JP2004330222A - Square steel pipe and manufacturing method for square steel pipe - Google Patents

Square steel pipe and manufacturing method for square steel pipe Download PDF

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Publication number
JP2004330222A
JP2004330222A JP2003126810A JP2003126810A JP2004330222A JP 2004330222 A JP2004330222 A JP 2004330222A JP 2003126810 A JP2003126810 A JP 2003126810A JP 2003126810 A JP2003126810 A JP 2003126810A JP 2004330222 A JP2004330222 A JP 2004330222A
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Japan
Prior art keywords
steel pipe
square steel
semi
hot
forming
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JP2003126810A
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Japanese (ja)
Inventor
Shin Nakajima
伸 中島
教雄 中島
Hiroshi Nakajima
拓 中島
Norio Nakajima
功雄 中島
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Nakajima Steel Pipe Co Ltd
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Nakajima Steel Pipe Co Ltd
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Priority to JP2003126810A priority Critical patent/JP2004330222A/en
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a square steel pipe in which proof strength and toughness are improved while keeping effects generated by hot forming. <P>SOLUTION: A semi-formed square steel pipe 5 is formed by welding after folding a steel plate 1 containing vanadium V as a chemical component. The square steel pipe is obtained by hot-forming the semi-formed square pipe 5 at the vicinity of an A<SB>3</SB>transformation point and then cooling it. The heated semi-formed square steel pipe can be hot-formed so as to be finished into the regular size and shape. The shape of each corner part, namely, the outer peripheral radius of the square steel pipe is formed in a uniform shape sharply. The square steel pipe can obtain high buckle strength with almost no residual stress by the hot forming. It has excellent secondary weldability. The square steel pipe has the improved proof strength and toughness by using the steel plate containing vanadium. The square steel pipe with the thinner plate thickness and the smaller size or the like can be adopted while obtaining sufficient design strength corresponding to the architecture. As a result, the reduction of weight and costs can be realized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【0001】
【発明の属する技術分野】
本発明は、たとえば建築用の柱材に使用される大径で厚肉の角形鋼管(正方体形状、直方体形状、五角形や六角形などの多角形状)、および角形鋼管を得るのに採用される角形鋼管の製造方法に関するものである。
【0002】
【従来の技術】
従来、この種の角形鋼管の製造方法としては、プレス成形機により平板素材(鋼板)の複数箇所をプレス成形し、シーム溶接を行うことで多角中空鋼管を形成する。そして多角中空鋼管を加熱炉内に搬入し、この加熱炉内での搬送中に高温加熱したのち、角形鋼管成形機に搬入して熱間成形を行っている(たとえば、特許文献1参照。)。
【0003】
また鋼板としては、重量%で0.01〜0.10%のバナジウムを含有している鋼を熱間圧延して得、この鋼板を冷間で曲げ加工したのち、継ぎ目部を溶接して鋼管とし、この鋼管を再加熱し冷却することで焼鈍しを行っている(たとえば、特許文献2参照。)。
【0004】
【特許文献1】
特開平9−99324号公報(第3頁、第1−4図)
【0005】
【特許文献2】
特開平7−150247号公報(第1頁)
【0006】
【発明が解決しようとする課題】
上記した特許文献1の角形鋼管によると、加熱した半成形角形鋼管を成形手段によって、正規の寸法かつ形状とした角形鋼管(最終製品)に仕上がるように熱間成形できる。その際に半成形角形鋼管は、全体がA変態点の近辺に加熱されていることから、角形鋼管は、各コーナ部の形状、すなわち外周半径を均等状にかつシャープに形成できる。さらに熱間成形によって角形鋼管は、残留応力が殆どなくて高い座屈強度が得られるとともに、二次溶接性に優れ、かつ充分な靭性を有するものにできる、などの効果を期待できる。
【0007】
ここで平板素材(鋼板)としては、通常、鉄(Fe)に複数の化学成分が、以下の重量%で添加されることで形成されている。すなわち、カーボン(C)が0.20%以下、シリコン(Si)が0.55%以下、マンガン(Mn)が0.60〜1.60%、リン(P)が0.03%以下、サルファ(S)が0.15%以下として添加され、残りのほぼ全てが鉄(Fe)として形成されている。
【0008】
しかし、このような平板素材を熱間成形して得た角形鋼管は、後述する機械的性質の比較からも明らかなように、その降伏点または耐力は235〜355(N/mm)であり、したがって、建築に応じて充分な設計基準強度(F値)を得るためには、その板厚が厚いもの、サイズの大きいものなどを採用しなければならず、重量が大に、かつ高価となる。
【0009】
また、特許文献2の鋼管によると、熱間成形を行わないことから、上述した熱間成形による効果は期待できない。
そこで本発明のうち請求項1記載の発明は、熱間成形による効果を保ちながらも、耐力と靭性とを向上し得る角形鋼管を提供することを目的としたものである。
【0010】
また請求項2記載の発明は、請求項1記載の角形鋼管を容易に製造し得る角形鋼管の製造方法を提供することを目的としたものである。
【0011】
【課題を解決するための手段】
前述した目的を達成するために、本発明の請求項1記載の角形鋼管は、化学成分としてバナジウムを添加している鋼板を折り曲げ加工したのち溶接して半成形角形鋼管とし、この半成形角形鋼管をA変態点の近辺に加熱して熱間成形したのち、冷却して得たことを特徴としたものである。
【0012】
したがって請求項1の発明によると、加熱した半成形角形鋼管を正規の寸法かつ形状に仕上がるように熱間成形し得、その際に、半成形角形鋼管の全体をA変態点の近辺に加熱していることから、角形鋼管は、各コーナ部の形状、すなわち外周半径を均等状にかつシャープに形成し得る。さらに熱間成形によって角形鋼管は、残留応力が殆どなくて高い座屈強度が得られるとともに、二次溶接性に優れたものとなる。しかも、化学成分としてバナジウムを添加している鋼板を使用したことで、耐力と靭性とを向上した角形鋼管とし得る。
【0013】
また本発明の請求項2記載の角形鋼管の製造方法は、化学成分としてバナジウムを添加して得た鋼板を折り曲げ加工したのち溶接して半成形角形鋼管とし、この半成形角形鋼管を加熱手段によってA変態点の近辺に加熱したのち、成形手段によって熱間成形し、そして冷却することで角形鋼管を得ることを特徴としたものである。
【0014】
したがって請求項2の発明によると、加熱手段によってA変態点の近辺に加熱した半成形角形鋼管を、成形手段によって正規の寸法かつ形状に仕上がるように熱間成形し得る。
【0015】
そして本発明の請求項3記載の角形鋼管の製造方法は、上記した請求項2記載の構成において、重量%で0.01〜0.10%のバナジウムを添加することを特徴としたものである。
【0016】
したがって請求項3の発明によると、バナジウムを最も好適に添加し得る。
【0017】
【発明の実施の形態】
以下に、本発明の実施の形態を説明する。ここで、使用される鋼板1は、鉄(Fe)に複数の化学成分が、以下の重量%で添加されることで形成されている。すなわち、カーボン(C)が0.20%以下、シリコン(Si)が0.55%以下、マンガン(Mn)が0.60〜1.60%、バナジウム(V)が0.01〜0.10%、リン(P)が0.03%以下、サルファ(S)が0.15%以下として添加され、残りのほぼ全てが鉄(Fe)として形成されている。
【0018】
次に、上記した成分からなる鋼板1を採用して、大径、厚肉でかつ正方体形状の角形鋼管を得る実施の形態を、図1〜図5に基づいて説明する。
図1に示すように、所定長さの鋼板1を長さ方向1Aに搬送し、トリミング開先加工機10に通して幅方向1Bにおける両側縁に開先2を加工する。次いで、鋼板1を前段成形プレス11に入れて、下金型12に対する上金型13の昇降動により、側縁寄りの二箇所に直角状(90度またはほぼ90度)のコーナ部3,3を折り曲げ成形する。その後、後段成形プレス14に入れて、下金型15に対する上金型16の昇降動により、中間の二箇所に鈍角(約105度)のコーナ部4,4を折り曲げ成形する。
【0019】
そして図2に示すように、仮付け溶接機17の部分で、四辺をロール18群(またはシリンダー)により外側から加圧することで、鈍角のコーナ部4,4を直角状のコーナ部6に成形しながら開先2どうしを突き合わせして、半成形角形鋼管5としながら、突き合わせ部に対して仮付け溶接7aを施工する。次いで、半成形角形鋼管5を内面溶接機19に移して内面溶接7bを施工する。さらに、半成形角形鋼管5を外面溶接機20に移して外面溶接7cを施工し、以て一辺に突き合わせ溶接部(シーム溶接部)7を有し、かつ各コーナ部6が直角状の大径で厚肉の半成形角形鋼管5を造管し得る。
【0020】
ここで半成形角形鋼管5は、後述する角形鋼管(最終製品)よりも寸法や形状を大きくして造管している。すなわち、対向された辺の外面間の寸法LLや各コーナ部6の外周半径LRを大きくして造管されている(図4参照)。
【0021】
この半成形角形鋼管5は、図3〜図5に示すように、搬入床23に渡されて搬送される。この搬入床23の終端部に搬送された半成形角形鋼管5は、ローラコンベヤ(搬送手段の一例。)24に渡され、このローラコンベヤ24により形成される搬送経路25上で搬送される。
【0022】
この搬送経路25中には、前記半成形角形鋼管5をA変態点(たとえば850〜1050℃)の近辺(前後)にまで全体加熱する加熱手段31と、加熱された半成形角形鋼管5を正規の寸法かつ形状に熱間成形する成形手段41とが配設されている。
【0023】
すなわち加熱手段31は、半成形角形鋼管5を加熱炉32に入れての燃焼加熱方式であって、その加熱炉32における前後方向の両端には、貫通孔により搬入口や搬出口が形成され、そして搬入口や搬出口には、それぞれ開閉扉33が設けられている。前記加熱炉32の一側下部でかつローラコンベヤ24のローラ間の中間位置に下部加熱バーナー34が配設され、そして、加熱炉32の他側上部でかつ前記下部加熱バーナー34に対して千鳥状に対峙する位置には、上部加熱バーナー35が配設されている。以上の32〜35などにより、前記半成形角形鋼管5をA変態点の近辺にまで全体加熱する加熱手段31の一例が構成される。
【0024】
前述したように、搬入床23の終端部に搬送された半成形角形鋼管5は、ローラコンベヤ24に渡され、このローラコンベヤ24により第1加熱手段31の加熱炉32に搬入される。この半成形角形鋼管5は、加熱炉32内にて搬送経路25上で搬送されながら、各バーナー34,35の燃焼熱によって徐々に均一的に加熱Hされ(図4参照)、そして850〜1050℃(A変態点の近辺)の高温を維持しながら、かつ周方向ならびに長さ方向において均一温度でかつ曲げなど生じることなく加熱Hされることになる。
【0025】
このようにしてA変態点の近辺の温度に加熱された半成形角形鋼管5を、開閉扉33を開動させることで、搬出口を通して加熱炉32から成形手段41へと搬出し得る。そして半成形角形鋼管5の終端が完全に搬出されたときに、搬出口の開閉扉33が閉動される。
【0026】
上述したように、加熱手段31によって加熱された半成形角形鋼管5は成形手段41に搬送され、この成形手段41によって正規の寸法かつ形状に熱間成形される。すなわち成形手段41は、図3、図5に示すように、前後4段(単数段または複数段)に設けられている。そして各成形手段41は、機枠42側に対して位置調整自在に、または交換自在に設けられた上下一対ならびに左右一対の成形ロール43などを介して、半成形角形鋼管5を絞り状に熱間成形させるものである。
【0027】
なお、成形手段41の周辺で、必要する箇所(成形手段41の前後、前のみ、後ろのみ、スタンド間など)には、必要とする数のデスケーラー装置45が設けられている。このデスケーラー装置45は、半成形角形鋼管5に対して水圧をかけた水を噴射するもので、この水噴射によりミルスケールなどを除去し、表面肌を良くし得る。
【0028】
したがって、加熱されて成形手段41に搬入された半成形角形鋼管5は、成形ロール43群によって絞り状に熱間成形され、このとき熱間成形は、複数段の成形手段41によって徐々(段階的)に絞り状に行われる。これにより半成形角形鋼管5は、正規の外面間の寸法Lでかつ正規の外周半径Rのコーナ部9とした角形鋼管(最終製品)8に仕上がるように熱間成形される。
【0029】
このようにして熱間成形された角形鋼管8は、冷却床48に受け取られる。この冷却床48はコンベヤ形式であって複数本の角形鋼管8を平行させて支持し、そして長さ方向に対して横方向へと搬送させる。この冷却床48での搬送中に、角形鋼管8は空冷形式で徐冷される。冷却床48での角形鋼管8群の搬送は、隣接した角形鋼管8の間を離した状態で、または隣接した角形鋼管8どうしを接触させ両側よりクランプした状態で搬送される。これにより角形鋼管8は、同じ雰囲気温度下で徐冷されることになり、以て冷却時の曲がりを少なくし得る。冷却床48の終端に達した角形鋼管8は、図示していない矯正装置、先端切断装置、後端切断装置、洗浄装置、防錆装置へと搬送され、それぞれで処理されたのち、製品としてストレージされる。
【0030】
このようにして得られる角形鋼管(最終製品)8は、加熱した半成形角形鋼管5を成形手段41によって、正規の寸法かつ形状に仕上がるように熱間成形し得る。その際に、半成形角形鋼管5の全体を850〜1050℃(A変態点の近辺)に加熱していることから、角形鋼管8は、各コーナ部の形状、すなわち外周半径を均等状にかつシャープに形成し得る。さらに熱間成形によって角形鋼管8は、残留応力が殆どなくて高い座屈強度が得られるとともに、二次溶接性に優れたものとなる。
【0031】
さらに角形鋼管8は、このような熱間成形による効果を保ちながらも、耐力と靭性とを向上し得る。なお以下において、従来品は、比較例品A、比較例品Bと称し、本願発明に基づく例品は、比較例品Aと同種のものを発明例品AV、比較例品Bと同種のものを発明例品BVと称す。
【0032】
【表1】
【0033】
【表2】
すなわち表1は従来品の機械的性質を示すもので、その降伏点または耐力(YP)は、比較例品Aは235〜355(N/mm)、比較例品Bは325〜445(N/mm)である。また、シャルピー吸収エネルギー()は、比較例品Aおよび比較例品Bは[板厚t>12]において下限27(J)である。
【0034】
これに対して、化学成分としてバナジウム(V)を添加した鋼板1を折り曲げ加工したのち溶接して半成形角形鋼管5とし、この半成形角形鋼管5をA変態点の近辺に加熱して熱間成形したのち、冷却して得た角形鋼管8、つまり発明例品によると、表2の機械的性質に示すように、引張強さ(TS)、降伏比(YR)、伸び(EI)は従来例品A,Bと同等の高いスペックを保ったまま、設計基準強度(F値)やシャルピー吸収エネルギー()を向上し得る。
【0035】
すなわち降伏点または耐力は、発明例品AVは275〜395(N/mm)、発明例品BVは355〜475(N/mm)であり、その下限ならびに上限を上げており、以て引張強さ(TS)、降伏比(YR)、伸び(EI)は従来例品A,Bと同等の高いスペックを保ったまま、設計基準強度(F値)を向上し得、以て耐力を向上し得る。
【0036】
また発明例品AVおよび発明例品BVのシャルピー吸収エネルギー()は[板厚t>12]において下限100(J)で、その下限を上げており、したがって、引張強さ(TS)、降伏比(YR)、伸び(EI)は従来例品A,Bと同等の高いスペックを保ったまま、シャルピー吸収エネルギー()を向上し得、以て靭性を向上し得る。
【0037】
次に発明例品AV、BVに対応する実験結果を説明する。
【0038】
【表3】
すなわち、表3の鋼種別化学成分値において、A−1〜A−4は発明例品AVに対応するものであり、またB−1〜B−4は発明例品BVに対応するものである。ここで、たとえばA−3は、辺の長さが600mmの四角かつ厚さが25mmであり、そしてカーボン(C)が0.16%、シリコン(Si)が0.21%、マンガン(Mn)が0.67%、バナジウム(V)が0.03%、リン(P)が0.018%、サルファ(S)が0.04%として添加され、残りのほぼ全てが鉄(Fe)として形成された鋼板1を示している。
【0039】
そして機械的性質、すなわち上記鋼板1を折り曲げ加工したのち溶接して半成形角形鋼管5とし、この半成形角形鋼管5をA変態点の近辺に加熱して熱間成形したのち、冷却して得た角形鋼管8の機械的性質が表4に示されている。
【0040】
【表4】
ここで降伏点又は耐力(YP)を見ると、A−1は315(N/mm)、A−2は308(N/mm)、A−3は288(N/mm)、A−4は295(N/mm)であり、いずれも275〜395(N/mm)に納まっており、またB−1は384(N/mm)、B−2は360(N/mm)、B−3は400(N/mm)、B−4は366(N/mm)であり、いずれも355〜475(N/mm)に納まっている。
【0041】
またシャルピー吸収エネルギー()を見ると、A−2は181(J)、A−3は130(J)、A−4は148(J)であり、いずれも100(J)以上であり、またB−1は229(J)、B−2は205(J)、B−4は264(J)であり、いずれも100(J)以上である。
【0042】
次に、本発明の別の実施の形態を図6に基づいて説明する。
すなわち、上述した実施の形態では、一枚の鋼板1を使用し、一辺に突き合わせ溶接部7を有する大径で厚肉の角形鋼管(最終製品)8を製造しているが、これは図6の(a)に示すように、二枚の鋼板を使用し、二辺に突き合わせ溶接部7を有する大径で厚肉の角形鋼管8を製造してもよい。
【0043】
また、上述した実施の形態では、正方体形状の角形鋼管8を製造しているが、これは直方体形状の角形鋼管8を製造してもよく、さらに図6の(b)に示すような五角形形状の角形鋼管8や、図6の(c)に示すような六角形形状の角形鋼管8など、各種の多角形状の角形鋼管8を製造してもよい。
【0044】
このような別の実施の形態においても、上述した実施の形態と同様に、引張強さ(TS)、降伏比(YR)、伸び(EI)は従来例品A,Bと同等の高いスペックを保ったまま、設計基準強度(F値)やシャルピー吸収エネルギー()を向上し得るものである。
【0045】
上記した実施の形態では、加熱手段31として、半成形角形鋼管5を加熱炉32に入れての燃焼加熱方式が採用されているが、この加熱手段としては、高周波誘導加熱方式などであってもよい。
【0046】
上記した実施の形態で示すように、成形手段41での熱間成形は、複数段で徐々に絞り成形するのが好ましいが、その段数は任意であり、場合によっては単数段でもよい。特に半成形角形鋼管5が薄肉の場合には、単数段、少数段での熱間成形が可能となる。
【0047】
上記した実施の形態では、大径で厚肉の角形鋼管8を製造しているが、これは大径で薄肉の角形鋼管、小径で厚肉の角形鋼管、小径で薄肉の角形鋼管などの製造であってもよい。たとえば、正規の外面間の寸法Lが300〜700mm、厚さtが9〜70mmの角形鋼管8を得るものであり、その際に半成形角形鋼管5におけるコーナ部6の大きい外周半径LRは厚さtの3.5〜7.0倍であり、これが角形鋼管8におけるコーナ部9の正規の外周半径Rが厚さtの1.0〜3.0倍となるようにシャープに形成される。
【0048】
上記した実施の形態では、前段成形プレス11や後段成形プレス14などプレス方式で鋼板1の成形を行っているが、これはロール方式で鋼板1の成形を行ってもよい。
【0049】
【発明の効果】
上記した本発明の請求項1によると、加熱した半成形角形鋼管を正規の寸法かつ形状に仕上がるように熱間成形でき、その際に、半成形角形鋼管の全体をA変態点の近辺に加熱していることから、角形鋼管は、各コーナ部の形状、すなわち外周半径を均等状にかつシャープに形成できる。さらに熱間成形によって角形鋼管は、残留応力が殆どなくて高い座屈強度を得ることができるとともに、二次溶接性に優れたものにできる。しかも、化学成分としてバナジウムを添加している鋼板を使用したことで、耐力と靭性とを向上した角形鋼管にできる。したがって、建築に応じて充分な設計基準強度を得たものでありながら、その板厚が薄いもの、サイズの小さいものなどを採用でき、以て軽量化と、コストダウンとを図ることができる。
【0050】
また上記した本発明の請求項2によると、加熱手段によってA変態点の近辺に加熱した半成形角形鋼管を、成形手段によって正規の寸法かつ形状に仕上がるように熱間成形でき、以て請求項1記載の角形鋼管を容易に製造できる。
【0051】
そして上記した本発明の請求項3によると、バナジウムを最も好適に添加できる。
【図面の簡単な説明】
【図1】本発明の実施の形態の一例を示し、角形鋼管の製造方法における鋼板成形工程までの説明図である。
【図2】同角形鋼管の製造方法における半成形角形鋼管の造管工程までの説明図である。
【図3】同角形鋼管の製造方法における加熱から熱間成形を含む工程斜視図である。
【図4】同角形鋼管の製造方法における加熱手段部分の正面図である。
【図5】同角形鋼管の製造方法における熱間成形工程の正面図である。
【図6】本発明の別の実施の形態を示し、(a)は二枚の鋼板を使用した角形鋼管の正面図、(b)は五角形形状の角形鋼管の正面図、(c)は六角形形状の角形鋼管の正面図である。
【符号の説明】
1 鋼板
2 開先
5 半成形角形鋼管
7 突き合わせ溶接部(シーム溶接部)
8 角形鋼管(最終製品)
9 コーナ部
10 トリミング開先加工機
11 前段成形プレス
14 後段成形プレス
17 仮付け溶接機
19 内面溶接機
20 外面溶接機
23 搬入床
24 ローラコンベヤ(搬送手段)
25 搬送経路
31 加熱手段
32 加熱炉
41 成形手段
43 成形ロール
45 デスケーラー装置
48 冷却床
LL 大きい外面間の寸法
L 正規の外面間の寸法
LR 大きい外周半径
R 正規の外周半径
H 加熱
[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to, for example, a large-diameter, thick-walled rectangular steel pipe (a rectangular shape, a rectangular parallelepiped shape, a polygonal shape such as a pentagon or a hexagon) used for a column material for building, and a rectangular shape employed for obtaining a rectangular steel tube. The present invention relates to a method for manufacturing a steel pipe.
[0002]
[Prior art]
Conventionally, as a method of manufacturing this type of rectangular steel pipe, a polygonal hollow steel pipe is formed by press-forming a plurality of portions of a flat plate material (steel plate) by a press forming machine and performing seam welding. Then, the polygonal hollow steel tube is carried into a heating furnace, heated at a high temperature during the conveyance in the heating furnace, and then carried into a rectangular steel tube forming machine to perform hot forming (for example, see Patent Document 1). .
[0003]
Further, as a steel sheet, a steel containing 0.01 to 0.10% by weight of vanadium is obtained by hot rolling, and the steel sheet is cold-bent and then welded at a joint to form a steel pipe. The steel pipe is annealed by reheating and cooling (for example, see Patent Document 2).
[0004]
[Patent Document 1]
JP-A-9-99324 (page 3, FIG. 1-4)
[0005]
[Patent Document 2]
JP-A-7-150247 (page 1)
[0006]
[Problems to be solved by the invention]
According to the square steel pipe of Patent Document 1 described above, the heated semi-formed square steel pipe can be hot formed by a forming means so as to be finished into a square steel pipe (final product) having a regular size and shape. Semi-molded RHS At that time, since the whole is heated to near the A 3 transformation point, square tube, the shape of each corner portion, that can be formed on the sharp and the outer peripheral radius evenly shaped. Furthermore, the rectangular steel pipe can be expected to have effects such as high buckling strength with almost no residual stress and excellent secondary weldability and sufficient toughness by hot forming.
[0007]
Here, the flat plate material (steel plate) is usually formed by adding a plurality of chemical components to iron (Fe) in the following weight%. That is, carbon (C) is 0.20% or less, silicon (Si) is 0.55% or less, manganese (Mn) is 0.60 to 1.60%, phosphorus (P) is 0.03% or less, sulfur (S) is added as 0.15% or less, and almost all of the remaining is formed as iron (Fe).
[0008]
However, the rectangular steel pipe obtained by hot forming such a flat plate material has a yield point or proof stress of 235 to 355 (N / mm 2 ), as apparent from a comparison of mechanical properties described later. Therefore, in order to obtain a sufficient design standard strength (F value) according to the construction, it is necessary to adopt a thick plate, a large plate, and the like. Become.
[0009]
Further, according to the steel pipe of Patent Document 2, since the hot forming is not performed, the effect by the hot forming described above cannot be expected.
Therefore, an object of the present invention is to provide a square steel pipe capable of improving proof stress and toughness while maintaining the effect of hot forming.
[0010]
Another object of the present invention is to provide a method of manufacturing a rectangular steel pipe capable of easily manufacturing the rectangular steel pipe according to the first aspect.
[0011]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, a rectangular steel pipe according to claim 1 of the present invention is obtained by bending a steel sheet to which vanadium is added as a chemical component and then welding it to form a semi-formed rectangular steel pipe. the After forming inter and heated to near the a 3 transformation point heat is obtained by, characterized in that obtained by cooling.
[0012]
Therefore, according to the invention of claim 1, to give a semi-molded RHS heating and hot molded to finished to the normal size and shape, in this case, heating the entire semi-molded RHS near the A 3 transformation point As a result, the rectangular steel pipe can form the shape of each corner portion, that is, the outer peripheral radius uniformly and sharply. Further, the rectangular steel pipe has little residual stress, has high buckling strength, and has excellent secondary weldability by hot forming. Moreover, since a steel sheet to which vanadium is added as a chemical component is used, a square steel pipe having improved proof stress and toughness can be obtained.
[0013]
The method for producing a square steel pipe according to claim 2 of the present invention is characterized in that a steel sheet obtained by adding vanadium as a chemical component is bent, then welded to form a semi-formed square steel pipe, and the semi-formed square steel pipe is heated by heating means. After heating to near the a 3 transformation point, hot-molded by a molding means, and is obtained by said obtaining a square tube by cooling.
[0014]
Therefore, according to the invention of claim 2, the half-formed square steel tube heated to near the A 3 transformation point by the heating means may be hot molded to finished to the normal size and shape by molding means.
[0015]
According to a third aspect of the present invention, there is provided a method of manufacturing a rectangular steel pipe according to the second aspect, wherein vanadium is added in an amount of 0.01 to 0.10% by weight. .
[0016]
Therefore, according to the invention of claim 3, vanadium can be most suitably added.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described. Here, the steel sheet 1 used is formed by adding a plurality of chemical components to iron (Fe) in the following weight%. That is, carbon (C) is 0.20% or less, silicon (Si) is 0.55% or less, manganese (Mn) is 0.60 to 1.60%, and vanadium (V) is 0.01 to 0.10. %, Phosphorus (P) is added as 0.03% or less, and sulfur (S) is added as 0.15% or less, and almost all of the remaining is formed as iron (Fe).
[0018]
Next, an embodiment of obtaining a large-diameter, thick-walled, square-shaped rectangular steel pipe by using the steel sheet 1 having the above-described components will be described with reference to FIGS.
As shown in FIG. 1, a steel plate 1 having a predetermined length is transported in a length direction 1A, and is passed through a trimming beveling machine 10 to form a groove 2 on both side edges in a width direction 1B. Next, the steel sheet 1 is put into the pre-stage forming press 11, and the upper die 13 is moved up and down with respect to the lower die 12, so that right-angled (90 ° or almost 90 °) corner portions 3, 3 are provided at two positions near the side edge. Is formed by bending. After that, it is put into the latter forming press 14 and the upper and lower dies 16 are moved up and down with respect to the lower dies 15 to bend and form the corner portions 4 and 4 at obtuse angles (about 105 degrees) at two intermediate positions.
[0019]
Then, as shown in FIG. 2, the four sides are pressed from outside by a group of rolls 18 (or cylinders) at the part of the tack welding machine 17 to form the obtuse corners 4 and 4 into the right-angled corners 6. While the groove 2 is butted against each other to form the semi-formed square steel pipe 5, the tack welding 7a is applied to the butted portion. Next, the semi-formed square steel pipe 5 is transferred to the inner surface welding machine 19 to perform the inner surface welding 7b. Further, the semi-formed square steel pipe 5 is transferred to the outer surface welding machine 20 to perform the outer surface welding 7c, thereby having a butt weld portion (seam weld portion) 7 on one side, and each corner portion 6 having a right-angled large diameter. Can form a thick semi-formed square steel pipe 5.
[0020]
Here, the semi-formed square steel pipe 5 is made larger in size and shape than a square steel pipe (final product) described later. That is, the pipe is formed by increasing the dimension LL between the outer surfaces of the opposed sides and the outer radius LR of each corner 6 (see FIG. 4).
[0021]
As shown in FIGS. 3 to 5, the semi-formed square steel pipe 5 is transferred to the carry-in floor 23 and transported. The semi-formed square steel pipe 5 conveyed to the terminal end of the loading floor 23 is transferred to a roller conveyor (an example of conveying means) 24 and conveyed on a conveying path 25 formed by the roller conveyor 24.
[0022]
During this conveyance path 25, the heating means 31 for heating the whole to near (front and back) of the semi-molded RHS 5 A 3 transformation point (e.g., from 850 to 1,050 ° C.), the semi-molded RHS 5 which is heated Forming means 41 for hot forming into a regular size and shape is provided.
[0023]
That is, the heating means 31 is a combustion heating method in which the semi-formed square steel pipe 5 is put in a heating furnace 32, and a carry-in port and a carry-out port are formed at both ends in the front-rear direction of the heating furnace 32 by through holes. An opening / closing door 33 is provided at each of the entrance and the exit. A lower heating burner 34 is disposed at a lower portion on one side of the heating furnace 32 and at an intermediate position between the rollers of the roller conveyor 24, and is staggered with respect to the lower heating burner 34 on the other side of the heating furnace 32. An upper heating burner 35 is disposed at a position facing the upper surface. Due more than 32 to 35, an example of a heating means 31 for heating the whole the semi-molded RHS 5 to the vicinity of the A 3 transformation point is constructed.
[0024]
As described above, the semi-formed square steel pipe 5 conveyed to the terminal end of the carrying-in floor 23 is transferred to the roller conveyor 24 and carried into the heating furnace 32 of the first heating means 31 by the roller conveyor 24. The semi-formed square steel pipe 5 is gradually and uniformly heated H by the combustion heat of the burners 34 and 35 while being transported on the transport path 25 in the heating furnace 32 (see FIG. 4), and 850 to 1050. ℃ while maintaining the high temperature (near the a 3 transformation point), and will be heated H without causing such uniform temperature at and bend in the circumferential direction and length direction.
[0025]
The semi-molded RHS 5 which is heated to a temperature in the vicinity of the A 3 transformation point in this manner, the opening and closing door 33 by causing the opening motion can be unloaded from the furnace 32 through the outlet port into the molding unit 41. Then, when the end of the semi-formed square steel pipe 5 is completely carried out, the opening / closing door 33 of the carry-out port is closed.
[0026]
As described above, the semi-formed square steel pipe 5 heated by the heating means 31 is conveyed to the forming means 41, and hot-formed into a regular size and shape by the forming means 41. That is, as shown in FIG. 3 and FIG. 5, the forming means 41 is provided in four stages (single stage or plural stages). Each of the forming means 41 heats the semi-formed square steel pipe 5 into a drawn shape via a pair of upper and lower forming rolls and a pair of right and left forming rolls 43 provided so as to be adjustable in position or exchangeable with respect to the machine frame 42 side. It is to be formed during the process.
[0027]
A necessary number of descaler devices 45 are provided at necessary locations around the forming means 41 (before and after, only before, only behind, between stands, etc.) of the forming means 41. The descaler device 45 injects water with water pressure applied to the semi-formed square steel pipe 5, and this water injection removes mill scale and the like, and can improve the surface skin.
[0028]
Therefore, the semi-formed square steel pipe 5 which has been heated and carried into the forming means 41 is hot-formed in a drawing shape by the group of forming rolls 43. At this time, the hot forming is performed gradually (stepwise) by a plurality of steps of the forming means 41. ). Thus, the semi-formed square steel pipe 5 is hot-formed so as to be finished into a square steel pipe (final product) 8 having a corner portion 9 having a regular outer surface dimension L and a regular outer radius R.
[0029]
The rectangular steel pipe 8 thus hot-formed is received by the cooling floor 48. The cooling floor 48 is of a conveyor type and supports a plurality of rectangular steel pipes 8 in parallel and transports them in a direction transverse to the longitudinal direction. During transportation on the cooling floor 48, the rectangular steel pipe 8 is gradually cooled in an air-cooled manner. The group of square steel pipes 8 is conveyed on the cooling floor 48 in a state where the adjacent square steel pipes 8 are separated from each other or in a state where the adjacent square steel pipes 8 are brought into contact with each other and clamped from both sides. Thereby, the square steel pipe 8 is gradually cooled under the same ambient temperature, and thus the bending at the time of cooling can be reduced. The rectangular steel pipe 8 reaching the end of the cooling floor 48 is transported to a straightening device, a leading end cutting device, a trailing end cutting device, a cleaning device, and a rust prevention device (not shown). Is done.
[0030]
The square steel pipe (final product) 8 thus obtained can be hot-formed by the forming means 41 so that the heated semi-formed square steel pipe 5 is finished to a regular size and shape. At that time, since the heating of the entire semi-molded RHS 5 from 850 to 1,050 ° C. (near the A 3 transformation point), square tube 8, the shape of each corner portion, i.e., the outer peripheral radius evenly shaped And it can be formed sharply. Further, the rectangular steel pipe 8 has almost no residual stress and high buckling strength and has excellent secondary weldability by hot forming.
[0031]
Furthermore, the square steel pipe 8 can improve the proof stress and the toughness while maintaining the effect of the hot forming. In the following, the conventional products are referred to as Comparative Product A and Comparative Product B, and the product based on the present invention is the same product as Comparative Product A and the same product as Invention Product AV and Comparative Product B. Is referred to as invention sample BV.
[0032]
[Table 1]
[0033]
[Table 2]
That is, Table 1 shows the mechanical properties of the conventional product. The yield point or proof stress (YP) of the comparative product A is 235 to 355 (N / mm 2 ), and that of the comparative product B is 325 to 445 (N). / Mm 2 ). Further, Charpy absorbed energy (V E O), the product of Comparative Example A and Comparative sample B is the lower limit 27 (J) in [plate thickness t> 12].
[0034]
In contrast, the vanadium (V) bending a steel plate 1 with added processed by welding after the semi-molded RHS 5 as chemical components, heating the semi-molded RHS 5 in the vicinity of the A 3 transformation point heat According to the rectangular steel pipe 8 obtained by cold forming and then cooling, that is, according to the invention example, as shown in the mechanical properties in Table 2, the tensile strength (TS), the yield ratio (YR), and the elongation (EI) are conventional product a, while maintaining the same high specifications and B, can improve the design strength (F value) and the Charpy absorbed energy (V E O).
[0035]
That yield point or proof stress, invention example products AV is 275~395 (N / mm 2), the invention example products BV is 355~475 (N / mm 2), and raising the lower limit and upper limit, Te following The tensile strength (TS), the yield ratio (YR), and the elongation (EI) can be improved to the design standard strength (F value) while maintaining the same high specifications as those of the conventional products A and B. Can improve.
[0036]
In addition, the Charpy absorbed energy ( V EO ) of the invention sample AV and the invention sample BV is 100 (J) as the lower limit in [plate thickness t> 12], and is higher than the lower limit. Therefore, the tensile strength (TS) , yield ratio (YR), elongation (EI) while the maintaining conventional product a, the same high specifications and B, to give improved Charpy absorbed energy (V E O), can improve the toughness Te following.
[0037]
Next, the experimental results corresponding to the invention samples AV and BV will be described.
[0038]
[Table 3]
That is, in the chemical composition values of steel types in Table 3, A-1 to A-4 correspond to the invention sample AV, and B-1 to B-4 correspond to the invention sample BV. . Here, for example, A-3 is a square having a side length of 600 mm and a thickness of 25 mm, and contains 0.16% of carbon (C), 0.21% of silicon (Si), and manganese (Mn). Is added as 0.67%, vanadium (V) is 0.03%, phosphorus (P) is 0.018%, and sulfur (S) is 0.04%, and almost all of the remaining is formed as iron (Fe). FIG.
[0039]
The mechanical properties, i.e. the weld to semi-molded RHS 5 After bending the steel plate 1, after the hot forming and heating the semi-molded RHS 5 in the vicinity of the A 3 transformation point, cooled Table 4 shows the mechanical properties of the obtained square steel pipe 8.
[0040]
[Table 4]
Looking at the yield point or proof stress (YP), A-1 is 315 (N / mm 2 ), A-2 is 308 (N / mm 2 ), A-3 is 288 (N / mm 2 ), A -4 is 295 (N / mm 2 ), all are within 275 to 395 (N / mm 2 ), B-1 is 384 (N / mm 2 ), and B-2 is 360 (N / mm 2 ). mm 2), B-3 is 400 (N / mm 2), B-4 is 366 (N / mm 2), both of which accommodated the 355~475 (N / mm 2).
[0041]
Also see a Charpy absorbed energy (V E O), A- 2 is 181 (J), A-3 is 130 (J), A-4 is 148 (J), in both 100 (J) or B-1 is 229 (J), B-2 is 205 (J), and B-4 is 264 (J), all of which are 100 (J) or more.
[0042]
Next, another embodiment of the present invention will be described with reference to FIG.
That is, in the above-described embodiment, a large-diameter, thick-walled rectangular steel pipe (final product) 8 having a butt weld 7 on one side is manufactured by using one steel sheet 1, which is shown in FIG. (A), a large-diameter, thick-walled rectangular steel pipe 8 having butt welds 7 on two sides may be manufactured using two steel plates.
[0043]
In the above-described embodiment, the rectangular steel pipe 8 having a rectangular parallelepiped shape is manufactured. However, the rectangular steel pipe 8 having a rectangular parallelepiped shape may be manufactured, and the rectangular steel pipe 8 may have a pentagonal shape as illustrated in FIG. And various polygonal rectangular steel pipes 8 such as the rectangular steel pipe 8 shown in FIG. 6C and the hexagonal rectangular steel pipe 8 as shown in FIG.
[0044]
Also in such another embodiment, as in the above-described embodiment, the tensile strength (TS), the yield ratio (YR), and the elongation (EI) are as high as those of the conventional products A and B. It is possible to improve the design reference strength (F value) and the Charpy absorbed energy ( V EO ) while keeping it.
[0045]
In the above-described embodiment, the combustion heating method in which the semi-formed square steel pipe 5 is put into the heating furnace 32 is adopted as the heating means 31, but the heating means may be a high frequency induction heating method or the like. Good.
[0046]
As shown in the above-described embodiment, the hot forming by the forming means 41 is preferably performed by drawing gradually in a plurality of stages, but the number of stages is optional, and in some cases, a single stage may be used. In particular, when the semi-formed square steel pipe 5 is thin, hot forming can be performed in a single step or a small number of steps.
[0047]
In the above-described embodiment, the large-diameter, thick-walled rectangular steel pipe 8 is manufactured. However, the large-diameter, thin-walled rectangular steel pipe, the small-diameter, thick-walled rectangular steel pipe, the small-diameter, thin-walled square steel pipe, and the like are manufactured. It may be. For example, a square steel pipe 8 having a regular outer surface dimension L of 300 to 700 mm and a thickness t of 9 to 70 mm is obtained. At this time, the large outer radius LR of the corner portion 6 of the semi-formed square steel pipe 5 is large. 3.5 to 7.0 times the thickness t, which is sharply formed such that the regular outer radius R of the corner portion 9 of the rectangular steel pipe 8 becomes 1.0 to 3.0 times the thickness t. .
[0048]
In the above-described embodiment, the steel sheet 1 is formed by a press method such as the pre-press 11 and the post-press 14. However, the steel sheet 1 may be formed by a roll method.
[0049]
【The invention's effect】
According to claim 1 of the present invention described above, the semi-molded RHS heating can hot molded to finished to the normal size and shape, in this case, the entire semi-molded RHS near the A 3 transformation point Due to the heating, the square steel pipe can be formed with a uniform shape and a sharp outer peripheral radius at each corner. Further, the rectangular steel pipe can have high buckling strength with almost no residual stress and have excellent secondary weldability by hot forming. Moreover, by using a steel sheet to which vanadium is added as a chemical component, a square steel pipe with improved proof stress and toughness can be obtained. Therefore, while having a sufficient design standard strength according to the construction, a thinner plate, a smaller one, and the like can be employed, thereby achieving weight reduction and cost reduction.
[0050]
Further, according to claim 2 of the present invention described above, the semi-formed square steel tube heated to near the A 3 transformation point by the heating means, can hot molded to finished to the normal size and shape by forming means, wherein Te following Item 1 can easily produce the square steel pipe.
[0051]
According to the third aspect of the present invention, vanadium can be most suitably added.
[Brief description of the drawings]
FIG. 1 shows an example of an embodiment of the present invention and is an explanatory diagram up to a steel plate forming step in a method for manufacturing a square steel pipe.
FIG. 2 is an explanatory view up to a pipe forming step of a semi-formed square steel pipe in a method of manufacturing the same square steel pipe.
FIG. 3 is a process perspective view including heating to hot forming in the method for manufacturing a square steel pipe.
FIG. 4 is a front view of a heating unit in the method of manufacturing a square steel pipe.
FIG. 5 is a front view of a hot forming step in the method for manufacturing a square steel pipe.
6A and 6B show another embodiment of the present invention, wherein FIG. 6A is a front view of a rectangular steel pipe using two steel plates, FIG. 6B is a front view of a pentagonal rectangular steel pipe, and FIG. It is a front view of a square steel pipe of a square shape.
[Explanation of symbols]
1 steel plate 2 groove 5 semi-formed square steel pipe 7 butt weld (seam weld)
8 Square steel pipe (final product)
9 Corner 10 Trimming beveling machine 11 Pre-stage forming press 14 Back-stage forming press 17 Temporary welding machine 19 Inner surface welding machine 20 Outer surface welding machine 23 Loading floor 24 Roller conveyor (conveying means)
25 Conveying path 31 Heating means 32 Heating furnace 41 Forming means 43 Forming roll 45 Descaler device 48 Cooling floor LL Dimension L between large outer surfaces L Dimension between regular outer surfaces LR Large outer radius R Regular outer radius H Heating

Claims (3)

化学成分としてバナジウムを添加している鋼板を折り曲げ加工したのち溶接して半成形角形鋼管とし、この半成形角形鋼管をA変態点の近辺に加熱して熱間成形したのち、冷却して得たことを特徴とする角形鋼管。And welded to semi-molded RHS After bending a steel plate that is added vanadium as a chemical component, after the hot forming and heating the semi-molded RHS near the A 3 transformation point, obtained by cooling A rectangular steel pipe characterized by the following. 化学成分としてバナジウムを添加して得た鋼板を折り曲げ加工したのち溶接して半成形角形鋼管とし、この半成形角形鋼管を加熱手段によってA変態点の近辺に加熱したのち、成形手段によって熱間成形し、そして冷却することで角形鋼管を得ることを特徴とする角形鋼管の製造方法。Folding a steel sheet obtained by the addition of vanadium processed by welding after the semi-molded RHS as chemical components, then heated to near the A 3 transformation point by the heating means of this semi-molded RHS, hot by molding means A method for producing a rectangular steel pipe, comprising obtaining a rectangular steel pipe by molding and cooling. 重量%で0.01〜0.10%のバナジウムを添加することを特徴とする請求項2記載の角形鋼管の製造方法。3. The method according to claim 2, wherein 0.01 to 0.10% by weight of vanadium is added.
JP2003126810A 2003-05-02 2003-05-02 Square steel pipe and manufacturing method for square steel pipe Pending JP2004330222A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102284567A (en) * 2011-07-14 2011-12-21 中国第一重型机械集团大连加氢反应器制造有限公司 Steel sheet pressure head heating device and use method thereof
JP2012188908A (en) * 2011-03-14 2012-10-04 Asahi Kasei Homes Co Frame reinforcement structure
WO2014142205A1 (en) * 2013-03-15 2014-09-18 日鐵住金建材株式会社 Roll-formed rectangular steel tube
CN113579652A (en) * 2021-07-29 2021-11-02 济钢集团有限公司 Production method and production device for producing sharp-angle square tubes
KR20220035492A (en) 2019-08-30 2022-03-22 제이에프이 스틸 가부시키가이샤 Rectangular steel pipe, manufacturing method thereof, and building structure

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012188908A (en) * 2011-03-14 2012-10-04 Asahi Kasei Homes Co Frame reinforcement structure
CN102284567A (en) * 2011-07-14 2011-12-21 中国第一重型机械集团大连加氢反应器制造有限公司 Steel sheet pressure head heating device and use method thereof
WO2014142205A1 (en) * 2013-03-15 2014-09-18 日鐵住金建材株式会社 Roll-formed rectangular steel tube
JPWO2014142205A1 (en) * 2013-03-15 2017-02-16 日鐵住金建材株式会社 Roll forming square steel pipe
KR20220035492A (en) 2019-08-30 2022-03-22 제이에프이 스틸 가부시키가이샤 Rectangular steel pipe, manufacturing method thereof, and building structure
CN113579652A (en) * 2021-07-29 2021-11-02 济钢集团有限公司 Production method and production device for producing sharp-angle square tubes

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