WO2002074460A1 - Hot rolling mill and hot rolling method - Google Patents

Hot rolling mill and hot rolling method Download PDF

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Publication number
WO2002074460A1
WO2002074460A1 PCT/JP2002/000667 JP0200667W WO02074460A1 WO 2002074460 A1 WO2002074460 A1 WO 2002074460A1 JP 0200667 W JP0200667 W JP 0200667W WO 02074460 A1 WO02074460 A1 WO 02074460A1
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WO
WIPO (PCT)
Prior art keywords
rolled
rolling
mill
mills
stage
Prior art date
Application number
PCT/JP2002/000667
Other languages
French (fr)
Japanese (ja)
Inventor
Ichiro Chikushi
Ryuro Kurahashi
Toshiharu Morimoto
Takashi Ohtani
Kazuaki Hakomori
Shinji Takaoka
Masanori Takahashi
Akio Adachi
Original Assignee
Nakayama Steel Works, Ltd.
Kawasaki Jukogyo Kabushiki Kaisha
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP2001077293A external-priority patent/JP3418738B2/en
Priority claimed from JP2001287427A external-priority patent/JP3413183B2/en
Priority claimed from JP2001287428A external-priority patent/JP3413184B2/en
Application filed by Nakayama Steel Works, Ltd., Kawasaki Jukogyo Kabushiki Kaisha filed Critical Nakayama Steel Works, Ltd.
Priority to KR1020027013155A priority Critical patent/KR20020093881A/en
Priority to DE60206851T priority patent/DE60206851T2/en
Priority to US10/220,728 priority patent/US7076983B2/en
Priority to EP02716450A priority patent/EP1279445B1/en
Priority to AT02716450T priority patent/ATE307687T1/en
Publication of WO2002074460A1 publication Critical patent/WO2002074460A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B1/24—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process
    • B21B1/26—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process by hot-rolling, e.g. Steckel hot mill
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
    • B21B45/0203—Cooling
    • B21B45/0209—Cooling devices, e.g. using gaseous coolants
    • B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
    • B21B45/0218—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes for strips, sheets, or plates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B13/00—Metal-rolling stands, i.e. an assembly composed of a stand frame, rolls, and accessories
    • B21B13/14—Metal-rolling stands, i.e. an assembly composed of a stand frame, rolls, and accessories having counter-pressure devices acting on rolls to inhibit deflection of same under load; Back-up rolls
    • B21B13/142—Metal-rolling stands, i.e. an assembly composed of a stand frame, rolls, and accessories having counter-pressure devices acting on rolls to inhibit deflection of same under load; Back-up rolls by axially shifting the rolls, e.g. rolls with tapered ends or with a curved contour for continuously-variable crown CVC
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2267/00—Roll parameters
    • B21B2267/02—Roll dimensions
    • B21B2267/06—Roll diameter
    • B21B2267/065—Top and bottom roll have different diameters; Asymmetrical rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2269/00—Roll bending or shifting
    • B21B2269/02—Roll bending; vertical bending of rolls
    • B21B2269/04—Work roll bending
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2269/00—Roll bending or shifting
    • B21B2269/12—Axial shifting the rolls
    • B21B2269/14—Work rolls
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B27/00—Rolls, roll alloys or roll fabrication; Lubricating, cooling or heating rolls while in use
    • B21B27/06—Lubricating, cooling or heating rolls
    • B21B27/10—Lubricating, cooling or heating rolls externally
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B21B3/02—Rolling special iron alloys, e.g. stainless steel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/002—Increasing friction between work and working rolls by using friction increasing substance
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
    • B21B45/0239—Lubricating
    • B21B45/0242—Lubricants
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
    • B21B45/0239—Lubricating
    • B21B45/0245—Lubricating devices
    • B21B45/0248—Lubricating devices using liquid lubricants, e.g. for sections, for tubes
    • B21B45/0251—Lubricating devices using liquid lubricants, e.g. for sections, for tubes for strips, sheets, or plates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
    • B21B45/0239—Lubricating
    • B21B45/0245—Lubricating devices
    • B21B45/0263—Lubricating devices using solid lubricants
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
    • B21B45/0269—Cleaning
    • B21B45/0275—Cleaning devices
    • B21B45/0278—Cleaning devices removing liquids
    • B21B45/0281—Cleaning devices removing liquids removing coolants
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling

Definitions

  • the present invention relates to a hot rolling apparatus and a hot rolling method, and more particularly to a hot rolling apparatus and a hot rolling method for producing a steel sheet having a microstructure mainly composed of fine-grain ferrite.
  • the large reduction rolling method of (1) is described in Japanese Patent Application Laid-Open No. 58-123238 / Japanese Patent Publication No. 5-65564.
  • this method promotes the strain-induced transformation from the austenite (a) phase to the ferrite (h) phase by applying a large reduction to the austenite grains, thereby miniaturizing the structure.
  • Nb (niobium) and Ti (titanium) are contained in the component to not only easily increase the tensile strength by the precipitation strengthening action of Nb and Ti, but also to increase Nb,
  • This is a method that promotes the strain-induced transformation from a phase to a phase when low-temperature rolling (ferrite region rolling) is performed by Ti's effect of suppressing austenite grains from recrystallizing, thereby reducing the size of ferrite grains.
  • Controlled rolling method there is a disadvantage that a finish rolling a low temperature range (8 0 0 e C below) significantly higher deformation resistance of the rolled material from doing, the thus load on the rolling apparatus is large.
  • the large rolling reduction method cannot be industrially implemented by a general hot strip mill as shown in the above-mentioned Japanese Patent Publication No. 5-65564, and requires special rolling equipment. Needed to use. As described in the above publications, This is because it is necessary to continuously apply a high rolling reduction (for example, 40% or more) that is difficult to achieve with a general rolling mill.
  • Rolling at high pressure that is, high rolling reduction tends to cause inconvenience due to rolling load. That is, the rolling load may reach the limit value (mill power limit and mechanical strength) inherent in the rolling equipment, and rolling may not be possible. Further, for the material to be rolled, a predetermined rolling reduction cannot be realized or a large edged opening is generated. The reason why the predetermined rolling reduction cannot be obtained is that the rolling load is large and the deformation resistance is high, especially when the strip thickness at the exit side of the rolling mill is 2 mm or less and the rolling reduction is 40% or more. This is because the roll flatness increases. In this case, no matter how much reduction is applied to perform high reduction rolling, the reduction rate does not improve. The reason why the edge drop is large is that a high load is applied near the edge (widthwise end) of the material to be rolled, and a good plate profile cannot be obtained.
  • Roll wear becomes severe, and the shape (crown) of the material to be rolled is further deteriorated.
  • High pressure rolling ⁇ In high-load rolling, thermal or mechanical This is because the load is high and roll wear is likely to progress. The portion of the material to be rolled that contacts the edge is subject to high rolling loads, and is especially prone to wear, which tends to significantly reduce the profile of the material to be rolled, which is important for quality. In addition, if the rolls are easily worn, the maintenance costs such as polishing and replacing the rolls will increase.o
  • an object of the present invention is to provide a hot rolling apparatus and a method for producing fine-grained steel, which solve the above-mentioned problems relating to the production of hot-rolled fine-grained steel sheets and enable smooth production of the steel sheets.
  • Another object of the present invention is to provide a continuous hot rolling method suitable for the production of hot-rolled fine-grained steel sheets, which is excellent in cost-effectiveness.
  • a further object of the present invention is to provide a continuous hot rolling method for smoothly manufacturing a thick plate using a hot rolling device capable of manufacturing a thin plate. Disclosure of the invention
  • the present invention relates to a hot rolling apparatus for rolling a material to be rolled to produce a steel sheet, comprising: a mill arranged at the front stage; and a multi-stand mill arranged at the latter stage, wherein the equivalent roll diameter is 600 mm.
  • cooling means for cooling the material to be rolled comprising: a mill arranged at the front stage; and a multi-stand mill arranged at the latter stage, wherein the equivalent roll diameter is 600 mm.
  • a mill having a pair of different diameter roll mills including a pair of different diameter rolls or a small diameter roll mill including a pair of work rolls each having a diameter of less than 600 mm;
  • cooling means for cooling the material to be rolled comprising: a mill arranged at the front stage; and a multi-stand mill arranged at the latter stage, wherein the equivalent roll
  • the “equivalent roll diameter” refers to the average value of the diameters of a pair of upper and lower pairs of different diameter single crawls with respect to different diameter roll mills.
  • the cooling means is a curtain wall type cooler.
  • the "curtain wall type cooler” is a type in which a large amount of cooling water is flowed in a laminar flow from above and below like a curtain, and applied to the upper and lower surfaces of the material to be rolled over the entire width.
  • Means cooling means are provided.
  • At least the mill arranged at the front stage includes a multi-stand CVC mill.
  • CVC mill is a roll whose outer diameter changes continuously in the axial direction. And mills that can move in the axial direction (CVC rolls).
  • the equivalent roll diameter of the pair of different diameter work rolls of the different diameter roll mill or the roll diameter of the work roll of the ultra small diameter roll mill is 550 mm or less.
  • the work roll of the different diameter roll mill or the work roll of the ultra small diameter mill has a CVC function and a bending function.
  • cv c function refers to a function in which a roll whose outer diameter continuously changes in the axial direction moves in the axial direction to control the change of the roll gap shape.
  • bending function refers to a function that changes the roll gap shape by applying a bending force (bending moment) to the roll.
  • a lubricant supply means for supplying a lubricant to a roll surface of the mill, which is attached to the mill of at least one of the mills among the mills arranged in the preceding stage and the subsequent stage.
  • the lubricant supply means supplies a lubricant containing fine solid lubricant in grease.
  • the hot rolling device is preferably arranged on the exit side of the mill of the last stage stand, disposed downstream of the cooling unit in the flow direction of the material to be rolled, and supplies the fluid to the material to be rolled.
  • the apparatus further includes a fluid spray for spraying to remove cooling water existing on the material to be rolled.
  • the fluid jet spray is formed in such a manner that, with respect to the material to be rolled, an obliquely downward direction from above the material to be rolled toward an upstream side in a flow direction of the material to be rolled, in a width direction of the material to be rolled It includes a plurality of nozzles that blow out pressurized water so as to spread out.
  • the present invention relates to a method for producing fine-grained steel by rolling a material to be rolled, comprising: a rolling device having a heated mill to be rolled; a mill arranged in a former stage and a mill arranged in a latter stage.
  • the mill disposed at the latter stage of the rolling device has a work roll having a diameter of not more than 550 mm, and the mill disposed at the latter stage of the rolling device has a flow of the material to be rolled. Rolling the rolled material so that the cumulative strain is 0.9 or more while cooling the rolled material before and after in the direction. I do.
  • strain is the thickness h of the material to be rolled on the entry side of each mill. The difference between the thickness hi at the outlet and the output side was divided by the average thickness of both.
  • “cumulative distortion” is defined as the number of mills in the subsequent multiple stands (for example, 3 stands, which may be 2 stands) (mills on the stands upstream from them are ignored because their influence is small).
  • the distortion is weighted and integrated taking into account the strength of the effect on the metal structure, and the distortion at the last stage, the previous stage, and the previous stage is further reduced by £ n , £ n- U £ When n -2,
  • ⁇ c ⁇ ⁇ 10 £ n -i / 2 10 £ n - 2 /4
  • the method for producing fine-grained steel according to the present invention includes using any one of the above-described hot rolling devices, wherein the material to be rolled is formed so that the cumulative strain of the material to be rolled at the subsequent stage of the rolling device is 0.9 or more. It is characterized by rolling.
  • the material to be rolled immediately after leaving the mill at the final stand is cooled at a temperature drop rate of 20 ° C. or more per second.
  • the material to be rolled has a carbon content of 0.5% or less and an alloy element content of 5% or less.
  • the present invention relates to a method for producing a steel sheet by continuously hot rolling a material to be rolled, comprising a plurality of stand mills in which the heated material to be rolled is arranged in tandem at a former stage and a latter stage.
  • the rolling device is supplied to a rolling device, and the material to be rolled is rolled using the rolling device so that the accumulated strain of the material to be rolled becomes 0.6 or more.
  • the rolled material is cooled on the outlet side of the mill.
  • the rolling end temperature of the material to be rolled is within a range of not less than the third transformation point—50 ° C. and not more than the Ar 3 transformation point + 50 ° C.
  • the “rolling end temperature” is measured by a thermometer installed downstream of the rolling mill in the flow direction of the material to be rolled (a few meters downstream from the arranged final stage mill). Surface temperature of the material to be rolled.
  • the average ferrite particle size inside the steel sheet obtained by rolling the material to be rolled is about 3 to Am.
  • the present invention relates to a continuous hot rolling method for producing a thick plate by rolling a material to be rolled, wherein the heated material to be rolled is subjected to a first stage and a second stage so that a thin plate can be produced by rolling the material to be rolled.
  • a rolling mill having a plurality of stands of mills arranged in tandem, and without using at least a part of the plurality of mills arranged in the latter stage of the rolling mill, on the input side of the rolling mill.
  • the cumulative strain of the material to be rolled becomes 0.25 or more using the at least three stands of the mill, or the rolling reduction in the last stage of the mills among the mills to be used is reduced.
  • the method is characterized in that the material to be rolled is cooled at the exit side of the mill at the final stage used, while the material to be rolled is rolled to 12% or more.
  • thin plate refers to a steel plate having a thickness of less than 6 mm
  • thick plate refers to a steel plate having a thickness of 6 mm or more (about 50 mm or less).
  • the rolling end temperature of the material to be rolled does not exceed the Ar 3 transformation point + 50 ° C.
  • rolling end temperature refers to the material to be rolled measured by a thermometer installed downstream of the rolling mill in the flow direction of the material to be rolled (downstream of several meters from the mill at the last stage arranged). Surface temperature.
  • the thick plate obtained by rolling the material to be rolled has an average ferrite particle size of about 3 to 10 zm inward from the surface by 1 Z4 of the thickness.
  • FIG. 1 is a side view conceptually showing the overall arrangement of a hot rolling apparatus according to one embodiment of the present invention.
  • FIGS. 2A, 2B, and 2C is a schematic diagram for explaining the CVC function of the first mill in the rolling mill shown in FIG.
  • FIG. 3 is a side view showing details of the final mill 6 and the like in the rolling mill shown in FIG.
  • FIG. 4 is a diagram showing the relationship between the grain size and the yield point of the crystal grains of the ferrite tissue for the steel sheet manufactured using the rolling mill shown in FIG.
  • Figures 5A, 5B, and 5C show the crystal structures of the steel sheet manufactured using the rolling mill shown in Figure 1 near the upper surface, near the center of the thickness, and near the lower surface.
  • FIG. 5A, 5B, and 5C show the crystal structures of the steel sheet manufactured using the rolling mill shown in Figure 1 near the upper surface, near the center of the thickness, and near the lower surface.
  • FIG. 6 is a diagram showing the relationship between the equivalent diameter of a single roll of a different diameter roll mill and the rolling load.
  • FIG. 7 is a diagram showing the effect of reducing edge drop in a roll mill with a different diameter.
  • Fig. 8 is a diagram showing the effect of reducing the wear on the surface of the mouth when a lubricant is used.
  • FIG. 9 FIG. 2 is a side view conceptually showing the overall arrangement of a hot rolling apparatus according to a modification of the embodiment shown in FIG.
  • FIG. 10 is a side view conceptually showing the overall arrangement of a continuous hot rolling apparatus according to another embodiment of the present invention.
  • FIGS. 11A, 11B, and 11C is a schematic diagram for explaining the CVC function with respect to the mill 10 and the like at the preceding stage in the rolling mill shown in FIG. .
  • FIG. 12 is a side view showing the details of the subsequent mills 40 to 60 of the rolling mill shown in FIG. 10 and the vicinity thereof.
  • FIG. 13 is a diagram showing the relationship between the cumulative strain and the ferrite grain size for various steel sheets obtained by test rolling.
  • Figure 14 is a diagram showing the relationship between the finishing temperature (rolling end temperature) and the ferrite grain size for various steel sheets obtained by test rolling.
  • FIG. 15 is a diagram showing the relationship between the ferrite grain size, tensile strength, and the like for various steel sheets obtained by test rolling.
  • FIG. 16 is a diagram showing the relationship between ferrite grain size, elongation, and the like for various steel sheets obtained by test rolling.
  • FIG. 17 is a diagram showing the relationship between the ferrite grain size and the tensile strength X elongation, etc., for various steel sheets obtained by test rolling.
  • FIG. 18A, FIG. 18B, and FIG. 18C show the steel sheet obtained by the example of the rolling method using the rolling device shown in FIG. Only 4
  • FIG. 3 is a diagram showing crystal structures at respective locations near the inside and near the center of the thickness.
  • FIG. 3 is a diagram showing a crystal structure at a location.
  • FIG. 20 is a diagram showing the relationship between the ferrite grain size, the tensile strength, and the yield point of the steel sheet produced according to the example of the present invention.
  • FIG. 21 is a diagram showing a temperature change of a Charpy impact value of a steel sheet produced according to an example of the present invention and a normal steel (non-fine-grained steel sheet).
  • FIG. 22 is a diagram showing the temperature change of the brittle fracture ratio of the steel sheet produced according to the example of the present invention.
  • the hot rolling apparatus is a finish rolling apparatus, and includes a heating furnace and a rough rolling apparatus on the upstream side (not shown) in the flow direction of the rolled material P, and on the downstream side ( (Not shown), a run-out table, a winder and the like are arranged.
  • This hot rolling apparatus is configured as follows so that a hot-rolled fine-grained steel sheet having a fine ferrite structure can be manufactured by continuously rolling a material P roughly-rolled on the upstream side. ing.
  • CV C mills 1, 2, and 3 are arranged in tandem as a three-stand mill that constitutes the former stage of the hot rolling mill.
  • the CVC mill 1 located at the most entry side of the hot rolling mill is configured as a quadruple mill consisting of a single crawl 1a and 1b and a backup roll 1c and 1d, as shown in Fig. 1.
  • Roll 1a ⁇ 1 Alligator has a crown (CVC, that is, continuous change in diameter) as shown in Fig. 2A.
  • the work rolls la ′ lb can be simultaneously moved (shifted) in opposite axial directions as shown in FIG. 2B and FIG. 2C, thereby adjusting the positional relationship between the rolls, that is, the roll gap. It is possible.
  • the diameter of the work roll la * lb was set to 700 mm, and the maximum shift amount was set to forward and reverse and 100 mm.
  • the two-stand CVC mills 2 and 3 do not differ from the CVC mill 1 in such configuration and function.
  • the reason why the CVC mills 1, 2, and 3 are arranged at the front stage is to appropriately maintain the crown (shape) of the material P to be rolled.
  • the crown is corrected in advance by these CVC mills 1, 2, and 3 placed in the preceding stage.
  • the medium drawing of the material P to be rolled is reduced.
  • the CVC mills 1, 2, and 3 have a greater ability to change the roll gap shape than means such as simply performing roll bending, and have a thicker material to be rolled, making it easier to control the crown. Since it is located at the center, it is advantageous in adjusting the crown and preventing instability of the threading plate in the subsequent stage of large pressure reduction.
  • so-called different-diameter roll mills 4, 5, and 6 are arranged in tandem as three-stand mills constituting a subsequent stage following the preceding stage.
  • the stand spacing of all six stands including the aforementioned CVC mills 1, 2, and 3 is equally 5.5m.
  • the roll mill 4 of the different diameter which corresponds to the fourth stand, counting from the CVC mill 1, is configured as a quadruple mill consisting of work rolls 4a and 4b and backup ports 4c and 4d, as shown in Fig. 1. Work rolls 4a and 4b with different diameters are used as shown in the figure.
  • each crawl 4a and 4b is driven to rotate by a motor (not shown), and the upper small-diameter roll 4a is rotatable.
  • the driving force is not applied.
  • a vendor (not shown) is attached to each crawl 4a and 4b, it is possible to bend each crawl 4a and 4b.
  • Each work roll 4a and 4b is also provided with a CVC function, so that both can be moved in the axial direction within a range of 10 Omm in each direction.
  • the diameter of work roll 4 a is 480 mm
  • the diameter of work roll 4 b is 600 mm
  • the average equivalent diameter of both is 540mm.
  • the other two stands of different diameter roll mills 5 and 6 at the rear are not different from the above different diameter roll mill 4.
  • the equivalent roll diameter of the work rolls of the different diameter roll mills 4, 5, 6 can be smaller than 540 mm, but is preferably 400 mm or more from the viewpoint of strength.
  • These three-stand roll mills 4, 5, and 6 have a small equivalent roll diameter and a shear force acting on the material P to be rolled because only one of the work rolls (4b, etc.) is driven. Rolling with a high rolling reduction (for example, a rolling reduction of 50%) can be performed even with a relatively low rolling load. For this reason, large rolling reduction or the like that forms a fine flat structure in the material P to be rolled can be performed with a small rolling load, and since the rolling load is small, problems due to roll flattening and edge drop do not occur.
  • a high rolling reduction for example, a rolling reduction of 50%
  • large rolling reduction or the like that forms a fine flat structure in the material P to be rolled can be performed with a small rolling load, and since the rolling load is small, problems due to roll flattening and edge drop do not occur.
  • the diagram X3 in Fig. 6 shows a steel plate with a thickness of 2.3 mm and a width of 730 mm in the different-diameter roll mill 6 of the sixth stand (C: 0.16%, Si: 0.22%, Mn: 0.82 It shows how the rolling load changes when the equivalent diameter of the work roll is changed when rolling is performed at the same rolling reduction (48%).
  • the diagram X5 in Fig. 7 shows that constant diameter roll mills 5 and 6 (each crawl 5a and 6a have a diameter of 480 mm, 5b and 6b have a diameter of 600 mm, and This represents the edge drop that occurs when rolling the same steel sheet as in Fig. 6 at a diameter of 540 mm).
  • the line X4 in Fig. 7 shows the edge drop when the same steel plate is rolled and manufactured with the same diameter (600 mm medium-sized diameter) instead of different diameters of the work rolls for comparison.
  • a pair of work rolls 4a each having a diameter of less than 600 mm are replaced with different-diameter roll mills 4, 5, 6 as shown in FIG. , ⁇ 4b, etc., the minimum diameter roll mill 4, ⁇ 5, 6 ⁇
  • lubricant supply means is arranged for each work roll of mills 1 to 6 in all six stands.
  • the means comprises, for example, an injection port facing the surface of the work roll as indicated by reference numerals 5e, 5f, 6e, and 6f in Fig. 3, and a lubricant feed pump and the like.
  • ⁇ instead of directly applying the lubricant to the surface of one crawl, it is also possible to apply the lubricant to the surface of the material P to be rolled and supply the lubricant to the surface of the roll indirectly.
  • the lubricant is for preventing abrasion of the roll surface and not for lowering the friction coefficient. Therefore, a lubricant containing fine solid lubricant such as calcium phosphate, mica, calcium carbonate, etc., in the grease is used.
  • a lubricant containing fine solid lubricant such as calcium phosphate, mica, calcium carbonate, etc.
  • the coefficient of friction // between each work roll and the material P to be rolled when using a lubricant is increased to about 0.28 or more. When such a coefficient of friction is secured, the roll slip of the material P to be rolled is appropriately prevented.
  • the shape of the material to be rolled P is long and easily maintained.
  • solid fine particles are included in grease instead of mineral oil, there is no risk of fine particles settling in the lubricant storage container, and solid fine particles are always uniformly dispersed on the roll surface There is also a merit that it is supplied as follows.
  • FIG. 8 shows the effect of reducing the wear of the roll by using a lubricant.
  • a diagram X6 shows a case where no lubricant is used, and a diagram X7 shows a case where the lubricant is used.
  • the horizontal axis in FIG. 8 indicates the magnitude of the load on the work roll, and the vertical axis indicates the amount of wear of the single crawl.
  • curtain wall type coolers 7 A, 7 B and 7 C are arranged on the respective outlet sides of the three stand different-diameter roll mills 4, 5, and 6 arranged at the subsequent stage. I have.
  • the cooler 7B As an example, as shown in FIG. 3, the cooler 7B has a large amount of room temperature cooling water from the upper and lower headers 7B a '7B b toward the entire width surface of the material P to be rolled.
  • the material to be rolled P is cooled strongly by pouring it into a curtain shape (curtain wall shape.
  • the thickness is 10 mm or more and the optimum thickness is 16 mm).
  • the amount of cooling water can be adjusted within the range of 100 to 500 m 3 / h per unit width (lm) of the material P to be rolled, and the temperature drop of the material P to be rolled by cooling is 20 ° C. / sec or more.
  • Curtain wall coolers usually use 350 m 3 / h of cooling water per unit width.
  • the temperature drop rate of the material P to be rolled is 1 times the product of the sheet thickness and the speed. 2 0 When it is 0 mm ⁇ mpm, it reaches 60 to 80 ° C / sec (around 40 ° C / sec including the temperature rise due to the heat generated during processing).
  • the above configurations and functions of the other coolers 7A and 7C are the same.
  • a force-type cooling device is arranged on the outlet side of each of the subsequent mills 4, 5, 6; however, the number of cooling devices is not limited to this. It can be appropriately changed depending on the type of rolled material and the like.
  • the ten-wall type cooler 7A, 7B, 7C By using such a ten-wall type cooler 7A, 7B, 7C, it is possible to suppress the temperature rise of the material P to be rolled due to the heat generated during processing during rolling, and to apply it to the large rolling reduction method or the controlled rolling method.
  • the material P to be rolled can be kept in a suitable temperature range, and the microstructure can be prevented from undergoing grain growth after rolling.
  • the run-out table (not shown) on the downstream side of the hot rolling mill shown in Fig. 1 also uses cooling water at a speed of 10 ° C / sec or more with cooling water to prevent grain growth. Has cooled.
  • a water-injection sprayer 8 is placed at a distance of several hundred mm to lm from the curtain wall cooler 7C. I have. This is for removing the cooling water on the upper surface of the material P to be rolled by the cooler 7C. As shown in FIG. 3, this spray 8 is sprayed from a plurality of nozzles 8a to the surface of the material P to be rolled from above the material P to the upstream side in the flow direction of the material P to be rolled.
  • the pressurized water has a plurality of nozzles 8a that blow out 300 liters per minute (a total of 4 nozzles in this example). As shown in FIG. 3, the plurality of nozzles 8a are arranged at intervals in the length direction of the material P to be rolled, and at intervals in the width direction thereof.
  • Each nozzle 8a blows out water so as to spread in the width direction of the material P to be rolled, and the spread angle of the material P to be rolled in the width direction is 15 to 30 °, and the spread angle in the length direction is 1 to 10 ° is preferable (in the present embodiment, they are 21 ° and 3 °, respectively).
  • the cooling means 7 can smoothly remove the cooling water placed on the material P to be rolled by the action of the cooling means 7.
  • water has a greater mass than a gas, so it imparts kinetic energy. It is easy to obtain, and is therefore suitable for use as a jet fluid.
  • pressurized water By blowing pressurized water obliquely downward toward the upstream side, it is possible to prevent the cooling water from reaching the downstream side (the side with the measuring instrument), and use nozzles that spread in the width direction of the material P to be rolled. The reason for this is that the cooling water can be removed from the entire width of the material P to be rolled, thereby providing a favorable effect.
  • a nozzle for cooling water for cooling for example, reference numeral 5 i ⁇ 5 j ⁇ 6 i ⁇ 6 j
  • the cooling water A drainer board for example, 5 g ⁇ 5 h ⁇ 6 g ⁇ 6 h
  • Example 1 C For a steel with the chemical composition of C: 0.16%, Si: 0.22%, Mn: 0.82% (excluding other significant components), the rolling mill shown in Fig. 1 C.
  • C The following Table 1-1 shows the pass schedule (rolling conditions) for Example 1.
  • 2 shows the pass schedules of Embodiments 2 and 3.
  • Table 1-3 shows the usage status of the ten-wall type coolers 7A, 7B and 7C in each of Examples 1-3
  • Table 1-4 shows the final stage mill for each of Examples 1-3. This is the finishing temperature of the material P to be rolled measured behind 6.
  • Table 3 750-780 The ferrite grain size and mechanical properties of the hot-rolled steel sheets obtained in Examples 1 to 3 are shown in Table 115.
  • “TS” is the tensile strength
  • “YP j is the yield point
  • “ EL j is the elongation. ”In Table 115, Tables 11-11 to 13 The main ones of the indicated rolling conditions are also shown.
  • TS Tensile strength
  • YP Yield point
  • EL Elongation
  • Table 15-5 in Examples 2 and 3 where the cumulative strain (the above-mentioned weighted integrated value, £ C ) was set at 0.92, A steel sheet with a ferrite structure with a diameter of about 4 m and excellent mechanical properties was obtained.
  • the ferrite particle size is about 4 m or less, and A steel sheet with particularly good properties was obtained.
  • Figure 4 shows the relationship between the grain size (the grain size D (jum) is 11-1 squared) and the yield point for the grains of the ferrite structure in the steel sheets obtained in Examples 1 to 3. It was done. As shown in the figure, when the cumulative strain in the latter three-stand mill was 0.65 (group X2 in Fig. 4), the grain size was 0.43 or less (particle size of 5.4 m or more) and the yield was low. is also not enough points, when the cumulative strain to 0. 92, grain size 0.5 about 5 (particle size of about 4 ⁇ M) becomes, the yield point is as high as 45 kg / mm 2 or more become.
  • 5A, 5B, and 5C are diagrams showing the crystal structures of the steel sheet obtained in Example 3 near the upper surface, near the center of the sheet thickness, and near the lower surface, respectively. Within thickness In each part, a fine ferrite structure with a grain size of the order of 3 m is formed.
  • a hot-rolled fine-grained steel sheet having a fine flat structure and an excellent balance of strength including tensile strength, ductility, toughness, and fatigue strength can be smoothly manufactured. Commercial production of steel sheets is also possible. The reasons are summarized below.o
  • the roll mills with different diameters of 4, 5, 6 or extra small diameter roll mills 4, 5, 6 or more, which are arranged at the subsequent stage, have a small equivalent diameter or a pair of two diameters.
  • curtain wall type coolers 7A, 7B, and 7C provided at the subsequent stage suppress the temperature rise due to the heat generated during processing of the material P to be rolled due to the rolling at a high reduction ratio of 0.9 or more.
  • the cooler 7 ⁇ 7 77C cools the rolled material ⁇ ⁇ strongly by the large amount of cooling water flowing as described above, so even if the rolled material ⁇ is accelerated, the large rolling reduction method can be used. It is possible to maintain the material P to be rolled in a temperature range (for example, from the Ar 3 transformation point to Ar 3 +50 C) suitable for the operation.
  • the coolers 7A, 7B, and 7C are placed not only at the outlet of the mill 6 at the last stage but also at the outlet of at least two mills at the subsequent stage. The heat generated during rolling in the stand mill is effectively removed to maintain an appropriate temperature. Since the same coolers 7 A, 7 B, and 7 C are provided on the outlet side of the mill at each stand, the material P to be rolled immediately after rolling at the mill at each stand is strongly cooled to stop grain growth of the microstructure. Action is also ensured.
  • the cooling devices 7A, 7B, and 7C apply cooling water over the entire width of the material P to be rolled, the material P to be rolled can be uniformly cooled without being biased in the width direction.
  • the above-mentioned problems i) and ii) relating to the implementation of the large rolling reduction method are solved, and the fine-grained steel by using a general hot strip mill type rolling device is solved.
  • the smooth production of steel sheets will be possible, and the commercial production of fine-grained steel sheets will be possible.
  • the temperature range of the material P to be rolled is maintained at 700 to 800 ° C (warm range) by appropriately using the power wall coolers 7A, 7B, and 7C, It is also possible to use the steel containing Nb ⁇ Ti as the material P to be rolled and to stably execute the above-mentioned controlled rolling method (thus producing a fine-grained steel sheet).
  • a fine-grained steel sheet having such a composition has a mechanical property (It is versatile in terms of tensile strength and ductility, etc.) and weldability, so it is widely used, relatively inexpensive, easily available, and recyclable. It is considered that demand is high. Therefore, steel sheets with such component contents have a high social contribution and economic rationale for their production.
  • the amount of C carbon
  • the amount of ferrite decreases and the steel is mainly composed of steel.
  • the amount of ferrite can be increased even with the same amount of C.
  • a ferrite-based organization can be obtained up to a C content of 0.5%.
  • the Ar 3 transformation point becomes too low, and it becomes difficult to obtain fine grains.
  • the material to be rolled is strongly reduced centering on the subsequent mill (that is, a high reduction in which the cumulative strain becomes 0.9 or more) and the material to be rolled is appropriately compressed. It is intended to produce high-quality fine-grained steel sheets with a ferrite grain size of about 4 zm or less while maintaining the temperature.
  • the hot rolling mill shown in Fig. 1 achieved the required reduction with a relatively low rolling load.
  • a structure capable of strongly cooling the material to be rolled With this, if the material to be rolled is subjected to sufficiently high pressure and strong cooling (temperature control), extremely high-quality hot-rolled fine-grained steel sheets can be industrially produced using a normal tandem rolling mill.
  • the high level of high pressure described in the above embodiment is always indispensable irrespective of the quality of the steel sheet, the production cost increases in relation to the configuration of the rolling mill and the consumption of the rolling roll. This is because the equipment for cooling also requires higher equipment and operating costs due to the heating of the material to be rolled.
  • the hot rolling apparatus and method according to the present embodiment solves such a problem.
  • the continuous hot rolling apparatus is a so-called finish rolling apparatus for the material P to be rolled, and a heating furnace and a roughing furnace are provided upstream (not shown) in the flow direction of the material P to be rolled.
  • This hot rolling machine is a tandem arrangement of a total of 6 stands of mills 10 to 60 equipped with a rolling roll and a rolling roll. Manufactures various hot-rolled steel sheets with a thickness of about 2 to 16 mm. Normal rolling can be performed smoothly to produce steel sheets with a general internal structure (average particle diameter of 10/11 or more), and fine-grained steel rolling can be performed by setting the operating conditions appropriately.
  • the rolling mill shown in FIG. 10 is configured as follows so that a hot-rolled steel sheet having a fine ferrite structure can be manufactured.
  • the CVC mill 10 ⁇ 20 ⁇ 30 was set up in the first three stands. Are placed in the system.
  • the CVC mill 10 which is located closest to the entry side of the hot rolling mill, is configured as a quadruple mill consisting of work rolls 101a and 101b and backup rolls 101c and 101d, as shown in Fig. 10.
  • 101 a ⁇ 10 lb has a crown (CVC, ie continuous change in diameter) as shown in Figure 11A.
  • the work rolls 101a and 101b can be simultaneously moved (shifted) in opposite axial directions as shown in FIG. 11B and FIG. 11C, thereby adjusting the positional relationship between the rolls, that is, the roll gap. It is possible.
  • the diameter of the work rolls 101a and 101b was set to 700 mm, and the maximum shift amount was set to 100 mm in both directions.
  • the other two-stand CVC mills 20 and 30 do not differ from the CVC mill 10 in such configuration and function.
  • the reason why the CVC mills 10, 20, and 30 are arranged at the front stage is to keep the shape (shape) of the material P to be rolled properly.
  • the later-stage roll mills 40, 50, and 60 which will be described later, a thermal crown and the like due to the heat generated during processing are likely to occur during the rolling of fine-grained steel.
  • the work rolls 101a and 101b of each CVC mill 10, 20, and 30 are equipped with an AC motor (not shown) equipped with variable speed control means, a speed reducer and a universal joint (neither shown). It is connected through it.
  • different diameter roll mills 40, 50 and 60 are also arranged in tandem.
  • the stand spacing of all six stands including the aforementioned CVC mills 10, 20, 30 is equally 5.5m.
  • the different-diameter roll mill 40 corresponding to the fourth stand, counting from the CVC mill 10, is configured as a quadruple mill composed of a single crawl 104a104b and a backup roll 104c * 104d as shown in FIG.
  • the crawls 104a and 104b have different diameters from each other. ⁇ ⁇ Motor (not shown) in which only the lower large-diameter roll 104b of one crawl 104a '104b is connected via a speed reducer (not shown) and a universal joint (not shown.
  • the upper small roll 104a is allowed to rotate freely and no driving force is applied.
  • Work rolls 104a and 104b are provided with a vendor (not shown). Therefore, it is possible to bend the work rolls 104a and 104b.
  • Each Crawl 104a / 104b is also provided with a CVC function, so that both can be moved in the axial direction within 100mm in each direction.
  • the diameter of work roll 104a is 480 mm
  • the diameter of work roll 104b is
  • the equivalent roll diameter which is the average of both, is as small as 540 mm.
  • the other two stands of different diameter roll mills 50 and 60 at the rear are not different from the above different diameter roll mill 40.
  • the three stand different diameter roll mills 40, 50, and 60 are relatively low because the equivalent roll diameter is small and only one of the single crawls 104b is driven to apply a shearing force to the material P to be rolled.
  • Rolling with a high rolling reduction for example, a rolling reduction of 50%
  • a rolling reduction of 50% can be performed even with a rolling load.
  • a curtain wall type cooler 10 In order to continuously roll fine-grained steel, it is necessary to sufficiently cool the material to be rolled P and maintain it in an appropriate temperature range. At each rear and / or front, as shown in Fig. 10, a curtain wall type cooler 10
  • Each of the coolers 107 is composed of a large amount of room-temperature cooling water (laminar flow) in a curtain shape (curtain wall shape) from the header provided above or below to the entire width surface of the material P to be rolled.
  • the thickness (curtain thickness) of the cooling water flowing in a curtain is required to be 10 mm or more, and it is desirable that the thickness is about 16 mm in terms of the cooling effect.
  • the amount of cooling water in each cooler 107 is 1 per unit width (lm) of the material P to be rolled.
  • the temperature drop rate of the material P to be rolled by cooling is 20 ° C / sec or more.
  • 350 m 3 / h of cooling water is used per unit width.
  • the temperature drop rate of the material P to be rolled is 1200 mm
  • the temperature reaches 60-80 ° C / sec (around 40 ° C / sec including the temperature rise due to the heat generated during processing).
  • the cooler 107 shown in FIG. 10 is provided above and below the material P to be rolled as shown in FIG.
  • the coolers 1 0 7 ⁇ 1 0 7 B 1 0 7D ⁇ 107E ⁇ 107G is arranged, and for the lower part, at the rear of the mill 40 ⁇ 500 ⁇ 60, the cooler is 10C ⁇ 107F ⁇ 107 H is arranged.
  • the cooler 107H is attached to the frame of the roller table T at the rear of the last mill 60, and the other coolers 107A to 107G are mounted on the housing of each stand. It is installed.
  • the output from the curtain wall type cooler 107 (107G)
  • the water spray 108 is arranged at a position about 100 mm to lm downstream. This is for removing the cooling water on the surface of the material P to be rolled by the cooler 107 G ′ 107 H. Pressurized water is blown from the upper side of the material to be rolled P obliquely downward toward the upstream side in the flow direction of the material to be rolled P toward the surface, so as to spread also in the width direction of the material to be rolled P.
  • the cooling water on the material P to be rolled can be removed smoothly by the action of the cooler 107, so that various measuring instruments (thermometers) on the downstream side can be used.
  • various values (rolling end temperature, etc.) of the material P to be rolled after rolling can be appropriately measured. If the measurement accuracy is high, it becomes possible to accurately control the rolling conditions such as the rolling end temperature by controlling the amount of cooling water.
  • the rolling end temperature of the material to be rolled P is measured by a thermometer installed downstream of the water spray 108 and about 2 m downstream of the final mill 60, and the calculation based on the measurement result is performed.
  • 'Each curtain wall type cooler 1 by operating means (not shown) Increase or decrease the amount of cooling water of 0 7 (especially, the cooler 10 7 ⁇ ⁇ 10 7 G-10 7 H) that holds the final stage mill 60.
  • the end-of-rolling temperature is controlled by the feed pack control and maintained within an appropriate range.
  • Hot rolled steel sheet can be produced. Specifically, while rolling so that the cumulative strain (the above-mentioned weighted integrated value e c ) becomes 0.6 or more, the curtain wall cooling at the rear of each of the subsequent mills 40.
  • the curtain wall cooling By performing strong cooling with a heater 107, it is possible to obtain a preferable fine-grained steel sheet with an average ferrite grain size of about 3 to 7 m while using steel with low carbon content and alloy element content as rolling materials.
  • the embodiment described later is an example.
  • Such good production is possible because, in the later stage where the influence on the metallographic structure is strong, the temperature of the rolled material P is increased by using a curtain wall cooler 107 with high cooling capacity.
  • Mills 40, 500, and 60 can avoid roll flattening and edge drop, and can control the crown by the CVC function of each mill 10 to 60. Meandering and deterioration of the shape can be suppressed. Therefore, in the present embodiment, fine-grained steel rolling can be smoothly performed with a margin, and the steel plate can be formed with high shape accuracy.
  • the favorable fine-grained steel sheet can be produced under the above conditions by using the hot rolling device shown in Fig. 10 to determine the cooling strength (rolling end temperature) and the degree of reduction (cumulative).
  • the inventors clarified through a number of tests conducted with various changes in distortion. The results of such tests and investigations and data on the examples in which preferred fine-grained steel sheets were obtained are shown below.
  • test rolling was performed for the steel types shown in Table 2-1 (which do not include other significant components) by changing the pass schedule and rolling end temperature in various ways. went. However, in either case, the final stage mill 60 The sheet thickness is 2-3mm, and the rolling speed is 8-9m / sec.
  • Fig. 14 shows the relationship between the finishing temperature and the particle size (vertical axis) using the horizontal axis as the horizontal axis. According to FIG. 14, it can be seen that the lower the finishing temperature, the smaller the ferrite particle size becomes.
  • Figure 15 shows the relationship between ferrite grain size and tensile strength (MPa)
  • Figure 16 shows the relationship between ferrite grain size and elongation (%).
  • the finishing temperature is set, for example, to the Ar 3 transformation point-50 ° C to the same transformation point + 20 ° C, and a steel sheet with excellent elongation is obtained,
  • Table 2-2 shows the sheet thickness at the exit side of each mill 10 to 60 ("coarse bar thickness” refers to the sheet thickness at the exit side of the roughing mill), rolling reduction (%), distortion, and cumulative strain.
  • Table 2-3 shows the use condition and the finishing temperature (rolling end temperature) of each curtain wall type cooler 7 at the rear of the mill 40-60.
  • Table 2-4 shows the ferrite grain size and mechanical properties at the center of the sheet thickness for the steel sheets of the examples obtained under the conditions of Tables 2-1 to 23.
  • 18A, 18B, and 18C show the crystal structures of the steel sheet of the embodiment near the upper surface, at a position inside by 1/4 of the thickness, and at the center of the thickness.
  • FIG. Average A fine structure with a grain size of about 4 to 6 m is formed.
  • the rolling for obtaining the data shown in FIGS. 13 to 17 and the rolling in this embodiment were performed by the rolling apparatus according to the present embodiment (see FIGS. 10 to 12). If the rolling is performed to about 0.9, it is presumed that it is not necessary to use the above-mentioned different diameter roll mills 40 to 60 as a subsequent stand. In other words, it is presumed that those mills having a diameter of about 600 to 70 Omm and a single crawl of the same diameter in the upper and lower directions are sufficient. Also, it is not expected that the thermal crown associated with the heat generated by machining will be remarkable if such a cumulative strain is sufficient. Therefore, it is considered that the necessity of adding the CVC function and the pending function to the mills 10 to 60 is low.
  • TS tensile strength
  • YP yield point
  • EL elongation
  • This process which also stops grain growth in the microstructure, makes it possible to produce hot-rolled fine-grained steel sheets with an average ferrite grain size of about 10 m or less.
  • the fine-grained steel sheet When the average ferrite grain size is 10 m or less, the fine-grained steel sheet has more mechanical properties than general (non-fine-grained) hot-rolled steel sheet with the same grain size exceeding 10 zm. It is expected to be extremely expensive and have a wide range of applications.
  • the fine-grained steel sheet having the above chemical composition and ferrite grain size has a high balance of mechanical properties (it is versatile in terms of tensile strength, elongation, ductility, etc.), and has high weldability. It is also excellent. Therefore, it is considered to be in high demand because it is widely used, relatively inexpensive, easily available, and recyclable. Therefore, the rolling method according to the present embodiment, which can manufacture such a steel sheet, has a high social contribution and a sufficient process for its production. It comes with reasonableness.
  • the hot rolling method according to the present embodiment relates to a method for manufacturing a thick plate using the hot rolling apparatus according to the embodiment shown in FIG.
  • the sheet thickness decreases and the rolling speed increases.
  • the reduction ratio is set lower in the later-stage mill, the maximum rotation speed of the work roll is increased, and the maximum output torque is set lower.
  • the allowable maximum output torque of the mill 10 to 60 is 125.0, 98, 2, 61.4, 34.1, 22.7, 19.5 (all units are tons (tf) m). is there.
  • the thickness 2 A good fine-grained steel hot-rolled steel sheet of about 6 mm can be produced.
  • the cumulative strain rolling so that the above-mentioned weighted integrated value becomes 0.6 or more, is strengthened by the ten-wheel cooler 107 at the rear of each of the subsequent mills 40-50-60.
  • a fine-grained steel sheet having an average ferrite grain size of about 4 to 6 zm could be produced, while using a steel having a low carbon content and a low alloying element content as the material to be rolled P.
  • the drive system of the rolling rolls increases the rolling speed as the rolling progresses and the thickness decreases.
  • the rolling speed is set higher (that is, the reduction ratio is smaller) and the rolling torque is set lower than that of the preceding mill.
  • the required contact arc length (contact length) on the entry side is long (the contact angle is large) even when the rolling reduction is constant compared to when the thin plate is rolled.
  • the torque is much higher than when rolling a sheet.
  • the present inventors used a continuous hot rolling apparatus according to the embodiment shown in FIG. 10, that is, a continuous hot rolling apparatus capable of manufacturing a thin steel sheet having a small thickness, and a thickness of 6 mm or more.
  • the rolling mill was operated in the following modes a) to d). That is,
  • the cumulative strain is 0.25 or more (preferably 0.29 or more), or the rolling reduction of the last mill among three or more mills to be used is 12% or more (preferably 14%).
  • the pass schedule is determined so that This is because it is difficult to reduce the ferrite grain size unless rolling at a downstream mill, which has a strong effect on the metal structure, is performed at a certain reduction rate.
  • a curtain wall cooler 107 As the cooler 107, at least one of the mills to be used immediately after the last mill is used. Preferably, all coolers 107 (107A-107H) are used, including the cooler in front of the last mill. This is because, in order to reduce the particle size of the filament, it is essential that the material P to be rolled immediately after rolling be sufficiently cooled and maintained in an appropriate temperature range, and that the grain growth after rolling be properly suppressed.
  • the rolling end temperature (the surface temperature of the material to be rolled P measured by a thermometer installed several meters downstream from the final mill 60) is increased to the Ar 3 transformation point +50. Do not exceed ° C (preferably below the Ar 3 transformation point). Although there should be a desirable lower limit, the production of fine-grained steel was not hindered even if the surface temperature dropped considerably. This means that as long as a steel sheet with a thickness of 6111111 or more is rolled at a speed of about 2 to 3111/3 ec, the temperature near the center of the sheet thickness of the material to be rolled P is about the Ar 3 transformation point regardless of the surface temperature. It is speculated that this is because
  • Example CD By performing rolling as described above, for steel types with a carbon content of 0.5% or less and an alloying element content of 5% or less, the average ferrite within 1/4 of the thickness from the surface inside Thick fine-grained hot-rolled steel sheets with a grain size of about 5 to 10 m could be produced.
  • An example of such a steel plate production is shown below as Example CD.
  • Comparative Example A relates to the production of thin steel sheets (2.07 mm thick) as described above, and Comparative Example B produces thick steel sheets using mills 10 to 60. This is an example in which rolling cannot be continued.
  • Examples C and D show an example in which a thick (12.2 mm thick) fine-grained steel sheet is smoothly and continuously produced using a rolling mill.
  • Table 3-1 shows the chemical composition of the steel sheet in Examples and Comparative Examples A to D (excluding significant amounts of components other than those indicated) and the temperature of the Ar 3 transformation point.
  • Figure 2 shows the rolling end temperature (finish-side temperature), the sheet width of each steel sheet, and the various forces at the rear of the mill 40-60.
  • Table 3-3 shows the sheet thickness at the exit side of each mill 10 to 60 ("coarse bar thickness” refers to the sheet thickness at the exit side of the roughing mill).
  • Table 3-4 'Table 3-5' Table 3-6 shows the rolling reduction (%), strain and cumulative strain, required rolling at each mill 10 to 60 when following the pass schedule in Table 3-3. It shows torque (t ⁇ ⁇ ) each time.
  • Table 3-7 shows the results of an investigation of the ferrite grain size and mechanical properties of the steel sheets produced in each of the examples and comparative examples A to D.
  • Comparative Example B the results are shown for a steel sheet obtained within a short time before rolling becomes impossible.
  • the particle size shown is measured at the center of the thickness in Comparative Example A, and measured at a position inside the surface by 1/4 of the thickness in Comparative Examples B and Examples (and D).
  • TS is the tensile strength
  • Y ⁇ is the yield point
  • EL is the elongation
  • L direction is the length direction (rolling direction)
  • C direction means the width direction.
  • T S tensile strength
  • YP yield point
  • E L elongation
  • Fig. 19A, Fig. 19B, and Fig. 19C show the values of the steel sheet obtained in Example D near the upper surface, 1/4 of the thickness inside, and at the center of the thickness. It is the figure which showed the crystal structure in that location. At the thickness of 1Z4, an average ferrite grain size of 5 to 10 zm is formed, and even at the center of the thickness, a fine structure with the same grain size of 10 m or less is formed.
  • FIGS. 20 to 22 show the results of examining and sorting out other mechanical properties of the steel sheet produced under Example D or the rolling conditions according to the example. That is, first, FIG. 20 is a diagram showing the relationship between the ferrite grain size, the tensile strength, and the yield point in a fine-grained steel sheet (the abscissa represents the ferrite grain size d (jum) by one-half). To the power). For the same fine-grained steel sheet, Fig. 21 shows the temperature change of Charpy impact value together with the change for ordinary steel (non-fine-grained steel sheet), and Fig. 22 shows the temperature dependence of brittle fracture rate. Is represented.
  • the thickness of the thick plate can be reduced without inconvenience due to insufficient torque.
  • Grain steel sheet can be manufactured. Mills near the entrance of a rolling mill with a drive system that can exhibit a high rolling torque with a low-speed specification without using them even if the latter mills and other mills may have insufficient torque. This is because if only a thick plate with a long contact arc length is rolled, sufficient rolling can be performed without insufficiency of torque.
  • the rolling speed does not increase because the mill at the last stage is not used, but the slow rolling speed has the advantage that it is easy to secure a longer cooling time due to the thick plate.
  • the thick plate to be rolled as described above can be made of fine-grained steel because it has a cumulative strain of 0.25 or more (or a rolling reduction of 12% or more in the final mill). This is because the reduction is applied to the material P to be rolled and the material to be rolled P is sufficiently cooled at the exit side of the last mill among the used mills as described above. . The stronger the above cooling performed on the outlet side of the mill, the more fine-grained steel with a smaller ferrite grain size can be obtained. In order to enhance the cooling, it is particularly preferable to perform cooling even before the last mill used, or to cool each outlet of a plurality of subsequent mills.
  • the continuous hot rolling method according to the present embodiment is particularly characterized in that the rolling end temperature does not exceed the Ar 3 transformation point + 50 ° C.
  • the rolling end temperature By controlling the cooling strength described above and setting the rolling end temperature as described above, at least the surface of the steel sheet (for example, a steel sheet having a carbon content of 0.5% or less and an alloy element content of 5% or less) can be obtained. In the vicinity, a fine structure with a ferrite particle size of less than 10 ⁇ m is formed.
  • the temperature range suitable for the large rolling reduction method is considered to be from the Ar 3 transformation point to the Ar 3 transformation point + 50 ° C. According to tests by the inventors, as described above, the rolling end temperature is A r It is sufficient that the temperature does not exceed 3 transformation point + 50 ° C. In the case of a thick plate, it is considered that the internal temperature is kept close to the Ar 3 transformation point even if the surface temperature drops.
  • the continuous hot rolling method of the present embodiment is a method in which the material P to be rolled is strongly cooled by the curtain wall cooler 107, so that the fine-grained steel Enables smooth production of boards. Since uniform cooling can be realized, there is also an advantage that the structure can be made uniform over the entire width of the steel sheet.
  • the continuous hot rolling method according to the present embodiment is particularly suitable for rolling a rolled material P having a carbon content of 0.5% or less and an alloy element content of 5% or less, so that the thickness from the surface is 1%. It is characterized in that a thick plate having an average ferrite grain size of about 3 to 10 m at a location located inside by / 4 is obtained.
  • Fine-grained steel sheets having such a chemical composition and ferrite grain size have a high balance of mechanical properties (versatile in terms of tensile strength and ductility), and have low-temperature toughness and weldability. Excellent (for example, see FIGS. 20 to 22). Therefore, it is considered to be in high demand because it is widely used, relatively inexpensive, easily available, and recyclable. Therefore, such a steel sheet has high social contribution and has sufficient economic rationality for its production.

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Abstract

A hot rolling mill, comprising the mills having the mills disposed on a front stage and the mills of a plurality of stands disposed on a rear stage and a cooling means disposed on the outlet side of the mills of at least two stands on the rear stage and cooling a rolled material, the mills further comprising the roll mills of different diameters having a pair of work rolls of different diameters of less than 600 mm in equivalent roll diameter or the very small diameter roll mills having the pair of work rolls of less than 600 mm in diameter, whereby a hot rolled fine grained steel plate can be manufactured smoothly.

Description

明 細 書 熱間圧延装置及び方法 技術分野  Description Hot rolling equipment and method
本発明は、 熱間圧延装置及び熱間圧延方法に係わり、 特に、 細粒フェライトを 主体とする微細組織を有する鋼板を製造するための熱間圧延装置および熱間圧延 方法に関する。 背景技術  The present invention relates to a hot rolling apparatus and a hot rolling method, and more particularly to a hot rolling apparatus and a hot rolling method for producing a steel sheet having a microstructure mainly composed of fine-grain ferrite. Background art
一般に、 鋼材の機械的性質を高めるための手段として、 鋼材の組織を微細化す ることがよく知られている。 鋼材の機械的性質が高くなれば、 鋼構造物の軽量化 がはかれるなど多くのメリットがもたらされる。 微細組織をもつ鋼、 すなわち細 粒鋼を製造するための方法がこれまでに数多く提案されてきたが、 代表的なもの として、 ①大圧下圧延法、 ②制御圧延法がある。  In general, it is well known that the structure of a steel material is refined as a means for enhancing the mechanical properties of the steel material. If the mechanical properties of steel materials increase, many benefits can be brought about, such as reducing the weight of steel structures. Many methods have been proposed to produce steel with a fine structure, that is, fine-grained steel, but representative methods include (1) a large rolling reduction method and (2) a controlled rolling method.
このうち①の大圧下圧延法については、 特開昭 5 8 - 1 2 3 8 2 3号公報ゃ特 公平 5— 6 5 5 6 4号公報などに記載がある。 すなわち、 同法は、 オーステナイ ト粒に大きな圧下を加えることによってオーステナイト （ァ） 相からフェライ ト (ひ） 相への歪誘起変態を促進し、 もって組織の微細化をはかるものである。 また、 ②の制御圧延法は、 N b (ニオブ） や T i (チタン） を成分に含有して N b、 T iの析出強化作用で高張力化が容易に図れるだけでなく、 N b、 T iの オーステナイ ト粒の再結晶抑制作用によって低温圧延 （フェライ ト領域圧延） を 施したときにァ相からひ相への歪誘起変態が促進されフェライト粒の微細化が図 れる方法である。  Among them, the large reduction rolling method of (1) is described in Japanese Patent Application Laid-Open No. 58-123238 / Japanese Patent Publication No. 5-65564. In other words, this method promotes the strain-induced transformation from the austenite (a) phase to the ferrite (h) phase by applying a large reduction to the austenite grains, thereby miniaturizing the structure. In the controlled rolling method (2), Nb (niobium) and Ti (titanium) are contained in the component to not only easily increase the tensile strength by the precipitation strengthening action of Nb and Ti, but also to increase Nb, This is a method that promotes the strain-induced transformation from a phase to a phase when low-temperature rolling (ferrite region rolling) is performed by Ti's effect of suppressing austenite grains from recrystallizing, thereby reducing the size of ferrite grains.
制御圧延法は、 仕上圧延を低温域 （8 0 0 eC以下） で行うことから被圧延材の 変形抵抗が著しく高く、 したがって圧延装置に対する負荷が大きいという不都合 がある。 一方、 大圧下圧延法は、 上記の特公平 5— 6 5 5 6 4号公報にも示され ているように一般的なホットストリップミルによっては工業的な実施ができず、 特殊な圧延装置を使用する必要があった。 上記の各公報に記載されているように、 一般的な圧延装置では実現が困難なほどの高い圧下率 （たとえば 4 0 %以上） を 連続的に施す圧延が必要だからである。 Controlled rolling method, there is a disadvantage that a finish rolling a low temperature range (8 0 0 e C below) significantly higher deformation resistance of the rolled material from doing, the thus load on the rolling apparatus is large. On the other hand, the large rolling reduction method cannot be industrially implemented by a general hot strip mill as shown in the above-mentioned Japanese Patent Publication No. 5-65564, and requires special rolling equipment. Needed to use. As described in the above publications, This is because it is necessary to continuously apply a high rolling reduction (for example, 40% or more) that is difficult to achieve with a general rolling mill.
上述した大圧下圧延法を実施して工業的 ·商業的に細粒鋼を製造する場合、 一 般的なホットストリップミル形式の圧延装置が使用できないことに加え、 つぎの ような課題がある。  When fine-grained steel is manufactured industrially or commercially by performing the above-described large rolling reduction method, there are the following problems in addition to the fact that a general hot strip mill-type rolling device cannot be used.
i) 大圧下、 つまり高圧下率の圧延を行うために、 圧延荷重に起因する不都合 が発生しがちである。 すなわち、 圧延荷重がその圧延装置に固有の限界値 （ミル パワー制限および機械強度） に達して圧延が不可能になる場合がある。 さらに、 被圧延材についても、 所定の圧下率が実現されなくなつたり大きなェッジド口ッ プが発生したりする。 所定の圧下率が得られなくなるのは、 とくに、 圧延装置の 出側での板厚が 2 mm以下で圧下率が 4 0 %以上の場合などに、 圧延荷重が大き いうえ変形抵抗が高いためにロール偏平が大きくなるからである。 この場合、 高 圧下圧延を行うべくいくら圧下をかけても圧下率が向上しなくなる。 エッジドロ ップが大きくなるのは、 被圧延材のエッジ （幅方向の端部） 付近に高荷重がかか るからであり、 良好な板プロフィールが得られない。  i) Rolling at high pressure, that is, high rolling reduction tends to cause inconvenience due to rolling load. That is, the rolling load may reach the limit value (mill power limit and mechanical strength) inherent in the rolling equipment, and rolling may not be possible. Further, for the material to be rolled, a predetermined rolling reduction cannot be realized or a large edged opening is generated. The reason why the predetermined rolling reduction cannot be obtained is that the rolling load is large and the deformation resistance is high, especially when the strip thickness at the exit side of the rolling mill is 2 mm or less and the rolling reduction is 40% or more. This is because the roll flatness increases. In this case, no matter how much reduction is applied to perform high reduction rolling, the reduction rate does not improve. The reason why the edge drop is large is that a high load is applied near the edge (widthwise end) of the material to be rolled, and a good plate profile cannot be obtained.
ii) 被圧延材の温度維持が困難であることも大きな課題である。 複数スタン ドのミルを用いて高圧下率の圧延を行うと、 加工発熱のために被圧延材の温度上 昇も著しくなり、 大圧下圧延法を行うに適した温度 （A r 3変態点〜 A r 3 + 5 0 °Cの範囲） に維持するのが容易でないからである。 被圧延材が加速されて送り速 度が増大すると、 歪み速度が高くなつて加工発熱が増すため、 温度の維持はます ます困難になる。 ii) It is also a big problem that it is difficult to maintain the temperature of the material to be rolled. When rolling at a high reduction rate using a mill with multiple stands, the temperature of the material to be rolled rises significantly due to the heat generated during processing, and the temperature (A r 3 transformation point to (In the range of Ar 3 + 50 ° C.). As the material to be rolled is accelerated and the feed rate is increased, maintaining the temperature becomes more difficult because the strain rate increases and the heat generated during processing increases.
iii) ロールの熱負荷に関連する不都合も発生しがちである。 高圧下率をもた らす高負荷の圧延を行うと、 被圧延材の加工発熱も高くなり、 それだけロールの 熱負荷が高くなる。 その結果、 ロールがそのセン夕一部で径が拡大するサーマル クラウンが発生しやすいのである。 サ一マルクラウンの程度によっては、 ロール を冷却するだけでは解消し得ない場合があり、 被圧延材の形状が悪くなつて安定 通板が困難になることもある。  iii) Inconveniences related to the heat load of the roll are also likely to occur. When high-load rolling with a high reduction rate is performed, the heat generated during processing of the material to be rolled increases, and the heat load of the roll increases accordingly. As a result, a thermal crown, in which the diameter of the roll increases in a portion of the roll, is likely to occur. Depending on the degree of the thermal crown, it may not be possible to solve the problem simply by cooling the roll, and in some cases, the shape of the material to be rolled may be poor, and stable threading may be difficult.
iv) ロールの摩耗が激しくなり、 被圧延材の形状 （クラウン） がさらに悪化 しゃすくなる。 高圧下率 ·高負荷の圧延では、 ロールにかかる熱的又は力学的な 負荷が高いため、 ロール摩耗が進行しやすくなるからである。 被圧延材のエッジ と接する部分では、 圧延負荷が高いためにとくに摩耗が進行しやすく、 品質上重 要な被圧延材のプロフィールを大幅に低下させがちである。 また、 ロールが摩耗 しやすいと、 ロールの研磨や交換といったメンテナンスのためのコストも上昇す る o iv) Roll wear becomes severe, and the shape (crown) of the material to be rolled is further deteriorated. High pressure rolling · In high-load rolling, thermal or mechanical This is because the load is high and roll wear is likely to progress. The portion of the material to be rolled that contacts the edge is subject to high rolling loads, and is especially prone to wear, which tends to significantly reduce the profile of the material to be rolled, which is important for quality. In addition, if the rolls are easily worn, the maintenance costs such as polishing and replacing the rolls will increase.o
そこで、 本発明の目的は、 細粒鋼熱延鋼板の製造に関する上記の問題を解決し て当該鋼板の円滑な製造を可能にする熱間圧延装置および細粒鋼製造方法を提供 Therefore, an object of the present invention is to provide a hot rolling apparatus and a method for producing fine-grained steel, which solve the above-mentioned problems relating to the production of hot-rolled fine-grained steel sheets and enable smooth production of the steel sheets.
^ Oしとにめる c ^ O to stop c
また、 本発明の目的は、 細粒鋼熱延鋼板の製造に適した連続熱間圧延方法であ つて費用対効果の面においても優れたものを提供することにある。  Another object of the present invention is to provide a continuous hot rolling method suitable for the production of hot-rolled fine-grained steel sheets, which is excellent in cost-effectiveness.
さらに、 本発明の目的は、 薄板を製造可能な熱間圧延装置を用いて厚板を円滑 に製造するための連続熱間圧延方法を提供することにある。 発明の開示  A further object of the present invention is to provide a continuous hot rolling method for smoothly manufacturing a thick plate using a hot rolling device capable of manufacturing a thin plate. Disclosure of the invention
本発明は、 被圧延材を圧延して鋼板を製造する熱間圧延装置において、 前段に 配置されたミルと、 後段に配置された複数スタンドのミルであって、 等価ロール 径が 6 0 0 mm未満の一対の異径ヮ一クロールを含む異径ロールミル又は各直径 が 6 0 0 mm未満の一対のワークロールを含む極小径ロールミルを有するミルと、 前記後段の少なくとも 1スタンドの前記ミルの出側に配置された、 前記被圧延材 を冷却する冷却手段と、 を備えたことを特徴とする。  The present invention relates to a hot rolling apparatus for rolling a material to be rolled to produce a steel sheet, comprising: a mill arranged at the front stage; and a multi-stand mill arranged at the latter stage, wherein the equivalent roll diameter is 600 mm. A mill having a pair of different diameter roll mills including a pair of different diameter rolls or a small diameter roll mill including a pair of work rolls each having a diameter of less than 600 mm; And cooling means for cooling the material to be rolled.
ここで、 「等価ロール径」 とは、 異径ロールミルに関して、 上下一対の異径ヮ 一クロールの直径の平均値のことである。  Here, the “equivalent roll diameter” refers to the average value of the diameters of a pair of upper and lower pairs of different diameter single crawls with respect to different diameter roll mills.
また、 好ましくは、 前記冷却手段は、 カーテンウォール型冷却器である。  Preferably, the cooling means is a curtain wall type cooler.
ここで、 「カーテンウォール型冷却器」 とは、 上方および下方から幕のように 連ねて大量の冷却水を層流状態で流し、 それを被圧延材の上下面に全幅にわたつ て当てる形式の冷却手段をいう。  Here, the "curtain wall type cooler" is a type in which a large amount of cooling water is flowed in a laminar flow from above and below like a curtain, and applied to the upper and lower surfaces of the material to be rolled over the entire width. Means cooling means.
また、 好ましくは、 前記前段及び前記後段に配置された前記ミルのうち、 少な くとも前記前段に配置されたミルは複数スタンドの C V Cミルを含む。  Preferably, among the mills arranged at the front stage and the rear stage, at least the mill arranged at the front stage includes a multi-stand CVC mill.
ここで、 「C V Cミル」 とは、 軸長方向に外径が連続的に変化するロールであ つて軸長方向への移動が可能なもの （C V Cロール） を含むミルをいう。 Here, the “CVC mill” is a roll whose outer diameter changes continuously in the axial direction. And mills that can move in the axial direction (CVC rolls).
また、 好ましくは、 前記異径ロールミルの前記一対の異径ワークロールの前記 等価ロール径又は前記極小径ロールミルの前記ワークロールのロール径は 5 5 0 mm以下である。  Preferably, the equivalent roll diameter of the pair of different diameter work rolls of the different diameter roll mill or the roll diameter of the work roll of the ultra small diameter roll mill is 550 mm or less.
また、 好ましくは、 前記異径ロールミルの前記ワークロール又は前記極小径口 —ルミルの前記ワークロールは、 C V C機能及びベンディング機能が付与されて いる。  Preferably, the work roll of the different diameter roll mill or the work roll of the ultra small diameter mill has a CVC function and a bending function.
ここで、 「cv c機能」 とは、 軸長方向に外径が連続的に変化したロールが軸 長方向へ移動してロールギャップ形状の変更制御を行う機能をいう。 また、 「ベ ンデイング機能」 とは、 ロールにベンディング力 （曲げモーメント） を作用させ てロールギャップ形状を変化させる機能をいう。  Here, the “cv c function” refers to a function in which a roll whose outer diameter continuously changes in the axial direction moves in the axial direction to control the change of the roll gap shape. The term "bending function" refers to a function that changes the roll gap shape by applying a bending force (bending moment) to the roll.
また、 好ましくは、 前記前段及び前記後段に配置された前記ミルのうち、 少な くともいずれか 1つのスタンドの前記ミルに付設された、 前記ミルのロール表面 に潤滑剤を供給する潤滑剤供給手段をさらに有する。  Further, preferably, a lubricant supply means for supplying a lubricant to a roll surface of the mill, which is attached to the mill of at least one of the mills among the mills arranged in the preceding stage and the subsequent stage. Has further.
また、 好ましくは、 前記潤滑剤供給手段は、 微粒の固体潤滑剤をグリース中に 含めた潤滑剤を供給する。  Preferably, the lubricant supply means supplies a lubricant containing fine solid lubricant in grease.
また、 前記熱間圧延装置は、 好ましくは、 最終段のスタンドの前記ミルの出側 において、 前記被圧延材の流れ方向における前記冷却手段の下流側に配置された、 前記被圧延材に流体を噴射して前記被圧延材上に存在する冷却水を除去する流体 噴射スプレーをさらに有する。  In addition, the hot rolling device is preferably arranged on the exit side of the mill of the last stage stand, disposed downstream of the cooling unit in the flow direction of the material to be rolled, and supplies the fluid to the material to be rolled. The apparatus further includes a fluid spray for spraying to remove cooling water existing on the material to be rolled.
また、 好ましくは、 前記流体噴射スプレーは、 前記被圧延材に対して、 前記被 圧延材の上方から前記被圧延材の流れ方向の上流側に向けて斜め下方へ、 前記被 圧延材の幅方向に広がるように加圧水を吹き出す複数のノズルを含む。  Also, preferably, the fluid jet spray is formed in such a manner that, with respect to the material to be rolled, an obliquely downward direction from above the material to be rolled toward an upstream side in a flow direction of the material to be rolled, in a width direction of the material to be rolled It includes a plurality of nozzles that blow out pressurized water so as to spread out.
本発明は、 被圧延材を圧延して細粒鋼を製造するための方法において、 加熱し た前記被圧延材を、 前段に配置されたミルと後段に配置されたミルとを有する圧 延装置に供給し、 前記圧延装置の前記後段に配置されたミルは直径が 5 5 0 mm 以下のワークロールを有し、 前記圧延装置の前記後段に配置された前記ミルの、 前記被圧延材の流れ方向における前および後ろにおいて前記被圧延材を冷却しな がら、 累積歪みが 0 . 9以上になるように前記被圧延材を圧延することを特徴と する。 The present invention relates to a method for producing fine-grained steel by rolling a material to be rolled, comprising: a rolling device having a heated mill to be rolled; a mill arranged in a former stage and a mill arranged in a latter stage. The mill disposed at the latter stage of the rolling device has a work roll having a diameter of not more than 550 mm, and the mill disposed at the latter stage of the rolling device has a flow of the material to be rolled. Rolling the rolled material so that the cumulative strain is 0.9 or more while cooling the rolled material before and after in the direction. I do.
ここで、 「歪み」とは、 各ミルの入側での被圧延材の厚さ h。と出側での厚さ hi の差を両者の平均厚さで除した  Here, “strain” is the thickness h of the material to be rolled on the entry side of each mill. The difference between the thickness hi at the outlet and the output side was divided by the average thickness of both.
ε= (h。一 h!) / { (h。十 /2}  ε = (h. one h!) / {(h. ten / 2}
をいう。 Say.
また、 「累積歪み」 とは、 後段の複数スタンド （例えば 3スタンド。 2スタン ドの場合もあり得る） の各ミル （それらより上流側のスタンドのミルは影響力が 小さいので無視する） での歪みを、 金属組織に対する影響の強さを考慮して加重 積算したもので、 最終段のスタンド、 その前のスタンド、 さらにその前のスタン ドでの歪みをそれそれ £n、 £ n- U £ n-2とするとき、 Also, “cumulative distortion” is defined as the number of mills in the subsequent multiple stands (for example, 3 stands, which may be 2 stands) (mills on the stands upstream from them are ignored because their influence is small). The distortion is weighted and integrated taking into account the strength of the effect on the metal structure, and the distortion at the last stage, the previous stage, and the previous stage is further reduced by £ n , £ n- U £ When n -2,
ε c = εη十 £n- i/2十 £n-2/4 ε c = ε η 10 £ n -i / 2 10 £ n - 2 /4
で表される £<=をいうものとする。 Let's say £ <=.
本発明による細粒鋼製造方法は、 上記いずれかの熱間圧延装置を用いて、 前記 圧延装置の前記後段における前記被圧延材の累積歪みが 0. 9以上になるように 前記被圧延材を圧延することを特徴とする。  The method for producing fine-grained steel according to the present invention includes using any one of the above-described hot rolling devices, wherein the material to be rolled is formed so that the cumulative strain of the material to be rolled at the subsequent stage of the rolling device is 0.9 or more. It is characterized by rolling.
また、 好ましくは、 最終スタンドの前記ミルを出た直後における前記被圧延材 を毎秒 20°C以上の温度降下率で冷却する。  Preferably, the material to be rolled immediately after leaving the mill at the final stand is cooled at a temperature drop rate of 20 ° C. or more per second.
また、 好ましくは、 前記被圧延材は、 炭素含有量が 0. 5%以下であり、 合金 元素の含有量が 5 %以下である。  Preferably, the material to be rolled has a carbon content of 0.5% or less and an alloy element content of 5% or less.
本発明は、 被圧延材を連続的に熱間圧延して鋼板を製造するための方法におい て、 加熱した前記被圧延材を、 前段及び後段にタンデムに配置された複数スタン ドのミルを有する圧延装置に供給し、 前記被圧延材の累積歪みが 0. 6以上にな るように前記圧延装置を用いて前記被圧延材を圧延しながら、 前記圧延装置の前 記後段の 1スタンド以上の前記ミルの出側において前記被圧延材を冷却すること を特徴とする。  The present invention relates to a method for producing a steel sheet by continuously hot rolling a material to be rolled, comprising a plurality of stand mills in which the heated material to be rolled is arranged in tandem at a former stage and a latter stage. The rolling device is supplied to a rolling device, and the material to be rolled is rolled using the rolling device so that the accumulated strain of the material to be rolled becomes 0.6 or more. The rolled material is cooled on the outlet side of the mill.
また、 好ましくは、 前記被圧延材の圧延終了温度を、 ΑΓ3変態点— 50°C以 上であって A r 3変態点 + 50°C以下の範囲内にする。  Preferably, the rolling end temperature of the material to be rolled is within a range of not less than the third transformation point—50 ° C. and not more than the Ar 3 transformation point + 50 ° C.
ここで、 「圧延終了温度」 とは、 被圧延材の流れ方向における圧延装置の下流 側 （配置された最終段のミルより数 m下流側） に設置された温度計により計測さ れる被圧延材の表面温度である。 Here, the “rolling end temperature” is measured by a thermometer installed downstream of the rolling mill in the flow direction of the material to be rolled (a few meters downstream from the arranged final stage mill). Surface temperature of the material to be rolled.
また、 好ましくは、 前記被圧延材を圧延して得られた鋼板の内部の平均フェラ ィ ト粒径が 3〜ア m程度である。  Preferably, the average ferrite particle size inside the steel sheet obtained by rolling the material to be rolled is about 3 to Am.
本発明は、 被圧延材を圧延して厚板を製造するための連続熱間圧延方法におい て、 加熱した前記被圧延材を、 被圧延材を圧延して薄板を製造できるように前段 及び後段にタンデムに配置された複数スタンドのミルを有する圧延装置に供給し、 前記圧延装置の前記後段に配置された複数の前記ミルのうちの少なくとも一部を 使用せずに、 前記圧延装置の入側寄りの少なくとも 3スタンドの前記ミルを使用 して、 前記被圧延材の累積歪みが 0 . 2 5以上になるか又は使用に供される前記 ミルのうちの最終段の前記ミルでの圧下率が 1 2 %以上になるように前記被圧延 材を圧延しながら、 使用に供される最終段の前記ミルの出側において前記被圧延 材を冷却することを特徴とする。  The present invention relates to a continuous hot rolling method for producing a thick plate by rolling a material to be rolled, wherein the heated material to be rolled is subjected to a first stage and a second stage so that a thin plate can be produced by rolling the material to be rolled. To a rolling mill having a plurality of stands of mills arranged in tandem, and without using at least a part of the plurality of mills arranged in the latter stage of the rolling mill, on the input side of the rolling mill. The cumulative strain of the material to be rolled becomes 0.25 or more using the at least three stands of the mill, or the rolling reduction in the last stage of the mills among the mills to be used is reduced. The method is characterized in that the material to be rolled is cooled at the exit side of the mill at the final stage used, while the material to be rolled is rolled to 12% or more.
ここで、 「薄板」 とは厚さが 6 mm未満の鋼板をいい、 「厚板」 とは厚さが 6 mm以上 （5 0 mm程度以下） の鋼板をいう。  Here, “thin plate” refers to a steel plate having a thickness of less than 6 mm, and “thick plate” refers to a steel plate having a thickness of 6 mm or more (about 50 mm or less).
また、 好ましくは、 前記被圧延材の圧延終了温度が A r 3変態点 + 5 0 °Cを超え ないようにする。 Preferably, the rolling end temperature of the material to be rolled does not exceed the Ar 3 transformation point + 50 ° C.
ここで、 「圧延終了温度」 とは、 被圧延材の流れ方向における圧延装置の下流 側 （配置された最終段のミルより数 m下流側） に設置された温度計により計測さ れる被圧延材の表面温度である。  Here, “rolling end temperature” refers to the material to be rolled measured by a thermometer installed downstream of the rolling mill in the flow direction of the material to be rolled (downstream of several meters from the mill at the last stage arranged). Surface temperature.
また、 好ましくは、 前記被圧延材を圧延して得られた前記厚板は、 その表面か らその厚さの 1 Z4だけ内側での平均フェライ ト粒径が 3〜 1 0 zm程度である。 図面の簡単な説明  Preferably, the thick plate obtained by rolling the material to be rolled has an average ferrite particle size of about 3 to 10 zm inward from the surface by 1 Z4 of the thickness. BRIEF DESCRIPTION OF THE FIGURES
図 1は、 本発明の一実施形態による熱間圧延装置の全体配置を概念的に示す側 面図である。  FIG. 1 is a side view conceptually showing the overall arrangement of a hot rolling apparatus according to one embodiment of the present invention.
図 2 A、 図 2 B、 図 2 Cの各図は、 図 1に示した圧延装置のうち、 前段にある ミル 1に関して C V C機能を説明するための模式図である。  Each of FIGS. 2A, 2B, and 2C is a schematic diagram for explaining the CVC function of the first mill in the rolling mill shown in FIG.
図 3は、 図 1に示した圧延装置のうち最終段のミル 6などについて詳細を示す 側面図である。 図 4は、 図 1に示した圧延装置を用いて製造した鋼板について、 フェライ ト組 織の結晶粒に関するグレーンサイズと降伏点との関係を示す線図である。 FIG. 3 is a side view showing details of the final mill 6 and the like in the rolling mill shown in FIG. FIG. 4 is a diagram showing the relationship between the grain size and the yield point of the crystal grains of the ferrite tissue for the steel sheet manufactured using the rolling mill shown in FIG.
図 5 A、 図 5 B、 図 5 Cの各図は、 図 1に示した圧延装置を用いて製造した鋼 板について、 上表面付近と板厚中央付近、 下表面付近でそれそれ結晶組織を示し た図である。  Figures 5A, 5B, and 5C show the crystal structures of the steel sheet manufactured using the rolling mill shown in Figure 1 near the upper surface, near the center of the thickness, and near the lower surface. FIG.
図 6は、 異径ロールミルのヮ一クロ一ルの等価径と圧延荷重との関係を示す線 図である。  FIG. 6 is a diagram showing the relationship between the equivalent diameter of a single roll of a different diameter roll mill and the rolling load.
図 7は、 異径ロールミルにおけるエッジドロップの低減効果を示す線図である c 図 8は、 潤滑剤を使用する場合の口ール表面の摩耗低減効果を示す線図である c 図 9は、 図 1に示した実施形態の一変形例による熱間圧延装置の全体配置を概 念的に示す側面図である。  Fig. 7 is a diagram showing the effect of reducing edge drop in a roll mill with a different diameter.c Fig. 8 is a diagram showing the effect of reducing the wear on the surface of the mouth when a lubricant is used.c Fig. 9 FIG. 2 is a side view conceptually showing the overall arrangement of a hot rolling apparatus according to a modification of the embodiment shown in FIG.
図 1 0は、 本発明の他の実施形態による連続熱間圧延装置について、 全体配置 を概念的に示す側面図である。  FIG. 10 is a side view conceptually showing the overall arrangement of a continuous hot rolling apparatus according to another embodiment of the present invention.
図 1 1 A、 図 1 1 B、 図 1 1 Cの各図は、 図 1 0に示した圧延装置のうち、 前 段にあるミル 1 0等に関して C V C機能を説明するための模式図である。  Each of FIGS. 11A, 11B, and 11C is a schematic diagram for explaining the CVC function with respect to the mill 10 and the like at the preceding stage in the rolling mill shown in FIG. .
図 1 2は、 図 1 0に示した圧延装置のうち後段のミル 4 0〜6 0とその付近に ついて詳細を示す側面図である。  FIG. 12 is a side view showing the details of the subsequent mills 40 to 60 of the rolling mill shown in FIG. 10 and the vicinity thereof.
図 1 3は、 試験圧延によって得た種々の鋼板に関し、 累積歪みとフェライ ト粒 径等との関係を示す線図である。  FIG. 13 is a diagram showing the relationship between the cumulative strain and the ferrite grain size for various steel sheets obtained by test rolling.
図 1 4は、 試験圧延によって得た種々の鋼板に関し、 仕上温度 （圧延終了温 度） とフェライ ト粒径等との関係を示す線図である。  Figure 14 is a diagram showing the relationship between the finishing temperature (rolling end temperature) and the ferrite grain size for various steel sheets obtained by test rolling.
図 1 5は、 試験圧延によって得た種々の鋼板に関し、 フェライ ト粒径と引張強 さ等との関係を示す線図である。  FIG. 15 is a diagram showing the relationship between the ferrite grain size, tensile strength, and the like for various steel sheets obtained by test rolling.
図 1 6は、 試験圧延によって得た種々の鋼板に関し、 フェライ ト粒径と伸び等 との関係を示す線図である。  FIG. 16 is a diagram showing the relationship between ferrite grain size, elongation, and the like for various steel sheets obtained by test rolling.
図 1 7は、 試験圧延によって得た種々の鋼板に関し、 フェライ ト粒径と引張強 さ X伸び等との関係を示す線図である。  FIG. 17 is a diagram showing the relationship between the ferrite grain size and the tensile strength X elongation, etc., for various steel sheets obtained by test rolling.
図 1 8 A、 図 1 8 B、 図 1 8 Cは、 図 1 0に示した圧延装置を用いた圧延方法 の実施例によって得た鋼板について、 上表面付近と、 それより厚さの 1 / 4だけ 内側の付近と、 厚さの中央付近との各箇所で結晶組織を示した図である。 FIG. 18A, FIG. 18B, and FIG. 18C show the steel sheet obtained by the example of the rolling method using the rolling device shown in FIG. Only 4 FIG. 3 is a diagram showing crystal structures at respective locations near the inside and near the center of the thickness.
図 19A、 図 19B、 図 19Cは、 本発明の実施例 Dによって得た鋼板につい て、 上表面付近と、 それより厚さの 1/4だけ内側の付近と、 厚さの中央付近と の各箇所で結晶組織を示した図である。  19A, 19B, and 19C show, for the steel sheet obtained according to Example D of the present invention, each of the vicinity of the upper surface, the vicinity of the inside by 1/4 of the thickness, and the vicinity of the center of the thickness. FIG. 3 is a diagram showing a crystal structure at a location.
図 20は、 本発明の実施例によって生産した鋼板について、 フェライ ト粒径と 引張強さおよび降伏点との関係を示す線図である。  FIG. 20 is a diagram showing the relationship between the ferrite grain size, the tensile strength, and the yield point of the steel sheet produced according to the example of the present invention.
図 21は、 本発明の実施例によって生産した鋼板と通常鋼 （非細粒鋼鋼板） と について、 シャルビ一衝撃値の温度変化を示す線図である。  FIG. 21 is a diagram showing a temperature change of a Charpy impact value of a steel sheet produced according to an example of the present invention and a normal steel (non-fine-grained steel sheet).
図 22は、 本発明の実施例によって生産した鋼板について、 脆性破面率の温度 変化を示す線図である。 発明を実施するための最良の形態  FIG. 22 is a diagram showing the temperature change of the brittle fracture ratio of the steel sheet produced according to the example of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION
以下、 本発明の一実施形態による熱間圧延装置及び同装置を用いた細粒鋼製造 方法について図面を参照して説明する。  Hereinafter, a hot rolling apparatus according to an embodiment of the present invention and a method for producing fine-grained steel using the apparatus will be described with reference to the drawings.
図 1に示した本実施形態による熱間圧延装置は仕上げ圧延装置であって、 被圧 延材 Pの流れ方向の上流側 （図示省略） には加熱炉と粗圧延装置があり、 下流側 (図示省略） にはランアウトテーブルや巻取り機などが配置されている。 この熱 間圧延装置は、 上流側で粗圧延された被圧延材 Pを連続圧延することによって微 細なフェライ ト組織を有する細粒鋼熱延鋼板を製造できるよう、 以下のように構 成されている。  The hot rolling apparatus according to the present embodiment shown in FIG. 1 is a finish rolling apparatus, and includes a heating furnace and a rough rolling apparatus on the upstream side (not shown) in the flow direction of the rolled material P, and on the downstream side ( (Not shown), a run-out table, a winder and the like are arranged. This hot rolling apparatus is configured as follows so that a hot-rolled fine-grained steel sheet having a fine ferrite structure can be manufactured by continuously rolling a material P roughly-rolled on the upstream side. ing.
まず、 熱間圧延装置の前段を構成する 3スタンドのミルとして、 いわゆる CV Cミル 1 · 2 · 3をタンデムに配置している。 熱間圧延装置の最も入側に位置す る CVCミル 1は、 図 1のようにヮ一クロール 1 a · 1 bとバックアップロール 1 c · 1 dとからなる 4重のミルとして構成し、 ワークロール 1 a · 1わに、 図 2Aに示すようなクラウン （CVC、 すなわち直径の連続的変化） をもたせてい る。 ワークロール l a ' lbは、 図 2 B及び図 2 Cのように互いに反対の軸長方 向へ同時に移動 （シフト） させることができ、 それによつてロール間の位置関係、 すなわちロールギャップを調整することが可能である。 ワークロール l a * lb の径は 700mmとし、 最大シフト量は正逆それそれに 100mmとした。 他の 2スタンドの CVCミル 2 · 3も、 このような構成および機能について CVCミ ル 1と相違はない。 First, so-called CV C mills 1, 2, and 3 are arranged in tandem as a three-stand mill that constitutes the former stage of the hot rolling mill. The CVC mill 1 located at the most entry side of the hot rolling mill is configured as a quadruple mill consisting of a single crawl 1a and 1b and a backup roll 1c and 1d, as shown in Fig. 1. Roll 1a · 1 Alligator has a crown (CVC, that is, continuous change in diameter) as shown in Fig. 2A. The work rolls la ′ lb can be simultaneously moved (shifted) in opposite axial directions as shown in FIG. 2B and FIG. 2C, thereby adjusting the positional relationship between the rolls, that is, the roll gap. It is possible. The diameter of the work roll la * lb was set to 700 mm, and the maximum shift amount was set to forward and reverse and 100 mm. other The two-stand CVC mills 2 and 3 do not differ from the CVC mill 1 in such configuration and function.
こうした CVCミル 1 · 2 · 3を前段に配置したのは、 被圧延材 Pのクラウン (形状） を好適に保っためである。 後段の異径ロールミル 4 · 5 · 6 (後述） で は圧延による加工発熱に起因したサ一マルクラゥン等が発生しやすいため、 前段 に置いたこれら CVCミル 1 · 2 · 3によってあらかじめ板クラウンを修正し、 被圧延材 Pの中絞り等を軽減するのである。  The reason why the CVC mills 1, 2, and 3 are arranged at the front stage is to appropriately maintain the crown (shape) of the material P to be rolled. In the later-stage roll mills 4, 5, and 6 (described later), thermal crowns and the like are likely to occur due to the processing heat generated by rolling. Therefore, the crown is corrected in advance by these CVC mills 1, 2, and 3 placed in the preceding stage. In addition, the medium drawing of the material P to be rolled is reduced.
つまり、 CVCミル 1 · 2 · 3は、 単にロールベンディングを行う等の手段に 比べてロールギャップ形状の変更能力が大きく、 しかも、 被圧延材が厚くてクラ ゥン制御の行いやすい前段の部分を中心に配置しているため、 クラウンを調整し て、 大圧下をする後段において通板の不安定化を防止するうえで有利である。 また、 本実施形態による熱間圧延装置は、 前段に続く後段を構成する 3スタン ドのミルとして、 いわゆる異径ロールミル 4 · 5 · 6をタンデム配置している。 前述の CVCミル 1 · 2 · 3を含む全 6スタンドのスタンド間隔は、 等しく 5. 5mである。 CVCミル 1から数えて第 4スタンドにあたる異径ロールミル 4は、 図 1のようにワークロール 4 a · 4 bとバックアップ口一ル 4 c · 4 dとからな る 4重のミルとして構成され、 ワークロール 4a · 4bとして図のように直径の 異なるものを使用している。  In other words, the CVC mills 1, 2, and 3 have a greater ability to change the roll gap shape than means such as simply performing roll bending, and have a thicker material to be rolled, making it easier to control the crown. Since it is located at the center, it is advantageous in adjusting the crown and preventing instability of the threading plate in the subsequent stage of large pressure reduction. In the hot rolling apparatus according to the present embodiment, so-called different-diameter roll mills 4, 5, and 6 are arranged in tandem as three-stand mills constituting a subsequent stage following the preceding stage. The stand spacing of all six stands including the aforementioned CVC mills 1, 2, and 3 is equally 5.5m. The roll mill 4 of the different diameter, which corresponds to the fourth stand, counting from the CVC mill 1, is configured as a quadruple mill consisting of work rolls 4a and 4b and backup ports 4c and 4d, as shown in Fig. 1. Work rolls 4a and 4b with different diameters are used as shown in the figure.
そして、 ヮ一クロール 4a · 4 bのうち下部にある大径のロール 4 bのみをモ —夕等 （図示せず） にて回転駆動し、 上部の小径のロール 4 aについては、 回転 自在にして駆動力をかけないように構成されている。 ヮ一クロール 4 a · 4 bに はベンダ一 （図示せず） を付設しているので、 ヮ一クロール 4 a · 4 bにべンデ ィングをかけることができる。 また各ワークロール 4 a · 4 bには CVC機能を も付与しており、 正逆各向きに 10 Ommの範囲内で軸長方向へ両者を移動させ ることができる。  Then, only the large-diameter roll 4b at the bottom of the single crawls 4a and 4b is driven to rotate by a motor (not shown), and the upper small-diameter roll 4a is rotatable. The driving force is not applied.ヮ Because a vendor (not shown) is attached to each crawl 4a and 4b, it is possible to bend each crawl 4a and 4b. Each work roll 4a and 4b is also provided with a CVC function, so that both can be moved in the axial direction within a range of 10 Omm in each direction.
このようにワークロール 4 a · 4 bにベンディング機能及び CVC機能を付与 することにより、 被圧延材の形状制御性能が向上し、 鋼板の良好なプロフィール を得ることができる。  By imparting the bending function and the CVC function to the work rolls 4a and 4b in this manner, the shape control performance of the material to be rolled is improved, and a good profile of the steel sheet can be obtained.
ワークロール 4 aの径は 480 mm, ワークロール 4 bの径は 600mmで、 両者の平均である等価口一ル径は 540mmである。 このような構成および機能 について、 後方にある他の 2スタンドの異径ロールミル 5 · 6も上記の異径ロー ルミル 4と相違はない。 なお、 異径ロールミル 4 · 5 · 6のワークロールの等価 ロール径は 540 mmよりも小さくすることもできるが、 強度の観点から 400 m m以上であることが好ましい。 The diameter of work roll 4 a is 480 mm, the diameter of work roll 4 b is 600 mm, The average equivalent diameter of both is 540mm. With respect to such a configuration and function, the other two stands of different diameter roll mills 5 and 6 at the rear are not different from the above different diameter roll mill 4. The equivalent roll diameter of the work rolls of the different diameter roll mills 4, 5, 6 can be smaller than 540 mm, but is preferably 400 mm or more from the viewpoint of strength.
これら 3スタンドの異径ロールミル 4 · 5 · 6は、 等価ロール径が小径である ことと、 一方のワークロール （4b等） のみを駆動するため被圧延材 Pに剪断力 が作用することから、 比較的低い圧延荷重でも圧下率の高い （たとえば圧下率 5 0%の） 圧延を実施できる。 そのため、 被圧延材 P中に微細なフヱライ ト組織を 形成する大圧下圧延等を小さな圧延荷重で行うことができ、 しかも、 圧延荷重が 小さいために、 ロール偏平やエッジドロップによる不都合も発生しない。  These three-stand roll mills 4, 5, and 6 have a small equivalent roll diameter and a shear force acting on the material P to be rolled because only one of the work rolls (4b, etc.) is driven. Rolling with a high rolling reduction (for example, a rolling reduction of 50%) can be performed even with a relatively low rolling load. For this reason, large rolling reduction or the like that forms a fine flat structure in the material P to be rolled can be performed with a small rolling load, and since the rolling load is small, problems due to roll flattening and edge drop do not occur.
図 6の線図 X3は、 第 6スタンドの異径ロールミル 6において厚さ 2. 3mm •幅 730mmの鋼板 （成分は C : 0. 16%、 S i ： 0. 22%、 Mn： 0. 82%) を等しい圧下率 （48%) で圧延製造するとき、 ワークロールの等価径 の変更とともに圧延荷重がどのように変化するかを示すものである。  The diagram X3 in Fig. 6 shows a steel plate with a thickness of 2.3 mm and a width of 730 mm in the different-diameter roll mill 6 of the sixth stand (C: 0.16%, Si: 0.22%, Mn: 0.82 It shows how the rolling load changes when the equivalent diameter of the work roll is changed when rolling is performed at the same rolling reduction (48%).
また、 図 7の線図 X 5は、 一定の異径ロールミル 5 · 6 (ヮ一クロール 5 a · 6 aの各径は 480mm、 5 b · 6 bは 600 mmで、 各ミルの等価口一ル径は 540mm) において、 図 6の場合と同じ鋼板を圧延製造するとき発生するエツ ジドロップを表すものである。 なお、 図 7中の線図 X4は、 ワークロールを異径 でなく同径 （600mmの中規模径） にして同じ鋼板を圧延製造する場合のエツ ジドロップを比較のために示している。  In addition, the diagram X5 in Fig. 7 shows that constant diameter roll mills 5 and 6 (each crawl 5a and 6a have a diameter of 480 mm, 5b and 6b have a diameter of 600 mm, and This represents the edge drop that occurs when rolling the same steel sheet as in Fig. 6 at a diameter of 540 mm). Note that the line X4 in Fig. 7 shows the edge drop when the same steel plate is rolled and manufactured with the same diameter (600 mm medium-sized diameter) instead of different diameters of the work rolls for comparison.
なお、 本実施形態の一変形例としては、 図 9に示したように、 後段に配置する ミルを、 異径ロールミル 4 · 5 · 6に代えて、 各直径が 600mm未満の一対の ワークロール 4a， · 4 b， 等を含む極小径ロールミル 4， · 5， · 6， とする こともできる。  As a modification of the present embodiment, as shown in FIG. 9, a pair of work rolls 4a each having a diameter of less than 600 mm are replaced with different-diameter roll mills 4, 5, 6 as shown in FIG. , · 4b, etc., the minimum diameter roll mill 4, · 5, 6 ·
また、 本実施形態による熱間圧延装置では、 6スタンドすべてのミル 1〜6の 各ワークロールに対して、 潤滑剤の供給手段を配置している。 同手段は、 たとえ ば図 3中の符号 5 e · 5 f · 6 e · 6 fのようにワークロールの表面に向いた噴 射口と、 そこへの潤滑剤の送りポンプ等とからなる。 また、 変形例としては、 ヮ 一クロール表面に潤滑剤を直接付与するのではなく、 被圧延材 Pの表面に潤滑剤 を付与して間接的に口ール表面に供給することもできる。 Further, in the hot rolling apparatus according to the present embodiment, lubricant supply means is arranged for each work roll of mills 1 to 6 in all six stands. The means comprises, for example, an injection port facing the surface of the work roll as indicated by reference numerals 5e, 5f, 6e, and 6f in Fig. 3, and a lubricant feed pump and the like. Also, as a modified example, ヮ Instead of directly applying the lubricant to the surface of one crawl, it is also possible to apply the lubricant to the surface of the material P to be rolled and supply the lubricant to the surface of the roll indirectly.
なお、 本実施形態による熱間圧延装置において、 潤滑剤は、 ロール表面の摩耗 を防ぐためのものであって摩擦係数を下げるためのものではない。 そこで、 潤滑 剤としては、 リン酸カルシウムや雲母、 炭酸カルシウム等といった微粒の固体潤 滑剤をグリース中に含めたものを使用する。 それら固体微粒子の配合により、 潤 滑剤使用時の各ワークロールと被圧延材 Pとの間の摩擦係数//は約 0 . 2 8又は それ以上と高めになる。 この程度の摩擦係数が確保されると被圧延材 Pのロール スリップが適切に防止される。  In the hot rolling apparatus according to the present embodiment, the lubricant is for preventing abrasion of the roll surface and not for lowering the friction coefficient. Therefore, a lubricant containing fine solid lubricant such as calcium phosphate, mica, calcium carbonate, etc., in the grease is used. By the addition of the solid fine particles, the coefficient of friction // between each work roll and the material P to be rolled when using a lubricant is increased to about 0.28 or more. When such a coefficient of friction is secured, the roll slip of the material P to be rolled is appropriately prevented.
上記のような潤滑剤を使えば、 ロール表面と被圧延材 Pとの間に上記の微粒子 が介在してロール ·被圧延材間の直接接触を防止するので、 ロール表面の摩耗が 抑制され、 被圧延材 Pの形状が長く良好に保たれやすい。 また、 鉱物油にではな くグリース中に固体微粒子を含めているので、 潤滑剤の貯留容器中で微粒子が沈 殿してしまう恐れがなく、 固体微粒子がロール表面上につねに均一に分散される ように供給されるというメリットもある。  If the above-mentioned lubricant is used, the fine particles intervene between the roll surface and the material to be rolled P to prevent direct contact between the roll and the material to be rolled, so that the abrasion of the roll surface is suppressed, The shape of the material to be rolled P is long and easily maintained. In addition, since solid fine particles are included in grease instead of mineral oil, there is no risk of fine particles settling in the lubricant storage container, and solid fine particles are always uniformly dispersed on the roll surface There is also a merit that it is supplied as follows.
図 8は、 潤滑剤の使用によるロールの摩耗低減効果を示すもので、 線図 X 6は 潤滑剤の不使用の場合を示し、 線図 X 7は潤滑剤の使用時を示す。 なお、 図 8の 横軸はワークロールの負荷の大きさを示し、 縦軸はヮ一クロールの摩耗量を示し ている。  FIG. 8 shows the effect of reducing the wear of the roll by using a lubricant. A diagram X6 shows a case where no lubricant is used, and a diagram X7 shows a case where the lubricant is used. The horizontal axis in FIG. 8 indicates the magnitude of the load on the work roll, and the vertical axis indicates the amount of wear of the single crawl.
また、 本実施形態による熱間圧延装置においては、 後段に配置した 3スタンド の異径ロールミル 4 · 5 · 6の各出側にカーテンウォール型冷却器 7 A · 7 B ■ 7 Cを配置している。 冷却器 7 Bを例として説明すると、 図 3に示すように冷却 器 7 Bは、 上下のヘッダ一 7 B a ' 7 B bより被圧延材 Pの全幅表面に向けて大 量の常温冷却水を層流状態で幕状 （カーテンウォール状。 厚さは 1 0 mm以上で あり最適厚さが 1 6 mm) に流し当てることにより、 被圧延材 Pを強く冷却する。 冷却水の量は、 被圧延材 Pの単位幅 （ l m) あたり 1 0 0〜 5 0 0 m3/hの範囲 内で調整可能で、 冷却による被圧延材 Pの温度降下は 2 0 °C/ s e c以上になる。 カーテンウォール型冷却器では、 通常は単位幅あたりに 3 5 0 m3/hの冷却水を 使用するが、 その場合の被圧延材 Pの温度降下率は、 板厚と速度との積が 1 2 0 0 mm · mp mであるとき 6 0〜8 0 °C/ s e c (加工発熱による温度上昇を含 めて 4 0 °C/ s e c前後） に達する。 他の冷却器 7 A · 7 Cについても、 以上の 構成および機能は同じである。 In the hot rolling apparatus according to the present embodiment, curtain wall type coolers 7 A, 7 B and 7 C are arranged on the respective outlet sides of the three stand different-diameter roll mills 4, 5, and 6 arranged at the subsequent stage. I have. Taking the cooler 7B as an example, as shown in FIG. 3, the cooler 7B has a large amount of room temperature cooling water from the upper and lower headers 7B a '7B b toward the entire width surface of the material P to be rolled. In a laminar flow state, the material to be rolled P is cooled strongly by pouring it into a curtain shape (curtain wall shape. The thickness is 10 mm or more and the optimum thickness is 16 mm). The amount of cooling water can be adjusted within the range of 100 to 500 m 3 / h per unit width (lm) of the material P to be rolled, and the temperature drop of the material P to be rolled by cooling is 20 ° C. / sec or more. Curtain wall coolers usually use 350 m 3 / h of cooling water per unit width. In that case, the temperature drop rate of the material P to be rolled is 1 times the product of the sheet thickness and the speed. 2 0 When it is 0 mm · mpm, it reaches 60 to 80 ° C / sec (around 40 ° C / sec including the temperature rise due to the heat generated during processing). The above configurations and functions of the other coolers 7A and 7C are the same.
なお、 本実施形態による熱間圧延装置では後段の各ミル 4 · 5 · 6の出側に力 一テンゥオール型冷却器を配置したが、 冷却器の設置台数はこれに限られるもの ではなく、 被圧延材の種類等によって適宜変更することができる。  In the hot rolling mill according to the present embodiment, a force-type cooling device is arranged on the outlet side of each of the subsequent mills 4, 5, 6; however, the number of cooling devices is not limited to this. It can be appropriately changed depending on the type of rolled material and the like.
このような力一テンウォール型冷却器 7 A · 7 B · 7 Cを使用することにより、 圧延中の加工発熱による被圧延材 Pの温度上昇を抑制して大圧下圧延法又は制御 圧延法に適した温度範囲に被圧延材 Pを保つとともに、 圧延後に微細組織が粒成 長を起こすことも抑制することができる。  By using such a ten-wall type cooler 7A, 7B, 7C, it is possible to suppress the temperature rise of the material P to be rolled due to the heat generated during processing during rolling, and to apply it to the large rolling reduction method or the controlled rolling method. The material P to be rolled can be kept in a suitable temperature range, and the microstructure can be prevented from undergoing grain growth after rolling.
なお、 図 1の熱間圧延装置の下流側にあるランアウトテーブル （図示せず） に おいても、 粒成長を防止すべく冷却水にて 1 0 °C/ s e c以上の速度で被圧延材 Pを冷却している。  The run-out table (not shown) on the downstream side of the hot rolling mill shown in Fig. 1 also uses cooling water at a speed of 10 ° C / sec or more with cooling water to prevent grain growth. Has cooled.
図 1の熱間圧延装置において最終段スタンドである異径ロールミル 6の出側に は、 カーテンウォール型冷却器 7 Cから数百 mm〜l mほど離して、 水噴射スプ レ一 8を配置している。 これは、 冷却器 7 Cによって被圧延材 Pの上面に載った 冷却水を除去するためのものである。 図 3に示したように、 このスプレー 8は、 複数配置したノズル 8 aより、 被圧延材 Pの表面に対して、 被圧延材 Pの上方か ら被圧延材 Pの流れ方向の上流側に向けて斜め下方へ、 被圧延材 Pの上面との角 度が 6 5 ° (又は 5 0〜8 0。 の範囲内） になるように、 1 0 k g/ c m2前後の 加圧水を 1個あたり毎分 3 0 0リットル吹き出すノズル 8 aを複数個備えている (この例では合計 4個） 。 複数のノズル 8 aは、 図 3に示したように被圧延材 P の長さ方向に間隔をおき、 かつその幅方向にも間隔をおいて配置されている。 各 ノズル 8 aは、 被圧延材 Pの幅方向に広がるように水を吹き出すもので、 被圧延 材 Pの幅方向への広がり角は 1 5〜3 0 ° 、 長さ方向への広がり角は 1〜 1 0 ° がよい （本実施形態ではそれそれ 2 1 ° 、 3 ° とした） 。 On the exit side of the different-diameter roll mill 6, which is the final-stage stand in the hot-rolling apparatus shown in Fig. 1, a water-injection sprayer 8 is placed at a distance of several hundred mm to lm from the curtain wall cooler 7C. I have. This is for removing the cooling water on the upper surface of the material P to be rolled by the cooler 7C. As shown in FIG. 3, this spray 8 is sprayed from a plurality of nozzles 8a to the surface of the material P to be rolled from above the material P to the upstream side in the flow direction of the material P to be rolled. diagonally downward toward, so that the angles are 6 5 ° with the upper surface of the rolled material P (or 5 0-8 within the range of 0.5), per one of the 1 0 kg / cm 2 before and after the pressurized water It has a plurality of nozzles 8a that blow out 300 liters per minute (a total of 4 nozzles in this example). As shown in FIG. 3, the plurality of nozzles 8a are arranged at intervals in the length direction of the material P to be rolled, and at intervals in the width direction thereof. Each nozzle 8a blows out water so as to spread in the width direction of the material P to be rolled, and the spread angle of the material P to be rolled in the width direction is 15 to 30 °, and the spread angle in the length direction is 1 to 10 ° is preferable (in the present embodiment, they are 21 ° and 3 °, respectively).
このような水噴射スプレー 8を使用すれば、 冷却手段 7の作用で被圧延材 P上 に載った冷却水を円滑に除去できるので、 その下流側にある各種計測器によって、 圧延後の被圧延材 、 即ち製造された鋼板に関する種々の計測を適切に行うこと が可能になる。 ここで、 水は気体よりも質量があるために運動エネルギーを付与 しゃすく、 入手も容易であるため、 噴射流体とするうえでまず好適である。 上流 側に向けて斜め下方へ加圧水を吹き出すことによって下流側 （計測器のある側） へ冷却水が至るのを防止できること、 さらには、 被圧延材 Pの幅方向に広がるノ ズルを使用することにより被圧延材 P上の全幅について冷却水を除去できること などが、 好作用をもたらす理由であると考えられる。 If such a water spray 8 is used, the cooling means 7 can smoothly remove the cooling water placed on the material P to be rolled by the action of the cooling means 7. Properly perform various measurements on materials, ie manufactured steel sheets Becomes possible. Here, water has a greater mass than a gas, so it imparts kinetic energy. It is easy to obtain, and is therefore suitable for use as a jet fluid. By blowing pressurized water obliquely downward toward the upstream side, it is possible to prevent the cooling water from reaching the downstream side (the side with the measuring instrument), and use nozzles that spread in the width direction of the material P to be rolled. The reason for this is that the cooling water can be removed from the entire width of the material P to be rolled, thereby providing a favorable effect.
そのほか、 各スタンドのミルのヮ一クロールに対しては、 図 3に示すように口 —ル冷却用水の噴射ノズル （たとえば符号 5 i · 5 j · 6 i · 6 j ) やそれによ る冷却水を取り除く水切り板 （たとえば符号 5 g · 5 h · 6 g · 6 h) を配置し ている。  In addition, for the single crawl of the mill at each stand, as shown in Fig. 3, a nozzle for cooling water for cooling (for example, reference numeral 5 i · 5 j · 6 i · 6 j) and the cooling water A drainer board (for example, 5 g · 5 h · 6 g · 6 h) that removes water is placed.
次に、 上述した熱間圧延装置 （図 1) を用いて熱間圧延を行った実施例を以下 に示す。  Next, examples in which hot rolling was performed using the above-described hot rolling apparatus (FIG. 1) will be described below.
C： 0. 16%、 S i ： 0. 22%、 Mn : 0. 82% (他に有意量の成分を 含まない） の化学成分を有する鋼について、 図 1に示した圧延装置により、 厚さ 2. 33mm ·幅 730 mmの鋼板を 3種類の条件 （実施例 1〜3) で製造した c 下記の表 1一 1に実施例 1についてのパススケジュール （圧延条件） を示し、 表 1一 2に実施例 2 · 3のパススケジュールを示す。 また表 1—3は、 各実施例 1 〜3での力一テンウォール型冷却器 7 A · 7B · 7 Cの使用状況、 表 1一 4は、 各実施例 1〜 3について最終段のミル 6の後方で測定した被圧延材 Pの仕上温度 である。 各表において 「粗パー」 は粗圧延装置を表し、 「F 1」 〜 「F6」 は第 1スタンド〜第 6スタンドの各ミル 1〜6をそれそれ表す。 なお、 圧延スピード についてはとくに制限を設けず、 一般のホットストリップミルで常用されている 圧延スピード （たとえば？〜 9m/s e c) を採用した。 [表 1 - 1] For a steel with the chemical composition of C: 0.16%, Si: 0.22%, Mn: 0.82% (excluding other significant components), the rolling mill shown in Fig. 1 C. A steel plate with a width of 2.33 mm and a width of 730 mm was manufactured under three types of conditions (Examples 1 to 3). C The following Table 1-1 shows the pass schedule (rolling conditions) for Example 1. 2 shows the pass schedules of Embodiments 2 and 3. Also, Table 1-3 shows the usage status of the ten-wall type coolers 7A, 7B and 7C in each of Examples 1-3, and Table 1-4 shows the final stage mill for each of Examples 1-3. This is the finishing temperature of the material P to be rolled measured behind 6. In each table, "rough par" represents a rough rolling machine, and "F1" to "F6" represent mills 1 to 6 of the first to sixth stands, respectively. The rolling speed was not particularly limited, and the rolling speed commonly used in general hot strip mills (for example,? To 9 m / sec) was adopted. [Table 1-1]
実施例 1 ススケシ、' L一ル （累積歪 = 0.65)  Example 1 Sukeshi, 'L' (Cumulative strain = 0.65)
Figure imgf000016_0001
Figure imgf000016_0001
[表 1一 3] [Table 1-1-3]
冷却条件 (カ-テンウォ-ル)  Cooling conditions (Carten wall)
Figure imgf000016_0002
Figure imgf000016_0002
[表 1一 4] [Table 1-4]
温度条件  Temperature conditions
実施例 仕上温度。 C  Example Finish temperature. C
1 800〜850  1 800-850
2 謂〜 850  2 so-called ~ 850
3 750〜780 実施例 1〜 3のそれそれによつて得られた熱間圧延鋼板についてフェライ ト粒 径と機械的性質とを表 1一 5に示す。 この表 1一 5において、 「T S」 は引張強 さ、 「YP j は降伏点、 「EL j は伸びである。 なお、 表 1一 5のうちには、 表 1一 1〜1一 3に示された圧延条件の主なものも併記している。 3 750-780 The ferrite grain size and mechanical properties of the hot-rolled steel sheets obtained in Examples 1 to 3 are shown in Table 115. In Table 1-15, “TS” is the tensile strength, “YP j is the yield point, and“ EL j is the elongation. ”In Table 115, Tables 11-11 to 13 The main ones of the indicated rolling conditions are also shown.
[表 1 - 5] [Table 1-5]
圧延条件および機械的特性  Rolling conditions and mechanical properties
Figure imgf000017_0001
Figure imgf000017_0001
TS ：引張強度， YP ：降伏点， EL ：伸び 表 1一 5に示すように、 累積歪み （前記した加重積算値である £C) を 0. 92 にとつた実施例 2 · 3では、 粒径が 4 m前後のフェライ ト組織を有していて機 械的性質にすぐれた鋼板を得ることができた。 後段の 3スタンド （F4〜F 6) の出側 （後面） においてカーテンウォール型冷却器 7 A〜7 Cを使用した実施例 3によっては、 フェライ ト粒径が 4〃m程度以下で、 機械的性質にもとくにすぐ れる鋼板が得られた。 TS: Tensile strength, YP: Yield point, EL: Elongation As shown in Table 15-5, in Examples 2 and 3 where the cumulative strain (the above-mentioned weighted integrated value, £ C ) was set at 0.92, A steel sheet with a ferrite structure with a diameter of about 4 m and excellent mechanical properties was obtained. Depending on the embodiment 3 in which curtain wall type coolers 7A to 7C are used on the exit side (rear side) of the subsequent three stands (F4 to F6), the ferrite particle size is about 4 m or less, and A steel sheet with particularly good properties was obtained.
図 4は、 実施例 1〜3により得られた鋼板についてフェライ ト組織の結晶粒に 関するグレーンサイズ （粒径 D (jum) を一 1ノ2乗したもの） と降伏点との関 係を図示したものである。 図のように、 後段 3スタンドのミルにおける累積歪み を 0. 65にした場合 （図 4中のグループ X2) にはグレーンサイズが 0. 43 以下 （粒径 5. 4 m以上） であって降伏点も十分ではないが、 累積歪みを 0. 92にした場合には、 グレーンサイズが 0. 5程度 （粒径が 4〃m程度） になり、 降伏点は 45 kg/mm2以上にまで高くなる。 Figure 4 shows the relationship between the grain size (the grain size D (jum) is 11-1 squared) and the yield point for the grains of the ferrite structure in the steel sheets obtained in Examples 1 to 3. It was done. As shown in the figure, when the cumulative strain in the latter three-stand mill was 0.65 (group X2 in Fig. 4), the grain size was 0.43 or less (particle size of 5.4 m or more) and the yield was low. is also not enough points, when the cumulative strain to 0. 92, grain size 0.5 about 5 (particle size of about 4〃M) becomes, the yield point is as high as 45 kg / mm 2 or more Become.
そして、 図 5A、 図 5 B、 図 5 Cは、 実施例 3で得た鋼板について、 上表面付 近と板厚中央付近、 下表面付近でそれそれ結晶組織を示した図である。 板厚内の いずれの部分にも、 粒径が 3 m台の微細なフェライ ト組織が形成されている。 このように本実施形態によれば、 微細なフヱライ ト組織を有し、 引張強さゃ延 性 ·靱性 ·疲労強度を含む強度バランスにすぐれた細粒鋼熱延鋼板を円滑に製造 でき、 同鋼板の商業的生産も可能である。 その理由をまとめると以下の通りであ る o 5A, 5B, and 5C are diagrams showing the crystal structures of the steel sheet obtained in Example 3 near the upper surface, near the center of the sheet thickness, and near the lower surface, respectively. Within thickness In each part, a fine ferrite structure with a grain size of the order of 3 m is formed. As described above, according to the present embodiment, a hot-rolled fine-grained steel sheet having a fine flat structure and an excellent balance of strength including tensile strength, ductility, toughness, and fatigue strength can be smoothly manufactured. Commercial production of steel sheets is also possible. The reasons are summarized below.o
a ) 後段に配置した 2スタンド以上の異径ロールミル 4 · 5 · 6又は極小径 ロールミル 4， · 5， · 6， は、 等価口一ル径又は双方 （一対） のヮ一クロール 径が小さいために、 低い圧延荷重で大圧下、 つまり高圧下率の圧延を行うことが できる。 同じ圧下率をもたらす圧延荷重は、 ワークロールの径が小さいほど小さ くなり、 概ねワーク口一ル径に比例するからである （図 6参照） 。 圧延荷重が小 さくなれば、 ロール偏平のために高圧下率圧延ができないという現象がなくなる ほか、 圧延ロールの扁平変形量が減る結果としてエッジドロップも軽減される a) The roll mills with different diameters of 4, 5, 6 or extra small diameter roll mills 4, 5, 6 or more, which are arranged at the subsequent stage, have a small equivalent diameter or a pair of two diameters. In addition, it is possible to perform rolling under a large rolling force with a low rolling load, that is, a rolling under a high rolling reduction. This is because the rolling load that provides the same rolling reduction becomes smaller as the diameter of the work roll becomes smaller, and is generally proportional to the diameter of the work opening (see Fig. 6). If the rolling load is reduced, the phenomenon that high-pressure reduction rolling cannot be performed due to flattening of the rolls will not be eliminated, and edge drop will also be reduced as a result of reduced flattening of the rolling rolls
(図 7参照） 。 (See Figure 7).
b ) 後段に設けたカーテンウォール型冷却器 7 A · 7 B · 7 Cが、 累積歪み が 0 . 9以上という高圧下率の圧延にともなう被圧延材 Pの加工発熱による温度 上昇を抑制する。 同冷却器 7 Α · 7 Β · 7 Cは、 上記のように流す大量の冷却水 によって被圧延材 Ρを強く冷却するので、 被圧延材 Ρが加速された場合にも、 大 圧下圧延法を行うに適した温度範囲 （たとえば、 A r 3変態点〜 A r 3 + 5 0 C) に被圧延材 Pを維持することが可能である。 このように圧延直後の被圧延材 Pを 強く冷却することにより、 被圧延材 P中の微細組織の粒成長を停止させることが 可能であり、 製造された鋼板中のフェライ ト組織の結晶粒径は 4 m程度以下に まで細かくなる。 最終段スタンドのミル 6の出側のみではなく後段の少なくとも 2スタンドのミルの出側に同冷却器 7 A · 7 B， 7 Cを配置するので、 最終ス夕 ンドのミル 6およびそれまでのスタンドのミルでの圧延時に発生する熱を効果的 に奪って適切な温度維持をはかる。 各スタンドのミルの出側に同冷却器 7 A · 7 B · 7 Cがあるために、 各スタンドのミルでの圧延直後の被圧延材 Pを強く冷却 して微細組織の粒成長を停止させる作用も確保される。 なお、 同冷却器 7 A · 7 B · 7 Cは、 被圧延材 Pの全幅にわたって冷却水を当てるものであるため、 幅方 向にも偏ることなく被圧延材 Pを均一に冷却できる。 以上述べたように本実施形態によれば、 大圧下圧延法の実施に関する前述の課 題 i )、 i i )が解決され、 一般的なホットストリップミル形式の圧延装置を使用する ことによる細粒鋼鋼板の円滑な製造が可能になり、 細粒鋼鋼板の商業的生産が可 能となる。 b) Curtain wall type coolers 7A, 7B, and 7C provided at the subsequent stage suppress the temperature rise due to the heat generated during processing of the material P to be rolled due to the rolling at a high reduction ratio of 0.9 or more. The cooler 7Α7 77C cools the rolled material 流 す strongly by the large amount of cooling water flowing as described above, so even if the rolled material 加速 is accelerated, the large rolling reduction method can be used. It is possible to maintain the material P to be rolled in a temperature range (for example, from the Ar 3 transformation point to Ar 3 +50 C) suitable for the operation. In this way, by cooling the rolled material P immediately after rolling, it is possible to stop the grain growth of the microstructure in the rolled material P, and to reduce the grain size of the ferrite structure in the manufactured steel sheet. Is reduced to about 4 m or less. The coolers 7A, 7B, and 7C are placed not only at the outlet of the mill 6 at the last stage but also at the outlet of at least two mills at the subsequent stage. The heat generated during rolling in the stand mill is effectively removed to maintain an appropriate temperature. Since the same coolers 7 A, 7 B, and 7 C are provided on the outlet side of the mill at each stand, the material P to be rolled immediately after rolling at the mill at each stand is strongly cooled to stop grain growth of the microstructure. Action is also ensured. Since the cooling devices 7A, 7B, and 7C apply cooling water over the entire width of the material P to be rolled, the material P to be rolled can be uniformly cooled without being biased in the width direction. As described above, according to the present embodiment, the above-mentioned problems i) and ii) relating to the implementation of the large rolling reduction method are solved, and the fine-grained steel by using a general hot strip mill type rolling device is solved. The smooth production of steel sheets will be possible, and the commercial production of fine-grained steel sheets will be possible.
また、 力一テンウォール型冷却器 7 A · 7 B · 7 Cを適切に使用して被圧延材 Pの温度範囲を 7 0 0〜8 0 0 °C (温間域） に保持すれば、 N bゃT iを含む鋼 を被圧延材 Pにして前記の制御圧延法を安定的に実施する （もって細粒鋼鋼板を 製造する） ことも可能である。  In addition, if the temperature range of the material P to be rolled is maintained at 700 to 800 ° C (warm range) by appropriately using the power wall coolers 7A, 7B, and 7C, It is also possible to use the steel containing Nb ゃ Ti as the material P to be rolled and to stably execute the above-mentioned controlled rolling method (thus producing a fine-grained steel sheet).
また、 炭素含有量が 0 . 5 %以下であり、 合金元素の含有量が 5 %以下の被圧 延材を圧延した場合、 このような成分の細粒鋼鋼板は、 その機械的性質のパラン ス （引張強さや延性等の面で汎用性がある） や溶接性の高さなどから用途が広く、 比較的安価であつて入手容易であるうえにリサイクル性もあること等から、 きわ めて需要が高いと考えられる。 したがってこのような成分含有量の鋼板なら、 社 会的貢献度が高いうえその生産に十分な経済合理性がともなう。  In addition, when a rolled material having a carbon content of 0.5% or less and an alloy element content of 5% or less is rolled, a fine-grained steel sheet having such a composition has a mechanical property (It is versatile in terms of tensile strength and ductility, etc.) and weldability, so it is widely used, relatively inexpensive, easily available, and recyclable. It is considered that demand is high. Therefore, steel sheets with such component contents have a high social contribution and economic rationale for their production.
一般に、 C (炭素） 量が多くなるとフェライ ト量が減少してパ一ライ ト主体の 鋼になるが、 本実施形態によれば同一の C量であってもフェライ ト量を増すこと ができ、 C量が 0 . 5 %まではフェライ ト主体の組織を得ることができる。  In general, when the amount of C (carbon) increases, the amount of ferrite decreases and the steel is mainly composed of steel. However, according to the present embodiment, the amount of ferrite can be increased even with the same amount of C. However, a ferrite-based organization can be obtained up to a C content of 0.5%.
なお、 本実施形態は被圧延材 P中の C以外の合金元素の有無を問わずに効果を もたらすが、 A r 3変態点〜 A r 3 + 5 0 °Cという温度範囲を熱間加工の最適温度 である 7 0 0〜 9 0 0 °Cの間におさめるためには、 当該変態点温度を合金元素の 合計量で調節するのが好ましい。 ただし、 合金元素の合計含有量が 5 %を超える と、 A r 3変態点が低くなりすぎて細粒が得られ難くなる。 Although the present embodiment brings about an effect regardless of the presence or absence of alloying elements other than C in the material P to be rolled, the temperature range from the Ar 3 transformation point to Ar 3 + 50 ° C. In order to keep the temperature within the optimum temperature of 700 to 900 ° C., it is preferable to adjust the transformation point temperature by the total amount of alloying elements. However, when the total content of alloying elements exceeds 5%, the Ar 3 transformation point becomes too low, and it becomes difficult to obtain fine grains.
次に、 本発明の他の実施形態による熱間圧延装置及び熱間圧延方法について説 明する。  Next, a hot rolling apparatus and a hot rolling method according to another embodiment of the present invention will be described.
上述した実施形態による熱間圧延方法は、 後段のミルを中心にして被圧延材を 強く圧下する （つまり累積歪みが 0 . 9以上になる高い圧下を行う） とともにそ の被圧延材を適切な温度に保ち、 もってフェライ ト粒径が 4 zm程度以下という 高品質の細粒鋼鋼板を製造するものである。 そのような方法を実現できるよう、 図 1に示した熱間圧延装置には、 比較的低い圧延荷重によって必要な圧下を実現 するとともに被圧延材を強く冷却できる構成を採用している。 これにより、 被圧 延材を十分に高圧下 ·強冷却 （温度管理） すれば、 通常のタンデムの圧延装置に てきわめて高品質の細粒鋼熱延鋼板を工業的に生産できる。 In the hot rolling method according to the above-described embodiment, the material to be rolled is strongly reduced centering on the subsequent mill (that is, a high reduction in which the cumulative strain becomes 0.9 or more) and the material to be rolled is appropriately compressed. It is intended to produce high-quality fine-grained steel sheets with a ferrite grain size of about 4 zm or less while maintaining the temperature. In order to realize such a method, the hot rolling mill shown in Fig. 1 achieved the required reduction with a relatively low rolling load. And a structure capable of strongly cooling the material to be rolled. With this, if the material to be rolled is subjected to sufficiently high pressure and strong cooling (temperature control), extremely high-quality hot-rolled fine-grained steel sheets can be industrially produced using a normal tandem rolling mill.
しかし、 上述した実施形態では、 設備上又は運転上の負担を軽減して最も効果 的に細粒鋼熱延鋼板を製造するという点において改良の余地がある。 つまり、 圧 下 ·冷却の各要件が被圧延材の金属組織に対してどれほどの影響力をもつのか等 をさらに検討することにより、 品質 （フェライ ト粒径など） の低下を極力抑制し ながら、 製造条件を緩和して低コス卜で細粒鋼鋼板を製造することができる。 そのような費用対効果の側面から圧延方法を改善することにより、 実用性に富 んでいながら品質 （粒径など） がやや低い水準にある細粒鋼鋼板について商業的 な生産を行うことが容易となる。 上記実施形態で説明した高いレベルの高圧下等 が、 鋼板の品質によらず常に不可欠であるとすれば、 圧延装置の構成や圧延ロー ルの消耗に関連して生産コストがかさみ、 また、 高圧下にともなう被圧延材の加 ェ発熱に起因して冷却用の手段にも同様に高めの設備費 ·運転費が必要だからで ある。  However, in the above-described embodiment, there is room for improvement in that the load on equipment or operation is reduced and a hot-rolled steel sheet of fine grain is manufactured most effectively. In other words, by further examining how much each of the requirements for reduction and cooling has on the metallographic structure of the material to be rolled, it is possible to minimize the decrease in quality (ferrite grain size, etc.) Fine-grained steel sheets can be manufactured at low cost by relaxing the manufacturing conditions. By improving the rolling method from such a cost-effective aspect, it is easy to commercialize fine-grained steel sheets that are practical but have a slightly lower quality (grain size, etc.). Becomes If the high level of high pressure described in the above embodiment is always indispensable irrespective of the quality of the steel sheet, the production cost increases in relation to the configuration of the rolling mill and the consumption of the rolling roll. This is because the equipment for cooling also requires higher equipment and operating costs due to the heating of the material to be rolled.
本実施形態による熱間圧延装置及び方法はこのような問題点を解決するもので ある。  The hot rolling apparatus and method according to the present embodiment solves such a problem.
図 1 0に示す本実施形態による連続熱間圧延装置は、 被圧延材 Pのいわゆる仕 上圧延装置であって、 被圧延材 Pの流れ方向の上流側 （図示省略） には加熱炉と 粗圧延装置があり、 下流側 （図示省略） にはランアウトテーブルゃ卷取り機など が配置されている。 この熱間圧延装置は、 それそれに圧延ロールを備える合計 6 スタンドのミル 1 0 ~ 6 0をタンデムに配置したもので、 上流側で粗圧延された 被圧延材 Pを連続圧延することにより、 通常は、 厚さが 2〜1 6 mm前後の種々 の熱延鋼板を製造する。 一般的な内部組織 （平均フヱライ ト粒径が 1 0 / Π1以上 のもの） をもつ鋼板を製造する通常圧延を円滑に行えるとともに、 運転条件を適 切に設定することにより細粒鋼圧延、 すなわち微細なフェライ ト組織を有する細 粒鋼熱延鋼板の製造を行えるよう、 図 1 0に示した圧延装置は以下のように構成 されている。  The continuous hot rolling apparatus according to the present embodiment shown in FIG. 10 is a so-called finish rolling apparatus for the material P to be rolled, and a heating furnace and a roughing furnace are provided upstream (not shown) in the flow direction of the material P to be rolled. There is a rolling mill, and a run-out table and a winder are arranged downstream (not shown). This hot rolling machine is a tandem arrangement of a total of 6 stands of mills 10 to 60 equipped with a rolling roll and a rolling roll. Manufactures various hot-rolled steel sheets with a thickness of about 2 to 16 mm. Normal rolling can be performed smoothly to produce steel sheets with a general internal structure (average particle diameter of 10/11 or more), and fine-grained steel rolling can be performed by setting the operating conditions appropriately. The rolling mill shown in FIG. 10 is configured as follows so that a hot-rolled steel sheet having a fine ferrite structure can be manufactured.
まず前段の 3スタンドとして、 いわゆる C V Cミル 1 0 · 2 0 · 3 0を夕ンデ ムに配置している。 熱間圧延装置の最も入側寄りに位置する CVCミル 10は、 図 10のようにワークロール 101 a · 101bとパックアップロール 101 c • 101 dとからなる 4重のミルとして構成され、 ワークロール 101 a · 10 lbに、 図 11Aに示すようなクラウン （CVC、 すなわち直径の連続的変化） をもたせている。 ワークロール 101 a · 101 bは、 図 11 B及び図 11 Cの ように互いに反対の軸長方向へ同時に移動 （シフト） させることができ、 それに よってロール間の位置関係、 すなわちロールギヤップを調整することが可能であ る。 ワークロール 101 a · 101 bの径は 700 mmとし、 最大シフト量は正 逆それそれに 100 mmとした。 他の 2スタンドの CVCミル 20 · 30も、 こ のような構成および機能について CVCミル 10と相違はない。 First, the so-called CVC mill 10 ・ 20 ・ 30 was set up in the first three stands. Are placed in the system. The CVC mill 10, which is located closest to the entry side of the hot rolling mill, is configured as a quadruple mill consisting of work rolls 101a and 101b and backup rolls 101c and 101d, as shown in Fig. 10. 101 a · 10 lb has a crown (CVC, ie continuous change in diameter) as shown in Figure 11A. The work rolls 101a and 101b can be simultaneously moved (shifted) in opposite axial directions as shown in FIG. 11B and FIG. 11C, thereby adjusting the positional relationship between the rolls, that is, the roll gap. It is possible. The diameter of the work rolls 101a and 101b was set to 700 mm, and the maximum shift amount was set to 100 mm in both directions. The other two-stand CVC mills 20 and 30 do not differ from the CVC mill 10 in such configuration and function.
こうした CVCミル 10 · 20 · 30を前段に配置したのは、 被圧延材 Pのク ラウン （形状） を好適に保っためである。 後述する後段の異径ロールミル 40 · 50 · 60では、 細粒鋼圧延の際、 加工発熱に起因したサーマルクラウン等が発 生しやすいため、 前段に置いたこれら CVCミル 10 · 20 · 30によってあら かじめ板クラウンを修正し、 被圧延材 Pの中絞り等を軽減できるようにしたので ある。 なお、 各 CVCミル 10 · 20 · 30のワークロール 101 a ' 101b 等には、 可変速制御手段を付属した交流モータ （図示せず） を、 減速機や自在継 手 （いずれも図示せず） を介してそれそれ接続している。  The reason why the CVC mills 10, 20, and 30 are arranged at the front stage is to keep the shape (shape) of the material P to be rolled properly. In the later-stage roll mills 40, 50, and 60, which will be described later, a thermal crown and the like due to the heat generated during processing are likely to occur during the rolling of fine-grained steel. By modifying the pre-steel crown, it was possible to reduce the medium drawing of the material P to be rolled. The work rolls 101a and 101b of each CVC mill 10, 20, and 30 are equipped with an AC motor (not shown) equipped with variable speed control means, a speed reducer and a universal joint (neither shown). It is connected through it.
続く後段の 3スタンドとしては、 いわゆる異径ロールミル 40 · 50 · 60を やはりタンデムに配置している。 前述の CVCミル 10 · 20 · 30を含む全 6 スタンドのスタンド間隔は、 等しく 5. 5mである。 CVCミル 10から数えて 第 4スタンドにあたる異径ロールミル 40は、 図 10のようにヮ一クロール 10 4 a · 104bとパックアップロール 104c * 104dとからなる 4重のミル として構成され、 この例では、 ヮ一クロール 104 a · 104bとして互いに直 径の異なるものを使用している。 ヮ一クロール 104a ' 104 bのうち下側に ある大径のロール 104bのみを、 減速機 （図示せず） および自在継手を介し接 続したモー夕 （図示せず。 可変速制御手段つき交流モータ） によって回転駆動し、 上側の小径のロール 104 aについては、 回転を自在にして駆動力をかけないこ ととした。 ワークロール 104 a · 104 bにはベンダ一 （図示せず） を付設し ているので、 ワークロール 1 04 a . 1 04 bにベンディングをかけることが可 能である。 また各ヮ一クロール 1 04 a · 104 bには CVC機能をも付与して おり、 正逆各向きに 100mmの範囲内で軸長方向へ両者を移動させることがで きる。 ワークロール 1 04 aの径は 480 mm、 ワークロール 1 04 bの径はAs the subsequent three stands, so-called different diameter roll mills 40, 50 and 60 are also arranged in tandem. The stand spacing of all six stands including the aforementioned CVC mills 10, 20, 30 is equally 5.5m. The different-diameter roll mill 40 corresponding to the fourth stand, counting from the CVC mill 10, is configured as a quadruple mill composed of a single crawl 104a104b and a backup roll 104c * 104d as shown in FIG. The crawls 104a and 104b have different diameters from each other.モ ー Motor (not shown) in which only the lower large-diameter roll 104b of one crawl 104a '104b is connected via a speed reducer (not shown) and a universal joint (not shown. AC motor with variable speed control means) ), The upper small roll 104a is allowed to rotate freely and no driving force is applied. Work rolls 104a and 104b are provided with a vendor (not shown). Therefore, it is possible to bend the work rolls 104a and 104b. Each Crawl 104a / 104b is also provided with a CVC function, so that both can be moved in the axial direction within 100mm in each direction. The diameter of work roll 104a is 480 mm, and the diameter of work roll 104b is
600mmとしたので、 両者の平均である等価ロール径は 540mmと小さい。 以上のような構成および機能について、 後方にある他の 2スタンドの異径ロール ミル 50 · 60も上記の異径ロールミル 40と相違はない。 Since it was 600 mm, the equivalent roll diameter, which is the average of both, is as small as 540 mm. With respect to the configuration and function as described above, the other two stands of different diameter roll mills 50 and 60 at the rear are not different from the above different diameter roll mill 40.
3スタンドの異径ロールミル 40 · 50 · 60は、 等価ロール径が小径である ことと、 一方のヮ一クロール 104bのみを駆動して被圧延材 Pに剪断力を作用 させることから、 比較的低い圧延荷重でも圧下率の高い （たとえば圧下率 50% の） 圧延を実施できる。 そのため、 小さな圧延荷重にて、 細粒鋼圧延のための大 圧下圧延等を極端な程度にまでも行うことができ、 しかもその際、 圧延荷重が小 さいために、 厚さ 2 mm前後の薄板の圧延であっても、 ロール偏平やエッジドロ ップによる不都合を回避することができる。  The three stand different diameter roll mills 40, 50, and 60 are relatively low because the equivalent roll diameter is small and only one of the single crawls 104b is driven to apply a shearing force to the material P to be rolled. Rolling with a high rolling reduction (for example, a rolling reduction of 50%) can be performed even with a rolling load. As a result, it is possible to perform extreme reduction rolling, etc. for fine-grained steel rolling with a small rolling load to an extreme extent, and at that time, because the rolling load is small, a thin plate with a thickness of about 2 mm Even in the case of rolling, it is possible to avoid inconvenience due to roll flattening and edge drop.
細粒鋼圧延を連続的に行うためには、 被圧延材 Pを十分に冷却して適切な温度 範囲に保つ必要があるため、 熱間圧延装置の後段のスタンドのミル 40 · 50 · 60の各後部及び 又は前部に、 図 1 0のとおりカーテンウォール型冷却器 1 0 In order to continuously roll fine-grained steel, it is necessary to sufficiently cool the material to be rolled P and maintain it in an appropriate temperature range. At each rear and / or front, as shown in Fig. 10, a curtain wall type cooler 10
7 (図 12に示す符号 1 07A〜 107H) を配置している。 冷却器 107のそ れそれは、 上方又は下方に設けたヘッダーから被圧延材 Pの全幅表面へ向けて、 幕状 （カーテンウォール状） に大量の常温冷却水 （ラミナ一フロー。 たとえば図7 (reference numerals 107A to 107H shown in FIG. 12). Each of the coolers 107 is composed of a large amount of room-temperature cooling water (laminar flow) in a curtain shape (curtain wall shape) from the header provided above or below to the entire width surface of the material P to be rolled.
12中の符号^) を流し当てる冷却手段である。 幕状に流す冷却水の厚さ （幕 厚） は 10mm以上必要であり、 1 6 mm程度あることが冷却効果の面で望まし い。 各冷却器 107における冷却水量は、 被圧延材 Pの単位幅 （ lm) あたり 1It is a cooling means to which the symbol ^) in 12 is poured. The thickness (curtain thickness) of the cooling water flowing in a curtain is required to be 10 mm or more, and it is desirable that the thickness is about 16 mm in terms of the cooling effect. The amount of cooling water in each cooler 107 is 1 per unit width (lm) of the material P to be rolled.
00-500m3/hの範囲内で調整可能とし、 冷却による被圧延材 Pの温度降下 率が 20°C/s e c以上になるようにする。 強い圧下を加える場合等には単位幅 あたりに 350m3/hの冷却水を使用するが、 その場合の被圧延材 Pの温度降下 率は、 板厚と速度との積が 1 200mm · mpmであるとき 60〜80°C/s e c (加工発熱による温度上昇を含めて 40°C/s e c前後） に達する。 Adjustable within the range of 00-500 m 3 / h, so that the temperature drop rate of the material P to be rolled by cooling is 20 ° C / sec or more. When applying a strong reduction, etc., 350 m 3 / h of cooling water is used per unit width.In this case, the temperature drop rate of the material P to be rolled is 1200 mm At some point, the temperature reaches 60-80 ° C / sec (around 40 ° C / sec including the temperature rise due to the heat generated during processing).
図 1 0に示した冷却器 107は、 図 1 2のとおり被圧延材 Pの上方および下方 の位置に複数配置され、 上方では、 ミル 4 0の後部とミル 5 0の前部および後部、 ミル 6 0の前部および後部にそれそれ冷却器 1 0 7 Α · 1 0 7 B · 1 0 7 D · 1 0 7 E · 1 0 7 Gを配置し、 下方については、 ミル 4 0 · 5 0 · 6 0の後部にそ れそれ冷却器 1 0 7 C · 1 0 7 F · 1 0 7 Hを配置している。 これらのうち冷却 器 1 0 7 Hは最終段のミル 6 0の後部においてローラテーブル Tのフレームに取 り付けられ、 他の冷却器 1 0 7 A〜 1 0 7 Gは、 各スタンドのハウジングに取り 付けられている。 The cooler 107 shown in FIG. 10 is provided above and below the material P to be rolled as shown in FIG. In the upper part, at the rear of the mill 40 and at the front and the rear of the mill 50, at the front and the rear of the mill 60, the coolers 1 0 7 Α 1 0 7 B 1 0 7D · 107E · 107G is arranged, and for the lower part, at the rear of the mill 40 · 500 · 60, the cooler is 10C · 107F · 107 H is arranged. Of these, the cooler 107H is attached to the frame of the roller table T at the rear of the last mill 60, and the other coolers 107A to 107G are mounted on the housing of each stand. It is installed.
このようなカーテンウォール型冷却器 7を後段 3スタンドのミル 4 0 · 5 0 · 6 0の各出側等にて使用することにより、 本実施形態による熱間圧延装置を用い て著しい加工発熱をともなう大圧下圧延法や制御圧延法を行う場合にも、 各ミル 4 0 - 5 0 - 6 0での温度上昇を抑制して被圧延材 Pを適切な温度範囲に保ち、 かつ、 圧延後に微細組織が粒成長を起こすことを抑制することができる。 なお、 図 1 0に示した熱間圧延装置の下流側にあるランアウトテーブル （図示せず） に おいても、 粒成長を防止すベく冷却水にて被圧延材 Pを冷却する。  By using such a curtain wall type cooler 7 at each output side of a mill 400, 500, 60 of the latter three stands, remarkable processing heat is generated by using the hot rolling apparatus according to the present embodiment. When performing the large rolling reduction method and the control rolling method, the temperature rise in each mill 40-50-60 is suppressed to keep the material P to be rolled in an appropriate temperature range, and the fineness after rolling is reduced. It is possible to suppress the structure from causing grain growth. In the run-out table (not shown) on the downstream side of the hot rolling apparatus shown in FIG. 10, the material P to be rolled is cooled with cooling water to prevent grain growth.
また、 図 1 0のように熱間仕上圧延装置では、 最終段スタンドであるミル 6 0 の出側であってカーテンウォール型冷却器 1 0 7 ( 1 0 7 G · 1 0 7 H ) から数 百 mm〜 l mほど下流側の位置に、 水噴射スプレー 1 0 8を配置している。 これ は、 冷却器 1 0 7 G ' 1 0 7 Hによって被圧延材 Pの表面に載った冷却水を除去 するためのもので、 複数配置したノズル （図示せず） より、 被圧延材 Pの表面に 対して、 被圧延材 Pの上方から被圧延材 Pの流れ方向の上流側に向けて斜め下方 へ、 被圧延材 Pの幅方向にも広がるように加圧水を吹き出すものである。 このよ うな水噴射スプレー 1 0 8を使用すれば、 冷却器 1 0 7の作用で被圧延材 P上に 載った冷却水を円滑に除去できるので、 その下流側にある各種計測器 （温度計な ど。 図示せず） によって、 圧延後の被圧延材 Pに関する種々の値 （圧延終了温度 など） を適切に計測できる。 計測の精度が高いと、 冷却水量の制御等を通して圧 延終了温度など圧延条件を正確に制御することが可能になる。  Also, as shown in Fig. 10, in the hot finish rolling mill, the output from the curtain wall type cooler 107 (107G The water spray 108 is arranged at a position about 100 mm to lm downstream. This is for removing the cooling water on the surface of the material P to be rolled by the cooler 107 G ′ 107 H. Pressurized water is blown from the upper side of the material to be rolled P obliquely downward toward the upstream side in the flow direction of the material to be rolled P toward the surface, so as to spread also in the width direction of the material to be rolled P. If such a water jet spray 108 is used, the cooling water on the material P to be rolled can be removed smoothly by the action of the cooler 107, so that various measuring instruments (thermometers) on the downstream side can be used. Thus, various values (rolling end temperature, etc.) of the material P to be rolled after rolling can be appropriately measured. If the measurement accuracy is high, it becomes possible to accurately control the rolling conditions such as the rolling end temperature by controlling the amount of cooling water.
この水噴射スプレー 1 0 8の下流側であって最終段のミル 6 0より約 2 m下流 側に設置した温度計によって被圧延材 Pの圧延終了温度を計測し、 その計測結果 を受けた演算 '操作手段 （図示せず） によって、 各カーテンウォール型冷却器 1 0 7 (とくに最終段のミル 6 0をはさむ冷却器 1 0 7 Ε · 1 0 7 G - 1 0 7 H ) の冷却水量を増減させる。 フィードパック制御によって圧延終了温度をコント口 ールし、 それを適切な範囲内に維持するのである。 The rolling end temperature of the material to be rolled P is measured by a thermometer installed downstream of the water spray 108 and about 2 m downstream of the final mill 60, and the calculation based on the measurement result is performed. 'Each curtain wall type cooler 1 by operating means (not shown) Increase or decrease the amount of cooling water of 0 7 (especially, the cooler 10 7 Ε · 10 7 G-10 7 H) that holds the final stage mill 60. The end-of-rolling temperature is controlled by the feed pack control and maintained within an appropriate range.
以上のように構成した連続熱間圧延装置では、 良好な生産性を確保するのに十 分な速度 （たとえば 7〜9 m/ s e c ) で、 厚さ 2〜 6 mm程度の良好な細粒鋼 熱延鋼板を生産することができる。 具体的には、 累積歪み （前記した加重積算値 である e c ) が 0 . 6以上になるように圧延しながら、 後段のミル 4 0 · 5 0 · 6 0の各後部においてカーテンウォール型冷却器 1 0 7により強冷却を行うこと により、 炭素含有量 ·合金元素含有量がともに低い鋼を被圧延材としながらも平 均フェライ ト粒径が 3〜 7 m程度の好ましい細粒鋼鋼板を生産できた。 細粒鋼 であっても伸びの低いことがあり得るが、 そのようなデメリットを排除すること も可能となった。 後に示す実施例はその一例である。 In the continuous hot rolling mill configured as described above, a fine-grained steel with a thickness of about 2 to 6 mm is used at a speed sufficient to ensure good productivity (for example, 7 to 9 m / sec). Hot rolled steel sheet can be produced. Specifically, while rolling so that the cumulative strain (the above-mentioned weighted integrated value e c ) becomes 0.6 or more, the curtain wall cooling at the rear of each of the subsequent mills 40. By performing strong cooling with a heater 107, it is possible to obtain a preferable fine-grained steel sheet with an average ferrite grain size of about 3 to 7 m while using steel with low carbon content and alloy element content as rolling materials. Produced. Although elongation may be low even with fine-grained steel, such disadvantages can be eliminated. The embodiment described later is an example.
このような良好な生産が可能であるのは、 金属組織上の影響が強い後段のス夕 ンドにおいて、 冷却能力の高いカーテンウォール型冷却器 1 0 7を使用して被圧 延材 Pの温度を適切な範囲に保ちながら、 小径の異径ロールミル 4 0 · 5 0 · 6 0により、 上記の累積歪みをもたらす高圧下率の圧延を実施できるからである。 ミル 4 0 · 5 0 · 6 0ではロール偏平やエッジドロップを回避でき、 また各ミル 1 0〜6 0の C V C機能によってクラウン制御が行えるために、 板厚の薄くなる 後段においても被圧延材 Pの蛇行や形状の悪化を抑制できる。 そのため、 本実施 形態では、 細粒鋼圧延を余裕をもって円滑に行い、 かつ鋼板を形状精度の高いも のとすることも可能である。  Such good production is possible because, in the later stage where the influence on the metallographic structure is strong, the temperature of the rolled material P is increased by using a curtain wall cooler 107 with high cooling capacity. This is because the rolling at a high reduction rate that causes the above-mentioned cumulative strain can be performed by the small diameter roll mills 40, 50, 60 while keeping the diameter in an appropriate range. Mills 40, 500, and 60 can avoid roll flattening and edge drop, and can control the crown by the CVC function of each mill 10 to 60. Meandering and deterioration of the shape can be suppressed. Therefore, in the present embodiment, fine-grained steel rolling can be smoothly performed with a margin, and the steel plate can be formed with high shape accuracy.
上記のような条件によって好ましい細粒鋼鋼板を生産できることは、 図 1 0に 示した熱間圧延装置を用い、 被圧延材 Pへの冷却の強さ （圧延終了温度） や圧下 の程度 （累積歪み） を種々に変えて行った多くの試験 '調査を通じて発明者らが 明らかにしたものである。 そのような試験 ·調査の結果と、 好ましい細粒鋼鋼板 を得た実施例に関するデータとを下記に示す。  The favorable fine-grained steel sheet can be produced under the above conditions by using the hot rolling device shown in Fig. 10 to determine the cooling strength (rolling end temperature) and the degree of reduction (cumulative The inventors clarified through a number of tests conducted with various changes in distortion. The results of such tests and investigations and data on the examples in which preferred fine-grained steel sheets were obtained are shown below.
本実施形態による連続熱間圧延装置を使用し、 表 2 — 1に示す鋼種 （他に有意 量の成分を含まない） について、 パススケジュールと圧延終了温度とを種々に変 更して試験圧延を行った。 ただしいずれの場合も、 最終段のミル 6 0の出側での 板厚は 2〜3mm、 圧延速度は 8 ~ 9 m/s e cである。 Using the continuous hot rolling mill according to the present embodiment, test rolling was performed for the steel types shown in Table 2-1 (which do not include other significant components) by changing the pass schedule and rolling end temperature in various ways. went. However, in either case, the final stage mill 60 The sheet thickness is 2-3mm, and the rolling speed is 8-9m / sec.
[表 2— 1] [Table 2-1]
鋼の化学成分 （重量％) 変態点 (°C)
Figure imgf000025_0001
試験圧延によって得た多くの鋼板に関し、 厚さの中央部においてフェライ ト 粒径を測定し、 圧延時の累積歪みおよび仕上温度 （圧延終了温度） との関係を調 査した。 累積歪みを横軸にとってフェライ ト粒径 （縦軸） との関係を表すと図 1 3のようになる。 図中、 記号きは仕上温度が Ar 3変態点 ± 10°Cの範囲内にあ るデ一夕を示し、 ▲は同温度が Α Γ 3変態点— 10°Cを下回ったデ一夕、 國は同 温度が Ar3変態点 + 10°Cを超えたデ一夕を示している （図 13〜図 17にお いて同じ） 。 Chemical composition of steel (% by weight) Transformation point (° C)
Figure imgf000025_0001
For many steel sheets obtained by test rolling, the ferrite grain size was measured at the center of the thickness, and the relationship between the cumulative strain during rolling and the finishing temperature (rolling end temperature) was investigated. Figure 13 shows the relationship between the ferrite grain size (vertical axis) and the cumulative strain on the horizontal axis. In the figure, symbols indicate that the finishing temperature is within the range of the Ar 3 transformation point ± 10 ° C, and ▲ indicates that the temperature was below the Α Γ 3 transformation point—10 ° C. Kuni has shown that the temperature exceeded the Ar3 transformation point + 10 ° C (the same in Figs. 13 to 17).
図 13によれば、 仕上温度が Ar 3変態点 + 10°Cを超える場合には累積歪み の増大とともにフェライ ト粒径が小さくなる傾向がやや見受けられるものの、 仕 上温度がそれ以外である場合には、 累積歪みを大きくしてもフェライ ト粒径はほ とんど小さくならない。  According to Fig. 13, when the finishing temperature exceeds the Ar 3 transformation point + 10 ° C, there is a slight tendency that the ferrite grain size decreases as the cumulative strain increases, but when the finishing temperature is other than that. However, the ferrite grain size hardly decreases even if the cumulative strain is increased.
一方、 仕上温度を横軸にとってフヱライ ト粒径 （縦軸） との関係を表したもの が図 14である。 この図 14によれば、 仕上温度が低いほどフェライ ト粒径が明 らかに小さくなることが分かる。  On the other hand, Fig. 14 shows the relationship between the finishing temperature and the particle size (vertical axis) using the horizontal axis as the horizontal axis. According to FIG. 14, it can be seen that the lower the finishing temperature, the smaller the ferrite particle size becomes.
また、 製造した各鋼板について機械的性質を調査し、 その結果をフ Xライ ト粒 径等と関係づけて図 15〜図 17にまとめた各図において横軸には、 粒径（ zm) を一 1ノ 2乗した値をとつている。  In addition, the mechanical properties of each manufactured steel sheet were investigated, and the results were correlated with the X-light particle size and other data in Figures 15 to 17, and in each figure, the horizontal axis represents the particle size (zm). It takes the value of 1 1 squared.
図 15はフェライ ト粒径と引張強さ （MP a) との関係を、 図 16はフェライ ト粒径と伸び （％) との関係をそれそれ示す。 これらによると、 フェライ ト粒径 が小さい （横軸の右寄り） ほど引張強さが高い傾向にあるものの、 仕上温度が A Γ 3変態点一 10°Cを下回る場合 （図中の▲) には、 フェライ ト粒の微細化につ れて伸びが低下することが分かる。 引張強さと伸びとの積 （MPax%) も、 図 17によれば Ar« 3変態点— 10°C未満の場合には微細化とともに小さくなる。 これらの結果に基づいて以下の事実を把握することができる。 すなわち、 a) 本実施形態による圧延装置 （図 10) によってフェライ ト粒径の小さい細 粒鋼熱延鋼板を得るうえでは、 累積歪みを高くするよりも仕上温度を低めに設定 する方が効果的である。 Figure 15 shows the relationship between ferrite grain size and tensile strength (MPa), and Figure 16 shows the relationship between ferrite grain size and elongation (%). According to these, the smaller the ferrite particle size (to the right of the horizontal axis), the higher the tensile strength tends to be. However, when the finishing temperature is lower than the AΓ3 transformation point-10 ° C (▲ in the figure), It can be seen that elongation decreases as the ferrite grains become finer. The product of tensile strength and elongation (MPax%) According to 17, when the Ar 3 3 transformation point is less than 10 ° C, it becomes smaller with miniaturization. The following facts can be grasped based on these results. In other words, a) In order to obtain a hot-rolled steel sheet with small ferrite grain size by the rolling mill according to the present embodiment (Fig. 10), it is more effective to set the finishing temperature lower than to increase the cumulative strain. It is.
b) しかし、 Ars変態点に比べて仕上温度をあまりに低くすると、 細粒化は 進んでも伸びが低下するため、 強度上のメリッ 卜が低下する。  b) However, if the finishing temperature is too low compared with the Ars transformation point, the elongation is reduced even though the grain size is reduced, and the strength advantage is reduced.
c ) 累積歪みを高くすべく高圧下をすることは圧延装置の構成やロールの消耗 等に関連してコストがかさむこと等を考え合わせると、 累積歪みをあまり高くせ ずたとえば 0. 6 (望ましくは 0. 65)以上で 0. 9未満の程度にしながら、 仕上温度を正確に管理することによって細粒鋼鋼板を得るのが費用対効果の点で 好ましい。 仕上温度を A r 3変態点 ± 50°Cの範囲内に保つなら、 フヱライ ト粒 径が 4〜 6〃mであって機械的強度のバランスにすぐれた細粒鋼鋼板を生産でき る。 とくに引張強さの高い鋼板を得るためには、 仕上温度をたとえば Ar 3変態 点— 50°C〜同変態点 +20°C程度にし、 伸びの点でもすぐれた鋼板を得ようと すれば、 たとえば A r 3変態点— 20°C〜同変態点 +50°C程度にするとよい。 ただし、 各強度の高さとそれらのバランスの点では、 Ar 3変態点 ± 10°Cの範 囲内に仕上温度を保つのが最も好ましい。  c) Considering that increasing the pressure under high pressure to increase the cumulative strain would increase the cost related to the configuration of the rolling mill and the consumption of rolls, etc. It is preferable from the viewpoint of cost-effectiveness to obtain a fine-grained steel sheet by accurately controlling the finishing temperature while keeping the value of 0.65 or more to less than 0.9. If the finishing temperature is kept within the range of the Ar 3 transformation point ± 50 ° C, fine-grained steel sheets with a fine grain diameter of 4 to 6 µm and an excellent balance of mechanical strength can be produced. In order to obtain a steel sheet with particularly high tensile strength, if the finishing temperature is set, for example, to the Ar 3 transformation point-50 ° C to the same transformation point + 20 ° C, and a steel sheet with excellent elongation is obtained, For example, the Ar 3 transformation point—about 20 ° C. to the same transformation point + 50 ° C. However, in terms of the strength of each strength and their balance, it is most preferable to keep the finishing temperature within the range of the Ar 3 transformation point ± 10 ° C.
こうして得た知見に基づいて良好な細粒鋼鋼板を製造した実施例を、 表 2— 2 〜表 2— 4および図 18に紹介する。 なお、 表中の 「F 10」 ~「F60」 は第 1スタンド〜第 6スタンドの各ミル 10〜60をそれそれ表す。  Examples of producing good fine-grained steel sheets based on the knowledge thus obtained are introduced in Tables 2-2 to 2-4 and FIG. In the table, "F10" to "F60" represent mills 10 to 60 of the first to sixth stands, respectively.
表 2— 2は、 各ミル 10〜60の出側における板厚 （ 「粗バ一厚」 は粗圧延装 置の出側での板厚をさす） 、 圧下率 （％) 、 歪み、 累積歪み、 および板幅を示し、 表 2— 3は、 ミル 40〜60の後部での各カーテンウォール型冷却器 7の使用状 況および仕上温度 （圧延終了温度） を示している。 表 2— 4は、 表 2—1〜表 2 一 3の条件によって得た実施例の鋼板について、 板厚中央部でのフェライ ト粒径 および機械的性質を示す。 そして、 図 18A、 図 18B、 図 18Cは、 実施例の 鋼板について、 上表面付近と、 それより厚さの 1/4だけ内側の位置、 厚さの中 央位置のそれそれの箇所で結晶組織を示した図である。 いずれの部分にも平均フ ェライ ト粒径が 4〜 6 m程度の微細な組織が形成されている。 Table 2-2 shows the sheet thickness at the exit side of each mill 10 to 60 ("coarse bar thickness" refers to the sheet thickness at the exit side of the roughing mill), rolling reduction (%), distortion, and cumulative strain. , And the sheet width, and Table 2-3 shows the use condition and the finishing temperature (rolling end temperature) of each curtain wall type cooler 7 at the rear of the mill 40-60. Table 2-4 shows the ferrite grain size and mechanical properties at the center of the sheet thickness for the steel sheets of the examples obtained under the conditions of Tables 2-1 to 23. 18A, 18B, and 18C show the crystal structures of the steel sheet of the embodiment near the upper surface, at a position inside by 1/4 of the thickness, and at the center of the thickness. FIG. Average A fine structure with a grain size of about 4 to 6 m is formed.
なお、 図 13〜図 17のデータを得るための圧延もこの実施例の圧延も、 本実 施形態による圧延装置 （図 10〜図 12参照） によって行ったものだが、 累積歪 みを 0. 6〜0. 9程度にする圧延なら、 後段のスタンドとして前記のような異 径ロールミル 40〜60を使用する必要はないと推定される。 つまり、 それらの ミルが直径 600〜70 Omm程度の上下同径のヮ一クロールを有するものであ つても足りると推測される。 また、 その程度の累積歪みで足りるなら加工発熱に ともなうサーマルクラウンも著しくないと予想されるため、 CVC機能やペンデ ィング機能についても、 ミル 10〜60に付与する必要性は低いと考えられる。  The rolling for obtaining the data shown in FIGS. 13 to 17 and the rolling in this embodiment were performed by the rolling apparatus according to the present embodiment (see FIGS. 10 to 12). If the rolling is performed to about 0.9, it is presumed that it is not necessary to use the above-mentioned different diameter roll mills 40 to 60 as a subsequent stand. In other words, it is presumed that those mills having a diameter of about 600 to 70 Omm and a single crawl of the same diameter in the upper and lower directions are sufficient. Also, it is not expected that the thermal crown associated with the heat generated by machining will be remarkable if such a cumulative strain is sufficient. Therefore, it is considered that the necessity of adding the CVC function and the pending function to the mills 10 to 60 is low.
[表 2— 2] [Table 2—2]
実施例  Example
Figure imgf000027_0001
Figure imgf000027_0001
[表 2— 3] [Table 2-3]
F40後面 F50後面 F60後面 仕上温度。 C  Rear of F40 Rear of F50 Rear of F60 Finishing temperature. C
実施例 使用 使用 使用 782  Example Use Use Use 782
[表 2 -4] [Table 2-4]
機械的特性  Mechanical properties
フェラ仆粒径 T S YP E L  Blower particle size T S YP E L
P.TS1 Mp a Mp a %  P.TS1 Mp a Mp a%
実施例 4.5 519 431 34  Example 4.5 519 431 34
T S ：引張強度、 YP ：降伏点、 E L ：伸び 本実施形態による連続熱間圧延方法によれば、 平均フェライ ト粒径が十分に微 細であって機械的性質にすぐれ、 実用上の品質が十分に高い細粒鋼熱延鋼板を、 緩和された製造条件にしたがってきわめて低コストで製造することができる。 すなわち、 a ) 複数スタンドのミルを用いて累積歪みが 0 . 6以上という高め の圧下を施すとともに、 b ) 後段の複数のミルの出側にて被圧延材 Pを強く冷却 することにより、 最終段およびそれまでのミルで圧延時に発生する加工発熱を効 果的に奪って適切な温度維持 （例えば A r 3変態点をはさんで ± 5 0 °Cの範囲内 に圧延終了温度をおさめる） をはかり微細組織の粒成長をも停止させる一という 処理により、 平均フェライ ト粒径が 1 0 m以下程度という細粒鋼熱延鋼板を製 造することが可能なのである。 TS: tensile strength, YP: yield point, EL: elongation According to the continuous hot rolling method of the present embodiment, a hot-rolled fine-grained steel sheet having a sufficiently fine average ferrite grain size, excellent mechanical properties, and sufficiently high practical quality can be relaxed. It can be manufactured at extremely low cost according to the manufacturing conditions. In other words, a) applying a higher reduction with a cumulative strain of 0.6 or more using a mill with a plurality of stands, and b) cooling the material P to be rolled strongly at the exit side of a plurality of mills at the subsequent stage, Maintain an appropriate temperature by effectively removing the heat generated during rolling by the step and the previous mill (for example, keep the rolling end temperature within ± 50 ° C across the Ar 3 transformation point) This process, which also stops grain growth in the microstructure, makes it possible to produce hot-rolled fine-grained steel sheets with an average ferrite grain size of about 10 m or less.
このような処理によつて細粒鋼鋼板を得ることができるのは、 発明者らが最近 の調査研究によって明らかにしたものである。 つまり、 被圧延材に対する高圧下 条件及び強冷却の条件のうち前者の条件を多少緩和しても （つまり累積歪みを 0 . 9にまで高めなくとも）、 フェライ ト粒径があまり粗くない高品質の細粒鋼鋼板 を製造できることが判明した。 具体的には、 炭素含有量が 0 . 5 %以下で合金元 素の含有量が 5 %以下の薄板について、 上記した累積歪みと冷却とにより平均フ ェライ ト粒径を 3〜ア m程度にすることが可能であった。  The fact that a fine-grained steel sheet can be obtained by such a treatment has been clarified by the inventors through recent research and research. In other words, even if the former condition of the high-pressure condition and the strong cooling condition for the material to be rolled is somewhat relaxed (that is, even if the cumulative strain is not increased to 0.9), the ferrite grain size is not so coarse and high quality. It was found that it was possible to manufacture fine-grained steel sheets. Specifically, the average ferrite grain size of a thin plate with a carbon content of 0.5% or less and an alloy element content of 5% or less is reduced to about 3 to Am by the above-described cumulative strain and cooling. It was possible to do.
累積歪みが 0 . 6以上で足りるとなると、 各ミル、 とくに後段のミルに必要な 圧下率は相当に （3 0 %程度に） 低くなり、 設備上および運転上必要な費用は大 幅に低減する。 このため、 被圧延材 Pの先端部がいずれかのミルにうまく嚙み込 まれないでスリップする、 という事態も生じにくい。  If the cumulative strain is 0.6 or more, the rolling reduction required for each mill, especially the subsequent mill, is considerably reduced (to about 30%), and the cost required for equipment and operation is significantly reduced. I do. For this reason, it is unlikely that the tip of the material P to be rolled slips because it does not fit into any of the mills.
また、 平均フェライ ト粒径が 1 0 m以下であれば、 その細粒鋼鋼板は、 同粒 径が 1 0 zmを超える一般 （非細粒鋼） の熱延鋼板に比べて機械的性質が格段に 高く、 広い用途をもつものと期待できる。 すなわち、 前記のような化学成分とフ ェライ ト粒径を有する細粒鋼鋼板は、 機械的性質のバランス （引張強さや伸び、 延性等の面で汎用性がある） が高いうえに溶接性などにもすぐれている。 そのた めに用途が広く、 また比較的安価であって入手容易であるうえにリサイクル性も あるので、 高い需要があるものと考えられる。 したがって、 かかる鋼板を製造し 得る本実施形態による圧延方法は、 社会的貢献度が高いうえその生産に十分な経 済合理性がともなうことになる。 When the average ferrite grain size is 10 m or less, the fine-grained steel sheet has more mechanical properties than general (non-fine-grained) hot-rolled steel sheet with the same grain size exceeding 10 zm. It is expected to be extremely expensive and have a wide range of applications. In other words, the fine-grained steel sheet having the above chemical composition and ferrite grain size has a high balance of mechanical properties (it is versatile in terms of tensile strength, elongation, ductility, etc.), and has high weldability. It is also excellent. Therefore, it is considered to be in high demand because it is widely used, relatively inexpensive, easily available, and recyclable. Therefore, the rolling method according to the present embodiment, which can manufacture such a steel sheet, has a high social contribution and a sufficient process for its production. It comes with reasonableness.
次に、 本発明の他の実施形態による熱間圧延方法について説明する。  Next, a hot rolling method according to another embodiment of the present invention will be described.
本実施形態による熱間圧延方法は、 図 10に示した上記実施形態による熱間圧 延装置を用いて厚板を製造するための方法に関するものである。  The hot rolling method according to the present embodiment relates to a method for manufacturing a thick plate using the hot rolling apparatus according to the embodiment shown in FIG.
図 10に示した上記実施形態による熱間圧延装置では、 CVCミル 10 · 20 • 30および異径ロールミル 40 · 50 · 60においては、 圧延の進行とともに 板厚が減少して圧延速度が増加することを考慮して、 後段のミルほど減速比を下 げ、 ワークロールの最大回転数を高めるとともに最大出力トルクを低く設定して いる。 ミル 10〜60の許容最大出力トルクはそれそれ、 125. 0、 98， 2、 6 1. 4、 34. 1、 22. 7、 19. 5 (いずれも単位はトン （t f ) · m) である。  In the hot rolling apparatus according to the above embodiment shown in FIG. 10, in the CVC mills 10, 20, and 30 and the roll mills with different diameters 40, 50, and 60, as the rolling progresses, the sheet thickness decreases and the rolling speed increases. In consideration of the above, the reduction ratio is set lower in the later-stage mill, the maximum rotation speed of the work roll is increased, and the maximum output torque is set lower. The allowable maximum output torque of the mill 10 to 60 is 125.0, 98, 2, 61.4, 34.1, 22.7, 19.5 (all units are tons (tf) m). is there.
そして、 図 10に示した上記実施形態による圧延装置のすべてのミル 10~6 0を使用して、 良好な生産性を確保し得る十分な速度 （たとえば 7〜9m/s e c) で、 厚さ 2〜6mm程度の良好な細粒鋼熱延鋼板を生産することができる。 具体的には、 累積歪み （前記した加重積算値である が 0. 6以上になるよう に圧延しながら、 後段のミル 40 - 50 - 60の各後部において力一テンウォー ル型冷却器 107により強冷却を行うことにより、 炭素含有量 ·合金元素含有量 がともに低い鋼を被圧延材 Pとしながらも平均フェライ ト粒径が 4〜6 zm程度 の好ましい細粒鋼鋼板を生産できた。 とくに、 累積歪みを 0. 9以上にとれば、 同じ鋼種において平均フェライ ト粒径を 4〃m以下にすることもできた。 後に示 す比較例 Aはその一例 （£C≥0. 6の場合） である。 このような生産が可能であ るのは、 金属組織上の影響が強い後段のスタンドにおいて、 冷却能力の高いカー テンウォール型冷却器 107を使用して被圧延材 Pの温度を適切な範囲に保ちな がら、 小径の異径ロールミル 40 · 50 · 60にて圧下率の高い圧延を実施でき るからである。 ミル 40 · 50 · 60ではロール偏平やエッジドロップを回避で き、 また各ミル 10〜60の CVC機能によってクラウン制御が行えるために、 板厚の薄くなる後段においても被圧延材 Pの蛇行や形状の悪化を抑制できる、 と いう点も、 そのような細粒鋼圧延を可能にする理由の一つである。 Then, using all the mills 10 to 60 of the rolling mill according to the above embodiment shown in FIG. 10, at a sufficient speed (for example, 7 to 9 m / sec) capable of ensuring good productivity, the thickness 2 A good fine-grained steel hot-rolled steel sheet of about 6 mm can be produced. Specifically, the cumulative strain (rolling so that the above-mentioned weighted integrated value becomes 0.6 or more, is strengthened by the ten-wheel cooler 107 at the rear of each of the subsequent mills 40-50-60. By cooling, a fine-grained steel sheet having an average ferrite grain size of about 4 to 6 zm could be produced, while using a steel having a low carbon content and a low alloying element content as the material to be rolled P. By setting the cumulative strain to 0.9 or more, it was possible to reduce the average ferrite grain size to 4 µm or less for the same steel type.Comparative Example A shown below is an example (for £ C ≥ 0.6) This kind of production is possible because the temperature of the material P to be rolled is appropriately adjusted by using a curtain wall type cooler 107 with a high cooling capacity in the latter stand where the metal structure is strongly affected. Small diameter roll mill 40, 50, 6 This is because rolling with a high rolling reduction can be performed at 0. Mills 40, 50, and 60 can avoid roll flattening and edge drop, and can perform crown control using the CVC function of each mill 10 to 60. One of the reasons for enabling such fine-grained steel rolling is that the meandering and deterioration of the shape of the material P to be rolled can be suppressed even at a later stage where the sheet thickness becomes thinner.
しかし、 同じように最終段のミル 60までを使用して、 薄板ではなく、 厚さが 6 mm以上の厚板の細粒鋼鋼板を生産する場合には、 当該最終段のミル 6 0 (又 はさらにその前段のミル 5 0等） において出力トルクが不足し、 圧延を継続でき ないこと （モータが停止するなど） がある。 厚板の場合は、 簿板と同程度 （又は 小さめ） の圧下率とする場合であっても、 薄板の場合よりも接触弧長が長くなり、 したがって大きな圧延トルクが必要になるからである。 最終段のミル 6 0やその 前のミル 5 0等では前述のとおり許容最大出力トルクが小さいため、 負荷が能力 を上回る結果、 圧延の継続ができなくなるわけである。 そのようなケースを、 後 述する比較例 Bに示す。 But in the same way, using up to the last mill 60, instead of a thin plate, When producing fine-grained steel sheets with a thickness of 6 mm or more, the output torque of the final mill 60 (or the previous mill 50, etc.) is insufficient and rolling cannot be continued. (Eg, the motor stops). This is because, even in the case of a thick plate, even when the rolling reduction is about the same as (or smaller than) a book plate, the contact arc length is longer than in the case of a thin plate, and therefore a large rolling torque is required. As described above, the allowable maximum output torque of the final mill 60 and the preceding mill 50 is small, so that the load exceeds the capacity and rolling cannot be continued. Such a case is shown in Comparative Example B described later.
後段のミ が十分な圧延トルクを発揮できない理由はつぎのように説明できる c まず、 後段のミルでは、 圧延ロールの駆動系が、 圧延が進んで板厚が減少したこ とにともなう圧延速度の増加に対応すベく高速仕様になっており、 前段のミルに 比べると回転速度が高く （つまり減速比が小さく） て圧延トルクが低くなるよう 設定されているのが一般的である。 これに対し、 厚板を圧延する場合には、 薄板 の圧延時と圧下率が一定であっても入側での接触弧長 （接触長） が長い （接触角 が大きい） ことから、 必要なトルクは、 薄板を圧延する場合よりも相当に大きく なる。 そのため、 トルクの低い後段のミルでは、 薄板を円滑に圧延することはで きても、 設備能力上、 必要な圧下を厚板に加えることによって厚い細粒鋼鋼板を 製造することが困難になり得るのである。 The reason why the latter mill cannot exert sufficient rolling torque can be explained as follows.c First, in the latter mill, the drive system of the rolling rolls increases the rolling speed as the rolling progresses and the thickness decreases. In general, the rolling speed is set higher (that is, the reduction ratio is smaller) and the rolling torque is set lower than that of the preceding mill. On the other hand, when a thick plate is rolled, the required contact arc length (contact length) on the entry side is long (the contact angle is large) even when the rolling reduction is constant compared to when the thin plate is rolled. The torque is much higher than when rolling a sheet. As a result, it is difficult to produce a thick fine-grained steel sheet by applying the necessary reduction to the thick plate because of the equipment capacity, even if the latter mill with a low torque can smoothly roll the thin plate. You get.
なお、 複数スタンドのミルをタンデムに配置した圧延装置における厚板細粒鋼 鋼板の製造に関する上記のような課題については、 これを提示した文献が見あた らない。 従来技術として本明細書中で参照した前記公報に記載された技術も、 厚 さが 3 mmもしくは 5 mm以下の薄い細粒鋼鋼板の製造、 又はリバース式の圧延 装置を用いての製造に関するものである。  In addition, there is no literature presenting the above-mentioned problems relating to the production of thick and fine-grained steel plates in a rolling mill in which a plurality of stands of mills are arranged in tandem. The technology described in the above-mentioned publication referred to in the present specification as the prior art also relates to the production of thin fine-grained steel sheets having a thickness of 3 mm or 5 mm or less, or the production using a reverse type rolling mill. It is.
そこで本発明者らは、 図 1 0に示した上記実施形態による連続熱間圧延装置、 つまり薄板の細粒鋼鋼板を製造し得る連続熱間圧延装置を用いて、 厚さが 6 mm 以上の厚板の細粒鋼鋼板をも生産するために、 下記 a ) 〜d ) の態様で圧延装置 を運転することとした。 すなわち、  Therefore, the present inventors used a continuous hot rolling apparatus according to the embodiment shown in FIG. 10, that is, a continuous hot rolling apparatus capable of manufacturing a thin steel sheet having a small thickness, and a thickness of 6 mm or more. In order to also produce thick fine-grained steel sheets, the rolling mill was operated in the following modes a) to d). That is,
a ) 出力トルクの小さい最終段のミル 6 0を使用しない。 その手前にあるミル 4 0 · 5 0についても、 板厚や圧下率 ·変形抵抗等から計算される所要トルクよ りも、 許容される最大出力トルクが小さい場合には使用しないこととする。 した がって、 最終段のミル 60よりも圧延装置の入側寄りのミル 10〜50のうちか ら圧延トルクを満たし得るもの 3スタンド以上を、 パススケジュールに応じて選 択し使用する。 a) Do not use the last mill 60 with small output torque. For the mill 40, 50 in front of it, the required torque calculated from the plate thickness, rolling reduction, deformation resistance, etc. Furthermore, if the maximum allowable output torque is small, it shall not be used. Therefore, three or more mills that can satisfy the rolling torque among the mills 10 to 50 closer to the entrance of the rolling mill than the final mill 60 are selected and used according to the pass schedule.
b) 累積歪みが 0. 25以上 （望ましくは 0. 29以上） になるか、 又は使用 する 3スタンド以上のミルのうちの最終段のミルでの圧下率が 12%以上 （望ま しくは 14%以上） になるようパススケジュールを定める。 金属組織に対する影 響力の強い下流側のミルでの圧延を一定以上の圧下率で行わないと、 フェライ ト 粒径を小さくすることは困難だからである。  b) The cumulative strain is 0.25 or more (preferably 0.29 or more), or the rolling reduction of the last mill among three or more mills to be used is 12% or more (preferably 14%). The pass schedule is determined so that This is because it is difficult to reduce the ferrite grain size unless rolling at a downstream mill, which has a strong effect on the metal structure, is performed at a certain reduction rate.
c) カーテンウォール型冷却器 107を使って鋼板を強く （表面の温度降下率 が毎秒 40°C程度になるように） 冷却する。 冷却器 107は、 使用に供されるミ ルのうちの最終段のミルの直後のものを少なくとも使用する。 好ましくは、 当該 最終段のミルの前部の冷却器を含むすべての冷却器 107 ( 107 A-107 H) を使用する。 フヱライ ト粒径を小さくするためには、 圧延直後の被圧延材 P を十分に冷却して適切な温度範囲に保ち、 圧延後の粒成長を的確に抑制すること が不可欠だからである。  c) Cool the steel plate strongly using a curtain wall cooler 107 (so that the surface temperature drop rate is about 40 ° C per second). As the cooler 107, at least one of the mills to be used immediately after the last mill is used. Preferably, all coolers 107 (107A-107H) are used, including the cooler in front of the last mill. This is because, in order to reduce the particle size of the filament, it is essential that the material P to be rolled immediately after rolling be sufficiently cooled and maintained in an appropriate temperature range, and that the grain growth after rolling be properly suppressed.
d) 上記 c) の冷却によって、 圧延終了温度 （最終段のミル 60より数 m下流 側に設置された温度計にて計測される被圧延材 Pの表面温度） が Ar3変態点 +5 0°Cを超えないように （望ましくは Ar3変態点以下に） する。 望ましい下限もあ るはずだが、 表面温度が相当に下がっても細粒鋼の生産に支障はなかった。 これ は、 厚さ 6111111以上の鋼板を2〜3111/3 e c程度の速度で圧延製造する限りは、 表面温度にかかわらず被圧延材 Pの板厚中心の付近は A r 3変態点程度の温度に保 たれているからだと推測される。 d) By the cooling in c) above, the rolling end temperature (the surface temperature of the material to be rolled P measured by a thermometer installed several meters downstream from the final mill 60) is increased to the Ar 3 transformation point +50. Do not exceed ° C (preferably below the Ar 3 transformation point). Although there should be a desirable lower limit, the production of fine-grained steel was not hindered even if the surface temperature dropped considerably. This means that as long as a steel sheet with a thickness of 6111111 or more is rolled at a speed of about 2 to 3111/3 ec, the temperature near the center of the sheet thickness of the material to be rolled P is about the Ar 3 transformation point regardless of the surface temperature. It is speculated that this is because
以上のように圧延を行うことにより、 炭素含有量が 0. 5%以下であり合金元 素の含有量が 5 %以下という鋼種について、 表面から厚さの 1/4だけ内側での 平均フェライ ト粒径が 5〜10 m程度の、 厚手の細粒鋼熱延鋼板を生産するこ とができた。 このような厚鋼板の生産に関するデ一夕を、 下記に実施例 C .Dと して示す。  By performing rolling as described above, for steel types with a carbon content of 0.5% or less and an alloying element content of 5% or less, the average ferrite within 1/4 of the thickness from the surface inside Thick fine-grained hot-rolled steel sheets with a grain size of about 5 to 10 m could be produced. An example of such a steel plate production is shown below as Example CD.
以上に述べた連続熱間圧延装置による薄板および厚板の細粒鋼熱延鋼板の生産 について、 圧延上のデ一夕を以下に示す。 各表において、 比較例 Aは、 前述のと おり薄手 （厚さ 2 . 0 7 mm) の鋼板の生産に関するものであり、 比較例 Bは、 ミル 1 0〜 6 0を用いて厚い鋼板を生産しようとして圧延を継続できなくなつた 例を示すものである。 そして実施例 C ' Dは、 圧延装置を用いて厚手 （厚さ 1 2 . 2 mm) の細粒鋼鋼板を円滑かつ継続的に生産した例を示している。 Production of hot-rolled fine-grained steel sheets of thin and thick sheets by the continuous hot rolling equipment described above The following shows the results of the rolling. In each table, Comparative Example A relates to the production of thin steel sheets (2.07 mm thick) as described above, and Comparative Example B produces thick steel sheets using mills 10 to 60. This is an example in which rolling cannot be continued. Examples C and D show an example in which a thick (12.2 mm thick) fine-grained steel sheet is smoothly and continuously produced using a rolling mill.
まず、 表 3— 1には、 各実施例 ·比較例 A〜Dにおける鋼板の化学成分 （表示 以外には有意量の成分を含まない） および A r 3変態点の温度を示し、 表 3— 2に、 圧延終了温度 （仕上出側温度） と各鋼板の板幅、 ミル 4 0〜6 0の後部での各力 一テンウォール型冷却器 1 0 7の使用状況を示す。 表 3— 3には、 各ミル 1 0〜 6 0の出側での板厚を示している （ 「粗バ一厚」 は粗圧延装置の出側での板厚を さす） 。 また、 表 3— 4 '表 3— 5 '表 3— 6は、 表 3— 3のパススケジュール にしたがうときの各ミル 1 0〜 6 0における圧下率 （％) 、 歪みおよび累積歪み、 所要圧延トルク （トン · πι) をそれそれ示している。 First, Table 3-1 shows the chemical composition of the steel sheet in Examples and Comparative Examples A to D (excluding significant amounts of components other than those indicated) and the temperature of the Ar 3 transformation point. Figure 2 shows the rolling end temperature (finish-side temperature), the sheet width of each steel sheet, and the various forces at the rear of the mill 40-60. Table 3-3 shows the sheet thickness at the exit side of each mill 10 to 60 ("coarse bar thickness" refers to the sheet thickness at the exit side of the roughing mill). Also, Table 3-4 'Table 3-5' Table 3-6 shows the rolling reduction (%), strain and cumulative strain, required rolling at each mill 10 to 60 when following the pass schedule in Table 3-3. It shows torque (t · πι) each time.
[表 3— 1 ] [Table 3-1]
鋼の化学成分 （重量％) 変態点  Chemical composition of steel (% by weight) Transformation point
実 施例 成分値 成分値 成分値 成分値 A r 3  Example Example Component value Component value Component value Component value A r 3
比 較例 C S i M n P [°C]  Comparative example C S i M n P [° C]
比較例 A 0.16 0.2 0.8 0.014 785  Comparative Example A 0.16 0.2 0.8 0.014 785
比較例 B 0.15 0.18 0.77 0.02 795  Comparative Example B 0.15 0.18 0.77 0.02 795
実施例 C 0.17 0.21 0.8 0.014 785  Example C 0.17 0.21 0.8 0.014 785
実施例 D 0. 17 0.21 0.8 0.014 785 Example D 0.17 0.21 0.8 0.014 785
[表 3— 2 ] [Table 3-2]
ハ0ススケシ、、ユ-ル 冷却条件 （力-テンウォ-ル） C 0 Susukeshi ,, Yu - Le cooling conditions (force - Ten'wo - Le)
Figure imgf000033_0001
Figure imgf000033_0001
[表 3— 3 ] [Table 3-3]
Figure imgf000033_0002
3— 4 ]
Figure imgf000033_0002
3— 4]
F10 F20 F30 F40 F50 F60 実施例 圧下率 圧下率 圧下率 圧下率 圧下率 圧下率 比較例 [%] [%] [%] [%] [%] [%] 比較例 A 44 41 41 42 37 28 比較例 B 22 21 22 22 19 実施例 C 34 22 15 14  F10 F20 F30 F40 F50 F60 Example Reduction rate Reduction rate Reduction rate Reduction rate Reduction rate Reduction rate Comparative example [%] [%] [%] [%] [%] [%] Comparative example A 44 41 41 42 37 28 Comparison Example B 22 21 22 22 19 Example C 34 22 15 14
実施例 D 35 22 15 21 [表 3— 5 ] Example D 35 22 15 21 [Table 3-5]
Figure imgf000034_0001
Figure imgf000034_0001
[表 3— 6 ] [Table 3-6]
Figure imgf000034_0002
表 3— 6によると、 圧延の継続が不能であった比較例 Βにおいては最終段のミ ル 6 0に必要なトルクが 2 3 トン · mと大きく、 前述したミル 6 0の許容最大ト ルク （ 1 9 . 5 トン * m) を上回っていることが分かる。 また実施例 Dにおいて は、 表 3— 5のとおり累積歪みが 0 . 3 8という強めの圧下をしているため、 使 用したミルのうちの最終段のミル 4 0には表 3— 6のように 3 0 トン · mもの大 きさのトルク （つまり、 より後段のミル 5 0又は 6 0には発揮し得ないトルク） が必要であることも見てとれる。
Figure imgf000034_0002
According to Table 3-6, in Comparative Example あ っ た where rolling could not be continued, the torque required for the last mill 60 was as large as 23 ton · m, and the allowable maximum torque of the above-mentioned mill 60 was large. (19.5 tons * m). Further, in Example D, as shown in Table 3-5, since the cumulative strain was reduced to 0.38, which is a strong reduction, the final mill 40 among the mills used was the one shown in Table 3-6. It can be seen that a torque as large as 30 tons · m is required (that is, a torque that cannot be exhibited by the later mill 50 or 60).
各実施例 ·比較例 A〜Dにて生産した鋼板についてフェライ ト粒径と機械的性 質とを調査した結果が表 3— 7である。 ただし比較例 Bについては、 圧延不能と なるまでの短時間内に得た鋼板についてのデ一夕を示している。 表示した粒径は、 比較例 Aでは厚さの中央で計測し、 比較例 B、 実施例 ( 、 Dでは表面から厚さの 1 / 4だけ内側の位置で計測したものである。 表中の 「T S」 は引張強さ、 「Y Ρ」 は降伏点、 「E L」 は伸びを表し、 「L方向」 は長さ方向 （圧延方向） 、 「c方向」 は幅方向を意味する。 いずれの場合にも、 フェライ ト粒径が十分に小 さく、 機械的性質にすぐれた鋼板が得られたことが分かる。 Table 3-7 shows the results of an investigation of the ferrite grain size and mechanical properties of the steel sheets produced in each of the examples and comparative examples A to D. However, in Comparative Example B, the results are shown for a steel sheet obtained within a short time before rolling becomes impossible. The particle size shown is measured at the center of the thickness in Comparative Example A, and measured at a position inside the surface by 1/4 of the thickness in Comparative Examples B and Examples (and D). "TS" is the tensile strength, "YΡ" is the yield point, "EL" is the elongation, "L direction" is the length direction (rolling direction), "C direction" means the width direction. In each case, it can be seen that a steel sheet having sufficiently small ferrite grain size and excellent mechanical properties was obtained.
[表 3- 7] [Table 3-7]
機械的特性  Mechanical properties
T S ：引張強度， YP ：降伏点， E L ：伸び  T S: tensile strength, YP: yield point, E L: elongation
Figure imgf000035_0001
図 1 9A、 図 1 9 B、 図 1 9 Cは、 実施例 Dによって得た鋼板について、 上表 面付近と、 それより厚さの 1/4だけ内側の位置、 厚さの中央位置のそれそれの 箇所で結晶組織を示した図である。 1Z4の厚さの位置では平均フェライト粒径 が 5〜1 0 zmの、 厚さの中央でも同粒径が 1 0〃m以下の、 それそれ微細な組 織が形成されている。
Figure imgf000035_0001
Fig. 19A, Fig. 19B, and Fig. 19C show the values of the steel sheet obtained in Example D near the upper surface, 1/4 of the thickness inside, and at the center of the thickness. It is the figure which showed the crystal structure in that location. At the thickness of 1Z4, an average ferrite grain size of 5 to 10 zm is formed, and even at the center of the thickness, a fine structure with the same grain size of 10 m or less is formed.
また図 2 0〜図 2 2は、 実施例 D又はそれに準じた圧延条件によって生産した 鋼板について、 他の機械的性質を調査し整理したものである。 すなわち、 まず図 2 0は、 細粒鋼鋼板におけるフェライ ト粒径と引張強さおよび降伏点との関係を 示す図である （横軸にはフェライ ト粒径 d (jum) を一 1/2乗した値をとつて いる） 。 そして同じ細粒鋼鋼板について、 図 2 1はシャルビ一衝撃値の温度変化 を通常鋼 （非細粒鋼鋼板） における変化と併記して表し、 図 2 2は、 脆性破面率 の温度依存性を表している。 そのほか、 生産した同じ鋼板について、 J I S Z 3 04 0 「溶接施工方法の確認試験方法」 に基づく溶接継手の継手引張試験 ·継手 曲げ試験 ·継手衝撃試験 ·マクロ試験 ·硬さ分布確認試験を、 それそれ複数の試 験片にて行ったところ、 細粒鋼鋼板の溶接性はいずれも良好であることを確認し た。 FIGS. 20 to 22 show the results of examining and sorting out other mechanical properties of the steel sheet produced under Example D or the rolling conditions according to the example. That is, first, FIG. 20 is a diagram showing the relationship between the ferrite grain size, the tensile strength, and the yield point in a fine-grained steel sheet (the abscissa represents the ferrite grain size d (jum) by one-half). To the power). For the same fine-grained steel sheet, Fig. 21 shows the temperature change of Charpy impact value together with the change for ordinary steel (non-fine-grained steel sheet), and Fig. 22 shows the temperature dependence of brittle fracture rate. Is represented. In addition, for the same steel plate produced, joint tensile tests for welded joints based on JISZ3040 “Confirmation test methods for welding construction methods”, joint bending tests, joint impact tests, macro tests, hardness distribution confirmation tests, etc. We conducted tests on multiple specimens and confirmed that the weldability of the fine-grained steel sheet was all good. Was.
以上述べたように本実施形態による連続熱間圧延方法によれば、 薄板を製造で きるよう配置された複数スタンドのミルを用いながらも、 トルク不足による不都 合を招くことなく厚板の細粒鋼鋼板を製造することができる。 最終段のミルなど 後段のミルではトルク不足になることがあっても、 それらを使用せずに、 いわば 低速仕様であって高い圧延トルクを発揮できる駆動系をもつ圧延装置の入側寄り のミルのみを使用するならば、 接触弧長の長い厚板を圧延する場合にもトルク不 足とならずに十分な圧下を行うことができるからである。 最終段のミル等を使用 しないので圧延速度は高くはならないが、 圧延速度が遅くなることによって、 厚 板であるがために長くなる冷却所要時間を確保しやすくなるという利点がある。 上記のようにして圧延する厚板を細粒鋼のものとすることができるのは、 累積 歪みが 0 . 2 5以上 （又は最終段のミルでの圧下率が 1 2 %以上） という強めの 圧下を被圧延材 Pに加えることと、 使用したミルのうちの最終段のミルの出側に おいて上記のように被圧延材 Pを十分に時間をかけて冷却することとによるもの である。 ミルの出側で行う上記の冷却が強いほど、 フェライ ト粒径の小さい細粒 鋼を得ることができる。 また、 冷却を強める意味では、 使用した最終段のミルの 前でも冷却を行ったり、 後段の複数のミルの各出側においても冷却を行ったりす るのがとくに好ましい。  As described above, according to the continuous hot rolling method according to the present embodiment, even though a mill having a plurality of stands arranged to manufacture a thin plate is used, the thickness of the thick plate can be reduced without inconvenience due to insufficient torque. Grain steel sheet can be manufactured. Mills near the entrance of a rolling mill with a drive system that can exhibit a high rolling torque with a low-speed specification without using them even if the latter mills and other mills may have insufficient torque. This is because if only a thick plate with a long contact arc length is rolled, sufficient rolling can be performed without insufficiency of torque. The rolling speed does not increase because the mill at the last stage is not used, but the slow rolling speed has the advantage that it is easy to secure a longer cooling time due to the thick plate. The thick plate to be rolled as described above can be made of fine-grained steel because it has a cumulative strain of 0.25 or more (or a rolling reduction of 12% or more in the final mill). This is because the reduction is applied to the material P to be rolled and the material to be rolled P is sufficiently cooled at the exit side of the last mill among the used mills as described above. . The stronger the above cooling performed on the outlet side of the mill, the more fine-grained steel with a smaller ferrite grain size can be obtained. In order to enhance the cooling, it is particularly preferable to perform cooling even before the last mill used, or to cool each outlet of a plurality of subsequent mills.
本実施形態による連続熱間圧延方法はとくに、 圧延終了温度が A r 3変態点 + 5 0 °Cを超えないようにすることを特徴とする。 The continuous hot rolling method according to the present embodiment is particularly characterized in that the rolling end temperature does not exceed the Ar 3 transformation point + 50 ° C.
上記した冷却の強さを管理して圧延終了温度を上記のように設定すれば、 鋼板 (たとえば炭素含有量が 0 . 5 %以下で合金元素の含有量が 5 %以下の鋼板） の 少なくとも表面付近には、 フェライ ト粒径が 1 0〃mを下回る程度の微細な組織 ができる。 大圧下圧延法に適した温度範囲は A r 3変態点〜 A r 3変態点 + 5 0 °C であるとされるが、 発明者らのテストによると、 上記のとおり圧延終了温度が A r 3変態点 + 5 0 °Cを超えない範囲であればよい。 厚板の場合、 表面の温度が下が つていても内部温度は A r 3変態点に近く維持されるからだと考えられる。 By controlling the cooling strength described above and setting the rolling end temperature as described above, at least the surface of the steel sheet (for example, a steel sheet having a carbon content of 0.5% or less and an alloy element content of 5% or less) can be obtained. In the vicinity, a fine structure with a ferrite particle size of less than 10 µm is formed. The temperature range suitable for the large rolling reduction method is considered to be from the Ar 3 transformation point to the Ar 3 transformation point + 50 ° C. According to tests by the inventors, as described above, the rolling end temperature is A r It is sufficient that the temperature does not exceed 3 transformation point + 50 ° C. In the case of a thick plate, it is considered that the internal temperature is kept close to the Ar 3 transformation point even if the surface temperature drops.
また、 本実施形態の連続熱間圧延方法は、 カーテンウォール型冷却器 1 0 7に よって被圧延材 Pを強く冷却するものであるため、 粒径がとくに微細な細粒鋼鋼 板について円滑な製造を可能にする。 均一な冷却を実現できるため鋼板の全幅に わたって組織を均一化できるという利点もある。 Further, the continuous hot rolling method of the present embodiment is a method in which the material P to be rolled is strongly cooled by the curtain wall cooler 107, so that the fine-grained steel Enables smooth production of boards. Since uniform cooling can be realized, there is also an advantage that the structure can be made uniform over the entire width of the steel sheet.
本実施形態による連続熱間圧延方法はとくに、 炭素含有量が 0 . 5 %以下であ り合金元素の含有量が 5 %以下である被圧延材 Pを圧延して、 表面から厚さの 1 / 4だけ内側にある箇所での平均フェライ ト粒径が 3〜1 0 m程度の厚板を得 ることを特徴とする。  The continuous hot rolling method according to the present embodiment is particularly suitable for rolling a rolled material P having a carbon content of 0.5% or less and an alloy element content of 5% or less, so that the thickness from the surface is 1%. It is characterized in that a thick plate having an average ferrite grain size of about 3 to 10 m at a location located inside by / 4 is obtained.
このような化学成分とフェライ ト粒径を有する細粒鋼鋼板は、 機械的性質のバ ランス （引張強さや延性等の面で汎用性がある） が高いうえ低温靱性ゃ溶接性な どにもすぐれている （たとえば図 2 0〜図 2 2を参照） 。 そのために用途が広く、 また比較的安価であって入手容易であるうえにリサイクル性もあるので、 高い需 要があるものと考えられる。 したがって、 かかる鋼板なら、 社会的貢献度が高い うえその生産に十分な経済合理性がともなうことになる。  Fine-grained steel sheets having such a chemical composition and ferrite grain size have a high balance of mechanical properties (versatile in terms of tensile strength and ductility), and have low-temperature toughness and weldability. Excellent (for example, see FIGS. 20 to 22). Therefore, it is considered to be in high demand because it is widely used, relatively inexpensive, easily available, and recyclable. Therefore, such a steel sheet has high social contribution and has sufficient economic rationality for its production.

Claims

請 求 の 範 囲 The scope of the claims
1 . 被圧延材を圧延して鋼板を製造する熱間圧延装置において、 1. In a hot rolling device that rolls a material to be rolled to produce a steel sheet,
前段に配置されたミルと、  A mill placed in the previous stage,
後段に配置された複数スタンドのミルであって、 等価ロール径が 6 0 0 mm未 満の一対の異径ワークロールを含む異径ロールミル又は各直径が 6 0 0 mm未満 の一対のワーク口一ルを含む極小径ロールミルを有するミルと、  A mill with a plurality of stands arranged at the subsequent stage, including a pair of different-diameter roll mills including a pair of different-diameter work rolls having an equivalent roll diameter of less than 600 mm, or a pair of work ports having a diameter of less than 600 mm. A mill having a very small diameter roll mill containing
前記後段の少なくとも 1スタンドの前記ミルの出側に配置された、 前記被圧延 材を冷却する冷却手段と、 を備えたことを特徴とする熱間圧延装置。  A hot rolling apparatus, comprising: a cooling unit that cools the material to be rolled, which is disposed on the exit side of the mill of at least one stand in the subsequent stage.
2 . 前記冷却手段は、 カーテンウォール型冷却器であることを特徴とする請 求項 1記載の熱間圧延装置。  2. The hot rolling apparatus according to claim 1, wherein the cooling means is a curtain wall type cooler.
3 . 前記前段及び前記後段に配置された前記ミルのうち、 少なくとも前記前 段に配置されたミルは複数スタンドの C V Cミルを含むことを特徴とする請求項 1又は 2に記載の熱間圧延装置。  3. The hot rolling apparatus according to claim 1, wherein, among the mills arranged at the front stage and the rear stage, at least the mill arranged at the front stage includes a CVC mill having a plurality of stands. .
4 . 前記異径口ールミルの前記一対の異径ワーク口一ルの前記等価口一ル径 又は前記極小径ロールミルの前記ワークロールのロール径は 5 5 0 mm以下であ ることを特徴とする請求項 1乃至 3のいずれか一項に記載の熱間圧延装置。  4. The equivalent diameter of the pair of different diameter work ports of the different diameter mill or the diameter of the work roll of the ultra-small diameter roll mill is not more than 550 mm. The hot rolling device according to claim 1.
5 . 前記異径ロールミルの前記ワークロール又は前記極小径ロールミルの前 記ワークロールは、 C V C機能及びベンディング機能が付与されていることを特 徴とする請求項 1乃至 4のいずれか一項に記載の熱間圧延装置。  5. The work roll of the different-diameter roll mill or the work roll of the ultra-small-diameter roll mill is characterized in that a CVC function and a bending function are provided. Hot rolling equipment.
6 . 前記前段及び前記後段に配置された前記ミルのうち、 少なくともいずれ か 1つのスタンドの前記ミルに付設された、 前記ミルのロール表面に潤滑剤を供 給する潤滑剤供給手段をさらに有することを特徴とする請求項 1乃至 5のいずれ か一項に記載の熱間圧延装置。  6. There is further provided a lubricant supply means for supplying a lubricant to the roll surface of the mill, which is attached to the mill of at least one of the stands among the mills arranged in the former stage and the latter stage. The hot rolling apparatus according to any one of claims 1 to 5, characterized in that:
7 . 前記潤滑剤供給手段は、 微粒の固体潤滑剤をグリース中に含めた潤滑剤 を供給することを特徴とする請求項 6に記載の熱間圧延装置。  7. The hot rolling apparatus according to claim 6, wherein the lubricant supply means supplies a lubricant containing fine solid lubricant in grease.
8 . 最終段のスタンドの前記ミルの出側において、 前記被圧延材の流れ方向 における前記冷却手段の下流側に配置された、 前記被圧延材に流体を噴射して前 記被圧延材上に存在する冷却水を除去する流体噴射スプレーをさらに有すること を特徴とする請求項 1乃至 7のいずれか一項に記載の熱間圧延装置。 8. On the exit side of the mill of the last stage stand, a fluid is sprayed on the material to be rolled, which is arranged downstream of the cooling means in the flow direction of the material to be rolled, on the material to be rolled. Further having a fluid jet spray to remove existing cooling water The hot rolling apparatus according to any one of claims 1 to 7, wherein:
9 . 前記流体噴射スプレーは、 前記被圧延材に対して、 前記被圧延材の上方 から前記被圧延材の流れ方向の上流側に向けて斜め下方へ、 前記被圧延材の幅方 向に広がるように加圧水を吹き出す複数のノズルを含むことを特徴とする請求項 8に記載の熱間圧延装置。  9. The fluid jet spray spreads obliquely downward from above the material to be rolled toward the upstream side in the flow direction of the material to be rolled, in the width direction of the material to be rolled. 9. The hot rolling apparatus according to claim 8, comprising a plurality of nozzles for blowing out pressurized water.
1 0 . 被圧延材を圧延して細粒鋼を製造するための方法において、  10. A method for producing fine-grained steel by rolling a material to be rolled,
加熱した前記被圧延材を、 前段に配置されたミルと後段に配置されたミルとを 有する圧延装置に供給し、 前記圧延装置の前記後段に配置されたミルは直径が 5 5 0 mm以下のワーク口一ルを有し、  The heated material to be rolled is supplied to a rolling mill having a mill arranged at a preceding stage and a mill arranged at a latter stage, and the mill arranged at the latter stage of the rolling device has a diameter of not more than 550 mm. Has a work opening,
前記圧延装置の前記後段に配置された前記ミルの、 前記被圧延材の流れ方向に おける前および後ろにおいて前記被圧延材を冷却しながら、 累積歪みが 0 . 9以 上になるように前記被圧延材を圧延することを特徴とする細粒鋼製造方法。  While cooling the material to be rolled before and after in the flow direction of the material to be rolled in the mill disposed in the subsequent stage of the rolling device, the material to be rolled is cooled so that the cumulative strain becomes 0.9 or more. A method for producing fine-grained steel, comprising rolling a rolled material.
1 1 . 請求項 1乃至 9のいずれか一項に記載の熱間圧延装置を用いて、 前記 圧延装置の前記後段における前記被圧延材の累積歪みが 0 . 9以上になるように 前記被圧延材を圧延することを特徴とする細粒鋼製造方法。  11. Using the hot rolling apparatus according to any one of claims 1 to 9, the rolling is performed so that the cumulative strain of the material to be rolled at the subsequent stage of the rolling apparatus is 0.9 or more. A method for producing fine-grained steel, comprising rolling a material.
1 2 . 最終スタンドの前記ミルを出た直後における前記被圧延材を毎秒 2 0 °C以上の温度降下率で冷却することを特徴とする請求項 1 0又は 1 1に記載の細 粒鋼製造方法。  12. The fine-grained steel production according to claim 10 or 11, wherein the material to be rolled immediately after leaving the mill in the final stand is cooled at a temperature drop rate of 20 ° C or more per second. Method.
1 3 . 前記被圧延材は、 炭素含有量が 0 . 5 %以下であり、 合金元素の含有 量が 5 %以下であることを特徴とする請求項 1 0乃至 1 2のいずれか一項に記載 の細粒鋼製造方法。  13. The material according to claim 10, wherein the material to be rolled has a carbon content of 0.5% or less and an alloy element content of 5% or less. 13. The method for producing fine-grained steel according to the above.
1 4 . 被圧延材を連続的に熱間圧延して鋼板を製造するための方法において、 加熱した前記被圧延材を、 前段及び後段にタンデムに配置された複数スタンド のミルを有する圧延装置に供給し、  14. A method for producing a steel sheet by continuously hot rolling a material to be rolled, wherein the heated material to be rolled is fed to a rolling mill having a plurality of stand mills arranged in tandem at a preceding stage and a succeeding stage. Supply,
前記被圧延材の累積歪みが 0 . 6以上になるように前記圧延装置を用いて前記 被圧延材を圧延しながら、 前記圧延装置の前記後段の 1スタンド以上の前記ミル の出側において前記被圧延材を冷却することを特徴とする連続熱間圧延方法。  While rolling the material to be rolled using the rolling device so that the accumulated strain of the material to be rolled becomes 0.6 or more, the material is rolled on the output side of the mill at one or more stands in the latter stage of the rolling device. A continuous hot rolling method characterized by cooling a rolled material.
1 5 . 前記被圧延材の圧延終了温度を、 A r s変態点— 5 0 °C以上であって A r 3変態点 + 5 0 °C以下の範囲内にすることを特徴とする請求項 1 4記載の連 続熱間圧延方法。 15. The rolling end temperature of the material to be rolled is set within a range of Ars transformation point—50 ° C. or more and Ar 3 transformation point + 50 ° C. or less. 4 listed Continuous hot rolling method.
1 6 . 前記被圧延材を圧延して得られた鋼板の内部の平均フェライト粒径が 3〜 7 / Hi程度であることを特徴とする請求項 1 4又は 1 5に記載の連続熱間圧 延方法。  16. The continuous hot pressure according to claim 14 or 15, wherein the average ferrite grain size inside the steel sheet obtained by rolling the material to be rolled is about 3 to 7 / Hi. Nob method.
1 7 . 被圧延材を圧延して厚板を製造するための連続熱間圧延方法において、 加熱した前記被圧延材を、 被圧延材を圧延して薄板を製造できるように前段及 び後段にタンデムに配置された複数スタンドのミルを有する圧延装置に供給し、 前記圧延装置の前記後段に配置された複数の前記ミルのうちの少なくとも一部 を使用せずに、 前記圧延装置の入側寄りの少なくとも 3スタンドの前記ミルを使 用して、 前記被圧延材の累積歪みが 0 . 2 5以上になるか又は使用に供される前 記ミルのうちの最終段の前記ミルでの圧下率が 1 2 %以上になるように前記被圧 延材を圧延しながら、 使用に供される最終段の前記ミルの出側において前記被圧 延材を冷却することを特徴とする連続熱間圧延方法。  17. A continuous hot rolling method for producing a thick plate by rolling a material to be rolled, wherein the heated material to be rolled is placed in a former stage and a latter stage so that a thin plate can be produced by rolling the material to be rolled. Supplying to a rolling mill having a plurality of stands of mills arranged in tandem, without using at least a part of the plurality of mills arranged at the subsequent stage of the rolling mill, near the entry side of the rolling mill. Using at least three of the mills described above, the cumulative strain of the material to be rolled becomes 0.25 or more, or the rolling reduction in the last stage of the mills among the mills to be used. Continuous rolling, wherein the rolled material is cooled so as to be at least 12%, and the rolled material is cooled on the exit side of the mill at the final stage to be used. Method.
1 8 . 前記被圧延材の圧延終了温度が A r 3変態点 + 5 0 °Cを超えないように することを特徴とする請求項 1 7に記載の連続熱間圧延方法。 18. The continuous hot rolling method according to claim 17, wherein the rolling end temperature of the material to be rolled does not exceed the Ar 3 transformation point + 50 ° C.
1 9 . 前記被圧延材を圧延して得られた前記厚板は、 その表面からその厚さ の 1 4だけ内側での平均フェライ ト粒径が 3〜 1 0 /m程度であることを特徴 とする請求項 1 7又は 1 8に記載の連続熱間圧延方法。  19. The thick plate obtained by rolling the material to be rolled is characterized in that the average ferrite particle diameter at the inner side of the surface by only 14 of its thickness is about 3 to 10 / m. The continuous hot rolling method according to claim 17 or 18.
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