JP2011011221A - Cooling device for hot-rolled steel sheet and controlling method for the same device, and device and method for manufacturing hot-rolled steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for cooling a hot-rolled steel sheet capable of uniformly cooling the hot-rolled steel sheet, a method for controlling the operation of the cooling device, a device for manufacturing a hot-rolled steel sheet, and a method for manufacturing a hot-rolled steel sheet.SOLUTION: The device for cooling a hot-rolled steel sheet is arranged between a final stand 11g in a line of hot-finishing rolling mills and a thermometer set on the downstream side from the final stand, and includes headers 21, 22 having a plurality of flat spray nozzles for jetting cooling water to a steel sheet 1 being conveyed on a pass line, wherein the headers are composed movably upward and downward. The method for controlling the operation of the cooling device controls the operation of the headers based on the result of measuring the temperature of the steel sheet by the thermometer set on the downstream side from the cooling device. The device for manufacturing a hot-rolled steel sheet is provided with the device for cooling a hot-rolled steel sheet. The method for manufacturing a hot-rolled steel sheet includes a step of treating a steel sheet by using the device for manufacturing a hot-rolled steel sheet.

Description

  The present invention relates to a hot-rolled steel sheet cooling device and an operation control method thereof, and a hot-rolled steel sheet manufacturing apparatus and a hot-rolled steel sheet manufacturing method. In particular, the present invention includes a hot-rolled steel sheet cooling device that can uniformly cool a hot-rolled steel sheet using a flat spray nozzle, an operation control method for the hot-rolled steel sheet cooling device, and a hot-rolled steel sheet cooling device. The present invention relates to a hot-rolled steel sheet manufacturing apparatus and a hot-rolled steel sheet manufacturing method using the manufacturing apparatus.

  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.

There have been disclosed several techniques that enable the production of hot-rolled steel sheets having fine crystal grains, or techniques that can be applied to the production of hot-rolled steel sheets having fine crystal grains. For example, Patent Document 1 discloses a method of manufacturing a hot-rolled steel sheet by multi-pass hot rolling a steel sheet or slab made of carbon steel or low alloy steel containing C: 0.01 to 0.3% by mass. A method for producing an ultrafine-grained hot-rolled steel sheet is disclosed, wherein the final rolling pass is terminated at a temperature of ₃ or more points of Ar and then cooled to 720 ° C. or less within 0.4 seconds. Further, in Patent Document 2, a final stand, a first cooling device, a second cooling device, and a winding device in a hot rolling finish rolling mill row are sequentially arranged in the steel plate conveying direction. In a hot-rolled steel plate manufacturing facility in which an uncooled region is provided between the first cooling device and the second cooling device, the first cooling device has a strip shape or an oval shape on the surface to be cooled of the steel plate. A nozzle that should form a jet collision area and a dam roll that dams the cooling water jetted from the nozzle, and a pool of cooling water is formed in the area between the roll of the final stand and the dam roll. In addition, a technique is disclosed in which a weir roll is disposed so that a steel sheet conveyed in the first cooling device is immersed in the cooling water of the pool. Patent Document 3 discloses a cooling facility for supplying cooling water to the upper surface of the steel sheet while passing the steel sheet at a position close to the entry side of the rolling mill for hot rolling the steel sheet and / or the exit side rolling mill. The cooling equipment is arranged so that the cooling water after supplying the steel plate with a header having a nozzle that injects bar-shaped cooling water toward the rolling mill side with a depression angle of 30 ° to 60 ° with respect to the upper surface of the steel plate is the rolling mill. A hot-rolling equipment for a steel sheet is disclosed, which is provided at a position where it can be dammed by a work roll. In Patent Document 3, it is preferable that the distance between the tip of the upper nozzle and the pass line is 500 mm to 1800 mm in order to avoid a situation in which the cooling water is dispersed and is not rod-shaped and has no function of blocking the cooling water. It is written.

Japanese Patent Laid-Open No. 2005-213595 Patent No. 4029865 JP 2007-61838 A

According to the technique disclosed in Patent Document 1, a steel plate having a temperature of Ar ₃ or higher is cooled to 720 ° C. within 0.4 seconds after the end of the final rolling pass. It is considered that a hot-rolled steel sheet having crystal grains having an average grain diameter of 2 μm or less (the same applies hereinafter) can be produced. However, Patent Document 1 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. Further, according to the technique disclosed in Patent Document 2, in order to immerse the steel plate in the pool of cooling water formed in the region between the roll of the final stand of the hot rolling mill row and the weir roll, It is considered that the cooling efficiency of the steel sheet can be improved. Here, the rapid cooling required when producing a hot-rolled steel sheet having ultrafine crystal grains has a cooling rate of at least 400 ° C./s or more as shown in Patent Document 1, for example. Is required to be rapidly cooled by nucleate boiling cooling. However, as disclosed in Patent Document 2, when the cooling water pool is positively formed to cool the steel sheet, the collision pressure of the cooling water that collides with the steel sheet surface is reduced to the extent that nucleate boiling cooling is possible. In order to manufacture a hot-rolled steel sheet that is difficult to increase and has ultrafine crystal grains, there has been a problem that further technical improvement is required. Moreover, in the rapid cooling required when manufacturing a hot-rolled steel sheet having ultrafine crystal grains, the collision pressure of cooling water that collides with the steel sheet surface needs to be a predetermined value or more. In the technique disclosed in No. 3, only the injection angle of the rod-shaped cooling water supplied to the steel sheet is mainly defined. Further, in Patent Document 3, the cooling water sprayed onto the steel sheet flows to the rolling roll bite part, so that cooling can be performed immediately after the roll bite part. However, the cooling water flowing on the steel sheet after the collision can sufficiently quench the steel sheet. In addition, the cooling of this portion hardly contributes to the formation of ultrafine crystal grains. Therefore, there is a problem that it is difficult to manufacture a hot-rolled steel sheet having ultrafine crystal grains even if this technique is simply used.

  On the other hand, FIG. 9 shows the spray spread angle of the cooling water sprayed from the flat spray nozzle, the collision area length of the cooling water colliding with the steel plate surface (hereinafter referred to as “spray collision length”), and the flat spray. It is a figure explaining the concept of the distance (henceforth "the distance between nozzle steel plates") of a nozzle and a steel plate. When cooling a steel sheet using cooling water sprayed from a flat spray nozzle (hereinafter, simply referred to as “nozzle”), cooling water supplied to the header according to the required cooling capacity, etc. When the pressure (feed water pressure) is changed and the flow rate of the cooling water injected from the nozzle is changed, the spray spread angle of the cooling water injected from the nozzle changes (see FIG. 10). When the spray spread angle of the cooling water is changed while the distance between the nozzle steel plates is constant, the spray collision length is changed. Here, the spray collision length when the steel sheet is uniformly cooled is L0. When the spray collision length L is set to L <L0, a portion where the cooling is relatively insufficient occurs between adjacent cooling water collision areas, so that the uniform cooling performance is impaired. On the other hand, when the spray collision length L is set to L> L0, since the site | part cooled comparatively excessively between adjacent cooling water collision areas arises, a cooling uniformity is impaired. That is, when the flow rate of the cooling water sprayed from the nozzle is changed, the spray collision length is changed, which makes it difficult to uniformly cool the steel sheet. When producing a hot-rolled steel sheet containing ultrafine-grained steel, if uniform cooling is impaired, differences in mechanical properties are likely to occur between parts of the hot-rolled steel sheet, and productivity of the hot-rolled steel sheet is reduced. This is considered to be a factor.

  Therefore, the present invention can uniformly cool a hot-rolled steel sheet, a hot-rolled steel sheet cooling apparatus, a hot-rolled steel sheet manufacturing apparatus, a hot-rolled steel sheet manufacturing method, and a hot-rolled steel sheet uniformly. It is an object of the present invention to provide an operation control method for a cooling device for a hot-rolled steel sheet that can be cooled.

  The present inventors conducted research on cooling of hot-rolled steel sheets using flat spray nozzles. As a result, it was found that the spray collision length can be kept constant by determining the distance between the nozzle steel plates according to the feed water pressure to the header (see FIG. 11). By keeping the spray collision length constant, it is considered that the hot-rolled steel sheet can be uniformly cooled. Furthermore, the present inventors have arranged the nozzle so that the jet collision area of the cooling water that has collided with the steel plate surface has the form described in FIG. 12 (hereinafter, the arrangement of the form is referred to as “staggered arrangement”). It was found that the uniform cooling of the steel sheet can be easily improved.

The inventors of the present invention conducted research on the production of hot-rolled steel sheets having ultrafine crystal grains (hereinafter sometimes referred to as “ultrafine grain steel”), and obtained the following knowledge.
(1) As shown in FIG. 8, after cooling in a temperature range of ₃ or more points of Ar, when cooling to 720 ° C. is completed within 0.2 seconds, the crystal grains can be further refined Become.
(2) Ar Cooling at a cooling rate of 600 ° C./s or more is necessary to finish cooling at a temperature of ₃ ° C. or more, for example, at a cooling rate of 100 ° C. from 820 ° C. to 720 ° C. within 0.2 seconds after rolling. is there. 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. Accordingly, the rapid cooling after rolling starts from within the position 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 (surface pressure) at which the cooling water sprayed onto the steel plate collides with the steel plate and the cooling rate of the steel plate (see FIG. 5), and the pressure at which the cooling water collides with the steel plate is increased. By making it, it becomes possible to increase the cooling rate of a steel plate. 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.

  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.

  A 1st aspect of this invention is arrange | positioned between the last stand (11g) in a hot finish rolling mill row | line | column (11), and the thermometer (14) arrange | positioned downstream of this last stand, and a pass line is arranged. A header (21, 22) including a plurality of flat spray nozzles (21a, 21a, ..., 22a, 22a, ...) provided so as to be able to inject cooling water toward the steel plate (1) to be conveyed; A header (21, 22) is a cooling device (20) for hot-rolled steel sheets, wherein the header (21, 22) is configured to be movable up and down.

  Here, the “downstream side” refers to the downstream side in the conveying direction of the steel plate (1).

  Moreover, in the said 1st aspect of this invention, it is preferable that the vertical motion of a header (21, 22) is controlled based on the temperature measurement result of the steel plate measured with the thermometer (14).

  Here, in the present invention, “the vertical movement of the headers (21, 22) is controlled” more specifically, vertical movement means for moving the headers (21, 22) up and down (for example, hydraulic cylinders, etc.) That is, the operation of a known driving means) is controlled. Further, “the vertical movement of the header (21, 22) is controlled based on the temperature measurement result of the steel plate measured by the thermometer (14)” means, for example, the steel plate measured by the thermometer (14). This means that the headers (21, 22) are moved up and down so as to reduce the temperature unevenness of (1).

  In the first aspect of the present invention, the pressure of the cooling water supplied to the headers (21, 22) is preferably controlled.

  Here, "the pressure of the cooling water supplied to the headers (21, 22) (hereinafter, sometimes referred to as" feed water pressure ") is controlled" means, for example, when the rolling speed changes, To the header when it is necessary to adjust the cooling capacity of the cooling device (20), such as when the heat transfer coefficient due to the surface change of the steel plate changes or when a disturbance such as a change in temperature before cooling occurs. It is controlled to change the feed water pressure.

  In the first aspect of the present invention, the cooling water sprayed from the flat spray nozzles (21a, 21a,..., 22a, 22a,...) The flat spray nozzle is preferably arranged so that all the points in the width direction of the steel plate pass through the jet collision area twice or more.

  Here, “the flat spray nozzle is arranged so that all the points in the width direction of the steel plate pass through the jet collision area twice or more” means that, for example, the jet collision area is shown in FIG. It means that a flat spray nozzle is arranged so as to form.

  Further, in the first aspect of the present invention, a strip formed by the cooling water sprayed from the flat spray nozzles (21a, 21a, ..., 22a, 22a, ...) colliding with the surface to be cooled of the steel plate or The elliptical jet collision areas are arranged at predetermined intervals in the sheet width direction of the steel sheet and the conveyance direction of the steel sheet, and the two jet collision areas adjacent to each other in the conveyance direction of the steel sheet are positioned in the sheet width direction of each other. It is preferable that they are arranged so as to be displaced.

  Here, “the two jet collision areas adjacent to each other in the conveying direction of the steel sheet are arranged so that the positions in the sheet width direction of the steel sheet are shifted from each other” means that, for example, the jet collision area is shown in FIG. It means that the flat spray nozzle is arranged so as to be in the form. For example, if the pitch in the width direction of the steel plate is Ap, the arrangement of the injection collision area of the nozzle row adjacent to the upstream side or the downstream side in the transport direction with respect to a certain nozzle row is shifted in the width direction of the steel plate. It is more preferable that it is shifted by Ap / 2.

  In the first aspect of the present invention, the headers (21, 22) are arranged on the upper surface side and the lower surface side of the steel plate, and the flat spray nozzles (21a, 21a, ..., 22a, 22a, ...) The high pressure jet water which is arranged so that the cooling water can be jetted toward the upper surface and the lower surface of the steel plate conveyed through the pass line and continuously jetted from the flat spray nozzle in the steel plate conveying direction is the work roll (11 gw) of the final stand. , 11gw) within the radius equivalent position to the housing post (11gh) exit side of the final stand, the steel plate may collide continuously with the upper and lower surfaces of the steel plate.

  Here, “the high-pressure jet water jetted continuously in the conveying direction of the steel plate from the flat spray nozzle” means a plurality of flat spray nozzles (21a, 21a arranged at predetermined intervals in the conveying direction of the steel plate (1). , ..., 22a, 22a, ...) refers to high-pressure jet water jetted continuously toward the upper and lower surfaces of the steel plate (1). Further, “the position corresponding to the radius of the work roll of the final stand” means, as shown in FIG. 4, a portion where the rolled steel plate (1) and the work rolls of the final stand (11 gw, 11 gw) are in contact (more specifically) 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 upper and lower surfaces of the steel plate (1) present 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).

  Further, in the first aspect of the present invention, the high-pressure jet water continuously collides with the upper surface and the lower surface of the steel plate in a 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. In the above section, it is preferable that the average value of the steel plate surface collision pressure of the high-pressure jet water in the section is 3.5 kPa or more on the upper surface of the steel plate and the lower surface of the steel plate.

  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 that one nozzle is responsible for may be obtained for each nozzle row arranged in the steel plate conveyance direction and averaged in the steel plate conveyance direction ( (See FIG. 4 and FIG. 7). In the present invention, for example, as shown in FIG. 6, when the nozzle pitch in the steel plate width direction is A and the nozzle pitch in the steel plate transport direction is B, that is, the header interval is B, the average collision pressure on the steel plate surface that one nozzle takes is The cooling water force (collision force) that collides with the parallelogram area whose area is represented by A × B can be calculated by dividing by the area A × B of the parallelogram.

  Further, in the first aspect of the present invention, the high-pressure jet water continuously collides with the upper surface and the lower surface of the steel plate in a 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 header (21) and flat spray nozzles (21a, 21a, ...) provided on the upper surface side of the steel plate, and the upper surface guide (23) provided between the flat spray nozzle and the pass line, It is preferable that they are not integrally formed.

  Here, the “upper surface guide (23)” means that the steel plate (1) rolled in the final stand (11g) is the work roll (11gwu) of the final stand or the nozzles (21a, 21a,...) Of the cooling device (20). ) Refers to a member of the cooling device (20) installed on the upper surface side of the steel plate (1) for the purpose of preventing collision with the steel plate.

  Further, in the first aspect of the present invention, the high-pressure jet water continuously collides with the upper surface and the lower surface of the steel plate in a 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 header (22) and flat spray nozzles (22a, 22a, ...) provided on the lower surface side of the steel plate, and the lower surface guide (24) provided between the flat spray nozzle and the pass line, It is preferable that they are not integrally formed.

  Further, in the first aspect of the present invention, the high-pressure jet water continuously collides with the upper surface and the lower surface of the steel plate in a 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. , A plurality of headers (21, 31, 22, 32) are provided, and at least a part of the headers are flat spray nozzles (31a, 31a) arranged in a plurality of rows in each of the conveying direction of the steel plate and the width direction of the steel plate. ,..., 32a, 32a,.

  The first aspect of the present invention is configured such that at least a part of the header is configured to be able to collectively supply cooling water to flat spray 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, It is preferable that the header is configured such that cooling water can be supplied collectively to flat spray nozzles (31a, 31a,...) 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 first aspect of the present invention is configured such that at least a part of the header is configured to be able to collectively supply cooling water to flat spray 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 arranged on the lower surface side of the steel plate, and among the headers provided on the lower surface side of the steel plate, at least the header (32) arranged on the most upstream side in the conveying direction of the steel plate, It is preferable that the header is configured so that the cooling water can be collectively supplied to the flat spray nozzles (32a, 32a,...) Arranged in a plurality of rows in each of the conveying direction of the steel plate and the width direction of the steel plate.

  In the first aspect of 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 and both end faces in the steel plate width direction of the final stand.

  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).

  The second aspect of the present invention includes a final stand (11g) in the hot finish rolling mill row (11), a hot-rolled steel sheet cooling device (20) according to the first aspect of the present invention, and a thermometer ( 14) in order in the conveyance direction of a steel plate (1), It is a manufacturing apparatus (10) of a hot-rolled steel plate characterized by the above-mentioned.

  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).

  A 4th aspect of this invention is arrange | positioned between the final stand (11g) in a hot finish rolling mill row | line | column (11), and the thermometer (14) arrange | positioned downstream of this final stand, and a pass line is arranged. Heat provided with a header (21, 22) having a plurality of flat spray nozzles (21a, 21a, ..., 22a, 22a, ...) provided so as to be able to inject cooling water toward the steel plate (1) to be conveyed. A method of controlling the operation of a cooling device (20) for a rolled steel sheet, wherein the headers (21, 22) are configured to be movable up and down, and based on the temperature measurement result of the steel sheet measured by a thermometer, An operation control method for a hot-rolled steel sheet cooling device, characterized in that vertical movement is controlled.

  In the fourth aspect of the present invention, the headers (21, 22) are arranged on the upper surface side and the lower surface side of the steel plate, and the flat spray nozzles (21a, 21a, ..., 22a, 22a, ...) The high pressure jet water, which is arranged so as to be able to inject cooling water toward the upper and lower surfaces of the steel plate (1) conveyed along the pass line, is continuously injected from the flat spray nozzle in the conveying direction of the steel plate. In the section from the position corresponding to the radius of the rolls (11gw, 11gw) to the housing post (11gh) exit side of the final stand, the upper surface and the lower surface of the steel plate may be continuously collided.

  In the present invention, since the header is configured to be movable up and down, the spray collision length can be kept constant by moving the header up and down even when the feed water pressure to the header is changed, for example. It becomes possible. By keeping the spray collision length constant, it is possible to cool the steel plate uniformly. Therefore, according to the present invention, the hot-rolled steel plate cooling device and the heat The manufacturing apparatus of a rolled steel sheet, the manufacturing method of a hot rolled steel sheet, and the operation control method of the cooling apparatus of a hot rolled steel sheet 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 which shows the example of the form of the cooling device of the hot-rolled steel plate of this invention. It is a figure explaining the concept of the steel roll conveyance direction average value of the position equivalent to the radius of the work roll of the last stand, the housing post exit side of the last stand, and the steel plate surface collision pressure of high-pressure jet water. 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 average value per nozzle of the steel plate surface collision pressure of high pressure jet water. Concept of the radius equivalent position of the work roll of the final stand, the housing post exit side of the final stand and the steel plate surface impinging pressure of the high pressure jet water in the steel rolling direction of the present invention according to another embodiment of the present invention FIG. It is a figure which shows the relationship between the required time for cooling to 720 degreeC, and the ferrite particle size obtained. It is a figure explaining the concept of the spray spread angle of the cooling water injected from the flat spray nozzle, the spray collision length, and the distance between nozzle steel plates. It is a figure which shows the relationship between feed water pressure and the injection spreading angle of cooling water. It is a figure which shows the relationship between the feed water pressure which maintains the spray collision length at a predetermined value, and the distance between nozzle steel plates. It is a figure which shows the example of a form of the jet water collision area of a cooling water.

  Hereinafter, the case where the present invention is applied to a hot-rolled steel sheet manufacturing apparatus capable of manufacturing ultrafine-grained steel will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and is ultrafine. The present invention can also be applied to the production of ordinary hot-rolled steel sheets that are not grain steel.

  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. In the following description, the upstream / downstream direction may be referred to as the passing plate direction, and the direction of the plate width of the steel plate to be passed in the direction orthogonal thereto may be referred to 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 control device 15 that controls the operation of the cooling device 20, a transport roll 12, a pinch roll 13, and a thermometer 14 are provided. In the manufacturing apparatus 10, the control device 15 is configured to control the operation of the cooling device 20 based on the temperature measurement result of the steel plate 1 measured by the thermometer 14. 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 thermometer 14, 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 grade of the temperature nonuniformity etc. in the board width direction of a steel plate is measured for the steel plate which passed the pinch roll 13 using the thermometer 14. FIG. The steel plate whose temperature has been measured by the thermometer 14 is then cooled to a predetermined winding temperature by another cooling device, and wound in a coil shape by a 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 sheet passing 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.

  2 and 3 are enlarged views of the final stand 11g, the cooling device 20, the transport roll 12, and the pinch roll 13 from FIG. 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. On the other hand, FIG. 3 shows a state of the cooling device 20 when the work rolls 11gw and 11gw of the final stand 11g are exchanged. Further, FIG. 4 shows the average value of the work rolls 11gw and 11gw corresponding to the radius of the final stand 11g, the exit side of the housing post 11gh of the final stand 11g, and the steel plate conveyance direction average value of the steel plate surface collision pressure of high-pressure jet water ( In the following, it is referred to as “cooling water collision pressure average value”). The left side of FIG. 4 is the upstream side in the conveyance direction of the steel sheet, and the right side of FIG. 4 is the downstream side in the conveyance direction of the steel sheet. Hereinafter, the cooling device 20 will be described in detail with reference to FIGS.

  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 header 21 to which a plurality of flat spray nozzles 21a, 21a,... (Hereinafter, simply referred to as “nozzle 21a” or the like) that inject high-pressure jet water toward the upper surface of the steel plate 1 are connected. 21 and headers 22, 22 to which a plurality of flat spray nozzles 22 a, 22 a, (hereinafter simply referred to as “nozzle 22 a”) for injecting high-pressure jet water toward the lower surface of the steel plate 1 are connected. It is equipped with. A plurality of nozzles 21 a, 21 a,... Arranged at a predetermined pitch in the steel plate width direction are connected to the header 21, and the plurality of headers 21, 21,. ing. Similarly, a plurality of nozzles 22a, 22a,... Arranged at a predetermined pitch in the steel plate width direction are connected to the header 22, and the plurality of headers 22, 22,. Is arranged in. The headers 21, 21,... Are configured to be able to supply cooling water to a plurality of nozzles 21 a, 21 a,... Arranged at a predetermined pitch in the width direction of the steel plate 1, and the headers 22, 22,. The cooling water can be collectively supplied to a plurality of nozzles 22a, 22a,... Arranged at a predetermined pitch in the width direction. The two rows of nozzles 21a and 21a on the upper surface side of the steel plate 1 and the two rows of nozzles 22a and 22a on the lower surface side of the steel plate 1 are arranged on the most upstream side in the conveyance direction of the steel plate 1. In order to be able to inject high-pressure jet water obliquely toward the upstream side, the respective axial directions are arranged so as to intersect the vertical plane. In the cooling device 20, an angle formed by the axial direction of the nozzles 21 a and 22 a arranged on the most upstream side in the conveying direction of the steel sheet 1 with respect to the vertical plane (hereinafter referred to as “vertical in-plane inclination angle”) is the nozzle. 21a and 22a and the vertical in-plane inclination angle given to the nozzles 21a and 22a adjacent to the downstream side in the conveying direction of the steel plate 1 are set to be equal to or greater than the vertical in-plane inclination angle. In the cooling device 20, the headers 21 and 21 and the headers 22 and 22 are configured to be movable up and down. Between the nozzle 21a and the upper surface of the steel plate 1, there are provided upper surface guides 23, 23 for preventing the nozzle 21a and the steel plate 1 from colliding with each other. Between the nozzle 22a and the lower surface of the steel plate 1, the nozzle 22a and Lower surface guides 24 and 24 for preventing a collision with the steel plate 1 are provided. In the cooling device 20, the vertical movements of the headers 21 and 21 and the headers 22 and 22 are controlled by the control device 15. Further, the cooling device 20 is configured so that the header 21 and the upper surface guide 23 provided in the vicinity of the work roll 11gwu of the final stand 11g can move up and down independently, and in the vicinity of the work roll 11gwd of the final stand 11g. The header 22 and the lower surface guide 24 provided are configured to be movable up and down independently.

  When the pressure (water supply pressure) of the cooling water supplied to the headers 21 and 21 and the headers 22 and 22 is changed, the high-pressure jet water jetted from the nozzles 21 a collides with the upper surface of the steel plate 1. The shape of the jet collision area (particularly, the spray collision length; the same applies hereinafter) and the shape of the jet collision area formed by the high-pressure jet water jetted from the nozzle 22a hitting the lower surface of the steel plate 1 are as follows. Change. Moreover, even if the thickness of the steel sheet 1 cooled by the cooling device 20 changes, the shape of the jet collision area formed by the high-pressure jet water sprayed from the nozzle 21a colliding with the upper surface of the steel sheet 1, and The shape of the jet collision area formed when the high-pressure jet water jetted from the nozzle 22a collides with the lower surface of the steel plate 1 can be changed. On the other hand, as described above, in order to manufacture ultrafine-grained steel, it is important to quench the steel plate 1 immediately after the introduction of rolling strain by the final stand 11g, and to quench the steel plate 1 immediately after the introduction of rolling strain. For this, it is important that the high pressure jet water collides with the upper surface and the lower surface of the steel plate 1 continuously from within the position corresponding to the radius of the work rolls 11gw and 11gw of the final stand 11g. Therefore, even if the feed water pressure to the headers 21 and 21 and the headers 22 and 22 and the thickness of the steel plate 1 are changed, the upper surface of the steel plate 1 existing within the position corresponding to the radius of the work rolls 11gw and 11gw of the final stand 11g. From the viewpoint of making the high-pressure jet water collide with the lower surface, the shape of the jet collision area formed by the high-pressure jet water jetted from the nozzle 21a colliding with the upper surface of the steel plate 1, and It is preferable that the cooling device 20 has a configuration in which the shape of the jet collision area formed by the high-pressure jet water ejected from the nozzle 22a colliding with the lower surface of the steel plate 1 does not change. From this point of view, in the cooling device 20, the headers 21 and 21 and the headers 22 and 22 are configured to be vertically movable, and the vertical motion is controlled by the control device 15. That is, by adopting a form in which the headers 21 and 21 and the headers 22 and 22 that can move up and down are provided, even if the feed water pressure to the headers 21 and 21 and the headers 22 and 22 and the thickness of the steel plate 1 change, the final Since it becomes possible to make high-pressure jet water collide with the upper surface and the lower surface of the steel plate 1 continuously from within the position corresponding to the work roll radius of the stand 11g, according to the present invention, ultra fine grain steel can be manufactured. Therefore, it is possible to provide a cooling device 20 that can perform the above-described operation.

  Further, the control device 15 that controls the operation of the cooling device 20 operates the operation of the cooling device 20 (specifically, based on the temperature measurement result of the steel sheet 1 measured by the thermometer 14 disposed on the downstream side of the cooling device 20). Are configured such that the water supply pressure to the headers 21 and 21 and the headers 22 and 22, the distance between the headers 21 and 21 and the steel plate 1, the distance between the headers 22 and 22 and the steel plate 1, and the like can be controlled. ing. Therefore, according to the cooling device 20, for example, the headers 21 and 21 and the headers 22 and 22 are controlled by controlling the operation of the control device 15 so as to reduce the cooling non-uniformity of the steel sheet 1 measured by the thermometer 14. Is moved up and down, whereby the steel sheet 1 can be cooled uniformly. By cooling the steel plate 1 using the cooling device 20 whose operation is controlled in this manner, the position from the position corresponding to the radius of the work rolls 11gw and 11gw of the final stand 11g to the exit side of the housing post 11gh of the final stand 11g. In the section, the upper and lower surfaces of the steel plate 1 can be uniformly cooled rapidly. Therefore, according to this invention, the cooling device 20 which can manufacture the hot rolled steel plate which has a substantially uniform ultrafine crystal grain can be provided.

  Moreover, in the cooling device 20, the header 21 and the upper surface guide 23 provided in the vicinity of the work roll 11gwu are both configured to be movable, and the header 22 and the lower surface guide 24 provided in the vicinity of the work roll 11gwd are provided. Both are configured to be movable. Therefore, for example, when exchanging the work rolls 11gw and 11gw of the final stand, the upper surface guide 23 and the header 21 provided close to the work roll 11gwu of the final stand are moved, and the work roll 11gwd of the final stand is moved. The lower surface guide 24 and the header 22 provided in the vicinity can be moved. Therefore, according to the cooling device 20, it becomes possible to improve the work efficiency of roll replacement.

  As shown in FIGS. 2 and 4, when the steel plate 1 is rapidly cooled using the cooling device 20, the collision area (jet collision area) of the high-pressure jet injected from the nozzle 21a is the work roll radius of the final stand 11g. It reaches the region on the roll bite side from the equivalent position, and the collision area (jet collision area) of the high-pressure jet injected from the nozzle 22a is closer to the roll bite side than the work roll radius equivalent position of the final stand 11g. Reach to the area. Further, as shown in FIG. 2 and FIG. 3, the cooling device 20 includes headers 21, 21,..., And a steel plate to which a plurality of nozzles 21a, 21a,. .., To which a plurality of nozzles 22a, 22a,... Arranged at a predetermined pitch in the width direction are connected, are arranged at a predetermined pitch in the conveying direction of the steel sheet. 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. It is possible to inject (substantially continuously, substantially continuously). By injecting high-pressure jet water onto the upper surface and the lower surface of the steel plate 1, even if stagnant water exists on the surface of the steel plate 1, the high-pressure jet water can penetrate the boiling film on the steel plate surface. Can be cooled by nucleate boiling (quenched). 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. 5 is a view 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. 5 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 (upper surface and lower surface) from 750 ° C. to 600 ° C. Yes, the horizontal axis of FIG. 5 is the average value [kPa] in the steel plate conveyance direction of the steel plate surface collision pressure of the high-pressure jet water. As shown in FIG. 5, 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. In addition, as shown in FIG. 6, the average value of high-pressure jet water impinging on the steel sheet surface in the steel sheet conveyance direction is such that the area is A when the nozzle pitch in the steel sheet width direction is A and the nozzle pitch in the steel sheet conveyance direction is B. The average collision pressure per flat spray nozzle calculated by dividing the force (collision force) of the cooling water that collided with the quadrilateral area represented by × B by the area A × B of the quadrilateral area. , Averaged over the relevant section in the transport direction.

  In this invention, the steel plate conveyance direction average value of the steel plate surface collision pressure of the high pressure jet water injected from the cooling device 20 to the steel plate 1 is not specifically limited. However, it is preferable to set it as 3.5 kPa or more from a viewpoint of making the steel plate 1 the form which can be rapidly cooled, suppressing the recovery | restoration etc. of an austenite grain. Moreover, in this invention, it is preferable to quench the steel plate 1 rapidly with an average cooling rate of 1000 degrees C / s or more from a viewpoint of making a crystal grain into the form which can be refined | miniaturized. In the present invention, it is preferable that the average collision pressure value of the cooling water is 8 kPa or more from the viewpoint of making the steel sheet 1 capable of being rapidly cooled 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 average collision pressure per flat spray nozzle is equal to the collision force of the high-pressure jet water ejected from the flat spray nozzle divided by the cooling area that the flat spray nozzle is responsible for. Therefore, even if the collision force is measured instead of measuring the pressure, the collision pressure average value of the cooling water can be calculated, and the collision force of the high-pressure jet water can be obtained from its flow rate and flow velocity. Since the flow velocity depends on the feed water pressure to the flat spray nozzle, the average value of the steel plate collision pressure 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 present invention, if the stagnant water exists on the surface of the steel plate, the pressure of the high-pressure jet water jetted from the nozzle 21a is reduced by the stagnant water, and the collision pressure of the high-pressure jet water when reaching the surface of the steel plate 1 is reduced. Easy to reduce. 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.

  Moreover, in the said description regarding the cooling device 20 of this invention, not only the area | region to the housing post 11gh exit side of the last stand 11g of a hot rolling mill row | line | column but the area | region downstream from the said area | region WHEREIN: , 21a, ..., 22a, 22a, ... are shown, but 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.

  Moreover, in the said description regarding the cooling device 20 of this invention, the header 21 arrange | positioned at the upper surface side of the steel plate 1 and the upper surface guide 23 are not comprised integrally, and the header 22 arrange | positioned at the lower surface side of the steel plate 1 and Although the form which is not comprised integrally with the lower surface guide 24 was illustrated, the cooling apparatus of the hot-rolled steel plate of this invention is not limited to the said form. The hot-rolled steel sheet cooling device of the present invention is configured such that the header and the lower surface guide disposed integrally on the lower surface side of the steel sheet, or the header and upper surface guide disposed on the upper surface side of the steel sheet are configured integrally. It is also possible to adopt a form. In order to make it possible to replace the roll provided in the final stand of the hot rolling mill row, a header 21 arranged close to the work roll 11gwu, an upper surface guide 23, a header 22 arranged close to the work roll 11gwd, and The lower surface guide 24 only needs to be configured to be movable, and these can be moved using a known means such as a hydraulic cylinder.

  Moreover, in the said description regarding the cooling device 20 of this invention, the some header 21,21, ... to which the some nozzle 21a, 21a, ... arrange | positioned by the predetermined pitch to the width direction of the steel plate 1 was connected is the steel plate 1. A plurality of headers 22, 22,... Connected to a plurality of nozzles 22 a, 22 a,... Arranged at a predetermined pitch in the conveyance direction and arranged at a predetermined pitch in the width direction of the steel plate 1 are the conveyance direction of the steel plate 1. However, the hot-rolled steel sheet cooling device of the present invention is not limited to this form. The cooling device of the present invention is a header configured to be able to collectively supply cooling water to a plurality of nozzles arranged at a predetermined pitch in the width direction of the steel plate and the conveying direction of the steel plate (hereinafter referred to as “collective header”). Can be arranged on the upper surface side and / or the lower surface side of the steel plate. FIG. 7 shows an example of a form of the hot-rolled steel sheet cooling device of the present invention provided with a collective header. FIG. 7 is a view for explaining an example of a cooling apparatus for hot-rolled steel sheets provided with a collective header. FIG. 7 shows the position corresponding to the radius of the work roll of the final stand and the housing post exit side of the final stand. Moreover, the concept of the steel plate conveyance direction average value of the steel plate surface collision pressure of high pressure jet water is also shown. 7, components similar to those of the manufacturing apparatus 10 and the cooling apparatus 20 are denoted by the same reference numerals as those used in FIG. 4, and description thereof is omitted as appropriate.

  As shown in FIG. 7, the hot-rolled steel sheet cooling device 30 of the present invention (hereinafter sometimes simply referred to as “cooling device 30”) is 3 on the uppermost stream side of the steel plate 1 on the uppermost stream side in the steel sheet conveying direction. A collective header 31 configured to be able to supply cooling water to the flat spray nozzles 31a, 31a,... (Hereinafter, simply referred to as “nozzle 31a”, etc.) constituting the flat spray nozzle row of the row. The flat spray nozzles 32a, 32a,... (Hereinafter, simply referred to as “nozzle 32a” or the like constituting the three flat spray nozzle rows on the uppermost stream side in the steel plate conveyance direction are also provided on the lower surface side of the steel plate 1. It is configured in the same manner as the cooling device 20 except that a collective header 32 configured to be able to collectively supply cooling water is provided. Two rows of nozzles 31a, 31a connected to the collective header 31 from the most upstream side in the conveying direction of the steel plate 1 are connected to be able to inject high-pressure jet water obliquely toward the upstream side in the conveying direction of the steel plate 1. The two rows of nozzles 32a, 32a connected to the collective header 32 from the most upstream side in the conveying direction of the steel plate 1 are connected so that high-pressure jet water can be injected obliquely toward the upstream side in the conveying direction of the steel plate 1. Has been. In the cooling device 30, the vertical in-plane inclination angles of the nozzles 31 a and 32 a arranged on the most upstream side in the conveyance direction of the steel plate 1 are the same as the nozzles 31 a and 32 a adjacent to the nozzles 31 a and 32 a and the downstream side in the conveyance direction of the steel plate 1. It is set to be equal to or greater than the given vertical in-plane tilt angle. 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 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.

  Thus, by using the cooling devices 20 and 30 of the present invention, it becomes possible to produce ultrafine-grained steel. Therefore, based on the temperature measurement result of the steel sheet 1 measured by the thermometer 14, the header 21 and / or the header 22 provided in the cooling device 20 moves up and down, and the headers 31, 21 and / or provided in the cooling device 30. By controlling the vertical movements of the headers 32 and 22, it is possible to provide a method for controlling the operation of a cooling device for hot-rolled steel sheets that can produce ultrafine-grained steel. And it becomes possible by using the manufacturing apparatus 10 provided with the cooling device 20, and the manufacturing apparatus of a hot-rolled steel plate provided with the cooling device 30 to manufacture ultra fine grain steel. 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 and manufacturing apparatus 10 of a hot-rolled steel plate provided with the cooling device 30, ultra-fine grain steel It is possible to provide a method for producing a hot-rolled steel sheet capable of producing

  The operation control method of the hot-rolled steel sheet cooling device according to the present invention is based on the temperature measurement result of the steel plate measured by the thermometer arranged on the lower process side of the cooling device, and the header provided on the upper surface side of the steel plate. If the vertical movement and / or the vertical movement of the header provided on the lower surface side of the steel plate are controlled, the form is not particularly limited. For example, when the cooling unevenness of the steel sheet 1 derived using the temperature measurement result by the thermometer 14 exceeds the target value, the header 21, the header 31, and / or so that the cooling unevenness of the steel sheet 1 is less than the target value. Or it can be set as the form which controls operation | movement of the cooling device 20 so that the header 22 and the header 32 may be moved up and down. In addition, when the distance between the nozzle steel plates is determined according to the feed water pressure to the headers 21, 31 and the headers 22, 32, based on the relationship between the predetermined feed water pressure and the distance between the nozzle steel plates, It is also possible to move the headers 21 and 31 and the headers 22 and 32 up and down. The header of the cooling device to which the operation control method of the cooling device for a hot-rolled steel sheet according to the present invention is applied, even after the positions of the upper surface guide and the lower surface guide are fixed after completion of the exchange work such as work rolls, etc. From the point of view of making the steel plate uniformly coolable by making it possible to move the header provided on the upper surface side and / or the header provided on the lower surface side of the steel plate up and down. It is preferable that the header and the upper surface guide provided on the upper surface side of the steel plate are not integrally configured, and the header and the lower surface guide provided on the lower surface side of the steel plate are not configured integrally. It is preferable to do.

  When the present invention is applied to the production of ultrafine-grained steel, the cooling apparatus for hot-rolled steel sheets according to the present invention including the collective headers 31 and 32 as in the cooling apparatus 30 has the following effects in addition to the above effects. Can be expected. That is, for example, when it is necessary to change the cooling stop temperature, the cooling water is collectively supplied to a plurality of flat spray nozzles arranged in a row in the width direction of the steel sheet if the collective header is not provided. It is also possible to control ON / OFF of the cooling water for each header. However, when a collective header is provided, the flow rate of cooling water sprayed from a plurality of nozzle rows connected to the collective header cannot be controlled for each nozzle row. Therefore, when a collective header is provided, it is expected that the cooling stop temperature can be changed by changing the feed water pressure to the collective header. In this case, as described above, simply changing the feed water pressure to the header changes the spray collision length, which may reduce the uniform cooling performance of the steel sheet, but the header can be moved up and down as in the present invention. If the water supply pressure to the collective header is changed, the steel plate can be uniformly cooled by moving the collective header up and down accordingly.

  In the present invention, the distance between the nozzle disposed on the upper surface side of the steel plate and the upper surface of the steel plate is not particularly limited, but the collision pressure average value of the cooling water is increased by bringing the nozzle closer to the steel plate surface. This makes it easy to cool the steel sheet. Therefore, in the present invention, it is preferable that the distance between the nozzle surface (jetting surface of high-pressure jet water) facing the steel plate and the steel plate surface is less than 500 mm from the viewpoint of making the steel plate easily cooled. More preferably, it is 350 mm or less.

  Moreover, in the said description, although the form in which the vertical in-plane inclination angle was provided to the nozzle arrange | positioned in the steel plate conveyance direction upstream was illustrated, this invention is not limited to the said form. However, by giving a vertical in-plane inclination angle to one or two or more nozzle rows including the nozzle row arranged at the position closest to the work roll of the final stand, in particular in the steel sheet conveying direction, Within the position corresponding to the radius of the work roll of the stand, it becomes easy to make the high-pressure jet water collide with the upper surface and the lower surface of the steel plate positioned closer to the roll bite, and it becomes easy to rapidly cool the steel plate after rolling. Therefore, from the viewpoint of making the steel sheet easy to cool rapidly, etc., one or more rows including nozzle rows arranged at the position closest to the work roll of the final stand (the uppermost stream side in the steel plate conveyance direction) It is preferable to give a vertical in-plane inclination angle to the nozzle rows (nozzle rows arranged on the upper surface side and the lower surface side of the steel plate). Is preferably increased. Furthermore, from the viewpoint of making the steel plate easier to cool, a vertical in-plane inclination angle is given to the nozzle row arranged on the most upstream side in the steel plate conveyance direction, and the steel plate is arranged on the most upstream side in the steel plate conveyance direction. More preferably, the distance between the surface of the nozzle row (jetting surface of high-pressure jet water) and the surface of the steel sheet is minimized.

  Using a rolling mill having a roll diameter of 700 mm (radius of 350 mm) and a distance of 1800 mm from the center of the rolling mill (roll bite position) to the housing post exit side, a steel plate containing 0.1 mass% C and 1 mass% Mn The test was performed by rolling at a delivery speed of 600 mpm so that the exit bit thickness at the roll bite position was 3 mm, and then rapidly cooling. The rolling end temperature was set to 820 ° C., and continuous cooling to 720 ° C. was performed with the average impingement pressure of the cooling spray being 3.5 kPa or more in the section from the position within 350 mm corresponding to the roll radius to 1800 mm on the housing post exit side. At that time, the function of controlling the distance between the upper surface side header and the steel plate, the lower surface side header and the steel plate was turned on, and the obtained ferrite grain size variation was comparatively investigated. The results are shown in Table 1. Condition No. 1-2 are examples (examples of the present invention). 3 to 4 are comparative examples. In Table 1, the average value of the collision pressure of the cooling water (the average value of the steel plate surface collision pressure of the high pressure jet water in the steel plate conveyance direction) is described as “average collision pressure”.

  As shown in Table 1, the condition No. of the present invention example including the header vertical movement control was entered. 1 and 2, the temperature unevenness after cooling was suppressed within 32 ° C., and as a result, the variation in the ferrite particle size was suppressed to 0.8 μm at maximum. In 3-4, the temperature non-uniformity after cooling became 53 ° C. or more, and the variation in ferrite grain size became 1.2 μm or more. That is, according to the present invention, it was possible to cool the steel plate uniformly.

  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 apparatus, a hot-rolled steel sheet manufacturing apparatus, and a hot-rolled steel sheet manufacturing method that involve such changes And the operation control method of the cooling apparatus of a hot-rolled steel sheet should also be understood as being included in the technical scope of the present invention.

  The hot-rolled steel sheet cooling apparatus, hot-rolled steel sheet manufacturing apparatus, hot-rolled steel sheet manufacturing method, and hot-rolled steel sheet cooling apparatus operation control method of the present invention are used for manufacturing hot-rolled steel sheets having ultrafine crystal grains. Can be used. 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 14 ... Thermometer 15 ... Control device 20 ... Hot-rolled steel sheet cooling device 21 ... Header 21a ... Nozzle 22 ... Header 22a ... Nozzle 23 ... Upper surface guide 24 ... Lower surface guide 30 ... Hot-rolled steel plate Cooling device 31 ... Collective header 31a ... Nozzle 32 ... Collective header 32a ... Nozzle

Claims (17)

A plurality of hot finish rolling mills arranged between a final stand and a thermometer arranged on the downstream side of the final stand, and provided with a plurality of jets capable of injecting cooling water toward the steel sheet conveyed through the pass line Comprising a header with a flat spray nozzle,
The said header is comprised so that vertical movement is possible, The cooling device of the hot-rolled steel plate characterized by the above-mentioned. The apparatus for cooling a hot-rolled steel sheet according to claim 1, wherein the vertical movement of the header is controlled based on a temperature measurement result of the steel sheet measured by the thermometer. The apparatus for cooling a hot-rolled steel sheet according to claim 1 or 2, wherein the pressure of the cooling water supplied to the header is controlled. The cooling water sprayed from the flat spray nozzle forms a belt-like or oval jet collision area on the surface to be cooled of the steel plate,
The said flat spray nozzle is arrange | positioned so that all the points of the width direction of the said steel plate may pass the said jet collision area 2 times or more, The any one of Claims 1-3 characterized by the above-mentioned. Hot-rolled steel sheet cooling device. A belt-shaped or oval-shaped jet collision area formed by the cooling water sprayed from the flat spray nozzle colliding with the surface to be cooled of the steel sheet is respectively in the sheet width direction of the steel sheet and the conveying direction of the steel sheet. Arranged at predetermined intervals,
The two jet collision areas adjacent to each other in the conveying direction of the steel plate are arranged so that positions in the plate width direction of the steel plate are shifted from each other. The cooling apparatus for hot-rolled steel sheets as described. The header is disposed on the upper surface side and the lower surface side of the steel plate,
The flat spray nozzle is arranged to be able to inject cooling water toward the upper surface and the lower surface of the steel sheet conveyed through a pass line,
The high-pressure jet water sprayed continuously in the conveying direction of the steel sheet from the flat spray nozzle is a 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 apparatus for cooling a hot-rolled steel sheet according to any one of claims 1 to 5, wherein the apparatus continuously collides with an upper surface and a lower surface. 7. The heat according to claim 6, wherein an average value in the steel plate conveyance direction of the steel plate surface collision pressure of the high-pressure jet water in the section is 3.5 kPa or more on the upper surface of the steel plate and the lower surface of the steel plate. A device for cooling rolled steel sheets. The header and the flat spray nozzle provided on the upper surface side of the steel plate, and the upper surface guide provided between the flat spray nozzle and the pass line are not integrally formed. The cooling apparatus for hot-rolled steel sheets according to claim 6 or 7. The header and the flat spray nozzle provided on the lower surface side of the steel plate, and the lower surface guide provided between the flat spray nozzle and the pass line are not integrally formed. The cooling apparatus for hot-rolled steel sheets according to any one of claims 6 to 8. 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 6 to 9, 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 10, wherein the header is configured to be able to supply cooling water to the flat spray nozzle. 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 10 or 11, wherein the header is configured such that cooling water can be supplied to the flat spray nozzle. 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 1-12 characterized by the above-mentioned. The cooling apparatus for hot-rolled steel sheets according to item 1. The final stand in the hot finish rolling mill, the cooling device for hot-rolled steel sheet according to any one of claims 1 to 13, and a thermometer are provided in order in the transport direction of the steel sheet, Hot rolled steel sheet manufacturing equipment. The manufacturing method of a hot-rolled steel sheet characterized by including 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 of the hot-rolled steel sheet of Claim 14. A plurality of hot finish rolling mills arranged between a final stand and a thermometer arranged on the downstream side of the final stand, and provided with a plurality of jets capable of injecting cooling water toward the steel sheet conveyed through the pass line A method for controlling the operation of a hot-rolled steel sheet cooling device comprising a header having a flat spray nozzle,
The header is configured to be movable up and down,
The operation control method of a cooling apparatus for a hot-rolled steel sheet, wherein the vertical movement of the header is controlled based on a temperature measurement result of the steel sheet measured by the thermometer. The header is disposed on the upper surface side and the lower surface side of the steel plate,
The flat spray nozzle is arranged to be able to inject cooling water toward the upper surface and the lower surface of the steel sheet conveyed through a pass line,
The high-pressure jet water sprayed continuously from the flat spray nozzle in the conveying direction of the steel plate is a 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 operation control method for a hot-rolled steel sheet cooling device according to claim 16, characterized in that the upper surface and the lower surface continuously collide with each other.

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