WO2008108483A1 - Mince tôle d'acier excellente en termes d'uniformité de résistance et de ténacité, son procédé de production et appareil pour celui-ci - Google Patents

Mince tôle d'acier excellente en termes d'uniformité de résistance et de ténacité, son procédé de production et appareil pour celui-ci Download PDF

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Publication number
WO2008108483A1
WO2008108483A1 PCT/JP2008/054246 JP2008054246W WO2008108483A1 WO 2008108483 A1 WO2008108483 A1 WO 2008108483A1 JP 2008054246 W JP2008054246 W JP 2008054246W WO 2008108483 A1 WO2008108483 A1 WO 2008108483A1
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WIPO (PCT)
Prior art keywords
cooling
cooling device
steel sheet
temperature
thin
Prior art date
Application number
PCT/JP2008/054246
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English (en)
Japanese (ja)
Inventor
Kenji Hayashi
Kenji Oi
Naoki Nakata
Akihide Nagao
Nobuo Shikanai
Original Assignee
Jfe Steel Corporation
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Publication date
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Publication of WO2008108483A1 publication Critical patent/WO2008108483A1/fr

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Classifications

    • 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
    • B21B45/0239—Lubricating
    • B21B45/0245—Lubricating devices
    • B21B45/0248—Lubricating devices using liquid lubricants, e.g. for sections, for tubes
    • B21B45/0251—Lubricating devices using liquid lubricants, e.g. for sections, for tubes for strips, sheets, or plates
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • B21B1/22—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 plates, strips, bands or sheets of indefinite length
    • B21B1/30—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 plates, strips, bands or sheets of indefinite length in a non-continuous process
    • B21B1/32—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 plates, strips, bands or sheets of indefinite length in a non-continuous process in reversing single stand mills, e.g. with intermediate storage reels for accumulating work

Definitions

  • the present invention relates to a method of manufacturing a steel plate using a reversing rolling mill and a transfer-type cooling device, and more particularly, a direct quenching and tempering process after hot rolling ( Thin wall with excellent homogeneity of material properties in the longitudinal direction of steel sheets subjected to direct quenching and temper treatment or accelerated cooling treatment
  • the present invention relates to a thick steel plate, a rolling-cooling method suitable for its production, and its production equipment.
  • the material of the thick copper plate depends on the microstructure, and in order to make the microstructure uniform, in the accelerated cooling process, the rolling finishing temperature—cooling start temperature (cooling start temperature) It is important to keep all cooling stop temperatures constant, and in the direct quenching-tempering process, it is important to keep the rolling finish temperature and the cooling start temperature constant.
  • the cooling start temperature also has a significant effect on the tissue.
  • the temperature decreases before the tail end of steel plate enters the cooling facility. Below the Ar transformation point, ferrite begins to form and ferritic strength decreases, making it difficult to secure a stable material.
  • the cooling stop temperature is specified in particular in the accelerated cooling process, and is extremely important in order to make the transformation ratio of the resulting structure constant, and the rolling finish temperature-cooling start temperature-cooling stop temperature are all It is important to maintain the uniformity of the material.
  • the cooling start temperature differs between the tip and tail of the steel sheet.
  • the cooling stop temperature varied in the longitudinal direction of the plate, making it difficult to create a uniform material.
  • the accelerated cooling process is an on-line heat treatment using a pass-through cooling device, but it takes time to roll the entire length of the steel plate when the steel plate is thin or the plate length is large. A large cooling start temperature difference occurs between the tip and the tail of the steel plate.
  • the direct quenching and tempering process is an on-line heat treatment using a through-type cooling device, and when the steel plate is thin or the plate length is large, there is a large difference in the quenching start temperature between the tip and tail of the steel plate. Arise.
  • the cooling start temperature during quenching affects the microstructure and it is difficult to obtain a homogeneous material in the longitudinal direction of the steel sheet.
  • Limiting the plate length of the steel sheet according to the thickness of the steel sheet so that the fluctuation range of the material falls within a predetermined range, or reheating and manufacturing by a quenching and tempering process may reduce manufacturing efficiency, Desirable, which increases manufacturing costs.
  • various methods for reducing the variation in the material of the copper plate have been proposed.
  • Japanese Laid-Open Patent Publication No. 9-310117 proposes to produce a copper material with little material change by controlling the cooling rate, and describes that the uniformity of the steel sheet in the thickness direction and between steel materials is improved. Has been.
  • the material change cannot be suppressed when the cooling start temperature or the rolling finishing temperature changes.
  • JP-A-3-173716 describes that the temperature drop at the four circumferences of the steel material is suppressed by a prior cooling method, and the entire material is rolled at a uniform temperature. although it constant, problems force s can not be enhanced application homogeneity in quenching material and accelerated coolant to exit the difference in the previous tail of Itacho subsequent cooling start temperature Nirre Te, .
  • the technique disclosed in Japanese Patent No. 3784265 is effective in suppressing variations between steel materials, and is not sufficient to make the materials in the plate length direction of the steel plates within the same steel plate uniform.
  • the cooling start temperature at the time of cooling cannot be kept constant, resulting in large variations in materials.
  • thermometer is installed on the inlet side of the cooling device, the temperature in the longitudinal direction of the steel sheet is measured, and the approach speed to the cooling device is increased stepwise to reduce the cooling.
  • a method for stabilizing the material by making the stop temperature uniform is disclosed.
  • JP-A-8-90042 discloses a method for keeping the cooling start temperature constant in the longitudinal direction of the steel sheet. Inserting a steel plate into the cooling device during hot rolling and keeping a temperature distribution in the longitudinal direction of the steel plate causes a temperature gradient at the leading edge of the steel plate at the end of rolling, and then inserts it into the cooling facility Sometimes the cooling start temperature is kept constant. Therefore, in the method described in JP-A-8-90042, the most important rolling finishing temperature that affects the toughness of the copper plate differs greatly in the longitudinal direction of the copper plate, and a certain toughness cannot be obtained in the longitudinal direction of the steel plate. .
  • the steel sheet transport speed during cooling is slower than the rolling speed, so the effect on the steel sheet material uniformity is
  • the cooling start temperature difference and cooling stop temperature difference are larger than the effect of the finishing temperature difference at the tip and tail ends.
  • the present invention provides a manufacturing method in which, when the length of the steel plate is long, a thin-walled steel plate having a uniform cooling start temperature and cooling stop temperature over the entire length of the copper plate and excellent strength and toughness uniformity is obtained.
  • An object of the present invention is to provide a manufacturing facility and a thin-walled steel plate.
  • the present invention is a direct quenching and tempering process or an accelerated cooling process, where the strength (TS) is 25MPa and the ductile-brittle fracture surface transition temperature (vTrs) is 10 ° C.
  • An object of the present invention is to provide a thin-walled steel sheet having excellent strength and toughness uniformity in the longitudinal direction of the steel sheet, a manufacturing method thereof, and a manufacturing facility thereof. Disclosure of the invention
  • the inventors of the present invention studied various rolling-cooling processes in which the hot rolling rolling finishing temperature and the subsequent cooling start temperature or the cooling stop temperature are made constant, respectively, The most stable effect in actual machine operation can be obtained by placing a cooling device with a short cooling zone near the rolling mill and applying an appropriate temperature gradient in the longitudinal direction of the steel plate before hot rolling, quenching or accelerated cooling. It was found effective.
  • the present invention has been made based on further studies based on the obtained knowledge. That is, the present invention 1.When water-cooling a steel sheet after finish rolling using a pass-through cooling device, in the first step, the steel sheet is water-cooled in advance so as to give a temperature gradient in the longitudinal direction of the steel sheet.
  • a method for producing a thin-walled steel sheet characterized in that water cooling is performed at a constant passing speed in the process.
  • the second-step pass cooling device is placed downstream of the reversible hot rolling mill.
  • the first-stage passing type cooling device is arranged downstream of the reversible hot rolling mill
  • the second-step passing type cooling device is arranged downstream of the first-step passing type cooling device.
  • the steel plate finished and rolled by the reversible hot rolling mill is cooled by the passage-type cooling device in the first step and is elongated in length.
  • a method for producing a thin-walled steel sheet characterized in that a temperature gradient is applied in the direction, and the steel sheet is water-cooled while passing through the passage-type cooling device in the second step at a constant speed.
  • a method for producing a thick steel plate using a rolling-cooling device in which a passing-type cooling device is disposed downstream or upstream of the reversible hot rolling mill, which is finish-rolled by the reversible hot rolling mill.
  • the steel sheet is first cooled by the through-type cooling device and then cooled in the next second step while being reversely fed.
  • the steel plate is cooled and longitudinally cooled.
  • a method for producing a thin-walled steel sheet characterized in that a temperature gradient is applied in the direction, and the reverse feed speed of the copper plate in cooling is a constant speed in the next second step.
  • the cooling start temperature at the tip and tail ends of the steel plate in cooling should be the Ar 3 transformation point or higher or the two-phase region temperature.
  • the above 6. The method for producing a thin-walled steel sheet according to 5, wherein a temperature gradient is applied by cooling in the first first step.
  • the first step is performed so that the cooling start temperature difference at the tip and tail ends of the steel plate during cooling is within 50 ° C. 7.
  • the temperature drop difference ⁇ ⁇ between the steel plate tip and tail ends satisfies equation (1) by changing the transport speed and / or the amount of water injected.
  • the first cooling step is performed so that the difference in cooling start temperature at the tip and tail ends of the steel sheet is within 30 ° C.
  • the length in the steel sheet conveyance direction of the cooling region of the through-type cooling device in the first step described in 10.2 or the cooling region of the through-type cooling device arranged on the downstream side or the upstream side of the reversible rolling mill in 5 is 0.4 m to The method for producing a thin-walled steel plate according to any one of 2 to 9, wherein the thickness is 4 m.
  • the compositional strength of the steel sheet is as follows: C O.01 to 0.20%, Si.O.01—0.80%, Mn: 0.50—2.50%, P: 0.020% or less, S: 0.0070% or less, sol.
  • the steel composition is Ti: 0.005-0.20%, Cu: 0.01—2.0 ⁇ / ⁇ , ⁇ i: 0.01—4.0%, Cr: 0.01—2.0%, ⁇ : 0.01—2.0%, Nb: 0.003—0.1%, V: 0.003-0.5%, W: 0.003-0.7%, ⁇ : 0.0005—0.0040%, Ca: 0.0001—0.0060%, Mg: 0.0001-0.0060%, REM: 0.0001—0.0200% 1 type or 2 11.
  • the second-pass pass-through cooling device is placed downstream of the reversible hot rolling mill.
  • the second-step passing type cooling device is arranged downstream of the first-step passing type cooling device. Manufacturing equipment for thin thick copper plates.
  • a production facility for thin-walled steel sheets which is equipped with a through-type cooling device that can cool the steel sheet after finishing rolling in the downstream or upstream side of the reversible hot rolling mill.
  • the length of the cooling region of the through-type cooling device in the first step described in 15.13 or the cooling region of the through-type cooling device arranged on the downstream side or the upstream side of the reversible rolling mill in 14 is 0.4 ⁇ . !
  • compositional power mass% C: 0.01—0.20%, Si: 0.01-0.80%, Mn: 0.50—2.50%, P: 0.020% or less, S: 0.0070% or less, sol.A1: 0.004—0.100% 17.
  • Ti 0.005-0.20%, Cu: 0.01—2.0%, Ni: 0.01—4.0%, Cr: 0.01—2.0%, Mo: 0.01—2.0%, Nb: 0.003—0.1 %, V: 0.003—0.5%, W: 0.003-0.7%, B: 0.0005—0.0040%, Ca: 0.0001—0.0060%, Mg: 0.0001-0.0060%, REM: 0.0001-0.0200% 18.
  • the steel plate temperatures such as the rolling finishing temperature, the cooling start temperature, and the cooling stop temperature referred to in the present invention are temperatures obtained by measuring the temperature of the steel plate surface with a radiation thermometer unless otherwise specified.
  • the plate thickness is 6mn! Plate length 20 ⁇ at 25mm! Direct quenching of thin-walled steel sheets up to 50m
  • the rolling finish temperature and cooling start temperature are all uniform over the entire length of the steel sheet, and in the accelerated cooling process, the rolling finish temperature, cooling start temperature, and cooling stop All of the temperature is uniform over the entire length of the steel sheet, and a thin and thick copper sheet with excellent strength and toughness uniformity is obtained, which is extremely useful in industry.
  • Figure 1 Schematic diagram showing an example of rolling-cooling equipment.
  • Fig. 2 is a schematic diagram illustrating the rolling-cooling method in the copper plate manufacturing method according to the present invention.
  • Fig. 2A shows Casel
  • Fig. 2B shows Case 2
  • Fig. 2C shows Case 3.
  • Fig. 3 is a schematic diagram for explaining the temperature difference in the longitudinal direction of the steel sheet in the rolling-cooling method according to the present invention.
  • Fig. 3A shows Casel
  • Fig. 3B shows Case 2
  • Fig. 3C shows Case 3.
  • Fig. 4 Cooling device with excellent drainage performance suitable as the first-stage pass-through cooling device in the present invention.
  • Fig. 4A does not use a draining roll, and the cooling water is retained on the steel plate by the cooling water injection nozzle.
  • Figure 4B shows a form in which cooling water jet nozzles and draining rolls are used together to retain the cooling water on the copper plate.
  • Figure 4C shows a form in which cooling water is retained on the steel sheet with the draining rolls without using the cooling water jet nozzle.
  • Fig. 5 Diagram showing the cooling rate of hot-rolled copper sheet during air cooling.
  • Fig. 6 An example of a schematic diagram of the passing-type cooling device in the second step.
  • Cooling tank 1: Cooling tank, 2: Retained cooling water, 3: Upper cooling water injection nozzle,
  • a cooling facility capable of adjusting the temperature in the longitudinal direction of the steel sheet is arranged in the vicinity of the upstream side or the downstream side of the finish rolling mill, and further, quenching or accelerated cooling is possible on the downstream side of the cooling facility.
  • the rolling finish temperature, cooling start temperature, and further cooling stop temperature are all made uniform over the entire length of the copper plate.
  • Fig. 1 schematically shows the arrangement of rolling mills and cooling devices in a rolling-cooling facility to which the present invention is applied.
  • 14 is a reheating fiirnace
  • 9 is a rolling mill
  • 10 is a rolling mill 9 (10) is the first-stage cooling device arranged upstream of the rolling mill
  • 11 is the second-type flow-type cooling device arranged on the downstream side.
  • a cooling device is shown.
  • the heating furnace 14 side of the rolling mill 9 is referred to as the upstream side of the rolling mill 9, and the passing cooling device 11 side of the second step is referred to as the downstream side.
  • a thick steel plate (not shown) is heated for rolling in a heating furnace 14, and after finish rolling, an appropriate temperature gradient is imparted in the longitudinal direction of the steel plate in the first-stage passing cooling device 10.
  • the steel plate after finish rolling is transferred to the passing water cooling device 11 in the second step for quenching or accelerated cooling, but the cooling start temperature is substantially the same in the longitudinal direction of the steel plate.
  • An appropriate temperature gradient is given in advance in the longitudinal direction of the steel sheet when passing through the passing type cooling device 10 in the first step.
  • FIGS. 2A, 2B, and 2C are schematic diagrams for explaining the rolling-cooling method in the copper plate manufacturing method according to the present invention.
  • P1 to P4 indicate a pass
  • P3 indicates a final (finishing) pass
  • P2 is a pass immediately before the final pass
  • P1 is a pass immediately before P2
  • P4 is an empty pass through which the steel sheet after finish rolling or finish rolling and water cooling passes through the rolling mill 9.
  • the empty pass means that the thick copper plate is passed through the rolling mill without rolling.
  • a represents a rolling operation by the rolling mill 9
  • bl b2 represents a water cooling operation by the first-stage passage type cooling device
  • c represents a water cooling operation by the second step passage-type cooling device.
  • the steel plate is not shown.
  • Fig. 2A shows the case where the first-stage through-type cooling device 10 and the second-step through-type cooling device 11 are arranged in this order on the downstream side of the rolling mill 9, and the steel sheets after finish rolling are sequentially passed through and cooled.
  • Fig. 2B shows the first-stage passing-type cooling device 10 upstream of the rolling mill 9 and the second-step passing-type cooling device 11 downstream of the rolling mill 9, and finish rolling ( The steel plate after P3) is cooled by the pass-through cooling device 10 in the first step in the empty pass (P4), and then passed through the rolling mill 9 in the empty pass (P4) and passed through the rolling mill 9 in the second step 11
  • Fig. 2A shows the case where the first-stage through-type cooling device 10 and the second-step through-type cooling device 11 are arranged in this order on the downstream side of the rolling mill 9, and the steel sheets after finish rolling are sequentially passed through and cooled.
  • Fig. 2B shows the first-stage passing-type cooling device 10 upstream of the rolling mill 9 and the second
  • a pass-through cooling device in this description, the pass-through cooling device 10 in the first step
  • the pass-through cooling device 10 in the first step is placed downstream of the rolling mill 9, and after cooling,
  • a case (Case 3) is shown in which cooling is performed by the above-described cooling device in the second step while back feeding.
  • the force P2 described with P3 as the final (finishing) pass can be used as the final (finishing) pass, and the rolling mill 9 can be empty in the P3 pass.
  • FIG. 2C shows the case where the first-stage passing type cooling device 10 is provided downstream of the rolling mill 9! However, it is also possible to provide the pass-type cooling device 10 of the first step on the upstream side of the rolling mill 9 and make P2 the final (finishing) pass.
  • 3A, 3B, and 3C schematically show the temperature distribution in the longitudinal direction of the steel sheet in Cases 1 to 3 shown in FIGS. 2A, 2B, and 2C, respectively.
  • 2A, 2B, 2C, 3A, 3B, and 3C the direction of the arrow indicates the traveling direction of the copper plate.
  • the traveling direction side of the copper plate is the tip of the steel plate, and the opposite direction is the direction of the copper plate. It is called the tail end of a steel plate.
  • the present invention will be described with reference to FIG. 2A, FIG. 2B, FIG. 2C, FIG. 3A, FIG. 3B, and FIG.
  • the steel plate is made to have a predetermined plate thickness in the final pass P3, then water-cooled by the first-stage passing cooling device 10 and then passed through the second step.
  • Water cooling is performed in the mold cooling device 11 to give the desired performance.
  • the water cooling bl is water cooled by the passage type cooling device 11 in the second step
  • the tail end of the steel plate in the longitudinal direction of the steel plate is ⁇ from the tip so that the cooling start temperature is substantially the same in the steel plate longitudinal direction. High temperature.
  • Water in the second-stage through-type cooling device 11 When the cold c is applied, the steel sheet is allowed to enter the second-stage cooling apparatus 11 in the second step at a constant speed, and the cooling stop temperature is made substantially the same in the longitudinal direction of the steel sheet.
  • the steel sheet is set to a predetermined plate thickness by the rolling mill 9 in the final pass P3, and then water-cooled by the first-stage pass-through cooling device 10 and then empty. It passes through the rolling mill 9 in pass P4 and is water-cooled in the second-stage passing cooling device 11 to give the desired performance.
  • the tail end portion in the longitudinal direction of the steel sheet is more than ⁇ ⁇ from the front end portion so that the cooling start temperature is substantially the same in the longitudinal direction of the steel sheet. High temperature.
  • water-cooling c is performed in the second-stage cooling device 11 in the second step, the steel sheet enters the second-step cooling device 11 in the second step at a constant speed, and the cooling stop temperature is substantially the same in the longitudinal direction of the copper plate. .
  • the temperature difference ⁇ applied to the tail end and the tip in the longitudinal direction of the steel sheet is the second-stage through-type cooling device 11 or the first-step through-type cooling device 10 that is reversely fed.
  • the cooling start temperature at the tail end of the steel sheet is applied so as to be the same as that at the tip.
  • the temperature gradient linearly in the longitudinal direction of the steel sheet.
  • the temperature gradient may be changed stepwise in the longitudinal direction of the steel sheet.
  • the power S, the cooling start temperature, and the cooling stop temperature are made substantially the same, making the cooling equipment capacity constant after applying a temperature gradient in the longitudinal direction of the steel sheet and making the conveyance speed during cooling constant. If the cooling capacity such as the amount of cooling water can be controlled, the conveying speed in the longitudinal direction of the steel sheet does not have to be constant.For example, the amount of cooling water is increased in proportion to the increase in the conveying speed. You may let them.
  • the technical feature of controlling the cooling start temperature and the cooling stop temperature in the second-stage through-type cooling device, which are the characteristics of the invention of the present application, substantially in the same direction with respect to the longitudinal direction of the steel sheet can be achieved. If there are, i.e., increasing the cooling water volume while increasing the conveying speed to increase the cooling capacity, or conversely decreasing the cooling water volume while decreasing the conveying speed to decrease the cooling capacity.
  • the cooling start temperature and cooling stop temperature can be made substantially the same while changing the conveying speed in the longitudinal direction of the steel sheet, the steel sheet longitudinal strength, which is the target of the present invention, is homogeneity of toughness. It is possible to produce a steel plate that is excellent in the quality.
  • the solid line in Fig. 5 shows the relationship between the thickness of the hot-rolled copper sheet at 700 ° C, 850 ° C, and 1000 ° C and the cooling rate when the copper sheet is cooled by air cooling.
  • An example is shown.
  • the solid line is the calculation result. The smaller the plate thickness, the smaller the heat capacity, and the higher the steel plate temperature, the more radiation and heat dissipation, so the cooling rate increases.
  • the cooling rate is slightly different depending on the transport mode and atmosphere. For example, when the plate thickness is 30 mm and the steel plate surface temperature is 800 ° C, the cooling rate is about 0.8 ° CZs. In general, after cooling with the first-stage through-type cooling device, the second-step through-type cooling device or again with the first-step through-type cooling equipment, bow I will be used for accelerated cooling and quenching when cooling continuously. Since the cooling start temperature is 700 ° C or higher, the cooling rate is higher than the broken line of 15Zh (° CZmm) in Fig. 5.
  • the temperature difference ⁇ T at the tip of the temperature gradient applied in the longitudinal direction of the steel sheet is 700 ° C or higher and 1000 ° C or lower.
  • a cooling device excellent in water-blocking property so that the cooling water does not flow out in the direction of conveying the steel sheet outside the cooling region as the passing-type cooling device in the first or second step.
  • FIGS 4A, 4B, and 4C show an example of a cooling device with excellent drainage performance.
  • 1 is a cooling bath
  • 2 is cooling water retained on the steel plate 4
  • 3 is upward cooling water.
  • Injection nozzle 4 is steel A plate
  • 5 is a transport roll
  • 6 is a lower cooling water nozzle
  • 7 is a cooling region
  • 8 is a draining ronor
  • 15 is a rod-shaped cooling water.
  • Fig. 4A shows a cooling device that ejects rod-shaped cooling water 7 from the upper cooling water injection nozzle 3 attached to the cooling tank 1 so as to face each other and retains the cooling water 2 on the copper plate 4, and
  • Fig. 4B shows the conveyance with the draining roll 8
  • Figure 4C shows two pairs of draining roll 8 and transport roll 5, and between the roll pairs, A cooling device for retaining cooling water 2 on steel plate 4 is shown.
  • the rod-shaped cooling water has a water density of 4 m 3 Zm 2 min or more.
  • the amount of water density force m 3 // !!! 2 ! ⁇ ! The amount of stagnant cooling water 2 that can be dammed up increases, and the cooling water discharged from the plate width end and the cooling supplied The amount of water is balanced and the retained cooling water 2 is kept constant.
  • the general plate width is 2 to 5 m. If cooling is performed with a water density of 401 3 cm 1 ⁇ 1 ⁇ ! 1 or more, the stagnant cooling water 2 can be kept constant at these plate widths. The desired temperature drop can be obtained while passing the steel plate being rolled.
  • a more preferable water density is 4 to: ⁇ 0 ⁇ 2 ⁇ .
  • the distance in the transport direction of the cooling region 7 is 0.4 ⁇ in the first-stage passing cooling system (including the case 3 passing cooling system)! It is preferably set to 4 m. If it is less than 4 m, it is necessary to take a long residence time in the cooling zone in order to cool the copper plate, and it takes too much time to pass the entire steel plate, making it difficult to create a sufficient temperature gradient. On the other hand, if it exceeds 4 m, it is difficult to provide uniform cooling in the cooling region, and it is difficult to provide a sufficient temperature gradient with a steel plate with a short plate length.
  • region in FIG. 4A, FIG. 4B, and FIG. 4C is shown by the black coating part of a steel plate.
  • cooling area 7 is appropriately set by increasing or decreasing the number of cooling baths and nozzles, or by increasing or decreasing the number of cooling unit units shown in FIGS. 4A, 4B, and 4C. It is possible.
  • both the passing speed and the cooling capacity may be used so that the cooling facility capacity such as the water injection amount of the first-stage passing cooling system can be controlled.
  • the second-stage pass-through cooling system is not particularly limited as long as it has the required cooling capacity and can perform uniform cooling.
  • a through-type cooling device 11 (which can also be used for direct quenching) as shown in FIG. 6 is used.
  • 4 is a steel plate
  • 8 is a draining roll and a draining drain
  • 21 is a slit jet nozzle
  • 22 is a circular pipe nozzle.
  • the steel plate 4 cooled by the first cooling device is conveyed through a plurality of cooling zones between 20 sets of water draining rolls and sewage draining rollers 8, while the upper side is a slit nozzle 21.
  • the lower side is cooled on-line by the cooling water from the circular tube nozzle 22 by the cooling water from.
  • thermometers are attached to the inlet side and the outlet side of the cooling device 11, respectively, so that the temperature of the thick copper plate can be measured before and after cooling.
  • Each cooling zone is partitioned by upper and lower draining rolls 8, and the amount of cooling water can be adjusted individually.
  • the cooling start temperature is appropriately selected from the Ar 3 transformation point or the two-phase region temperature depending on the desired characteristics. This is because, in order to secure the desired strength by generating transformation phases such as martensite and bainite by quenching or accelerated cooling from the temperature range including the austenite phase, the cooling start temperature of quenching and accelerated cooling is the Ar 3 transformation point.
  • the above-mentioned temperature must be in the two-phase temperature range and the temperature range in which the austenite phase is present. What is necessary is just to select suitably according to the intensity
  • Tempering can be carried out in a conventional manner.
  • an off-line atmosphere furnace or an on-line induction heating device can be used, and the tempering temperature is below the ACl transformation point, which is the temperature range where no austenite phase is generated.
  • the tempering temperature is below the ACl transformation point, which is the temperature range where no austenite phase is generated.
  • the cooling start temperature in the second-step pass-type cooling device or further the cooling stop temperature. It is preferable that the difference between the maximum value and the minimum value in the longitudinal direction of the copper plate be 50 ° C or less. .
  • the difference in strength between the tip and tail ends of the steel sheet increases the difference in toughness. More preferably, it is 30 ° C or less.
  • cooling b2 using the pass-through cooling device 10 in the first step.
  • the cooling method according to the present invention can be applied to a steel sheet having a composition suitable for direct quenching and tempering or an accelerated cooling process.
  • the direct quenching and tempering process described below or an accelerated cooling process is assumed.
  • the component composition is preferred.
  • % In the component composition is mass%.
  • C must be at least 0.01% to ensure the strength of the steel sheet, and if added over 0.20%, the weldability will be significantly reduced, so 0.01% or more and 0.20% or less (hereinafter, 0. 01 -0. 2 0%).
  • Si is an element necessary for deoxidation, but if it is less than 0.01%, the effect is small.If it exceeds 0.80%, weldability and base metal toughness are significantly reduced. 80%.
  • Mn 0.5— 2. 50% Mn is necessary to ensure the strength of the steel sheet as in C, and if added in excess, the weldability is impaired, so 0.5-2.50%.
  • P and S are elements that are unavoidably contained in steel as impurities, and deteriorate the toughness of the steel base material and weld heat affected zone, so it is preferable to reduce it as much as possible in consideration of economy.
  • Mashigu P 0.020 mass% or less
  • S 0.0070 mass% or less.
  • A1 is a deoxidizing element, and if it is less than 0.004%, its effect is not sufficient, and adding too much will cause toughness deterioration, so it should be 0.004-0.10% or less.
  • the preferred basic component composition of the present invention is the above force S, and in the case of further improving desired characteristics, Ti, Cu, Ni, Cr, Mo, Nb, V, W, B, Ca, Mg, REM or Add two or more kinds as selective elements.
  • Ti has the strength to ensure the toughness of the base metal and the toughness in the heat affected zone.
  • the force with the specified range is good. If added over 0.20%, the toughness will decrease significantly. 0.20%.
  • Cu is an element to increase the strength and exerts its effect at 0.01% or more, and if added over 2.0%, the steel sheet surface properties deteriorate due to hot brittleness. To do.
  • Ni can improve the toughness while increasing the strength of the base metal, and is effective at 0.01% or more, and the effect is saturated and economically disadvantageous at 4.0% or more. -4.0%.
  • Cr and Mo are both effective in increasing the strength, and the effect is exhibited at 0.01% or more. If added over 2.0%, the toughness will deteriorate significantly. If added, the content should be 0.01-2.0%.
  • Nb 0.003-0.1%
  • V 0.003-0.5%
  • Nb and V are elements that improve the strength and toughness of the base metal. Addition of 0.003% or more produces an effect. Also, if it exceeds 0.1% and 0.5%, respectively, the toughness may be lowered. Therefore, when adding, Nb: 0.003-0.1% and V: 0.003-0.5%.
  • W is an element that improves strength and corrosion resistance. If it is less than 0.003%, the effect is not good. If it exceeds 0.7%, the weld heat affected zone toughness may be deteriorated.
  • Ca, Mg. REM works to fix S in steel and improve the toughness of the copper sheet, and has an effect S with an applied force of 0.0001% or more. And then force, respectively 0.0060%, 0.0060%, in order to rather degrade the intervening amount increases and toughness of the copper is added Te Etsumen the 0.0200 o / o, the case of adding the, Ca: 0.0001-0.0060%, Mg: 0.0001-0.0060%, REM: 0.0001-0.020 0%.
  • the balance other than the above components is composed of Fe and inevitable impurities.
  • the molten copper having the above composition is melted by a conventional method using a melting means such as a converter or an electric furnace, and a slab or the like is prepared by a conventional method such as a continuous forging method or an ingot-bundling method. It is preferable to use a steel material.
  • the melting method and the forging method are not limited to the methods described above.
  • the dimensions of the thin-walled steel plate targeted by the present invention are the plate thickness of 6-25mm and the plate length of 20 ⁇ ! ⁇ 50m steel plate.
  • the plate thickness is less than 6mm, the air cooling rate is high, so the rolling temperature and cooling start temperature- Not all stop temperatures can be made uniform.
  • the plate thickness is 25 mm or more, the cooling rate during air cooling is small, so that the temperature difference between the tip and tail ends of the steel plate is small without using the temperature gradient control method of the present invention. If the length of the steel sheet is less than 20 m, the required product length may not be obtained, or the productivity is inferior, and even if the temperature gradient control method of the present invention is not used, The temperature difference between the tip and tail is small.
  • the temperature gradient control according to the present invention has a large temperature difference between the leading edge and the trailing edge of the steel sheet, which takes time for rolling and cooling, and the temperature drop at the tail edge of the steel sheet is large. Even with this method, it becomes difficult to reduce the temperature difference between the tip and tail of the copper plate.
  • the mechanical performance of the thin steel plate targeted by the present invention is that the difference in tensile strength is ⁇ 25 MPa between the tip and tail of the steel plate, and the difference in ductile-brittle fracture surface transition temperature (toughness) (vTrs). Is a thin-walled steel plate within the range of ⁇ 10 ° C.
  • a thick steel plate was produced by the rolling-cooling method according to Casel of the present invention, and the mechanical properties (strength and toughness) of the entire length of the steel plate were investigated.
  • the first-stage pass-through cooling system uses a cooling facility (Fig. 4C) with a cooling area lm between two draining rolls (Fig. 4C).
  • the accelerated cooling equipment shown in Fig. 6 was used as the equipment.
  • the tip and tail edges of the steel plate having the cooling start temperature and the cooling stop temperature in the second-stage through-type cooling device are provided by Casel, while the temperature gradient is given by the first-type through-type cooling device.
  • the steel plate was manufactured under the manufacturing conditions in which the difference was 50 ° C.
  • the manufacturing conditions in which cooling was performed only with the passing type cooling device in the second step without using the passing type cooling device in the first step was kept constant at lmZs.
  • a tensile test piece having a full thickness was collected and subjected to a tensile test in accordance with the standard of JIS Z 2241 (1998) to obtain the tensile strength TS.
  • a Charpy impact test specimen with a V-notch standard dimension was taken from the position in the plate thickness direction 1Z2 in accordance with JIS Z 2202 (1998), and impact in accordance with JIS Z 2242 (1998). Conducted tests to determine ductile- brittle fracture transition temperature and vTrs.
  • Table 1 shows the composition of the test steel, and Table 2 shows the strength and toughness of the steel sheet obtained.
  • Nol, 2, 6, 7, 11, 12 with a temperature difference ⁇ between the tip and tail in the first-stage pass-through cooling system are YS (yield strength) and TS ( The difference in tensile strength was uniform within ⁇ 25 MPa, and the toughness was good.
  • the toughness at the tip of the steel sheet decreased for Nos. 3, 8 and 13 where the temperature difference between the tip and tail ends of the steel sheet with a finishing temperature of 50 ° C or more was large.
  • No4, 9, and 14 are YS at the tip and tail of the steel plate, where the temperature difference between the tip and tail of the steel plate at the cooling start temperature is large at 50 ° C or more.
  • the TS difference was large and the toughness of the tail end was lowered, and a uniform steel plate could not be obtained.
  • Example 2 Thick steel plates were produced by the cooling method according to the present invention, and the mechanical properties (strength and toughness) of the entire length of the steel plate were investigated.
  • the first-stage pass-through cooling system uses a cooling facility (Fig. 4C) with a cooling area of lm between two draining rolls (Fig. 4C).
  • the direct quenching equipment shown in Fig. 6 was used as the cooling device.
  • the tempering conditions after direct quenching were the tempering temperatures shown in Tables 4 and 5.
  • a steel plate having a thickness of 6 to 25 mm was produced from a slab having a thickness of 250 mm using various hot rolling conditions, and the steel plates obtained after direct quenching and tempering shown in Tables 4 and 5 were used.
  • tensile test specimens of full thickness were collected and subjected to a tensile test in accordance with JIS Z 2241 (1998) to determine the tensile strength TS.
  • a Charpy impact test specimen with a V-notch standard dimension was taken from the position in the plate thickness direction 12 in accordance with the provisions of JIS Z 2202 (199 8), and conformed to the provisions of JIS Z 2 242 (1998).
  • An impact test was conducted to determine the ductile-brittle fracture surface transition temperature vTrs. However, for sheet thicknesses of llmmt or less, vTrs was determined using a half-size Charpy specimen.
  • Table 3 shows the composition of the test steel, and Tables 4 and 5 show the strength and toughness of the copper plates obtained.
  • the TS difference between the tip and tail of the copper plate was uniform within ⁇ 25 MPa, and the toughness difference (vTrs difference) was good within ⁇ 10 ° C.
  • the comparative examples Nos. 27 to 39
  • uniform steel sheets with large TS difference between the tip and tail and Z or toughness difference (vTrs) could not be obtained.
  • Thick steel plates were produced by the cooling method according to the present invention, and the mechanical properties (strength and toughness) of the entire length of the steel plate were investigated.
  • the first-stage pass-through cooling system uses a cooling facility (Fig. 4C) with a cooling area of lm between two draining rolls (Fig. 4C).
  • the cooling device the accelerated cooling equipment shown in Fig. 6 was used.
  • a steel plate having a thickness of 6 to 25 mm was produced using various hot rolling conditions such as a 250 mm cross-sectional slab force, and a full thickness tensile test piece was collected from the obtained thick steel plate.
  • Tensile tests were conducted in accordance with JIS Z 2241 (1998) to determine the tensile strength TS. Board In accordance with JIS Z 2202 (1998), a V-notch standard size Charpy impact test piece is taken from the position in the thickness direction 1 2 and subjected to an impact test according to JIS Z 2242 (1998).
  • the ductile one brittle fracture surface transition temperature vTrs was obtained. However, for sheet thicknesses of llmmt or less, vTrs was determined using half-size Charpy specimens.
  • Table 3 shows the composition of the test steel, and Tables 6 and 7 show the strength and toughness of the copper plates obtained.
  • the TS difference between the tip and tail ends of the steel sheet was uniform within ⁇ 25 MPa, and the toughness difference (vTrs difference) was good within ⁇ 10 ° C.
  • the comparative examples Nos. 27 to 39 were strong enough to obtain a uniform steel sheet with a large TS difference and Z or toughness difference (vTrs) between the tip and tail of the copper plate.
  • the rolling finishing temperature and the cooling start temperature, or the cooling stop temperature are all uniform over the entire length of the steel plate, and the strength and toughness are uniform over the entire length of the steel plate.
  • a thin thick copper plate with excellent resistance is obtained, which is extremely useful industrially.

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Abstract

L'invention concerne un procédé pour produire une tôle d'acier d'épaisseur donnée, excellente en termes d'uniformité des propriétés de matériau le long de la longueur de la tôle d'acier, avec l'utilisation d'un laminoir en va-et-vient et d'une unité de refroidissement à passage continu. En particulier, l'invention concerne un procédé de laminage-refroidissement à l'aide d'un appareil de laminage-refroidissement ayant une unité de refroidissement à passage continu de premier étage et une unité de refroidissement à passage continu de second étage disposées en aval d'un laminoir à chaud en va-et-vient, le procédé consistant à : 1. au moment du laminage, juste avant d'effectuer le laminage final dans le laminage de finition, refroidir la tôle d'acier par l'unité de refroidissement à passage continu de premier étage, de telle sorte que la température de finition du laminage final au niveau de la zone d'extrémité avant de la tôle d'acier est identique à celle au niveau de la zone d'extrémité arrière de la tôle d'acier ; 2. au moment du refroidissement de la tôle d'acier après le laminage de finition au moyen de l'unité de refroidissement à passage continu de second étage, refroidir la tôle d'acier au moyen de l'unité de refroidissement à passage continu de premier étage, de telle sorte que la température de début de refroidissement au niveau de la zone d'extrémité avant de la tôle d'acier est identique à celle au niveau de la zone d'extrémité arrière de la tôle d'acier ; et 3. refroidir la tôle d'acier par passage de celle-ci à travers l'unité de refroidissement à passage continu de second étage à une vitesse constante.
PCT/JP2008/054246 2007-03-05 2008-03-04 Mince tôle d'acier excellente en termes d'uniformité de résistance et de ténacité, son procédé de production et appareil pour celui-ci WO2008108483A1 (fr)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011045896A (ja) * 2009-08-26 2011-03-10 Jfe Steel Corp 熱延鋼板の冷却設備および冷却方法
JP2011147962A (ja) * 2010-01-21 2011-08-04 Jfe Steel Corp 厚鋼板の製造方法および水冷パス数の決定方法
JP2017131922A (ja) * 2016-01-27 2017-08-03 Ｊｆｅスチール株式会社 熱延鋼帯の製造設備列および熱延鋼帯の製造方法
WO2017130765A1 (fr) * 2016-01-26 2017-08-03 Ｊｆｅスチール株式会社 Ligne d'appareillages de production pour bandes d'acier laminées à chaud et procédé de production pour bande d'acier laminée à chaud
JP2018001211A (ja) * 2016-06-30 2018-01-11 Ｊｆｅスチール株式会社 熱延鋼帯の製造方法および熱延鋼帯の製造設備
CN108273857A (zh) * 2017-12-29 2018-07-13 南京钢铁股份有限公司 一种提高单机架轧机中间坯冷却穿水效率的方法

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JP2005279703A (ja) * 2004-03-29 2005-10-13 Jfe Steel Kk 鋼板の製造方法及びその製造設備
JP2006035233A (ja) * 2004-07-22 2006-02-09 Sumitomo Metal Ind Ltd 鋼板の冷却装置、熱延鋼板の製造装置及び製造方法

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JPH0538515A (ja) * 1991-08-05 1993-02-19 Nkk Corp 厚鋼板の強制冷却方法及びその装置
JP2000280017A (ja) * 1999-03-31 2000-10-10 Nkk Corp 鋼板の冷却方法およびその装置
JP2004322118A (ja) * 2003-04-22 2004-11-18 Sumitomo Metal Ind Ltd 厚鋼板の圧延方法
JP2005002372A (ja) * 2003-06-09 2005-01-06 Nippon Steel Corp 材質の異方性及びばらつきの小さい厚鋼板の製造方法
JP2005279703A (ja) * 2004-03-29 2005-10-13 Jfe Steel Kk 鋼板の製造方法及びその製造設備
JP2006035233A (ja) * 2004-07-22 2006-02-09 Sumitomo Metal Ind Ltd 鋼板の冷却装置、熱延鋼板の製造装置及び製造方法

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011045896A (ja) * 2009-08-26 2011-03-10 Jfe Steel Corp 熱延鋼板の冷却設備および冷却方法
JP2011147962A (ja) * 2010-01-21 2011-08-04 Jfe Steel Corp 厚鋼板の製造方法および水冷パス数の決定方法
CN108495723A (zh) * 2016-01-26 2018-09-04 杰富意钢铁株式会社 热轧钢带的制造设备列和热轧钢带的制造方法
US11007556B2 (en) 2016-01-26 2021-05-18 Jfe Steel Corporation Production equipment line for hot-rolled steel strip and production method for hot-rolled steel strip
WO2017130765A1 (fr) * 2016-01-26 2017-08-03 Ｊｆｅスチール株式会社 Ligne d'appareillages de production pour bandes d'acier laminées à chaud et procédé de production pour bande d'acier laminée à chaud
CN108495723B (zh) * 2016-01-26 2019-08-02 杰富意钢铁株式会社 热轧钢带的制造设备列和热轧钢带的制造方法
JP2017131906A (ja) * 2016-01-26 2017-08-03 Ｊｆｅスチール株式会社 熱延鋼帯の製造設備列および熱延鋼帯の製造方法
CN108602102A (zh) * 2016-01-27 2018-09-28 杰富意钢铁株式会社 热轧钢带的制造设备列和热轧钢带的制造方法
WO2017130767A1 (fr) * 2016-01-27 2017-08-03 Ｊｆｅスチール株式会社 Ligne d'équipement de production pour bandes d'acier laminées à chaud et procédé de production pour bande d'acier laminée à chaud
CN108602102B (zh) * 2016-01-27 2019-11-01 杰富意钢铁株式会社 热轧钢带的制造设备列和热轧钢带的制造方法
JP2017131922A (ja) * 2016-01-27 2017-08-03 Ｊｆｅスチール株式会社 熱延鋼帯の製造設備列および熱延鋼帯の製造方法
US11020780B2 (en) 2016-01-27 2021-06-01 Jfe Steel Corporation Production equipment line for hot-rolled steel strip and production method for hot-rolled steel strip
JP2018001211A (ja) * 2016-06-30 2018-01-11 Ｊｆｅスチール株式会社 熱延鋼帯の製造方法および熱延鋼帯の製造設備
CN108273857A (zh) * 2017-12-29 2018-07-13 南京钢铁股份有限公司 一种提高单机架轧机中间坯冷却穿水效率的方法

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