π / 2, and FIG. 8C is a diagram in which the header in FIG. It is the figure which looked at the flat spray nozzle from the front. In the cooling device of the present invention, it is preferable to set the nozzle twist angle θ3 = 0 from the viewpoint of facilitating uniform cooling of the steel sheet. Therefore, in the cooling device 20, the nozzle torsion angle is not given to the nozzles 21a and 22a.

  FIG. 9 is a diagram for explaining a collision zone shape. Fig.9 (a) and FIG.9 (c) are figures which show three-dimensional arrangement | positioning with the flat spray nozzle and the jet collision area | region formed in the steel plate surface. FIG. 9B is a diagram in which only the collision zone shape is extracted from FIG. 9A, and FIG. 9D is a diagram in which only the collision zone shape is extracted from FIG. 9C. As shown in FIG. 9 (a), the distance from one end in the long axis direction of the jet collision area to the injection hole of the flat spray nozzle, and the distance from the other end in the long axis direction of the jet collision area to the injection hole of the flat spray nozzle When the flat spray nozzles are arranged so that they are equal to each other, the collision area becomes a symmetric shape as shown in FIG. When the flat spray nozzle is arranged in this manner, the steel plate can be cooled uniformly, and the drainage can be improved. On the other hand, as shown in FIG. 9C, the distance from one end in the major axis direction of the jet collision area to the injection hole of the flat spray nozzle, and the injection hole of the flat spray nozzle from the other end in the major axis direction of the jet collision area. If the flat spray nozzle is arranged so that the distance to the distance is not equal, the collision area becomes asymmetrical as shown in FIG. When the flat spray nozzle is arranged in this way, it becomes difficult to cool the steel plate uniformly. This is a uniform cooling property when the distance from one end of the jet collision area to the flat spray nozzle is equal to the distance from the other end of the jet collision area to the flat spray nozzle. This is because the flat spray nozzle is designed to ensure the above. Therefore, in the present invention, it is preferable to arrange a flat spray nozzle as shown in FIG.

  FIG. 10 is a diagram showing an example of a collision zone shape by high-pressure jet water extracted from the cooling device 20 by extracting three flat spray nozzle rows adjacent in the steel plate conveyance direction. The arrows in FIG. 10 indicate the direction of drainage. The vertical direction of the paper surface of FIG. 10 is the width direction of the steel plate, and the horizontal direction of the paper surface of FIG. 10 is the conveyance direction of the steel plate. Of the three flat spray nozzle rows shown in FIG. 10, the horizontal plane tilt angle given to the flat spray nozzle row arranged on the most upstream side is d1, and the flat spray nozzle row adjacent to this flat spray nozzle row A given horizontal plane inclination angle is d2, and a horizontal plane inclination angle given to the flat spray nozzle array arranged on the most downstream side is d3. Further, it is assumed that the inclination angle in the horizontal plane given in the counterclockwise direction is represented by a positive angle, and the inclination angle in the horizontal plane given in the clockwise direction is represented by a negative angle. At this time, in the embodiment shown in FIG. 10, d1> 0, d2 <0, and d3> 0. That is, in the cooling device 20, the flat spray nozzles adjacent to the conveying direction of the steel plate are the first flat spray nozzle and the second flat spray nozzle, and the inclination angle in the horizontal plane given to the first flat spray nozzle is α [rad] ( When 0 <| α | <π) and β [rad] (0 <| β | <π) as the inclination angle in the horizontal plane applied to the second flat spray nozzle, α · β <0. When the horizontal plane inclination angle is given in such a form, as shown in FIG. 10, the drainage of the cooling water sprayed from the flat spray nozzle row to which the horizontal plane inclination angle d1 toward the upper side in FIG. 10 is given is inhibited. Without this, it becomes possible to drain the cooling water sprayed from the flat spray nozzle row to which the in-plane inclination angle d2 is given to the lower side of the drawing in FIG. Similarly, the horizontal plane inclination angle d3 is given without impeding the drainage of the cooling water sprayed from the flat spray nozzle row to which the horizontal plane inclination angle d2 going downward in FIG. 10 is given. It becomes possible to drain the cooling water sprayed from the flat spray nozzle row to the upper side in FIG. That is, by adopting such a form, even when a horizontal plane tilt angle is given to a plurality of flat spray nozzles adjacent in the conveying direction of the steel sheet, it becomes possible to improve drainage, in addition to the effect. Furthermore, it becomes possible to improve the uniformity of cooling in the steel plate width direction.

  In the present invention, the direction of the inclination angle in the horizontal plane given to the flat spray nozzle array arranged on the most upstream side is not particularly limited, but it is easy to improve the equipment maintenance of the final stand, etc. From this point of view, it is preferable to provide a tilt angle in the horizontal plane so that the cooling water sprayed from the flat spray nozzle row arranged on the most upstream side is drained to the working side of the final stand. Usually, a universal joint, a speed reducer, and the like are arranged on the drive shaft side of the rolling roll, and there are many hydraulic devices, measurement wirings, and the like. If a large amount of water splashes on these devices, the frequency of occurrence of failures and the like increases, resulting in a decrease in facility maintainability. Therefore, the facility maintainability can be improved by draining to the working side of the final stand.

  In addition, as described above, in the present invention, it is possible to specify the water flow direction on the surface of the steel sheet by providing the flat spray nozzle with an inclination angle in the horizontal plane. In the case where the nozzle is not given a tilt angle in the horizontal plane as in the past, it was difficult to specify the direction of water flow on the steel sheet surface. It was necessary to apply. On the other hand, in the present invention, it becomes possible to specify the direction of water flow on the surface of the steel sheet, so it is possible to improve equipment maintainability by taking measures against water scattering at one end in the width direction of the steel sheet. . Therefore, according to the present invention, the facility maintenance cost can be reduced.

  Further, in the present invention, when a vertical in-plane inclination angle is given to a plurality of rows of flat spray nozzles in the steel plate conveyance direction, a large vertical in-plane inclination angle is given to each of the flat spray nozzle rows adjacent to the steel plate conveyance direction. Although there is no particular limitation, from the viewpoint of making it difficult to prevent the cooling of the steel plate by the high-pressure jet water sprayed from the upstream flat spray nozzle row, the flat spray disposed on the downstream side It is preferable that the vertical in-plane inclination angle of the nozzle row be equal to or smaller than the in-vertical in-plane inclination angle of the flat spray nozzle row arranged on the upstream side. In the cooling device 20 described above, the vertical in-plane inclination angle of the flat spray nozzle row arranged on the downstream side is set to be equal to or smaller than the in-vertical inclination angle of the flat spray nozzle row arranged on the upstream side.

  In the present invention, the amount of water per unit time of high-pressure jet water sprayed from each flat spray nozzle adjacent in the steel plate conveyance direction toward the steel plate is not particularly limited. However, from the viewpoint of making it difficult to prevent the cooling of the steel plate by the high-pressure jet water jetted from the upstream flat spray nozzle row, the high-pressure jet water jetted from the flat spray nozzle row arranged on the downstream side The amount of water per unit time is preferably set to be equal to or less than the amount of water per unit time of high-pressure jet water ejected from a flat spray nozzle row disposed adjacent to the upstream side of the flat spray nozzle.

  In the above description related to the present invention, an example in which a plurality of flat spray nozzles arranged in the width direction of the steel plate is connected to one header, and the flat spray nozzles adjacent in the conveyance direction of the steel plate are connected to different headers is exemplified. However, the present invention is not limited to this form. FIG. 11 is an enlarged schematic view of a part of the cooling device 30 for hot-rolled steel sheets according to another embodiment of the present invention. 11, components similar to those of the manufacturing apparatus 10 illustrated in FIG. 1 are denoted by the same reference numerals as those used in FIG. 1, and description thereof is omitted as appropriate. Moreover, in FIG. 11, the description of the upper surface guide and the lower surface guide is omitted, and the steel plate conveyance direction of the steel plate surface collision pressure of the high-pressure jet water sprayed from each flat spray nozzle row arranged on the upper surface side of the steel plate. The concept of average value (average collision pressure for each nozzle row) and the average value in the steel plate conveyance direction of the steel plate surface collision pressure of high-pressure jet water averaged in the steel plate conveyance direction in the continuous cooling region (average collision pressure in the continuous cooling region) The concept of is also shown.

  As shown in FIG. 11, the hot-rolled steel sheet cooling device 30 of the present invention (hereinafter sometimes simply referred to as “cooling device 30”) has three rows of flat plates on the uppermost stream side on the upper surface side of the steel plate 1. A header 31 configured to be able to supply cooling water to each flat spray nozzle 31a, 31a,... (Hereinafter, simply referred to as “nozzle 31a” or the like) constituting the spray nozzle row is provided. Cooling water can also be supplied to the flat spray nozzles 32a, 32a,... (Hereinafter sometimes simply referred to as “nozzle 32a”, etc.) constituting the uppermost three rows of flat spray nozzle rows on the lower surface side. The cooling apparatus 20 is configured in the same manner except that the header 32 is configured. Two rows of nozzles 31a, 31a connected to the header 31 from the most upstream side in the conveying direction of the steel plate 1, and two rows of nozzles 32a, 32a connected to the header 32 from the most upstream side in the conveying direction of the steel plate 1. Is provided with a vertical in-plane tilt angle, and all nozzles (nozzle 31a, nozzle 32a, nozzle 21a, and nozzle 22a) provided in the cooling device 30 are provided with a tilt angle in a horizontal plane. Yes. In the cooling device 30, the vertical in-plane inclination angle given to the nozzles 31 a and 32 a arranged on the most upstream side in the conveyance direction of the steel plate 1 is the nozzle adjacent to the nozzles 31 a and 32 a and the downstream side in the conveyance direction of the steel plate 1. The inclination angle is greater than or equal to the vertical in-plane inclination angle given to 31a and 32a. Further, the high-pressure jet water sprayed from the nozzles 31a and 32a arranged on the most upstream side in the transport direction of the steel plate 1 is moved to the area closer to the roll bite portion than the position corresponding to the radius of the work rolls 11gwu and 11gwd of the final stand 11g. Has reached. Therefore, even with such a cooling device 30, it is possible to produce ultrafine-grained steel as with the cooling device 20.

  FIG. 12 is a diagram showing the relationship between the average value of the steel plate surface collision pressure of the high-pressure jet water and the average cooling rate of the steel plate. The vertical axis in FIG. 12 is the average cooling rate [° C./s] when the temperature of the steel plate having a thickness of 3 mm with no cooling water remaining on the surface is cooled from both sides from 750 ° C. to 600 ° C. The horizontal axis represents the average value [kPa] in the steel plate conveyance direction of the steel plate surface collision pressure of the high-pressure jet water. Moreover, FIG. 13 is a figure explaining the steel plate conveyance direction average value of the steel plate surface collision pressure of high pressure jet water. As shown in FIG. 12, there is a correlation between the average value of the steel plate surface collision pressure of the high-pressure jet water and the average cooling rate of the steel plate, and the average value of the high-pressure water jet surface collision pressure of the steel plate surface When the is increased, the average cooling rate of the steel sheet can be increased. Moreover, as shown in FIG. 13, the steel plate conveyance direction average value of the steel plate surface collision pressure of the high-pressure jet water is A, the nozzle pitch in the steel plate width direction of the cooling water reaching the steel plate surface, and the nozzle pitch in the steel plate conveyance direction. Per nozzle, which is derived by dividing the cooling water force (collision force) reaching the quadrilateral area represented by A × B by the area A × B of the quadrilateral area. Is averaged over the relevant section in the transport direction.

  In the present invention, the average value of the steel plate surface collision pressure of the high-pressure jet water sprayed from the cooling devices 20 and 30 to the steel plate 1 (hereinafter referred to as “the steel plate surface collision pressure average value”) is particularly limited. Is not to be done. However, from the standpoint of making the steel sheet 1 into a form that can be rapidly cooled while suppressing recovery of austenite grains and the like, the steel sheet surface collision pressure average value is preferably 3.5 kPa or more. By setting the steel plate surface collision pressure average value to 3.5 kPa or higher, the steel plate can be rapidly cooled at an average cooling rate of 600 ° C./s or higher. In the present invention, it is preferable to rapidly cool the steel sheet at an average cooling rate of 1000 ° C./s or more from the viewpoint of making the crystal structure more finely sized. In the present invention, the steel sheet surface collision pressure average value is more preferably 8 kPa or more from the viewpoint of making the steel sheet rapidly coolable at an average cooling rate of 1000 ° C./s or more. The cooling rate varies depending on the plate thickness, and is approximately inversely proportional to the plate thickness. If the hot-rolled steel sheet cooling device of the present invention has the ability to rapidly cool a steel sheet having a thickness of 3 mm at an average cooling rate of 1000 ° C./s, an average cooling of a steel sheet having a thickness of 5 mm is 600 ° C./s. It becomes possible to rapidly cool at a speed.

As described above, the steel plate surface collision pressure average value is equal to a value obtained by dividing the collision force of the high-pressure jet water ejected from the flat spray nozzle by the cooling area of the flat spray nozzle. Therefore, even if the impact force is measured instead of measuring the pressure, the steel plate surface impact pressure average value can be calculated, and the impact force of the high-pressure jet water can be obtained from the flow rate and flow velocity. Since it depends on the feed water pressure to the flat spray nozzle, the steel plate surface collision pressure average value can be estimated from the feed water pressure to the flat spray nozzle if a predetermined pressure loss is expected. An example of a method of calculating the steel plate surface collision pressure average value is described below.
Steel plate collision pressure average value Ps = F / (A · B) · 10 ³ [kPa]
Here, A is the steel plate width direction nozzle pitch [mm], B is the transport direction nozzle pitch [mm], and F is the impinging force [N] of the high-pressure jet water against the steel plate surface. The collision force F can be obtained by the following equation.
Collision force F = 0.745 ・ C ・ q ・ P ^0.5 [N]
Here, C is a loss factor (about 0.8 to 1.0), q is a flow rate [L / min] of a flat spray nozzle, and P is a feed water pressure [MPa]. The flow rate of the flat spray nozzle is determined in relation to the feed water pressure according to the nozzle type (characteristic).

  In the above description regarding the present invention, the flat spray nozzles 21a and 22a are disposed not only in the section from the final stand 11g of the hot rolling mill row to the housing post 11gh exit side, but also in the area downstream of the section. However, the present invention is not limited to this form. However, from the viewpoint of making it possible to provide a cooling device capable of performing the rapid cooling even if it is required to rapidly cool the steel sheet to a temperature lower than 720 ° C. within a short time after the end of rolling, It is preferable that flat spray nozzles are continuously arranged in a section of the last stand of the rolling mill row up to the housing post exit side and an area downstream of the section.

  In the above description of the present invention, the flat spray nozzles provided with the vertical in-plane inclination angle and the horizontal in-plane inclination angle are exemplified on the upper surface side and the lower surface side of the steel plate. It is not limited to. Since the high-pressure jet water sprayed to the lower surface side of the steel sheet falls to the lower side of the steel sheet due to gravity, the drainage property on the lower surface side of the steel plate is usually better than the drainage property on the upper surface side of the steel plate. Therefore, this invention can also be set as the form by which the flat spray nozzle provided with the vertical in-plane inclination angle and the horizontal in-plane inclination angle is arrange | positioned only on the upper surface side of a steel plate. However, from the viewpoint of ensuring cooling uniformity on the upper surface side and the lower surface side of the steel plate, flat spray nozzles to which a vertical in-plane tilt angle and a horizontal plane tilt angle are provided are installed on the upper and lower surfaces of the steel plate. It is preferable to adopt a form.

  In the present invention, when the stagnant water is present on the surface of the steel plate, the pressure of the high-pressure jet water ejected from the nozzle 21a is reduced by the stagnant water, and the collision pressure of the high-pressure jet water on the surface of the steel plate 1 is likely to be reduced. Therefore, it is preferable to reduce the accumulated water on the surface of the steel plate 1 from the viewpoint of making the steel plate 1 easily cooled. From such a viewpoint, in the present invention, it is preferable that a space capable of discharging cooling water is secured between both end faces in the steel plate width direction of the cooling device 20 and both end faces in the steel plate width direction of the final stand 11g.

  Further, in the above description regarding the cooling device 20 of the present invention, the header 21 and the upper surface guide 23 disposed on the upper surface side of the steel plate 1 are integrally configured, and the header 22 and the lower surface disposed on the lower surface side of the steel plate 1. Although the form comprised integrally with the guide 24 was illustrated, the cooling apparatus of the hot-rolled steel plate of this invention is not limited to the said form. In the cooling apparatus for hot-rolled steel sheets of the present invention, the header and the lower surface guide disposed on the lower surface side of the steel sheet are not integrally configured, and the header and the upper surface guide disposed on the upper surface side of the steel sheet are not integrally configured. It is also possible to adopt a form. However, from the viewpoint of making it possible to replace the roll provided in the final stand of the hot rolling mill row and making it easy to improve its efficiency, a header and an upper surface guide disposed on the upper surface side of the steel plate are used. It is preferable to perform the retracting or returning operation at the same time, and therefore it is preferable to configure it integrally. Similarly, it is preferable that the header disposed on the lower surface side of the steel plate and the lower surface guide are configured integrally. In the present invention, the header and upper surface guide installed on the upper surface side of the steel plate, and the header and lower surface guide installed on the lower surface side of the steel plate can be moved using known means such as a hydraulic cylinder.

  Thus, by using the cooling devices 20 and 30 of the present invention, it becomes possible to produce ultrafine-grained steel. Therefore, it becomes possible to manufacture ultra-fine grained steel by using the manufacturing apparatus 10 including the cooling device 20 and the manufacturing apparatus for hot-rolled steel sheets according to the present invention including the cooling device 30. Furthermore, by setting it as the form which has the process of processing the steel plate rolled by the last stand in a hot finishing rolling mill row | line | column using the manufacturing apparatus 10 or the manufacturing apparatus 10 of the hot-rolled steel sheet of this invention provided with the cooling device 30, It becomes possible to provide the manufacturing method of a hot-rolled steel plate which can manufacture fine grain steel.

Using a test rolling mill with a scale of about 1/4 of a hot rolled actual machine and a cooling device having symmetrical headers on the upper surface side and the lower surface side of the steel sheet, the experiment was conducted under the following experimental conditions, and cooling immediately after rolling. Possibilities, cooling uniformity of the steel sheet, and water splash countermeasure costs were evaluated. Conditions common to each experiment are described first, and subsequently, different conditions for each experiment are shown in Tables 1 to 5.
<Common conditions>
Sheet width of steel plate to be cooled: 300 mm
Thickness of steel plate to be cooled: 2 mm
Steel plate temperature after rolling: 850 ° C
Steel sheet rolling speed: 200 mpm
Jet water pressure: 1.5 MPa
Flat spray nozzle spread: approx. 100mm at steel plate collision position
Nozzle pitch in the steel plate width direction: 50 mm
Number of nozzles in the width direction of the steel plate: 8 Water supply amount per header: 144 L / min
Number of header rows in the steel plate transport direction: 4 rows

<Conditions for each experiment>
Table 1 shows the conditions of Example 1 (Invention Example), Table 2 shows the conditions of Example 2 (Invention Example), Table 3 shows the conditions of Comparative Example 1, Table 4 shows the conditions of Comparative Example 2. Table 5 shows the conditions of Comparative Example 3. In Tables 1 to 5, “first row” means a flat spray nozzle row disposed on the most upstream side in the conveying direction of the steel sheet (the side closest to the final stand of the hot rolling mill row), and thereafter As the steel sheet moves to the downstream side in the conveyance direction, it is expressed as “second row”, “third row”, and “fourth row”. In Tables 1 and 2, “+” means that a tilt angle within the horizontal plane is given so that the work is drained to the final stand, and “−” means that the final stand is driven. It means that a tilt angle in the horizontal plane was given so that it was drained.

<Result>
The results of Example 1, Example 2, and Comparative Examples 1 to 3 are also shown in Table 6.

In Table 6, “cooling immediately after rolling” indicates that the steel plate could be cooled from within the radius equivalent of the work roll of the final stand, and the steel plate could not be cooled from within the radius equivalent of the work roll of the final stand. The thing was set as x. In addition, “Water splash countermeasure cost and equipment maintainability” is the one that the water splash countermeasure cost was low and the equipment maintainability was good because the water splash countermeasure could be focused only on the drive side or work side of the final stand. ○, and it was necessary to take measures against water splashing on the drive side and work side of the final stand. The “cooling uniformity” was evaluated according to the following criteria.
A: Temperature variation in the width direction is less than 20 ° C. ○: Temperature variation in the width direction is 20 ° C. or more and less than 30 ° C. Δ: Temperature variation in the width direction is 30 ° C. or more and less than 40 ° C. ×: Temperature variation in the width direction is 40 ° C. or more. As described above, there is a correlation between cooling uniformity and drainage. In Example 1 and Example 2 cooled using a flat spray nozzle having a horizontal plane tilt angle, the direction of water flow could be specified on the steel sheet surface, so compared to Comparative Examples 1 to 3, It was possible to improve the performance.

  From Table 6, according to the present invention, it was possible to cool immediately after rolling and to cool the steel sheet uniformly (suppressing temperature unevenness in the width direction to less than 30 ° C.) by improving drainage. It was. Therefore, it becomes possible to manufacture ultrafine-grained steel by using the cooling device of the present invention. In contrast, Comparative Example 1 in which only the nozzle torsion angle was not imparted to the nozzle without imparting a vertical in-plane tilt angle improved drainage and was able to cool the steel plate uniformly. Could not cool. Further, in Comparative Example 2 in which only the vertical in-plane inclination angle was given and the horizontal in-plane inclination angle and the nozzle twist angle were not given, the drainage performance was lowered, and the temperature unevenness in the width direction was 40 ° C. or more. In addition, in Comparative Example 2, since the inclination angle in the horizontal plane was not given, it was necessary to take measures against water scattering on the drive side and the work side of the final stand, and the cost for water scattering countermeasures increased. Further, in Comparative Example 3 in which the vertical in-plane tilt angle and the nozzle twist angle were given to the nozzle, the collision area of the high-pressure jet formed by colliding with the steel plate surface was asymmetrical. The cooling uniformity was lower than 2. In addition, in Comparative Example 3, the vertical in-plane inclination angle and the nozzle torsion angle were imparted to the nozzle, while the horizontal in-plane inclination angle was not imparted, so the drainage performance was lower than in Examples 1 and 2.

  Although the present invention has been described in connection with embodiments that are presently practical and preferred, the present invention is not limited to the embodiments disclosed herein, but is claimed. Can be appropriately changed without departing from the scope or spirit of the invention that can be read from the entire specification and the specification, and a hot-rolled steel sheet cooling device, a hot-rolled steel sheet manufacturing apparatus, and a hot-rolled steel sheet Manufacturing methods should also be understood as being within the scope of the present invention.

  The apparatus for cooling a hot-rolled steel sheet, the apparatus for producing a hot-rolled steel sheet, and the method for producing a hot-rolled steel sheet according to the present invention can be used for producing a hot-rolled steel sheet having ultrafine crystal grains. Moreover, the hot-rolled steel sheet having ultrafine crystal grains can be used as a material used for applications such as automobiles, household appliances, machine structures, and buildings.

DESCRIPTION OF SYMBOLS 1 ... Steel plate 10 ... Hot-rolled steel plate manufacturing apparatus 11 ... Hot finishing rolling mill row 11g ... Final stand 11gh ... Final stand housing post 11gw ... Final stand work roll 11gwu ... Final stand work roll 11gwd ... Final stand work Roll 12 ... Transport roll 13 ... Pinch roll 20 ... Hot rolled steel sheet cooling device 21 ... Header 21a ... Flat spray nozzle 22 ... Header 22a ... Flat spray nozzle 23 ... Upper surface guide 24 ... Lower surface guide 30 ... Hot rolled steel plate cooling device 31 ... Header 31a ... Flat spray nozzle 32 ... Header 32a ... Flat spray nozzle

Claims (11)

A hot roll comprising a header having a plurality of flat spray nozzles arranged downstream of a final stand in a hot finish rolling mill row and provided so as to be able to inject high-pressure jet water toward a steel plate conveyed through a pass line. A steel sheet cooling device,
In the section from the position corresponding to the radius of the work roll of the final stand to the housing post exit side of the final stand, the high-pressure jet water is continuously fed from the flat spray nozzle in the conveying direction of the steel plate toward the steel plate. Configured to be jettable,
Torsion angle β, which is an angle formed by the longitudinal direction of the jet collision area formed by the high-pressure jet water sprayed from the flat spray nozzle colliding with the surface to be cooled of the steel sheet and the sheet width direction of the steel sheet Is β ≠ 0 ,
The high-pressure jet water sprayed from the flat spray nozzle disposed at least on the most upstream side in the transport direction of the steel sheet is sprayed in a direction intersecting the vertical plane toward the upstream side in the transport direction of the steel sheet,
At least the flat spray nozzle that injects the high-pressure jet water in a direction intersecting a vertical plane toward the upstream side in the conveyance direction of the steel sheet is an inclination in a horizontal plane that is an angle formed between the axial direction and the conveyance direction of the steel sheet. An apparatus for cooling a hot-rolled steel sheet, wherein the angle θ2 is θ2 ≠ 0 .
The apparatus for cooling a hot-rolled steel sheet according to claim 1, wherein a nozzle twist angle is not given to at least a part of the flat spray nozzle. Each of the flat spray nozzles adjacent to the conveying direction of the steel plate is given an inclination angle in the horizontal plane,
The flat spray nozzle adjacent to the conveying direction of the steel sheet to which the inclination angle in the horizontal plane is given is defined as a first flat spray nozzle and a second flat spray nozzle, and the inclination in the horizontal plane given to the first flat spray nozzle. When the angle is α [rad] (0 <| α | <π) and the inclination angle in the horizontal plane applied to the second flat spray nozzle is β [rad] (0 <| β | <π), α The cooling device for hot-rolled steel sheets according to claim 1 or 2, wherein β <0. The said high-pressure jet water is sprayed toward at least the upper surface of the said steel plate, The cooling apparatus of the hot rolled steel plate of any one of Claims 1-3 characterized by the above-mentioned. The steel sheet conveyance direction average value of the steel plate surface collision pressure of the high-pressure jet water in the section is 3.5 kPa or more. The hot-rolled steel sheet according to any one of claims 1 to 4, Cooling system. The space which can discharge | emit cooling water is ensured between the steel plate width direction both end surfaces of the said cooling device, and the steel plate width direction both end surfaces of the said last stand, The one of Claims 1-5 characterized by the above-mentioned. The cooling apparatus for hot-rolled steel sheets according to item 1. A plurality of the headers are provided, and at least a part of the headers is configured to be able to collectively supply cooling water to the flat spray nozzles arranged in a plurality of rows in each of the conveying direction of the steel plate and the width direction of the steel plate. The apparatus for cooling a hot-rolled steel sheet according to any one of claims 1 to 6, wherein: A plurality of the headers are arranged on the upper surface side of the steel plate,
Among the headers provided on the upper surface side of the steel plate, at least the headers arranged on the most upstream side in the conveying direction of the steel plate are arranged in a plurality of rows in each of the conveying direction of the steel plate and the width direction of the steel plate. The apparatus for cooling a hot-rolled steel sheet according to claim 7, wherein the header is configured to be able to supply cooling water to the nozzles collectively. A plurality of the headers are arranged on the lower surface side of the steel plate,
Among the headers provided on the lower surface side of the steel plate, at least the headers arranged on the most upstream side in the conveying direction of the steel plate are arranged in a plurality of rows in each of the conveying direction of the steel plate and the width direction of the steel plate. The apparatus for cooling a hot-rolled steel sheet according to claim 7 or 8, wherein the header is configured so that cooling water can be supplied to the nozzles collectively. A hot stand steel sheet comprising a final stand in a hot finish rolling mill and a cooling device for a hot rolled steel sheet according to any one of claims 1 to 9 in order in the conveying direction of the steel sheet. manufacturing device. A method for manufacturing a hot-rolled steel sheet, comprising the step of processing a steel sheet rolled at a final stand in a hot finish rolling mill using the hot-rolled steel sheet manufacturing apparatus according to claim 10.

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