US20120017660A1 - Steel plate manufacturing facility and manufacturing method - Google Patents

Steel plate manufacturing facility and manufacturing method Download PDF

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Publication number
US20120017660A1
US20120017660A1 US13/256,288 US201013256288A US2012017660A1 US 20120017660 A1 US20120017660 A1 US 20120017660A1 US 201013256288 A US201013256288 A US 201013256288A US 2012017660 A1 US2012017660 A1 US 2012017660A1
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Prior art keywords
steel plate
cooling
descaler
spraying
cooling water
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US13/256,288
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English (en)
Inventor
Takashi Kuroki
Naoki Nakata
Kenji Hirata
Takayuki Furumai
Yukio Fujii
Motoji Terasaki
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JFE Steel Corp
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JFE Steel Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/04—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing
    • B21B45/08—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing hydraulically
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B39/00—Arrangements for moving, supporting, or positioning work, or controlling its movement, combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B39/00—Arrangements for moving, supporting, or positioning work, or controlling its movement, combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B39/02—Feeding or supporting work; Braking or tensioning arrangements, e.g. threading arrangements
    • B21B39/08—Braking or tensioning arrangements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
    • B21B45/0203—Cooling
    • B21B45/0209—Cooling devices, e.g. using gaseous coolants
    • B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
    • B21B45/0218—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes for strips, sheets, or plates

Definitions

  • the present invention relates to a steel plate manufacturing facility and manufacturing method of hot rolling, hot leveling, and cooling a steel plate.
  • Patent Literature 1 discloses a method of performing descaling at least one of just before and just after a final pass of finish rolling, subsequently performing hot leveling, then performing descaling, and starting accelerated cooling.
  • Patent Literature 2 discloses a method of performing finish rolling and hot leveling, performing descaling just before controlled cooling, and performing controlled cooling.
  • Patent Literature 1 and Patent Literature 2 do not mention a pressure at the point of impact of cooling water on each surface of a steel plate during descaling, pressures at the point of impact derived on the basis of spraying pressures and spraying distances of nozzles described in Patent Literature 1 and Patent Literature 2 and a typical kind of nozzle are estimated to be 0.08 to 1.00 MPa in Patent Literature 1 (when Everloy Descaling Nozzles DNX or DNH are used under conditions described in paragraph Nos.
  • a pressure at the point of impact is 0.08 to 1.00 MPa on the basis of a spray angle of 23° and Expressions (1) and (2) which will be described in paragraph Nos. (0030) and (0031) in this specification) and to be approximately 0.06 to 0.08 MPa in Patent Literature 2 (when Everloy Descaling Nozzles DNX are used under conditions described in paragraph No. (0024) in Patent Literature 2, a pressure at the point of impact is 0.06 to 0.08 MPa on the basis of a spray angle of 37° and Expressions (1) and (2) which will be described in paragraph Nos. (0030) and (0031) in the specification).
  • the pressures at the point of impact of cooling water are low and the disclosed methods do not offer the performance of achieving uniform descaling. Accordingly, the surface condition of a scale removed portion differs from that of a portion where scale is not removed. Disadvantageously, uniform cooling is not achieved during controlled cooling.
  • the present invention focused on the above-described unsolved problems of related art.
  • the present invention provides a facility and method for manufacturing a steel plate excellent in steel plate shape and mechanical property by performing uniform descaling in a descaling step and achieving uniform cooling in a cooling step.
  • a steel plate manufacturing facility includes a hot rolling mill, a hot leveler, a descaler, and cooling equipment arranged in that order from the upstream side in a conveying direction, wherein a pressure P [MPa] at the point of impact of cooling water sprayed from the descaler to each surface of a steel plate is greater than or equal to 1.5 MPa.
  • the present inventors discovered that when descaling was performed after hot leveling, so long as a pressure at the point of impact of cooling water sprayed from the descaler to the steel plate was 1.5 MPa or higher, the scale thickness of a product decreased and was made uniform. The reason is that scale was temporarily and uniformly removed completely by descaling at a high pressure at the point of impact and, after that, scale was thinly and uniformly reproduced. According to preferred aspects of the invention, therefore, since the scale thickness of the steel plate is thinned and made uniform before passing through the cooling equipment, the steel plate can be uniformly cooled with little surface temperature deviation among positions in the width direction of the steel plate while passing through the cooling equipment. Thus, the steel plate is excellent in steel plate shape and mechanical property.
  • the descaler removes scale produced on each surface of the steel plate after hot leveling of the steel plate by the hot leveler, spraying nozzles of the descaler can be moved closer to the surfaces of the hot-leveled steel plate, thereby improving the descaling performance.
  • the cooling water spraying performance of the descaler for providing a predetermined pressure at the point of impact can be set to low.
  • the distance L [m] between the descaler and the cooling equipment satisfies the expression L ⁇ V ⁇ 5 ⁇ 10 ⁇ 9 ⁇ exp(25000/T). According to preferred aspects of the invention, cooling of the steel plate by the cooling equipment can be stabilized.
  • the components are arranged such that the distance L between the descaler and the cooling equipment is less than or equal to 12 m. According to embodiments of the invention, cooling of the steel plate by the cooling equipment is very stable.
  • the distance H between each spraying nozzle of the descaler and the surface of the steel plate is greater than or equal to 40 mm and less than or equal to 140 mm.
  • the spraying pressure and spray flow rate of the descaler for providing a predetermined pressure at the point of impact are low, thus reducing the pump capacity of the descaler.
  • the cooling equipment includes a header supplying cooling water to the upper surface of the steel plate, cooling water spraying nozzles extending from the header and spraying rod-like cooling water, and a dividing plate disposed between the steel plate and the header, and the dividing plate includes a plurality of water supply inlets receiving the lower ends of the cooling water spraying nozzles and a plurality of drain outlets draining the cooling water supplied to the upper surface of the steel plate onto the dividing plate.
  • cooling water supplied from the cooling water spraying nozzles through the water supply inlets cools the upper surface of the steel plate to turn to high-temperature drainage water and the drainage water flows from the drain outlets onto the dividing plate so that the drainage water after cooling is immediately eliminated from the steel plate.
  • the cooling equipment offers adequate cooling performance that is uniform in the width direction.
  • the steel plate since the scale thickness of the steel plate is thinned and made uniform before the cooling step, the steel plate can be uniformly cooled with little surface temperature deviation among positions in the width direction of the steel plate in the cooling step. Thus, the steel plate excellent in steel plate shape and mechanical property can be manufactured.
  • the period of time t [s] between the completion of the descaling step and the start of the cooling step satisfies the expression t ⁇ 5 ⁇ 10 ⁇ 9 ⁇ exp(25000/T). According to exemplary embodiments of the invention, cooling of the steel plate in the cooling step can be stabilized.
  • uniform descaling can be performed in the descaling step and uniform cooling can be achieved in the cooling step, so that the steel plate excellent in steel plate shape and mechanical property can be manufactured.
  • FIG. 1 is a diagram illustrating the outline of a hot rolling facility according to an exemplary embodiment of the present invention.
  • FIG. 2 is a diagram illustrating cooling equipment constituting the hot rolling facility according to an exemplary embodiment of the present invention.
  • FIG. 3 is a diagram illustrating a dividing plate constituting an exemplary embodiment of the cooling equipment.
  • FIG. 4 is a diagram illustrating the flow of cooling water and that of drainage water in the cooling equipment.
  • FIG. 5 is a graph illustrating the relationship between the pressure at the point of impact of cooling water from a descaler and the thickness of scale produced on each surface of a steel plate product.
  • FIG. 6 is a graph illustrating the relationship between the position from the center of a steel plate in the width direction thereof and the temperature in a cooling step in an exemplary embodiment of the present invention.
  • FIG. 7 is a graph illustrating the relationship between the position from the center of a steel plate in the width direction thereof and the temperature in the cooling step in a related-art facility which does not include a descaling step before the cooling step.
  • FIG. 8 is a graph illustrating the relationship between the spraying pressure and the spraying distance for providing a pressure at the point of impact of 1.5 MPa while setting a spray flow rate, a spray angle of nozzle, and an angle between the spray direction and the vertical line in the descaler to predetermined values.
  • a hot rolling facility includes a heating furnace 2 , a hot rolling mill 3 , a first hot leveler 5 , a descaler 4 , cooling equipment 6 , and a second hot leveler 7 arranged in that order from the upstream side in a conveying direction of a steel plate 1 .
  • a slab discharged from the heating furnace 2 is passed through the hot rolling mill 3 multiple times, thus resulting in a rolled steel plate 1 having a predetermined thickness.
  • the hot-rolled steel plate 1 is conveyed on a table roller (not illustrated) from the upstream side to the first hot leveler 5 on the downstream side.
  • the hot rolling mill 3 may include a rough rolling mill and a finish rolling mill.
  • the first hot leveler 5 is configured to remove strain caused in the steel plate 1 during hot rolling.
  • the illustrated hot leveler is of the roller leveler type in which the steel plate 1 is nipped between leveling rolls arranged one above the other in a staggered layout.
  • the hot leveler is not limited to this type, but a skin-pass mill or a press machine may be used.
  • the hot rolling mill 3 includes a rough rolling mill and a finish rolling mill, the finish rolling mill may perform skin-pass rolling.
  • the second hot leveler 7 is configured to remove strain caused in the steel plate 1 during cooling by the cooling equipment 6 .
  • This hot leveler does not have to be used in the present invention.
  • the second hot leveler 7 used is of the roller leveler type.
  • the hot leveler is not limited to this type, but a skin-pass mill or a press machine may be used.
  • the cooling equipment 6 is configured to perform controlled cooling on a high-temperature steel plate 1 subjected to hot rolling under predetermined temperature conditions to control the structure of the steel plate 1 in order to obtain desired material properties. Any cooling equipment may be used so long as desired cooling conditions are provided. It is preferred to use cooling equipment capable of uniformly cooling the upper and lower surfaces of the steel plate 1 in the length and width directions.
  • the present embodiment therefore uses the cooling equipment 6 , illustrated in FIG. 2 , which has high cooling performance and is excellent in cooling uniformity, especially in the width direction.
  • the cooling equipment 6 in the present embodiment includes an upper header 10 which supplies cooling water to the upper surface of the steel plate 1 , upper cooling water spraying nozzles 11 which downwardly extend from the upper header 10 toward the steel plate 1 , a dividing plate 12 which is horizontally disposed between the upper header 10 and the steel plate 1 so as to extend in the width direction of the steel plate and has many holes, a lower header 13 which supplies cooling water to the lower surface of the steel plate 1 , lower cooling water spraying nozzles 15 which upwardly extend from the lower header 13 toward the steel plate 1 , and squeezing rolls 16 and 17 arranged on the upstream and downstream sides of the steel plate 1 in the conveying direction.
  • the dividing plate 12 has the many (multiple) holes 18 arranged in a grid pattern.
  • the upper cooling water spraying nozzles 11 are inserted in predetermined holes 18 in a staggered layout. Lower openings of the holes 18 , receiving the upper cooling water spraying nozzles 11 , each serve as a water supply inlet 19 . Lower openings of the holes 18 , which do not receive the upper cooling water spraying nozzles 11 , each serve as a drain outlet 20 .
  • the tips of the upper cooling water spraying nozzles 11 are received in the holes 18 (the water supply inlets 19 ) such that the level of each tip is higher than the lower end of the dividing plate 12 .
  • a broken line in FIG. 3 is parallel to the conveying direction of the steel plate and both ends of the dividing plate 12 in the width direction of the steel plate are not illustrated.
  • FIG. 4 is a side elevational view of one end of the steel plate when viewed from the conveying direction of the steel plate.
  • cooling water supplied from the upper cooling water spraying nozzles 11 through the water supply inlets 19 cools the upper surface of the steel plate 1 to turn to high-temperature drainage water and then flows onto the dividing plate 12 through the drain outlets 20 .
  • Cooling water supplied from the lower cooling water spraying nozzles 15 cools the lower surface of the steel plate 1 and flows downward.
  • cooling water supplied to the upper surface of the steel plate 1 is drained while flowing on the upper surface of the steel plate 1 in the width direction.
  • the flow of this drainage water prevents cooling water supplied from the upper cooling water spraying nozzles 11 from reaching the upper surface of the steel plate 1 , particularly in the vicinity of each end of the plate in the width direction, so that the cooling performance degrades in the vicinity of the end of the plate in the width direction and uniform cooling cannot be performed in the width direction.
  • a temperature distribution in the width direction of the steel plate 1 is U-shaped such that the temperature of the center of the plate is low and the temperature of each end thereof is high.
  • the cooling equipment 6 in the present embodiment is configured such that drainage water after cooling is immediately drained from the upper surface of the steel plate 1 onto the dividing plate 12 . Cooling water sprayed from the upper cooling water spraying nozzles 11 sequentially comes into contact with the steel plate 1 , thus providing adequate cooling performance.
  • cooling water supplied to the upper surface of the steel plate 1 does not tend to upwardly pass through the dividing plate 12 , so that the water flows toward the ends of the steel plate 1 in the width direction between the upper surface of the steel plate 1 and the dividing plate 12 .
  • the flow of drainage water prevents cooling water supplied from the upper cooling water spraying nozzles 11 from reaching the upper surface of the steel plate 1 .
  • the cooling performance degrades in the vicinity of the ends of the plate in the width direction and uniform cooling cannot be performed in the width direction.
  • the cooling equipment 6 illustrated in FIG.
  • the present embodiment in the present embodiment is provided with the holes 18 which serve as the water supply inlets 19 and the drain outlets 20 to share their functions, cooling water and drainage water after cooling smoothly flow. Furthermore, since the tips of the upper cooling water spraying nozzles 11 are received in the holes 18 of the dividing plate 12 , drainage water flowing over the dividing plate 12 in the width direction does not interfere with cooling water sprayed from the upper cooling water spraying nozzles 11 and uniform cooling is achieved in the width direction, thus providing a uniform temperature distribution in the width direction, as illustrated in FIG. 6 .
  • total cross-sectional area of the drain outlets 20 be equal to or more than 1.5 times as large as the total area of openings (hereinafter, referred to as “total inner-diameter cross-sectional area”) of the upper cooling water spraying nozzles 11 , because cooling water is immediately drained through the drain outlets 20 . If this value is less than 1.5 times, the flow resistance of each drain outlet increases, so that remaining water does not tend to be drained onto the dividing plate.
  • the remaining water flows between the upper surface of the steel plate and the dividing plate toward the ends of the steel plate in the width direction, thereby degrading the cooling performance, particularly, in the vicinity of the ends of the steel plate in the width direction.
  • cross-sectional diameter the area of opening of each drain outlet
  • the stiffness of the dividing plate 12 is lowered.
  • the dividing plate 12 tends to be damaged when hitting against a steel plate. It is therefore preferred that the ratio of the total cross-sectional area of the drain outlets 20 to the total inner-diameter cross-sectional area of the upper cooling water spraying nozzles 11 be in the range of 1.5 to 20.
  • each upper cooling water spraying nozzle 11 In order to allow cooling water to pass through remaining water, reach a steel plate, and achieve uniform cooling in the width direction, it is preferred to optimize the inner diameter and length of each upper cooling water spraying nozzle 11 , the spraying velocity of cooling water, and the distance between nozzles.
  • the inner diameter of each nozzle is preferably 3 to 8 mm. If the inner diameter is less than 3 mm, the flux of water sprayed from the nozzle diminishes and the force of water becomes weak. Whereas, if the nozzle diameter is greater than 8 mm, the flow rate decreases and the force to pass through the remaining water becomes weak.
  • each upper cooling water spraying nozzle 11 is preferably 120 to 240 mm. If the upper cooling water spraying nozzle 11 is shorter than 120 mm, the distance between the lower surface of the upper header 10 and the upper surface of the dividing plate 12 is too short, so that a drain space above the dividing plate 12 is reduced and drainage water after cooling cannot be smoothly drained. Whereas, if the upper cooling water spraying nozzle 11 is longer than 240 mm, the pressure loss of the upper cooling water spraying nozzle 11 increases, so that the force to pass through remaining water becomes weak.
  • the spraying velocity of cooling water from the nozzles is preferably 6 m/s or higher. If the spraying velocity is less than 6 m/s, the force of cooling water passing through the remaining water is extremely weakened. It is preferred that the spraying velocity be 8 m/s or higher, because higher cooling performance is ensured.
  • the distance between the lower end of each upper cooling water spraying nozzle 11 and the upper surface of the steel plate 1 is preferably 30 to 120 mm. If the distance is less than 30 mm, the frequency of collision of the steel plate 1 with the dividing plate 12 extremely increases. It is therefore difficult to maintain the facility. If the distance is greater than 120 mm, the force of cooling water passing through the remaining water is extremely weakened.
  • the water flow rate at which the cooling equipment 6 in the present embodiment achieves maximum effect is 1.5 m 3 /m 2 ⁇ min or higher. If the water flow rate is lower than this value, the thickness of layer of the remaining water does not become so thick. Even in the application of known technology to cool a steel plate while allowing free fall of rod-like cooling water, in some cases, strip temperature deviation in the width direction is not so large. Whereas, if the water flow rate is higher than 4.0 m 3 /m 2 ⁇ min, the cooling equipment 6 in the present embodiment is effectively used but has practical use problems, for example, high facility cost. The most practical water flow rate is therefore 1.5 to 4.0 m 3 /m 2 ⁇ min.
  • the cooling equipment 6 illustrated in FIG. 2 includes the lower header 13 which is the same as the cooling equipment above the upper surface and includes the lower cooling water spraying nozzles 15 .
  • the cooling equipment 6 illustrated in FIG. 2 includes the lower header 13 which is the same as the cooling equipment above the upper surface and includes the lower cooling water spraying nozzles 15 .
  • sprayed cooling water hits against the steel plate and then freely falls.
  • the strip temperature deviation in the width direction is not so a big problem, like the problem on the upper surface of the steel plate. Therefore, cooling equipment below the lower surface of the steel plate is not particularly limited.
  • the descaler 4 is configured to remove scale produced on each surface of the steel plate 1 after hot rolling while spraying high-pressure water from a plurality of spraying nozzles directed toward the surface of the steel plate 1 subjected to removal of strain, caused in the steel plate 1 , through the first hot leveler 5 .
  • the pressure P [MPa] at the point of impact of high-pressure water sprayed from the spraying nozzles of the descaler 4 to each surface of the steel plate 1 is set to 1.5 MPa or higher, the descaler 4 removes scale produced on the surface of the steel plate 1 , and after that, the cooling equipment 6 cools the steel plate 1 , thus improving the steel plate shape and mechanical property of the steel plate 1 .
  • Pc pressure at the point of impact [kgf/cm 2 ]
  • Q spray flow rate [L/min]
  • A spray area [cm 2 ]
  • Ps spraying pressure [kgf/cm 2 ].
  • the spray area A is obtained using the following expression (2) by spray experiment:
  • B spraying width [cm] of spray
  • T spraying thickness [cm] of spray
  • H spraying distance (the distance between each spraying nozzle of the descaler 4 and each surface of the steel plate 1 ) [cm]
  • ⁇ spray angle [°] of nozzle (the angle of spread of descaling water sprayed from the nozzles).
  • the form of expression to obtain the pressure Pc at the point of impact is not limited to this expression.
  • Spray experiment may actually be performed and an expression expressing the regression of a pressure at a direct cooling point or impact point measured by a pressure sensor may be used.
  • FIG. 8 is a graph illustrating the relationship between the spraying pressure Ps and the spraying distance H for achieving a pressure P at the point of impact of 1.5 MPa when the spray flow rate Q is 64 L/min, the spray angle ⁇ of nozzle (the angle of spread water sprayed) is 32°, and the angle between the spray direction and the vertical line (the angle by which the center axis of sprayed water is deviated from the vertical direction relative to the steel plate to the upstream side of the traveling direction of the steel plate) is 15°.
  • the spraying direction H may be less than or equal to 175 mm
  • the spraying direction H may be less than or equal to 150 mm
  • the spraying pressure Ps is 17.7 MPa
  • the spraying distance H may be less than or equal to 130 mm
  • the spraying pressure Ps is 14.7 MPa
  • the spraying distance may be less than or equal to 125 mm.
  • the spraying distance H be less than or equal to 140 mm. More preferably, the spraying distance H is less than or equal to 100 mm.
  • the spraying distance H is greater than or equal to 40 mm and is less than or equal to 140 mm in consideration of contact between the nozzles and the steel plate 1 .
  • the spraying pressure of a pump used in the normal descaler 4 is less than or equal to 14.7 MPa (150 kgf/cm 2 ). Accordingly, a spraying pressure at the tip of each nozzle is further lower than 14.7 MPa by pressure loss in a path. It is therefore preferred to use a pump having a spraying pressure that allows a higher spraying pressure Ps than normal.
  • the upper limit of the spraying pressure Ps is not especially determined. If the spraying pressure Ps is set to high, energy required electric power becomes enormous. It is therefore preferred that the spraying pressure Ps be less than or equal to 50 MPa.
  • a pump providing a spraying pressure Ps of 50 MPa exhibits a maximum spraying pressure among existing commercially available pumps.
  • the descaler 4 in which the pressure P at the point of impact of high-pressure water is set to 1.5 MPa or higher, removes scale produced on the surfaces of the steel plate 1 , thereby eliminating a variation in scale thickness distribution.
  • the steel plate 1 can be uniformly cooled with little surface temperature deviation among positions in the width direction as illustrated in FIG. 6 . Consequently, the steel plate 1 excellent in steel plate shape and mechanical property can be manufactured.
  • strip temperature deviation in the width direction of a steel plate passed through the cooling equipment without being subjected to surface treatment by the descaler is approximately 40° C.
  • strip temperature deviation in the width direction of a steel plate subjected to the above-described descaling according to exemplary embodiments of the present invention and then cooled by general cooling equipment is reduced to approximately 10° C.
  • strip temperature deviation in the width direction of the steel plate 1 passed through the descaler 4 , subjected to descaling according to exemplary embodiments of the present invention, and then subjected to uniform cooling in the width direction by the cooling equipment 6 , illustrated in FIG. 2 in the present embodiment is reduced to approximately 4° C.
  • ⁇ 2 a ⁇ exp( ⁇ Q/RT ) ⁇ t (5)
  • ⁇ scale thickness
  • a constant number
  • Q activation energy
  • R constant number
  • t period of time
  • the scale growth was simulated at various temperatures for various periods of time in consideration of scale growth after scale removal by the descaler 4 , thereby obtaining the constant numbers in the above-described expression. Furthermore, after diligent study of scale thickness and cooling stability, it was found that cooling is stable at a scale thickness of 15 ⁇ m or less, cooling is more stable at a scale thickness of 10 ⁇ m or less, and cooling is very stable at a scale thickness of 5 ⁇ m or less.
  • T temperature [K] of the steel plate before cooling.
  • the distance L between the descaler 4 and the cooling equipment 6 is set so as to satisfy the following expression (9) with respect to conveying velocity V of the steel plate 1 and the period of time t (the period of time between the completion of processing by the descaler 4 and the start of processing by the cooling equipment 6 ).
  • the above-described expression (9) should satisfy the following expression (12) on the basis of the above-described expression (8).
  • cooling is stable when the distance L between the descaler 4 and the cooling equipment 6 is in the range of 12 to 107 m or less, cooling is more stable when the distance L is in the range of 5 to 47 m or less, and cooling is very stable when the distance L is in the range of 1.3 to 12 m or less on the basis of the above-described expressions (10) to (12).
  • the distance L as a condition required for very stable cooling at this conveying velocity V should be less than or equal to 2.5 m.
  • the pressure P [MPa] at the point of impact of spray from the spraying nozzles of the descaler 4 to each surface of the steel plate 1 is set to 1.5 or higher to make scale produced on the steel plate 1 uniform, and uniform cooling is achieved by the cooling equipment 6 , so that the steel plate 1 excellent in shape and mechanical property can be manufactured.
  • the spraying nozzles of the descaler 4 can be moved closer to each surface of the steel plate 1 .
  • the spraying distance H the distance between each spraying nozzle of the descaler 4 and the surface of the steel plate 1
  • the descaling performance is improved.
  • the spraying pressure Ps, the spray flow rate Q, and the like for achieving a predetermined pressure P at the point of impact can be set to low, thus reducing the pumping performance of the descaler 4 .
  • the cooling equipment 6 in the present embodiment is configured such that, as illustrated in FIG. 4 , cooling water supplied from the upper cooling water spraying nozzles 11 through the water supply inlets 19 cools the upper surface of the steel plate 1 to turn to high-temperature drainage water and the drainage water flows through the holes 18 , which do not receive the upper cooling water spraying nozzles 11 , as drain flow paths onto the dividing plate 12 in the width direction of the steel plate 1 so that the drainage water after cooling is immediately removed from the steel plate 1 . Cooling water flowing from the upper cooling water spraying nozzles 11 through the water supply inlets 19 sequentially comes into contact with the steel plate 1 , thereby providing adequate cooling performance that is uniform in the width direction.
  • strain caused during rolling is leveled by the first hot leveler 5 and surface treatment is performed on the steel plate 1 by the descaler 4 to stabilize the controllability of cooling.
  • the steel plate 1 to be processed by the second hot leveler 7 originally has high flatness and the temperature of the steel plate 1 is uniform.
  • the second hot leveler 7 therefore does not need so high leveling reaction force.
  • the distance between the cooling equipment 6 and the second hot leveler 7 may be longer than a maximum length of the steel plate 1 to be manufactured on lines.
  • the second hot leveler 7 often performs reverse leveling or the like, the effect of preventing a trouble caused when the reversed steel plate 1 bounces on a conveying roll and hits against the cooling equipment 7 and the effect of making slight temperature deviation, caused during cooling, uniform to prevent the occurrence of a warp caused by temperature deviation after leveling can be expected.
  • the steel plate 1 , rolled by the hot rolling mill 3 , having a thickness of 30 mm and a width of 3500 mm was passed through the first hot leveler 5 and the descaler 4 and was then controlled such that the steel plate was cooled from 820° C. to 420° C.
  • the period of time t between the completion of removal of scale on the steel plate 1 by the descaler 4 and the start of cooling of the steel plate 1 by the cooling equipment 6 is less than or equal to 42 s, preferably, less than or equal to 19 s, and more preferably, less than or equal to 5 s.
  • the spraying pressure of nozzles was 17.7 MPa
  • the spray flow rate per nozzle was 64 L/min/nozzle
  • the spraying distance (the distance between each spraying nozzle of the descaler 4 and each surface of the steel plate 1 ) was 130 mm
  • the spray angle of nozzle was 32°
  • the angle between the spray direction and the vertical line was 15°
  • the nozzles were aligned in the width direction such that the spraying areas of the neighboring nozzles overlap to some extent
  • the pressure at the point of impact in each position in the width direction was 1.5 MPa.
  • the cooling facility 6 was a facility provided with flow paths configured such that cooling water supplied to the upper surface of the steel plate flowed over the dividing plate as illustrated in FIG. 2 and the water was drained on one side in the width direction of the steel plate as illustrated in FIG. 4 .
  • the dividing plate was provided with 12 mm diameter holes arranged in a grid pattern such that the water supply inlets arranged in a staggered layout received the upper cooling water spraying nozzles and the other holes were used as drain outlets.
  • the distance between the lower surface of the upper header and the upper surface of the dividing plate was 100 mm.
  • the upper cooling water spraying nozzles each had an inner diameter of 5 mm, an outer diameter of 9 mm, and a length of 170 mm. The tips of the nozzles projected into the header. The spraying velocity of rod-like cooling water was 8.9 m/s. Ten rows of nozzles were arranged in a zone, serving as a 1-m distance between table rollers, with a 50-mm nozzle pitch in the width direction of the steel plate. The water flow rate on the upper surface was 2.1 m 3 /m 2 ⁇ min. The lower end of each nozzle for upper surface cooling was placed in the middle between the upper and lower surfaces of the dividing plate having a thickness of 25 mm such that the distance between the lower end of the nozzle and the surface of the steel plate was 80 mm.
  • the same cooling facility as the upper surface cooling facility was used, except that the facility included no dividing plate.
  • the spraying velocity and water flow rate of rod-like cooling water were 1.5 times as high as those for the upper surface.
  • the distance L between the descaler 4 and the cooling equipment 6 , the steel plate conveying velocity V, and the period of time between the descaler 4 and the cooling equipment 6 were variously changed.
  • descaling is a process of removing scale on the steel plate 1 by the descaler 4
  • controlled cooling is a process of cooling the steel plate 1 by the cooling equipment 6 .
  • the period of time t between the completion of removal of scale on the steel plate 1 by the descaler 4 and the start of cooling of the steel plate 1 by the cooling equipment 6 was less than or equal to 19 S that was the condition for more stable cooling by the cooling equipment 6 based on the above-described expression (6), irrespective of the steel plate conveying velocity V.
  • the releveling rate was less than or equal to 5%, namely, it was good.
  • Example 5 in which the distance between the descaler 4 and the cooling equipment 6 was 2.5 m, the spraying pressure of nozzles was 17.7 MPa, the spray flow rate per nozzle was 64 L/min/nozzle, the spraying distance (the distance between each spraying nozzle of the descaler 4 and each surface of the steel plate 1 ) was 90 mm, the spray angle of nozzle was 40°, the angle between the spray direction and the vertical line was 15°, and the pressure at the point of impact was thereby 2.4 MPa, the releveling rate was 1%, namely, it was very good.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Metal Rolling (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)
US13/256,288 2009-03-25 2010-03-23 Steel plate manufacturing facility and manufacturing method Abandoned US20120017660A1 (en)

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JP2009-073994 2009-03-25
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JP2010006722A JP5614040B2 (ja) 2009-03-25 2010-01-15 厚鋼板の製造設備及び製造方法
JP2010-006722 2010-01-15
PCT/JP2010/055497 WO2010110473A1 (ja) 2009-03-25 2010-03-23 厚鋼板の製造設備及び製造方法

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CN103212594A (zh) * 2013-04-08 2013-07-24 张家港联峰钢铁研究所有限公司 自动脱落氧化铁皮盒出口装置
US20130305799A1 (en) * 2011-05-16 2013-11-21 Ns Plant Designing Corporation Rolling mill roll-cleaning device and cleaning method
CN105102142A (zh) * 2013-03-27 2015-11-25 杰富意钢铁株式会社 厚钢板的制造设备及制造方法
TWI569898B (zh) * 2013-03-27 2017-02-11 Jfe Steel Corp Manufacture method and manufacturing equipment of thick steel plate
CN106604785A (zh) * 2014-08-26 2017-04-26 杰富意钢铁株式会社 厚钢板的制造方法
CN106794500A (zh) * 2014-08-26 2017-05-31 杰富意钢铁株式会社 厚钢板的制造设备及制造方法
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CN114345959A (zh) * 2022-02-24 2022-04-15 山东绿钢环保科技股份有限公司 一种可获取优良表面形貌的无酸除鳞系统及除鳞方法

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EP2412455B1 (en) 2009-03-25 2018-03-14 JFE Steel Corporation Method of manufacturing a steel plate
US20130305799A1 (en) * 2011-05-16 2013-11-21 Ns Plant Designing Corporation Rolling mill roll-cleaning device and cleaning method
US9433986B2 (en) * 2011-05-16 2016-09-06 Nippon Steel & Sumikin Engineering Co., Ltd. Rolling mill roll-cleaning device and cleaning method
CN105102142A (zh) * 2013-03-27 2015-11-25 杰富意钢铁株式会社 厚钢板的制造设备及制造方法
TWI565541B (zh) * 2013-03-27 2017-01-11 Jfe Steel Corp Manufacturing equipment and manufacturing method of thick steel plate
TWI569898B (zh) * 2013-03-27 2017-02-11 Jfe Steel Corp Manufacture method and manufacturing equipment of thick steel plate
CN103212594A (zh) * 2013-04-08 2013-07-24 张家港联峰钢铁研究所有限公司 自动脱落氧化铁皮盒出口装置
CN106604785A (zh) * 2014-08-26 2017-04-26 杰富意钢铁株式会社 厚钢板的制造方法
CN106794500A (zh) * 2014-08-26 2017-05-31 杰富意钢铁株式会社 厚钢板的制造设备及制造方法
CN106604785B (zh) * 2014-08-26 2019-01-11 杰富意钢铁株式会社 厚钢板的制造方法
CN109317524A (zh) * 2017-07-31 2019-02-12 上海东新冶金技术工程有限公司 热镀锌用光整机高压喷淋装置及其使用方法
CN114345959A (zh) * 2022-02-24 2022-04-15 山东绿钢环保科技股份有限公司 一种可获取优良表面形貌的无酸除鳞系统及除鳞方法

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CN102361704A (zh) 2012-02-22
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EP2412455A4 (en) 2013-05-29
KR101563206B1 (ko) 2015-10-26
KR20110115163A (ko) 2011-10-20
KR20140004265A (ko) 2014-01-10
JP5614040B2 (ja) 2014-10-29
EP2412455A1 (en) 2012-02-01
EP2412455B1 (en) 2018-03-14

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