WO2002074460A1 - Laminoir a chaud et procede de laminage a chaud - Google Patents

Laminoir a chaud et procede de laminage a chaud 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
English (en)
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/ja
Priority claimed from JP2001287427A external-priority patent/JP3413183B2/ja
Priority claimed from JP2001287428A external-priority patent/JP3413184B2/ja
Application filed by Nakayama Steel Works, Ltd., Kawasaki Jukogyo Kabushiki Kaisha filed Critical Nakayama Steel Works, Ltd.
Priority to EP02716450A priority Critical patent/EP1279445B1/fr
Priority to DE60206851T priority patent/DE60206851T2/de
Priority to US10/220,728 priority patent/US7076983B2/en
Priority to KR1020027013155A priority patent/KR20020093881A/ko
Priority to AT02716450T priority patent/ATE307687T1/de
Publication of WO2002074460A1 publication Critical patent/WO2002074460A1/fr

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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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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Metal Rolling (AREA)
  • Manufacturing Cores, Coils, And Magnets (AREA)
  • Lubricants (AREA)

Abstract

L'invention concerne un laminoir à chaud comprenant des cylindres répartis en des cylindres disposés dans une étage de tête et des cylindres de plusieurs cages disposés sur un étage arrière. Il comprend aussi des moyens de refroidissement disposés côté sortie des cylindres d'au moins deux cages de l'étage arrière servant à refroidir un matériau laminé, les cylindres comprenant aussi des cylindres lamineurs de différents diamètres dont une paire de cylindres lamineurs de diamètres différents, inférieurs à 600 mm en diamètre de cylindre équivalent, ou des cylindres lamineurs de très petits diamètres dont la paire de cylindres lamineurs possède un diamètre inférieur à 600 mm. Dans ce laminoir à chaud, il est possible de fabriquer avec régularité une plaque d'acier à grain fin laminée à chaud.
PCT/JP2002/000667 2001-03-16 2002-01-29 Laminoir a chaud et procede de laminage a chaud WO2002074460A1 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
EP02716450A EP1279445B1 (fr) 2001-03-16 2002-01-29 Laminoir a chaud et procede de laminage a chaud
DE60206851T DE60206851T2 (de) 2001-03-16 2002-01-29 Warmwalzwerk und warmwalzverfahren
US10/220,728 US7076983B2 (en) 2001-03-16 2002-01-29 Apparatus and method for hot rolling
KR1020027013155A KR20020093881A (ko) 2001-03-16 2002-01-29 열간압연장치 및 열간압연방법
AT02716450T ATE307687T1 (de) 2001-03-16 2002-01-29 Warmwalzwerk und warmwalzverfahren

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
JP2001-77293 2001-03-16
JP2001077293A JP3418738B2 (ja) 2001-03-16 2001-03-16 熱間圧延機および細粒鋼製造方法
JP2001-287427 2001-09-20
JP2001287427A JP3413183B2 (ja) 2001-09-20 2001-09-20 連続熱間圧延方法および連続熱間圧延設備
JP2001287428A JP3413184B2 (ja) 2001-09-20 2001-09-20 連続熱間圧延方法および連続熱間圧延設備
JP2001-287428 2001-09-20

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KR (1) KR20020093881A (fr)
CN (1) CN1275711C (fr)
AT (1) ATE307687T1 (fr)
DE (1) DE60206851T2 (fr)
TW (1) TW565474B (fr)
WO (1) WO2002074460A1 (fr)

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CN102303052A (zh) * 2011-07-21 2012-01-04 中冶东方工程技术有限公司 一种用于热连轧板带的中间附加冷却设备及方法

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CN101474633B (zh) * 2009-01-20 2011-01-05 北京科技大学 一种镁合金薄带卷异辊径连轧设备
WO2011048671A1 (fr) * 2009-10-21 2011-04-28 東芝三菱電機産業システム株式会社 Dispositif de réglage de commandes et procédé de réglage de commandes
JP4823400B1 (ja) * 2010-03-31 2011-11-24 住友金属工業株式会社 熱延鋼板の製造装置及び製造方法
DE102013107010A1 (de) * 2013-07-03 2015-01-22 Thyssenkrupp Steel Europe Ag Anlage und Verfahren zum Warmwalzen von Stahlband
US10870138B2 (en) 2013-12-24 2020-12-22 Arcelormittal Hot rolling method
DE102017220891A1 (de) * 2017-11-22 2019-05-23 Sms Group Gmbh Verfahren zum Kühlen eines metallischen Guts und Kühlbalken
CN112912185B (zh) * 2018-11-13 2023-08-01 松下知识产权经营株式会社 辊压装置、以及控制装置
CN109513746A (zh) * 2018-12-05 2019-03-26 德龙钢铁有限公司 一种用于小规格连铸坯的热轧带钢方法及粗轧装置
EP3670011B1 (fr) * 2018-12-21 2022-09-28 Primetals Technologies Austria GmbH Refroidissement de la bande métallique dans une cage de laminoir

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US5636543A (en) * 1993-03-18 1997-06-10 Hitachi, Ltd. Hot steel plate rolling mill system and rolling method
JPH1053812A (ja) * 1992-03-23 1998-02-24 Nippon Steel Corp 高強度高靭性構造用鋼板の製造法
JPH10180338A (ja) * 1996-12-24 1998-07-07 Kawasaki Steel Corp 熱間仕上圧延におけるスケール疵防止方法
EP0885974A1 (fr) * 1997-06-16 1998-12-23 Sms Schloemann-Siemag Aktiengesellschaft Procédé et dispositif pour le laminage de bandes larges à chaud dans une installation compacte de production de bandes
JPH1171615A (ja) * 1997-08-29 1999-03-16 Nippon Steel Corp 低温靱性に優れた厚鋼板の製造方法
JP2000084611A (ja) * 1998-09-08 2000-03-28 Nippon Steel Corp 熱間ストリップの冷却制御方法及びその装置
JP2000197909A (ja) * 1998-10-28 2000-07-18 Nippon Steel Corp 熱間圧延における固形潤滑方法
EP1033182A1 (fr) * 1998-09-08 2000-09-06 Kawasaki Jukogyo Kabushiki Kaisha Laminoir a bandes a chaud

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JPS56126907U (fr) * 1980-02-27 1981-09-26
JPH0494802A (ja) * 1990-08-13 1992-03-26 Nippon Steel Corp 高圧下熱間圧延機
JPH1053812A (ja) * 1992-03-23 1998-02-24 Nippon Steel Corp 高強度高靭性構造用鋼板の製造法
US5636543A (en) * 1993-03-18 1997-06-10 Hitachi, Ltd. Hot steel plate rolling mill system and rolling method
JPH10180338A (ja) * 1996-12-24 1998-07-07 Kawasaki Steel Corp 熱間仕上圧延におけるスケール疵防止方法
EP0885974A1 (fr) * 1997-06-16 1998-12-23 Sms Schloemann-Siemag Aktiengesellschaft Procédé et dispositif pour le laminage de bandes larges à chaud dans une installation compacte de production de bandes
JPH1171615A (ja) * 1997-08-29 1999-03-16 Nippon Steel Corp 低温靱性に優れた厚鋼板の製造方法
JP2000084611A (ja) * 1998-09-08 2000-03-28 Nippon Steel Corp 熱間ストリップの冷却制御方法及びその装置
EP1033182A1 (fr) * 1998-09-08 2000-09-06 Kawasaki Jukogyo Kabushiki Kaisha Laminoir a bandes a chaud
JP2000197909A (ja) * 1998-10-28 2000-07-18 Nippon Steel Corp 熱間圧延における固形潤滑方法

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Publication number Priority date Publication date Assignee Title
CN102303052A (zh) * 2011-07-21 2012-01-04 中冶东方工程技术有限公司 一种用于热连轧板带的中间附加冷却设备及方法

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EP1279445A4 (fr) 2004-03-24
DE60206851D1 (de) 2005-12-01
DE60206851T2 (de) 2006-04-20
ATE307687T1 (de) 2005-11-15
EP1279445A1 (fr) 2003-01-29
KR20020093881A (ko) 2002-12-16
CN1458867A (zh) 2003-11-26
CN1275711C (zh) 2006-09-20
EP1279445B1 (fr) 2005-10-26
TW565474B (en) 2003-12-11

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