JP4905180B2 - Steel cooling device and cooling method - Google Patents

Description

  The present invention relates to a steel material cooling apparatus and a steel material cooling method using the same.

  In the process of manufacturing steel materials by hot rolling, it is common to supply cooling water or air cooling to control the rolling temperature, but in recent years, cooling water has been injected to increase the cooling rate. Development of technology to increase the strength of steel materials by obtaining a finer structure has been active.

  For example, a laminar cooling water group (rod-shaped cooling water group) is injected by a circular laminar cooling nozzle that is provided in plural in the steel material width direction at a predetermined interval just above the roller table as the upper surface cooling of the steel material. On the other hand, cooling water is sprayed by the spray nozzle provided between roller tables as cooling of the lower surface of steel materials.

  At that time, in the case of cooling by the rod-shaped cooling water group, the cooling capacity of the portion where the injected rod-shaped cooling water directly collides with the steel material (direct injection portion) is the portion where the cooling water after flowing into the steel material flows on the steel material Since the cooling capacity of the (flowing water part) and the cooling water flowing on the steel material interferes with each other (interference part), the cooling unevenness occurs corresponding to the positions of the direct injection part, the flowing water part and the interference part. As one of the methods for reducing this cooling unevenness, the shape of the region (interference part) where the interference flow formed by the collision of the cooling water (fluid water) after colliding with the steel material is controlled (for example, hexagonal) And there is something.

  For example, in Patent Document 1, a plurality of headers in which nozzles are arranged at equal intervals in the width direction are installed in a conveying direction between table rollers (in a grid pattern or a staggered pattern), and the steel material is uniformly cooled in the width direction. A method has been proposed.

Further, in Patent Document 2, in a method of cooling a steel material being conveyed on a roller table by a columnar jet group (rod-shaped cooling water group), a plurality of nozzles provided at right angles to the steel material are provided as nozzles in the steel material width direction. A method has been proposed in which the pitch is 3 to 10 times the nozzle diameter, and the nozzle pitch in the steel material transport direction is equal to or less than the nozzle pitch in the steel material width direction in a staggered manner at regular intervals.
JP-A-7-214136 JP-A-10-263669

  In general, the fact that the shape of the interference part (interference flow) is preferably a hexagon is proved from geometric facts as described below, and is known.

  In other words, the shapes that can be laid out without gaps are triangles, squares, and hexagons, and if the total length of the sides forming the shape is the same, the enclosed area increases as the corners of the polygon increase, and the circle is the largest. It is a well-known fact that it is preferable to make the structure hexagonal from the geometric fact that For example, in the natural world, such structures are found in beehives, insect eyes, etc., and in the case of artifacts, in buildings, automobiles and aircraft wings, floors and sidewalls, luggage racks, partitions, yachts, skis, astronomical telescopes It is also applied to the base of the camera, various filters, and the sensor part of the CCD camera.

  However, in the techniques described in Patent Documents 1 and 2, the nozzle arrangement is simply arranged in a grid pattern or a zigzag pattern, and the shape of the interference portion is set to a predetermined shape (for example, a hexagon). Unevenness cannot be solved sufficiently, and there is a big problem in ensuring the uniformity of cooling.

  That is, in the technology of Patent Document 1, temperature unevenness occurs in the width direction at half-pitch intervals of the nozzles, and in the technology of Patent Document 2, temperature unevenness occurs in the width direction at 1/4 pitch intervals of the nozzles.

  The present invention has been made in view of the above circumstances, and in the case of supplying cooling water to a steel material, a steel material cooling device capable of cooling the steel material uniformly and stably at a high cooling rate, and The object is to provide a cooling method.

  In order to solve the above problems, the present invention has the following features.

[1] In a steel material cooling apparatus having a nozzle group for injecting rod-shaped cooling water, the density of water is 4 m ³ / m ² mim or more, and the rod-shaped cooling water injected from each nozzle at a speed of 10 m / s or more. The diameter of the rod-shaped cooling water in the direct injection part that collides with the steel plate is smaller than twice the inner diameter of the nozzle tip, the positions of the direct injection parts are regularly arranged, and the regular arrangement thereof A steel material cooling device characterized in that a straight line connecting direct injection portions located at corresponding positions in the steel plate conveyance direction is inclined at a predetermined angle with respect to the steel plate conveyance direction.

  [2] The steel material cooling device according to [1], wherein the regular arrangement of the direct injection portions is a grid pattern or a staggered pattern.

[3] In the method for cooling a steel material using a nozzle group for injecting rod-shaped cooling water, the water density is 4 m ³ / m ² mim or more, and rod-shaped cooling water ejected from each nozzle at a speed of 10 m / s or more. The diameter of the rod-shaped cooling water at the direct injection part that collides with the steel plate is smaller than twice the inner diameter of the nozzle tip, and the position of the direct injection part is regularly arranged, and the regular arrangement thereof And a straight line connecting the direct injection portions at corresponding positions in the steel plate conveyance direction is inclined by a predetermined angle with respect to the steel plate conveyance direction.

  [4] The method for cooling a steel material according to [3], wherein the regular arrangement of the direct injection portions is a grid pattern or a staggered pattern.

  By using the present invention, the steel material can be uniformly and stably cooled to the target temperature at a high cooling rate. As a result, a high quality steel material can be manufactured.

  A steel sheet cooling apparatus according to an embodiment of the present invention will be described. The present invention can be applied to all steel materials such as thick plates, shaped steels, and steel pipes, but will be described below by taking steel plates as an example.

  1 and 2 are explanatory views of a steel sheet cooling apparatus according to an embodiment of the present invention.

  The cooling device according to this embodiment is a passage-type cooling device installed on a hot rolling line for steel plates, and includes one or a plurality of cooling units 20 shown in FIG. 1 or cooling units 30 shown in FIG. ing.

  And the cooling unit 20 shown in FIG. 1 has the upper header 21 installed in the upper surface side of the steel plate 10, and the upper nozzle attached to the upper header 21 in order to inject the rod-shaped cooling water 23 toward the steel plate 10 upper surface. 22 and a draining roll 25 for draining the stagnant water 24 on the upper surface of the steel plate 10, and rod-shaped cooling water from between the table rollers (not shown) for conveying the steel plate 10 toward the lower surface of the steel plate 10. In order to inject 28, a lower header 26 installed on the lower surface side of the steel plate 10 and a lower nozzle 28 attached to the lower header 26 are provided.

  Here, the upper nozzle 22 is a circular pipe nozzle and is attached so that rod-shaped cooling water can be supplied to the entire width of the steel plate, and the nozzle row is arranged in a plurality of rows (here, 6 rows) in the steel plate conveyance direction. Yes. Note that the injection angle θ in the steel plate conveyance direction is 90 °.

  Similarly to the upper nozzle 22, the lower nozzle 27 is also a circular nozzle, and is attached so that rod-shaped cooling water can be supplied to the entire width of the steel plate. , 6 columns). Note that the injection angle θ in the steel plate conveyance direction is 90 °.

  And in this embodiment, as shown in Drawing 3 and Drawing 4, while the position of direct injection part 40 where the rod-shaped cooling water injected from the circular tube nozzle collides with steel plate 10 is arranged regularly, Under the regular arrangement, a straight line connecting the direct injection portions at corresponding positions in the steel plate conveyance direction is inclined by a predetermined angle φ with respect to the steel plate conveyance direction.

  That is, in FIG. 3, the direct injection part 40 is arranged in a grid pattern (that is, the direct injection part 40 is arranged at a virtual cross point of the grid pattern), and at a corresponding position in the steel plate conveyance direction. A straight line (A line in FIG. 3) connecting certain direct injection portions is inclined by a predetermined angle φ (for example, 2.4 °) with respect to the steel plate conveyance direction (X line in FIG. 3). In other words, the direct injection portion 40 arranged in a grid pattern is rotated by a predetermined angle φ within the steel plate surface.

  Moreover, in FIG. 4, the direct injection part 40 is arrange | positioned in zigzag form (namely, from what arrange | positioned the direct injection part 40 in a grid pattern, the direct injection part 40 is the space | interval in the steel plate width direction every other row. And a straight line (line A in FIG. 4) connecting the direct injection portions located at corresponding positions in the steel plate transport direction is in the steel plate transport direction (X-ray in FIG. 4). It is inclined by a predetermined angle φ (for example, 1.2 °). In other words, the direct injection portions 40 arranged in a staggered pattern are rotated by a predetermined angle φ within the steel plate surface.

  By arranging the direct injection part 40 as described above, the steel plate width direction position of the direct injection part 40 having a higher cooling ability than the flowing water part and the interference part is slightly shifted for each row in the steel sheet conveyance direction. By simply arranging in a grid pattern or a staggered pattern, the cooling unevenness of the steel sheet can be greatly reduced as compared with the case where the steel sheet width direction position of the direct injection portion 40 is fixed in the steel sheet conveying direction.

  In the cooling region, in order to generate the same number of direct injection portions in the steel plate width direction and the steel plate longitudinal direction, the inclination angle φ is preferably set as follows.

φ = n × sin ⁻¹ (tan η / (M · N))
Here, n is an integer, M is a value determined by the arrangement pattern (M = 1 for grid-like arrangement, M = 2 for zigzag arrangement), and N connects the direct injection portions at corresponding positions in the steel plate conveyance direction. The number of direct injection parts on the straight line (on line A in FIGS. 3 and 4), and η is the straight line (line B in FIGS. 3 and 4) connecting the diagonally adjacent direct injection parts to each other in the steel plate conveyance direction The angle between

  In this case, the nozzle group is preferably installed so that the shape of the interference part (interference flow) is a triangle, a quadrangle, or a hexagon, and more preferably a hexagon.

  In addition, the deviation of the cooling start position or the cooling end position in the steel sheet width direction caused by rotating the tilt angle φ can be adjusted as appropriate by appropriately adjusting the upstream and downstream nozzle positions in the steel sheet conveying direction according to the regular arrangement. preferable.

  By the way, in this embodiment, if the interval between the direct injection parts becomes wide, the difference in cooling capacity between the direct injection part and the flowing water part or the interference part becomes large, but since the cooling is performed while passing the steel plate, As a whole, there is no problem in uniform cooling because each part of the steel sheet passes through a weak part and a strong part in the same way.

  However, when cooling by stopping the steel sheet, it is preferable to adjust the interval between the direct injection portions because the cooling unevenness occurs when the interval between the direct injection portions becomes wide. Specifically, the cooling can be uniformly performed if the interval P between the direct injection portions is 10 Dk or less with respect to the diameter Dk of the cooling water in the direct injection portion.

  Incidentally, when cooling a steel plate with a cooling medium (for example, cooling water), it is necessary to make the cooling water reach the steel plate and collide with it in order to surely perform the cooling. For that purpose, it is necessary to break the water film on the surface of the steel plate to allow the fresh cooling water to reach the steel plate, not a cooling water flow with weak penetrating force like droplets ejected from the spray nozzle, It is not a plate-shaped laminar water, but a columnar laminar flow (bar-shaped cooling water) similar to that flowing continuously from a tap. Note that the laminar flow using a circular tube laminar nozzle that has been used in the past is a free-falling flow. Therefore, if there is a stagnant water film, it is difficult for cooling water to reach the steel plate, and cooling is performed with or without stagnant water. There is a difference in ability.

  Therefore, the diameter Dk of the cooling water at the position where the rod-shaped cooling water injected from the circular tube nozzle collides with the steel plate (direct injection portion) is preferably smaller than twice the inner diameter D of the nozzle tip (that is, Dk). <2D). When the diameter Dk of the cooling water at the direct injection part (collision point) is larger than that, the cooling water when reaching the steel plate becomes only a cooling water flow having a weak penetration force like a droplet group ejected from the spray nozzle. It is.

Further, when the cooling water is jetted at a speed of 10 m / s or more, the cooling water film on the steel plate surface is broken (especially on the upper surface of the steel plate), and fresh cooling water can reach the steel plate. That is, in a cooling device that cools a hot-rolled steel sheet, when the water density is 4 m ³ / m ² mim or more, the cooling water to be sprayed breaks through the water film staying on the steel sheet and uniformly cools it. The velocity V of the cooling water to be injected is preferably 10 m / s or more.

  The inner diameter D of the upper nozzle 22 and the lower nozzle 27 is not particularly defined, but the inner diameter D of the upper nozzle 22 and the lower nozzle 27 is 3 to 8 mm in order to prevent the nozzle from clogging and to ensure the cooling water injection speed. It is preferable to be within the range.

  By the way, if the upper and lower sides of the steel sheet are not cooled in the same way, the steel sheet may bend and warp and the product directivity may decrease, so the cooling capacity for the upper and lower sides of the steel sheet is the same. However, if the cooling capacity is the same, the upper header 21 and the lower header 26 may be the same or different. Further, the inner diameters of the upper nozzle 22 and the lower nozzle 27 may be different.

  On the other hand, the cooling unit 30 shown in FIG. 2 has a pair of upper headers 31 installed so as to face each other in the steel plate conveyance direction on the upper surface side of the steel plate 10 in order to inject the rod-shaped cooling water 33 toward the upper surface of the steel plate 10. And a lower header 36 installed on the lower surface side of the steel plate 10 in order to inject the rod-shaped cooling water 38 toward the lower surface of the steel plate 10, and an upper nozzle 32 attached to each upper header 31. A lower nozzle 38 attached to the lower header 36 is provided.

  Here, the injection angle θ of the upper nozzle 32 is not particularly defined, but is preferably 30 ° to 90 °. This is because if the injection angle is smaller than 30 °, the vertical velocity component of the rod-shaped cooling water 33 becomes small, the collision with the steel plate 10 becomes weak, and uneven cooling occurs.

  Further, an intermediate header may be provided between the opposing upper headers to increase the cooling capacity between the opposing headers, and the number thereof may be any number.

  Other points are the same as those of the cooling unit 20 described above.

  And by installing the cooling device provided with the cooling unit 20 or the cooling unit 30 as described above in the hot rolling line for thick steel plate or thin steel rice, the steel plate is uniformly and stably at a high cooling rate to the target temperature. As a result, a high-quality steel sheet can be manufactured.

  It goes without saying that the cooling device of the present invention can be used for cooling steel materials such as shaped steel and steel pipes.

  Examples of the present invention are described below.

  FIG. 5 is a diagram showing a hot rolling line for thick steel plates used in the examples of the present invention and a conveyance pattern there.

  This thick steel plate hot rolling line includes a heating furnace 11, a reversible rolling mill 12, a hot leveler 13, and a cooling device 14, and performs accelerated cooling after finish rolling. Here, the slab extracted from the heating furnace 11 is subjected to rough rolling and finish rolling by a reversible rolling mill 12 to a plate thickness of 12 mm, and then passed through a hot leveler 13 and is conveyed at a cooling device 14 at a conveying speed of 1 m / s. Then, accelerated cooling with a temperature drop of 150 ° C. was performed.

  Then, as Example 1 of the present invention, the cooling unit 20 shown in FIG. At that time, the direct injection part 40 is arranged as shown in FIG. 3, and the nozzle diameter D = 3 mm, the direct injection part interval P = 30 mm, the inclination angle φ = 2.4 °, the number of direct injection parts N = 24, rod-like cooling. The water injection speed V was set to 10 m / s.

  In addition, as Example 2 of the present invention, four units of the cooling unit 20 shown in FIG. At that time, the direct injection part 40 is arranged as shown in FIG. 4, the nozzle diameter D = 3 mm, the direct injection part interval P = 30 mm, the inclination angle φ = 1.2 °, the number of direct injection parts N = 24, rod-like cooling. The water injection speed V was set to 10 m / s.

  Further, as Invention Example 3, four cooling units 30 shown in FIG. At that time, the direct injection part 40 is arranged as shown in FIG. 3, and the nozzle diameter D = 3 mm, the direct injection part interval P = 30 mm, the inclination angle φ = 2.4 °, the number of direct injection parts N = 24, rod-like cooling. The water injection angle θ = 90 ° and the injection speed V = 10 m / s.

  Further, as Invention Example 4, four units of the cooling unit 30 shown in FIG. At that time, the direct injection part 40 is arranged as shown in FIG. 3, the nozzle diameter D = 3 mm, the direct injection part interval P = 30 mm, the inclination angle φ = 1.2 °, the direct injection part number N = 24, and the rod shape The cooling water injection angle θ = 90 ° and the injection speed V = 10 m / s.

  On the other hand, as Comparative Examples 1, 2, 3, and 4, the other conditions were the same as those of Examples 1, 2, 3, and 4 of the present invention, respectively, but the steel sheet was subjected to the condition that there was no inclination angle φ (ie, φ = 0). Was cooled.

  And in each case, after cooling, the steel plate width direction temperature was continuously measured using the radiation thermometer, and the temperature distribution of the steel plate upper surface was investigated. We compared the temperature variation (difference between the highest temperature and the lowest temperature) in the stationary part except the cutting edge, the rearmost edge, and the widthwise edge of the steel sheet. The magnitude of the temperature variation almost corresponded to the variation in mechanical properties of the product such as tensile strength.

  As a result, in the inventive examples 1 to 4, the temperature variation (standard deviation 3σ) was 20 ° C., which was almost the same as the temperature variation 20 ° C. in air cooling, and there was no temperature variation due to cooling (cooling variation). As a result, it was possible to produce a high-quality steel sheet with small variations in product strength.

  On the other hand, in Comparative Examples 1 and 3, streak-like temperature unevenness at intervals of 15 mm occurred between the direct injection part and a temperature variation of 48 ° C. with a standard deviation of 3σ. Further, in Comparative Examples 2 and 4, streaky temperature irregularities occurred at intervals of 13 mm, and a temperature variation of 37 ° C. with a standard deviation of 3σ was obtained. And in Comparative Examples 1-4, the intensity | strength dispersion | variation in a product was large corresponding to the striped temperature nonuniformity of the steel plate width direction.

  From the above results, the effectiveness of the present invention was confirmed.

It is explanatory drawing of the cooling device in one Embodiment of this invention. It is explanatory drawing of the cooling device in one Embodiment of this invention. It is the figure which showed an example of the direct injection part arrangement | positioning in one Embodiment of this invention. It is the figure which showed the other example of the direct injection part arrangement | positioning in one Embodiment of this invention. It is explanatory drawing of the hot rolling line and conveyance pattern of the thick steel plate in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Heating furnace 12 Rolling machine 13 Hot leveler 14 Cooling device 20 Cooling unit 21 Upper header 22 Circular pipe nozzle 23 Bar-shaped cooling water 24 Stagnating water 25 Draining roll 26 Lower header 27 Circular pipe nozzle 28 Bar-shaped cooling water 30 Cooling unit 31 Upper header 32 yen Pipe nozzle 33 Bar-shaped cooling water 34 Stagnant water 36 Lower header 37 Circular pipe nozzle 38 Bar-shaped cooling water 40 Direct injection part (collision point)

Claims (4)

In a steel cooling device having a nozzle group for injecting rod-shaped cooling water, the water density is 4 m ³ / m ² mim or more, and the rod-shaped cooling water injected from each nozzle at a speed of 10 m / s or more collides with the steel plate. The diameter of the rod-shaped cooling water in the direct injection part is smaller than twice the inner diameter of the nozzle tip, the position of the direct injection part is regularly arranged, and A steel material cooling apparatus, wherein a straight line connecting the direct injection portions located at corresponding positions in the steel plate conveyance direction is inclined by a predetermined angle with respect to the steel plate conveyance direction.   The steel material cooling device according to claim 1, wherein the regular arrangement of the direct injection portions is a grid pattern or a staggered pattern. In the method for cooling a steel material using a nozzle group for injecting rod-shaped cooling water, the water density is 4 m ³ / m ² mim or more, and the rod-shaped cooling water injected from each nozzle at a speed of 10 m / s or more is applied to the steel plate. The diameter of the rod-shaped cooling water at the impinging direct injection part is smaller than twice the inner diameter of the nozzle tip, and the position of the direct injection part is regularly arranged, and under the regular arrangement And a straight line connecting the direct injection portions at corresponding positions in the steel plate conveyance direction is inclined by a predetermined angle with respect to the steel plate conveyance direction.   The method for cooling a steel material according to claim 3, wherein the regular arrangement of the direct injection portions is a grid pattern or a staggered pattern.

Images