EP3187275B1 - Procédé de fabrication de plaque d'acier épaisse - Google Patents

Procédé de fabrication de plaque d'acier épaisse Download PDF

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Publication number
EP3187275B1
EP3187275B1 EP15836450.5A EP15836450A EP3187275B1 EP 3187275 B1 EP3187275 B1 EP 3187275B1 EP 15836450 A EP15836450 A EP 15836450A EP 3187275 B1 EP3187275 B1 EP 3187275B1
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EP
European Patent Office
Prior art keywords
descaling
steel plate
cooling
water
jetting
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EP15836450.5A
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German (de)
English (en)
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EP3187275A4 (fr
EP3187275A1 (fr
Inventor
Yuta TAMURA
Kenji Adachi
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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
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
    • 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
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/38—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling sheets of limited length, e.g. folded sheets, superimposed sheets, pack rolling
    • 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
    • B21B45/06—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 of strip material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2261/00—Product parameters
    • B21B2261/20—Temperature

Definitions

  • the present invention relates to a method for manufacturing a steel plate.
  • a steel plate In the process of manufacturing a steel plate by hot rolling, controlled cooling has been increasingly applied.
  • a steel plate (not shown) in a heating furnace 1, the steel plate is descaled at a descaling apparatus 2. Then, after rolling the steel plate by a rolling apparatus 3, the steel plate is subjected to correction by a shape correcting apparatus 4. Thereafter, an accelerated cooling apparatus 5 performs controlled cooling by water cooling or air cooling.
  • the direction of an arrow indicates a conveyance direction of a steel plate.
  • cooling stop temperature the surface temperature of the steel plate when accelerated cooling is stopped in a steel plate width direction (hereunder, referred to as "cooling stop temperature") is known to have a distribution that varies, for example, as shown in Fig. 3 . Accordingly, since there are variations in the cooling stop temperature of the steel plate, uniform material quality cannot be obtained.
  • the cooling stop temperature when the steel plate having a plate thickness of 25 mm is cooled from 800°C to a target temperature of 500°C is 460°C at the portion where the scale thickness is 40 ⁇ m, and is 500°C at the portion where the scale thickness is 20 ⁇ m.
  • the cooling stop temperature of the portion where the scale thickness is 40 ⁇ m is lower than the target temperature by 40°C. As a result, uniform material quality cannot be obtained.
  • Patent Literature 1 discloses a method of realizing a uniform cooling stop temperature by making the cooling speed uniform by controlling the scale thickness.
  • the jetting water amount for descaling at a tail end side of a steel plate is controlled to be greater than the jetting water amount for descaling at a leading end side of the steel plate when the cooling stop temperature of the tail end of the steel plate becomes lower than the cooling stop temperature of the leading end of the steel plate.
  • residual thickness and scale removal percentage in a longitudinal direction of a steel plate the heat transfer coefficient of surfaces of the steel plate during controlled cooling is changed to make uniform the cooling stop temperature in the longitudinal direction of the steel plate.
  • JP 2012 152761 A shows a method for manufacturing a steel plate by performing a hot rolling step, a hot correction step, and an accelerated cooling step in this order, the method further comprising: a descaling step in which jetting of descaling water is performed two times between the hot correction step and the accelerated cooling step.
  • the cooling stop temperature is made uniform by adjusting the cooling water amount and the conveyance velocity.
  • the cooling speed is non-uniform when there are variations in the scale thickness. Therefore, it is difficult not only to make the cooling speed uniform, but also to make the cooling stop temperature uniform.
  • An object of the present invention to solve the above-described problems and to provide a method for manufacturing a steel plate, which can ensure a high-quality steel plate having less variation in quality.
  • the present invention is made in order to solve the above-described existing problems.
  • the gist of the present invention is as follows:
  • the present invention it is possible to make the cooling speed and the cooling stop temperature uniform. As a result, it is possible to manufacture a high-quality steel plate having less variation in quality.
  • Fig. 4 is a schematic view of a facility for manufacturing a steel plate according to an embodiment of the present invention.
  • the direction of an arrow corresponds to a conveyance direction of a steel plate.
  • a heating furnace 1 From an upstream side in the t conveyance direction of the steel plate, a heating furnace 1, a descaling apparatus 2, a rolling apparatus 3, a shape correcting apparatus 4, a descaling apparatus 6, a descaling apparatus 7, and an accelerated cooling apparatus 5 are set in this order.
  • the steel plate is descaled for primary scale removal in the descaling apparatus 2.
  • the descaling apparatus 6 and the descaling apparatus 7 perform descaling for completely removing scale. Thereafter, the accelerated cooling apparatus 5 performs controlled cooling by water cooling or air cooling.
  • two descaling apparatuses that is, the descaling apparatus 6 and the descaling apparatus 7 are set between the shape correcting apparatus 4 and the accelerated cooling apparatus 5.
  • the descaling apparatus shown in Fig. 4 is configured in only two rows. Descaling apparatus may be configured in three or more rows.
  • energy density of descaling water that is jetted to surfaces of the steel plate from the descaling apparatus 6 and the descaling apparatus 7 is greater than or equal to 0.07 J/mm 2 in total for the two rows of jetting nozzles, and the descaling water is jetted from the descaling apparatus 7 after 0.5 s or more after jetting the descaling water from the descaling apparatus 6, and the surface temperature of the steel plate just before the descaling water is jetted from the descaling apparatus 7 is made lower than or equal to a Ar 3 transformation point.
  • energy density is greater than or equal to 0.07 J/mm 2 in total for all rows of jetting nozzles of the descaling apparatus, and final-descaling water is jetted after 0.5 s or more after jetting just-before-final-descaling water from the descaling apparatus, and the surface temperature of the steel plate just before the final-descaling water is jetted is made lower than or equal to the Ar 3 transformation point. This allows the scale to be completely removed, so that uniform cooling can be realized.
  • a descaling header 6-1 of the descaling apparatus 6 and a descaling header 7-1 of the descaling apparatus 7 are set in two rows in a longitudinal direction of the steel plate.
  • Descaling water is jetted from a plurality of jetting nozzles 6-2 and 7-2 of the descaling headers to a steel plate 1, to form a spray pattern 22 as shown in Fig. 6(b) .
  • the jetting nozzles 6-2 and the jetting nozzles 7-2 be separated from each other by 500 mm or more in the longitudinal direction of the thick steel plate, that is, the conveyance direction of the steel plate. It is desirable that jetting patterns in the width direction be in a staggered arrangement in which the jetting nozzles 6-2 and the jetting nozzles 7-2 are shifted from each other in the width direction.
  • the descaling apparatus shown in Fig. 5(a) is configured in two rows. The same effects are obtained even if the number of rows is three or more.
  • the nozzle rows be separated by 500 mm or more in the longitudinal direction and be in a staggered arrangement.
  • the upper limit be three rows.
  • the energy density of the descaling water that is jetted to the surfaces of the steel plate is greater than or equal to 0.07 J/mm 2 in total for the two jettings, and the descaling water is jetted to the surfaces of the steel plate from the descaling apparatus 7 after 0.5 s or more after jetting the descaling water from the descaling apparatus 6 to the surfaces of the steel plate, and the surface temperature of the steel plate just before starting the jetting of the descaling water from the descaling apparatus is made lower than or equal to the Ar 3 transformation point, the scale can be more efficiently removed.
  • the energy density in total for the two descalings can be calculated by totaling up the energy density of each descaling calculated by an expression described later.
  • the inventors carried out studies and found out that, when the energy density of the descaling water that is jetted to the surfaces of the steel plate is greater than or equal to 0.07 J/mm 2 in total for two or more jettings, and when the surface temperature of the steel plate just before the final-descaling water is jetted is made lower than or equal to the Ar 3 transformation point, it is possible to transform the surfaces of the, and, due to the transformation of base iron, cause an interface between the scale and the base iron to be shifted and reduce scale adhesion. Therefore, the scale is easily removed by the descaling, and the scale can be peeled off by the descaling water having a smaller energy density.
  • the inventors also carried out studies on the energy density at the time of the first descaling by the descaling apparatus 6 and the energy density at the time of the second descaling by the descaling apparatus 7.
  • the first descaling causes the base iron surface layer to undergo ferrite transformation before jetting the second-descaling water
  • the scale peeling effect by the second descaling is increased. Therefore, by applying the required energy for transforming the base iron surface layer in the first descaling and performing the second descaling with a large energy density, the scale can be effectively peeled off. More specifically, it is desirable that the energy density at the time of the first descaling be greater than or equal to 0.02 J/mm 2 .
  • the energy density of the descaling water has no upper limit as descaling capability.
  • the energy density is greater than 0.7 J/mm 2 in total for the two descalings, for example, the pump discharge pressure becomes extraordinarily high. Therefore, it is desirable that the energy density be less than or equal to 0.7 J/mm 2 .
  • the energy density for the just-before-final descaling be greater than or equal to 0.02 J/mm 2
  • the total energy density of the descaling water for all the number of the descalings be less than or equal to 0.7 J/mm 2 .
  • the inventors carried out further studies and found out that, as a simple definition of energy density E (J/mm 2 ) of descaling water that is jetted to the steel plate, the expression “water amount density x jetting pressure x collision time” may be used.
  • the water amount density (m 3 /(mm 2 ⁇ min)) is a value that is calculated by using "jetting flow rate of descaling water ⁇ collision area of descaling water”.
  • the collision time (s) is a value that is calculated by using "collision thickness of descaling water ⁇ conveyance velocity of steel plate".
  • the relationship between the energy density of high-pressure water, which is calculated based on this simple definition, and the scale peeling percentage is also as shown in Fig. 6 .
  • the following Expression (3) can be derived based on Expression (2) above. That is, when the time t [s] from after the completion of the removal of the scale on the steel plate by the descaling apparatuses 6 and 7 to the start of the cooling of the steel plate by the accelerated cooling apparatus 5 satisfies the following Expression (3), the cooling by the accelerated cooling apparatus 5 becomes stable: t ⁇ 5 ⁇ 10 ⁇ 9 ⁇ exp 25000 / T where T: temperature [K] of steel plate before cooling.
  • the following Expression (5) can be derived based on Expression (2) above. That is, when the time t [s] from after the completion of the removal of the scale on the steel plate by the descaling apparatuses 6 and 7 to the start of the cooling of the steel plate by the accelerated cooling apparatus 5 satisfies the following Expression (5), the cooling by the accelerated cooling apparatus 5 becomes very stable: t ⁇ 5.6 ⁇ 10 ⁇ 9 ⁇ exp 25000 / T
  • the upper surface cooling facility of the accelerated cooling apparatus 5 includes an upper header 11 that supplies cooling water to an upper surface of a steel plate 10, cooling water injection nozzles 13 that are suspended from the upper header 11 and that are used for jetting rod-shaped cooling water, and a partition wall 15 that is set between the steel plate 10 and the upper header 11. It is desirable that the partition wall 15 have a plurality of water supply ports 16 in which lower end portions of the cooling water injection nozzles 13 are inserted, and a plurality of water drainage ports 17 for draining away the cooling water, supplied to the upper surface of the steel plate 10, to an upper side of the partition wall 15.
  • the upper surface cooling facility includes the upper header 11 that supplies cooling water to the upper surface of the steel plate 10, the cooling water injection nozzles 13 that are suspended from the upper header 11, and the partition wall 15 that is set horizontally along the width direction of the steel plate and between the upper header 11 and the steel plate 10, and that has a plurality of through holes (the water supply ports 16 and the water drainage ports 17).
  • the cooling water injection nozzles 13 are circular tube nozzles for jetting rod-shaped cooling water. Ends of the cooling water injection nozzles 13 are inserted into the through holes (the water supply ports 16) in the partition wall 15, and are situated above a lower end portion of the partition wall 15.
  • cooling water injection nozzles 13 In order to prevent the cooling water injection nozzles 13 from being clogged by sucking in foreign matter at a bottom portion in the upper header 11, it is desirable that the cooling water injection nozzles 13 penetrate the upper header 11 such that upper ends of the cooling water injection nozzles 13 protrude into the upper header 11.
  • the term "rod-shaped cooling water” refers to cooling water which is jetted in a state in which the cooling water is compressed to a certain extent from circular nozzle jetting ports (including elliptical and polygonal nozzle jetting ports), and which is a continuous and straight stream, the jetting velocity of the cooling water from the nozzle jetting ports being 6 m/s or higher and, desirably, 8 m/s or higher, and, the cross section of the stream jetted from the nozzle jetting ports being maintained in a substantially circular shape. That is, the cooling water differs from that which flows so as to fall freely from round tube laminar nozzles, and that which is jetted in liquid drops like a spray.
  • the ends of the cooling water injection nozzles 13 are inserted into the through holes so as to be set above the lower end portion of the partition wall 15, so that, even if a steel plate whose end is warped upward moves in, the cooling water jetting nozzles 13 are prevented from becoming damaged by the injection wall 15. This makes it possible to perform cooling for a long time with the cooling water injection nozzles 13 in a good state. Therefore, it is possible to prevent the occurrence of temperature unevenness in the steel plate without, for example, repairing the facility.
  • the ends of the circular tube nozzles 13 are inserted in the through holes, as shown in Fig. 16 , the ends of the circular tube nozzles 13 do not interfere with the flow in the width direction of drainage water that flows along an upper surface of the partition wall 15 and that is indicated by a dotted arrow. Therefore, the cooling water jetted from the cooling water injection nozzles 13 can evenly reach the upper surface of the steel plate regardless of locations in the width direction, so that uniform cooling can be performed in the width direction.
  • the partition wall 15 has a plurality of through holes, each having a diameter of 10 mm, in a grid pattern and at a pitch of 80 mm in the width direction of the steel plate and at a pitch of 80 mm in the conveyance direction.
  • the cooling water injection nozzles 13, each having an outside diameter of 8 mm, an inside diameter of 3 mm, and a length of 140 mm, are inserted in the water supply ports 16.
  • the cooling water injection nozzles 13 are arranged in a staggered manner.
  • the through holes in which the cooling water injection nozzles 13 are not inserted correspond to the water drainage ports 17 for the cooling water.
  • the plurality of through holes in the partition wall 15 of the accelerated cooling apparatus include the water supply ports 16 and the water drainage ports 17 that are substantially the same in number, with their roles and functions being divided among the water supply ports 16 and the water drainage ports 17.
  • the total sectional area of the water drainage ports 17 is sufficiently larger than the total sectional area of the inside of the circular tube nozzles 13, which are the cooling water injection nozzles 13, and is approximately 11 times the total sectional area of the inside of the circular tube nozzles 13.
  • the cooling water supplied to the upper surface of the steel plate fills a space between a surface of the steel plate and the partition wall 15, flows through the water drainage ports 17, is guided to a location above the partition wall 15, and is quickly discharged.
  • Fig. 12 is a front view illustrating flow of drain cooling water near an end portion at the upper side of the partition wall in the width direction of the steel plate.
  • a draining direction of the water drainage ports 17 is upward in a direction that is opposite to a cooling water injection direction.
  • the drain cooling water that has flown out to a location above the partition wall 15 changes direction towards an outer side in the width direction of the steel plate, flows to a water drain flow path between the upper header 11 and the partition wall 15, and is drained off.
  • the water drainage ports 17 are inclined in the width direction of the steel plate to cause the draining direction to be in an oblique direction towards the outer side in the width direction of the steel plate. This allows drainage water 19 at the upper side of the partition wall 15 to flow smoothly in the width direction of the steel plate, and the water drainage is accelerated. Therefore, this is desirable.
  • the accelerated cooling apparatus 5 includes the water supply ports 16 and the water drainage ports 17 that are separately provided. Since the roles of supplying water and draining off water are divided among the water supply ports 16 and the water drainage ports 17, the drain cooling water flows through the water drainage ports 17 in the partition wall 15 and smoothly flows to a location above the partition wall 15. Therefore, the drain water after the cooling is quickly drained off from the upper surface of the steel plate, so that cooling water that is subsequently supplied can easily penetrate the stagnant water film, and, thus, a sufficient cooling capacity can be provided.
  • the temperature distribution of the steel plate in the width direction thereof in this case is a uniform temperature distribution, so that a uniform temperature distribution can be provided in the width direction.
  • the cooling water is quickly discharged.
  • This can be realized, for example, when ports having a size that is greater than the outside diameter of the circular tube nozzles 13 are formed in the partition wall 15, and the number of water drainage ports is greater than or equal to the number of water supply ports.
  • the total sectional area of the water drainage ports 17 is less than 1.5 times the total sectional area of the inside of the circular tube nozzles 13, the flow resistance at the water drainage ports is increased and, thus, it becomes difficult to drain off stagnant water. As a result, the amount of cooling water that can penetrate the stagnant water film and reach the surface of the steel plate is considerably reduced, thereby reducing the cooling capacity. Therefore, this is not desirable. It is more desirable that the total sectional area of the water drainage ports 17 be greater than or equal to 4 times the total sectional area of the inside of the circular tube nozzles 13.
  • the ratio between the total sectional area of the water drainage ports and the total sectional area of the inside of the circular tube nozzles 13 be in the range of 1.5 to 20.
  • gaps between outer peripheral surfaces of the circular tube nozzles 13, which are inserted in the water supply ports 16 in the partition wall 15, and inner surfaces defining the water supply ports 16 be less than or equal to 3 mm in size.
  • the gaps are large, due to the effects of accompanied flow of the cooling water that is jetted from the circular tube nozzles 13, the drain cooling water discharged to the upper surface of the partition wall 15 is sucked into the gaps between the water supply ports 16 and the outer peripheral surfaces of the circular tube nozzles 13, and is re-supplied to the steel plate. Therefore, the cooling efficiency is reduced.
  • the outside diameter of the circular tube nozzles 13 be substantially the same as the size of the water supply ports 16.
  • gaps of up to 3 mm, at which the effects are substantially small are allowed. It is more desirable that the gaps be less than or equal to 2 mm in size.
  • the inside diameter and length of the circular tube nozzles 13, the jetting velocity of the cooling water, and nozzle distance also need to be optimal values.
  • the nozzle inside diameter be 3 to 8 mm.
  • the nozzle inside diameter is less than 3 mm, a flux of water that is jetted from the nozzles becomes thinner, and, thus, water strength is reduced.
  • the nozzle diameter exceeds 8 mm, the flow rate is reduced, as a result of which the force for causing the cooling water to penetrate the stagnant water film is reduced.
  • each circular tube nozzle 13 be 120 to 240 mm.
  • the length of each circular tube nozzle 13 refers to the length from an inlet at the upper end of each nozzle that penetrates the header by a certain amount to a lower end of each nozzle inserted in the corresponding water supply port in the partition wall.
  • each circular tube nozzle 13 is shorter than 120 mm, the distance between a lower surface of the header and the upper surface of the partition wall becomes too small (for example, when the header thickness is 20 mm, a protruding amount of the upper end of each nozzle into the header is 20 mm, and an insertion amount of the lower end of each nozzle into the partition wall is 10 mm, the distance becomes less than 70 mm).
  • the jetting velocity of the cooling water from the nozzles needs to be greater than or equal to 6 m/s, and, desirably, greater than or equal to 8 m/s. This is because, when the jetting velocity is less than 6 m/s, the force for causing the cooling water to penetrate the stagnant water film becomes extremely weak. When the jetting velocity is greater than or equal to 8 m/s, a higher cooling capacity can be provided. Therefore, this is desirable.
  • the distance from the lower end of each cooling water injection nozzle 13, used for cooling the upper surface of the steel plate, to the surface of the steel plate 10 may be 30 to 120 mm. When this distance is less than 30 mm, the frequency with which the steel plate 10 collides with the partition wall 15 is extremely high. Therefore, it becomes difficult to maintain the facility. When this distance exceeds 120 mm, the force for causing the cooling water to penetrate the stagnant water film becomes extremely weak.
  • draining rollers 20 may be set in front of and behind the upper header 11 so as to prevent the cooling water from spreading in the longitudinal direction of the steel plate. This causes a cooling zone length to be constant, and facilitates temperature control.
  • the draining rollers 20 intercept the flow of the cooling water in the conveyance direction of the steel plate, the drain cooling water flows to the outer side in the width direction of the steel plate. However, the cooling water tends to stagnate near the draining rollers 20.
  • the cooling water injection nozzles in an uppermost-stream-side row in the conveyance direction of the steel plate be tilted towards an upstream side in the conveyance direction of the steel plate by 15 to 60 degrees, and the cooling water injection nozzles in a lowermost-stream-side row in the conveyance direction of the steel plate be tilted towards a downstream side in the conveyance direction of the steel plate by 15 to 60 degrees.
  • the distance between the lower surface of the upper header 11 and the upper surface of the partition wall 15 be such that the sectional area of a flow path in the width direction of the steel plate in a space surrounded by the lower surface of the header and the upper surface of the partition wall be greater than or equal to 1.5 times the total sectional area of the inside of the cooling water injection nozzles.
  • This distance is, for example, desirably greater than or equal to approximately 100 mm.
  • the drain cooling water discharged to the upper surface of the partition wall 15 from the water drainage ports 17 in the partition wall may not be smoothly discharged in the width direction of the steel plate.
  • the range of the water amount density that is most effective is greater than or equal to 1.5 m 3 /(m 2 ⁇ min).
  • the water amount density is lower than this value, the stagnant water film does not become so thick, and, even if a publicly known technology of cooling the steel plate by causing the rod-shaped cooling water to fall freely is applied, there are cases in which the degree of temperature unevenness in the width direction does not become so large.
  • the water amount density is greater than 4.0 m 3 /(m 2 ⁇ min)
  • the use of the technology according to the present invention is effective.
  • the range of 1.5 to4.0 m 3 /(m 2 ⁇ min) is the most practical water amount density.
  • the cooling technology according to the present invention In applying the cooling technology according to the present invention, the case of disposing the draining rollers in front of and behind the cooling header is particularly effective.
  • the cooling technology according to the present invention is applicable to the case in which the draining rollers are not provided.
  • a cooling apparatus at a side of a lower surface of the steel plate is not particularly limited.
  • a cooling lower header 12 provided with circular tube nozzles 14 as in the cooling apparatus at the side of the upper surface of the steel plate is given.
  • a partition wall 15 for discharging drain cooling water in the width direction of the steel plate like the one used in cooling the upper surface of the steel plate, need not be used.
  • a publicly known technology of supplying, for example, membranous cooling water or cooling water in the form of a spray may be used.
  • the heating furnace 1 and the descaling apparatus 2 according to the present invention are not particularly limited, and conventional machines may be used for the heating furnace 1 and the descaling apparatus 2.
  • the descaling apparatus 2 need not have the same structure as the descaling apparatuses 6 and 7 according to the present invention.
  • the temperatures of the steel plates are surface temperatures of the steel plates.
  • Each steel plate according to the present invention was manufactured by using a facility for manufacturing a steel plate such as that shown in Fig. 4 .
  • the slab was subjected to primary scale removal in the descaling apparatus 2, was subjected to hot rolling at the rolling apparatus 3, and was subjected to shape correction in the shape correcting apparatus 4.
  • descaling was performed.
  • two descaling apparatuses that is, the descaling apparatus 6 and the descaling apparatus 7, were set; and the descaling was performed two times on surfaces of the steel plates.
  • descaling apparatus When the descaling was to be performed three or more times, descaling apparatus was configured in three or more rows, and nozzle rows were separated by 500 mm or more in the longitudinal direction and arranged in a staggered arrangement. After completing the descaling, controlled cooling of each steel plate was performed by using the accelerated cooling apparatus 5.
  • the descaling apparatus 6 and the descaling apparatus 7 were such that the jetting distance (the distance from the jetting nozzles of the descaling apparatus to the surfaces of the steel plates) was 130 mm, the nozzle jetting angle was 66 degrees, and the attack angle was 15 degrees. After the descaling by the descaling apparatus 7, each steel plate was cooled to 500°C by the accelerated cooling apparatus 5.
  • the nozzles of the descaling apparatus 6 and the nozzles of the descaling apparatus 7 were such that jetting areas of adjacent nozzles were arranged side by side in the width direction so as to overlap each other to a certain extent.
  • the distance between the descaling apparatus 6 and the descaling 7 was such that the descaling apparatus 6 and the descaling 7 were separated 1.1 m from each other in the longitudinal direction.
  • the nozzles were flat spray nozzles.
  • the jetting flow rate per nozzle and the nozzle jetting pressure at the time of the descaling after the hot rolling were the same for the descaling apparatus 6 and the descaling apparatus 7, and the conditions shown in Table 1 were used.
  • the Ar 3 transformation point of each steel sheet used was 780°C. After finishing the rolling at the rolling apparatus 3, the plate thickness was 30 mm, and the temperature of each steel plate was 830°C or 840°C.
  • T in Table 1 denotes the temperature (K) of each steel plate before cooling.
  • the energy density was 0.07 J/mm 2 .
  • the surface temperature of the steel plate at the time of the second descaling was 785°C. Since the second descaling was performed in a state in which austenite was not transformed into ferrite at the surfaces of the steel plate, the scale remained on part of the steel plate, and temperature unevenness was 40°C.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Metal Rolling (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)

Claims (3)

  1. Procédé de fabrication d'une plaque d'acier en effectuant une étape de laminage à chaud, une étape de correction à chaud, et une étape de refroidissement accéléré dans cet ordre, le procédé comprenant en outre :
    une étape de décalaminage dans laquelle la projection d'eau de décalaminage est effectuée deux ou plus de deux fois entre l'étape de correction à chaud et l'étape de refroidissement accéléré,
    dans lequel, lors l'étape de décalaminage, une densité d'énergie de l'eau de décalaminage qui est projetée sur une surface de la plaque d'acier est supérieure ou égale à 0,07 J/mm2 au total pour la projection effectuée deux ou plus de deux fois, une eau de décalaminage final est projetée au moins 0,5 seconde ou plus après la projection d'eau juste avant le décalaminage final, et une température de surface de la plaque d'acier juste avant la projection d'eau de décalaminage final est inférieure ou égale à un point de transformation Ar3.
  2. Procédé de fabrication d'une plaque d'acier selon la revendication 1,
    dans lequel la projection d'eau de décalaminage est effectuée deux fois entre l'étape de correction à chaud et l'étape de refroidissement accéléré.
  3. Procédé de fabrication d'une tôle d'acier selon la revendication 1 ou la revendication 2,
    dans lequel un temps t[s] allant de l'achèvement de l'étape de décalaminage jusqu'au début de l'étape de refroidissement accéléré satisfait à l'expression t ≤ 5 x 10-9 x exp(25000/T),
    où une température de la plaque d'acier avant refroidissement est T[K].
EP15836450.5A 2014-08-26 2015-08-14 Procédé de fabrication de plaque d'acier épaisse Active EP3187275B1 (fr)

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JP2014171046 2014-08-26
PCT/JP2015/004056 WO2016031169A1 (fr) 2014-08-26 2015-08-14 Procédé de fabrication de plaque d'acier épaisse

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JPH06330155A (ja) 1993-05-26 1994-11-29 Kawasaki Steel Corp 厚鋼板の冷却方法
JP3796133B2 (ja) * 2000-04-18 2006-07-12 新日本製鐵株式会社 厚鋼板冷却方法およびその装置
JP2003181522A (ja) * 2001-12-14 2003-07-02 Nippon Steel Corp 表面性状の優れた鋼板の製造方法及びその装置
CN101215624B (zh) * 2008-01-08 2011-07-06 济南钢铁股份有限公司 一种高强韧厚钢板的在线淬火生产工艺方法
JP5614040B2 (ja) * 2009-03-25 2014-10-29 Ｊｆｅスチール株式会社 厚鋼板の製造設備及び製造方法
JP4874437B2 (ja) * 2010-03-15 2012-02-15 新日本製鐵株式会社 厚鋼板の製造装置
JP5640614B2 (ja) * 2010-09-30 2014-12-17 Ｊｆｅスチール株式会社 ラインパイプ用高強度鋼板及びその製造方法並びにラインパイプ用高強度鋼板を用いた高強度鋼管
JP5764936B2 (ja) * 2011-01-24 2015-08-19 Ｊｆｅスチール株式会社 厚鋼板のデスケーリング設備およびデスケーリング方法
CN102899557B (zh) * 2012-11-02 2014-12-03 湖南华菱湘潭钢铁有限公司 一种低合金中厚钢板的生产方法

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EP3187275A4 (fr) 2017-09-06
JPWO2016031169A1 (ja) 2017-04-27
WO2016031169A1 (fr) 2016-03-03
KR20170033423A (ko) 2017-03-24
EP3187275A1 (fr) 2017-07-05
BR112017004022A2 (pt) 2017-12-05
BR112017004022B1 (pt) 2022-08-02
KR101940429B1 (ko) 2019-01-18
CN106604785A (zh) 2017-04-26
CN106604785B (zh) 2019-01-11
JP6108041B2 (ja) 2017-04-05

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