EP1279445B1 - Warmwalzwerk und warmwalzverfahren - Google Patents

Warmwalzwerk und warmwalzverfahren Download PDF

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Publication number
EP1279445B1
EP1279445B1 EP02716450A EP02716450A EP1279445B1 EP 1279445 B1 EP1279445 B1 EP 1279445B1 EP 02716450 A EP02716450 A EP 02716450A EP 02716450 A EP02716450 A EP 02716450A EP 1279445 B1 EP1279445 B1 EP 1279445B1
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EP
European Patent Office
Prior art keywords
steel
rolled
mills
diameter
rolling
Prior art date
Legal status (The legal status 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 status listed.)
Expired - Lifetime
Application number
EP02716450A
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English (en)
French (fr)
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EP1279445A1 (de
EP1279445A4 (de
Inventor
Ichiro Chikushi
Ryuro Kurahashi
Toshiharu Morimoto
Takashi Ohtani
Kazuaki Hakomori
Shinji Takaoka
Masanori Takahashi
Akio Adachi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nakayama Steel Works Ltd
Kawasaki Heavy Industries Ltd
Kawasaki Motors Ltd
Original Assignee
Nakayama Steel Works Ltd
Kawasaki Heavy Industries Ltd
Kawasaki Jukogyo KK
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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 Heavy Industries Ltd, Kawasaki Jukogyo KK filed Critical Nakayama Steel Works Ltd
Publication of EP1279445A1 publication Critical patent/EP1279445A1/de
Publication of EP1279445A4 publication Critical patent/EP1279445A4/de
Application granted granted Critical
Publication of EP1279445B1 publication Critical patent/EP1279445B1/de
Anticipated expiration legal-status Critical
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    • 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 manufacturing a steel plate having a micro-structure mainly composed of fine ferrite.
  • the high-pressure rolling method is described in Japanese Patent Laid-Open Publication No. 123823/1983 and Japanese Patent Publication 65564/1993. Namely, the method applies high pressure to austenite particles, thereby promotes the straining transformation from the austenite ( ⁇ ) phase to the ferrite ( ⁇ ) phase, and refines the structure.
  • control rolling method is a method for realizing refinement of ferrite particles containing components of Nb (niobium) and Ti (titanium) which can be easily increased in tension by the deposition increasing operation of Nb and Ti and also promotes the straining transformation from they phase to the ⁇ phase when the cold rolling (ferrite region rolling) is executed by the recrystallization suppression operation for austenite particles of Nb and Ti.
  • the control rolling method executes the finishing rolling in the low temperature zone (800°C or less), so that it has a disadvantage that the deformation resistance of steel to be rolled is extremely high, thus the load on the strip rolling apparatus is large.
  • the high-pressure rolling method as indicated in Japanese Patent Publication 65564/1993 aforementioned, cannot be executed industrially by a general hot strip mill and requires use of a special rolling apparatus. The reason is that, as described in the aforementioned patent publications, continuous rolling at a high pressurization rate (for example, 40% or more) which cannot be realized by a general rolling apparatus is required.
  • Document EP 1 033 182 A1 discloses a hot rolling apparatus for rolling a steel to manufacture a steel plate comprising a mill arranged on a preceding stage, and mills of a plurality of stands on a later stage.
  • the mills of a plurality of stands comprise different-diameter roll mills including a pair of different-diameter work rolls.
  • an object of the present invention is to solve the aforementioned problems concerning manufacture of hot rolled steel plates of fine-particle steel by providing a hot rolling apparatus for enabling smooth manufacture of those steel plates and a fine-particle steel manufacturing method.
  • Another object of the present invention is to provide a continuous hot rolling method suited to manufacture of hot rolled steel plates of fine-particle steel which is superior in respect of cost to effect.
  • Still another object of the present invention is to provide a continuous hot rolling method for smooth manufacture of thick plates using a hot rolling apparatus capable of manufacturing thin plates.
  • the present invention is a hot rolling apparatus for rolling a steel to be rolled to manufacture a steel plate, comprising: a mill arranged on the preceding stage, mills of a plurality of stands arranged on the later stage, said mills of plurality of stands comprising different-diameter roll mills including a pair of different-diameter work rolls having an equivalent roll diameter of less than 600 mm or minimum-diameter roll mills including a pair of work rolls having a diameter of less than 600 mm, and a cooling unit for cooling the steel to be rolled which is arranged on the exit side of the mill of at least one stand on the later stage.
  • the "equivalent roll diameter” is referred to as a mean value of the diameters of the upper and lower paired different-diameter work rolls regarding the different-diameter roll mill.
  • the cooling unit is preferably a curtain-wall type cooler.
  • the "curtain-wall type cooler” is referred to as a cooling unit of a type such as to let a large mount of cooling water flow in a laminar flow state by putting in a row from above and underneath like a curtain and hit it against the top and bottom of steel to be rolled overall the width.
  • At least the mill arranged on the preceding stage preferably includes CVC mills of a plurality of stands.
  • CVC mill is referred to as a mill including a CVC roll which has an outer diameter continuously changed in the long axial direction and can move in the long axial direction.
  • the equivalent roll diameter of the pair of different-diameter work rolls of the different-diameter roll mills or the roll diameter of the work rolls of the minimum-diameter roll mills is preferably 550 mm or less.
  • the work rolls of the different-diameter roll mills or the work rolls of the minimum-diameter roll mills are provided with a CVC function and a bending function.
  • CVC function is referred to as a function for a roll having an outer diameter continuously changed in the long axial direction to move in the long axial direction and change and control the roll gap shape.
  • bending function is referred to as a function for operating the bending force (bending moment) on the rolls and changing the roll gap shape.
  • the hot rolling apparatus preferably has a lubricant feed unit for feeding a lubricant onto the roll surfaces of the mills additionally which is installed on the mill of at least any one stand among the mills arranged on the preceding stage and later stage.
  • the lubricant feed unit preferably feeds a lubricant containing a fine-particle solid lubricant in grease.
  • the hot rolling apparatus preferably has a fluid jet spray additionally for jetting a fluid to the steel to be rolled and removing cooling water existing on the steel to be rolled, which is arranged on the downstream side of the cooling unit in the flow direction of the steel to be rolled on the exit side of the mill of the stand on the last stage.
  • the fluid jet spray preferably includes a plurality of nozzles for blowing out pressurized water so as to spread in the width direction of the steel to be rolled slantwise downward from above the steel to be rolled toward the upstream side in the flow direction of the steel to be rolled for the steel to be rolled.
  • the present invention is a method for rolling a steel to be rolled to manufacture a fine-particle steel, wherein the method feeds the heated steel to be rolled to a strip rolling apparatus having a mill arranged on the preceding stage and a mill arranged on the later stage, and the mill arranged on the later stage of the rolling apparatus has work rolls with a diameter of 550 mm or less, and the method cools the steel to be rolled before and after the mill arranged on the later stage of the rolling apparatus in the flow direction of the steel to be rolled and rolls the steel to be rolled so that the cumulative strain becomes 0.9 or more.
  • strain is referred to as the value indicated below, which is obtained by dividing the difference between the thickness h 0 of the steel to be rolled on the entrance side of each mill and the thickness h 1 on the exit side by the mean thickness of the two.
  • ⁇ (h 0 - h 1 )/ ⁇ (h 0 + h 1 )/2 ⁇
  • the fine-particle steel manufacturing method of the present invention rolls the steel to be rolled using any of the aforementioned hot rolling apparatuses so that the cumulative strain of the steel to be rolled on the later stage of the rolling apparatus becomes 0.9 or more.
  • the steel to be rolled immediately after it leaves the mill of the last stand is preferably cooled at a temperature lowering rate per second of 20°C or more.
  • the steel P to be rolled preferably has a carbon content of 0.5% or less and an alloy element content of 5% or less.
  • the "thin plate” is referred to as a steel plate with a thickness of less than 6 mm and a “thick plate” is referred to as a steel plate with a thickness of 6 mm or more (less than about 50 mm).
  • the “rolling end temperature” is the surface temperature of the steel to be rolled measured by a thermometer installed on the downstream side (the downstream side of the arranged last stage of mill by several m) of the rolling apparatus in the flow direction of the steel to be rolled.
  • the hot rolling apparatus of this embodiment shown in Fig. 1 is a finishing rolling apparatus, and on the upstream side (not shown in the drawing) in the flow direction of steel P to be rolled, a heating furnace and a rough rolling apparatus are installed, and on the downstream side (not shown in the drawing), a run-out table and a winder are arranged.
  • the hot rolling apparatus is structured as indicated below so as to continuously roll the steel P to be rolled roughly rolled on the upstream side, thereby manufacture hot rolled steel plates of fine-particle steel having a fine ferrite structure.
  • CVC mills 1, 2, and 3 are arranged tandem.
  • the CVC mill 1 positioned closest to the entrance side of the hot rolling apparatus is structured as a quadrupole mill composed of work rolls 1a and 1b and backup rolls 1c and 1d as shown in Fig. 1 and the work rolls 1a and 1b have crowns (CVC, that is, continuous diameter changes) as shown in Fig. 2A.
  • the work rolls 1a and 1b, as shown in Figs. 2B and 2C, can move (shift) in the long axial directions opposite to each other at the same time, thus the position relationship between the rolls, that is, the roll gap can be adjusted.
  • the diameter of the work rolls 1a and 1b is set to 700 mm and the maximum shift amount is set to 100 mm in both forward and backward directions.
  • the CVC mills 2 and 3 of the other two stands are not different from the CVC mill 1 in the constitution and function.
  • the reason that the CVC mills 1, 2, and 3 are arranged on the preceding stage like this is that the crown (shape) of the steel P to be rolled is to be kept suitably.
  • different-diameter roll mills 4, 5, and 6 (described later) on the later stage thermal crowns caused by working heat generation due to rolling are easily formed, so that plate crowns are corrected beforehand by the CVC mills 1, 2, and 3 installed on the preceding stage and the medium drawing of the steel P to be rolled is reduced.
  • the CVC mills 1, 2, and 3 have a large changing capacity of the roll gap shape compared with the means of simply executing roll bending and are arranged around the part of the preceding stage where steel to be rolled is thick and the crown control can be easily executed, so that it is advantageous in prevention of non-stabilization of plate flowing on the later stage where crowns are adjusted and large pressure is applied.
  • the hot rolling apparatus of this embodiment as mills of 3 stands constituting the later stage following the preceding stage, has the so-called different-diameter roll mills 4, 5, and 6 arranged tandem.
  • the stand intervals of all the 6 stands including the CVC mills 1, 2, and 3 aforementioned are all equal such as 5.5 m.
  • the different-diameter roll mill 4 corresponding to the 4th stand counted from the CVC mill 1 is structured as a quadrupole mill composed of work rolls 4a and 4b and backup rolls 4c and 4d as shown in Fig. 1 and the work rolls 4a and 4b have different diameters as shown in the drawing.
  • the work rolls 4a and 4b are respectively provided with a bender (not shown in the drawing), so that the work rolls 4a and 4b can be provided with bending. Further, the work rolls 4a and 4b are given the CVC function and can be moved forward and backward in the long axial direction within a range of 100 mm.
  • the work rolls 4a and 4b are given the bending function and CVC function like this, the shape control capacity for steel to be rolled is improved and a good profile of steel plates can be obtained.
  • the diameter of the work roll 4a is 480 mm, and the diameter of the work roll 4b is 600 mm, and the equivalent roll diameter which is a mean value of the two is 540 mm.
  • the different-diameter roll mills 5 and 6 of the other 2 stands positioned behind are not different from the different-diameter roll mill 4.
  • the equivalent roll diameter of the work rolls of the different-diameter roll mills 4, 5, and 6 can be made smaller than 540 mm, it is preferably 400 mm or more from the viewpoint of strength.
  • the equivalent roll diameter is small and since only one work roll (4b, etc.) is driven, shearing force operates on the steel P to be rolled, so that the different-diameter roll mills 4, 5, and 6 of 3 stands can execute rolling at a high pressurization rate (for example, a pressurization rate of 50%) even at a comparatively low rolling load. Therefore, high-pressure rolling for forming a fine ferrite structure in the steel P to be rolled can be executed at a small rolling load and moreover, since the rolling load is small, faults due to the roll flatness and edge drops are not caused.
  • the chart X5 shown in Fig. 7 shows edge drops generated when the fixed different-diameter roll mills 5 and 6 (the diameters of the work rolls 5a and 6a are 480 mm, and those of the work rolls 5b and 6b are 600 mm, and the equivalent roll diameter of each mill is 540 mm) roll and manufacture the same steel plate as that shown in Fig. 6.
  • the chart X4 shown in Fig. 7 shows edge drops for comparison when the different diameters of the work rolls are made equal (a medium scale diameter of 600 mm) and the same steel plate is rolled and manufactured.
  • the mills arranged on the later stage, in place of the different-diameter roll mills 4, 5, and 6, may be changed to minimum-diameter roll mills 4', 5', and 6' including a pair of work rolls 4a' and 4b' with a diameter of less than 600 mm.
  • a lubricant feed unit is arranged for each work roll of the mills 1 to 6 of all the 6 stands.
  • the unit is composed of, for example, injection ports directed toward the surface of each work roll such as numerals 5e, 5f, 6e, and 6f shown in Fig. 3 and lubricant feed pumps to them.
  • a lubricant is fed to the surface of the steel P to be rolled, thereby indirectly fed to the roll surfaces.
  • the lubricant is used to prevent each roll surface from wear and not used to lower the coefficient of friction. Therefore, as a lubricant, a fine-particle solid lubricant such as tribasic calcium phosphate, mica, or calcium carbonate included in grease is used. By blending those solid fine particles, the coefficient of friction ⁇ between each work roll and the steel P to be rolled when a lubricant is used becomes rather higher such as about 0.28 or more. When such a degree of coefficient of friction is ensured, the steel P to be rolled is properly prevented from roll slip.
  • a fine-particle solid lubricant such as tribasic calcium phosphate, mica, or calcium carbonate included in grease is used.
  • the aforementioned fine particles lie between each roll surface and the steel P to be rolled and the direct contact between the rolls and the steel P can be prevented, so that the wear of the roll surfaces is suppressed and the shape of the steel P can be easily kept satisfactorily for a long time.
  • solid fine particles are included in grease instead of mineral oil, so that there is an advantage that there is no possibility that fine particles may be precipitated in a storage container of a lubricant and the lubricant is fed so that solid fine particles are always dispersed uniformly on each roll surface.
  • Fig. 8 shows the roll wear reduction effect due to use of a lubricant
  • the chart X6 indicates a case of no use of a lubricant
  • the chart X7 indicates a case of use of a lubricant.
  • the transverse axis of Fig. 8 indicates the magnitude of load of work rolls and the ordinate axis indicates the wear amount of work rolls.
  • curtain wall type coolers 7A, 7B, and 7C are arranged on each exit side of the different-diameter roll mills 4, 5, and 6 of the 3 stands arranged on the later stage.
  • the cooler 7B will be explained as an example. As shown in Fig. 3, the cooler 7B lets a large amount of cooling water at the normal temperature flow in a curtain shape (curtain wall state, with a thickness of 10 mm or more, a most suitable thickness of 16 mm) in a laminar flow state toward the full-width surface of the steel P to be rolled from upper and lower headers 7Ba and 7Bb, thereby strongly cools the steel P to be rolled.
  • the amount of cooling water can be adjusted within the range from 100 to 500 m 3 /h per unit width (1 m) of the steel P to be rolled and the temperature lowering speed of the steel P is 20°C/s or more.
  • cooling water 350 m 3 /h per unit width is generally used.
  • the temperature lowering rate of the steel P to be rolled in this case reaches 60 to 80°C/s (40°C/s or so including the raised temperature due to working heat generation) when the product of plate thickness and speed is 1200 mm ⁇ mpm.
  • the other coolers 7A and 7C also have the same constitution and function.
  • the curtain wall type coolers are arranged on the exit sides of the mills 4, 5, and 6 on the later stage.
  • the number of coolers to be installed is not limited to it and can be properly changed depending on the kind of steel to be rolled.
  • the curtain wall type coolers 7A, 7B, and 7C By use of the curtain wall type coolers 7A, 7B, and 7C, the temperature rise of the steel P to be rolled due to working heat generation during rolling is suppressed, and the steel P to be rolled is kept within the temperature range suited to the high-pressure rolling method or control rolling method, and an occurrence of particle growth of the micro-structure after rolling can be suppressed.
  • run-out table (not shown in the drawing) on the downstream side of the hot rolling apparatus shown in Fig. 1 also cools the steel P to be rolled by cooling water at a speed of 10°C/s or more so as to prevent particle growth.
  • a water jet spray 8 is arranged away from the curtain wall type cooler 7C by several hundreds mm to 1 m. This is to remove cooling water put on the top of the steel P to be rolled by the cooler 7C. As shown in Fig.
  • the spray 8 has a plurality of nozzles 8a (4 each in total in this example) for respectively blowing out 300 liters per minute of pressurized water of about 10 kg/cm 2 slantwise downward to the upstream side in the flow direction of the steel P to be rolled from above the steel P to the surface of the steel P so as to form an angle of 65° (or within the range from 50 to 80°) with the top of the steel P.
  • the plurality of nozzles 8a as shown in Fig. 3, are arranged at an interval in the length direction of the steel P to be rolled and at an interval also in the width direction thereof.
  • the nozzles 8a blow out water so as to spread in the width direction of the steel P to be rolled, and the spread angle in the width direction of the steel P is preferably set to 15 to 30°, and the spread angle in the length direction is preferably set to 1 to 10° (respectively set to 21° and 3° in this embodiment).
  • cooling water put on the steel P by the operation of the cooling unit 7 can be smoothly removed, so that by various measuring instruments installed on the downstream side, various measurements concerning the steel P to be rolled after rolling, that is, the manufactured steel plate can be executed properly.
  • water is heavier than gas, so that it can be easily given kinetic energy and can be easily obtained, thus water is suitable for a jet fluid.
  • cooling water can be prevented from reaching the downstream side (the side of the measuring instruments) and furthermore by use of the nozzles spreading in the width direction of the steel P to be rolled, cooling water can be removed from the top of the steel P to be rolled in full width.
  • jet nozzles for example, numerals 5i, 5j, 6i, 6j
  • water draining plates for example, numerals 5g, 5h, 6g, 6h
  • a steel plate with a thickness of 2.33 mm and a width of 730 mm was manufactured by the rolling apparatus shown in Fig. 1 under three kinds of conditions (Embodiments 1 to 3).
  • Table 1-1 indicated below shows the pass schedule (rolling conditions) of Embodiment 1 and Table 1-2 shows the pass schedule of Embodiments 2 and 3.
  • Table 1-3 shows the use state of the curtain wall type coolers 7A, 7B, and 7C of Embodiments 1 to 3 and Table 1-4 shows the finishing temperature of the steel P to be rolled measured behind the mill 6 on the last stage of Embodiments 1 to 3.
  • “rough bar” indicates a rough rolling apparatus and "F1" to “F6” indicate the mills 1 to 6 of the first stand to the sixth stand.
  • the rolling speed is not specially limited and the rolling speed (for example, 7 to 9 m/s) commonly used in a general hot strip mill is adopted.
  • Table 1-5 The ferrite particle diameter and mechanical properties of hot rolled plates obtained from Embodiments 1 to 3 are shown in Table 1-5.
  • Table 1-5 “TS” indicates tensile strength, "YP” a yielding point, and "EL” an elongation. Further, in Table 1-5, the main ones of the rolling conditions shown in Tables 1-1 to 1-3 are additionally recorded.
  • Embodiment Curtain Wall Cooling Cumulative Strain Ferrite particle diameter ⁇ m TS kg/mm 2 YP kg/mm 2 EL % 1 F6 0.65 6 ⁇ 9 40 ⁇ 50 30 ⁇ 40 25 ⁇ 30 2 F6 0.92 4 ⁇ 4.5 55 ⁇ 65 45 ⁇ 55 25 ⁇ 30 3 F4,F5,F6 0.92 3.5 ⁇ 4 57 ⁇ 65 49 ⁇ 57 26 ⁇ 30 TS: Tensile strength, YP: Yielding point, EL: Elongation
  • Embodiments 2 and 3 that the cumulative strain ( ⁇ c which is the aforementioned totalized value) is set to 0.92, a steel plate having a ferrite structure with a particle diameter of about 4 ⁇ m and superior mechanical properties can be obtained.
  • the curtain wall type coolers 7A to 7C are used on the exit side (the back surface) of the 3 stands (F4 to F6) on the later stage, a steel plate having a ferrite particle diameter of about 4 ⁇ m or less and particularly superior mechanical properties is obtained.
  • Fig. 4 is a drawing showing the relation between the grain size (the particle diameter D ( ⁇ m) to the power of -1/2) concerning crystalline grains of the ferrite structure of steel plates obtained by Embodiments 1 to 3 and the yielding point.
  • the grain size is 0.43 or less (particle diameter of 5.4 ⁇ m or more) and the yielding point is not sufficient.
  • the cumulative strain is set to 0.92, the grain size becomes about 0.5 (particle diameter of about 4 ⁇ m) and the yielding point is increased to 45 kg/mm 2 or more.
  • Figs. 5A, 5B, and 5C are drawings showing the crystalline structures of the steel plate obtained in Embodiment 3 in the neighborhood of the top surface, the neighborhood of the center of the plate thickness, and the neighborhood of the bottom surface, respectively. At any part in the plate thickness, a fine ferrite structure with a particle diameter of 3 ⁇ m or so is formed.
  • a hot rolled plate of fine-particle steel having a fine ferrite structure and a superior strength balance including the tensile strength, ductility, toughness, and fatigue strength can be manufactured smoothly and the steel plate can be produced commercially. The reasons are summarized as indicated below.
  • the aforementioned problems i) and ii) concerning execution of the high-pressure rolling method are solved and, by use of a rolling apparatus of a general hot strip mill type, a fine-particle steel plate can be manufactured smoothly and a fine-particle steel plate can be produced commercially.
  • the curtain wall type coolers 7A, 7B, and 7C are properly used so as to keep the temperature range of the steel P to be rolled between 700°C and 800°C (temperature zone), using steel containing Nb and Ti as steel P to be rolled, the aforementioned control rolling method can be executed stably (consequently a fine-particle steel plate can be manufactured).
  • a fine-particle steel plate having such components can be widely used due to the balanced mechanical properties (general-purpose from the viewpoint of tensile strength and ductility) and high weldability, and be obtained easily due to a comparatively low price, and moreover has a good cyclic property, so that it is considered to be highly demanded. Therefore, for a steel plate having such component contents, the commercial contribution degree is high and sufficient economical rationality accompanies the production thereof.
  • the ferrite amount is reduced and steel mainly composed of pearlite is obtained.
  • the ferrite amount can be increased and when the C amount is not more than 0.5%, a structure mainly composed of ferrite can be obtained.
  • this embodiment obtains good results regardless of existence of alloy elements other than C in the steel P to be rolled.
  • the temperature range of Ar 3 transformation point to Ar 3 + 50°C between 700°C and 900°C which is a most suitable temperature range for hot rolling, it is preferable to adjust the transformation point temperature depending on the total amount of alloy elements.
  • the Ar 3 transformation point becomes extremely low and fine particles cannot be easily obtained.
  • the hot rolling method by the aforementioned embodiment strongly pressurizes (that is, high pressurization at a cumulative strain of 0.9 or more) steel to be rolled mainly by the mills on the later stage, keeps the steel to be rolled at a proper temperature, thereby manufactures a fine-particle steel plate of high quality that the ferrite particle diameter is about 4 ⁇ m or less.
  • the hot rolling apparatus shown in Fig. 1 adopts a constitution for realizing necessary pressurization at a comparatively low rolling load and strongly cooling steel to be rolled. By doing this, if steel to be rolled is strongly cooled (temperature control) under sufficiently high pressure, by a rolling apparatus generally tandem, a hot rolled steel plate of fine-particle steel of extremely high quality can be produced industrially.
  • the hot rolling apparatus and method according this embodiment solve those problems.
  • the continuous hot rolling apparatus is a so-called finishing rolling apparatus for the steel P to be rolled, and on the upstream side (not shown in the drawing) in the flow direction of the steel P to be rolled, a heating furnace and a rough rolling apparatus are installed, and on the downstream side (not shown in the drawing), a run-out table and a winder are arranged.
  • the hot rolling apparatus is composed of mills 10 to 60 of 6 stands in total respectively having rolls which are arranged tandem, continuously rolls the steel P to be rolled roughly rolled on the upstream side, thereby generally manufactures various hot rolled plates with a thickness of about 2 to 16 mm.
  • the rolling apparatus shown in Fig. 10 is structured as indicated below.
  • the CVC mill 10 positioned closest to the entrance side of the hot rolling apparatus is structured as a quadrupole mill composed of work rolls 101a and 101b and backup rolls 101c and 101d as shown in Fig. 10 and the work rolls 101a and 101b have crowns (CVC, that is, continuous diameter changes) as shown in Fig. 11A.
  • the work rolls 101a and 101b, as shown in Figs. 11B and 11C, can move (shift) in the long axial directions opposite to each other at the same time, thus the position relationship between the rolls, that is, the roll gap can be adjusted.
  • the diameter of the work rolls 101a and 101b is set to 700 mm and the maximum shift amount is set to 100 mm in both forward and backward directions.
  • the CVC mills 20 and 30 of the other two stands are not different from the CVC mill 10 in the constitution and function.
  • the so-called different-diameter roll mills 40, 50, and 60 are arranged tandem.
  • the stand intervals of all the 6 stands including the CVC mills 10, 20, and 30 aforementioned are all equal such as 5.5 m.
  • the different-diameter roll mill 40 corresponding to the 4th stand counted from the CVC mill 10 is structured as a quadrupole mill composed of work rolls 104a and 104b and backup rolls 104c and 104d as shown in Fig. 10 and in this example, the work rolls 104a and 104b have different diameters.
  • the work rolls 104a and 104b are driven to rotate by a motor (not shown in the drawing, an AC motor with a variable speed control means) connected via the speed reducer (not shown in the drawing) and the universal coupling and the upper roll 104a with a small diameter is structured so as to freely rotate free of driving force.
  • the work rolls 104a and 104b are respectively provided with a bender (not shown in the drawing), so that the work rolls 104a and 104b can be provided with bending.
  • the work rolls 104a and 104b are given the CVC function and can be moved forward and backward in the long axial direction within a range of 100 mm.
  • the diameter of the work roll 104a is 480 mm and the diameter of the work roll 104b is 600 mm, so that the equivalent roll diameter which is a mean value of the two is small such as 540 mm.
  • the different-diameter roll mills 50 and 60 of the other 2 stands positioned behind are not different from the different-diameter roll mill 40.
  • the equivalent roll diameter is small, and only one work roll 104b is driven, thus shearing force operates on the steel P to be rolled, so that the different-diameter roll mills 40, 50, and 60 of 3 stands can execute rolling at a high pressurization rate (for example, a pressurization rate of 50%) even at a comparatively low rolling load. Therefore, high-pressure rolling for rolling fine-particle steel can be executed extremely at a small rolling load and moreover, at that time, the rolling load is small, so that even for rolling a thin plate with a thickness of about 2 mm, faults due to the roll flatness and edge drops can be avoided.
  • a high pressurization rate for example, a pressurization rate of 50%
  • curtain wall type coolers 107 (numerals 107A to 107H shown in Fig. 12) are arranged.
  • the coolers 107 are cooling unit for flowing and hitting a large amount of cooling water at normal temperature (laminar flow, for example, numeral f shown in Fig. 12) in a curtain shape (curtain wall shape) toward the full-width surface of the steel P to be rolled from the headers installed above or below.
  • the thickness of cooling water to flow in a curtain shape must be 10 mm or more and is preferably about 16 mm from the viewpoint of the cooling effect.
  • the amount of cooling water of each cooler 107 can be adjusted within the range from 100 to 500 m 3 /h per unit width (1 m) of the steel P to be rolled and the temperature lowering rate of the steel P to be rolled by cooling is set to 20°C/s or more.
  • cooling water of 350 m 3 /h per unit width is used.
  • the temperature lowering rate of the steel P to be rolled at that time reaches 60 to 80°C/s (about 40°C/s including the temperature rise due to working heat generation) when the produce of plate thickness and speed is 1200 mm ⁇ mpm.
  • the plurality of coolers 107 shown in Fig. 10, as shown in Fig. 12, are arranged above and below the steel P to be rolled, and above the steel P to be rolled, the coolers 107A, 107B, 107D, 107E, and 107G are respectively arranged on the back of the mill 40, the front and back of the mill 50, and the front and back of the mill 60, and below the steel P to be rolled, the coolers 107C, 107F, and 107H are respectively arranged on the backs of the mills 40, 50, and 60.
  • the cooler 107H is mounted to the frame of the roller table T on the back of the mill 60 on the last stage and the other coolers 107A to 107G are mounted to the housings of the respective stands.
  • the curtain wall type coolers 7 By using the curtain wall type coolers 7 on each exit side of the mills 40. 50, and 60 of the 3 stands on the later stage, even when the high-pressure rolling method and control rolling method accompanied by remarkable working heat generation are to be executed using the hot rolling apparatus of this embodiment, the temperature rise of the mills 40, 50, and 60 is suppressed, and the steel P to be rolled is kept within a proper temperature range, and an occurrence of particle growth of the fine-particle structure can be suppressed after rolling. Further, even in a run-out table (not shown in the drawing) on the downstream side of the hot rolling apparatus shown in Fig. 10, the steel P to be rolled is cooled by cooling water so as to prevent particle growth.
  • a water jet spray 108 is arranged on the exit side of the mill 60 which is a stand on the last stage and at a position on the downstream side by several hundreds mm to 1 m from the curtain wall type coolers (107G, 107H).
  • cooling water put on the surface of the steel P to be rolled is removed by the coolers 107G and 107H and from a plurality of nozzles (not shown in the drawing), to the surface of the steel P to be rolled, pressurized water is blown out slantwise downward to the upstream side in the flow direction of the steel P to be rolled from above the steel P to be rolled so as to spread also in the width direction of the steel P to be rolled.
  • cooling water put on the steel P to be rolled by the operation of the cooling unit 107 can be smoothly removed, so that by various measuring instruments (thermometer, etc., not shown in the drawing) installed on the downstream side, various values (rolling end temperature, etc.) concerning the steel P to be rolled after rolling can be measured properly.
  • various measuring instruments thermometer, etc., not shown in the drawing
  • various values rolling end temperature, etc.
  • the rolling conditions such as the rolling end temperature can be accurately controlled under control of the amount of cooling water.
  • thermometer installed at a position on the downstream side of the water jet spray 108 and on the downstream side by about 2 m from the mill 60 on the last stage, the rolling end temperature of the steel P is measured and by a calculation operation means (not shown in the drawing) receiving the measured results, the amount of cooling water of each curtain wall type cooler 107 (particularly the coolers 107E, 107G, and 107H holding the mill 60 on the last stage) is increased or decreased.
  • the rolling end temperature is controlled by the feedback control and kept within a proper range.
  • a good hot rolled steel plate of fine-particle steel with a thickness of about 2 to 6 mm can be produced.
  • a cumulative strain ( ⁇ c which is the aforementioned totalized value) of 0.6 or more and strongly cooling by the curtain wall type coolers 107 on each back of the mills 40, 50, and 60 on the later stage a preferable fine-particle steel plate with a mean ferrite particle diameter of about 3 to 7 ⁇ m can be produced by using steel having a low carbon content and alloy element content as steel to be rolled.
  • Some fine-particle steel may have a short elongation and such a disadvantage can be removed.
  • the embodiment which will be described later is an example thereof.
  • Test rolling is executed by using the continuous hot rolling apparatus in this embodiment and variously changing the pass schedule and rolling end temperature for the steel kind (no other significant components included) shown in Table 2-1.
  • the plate thickness on the exit side of the mill 60 on the last stage is 2 to 3 mm and the rolling speed is 8 to 9 m/s.
  • the ferrite particle diameter at the center of the thickness is measured and the relation between the cumulative strain during rolling and the finishing temperature (rolling end temperature) is checked.
  • the relation between the cumulative strain (transverse axis) and the ferrite particle diameter (ordinate axis) is indicated as shown in Fig. 13.
  • symbol ⁇ indicates data when the finishing temperature is within the range of Ar 3 transformation point ⁇ 10°C
  • ⁇ indicates data when the finishing temperature becomes lower than the Ar 3 transformation point - 10°C
  • ⁇ indicates data when the finishing temperature becomes higher than the Ar 3 transformation point + 10°C (Figs. 13 to 17).
  • Fig. 13 shows that when the finishing temperature becomes higher than the Ar 3 transformation point + 10°C, a tendency that the ferrite particle diameter reduces in accordance with the cumulative strain increases is seen slightly, while when the finishing temperature is other than it, even if the cumulative strain is increased, the ferrite particle diameter is little reduced.
  • Fig. 14 shows that as the finishing temperature lowers, the ferrite particle diameter is clearly reduced.
  • the transverse axis indicates a value of particle diameter ( ⁇ m) to the power -1/2.
  • Fig. 15 shows the relation between the ferrite particle diameter and the tensile strength (MPa) and Fig. 16 shows the relation between the ferrite particle diameter and the elongation (%).
  • the drawings show that as the ferrite particle diameter reduces (on the right of the transverse axis), the tensile strength is apt to increase, while when the finishing temperature becomes lower than the Ar 3 transformation point - 10°C ( ⁇ in the drawing), as the ferrite particle diameter is refined, the elongation is reduced.
  • the product (MPa x %) of tensile strength and elongation, as shown in Fig. 17, is also reduced as the ferrite particle diameter is refined when the finishing temperature is lower than the Ar 3 transformation point - 10°C.
  • Table 2-2 shows the plate thickness ( "Rough bar thickness” indicates the plate thickness on the exit side of the rough rolling apparatus), pressurization rate (%), strain, cumulative strain, and plate width on the exit side of each of the mills 10 to 60 and Table 2-3 shows the use state of each curtain wall type cooler 7 on the back of each of the mills 40 to 60 and the finishing temperature (rolling end temperature).
  • Table 2-4 shows the ferrite particle diameter and mechanical properties of the steel plates of the embodiments obtained under the conditions shown in Tables 2-1 to 2-3 at the center of the plate thickness.
  • Figs. 18A, 18B, and 18C are drawings showing the crystalline structure of the steel plates of the embodiment in the neighborhood of the top surface, the position inward from it by 1/4 of the thickness, and the center position of the thickness, respectively. At every part, a fine structure with a mean ferrite particle diameter 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 are executed by the rolling apparatus (refer to Figs. 10 to 12) of this embodiment.
  • a cumulative strain of about 0.6 to 0.9 it is inferred that there is no need to use the different-diameter roll mills 40 to 60 mentioned above as stands on the later stage. Namely, even if these mills have upper and lower work rolls having the same diameter such as about 600 to 700 mm, they are inferred to be enough. Further, if such a degree of cumulative strain is enough, a thermal crown accompanying working heat generation is expected not to be remarkable, so that the necessity of giving the CVC function and bending function to the mills 10 to 60 is considered to be low.
  • a hot rolled steel plate of fine-particle steel having a sufficiently fine mean ferrite particle diameter, superior mechanical properties, and sufficiently high practical quality can be manufactured at an extremely low cost under a moderated condition.
  • a hot rolled steel plate of fine-particle steel with a mean ferrite particle diameter of about 10 ⁇ m or less can be manufactured.
  • a fine-structure steel plate by this process is made clear by the latest investigation and study by the inventors. Namely-, it is ascertained that among the high pressurization condition and strongly cooling condition for steel to be rolled, even if the former condition is slightly relaxed (that is, even if the cumulative strain is increased up to 0.9), a high-quality fine-particle steel plate with a ferrite particle diameter not so rough can be manufactured. Concretely, the mean ferrite particle diameter can be reduced to about 3 to 7 ⁇ m by the aforementioned cumulative strain and cooling.
  • the fine-particle steel plate has mechanical properties particularly higher than those of a general (non-fine-particle steel) hot rolled steel plate having a particle diameter of more than 10 ⁇ m and can be expected to be widely used.
  • the mechanical property balance general-purpose from the viewpoint of tensile strength, elongation, and ductility
  • the weldability is superior. Therefore, the fine-particle steel plate is widely used, can be obtained easily due to a comparatively low price, and moreover has a good cyclic property, so that it is considered to be highly demanded. Therefore, in the rolling method of this embodiment for manufacturing such a steel plate, the commercial contribution degree is high and sufficient economical rationality accompanies the production thereof.
  • the hot rolling method of this embodiment relates to the method for manufacturing a thick plate using the hot rolling apparatus of the aforementioned embodiment shown in Fig. 10.
  • the plate thickness is reduced and the rolling speed is increased, the reduction ratio is reduced more for the mills on the later stage, and the maximum number of rotations of the work rolls is increased, and the maximum output torque is set low.
  • the allowable maximum output torque values of the mills 10 to 60 are respectively 125.0, 98.2, 61.4, 34.1, 22.7, and 19.5 (the unit is ton (tf).m).
  • a preferable fine-particle steel plate with a mean ferrite particle diameter of about 4 to 6 ⁇ m can be produced by using steel having a low carbon content and alloy element content as the steel P to be rolled.
  • the cumulative strain is set to 0.9 or more, the mean ferrite particle diameter of the same steel kind can be reduced to 4 ⁇ m or less.
  • the comparison example A which will be indicated later is an example (when ⁇ c 0.6) thereof.
  • the reason that the mills on the later stage cannot realize sufficient rolling torque can be explained as indicated below.
  • the roll driving system is under a high-speed specification so as to correspond to an increase in the rolling speed accompanying a decrease in the plate thickness due to progressing of rolling and as compared with the mills on the preceding stage, the mills on the later stage are generally set so that the rotational speed is high (that is, the reduction ratio is small) and the rolling torque is low.
  • the inventors to produce a thick fine-particle steel plate with a thickness of 6 mm or more using the continuous hot rolling apparatus of the aforementioned embodiment shown in Fig. 10, that is, a continuous hot rolling apparatus capable of manufacturing a thin fine-particle steel plate, operate the rolling apparatus in the states of a) to d) indicated below. Namely:
  • a thick hot rolled steel plate of fine-particle steel with a mean ferrite particle diameter of about 5 to 10 ⁇ m on the inside of the surface by 1/4 of the thickness can be produced for the steel kind having a carbon content of 0.5% and an alloy element content of 5%.
  • Data concerning production of such a thick steel plate is indicated below as Embodiments C and D.
  • Comparison A as described above, relates to production of thin (thickness of 2.07 mm) steel plates and Comparison B indicates an example that in production of thick steel plates using the mills 10 to 60, the rolling cannot be continued. And, Embodiments C and D indicate examples that thick (thickness of 12.2 mm) fine-particle steel plates are produced smoothly and continuously using the rolling apparatus.
  • Table 3-1 indicates chemical components (no significant components other than the indicated ones are included) of steel plates and the temperature at the Ar 3 transformation point in the embodiments and Comparison examples A to D and Table 3-2 indicates the rolling end temperature (finishing temperature on the exit side), the plate width of each steel plate, and the use state of the curtain wall type coolers 107 on each back of the mills 40 to 60.
  • Table 3-3 indicates the plate thickness on each exit side of the mills 10 to 60 ("Rough bar thickness" indicates the plate thickness on the exit side of the rough rolling apparatus).
  • Tables 3-4, 3-5, and 3-6 indicate the pressurization rate (%), strain, cumulative strain, and required rolling torque (ton.m) of the mills 10 to 60 when the pass schedule in Table 3-3 is applied.
  • Table 3-6 shows that in Comparison example B that the rolling cannot be continued, the torque necessary to the mill 60 on the last stage is large such as 23 ton.m and it is larger than the aforementioned allowable maximum torque (19.5 ton.m) of the mill 60. Further, in Embodiment D, as shown in Table 3-5, stronger pressurization such as a cumulative strain of 0.38 is applied, so that it is found in Table 3-6 that in the mill 40 on the last stage among the mills used, large torque such as 30 ton.m (that is, torque not realized in the mill 50 or 60 on the later stage) is necessary.
  • Figs. 19A, 19B, and 19C are drawings showing the crystalline structure of steel plates obtained by the embodiment D in the neighborhood of the top surface, the position inward from it by 1/4 of the thickness, and the central position of the thickness, respectively.
  • a fine structure with a mean ferrite particle diameter of 5 to 10 ⁇ m is formed and at the center of the thickness, a fine structure with a mean ferrite particle diameter of 10 ⁇ m or less is formed.
  • Figs. 20 to 22 show other mechanical properties of steel plates produced under the rolling condition of Embodiment D or similar to it which are checked and arranged.
  • Fig. 20 is a drawing showing the relation between the ferrite particle diameter, the tensile strength, and the yielding point of a fine-particle steel plate (the transverse axis indicates a value of the ferrite particle diameter d ( ⁇ m) to the power -1/2).
  • Fig. 21 shows temperature changes of the Charpy impact value together with changes of normal steel (non-fine particle steel plates)
  • Fig. 22 shows the temperature dependency of the brittle fracture rate.
  • the welding coupling tensile test, coupling bending test, coupling impact test, micro test, and hardness distribution check test based on JIS Z 3040, "Check test method for welding method" are executed for a plurality of test samples and it is confirmed that the weldability of fine-particle steel plates is satisfactory.
  • a thick plate of fine-particle steel can be rolled as mentioned above is that stronger pressurization such as a cumulative strain of 0.25 or more (or the pressurization rate at the mill on the last stage is 12% or more) is applied to the steel P to be rolled and on the exit side of the mill on the last stage among the mills used, the steel P is cooled for a sufficient time.
  • stronger pressurization such as a cumulative strain of 0.25 or more (or the pressurization rate at the mill on the last stage is 12% or more) is applied to the steel P to be rolled and on the exit side of the mill on the last stage among the mills used, the steel P is cooled for a sufficient time.
  • fine-particle steel with a smaller ferrite particle diameter can be obtained.
  • the continuous hot rolling method of this embodiment is particularly characterized in that the rolling end temperature is set not to exceed the Ar 3 transformation point + 50°C.
  • the rolling end temperature is set as mentioned above, at least in the neighborhood of the surface of a steel plate (for example, a steel plate having a carbon content of 0.5% or less and an alloy element content of 5% or less), a fine structure with a ferrite particle diameter of less than 10 ⁇ m is formed.
  • the temperature range suited to the high-pressure rolling method is assumed to be from Ar 3 transformation point to Ar 3 transformation point + 50°C. However, according to the test made by the inventors, it is enough that the rolling end temperature is within the range not exceeding the Ar 3 transformation point + 50°C, as mentioned above. The reason is considered to be that, in a case of a thick plate, even if the surface temperature is low, the internal temperature is kept close to the Ar 3 transformation point.
  • the continuous hot rolling method of this embodiment strongly cools the steel P to be rolled by the curtain wall type coolers 107, so that a fine-particle steel plate with a particle diameter which is particularly fine can be manufactured smoothly. Since uniform cooling can be realized, there is an advantage that the structure can be made uniform in full width of the steel plate.
  • the continuous hot rolling method of this embodiment is particularly characterized in that the steel P to be rolled having a carbon content of 0.5% or less and an alloy element content of 5% or less is rolled and a thick plate with a mean ferrite particle diameter of about 3 to 10 ⁇ m at the part inside the surface by 1/4 of the thickness can be obtained.
  • a fine-particle steel plate having the chemical components and ferrite particle diameter mentioned above has a high mechanical property balance (general-purpose from the viewpoint of tensile strength and ductility) and moreover low temperature brittleness and high weldability (for example, refer to Figs. 20 to 22). Therefore, such a fine-particle steel plate is widely used, can be obtained easily due to a comparatively low price, and moreover has a good cyclic property, so that it is considered to be highly demanded. Therefore, for such a steel plate, the commercial contribution degree is high and sufficient economical rationality accompanies the production thereof.

Claims (12)

  1. Warmwalzvorrichtung zum Walzen eines zur Herstellung eines Stahlblechs zu walzenden feinkörnigen Stahls, aufweisend:
    ein auf einem Vorgerüst angeordnetes Walzwerk (1, 2, 3),
    Walzwerke (4, 5, 6) von wenigstens zwei auf einem Folgegerüst angeordneten Stationen, wobei die Walzwerke von wenigstens zwei Stationen Walzwerke mit Walzen unterschiedlichen Durchmessers, die ein Paar von Arbeitswalzen unterschiedlichen Durchmessers (4a, 4b, 5a, 5b, 6a, 6b) umfassen oder Walzwerke mit Walzen eines Minimaldurchmessers (4', 5', 6'), die ein Paar Arbeitswalzen (4a', 4b') umfassen, umfassen,
    dadurch gekennzeichnet, dass die Arbeitswalzen der Arbeitswalzen unterschiedlichen Durchmessers (4a, 4b, 5a, 5b, 6a, 6b) einen äquivalenten Walzendurchmesser von weniger als 600 mm besitzen, wobei eine Walze des Walzenpaars direkt angetrieben ist und die Arbeitswalzen (4a', 4b') der Walzwerke mit Walzen eines Minimaldurchmessers (4', 5', 6') einen Durchmesser von wenigers als 600 mm aufweisen,
    wobei die Warmwalzvorrichtung desweiteren
    Kühleinheiten (7A, 7B, 7C) zum Kühlen des Stahls aufweist, so dass ein Kornwachstum in einer Mikro-Struktur des Stahls, nachdem er gewalzt wurde, unterdrückt werden kann, wobei die Kühleinheiten (7A, 7B, 7C) auf Austrittsseiten der Walzwerke (4, 5, 6) von wenigstens zwei Stationen auf dem Folgegerüst angeordnet sind, wobei die wenigstens zwei Stationen eine letzte Station auf dem Folgegerüst umfassen.
  2. Warmwalzvorrichtung nach Anspruch 1, wobei die Kühleinheit (7A, 8A, 9A) ein Vorhangswand-Kühler ist.
  3. Warmwalzvorrichtung nach Anspruch 1, wobei von den Walzwerken (1, 2, 3, 4, 5, 6), die auf dem Vorgerüst und dem Folgegerüst angeordnet sind, wenigstens das auf dem Vorgerüst (1, 2, 3) angeordnete Walzwerk CVC-Walzwerke einer Mehrzahl von Stationen umfasst.
  4. Warmwalzvorrichtung nach Anspruch 1, wobei der äquivalente Walzendurchmesser des Paars Bearbeitungswalzen unterschiedlichen Durchmessers der Walzwerke mit Walzen unterschiedlichen Durchmessers (4, 5, 6) oder der Durchmesser der Arbeitswalzen der Walzen-Walzwerke mit Walzen eines Minimaldurchmessers (4' 5', 6') 550 mm oder weniger beträgt.
  5. Warmwalzvorrichtung nach Anspruch 1, wobei die Arbeitswalzen der Walzwerke mit Walzen unterschiedlichen Durchmessers (4, 5, 6) oder die Arbeitswalzen der Walzwerke mit Walzen eines Minimaldurchmessers (4', 5', 6') mit einer CVC-Funktion und einer Biegefunktion versehen sind.
  6. Warmwalzvorrichtung nach Anspruch 1, die desweiteren eine Schmierstoffzuführeinheit (5e, 5f, 6e, 6f) zum Zuführen eines Schmierstoffs auf eine Walzenoberfläche des Walzwerks aufweist, wobei die Schmierstoffzuführeinheit auf dem Walzwerk wenigstens einer Station von den auf dem Vorgerüst und dem Folgegerüst angeordneten Walzwerken angebracht ist.
  7. Warmwalzvorrichtung nach Anspruch 6, wobei die Schmierstoffzuführeinheit einen Schmierstoff zuführt, der einen feinkörnigen festen Schmierstoff in Fett enthält.
  8. Warmwalzvorrichtung nach Anspruch 1, die desweiteren einen Flüssigkeitsaufstrahlarm (8) zum Aufstrahlen einer Flüssigkeit auf den zu walzenden Stahl und Entfernen von auf dem zu walzenden Stahl vorliegenden Kühlwassers aufweist, wobei der Flüssigkeitsaufstrahlarm (8) in einer Laufrichtung des zu walzenden Stahls hinter der Kühleinheit auf einer Austrittsseite des Walzwerks auf einem Folgegerüst angeordnet ist.
  9. Warmwalzvorrichtung nach Anspruch 8, wobei der Flüssigkeitsaufstrahlarm (8) eine Mehrzahl von Düsen (8a) umfasst, um unter Druck stehendes Wasser in Richtung des zu walzenden Stahls hin auszublasen, um sich in einer Breitenrichtung des zu walzenden Stahls von oberhalb des zu walzenden Stahls schräg nach unten entgegen einer Laufrichtung des zu walzenden Stahls auszubreiten.
  10. Feinkörnigen Stahl erzeugendes Verfahren zum Walzen eines zu walzenden Stahls unter Verwendung einer Warmwalzvorrichtung nach Anspruch 1, dadurch gekennzeichnet, dass eine Summendehnung des zu walzenden Stahls auf dem Folgegerüst des Walzwerks 0,9 oder mehr wird, während ein Kornwachstum in einer Mikro-Struktur des Stahls nach dem Walzen durch Kühlen des Stahls mit den Kühleinheiten (7A, 7B, 7C) unterdrückt wird.
  11. Feinkörnigen Stahl erzeugendes Verfahren nach Anspruch 10, wobei der zu walzende Stahl unmittelbar nach Verlassen des Walzwerks eines letzten Gerüsts bei einer Temperaturerniedrigungsrate von 20°C pro Sekunde oder mehr gekühlt wird.
  12. Feinkörnigen Stahl erzeugendes Verfahren nach Anspruch 10, wobei der zu walzende Stahl einen Kohlenstoffgehalt von 0,5 % oder weniger und einen Gehalt an Legierungselementen von 5 % oder weniger aufweist.
EP02716450A 2001-03-16 2002-01-29 Warmwalzwerk und warmwalzverfahren Expired - Lifetime EP1279445B1 (de)

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JP2001077293 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
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
JP2001287428 2001-09-20
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
JP2001287427 2001-09-20
PCT/JP2002/000667 WO2002074460A1 (fr) 2001-03-16 2002-01-29 Laminoir a chaud et procede de laminage a chaud

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WO2011048671A1 (ja) * 2009-10-21 2011-04-28 東芝三菱電機産業システム株式会社 制御設定装置及び制御設定方法
WO2011125670A1 (ja) * 2010-03-31 2011-10-13 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
CN102303052B (zh) * 2011-07-21 2013-09-18 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
DE102013107010A1 (de) 2013-07-03 2015-01-22 Thyssenkrupp Steel Europe Ag Anlage und Verfahren zum Warmwalzen von Stahlband
MX2016008454A (es) * 2013-12-24 2016-10-14 Arcelormittal Metodo de laminacion en caliente.
DE102017220891A1 (de) * 2017-11-22 2019-05-23 Sms Group Gmbh Verfahren zum Kühlen eines metallischen Guts und Kühlbalken
US20210394246A1 (en) * 2018-11-13 2021-12-23 Panasonic Intellectual Property Management Co., Ltd. Roll press device and control device
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EP3670011B1 (de) * 2018-12-21 2022-09-28 Primetals Technologies Austria GmbH Kühlung von metallband in einem walzgerüst

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CN1275711C (zh) 2006-09-20
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WO2002074460A1 (fr) 2002-09-26
EP1279445A4 (de) 2004-03-24
TW565474B (en) 2003-12-11
ATE307687T1 (de) 2005-11-15
KR20020093881A (ko) 2002-12-16

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