JP6640697B2 - Method of manufacturing steel material and method of cooling slab - Google Patents

Description

  The present invention relates to a method for manufacturing a steel material and a method for cooling a slab.

  In the production of a steel product, a cooling process is performed on the steel product in order to control the surface temperature of the steel product and the structure of the surface of the steel product. In order to perform such a cooling process, a steel material cooling method of spraying a cooling mist on a steel material in a transport state is used.

  If a plurality of nozzles for cooling steel mist are used to cool a wide area of steel, cost and maintainability deteriorate. For this reason, a steel material cooling mist nozzle tip has been proposed in which two spray slits for injecting a cooling mist are formed so that a single steel material cooling mist nozzle tip can cool a wide range of area (Japanese Patent No. 4936904). Reference).

Japanese Patent No. 4936904 Japanese Patent No. 4556720

  However, in the nozzle tip for steel material cooling mist described in Patent Document 1, since the cooling mist is injected only from the two slits, it can be said that the injection region can be sufficiently widened. Absent.

  Further, the nozzle tip for steel material cooling mist described in the above publication aims at equalizing the injection amount in the injection region, but since the cooling mist is injected from two injection slits of the same shape, the injection slit In addition, the uniformity of the injection amount in the direction orthogonal to the longitudinal direction is not sufficiently achieved. That is, in one side of one of the ejection slits (for example, the ejection area on the right side of the right ejection slit) in the ejection area, there is a portion where the cooling mist is not ejected from the other ejection slit. It cannot be said that the conversion has been sufficiently planned. Therefore, in order to cool a wide range of steel materials, a large number of nozzle tips for cooling mist of steel materials may be required.

  In view of the above inconvenience, one of the inventors of the present application, Hiroaki Sakai, Tetsuya Maruoka, and Daijiro Hagino, has completed the invention according to Japanese Patent Application No. 2006-124396 (hereinafter sometimes referred to as a prior application). The invention according to the earlier application is directed to a mist supply chamber in which the nozzle tip is provided with a supply port to which the mist is supplied, at least three ejection slits formed in a front end surface in the same direction in plan view, and a mist filling chamber communicating with the ejection slit. A flow path for supplying mist from the supply port to the mist filling chamber; and a shielding portion disposed between the supply port and the mist filling chamber, for closing a part of the flow path. In the longitudinal section perpendicular to the longitudinal direction of the ejection slit, the at least three ejection slits are radially arranged, and among the at least three ejection slits, the ejection slit outside the center ejection slit is flatter. The length of the view is small, and the portion where the outer ejection slit is formed on the front end face is inclined from the center side to the rear end side from the outer edge side. With this nozzle tip, it is possible to widen the injection area and make the injection amount uniform in the injection area.

  The inventors of the present invention have further studied diligently, and have devised a method of efficiently and reliably cooling a steel material using the nozzle tip of the invention according to the prior application. That is, an object of the present invention is to provide a manufacturing method capable of manufacturing a desired steel material at low cost by efficiently and surely cooling a cooling surface of a slab. Another object of the present invention is to provide a method of cooling a slab that can efficiently and surely cool a cooling surface of a steel material.

  The present invention has been made in order to solve the above-described problems, and a plurality of nozzle tips arranged at predetermined intervals in a transport direction with respect to a cooling surface of a front surface or a back surface of a continuously transported slab. A method for manufacturing a steel material having a cooling step of cooling the slab by injecting mist from the tip end face, wherein the nozzle tip is provided with the supply port to which the mist is supplied, and the tip end face has the same direction in plan view. At least three ejection slits formed along the mist, a mist filling chamber communicating with the ejection slit, a flow path for supplying mist from the supply port to the mist filling chamber, and a space between the supply port and the mist filling chamber. And a shielding portion for closing a part of the flow path, wherein the at least three injection slits are radially arranged in a vertical cross section perpendicular to the injection slit longitudinal direction. Of the three injection slits, the outer injection slit has a smaller length in plan view than the central injection slit, and the location where the outer injection slit is formed on the front end surface is from the center side to the outer edge side. A plurality of nozzle tips are arranged such that the direction of forming the injection slit is orthogonal to the direction of transport of the slab, and the interval between the nozzle tips adjacent to each other in the transport direction is 500 mm or more and 1300 mm. It is characterized by the following.

  In the steel material cooling mist nozzle tip, the mist supplied from the supply port is supplied to the mist filling chamber through the flow path partially closed by the shielding portion, and supplied to the mist filling chamber. The mist is sprayed from the at least three spray slits. Since the at least three injection slits are radially arranged in a vertical cross section in a direction orthogonal to the slit longitudinal direction (hereinafter, sometimes referred to as a slit orthogonal direction), the steel material cooling mist nozzle tip is arranged in the slit orthogonal direction. Mist can be sprayed over a wide area. In addition, in the steel material cooling mist nozzle tip, the outer injection slit has a smaller length in plan view than the central injection slit, and the tip end portion where the outer injection slit is formed is located from the center side to the outer edge side. Since it is inclined to the rear end side, it is possible to make the ejection width uniform between the central portion and the outer portion in the direction orthogonal to the slit. That is, since the steel material cooling mist nozzle tip can spray a uniform mist over a wide range, it is possible to efficiently cool the slab even if it is arranged at wide intervals, and to simplify the cooling equipment in the production of steel. It is possible to improve the quality of the steel material while reducing the cost and maintenance cost.

  It is preferable that the facing distance between the tip surface of the nozzle tip and the cooling surface of the slab is 100 mm or more and 400 mm or less. If the lower limit is not satisfied, the mist injection area may be narrowed. On the other hand, if the upper limit is exceeded, the collision pressure of the mist against the cooling surface becomes insufficient, and the equipment may need to be modified in order to secure the pressure of the liquid and gas for generating the mist.

  The step of cooling the slab is a step of cooling the slab in a cooling zone in which a plurality of rolls for conveying the slab in contact with the cooling surface are arranged at a pitch of 500 mm or more and 2,000 mm or less. It is preferable that the average number of the nozzle chips disposed between the rolls adjacent to each other in the transport direction is three or less. Since the nozzle tip can spray a uniform mist over a wide range, the number of rolls can be reduced to three or less in cooling zones arranged at a wide interval of 500 mm or more and 2000 mm or less. In addition, since the nozzle tip can spray mist over a wide range, by disposing the nozzle tip away from the roll, it is possible to spread the mist to near the contact point between the roll and the cast slab.

  It is preferable that the cooling area of one nozzle tip includes a rectangular area of 500 mm or more in the direction of transport of the slab and 300 mm or more in the direction perpendicular to the direction of transport. By including such a wide cooling region in one nozzle tip, it is possible to efficiently cool a cast piece with a few nozzle tips.

The distribution of water in a section in which the cooling region of the nozzle tip is divided into five sections in the direction of transport of the slab is 80% or more in the other four sections when the largest section of the water amount is 100%. Is preferably 1.0 × 10 ⁻⁴ MPa or more. By spraying a uniform amount of water over a wide range, the nozzle tip does not cause unevenness in cooling of the slab, can improve the quality of the slab, and the collision pressure is 1.0 × 10 ⁻⁴ MPa. As described above, the control of the surface structure of the steel material such as the removal of scale can be effectively performed.

  A method of cooling a slab according to another aspect of the present invention is directed to a method of cooling a slab that is continuously conveyed, with respect to a cooling surface on a front surface or a back surface of the slab. A slab cooling method for cooling the slab by injecting mist from a surface, wherein the nozzle tip is formed along the same direction in plan view on a supply port to which the mist is supplied, a tip end surface. At least three jetting slits, a mist filling chamber communicating with the jetting slit, a flow path for supplying mist from the supply port to the mist filling chamber, and disposed between the supply port and the mist filling chamber, A shielding portion for closing a part of the flow path, wherein the at least three injection slits are radially arranged in a vertical cross section in a direction orthogonal to a longitudinal direction of the injection slit, and among the at least three injection slits, The length of the outer ejection slit is smaller in plan view than the center ejection slit, and the portion where the outer ejection slit is formed on the front end surface is inclined toward the rear end side from the center side to the outer edge side. A plurality of nozzle chips are arranged so that the direction of formation of the injection slit is orthogonal to the direction of conveyance of the slab, and the interval between the nozzle chips adjacent in the conveyance direction is 500 mm or more and 1300 mm or less.

  In the steel material cooling mist nozzle tip, the mist supplied from the supply port is supplied to the mist filling chamber through the flow path partially closed by the shielding portion, and supplied to the mist filling chamber. The mist is sprayed from the at least three spray slits. Since the at least three injection slits are radially arranged in a vertical cross section in a direction orthogonal to the slit longitudinal direction (hereinafter, sometimes referred to as a slit orthogonal direction), the steel material cooling mist nozzle tip is arranged in the slit orthogonal direction. Mist can be sprayed over a wide area. In addition, in the steel material cooling mist nozzle tip, the outer injection slit has a smaller length in plan view than the central injection slit, and the tip end portion where the outer injection slit is formed is located from the center side to the outer edge side. Since it is inclined to the rear end side, it is possible to make the ejection width uniform between the central portion and the outer portion in the direction orthogonal to the slit. That is, since a uniform mist can be jetted over a wide range, the cast slab can be efficiently cooled even if the steel material cooling mist nozzle tips are arranged at wide intervals.

  As described above, the method for manufacturing a steel material and the method for cooling a slab of the present invention achieve uniform cooling of the slab with a small number of nozzle chips by using a steel material cooling mist nozzle tip capable of injecting mist in a wide range. be able to.

It is a schematic plan view showing a cooling process of a cast piece in a steel material manufacturing method which is one embodiment of the present invention. It is a schematic plan view which shows the cooling process of the slab in the conventional steel material manufacturing method. It is a schematic perspective view of the nozzle tip for steel material cooling mist of one embodiment of the present invention. It is a schematic front view which shows the front-end | tip surface of the nozzle tip for steel material cooling mist of FIG. FIG. 4 is a schematic bottom view of a distal end member constituting the nozzle tip for steel mist of FIG. 3. FIG. 5 is a sectional view taken along the line II of FIG. 4. FIG. 2 is a sectional view taken along line II-II of FIG. 4. FIG. 3 is a sectional view taken along line III-III of FIG. 4. It is a schematic plan view of the nozzle tip for steel material cooling mist used in Example 2. FIG. 4 is a schematic front view showing a tip end surface of a nozzle tip for steel material cooling mist used in Comparative Example 1. It is a schematic plan view which shows a part of process of manufacturing a steel material by continuous casting equipment.

[First embodiment]
[Manufacture of steel products]
FIG. 11 schematically shows a process of manufacturing a steel material by the continuous casting facility 30. The molten steel cooled by the mold 31 upstream of the facility is supported and guided by rolls 32, becomes a slab 34 while continuing cooling in the secondary cooling zone 33, and is sent downstream of the facility. Thereafter, the slab 34 is sent to a horizontal band 35, cut to a predetermined length by a cutter 36, further cooled in a tertiary cooling zone 37, and conveyed to the next facility by being loaded on a pallet or the like.

[Slab cooling process]
FIG. 1 schematically shows a part of a slab cooling step in a method for manufacturing a steel material according to an embodiment of the present invention. A slab 1 cast by a continuous casting machine is conveyed by a roll 4, and simultaneously with this conveyance, a mist 3 is sprayed from a nozzle tip 2 toward a cooling surface of the slab 1 to uniformly cool the slab 1. Cool. Cooling the cooling surface uniformly and lowering the cooling surface to a predetermined temperature within a predetermined time are very important factors for maintaining the quality of the slab 1. For this reason, a large number of nozzle tips are required in a continuous casting facility.

  When a large number of nozzle tips 2 are required, not only the cost but also the maintenance cost become large. If the nozzle tip 2 is clogged or the like, the quality of the slab may be reduced, and frequent maintenance is required. In addition, if a large number of two-fluid nozzle tips 2 are arranged, the layout design and the arrangement of liquid / gas pipes for mist generation may be complicated.

  FIGS. 3 to 8 show a nozzle tip 2 used for cooling a slab in a method for manufacturing a steel material according to an embodiment of the present invention. The nozzle tip is a member that injects the mist 3 supplied from the supply port 10 from the front end face 11, is mounted on a known cooling water sprinkler (not shown), and injects the mist 3 toward the steel material. The cooling water sprinkler mixes a liquid (water) and a gas (pressurized air) to form a mist (two fluids), and supplies the mist to the nozzle tip from the supply port 10. Here, as the gas, pressurized air from an air facility in a factory can be suitably used. The nozzle tip cools the steel material by spraying a mist on the steel material, and removes scale, a water film, and the like on the surface of the steel material by collision pressure.

<Nozzle tip>
Since the nozzle tip 2 used for cooling the slab according to one embodiment of the present invention can cool a wide area, a location where the mist 3 needs to be sprayed over a wide area of the slab. It is preferably used. Specifically, in a continuous casting facility, the nozzle tip is suitably used in a place where the pitch between rolls on the downstream side is as wide as 500 mm or more and 2000 mm or less, or where no roll 4 exists.

  As shown in FIGS. 6 to 8, the nozzle tip includes six spray slits 13 formed in the front end surface 11 along the same direction in plan view, a mist filling chamber 14 communicating with the spray slit 13, A flow path 15 for supplying mist from the supply port 10 to the mist filling chamber 14, and a shielding part 16 disposed between the supply port 10 and the mist filling chamber 14 and closing a part of the flow path 15 And For this reason, the mist supplied from the supply port 10 is supplied to the mist filling chamber 14 through the flow path 15 partly closed by the shielding portion 16, and the mist supplied to the mist filling chamber 14 is Then, the fuel is injected from the injection slit 13 toward the steel material. The plan view refers to a state in which the tip surface of the nozzle tip is viewed from the normal direction of the tip surface of the nozzle tip.

  The nozzle tip has a cylindrical tubular member 20 provided at the rear end and having the supply port 10, and a closed tubular distal end member 21 in which the injection slit 13 is formed in a lid 21 a at the distal end. I have. The tip member 21 is formed in a polygonal shape in plan view. The tubular member 20 and the tip member 21 are integrally fixed. Specifically, the tip member 21 is externally fitted to the tip of the tubular member 20. The cylindrical member 20 is mounted on the cooling water sprinkler. The flow path 15 having a circular cross section is formed inside the cylindrical member 20 and the tip member 21. The diameter of the flow path 15 of the tip member 21 is larger than the diameter of the flow path 15 of the tubular member 20.

(Mist filling room)
The mist filling chamber 14 is formed in the tip member 21 so as to be continuous with the flow path 15. The mist filling chamber 14 has a shape having a long axis in plan view, and is arranged such that the long axis of the mist filling chamber 14 intersects (orthogonally) with the injection slit 13 in plan view. Specifically, the mist filling chamber 14 has a substantially rectangular shape in plan view, and has a shape formed by an arc in which a pair of short sides bulges outward toward the center. The length of the long axis of the mist filling chamber 14 (the interval between the most distant portions of the pair of short sides) is substantially equal to the width of the flow path 15 (the flow path 15 in the distal end member 21), and The length (the interval between a pair of long sides) is smaller than the width of the flow path 15. As shown in FIGS. 6 to 8, the mist filling chamber 14 has a rear end side portion 14 a having the same cross-sectional shape as the plan view and a front end side which is continuous from the rear end side portion and whose inner diameter becomes narrower toward the front end. The distal end portion 14b communicates with the injection slit 13 as shown in FIGS. The top surface 14c of the distal end portion 14b is a three-dimensional curved surface that curves in the major axis direction (slit orthogonal direction Y) and the minor axis direction (slit longitudinal direction X).

(Shielding part)
As shown in FIG. 6 to FIG. 8, the nozzle tip is extended over the ring portion 23 fitted inside the flow channel 15 (the flow channel 15 of the distal end member 21) and the rear end of the ring portion 23. A shielding member 24 having the plate-shaped shielding portion 16 fixed thereto is provided. The shielding member 24, the cylindrical member 20, and the distal end member 21 are made of metal, although the material is not particularly limited.

  The shielding portion 16 has substantially the same shape as the mist filling chamber 14 in a plan view, and overlaps the mist filling chamber 14 in a plan view. Therefore, the supply of the mist linearly from the supply port 10 to the mist filling chamber 14 can be accurately suppressed by the shielding portion 16, and the pressure in the mist filling chamber 14 can be made uniform. The ratio of the area where the shielding portion 16 overlaps the mist filling chamber 14 to the area of the mist filling chamber 14 in plan view is preferably 90% or more, and the lower limit of this ratio is more preferably 95% and 100%. % Is more preferred. If the ratio is less than the above lower limit, there is a possibility that the pressure in the mist filling chamber 14 may not be uniform. Further, the ratio of the area where the shielding portion 16 overlaps the mist filling chamber 14 to the area of the shielding portion 16 in plan view is preferably 90% or more, and the lower limit of this ratio is more preferably 95% and 100%. Is more preferred. If this ratio is less than the above lower limit, there is a possibility that the portion where the flow path 15 is blocked by the shielding portion 16 is large and the pressure loss becomes too large.

(Spray slit)
The six injection slits 13 are formed by grooves penetrating the lid 21 a of the cylindrical member 20 to the mist filling chamber 14. As shown in FIG. 4, of the six injection slits 13, the length of the injection slit 13 outside the central injection slit 13 is smaller in plan view. Specifically, in plan view, the central pair of ejection slits 13 is the longest, and the length in plan view is gradually reduced in accordance with the outer ejection slits 13.

  The six injection slits 13 are symmetrical with respect to a line in plan view, and the symmetric axes of the six injection slits 13 are parallel to the slit longitudinal direction X and the slit orthogonal direction Y. Specifically, the six ejection slits 13 are line-symmetric with respect to a virtual straight line parallel to the slit longitudinal direction X between the pair of central ejection slits 13. Further, the six injection slits 13 have a virtual straight line connecting the centers of gravity, and the six injection slits 13 are also line objects with respect to this virtual straight line. In addition, the six injection slits 13 are symmetric in plan view.

  The six injection slits 13 are arranged radially in a vertical section in the slit orthogonal direction Y. That is, the ejection slits 13 are inclined outward with respect to the center axis of the flow path 15, and the inclination angle of the ejection slit 13 on the outer side is larger than that on the center side. In other words, the inclination angle increases from the ejection slit 13 on the center side to the ejection slit 13 on the outside.

  The ends of the jet slits 13 in the slit longitudinal direction X are inclined outward from the inside toward the tip. That is, in each of the ejection slits 13, the inner diameter in the longitudinal direction of the slit is widened from the inside to the tip. In other words, the diameter of each of the injection slits 13 is gradually increased from the top surface 14c of the mist filling chamber 14 to the length of the front end surface 11 along the front end side.

(Tip surface)
The tip surface 11 of the nozzle chip is a three-dimensional curved surface except for the central portion 11b, and is specifically a part of a spherical surface. The radius of curvature of the three-dimensional curved surface of the distal end surface 11 is larger than the inner diameter of the flow channel 15. The central portion 11b is a flat surface.

  That is, the edge 11a of the tip surface 11 of the nozzle tip is a three-dimensional curved surface. For this reason, the position of the front end surface 11 where the outermost ejection slit 13 is formed is inclined toward the rear end from the center to the outer edge as shown in FIG. Further, as shown in FIG. 8, the position of the front end face 11 where the outer ejection slit 13 is formed is inclined in the slit orthogonal direction Y and also in the slit longitudinal direction X from the center side to the rear end side from the center side to the outer edge side. are doing.

  Further, the positions of the distal end surfaces 11 where the ends in the longitudinal direction of the ejection slit 13 at the center are respectively exposed are inclined from the center side to the rear end side from the center side to the outer edge side. Further, the portion of the front end face 11 where the longitudinal end of the injection slit 13 on the center side is exposed is inclined in the slit longitudinal direction X and also in the slit orthogonal direction Y from the center side to the outer edge side in the slit orthogonal direction Y. It is inclined.

  The position of the front end face 11 where the intermediate ejection slit 13 (the ejection slit 13 disposed between the outermost ejection slit 13 and the center ejection slit 13) is formed is located at the rear end side from the center side to the outer edge side. It is inclined. Further, the portion of the front end face 11 where the intermediate ejection slit 13 is formed is inclined in the slit orthogonal direction Y and also in the slit longitudinal direction X from the center side to the rear end side from the center side to the outer edge side. That is, in the nozzle tip of the present embodiment, the portion of the tip end surface 11 where the ejection slit 13 is formed other than the central portion in the slit longitudinal direction X of the most central ejection slit 13 is a three-dimensional curved surface.

[advantage]
Since the nozzle tip has six jetting slits 13, it is possible to jet a mist in a wide range in the slit orthogonal direction Y, and the six jetting slits 13 are radially formed in a vertical cross section in the slit orthogonal direction Y. The mist can be sprayed in a wider range in the direction Y orthogonal to the slit. Further, since the end portions of the ejection slit 13 in the slit longitudinal direction X are inclined outward from the inside toward the front end side, mist can be ejected in a wide range also in the slit longitudinal direction X.

  In addition, the length of the outer ejection slit 13 in plan view is smaller than that of the central ejection slit 13, and the position of the distal end surface 11 where the outer ejection slit 13 is formed is inclined from the center side to the rear edge side toward the outer edge side. As a result, it is possible to equalize the injection width between the central portion and the outer portion in the slit orthogonal direction Y, and to obtain a sufficient mist collision pressure in each portion of the injection region. In particular, the central pair of ejection slits 13 is the longest, and the length in plan view is sequentially reduced in accordance with the outer ejection slits 13, so that the ejection width of each portion in the slit orthogonal direction Y is made uniform and sufficient mist collision pressure is obtained. More secure.

  Further, since the position of the front end surface 11 where the outer ejection slit 13 is formed is inclined from the center side to the rear end side from the center side to the outer edge side, it is easy to sufficiently secure the inclination angle of the outer ejection slit 13. The depth of the injection slit 13 (the distance through which the mist passes through the ejection slit) increases, and it is possible to suppress the pressure loss from becoming too large.

  In addition, the location of the front end surface 11 at the end of the central ejection slit 13 and the middle ejection slit 13 in the longitudinal direction is inclined from the center side to the rear end side from the center side to the outer edge side. It is possible to optimize the slit depth between the central portion in the direction and the vicinity of the end portion, so that the injection amount in the longitudinal direction of the injection slit 13 and the collision pressure of the mist can be optimized.

  Furthermore, since the six ejection slits intersect (orthogonally) in a plan view with the long axis of the mist filling chamber 14, the mist filled in the mist filling chamber 14 is easily supplied uniformly to the six ejection slits 13, The injection amount in the slit orthogonal direction Y and the mist collision pressure in the injection region can be more reliably made uniform.

  Also, since the six injection slits 13 are line-symmetric in plan view, and the symmetric axes of the six injection slits 13 are parallel to the slit longitudinal direction X and the slit orthogonal direction Y, the slit orthogonal direction Y and the slit Optimization of the injection amount and the mist collision pressure in the longitudinal direction X can be improved. Furthermore, since the six injection slits 13 are symmetrical in plan view, the injection amount and the mist collision pressure can be optimized over the entire injection region.

  The nozzle tip is not limited to the above embodiment, and the shape, material, and the like can be appropriately changed in design. In addition, although the description has been given of the one having six injection slits, the present invention is not limited to this, and it is sufficient that the invention has three or more injection slits. The lower limit of the number of the injection slits is preferably four, and more preferably six. Further, the upper limit of the number of the ejection slits is preferably 12 lines, and more preferably 10 lines. The number of the ejection slits may be an odd number, but is preferably an even number, so that the injection amount in the direction orthogonal to the slit can be easily made uniform. In addition, in addition to the plurality of ejection slits formed along the same direction as described above, for example, a spindle-shaped ejection port may be formed on the distal end surface within a range that does not impair the effects of the present invention.

  The opposing distance D between the tip surface of the nozzle tip 2 and the cooling surface of the slab 1 is preferably set to 100 mm or more and 400 mm or less, more preferably 200 mm or more and 300 mm or less. If the opposing distance D does not satisfy the lower limit, the cooling area of the nozzle tip 2 may be narrowed, and the cooling of the slab 1 may be uneven. On the other hand, when the upper limit is exceeded, the liquid and gas for generating the mist 3 to be supplied to the nozzle tip 2 are supplied to the nozzle tip 2 in order to set the collision pressure of the mist 3 against the cooling surface in the cooling area of the nozzle tip 2 to be a desired value. There is a possibility that the equipment needs to be changed, for example, by making the piping capable of withstanding high pressure.

  The water amount distribution in a section in which the cooling region of the nozzle tip 2 is divided into five in the direction of transport of the slab 1 is that when the largest section of the water amount is 100%, the other four sections are 80% or more. preferable. Even if the nozzle tip 2 can spray the mist 3 in a wide range, if the same amount of water cannot be sprayed on the sprayed area, the slab 1 may not be cooled uniformly. The cooling area is divided into five in the conveying direction of the slab 1, and the difference between the section having the largest amount of water and the other four sections is within the above range, whereby the slab 1 can be uniformly cooled. It becomes possible stably.

  It is preferable that the cooling area of one nozzle tip 2 includes a rectangular area of 500 mm or more in the transport direction of the slab 1 and 300 mm or more in the direction orthogonal to the transport direction. When the cooling region includes a rectangular region that is equal to or larger than the above range, the number of the nozzle chips can be significantly reduced in the step of cooling the slab 1. In addition, since the cooling region includes a rectangular region, the slab 1 can be cooled without unevenness.

The collision pressure of the mist 3 against the cooling surface in the cooling area of the nozzle tip 2 is preferably 1.0 × 10 ⁻⁴ Mpa or more, and more preferably 6.0 × 10 ⁻⁴ Mpa or more. The mist 3 is sprayed at a high pressure by the nozzle tip 2 to cool the slab 1, so that the scale and the water film on the steel material surface are removed by the collision pressure together with the cooling. By having the above collision pressure, scale and the like can be effectively removed. The collision pressure refers to a collision force of a mist applied to a certain region (cooling region V) when the region is set, and the collision force is calculated by the following equation (1).
[Equation 1]
H = r · Q · Cv · V
Here, H is the collision force [N]. r is the specific weight of water [kg / m ³ ]. Q is the flow rate [m ³ / s]. Cv is a flow velocity decay coefficient in the atmosphere. V is the flow velocity [m / s] immediately after exiting the nozzle.

<Roll>
Rolls 4 are arranged throughout the continuous casting facility to transport slab 1 from upstream to downstream of the facility. Depending on the location where the roll 4 is disposed, the load applied to the roll 4 by the slab 1, and the like, an optimal material, shape, and the like are appropriately adopted. For example, a roll having a diameter of 300 mm or more and 500 mm or less is widely used. In the slab cooling step and the slab cooling method, the nozzle tip 2 can spray the mist 3 in a wide range, that is, the mist 3 can be sprayed in a wide angle, so that the contact between the slab 1 and the roll 4 can be achieved. Since the mist 3 reaches the vicinity of the point, the area where the mist 3 does not hit (the non-cooling area W) can be minimized, and the cooling efficiency of the slab 1 can be improved.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not to be construed as being limited based on the description of the examples.

(Test method)
The mist was supplied to the supply ports of the nozzle chips of Examples 1 and 2 and Comparative Example 1 under the injection conditions shown in Table 1, and the mist was directed from the injection slit toward the slab conveyed at a conveyance speed of 0.07 m / sec. Was injected. The width, thickness and length of the used slabs are all 300 × 400 × 12000 mm. The test results were compared with the conventional cooling method (Comparative Example 1) according to the cooling rate [%]. The cooling rate is defined as the surface area of the slab that is exposed to the mist to be sprayed between the rolls (cooling area) and the surface area of the slab to which the mist to be sprayed cannot reach due to the shade of the roll (uncooled). Area) and the area obtained by adding the cooling area to the area, and is calculated by the following equation 2.
[Equation 2]
R = V / V + W
Here, R is a cooling rate [%]. V is a cooling area [mm ² ]. W is an uncooled area [mm ² ]. (Fig. 1)

(Example 1)
As shown in FIGS. 3 to 8, the nozzle tip has six ejection slits formed on the front end surface having a three-dimensional curved surface, and has a shielding portion in the flow path, the nozzle size is 29 × 34 mm, and the inside diameter of the supply port is Is 19 mm, the longitudinal lengths of the central, middle and outer ejection slits in plan view are 24 mm, 19 mm and 16 mm, respectively, and the width of each ejection slit (length in the direction perpendicular to the slit) is 1.5 mm. Was prepared as the nozzle tip of Example 1. The nozzle pitch was 600 mm, and the opposing distance (the distance between the cooling surface and the tip surface of the nozzle tip) was 200 mm.

(Example 2)
As shown in FIG. 9, a nozzle tip having a substantially hemispherical tip surface, 10 ejection slits formed, and a shielding portion in the flow path, the nozzle size is 34 × 34 mm, and the inside diameter of the supply port is 19 mm. A nozzle tip of Example 2 in which the length in the longitudinal direction of the ejection slits from the center to the outside in plan view is 27 mm to 17 mm, and the width of each ejection slit (length in the direction perpendicular to the slit) is 1 mm is prepared. did. The nozzle pitch was 1200 mm and the opposing distance was 300 mm.

(Comparative Example 1)
As shown in FIG. 10, a nozzle tip of Comparative Example 1 was prepared having the same configuration as that of Example 1 except that the number of the ejection slits 13 was two and the shape in plan view was the same. The length of each ejection slit 13 in the longitudinal direction is 24 mm, the width (length in the direction perpendicular to the slit) is 2.7 mm, the nozzle pitch is 200 mm, and the opposing distance is 200 mm.

(result)
The test results are shown in the column of cooling rate [%] in Table 1. Although the nozzle pitch in the first embodiment is three times the conventional one and the nozzle pitch in the second embodiment is six times the conventional one, a better cooling rate than the conventional cooling rate can be obtained.

  From Example 1 and Example 2, the process and method of cooling a slab using a nozzle tip capable of spraying mist over a wide area not only can simplify the equipment, but also provide a cooling efficiency superior to the conventional cooling method. It was found to have.

  The method for manufacturing a steel material and the method for cooling a slab of the present invention can simplify a facility with a small number of nozzle tips for a steel material cooling mist, and can obtain an excellent cooling effect. It can be suitably used.

1 Slab 2 Nozzle tip 3 Mist 4 Roll 5 Nozzle tip (conventional nozzle)
Reference Signs List 10 Supply port 11 Tip surface 11a Edge 11b Flat surface 13 Injection slit 14 Mist filling chamber 14a Rear end side 14b of mist filling chamber 14c Tip side of mist filling chamber 14c Top surface of mist filling chamber 15 Flow path 16 Shielding section 20 Tube member 21 Tip member 21a Lid 23 Ring 24 Shielding member 30 Continuous casting equipment 31 Mold 32 Roll 33 Secondary cooling zone 34 Slab 35 Horizontal band 36 Cutting machine 37 Tertiary cooling zone D Counter distance L Roll pitch V Cooling area W Non-cooling Area X Slit longitudinal direction Y Slit orthogonal direction

Claims (6)

Cooling that cools the slab by injecting mist from the tip surfaces of a plurality of nozzle tips arranged at predetermined intervals in the conveying direction with respect to the cooling surface on the front or back surface of the slab that is continuously conveyed A method of manufacturing a steel material having a process,
The nozzle tip is
A supply port to which the mist is supplied,
At least three injection slits formed on the tip end surface in the same direction in plan view,
Mist filling chamber communicating with the injection slit,
A flow path for supplying mist from the supply port to the mist filling chamber, and a shielding portion disposed between the supply port and the mist filling chamber, and closing a part of the flow path,
In the vertical cross section orthogonal to the longitudinal direction of the injection slit, the at least three injection slits are radially arranged,
Of the at least three injection slits, the outer injection slit has a smaller length in plan view than the central injection slit,
The location where the outer ejection slit is formed on the front end surface is inclined from the center side to the rear end side according to the outer edge side,
A plurality of nozzle tips are arranged such that the direction of forming the injection slit is orthogonal to the direction of transport of the slab,
A method for producing a steel material, wherein an interval between the nozzle tips adjacent in the transport direction is 500 mm or more and 1300 mm or less.   The method for producing a steel material according to claim 1, wherein a facing distance between the tip surface of the nozzle tip and the cooling surface is 100 mm or more and 400 mm or less.   The cooling step includes a step of cooling the slab in a cooling zone in which a roll for conveying the plurality of slabs in contact with the cooling surface is arranged at a pitch of 500 mm or more and 2,000 mm or less. The method according to claim 1, wherein an average number of the nozzle tips disposed between the adjacent rolls is three or less. 4. Region one of the nozzle tip is cooled, in a direction orthogonal to the 500mm or more and the conveying direction in the conveying direction of the slab according to claim 1 comprising a rectangular area of more than 300 mm, the steel according to claim 2 or claim 3 Production method. The distribution of water in a section in which the cooling region of the nozzle tip is divided into five sections in the direction of transport of the slab is 80% or more in the other four sections when the largest section of the water amount is 100%. The method for producing a steel material according to claim ⁴ , wherein a collision pressure against the steel is 1.0 × 10 ⁻⁴ MPa or more. By casting mist from the tip surfaces of a plurality of nozzle tips arranged at predetermined intervals in the transport direction with respect to the cooling surface on the front surface or the back surface of the continuously transported slab, the slab is cooled. A method of cooling a piece,
The nozzle tip is
A supply port to which the mist is supplied,
At least three injection slits formed on the tip end surface in the same direction in plan view,
Mist filling chamber communicating with the injection slit,
A flow path for supplying mist from the supply port to the mist filling chamber, and a shielding portion disposed between the supply port and the mist filling chamber, and closing a part of the flow path,
In the vertical cross section orthogonal to the longitudinal direction of the injection slit, the at least three injection slits are radially arranged,
Of the at least three injection slits, the outer injection slit has a smaller length in plan view than the central injection slit,
The location where the outer ejection slit is formed on the front end surface is inclined from the center side to the rear end side according to the outer edge side,
A plurality of nozzle tips are arranged such that the direction of forming the injection slit is orthogonal to the direction of transport of the slab,
A method of cooling a slab, wherein the interval between the nozzle chips adjacent in the transport direction is 500 mm or more and 1300 mm or less.

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