WO2020209060A1 - Tube carré en acier, son procédé de fabrication, et structure de construction - Google Patents

Tube carré en acier, son procédé de fabrication, et structure de construction Download PDF

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Publication number
WO2020209060A1
WO2020209060A1 PCT/JP2020/013236 JP2020013236W WO2020209060A1 WO 2020209060 A1 WO2020209060 A1 WO 2020209060A1 JP 2020013236 W JP2020013236 W JP 2020013236W WO 2020209060 A1 WO2020209060 A1 WO 2020209060A1
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Prior art keywords
steel pipe
square
square steel
corner
less
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PCT/JP2020/013236
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English (en)
Japanese (ja)
Inventor
昌士 松本
晃英 松本
井手　信介
岡部　能知
Original Assignee
Ｊｆｅスチール株式会社
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Application filed by Ｊｆｅスチール株式会社 filed Critical Ｊｆｅスチール株式会社
Priority to KR1020217032028A priority Critical patent/KR20210135287A/ko
Priority to JP2020544049A priority patent/JP6874913B2/ja
Priority to CN202080026557.6A priority patent/CN113677448B/zh
Publication of WO2020209060A1 publication Critical patent/WO2020209060A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D5/00—Bending sheet metal along straight lines, e.g. to form simple curves
    • B21D5/06—Bending sheet metal along straight lines, e.g. to form simple curves by drawing procedure making use of dies or forming-rollers, e.g. making profiles
    • B21D5/10—Bending sheet metal along straight lines, e.g. to form simple curves by drawing procedure making use of dies or forming-rollers, e.g. making profiles for making tubes
    • B21D5/12—Bending sheet metal along straight lines, e.g. to form simple curves by drawing procedure making use of dies or forming-rollers, e.g. making profiles for making tubes making use of forming-rollers
    • 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
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
    • E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
    • E04B1/18—Structures comprising elongated load-supporting parts, e.g. columns, girders, skeletons
    • E04B1/24—Structures comprising elongated load-supporting parts, e.g. columns, girders, skeletons the supporting parts consisting of metal
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • 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

Definitions

  • the present invention particularly relates to a square steel pipe used as a building member of a large building such as a factory, a warehouse, or a commercial facility, a manufacturing method thereof, and a building structure.
  • the energy needs to be 70J or more.
  • Square steel pipes are generally manufactured by using hot-rolled steel plates (steel strips) or thick steel plates as materials and cold press bending or roll forming them.
  • Square steel pipes manufactured by cold press bending are manufactured by forming a thick steel plate into a square or U shape by press bending and joining them by submerged arc welding.
  • the square steel pipe manufactured by roll forming is made of hot-rolled steel plate into a cylindrical open pipe shape by roll forming, and after the butt portion is welded by electric stitching, it remains cylindrical by rolls arranged vertically and horizontally. It is manufactured by adding a few percent of the drawing in the direction of the pipe axis and then forming it into a square shape.
  • Patent Document 1 proposes a square steel pipe characterized in that the surface integral of the bainite structure is 40% or more in the microstructure of the flat plate portion.
  • Patent Document 2 proposes a square steel pipe having a low yield ratio and high toughness, which is characterized in that all pipes are strain-removed and annealed after being made by cold forming.
  • the Vickers hardness of the corner surface layer of the square steel pipe described in Patent Document 1 is 350 HV or less. However, the hardness of the surface layer portion of the corner portion is still large, and further reduction of the hardness is required to suppress fracture and surface cracking starting from the corner portion.
  • the present invention has been made in view of the above circumstances, and is a square steel pipe having a small influence on work hardening of corners and suppressing surface cracking, a method for manufacturing the same, and a building structure using the square steel pipe of the present invention.
  • the purpose is to provide.
  • the present inventors conducted diligent studies to solve the above problems and obtained the following findings.
  • the forming roll is used to reduce the curvature of the part corresponding to the flat plate part of the square steel pipe that is the final product, and the forming is performed so that the cross section changes from a cylindrical shape to a rectangular cross section. Is going. This is done so that the forming roll pushes in the part corresponding to the central part of the flat plate part of the square steel pipe of the final product, and the corner part is an L-shaped corner part so as to follow the deformation of the flat plate part.
  • a square steel pipe having a Vickers hardness on the inner surface side of the corner is larger than a Vickers hardness on the outer surface side of the corner. It was.
  • a square steel pipe having a Vickers hardness on the inner surface side of the corner is larger than the Vickers hardness on the outer surface side of the corner is formed from a cylindrical steel pipe to a square steel pipe, the roll does not come into contact with the vicinity of the corner during square forming. As described above, it is obtained by setting the roll gap during square forming and the caliber curvature of the roll and forming the square steel pipe from the cylindrical steel pipe.
  • the present invention is based on the above findings, and its features are as follows.
  • the yield strength of the flat plate portion is 385 MPa or more
  • the tensile strength is 520 MPa or more
  • the yield ratio is 0.90 or less.
  • the Vickers hardness of the corner is larger than the Vickers hardness of the outer surface of the corner
  • the Vickers hardness of the inner surface of the corner is 280 HV or less
  • the Vickers hardness of the outer surface of the corner is 280 HV or less.
  • the difference between the Vickers hardness on the outer surface side of the corner and the Vickers hardness on the inner surface side of the corner is 80 HV or less.
  • C 0.04 to 0.50%
  • Si 2.0% or less
  • Mn 0.5 to 3.0%
  • P 0.10% or less
  • S 0.050 % Or less
  • Al 0.005 to 0.10%
  • N 0.010% or less
  • the balance has a component composition consisting of Fe and unavoidable impurities.
  • the steel structure at t / 4 (t is the pipe thickness) from the pipe surface contains ferrite with a volume ratio of more than 30% and bainite with a volume ratio of 10% or more, and the total volume ratio of ferrite and bainite is 70%.
  • the square steel pipe according to [1], which is 95% or more and the balance is one or more selected from pearlite, martensite, and austenite. [3] Further, in mass%, one selected from Nb: 0.005 to 0.150%, Ti: 0.005 to 0.150%, V: 0.005 to 0.150% or The square steel pipe according to [2], which contains two or more types.
  • the square forming step for performing the square forming is In the cross section perpendicular to the pipe axis direction, the adjacent side lengths are H 1 (mm) and H 2 (mm) (H 1 ⁇ H 2 ), respectively, and from the center position of H 1 and H 2 to the inside of the steel pipe.
  • H 1 Side length (short side) (mm)
  • H 2 Side length (long side) (mm)
  • t Tube thickness (mm) Is.
  • a steel material having the component composition according to any one of [2] to [4] is heated to a heating temperature of 1100 to 1300 ° C., and then roughly rolled to a rough rolling end temperature of 850 to 1150 ° C. Finish rolling is performed at a finish rolling end temperature of 750 to 850 ° C, and the total reduction rate at 930 ° C or lower in both rough rolling and finish rolling is 65% or more, and then cooling starts at the plate thickness center temperature.
  • Cooling stop temperature 450 to 650 ° C at a cooling rate at which the average cooling rate until cooling stop is 10 to 30 ° C / s, winding, allowing to cool, and then rolling to form a cylindrical shape.
  • the roll-formed steel plate is electro-stitched and welded to form an electro-sewn steel pipe, and then the electro-sewn steel pipe is square-formed into a square steel pipe.
  • the side lengths are H 1 (mm) and H 2 (mm) (H 1 ⁇ H 2 ), respectively, and the intersection of straight lines drawn from the center positions of H 1 and H 2 toward the inside of the steel pipe is the center of the square steel pipe.
  • H 1 Side length (short side) (mm)
  • H 2 Side length (long side) (mm)
  • t Tube thickness (mm) Is.
  • a square steel pipe having a small effect on work hardening of the corners and suppressing surface cracking can be obtained. This can greatly contribute to the reduction of construction costs for large buildings such as factories, warehouses, and commercial facilities. Further, according to the method for manufacturing a square steel pipe of the present invention, it is possible to manufacture a high-strength square steel pipe in a short period of time with high productivity as compared with cold press bending.
  • FIG. 1 is a schematic view showing an example of an electric resistance welded steel pipe manufacturing facility.
  • FIG. 2 is a schematic view showing a molding process of a square steel pipe.
  • FIG. 3 is a schematic view showing a cross section of a square steel pipe perpendicular to the pipe axis direction.
  • FIG. 4 is a perspective view schematically showing an example of a building structure using the square steel pipe of the present invention.
  • the square steel pipe of the present invention has a flat plate portion and a square portion, and the flat plate portion has a yield strength (YS) of 385 MPa or more, a tensile strength (TS) of 520 MPa or more, and a yield ratio of 0.90 or less.
  • the Vickers hardness of the corner is larger on the inner surface side of the corner than the Vickers hardness on the outer surface side of the corner, the Vickers hardness on the outer surface side of the corner is 280 HV or less, and the outer surface of the corner.
  • the difference between the Vickers hardness on the side and the Vickers hardness on the inner surface side of the corner is 80 HV or less, and the Charpy absorption energy vE 0 at 0 ° C. on the outer surface side of the corner is 70 J or more.
  • Square steel pipes are work-hardened larger at the corners than at the flat plates.
  • the outer surface of the corner is a tensile stress field in the circumferential direction, it is necessary to ensure the toughness of the outer surface of the corner in order to suppress brittle fracture of the corner in the final product. That is, the Charpy absorption energy vE 0 at 0 ° C. on the outer surface of the corner is required to be 70 J or more, the yield strength (YS) of the flat plate portion is 385 MPa or more, the tensile strength (TS) is 520 MPa or more, and the yield ratio is 0.90. It is required to be as follows.
  • the Vickers hardness on the inner surface side of the corner is larger than the Vickers hardness on the outer surface side of the corner, the Vickers hardness on the outer surface side of the corner is 280 HV or less, and the outer surface side of the corner.
  • the difference between the Vickers hardness and the Vickers hardness on the inner surface side of the corner is 80 HV or less.
  • the Vickers hardness on the inner surface side of the corner is larger than the Vickers hardness on the outer surface side of the corner, and the Vickers hardness on the outer surface side of the corner is 280 HV or less, so that work hardening by bending is performed.
  • a small square steel pipe can be obtained.
  • the difference between the Vickers hardness on the outer surface side of the corner portion and the Vickers hardness on the inner surface side of the corner portion is set to 80 HV or less.
  • the difference between the Vickers hardness on the outer surface side of the corner and the Vickers hardness on the inner surface side of the corner exceeds 80 HV, work hardening on the inner surface side of the corner progresses and the residual stress on the inner surface of the corner becomes remarkable. It has an adverse effect on cracks in the plating applied in the post-treatment.
  • the Vickers hardness on the outer surface side of the corner in the present invention is the Vickers hardness inside 1 ⁇ 0.2 mm from the outer surface of the corner, and the Vickers hardness on the inner surface side of the corner is 1 ⁇ from the inner surface of the corner. It refers to the Vickers hardness inside 0.2 mm.
  • the square steel pipe of the present invention has C: 0.04 to 0.50%, Si: 2.0% or less, Mn: 0.5 to 3.0%, P: 0.10% or less, S in mass%. : 0.050% or less, Al: 0.005 to 0.10%, N: 0.010% or less, the balance has a component composition consisting of Fe and unavoidable impurities, and t / 4 (t / 4) from the tube surface.
  • the steel structure at the position (t is the pipe thickness) contains ferrite with a volume ratio of more than 30% and bainite with a volume ratio of 10% or more, and the total volume ratio of ferrite and bainite is 70% or more and 95% or less, and the balance. Is preferably composed of one or more selected from pearlite, martensite and austenite.
  • C 0.04 to 0.50%
  • C is an element that increases the strength of steel by solid solution strengthening. Further, C is an element that promotes the formation of pearlite, enhances hardenability, contributes to the formation of martensite, and contributes to the stabilization of austenite, and thus contributes to the formation of a hard phase. It is preferable to contain 0.04% or more of C in order to secure the desired strength. However, when the C content exceeds 0.50%, the proportion of the hard phase increases, the toughness decreases, and the weldability also deteriorates. Therefore, the C content is preferably 0.04% or more and 0.50% or less. More preferably, the C content is C: more than 0.12% and 0.25% or less.
  • Si 2.0% or less Si is an element that increases the strength of steel by solid solution strengthening, and can be contained as needed.
  • the content of Si is preferably 0.01% or more.
  • the Si content is preferably 2.0% or less. More preferably, the Si content is 0.01% or more and 0.5% or less.
  • Mn 0.5-3.0%
  • Mn is an element that increases the strength of steel by solid solution strengthening and also contributes to the miniaturization of the structure by lowering the ferrite transformation start temperature. It is preferable to contain 0.5% or more of Mn in order to secure the desired strength and structure. However, if the Mn content exceeds 3.0%, the weldability deteriorates. Therefore, the Mn content is preferably 0.5% or more and 3.0% or less. More preferably, the Mn content is 0.5% or more and 2.0% or less.
  • P 0.10% or less P is segregated at the grain boundaries and causes inhomogeneity of the material. Therefore, it is preferable to reduce P as an unavoidable impurity as much as possible.
  • a content of 0.10% or less is acceptable. Therefore, the P content is preferably in the range of 0.10% or less. More preferably, the P content is 0.03% or less.
  • S 0.050% or less S is usually present as MnS in steel, but MnS is thinly stretched in the hot rolling step and adversely affects ductility. Therefore, in the present invention, it is preferable to reduce as much as possible.
  • a content of 0.050% or less is acceptable. Therefore, the S content is preferably 0.050% or less. More preferably, the S content is 0.015% or less.
  • Al 0.005 to 0.10%
  • Al is an element that acts as a potent antacid. In order to obtain such an effect, it is preferable to contain 0.005% or more of Al. However, if the Al content exceeds 0.10%, the weldability deteriorates, and the amount of alumina-based inclusions increases, resulting in deterioration of the surface texture. Therefore, the Al content is preferably 0.005% or more and 0.10% or less. More preferably, the Al content is 0.010% or more and 0.07% or less.
  • N 0.010% or less
  • N is an unavoidable impurity and is an element having an action of lowering toughness by firmly fixing the movement of dislocations.
  • a content of 0.010% or less is acceptable. Therefore, the N content is preferably 0.010% or less. More preferably, the N content is 0.0080% or less.
  • Nb 0.005 to 0.150%
  • Ti 0.005 to 0.150%
  • V One or more selected from 0.005 to 0.150% may be contained.
  • Nb 0.005 to 0.150%
  • Ti 0.005 to 0.150%
  • V 0.005 to 0.150%
  • Nb, Ti, V Both are elements that form fine carbides and nitrides in steel and contribute to the improvement of steel strength through precipitation strengthening, and can be contained as needed.
  • the content of Nb: 0.005% or more, Ti: 0.005% or more, and V: 0.005% or more is preferable.
  • excessive content leads to an increase in yield ratio and a decrease in toughness. Therefore, when Nb, Ti, and V are contained, Nb: 0.005 to 0.150%, Ti: 0.005 to 0.150%, and V: 0.005 to 0.150%.
  • Nb 0.008 to 0.10%
  • V 0.008 to 0.10%.
  • Cr 0.01 to 1.0%
  • Mo 0.01 to 1.0%
  • Cu 0.01 to 0.50%
  • Ni 0.01 to 0.30%
  • One or two or more selected from Ca: 0.0005% to 0.010% and B: 0.0003 to 0.010% may be contained.
  • Cr 0.01 to 1.0%, Mo: 0.01 to 1.0%, Cu: 0.01 to 0.50%, Ni: 0.01 to 0.30%, Ca: 0.0005 to One or more selected from 0.010%, B: 0.0003 to 0.010% Cr, Mo, Cu, Ni are elements that increase the strength of steel by solid melt strengthening. Further, since all of them are elements that enhance the hardenability of steel and contribute to the stabilization of austenite, they are elements that contribute to the formation of hard martensite and austenite, and can be contained as needed. In order to obtain such an effect, it is preferable to contain Cr: 0.01% or more, Mo: 0.01% or more, Cu: 0.01% or more, and Ni: 0.01% or more.
  • Cr 0.01 to 1.0%
  • Mo 0.01 to 1.0%
  • Cu 0.01 to 0.50%
  • Ni It is set to 0.01 to 0.30%.
  • Cr 0.1 to 0.5%
  • Mo 0.1 to 0.5%
  • Cu 0.1 to 0.40%
  • Ni 0.1 to 0.20%.
  • Ca is an element that contributes to improving the toughness of steel by spheroidizing sulfides such as MnS that are thinly stretched in the hot rolling process, and can be contained as needed. In order to obtain such an effect, it is preferable to contain 0.0005% or more of Ca. However, if the Ca content exceeds 0.010%, Ca oxide clusters may be formed in the steel and the toughness may deteriorate. Therefore, when Ca is contained, the Ca content is set to 0.0005 to 0.010%. Preferably, the Ca content is 0.0010 to 0.0050%.
  • B is an element that contributes to the miniaturization of the structure by lowering the ferrite transformation start temperature. In order to obtain such an effect, it is preferable to contain 0.0003% or more of B. However, when the B content exceeds 0.010%, the yield ratio increases. Therefore, when B is contained, the B content is set to 0.0003 to 0.010%. Preferably, the B content is 0.0005 to 0.0050%.
  • the rest other than the above components are Fe and unavoidable impurities.
  • the steel structure at a position t / 4 (t is the pipe thickness) from the pipe surface contains ferrite having a volume ratio of more than 30% and bainite having a volume ratio of 10% or more, and the volume ratio of ferrite and bainite.
  • the total is 70% or more and 95% or less, and the balance is preferably one or more selected from pearlite, martensite, and austenite.
  • the volume ratio is preferably more than 30%.
  • bainite is a structure with intermediate hardness and increases the strength of steel. Since the desired yield strength and tensile strength cannot be obtained with ferrite alone, the volume fraction is preferably 10% or more.
  • the desired yield strength or yield ratio cannot be obtained, and if it exceeds 95%, the desired yield strength or yield ratio cannot be obtained.
  • the balance is preferably composed of one or more selected from pearlite, martensite, and austenite.
  • Pearlite, martensite, and austenite are hard structures, and in particular, they increase the tensile strength of steel and lower the yield ratio of steel pipe materials by mixing with soft ferrite.
  • the total volume fraction is preferably 5% or more and 30% or less.
  • the steel structure of the square steel pipe is uniform in the width direction of the steel pipe, both the structure of the square portion and the flat plate portion satisfy the scope of the present invention.
  • the t / 4 position from the pipe surface can be within a range of ⁇ 0.2 mm from the t / 4 position.
  • the pipe surface may be either the outer surface or the inner surface of the pipe.
  • a steel material such as a slab having the above-mentioned chemical components is heated to a temperature of 1100 to 1300 ° C., and then rough-rolled to a rough rolling end temperature of 850 to 1150 ° C. Finish rolling end temperature: 750 to 850 ° C.
  • the plate thickness center temperature After a hot rolling process in which the total reduction ratio at 930 ° C. or lower in both rough rolling and finish rolling is 65% or more, the plate thickness center temperature.
  • the material is cooled to a cooling stop temperature of 450 to 650 ° C., rolled up, and then allowed to cool.
  • the temperature is the surface temperature of the steel material, steel plate, etc. unless otherwise specified. This surface temperature can be measured with a radiation thermometer or the like.
  • the average cooling rate shall be ((temperature before cooling-temperature after cooling) / cooling time) unless otherwise specified.
  • the cooling method is water cooling such as injection of water from a nozzle, cooling by injection of cooling gas, or the like. It is preferable to perform a cooling operation on both sides of the hot-rolled steel sheet so that both sides of the hot-rolled steel sheet are cooled under the same conditions.
  • the core temperature of the steel sheet in these hot rolling is not specified, but this time, it is calculated by the unsteady heat transfer calculation by the difference calculation. Specifically, the calculation is performed using the physical property values of the material such as the thermal conductivity, specific heat, and density of the steel sheet, and the heat transfer coefficient obtained from the water amount density of the cooling water and the outer surface temperature of the steel sheet as the boundary condition.
  • the method for producing the steel material having the above-mentioned composition is not particularly limited, and the steel material is melted by a commonly known melting method such as a converter, an electric furnace, or a vacuum melting furnace, and is melted by a commonly known casting method such as a continuous casting method. , Manufactured to the desired dimensions.
  • the molten steel may be further subjected to secondary refining such as ladle refining. Further, there is no problem even if the ingot-block rolling method is applied instead of the continuous casting method.
  • Heating temperature 1100 to 1300 ° C
  • the heating temperature in the hot rolling step is preferably 1100 to 1300 ° C.
  • Rough rolling end temperature 850 to 1150 ° C If the rough rolling end temperature is less than 850 ° C., the steel sheet temperature becomes lower than the ferrite transformation start temperature during the subsequent finish rolling, and the risk of ferrite formation increases. The produced ferrite becomes processed ferrite grains elongated in the rolling direction by the subsequent rolling, which causes an increase in the yield ratio. On the other hand, when the rough rolling end temperature exceeds 1150 ° C., the amount of reduction in the austenite unrecrystallized temperature range is insufficient, fine austenite grains cannot be obtained, and it becomes difficult to secure the desired toughness of the hot-rolled steel sheet. In addition, it becomes difficult to suppress the formation of coarse bainite. Therefore, the rough rolling end temperature is preferably 850 to 1150 ° C.
  • Finish rolling end temperature 750 to 850 ° C
  • the finish rolling end temperature is less than 750 ° C.
  • the steel sheet temperature becomes lower than the ferrite transformation start temperature during rolling, and the risk of ferrite formation increases.
  • the ferrite produced in the above becomes processed ferrite grains elongated in the rolling direction by the subsequent rolling, which causes an increase in the yield ratio.
  • the finish rolling end temperature exceeds 850 ° C.
  • the finish rolling end temperature is preferably 750 to 850 ° C.
  • Total rolling reduction at 930 ° C or lower in both rough rolling and finish rolling 65% or more
  • ferrite produced in the subsequent cooling and winding steps by refining the subgrains in austenite in hot rolling. , Bainite and the residual structure are refined to obtain a hot-rolled steel sheet with the desired strength and toughness.
  • the total rolling reduction at 930 ° C. or lower in both rough rolling and finish rolling was set to 65% or more.
  • the total rolling reduction at 930 ° C. or lower in both rough rolling and finish rolling is less than 65%, sufficient machining strain cannot be introduced in hot rolling, so that a structure having desired toughness cannot be obtained. ..
  • Average cooling rate from the start of cooling to the stop of cooling 10 to 30 ° C / s If the cooling rate is less than 10 ° C./s, the nucleation frequency of ferrite decreases and the ferrite grains become coarse, so that a structure having the desired strength and toughness cannot be obtained. On the other hand, when the cooling rate exceeds 30 ° C./s, a large amount of martensite is generated at the t / 4 position of the steel sheet, and the total volume fraction of ferrite and bainite becomes less than 70%.
  • Cooling stop temperature 450-650 ° C
  • the cooling stop temperature is less than 450 ° C.
  • a large amount of martensite is generated at the t / 4 position of the steel sheet, and the total volume fraction of ferrite and bainite is less than 70%.
  • the cooling stop temperature exceeds 650 ° C.
  • the nucleation frequency of ferrite decreases, the ferrite grains become coarse, and the volume fraction of bainite cannot be 10% or more because it exceeds the bainite transformation start temperature. ..
  • the hot-rolled steel plate (steel strip) 1 which is the material of the electric-sewn steel pipe, is manufactured into the electric-sewn steel pipe by using the manufacturing equipment as shown in FIG.
  • the hot-rolled steel sheet 1 is subjected to side-entry straightening by a leveler 2, it is intermediately formed by a cage roll group 3 composed of a plurality of rolls to form a cylindrical open pipe, and then a finpass roll composed of a plurality of rolls.
  • Finish molding (roll molding) is performed in group 4.
  • the width end portion of the steel strip 1 is electrically resistance welded by the welding machine 6 while being pressure-welded with the squeeze roll 5 to obtain the electrosewn steel pipe 7.
  • the manufacturing equipment for the electrosewn steel pipe 7 is not limited to the pipe making process as shown in FIG.
  • FIG. 2 is a schematic view showing a molding process of a square steel pipe according to an embodiment of the present invention.
  • the electrosewn steel pipe 7 is reduced in diameter by a sizing roll group (sizing stand) 8 composed of a plurality of rolls while maintaining a cylindrical shape, and then a square forming roll group (square forming stand) composed of a plurality of rolls.
  • 9 is sequentially formed into a shape such as R1, R2, and R3 to form a square steel pipe 10.
  • the roll of the square forming stand is a hole-shaped roll having a caliber curvature, and the radius of curvature of the caliber increases as the stand becomes a latter stage, forming a flat plate portion and a square portion of a square steel pipe.
  • the number of stands of the sizing roll group 8 and the square forming roll group 9 is not particularly limited.
  • a square steel pipe formed by a method of roll forming, welding, and square forming to obtain a square steel pipe is once formed into a cylindrical shape from a steel plate and then formed into a square shape.
  • a manufacturing method not only bending deformation in the circumferential direction but also distortion in the longitudinal direction due to drawing deformation occurs.
  • the neutral axis of bending in the circumferential direction moves to the outer surface side, and the inner surface side The hardness increases.
  • the present inventors set the roll gap during square forming and the caliber curvature of the roll so that the roll does not come into contact with the vicinity of the corner during square forming, and formed the square steel pipe from the cylindrical steel pipe.
  • the adjacent side lengths are H 1 (mm) and H 2 (mm) (however, H 1 ⁇ H, respectively).
  • 2 and H 1 and H 2 are the side lengths of the final product, respectively.
  • the intersection of the straight lines drawn from the center positions of H 1 and H 2 toward the inside of the steel pipe is the central part of the square steel pipe.
  • a point offset by 1/2 (H 2- H 1 ) in the long side direction from the center of the square steel pipe is defined as an offset point.
  • the central angle ⁇ formed by the straight line drawn from the point to the center of the corner of the square steel pipe and the straight line drawn from the offset point toward the arc part of the corner or the flat plate part of the square steel pipe satisfies the following equation (1). , The processing hardening due to bending is small, and surface cracking can be suppressed.
  • H 1 Side length (short side) (mm)
  • H 2 Side length (long side) (mm)
  • t Tube thickness (mm) Is.
  • the radius of curvature of the caliber of the roll and the radius of curvature of the flat plate portion of the square steel pipe are almost equal on the rear stand side, so that the contact width between the hole roll and the square steel pipe in the circumferential direction on the rear stand is large.
  • the desired corner size is obtained while increasing and expanding from the center side of the flat plate portion to the corner portion side.
  • the ratio t / H of the pipe thickness t and the side length H which is the wall thickness of the final product of the square steel pipe
  • the rigidity of deformation increases, so that the contact width between the hole roll and the square steel pipe in the circumferential direction increases. It is necessary to secure up to the vicinity of the corner.
  • the region where the hole roll and the square steel pipe do not contact is formed from the apex of the corner through all the square forming stands. It is necessary to control the distance in the circumferential direction corresponding to the wall thickness.
  • the region is a region on the outer surface side of the steel pipe that satisfies the above (1) with reference to the center of the corner of the final shape of the square steel pipe.
  • FIG. 4 is a perspective view schematically showing a building structure according to an embodiment of the present invention.
  • a plurality of square steel pipes 10 of the present invention are erected and used as pillars.
  • a plurality of girders 11 made of a steel material such as H-shaped steel are erected between adjacent square steel pipes 10.
  • a plurality of small beams 12 made of a steel material such as H-shaped steel are erected between the adjacent large beams 11.
  • the girder 11 made of a steel material such as H-shaped steel is erected between the adjacent square steel pipes 10.
  • studs 14 are provided as needed for mounting walls and the like.
  • the building structure of the present invention uses the square steel pipe 10 of the present invention having a small Vickers hardness on the outer surface side of the corner, that is, the influence of work hardening is small, the corner heat-affected zone generated during butt welding is used. Surface cracks due to stress release are unlikely to occur.
  • Molten steel having the composition shown in Table 1 was melted in a converter and made into a slab (steel material) by a continuous casting method. These were heated, hot-rolled (coarse-rolled and finish-rolled), water-cooled, and wound under the conditions shown in Table 1, and then allowed to cool to obtain a hot-rolled steel sheet having a predetermined finished sheet thickness.
  • the hot-rolled steel sheet obtained in succession is formed into a cylindrical open pipe shape by roll forming, and after the butt portion is welded by electric stitching, the rolls arranged vertically and horizontally keep the shape cylindrical and a few percent in the pipe axis direction. A squeeze was added to obtain a cylindrical steel pipe.
  • a square steel pipe in which the curvature of the corner portion becomes (2.5 ⁇ 0.5) times the plate thickness is obtained through a two-stage sizing stand and then a four-stage square forming stand. Obtained.
  • the gap and the caliber curvature of the hole-shaped roll of the square forming stand were changed to control the contact width between the roll and the corner in the circumferential direction in the vicinity of the corner.
  • the contact width obtained from the condition of the caliber curvature of the gap of the pore-shaped roll set was calculated by using the structural analysis by the finite element method regarding the deformation from the cylindrical steel pipe to the square steel pipe. ..
  • ⁇ was calculated from the equation (1) (allowable ⁇ lower limit in Table 2), and the steel pipe was manufactured so as not to contact the range of the forming ⁇ .
  • the distance L1 from the position of the center of the flat plate portion of the pipe to the circumferential end of the contact portion was measured, and the molding ⁇ was calculated from the L1.
  • a test piece was collected from the obtained square steel pipe, and a microstructure observation, a tensile test, a Charpy impact test, and a hardness test were carried out.
  • the structure was observed using a scanning electron microscope (SEM) at a position t / 4 from the pipe surface (outer surface of the steel pipe) of the square steel pipe flat plate portion.
  • SEM scanning electron microscope
  • the area ratio obtained by observing the tissue was used as the volume fraction of each tissue. From the obtained SEM image, the area ratios of ferrite, pearlite, bainite and the residual structure were determined. Since it is difficult to distinguish between martensite and austenite in the SEM image, the area ratio of the tissue observed as martensite or austenite is measured from the obtained SEM image, and then the volume ratio of austenite measured by the method described later is subtracted. The value was taken as the volume ratio of martensite.
  • the observation sample was prepared so that the observation surface had a cross section in the rolling direction during hot rolling, polished, and then nital-corroded.
  • the magnification was 2000 times and the observation area was 2500 ⁇ m 2 .
  • Observation was performed in 5 or more visual fields, and the average value of the tissues obtained in each visual field was calculated as the area ratio.
  • ferrite is a product of diffusion transformation, and exhibits a structure with low dislocation density and almost recovery. This includes polygonal ferrite and pseudopolygonal ferrite. Bainite is a double-phase structure of lath-shaped ferrite and cementite with high dislocation density.
  • the volume fraction of austenite was measured by X-ray diffraction.
  • the sample for measurement was prepared by grinding so that the diffraction surface was at a position of t / 4 from the tube surface of the square steel pipe flat plate portion, and then performing chemical polishing to remove the surface processed layer.
  • the K ⁇ ray of Mo was used for the measurement, and the volume fraction of austenite was obtained from the integrated intensities of the (200), (220) and (311) planes of fcc iron and the (200) and (211) planes of bcc iron.
  • JIS No. 5 tensile test pieces and JIS No. 12B tensile test pieces were taken from the flat plate portion of the square steel pipe so that the tensile direction was parallel to the pipe axis direction, and these were used to comply with the regulations of JIS Z 2241.
  • the yield strength and tensile strength were measured, and the yield ratio defined by (yield strength) / (tensile strength) was calculated.
  • the number of test pieces was 3 each, and the average value thereof was used as a representative value.
  • the Charpy impact test was carried out according to JIS Z 2242 using a V-notch test piece collected so that the longitudinal direction of the test piece was parallel to the longitudinal direction of the pipe at the t / 4 position from the pipe surface at the corner of the square steel pipe. According to this, the test temperature was 0 ° C., and the absorbed energy (J) was determined. The number of test pieces was 3 each, and the average value thereof was used as a representative value. The case where the average value is 70 J or more is evaluated as ⁇ , and the case where the average value is less than 70 J is evaluated as x.
  • the position 1 mm inside from the outer surface and inner surface of the corner of the square steel pipe is specified by JIS Z2244: 2009 using a Micro Vickers hardness tester.
  • the test force was 9.8 N in accordance with the above.
  • the positions of the corners 1 mm inside from the outer surface and the inner surface refer to the positions within a range of 1 ⁇ 0.2 mm from the outer surface side and the inner surface side.
  • the hardness was measured at 5 points at each position, and the average value thereof was used as a representative value.
  • the roll-formed steel plate is electrosewn and welded to form an electrosewn steel pipe, but a seamless steel pipe may be formed into a cylindrical shape.

Abstract

Un but de la présente invention est de fournir : un tube carré en acier dans lequel il y a peu d'effet lors de l'usinage et du durcissement des coins et la fissuration de surface est supprimée ; un procédé de fabrication de ce dernier ; et une structure de construction qui utilise le tube en acier carré selon la présente invention.　La présente invention concerne un tube en acier carré comprenant des parties plates et des coins, les parties plates ayant une limite d'élasticité de 385 MPa ou plus, une résistance à la traction de 520 MPa ou plus et un rapport d'élasticité de 0,90 ou moins ; la dureté des coins est telle que le côté de surface interne des coins a une dureté Vickers supérieure à celle du côté de surface externe des coins, la dureté Vickers du côté de surface externe des coins étant inférieure ou égale à 280 HV et la différence entre la dureté Vickers du côté de surface externe des coins et la dureté Vickers du côté de surface interne des coins étant inférieure ou égale à 80 HV ; et l'énergie d'absorption Charpy vE0 du côté de surface externe des coins à 0 °C est de 70 J ou plus.
PCT/JP2020/013236 2019-04-08 2020-03-25 Tube carré en acier, son procédé de fabrication, et structure de construction WO2020209060A1 (fr)

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JP2020544049A JP6874913B2 (ja) 2019-04-08 2020-03-25 角形鋼管およびその製造方法ならびに建築構造物
CN202080026557.6A CN113677448B (zh) 2019-04-08 2020-03-25 方形钢管及其制造方法以及建筑构造物

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WO2023053837A1 (fr) * 2021-09-29 2023-04-06 Ｊｆｅスチール株式会社 Tuyau en acier rectangulaire et procédé de fabrication associé, feuille d'acier laminée à chaud et procédé de fabrication associé, et structure de construction

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KR102576184B1 (ko) 2023-01-26 2023-09-08 동양철관 주식회사 각형 강관의 제조방법
KR102591023B1 (ko) 2023-05-10 2023-10-19 동양철관 주식회사 각형 강관의 내측부 교정장치

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