WO2022201565A1 - Method for producing hot-rolled steel sheet, method for predicting temperature history of hot-rolled steel sheet, and method for predicting hardened section of hot-rolled steel sheet - Google Patents

Method for producing hot-rolled steel sheet, method for predicting temperature history of hot-rolled steel sheet, and method for predicting hardened section of hot-rolled steel sheet Download PDF

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Publication number
WO2022201565A1
WO2022201565A1 PCT/JP2021/022717 JP2021022717W WO2022201565A1 WO 2022201565 A1 WO2022201565 A1 WO 2022201565A1 JP 2021022717 W JP2021022717 W JP 2021022717W WO 2022201565 A1 WO2022201565 A1 WO 2022201565A1
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WIPO (PCT)
Prior art keywords
coil
unevenness
hot
temperature history
winding
Prior art date
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PCT/JP2021/022717
Other languages
French (fr)
Japanese (ja)
Inventor
浩樹 福島
祐太 佐野
正宜 小林
冬馬 北川
俊夫 村上
崇広 小原
昌広 乾
健之 飯島
貴志 寺岡
拓馬 米田
晃平 小渡
駿 原田
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株式会社神戸製鋼所
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Application filed by 株式会社神戸製鋼所 filed Critical 株式会社神戸製鋼所
Priority to KR1020237034182A priority Critical patent/KR20230154962A/en
Priority to US18/551,907 priority patent/US20240167117A1/en
Priority to CN202180096254.6A priority patent/CN117098615A/en
Publication of WO2022201565A1 publication Critical patent/WO2022201565A1/en

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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B38/00—Methods or devices for measuring, detecting or monitoring specially adapted for metal-rolling mills, e.g. position detection, inspection of the product
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B38/00—Methods or devices for measuring, detecting or monitoring specially adapted for metal-rolling mills, e.g. position detection, inspection of the product
    • B21B38/006—Methods or devices for measuring, detecting or monitoring specially adapted for metal-rolling mills, e.g. position detection, inspection of the product for measuring temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C47/00—Winding-up, coiling or winding-off metal wire, metal band or other flexible metal material characterised by features relevant to metal processing only
    • B21C47/02—Winding-up or coiling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C47/00—Winding-up, coiling or winding-off metal wire, metal band or other flexible metal material characterised by features relevant to metal processing only
    • B21C47/26—Special arrangements with regard to simultaneous or subsequent treatment of the material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C51/00—Measuring, gauging, indicating, counting, or marking devices specially adapted for use in the production or manipulation of material in accordance with subclasses B21B - B21F
    • 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
    • B21B2001/225—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 by hot-rolling

Definitions

  • the present invention relates to a hot-rolled steel sheet manufacturing method, a hot-rolled steel sheet temperature history prediction method, and a hot-rolled steel sheet hardened portion prediction method.
  • a hot-rolled steel sheet is manufactured by winding a hot-rolled steel strip into a coil and cooling the wound coil to about room temperature.
  • This hot-rolled steel sheet is drawn out again into a strip shape, subjected to pickling and cold rolling, and turned into a cold-rolled steel sheet.
  • a problem in the production of this cold-rolled steel sheet is breakage of the steel material during threading. When the steel material breaks, it is necessary to stop the threading line and carry out restoration work, which increases the cost for restoration and lowers the production efficiency. Moreover, breakage of the steel material causes equipment failure.
  • One of the causes of breakage during cold rolling of highly hardenable steel is cracks at the edges of the steel. If a crack occurs at the edge of the steel material during cold rolling, stress concentrates on the cracked portion during threading, the crack grows, and the steel material is likely to break.
  • the cause of these cracks is the poor winding shape of the hot-rolled coil. That is, if there is a winding defect in the coil after hot rolling, the unevenness of the end face of the coil increases. If there is a large protrusion on the coil end surface, the protrusion functions as a fin, thereby increasing the cooling rate of the protrusion during cooling of the coil.
  • the cooling rate of the projections increases, hard phases such as bainite and martensite tend to coexist in the projections. As a result, voids are generated during cold rolling of the steel material, and the growth of these voids tends to cause cracks at the ends.
  • the inventors found that by predicting the temperature history of the unevenness (especially the protrusions) of the coil end face, it is possible to detect in advance the possibility of steel breakage in the post-process.
  • Patent Document 1 temperature unevenness on a run-out table (ROT) of a hot-rolled steel sheet is predicted, and the temperature of the rolled steel sheet before being wound on a coiler is reduced so that the predicted temperature unevenness is reduced. Controlling manufacturing conditions is described.
  • ROT run-out table
  • Patent Document 2 in calculating the telescopic amount of the coil end face by scanning the end face of a metal plate coil with a rangefinder over the coil diameter and measuring the distance between the rangefinder and the coil end face, the coil end A technique is described to identify whether the part measurement is a tongue-shaped part or a telescopic part.
  • the difference in the measured distance between the innermost wound metal plates at both ends of the coil inner diameter or the difference in the measured distance between the outermost wound metal plates at both ends of the coil outer diameter exceeds each threshold. It is described that the telescopic amount of the coil is calculated by excluding the innermost and/or outermost winding distance data for which the tongue shape part of the coil end is measured. ing.
  • Patent Documents 1 and 2 do not consider the relationship between the unevenness of the coil end face and the cracks at the coil end.
  • the present invention has been made based on the circumstances described above, and aims to provide a method for manufacturing a hot-rolled steel sheet and a method for predicting the temperature history of a hot-rolled steel sheet, which can predict the temperature history of the unevenness of the coil end face. aim.
  • Another object of the present invention is to provide a method for predicting a hardened portion of a hot-rolled steel sheet, which can predict the presence or absence of breakage of the steel material in the post-process based on the temperature history of the unevenness of the end face of the coil.
  • a method for manufacturing a hot-rolled steel sheet includes a measurement step of measuring the surface temperature of a hot-rolled steel strip, and a case in which the steel strip is wound into a coil shape without unevenness on the end face.
  • the method for manufacturing the hot-rolled steel sheet can predict the temperature history of the irregularities on the end face of the coil formed by winding the steel strip as it cools.
  • the method for manufacturing the hot-rolled steel sheet includes a second calculation step of calculating the phase transformation rate using the temperature history predicted in the first prediction step, and using the phase transformation rate calculated in the second calculation step. It is preferable to further include a second prediction step of predicting the hardened portion of the steel strip.
  • the hot-rolled steel sheet manufacturing method includes the second calculation step and the second prediction step, so that it is possible to predict the presence or absence of breakage of the steel material in the subsequent steps.
  • the derivation step it is preferable to obtain the size of the unevenness based on the median value of the measured values of the displacement gauge. In this way, in the derivation step, by obtaining the size of the unevenness based on the median value of the measured values of the displacement gauge, the temperature history of the unevenness of the end face of the coil can be easily and accurately measured in a cooled state. Easy to predict.
  • the derivation step it is preferable to obtain the size of the unevenness using a two-dimensional coordinate system defined by the projecting direction of the unevenness and the scanning direction of the displacement meter.
  • the size of the unevenness is obtained using a two-dimensional coordinate system defined by the projecting direction of the unevenness and the scanning direction of the displacement meter, whereby the unevenness of the end surface of the coil is obtained. It is easy to predict the temperature history in the cold state easily and accurately.
  • a temperature history prediction method for a hot-rolled steel sheet comprises a measuring step of measuring the surface temperature of a hot-rolled steel strip, and winding the steel strip into a coil shape having no unevenness on the end face.
  • the temperature history prediction method for the hot-rolled steel sheet can predict the temperature history of the irregularities on the end face of the coil formed by winding the steel strip as it cools.
  • a method for predicting a hardened portion of a hot-rolled steel sheet comprises a measuring step of measuring the surface temperature of a hot-rolled steel strip; A first calculation step of calculating the temperature history in a cooled state after winding assuming that the steel strip was taken based on the surface temperature measured in the measurement step; and a derivation step of scanning the end face of the coil wound in the winding step with a displacement meter and deriving the size of the unevenness of the end face over the radius of the coil.
  • the hot-rolled steel sheet hardened portion prediction method can predict the presence or absence of breakage of the steel material in the post-process based on the temperature history of the unevenness of the end face of the coil.
  • the method for manufacturing a hot-rolled steel sheet according to one aspect of the present invention and the temperature history prediction method for a hot-rolled steel sheet according to another aspect of the present invention can predict the temperature history of the unevenness of the end surface of the coil.
  • a method for predicting hardened portions of a hot-rolled steel sheet according to another aspect of the present invention can predict the presence or absence of breakage of a steel material in a post-process based on the temperature history of irregularities on the end face of a coil.
  • FIG. 1 is a flowchart showing a method for manufacturing a hot-rolled steel sheet according to one embodiment of the present invention.
  • FIG. 2 is a schematic diagram showing a hot-rolled steel sheet manufacturing facility used in the hot-rolled steel sheet manufacturing method of FIG.
  • FIG. 3 is an explanatory diagram of the temperature history calculation procedure of the virtual coil in the first calculation step of the hot-rolled steel sheet manufacturing method of FIG. 1 .
  • FIG. 4 is a schematic diagram showing the scanning position of the end surface of the coil by the displacement gauge in the derivation step of the hot-rolled steel sheet manufacturing method of FIG.
  • FIG. 5 is an explanatory diagram of a derivation procedure of the size of irregularities in the derivation step of the hot-rolled steel sheet manufacturing method of FIG. 1 .
  • FIG. 1 is a flowchart showing a method for manufacturing a hot-rolled steel sheet according to one embodiment of the present invention.
  • FIG. 2 is a schematic diagram showing a hot-rolled steel sheet manufacturing facility used in the hot-rolled steel sheet
  • FIG. 6 is a flowchart showing a method for manufacturing a hot-rolled steel sheet according to a different form from the method for manufacturing a hot-rolled steel sheet in FIG.
  • FIG. 1 is a graph showing a temperature history in a naturally cooled state with reference to immediately after winding of the upper end surface of the virtual coil according to the first calculation step of 1.
  • FIG. FIG. 10 is a graph showing measurement results of the shape of unevenness of the end surface of the coil by the displacement meter and the result of derivation of the size of unevenness of the end surface of the coil by the derivation unit in derivation step 1;
  • FIG. 1 is a graph showing a temperature history in a naturally cooled state with reference to immediately after winding of the upper end surface of the virtual coil according to the first calculation step of 1.
  • FIG. FIG. 10 is a graph showing measurement results of the shape of unevenness of the end surface of the coil by the displacement meter and the result of derivation of the size of unevenness of the end surface of the coil by the deriv
  • FIG. 1 is a graph showing the temperature history of the end surface of the coil in a naturally cooled state with reference to immediately after winding of the end surface predicted in the first prediction step of 1, and the measured value of the temperature of this end surface.
  • FIG. 10 shows No. 2 is a graph showing the temperature history of the upper end face in a naturally cooled state with reference to immediately after winding of the virtual coil calculated in the first calculation step of 2.
  • FIG. 11 shows No. 10 is a graph showing measurement results of the shape of unevenness of the end surface of the coil by the displacement gauge and derivation results of the size of unevenness of the end surface of the coil by the derivation unit in the derivation step 2;
  • FIG. 12 shows No. 2 is a graph showing the temperature history in the cold state immediately after winding of the end face of the coil predicted in the first prediction step of 2, and the measured value of the temperature of this end face.
  • Derivation step S4 and a step of predicting the temperature history of the unevenness in a cooled state using the temperature history calculated in the first calculation step S2 and the size of the unevenness derived in the derivation step S4 (first 1 prediction step S5).
  • the measuring step S1, the first calculating step S2, the winding step S3, the deriving step S4, and the first predicting step S5 constitute a temperature history prediction method for a hot rolled steel sheet according to one aspect of the present invention.
  • coil shape means spiral shape when viewed in the axial direction.
  • Coil end face refers to a plane perpendicular to the central axis of the coil. That is, the term “end face of the coil” refers to a face formed by the ends of the steel strip in the width direction.
  • the hot-rolled steel sheet manufacturing method by predicting the temperature history of the unevenness of the end face of the coil, the possibility of steel breakage when manufacturing a cold-rolled sheet using this hot-rolled steel sheet can be predicted in advance. can perceive.
  • the manufacturing equipment 1 of FIG. 2 includes a plurality of pairs of rolling rolls 2a, a conveying section 2b for conveying the steel strip X hot-rolled by these rolling rolls 2a, and a coil of the steel strip X conveyed to the conveying section 2b.
  • a hot rolling device 2 that constitutes a hot rolling line and has a winder 2c that winds the steel strip X into a shape, a measuring device 3 that measures the surface temperature of the strip-shaped steel material X that is being transported to the transport section 2b, and a strip-shaped steel material X.
  • the temperature history of a coil (virtual coil) in a naturally cooled state is calculated based on the surface temperature of the strip-shaped steel material X measured by the measuring device 3, assuming that the steel material X is wound in a coil shape with no unevenness on the end face.
  • a calculation device 4 that calculates by the calculation device 4, a derivation device 5 that constitutes a derivation line for deriving the size of unevenness of the end surface E of the coil X1 wound by the winder 2c over the radius of the coil X1, and the calculation device 4 a prediction device 6 for predicting the temperature history of the unevenness in the cooled state by using the obtained temperature history and the size of the unevenness derived by the derivation device 5 .
  • the manufacturing facility 1 also includes a cooling device 7 for cooling the coil X1 after passing through the lead-out line.
  • the manufacturing equipment 1 further includes a cold rolling device for cold-rolling the coil X1 after being naturally cooled by the cooling device 7, an annealing device for annealing the steel strip after being cold-rolled by the cold rolling device, and the like. may be provided.
  • the hot rolling apparatus 2 performs rough rolling and finish rolling on a thick steel plate heated in a heating furnace (not shown), and then conveys the rolled steel strip X to the winder 2c by the conveying unit 2b. It is wound into a coil by the winder 2c.
  • the transport section 2b has, for example, a plurality of transport rollers.
  • the measuring device 3 has a non-contact temperature sensor 3a such as a thermography.
  • the measuring device 3 measures the surface temperature of the steel strip X after hot rolling and before being wound by the winder 2c.
  • the measuring device 3 measures the temperature of the entire surface area (entire length and width) of the steel strip X. As shown in FIG.
  • the computing device 4 is composed of, for example, a computer.
  • the calculation device 4 assumes that a coil (virtual coil) formed by, for example, winding the steel strip X and having no unevenness on the end surface is cylindrical, and calculates the temperature history of the virtual coil in a cooled state in a two-dimensional polar coordinate system. Calculated by model.
  • the lead-out device 5 scans the conveyor 5a that conveys the coil X1 wound by the winding machine 2c, and the end face E of the coil X1 that is being conveyed on the conveyor 5a, and a displacement meter that measures the shape of this end face E. 5b, and a derivation part 5c for deriving the size of unevenness of the end face E of the coil X1 based on the shape measured by the displacement meter 5b.
  • the displacement gauge 5b measures the shape of the end face E of the coil X1 over the radius of the coil X1, preferably over the diameter.
  • a laser displacement meter for example, is used as the displacement meter 5b.
  • the displacement gauge 5b has a laser irradiator that irradiates the end face E of the coil X1 with laser light and a light receiving element that receives part of the light beam reflected by the end face E.
  • FIG. The displacement meter 5b reads the reflected light of the laser beam irradiated to the end face E from the laser irradiation part by the light receiving element.
  • the displacement meter 5b is configured to be able to measure the shape of the end surface E of the coil X1 by a triangulation method.
  • the derivation unit 5c is composed of, for example, a computer.
  • the displacement gauge 5b and the lead-out portion 5c may be configured integrally.
  • the prediction device 6 is composed of, for example, a computer.
  • the prediction device 6 predicts the uneven temperature history of the end surface E of the coil X1 when it is assumed that the coil X1 actually wound by the winder 2c is cooled by the cooling device 7 or the like.
  • the cooling device 7 cools the coil X1 after the shape of the end surface E has been measured by the lead-out device 5.
  • the coil X1 wound by the winder 2c is heated to about 500° C. or higher.
  • the cooling device 7 air-cools the heated coil X1 to normal temperature. Since the manufacturing equipment 1 cools the coil X1 wound by the winder 2c, if there is a large protrusion on the end surface E of the coil X1, the cooling rate of this protrusion is faster than that of other portions. Cheap.
  • the steel strip X is formed by heating and hot-rolling a slab.
  • the steel strip X has a composition of, for example, carbon, silicon, manganese, phosphorus, sulfur, chromium, nickel, molybdenum and copper, with the balance being iron and unavoidable impurities.
  • the coiling temperature in the coiling step S3 can be set to the Ms (martensitic transformation start temperature) of the steel strip X or higher.
  • the upper limit of the carbon equivalent Ceq of the steel strip X represented by the following formula (1) is preferably 0.75%, more preferably 0.70%. If the carbon equivalent Ceq of the steel strip X exceeds the above upper limit, there is a high possibility that a martensite phase will form when the cooling rate during standing cooling is high.
  • the lower limit of the carbon equivalent Ceq is not particularly limited, but can be set to 0.55%, for example. If the carbon equivalent Ceq is less than the lower limit, the transformation is almost completed by the winding step S3, so the martensite phase is difficult to generate, and the possibility of edge cracking in the coil X1 in the subsequent step is low.
  • the method for manufacturing the hot-rolled steel sheet is preferably used when the carbon equivalent Ceq of the steel strip X is equal to or higher than the above lower limit.
  • Ceq[%] [C]+[Si]/24+[Mn]/6+[Ni]/40+[Cr]/5+[Mo]/4+[V]/14 (1)
  • [C], [Si], [Mn], [Ni], [Cr], [Mo] and [V] are the contents of C, Si, Mn, Ni, Cr, Mo and V, respectively (mass %).
  • the measurement step S1 is performed by the measurement device 3 .
  • the surface temperature of the steel strip X after hot rolling and before being wound by the winder 2c is measured over the entire surface area (full length and width) of the steel strip X.
  • the first calculation step S ⁇ b>2 is performed by the calculation device 4 .
  • the first calculation step S2 for example, it is assumed that a coil (virtual coil) formed by winding the strip-shaped steel material X and having no unevenness on the end face is cylindrical, and the temperature history of this virtual coil in the cooling state is calculated in the polar coordinate system. Calculated using a two-dimensional model.
  • the first calculation step S2 may be performed before the winding step S3 or after the winding step S3. It is also possible to perform the first calculation step S2 after the derivation step S4.
  • the coordinates of the intersection of the virtual plane including one end surface (upper end surface in FIG. 3) of the virtual coil X2 and the center axis of the virtual coil X2 are defined as the origin O (0, 0).
  • the temperature of the virtual coil X2 in the cooled state is calculated. Compute history.
  • the first calculation step S2 a plurality of calculation points are provided in each of the central axis direction and the radial direction of the virtual coil X2, and the temperature history in the cold state is calculated for each calculation point.
  • the calculation point inside the virtual coil X2 (the calculation point of the portion not exposed to the outside air) is calculated by the following formula (2), and the calculation point of the portion exposed to the outside air is For, the following formula (3) is used to calculate the temperature history of the virtual coil X2 in the cold state, with the temperature after t hours at the calculation point of the virtual coil X2 based on immediately after winding as ⁇ [°C] .
  • H enthalpy [kcal/kg]
  • ⁇ density of the portion corresponding to the calculation point of the steel strip [kg/m 3 ]
  • ⁇ r radial heat Conductivity [kcal/m/hr/°C]
  • ⁇ z Axial thermal conductivity [kcal/m/hr/°C]
  • ⁇ Emissivity [ ⁇ ]
  • ⁇ Stefan Boltzmann constant [kcal/m 2 /hr /°C 4 ]
  • F 12 shape factor [ ⁇ ]
  • ⁇ natural convection heat transfer coefficient [kcal/hr/m 2 /°C]
  • V volume of the portion corresponding to the calculation point of the steel strip [m 3 ]
  • A Means the surface area [m 2 ] of the portion corresponding to the calculated point of the steel strip.
  • q is a boundary condition.
  • This boundary condition is given by the following formula (4) for the inner peripheral surface of the virtual coil X2, and by the following formula (5) for the end surfaces and the outer peripheral surface of the virtual coil X2.
  • T the surface temperature [°C] of the portion corresponding to the calculation point measured in the measurement step S1
  • T f the ambient temperature [°C] during cooling.
  • the steel strip X whose surface temperature has been measured in the measuring step S1 is wound into a coil by the winding machine 2c at a high temperature.
  • the coiling temperature in the coiling step S3 is preferably equal to or higher than the Ms temperature of the steel strip X from the viewpoint of preventing the formation of the martensite phase.
  • the lower limit of the winding temperature is preferably 400°C, more preferably 500°C, and even more preferably 560°C.
  • the upper limit of the winding temperature is preferably 700°C, more preferably 670°C.
  • the "winding temperature” refers to the surface temperature of the steel strip X immediately before winding.
  • the lead-out step S4 is performed by the lead-out device 5 .
  • the end surface E of the coil X1 conveyed on the conveyor 5a is scanned by the displacement meter 5b, and the uneven shape of the end surface E is measured over the radius of the coil X1. and preferably measured across the diameter.
  • the derivation unit 5c uses a two-dimensional coordinate system defined by the projecting direction of the unevenness (the direction of the central axis of the coil X1) and the scanning direction of the displacement meter 5b (the radial direction of the coil X1). The size of the unevenness of the end face E is obtained.
  • the size of the unevenness of the end surface E is obtained using the above-described two-dimensional coordinate system, and the unevenness of the end surface E of the coil X1 is allowed to cool in a first prediction step S5 described later. temperature history can be easily and accurately predicted.
  • the derivation step S4 it is preferable to obtain the size of the unevenness of the end surface E based on the median value of the measured values by the displacement meter 5b. Specifically, in the derivation step S4, after the displacement meter 5b continuously measures the end face E of the coil X1 over the radius, the derivation unit 5c measures the unevenness of the end face E with reference to the median value of the measured values of the displacement meter 5b. It is preferable to ask for size.
  • the size of the unevenness of the end surface E is determined based on the above-mentioned median value, and a large protruding portion due to winding misalignment is obtained at the end on the outer peripheral side and / or the inner peripheral side of the coil X1. Even when a (telescope) is formed, the size of unevenness of the entire coil X1 can be appropriately measured. As a result, the first prediction step S5 facilitates easy and accurate prediction of the temperature history of the uneven end face E of the coil X1 in the cooled state.
  • FIG. 4 An example of the derivation procedure for the size of the unevenness of the end face E of the coil X1 in the derivation step S4 will be described with reference to FIGS. 4 and 5.
  • FIG. 1 the end face E of the coil X1 conveyed on the conveyor 5a is scanned by the displacement meter 5b, and the uneven shape of the end face E is measured over the radius of the coil X1.
  • the reference plane R of the end face E is set based on the median value of the measured values by the displacement meter 5b.
  • the coordinates of the intersection of the central axis Z of the coil X1 and the reference plane R are assumed to be the origin O (0, 0), the coordinates in the central axis direction with the origin O as the reference are z [m], and the origin O is assumed as the reference.
  • the size of the unevenness of the end surface E is obtained.
  • the coil X1 is divided into a plurality of regions in the radial direction, and the unevenness of each region is averaged. derived as At this time, it is also possible that the lengths of the regions in the radial direction of the coil X1 are not the same.
  • the length of a pair of regions located at both ends in the radial direction may be set smaller than the other regions so as to easily reflect the unevenness caused by the telescope. It is also possible to set a certain threshold value, and treat the amount of protrusion below this threshold value as not corresponding to unevenness.
  • the first prediction step S ⁇ b>5 is performed by the prediction device 6 .
  • the temperature history of the unevenness of the end face E of the coil X1 in the cooling state is predicted with reference to immediately after winding.
  • the temperature history of the unevenness of the end surface E in the cooled state is predicted using the above-described formulas (2) to (5).
  • the boundary condition of the above formula (3) is given by the above formula (5).
  • the method for manufacturing a hot-rolled steel sheet can predict the temperature history of the unevenness of the end face E of the coil X1 formed by winding the steel strip X in a cooled state. Therefore, according to the method for manufacturing a hot-rolled steel sheet, it is possible to detect in advance the possibility of steel breakage when the steel strip X is used to manufacture a cold-rolled steel sheet.
  • the method for predicting the temperature history of the hot-rolled steel sheet can predict the temperature history of the irregularities of the end face E of the coil X1 formed by winding the steel strip X in the cooled state. Therefore, according to the hot-rolled steel sheet temperature history prediction method, the possibility of steel breakage when the steel strip X is used to manufacture the cold-rolled steel sheet can be detected in advance.
  • Derivation step S14 and a step of predicting the temperature history of the unevenness in a cooled state using the temperature history calculated in the first calculation step S12 and the size of the unevenness derived in the derivation step S14 (first 1 prediction step S15), a step of calculating a phase transformation rate (ferrite-pearlite transformation rate) using the temperature history predicted in the first prediction step S15 (second calculation step S16), and a second calculation step S16. and a step of predicting the hardened portion of the steel strip using the calculated phase transformation rate (second prediction step S17).
  • the measuring step S11, the first calculating step S12, the winding step S13, the deriving step S14, the first predicting step S15, the second calculating step S16, and the second predicting step S17 are performed to determine the hardness of the hot-rolled steel sheet according to one aspect of the present invention. Construct a partial prediction method.
  • the measurement step S11, the first calculation step S12, the winding step S13, and the derivation step S14 can be performed in the same procedure as the measurement step S1, the first calculation step S2, the winding step S3, and the derivation step S4 in FIG. Therefore, the explanation is omitted.
  • the first calculation step S12 the following equation (6) is used instead of the above equation (2), and the following equation ( 7) may be used to calculate the temperature history.
  • the first prediction step S15 the temperature history of the steel strip is obtained by adding the transformation heating value Q t [kcal/m 3 /hr] calculated in the second calculation step S16 which will be described later. Specifically, in the first prediction step S15, the following formula (6) is used instead of the above formula (2), and the following formula (7) is used instead of the above formula (3) to calculate the temperature history. Predict.
  • the first prediction step S15 uses the following formula (6) instead of the above formula (2), and uses the following formula (7) instead of the above formula (3). It can be performed in the same procedure as S5.
  • the second calculation step S16 can be performed, for example, by a computer.
  • the phase transformation rate is calculated from an isothermal transformation formula including the influence of the ⁇ grain size.
  • the transformation heat generation amount Qt corresponding to the calculated phase transformation rate is calculated.
  • the phase transformation rate X[-] is calculated by the following formulas (8) and (9), and the transformation heat value at time t is calculated using the following formula (10).
  • Q t [kcal/m 3 /hr].
  • the transformation heat generation amount Qt calculated in the second calculation step S16 is used for predicting the temperature history in the first prediction step S15 described above. Further, this transformation heat value Qt may be used for calculating the temperature history in the above-described first calculation step S12.
  • S nucleation area term
  • K temperature dependent term
  • Q total total transformation heat value [kcal/m 3 /hr]
  • T first calculation step S12 or It means the temperature [°C] of the calculation point calculated in the first prediction step S15.
  • a, b, c, m, and n in the above formulas (8) to (10) mean constants adjusted for each type of steel material. These constants can be determined, for example, by creating a TTT diagram using a hot-rolled crop after rough rolling, and adjusting the calculated values to match the experimental values. However, since the transformation rate is affected by the state of the structure before transformation such as the austenite grain size, it changes depending on the hot rolling conditions. Therefore, the value of c is adjusted for each hot rolling condition.
  • the second prediction step S17 can be performed, for example, by a computer.
  • the hardened portion of the end surface of the coil wound in the winding step S13 is predicted using the phase transformation rate calculated in the second calculation step S16.
  • the second prediction step S17 for example, the relationship between the phase transformation rate and hardness is obtained in advance, and the hardened portion is predicted from the calculated phase transformation rate.
  • the second prediction step S17 for example, by setting in advance a hardness threshold at which fracture may occur in the steel material in a post-process such as a cold rolling step, and by comparing this threshold with the calculated phase transformation rate, Presence or absence of breakage of the steel material in the process may be predicted.
  • a threshold value of the phase transformation rate at which the steel material can be fractured in the post-process such as the cold rolling process is set in advance, and the calculated value is compared with the threshold value to determine the steel material. Presence or absence of breakage may be predicted.
  • the phase transformation rate calculated in the second calculation step S16 can be used to predict the presence or absence of breakage of the steel material in the subsequent steps. According to the hot-rolled steel sheet manufacturing method, the risk of breakage of the steel material during threading can be reduced by previously removing the hardened portion that causes breakage in the post-process.
  • the method for predicting the hardened portion of the hot-rolled steel sheet can predict the presence or absence of breakage of the steel material in the subsequent process using the phase transformation rate calculated in the second calculation process S16.
  • the derivation step it is possible to obtain the size of the unevenness of the end surface of the coil based on the average value, mode, etc. of the unevenness of the end surface of the coil.
  • the median value of the measured values is It is preferable to determine the size of the unevenness of the end face of the coil with reference to .
  • the measurement result of the displacement meter may be directly derived as the size of the unevenness of the end face of the coil.
  • FIG. 7 shows the temperature history of the imaginary coil in the air-cooled state immediately after the coiling of the upper end surface 410 mm away from the central axis in the radial direction.
  • the strip-shaped steel material X was actually wound by the winder 2c (winding process).
  • the end face E of the wound coil X1 was scanned across the diameter with a displacement meter 5b (a laser displacement meter "IL-2000" manufactured by KEYENCE) to measure the uneven shape of the end face E of the coil X1.
  • the reference plane of the end face E is set based on the median value of the measured values by the displacement meter 5b, and the end face E is measured using a two-dimensional coordinate system defined by the projecting direction of the unevenness and the scanning direction of the displacement meter 5b.
  • the size of the unevenness was derived by the lead-out portion 5c (lead-out step).
  • the unevenness of the end surface E of the coil X1 was positive when protruded toward the displacement gauge 5b, and negative when recessed toward the conveyor 5a.
  • the coil X1 is divided into 13 regions in the radial direction, the size of unevenness is averaged for each region, the average value is dropped into a two-dimensional coordinate system, and the size of unevenness of this region is derived.
  • the length of a pair of regions located at both ends in the radial direction is set smaller than the length of the other regions so as to easily reflect the unevenness caused by the telescope. Specifically, the length of the regions located at both ends in the radial direction was set to 1/2 the length of the other regions.
  • FIG. 8 shows the result of measurement of the uneven shape of the end surface E of the coil X1 by the displacement meter 5b and the result of derivation of the size of the unevenness of the end surface E of the coil X1 by the derivation unit 5c in this derivation process.
  • FIG. 9 shows the prediction result of the first prediction step for the end face E of the coil X1 at a position 410 mm away from the central axis in the radial direction. Further, FIG. 9 shows measured values of the temperature of the end surface E of the coil X1 corresponding to the position predicted in the first prediction step 23 minutes after immediately after winding.
  • FIG. 10 shows the temperature history of the imaginary coil in the air-cooled state immediately after the coiling of the upper end face 410 mm away from the central axis in the radial direction.
  • FIG. 11 shows the result of measurement of the unevenness shape of the end surface E of the coil X1 by the displacement meter 5b and the result of derivation of the size of the unevenness of the end surface E of the coil X1 by the derivation unit 5c in the derivation step.
  • FIG. 12 shows the measured values of the temperature after minutes.
  • No. 1 determined to have unevenness in the above derivation process. 1 and No. 1 judged to have no unevenness. 2, the prediction result obtained by the first prediction step and the actual measurement value substantially match each other. From this, No. 1 and no. 2 can predict the uneven temperature history of the end face E of the coil X1 with sufficient accuracy.
  • the Vickers hardness of calculation point A with a small phase transformation rate is higher than calculation points B and C with a large phase transformation rate. From this, it can be seen that the phase transformation rate correlates with the hardness of the coil. Therefore, the hardened portion of the coil can be predicted by calculating the phase transformation rate in the second calculation step. In addition, by setting in advance a threshold value of hardness or phase transformation rate at which steel fracture can occur in a post-process such as a cold rolling process, and comparing this threshold value with the calculated phase transformation rate, It is possible to predict whether or not the steel will break.
  • the hot-rolled steel sheet manufacturing method is suitable for detecting in advance the possibility of steel breakage during the manufacture of cold-rolled steel sheets.
  • Hot-rolled steel sheet manufacturing equipment Hot rolling device 2a Rolling roll 2b Conveying unit 2c Winding machine 3 Measuring device 3a Non-contact temperature sensor 4 Calculating device 5 Deriving device 5a Conveyor 5b Displacement gauge 5c Deriving unit 6 Prediction device 7 Cooling Apparatus X Steel strip X1 Coil X2 Virtual coil E End face O Origin R Reference plane Z of coil end face Central axis of coil

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Abstract

The purpose of the present invention is to provide a method for producing a hot-rolled steel sheet in which it is possible to predict the temperature history of unevenness in the end faces of a coil. A method for producing a hot-rolled steel sheet according to an embodiment of the present invention comprises: a step in which the surface temperature of a band-shaped steel material obtained by hot rolling is measured; a step in which the temperature history in a cooling state after winding when it is assumed that the band-shaped steel material is wound into a coil shape with no unevenness in the end faces thereof is calculated on the basis of the surface temperature measured in the measurement step; a step in which the band-shaped steel material is actually wound into a coil shape after the measurement step; a step in which the end faces of the coil wound in the winding step are scanned with a displacement gauge and the magnitude of unevenness in the end faces is derived across the radius of the coil; and a step in which the temperature history of the unevenness while in the cooling state is predicted using the temperature history calculated in the calculation step and the magnitude of the unevenness derived in the derivation step.

Description

熱延鋼板の製造方法、熱延鋼板の温度履歴予測方法及び熱延鋼板の硬質化部予測方法Method for manufacturing hot-rolled steel sheet, method for predicting temperature history of hot-rolled steel sheet, and method for predicting hardened portion of hot-rolled steel sheet
　本発明は、熱延鋼板の製造方法、熱延鋼板の温度履歴予測方法及び熱延鋼板の硬質化部予測方法に関する。 The present invention relates to a hot-rolled steel sheet manufacturing method, a hot-rolled steel sheet temperature history prediction method, and a hot-rolled steel sheet hardened portion prediction method.
　熱延鋼板は、熱間圧延された帯状鋼材をコイル状に巻き取り、巻き取られたコイルを常温程度まで冷却して製造される。この熱延鋼板は、再度帯状に繰り出して酸洗及び冷間圧延を施され、冷延鋼板となる。この冷延鋼板の製造上の問題点として、通板時における鋼材の破断が挙げられる。鋼材に破断が生じると、通板ラインを停止して復旧作業を行うことを要し、復旧のためのコストが嵩むと共に、生産効率が低下する。また、鋼材の破断は、設備故障の原因ともなる。 A hot-rolled steel sheet is manufactured by winding a hot-rolled steel strip into a coil and cooling the wound coil to about room temperature. This hot-rolled steel sheet is drawn out again into a strip shape, subjected to pickling and cold rolling, and turned into a cold-rolled steel sheet. A problem in the production of this cold-rolled steel sheet is breakage of the steel material during threading. When the steel material breaks, it is necessary to stop the threading line and carry out restoration work, which increases the cost for restoration and lowers the production efficiency. Moreover, breakage of the steel material causes equipment failure.
特開２０１４－５９３号公報Japanese Patent Application Laid-Open No. 2014-593 特開２０１０－１１２９５８号公報JP 2010-112958 A
　焼き入れ性の高い鋼材の冷間圧延時の破断の原因のひとつとして、鋼材の端部の亀裂が挙げられる。冷間圧延中の鋼材の端部に亀裂が生じていると、通板時にこの亀裂部分に応力が集中し、亀裂が成長し、鋼材の破断へとつながりやすい。 One of the causes of breakage during cold rolling of highly hardenable steel is cracks at the edges of the steel. If a crack occurs at the edge of the steel material during cold rolling, stress concentrates on the cracked portion during threading, the crack grows, and the steel material is likely to break.
　この亀裂の原因として、熱間圧延されたコイルの巻き取り形状の不良が挙げられる。つまり、熱間圧延後のコイルに巻き取り不良があると、コイルの端面の凹凸が大きくなる。コイル端面に大きな凸部があると、凸部がフィンの機能を果たすことでコイルの冷却時に凸部の冷却速度が速くなる。凸部の冷却速度が速くなると、凸部にベイナイトやマルテンサイト等の硬質の相が混在しやすくなる。その結果、鋼材の冷間圧延時にボイドが発生し、かつこのボイドが成長することで、端部の亀裂を招来しやすくなる。 　The cause of these cracks is the poor winding shape of the hot-rolled coil. That is, if there is a winding defect in the coil after hot rolling, the unevenness of the end face of the coil increases. If there is a large protrusion on the coil end surface, the protrusion functions as a fin, thereby increasing the cooling rate of the protrusion during cooling of the coil. When the cooling rate of the projections increases, hard phases such as bainite and martensite tend to coexist in the projections. As a result, voids are generated during cold rolling of the steel material, and the growth of these voids tends to cause cracks at the ends.
　このような観点から、本発明者らは、コイルの端面の凹凸（特に凸部）の温度履歴を予測することで、後工程における鋼材の破断の可能性を事前に察知できることを見出した。 From this point of view, the inventors found that by predicting the temperature history of the unevenness (especially the protrusions) of the coil end face, it is possible to detect in advance the possibility of steel breakage in the post-process.
　なお、特許文献１には、熱間圧延された圧延鋼板のランアウトテーブル（ＲＯＴ）上での温度むらを予測し、この予測した温度むらが小さくなるようにコイラに巻き取られる前の圧延鋼板の製造条件を制御することが記載されている。 In addition, in Patent Document 1, temperature unevenness on a run-out table (ROT) of a hot-rolled steel sheet is predicted, and the temperature of the rolled steel sheet before being wound on a coiler is reduced so that the predicted temperature unevenness is reduced. Controlling manufacturing conditions is described.
　また、特許文献２には、金属板コイルの端面にコイル直径に亘って距離計を走査させ、距離計とコイル端面との距離を測定してコイル端面のテレスコープ量を算出するに当たり、コイルエンド部の測定値がタング形状部であるか、テレスコープ形状であるかを識別する技術が記載されている。特許文献２には、コイル内直径両端の最内巻金属板同士の測定距離の差、又はコイル外直径両端の最外巻金属板同士の測定距離の差がそれぞれ閾値を超えるコイルは、金属板のコイルエンドのタング形状部を測定していると判定し、このタング形状部を測定した最内巻及び／又は最外巻距離データを除外してコイルのテレスコープ量を算出することが記載されている。 Further, in Patent Document 2, in calculating the telescopic amount of the coil end face by scanning the end face of a metal plate coil with a rangefinder over the coil diameter and measuring the distance between the rangefinder and the coil end face, the coil end A technique is described to identify whether the part measurement is a tongue-shaped part or a telescopic part. In Patent Document 2, the difference in the measured distance between the innermost wound metal plates at both ends of the coil inner diameter or the difference in the measured distance between the outermost wound metal plates at both ends of the coil outer diameter exceeds each threshold. It is described that the telescopic amount of the coil is calculated by excluding the innermost and/or outermost winding distance data for which the tongue shape part of the coil end is measured. ing.
　しかしながら、特許文献１、２では、コイル端面の凹凸とコイル端部の亀裂との関係については検討されていない。 However, Patent Documents 1 and 2 do not consider the relationship between the unevenness of the coil end face and the cracks at the coil end.
　本発明は、上述のような事情に基づいてなされたものであり、コイルの端面の凹凸の温度履歴を予測可能な熱延鋼板の製造方法及び熱延鋼板の温度履歴予測方法を提供することを目的とする。また、本発明は、コイルの端面の凹凸の温度履歴に基づいて後工程における鋼材の破断の有無を予測可能な熱延鋼板の硬質化部予測方法を提供することを目的とする。 SUMMARY OF THE INVENTION The present invention has been made based on the circumstances described above, and aims to provide a method for manufacturing a hot-rolled steel sheet and a method for predicting the temperature history of a hot-rolled steel sheet, which can predict the temperature history of the unevenness of the coil end face. aim. Another object of the present invention is to provide a method for predicting a hardened portion of a hot-rolled steel sheet, which can predict the presence or absence of breakage of the steel material in the post-process based on the temperature history of the unevenness of the end face of the coil.
　本発明の一態様に係る熱延鋼板の製造方法は、熱間圧延された帯状鋼材の表面温度を測定する測定工程と、上記帯状鋼材を端面に凹凸のないコイル状に巻き取ったと仮定した場合の巻取り後における放冷状態での温度履歴を、上記測定工程で測定された上記表面温度に基づいて算出する第１算出工程と、上記測定工程後の上記帯状鋼材を実際にコイル状に巻き取る巻取工程と、上記巻取工程で巻き取られたコイルの端面を変位計で走査し、上記端面の凹凸の大きさを上記コイルの半径に亘って導出する導出工程と、上記第１算出工程で算出された温度履歴と上記導出工程で導出された凹凸の大きさとを用いて、上記凹凸の放冷状態での温度履歴を予測する第１予測工程とを備える。 A method for manufacturing a hot-rolled steel sheet according to an aspect of the present invention includes a measurement step of measuring the surface temperature of a hot-rolled steel strip, and a case in which the steel strip is wound into a coil shape without unevenness on the end face. A first calculation step of calculating the temperature history in a cooled state after winding based on the surface temperature measured in the measurement step, and actually winding the steel strip after the measurement step into a coil a derivation step of scanning the end face of the coil wound in the winding step with a displacement meter to derive the size of the unevenness of the end face over the radius of the coil; and a first prediction step of predicting the temperature history of the unevenness in a cooled state by using the temperature history calculated in the step and the size of the unevenness derived in the derivation step.
　当該熱延鋼板の製造方法は、上記帯状鋼材が巻き取られて形成されたコイルの端面の凹凸の放冷状態での温度履歴を予測することができる。 The method for manufacturing the hot-rolled steel sheet can predict the temperature history of the irregularities on the end face of the coil formed by winding the steel strip as it cools.
　当該熱延鋼板の製造方法は、上記第１予測工程で予測された温度履歴を用いて相変態率を算出する第２算出工程と、上記第２算出工程で算出された相変態率を用いて上記帯状鋼材の硬質化部を予測する第２予測工程とをさらに備えるとよい。当該熱延鋼板の製造方法は、上記第２算出工程及び上記第２予測工程を備えることで、後工程における鋼材の破断の有無を予測することができる。 The method for manufacturing the hot-rolled steel sheet includes a second calculation step of calculating the phase transformation rate using the temperature history predicted in the first prediction step, and using the phase transformation rate calculated in the second calculation step. It is preferable to further include a second prediction step of predicting the hardened portion of the steel strip. The hot-rolled steel sheet manufacturing method includes the second calculation step and the second prediction step, so that it is possible to predict the presence or absence of breakage of the steel material in the subsequent steps.
　上記導出工程で、上記変位計による測定値の中央値を基準として上記凹凸の大きさを求めるとよい。このように、上記導出工程で、上記変位計による測定値の中央値を基準として上記凹凸の大きさを求めることによって、上記コイルの端面の凹凸の放冷状態での温度履歴を容易かつ正確に予測しやすい。 In the derivation step, it is preferable to obtain the size of the unevenness based on the median value of the measured values of the displacement gauge. In this way, in the derivation step, by obtaining the size of the unevenness based on the median value of the measured values of the displacement gauge, the temperature history of the unevenness of the end face of the coil can be easily and accurately measured in a cooled state. Easy to predict.
　上記導出工程で、上記凹凸の飛び出し方向と上記変位計による走査方向とで規定される２次元座標系を用いて上記凹凸の大きさを求めるとよい。このように、上記導出工程で、上記凹凸の飛び出し方向と上記変位計による走査方向とで規定される２次元座標系を用いて上記凹凸の大きさを求めることによって、上記コイルの端面の凹凸の放冷状態での温度履歴を容易かつ正確に予測しやすい。 In the derivation step, it is preferable to obtain the size of the unevenness using a two-dimensional coordinate system defined by the projecting direction of the unevenness and the scanning direction of the displacement meter. In this manner, in the deriving step, the size of the unevenness is obtained using a two-dimensional coordinate system defined by the projecting direction of the unevenness and the scanning direction of the displacement meter, whereby the unevenness of the end surface of the coil is obtained. It is easy to predict the temperature history in the cold state easily and accurately.
　本発明の他の一態様に係る熱延鋼板の温度履歴予測方法は、熱間圧延された帯状鋼材の表面温度を測定する測定工程と、上記帯状鋼材を端面に凹凸のないコイル状に巻き取ったと仮定した場合の巻取り後における放冷状態での温度履歴を、上記測定工程で測定された上記表面温度に基づいて算出する第１算出工程と、上記測定工程後の上記帯状鋼材を実際にコイル状に巻き取る巻取工程と、上記巻取工程で巻き取られたコイルの端面を変位計で走査し、上記端面の凹凸の大きさを上記コイルの半径に亘って導出する導出工程と、上記第１算出工程で算出された温度履歴と上記導出工程で導出された凹凸の大きさとを用いて、上記凹凸の放冷状態での温度履歴を予測する第１予測工程とを備える。 A temperature history prediction method for a hot-rolled steel sheet according to another aspect of the present invention comprises a measuring step of measuring the surface temperature of a hot-rolled steel strip, and winding the steel strip into a coil shape having no unevenness on the end face. A first calculation step of calculating the temperature history in a cooled state after winding based on the surface temperature measured in the measurement step, and the steel strip after the measurement step is actually measured. A winding step of winding the coil into a coil shape, a deriving step of scanning the end face of the coil wound in the winding step with a displacement meter and deriving the size of the unevenness of the end face over the radius of the coil; and a first prediction step of predicting the temperature history of the unevenness in a cooled state using the temperature history calculated in the first calculation step and the size of the unevenness derived in the derivation step.
　当該熱延鋼板の温度履歴予測方法は、上記帯状鋼材が巻き取られて形成されたコイルの端面の凹凸の放冷状態での温度履歴を予測することができる。 The temperature history prediction method for the hot-rolled steel sheet can predict the temperature history of the irregularities on the end face of the coil formed by winding the steel strip as it cools.
　本発明の他の一態様に係る熱延鋼板の硬質化部予測方法は、熱間圧延された帯状鋼材の表面温度を測定する測定工程と、上記帯状鋼材を端面に凹凸のないコイル状に巻き取ったと仮定した場合の巻取り後における放冷状態での温度履歴を、上記測定工程で測定された上記表面温度に基づいて算出する第１算出工程と、上記測定工程後の上記帯状鋼材を実際にコイル状に巻き取る巻取工程と、上記巻取工程で巻き取られたコイルの端面を変位計で走査し、上記端面の凹凸の大きさを上記コイルの半径に亘って導出する導出工程と、上記第１算出工程で算出された温度履歴と上記導出工程で導出された凹凸の大きさとを用いて、上記凹凸の放冷状態での温度履歴を予測する第１予測工程と、上記第１予測工程で予測された温度履歴を用いて相変態率を算出する第２算出工程と、上記第２算出工程で算出された相変態率を用いて上記帯状鋼材の硬質化部を予測する第２予測工程とを備える。 A method for predicting a hardened portion of a hot-rolled steel sheet according to another aspect of the present invention comprises a measuring step of measuring the surface temperature of a hot-rolled steel strip; A first calculation step of calculating the temperature history in a cooled state after winding assuming that the steel strip was taken based on the surface temperature measured in the measurement step; and a derivation step of scanning the end face of the coil wound in the winding step with a displacement meter and deriving the size of the unevenness of the end face over the radius of the coil. a first prediction step of predicting the temperature history of the unevenness in a cooled state using the temperature history calculated in the first calculation step and the size of the unevenness derived in the derivation step; a second calculation step of calculating the phase transformation rate using the temperature history predicted in the prediction step; and a second calculation step of predicting the hardened portion of the steel strip using the phase transformation rate calculated in the second calculation step. and a prediction step.
　当該熱延鋼板の硬質化部予測方法は、コイルの端面の凹凸の温度履歴に基づいて後工程における鋼材の破断の有無を予測することができる。 The hot-rolled steel sheet hardened portion prediction method can predict the presence or absence of breakage of the steel material in the post-process based on the temperature history of the unevenness of the end face of the coil.
　以上説明したように、本発明の一態様に係る熱延鋼板の製造方法及び他の一態様に係る熱延鋼板の温度履歴予測方法は、コイルの端面の凹凸の温度履歴を予測することができる。また、本発明の他の一態様に係る熱延鋼板の硬質化部予測方法は、コイルの端面の凹凸の温度履歴に基づいて後工程における鋼材の破断の有無を予測することができる。 As described above, the method for manufacturing a hot-rolled steel sheet according to one aspect of the present invention and the temperature history prediction method for a hot-rolled steel sheet according to another aspect of the present invention can predict the temperature history of the unevenness of the end surface of the coil. . In addition, a method for predicting hardened portions of a hot-rolled steel sheet according to another aspect of the present invention can predict the presence or absence of breakage of a steel material in a post-process based on the temperature history of irregularities on the end face of a coil.
図１は、本発明の一実施形態に係る熱延鋼板の製造方法を示すフロー図である。FIG. 1 is a flowchart showing a method for manufacturing a hot-rolled steel sheet according to one embodiment of the present invention. 図２は、図１の熱延鋼板の製造方法で用いる熱延鋼板の製造設備を示す模式図である。FIG. 2 is a schematic diagram showing a hot-rolled steel sheet manufacturing facility used in the hot-rolled steel sheet manufacturing method of FIG. 図３は、図１の熱延鋼板の製造方法の第１算出工程による仮想コイルの温度履歴算出手順の説明図である。FIG. 3 is an explanatory diagram of the temperature history calculation procedure of the virtual coil in the first calculation step of the hot-rolled steel sheet manufacturing method of FIG. 1 . 図４は、図１の熱延鋼板の製造方法の導出工程における変位計によるコイルの端面の走査位置を示す模式図である。FIG. 4 is a schematic diagram showing the scanning position of the end surface of the coil by the displacement gauge in the derivation step of the hot-rolled steel sheet manufacturing method of FIG. 図５は、図１の熱延鋼板の製造方法の導出工程による凹凸の大きさの導出手順の説明図である。FIG. 5 is an explanatory diagram of a derivation procedure of the size of irregularities in the derivation step of the hot-rolled steel sheet manufacturing method of FIG. 1 . 図６は、図１の熱延鋼板の製造方法とは異なる形態に係る熱延鋼板の製造方法を示すフロー図である。FIG. 6 is a flowchart showing a method for manufacturing a hot-rolled steel sheet according to a different form from the method for manufacturing a hot-rolled steel sheet in FIG. 図７は、Ｎｏ．１の第１算出工程による仮想コイルの上端面の巻取り直後を基準とする放冷状態での温度履歴を示すグラフである。FIG. 1 is a graph showing a temperature history in a naturally cooled state with reference to immediately after winding of the upper end surface of the virtual coil according to the first calculation step of 1. FIG. 図８は、Ｎｏ．１の導出工程における変位計によるコイルの端面の凹凸の形状の測定結果及び導出部によるコイルの端面の凹凸の大きさの導出結果を示すグラフである。FIG. 10 is a graph showing measurement results of the shape of unevenness of the end surface of the coil by the displacement meter and the result of derivation of the size of unevenness of the end surface of the coil by the derivation unit in derivation step 1; 図９は、Ｎｏ．１の第１予測工程で予測されたコイルの端面の巻取り直後を基準とする放冷状態での温度履歴、及びこの端面の温度の実測値を示すグラフである。FIG. 1 is a graph showing the temperature history of the end surface of the coil in a naturally cooled state with reference to immediately after winding of the end surface predicted in the first prediction step of 1, and the measured value of the temperature of this end surface. 図１０は、Ｎｏ．２の第１算出工程で算出された仮想コイルの巻取り直後を基準とする上端面の放冷状態での温度履歴を示すグラフである。FIG. 10 shows No. 2 is a graph showing the temperature history of the upper end face in a naturally cooled state with reference to immediately after winding of the virtual coil calculated in the first calculation step of 2. FIG. 図１１は、Ｎｏ．２の導出工程における変位計によるコイルの端面の凹凸の形状の測定結果及び導出部によるコイルの端面の凹凸の大きさの導出結果を示すグラフである。FIG. 11 shows No. 10 is a graph showing measurement results of the shape of unevenness of the end surface of the coil by the displacement gauge and derivation results of the size of unevenness of the end surface of the coil by the derivation unit in the derivation step 2; 図１２は、Ｎｏ．２の第１予測工程で予測されたコイルの端面の巻取り直後を基準とする放冷状態での温度履歴、及びこの端面の温度の実測値を示すグラフである。FIG. 12 shows No. 2 is a graph showing the temperature history in the cold state immediately after winding of the end face of the coil predicted in the first prediction step of 2, and the measured value of the temperature of this end face.
　以下、本発明の実施の形態について適宜図面を参照しつつ詳説する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
［第一実施形態］
＜熱延鋼板の製造方法＞
　図１の熱延鋼板の製造方法は、熱間圧延された帯状鋼材の表面温度を測定する工程（測定工程Ｓ１）と、上記帯状鋼材を端面に凹凸のないコイル状に巻き取ったと仮定した場合の巻取り後における放冷状態での温度履歴を測定工程Ｓ１で測定された上記表面温度に基づいて算出する工程（第１算出工程Ｓ２）と、測定工程Ｓ１後の上記帯状鋼材を実際にコイル状に巻き取る工程（巻取工程Ｓ３）と、巻取工程Ｓ３で巻き取られたコイルの端面を変位計で走査し、上記端面の凹凸の大きさを上記コイルの半径に亘って導出する工程（導出工程Ｓ４）と、第１算出工程Ｓ２で算出された温度履歴と導出工程Ｓ４で導出された凹凸の大きさとを用いて、上記凹凸の放冷状態での温度履歴を予測する工程（第１予測工程Ｓ５）とを備える。測定工程Ｓ１、第１算出工程Ｓ２、巻取工程Ｓ３、導出工程Ｓ４及び第１予測工程Ｓ５は、本発明の一態様に係る熱延鋼板の温度履歴予測方法を構成する。なお、「コイル状」とは、軸方向視において渦巻き状であることをいう。「コイルの端面」とは、コイルにおける中心軸と垂直な面をいう。すなわち、「コイルの端面」とは、帯状鋼材の幅方向の端によって形成される面をいう。 [First embodiment]
<Method for manufacturing hot-rolled steel sheet>
The method for manufacturing a hot-rolled steel sheet shown in FIG. A step of calculating the temperature history in a cooled state after winding based on the surface temperature measured in the measuring step S1 (first calculating step S2), and actually coiling the steel strip after the measuring step S1 a step of winding in a shape (winding step S3); and a step of scanning the end face of the coil wound in the winding step S3 with a displacement meter and deriving the size of the unevenness of the end face over the radius of the coil. (Derivation step S4), and a step of predicting the temperature history of the unevenness in a cooled state using the temperature history calculated in the first calculation step S2 and the size of the unevenness derived in the derivation step S4 (first 1 prediction step S5). The measuring step S1, the first calculating step S2, the winding step S3, the deriving step S4, and the first predicting step S5 constitute a temperature history prediction method for a hot rolled steel sheet according to one aspect of the present invention. In addition, "coil shape" means spiral shape when viewed in the axial direction. "Coil end face" refers to a plane perpendicular to the central axis of the coil. That is, the term "end face of the coil" refers to a face formed by the ends of the steel strip in the width direction.
　当該熱延鋼板の製造方法によると、上記コイルの端面の凹凸の温度履歴を予測することで、この熱延鋼板を用いて冷間圧延板を製造する際の鋼材の破断の可能性を事前に察知することができる。 According to the hot-rolled steel sheet manufacturing method, by predicting the temperature history of the unevenness of the end face of the coil, the possibility of steel breakage when manufacturing a cold-rolled sheet using this hot-rolled steel sheet can be predicted in advance. can perceive.
　当該熱延鋼板の製造方法について説明するにあたり、まず図２を参照して当該熱延鋼板の製造方法を実施可能な熱延鋼板の製造設備１（以下、単に「製造設備１」ともいう）について説明する。 Before explaining the method for manufacturing the hot-rolled steel sheet, first, referring to FIG. explain.
〔熱延鋼板の製造設備〕
　図２の製造設備１は、複数対の圧延ロール２ａと、これらの圧延ロール２ａによって熱間圧延された帯状鋼材Ｘを搬送する搬送部２ｂと、搬送部２ｂに搬送された帯状鋼材Ｘをコイル状に巻き取る巻取機２ｃとを有し、熱間圧延ラインを構成する熱間圧延装置２と、搬送部２ｂに搬送されている帯状鋼材Ｘの表面温度を測定する測定装置３と、帯状鋼材Ｘを端面に凹凸のないコイル状に巻き取ったと仮定した場合のコイル（仮想コイル）の放冷状態での温度履歴を、測定装置３で測定された帯状鋼材Ｘの表面温度に基づいて算出する算出装置４と、巻取機２ｃで巻き取られたコイルＸ１の端面Ｅの凹凸の大きさをコイルＸ１の半径に亘って導出する導出ラインを構成する導出装置５と、算出装置４で算出された温度履歴と導出装置５で導出された凹凸の大きさとを用いて、上記凹凸の放冷状態での温度履歴を予測する予測装置６とを備える。また、当該製造設備１は、上記導出ライン通過後のコイルＸ１を放冷する放冷装置７を備える。なお、当該製造設備１は、放冷装置７による放冷後のコイルＸ１を冷間圧延する冷間圧延装置、上記冷間圧延装置による冷間圧延後の帯状鋼材を焼鈍する焼鈍装置等をさらに備えていてもよい。 [Manufacturing equipment for hot-rolled steel sheets]
The manufacturing equipment 1 of FIG. 2 includes a plurality of pairs of rolling rolls 2a, a conveying section 2b for conveying the steel strip X hot-rolled by these rolling rolls 2a, and a coil of the steel strip X conveyed to the conveying section 2b. A hot rolling device 2 that constitutes a hot rolling line and has a winder 2c that winds the steel strip X into a shape, a measuring device 3 that measures the surface temperature of the strip-shaped steel material X that is being transported to the transport section 2b, and a strip-shaped steel material X. The temperature history of a coil (virtual coil) in a naturally cooled state is calculated based on the surface temperature of the strip-shaped steel material X measured by the measuring device 3, assuming that the steel material X is wound in a coil shape with no unevenness on the end face. a calculation device 4 that calculates by the calculation device 4, a derivation device 5 that constitutes a derivation line for deriving the size of unevenness of the end surface E of the coil X1 wound by the winder 2c over the radius of the coil X1, and the calculation device 4 a prediction device 6 for predicting the temperature history of the unevenness in the cooled state by using the obtained temperature history and the size of the unevenness derived by the derivation device 5 . The manufacturing facility 1 also includes a cooling device 7 for cooling the coil X1 after passing through the lead-out line. The manufacturing equipment 1 further includes a cold rolling device for cold-rolling the coil X1 after being naturally cooled by the cooling device 7, an annealing device for annealing the steel strip after being cold-rolled by the cold rolling device, and the like. may be provided.
　熱間圧延装置２は、加熱炉（不図示）で加熱された厚鋼板に粗圧延及び仕上圧延を施したうえで、圧延後の帯状鋼材Ｘを搬送部２ｂによって巻取機２ｃに搬送し、巻取機２ｃでコイル状に巻き取る。搬送部２ｂは、例えば複数の搬送ローラを有する。 The hot rolling apparatus 2 performs rough rolling and finish rolling on a thick steel plate heated in a heating furnace (not shown), and then conveys the rolled steel strip X to the winder 2c by the conveying unit 2b. It is wound into a coil by the winder 2c. The transport section 2b has, for example, a plurality of transport rollers.
　測定装置３は、サーモグラフィ等の非接触温度センサ３ａを有する。測定装置３は、熱間圧延後かつ巻取機２ｃに巻き取られる前の帯状鋼材Ｘの表面温度を測定する。測定装置３は、帯状鋼材Ｘの表面の全領域（全長全幅）の温度を測定する。 The measuring device 3 has a non-contact temperature sensor 3a such as a thermography. The measuring device 3 measures the surface temperature of the steel strip X after hot rolling and before being wound by the winder 2c. The measuring device 3 measures the temperature of the entire surface area (entire length and width) of the steel strip X. As shown in FIG.
　算出装置４は、例えばコンピュータから構成される。算出装置４は、例えば帯状鋼材Ｘを巻き取って形成される端面に凹凸のないコイル（仮想コイル）を円筒形と仮定し、この仮想コイルの放冷状態での温度履歴を極座標系の２次元モデルによって算出する。 The computing device 4 is composed of, for example, a computer. The calculation device 4 assumes that a coil (virtual coil) formed by, for example, winding the steel strip X and having no unevenness on the end surface is cylindrical, and calculates the temperature history of the virtual coil in a cooled state in a two-dimensional polar coordinate system. Calculated by model.
　導出装置５は、巻取機２ｃで巻き取られたコイルＸ１を搬送するコンベア５ａと、コンベア５ａ上を搬送されているコイルＸ１の端面Ｅを走査し、この端面Ｅの形状を測定する変位計５ｂと、変位計５ｂで測定された形状に基づいてコイルＸ１の端面Ｅの凹凸の大きさを導出する導出部５ｃとを有する。変位計５ｂは、コイルＸ１の端面Ｅの形状をコイルＸ１の半径に亘って測定し、好ましくは直径に亘って測定する。変位計５ｂとしては、例えばレーザー変位計が用いられる。変位計５ｂは、コイルＸ１の端面Ｅにレーザー光を照射するレーザー照射部と、端面Ｅで反射された光線の一部を受光する受光素子とを有する。変位計５ｂは、上記レーザー照射部から端面Ｅに照射されたレーザー光の反射光を上記受光素子によって読み取る。変位計５ｂは、三角測距方式によってコイルＸ１の端面Ｅの形状を測定可能に構成される。導出部５ｃは、例えばコンピュータから構成される。変位計５ｂと導出部５ｃとは、一体的に構成されていてもよい。 The lead-out device 5 scans the conveyor 5a that conveys the coil X1 wound by the winding machine 2c, and the end face E of the coil X1 that is being conveyed on the conveyor 5a, and a displacement meter that measures the shape of this end face E. 5b, and a derivation part 5c for deriving the size of unevenness of the end face E of the coil X1 based on the shape measured by the displacement meter 5b. The displacement gauge 5b measures the shape of the end face E of the coil X1 over the radius of the coil X1, preferably over the diameter. A laser displacement meter, for example, is used as the displacement meter 5b. The displacement gauge 5b has a laser irradiator that irradiates the end face E of the coil X1 with laser light and a light receiving element that receives part of the light beam reflected by the end face E. FIG. The displacement meter 5b reads the reflected light of the laser beam irradiated to the end face E from the laser irradiation part by the light receiving element. The displacement meter 5b is configured to be able to measure the shape of the end surface E of the coil X1 by a triangulation method. The derivation unit 5c is composed of, for example, a computer. The displacement gauge 5b and the lead-out portion 5c may be configured integrally.
　予測装置６は、例えばコンピュータから構成される。予測装置６は、巻取機２ｃで実際に巻き取られたコイルＸ１が放冷装置７等で放冷されたと想定した場合のコイルＸ１の端面Ｅの凹凸の温度履歴を予測する。 The prediction device 6 is composed of, for example, a computer. The prediction device 6 predicts the uneven temperature history of the end surface E of the coil X1 when it is assumed that the coil X1 actually wound by the winder 2c is cooled by the cooling device 7 or the like.
　放冷装置７は、導出装置５で端面Ｅの形状を測定された後のコイルＸ１を放冷する。当該製造設備１では、巻取機２ｃによる巻き取り後のコイルＸ１は５００℃程度又はそれ以上に加熱されている。放冷装置７は、この加熱されたコイルＸ１を常温まで空冷する。当該製造設備１は、巻取機２ｃで巻き取られたコイルＸ１を放冷するため、コイルＸ１の端面Ｅに大きな凸部が存在すると、この凸部の冷却速度が他の部分よりも速くなりやすい。 The cooling device 7 cools the coil X1 after the shape of the end surface E has been measured by the lead-out device 5. In the manufacturing equipment 1, the coil X1 wound by the winder 2c is heated to about 500° C. or higher. The cooling device 7 air-cools the heated coil X1 to normal temperature. Since the manufacturing equipment 1 cools the coil X1 wound by the winder 2c, if there is a large protrusion on the end surface E of the coil X1, the cooling rate of this protrusion is faster than that of other portions. Cheap.
〔帯状鋼材〕
　帯状鋼材Ｘは、スラブを加熱し、熱間圧延することで形成される。帯状鋼材Ｘは、例えば炭素、ケイ素、マンガン、リン、硫黄、クロム、ニッケル、モリブデン及び銅、並びに残部が鉄及び不可避的不純物である組成を有する。帯状鋼材Ｘに冷間圧延を施す場合、巻取工程Ｓ３における巻取温度は、帯状鋼材ＸのＭｓ（マルテンサイト変態開始温度）以上とすることができる。 [Strip steel]
The steel strip X is formed by heating and hot-rolling a slab. The steel strip X has a composition of, for example, carbon, silicon, manganese, phosphorus, sulfur, chromium, nickel, molybdenum and copper, with the balance being iron and unavoidable impurities. When the steel strip X is subjected to cold rolling, the coiling temperature in the coiling step S3 can be set to the Ms (martensitic transformation start temperature) of the steel strip X or higher.
　帯状鋼材Ｘの下記式（１）で表される炭素当量Ｃｅｑの上限としては、０．７５％が好ましく、０．７０％がより好ましい。帯状鋼材Ｘの炭素当量Ｃｅｑが上記上限を超えると、放冷時の冷却速度が大きい場合にマルテンサイトの相が生成するおそれが高くなる。一方、上記炭素当量Ｃｅｑの下限としては、特に限定されないが、例えば０．５５％とすることができる。上記炭素当量Ｃｅｑが上記下限に満たない場合、概ね巻取工程Ｓ３までに変態が完了するため、マルテンサイトの相は生成され難く、後工程でコイルＸ１にエッジ割れを生じるおそれが低い。そのため、当該熱延鋼板の製造方法は、帯状鋼材Ｘの炭素当量Ｃｅｑが上記下限以上である場合に、好適に用いられる。
Ｃｅｑ［％］＝［Ｃ］＋［Ｓｉ］／２４＋［Ｍｎ］／６＋［Ｎｉ］／４０＋［Ｃｒ］／５＋［Ｍｏ］／４＋［Ｖ］／１４・・・（１）
　但し、［Ｃ］、［Ｓｉ］、［Ｍｎ］、［Ｎｉ］、［Ｃｒ］、［Ｍｏ］及び［Ｖ］は、それぞれＣ、Ｓｉ、Ｍｎ、Ｎｉ、Ｃｒ、Ｍｏ及びＶの含有量（質量％）を示す。 The upper limit of the carbon equivalent Ceq of the steel strip X represented by the following formula (1) is preferably 0.75%, more preferably 0.70%. If the carbon equivalent Ceq of the steel strip X exceeds the above upper limit, there is a high possibility that a martensite phase will form when the cooling rate during standing cooling is high. On the other hand, the lower limit of the carbon equivalent Ceq is not particularly limited, but can be set to 0.55%, for example. If the carbon equivalent Ceq is less than the lower limit, the transformation is almost completed by the winding step S3, so the martensite phase is difficult to generate, and the possibility of edge cracking in the coil X1 in the subsequent step is low. Therefore, the method for manufacturing the hot-rolled steel sheet is preferably used when the carbon equivalent Ceq of the steel strip X is equal to or higher than the above lower limit.
Ceq[%]=[C]+[Si]/24+[Mn]/6+[Ni]/40+[Cr]/5+[Mo]/4+[V]/14 (1)
However, [C], [Si], [Mn], [Ni], [Cr], [Mo] and [V] are the contents of C, Si, Mn, Ni, Cr, Mo and V, respectively (mass %).
（測定工程）
　測定工程Ｓ１は、測定装置３によって行う。測定工程Ｓ１では、熱間圧延後かつ巻取機２ｃに巻き取られる前の帯状鋼材Ｘの表面温度を、帯状鋼材Ｘの表面の全領域（全長全幅）に亘って測定する。 (Measurement process)
The measurement step S1 is performed by the measurement device 3 . In the measuring step S1, the surface temperature of the steel strip X after hot rolling and before being wound by the winder 2c is measured over the entire surface area (full length and width) of the steel strip X.
（第１算出工程）
　第１算出工程Ｓ２は、算出装置４によって行う。第１算出工程Ｓ２では、例えば帯状鋼材Ｘを巻き取って形成される端面に凹凸のないコイル（仮想コイル）を円筒形と仮定し、この仮想コイルの放冷状態での温度履歴を極座標系の２次元モデルによって算出する。第１算出工程Ｓ２は、巻取工程Ｓ３の前に行ってもよく、巻取工程Ｓ３の後に行ってもよい。また、第１算出工程Ｓ２を導出工程Ｓ４の後に行うことも可能である。 (First calculation step)
The first calculation step S<b>2 is performed by the calculation device 4 . In the first calculation step S2, for example, it is assumed that a coil (virtual coil) formed by winding the strip-shaped steel material X and having no unevenness on the end face is cylindrical, and the temperature history of this virtual coil in the cooling state is calculated in the polar coordinate system. Calculated using a two-dimensional model. The first calculation step S2 may be performed before the winding step S3 or after the winding step S3. It is also possible to perform the first calculation step S2 after the derivation step S4.
　図３を参照して、第１算出工程Ｓ２による仮想コイルＸ２の放冷状態での温度履歴の算出手順の一例について説明する。第１算出工程Ｓ２では、仮想コイルＸ２の一方の端面（図３では上端面）を含む仮想平面と仮想コイルＸ２の中心軸との交点の座標を原点Ｏ（０、０）とし、原点Ｏを基準とする中心軸方向の座標をｚ［ｍ］、原点Ｏを基準とする径方向の座標をｒ［ｍ］とする極座標系の２次元モデルを用いて仮想コイルＸ２の放冷状態での温度履歴を算出する。第１算出工程Ｓ２では、仮想コイルＸ２の中心軸方向及び半径方向にそれぞれ複数の算出点を設け、各算出点に対して放冷状態での温度履歴を算出する。具体的には、第１算出工程Ｓ２では、仮想コイルＸ２の内部の算出点（外気に露出してない部分の算出点）については下記式（２）、外気に露出している部分の算出点については下記式（３）を用い、巻取り直後を基準とする仮想コイルＸ２の算出点におけるｔ時間後の温度をΦ［℃］として、仮想コイルＸ２の放冷状態での温度履歴を算出する。 An example of the procedure for calculating the temperature history of the virtual coil X2 in the cooling state in the first calculation step S2 will be described with reference to FIG. In the first calculation step S2, the coordinates of the intersection of the virtual plane including one end surface (upper end surface in FIG. 3) of the virtual coil X2 and the center axis of the virtual coil X2 are defined as the origin O (0, 0). Using a two-dimensional model of a polar coordinate system in which z [m] is the coordinate in the central axis direction as a reference and r [m] is the coordinate in the radial direction with the origin O as a reference, the temperature of the virtual coil X2 in the cooled state is calculated. Compute history. In the first calculation step S2, a plurality of calculation points are provided in each of the central axis direction and the radial direction of the virtual coil X2, and the temperature history in the cold state is calculated for each calculation point. Specifically, in the first calculation step S2, the calculation point inside the virtual coil X2 (the calculation point of the portion not exposed to the outside air) is calculated by the following formula (2), and the calculation point of the portion exposed to the outside air is For, the following formula (3) is used to calculate the temperature history of the virtual coil X2 in the cold state, with the temperature after t hours at the calculation point of the virtual coil X2 based on immediately after winding as Φ [°C] .
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000002
Figure JPOXMLDOC01-appb-M000002
　なお、上記式（２）及び上記式（３）において、Ｈ：エンタルピー［ｋｃａｌ／ｋｇ］、ρ：帯状鋼材の算出点に対応する部分の密度［ｋｇ／ｍ３］、λｒ：径方向熱伝導率［ｋｃａｌ／ｍ／ｈｒ／℃］、λｚ：軸方向熱伝導率［ｋｃａｌ／ｍ／ｈｒ／℃］、ε：放射率［－］、σ：ステファンボルツマン定数［ｋｃａｌ／ｍ２／ｈｒ／℃４］、Ｆ１２：形態係数［－］、α：自然対流熱伝達率［ｋｃａｌ／ｈｒ／ｍ２／℃］、Ｖ：帯状鋼材の算出点に対応する部分の体積［ｍ３］、Ａ：帯状鋼材の算出点に対応する部分の表面面積［ｍ２］を意味する。また、上記式（３）において、ｑは境界条件である。この境界条件は、仮想コイルＸ２の内周面については下記式（４）、仮想コイルＸ２の端面及び外周面については下記式（５）で与えられる。下記式（４）及び下記式（５）において、Ｔ：算出点に対応する部分の測定工程Ｓ１で測定された表面温度［℃］、Ｔｆ：放冷時の雰囲気温度［℃］を意味する。 In the above formulas (2) and (3), H: enthalpy [kcal/kg], ρ: density of the portion corresponding to the calculation point of the steel strip [kg/m 3 ], λ r : radial heat Conductivity [kcal/m/hr/°C], λ z : Axial thermal conductivity [kcal/m/hr/°C], ε: Emissivity [−], σ: Stefan Boltzmann constant [kcal/m 2 /hr /°C 4 ], F 12 : shape factor [−], α: natural convection heat transfer coefficient [kcal/hr/m 2 /°C], V: volume of the portion corresponding to the calculation point of the steel strip [m 3 ], A: Means the surface area [m 2 ] of the portion corresponding to the calculated point of the steel strip. Also, in the above equation (3), q is a boundary condition. This boundary condition is given by the following formula (4) for the inner peripheral surface of the virtual coil X2, and by the following formula (5) for the end surfaces and the outer peripheral surface of the virtual coil X2. In the following formulas (4) and (5), T: the surface temperature [°C] of the portion corresponding to the calculation point measured in the measurement step S1, and T f : the ambient temperature [°C] during cooling. .
Figure JPOXMLDOC01-appb-M000003
Figure JPOXMLDOC01-appb-M000003
Figure JPOXMLDOC01-appb-M000004
Figure JPOXMLDOC01-appb-M000004
（巻取工程）
　巻取工程Ｓ３では、測定工程Ｓ１で表面温度が測定された後の帯状鋼材Ｘを高温下で巻取機２ｃによってコイル状に巻き取る。巻取工程Ｓ３における巻取温度は、マルテンサイトの相の生成を防ぐ観点から、帯状鋼材ＸのＭｓ温度以上であることが好ましい。上記巻取温度の下限としては、４００℃が好ましく、５００℃がより好ましく、５６０℃がさらに好ましい。一方、上記巻取温度の上限としては、７００℃が好ましく、６７０℃がより好ましい。上記巻取温度が上記下限に満たないと、帯状鋼材Ｘの強度が大きくなり過ぎて、冷間圧延工程等の後工程において装置への負荷が大きくなるおそれがある。逆に、上記巻取温度が上記上限を超えると、帯状鋼材Ｘ表面のスケール厚みが大きくなるおそれがある。なお、「巻取温度」とは、巻取り直前の帯状鋼材Ｘの表面温度をいう。 (winding process)
In the winding step S3, the steel strip X whose surface temperature has been measured in the measuring step S1 is wound into a coil by the winding machine 2c at a high temperature. The coiling temperature in the coiling step S3 is preferably equal to or higher than the Ms temperature of the steel strip X from the viewpoint of preventing the formation of the martensite phase. The lower limit of the winding temperature is preferably 400°C, more preferably 500°C, and even more preferably 560°C. On the other hand, the upper limit of the winding temperature is preferably 700°C, more preferably 670°C. If the coiling temperature is less than the lower limit, the strength of the steel strip X becomes too high, which may increase the load on the apparatus in subsequent processes such as the cold rolling process. Conversely, if the coiling temperature exceeds the upper limit, the scale thickness on the surface of the steel strip X may increase. The "winding temperature" refers to the surface temperature of the steel strip X immediately before winding.
（導出工程）
　導出工程Ｓ４は、導出装置５によって行う。図２及び図４に示すように、導出工程Ｓ４では、コンベア５ａ上を搬送されるコイルＸ１の端面Ｅを変位計５ｂによって走査し、端面Ｅの凹凸の形状をコイルＸ１の半径に亘って測定し、好ましくは直径に亘って測定する。さらに、導出工程Ｓ４では、導出部５ｃによって、凹凸の飛び出し方向（コイルＸ１の中心軸方向）と変位計５ｂによる走査方向（コイルＸ１の半径方向）とで規定される２次元座標系を用いて端面Ｅの凹凸の大きさを求める。当該熱延鋼板の製造方法は、上記２次元座標系を用いて端面Ｅの凹凸の大きさを求めることで、後述の第１予測工程Ｓ５により、コイルＸ１の端面Ｅの凹凸の放冷状態での温度履歴を容易かつ正確に予測しやすい。 (Extraction process)
The lead-out step S4 is performed by the lead-out device 5 . As shown in FIGS. 2 and 4, in the lead-out step S4, the end surface E of the coil X1 conveyed on the conveyor 5a is scanned by the displacement meter 5b, and the uneven shape of the end surface E is measured over the radius of the coil X1. and preferably measured across the diameter. Furthermore, in the derivation step S4, the derivation unit 5c uses a two-dimensional coordinate system defined by the projecting direction of the unevenness (the direction of the central axis of the coil X1) and the scanning direction of the displacement meter 5b (the radial direction of the coil X1). The size of the unevenness of the end face E is obtained. In the method for manufacturing the hot-rolled steel sheet, the size of the unevenness of the end surface E is obtained using the above-described two-dimensional coordinate system, and the unevenness of the end surface E of the coil X1 is allowed to cool in a first prediction step S5 described later. temperature history can be easily and accurately predicted.
　導出工程Ｓ４では、変位計５ｂによる測定値の中央値を基準として端面Ｅの凹凸の大きさを求めることが好ましい。具体的には、導出工程Ｓ４では、変位計５ｂによってコイルＸ１の端面Ｅを半径に亘って連続計測した後、導出部５ｃによって変位計５ｂによる計測値の中央値を基準として端面Ｅの凹凸の大きさを求めることが好ましい。当該熱延鋼板の製造方法は、上記中央値を基準として端面Ｅの凹凸の大きさを求めることで、コイルＸ１の外周側及び／又は内周側の端部に巻きずれに起因する大きな突出部分（テレスコープ）が形成されているような場合でも、コイルＸ１全体の凹凸の大きさを適切に測定することができる。その結果、第１予測工程Ｓ５により、コイルＸ１の端面Ｅの凹凸の放冷状態での温度履歴を容易かつ正確に予測しやすい。 In the derivation step S4, it is preferable to obtain the size of the unevenness of the end surface E based on the median value of the measured values by the displacement meter 5b. Specifically, in the derivation step S4, after the displacement meter 5b continuously measures the end face E of the coil X1 over the radius, the derivation unit 5c measures the unevenness of the end face E with reference to the median value of the measured values of the displacement meter 5b. It is preferable to ask for size. In the method for manufacturing the hot-rolled steel sheet, the size of the unevenness of the end surface E is determined based on the above-mentioned median value, and a large protruding portion due to winding misalignment is obtained at the end on the outer peripheral side and / or the inner peripheral side of the coil X1. Even when a (telescope) is formed, the size of unevenness of the entire coil X1 can be appropriately measured. As a result, the first prediction step S5 facilitates easy and accurate prediction of the temperature history of the uneven end face E of the coil X1 in the cooled state.
　図４及び図５を参照して、導出工程Ｓ４によるコイルＸ１の端面Ｅの凹凸の大きさの導出手順の一例について説明する。まず、導出工程Ｓ４では、コンベア５ａ上を搬送されるコイルＸ１の端面Ｅを変位計５ｂによって走査し、端面Ｅの凹凸の形状をコイルＸ１の半径に亘って測定する。次に、変位計５ｂによる測定値の中央値を基に端面Ｅの基準面Ｒを設定する。続いて、コイルＸ１の中心軸Ｚと基準面Ｒとの交点の座標を原点Ｏ（０、０）とし、原点Ｏを基準とする中心軸方向の座標をｚ［ｍ］、原点Ｏを基準とする径方向の座標をｒ［ｍ］とする極座標系の２次元モデルを用い、端面Ｅの凹凸の大きさを求める。具体的には、コイルＸ１を径方向に複数の領域に分割したうえ、領域ごとに凹凸の大きさを平均し、この平均値を２次元座標系に落とし込むことで、この領域の凹凸の大きさとして導出する。この際、コイルＸ１の径方向における各領域の長さを同じとしないことも可能である。例えはテレスコープに起因する凹凸を反映しやすいよう、径方向において両端に位置する一対の領域の長さを他の領域に対して小さく設定してもよい。また、一定の閾値を設け、この閾値以下の飛び出し量は凹凸に相当しないものとして取り扱うことも可能である。 An example of the derivation procedure for the size of the unevenness of the end face E of the coil X1 in the derivation step S4 will be described with reference to FIGS. 4 and 5. FIG. First, in the lead-out step S4, the end face E of the coil X1 conveyed on the conveyor 5a is scanned by the displacement meter 5b, and the uneven shape of the end face E is measured over the radius of the coil X1. Next, the reference plane R of the end face E is set based on the median value of the measured values by the displacement meter 5b. Subsequently, the coordinates of the intersection of the central axis Z of the coil X1 and the reference plane R are assumed to be the origin O (0, 0), the coordinates in the central axis direction with the origin O as the reference are z [m], and the origin O is assumed as the reference. Using a two-dimensional model of a polar coordinate system in which r [m] is the coordinate in the radial direction, the size of the unevenness of the end surface E is obtained. Specifically, the coil X1 is divided into a plurality of regions in the radial direction, and the unevenness of each region is averaged. derived as At this time, it is also possible that the lengths of the regions in the radial direction of the coil X1 are not the same. For example, the length of a pair of regions located at both ends in the radial direction may be set smaller than the other regions so as to easily reflect the unevenness caused by the telescope. It is also possible to set a certain threshold value, and treat the amount of protrusion below this threshold value as not corresponding to unevenness.
（第１予測工程）
　第１予測工程Ｓ５は、予測装置６によって行う。第１予測工程Ｓ５では、巻取り直後を基準とするコイルＸ１の端面Ｅの凹凸の放冷状態での温度履歴を予測する。第１予測工程Ｓ５では、上述の式（２）～（５）を用いて端面Ｅの凹凸の放冷状態での温度履歴を予測する。この際、基準面Ｒについては、上記式（３）の境界条件を上記式（５）によって与える。 (First prediction step)
The first prediction step S<b>5 is performed by the prediction device 6 . In the first prediction step S5, the temperature history of the unevenness of the end face E of the coil X1 in the cooling state is predicted with reference to immediately after winding. In the first prediction step S5, the temperature history of the unevenness of the end surface E in the cooled state is predicted using the above-described formulas (2) to (5). At this time, for the reference plane R, the boundary condition of the above formula (3) is given by the above formula (5).
＜利点＞
　当該熱延鋼板の製造方法は、帯状鋼材Ｘが巻き取られて形成されたコイルＸ１の端面Ｅの凹凸の放冷状態での温度履歴を予測することができる。従って、当該熱延鋼板の製造方法によると、帯状鋼材Ｘを用いて冷間圧延板を製造する際における鋼材破断の可能性を事前に察知することができる。 <Advantages>
The method for manufacturing a hot-rolled steel sheet can predict the temperature history of the unevenness of the end face E of the coil X1 formed by winding the steel strip X in a cooled state. Therefore, according to the method for manufacturing a hot-rolled steel sheet, it is possible to detect in advance the possibility of steel breakage when the steel strip X is used to manufacture a cold-rolled steel sheet.
　当該熱延鋼板の温度履歴予測方法は、帯状鋼材Ｘが巻き取られて形成されたコイルＸ１の端面Ｅの凹凸の放冷状態での温度履歴を予測することができる。従って、当該熱延鋼板の温度履歴予測方法によると、帯状鋼材Ｘを用いて冷間圧延板を製造する際における鋼材破断の可能性を事前に察知することができる。 The method for predicting the temperature history of the hot-rolled steel sheet can predict the temperature history of the irregularities of the end face E of the coil X1 formed by winding the steel strip X in the cooled state. Therefore, according to the hot-rolled steel sheet temperature history prediction method, the possibility of steel breakage when the steel strip X is used to manufacture the cold-rolled steel sheet can be detected in advance.
［第二実施形態］
＜熱延鋼板の製造方法＞
　図６の熱延鋼板の製造方法は、熱間圧延された帯状鋼材の表面温度を測定する工程（測定工程Ｓ１１）と、上記帯状鋼材を端面に凹凸のないコイル状に巻き取ったと仮定した場合の巻取り後における放冷状態での温度履歴を測定工程Ｓ１１で測定された上記表面温度に基づいて算出する工程（第１算出工程Ｓ１２）と、測定工程Ｓ１１後の上記帯状鋼材を実際にコイル状に巻き取る工程（巻取工程Ｓ１３）と、巻取工程Ｓ１３で巻き取られたコイルの端面を変位計で走査し、上記端面の凹凸の大きさを上記コイルの半径に亘って導出する工程（導出工程Ｓ１４）と、第１算出工程Ｓ１２で算出された温度履歴と導出工程Ｓ１４で導出された凹凸の大きさとを用いて、上記凹凸の放冷状態での温度履歴を予測する工程（第１予測工程Ｓ１５）と、第１予測工程Ｓ１５で予測された温度履歴を用いて相変態率（フェライト・パーライト変態率）を算出する工程（第２算出工程Ｓ１６）と、第２算出工程Ｓ１６で算出された相変態率を用いて上記帯状鋼材の硬質化部を予測する工程（第２予測工程Ｓ１７）とを備える。測定工程Ｓ１１、第１算出工程Ｓ１２、巻取工程Ｓ１３、導出工程Ｓ１４、第１予測工程Ｓ１５、第２算出工程Ｓ１６及び第２予測工程Ｓ１７は、本発明の一態様に係る熱延鋼板の硬質化部予測方法を構成する。測定工程Ｓ１１、第１算出工程Ｓ１２、巻取工程Ｓ１３及び導出工程Ｓ１４については、図１の測定工程Ｓ１、第１算出工程Ｓ２、巻取工程Ｓ３及び導出工程Ｓ４と同様の手順で行うことができるため、説明を省略する。なお、第１算出工程Ｓ１２では、後述する第１予測工程Ｓ１５と同様に、上述の式（２）に代えて下記式（６）を用い、かつ上述の式（３）に代えて下記式（７）を用いて温度履歴を算出してもよい。 [Second embodiment]
<Method for manufacturing hot-rolled steel sheet>
The method for manufacturing a hot-rolled steel sheet shown in FIG. A step of calculating the temperature history in a cooled state after winding based on the surface temperature measured in the measuring step S11 (first calculating step S12), and actually coiling the steel strip after the measuring step S11. a step of winding in a shape (winding step S13); and a step of scanning the end face of the coil wound in the winding step S13 with a displacement meter and deriving the size of the unevenness of the end face over the radius of the coil. (Derivation step S14), and a step of predicting the temperature history of the unevenness in a cooled state using the temperature history calculated in the first calculation step S12 and the size of the unevenness derived in the derivation step S14 (first 1 prediction step S15), a step of calculating a phase transformation rate (ferrite-pearlite transformation rate) using the temperature history predicted in the first prediction step S15 (second calculation step S16), and a second calculation step S16. and a step of predicting the hardened portion of the steel strip using the calculated phase transformation rate (second prediction step S17). The measuring step S11, the first calculating step S12, the winding step S13, the deriving step S14, the first predicting step S15, the second calculating step S16, and the second predicting step S17 are performed to determine the hardness of the hot-rolled steel sheet according to one aspect of the present invention. Construct a partial prediction method. The measurement step S11, the first calculation step S12, the winding step S13, and the derivation step S14 can be performed in the same procedure as the measurement step S1, the first calculation step S2, the winding step S3, and the derivation step S4 in FIG. Therefore, the explanation is omitted. Note that in the first calculation step S12, the following equation (6) is used instead of the above equation (2), and the following equation ( 7) may be used to calculate the temperature history.
（第１予測工程）
　第１予測工程Ｓ１５では、後述の第２算出工程Ｓ１６で算出される各時間の変態発熱量Ｑｔ［ｋｃａｌ／ｍ３／ｈｒ］を加算して上記帯状鋼材の温度履歴を求める。具体的には、第１予測工程Ｓ１５では、上述の式（２）に代えて下記式（６）を用い、かつ上述の式（３）に代えて下記式（７）を用いて温度履歴を予測する。第１予測工程Ｓ１５は、上述の式（２）に代えて下記式（６）を用い、かつ上述の式（３）に代えて下記式（７）を用いる以外、図１の第１予測工程Ｓ５と同様の手順で行うことができる。 (First prediction step)
In the first prediction step S15, the temperature history of the steel strip is obtained by adding the transformation heating value Q t [kcal/m 3 /hr] calculated in the second calculation step S16 which will be described later. Specifically, in the first prediction step S15, the following formula (6) is used instead of the above formula (2), and the following formula (7) is used instead of the above formula (3) to calculate the temperature history. Predict. The first prediction step S15 uses the following formula (6) instead of the above formula (2), and uses the following formula (7) instead of the above formula (3). It can be performed in the same procedure as S5.
Figure JPOXMLDOC01-appb-M000005
Figure JPOXMLDOC01-appb-M000005
Figure JPOXMLDOC01-appb-M000006
Figure JPOXMLDOC01-appb-M000006
（第２算出工程）
　第２算出工程Ｓ１６は、例えばコンピュータによって行うことができる。第２算出工程１６では、γ粒径の影響を含んだ等温変態式から相変態率を算出する。また、第２算出工程Ｓ１６では、この算出された相変態率に応じた変態発熱量Ｑｔを算出する。具体的には、第２算出工程Ｓ１６では、下記式（８）及び下記式（９）によって相変態率Ｘ［－］を算出すると共に、下記式（１０）を用いて時間ｔにおける変態発熱量Ｑｔ［ｋｃａｌ／ｍ３／ｈｒ］を算出する。第２算出工程Ｓ１６で算出された変態発熱量Ｑｔは、上述の第１予測工程Ｓ１５における温度履歴の予測に使用される。また、この変態発熱量Ｑｔは、上述の第１算出工程Ｓ１２における温度履歴の算出に用いられてもよい。 (Second calculation step)
The second calculation step S16 can be performed, for example, by a computer. In the second calculation step 16, the phase transformation rate is calculated from an isothermal transformation formula including the influence of the γ grain size. Further, in the second calculation step S16, the transformation heat generation amount Qt corresponding to the calculated phase transformation rate is calculated. Specifically, in the second calculation step S16, the phase transformation rate X[-] is calculated by the following formulas (8) and (9), and the transformation heat value at time t is calculated using the following formula (10). Calculate Q t [kcal/m 3 /hr]. The transformation heat generation amount Qt calculated in the second calculation step S16 is used for predicting the temperature history in the first prediction step S15 described above. Further, this transformation heat value Qt may be used for calculating the temperature history in the above-described first calculation step S12.
Figure JPOXMLDOC01-appb-M000007
Figure JPOXMLDOC01-appb-M000007
Figure JPOXMLDOC01-appb-M000008
Figure JPOXMLDOC01-appb-M000008
Figure JPOXMLDOC01-appb-M000009
Figure JPOXMLDOC01-appb-M000009
　なお、上記式（８）から（１０）において、Ｓ：核生成面積項、Ｋ：温度依存項、Ｑｔｏｔａｌ：総変態発熱量［ｋｃａｌ／ｍ３／ｈｒ］、Ｔ：第１算出工程Ｓ１２又は第１予測工程Ｓ１５で算出された算出点の温度［℃］を意味する。また、上記式（８）から（１０）におけるａ、ｂ、ｃ、ｍ、ｎは、鋼材の品種毎に調整される定数を意味する。これらの定数は、例えば粗圧延後の熱延クロップを用いてＴＴＴ線図を作成し、計算値が実験値と適合するように調整して決定することができる。但し、変態速度はオーステナイト粒径等の変態前組織の状態に影響されるため、熱間圧延条件によって変化する。そのため、ｃの値は、熱間圧延条件ごとに調整される。 In the above formulas (8) to (10), S: nucleation area term, K: temperature dependent term, Q total : total transformation heat value [kcal/m 3 /hr], T: first calculation step S12 or It means the temperature [°C] of the calculation point calculated in the first prediction step S15. Further, a, b, c, m, and n in the above formulas (8) to (10) mean constants adjusted for each type of steel material. These constants can be determined, for example, by creating a TTT diagram using a hot-rolled crop after rough rolling, and adjusting the calculated values to match the experimental values. However, since the transformation rate is affected by the state of the structure before transformation such as the austenite grain size, it changes depending on the hot rolling conditions. Therefore, the value of c is adjusted for each hot rolling condition.
（第２予測工程）
　第２予測工程Ｓ１７は、例えばコンピュータによって行うことができる。第２予測工程Ｓ１７では、第２算出工程Ｓ１６で算出された相変態率を用いて巻取工程Ｓ１３で巻き取られたコイルの端面の硬質化部を予測する。第２予測工程Ｓ１７では、例えば相変態率と硬度との関係を予め求めておき、算出された相変態率から硬質化部を予測する。第２予測工程Ｓ１７では、例えば冷間圧延工程等の後工程において鋼材に破断が生じ得る硬度の閾値を予め設定しておき、この閾値と算出された相変態率とを比較することで、後工程における鋼材の破断の有無を予測してもよい。また、第２予測工程Ｓ１７では、冷間圧延工程等の後工程において鋼材に破断が生じ得る相変態率の閾値を予め設定しておき、算出された値をこの閾値とを比較することで鋼材の破断の有無を予測してもよい。 (Second prediction step)
The second prediction step S17 can be performed, for example, by a computer. In the second prediction step S17, the hardened portion of the end surface of the coil wound in the winding step S13 is predicted using the phase transformation rate calculated in the second calculation step S16. In the second prediction step S17, for example, the relationship between the phase transformation rate and hardness is obtained in advance, and the hardened portion is predicted from the calculated phase transformation rate. In the second prediction step S17, for example, by setting in advance a hardness threshold at which fracture may occur in the steel material in a post-process such as a cold rolling step, and by comparing this threshold with the calculated phase transformation rate, Presence or absence of breakage of the steel material in the process may be predicted. Further, in the second prediction step S17, a threshold value of the phase transformation rate at which the steel material can be fractured in the post-process such as the cold rolling process is set in advance, and the calculated value is compared with the threshold value to determine the steel material. Presence or absence of breakage may be predicted.
＜利点＞
　当該熱延鋼板の製造方法は、第２算出工程Ｓ１６で算出された相変態率を用いて後工程における鋼材の破断の有無を予測することができる。当該熱延鋼板の製造方法によると、後工程で破断の原因となる硬質化部を予め切除することで、通板時における鋼材の破断のリスクを低減することができる。 <Advantages>
In the method for manufacturing a hot-rolled steel sheet, the phase transformation rate calculated in the second calculation step S16 can be used to predict the presence or absence of breakage of the steel material in the subsequent steps. According to the hot-rolled steel sheet manufacturing method, the risk of breakage of the steel material during threading can be reduced by previously removing the hardened portion that causes breakage in the post-process.
　当該熱延鋼板の硬質化部予測方法は、第２算出工程Ｓ１６で算出された相変態率を用いて後工程における鋼材の破断の有無を予測することができる。 The method for predicting the hardened portion of the hot-rolled steel sheet can predict the presence or absence of breakage of the steel material in the subsequent process using the phase transformation rate calculated in the second calculation process S16.
［その他の実施形態］
　上記実施形態は、本発明の構成を限定するものではない。従って、上記実施形態は、本明細書の記載及び技術常識に基づいて上記実施形態各部の構成要素の省略、置換又は追加が可能であり、それらは全て本発明の範囲に属するものと解釈されるべきである。 [Other embodiments]
The above embodiments do not limit the configuration of the present invention. Therefore, in the above embodiment, the components of each part of the above embodiment can be omitted, replaced, or added based on the description of the present specification and common general technical knowledge, and all of them are interpreted as belonging to the scope of the present invention. should.
　例えば上記導出工程では、上記コイルの端面の凹凸の平均値、最頻値等を基にこの端面の凹凸の大きさを求めることも可能である。但し、上述のように、上記導出工程では、テレスコープ等の大きな突出部分が存在する場合でも、上記コイルの全体の凹凸の大きさを適切に測定することができる観点から、測定値の中央値を基準として上記コイルの端面の凹凸の大きさを求めることが好ましい。 For example, in the derivation step, it is possible to obtain the size of the unevenness of the end surface of the coil based on the average value, mode, etc. of the unevenness of the end surface of the coil. However, as described above, in the derivation step, even if there is a large projecting portion such as a telescope, the median value of the measured values is It is preferable to determine the size of the unevenness of the end face of the coil with reference to .
　上記導出工程では、コイルの端面の凹凸の飛び出し方向と変位計による走査方向とで規定される２次元座標系を用いて上記凹凸の大きさを求めなくてもよい。例えば上記導出工程では、変位計による測定結果をそのままコイルの端面の凹凸の大きさとして導出してもよい。 In the derivation step, it is not necessary to obtain the size of the unevenness using a two-dimensional coordinate system defined by the projection direction of the unevenness on the end surface of the coil and the scanning direction of the displacement meter. For example, in the derivation step, the measurement result of the displacement meter may be directly derived as the size of the unevenness of the end face of the coil.
　以下、実施例によって本発明をさらに詳細に説明するが、本発明はこれらの実施例に限定されるものではない。 The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.
［Ｎｏ．１］
　図２に示す製造設備１を用いて熱延鋼板を製造した。まず、非接触温度センサ３ａ（ＦＬＩＲ社製のサーモグラフィ「ＣＰＡ－ＳＣ７１００」）を用い、熱間圧延後かつ巻取機２ｃに巻き取られる前の帯状鋼材Ｘの表面温度を帯状鋼材Ｘの表面の全領域（全長全幅）に亘って測定した（測定工程）。次に、この帯状鋼材Ｘを端面に凹凸のないコイル状に巻き取ったと仮定した場合のコイル（仮想コイル）の放冷状態での温度履歴を、上記式（２）～（５）を用いて算出した（第１算出工程）。この第１算出工程では、仮想コイルの中心軸方向に１０個、半径方向に５０個（合計：１０×５０個）の算出点を設けたうえ、各算出点に対して放冷状態での温度履歴を算出した。上記仮想コイルにおける中心軸から半径方向に４１０ｍｍ離れた上端面の巻取り直後を基準とする放冷状態での温度履歴を図７に示す。 [No. 1]
A hot-rolled steel sheet was manufactured using the manufacturing equipment 1 shown in FIG. First, using a non-contact temperature sensor 3a (FLIR thermography CPA-SC7100), the surface temperature of the steel strip X after hot rolling and before being wound by the winder 2c is measured. It was measured over the entire area (full length and width) (measurement step). Next, the temperature history of the coil (hypothetical coil) when it is assumed that the strip-shaped steel material X is wound into a coil shape without unevenness on the end surface is calculated using the above equations (2) to (5). calculated (first calculation step). In this first calculation step, 10 calculation points are provided in the central axis direction of the virtual coil and 50 calculation points are provided in the radial direction (total: 10 x 50 points). History was calculated. FIG. 7 shows the temperature history of the imaginary coil in the air-cooled state immediately after the coiling of the upper end surface 410 mm away from the central axis in the radial direction.
　続いて、帯状鋼材Ｘを巻取機２ｃで実際に巻き取った（巻取工程）。次に、巻き取られたコイルＸ１の端面Ｅを直径に亘って変位計５ｂ（ＫＥＹＥＮＣＥ社製のレーザー変位計「ＩＬ－２０００」）で走査し、コイルＸ１の端面Ｅの凹凸の形状を測定した。さらに、変位計５ｂによる測定値の中央値を基に端面Ｅの基準面を設定したうえ、凹凸の飛び出し方向と変位計５ｂによる走査方向とで規定される２次元座標系を用いて端面Ｅの凹凸の大きさを導出部５ｃにより導出した（導出工程）。なお、コイルＸ１の端面Ｅの凹凸は、変位計５ｂ側に突出している場合をプラス、コンベア５ａ側に凹んでいる場合をマイナスとした。この導出工程では、コイルＸ１を半径方向に１３の領域に分割し、領域ごとに凹凸の大きさを平均し、この平均値を２次元座標系に落とし込み、この領域の凹凸の大きさとして導出した。この導出工程では、テレスコープに起因する凹凸を反映しやすいよう、径方向において両端に位置する一対の領域の長さを他の領域の長さに対して小さく設定した。具体的には、径方向両端に位置する領域の長さを他の領域の長さの１／２に設定した。また、凹凸の閾値を１０ｍｍに設定し、各領域の凹凸の平均値について１０ｍｍ未満の値は切り捨てた。この導出工程における変位計５ｂによるコイルＸ１の端面Ｅの凹凸の形状の測定結果及び導出部５ｃによるコイルＸ１の端面Ｅの凹凸の大きさの導出結果を図８に示す。 Subsequently, the strip-shaped steel material X was actually wound by the winder 2c (winding process). Next, the end face E of the wound coil X1 was scanned across the diameter with a displacement meter 5b (a laser displacement meter "IL-2000" manufactured by KEYENCE) to measure the uneven shape of the end face E of the coil X1. . Further, the reference plane of the end face E is set based on the median value of the measured values by the displacement meter 5b, and the end face E is measured using a two-dimensional coordinate system defined by the projecting direction of the unevenness and the scanning direction of the displacement meter 5b. The size of the unevenness was derived by the lead-out portion 5c (lead-out step). The unevenness of the end surface E of the coil X1 was positive when protruded toward the displacement gauge 5b, and negative when recessed toward the conveyor 5a. In this derivation process, the coil X1 is divided into 13 regions in the radial direction, the size of unevenness is averaged for each region, the average value is dropped into a two-dimensional coordinate system, and the size of unevenness of this region is derived. . In this derivation step, the length of a pair of regions located at both ends in the radial direction is set smaller than the length of the other regions so as to easily reflect the unevenness caused by the telescope. Specifically, the length of the regions located at both ends in the radial direction was set to 1/2 the length of the other regions. Moreover, the threshold value of unevenness was set to 10 mm, and the average value of unevenness in each region was rounded down to values less than 10 mm. FIG. 8 shows the result of measurement of the uneven shape of the end surface E of the coil X1 by the displacement meter 5b and the result of derivation of the size of the unevenness of the end surface E of the coil X1 by the derivation unit 5c in this derivation process.
　続いて、導出工程で導出されたコイルＸ１の端面Ｅの凹凸部分について、巻取り直後を基準とする放冷状態での温度履歴を、上記第１算出工程による算出結果と上記式（２）～（５）とを用いて予測した（第１予測工程）。中心軸から半径方向に４１０ｍｍ離れた位置におけるコイルＸ１の端面Ｅの第１予測工程による予測結果を図９に示す。また、図９に、第１予測工程で予測した位置に対応するコイルＸ１の端面Ｅの巻取り直後から２３分後の温度の実測値を示す。 Subsequently, the temperature history of the uneven portion of the end surface E of the coil X1 derived in the deriving step in the state immediately after the coiling is taken as a reference is calculated by the calculation result of the first calculation step and the above formula (2) to (5) was used for prediction (first prediction step). FIG. 9 shows the prediction result of the first prediction step for the end face E of the coil X1 at a position 410 mm away from the central axis in the radial direction. Further, FIG. 9 shows measured values of the temperature of the end surface E of the coil X1 corresponding to the position predicted in the first prediction step 23 minutes after immediately after winding.
［Ｎｏ．２］
　Ｎｏ．１と同様の製造設備１を用い、Ｎｏ．１と同様にして、測定工程、第１算出工程、巻取工程、導出工程及び第１予測工程を行った。上記仮想コイルにおける中心軸から半径方向に４１０ｍｍ離れた上端面の巻取り直後を基準とする放冷状態での温度履歴を図１０に示す。また、上記導出工程における変位計５ｂによるコイルＸ１の端面Ｅの凹凸の形状の測定結果及び導出部５ｃによるコイルＸ１の端面Ｅの凹凸の大きさの導出結果を図１１に示す。さらに、中心軸から半径方向に４１０ｍｍ離れた位置におけるコイルＸ１の端面Ｅの第１予測工程による予測結果、及び第１予測工程で予測した位置に対応するコイルＸ１の端面Ｅの巻取り直後から２４分後の温度の実測値を図１２に示す。 [No. 2]
No. Using the same manufacturing equipment 1 as No. 1, No. 1, the measurement process, the first calculation process, the winding process, the derivation process, and the first prediction process were performed. FIG. 10 shows the temperature history of the imaginary coil in the air-cooled state immediately after the coiling of the upper end face 410 mm away from the central axis in the radial direction. FIG. 11 shows the result of measurement of the unevenness shape of the end surface E of the coil X1 by the displacement meter 5b and the result of derivation of the size of the unevenness of the end surface E of the coil X1 by the derivation unit 5c in the derivation step. Furthermore, the prediction result of the first prediction step of the end face E of the coil X1 at a position 410 mm away in the radial direction from the central axis, and the end face E of the coil X1 corresponding to the position predicted in the first prediction step 24 from immediately after winding FIG. 12 shows the measured values of the temperature after minutes.
　図７から図１２に示すように、上記導出工程によって凹凸ありと判定されたＮｏ．１及び凹凸なしと判定されたＮｏ．２共に、上記第１予測工程による予測結果と実測値とが略一致している。このことから、Ｎｏ．１及びＮｏ．２共に、コイルＸ１の端面Ｅの凹凸の温度履歴を十分正確に予測できていることが分かる。 　As shown in Figs. 7 to 12, No. 1 determined to have unevenness in the above derivation process. 1 and No. 1 judged to have no unevenness. 2, the prediction result obtained by the first prediction step and the actual measurement value substantially match each other. From this, No. 1 and no. 2 can predict the uneven temperature history of the end face E of the coil X1 with sufficient accuracy.
［Ｎｏ．３］
　Ｎｏ．１と同様の製造装置１を用い、測定工程、第１算出工程、巻取工程、導出工程及び第１予測工程を行った。また、Ｎｏ．３では、上述の式（８）及び式（９）を用いてコイルの端面の相変態率を算出すると共に、上述の式（１０）を用いて変態発熱量を算出した（第２算出工程）。Ｎｏ．３では、第１算出工程及び第１予測工程で、上述の式（６）及び式（７）を用いて温度履歴を予測した。さらに、Ｎｏ．３では、第２算出工程で相変態率を算出した位置（算出点）のビッカース硬度［Ｈｖ］を実測した。Ｎｏ．３で算出された相変態率及びＮｏ．３で測定されたビッカース硬度を表１に示す。 [No. 3]
No. 1, the measurement process, the first calculation process, the winding process, the derivation process, and the first prediction process were performed. Also, No. In 3, the phase transformation rate of the end face of the coil was calculated using the above formulas (8) and (9), and the transformation heat value was calculated using the above formula (10) (second calculation step). . No. 3, the temperature history was predicted using the above equations (6) and (7) in the first calculation step and the first prediction step. Furthermore, No. In 3, the Vickers hardness [Hv] at the position (calculation point) where the phase transformation rate was calculated in the second calculation step was actually measured. No. The phase transformation rate calculated in No. 3 and No. Table 1 shows the Vickers hardness measured in No. 3.
Figure JPOXMLDOC01-appb-T000010
Figure JPOXMLDOC01-appb-T000010
　表１に示すように、相変態率の小さい算出点Ａは、相変態率の大きい算出点Ｂ及びＣよりもビッカース硬度が大きくなっている。このことから、相変態率は、コイルの硬度と相関していることが分かる。そのため、第２算出工程によって相変態率を算出することで、コイルの硬質化部を予測できる。また、冷間圧延工程等の後工程において鋼材の破断が生じ得る硬度又は相変態率の閾値を予め設定しておき、この閾値と算出された相変態率とを比較することで、後工程において鋼材に破断が生じるか否かを予測することができる。 As shown in Table 1, the Vickers hardness of calculation point A with a small phase transformation rate is higher than calculation points B and C with a large phase transformation rate. From this, it can be seen that the phase transformation rate correlates with the hardness of the coil. Therefore, the hardened portion of the coil can be predicted by calculating the phase transformation rate in the second calculation step. In addition, by setting in advance a threshold value of hardness or phase transformation rate at which steel fracture can occur in a post-process such as a cold rolling process, and comparing this threshold value with the calculated phase transformation rate, It is possible to predict whether or not the steel will break.
　以上説明したように、本発明の一態様に係る熱延鋼板の製造方法は、冷間圧延板の製造時等における鋼材の破断の可能性を事前に察知するのに適している。 As described above, the hot-rolled steel sheet manufacturing method according to one aspect of the present invention is suitable for detecting in advance the possibility of steel breakage during the manufacture of cold-rolled steel sheets.
１　熱延鋼板の製造設備
２　熱間圧延装置
２ａ　圧延ロール
２ｂ　搬送部
２ｃ　巻取機
３　測定装置
３ａ　非接触温度センサ
４　算出装置
５　導出装置
５ａ　コンベア
５ｂ　変位計
５ｃ　導出部
６　予測装置
７　放冷装置
Ｘ　帯状鋼材
Ｘ１　コイル
Ｘ２　仮想コイル
Ｅ　端面
Ｏ　原点
Ｒ　コイルの端面の基準面
Ｚ　コイルの中心軸 1 Hot-rolled steel sheet manufacturing equipment 2 Hot rolling device 2a Rolling roll 2b Conveying unit 2c Winding machine 3 Measuring device 3a Non-contact temperature sensor 4 Calculating device 5 Deriving device 5a Conveyor 5b Displacement gauge 5c Deriving unit 6 Prediction device 7 Cooling Apparatus X Steel strip X1 Coil X2 Virtual coil E End face O Origin R Reference plane Z of coil end face Central axis of coil

Claims (6)

  1. 　熱間圧延された帯状鋼材の表面温度を測定する測定工程と、
    　上記帯状鋼材を端面に凹凸のないコイル状に巻き取ったと仮定した場合の巻取り後における放冷状態での温度履歴を、上記測定工程で測定された上記表面温度に基づいて算出する第１算出工程と、
    　上記測定工程後の上記帯状鋼材を実際にコイル状に巻き取る巻取工程と、
    　上記巻取工程で巻き取られたコイルの端面を変位計で走査し、上記端面の凹凸の大きさを上記コイルの半径に亘って導出する導出工程と、
    　上記第１算出工程で算出された温度履歴と上記導出工程で導出された凹凸の大きさとを用いて、上記凹凸の放冷状態での温度履歴を予測する第１予測工程と
    　を備える熱延鋼板の製造方法。     a measuring step of measuring the surface temperature of the hot-rolled steel strip;
    A first calculation for calculating a temperature history in a naturally cooled state after winding, assuming that the steel strip is wound into a coil having no unevenness on the end surface, based on the surface temperature measured in the measuring step. process and
    a winding step of actually winding the steel strip after the measuring step into a coil;
    a derivation step of scanning the end face of the coil wound in the winding step with a displacement meter to derive the size of the unevenness of the end face over the radius of the coil;
    a first prediction step of predicting the temperature history of the unevenness in a naturally cooled state using the temperature history calculated in the first calculation step and the size of the unevenness derived in the derivation step; manufacturing method.
  2. 　上記第１予測工程で予測された温度履歴を用いて相変態率を算出する第２算出工程と、
    　上記第２算出工程で算出された相変態率を用いて上記帯状鋼材の硬質化部を予測する第２予測工程と
    　をさらに備える請求項１に記載の熱延鋼板の製造方法。     a second calculation step of calculating a phase transformation rate using the temperature history predicted in the first prediction step;
    The method for producing a hot-rolled steel sheet according to claim 1, further comprising: a second prediction step of predicting the hardened portion of the steel strip using the phase transformation rate calculated in the second calculation step.
  3. 　上記導出工程で、上記変位計による測定値の中央値を基準として上記凹凸の大きさを求める請求項１又は請求項２に記載の熱延鋼板の製造方法。 The method for producing a hot-rolled steel sheet according to claim 1 or claim 2, wherein in the derivation step, the size of the unevenness is obtained based on the median value of the measured values of the displacement gauge.
  4. 　上記導出工程で、上記凹凸の飛び出し方向と上記変位計による走査方向とで規定される２次元座標系を用いて上記凹凸の大きさを求める請求項１又は請求項２に記載の熱延鋼板の製造方法。 3. The hot-rolled steel sheet according to claim 1 or 2, wherein in the derivation step, the size of the unevenness is obtained using a two-dimensional coordinate system defined by the projection direction of the unevenness and the scanning direction of the displacement meter. Production method.
  5. 　熱間圧延された帯状鋼材の表面温度を測定する測定工程と、
    　上記帯状鋼材を端面に凹凸のないコイル状に巻き取ったと仮定した場合の巻取り後における放冷状態での温度履歴を、上記測定工程で測定された上記表面温度に基づいて算出する第１算出工程と、
    　上記測定工程後の上記帯状鋼材を実際にコイル状に巻き取る巻取工程と、
    　上記巻取工程で巻き取られたコイルの端面を変位計で走査し、上記端面の凹凸の大きさを上記コイルの半径に亘って導出する導出工程と、
    　上記第１算出工程で算出された温度履歴と上記導出工程で導出された凹凸の大きさとを用いて、上記凹凸の放冷状態での温度履歴を予測する第１予測工程と
    　を備える熱延鋼板の温度履歴予測方法。     a measuring step of measuring the surface temperature of the hot-rolled steel strip;
    A first calculation for calculating a temperature history in a naturally cooled state after winding, assuming that the steel strip is wound into a coil having no unevenness on the end surface, based on the surface temperature measured in the measuring step. process and
    a winding step of actually winding the steel strip after the measuring step into a coil;
    a derivation step of scanning the end face of the coil wound in the winding step with a displacement meter to derive the size of the unevenness of the end face over the radius of the coil;
    a first prediction step of predicting the temperature history of the unevenness in a naturally cooled state using the temperature history calculated in the first calculation step and the size of the unevenness derived in the derivation step; temperature history prediction method.
  6. 　熱間圧延された帯状鋼材の表面温度を測定する測定工程と、
    　上記帯状鋼材を端面に凹凸のないコイル状に巻き取ったと仮定した場合の巻取り後における放冷状態での温度履歴を、上記測定工程で測定された上記表面温度に基づいて算出する第１算出工程と、
    　上記測定工程後の上記帯状鋼材を実際にコイル状に巻き取る巻取工程と、
    　上記巻取工程で巻き取られたコイルの端面を変位計で走査し、上記端面の凹凸の大きさを上記コイルの半径に亘って導出する導出工程と、
    　上記第１算出工程で算出された温度履歴と上記導出工程で導出された凹凸の大きさとを用いて、上記凹凸の放冷状態での温度履歴を予測する第１予測工程と、
    　上記第１予測工程で予測された温度履歴を用いて相変態率を算出する第２算出工程と、
    　上記第２算出工程で算出された相変態率を用いて上記帯状鋼材の硬質化部を予測する第２予測工程と
    　を備える熱延鋼板の硬質化部予測方法。
          a measuring step of measuring the surface temperature of the hot-rolled steel strip;
    A first calculation for calculating a temperature history in a naturally cooled state after winding, assuming that the steel strip is wound into a coil having no unevenness on the end surface, based on the surface temperature measured in the measuring step. process and
    a winding step of actually winding the steel strip after the measuring step into a coil;
    a derivation step of scanning the end face of the coil wound in the winding step with a displacement meter to derive the size of the unevenness of the end face over the radius of the coil;
    a first prediction step of predicting the temperature history of the unevenness in a cooled state using the temperature history calculated in the first calculation step and the size of the unevenness derived in the derivation step;
    a second calculation step of calculating a phase transformation rate using the temperature history predicted in the first prediction step;
    and a second prediction step of predicting the hardened portion of the steel strip using the phase transformation rate calculated in the second calculation step.
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