WO2020209060A1 - Square steel tube, method for manufacturing same, and building structure - Google Patents

Square steel tube, method for manufacturing same, and building structure Download PDF

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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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steel pipe
square
corner
square steel
less
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PCT/JP2020/013236
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French (fr)
Japanese (ja)
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昌士 松本
晃英 松本
井手 信介
岡部 能知
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Jfeスチール株式会社
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Priority to JP2019-073314 priority
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Publication of WO2020209060A1 publication Critical patent/WO2020209060A1/en

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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/60Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21DWORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D5/00Bending sheet metal along straight lines, e.g. to form simple curves
    • B21D5/06Bending 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
    • B21D5/10Bending 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
    • B21D5/12Bending 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
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226Hot rolling
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D9/00Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/08Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/001Ferrous alloys, e.g. steel alloys containing N
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/06Ferrous alloys, e.g. steel alloys containing aluminium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • EFIXED CONSTRUCTIONS
    • E04BUILDING
    • E04BGENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
    • E04B1/00Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
    • E04B1/18Structures comprising elongated load-supporting parts, e.g. columns, girders, skeletons
    • E04B1/24Structures comprising elongated load-supporting parts, e.g. columns, girders, skeletons the supporting parts consisting of metal
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/002Bainite
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/005Ferrite
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips

Abstract

A purpose of the present invention is to provide: a square steel tube wherein there is little effect upon the machining and hardening of corners and surface cracking is suppressed; a method for manufacturing the same; and a building structure that uses the square steel tube according to the present invention. The present invention pertains to a square steel tube comprising flat parts and corners, wherein: the flat parts have a yield strength of 385 MPa or greater, a tensile strength of 520 MPa or greater, and a yield ratio of 0.90 or less; the hardness of the corners is such that the inner surface side of the corners has greater Vickers hardness than the outer surface side of the corners, the Vickers hardness of the outer surface side of the corners is 280 HV or less, and the difference between the Vickers hardness of the outer surface side of the corners and the Vickers hardness of the inner surface side of the corners is 80 HV or less; and and the Charpy absorption energy vE0 of the outer surface side of the corners at 0°C is 70 J or greater.

Description

角形鋼管およびその製造方法ならびに建築構造物Square steel pipe and its manufacturing method and building structure
 本発明は、特に工場、倉庫、商業施設などの大型建築物の建築部材に用いられる角形鋼管およびその製造方法ならびに建築構造物に関する。 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.
 近年、工場、倉庫、商業施設などの大型建築物に用いられる建築構造部材は、軽量化による施工コスト削減のため高強度化が進んでいる。特に建築物の柱材として用いられる角形鋼管においては、降伏強度が385MPa以上、引張強度が520MPa以上のものが求められており、さらに耐震性の観点から高い塑性変形能と優れた靱性も同時に必要となる。 In recent years, building structural members used in large buildings such as factories, warehouses, and commercial facilities have been increasing in strength to reduce construction costs by reducing weight. In particular, square steel pipes used as column materials for buildings are required to have a yield strength of 385 MPa or more and a tensile strength of 520 MPa or more, and from the viewpoint of earthquake resistance, high plastic deformability and excellent toughness are also required at the same time. It becomes.
 このような高い変形性能と優れた靱性をもった角形鋼管とは、具体的には、平板部の管軸方向降伏比(=降伏強度/引張強度)を0.90以下、0℃におけるシャルピー吸収エネルギーを70J以上とする必要がある。 A square steel pipe having such high deformation performance and excellent toughness specifically means that the flat plate portion has a yield ratio (= yield strength / tensile strength) in the pipe axis direction of 0.90 or less and Charpy absorption at 0 ° C. The energy needs to be 70J or more.
 角形鋼管は、一般に熱延鋼板(鋼帯)または厚鋼板を素材として、これらを冷間でプレス曲げ成形あるいはロール成形することにより製造される。 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.
 冷間でプレス曲げ成形により製造される角形鋼管は、厚鋼板をプレス曲げ成形により断面形状をロの字型あるいはコの字型となし、これらをサブマージアーク溶接により接合して製造される。また、ロール成形により製造される角形鋼管は、熱延鋼板をロール成形により円筒状のオープン管形状となし、その突合せ部分を電縫溶接した後、上下左右に配置されたロールにより円筒状のまま管軸方向に数%の絞りを加え、続けて角形に成形して製造される。 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. In addition, 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.
 一方で、冷間でプレス曲げ成形により製造される角形鋼管の場合、角部の曲げ変形による加工硬化が著しく、角部の靱性と塑性変形能が損なわれるため、耐震強度が悪化し、角部を起点に破壊しやすくなる。特にベイナイトなどの硬質の第2相を含む建築部材向け高強度材では加工硬化が顕著になる。 On the other hand, in the case of square steel pipes manufactured by cold press bending, work hardening due to bending deformation of the corners is remarkable, and the toughness and plastic deformability of the corners are impaired, resulting in deterioration of seismic strength and corners. It becomes easy to destroy from the starting point. In particular, work hardening becomes remarkable in high-strength materials for building members including the hard second phase such as bainite.
 そこで、高強度の角形鋼管を製造する場合には、成形時の角部の加工硬化による靱性の悪化の影響を小さくするような素材や、角部の加工硬化を抑制するような製造方法を選択する必要がある。 Therefore, when manufacturing high-strength square steel pipes, select a material that reduces the effect of deterioration of toughness due to work hardening of the corners during molding, and a manufacturing method that suppresses work hardening of the corners. There is a need to.
 特許文献1では、平板部のミクロ組織において、ベイナイト組織の面積分率:40%以上であることを特徴とする角形鋼管が提案されている。 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.
 特許文献2では、冷間成形により造管した後に全管ひずみ取り焼鈍を施すことを特徴とした低降伏比、高靱性の角形鋼管が提案されている。 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.
特許第5385760号公報Japanese Patent No. 5385760 特許第4957671号公報Japanese Patent No. 4957671
 特許文献1に記載の角形鋼管は角部表層部のビッカース硬さが350HV以下である。しかしながら、依然として角部表層部の硬さは大きく、角部を起点とした破壊や表面割れなどを抑制するには更なる硬さの減少が求められている。 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.
 また、特許文献2に記載の角形鋼管は造管後に熱処理を要するため、冷間加工ままの角形鋼管と比較してコストが非常に高くなる。 Further, since the square steel pipe described in Patent Document 2 requires heat treatment after the pipe is made, the cost is very high as compared with the square steel pipe as it is cold-worked.
 本発明は上記の事情を鑑みてなされたものであって、角部の加工硬化への影響が小さく、表面割れを抑制した角形鋼管およびその製造方法ならびに本発明の角形鋼管を用いた建築構造物を提供することを目的とする。 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.
 本発明者らは上記課題を解決すべく鋭意検討を行い、以下の知見を得た。 The present inventors conducted diligent studies to solve the above problems and obtained the following findings.
 ロール成形による角形鋼管の製造の角成形スタンドでは、成形ロールを用いて最終製品となる角形鋼管の平板部に該当する部位の曲率を小さくし、断面円筒形状から断面矩形形状になるように成形を行っている。これは、成形ロールが最終製品の角形鋼管の平板部の中心部に該当する箇所を押し込むようにして成形を行っており、角部は平板部の変形に追随するようにL型の角部を形成する。 In the square forming stand for manufacturing square steel pipes by roll forming, 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. Form.
 したがって、角部全体に直接ロールを接触せずとも曲率をもった角部を形成することは可能である。一方で、鋼管素材がロールと接触することにより、平板部の平坦度や角部の曲率などの寸法精度は向上するものの、ロールからのせん断力を受けるため、ロールとの接触部を中心とした加工硬化が発生することが明らかである。そのため、角部の過度な加工硬化を抑制するためには寸法精度と両立できるようにロールと角部の接触部を制御する必要がある。 Therefore, it is possible to form a curved corner without directly contacting the entire corner with the roll. On the other hand, when the steel pipe material comes into contact with the roll, the dimensional accuracy such as the flatness of the flat plate and the curvature of the corners is improved, but since it receives the shearing force from the roll, it is centered on the contact part with the roll. It is clear that work hardening occurs. Therefore, in order to suppress excessive work hardening of the corners, it is necessary to control the contact portion between the roll and the corners so as to be compatible with dimensional accuracy.
 本発明者らは、曲げ加工による加工硬化が小さい角形鋼管を得るためには、角部外表面側のビッカース硬さよりも角部内表面側のビッカース硬さの方が大きい角形鋼管が良いことがわかった。そして、角部外表面側のビッカース硬さよりも角部内表面側のビッカース硬さの方が大きい角形鋼管は、円筒鋼管から角形鋼管へ成形するときに、角成形時に角部近傍にロールが接触しないように、角成形中のロールギャップやロールのカリバー曲率を設定し、円筒鋼管から角形鋼管を成形することにより、得られる。これは、鋼管外表面の曲率変化は、鋼管内表面の曲率変化よりも小さいため、曲げ加工による加工硬化が小さく、かつ、ロールのせん断力の影響を受けにくいためと考えられる。 The present inventors have found that in order to obtain a square steel pipe with less work hardening due to bending, 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. When 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. It is considered that this is because the change in curvature of the outer surface of the steel pipe is smaller than the change in curvature of the inner surface of the steel pipe, so that work hardening due to bending is small and it is not easily affected by the shearing force of the roll.
 また、種々の角成形のロールギャップやロールのカリバー曲率を変更した成形を行い、角部の硬さを調査したところ、角部に直接ロールが接触していない場合でも、角部の直近までロールが接触している条件では角部表面の硬さが増加することを見出した。このことは、ロールとの接触により周方向にもせん断応力が作用するため、ロールとの接触部近傍では加工硬化が発生する。このせん断応力が作用する領域は、被成形材の剛性、すなわち、鋼管素材の肉厚(管厚)t、最終製品の辺長H(H、H)によって変化するということがわかった。 In addition, when the roll gap of various square moldings and the caliber curvature of the rolls were changed and the hardness of the corners was investigated, even if the rolls were not in direct contact with the corners, the rolls were rolled to the immediate vicinity of the corners. It was found that the hardness of the corner surface increases under the condition of contact. This means that shear stress also acts in the circumferential direction due to contact with the roll, so work hardening occurs in the vicinity of the contact portion with the roll. It was found that the region where this shear stress acts changes depending on the rigidity of the material to be formed, that is, the wall thickness (pipe thickness) t of the steel pipe material and the side length H (H 1 , H 2 ) of the final product.
 本発明は上記知見に基づくものであり、その特徴は以下の通りである。
[1]平板部と角部を有する角形鋼管において、前記平板部の降伏強度が385MPa以上および引張強度が520MPa以上ならびに降伏比が0.90以下であり、
前記角部のビッカース硬さは、角部外表面側のビッカース硬さよりも角部内表面側のビッカース硬さの方が大きく、前記角部外表面側のビッカース硬さが280HV以下であり、かつ前記角部外表面側のビッカース硬さと前記角部内表面側のビッカース硬さとの差が80HV以下であり、
角部外表面側の0℃のシャルピー吸収エネルギーvEが70J以上である角形鋼管。
[2]質量%で、C:0.04~0.50%、Si:2.0%以下、Mn:0.5~3.0%、P:0.10%以下、S:0.050%以下、Al:0.005~0.10%、N:0.010%以下を含有し、残部がFeおよび不可避的不純物からなる成分組成を有し、
かつ、管表面からt/4(tは管厚)の位置における鋼組織が、体積率で30%超のフェライトおよび10%以上のベイナイトを含み、かつフェライトとベイナイトの体積率の合計が70%以上95%以下であり、残部がパーライト、マルテンサイト、オーステナイトから選択される1種または2種以上からなる[1]に記載の角形鋼管。
[3]さらに、質量%で、Nb:0.005~0.150%、Ti:0.005~0.150%、V:0.005~0.150%のうちから選ばれた1種または2種以上を含有する[2]に記載の角形鋼管。
[4]さらに、質量%で、Cr:0.01~1.0%、Mo:0.01%~1.0%、Cu:0.01~0.50%、Ni:0.01~0.30%、Ca:0.0005~0.010%、B:0.0003~0.010%のうちから選ばれた1種または2種以上を含有する[2]または[3]に記載の角形鋼管。
[5][1]に記載の角形鋼管の製造方法であって、円筒形状へと成形した後、角形形状へと角成形を行う角形鋼管の製造方法において、前記角成形を行う角成形工程は、管軸方向に対して垂直な断面において、隣り合う辺長をそれぞれH(mm)およびH(mm)(H≦H)とし、HおよびHの中心位置から鋼管内部に向かって引いた直線同士が交わる交点を角形鋼管中央部としたとき、Hの中心位置から鋼管内部に向かって引いた直線上において、前記角形鋼管中央部から長辺方向に1/2(H-H)だけオフセットさせた点をオフセット点とし、オフセット点から角形鋼管の角部中央へ引いた直線と、オフセット点から角部の円弧部あるいは角形鋼管の平板部へ向かって引かれる直線とが成す中心角θが下記式(1)を満たす角形鋼管の製造方法。
The present invention is based on the above findings, and its features are as follows.
[1] In a square steel pipe having a flat plate portion and a square portion, the yield strength of the flat plate portion is 385 MPa or more, the tensile strength is 520 MPa or more, and 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, and 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.
A square steel pipe having a Charpy absorption energy vE 0 of 0 ° C. on the outer surface side of the corner portion of 70 J or more.
[2] In terms of mass%, 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, and the balance has a component composition consisting of Fe and unavoidable impurities.
In addition, 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.
[4] Further, in terms of mass%, Cr: 0.01 to 1.0%, Mo: 0.01% to 1.0%, Cu: 0.01 to 0.50%, Ni: 0.01 to 0. [2] or [3], which contains one or more selected from .30%, Ca: 0.0005 to 0.010%, and B: 0.0003 to 0.010%. Square steel pipe.
[5] In the method for manufacturing a square steel pipe according to [1], in which the square steel pipe is formed into a cylindrical shape and then squarely formed into a square shape, 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. when the intersection headed straight lines drawn intersects the square tube central portion, on a straight line drawn toward the steel tube inside from the center of the H 1, 1/2 from the square tube center portion in the long side direction (H The point offset by 2- H 1 ) is defined as the offset point, and the straight line drawn from the offset point to the center of the corner of the square steel pipe and the straight line drawn from the offset point toward the arc of the corner or the flat plate of the square steel pipe. A method for manufacturing a square steel pipe in which the central angle θ formed by the above satisfies the following equation (1).
Figure JPOXMLDOC01-appb-M000003
ただし、
:辺長(短辺)(mm)
:辺長(長辺)(mm)
t:管厚(mm)
である。
[6][2]~[4]のいずれかに記載の成分組成を有する鋼素材を加熱温度:1100~1300℃に加熱した後、粗圧延終了温度:850~1150℃とする粗圧延を施し、仕上圧延終了温度:750~850℃とする仕上圧延を施し、かつ粗圧延と仕上圧延の両方における930℃以下での合計圧下率が65%以上とし、次いで、板厚中心温度で冷却開始から冷却停止までの平均冷却速度が10~30℃/sとなる冷却速度で冷却停止温度:450~650℃まで冷却し巻取り、その後放冷し、続いてロール成形により、円筒形状へと成形した後、ロール成形した鋼板を電縫溶接して電縫鋼管とした後、前記電縫鋼管を角形鋼管へと角成形を行う角成形工程において、管軸方向に対して垂直な断面において、隣り合う辺長をそれぞれH(mm)およびH(mm)(H≦H)とし、HおよびHの中心位置から鋼管内部に向かって引いた直線同士が交わる交点を角形鋼管中央部としたとき、Hの中心位置から鋼管内部に向かって引いた直線上において、前記角形鋼管中央部から長辺方向に1/2(H-H)だけオフセットさせた点をオフセット点とし、オフセット点から角形鋼管の角部中央へ引いた直線と、オフセット点から角部の円弧部あるいは角形鋼管の平板部へ向かって引かれる直線とが成す中心角θが下記式(1)を満たす角形鋼管の製造方法。
Figure JPOXMLDOC01-appb-M000003
However,
H 1 : Side length (short side) (mm)
H 2 : Side length (long side) (mm)
t: Tube thickness (mm)
Is.
[6] 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. After that, 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. Then, on the straight line drawn from the center position of H 1 toward the inside of the steel pipe, the point offset from the center of the square steel pipe in the long side direction by 1/2 (H 2- H 1 ) is defined as the offset point. , The central angle θ formed by the straight line drawn from the offset point to the center of the corner of the square steel pipe and the straight line drawn from the offset point toward the arc portion of the corner or the flat plate portion of the square steel pipe satisfies the following equation (1). Manufacturing method of square steel pipe.
Figure JPOXMLDOC01-appb-M000004
ただし、
:辺長(短辺)(mm)
:辺長(長辺)(mm)
t:管厚(mm)
である。
[7][1]~[4]のいずれかに記載の角形鋼管を用いた建築構造物。
Figure JPOXMLDOC01-appb-M000004
However,
H 1 : Side length (short side) (mm)
H 2 : Side length (long side) (mm)
t: Tube thickness (mm)
Is.
[7] A building structure using the square steel pipe according to any one of [1] to [4].
 本発明の角形鋼管によれば、角部の加工硬化への影響が小さく、表面割れを抑制した角形鋼管を得られる。これにより、工場、倉庫、商業施設などの大型建築物の施工コスト削減に大きく貢献することができる。また、本発明の角形鋼管の製造方法によれば、冷間プレス曲げ成形と比較して生産性が高く短期間で高強度角形鋼管を製造することが可能となる。 According to the square steel pipe of the present invention, 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.
図1は、電縫鋼管の製造設備の一例を示す模式図である。FIG. 1 is a schematic view showing an example of an electric resistance welded steel pipe manufacturing facility. 図2は、角形鋼管の成形過程を示す模式図である。FIG. 2 is a schematic view showing a molding process of a square steel pipe. 図3は、角形鋼管の管軸方向に対して垂直な断面を示す模式図である。FIG. 3 is a schematic view showing a cross section of a square steel pipe perpendicular to the pipe axis direction. 図4は、本発明の角形鋼管を使用した建築構造物の一例を模式的に示す斜視図である。FIG. 4 is a perspective view schematically showing an example of a building structure using the square steel pipe of the present invention.
 本発明の角形鋼管は、平板部と角部を有しており、平板部の降伏強度(YS)が385MPa以上および引張強度(TS)が520MPa以上ならびに降伏比が0.90以下であり、角部のビッカース硬さは、角部外表面側のビッカース硬さよりも角部内表面側のビッカース硬さの方が大きく、角部外表面側のビッカース硬さが280HV以下であり、かつ角部外表面側のビッカース硬さと角部内表面側のビッカース硬さとの差が80HV以下であり、角部外表面側の0℃のシャルピー吸収エネルギーvEが70J以上であることを特徴とする。 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.
 角形鋼管は平板部よりも角部の方が大きく加工硬化する。特に、角部外表面は周方向への引張応力場となっているため、最終製品における角部の脆性破壊を抑制するために、角部外表面の靱性を確保する必要がある。すなわち、角部外表面において0℃のシャルピー吸収エネルギーvEは70J以上が求められるとともに、平板部の降伏強度(YS)が385MPa以上および引張強度(TS)が520MPa以上ならびに降伏比が0.90以下であることが求められる。 Square steel pipes are work-hardened larger at the corners than at the flat plates. In particular, since 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.
 また、本発明では、角部外表面側のビッカース硬さよりも角部内表面側のビッカース硬さの方が大きく、角部外表面側のビッカース硬さが280HV以下であり、かつ角部外表面側のビッカース硬さと角部内表面側のビッカース硬さとの差が80HV以下とする。本発明では、角部外表面側のビッカース硬さよりも角部内表面側のビッカース硬さの方が大きく、角部外表面側のビッカース硬さが280HV以下とすることにより、曲げ加工による加工硬化が小さい角形鋼管を得ることができる。角部外表面側のビッカース硬さが280HVを超えると、外表面側の加工硬化が進行しているため、角部の延性が著しく悪化する。また、曲げ変形により表面の加工硬化が大きな角部の靱性を確保するために、角部外表面側のビッカース硬さと角部内表面側のビッカース硬さとの差を80HV以下とする。角部外表面側のビッカース硬さと角部内表面側のビッカース硬さとの差が80HV超えの場合、角部内表面側の加工硬化が進展しており、角部内表面の残留応力が顕著になるため、後処理で施すめっきの割れなどに悪影響を及ぼす。 Further, in the present invention, 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. In the present invention, 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. When the Vickers hardness on the outer surface side of the corner exceeds 280 HV, work hardening on the outer surface side is progressing, so that the ductility of the corner is significantly deteriorated. Further, in order to secure the toughness of the corner portion where work hardening of the surface is large due to bending deformation, 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. When 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.
 なお、本発明における角部外表面側のビッカース硬さとは、角部外表面から1±0.2mm内部におけるビッカース硬さであり、角部内表面側のビッカース硬さとは、角部内表面から1±0.2mm内部におけるビッカース硬さのことをいう。 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.
 本発明の角形鋼管は、質量%で、C:0.04~0.50%、Si:2.0%以下、Mn:0.5~3.0%、P:0.10%以下、S:0.050%以下、Al:0.005~0.10%、N:0.010%以下を含み、残部がFeおよび不可避的不純物からなる成分組成を有し、管表面からt/4(tは管厚)の位置における鋼組織が、体積率で30%超のフェライトと、10%以上のベイナイトとを含み、フェライトとベイナイトの体積率の合計が70%以上95%以下であり、残部がパーライト、マルテンサイト、オーステナイトから選択される1種または2種以上からなることが好ましい。 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.
 本発明において、鋼素材の好ましい成分組成を限定した理由を以下に説明する。なお、本明細書において、特に断りがない限り、鋼組成を示す「%」は「質量%」である。 The reason for limiting the preferable component composition of the steel material in the present invention will be described below. In this specification, unless otherwise specified, "%" indicating the steel composition is "mass%".
 C:0.04~0.50%
 Cは固溶強化により鋼の強度を上昇させる元素である。また、Cはパーライトの生成を促進し、焼入れ性を高めてマルテンサイトの生成に寄与し、オーステナイトの安定化に寄与する元素であることから、硬質相の形成にも寄与する元素である。所望の強度を確保するために0.04%以上のCを含有することが好ましい。しかしながら、C含有量が0.50%を超えると硬質相の割合が高くなり靱性が低下し、また溶接性も悪化する。このため、C含有量は0.04%以上0.50%以下とすることが好ましい。より好ましくは、C含有量はC:0.12%超0.25%以下である。
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%以下
 Siは固溶強化により鋼の強度を上昇させる元素であり、必要に応じて含有できる。このような効果を得るためには、0.01%以上のSiの含有が好ましい。一方、Si含有量が2.0%を超えると溶接性が悪化する。このため、Si含有量は2.0%以下とすることが好ましい。より好ましくは、Si含有量は0.01%以上0.5%以下である。
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. In order to obtain such an effect, the content of Si is preferably 0.01% or more. On the other hand, if the Si content exceeds 2.0%, the weldability deteriorates. Therefore, 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は固溶強化により鋼の強度を上昇させる元素であり、またフェライト変態開始温度を低下させることで組織の微細化に寄与する元素である。所望の強度および組織を確保するために0.5%以上のMnを含有することが好ましい。しかしながら、Mn含有量が3.0%を超えると溶接性が悪化する。このため、Mn含有量は0.5%以上3.0%以下とすることが好ましい。より好ましくは、Mn含有量は0.5%以上2.0%以下である。
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%以下
 Pは、粒界に偏析し材料の不均質を招くため、不可避的不純物としてできるだけ低減することが好ましい。なお、含有する場合0.10%以下の含有量は許容できる。このため、P含有量は0.10%以下の範囲内とすることが好ましい。より好ましくは、P含有量は0.03%以下である。
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. When it is contained, 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%以下
 Sは、鋼中では通常、MnSとして存在するが、MnSは、熱間圧延工程で薄く延伸され、延性に悪影響を及ぼす。このため、本発明ではできるだけ低減することが好ましい。なお、含有する場合は0.050%以下の含有量は許容できる。このため、S含有量は0.050%以下とすることが好ましい。より好ましくは、S含有量は0.015%以下である。
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. When it is contained, 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:0.005~0.10%
 Alは、強力な脱酸剤として作用する元素である。このような効果を得るためには、0.005%以上のAlを含有することが好ましい。しかしながら、Al含有量が0.10%を超えると溶接性が悪化するとともに、アルミナ系介在物が多くなり、表面性状が悪化する。このため、Al含有量は0.005%以上0.10%以下とすることが好ましい。より好ましくは、Al含有量は0.010%以上0.07%以下である。
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%以下
 Nは、不可避的不純物であり、転位の運動を強固に固着することで靭性を低下させる作用を有する元素である。本発明では、Nは不純物としてできるだけ低減することが望ましい。なお、含有する場合は0.010%以下の含有量は許容できる。このため、N含有量は0.010%以下とすることが好ましい。より好ましくは、N含有量は0.0080%以下である。
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. In the present invention, it is desirable to reduce N as an impurity as much as possible. When it is contained, 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.
 上記の成分が本発明における電縫鋼管の鋼素材の基本の成分組成であるが、これらに加えてさらに、Nb:0.005~0.150%、Ti:0.005~0.150%、V:0.005~0.150%のうちから選ばれた1種または2種以上を含有させてもよい。 The above components are the basic composition of the steel material of the electric resistance pipe in the present invention, but in addition to these, 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:0.005~0.150%、Ti:0.005~0.150%、V:0.005~0.150%のうちから選ばれた1種または2種以上
 Nb、Ti、Vは、いずれも鋼中で微細な炭化物、窒化物を形成し、析出強化を通じて鋼の強度向上に寄与する元素であり、必要に応じて含有できる。このような効果を得るためには、Nb:0.005%以上、Ti:0.005%以上、V:0.005%以上の含有が好ましい。一方で、過度の含有は降伏比の上昇および靱性の低下を招く。このためNb、Ti、Vを含有する場合は、Nb:0.005~0.150%、Ti:0.005~0.150%、V:0.005~0.150%とする。好ましくは、Nb:0.008~0.10%、Ti:0.008~0.10%、V:0.008~0.10%である。
One or more selected from 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. In order to obtain such an effect, the content of Nb: 0.005% or more, Ti: 0.005% or more, and V: 0.005% or more is preferable. On the other hand, 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%. Preferably, Nb: 0.008 to 0.10%, Ti: 0.008 to 0.10%, V: 0.008 to 0.10%.
 上記に加えてさらに、Cr:0.01~1.0%、Mo:0.01~1.0%、Cu:0.01~0.50%、Ni:0.01~0.30%、Ca:0.0005%~0.010%、B:0.0003~0.010%のうちから選ばれた1種または2種以上を含有させてもよい。 In addition to the above, 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:0.01~1.0%、Mo:0.01~1.0%、Cu:0.01~0.50%、Ni:0.01~0.30%、Ca:0.0005~0.010%、B:0.0003~0.010%のうちから選ばれた1種または2種以上
 Cr、Mo、Cu、Niは、固溶強化により鋼の強度を上昇させる元素であり、またいずれも鋼の焼入れ性を高め、オーステナイトの安定化に寄与する元素であることから、硬質なマルテンサイトおよびオーステナイトの形成に寄与する元素であり、必要に応じて含有できる。このような効果を得るためには、Cr:0.01%以上、Mo:0.01%以上、Cu:0.01%以上、Ni:0.01%以上の含有が好ましい。一方で、過度の含有は靱性の低下および溶接性の悪化を招く。このためCr、Mo、Cu、Niを含有する場合は、Cr:0.01~1.0%、Mo:0.01~1.0%、Cu:0.01~0.50%、Ni:0.01~0.30%とする。好ましくは、Cr:0.1~0.5%、Mo:0.1~0.5%、Cu:0.1~0.40%、Ni:0.1~0.20%である。
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. On the other hand, excessive content causes a decrease in toughness and a deterioration in weldability. Therefore, when Cr, Mo, Cu, and Ni are contained, 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%. Preferably, 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は、熱間圧延工程で薄く延伸されるMnS等の硫化物を球状化することで鋼の靱性向上に寄与する元素であり、必要に応じて含有できる。このような効果を得るためには、0.0005%以上のCaを含有することが好ましい。しかしながら、Ca含有量が0.010%を超えると、鋼中にCa酸化物クラスターが形成され靱性が悪化する場合がある。このため、Caを含有する場合は、Ca含有量は0.0005~0.010%とする。好ましくは、Ca含有量は0.0010~0.0050%である。 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は、フェライト変態開始温度を低下させることで組織の微細化に寄与する元素である。このような効果を得るためには、0.0003%以上のBを含有することが好ましい。しかしながら、B含有量が0.010%を超えると降伏比が上昇する。このため、Bを含有する場合は、B含有量は0.0003~0.010%とする。好ましくは、B含有量は0.0005~0.0050%である。 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%.
 上記成分以外の残部はFeおよび不可避的不純物である。 The rest other than the above components are Fe and unavoidable impurities.
 次に、本発明の角形鋼管の好ましい鋼組織を限定した理由を説明する。 Next, the reason for limiting the preferable steel structure of the square steel pipe of the present invention will be described.
 本発明の角形鋼管は、管表面からt/4(tは管厚)の位置における鋼組織が、体積率で30%超のフェライトおよび10%以上のベイナイトを含み、かつフェライトとベイナイトの体積率の合計が70%以上95%以下であり、残部がパーライト、マルテンサイト、オーステナイトから選択される1種または2種以上からなることが好ましい。 In the square steel pipe of the present invention, 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.
 フェライトは軟質な組織であり、他の硬質な組織と混合させることで、鋼管素材の降伏比を低くする。このような効果を得るためには、30%超の体積率とすることが好ましい。 Ferrite has a soft structure, and by mixing it with other hard structures, the yield ratio of the steel pipe material is lowered. In order to obtain such an effect, the volume ratio is preferably more than 30%.
 また、ベイナイトは中間的な硬さを有する組織であり、鋼の強度を上昇させる。フェライトだけでは所望の降伏強度および引張強度が得られないため、10%以上の体積率とすることが好ましい。 In addition, 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.
 さらに、フェライトとベイナイトの体積率の合計が70%未満であると所望の降伏強度または降伏比が得られず、また、95%を超えると所望の降伏強度または降伏比が得られない。 Further, if the total volume fraction of ferrite and bainite is less than 70%, 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.
 残部は、パーライト、マルテンサイト、オーステナイトから選択される1種または2種以上からなることが好ましい。パーライト、マルテンサイト、オーステナイトは硬質な組織であり、特に鋼の引張強度を上昇させるとともに、軟質なフェライトと混合させることで鋼管素材の降伏比が低くなる。なお、このような効果を得るためには、合計で5%以上30%以下の体積率であることが好ましい。 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. In order to obtain such an effect, the total volume fraction is preferably 5% or more and 30% or less.
 なお、角形鋼管の鋼組織は鋼管幅方向に均一のため、角部、平板部のいずれの組織も本発明の範囲を満たす。また、管表面からt/4位置とは、t/4位置から±0.2mmの範囲も許容できる。また、管表面とは、管の外表面および内表面のいずれでも構わない。 Since 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. Further, the t / 4 position from the pipe surface can be within a range of ± 0.2 mm from the t / 4 position. Further, the pipe surface may be either the outer surface or the inner surface of the pipe.
 次に、本発明の角形鋼管の製造方法について説明する。 Next, the method for manufacturing the square steel pipe of the present invention will be described.
 本発明では、特に限定されないが、例えば、上記した化学成分を有するスラブ等の鋼素材を、1100~1300℃の温度に加熱した後、粗圧延終了温度:850~1150℃とする粗圧延を施し、仕上圧延終了温度:750~850℃とする仕上圧延を施し、かつ粗圧延と仕上圧延の両方における930℃以下での合計圧下率が65%以上となる熱延工程の後、板厚中心温度で冷却開始から冷却停止までの平均冷却速度が10~30℃/sとなる冷却速度で冷却停止温度:450~650℃まで冷却し巻取り、その後放冷する。なお、以下の製造方法の説明において、温度は特に断らない限り鋼素材や鋼板等の表面温度とする。この表面温度は、放射温度計等で測定することができる。また、平均冷却速度は特に断らない限り((冷却前の温度-冷却後の温度)/冷却時間)とする。また、冷却方法は、ノズルからの水の噴射等の水冷や、冷却ガスを噴射による冷却等で行われる。なお、熱延鋼板の両面が同条件で冷却されるように、鋼板両面に冷却操作を施すことが好ましい。また、これらの熱間圧延における鋼板の中心温度は特に指定はないが、今回、差分計算による非定常伝熱計算により算出する。具体的には鋼板の熱伝導率、比熱、密度などの材料の物性値を用いて、冷却水の水量密度および鋼板の外表面温度から求められる熱伝達係数を境界条件として計算を行う。 In the present invention, for example, 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. 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. At a cooling rate at which the average cooling rate from the start of cooling to the stop of cooling is 10 to 30 ° C./s, the material is cooled to a cooling stop temperature of 450 to 650 ° C., rolled up, and then allowed to cool. In the following description of the manufacturing method, 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. Further, 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.
 上記した成分組成を有する鋼素材の製造方法は特に限定されず、転炉、電気炉、真空溶解炉等の通常公知の溶製方法で溶製し、連続鋳造法等の通常公知の鋳造方法により、所望寸法に製造される。溶鋼にはさらに、取鍋精錬等の二次精錬を施してもよい。また、連続鋳造法に代えて、造塊-分塊圧延法を適用しても何ら問題はない。 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.
 加熱温度:1100~1300℃
 加熱温度が1100℃未満である場合、被圧延材の変形抵抗が大きくなり圧延が困難となる。一方、加熱温度が1300℃を超えると、オーステナイト粒が粗大化し、後の圧延において微細なオーステナイト粒が得られず、所望の熱延鋼板の靱性を確保することが困難となり、また粗大なベイナイトの生成を抑制することが困難となる。このため、熱間圧延工程における加熱温度は1100~1300℃であることが好ましい。
Heating temperature: 1100 to 1300 ° C
When the heating temperature is less than 1100 ° C., the deformation resistance of the material to be rolled becomes large and rolling becomes difficult. On the other hand, when the heating temperature exceeds 1300 ° C., the austenite grains become coarse, and fine austenite grains cannot be obtained in the subsequent rolling, it becomes difficult to secure the toughness of the desired hot-rolled steel sheet, and the coarse bainite It becomes difficult to suppress the production. Therefore, the heating temperature in the hot rolling step is preferably 1100 to 1300 ° C.
 粗圧延終了温度:850~1150℃
 粗圧延終了温度が850℃未満である場合、後の仕上圧延中に鋼板温度がフェライト変態開始温度以下になりフェライトが生成する危険性が増大する。生成したフェライトは、その後の圧延により圧延方向に伸長した加工フェライト粒となり、降伏比上昇の原因となる。一方、粗圧延終了温度が1150℃を超えると、オーステナイト未再結晶温度域での圧下量が不足し、微細なオーステナイト粒が得られず、所望の熱延鋼板の靱性を確保することが困難となり、また粗大なベイナイトの生成を抑制することが困難となる。このため、粗圧延終了温度は850~1150℃であることが好ましい。
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.
 仕上圧延終了温度:750~850℃
 仕上圧延終了温度が750℃未満である場合、圧延中に鋼板温度がフェライト変態開始温度以下になりフェライトが生成する危険性が高くなる。前記において生成したフェライトは、その後の圧延により圧延方向に伸長した加工フェライト粒となり、降伏比上昇の原因となる。一方、仕上圧延終了温度が850℃を超えると、オーステナイト未再結晶温度域での圧下量が不足し、微細なオーステナイト粒が得られず、所望の熱延鋼板の靱性を確保することが困難となり、また粗大なベイナイトの生成を抑制することが困難となる。このため、仕上圧延終了温度は750~850℃であることが好ましい。
Finish rolling end temperature: 750 to 850 ° C
When 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. On the other hand, when the finish rolling end temperature exceeds 850 ° 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 finish rolling end temperature is preferably 750 to 850 ° C.
 粗圧延と仕上圧延の両方における930℃以下での合計圧下率:65%以上
 本発明では、熱間圧延においてオーステナイト中のサブグレインを微細化することで、続く冷却、巻取工程において生成するフェライト、ベイナイトおよび残部組織を微細化し、所望の強度および靱性を有する熱延鋼板を得る。熱間圧延においてオーステナイト中のサブグレインを微細化するためには、オーステナイト未再結晶温度域での圧下率を高くし、十分な加工ひずみを導入する必要がある。前記を達成するため、粗圧延と仕上圧延の両方における930℃以下での合計圧下率を65%以上とした。粗圧延と仕上圧延の両方における930℃以下での合計圧下率が65%未満である場合、熱間圧延において十分な加工ひずみを導入することができないため、所望の靱性を有する組織が得られない。
Total rolling reduction at 930 ° C or lower in both rough rolling and finish rolling: 65% or more In the present invention, 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. In order to miniaturize the subgrains in austenite in hot rolling, it is necessary to increase the rolling reduction in the austenite unrecrystallized temperature range and introduce sufficient machining strain. In order to achieve the above, the total rolling reduction at 930 ° C. or lower in both rough rolling and finish rolling was set to 65% or more. When 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. ..
 冷却開始から冷却停止までの平均冷却速度:10~30℃/s
 冷却速度が10℃/s未満では、フェライトの核生成頻度が減少し、フェライト粒が粗大化するため、所望の強度や靱性を有する組織が得られない。一方で、冷却速度が30℃/sを超えると、鋼板のt/4の位置において多量のマルテンサイトが生成し、フェライトとベイナイトの体積率の合計が70%未満となる。
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%.
 冷却停止温度:450~650℃
 冷却停止温度が450℃未満では、鋼板のt/4の位置において多量のマルテンサイトが生成し、フェライトとベイナイトの体積率の合計が70%未満となる。一方で、冷却停止温度が650℃を超えると、フェライトの核生成頻度が減少し、フェライト粒が粗大化するとともに、ベイナイト変態開始温度を上回るためベイナイトの体積率を10%以上とすることができない。
Cooling stop temperature: 450-650 ° C
When 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%. On the other hand, when 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. ..
 次に、熱間圧延後の造管工程について説明する。 Next, the pipe making process after hot rolling will be described.
 電縫鋼管の素材である熱延鋼板(鋼帯)1を、図1に示すような製造設備を用いて電縫鋼管を製造する。例えば、熱延鋼板1をレベラー2による入側矯正を施した後、複数のロールからなるケージロール群3で中間成形されて円筒状のオープン管とされた後、複数のロールからなるフィンパスロール群4で仕上げ成形(ロール成形)される。仕上げ成形の後は、スクイズロール5で圧接しながら鋼帯1の幅端部を溶接機6で電気抵抗溶接して電縫鋼管7を得る。なお、本発明では、電縫鋼管7の製造設備は図1のような造管工程に限定されない。 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. For example, after 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. After the finish molding, 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. In the present invention, the manufacturing equipment for the electrosewn steel pipe 7 is not limited to the pipe making process as shown in FIG.
 その後、得られた電縫鋼管7を、上下左右に配置されたロールにより円筒状のまま管軸方向に数%の絞りを加え、続けて角形に成形して角形鋼管を得る。図2は、本発明の一実施形態における、角形鋼管の成形過程を示す模式図である。図2に示すように、電縫鋼管7は複数のロールからなるサイジングロール群(サイジングスタンド)8によって円筒形状のまま縮径された後、複数のロールからなる角成形ロール群(角成形スタンド)9によって、順次R1、R2、R3のような形状に成形され、角形鋼管10となる。角成形スタンドのロールは、カリバー曲率をもった孔型ロールであり、後段スタンドになるに従って、カリバー曲率半径が大きくなり、角形鋼管の平板部と角部を形成する。なお、サイジングロール群8および角成形ロール群9のスタンド数は特に制限されない。 After that, the obtained electrosewn steel pipe 7 is drawn into a cylindrical shape by a few percent in the direction of the pipe axis with rolls arranged vertically and horizontally, and subsequently formed into a square shape to obtain a square steel pipe. FIG. 2 is a schematic view showing a molding process of a square steel pipe according to an embodiment of the present invention. As shown in FIG. 2, 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.
 次に、本発明の角成形の製造条件について、説明する。 Next, the manufacturing conditions for square molding of the present invention will be described.
 ロール成形した後、溶接し、角成形して角鋼管を得る方法により成形される角形鋼管は、鋼板から一度、円筒形状に成形された後、角形形状へと成形される。このような製造方法では、周方向の曲げ変形だけではなく、絞り変形による長手方向のひずみが発生するため、結果として周方向の曲げの中立軸が外表面側へと移動し、内表面側の硬さが大きくなる。 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. In such a manufacturing method, not only bending deformation in the circumferential direction but also distortion in the longitudinal direction due to drawing deformation occurs. As a result, the neutral axis of bending in the circumferential direction moves to the outer surface side, and the inner surface side The hardness increases.
 前述したように、鋼管素材がロールと接触することにより、平板部の平坦度や角部の曲率などの寸法精度は向上するものの、ロールからのせん断力を受けるため、ロールとの接触部を中心とした加工硬化が発生することが明らかである。そのため、角部の過度な加工硬化を抑制するためには寸法精度と両立できるようにロールと角部の接触部を制御する必要がある。 As described above, when the steel pipe material comes into contact with the roll, the dimensional accuracy such as the flatness of the flat plate and the curvature of the corners is improved, but since it receives the shearing force from the roll, it is centered on the contact part with the roll. It is clear that work hardening occurs. Therefore, in order to suppress excessive work hardening of the corners, it is necessary to control the contact portion between the roll and the corners so as to be compatible with dimensional accuracy.
 そこで本発明者らは角成形時に角部近傍にロールが接触しないように、角成形中のロールギャップやロールのカリバー曲率を設定し、円筒鋼管から角形鋼管を成形した。その結果、図3に示すように、角成形工程において、管軸方向に対して垂直な断面において、隣り合う辺長をそれぞれH(mm)およびH(mm)(ただし、H≦Hであり、H、Hはそれぞれ最終製品の辺長である。)とし、HおよびHの中心位置から鋼管内部に向かって引いた直線同士が交わる交点を角形鋼管中央部としたとき、Hの中心位置から鋼管内部に向かって引いた直線上において、前記角形鋼管中央部から長辺方向に1/2(H-H)だけオフセットさせた点をオフセット点とし、オフセット点から角形鋼管の角部中央へ引いた直線と、オフセット点から角部の円弧部あるいは角形鋼管の平板部へ向かって引かれる直線とが成す中心角θが下記式(1)を満たすことにより、曲げ加工による加工硬化が小さく、表面割れを抑制できる。 Therefore, 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. As a result, as shown in FIG. 3, in the square forming step, in the cross section perpendicular to the pipe axis direction, 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. Then, on a straight line drawn from the center position of H 1 toward the inside of the 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 θ 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.
Figure JPOXMLDOC01-appb-M000005
ただし、
:辺長(短辺)(mm)
:辺長(長辺)(mm)
t:管厚(mm)
である。
Figure JPOXMLDOC01-appb-M000005
However,
H 1 : Side length (short side) (mm)
H 2 : Side length (long side) (mm)
t: Tube thickness (mm)
Is.
 角成形工程において、後段スタンド側では、ロールのカリバー曲率半径と、角形鋼管の平板部の曲率半径がほぼ同等の値になるため、後段スタンドでは孔型ロールと角形鋼管の周方向の接触幅が増加し、平板部中心側から角部側へと拡大しながら所望の角部寸法を得る。特に、角形鋼管の最終製品の肉厚である管厚tと辺長Hの比t/Hが大きくなると、変形の剛性が大きくなるため、より孔型ロールと角形鋼管の周方向の接触幅を角部近傍まで確保する必要がある。一方、角成形のときに、角形鋼管の角部へ直接孔型ロールを接触させて角成形を行った場合、孔型ロールのせん断力による角部の加工硬化が顕著になる。
このような過度な加工硬化が発生させずに、所望の角部の曲率半径を得るためには、角成形の全スタンドを通して、孔型ロールと角形鋼管が接触しない領域が、角部の頂点から肉厚に相当する周方向の距離までに制御する必要がある。その領域は角形鋼管の最終形状の角部中央を基準に、上記(1)を満たす鋼管外表面側の領域である。孔型ロールと角形鋼管の接触位置の制御方法としては、例えば孔型ロールのカリバー曲率半径やロール間ギャップを調整する方法などがあるが、この限りではない。
In the square forming process, 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. In particular, when 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, increases, 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. On the other hand, in the case of square forming, when the hole-shaped roll is brought into direct contact with the corner portion of the square steel pipe to perform square forming, the work hardening of the corner portion due to the shearing force of the hole-shaped roll becomes remarkable.
In order to obtain the desired radius of curvature of the corner without causing such excessive work hardening, 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. As a method of controlling the contact position between the hole roll and the square steel pipe, for example, there is a method of adjusting the radius of curvature of the caliber of the hole roll and the gap between the rolls, but the method is not limited to this.
 次に、本発明の角形鋼管を使用した建築構造物について説明する。 Next, a building structure using the square steel pipe of the present invention will be described.
 図4は、本発明の実施形態に係る建築構造物を模式的に示す斜視図である。図4に示すように、本実施形態の建築構造物は、本発明の角形鋼管10が複数立設され、柱材として用いられている。隣り合う角形鋼管10の間には、H形鋼等の鋼材からなる大梁11が複数架設されている。また、隣り合う大梁11の間には、H形鋼等の鋼材からなる小梁12が複数架設されている。角形鋼管10とダイアフラム13とを溶接し、それに大梁11となるH型鋼を溶接することによって、隣り合う角形鋼管10の間にH形鋼等の鋼材からなる大梁11が架設されている。また、壁等の取り付けのため、必要に応じて間柱14が設けられる。 FIG. 4 is a perspective view schematically showing a building structure according to an embodiment of the present invention. As shown in FIG. 4, in the building structure of the present embodiment, 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. Further, a plurality of small beams 12 made of a steel material such as H-shaped steel are erected between the adjacent large beams 11. By welding the square steel pipe 10 and the diaphragm 13 and welding the H-shaped steel to be the girder 11, the girder 11 made of a steel material such as H-shaped steel is erected between the adjacent square steel pipes 10. In addition, studs 14 are provided as needed for mounting walls and the like.
 本発明の建築構造物は、角部外表面側のビッカース硬さが小さい、すなわち加工硬化の影響が小さい本発明の角形鋼管10を使用するため、突合せ溶接の際に生じる角部熱影響部における応力解放による表面割れなどが生じにくい。 Since 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.
 以下、実施例に基づき、本発明についてさらに説明する。 Hereinafter, the present invention will be further described based on Examples.
 表1に示す成分組成を有する溶鋼を転炉で溶製し、連続鋳造法でスラブ(鋼素材)とした。これらを表1に示す条件で加熱、熱間圧延(粗圧延および仕上圧延)、水冷、巻取を施した後、放冷して所定の仕上げ板厚を有する熱延鋼板とした。続けて得られた熱延鋼板をロール成形により円筒状のオープン管形状となし、その突合せ部分を電縫溶接した後、上下左右に配置されたロールにより円筒状のまま管軸方向に数%の絞りを加えて、円筒鋼管を得た。 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.
Figure JPOXMLDOC01-appb-T000006
 続いて、得られた円筒鋼管から、2段のサイジングスタンドを経た後、4段の角成形スタンドを経て角部の曲率が板厚の(2.5±0.5)倍となる角形鋼管を得た。このとき、角成形において、角成形スタンドの孔型ロールのギャップやカリバー曲率を変更して、角部近傍におけるロールと角部の周方向の接触幅を制御した。各角成形スタンドにおける接触幅は、円筒鋼管から角形鋼管への変形に関する有限要素法による構造解析を用いて、設定している孔型ロールのギャップのカリバー曲率の条件から得られる接触幅を算出した。上記接触幅は、式(1)からθを算出し(表2中の許容θ下限)、成形θの範囲を接触しないように鋼管を製造した。なお、成形θは、管の平板部中央の位置から接触部の周方向端部までの距離L1を測定し、そのL1から成形θを算出した。
Figure JPOXMLDOC01-appb-T000006
Subsequently, from the obtained 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. At this time, in the square forming, 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. For the contact width at each square forming stand, 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. .. For the contact width, θ was calculated from the equation (1) (allowable θ lower limit in Table 2), and the steel pipe was manufactured so as not to contact the range of the forming θ. For the molding θ, 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 θ was calculated from the L1.
 得られた角形鋼管から試験片を採取して、組織観察、引張試験、シャルピー衝撃試験、硬さ試験を実施した。 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.
 組織観察は、走査型電子顕微鏡(SEM)を用いて角形鋼管平板部の管表面(鋼管外表面)からt/4の位置において行った。ここでは、組織観察により得られた面積率を、各組織の体積率とした。得られたSEM像から、フェライト、パーライト、ベイナイトおよび残部組織の面積率を求めた。なお、SEM像ではマルテンサイトとオーステナイトの識別が難しいため、得られたSEM像からマルテンサイトあるいはオーステナイトとして観察された組織の面積率を測定し、それから後述する方法で測定したオーステナイトの体積率を差し引いた値をマルテンサイトの体積率とした。観察用試料は、観察面が熱間圧延時の圧延方向断面となるように採取し、研磨した後、ナイタール腐食して作製した。観察条件として、倍率を2000倍とし、観察面積は2500μmとした。5視野以上観察を行い、各視野で得られた組織の平均値を面積率として算出した。 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. Here, 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. As the observation conditions, the magnification was 2000 times and the observation area was 2500 μm 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.
 ここで、フェライトは拡散変態による生成物のことであり、転位密度が低くほぼ回復した組織を呈する。ポリゴナルフェライトおよび擬ポリゴナルフェライトがこれに含まれる。また、ベイナイトは転位密度が高いラス状のフェライトとセメンタイトの複相組織である。 Here, 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.
 オーステナイトの体積率測定は、X線回折により行った。測定用試料は、回折面が角形鋼管平板部の管表面からt/4の位置となるように研削した後、化学研磨をして表面加工層を除去して作製した。測定にはMoのKα線を使用し、fcc鉄の(200)、(220)、(311)面とbcc鉄の(200)、(211)面の積分強度からオーステナイトの体積率を求めた。 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 Kα 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.
 引張試験は、引張方向が管軸方向と平行になるように、角形鋼管の平板部からJIS5号引張試験片およびJIS12B号引張試験片をそれぞれ採取し、これらを用いてJIS Z 2241の規定に準拠して実施し、降伏強度、引張強度を測定し、(降伏強度)/(引張強度)で定義される降伏比を算出した。試験片本数は各3本とし、それらの平均値を代表値とした。 In the tensile test, 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.
 シャルピー衝撃試験は、角形鋼管の角部の管表面からt/4位置において試験片長手方向が管の長手方向と平行となるように採取したVノッチ試験片を用いて、JIS Z 2242の規定に準拠して、試験温度:0℃で実施し、吸収エネルギー(J)を求めた。なお、試験片本数は各3本とし、それらの平均値を代表値とした。平均値が70J以上となる場合を○、70J未満となる場合を×とした。 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.
 硬さ試験は、管軸方向に対して垂直な断面において、角形鋼管の角部の外表面および内表面から1mm内側の位置を、マイクロビッカース硬さ試験機を用いて、JIS Z2244:2009の規定に準拠して、試験力9.8Nで行った。ここで角部の外表面および内表面からの1mm内側の位置とは、外表面側、内表面側から1±0.2mmの範囲の位置のことを指す。それぞれの位置で硬さを各5点測定し、それらの平均値を代表値とした。 In the hardness test, in a cross section perpendicular to the pipe axis direction, 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. Here, 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.
 また、表面割れについては、得られた角形鋼管を用いて、柱-通しダイアフラム溶接継手の溶接実験を行った。溶接条件は溶接ワイヤJISZ3312 GJ59JA1UC3M1T、入熱条件40kJ/cm以下、パス間温度350℃以下とし、7層9パスにて行った。溶接後、溶接部周辺において鋼材表面の割れ発生の有無を判定した。 For surface cracks, a welding experiment was conducted on a column-through diaphragm welded joint using the obtained square steel pipe. Welding conditions were welding wire JISZ3312 GJ59JA1UC3M1T, heat input condition 40 kJ / cm or less, inter-pass temperature 350 ° C. or less, and 7 layers and 9 passes were used. After welding, the presence or absence of cracks on the steel surface was determined around the weld.
 これらの結果を表2に示す。 Table 2 shows these results.
 表2から、本発明例はいずれも、靱性に優れるとともに、表面割れが起こっていない。 From Table 2, all of the examples of the present invention have excellent toughness and no surface cracks have occurred.
 以上から、角成形条件を本発明の範囲内とすることで、大型建築物の建築部材等に用いられる、靱性に優れるとともに表面割れを抑制した角形鋼管を提供することができる。なお、本実施例では、ロール成形した鋼板を電縫溶接して電縫鋼管とする態様で説明したが、円筒形状へと成形するのは、シームレス鋼管であってもよい。 From the above, by setting the square forming conditions within the scope of the present invention, it is possible to provide a square steel pipe having excellent toughness and suppressing surface cracking, which is used for building members of large buildings and the like. In this embodiment, 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.
Figure JPOXMLDOC01-appb-T000007
Figure JPOXMLDOC01-appb-T000007
 1  鋼帯
 2  レベラー
 3  ケージロール群
 4  フィンパスロール群
 5  スクイズロール
 6  溶接機
 7  電縫鋼管
 8  サイジングロール群
 9  角成形ロール群
 10 角形鋼管
 11 大梁
 12 小梁
 13 ダイアフラム
 14 間柱
 H 辺長(短辺)
 H 辺長(長辺)
 θ  Hの中心位置から鋼管内部に向かって引いた直線上において、角形鋼管中央部から長辺方向に1/2(H-H)だけオフセットさせた点をオフセット点とし、オフセット点から角形鋼管の角部中央へ引いた直線と、オフセット点から角部の円弧部と直線部との接続点に向かって引かれる線で定まる中心角
 t  管厚
1 Steel strip 2 Leveler 3 Cage roll group 4 Finpass roll group 5 Squeeze roll 6 Welder 7 Electric sewn steel pipe 8 Sizing roll group 9 Square forming roll group 10 Square steel pipe 11 Large beam 12 Small beam 13 Diaphragm 14 Stud H 1 Side length ( short side)
H 2 side length (long side)
On a straight line drawn from the center position of θ H 1 toward the inside of the steel pipe, the point offset from the center of the square steel pipe in the long side direction by 1/2 (H 2- H 1 ) is defined as the offset point, and from the offset point. Central angle t pipe thickness determined by the straight line drawn to the center of the corner of the square steel pipe and the line drawn from the offset point toward the connection point between the arc and straight line of the corner.

Claims (7)

  1.  平板部と角部を有する角形鋼管において、前記平板部の降伏強度が385MPa以上および引張強度が520MPa以上ならびに降伏比が0.90以下であり、
    前記角部のビッカース硬さは、角部外表面側のビッカース硬さよりも角部内表面側のビッカース硬さの方が大きく、前記角部外表面側のビッカース硬さが280HV以下であり、かつ前記角部外表面側のビッカース硬さと前記角部内表面側のビッカース硬さとの差が80HV以下であり、
    角部外表面側の0℃のシャルピー吸収エネルギーvEが70J以上である角形鋼管。
    In a square steel pipe having a flat plate portion and a square portion, the yield strength of the flat plate portion is 385 MPa or more, the tensile strength is 520 MPa or more, and 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, and 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.
    A square steel pipe having a Charpy absorption energy vE 0 of 0 ° C. on the outer surface side of the corner portion of 70 J or more.
  2.  質量%で、C:0.04~0.50%、
    Si:2.0%以下、
    Mn:0.5~3.0%、
    P:0.10%以下、
    S:0.050%以下、
    Al:0.005~0.10%、
    N:0.010%以下を含有し、残部がFeおよび不可避的不純物からなる成分組成を有し、
    かつ、管表面からt/4(tは管厚)の位置における鋼組織が、体積率で30%超のフェライトおよび10%以上のベイナイトを含み、かつフェライトとベイナイトの体積率の合計が70%以上95%以下であり、残部がパーライト、マルテンサイト、オーステナイトから選択される1種または2種以上からなる請求項1に記載の角形鋼管。
    By mass%, C: 0.04 to 0.50%,
    Si: 2.0% or less,
    Mn: 0.5-3.0%,
    P: 0.10% or less,
    S: 0.050% or less,
    Al: 0.005 to 0.10%,
    N: Contains 0.010% or less, and has a component composition in which the balance is composed of Fe and unavoidable impurities.
    In addition, 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 claim 1, wherein the ratio is 95% or more and the balance is one or more selected from pearlite, martensite, and austenite.
  3.  さらに、質量%で、Nb:0.005~0.150%、
    Ti:0.005~0.150%、
    V:0.005~0.150%のうちから選ばれた1種または2種以上を含有する請求項2に記載の角形鋼管。
    Further, in mass%, Nb: 0.005 to 0.150%,
    Ti: 0.005 to 0.150%,
    V: The square steel pipe according to claim 2, which contains one or more selected from 0.005 to 0.150%.
  4.  さらに、質量%で、Cr:0.01~1.0%、
    Mo:0.01%~1.0%、
    Cu:0.01~0.50%、
    Ni:0.01~0.30%、
    Ca:0.0005~0.010%、
    B:0.0003~0.010%のうちから選ばれた1種または2種以上を含有する請求項2または3に記載の角形鋼管。
    Further, in mass%, Cr: 0.01 to 1.0%,
    Mo: 0.01% -1.0%,
    Cu: 0.01-0.50%,
    Ni: 0.01-0.30%,
    Ca: 0.0005-0.010%,
    B: The square steel pipe according to claim 2 or 3, which contains one or more selected from 0.0003 to 0.010%.
  5.  請求項1に記載の角形鋼管の製造方法であって、円筒形状へと成形した後、角形形状へと角成形を行う角形鋼管の製造方法において、前記角成形を行う角成形工程は、管軸方向に対して垂直な断面において、隣り合う辺長をそれぞれH(mm)およびH(mm)(H≦H)とし、HおよびHの中心位置から鋼管内部に向かって引いた直線同士が交わる交点を角形鋼管中央部としたとき、Hの中心位置から鋼管内部に向かって引いた直線上において、前記角形鋼管中央部から長辺方向に1/2(H-H)だけオフセットさせた点をオフセット点とし、オフセット点から角形鋼管の角部中央へ引いた直線と、オフセット点から角部の円弧部あるいは角形鋼管の平板部へ向かって引かれる直線とが成す中心角θが下記式(1)を満たす角形鋼管の製造方法。
    Figure JPOXMLDOC01-appb-M000001
    ただし、
    :辺長(短辺)(mm)
    :辺長(長辺)(mm)
    t:管厚(mm)
    である。
    In the method for manufacturing a square steel pipe according to claim 1, in the method for manufacturing a square steel pipe in which a square steel pipe is formed into a cylindrical shape and then squarely formed into a square shape, the square forming step of performing the square forming is a pipe shaft. In the cross section perpendicular to the direction, the adjacent side lengths are H 1 (mm) and H 2 (mm) (H 1 ≤ H 2 ), respectively, and the pipe is pulled from the center position of H 1 and H 2 toward the inside of the steel pipe. when in the straight lines intersect the intersection was RHS central, on a straight line drawn toward the steel tube inside from the center of the H 1, 1/2 from the square tube center portion in the long side direction (H 2 -H The point offset by 1 ) is defined as the offset point, and a straight line drawn from the offset point to the center of the corner of the square steel pipe and a straight line drawn from the offset point toward the arc portion of the corner or the flat plate portion of the square steel pipe are formed. A method for manufacturing a square steel pipe having a central angle θ satisfying the following formula (1).
    Figure JPOXMLDOC01-appb-M000001
    However,
    H 1 : Side length (short side) (mm)
    H 2 : Side length (long side) (mm)
    t: Tube thickness (mm)
    Is.
  6.  請求項2~4のいずれかに記載の成分組成を有する鋼素材を加熱温度:1100~1300℃に加熱した後、粗圧延終了温度:850~1150℃とする粗圧延を施し、仕上圧延終了温度:750~850℃とする仕上圧延を施し、かつ粗圧延と仕上圧延の両方における930℃以下での合計圧下率が65%以上とし、次いで、板厚中心温度で冷却開始から冷却停止までの平均冷却速度が10~30℃/sとなる冷却速度で冷却停止温度:450~650℃まで冷却し巻取り、その後放冷し、続いてロール成形により、円筒形状へと成形した後、ロール成形した鋼板を電縫溶接して電縫鋼管とした後、前記電縫鋼管を角形鋼管へと角成形を行う角成形工程において、管軸方向に対して垂直な断面において、隣り合う辺長をそれぞれH(mm)およびH(mm)(H≦H)とし、HおよびHの中心位置から鋼管内部に向かって引いた直線同士が交わる交点を角形鋼管中央部としたとき、Hの中心位置から鋼管内部に向かって引いた直線上において、前記角形鋼管中央部から長辺方向に1/2(H-H)だけオフセットさせた点をオフセット点とし、オフセット点から角形鋼管の角部中央へ引いた直線と、オフセット点から角部の円弧部あるいは角形鋼管の平板部へ向かって引かれる直線とが成す中心角θが下記式(1)を満たす角形鋼管の製造方法。
    Figure JPOXMLDOC01-appb-M000002
    ただし、
    :辺長(短辺)(mm)
    :辺長(長辺)(mm)
    t:管厚(mm)
    である。
    A steel material having the component composition according to any one of claims 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. to achieve a finish rolling end temperature. : Finish rolling at 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 the average from the start of cooling to the stop of cooling at the center temperature of the plate thickness. Cooling stop temperature: 450 to 650 ° C at a cooling rate of 10 to 30 ° C / s, winding, allowing to cool, and then roll forming into a cylindrical shape and then roll forming. In a square forming step in which a steel plate is electrosewn to form an electrosewn steel pipe and then the electrosewn steel pipe is square-formed into a square steel pipe, adjacent side lengths are set to H in a cross section perpendicular to the pipe axis direction. When 1 (mm) and H 2 (mm) (H 1 ≤ H 2 ) are set 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 central part of the square steel pipe, H on a straight line drawn toward the steel tube inside the first center position, a point from the RHS central portion is offset by 1/2 (H 2 -H 1) in the longitudinal direction and the offset point, rectangular from the offset point A method for manufacturing a square steel pipe in which the central angle θ formed by a straight line drawn to the center of the corner of the steel pipe and a straight line drawn from the offset point toward the arc portion of the corner or the flat plate portion of the square steel pipe satisfies the following equation (1). ..
    Figure JPOXMLDOC01-appb-M000002
    However,
    H 1 : Side length (short side) (mm)
    H 2 : Side length (long side) (mm)
    t: Tube thickness (mm)
    Is.
  7.  請求項1~4のいずれかに記載の角形鋼管を用いた建築構造物。 A building structure using the square steel pipe according to any one of claims 1 to 4.
PCT/JP2020/013236 2019-04-08 2020-03-25 Square steel tube, method for manufacturing same, and building structure WO2020209060A1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011094214A (en) * 2009-10-30 2011-05-12 Kobe Steel Ltd Cold-formed square steel tube having excellent earthquake resistance
JP2016011439A (en) * 2014-06-27 2016-01-21 新日鐵住金株式会社 Thick steel plate for cold press molding rectangular steel tube, cold press molding rectangular steel tube and weld joint
JP2017078196A (en) * 2015-10-20 2017-04-27 Jfeスチール株式会社 Production method of thick hot rolled steel strip for steel tube and production method of square steel tube
JP2018053281A (en) * 2016-09-27 2018-04-05 新日鐵住金株式会社 Rectangular steel tube
WO2020039980A1 (en) * 2018-08-23 2020-02-27 Jfeスチール株式会社 Square steel pipe, manufacturing method thereof, and building structure

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4278149B2 (en) * 2003-03-18 2009-06-10 Jfeスチール株式会社 Shaped steel and wall body using the shaped steel
JP4957671B2 (en) 2008-07-10 2012-06-20 住友金属工業株式会社 Steel pipes for low yield ratio columns for construction, steel plates used therefor, and methods for producing them
JP5594165B2 (en) * 2011-01-28 2014-09-24 Jfeスチール株式会社 Manufacturing method of thick hot rolled steel sheet for square steel pipes for building structural members
JP6565887B2 (en) * 2016-12-12 2019-08-28 Jfeスチール株式会社 Method for producing hot rolled steel sheet for low yield ratio square steel pipe and method for producing low yield ratio square steel pipe

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011094214A (en) * 2009-10-30 2011-05-12 Kobe Steel Ltd Cold-formed square steel tube having excellent earthquake resistance
JP2016011439A (en) * 2014-06-27 2016-01-21 新日鐵住金株式会社 Thick steel plate for cold press molding rectangular steel tube, cold press molding rectangular steel tube and weld joint
JP2017078196A (en) * 2015-10-20 2017-04-27 Jfeスチール株式会社 Production method of thick hot rolled steel strip for steel tube and production method of square steel tube
JP2018053281A (en) * 2016-09-27 2018-04-05 新日鐵住金株式会社 Rectangular steel tube
WO2020039980A1 (en) * 2018-08-23 2020-02-27 Jfeスチール株式会社 Square steel pipe, manufacturing method thereof, and building structure

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