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WO2025126572A1 - Procédé de commande d'installation de production de tôle d'acier et installation de production de tôle d'acier - Google Patents

Procédé de commande d'installation de production de tôle d'acier et installation de production de tôle d'acier Download PDF

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Publication number
WO2025126572A1
WO2025126572A1 PCT/JP2024/029233 JP2024029233W WO2025126572A1 WO 2025126572 A1 WO2025126572 A1 WO 2025126572A1 JP 2024029233 W JP2024029233 W JP 2024029233W WO 2025126572 A1 WO2025126572 A1 WO 2025126572A1
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Prior art keywords
steel sheet
zone
heat treatment
mechanical property
cooling
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PCT/JP2024/029233
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English (en)
Japanese (ja)
Inventor
顕一 大須賀
玄太郎 武田
由康 川崎
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JFE Steel Corp
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JFE Steel Corp
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    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire

Definitions

  • the present invention relates to a method for controlling a steel sheet manufacturing facility and to a steel sheet manufacturing facility. More specifically, the present invention relates to a method for manufacturing steel sheets used for automobile structural materials, etc., and in particular, to a method for reducing the introduction cost of manufacturing facilities while suppressing the occurrence of material variations in the longitudinal direction of the steel strip.
  • the continuously cast slab is subjected to extensive processing by hot rolling and cold rolling until it reaches the final plate thickness.
  • the cold-worked structure is restored, recrystallized, and the grains grow, and the transformation structure is controlled.
  • the mechanical properties of the product are adjusted by the cooling process after annealing.
  • automobile body structural members are generally manufactured by press processing, and products that combine high strength and high workability are required.
  • zinc plating is often performed as a material for automobile parts in order to provide rust resistance.
  • alloyed hot-dip galvanized steel sheets in which zinc and iron are alloyed by heating after plating, are widely used.
  • Patent Document 1 discloses a method in which the material is rapidly cooled to below the martensite transformation temperature in the cooling zone on the exit side of the annealing furnace, then reheated and tempered.
  • Patent Document 2 discloses a method of obtaining the desired properties of the plating layer and the mechanical properties of the steel sheet by providing a tempering process in which, without transforming the steel strip into martensite in the cooling zone of the annealing furnace, alloying is performed in a state in which the austenite phase remains, and then the martensite structure is obtained by rapid cooling.
  • a tempering process in which, without transforming the steel strip into martensite in the cooling zone of the annealing furnace, alloying is performed in a state in which the austenite phase remains, and then the martensite structure is obtained by rapid cooling.
  • coils are joined together and heat treated continuously, so that it is necessary to change the operating conditions when the plate thickness, components, and target mechanical properties change.
  • Patent Document 2 does not disclose a method for dealing with such a problem.
  • Patent Document 3 a technology for controlling the material quality of a steel sheet by a material quality prediction model using the operation parameters of a continuous annealing facility and transformation rate information of the steel sheet acquired downstream of the continuous annealing facility as input data is disclosed in Patent Document 3.
  • This technology claims that material quality fluctuations can be suppressed by controlling the operation conditions of the manufacturing equipment downstream of the position where transformation rate information of the steel sheet is acquired, called the material quality control zone.
  • the material quality control zone the operation conditions of the manufacturing equipment downstream of the position where transformation rate information of the steel sheet is acquired.
  • the present invention has been made in consideration of the above problems, and aims to provide a method for controlling steel plate manufacturing equipment and steel plate manufacturing equipment that makes it possible to precisely obtain the desired mechanical properties for the manufactured steel plate.
  • the inventors conducted extensive research to solve these problems, and came to the following conclusion.
  • the mechanical properties, particularly the elongation value, when the following material passes through the steel sheet are predicted based on the heating temperature in the tempering zone of the preceding material before and after the joint of the steel strip where the target mechanical properties change.
  • the inventors came up with the idea of changing the heat treatment conditions of the continuous annealing facility, particularly the steel sheet heating temperature in the rapid heating zone, in real time before the following material passes through in order to reduce the difference between the predicted value and the target elongation value. Even if there is a delay in changing the heat treatment conditions in the tempering zone when the following material passes through, the heat treatment conditions in the rapid heating zone can be changed to match the heat treatment conditions, thereby making it possible to obtain the target mechanical properties over the entire length.
  • a continuous annealing facility for steel sheets having a heating zone, a soaking zone, a rapid heating zone, and a cooling zone in this order in a steel sheet transport direction;
  • a post-annealing heat treatment facility having at least a rapid cooling zone and a tempering zone in this order downstream of the cooling zone in the steel sheet transport direction;
  • Temperature measuring devices for the steel plate are installed at least in the rapid heating zone and the tempering zone;
  • a method for controlling a steel sheet heating temperature in a continuous annealing facility in a steel sheet manufacturing facility comprising: A mechanical property prediction step of predicting mechanical property values including an elongation value and a hole expansion ratio of the steel sheet based on the steel sheet heating temperature in the tempering zone measured by the temperature measuring device; a heat treatment condition calculation step of correcting the mechanical property values predicted in the mechanical property prediction step to target mechanical property values of the steel sheet, and determining heat treatment conditions based on the corrected mechanical property values; a heat
  • the steel sheet manufacturing facility further includes a transformation rate measuring device for measuring an austenite fraction of the steel sheet at at least one location from the soaking zone exit side to the tempering zone exit side in the steel sheet transport direction,
  • a transformation rate measuring device for measuring an austenite fraction of the steel sheet at at least one location from the soaking zone exit side to the tempering zone exit side in the steel sheet transport direction
  • the method for controlling steel sheet manufacturing equipment according to claim 1 or 2 further comprising predicting mechanical property values of the steel sheet based on the steel sheet heating temperature in the tempering zone measured by the temperature measuring device and the austenite fraction measured by the transformation ratio measuring device.
  • a continuous annealing facility for steel sheets having a heating zone, a soaking zone, a rapid heating zone, and a cooling zone in this order in a steel sheet transport direction;
  • a post-annealing heat treatment facility having at least a rapid cooling zone and a tempering zone in this order downstream of the cooling zone in the steel sheet transport direction;
  • Temperature measuring devices for the steel plate are installed at least in the rapid heating zone and the tempering zone;
  • a steel sheet manufacturing facility comprising: A mechanical property prediction unit that predicts mechanical property values including elongation value and hole expandability of the steel sheet based on the steel sheet heating temperature in the tempering zone measured by the temperature measuring device; a heat treatment condition calculation unit that corrects the mechanical property values predicted by the mechanical property prediction unit to target mechanical property values of the steel sheet and determines heat treatment conditions based on the corrected mechanical property values; and a heat treatment condition control unit that controls the steel sheet heating temperature in at least the rapid heating zone in the continuous annealing equipment based on the heat treatment conditions determined by the heat treatment condition calculation unit
  • a transformation rate measuring device is further provided which measures an austenite fraction of the steel sheet at at least one location from the soaking zone exit side to the tempering zone exit side in the steel sheet transport direction,
  • the steel plate manufacturing facility according to claim 4 or 5 wherein mechanical property values of the steel plate are predicted based on the steel plate heating temperature in the tempering zone measured by the temperature measuring device and the austenite fraction measured by the transformation ratio measuring device.
  • the present invention makes it possible to precisely obtain the desired mechanical properties for the manufactured steel plate.
  • FIG. 1 is a diagram for explaining a configuration of a steel sheet manufacturing facility according to the present invention.
  • FIG. 2 is a flow chart for explaining a method for controlling a steel sheet manufacturing facility according to the present invention.
  • FIG. 1 is a schematic diagram of a steel sheet manufacturing facility 1 according to an embodiment of the present invention.
  • a steel sheet S wound into a coil in a previous process is unwound by a payoff reel 2 and enters a looper 4 along the steel sheet conveying direction (see symbol X in FIG. 1).
  • the looper 4 is a facility for securing the surplus length of the steel sheet in order to continuously pass the steel sheet S when the steel sheets S (coils) are joined together by a welder 3.
  • the steel sheet S After passing through the looper 4, the steel sheet S enters a continuous annealing facility 5.
  • a heating zone 7 is installed at the entrance side of the continuous annealing facility 5.
  • a preheating zone 6 utilizing the combustion exhaust gas generated in the heating zone 7 may be installed before the heating zone 7.
  • the continuous annealing equipment 5 is configured with a heating zone 7, a soaking zone 8, a rapid heating zone 9, and a cooling zone 10 (first cooling zone 10A and second cooling zone 10B) in this order.
  • the cooling zone 10 may be configured with only the first cooling zone 10A in accordance with the cooling amount and strip threading speed required according to the desired mechanical properties, or may be configured with two cooling zones including the first cooling zone 10A and the second cooling zone 10B as shown in FIG.
  • a post-annealing heat treatment facility 11 Downstream of the cooling zone 10 in the steel sheet transport direction X, a post-annealing heat treatment facility 11 is installed, which is configured of a rapid cooling zone 15 and a tempering zone 16 in this order.
  • the post-annealing heat treatment facility 11 may be a steel sheet plating facility (galvannealed steel sheet), and may have a plating immersion zone (galvannealed steel sheet) 12 and a plating alloying zone 13 in this order before the rapid cooling zone 15 in the steel sheet transport direction X.
  • the steel sheet manufacturing facility 1 of the present invention may be a galvannealed steel sheet manufacturing facility or a galvannealed steel sheet manufacturing facility.
  • the post-annealing heat treatment equipment 11 may be provided with a holding zone 14.
  • the tempering zone 16 is configured with a heating device (tempering zone heating device) 17, a heat retention device (tempering zone heat retention device) 18, and a cooling device (tempering zone cooling device) 19, in this order.
  • the steel sheet manufacturing equipment 1 of the present invention is provided with temperature measuring devices 20 for measuring the surface temperature of the steel sheet at least in the rapid heating zone 9 and the tempering zone 16, making it possible to monitor the temperature change of the steel sheet.
  • temperature measuring devices 20 for measuring the surface temperature of the steel sheet at least in the rapid heating zone 9 and the tempering zone 16, making it possible to monitor the temperature change of the steel sheet.
  • at least one location between the exit side of the soaking zone 8 and the exit side of the tempering zone 16 may be provided with a transformation rate measuring device 21 for measuring the austenite fraction of the steel sheet 1.
  • the steel sheet manufacturing equipment 1 of the present invention may have a management device 30, which has a mechanical property prediction unit 31 that predicts mechanical property values including the elongation value and hole expansion ratio of the steel sheet S based on the steel sheet heating temperature in the tempering zone 16 measured by the temperature measurement device 20, a heat treatment condition calculation unit 32 that corrects the mechanical property values predicted by the mechanical property prediction unit 31 to target mechanical property values of the steel sheet S (target elongation value, target hole expansion ratio, etc.) and determines heat treatment conditions based on the corrected mechanical property values, and a heat treatment condition control unit 33 that controls the steel sheet heating temperature in at least the rapid heating zone 9 among the various facilities constituting the continuous annealing equipment 5 based on the heat treatment conditions determined by the heat treatment condition calculation unit 32.
  • a management device 30 which has a mechanical property prediction unit 31 that predicts mechanical property values including the elongation value and hole expansion ratio of the steel sheet S based on the steel sheet heating temperature in the tempering zone 16 measured by the temperature measurement device 20, a heat treatment condition calculation unit
  • the steel plate manufacturing equipment 1 of the present invention has a mechanical property prediction unit 31, a heat treatment condition calculation unit 32 and a heat treatment condition control unit 33, and is therefore capable of suppressing deviations in the mechanical properties of the obtained steel plate from the desired mechanical properties.
  • the functionality of these devices will be described in detail below with reference to FIG.
  • Pre-tropical zone 6 The steel sheet S discharged from the pay-off reel 2 at a temperature between room temperature and about 100° C. passes through the looper 4 and enters the preheating zone 6.
  • the preheating zone 6 is used to improve energy efficiency in the heating zone 7 and soaking zone 8 described below, but even if the steel sheet manufacturing equipment 1 has the preheating zone 6, heating of the steel sheet S such as a thin steel sheet may be started in the steel sheet conveying direction X from the next heating zone 7 without heating in the preheating zone 6.
  • the steel sheet S is heated in the preheating zone 6, the steel sheet S such as a thin steel sheet is heated to about 200°C.
  • a possible method for heating the preheating zone 6 is a method that utilizes high-temperature exhaust gas generated in the next heating zone 7, but is not particularly limited as long as the target temperature is reached.
  • the steel sheet S enters the heating zone 7, where the steel sheet temperature is heated to a heating temperature of 600°C or more, which is approximately the same as the annealing temperature (soaking temperature), in order to maximize the holding time in the soaking zone.
  • This heating temperature may be 700°C or less.
  • a direct-fire heating furnace method is preferably adopted because it has a high heating capacity and allows the volume of the furnace to be small, and when plating the steel sheet S, it is possible to flexibly control the oxidation-reduction reaction of the steel sheet surface to ensure plating properties in the subsequent process. This method makes it possible to heat the steel sheet to the desired temperature in a short time, making it easy to control the state of the steel sheet surface.
  • the steel sheet heated in the heating zone 7 is maintained or gradually heated.
  • a heating method for the soaking zone 8 it is preferable to adopt a radiant heating method (radiant tube heating) using gas combustion because of its high efficiency and heating uniformity, but there is no particular limitation.
  • the final annealing temperature is determined in the subsequent rapid heating zone 9. If the fine ⁇ phase is heated to the ⁇ / ⁇ two-phase region in the subsequent rapid heating zone 9 in a short time, the transformation from ⁇ phase to ⁇ phase will progress rapidly, making it difficult to obtain a structure with the target fraction.
  • the recrystallization of the ⁇ phase will progress and slow heating or holding at a temperature equal to or higher than the A1 transformation point will be performed.
  • the residence time in the recrystallization temperature range can be secured and the remaining of the unrecrystallized ⁇ phase can be suppressed.
  • the residence time in this temperature range is preferably 20 seconds or more.
  • the residence time in this temperature range is preferably 60 seconds or less.
  • the residence time in the recrystallization temperature range is secured for the above-mentioned time (20 seconds or more, or even 60 seconds or less).
  • the steel may be slowly heated to a temperature equal to or higher than the A1 transformation point as long as the temperature is equal to or lower than the target annealing temperature described below.
  • the heating rate during slow heating within the recrystallization temperature range is preferably 5° C./s or less. This is because there is a concern that if the steel is heated at a rate exceeding 5° C./s, it may not be possible to suppress the remaining unrecrystallized ⁇ phase.
  • Rapid heating zone 9 After the recrystallization of the ⁇ phase has progressed in the soaking zone 8, the steel sheet S needs to be heated in the rapid heating zone 9 to a target annealing temperature set in a temperature range higher than the A1 transformation point of the steel sheet S and lower than the A3 transformation point. Since the temperature reached at this time has a large effect on the final material properties, it is preferable to select an induction heating method that responds quickly to temperature control as the heating method. In addition, since the steel sheet S is heated to a high temperature above the A1 transformation point, it is preferable to use a transverse type induction heating device because the temperature exceeds the Curie point at which the magnetism of the steel sheet S changes.
  • the heating rate is 10° C./s or more. It is also desirable to reduce the length of the equipment and reduce construction costs. Taking the equipment costs into consideration, it is more preferable to set the heating rate at 20° C./s or more. On the other hand, when the heating rate is increased to increase the temperature rise, local high temperature areas are generated in the width direction, which impairs the uniformity of the material of the entire steel sheet, so the heating rate is preferably 200° C./s or less.
  • the heating rate is more preferably 100° C./s or less.
  • the transformation from ⁇ -phase to ⁇ -phase may not reach equilibrium immediately after heating. In this case, if the steel is held near the target annealing temperature, the transformation from ⁇ -phase to ⁇ -phase may proceed further even if the steel is held isothermally. Since the holding time varies depending on the line speed, there is a concern that the material control may become complicated by holding the steel near the target annealing temperature.
  • a rapid heating device such as an induction heating device used in the rapid heating zone 9 is preferably installed immediately before the cooling zone 10 regardless of the structure of the soaking zone 8. If it is an addition to an existing furnace, it may be installed at the connection between the soaking zone 8 and the cooling zone 10. In addition, if the soaking zone 8 is divided into multiple sections, multiple rapid heating devices may be installed in places other than immediately before the cooling zone 10.
  • a first rapid heating device installed after the upstream soaking zone 8 heats the steel sheet from the low temperature section to the high temperature section, and a second rapid heating device for the purpose of temperature adjustment for material control is installed after the downstream soaking zone 8 and immediately before entering the cooling zone 10.
  • Cooling Zone 10 (First Cooling Zone 10A, Second Cooling Zone 10B) After being heated to the target annealing temperature in the rapid heating zone 9, the steel sheet S is transported to the cooling zone 10 and cooled. It is preferable to set the cooling rate in order to prevent ferrite transformation during cooling due to insufficient cooling rate and to prevent rapid bainite transformation after cooling is stopped due to excessive cooling rate.
  • the cooling rate is preferably in the range of 5°C/s or more. Also, the cooling rate is preferably in the range of 30°C/s or less.
  • the cooling stop temperature is preferably in the range of the martensite transformation start temperature or more and 550°C or less, and more preferably in the range of 450°C or more and 550°C or less.
  • the holding time after reaching the cooling stop temperature is preferably 1 second or more, more preferably 20 seconds or more, and is preferably 100 seconds or less, more preferably 50 seconds or less.
  • the cooling method may be, but is not limited to, gas jet cooling, which causes a compressed gas jet to collide with the material, roll cooling, which causes cooling by contact with a roll through which a coolant is passed, water cooling using a water jet, mist cooling, which is a mixture of compressed gas and minute water droplets, etc.
  • gas jet cooling was adopted, which can ensure a target cooling rate while preventing unstable temperature changes due to boiling and controlling the cooling stop temperature with high precision.
  • the cooling zone 10 may be divided into two zones, a first cooling zone (rapid cooling zone) 10A and a second cooling zone (slow cooling/holding zone) 10B.
  • the steel sheet S is transported to a post-annealing heat treatment facility 11.
  • the post-annealing heat treatment facility 11 may be a steel sheet plating facility, and the steel sheet S is transported to this steel sheet plating facility and subjected to a plating treatment (e.g., a zinc plating treatment) in a plating immersion zone 12.
  • the plating method may be a hot-dip galvanizing method in which the steel sheet is immersed in a galvanizing bath containing molten zinc.
  • the post-annealing heat treatment equipment (steel sheet plating equipment) 11 may be equipped with a device for scraping off excess molten zinc.
  • a plating alloying zone 13 for promoting the Zn-Fe alloying reaction may be provided downstream of the plating immersion zone 12. Since the temperature of the steel sheet at this time is lowered to about 430°C, the temperature is raised to a temperature (about 500°C) required for the alloying reaction in the plating alloying zone 13.
  • the heating method in the plating alloying zone 13 may be a gas heating method using combustion exhaust gas, induction heating, electric heating, or the like, but is not particularly limited. In the present invention, an induction heating method that has little effect on the plating surface and allows fine output control may be adopted.
  • a holding zone 14 may be provided downstream of the plating alloying zone 13 in order to ensure the time required for the alloying reaction to proceed.
  • Rapid cooling zone 15 When the steel sheet S is subjected to a plating treatment (when the post-annealing heat treatment equipment 11 is used as a steel sheet plating equipment), a rapid cooling zone 15 is provided following the plating alloying zone 13 or the holding zone 14 in order to transform the untransformed austenite phase into a martensite structure after the plating alloying reaction is completed. When the steel sheet S is not subjected to a plating treatment, the rapid cooling zone 15 may be provided downstream of the cooling zone 10 in the steel sheet transport direction X.
  • the cooling method in the rapid cooling zone 15 may be gas jet cooling in which a compressed gas jet is collided, water cooling by a water jet, mist cooling in which compressed gas and minute water droplets are mixed, and the like, but is not particularly limited.
  • a combination of mist cooling and gas jet cooling may be used in order to realize rapid cooling while controlling the cooling stop temperature with high precision.
  • the cooling rate at this time is preferably 50°C/s or higher.
  • the cooling rate is preferably 1000°C/s or less because excessively rapid cooling may cause the flatness of the steel sheet to be lost due to thermal deformation during cooling.
  • the cooling stop temperature is preferably 200°C or less to prevent self-tempering after cooling.
  • tempering zone 16 After the martensite structure is created in the rapid cooling zone 15, tempering is performed in the tempering zone 16.
  • the tempering zone 16 is configured in the following order from the inlet in the steel sheet conveying direction X: a heating device (tempering zone heating device) 17, a heat retention device (tempering zone heat retention device) 18, and a cooling device (tempering zone cooling device) 19.
  • the heating temperature in the heating device 17 may be set from the viewpoint of obtaining the effect of improving toughness by tempering while maintaining the martensite structure.
  • the heating temperature in the heating device 17 is preferably 250°C or higher, more preferably 300°C or higher.
  • the heating temperature in the heating device 17 is preferably 500°C or lower, more preferably 400°C or lower.
  • the temperature of the steel sheet heated in the heating device 17 is maintained, and the retention time in the heat retention device 18 may be set from the viewpoint of preventing excessive expansion of the line length while obtaining a sufficient effect of tempering.
  • the retention time in the heat retaining device 18 is preferably 20 seconds or more, more preferably 30 seconds or more, and is preferably 100 seconds or less, more preferably 60 seconds or less.
  • the cooling device 19 cools the steel sheet S to room temperature. With this configuration, an appropriate tempering process can be performed, and the target mechanical properties can be obtained.
  • the heating device 17 can be selected from methods such as gas burners, electrical heating, and induction heating, but in the present invention, an induction heating method may be adopted from the viewpoint of controllability.
  • the heat retention device 18 preferably adopts a radiant heating method from the heater body and furnace wall using an electric heater, but is not particularly limited.
  • the furnace temperature may be controlled to be approximately the same as the target tempering temperature.
  • the cooling device 19 is preferably a mist cooling method, and a gas jet device is preferably also installed to remove moisture attached to the surface at the same time as cooling, but is not particularly limited as long as it can be adjusted to the target cooling rate.
  • the method of temperature measurement by the temperature measuring device 20 is not particularly limited, but it is preferable to use a radiation thermometer that senses infrared rays emitted by the steel sheet to measure the temperature. Since the radiation thermometer is affected by the reflected light of infrared rays emitted by the surrounding furnace body, a cover may be provided between the measurement unit and the detection unit of the radiation thermometer. In addition, since the radiation thermometer is also affected by the emissivity of the steel sheet surface, a multiple reflection type measurement method that utilizes a wedge-shaped space between the in-furnace transport roll and the steel sheet S may be used as the temperature measurement method.
  • Transformation rate measuring device 21 It is preferable that one or more transformation rate measuring devices 21 for measuring the austenite fraction of the steel sheet S are provided from the exit side of the soaking zone 8 to the exit side of the tempering zone 16 . This is because predicting the mechanical property values (e.g., elongation value, hole expansion ratio) of the steel sheet S based on the measured austenite fraction improves the prediction accuracy of the mechanical property values of the steel sheet S, compared to predicting the mechanical property values such as the elongation value and hole expansion ratio of the steel sheet S only from the steel sheet heating temperature in the tempering zone 16.
  • the mechanical property values e.g., elongation value, hole expansion ratio
  • This transformation ratio measuring device 21 makes it possible to obtain information on the fractions (transformation ratios) of the ⁇ phase and the ⁇ phase of the steel sheet after the target annealing temperature is reached.
  • This transformation rate measuring device 21 is provided for the purpose of adjusting the operating conditions of the continuous annealing equipment 5 based on the measured austenite fraction, and makes it possible to stably obtain desired mechanical properties.
  • the transformation rate measuring device 21 may be a magnetic detector, i.e., a device for measuring the magnetic transformation rate of the steel sheet S (steel strip), and can measure the austenite fraction as a magnetic transformation rate measuring device composed of a driving coil that generates a magnetic field and a detection coil that measures the magnetic field that has passed through the steel sheet S.
  • a method applying an X-ray diffraction method may be adopted.
  • the ⁇ phase and the ⁇ phase each produce a diffraction peak at a unique angle when an X-ray is irradiated onto a steel sheet due to the difference in crystal structure between the phases, and the austenite fraction can be quantified based on the intensity of this diffraction peak.
  • the elongation value is determined, for example, based on the test method of JIS Z2241 (2011).
  • the samples for measuring the elongation value are preferably taken from the steel sheet shear-cut after the treatment by the tempering zone cooling device 19 in the present invention and immediately before winding by the coiler. For each coil, samples are taken from the head and tail ends of the coil during operation.
  • the hole expansion ratio is determined, for example, based on the test method of JIS Z2256 (2010).
  • the samples for measuring the hole expansion ratio are preferably taken from the shear-cut steel sheet immediately before winding on the coiler. For each coil, samples are taken from the head and tail ends of the coil during operation.
  • FIG. 2 is a flow chart for explaining a method for controlling a steel sheet manufacturing facility according to the present invention.
  • the configurations of the mechanical property prediction unit 31, the heat treatment condition calculation unit 32, and the heat treatment condition control unit 33 of the management device 30 and the processes performed by these units will be described with reference to the flowchart of FIG.
  • Step S1 mechanical property prediction unit 31, mechanical property prediction step
  • step S2 mechanical property prediction step
  • the coil requires a change in manufacturing conditions at the joint portion of the steel sheet S (coil), i.e., at the connection position between the preceding material and the succeeding material (step S2). If a change in manufacturing conditions is not required, the steel sheet manufacturing equipment 1 continues manufacturing the steel sheet S without changing the manufacturing conditions.
  • This determination in step S2 may be made by a control unit (not shown) in the management device 30 of the steel sheet manufacturing equipment 1, or may be made by another control unit (not shown) of the steel sheet manufacturing equipment 1.
  • the management device 30 determines that the manufacturing conditions need to be changed.
  • the mechanical property prediction unit 31 predicts the mechanical property values of the steel sheet S (successor material) based on the operating conditions (steel sheet heating temperature) in the tempering zone (reheating zone) 16. Examples of the mechanical property values include elongation value and hole expansion ratio.
  • Other operational conditions input to the mechanical property prediction unit 31 include the operational conditions of the equipment downstream of the rapid heating zone 9, and the mechanical properties are predicted when the subsequent material completes the process up to the tempering zone (reheating zone) 16 under these operational conditions.
  • the austenite fraction result measured by the transformation rate measurement device 21 is further added to the operational conditions, and the mechanical property values are predicted based on this austenite fraction and the operational conditions, thereby improving the prediction accuracy of the mechanical property values. Since temperature measurement alone results in indirect prediction of the structure, by further directly measuring the austenite fraction, the prediction accuracy of the mechanical properties after the heat treatment process is improved.
  • the method of predicting mechanical properties performed by the mechanical property prediction unit 31 with regard to elongation value and hole expansion ratio, for example, a method using an empirical formula calculated by performing regression analysis based on the results of heat treatment experiments, or an elongation value prediction database constructed using a data science method based on operating conditions and material measurement results, etc., can be considered, but is not particularly limited.
  • a regression analysis method based on the experimental results of heat treatment of each steel sheet can be used.
  • heat treatment simulating an actual machine is performed offline or experimentally, and in this case, regression analysis is performed based on the results of the test method of JIS Z2241 (2011) for elongation value, and regression analysis is performed based on the results of the test method of JIS Z2256 (2010) for hole expansion ratio to predict elongation value and hole expansion ratio.
  • the mechanical property prediction unit 31 can record data in a memory unit 34 having the above-mentioned elongation value prediction database, and can predict the elongation value, etc. of the steel sheet S based on the data.
  • Heat treatment condition calculation unit 32, heat treatment condition calculation step S4 In the heat treatment condition calculation step S4, the mechanical property values of the steel sheet S (successor material) predicted by the mechanical property prediction unit 31 in the mechanical property prediction step S3 are corrected to target mechanical property values, and the heat treatment conditions in the continuous annealing equipment 5 are calculated based on the corrected mechanical property values.
  • the term "correction” used here refers to changing the mechanical characteristic values for calculating the heat treatment conditions from predicted mechanical characteristic values to preset target mechanical characteristic values.
  • the heat treatment condition calculation unit 32 determines that the target mechanical characteristic values can be corrected by simply changing the steel sheet heating conditions in the rapid heating zone 9 (step S5), it calculates and determines the conditions of the steel sheet heating temperature in the rapid heating zone 9 (step S6a).
  • the heat treatment condition calculation unit 32 calculates the steel sheet cooling conditions in the cooling zone 10 in addition to the heating temperature in the rapid heating zone 9 (step S6b).
  • a method for determining the heat treatment conditions for example, an empirical formula calculated by performing regression analysis based on the results of an experiment, or a method using a heat treatment condition database constructed by a data science method based on the operating conditions and the material measurement results can be considered, but is not particularly limited.
  • a regression analysis method based on the experimental results of the heat treatment of each steel sheet can be used.
  • a heat treatment simulating an actual machine is performed offline or experimentally, and a regression analysis is performed based on the results to predict the elongation value, hole expansion ratio, etc.
  • the cooling conditions of the steel sheet in the cooling zone 10 are not particularly limited, but include, for example, a cooling stop temperature and a cooling rate in the cooling zone 10.
  • the cooling stop temperature and the cooling rate can be obtained by measuring with a thermometer installed in the cooling zone 10.
  • the heat treatment condition calculation unit 32 can record data in the memory unit 34 having the above-mentioned heat treatment condition database, and can calculate and determine the heat treatment conditions for the steel sheet S based on the data.
  • the heat treatment condition control unit 33 controls the steel sheet heating temperature in the rapid heating zone 9, or further the steel sheet cooling conditions in the cooling zone 10, based on the heat treatment conditions determined by the heat treatment condition calculation unit 32.
  • the mechanical properties (elongation value, hole expansion ratio) of the steel sheet S (trailing zone) can be controlled with greater precision.
  • the management device 30 judges whether the heat treatment conditions determined based on the steel sheet heating temperature measured in the tempering zone (reheat zone) 16 satisfy the target heat treatment conditions of the following material (step S8). If it is judged that the target heat treatment conditions of the following material are satisfied, the management device 30 stops the control in the above-mentioned mechanical property prediction step S3, heat treatment condition calculation step S4, and heat treatment condition control step S7, and adjusts the heat treatment conditions (steady heat treatment conditions) other than the above target heat treatment conditions for the following material (transition to a steady state).
  • the steady state here refers to a state in which the heat treatment conditions, including the target heat treatment conditions, have reached the desired conditions. This ends the process of controlling the steel sheet manufacturing equipment in the present invention. On the other hand, if it is judged that the target heat treatment conditions of the following material are not satisfied, mechanical property prediction is performed again (step S3).
  • the control delay in the tempering zone 16 can be cancelled out by inputting information on the steel sheet heating temperature to the mechanical property prediction unit 31, calculating the heat treatment conditions in the continuous annealing equipment 5 required to correct the values to the target mechanical property values in the heat treatment condition calculation unit 32, and controlling the heat treatment conditions in the rapid cooling zone 9 and/or cooling zone 10 by the heat treatment condition control unit 33.
  • the deviation of the mechanical properties of the resulting steel plate from the desired mechanical properties can be reduced, and the target mechanical properties can be stably obtained in the longitudinal direction compared to conventional steel plate manufacturing equipment.
  • Thin steel sheets were manufactured using the steel sheet manufacturing equipment according to the embodiment of the present invention described above.
  • three types of products with strength levels of 780 MPa, 980 MPa, and 1180 MPa were manufactured in succession. Five pieces of each strength were passed through in succession, and 10 sets of 15 pieces of the three types were manufactured in one set, for a total of 150 pieces in each example.
  • the plate thickness was in the range of 1.0 to 2.0 mm, and the manufacturing order was determined so that the plate thickness was approximately constant within the set, and the sets in which the plate thickness gradually changed were connected to manufacture.
  • products with the same strength included in the same set were all manufactured using slabs cast in different lots in a continuous casting machine. More specifically, although within the manufacturing control range, the chemical compositions of each slab vary and the transformation behavior is not uniform.
  • Each slab was hot-rolled, pickled, annealed and cold-rolled as required, and then heat-treated using a conventional annealing facility or the annealing facility of the present invention, followed by cooling, plating and other post-treatments.
  • the measurement results of samples taken 10 m from the coil tip of the final product were used as representative values to examine the characteristic variation between products of the same strength.
  • samples for analysis were taken every 10 m within a range of 100 m before and after the connection point, and the area where the mechanical properties did not meet the shipping standard was examined, and the ratio of the shippable length to the original coil length was calculated as the yield of the connection. A connection yield of 90% or more was considered to be acceptable.
  • the tensile test specimen was JIS No. 5, and the tensile test was performed in accordance with JIS Z2241 (2011).
  • the required strength ranges are 780 MPa or more, 980 MPa or more, and 1180 MPa or more, respectively, and the ductility is 17% or more, 15% or more, and 12% or more.
  • the hole expansion test was performed in accordance with JIS Z2256 (2010). The required hole expansion ratios are 65% or more, 50% or more, and 40% or more for the strengths of 780 MPa class, 980 MPa class, and 1180 MPa class, respectively.
  • the operating conditions of the annealing furnace were controlled so that the steel plate temperature was within the specified range for each product.
  • the line speed was in the range of 60 to 120 mpm, and the change in steel plate temperature due to plate thickness was controlled.
  • the steel plate temperature at the exit of the heating zone was kept in the range of 600 to 700°C, and the annealing temperature was in the range of 750 to 870°C.
  • the furnace temperature in the soaking zone was controlled so that the steel plate temperature at the exit was the target value. After cooling, hot-dip galvanizing, alloying treatment, etc., multiple material test pieces were taken from the final product to investigate the variation in mechanical properties.
  • Table 1 shows the production results under each production condition.
  • Comparative Example 1 is an example in which a product was manufactured from the above-mentioned material by using a conventional CGL described in Cited Document 1, which is composed of a preheating zone, a heating zone, a soaking zone, a cooling zone, a plating zone, a plating alloying zone, and a final cooling zone.
  • Comparative Example 2 is an example in which a tempering zone was provided after the plating alloying zone in comparison with Comparative Example 1.
  • Comparative Example 3 is an example in which a rapid heating zone having an induction heating device is provided at the outlet of the uniform heating zone of Comparative Example 2.
  • Comparative Example 4 is an example in which a transformation rate measuring device was installed downstream of the induction heating device of Comparative Example 3. In these comparative examples, even when a tempering zone (reheating zone) was used, control of the continuous annealing equipment based on the steel sheet heating temperature in the tempering zone was "not performed.”
  • tempering in the tempering zone improved ductility compared to Comparative Example 1, making it possible to manufacture products that met the pass criteria; however, delays in controlling the heating temperature in the annealing furnace and the tempering zone meant that the steel sheet temperature control was off target in many areas. Furthermore, there was a large variation in mechanical properties even within the coil, and there were large areas in the joints that did not meet the material testing criteria, resulting in low yields at the joints.
  • Example 1 shows the results of manufacturing a product from the above-mentioned material using the method for controlling steel sheet manufacturing equipment according to the present invention.
  • Example 3 is an example in which a transformation rate measuring device is installed downstream of the induction heating device of Example 1.
  • control of the continuous annealing equipment based on the steel sheet heating temperature in the tempering zone was "implemented.”
  • the TS variation was further improved by controlling the annealing temperature based on the austenite fraction measured by the transformation rate measuring device.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Control Of Heat Treatment Processes (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)

Abstract

La présente invention concerne une technique permettant d'obtenir avec précision, pour une tôle d'acier à produire, des caractéristiques mécaniques souhaitées.　Un procédé de commande d'une installation de production de tôle d'acier comprend : une étape de prédiction de caractéristiques mécaniques (S3) consistant à prédire des valeurs de caractéristiques mécaniques comprenant la valeur d'allongement et le degré d'expansion de trou d'une tôle d'acier, sur la base d'une température de chauffage de tôle d'acier dans une zone de trempe (16) mesurée par un dispositif de mesure de température (20) ; une étape de calcul de condition de traitement thermique (S4) consistant à corriger les valeurs de caractéristiques mécaniques prédites dans l'étape de prédiction de caractéristiques mécaniques (S3) pour cibler des valeurs de caractéristiques mécaniques de la tôle d'acier (S) et à déterminer une condition de traitement thermique sur la base des valeurs de caractéristiques mécaniques corrigées ; et une étape de commande de condition de traitement thermique (S8) consistant à réguler, sur la base de la condition de traitement thermique déterminée dans l'étape de calcul de condition de traitement thermique (S4), la température de chauffage de tôle d'acier dans au moins une zone de chauffage rapide (9) dans un équipement de recuit continu.
PCT/JP2024/029233 2023-12-14 2024-08-19 Procédé de commande d'installation de production de tôle d'acier et installation de production de tôle d'acier Pending WO2025126572A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006328544A (ja) * 2006-07-13 2006-12-07 Jfe Steel Kk 高強度冷延鋼板の製造方法
JP2012201956A (ja) * 2011-03-28 2012-10-22 Kobe Steel Ltd 冷延鋼板の製造条件決定方法、製造条件決定装置および製造条件決定プログラム
JP2022024340A (ja) * 2020-07-16 2022-02-09 Ｊｆｅスチール株式会社 鋼帯の材質予測方法、材質制御方法、製造方法および材質予測モデルの生成方法
WO2022209364A1 (fr) * 2021-03-30 2022-10-06 Ｊｆｅスチール株式会社 Équipement de recuit continu, procédé de recuit continu, procédé de fabrication de tôle d'acier laminée à froid et procédé de fabrication de tôle d'acier plaquée
CN115392104A (zh) * 2021-05-24 2022-11-25 上海梅山钢铁股份有限公司 一种基于退火工艺预测冷轧连续退火带钢力学性能的方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006328544A (ja) * 2006-07-13 2006-12-07 Jfe Steel Kk 高強度冷延鋼板の製造方法
JP2012201956A (ja) * 2011-03-28 2012-10-22 Kobe Steel Ltd 冷延鋼板の製造条件決定方法、製造条件決定装置および製造条件決定プログラム
JP2022024340A (ja) * 2020-07-16 2022-02-09 Ｊｆｅスチール株式会社 鋼帯の材質予測方法、材質制御方法、製造方法および材質予測モデルの生成方法
WO2022209364A1 (fr) * 2021-03-30 2022-10-06 Ｊｆｅスチール株式会社 Équipement de recuit continu, procédé de recuit continu, procédé de fabrication de tôle d'acier laminée à froid et procédé de fabrication de tôle d'acier plaquée
CN115392104A (zh) * 2021-05-24 2022-11-25 上海梅山钢铁股份有限公司 一种基于退火工艺预测冷轧连续退火带钢力学性能的方法

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