JP2006035233A - Cooling device for steel plate, and manufacturing method and manufacturing device for hot-rolled steel plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling device for a steel plate, which reduces the irregularity of cooling, to provide a manufacturing device for a hot-rolled steel plate, which is equipped with the cooling device, and to provide a manufacturing method for a hot-rolled steel, which includes a process for treating a hot-rolled steel by the manufacturing device. <P>SOLUTION: In the cooling device, a plurality of cooling nozzle bands, which cool a steel plate 16 carried on carrying rolls 29, are arranged in the upper and under sides of the steel plate 16, are aligned in rows in the carrying direction of the steel plate 16, and are equipped with a plurality of cooling nozzles arranged at prescribed intervals in the width direction of the plate. Further, the cooling device for a steel plate is provided with 1st guide plates 22a, 22b, 22c which are set between the cooling nozzles in the upper side of the steel plate 16 and a pass line, and which have inflow holes, through which cooling water sprayed from cooling nozzles toward the steel plate 16 passes, and also have outflow holes, through which the cooling water passes in the direction from the steel plate 16 toward cooling nozzles. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cooling device that can uniformly cool a steel plate, a hot-rolled steel plate manufacturing apparatus including the cooling device, and a hot-rolled steel plate manufacturing method.

  Steel materials used in automobile materials and structural materials are required to have excellent mechanical properties such as strength, workability, and toughness. To improve these mechanical properties comprehensively, the steel structure must be refined. Is effective. Therefore, many manufacturing methods for obtaining a steel material having a fine structure have been sought. In addition, the microstructure refinement method has recently attracted attention as a method for realizing the production of an inexpensive high-strength hot-rolled steel sheet with a reduced amount of alloy elements.

  As a method for refining the microstructure, particularly in the latter stage of finish rolling, a method is known in which high-pressure rolling is performed to refine the austenite grains and to accumulate rolling strain in the steel sheet to refine the ferrite grains obtained after rolling. It has been. Further, it is effective to cool the steel sheet to 600 to 700 ° C. in the shortest possible time after rolling from the viewpoint of promoting the ferrite transformation by suppressing recrystallization and recovery of austenite. That is, following the finish rolling, it is effective to install a cooling device capable of cooling at a cooling rate several times that conventionally performed on the run-out table and quench the rolled steel sheet rapidly.

  However, the higher the cooling capacity of the cooling device, the shorter the device length that the cooling device that can be cooled to the target cooling temperature should be, and the cooling device becomes compact. On the other hand, the cooling capacity of the device (especially the steel plate width) If there is even a slight non-uniformity in the cooling capacity in the direction), the influence of the non-uniformity tends to expand, and the risk of large temperature unevenness in the steel sheet after cooling increases. In other words, when applying a cooling device having an excellent cooling capacity to an actual machine, it is necessary to consider not only the realization of the target cooling rate, but also to further increase the uniformity of the cooling capacity compared to the conventional cooling device. . In the conventional cooling of hot-rolled steel sheets, the temperature distribution in the width direction of the steel sheet after cooling is not a problem for the cooling device in the run-out table, etc., except for the prevention of overcooling at the end of the steel sheet. However, little technology has been developed to improve the temperature uniformity in the width direction of the steel sheet. In other words, the cooling device has only been devised mainly to obtain a uniform flow rate distribution.

  However, as described above, if the cooling device is made compact by increasing the cooling capability of the cooling device, a device that can eliminate even a slight non-uniformity of the cooling capability is required. In particular, in order to increase the cooling capacity, it is necessary to increase the amount of cooling water per unit area sprayed onto the steel sheet, that is, the flow density, but if the flow density is increased, the amount of cooling water (residual water) that accumulates on the steel sheet is increased. The amount also increases. This stagnant water flows from the central part of the steel plate toward the end, and its flow rate increases as it approaches the end of the steel plate, thereby causing uneven cooling in the steel plate width direction. And when the amount of staying water increases with the increase in flow density, the degree of uneven cooling in the steel plate width direction further increases. That is, as the cooling device has a higher cooling capacity, cooling unevenness due to stagnant water on the steel sheet is more likely to occur.

Until now, several techniques related to a steel sheet cooling apparatus have been disclosed. For example, in Patent Literature 1, a cooling device is installed from within 6 m behind the final finish rolling mill, and cooling is provided with a means for conveying the steel sheet to a narrow gap sandwiched by guides in the region from the rolling mill to the cooling device. Techniques relating to the apparatus are disclosed. Moreover, as a technique regarding the rapid cooling apparatus for hot-rolled steel sheets, for example, Patent Document 2 discloses an upper cooling water nozzle that is provided at the center between adjacent upper rolls and that discharges cooling water toward the upper surface of the steel sheet. And the technique regarding the apparatus which cools while removing the stagnant water on a steel plate by providing the water supply nozzle which attracts | sucks the cooling water discharged from the upper cooling water nozzle in the vicinity of each upper roll is disclosed. Further, in Patent Document 3, a cover is provided on the upper and lower sides of the steel plate between two sets of upper and lower rollers, a slit-like water supply nozzle is attached to each cover, and the end of the cover close to the roller surface is curved in a direction away from the steel plate. And a cooling device configured to discharge the cooling water sprayed from the nozzle through the cooling water chamber formed between the cover and the steel plate from the arc-shaped end. Yes.
JP 2001-246410 A Japanese Patent Publication No. 7-8374 Japanese Patent Publication No. 3-10407

  However, in the technique disclosed in Patent Document 1, when the flow density is increased in order to increase the cooling rate, the amount of cooling water flowing out from the central portion of the steel plate to the end portion increases particularly on the upper surface side of the steel plate. Therefore, there is a problem that the tendency of uneven cooling in the steel plate width direction becomes more prominent as the cooling rate is increased. In addition, in the technique disclosed in Patent Document 1, the guides provided up and down as the guide means for the steel plate between the final finish rolling mill and the cooling device are relatively long at a maximum of 6 m and between the upper and lower guides. It is necessary to gradually widen the gap toward the cooling device. Therefore, in addition to the frequency with which the steel plate comes into contact with the guide, cooling water cannot be injected in the section where the guide is provided, and a part of the steel plate surface is peeled off due to frictional heat and burned into the guide. There was a problem that it was easy to get wrinkles.

  Further, according to the technique disclosed in Patent Document 2, it is considered that cooling unevenness in the width direction of the steel plate can be reduced, but when the flow rate density is increased in order to increase the cooling rate, it should be supplied. The amount of cooling water also increases. However, since there is a limit to the amount of water that can be sucked by vacuum or the like, it is practically impossible to suck all the cooling water that accumulates 100 mm or more under high flow density conditions, for example. Therefore, a part of the cooling water flows out in the direction of the end, and there is a problem that the tendency of uneven cooling caused by being overcooled at the end cannot be eliminated.

  Furthermore, according to the technique disclosed in Patent Document 3, the flow of cooling water in the width direction of the steel plate on the steel plate can be suppressed, and the discharged cooling water flows out on the cover to cool the steel plate. Is not affected, it is considered that the occurrence of uneven cooling in the width direction of the steel sheet can be eliminated. However, the arc-shaped end provided in the vicinity of the restraining roll of the cover needs to be close to a position several tens of millimeters above the steel plate, but in order to prevent the steel plate tip from striking the cooling device, the steel plate After the leading end of the steel plate passes and the steel plate is restrained by the restraining roll, it is necessary to lower the nozzle and the cover and set them to a predetermined height. Furthermore, it takes at least about 5 to 10 seconds to lower the nozzle and the cover from the retracted position about 1 m above to the position just above the steel plate. Therefore, even if the cooling water injection is started in advance, the cooling is performed in a state in which the cooling capacity is greatly reduced while the apparatus is being lowered. Usually, since the steel plate is transported at a speed of about 10 to 15 m / second per second, the technique disclosed in Patent Document 3 sufficiently cools at least a portion of several tens of meters from the front end of the steel plate. There was a problem that it was unavoidable to wind in a state where there was no cooling and uneven cooling in the conveying direction of the steel sheet was likely to occur.

  The present invention has been made to solve the above-described problems, and is a steel sheet cooling apparatus capable of reducing uneven cooling, a hot-rolled steel sheet manufacturing apparatus including the cooling apparatus, and hot rolling. It is an object of the present invention to provide a method for manufacturing a hot-rolled steel sheet including a processing step by the manufacturing apparatus for the steel sheet.

  The present inventor does not need to close a vacuum device or a cover for guiding cooling water on the steel plate, that is, it is not necessary to retract the steel plate every time it enters the cooling device. A cooling device that can eliminate the occurrence of uneven cooling in the width direction of the steel sheet due to the flow of stagnant water on the steel sheet was studied. In FIG. 9, the shape of the stagnant water formed on the steel plate in a cooling device and the mode of the flow of cooling water are schematically shown. In FIG. 9, the arrow indicates the direction of the flow of the cooling water, and the length of the arrow corresponds to the flow speed. That is, a long arrow indicates that the flow of the cooling water is fast. Moreover, in FIG. 9, the left-right direction of a paper surface is a steel plate width direction, and the direction perpendicular | vertical to a paper surface is a steel plate conveyance direction.

In the cooling device shown in FIG. 9, a cooling water jet 93 a, 93 a,... Is ejected from a cooling nozzle 92 a, 92 a,. While being cooled, cooling water jets 93b, 93b,... Are jetted from cooling nozzles 92b, 92b,. And the cooling water sprayed from the cooling nozzles 92a, 92a, ... stays on the upper surface of the steel plate 96 to form the staying water 91.
As shown in FIG. 9, the stagnant water 91 flows out from the end in the plate width direction of the steel plate 96 toward the transport roll 99, so that the stagnant water 91 at the center of the steel plate has a height of the stagnant water 91 at the end of the steel plate. Higher than the height of On the other hand, due to the difference in hydrostatic pressure caused by the difference in liquid height, a flow of cooling water in the width direction of the steel sheet occurs from the center of the steel sheet toward the end of the steel sheet. Therefore, the liquid height of the stagnant water 91 is maximized at the central part of the steel sheet, and the liquid height gradually decreases from the central part of the steel sheet toward the end of the steel sheet, resulting in a crown-shaped distribution. On the other hand, the flow rate of the cooling water in the steel plate width direction increases as it approaches the end of the steel plate.

FIG. 10 shows the relationship between the flow rate density of the cooling water and the height of the stagnant water in the central part in the width direction of the steel plate when the plate width of the steel plate is 1.6 m. In FIG. 10, the vertical axis represents the height of the staying water at the central portion in the width direction of the steel plate, and the horizontal axis represents the flow rate density of the cooling water. From FIG. 10, the height of the stagnant water increases almost linearly as the cooling water flow density increases, and when the cooling water flow density is 20 m ³ / m ² · min, the stagnant water height is about 400 mm. You can see that Further, FIG. 11 shows the distance from the center in the width direction of the steel plate when the cooling water having a flow rate density of 20 m ³ / m ² · min is injected onto the steel plate having a plate width of 1.6 m, and the staying water height. And the relationship with the flow rate of the cooling water in the steel plate width direction (the flow rate averaged in the stagnant water height direction of the stagnant water flow flowing from the center of the steel plate width direction to the end) is shown. In FIG. 11, the left vertical axis, the right vertical axis, and the horizontal axis are the height of accumulated water, the flow rate of cooling water in the steel plate width direction, and the distance from the center of the steel plate width direction, respectively. . From FIG. 11, it can be seen that the height of the staying water has a crown-shaped distribution of about 400 mm at the center of the steel plate and about 300 mm at the end of the steel plate. Here, the higher the stay water on the steel plate, the lower the collision pressure when the cooling water jet collides with the steel plate, and the cooling capacity decreases. Therefore, when the above-mentioned crown-shaped distribution of stagnant water occurs on the steel sheet, the cooling capacity at the central part of the steel sheet decreases, so that a cooling capacity distribution in which the cooling capacity increases toward the end of the steel sheet occurs. Further, it can be seen from FIG. 11 that the flow rate of the cooling water increases almost linearly as it approaches the end of the steel plate, and the flow rate at the end of the steel plate is 0.8 m / sec. When such a flow velocity distribution occurs, a cooling effect due to the cooling water flow in the steel sheet width direction is added, and the cooling capacity tends to increase toward the end of the steel sheet. Therefore, the cooling capacity distribution in the steel sheet width direction is further enhanced. Is done.

  The inventor has completed the invention based on these findings. 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 embodiment.

  1st this invention is a steel plate cooling device (4) provided with the some cooling nozzle zone which should cool the steel plate (16) conveyed by the pass line on a conveyance roll (29, 29, ...), The plurality of cooling nozzle bands are provided on the upper surface side and the lower surface side of the steel plate (16) and are arranged in the conveying direction of the steel plate (16), and the cooling nozzle bands are predetermined in the plate width direction of the steel plate (16). A plurality of cooling nozzles (32a, 32a, ..., 32b, 32b, ...) arranged at intervals are provided, and the plurality of cooling nozzles (32a, 32a, ..., 32b, 32b, ...) cool the steel plate (16). The first guide plate (22a, 22b, 22c) is provided between the cooling nozzle (32a, 32a,...) Provided on the upper surface side of the steel plate (16) and the pass line. In addition, the first guide plate (22a, 22 , 22c) are the inflow holes (33a, 33a,...) Through which the cooling water jetted from the cooling nozzles (32a, 32a,...) Toward the steel plate (16) should pass, and the cooling water from the steel plate (16). The above problem is solved by a steel plate cooling device (4) characterized by having outflow holes (35a, 35a, ...) that should pass in the direction of the cooling nozzles (32a, 32a, ...).

  In said invention, it is preferable that the side wall (36a, 36b) is provided in the plate | board width direction both ends side of the steel plate (16) while being the upper surface side of a pass line.

  In the present invention, the distance between the upper side of the side walls (36a, 36b) and the pass line is preferably larger than the distance between the cooling water injection port of the cooling nozzle (32a, 32a,...) And the pass line. .

  Furthermore, in the present invention described above, the second is between the cooling nozzles (32b, 32b,...) Provided on the lower surface side of the steel plate (16) and the pass line formed by the transport rolls (29, 29,...). Guide plates (24a, 24b, 24c, 24d) are provided, and the second guide plates (24a, 24b, 24c, 24d) are directed from the cooling nozzles (32b, 32b,...) Toward the steel plate (16). Inflow holes (33b, 33b,...) Through which the injected cooling water should pass and outflow holes (35b, 35b) through which the cooling water should pass from the steel plate (16) in the direction of the cooling nozzles (32b, 32b,...). ,...

  Furthermore, in the present invention described above, it is preferable that side walls (36c, 36d) are provided on the lower surface side of the pass line and on both ends in the plate width direction of the steel plate (16).

In addition, in the present invention, the average flow rate of the cooling water per cooling nozzle (32a, 32a,..., 32b, 32b,...) Is Q _N (m ³ / min), and the plate width of the steel plate (16). cooling nozzle in a direction (32a, 32a, ..., 32b , 32b, ...) P W (m) average arrangement interval, an average interval _P L of the cooling nozzle zone in the transport direction of the steel plate (16) (m), and When the number of cooling nozzle bands in the conveying direction of the steel plate (16) is N _L , the flow density W _D (m ³ / m ² · min) defined by the equation (1) is 6.0 or more. it is preferable to satisfy the formula (2) effective cooling length is defined by _L C (m) and flow density _{W D} Togashiki (3).
W _D = Q _N / (P _W · P _L ) (1)
L _C = P _L · N _L (2)
^{_{8.5 / W D 3/5 ≦ L C}} ≦ 36.7 / W D 2/3 (3)

  The second aspect of the present invention is the final stand (2a) in the hot rolling finish rolling mill row (2), the steel sheet cooling device (4) according to the first aspect of the present invention, and the draining means (8) for draining the cooling water. , 14) in order in the conveying direction of the steel plate (16), the above-mentioned problem is solved by a manufacturing apparatus for a hot-rolled steel plate.

  In the second aspect of the present invention, a pool of cooling water is formed in a region between the rolls (21a, 21b) of the final stand (2a) and the draining means (14), and the steel plate (16) is used for cooling the pool. It is preferable that the draining means (8, 14) is arranged so as to be immersed in water.

  Moreover, in the said 2nd this invention, the cooling nozzle (32a, 32a, ...) of the cooling device provided in the upper surface side of the steel plate (16) is a cooling water injection port of a cooling nozzle (32a, 32a, ...). Is preferably provided so as to be immersed in the cooling water of the pool.

  Furthermore, in the second aspect of the present invention, the cooling nozzles (32a, 32a, ..., 32b, 32b, ...) included in the cooling nozzle band closest to the final stand (2a) among the cooling nozzle bands included in the cooling device (4). ) Is preferably directed to the steel plate to be positioned at the outlet of the final stand (2a).

  3rd this invention processes the steel plate (16) rolled by the last stand (2a) in a hot-rolling finish rolling mill row | line | column (2) using the manufacturing apparatus of the hot-rolled steel plate concerning 2nd this invention. The said subject is solved by the manufacturing method of a hot-rolled steel plate characterized by including a process.

  According to 1st this invention, since it becomes possible to reduce especially the cooling nonuniformity in a steel plate width direction, the cooling device (4) of the steel plate which can reduce a cooling nonuniformity can be provided. .

  Moreover, the side wall (36a, 36b) is provided on the both sides of the plate width direction of the steel plate (16) on the upper surface side of the pass line, thereby suppressing the flow of cooling water in the steel plate width direction at the steel plate end portion. And the space between the steel plate (16) and the first guide plates (22a, 22b, 22c) can be easily filled with cooling water. Therefore, according to 1st this invention, the cooling device (4) of a steel plate which can reduce a cooling nonuniformity easily can be provided.

  Further, the distance between the upper side of the side wall (36a, 36b) and the pass line is larger than the distance between the cooling water injection port of the cooling nozzle (32a, 32a,...) And the pass line, so that the cooling nozzle (32a, 32a). ,...) Can reach the surface of the steel plate (16) without being affected by the height distribution of the stagnant water (31) and the flow of cooling water in the width direction of the steel plate. It becomes possible. Therefore, according to 1st this invention, the cooling device (4) of the steel plate which can reduce a cooling nonuniformity further can be provided.

  Furthermore, by providing the second guide plates (24a, 24b, 24c, 24d), the space between the steel plate (16) and the second guide plates (24a, 24b, 24c, 24d) It becomes possible to fill with cooling water sprayed from the cooling nozzles (32b, 32b,...). Therefore, according to 1st this invention, it becomes possible to improve the cooling capability of the cooling device (4) of a steel plate.

  Furthermore, the side wall (36c, 36d) is provided on the lower surface side of the pass line and on both ends in the plate width direction of the steel plate (16), so that the steel plate (16) and the second guide plates (24a, 24b). 24c, 24d) can be easily filled with the cooling water sprayed from the cooling nozzles (32b, 32b,...), And the lower surface side of the steel plate (16) is also in the steel plate width direction. Uniform cooling is possible. Therefore, according to 1st this invention, while being able to improve cooling capacity, the cooling device (4) of a steel plate which can reduce a cooling nonuniformity further can be provided.

In addition, the flow density W _D (m ³ / m ² · min) defined by the equation (1) is 6.0 or more, and the effective cooling length L _C (m) defined by the equation (2) by satisfying flow density W _D Togashiki (3), while having a cooling capacity required for the refinement of the crystal grains, comprising an effective cooling length L _C can be suppressed to below 8m. Therefore, according to 1st this invention, the cooling device (4) of a steel plate can be arrange | positioned, without remodeling the rolling line of the conventional hot-rolled steel plate significantly.

  According to the second aspect of the present invention, the steel plate (16) that has passed through the final stand (2a) of the hot rolling finish rolling mill row (2) is cooled by the steel plate cooling device (4) that can uniformly cool the steel plate. Can do. If the steel plate is cooled by a steel plate cooling device capable of uniformly cooling the rolled steel plate, a high-strength hot-rolled steel plate can be produced. According to the second aspect of the present invention, the high-strength hot-rolled steel plate The manufacturing apparatus of the hot-rolled steel plate which can manufacture can be provided.

  In addition, the steel plate (16) that has passed through the final stand (2a) of the hot rolling finish rolling mill row (2) is immersed in a pool of cooling water, so that the steel plate (16) after rolling can be rapidly cooled. The rapid cooling of the steel sheet after rolling is effective for producing a high-strength hot-rolled steel sheet. Therefore, according to 2nd this invention, the manufacturing apparatus of the hot-rolled steel plate which can manufacture a high intensity | strength hot-rolled steel plate easily can be provided.

  Furthermore, the cooling water injection port of the cooling nozzle (32a, 32a,...) Is immersed in the cooling water of the pool, so that the steel plate (16) that has passed through the final stand (2a) of the hot rolling finish rolling mill row (2). It becomes easy to rapidly cool evenly. Therefore, according to 2nd this invention, the manufacturing apparatus of the hot-rolled steel plate which can manufacture a high strength hot-rolled steel plate still more easily can be provided.

  In addition, the cooling nozzles of the cooling nozzles (32a, 32a, ..., 32b, 32b, ...) included in the cooling nozzle band closest to the final stand (2a) among the cooling nozzle bands included in the cooling device (4) are provided. The steel plate (16) immediately after passing through the final stand (2a) can be easily and rapidly cooled by being directed to the steel plate to be positioned at the exit of the final stand (2a). Therefore, according to this invention, the manufacturing apparatus of the hot-rolled steel plate which can manufacture a high strength hot-rolled steel plate still more easily can be provided.

  According to 3rd this invention, the manufacturing method of the hot-rolled steel plate which can manufacture a high intensity | strength hot-rolled steel plate can be provided.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is an external view schematically showing an embodiment of a hot-rolled steel sheet manufacturing apparatus provided with the steel sheet cooling apparatus of the present invention. In FIG. 1, the steel sheet is conveyed from the left to the right direction, and the vertical direction in the drawing is the vertical direction. Hereinafter, the left side of FIG. 1 may be described as the upstream side, and the right side of the paper may be described as the downstream side.

  As shown in FIG. 1, a rough bar 1 extracted from a heating furnace and rolled by a roughing mill is continuously rolled to a predetermined thickness by a hot rolling finish rolling mill row 2 while being controlled in temperature. The steel sheet cooling device 4 of the invention (hereinafter sometimes referred to as “first cooling device”) 4 is rapidly cooled. Here, the first cooling device 4 is installed as close as possible to the rolling roll from the inside of the housing of the final stand 2a of the hot rolling finish rolling mill row. Then, the steel plate 16 that has passed through the first cooling device 4 is air-cooled for several seconds while being transported on the run-out tables 9, 9,..., And then cooled to a predetermined winding temperature by the second cooling device 5. Then, it is wound into a coil by the winder 3.

  A pinch roll 8 also serving as a draining means is provided on the exit side of the first cooling device 4, and a draining header 14 is provided on the upper surface side of the steel plate 16 on the downstream side of the pinch roll 8. Yes. Also, draining headers 15a and 15b are provided on the upper surface side of the steel plate 16 also on the entry side and the exit side of the second cooling device 5, and immediately after or immediately before each draining header 14, 15a and 15b. On the upper surface side of the steel plate 16, thermometers 6, 7a and 7b are provided. A thermometer 10 is provided on the upper surface side of the steel plate 16 between the final stand 2a of the hot rolling finish rolling mill row 2 and the stand 2b disposed immediately before the stand 2a. The finishing temperature of the steel plate 16 in the hot rolling finish rolling mill row 2 is estimated from the temperature measured by the thermometer 10 before the steel plate 16 is rolled by the final stand 2a, and is rapidly cooled by the first cooling device 4. The steel plate temperature after breaking is measured by the thermometer 6, and the steel plate temperature before and after cooling by the second cooling device 5 is measured by the thermometers 7a and 7b. On the other hand, the second cooling device 5 is a general run-out cooling device, in which the circular tube laminar nozzle headers 11, 11,... Spray nozzle headers 12, 12,... Are respectively provided.

  In the apparatus for manufacturing a hot-rolled steel sheet provided with the cooling device 4 according to the present invention, it is preferable to arrange the pinch roll 8 on the downstream side of the device 4. By adopting such a configuration, it becomes possible to prevent the cooling water sprayed in the cooling device 4 from flowing out to the downstream side of the steel plate 16, and the corrugation of the steel plate 16 in the cooling device 4 can be prevented. In particular, it is possible to improve the sheet passing property of the steel plate 16 at the time before the tip of the steel plate 16 bites into the winder 3.

FIG. 2 schematically shows an enlarged vertical section of the first cooling device 4. In FIG. 2, the horizontal direction in the figure is the steel plate conveyance direction and the horizontal direction, while the direction perpendicular to the paper surface is the steel plate width direction. Note that the vertical arrows in FIG. 2 indicate the moving direction of the upper roll 8 a in the pinch roll 8.
As shown in FIG. 2, the first cooling device 4 includes a first guide plate 22a and a second guide plate 24a. The first guide plate (hereinafter referred to as “upper guide plate”) 22a is disposed so as to be further away from the pass line formed by the transport rolls 29, 29, 29 toward the downstream side. The upper guide plates 22b and 22c following the guide plate 22a are disposed so as to be substantially parallel to the pass line or inclined so that the downstream side of the guide plate is slightly away from the pass line. On the other hand, a second guide plate (hereinafter referred to as “lower guide plate”) 24a and lower guide plates 24b, 24c, and 24d following the second guide plate are substantially parallel to the above-mentioned pass line, or of the guide plate. The downstream side is arranged so as to be inclined slightly away from the pass line. Conveying rolls 29, 29, 29 are arranged between the lower guide plates 24a, 24b, 24c, 24d, and the steel plate 16 rolled down by the rolls 21a, 21b of the final stand 2a of the hot rolling finish rolling mill row is The upper guide plates 22a, 22b, 22c and the lower guide plates 24a, 24b, 24c, 24d are guided into the first cooling device 4.

  On the outside of the upper guide plates 22a, 22b, 22c and the lower guide plates 24a, 24b, 24c, 24d, the cooling headers 26a, 26a, ..., 26b, 26b, ..., and 27a, 27a, ..., and 27b, 27b,... Are provided. .., 27a, 27a,..., And 27b, 27b,..., And 27b, 27b,... Have conduits attached at predetermined intervals in the steel plate conveyance direction. A cooling nozzle is attached to the end of the conduit. Further, the upper guide plates 22a, 22b, 22c and the lower guide plates 24a, 24b, 24c, 24d are provided with inflow holes through which the cooling water jet injected from the cooling nozzle toward the steel plate 16 should pass. The size and shape of the inflow hole prevents the cooling water jet from interfering with the guide plate and prevents the longitudinal end of the steel plate 16 from striking the inflow hole, as will be described later. From the viewpoint, it is designed for each guide plate.

By providing such a configuration, the first cooling device 4 has the following characteristics.
1) By continuously installing the upper guide plates 22a, 22b, 22c and the lower guide plates 24a, 24b, 24c, 24d from the exits of the rolls 21a, 21b, it is possible to prevent sticking particularly when entering the front end of the steel plate. However, since it is possible to guide the steel plate 16 into the first cooling device 4, it is not necessary to retract the cooling device 4 when the front end of the steel plate 16 enters. Therefore, the length of the unsteady cooling part at the front end of the steel plate can be shortened, and the cooling unevenness in the conveying direction of the steel plate 16 can be reduced.

  2) The steel plate 16 can be cooled by the first cooling device 4 immediately after passing through the hot rolling finish rolling mill row 2. Therefore, it is possible to rapidly cool the steel plate 16 without recovering the accumulated strain by performing strong reduction in the hot rolling finish rolling mill row 2, and it is possible to further promote the refinement of the structure in the steel plate 16. become.

  3) Before the tip of the steel plate enters the first cooling device 4, the cooling water in the first cooling device 4 is started in advance so that the tip of the steel plate is waved in the cooling device 4. Even if it becomes like the steel plate 20 and comes into contact with the guide plate, the cooling water is sprayed in the direction away from the guide plate. Therefore, even when the steel plate 20 collides with the guide plate, the impact of the collision can be reduced. In addition, since the frictional heat between the steel plate 16 and the guide plate can be reduced by the cooling water sprayed in advance, it is possible to suppress the peeling of the steel plate surface layer caused by the frictional heat. The wrinkles formed on the guide plate and the steel plate can be reduced.

  In addition, the region surrounded by the roll 21a, the steel plate 16, the upper roll 8a of the pinch roll, and the side wall described later (hereinafter sometimes referred to as “cooling chamber”) is filled with the cooling water, and the cooling water When the pool is formed, the first cooling device 4 is in a steady cooling state, and a predetermined cooling capacity can be obtained. Therefore, by adopting a configuration in which the pinch roll 8 is provided on the exit side of the first cooling device 4, the length of the unsteady cooling part at the front end of the steel plate can be further shortened.

In FIG. 3, the state of the flow of a staying water in the steel plate board width direction cross section of the 1st cooling device 4 is shown roughly. In FIG. 3, the direction perpendicular to the paper surface is the steel plate conveyance direction, while the left-right direction of the paper surface is the steel plate width direction. In FIG. 3, arrows indicate the flow of cooling water.
As shown in FIG. 3, in the first cooling device 4, the upper guide plate (corresponding to 22a, 22b, and 22c in FIG. 2 corresponds to the upper guide plate 37a in the description of FIG. ")" Is provided. In addition, a lower guide plate (corresponding to 24a, 24b, 24c, and 24d in FIG. 2; simply described as “lower guide plate 37b” in the description of FIG. 3) is provided on the lower surface side of the steel plate 16. A transport roll 29 is disposed. On the other hand, upper side walls 36a and 36b are provided on the upper surface side of the steel plate 16, and lower side walls 36c and 36d are provided on the lower surface side of the steel plate 16, respectively. A cooling chamber is formed surrounded by the roll and the side wall. Therefore, in the first cooling device 4, the cooling water sprayed toward the steel plate 16 is accumulated in the cooling chamber, and is immersed in the pool of accumulated water formed in the cooling chamber, so that the steel plate 16 is cooled. The

  From the cooling nozzles (hereinafter referred to as “upper nozzle” and “lower nozzle”) 32a, 32a,..., And 32b, 32b,. The cooling water jet injected toward the steel plate 16 flows into the cooling chamber through the inflow holes 33a, 33a,..., 33b, 33b, provided in the upper guide plate 37a and the lower guide plate 37b. collide. And the cooling water which collided with the upper surface side and lower surface side of the steel plate 16 goes out of the cooling chamber from the outflow holes 35a, 35a,... And 35b, 35b,. And discharged.

  In the first cooling device 4 shown in FIG. 3, the stagnant water is prevented from flowing out from the end of the steel plate 16 by the side walls 36 a, 36 b, 36 c, and 36 d provided on both ends in the plate width direction of the steel plate 16. The cooling water staying in the cooling chamber is discharged from the outflow holes 35a, 35a,... And 35b, 35b,. Therefore, the cooling water that has been injected from the cooling nozzles 32a, 32a,..., 32b, 32b,... Into the cooling chamber and collided with the steel plate 16 is suppressed from flowing in the width direction of the steel plate and into the cooling chamber. It passes through between the inflowing cooling water jets and is discharged from the outflow holes 35a, 35a,... And 35b, 35b,. Therefore, since the flow of the cooling water in the steel plate width direction hardly occurs in the cooling chamber, uniform cooling can be performed in the steel plate width direction.

  In the first cooling device 4 shown in FIG. 3, the distance between the upper ends of the upper side walls 36a and 36b and the steel plate 16 is made larger than the distance between the cooling water injection port and the steel plate 16 in the upper nozzles 32a, 32a,. It is preferable. Even if it is a case where the injection pressure of the cooling water injected from the upper nozzles 32a, 32a,... The liquid height can be made higher than the position of the cooling water injection port in the upper nozzles 32a, 32a,. Therefore, under the steady operation state of the first cooling device 4 in which the cooling chamber is filled with cooling water, the cooling water injection ports in the upper nozzles 32a, 32a,. Can be placed in cooling water. That is, as shown in FIG. 3, by disposing the cooling water injection ports in the upper nozzles 32a, 32a,... At positions lower than the upper ends of the upper side walls 36a and 36b, the stagnant water in the steel plate width direction with respect to the cooling water jet It becomes possible to completely eliminate the influence of the height distribution. On the other hand, as described above, in the first cooling device 4, since the flow of the cooling water in the steel plate width direction hardly occurs at the position lower than the upper ends of the upper side walls 36a and 36b, the steel plate width direction with respect to the cooling water jet. It is possible to eliminate the influence of the cooling water flow. Therefore, by using the first cooling device 4 having such a configuration, the collision pressure of the cooling water jet on the steel plate 16 can be completely equalized in all the cooling nozzles in the steel plate width direction. It becomes possible to perform further uniform cooling in the plate width direction.

Note that all times a sufficiently high flow density (e.g., flow density W _D defined by the following formula (1) 8.0 ^(m 3 / m 2 ^· min) approximately) in a situation where cooling water is injected When used, or when the upper guide plate 37a and the upper nozzles 32a, 32a,... Can be sufficiently close to the steel plate 16 and the side walls 36a, 36b, 36c, and 36d are not present, the upper guide plate When the space between 37a and the steel plate 16 can be filled with cooling water, the first cooling device 4 that does not include the side walls 36a, 36b, 36c, and 36d may be used. In the cooling device 4 of this form, it is considered that the cooling water flow in the width direction of the steel plate occurs particularly in the vicinity of the end portion of the steel plate, so that the cooling ability of the steel plate end portion is likely to increase. Most of the cooling water is discharged from 35a. Therefore, even if it is the cooling device 4 provided with such a form, the cooling device 4 which can perform the uniform cooling in the steel plate width direction than before can be provided.

  As in the first cooling device 4 shown in FIG. 3, the lower guide plate 37b and / or the lower side walls 36c and 36d are also arranged on the lower surface side of the steel plate 16, and cooling water is also provided between the steel plate 16 and the lower guide plate 37b. By satisfy | filling with, it can be set as the cooling device 4 which has the outstanding cooling capability and can perform the uniform cooling in a steel plate width direction more reliably. Here, the cooling unevenness caused by the staying water is a phenomenon that usually occurs on the upper surface side of the steel sheet. Therefore, in the case where importance is attached only to the uniform cooling in the steel plate width direction, the cooling device 4 may be provided without the lower guide plate 37b and / or the lower side walls 36c and 36d.

  Moreover, it is preferable that the 1st cooling device 4 concerning this invention is equipped with the side guides 38a and 38b from a viewpoint that the meandering of the steel plate 16 in the said cooling device 4 is suppressed. The side guides 38a and 38b are configured to be movable in the steel plate width direction via the drive arms 39a and 39b. By setting it as the form which can move to the said direction, the conveyance position of the steel plate 16 conveyed in the inside of the cooling device 4 can be controlled to the center part of the cooling device 4 in a steel plate width direction. In addition to the above functions, the side guides 38a and 38b also have a function of blocking the flow of cooling water flowing from both sides of the steel plate 16 (between the upper side walls 36a and 36b and both ends of the steel plate 16). And 38b can provide the 1st cooling device 4 which can perform the uniform cooling in a steel plate width direction more reliably.

  In addition, the 1st cooling device 4 concerning this invention is between the lower guide plate 37b and the conveyance rolls 29, 29, ..., or the upper guide plate 37a on the cooling device 4 entrance side, the lower guide plate 37b, and the rolling roll 21a. And 21b or on the exit side of the cooling device 4 may be provided with a pinch roll 8 (see FIG. 1). When the first cooling device 4 includes the pinch roll 8, the pinch roll 8, the upper guide plate 37a, the lower guide plate 37b, and the like, from the viewpoint of avoiding contact between the pinch roll 8 and the upper guide plate 37a and the lower guide plate 37b. Since it is necessary to provide a gap of about 10 to 20 mm between the cooling water and the cooling water, the cooling water is discharged out of the cooling chamber. Therefore, from the viewpoint of preventing the occurrence of uneven cooling in the steel plate width direction, in the first cooling device 4 including the pinch roll 8, it is preferable that the gap is uniform in the steel plate width direction.

  In the first cooling device 4 according to the present invention, by installing the upper side walls 36a and 36b, uniform cooling in the width direction of the steel plate is performed even if the distance between the upper guide plate 37a and the pass line is about 500 mm. can do. Therefore, the cooling device 4 of the present invention can be applied as a thick steel plate cooling device, or a pinch roll is arranged on the entry side of the cooling device 4 or immediately after the hot rolling finish rolling mill row 2. It is possible to apply as a cooling device for hot-rolled steel sheets that can reduce the unsteady cooling region at the tip of the steel sheet. Here, for example, when the first cooling device 4 according to the present invention is provided in a manufacturing apparatus for hot-rolled steel sheets, the position where the cooling device 4 should be arranged is not particularly limited, but hot-rolling finish rolling Immediately after the final stand 2 a in the machine row 2, it is preferable to dispose as close as possible to the rolling rolls 21 a and 21 b of the final stand 2 a from the inside of the housing. By arranging in this way, the steel plate 16 immediately after rolling by the hot rolling finish rolling mill row 2 can be rapidly cooled, and the tip of the steel plate 16 can be stably guided to the cooling device 4. Therefore, it is possible to provide a hot-rolled steel plate manufacturing apparatus in which the tip of the steel plate 16 can be used as a steady cooling unit without retracting the cooling device 4.

From the viewpoint of further shortening the time from when the steel plate 16 is reduced by the final stand 2a until the cooling is started, the first cooling device 4 according to the present invention uses the final stand of the hot rolling finish rolling mill row 2. It is preferable that the injection direction of the cooling water injected from the cooling header closest to the 2a rolling rolls 21a and 21b is the direction from the cooling header to the rolls 21a and 21b. By injecting the cooling water in such a direction from the cooling header closest to the rolls 21a and 21b, it becomes possible to inject the cooling water toward the steel plate 16 immediately after passing through the rolls 21a and 21b. Therefore, since the time for recovering the rolling strain accumulated by rolling can be made substantially zero, a steel sheet having a finer structure can be manufactured.
Moreover, the apparatus length of the 1st cooling device 4 concerning this invention is although it does not specifically limit, From a viewpoint of making maintenance work easy while ensuring favorable plate | board property, it is as short as possible. It is preferable to do. The preferred apparatus length is 8 m or less, more preferably 5 m or less.

Based on the cooling performance measurement result of the cooling nozzle performed by the present inventor, the steel sheet having a thickness of 3 mm was cooled from 850 ° C. to 650 ° C. by ΔTc = 200 ° C. using the first cooling device 4 according to the present invention. When performing, the relationship between the flow density W _D (m ³ / m ² · min) and the steel sheet cooling rate V _C (° C./second) in the region of 0.75 mm from the surface was estimated. The result is shown in FIG. In FIG. 4, the vertical axis represents the cooling rate V _C (° C./second), and the horizontal axis represents the flow density W _D (m ³ / m ² · min). In the following, cooling for lowering the steel plate temperature by X ° C. is described as “ΔT _C = Cooling at X ° C.”.
In the cooling of the ΔT _C = 200 ℃, supply water to the cooling nozzle is 1.5 MPa, the interval _{P L} of the cooling nozzle band in the steel plate conveyance direction and 0.1 m, flow rate of the cooling water in the upper surface and the lower surface side of the steel plate The density was the same.

The average flow of the cooling water per one cooling nozzle Q _{N (m} 3 ^/ min), when the average arrangement interval of the cooling nozzles in the steel sheet width direction and P _{W (m),} flow density W _D is
W _D = Q _N / (P _W · P _L ) (1)
Given in. Here, since the cooling efficiency increases as the average arrangement interval _PW of the cooling nozzles is reduced, the cooling device can be made more compact. When the cooling device 4 of the present invention is applied to an actual machine, P _W is preferably 0.04 m or more from the viewpoint of efficiently performing maintenance work, etc., and 0.16 m from the viewpoint of ensuring cooling uniformity in the plate width direction. The following is preferable. FIG. 4 shows the relationship between the flow rate density W _D and the cooling rate V _C in each case of P _W = 0.04 m, 0.08 m, and 0.16 m.
On the other hand, the cooling water efficiency increases as the water supply pressure to the cooling nozzle is increased. However, from the viewpoint of making the operating conditions appropriate when the actual machine is applied, the water supply pressure to the cooling nozzle is about 1.5 MPa. It is preferable to do.
Therefore, the cooling rate V _C when the terms of these conditions are satisfied, cooling the steel sheet having a thickness of 3 mm,
109 · W _D ^2/3 ≦ V _C ≦ 177 · W _D ^3/5 (i)
It is preferable that In FIG. 4, V _C = 109 · W _D ^2/3 is indicated by a one-dot chain line, and V _C = 177 · W _D ^3/5 is indicated by a broken line. From FIG. 4, the values in each case of P _W = 0.04 m, 0.08 m, and 0.16 m are located in a region that satisfies the above formula (i).

Here, when the cooling device 4 according to the present invention is applied as a cooling device for a hot-rolled steel sheet and the steel sheet is rapidly cooled after hot-rolling finish rolling to reduce the crystal grains of the steel sheet, It is necessary to perform cooling at ΔT _C = 100 to 200 ° C. Meanwhile, the sheet passing speed V _P of the steel sheet in after the speed begun wound by winder is increased, is about 15-20 meters / sec. Therefore, when the total number of nozzle bands provided in the first cooling device 4 is N _L , the device length in the steel sheet conveyance direction that the cooling device 4 should be provided (hereinafter referred to as “effective cooling length”). _Lc (m) is given by:
L _C = P _L · N _L = V _P · ΔT _C / V _C (ii)
That is, from the above formulas (i) and (ii), the effective cooling length required for cooling a steel plate having a thickness of 3 mm by applying the cooling device 4 according to the present invention as a cooling device for a hot-rolled steel plate. range of L _C is,
15 · 100 / (177 · W _D ^3/5 ) ≦ L _C ≦ 20 · 200 / (109 · W _D ^2/3 )
Than,
^{_{8.5 / W D 3/5 ≦ L C}} ≦ 36.7 / W D 2/3 (3)
It becomes. Therefore, by limiting the effective cooling length L _C of the cooling device 4 according to the present invention to the range of the above formula (3), the cooling device 4 can have a cooling capability necessary for crystal grain refinement and good operability. The cooling device 4 can be provided.

By the way, in the conventional hot-rolled steel sheet rolling line, the distance from the final stand of the hot-rolling finish rolling mill row to the cooling device is usually about 10 m, and various measuring instruments are arranged between about 10 m. Yes. Therefore, if the measuring instruments are arranged in a 2 m section, an 8 m section can be secured. Therefore, Osaere the device length L _C of the steel plate conveyance direction of the cooling apparatus 4 according to the present invention below 8m, without moving the conventional cooling device, the cooling according to the present invention in the rolling line of the conventional hot rolled steel sheet A device 4 can be arranged. That, and the effective cooling length L _C of the cooling apparatus 4 according to the present invention by suppressing below 8m, the apparatus for manufacturing a hot-rolled steel sheet from the conventional apparatus for producing hot-rolled steel sheet capable of refining crystal grains of the steel sheet Costs for remodeling can be reduced.

Here, in order to set L _C to 8 m or less when ΔT _C = 200 ° C. and V _P = 20 m / second which gives the maximum value of L _C in the above formula (3), the cooling rate V is calculated from formula (ii). _C needs to be 500 ° C./second or more. Then, to the according cooling rate _{V C,} from 4, it is necessary that the flow density _{W D 5.65m} ³ / ^{m 2} or level minutes or more at minimum. Accordingly, in the cooling device 4, the flow density _{W D} is 6.0 or more, when satisfying the expression effective cooling length is defined by (ii) _L C (m) and flow density _{W D} Togashiki (3) The cooling device 4 can reduce the cost when remodeling from a conventional hot-rolled steel plate manufacturing device to a hot-rolled steel plate manufacturing device that can refine crystal grains of the steel plate. .

  In addition, although the said Formula (3) is a formula derived supposing the case where the steel plate of 3 mm in thickness is cooled, when cooling the steel plate thicker than 3 mm, the cooling rate of a steel plate is set. Therefore, by reducing the sheet passing speed of the steel plate accordingly, the cooling device 4 can be provided with a cooling capability necessary for refining crystal grains and having good operability. On the other hand, when cooling a steel plate having a thickness of less than 3 mm, the cooling rate of the steel plate increases, and accordingly, the cooling device 4 having the same effect is obtained by increasing the plate passing rate of the steel plate. can do. Therefore, by setting it as the cooling device 4 which satisfy | fills said Formula (3), it is possible to set it as the cooling device 4 which can cool all the hot-rolled steel plates provided with the plate | board thickness in a normal manufacturing range.

  For convenience, in the above description, the mode in which the pinch roll 8 and the draining header 14 are provided on the downstream side of the first cooling device 4 has been described. However, during normal operation of the cooling device 4 according to the present invention, high-pressure cooling water is used. As a result, a surface flaw caused by a collision between the steel plate 16 and the upper guide plate 37a and the lower guide plate 37b hardly occurs. Therefore, the form which the pinch roll 8 is not provided in the downstream of the said apparatus 4 may be sufficient as the manufacturing apparatus of the hot rolled steel plate provided with the cooling apparatus 4 and the said cooling apparatus 4 concerning this invention. As a specific example of the form in which the pinch roll 8 is not provided, a form in which the draining header 14 is provided on the upper surface side of the steel sheet on the downstream side of the apparatus 4 can be exemplified. In the case where the pinch roll 8 is not provided on the downstream side of the first cooling device 4 and the draining header 14 is provided, a large amount of cooling water is jetted in the first cooling device 4. 14 preferably has an excellent draining ability. Normally, a draining header is used in which spray nozzles are arranged at predetermined intervals in the plate width direction. However, a slit nozzle having a uniform gap in the plate width direction is used as a nozzle with excellent draining ability. Better to be. For example, when a slit nozzle is used for the header 14, it is preferable that the slit gap of the nozzle be about 3 to 10 mm and high-pressure water around 1.0 MPa can be injected. Furthermore, when the pinch roll 8 is not provided on the downstream side of the first cooling device 4, a spray type draining header is installed on the downstream side (immediately after) the draining header 14, and the draining header is provided. It is preferable that water is injected from the upper surface side of the steel plate 16 to the upstream side, or is injected from both end sides in the steel plate width direction toward the steel plate 16. By setting it as such a form, it becomes possible to drain completely the water which still passes through the draining header 14 and remains on the steel plate surface.

  The operation method of the first cooling device 4 according to the present invention will be described below. In the non-rolling time from when the steel plate is taken up by the winder 3 until rolling of the next steel plate is started, the injection of the cooling water in the first cooling device 4 is stopped. And when the pinch roll 8 is provided in the downstream of the 1st cooling device 4, the upper roll 8a of a pinch roll to the position higher than the upper guide plate 37a of the cooling device 4 during the said non-rolling time. Is moved, and then rolling of the next steel sheet is started. Cooling nozzles 32a, 32a,..., And 32b, 32b,... Provided in the cooling device 4 a few seconds before the leading end of the next steel plate bites into the final stand 2a of the hot rolling finish rolling mill row 2 and The cooling water injection is started in the draining headers 14, 15 a, 15 b, and the cooling water injection pressure is controlled to be almost a predetermined value immediately after the front end of the steel plate passes through the cooling device 4. Here, when the pinch roll 8 is provided on the downstream side of the first cooling device 4, the upper roll 8 a is lowered immediately after the tip of the steel plate 16 passes through the pinch roll 8, and the pinch of the steel plate 16 is moved. Start.

By starting the injection of cooling water before the front end of the steel plate 16 is conveyed into the first cooling device 4, it becomes possible to shorten the length of the unsteady cooling part at the front end of the steel plate, The cooling water sprayed from the nozzles 32a, 32a,..., 32b, 32b,. That is, when the steel plate 16 floats and approaches the upper guide plate 37a, the collision force that the steel plate 16 receives from the cooling water jet injected from the cooling nozzles 32a, 32a,. The force of acts. Therefore, even when the steel plate 16 collides with the upper guide plate 37a, the impact force is alleviated by the collision force received from the cooling water jet, and the frictional heat between the steel plate 16 and the upper guide plate 37a is reduced. Therefore, it becomes possible to reduce the scratches generated on the steel sheet surface.
Therefore, if a hot-rolled steel sheet is manufactured by a hot-rolled steel sheet manufacturing apparatus provided with the cooling device 4 operated in this manner on the downstream side of the hot-rolling finish rolling mill row 2, the steel sheet immediately after being rolled by the rolling mill row 2 is used. The steel plate 16 can be rapidly cooled. That is, by manufacturing a hot-rolled steel sheet by such a manufacturing method, it becomes possible to manufacture a hot-rolled steel sheet having a refined structure.

The hot-rolled steel sheet was manufactured using the test apparatus which assumed the manufacturing apparatus (refer FIG. 1) of a hot-rolled steel sheet provided with the 1st cooling device concerning this invention. The hot-rolled steel sheet according to this example has C: 0.10%, Si: 0.05%, Mn: 1.05%, P: 0.02%, S: 0.003%, Al: 0.02. %, And the balance is made of general-purpose materials that are Fe and inevitable impurities. The slab heated to 1100 ° C. is extracted from the heating furnace, and the coarse bar 1 having a thickness of 30 mm by rolling with a roughing mill becomes a steel plate with a thickness of 3 mm by rolling with the subsequent hot rolling finish rolling mill row 2. Here, in the above rolling, the temperature of the steel plate is 950 to 1000 ° C. after the rough rolling, and the steel plate temperature is appropriately referred to the temperature measurement result of the thermometer 10 so that it is 830 ± 10 ° C. immediately before the final finish rolling. Controlled.
In this example, the steel plate conveyance speed until the tip of the steel plate 16 that has passed through the final stand 2a of the hot rolling finish rolling mill row 2 bites into the winder 3 is constant at 600 mpm, and then becomes 1200 mpm at 20 mpm / second. The steel plate conveyance speed after that was made constant at 1200 mpm.

  In the present embodiment, the steel plate 16 that has been rolled by the hot rolling finish rolling mill row 2 is controlled while controlling the steel plate temperature after cooling using the result measured by the thermometer 6 to be 680 ± 20 ° C. 1 was cooled at a cooling rate of 1050 ° C./second. Furthermore, while controlling the steel plate 16 that has been cooled by the first cooling device 4 with the temperature measured by the thermometer 7b so that the steel plate temperature after cooling becomes 500 ± 15 ° C., the second cooling device 5 was cooled at a cooling rate of 70 ° C./second. Here, the temperature control at the time of cooling by the first cooling device 4 and the second cooling device 5 controls the on / off control of the cooling water injection for each cooling header while taking into account the change in the plate passing speed of the steel plate 16. This was done by adjusting the number of headers for injecting cooling water.

On the nozzle 32a provided in the first cooling apparatus 4 according to the present embodiment, 32a, ..., and, the lower nozzle 32 b, 32 b, in ..., the nozzle spacing _{P L} of the steel sheet conveyance direction 0.1 m, steel plate width direction The nozzle spacing P _W is 0.04 m, the cooling water pressure supplied to the nozzle is 1.5 MPa, the cooling water flow rate Q _N per nozzle is 0.08 m ³ / min, and the cooling water flow density. W _D was ^20m 3 / ^{m 2} · min. These upper nozzles 32a, 32a,..., And lower nozzles 32b, 32b,... Are provided for each nozzle with cooling headers 26a, 26a,..., 26b, 26b, and 27a, 27a,. It attaches to the front-end | tip of the water conduit provided in 27b, 27b, ... (refer FIG.2 and FIG.3). In the first cooling device 4 according to the present example, 32 and 24 cooling headers were provided on the upper surface side and the lower surface side of the steel plate, respectively. By the way, the amount of decrease in the steel plate temperature obtained in the first cooling device 4 is the number of cooling headers used if the number of cooling nozzles attached to the cooling header and the cooling water flow rate per cooling nozzle are constant. Is almost proportional to Therefore, when the plate passing speed of the steel plate is 600 mpm, the steel plate 16 is cooled using the half cooling headers (16 on the upper surface side and 12 on the lower surface side) located on the upstream side in the cooling device 4. The number of cooling headers used was increased as the plate passing speed increased, and when the plate passing speed was 1200 mpm, the steel plate 16 was cooled using all the cooling headers. Hereinafter, in the description regarding the arrangement conditions of the cooling header, the cooling nozzle, and the upper guide plate and the lower guide plate, reference will be made to FIG. 2 and FIG.

  In this embodiment, the upper guide plates 22a, 22b, and 22c and the lower guide plates 24a, 24b, 24c, and 24d provided in the first cooling device 4 are 30 mm in thickness, and are formed by the transport rolls 29, 29, and 29, respectively. The distance between the pass line and the upper guide plates 22b and 22c is about 300 mm, and the distance between the pass line and the lower guide plates 24a, 24b, 24c and 24d is about 15 mm. The upper guide plate 22a is arranged so that the distance between the upstream end of the guide plate 22a and the bite exit of the upper roll 21a of the final stand 2a in the hot rolling finish rolling mill row 2 is about 10 to 20 mm. . The downstream end of the guide plate 22a is further away from the pass line than the upstream end, and the distance between the downstream end and the guide plate 22b and the pass line is substantially the same. The upper guide plate 22a is disposed on the upper side. Further, the lower guide plate 24a arranged so that the distance to the pass line is about 300 mm, the distance between the upstream end of the guide plate 24a and the bite exit of the lower roll 21b of the final stand 2a. Was arranged to be about 10 to 20 mm. On the other hand, the distance between the cooling water injection port and the upper guide plates 22a, 22b, 22c in the cooling nozzles provided in the cooling headers 26a, 26a,..., 26b, 26b,. The distances between the cooling water injection ports and the lower guide plates 24a, 24b, 24c, 24d in the cooling nozzles provided in 27a, ..., 27b, 27b, ... are about 100 mm.

  In the cooling device 4 according to the present embodiment, even when the guide plates 37a and 37b collide with the steel plate 16, the support frame that supports the upper guide plate 37a and the lower guide plate 37b is prevented from being damaged. The support frame was given sufficient rigidity. Further, from the viewpoint of facilitating maintenance work of the cooling device 4, the cooling device 4 according to the present embodiment moves the upper guide plates 22b and 22c away from the pass line (upward) together with the cooling headers 26a, 26a,. The structure can be evacuated. In addition, the cooling device 4 has a structure in which the upper guide plate 22a can be moved and retracted obliquely upward with the cooling headers 26b, 26b,... After the guide plate 22b is retracted.

In the present embodiment, the cooling device 4 is provided with 32 cooling headers 26a, 26a,..., 26b, 26b,. On the other hand, three conveying rolls 29, 29, 29 and 24 cooling headers 27a, 27a,... And 27b, 27b,. .., And 27 b, 27 b,... Are provided on the upstream side and the downstream side of each transport roll so that six transport headers 29, 29, 29 and cooling headers 27 a, 27 a,. ... and 27b, 27b, ... are arranged. Here, as described above, in this embodiment, since P _L = 0.1 m, the effective cooling length L _C is 3.2 m on the upper surface side of the steel plate 16 and 2.4 m on the lower surface side. Further, from Q _N = 0.08 m ³ / min, P _L = 0.1 m, and P _W = 0.04 m, W _D = Q _N / (P _W · P _L ) = 20 m ³ / m ² · min. Therefore, the effective cooling length L _C on the upper surface side and the lower surface side of the steel plate 16 according to the present example satisfies Expression (3). Note that all the cooling headers provided in the cooling device 4 according to the present embodiment can be used / not used with one ON / OFF valve for each cooling header. In addition, since 4 to 8 cooling headers are used as one bank and a cooling water flow rate adjusting valve is provided for each bank, the cooling device 4 according to the present embodiment adjusts the cooling water flow rate for each bank. You can also

The cooling nozzle provided in the cooling device 4 according to the present embodiment was a flat type spray nozzle capable of forming a fan-shaped cooling water jet (for example, a thickness of about 2 to 3 mm). FIG. 5 schematically shows the collision position of the cooling water jet on the steel plate surface. In FIG. 5, the white circle represents the position immediately below (or just above) the cooling nozzle, and the thick line represents the collision position of the cooling water jet. In addition, the up-down direction in FIG. 5 is a conveyance direction of a steel plate.
In the present embodiment, the cooling nozzles are arranged so that the cooling water jet can pass at least twice over all positions in the width direction on the steel sheet surface for any cooling nozzle band provided in the cooling device 4. That is, between the cooling nozzle interval P _W , the cooling water jet collision width L, and the torsion angle β,
L = 2P _W / cos β
The cooling nozzle was arranged so that In addition, from the viewpoint of achieving uniform cooling ability in the steel plate width direction, the cooling nozzles were twisted in directions opposite to each other in the cooling nozzle bands adjacent in the steel plate conveyance direction. Moreover, in the cooling device 4 according to the present embodiment, the injection direction of the cooling water injected from the cooling water injection port of each cooling nozzle is basically the vertical direction or the reverse direction of the vertical direction (the direction from the bottom to the top). On the other hand, in the cooling headers 26b and 27b closest to the rolls 21a and 21b, the outlets of the rolls 21a and 21b are from the viewpoint of starting the rapid cooling of the steel sheet from a position as close as possible to the outlets of the rolls 21a and 21b. It was set as the direction which goes to the steel plate which should be located in.

  The upper guide plate 37a and the lower guide plate 37b provided in the cooling device 4 according to the present embodiment discharge the cooling water that has collided with the inflow holes 33a and 33b through which the injected cooling water jet should pass and the steel plate 16. Outflow holes 35a and 35b to be provided are provided. An example of the shape of the inflow hole 33b and the outflow hole 35b provided in the lower guide plate 37b is shown in FIG. In FIG. 6, the horizontal direction in the figure is the steel plate width direction, and the vertical direction in the figure is the conveyance direction of the steel sheet.

  The lower guide plate 37b is provided with parallelogram-shaped inflow holes 33b, 33b,... At locations corresponding to the collision positions of the cooling water jets indicated by bold lines in FIG. , 33b,... Are provided in the steel plate width direction at the same 40 mm intervals as the cooling nozzle intervals. In the lower guide plate 37b according to the present embodiment, from the viewpoint of providing a gap through which a cooling water jet having a thickness of about 2 to 3 mm can pass, the width of the gap provided in the inflow holes 33b, 33b,. It was. Furthermore, parallelogram-shaped strip-shaped outflow holes 35b, 35b,... Are provided in the lower guide plate 37b between the inflow holes 33b, 33b,. Yes. In the lower guide plate 37b according to the present embodiment, the width of the gap provided in the outflow holes 35b, 35b,... Is 10 mm from the viewpoint of facilitating the discharge of the cooling water. In addition, the inclination of the inflow holes 33b, 33b,... And the outflow holes 35b, 35b,... (The angle formed by the long sides of the parallelogram in the horizontal plane with respect to the plate width direction, and the twist angle β of the cooling nozzle ) Is 45 °, and the width between the inflow holes 33b, 33b,... And the outflow holes 35b, 35b,... (Hereinafter referred to as “beam portion”) D is 6.1 mm. . Note that the guide plate 37b is provided with an A- in FIG. 6 from the viewpoint of suppressing the sticking of the steel plate 16 even when the tip of the steel plate 16 conveyed through the cooling device 4 collides with the guide plate 37b. As shown in the A cross section, chamfered portions B, B, and B were provided.

FIG. 7 shows a shape example of the inflow hole 33a and the outflow hole 35a provided in the upper guide plate 37a of the cooling device 4 according to the present embodiment. In the upper guide plate 37a, the shape of the outflow holes 35a, 35a, ... is the same as the shape of the outflow holes 35b, 35b, ... in the lower guide plate 37b. On the other hand, the distance between the upper guide plate 37a and the cooling water injection ports in the cooling nozzles provided in the cooling headers 26a, 26a,... And 26b, 26b,. Yes, the injected cooling water jet has not spread so much. For this reason, the shape of the inflow holes 33a, 33a,... In the upper guide plate 37a does not necessarily need to be a band shape, and therefore, in this embodiment, the inflow holes 33a, 33a,. Further, the beam portion of the upper guide plate 37a is provided with a chamfered portion from the same viewpoint as in the case of the lower guide plate 37b.
For convenience, inflow holes 33a, 33a,..., 33b, 33b,... And outflow holes 35a, 35a,..., And 35b, 35b,. 6 and 7, the forms of the inflow holes and outflow holes that can be provided in the cooling device 4 of the present invention are not limited to these forms. The shape of the inflow hole and the outflow hole is not particularly limited as long as the cooling water can be passed smoothly. For example, an arbitrary shape is appropriately selected from shapes such as a rectangle, a hexagon, and an ellipse. be able to.

In the present embodiment, as the second cooling device 5, a typical cooling device conventionally used for cooling the steel plate in the run-out table is used, and the circular tube laminar nozzle headers 11, 11, Are arranged on the lower surface side with conical spray nozzle headers 12, 12,... (See FIG. 1). The flow rate density in the second cooling device 5 according to the present example is 1.2 m ³ / m ² · min on the upper surface side of the steel plate 16 and 0.9 m ³ / m ² · min on the lower surface side of the steel plate 16. 16 headers and 32 headers were provided on the upper surface side and the lower surface side, respectively. In the second cooling device 5, the header provided on the upper surface side of the steel plate 16 is turned on for each header, and the header provided on the lower surface side of the steel plate 16 is turned on every two headers. / OFF control is possible.

  In the present embodiment, the upper guide plate 22a of the cooling device 4 has a flat plate shape, but the cooling device 4 according to the present invention is curved upward on the downstream side like a guide used in a normal rolling mill. An upper guide plate having a certain shape may be provided. Moreover, although the cooling nozzle concerning a present Example was made into the flat type nozzle, the form which can be used as a cooling nozzle concerning this invention is not limited to a flat type, For example, the cooling water jet injected Even if the collision part is an ellipse or an oval nozzle, it can be used suitably.

As a result of manufacturing a hot-rolled steel sheet using a test apparatus having the above-described form, the following was confirmed.
1) By rapidly cooling the steel plate 16 immediately after rolling by the hot rolling finish rolling mill row 2 using the first cooling device 4, fine-grained steel having an average 2 μm ferrite grain as a main phase can be produced. It was. That is, it was confirmed that a hot-rolled steel sheet having a fine structure can be produced by using the cooling device 4 of the present invention.

  2) In the 1st cooling device 4 concerning a present Example, upper guide plate 22a, 22b, 22c and lower guide plate 24a, 24b, 24c, 24d are continuously installed from the exit of roll 21a, 21b. Therefore, it is not necessary to retract the cooling device member disposed on the upper surface side of the pass line to the upper side of the pass line before the front end of the steel plate 16 enters the cooling device 4. Furthermore, in the 1st cooling device 4 concerning a present Example, before the front-end | tip of the steel plate 16 approachs into the said cooling device 4, the front-end | tip of the steel plate 16 is hot-rolled by finish rolling. Within 0.5 seconds after passing through the machine row 2, a steady cooling state in the cooling device 4 could be realized. On the other hand, in the conventional manufacturing apparatus, it takes about 7 to 8 seconds for the cooling device retreated above the pass line to return to the position where the steel sheet should be cooled again and to realize the steady cooling state. It was. Therefore, it was confirmed that the length of the unsteady cooling part (cutting allowance) at the front end of the steel sheet can be reduced by manufacturing the hot-rolled steel sheet using the cooling device 4 of the present invention. That is, for example, if the plate passing speed of the steel plate front end portion is 600 mpm, the unsteady cooling portion length can be reduced by about 70 m by manufacturing the hot-rolled steel plate using the cooling device 4 of the present invention.

3) A width thermometer capable of measuring the temperature distribution in the width direction of the steel plate is installed on the further downstream side of the thermometer 6 arranged on the downstream side of the first cooling device 4, and is cooled by the first cooling device 4. The measurement result of the temperature distribution in the steel plate width direction of the upper surface of the steel plate 16 after the heating is shown in FIG. For comparison, a mode using the first cooling device 4 including the side wall and the outflow hole (Example 1), a mode using the first cooling device 4 including the outflow hole but not including the side wall (implementation). The temperature distribution was measured for Example 2) and a form (comparative example) using the first cooling device that was not provided with a side wall and closed the outflow hole.
As shown in FIG. 8, the steel plate 16 cooled by the cooling device 4 according to the example 1 has a temperature difference in the width direction of the steel plate (hereinafter referred to as “temperature deviation”) within 15 ° C. It was. Therefore, it was confirmed that the steel plate with which the cooling nonuniformity in the steel plate width direction was reduced was obtained by cooling using the cooling device 4 concerning this invention. In addition, the steel plate 16 cooled by the cooling device 4 according to Example 2 was configured such that the cooling device 4 did not include a side wall, and therefore, a cooling water flow in the width direction of the steel plate was generated particularly in the vicinity of the end of the steel plate. A temperature drop near the edge was observed, but the temperature deviation remained at about 20 ° C. Therefore, even if it was a form which is not provided with a side wall, it was confirmed by cooling using the cooling device 4 of this invention that the steel plate with which the cooling nonuniformity in the steel plate width direction was reduced was obtained. On the other hand, the steel plate cooled by the cooling device of the comparative example not provided with the side wall and the outflow hole has an uneven temperature difference due to the cooling water flow in the steel plate width direction generated in the cooling device, and the temperature deviation is about Expanded to 40 ° C.
That is, the cooling unevenness in the steel plate after cooling can be reduced by performing rapid cooling with the cooling device according to the present invention. Therefore, if a steel plate is produced using the cooling device of the present invention, it is possible to produce a fine-grained steel having a uniform grain size distribution and a ferrite fraction in the steel plate and having little variation in mechanical properties. .

BRIEF DESCRIPTION OF THE DRAWINGS It is an external view which shows roughly embodiment of the manufacturing apparatus of the hot-rolled steel plate provided with the cooling device of the steel plate of this invention. It is a figure which shows roughly the vertical direction cross section of the cooling device of the steel plate of this invention. It is a figure which shows the flow of a staying water schematically. It is a figure which shows the relationship between a flow rate density and the cooling rate of a steel plate. It is a figure which shows roughly the collision position of the cooling water jet on the steel plate surface. It is a figure which shows the example of a shape of the inflow hole provided in a lower guide plate, and an outflow hole. It is a figure which shows the example of a shape of the inflow hole provided in an upper guide plate, and an outflow hole. It is a figure which shows the temperature distribution measurement result of the steel plate width direction in the steel plate after cooling with a cooling device. It is a figure which shows roughly the shape of the stagnant water formed on a steel plate, and the mode of the flow of cooling water. It is a figure which shows the relationship between the flow rate density of a cooling water, and the height of the staying water in the steel plate board width direction center part. It is a figure which shows the relationship between the distance from the center of a steel plate width direction, a stagnant water height, and the flow velocity of the cooling water in a steel plate width direction.

Explanation of symbols

2 Hot-rolling finishing rolling mill row 2a Final stand 4 Cooling device 14 Draining means 16 Steel plate 21a, 21b Rolls 22a, 22b, 22c, 37a First guide plate (upper guide plate)
24a, 24b, 24c, 24d, 37b Second guide plate (lower guide plate)
29 Transport rolls 32a, 32b Cooling nozzles 33a, 33b Inflow holes 35a, 35b Outflow holes 36a, 36b, 36c, 36d Side walls

Claims (11)

A steel sheet cooling device including a plurality of cooling nozzle bands to cool a steel sheet conveyed on a pass line on a transport roll,
The plurality of cooling nozzle bands are provided on the upper surface side and the lower surface side of the steel plate and form a row in the conveying direction of the steel plate,
The cooling nozzle band includes a plurality of cooling nozzles arranged at predetermined intervals in the plate width direction of the steel plate,
The plurality of cooling nozzles spray cooling water to cool the steel plate,
A first guide plate is provided between the cooling nozzle provided on the upper surface side of the steel plate and the pass line, and the first guide plate is jetted from the cooling nozzle toward the steel plate. A steel plate cooling apparatus, comprising: an inflow hole through which the cooling water should pass; and an outflow hole through which the cooling water should pass from the steel plate toward the cooling nozzle. 2. The steel sheet cooling apparatus according to claim 1, wherein side walls are provided on both ends of the steel sheet in the plate width direction, on the upper surface side of the pass line. The steel sheet cooling device according to claim 2, wherein a distance between an upper side of the side wall and the pass line is larger than a distance between a cooling water injection port of the cooling nozzle and the pass line. It is a cooling device of the steel plate given in any 1 paragraph of Claims 1-3,
Furthermore, a second guide plate is provided between the cooling nozzle provided on the lower surface side of the steel plate and the pass line, and the second guide plate is sprayed from the cooling nozzle toward the steel plate. A steel plate cooling apparatus comprising: an inflow hole through which the cooling water should pass; and an outflow hole through which the cooling water should pass from the steel plate toward the cooling nozzle. 5. The steel sheet cooling apparatus according to claim 1, wherein side walls are provided on both lower sides of the pass line and on both ends of the steel plate in the plate width direction. The average flow rate of the cooling water per cooling nozzle is Q _N (m ³ / min),
The average arrangement interval of the cooling nozzles in the plate width direction of the steel plate is P _W (m),
The average interval of the cooling nozzle bands in the conveying direction of the steel plate is P _L (m),
When the total number of the cooling nozzle bands in the conveying direction of the steel sheet is N _L ,
The flow density W _D (m ³ / m ² · min) defined by the formula (1) is 6.0 or more,
And satisfies the equation the effective cooling length is defined by (2) L _{C (m)} flow density W _D Togashiki (3), the steel sheet according to any one of claims 1 to 5 Cooling system.
W _D = Q _N / (P _W · P _L ) (1)
L _C = P _L · N _L (2)
8.5 / W _D ^3/5 ≦ L _c ≦ 36.7 / W _D ^2/3 (3) It is equipped with the final stand in a hot rolling finishing rolling mill row | line | column, the cooling device of the steel plate of any one of Claims 1-6, and the draining means which drains a cooling water in order in the conveyance direction of a steel plate. An apparatus for producing a hot-rolled steel sheet. The cooling water pool is formed in a region between the roll of the final stand and the draining means, and the draining means is arranged so that the steel sheet is immersed in the cooling water of the pool. The apparatus for producing a hot-rolled steel sheet according to claim 7, characterized in that The cooling nozzle of the cooling device provided on the upper surface side of the steel plate is provided so that a cooling water injection port of the cooling nozzle is immersed in the cooling water of the pool. The manufacturing apparatus of the hot rolled sheet steel of 8. The cooling nozzle of the cooling nozzle provided in the cooling nozzle zone closest to the final stand among the cooling nozzle zones provided in the cooling device is directed to a steel plate to be positioned at the final stand outlet. The apparatus for manufacturing a hot-rolled steel sheet according to any one of claims 7 to 9. The manufacturing method of the hot-rolled steel sheet according to any one of claims 7 to 10 includes a step of processing the steel sheet rolled at the final stand in the hot-rolling finish rolling mill row. A method for producing rolled steel sheets.

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