JPWO2020054051A1 - Manufacturing method of steel pipe and press die - Google Patents

Manufacturing method of steel pipe and press die Download PDF

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JPWO2020054051A1
JPWO2020054051A1 JP2018034145A JP2019547161A JPWO2020054051A1 JP WO2020054051 A1 JPWO2020054051 A1 JP WO2020054051A1 JP 2018034145 A JP2018034145 A JP 2018034145A JP 2019547161 A JP2019547161 A JP 2019547161A JP WO2020054051 A1 JPWO2020054051 A1 JP WO2020054051A1
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molded
steel pipe
mold
arc
die
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JP6791397B2 (en
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正之 堀江
正之 堀江
洸介 日当
洸介 日当
友裕 川野
友裕 川野
征哉 田村
征哉 田村
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Jfeスチール株式会社
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21CMANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C37/00Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
    • B21C37/06Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
    • B21C37/08Making tubes with welded or soldered seams
    • B21C37/0815Making tubes with welded or soldered seams without continuous longitudinal movement of the sheet during the bending operation
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21CMANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C37/00Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
    • B21C37/06Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
    • B21C37/08Making tubes with welded or soldered seams
    • 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
    • B21D3/00Straightening or restoring form of metal rods, metal tubes, metal profiles, or specific articles made therefrom, whether or not in combination with sheet metal parts
    • B21D3/16Straightening or restoring form of metal rods, metal tubes, metal profiles, or specific articles made therefrom, whether or not in combination with sheet metal parts of specific articles made from metal rods, tubes, or profiles, e.g. crankshafts, by specially adapted methods or means
    • 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
    • B21D5/01Bending sheet metal along straight lines, e.g. to form simple curves between rams and anvils or abutments
    • B21D5/015Bending sheet metal along straight lines, e.g. to form simple curves between rams and anvils or abutments for making tubes

Abstract

幅方向両端部に端曲げ加工が施された板材に、幅方向に沿って3回以上の曲げ加工を施してU字状断面をなす成形体を成形し、成形体にプレス加工を施すことにより、長手方向にシームギャップ部を有するオープン管とした後、シームギャップ部を接合して鋼管とする鋼管の製造方法であって、端曲げ加工前の板材の幅を板幅Wとしたとき、成形体は、板幅端部からW/4だけ離れた部位を中心に、他の領域に比較して小さな曲率を付与した軽加工部、または、曲げ加工を省略した未加工部を有し、オープン管の形状が、U字状断面の最下部を中心に板幅Wの20[%]以上の範囲と、板幅端から板幅Wの10[%]以上の範囲とが、鋼管の外径と同径または略同径の円弧に内接する形状となるように、プレス加工する。A plate material whose ends have been bent at both ends in the width direction is bent three times or more along the width direction to form a molded body having a U-shaped cross section, and the molded body is pressed. This is a method for manufacturing a steel pipe in which an open pipe having a seam gap portion in the longitudinal direction is formed and then the seam gap portion is joined to form a steel pipe, and the width of the plate material before end bending is defined as the plate width W. The body has a lightly machined part that is given a smaller curvature than other areas, or an unprocessed part that omits bending, centering on a part that is W / 4 away from the end of the plate width, and is open. The outer diameter of the steel pipe has a range of 20 [%] or more of the plate width W centered on the bottom of the U-shaped cross section and a range of 10 [%] or more of the plate width W from the end of the plate width. Pressing is performed so that the shape is inscribed in an arc having the same or substantially the same diameter as.

Description

本発明は、鋼管の製造方法、及び、その鋼管の製造方法に使用されるプレス金型に関するものである。 The present invention relates to a method for manufacturing a steel pipe and a press die used in the method for manufacturing the steel pipe.
従来、鋼管を成形する技術としては、UOE成形技術が広く普及している。このUOE成形技術は、鋼板を、まずU字状にプレス加工し、次いでO字状にプレス加工して、周方向で互いに向き合った板幅端間にシームギャップ部を有する管体であるオープン管とし、このオープン管のシームギャップ部を、溶接により突き合わせ接合することで鋼管とした後、さらに鋼管の径を拡大する拡管を行うものである。しかし、UOE成形技術では、鋼板をU字状やO字状にプレス加工を施してオープン管を成形する工程において、高いプレス力を必要とすることから、大掛かりなプレス機を使用せざるを得ない状況にある。 Conventionally, UOE forming technology has been widely used as a technology for forming steel pipes. This UOE forming technology is an open pipe which is a pipe body in which a steel plate is first pressed into a U shape and then pressed into an O shape, and has a seam gap between the width ends facing each other in the circumferential direction. Then, the seam gap portion of this open pipe is butt-joined by welding to form a steel pipe, and then the pipe is expanded to further expand the diameter of the steel pipe. However, the UOE forming technology requires a high pressing force in the process of pressing a steel plate into a U-shape or an O-shape to form an open tube, so that a large-scale press machine must be used. There is no situation.
そこで、鋼管を製造するにあたって、プレス力を軽減してオープン管を成形する技術としては、例えば、鋼板の幅方向端部に曲げ加工を施して端曲げ部を付与した後、パンチ支持体に支持されたパンチと、ダイとによる複数回の3点曲げプレスを行って、鋼板を略円形にし、オープン管を成形するプレスベンド方式が実用化されている。一方で、このプレスベンド方式で成形したオープン管のシームギャップ部の開き量は、パンチ支持体の幅よりも大きくなるが、この開き量が大きすぎると、シームギャップ部を溶接するために、互いに向き合った板幅端を突き当ててシームギャップ部を閉じるために必要な力が大きくなり、シームギャップ部を閉じるための設備が大型化する。また、開き量が大きすぎるシームギャップ部を溶接した後の溶接部分には、スプリングバックによりシームギャップ部が開こうとする力が作用するため、溶接欠陥が生じやすく、その力が大きすぎると溶接部分が破断してしまう。 Therefore, in manufacturing a steel pipe, as a technique for forming an open pipe by reducing the pressing force, for example, the widthwise end portion of the steel sheet is bent to give the end bent portion, and then the steel pipe is supported by the punch support. A press bend method has been put into practical use in which a steel plate is formed into a substantially circular shape by performing a plurality of three-point bending presses with a punch and a die to form an open pipe. On the other hand, the opening amount of the seam gap portion of the open pipe formed by this press bend method is larger than the width of the punch support, but if this opening amount is too large, the seam gap portions are welded to each other. The force required to close the seam gap by abutting the width edges facing each other increases, and the equipment for closing the seam gap increases in size. In addition, a force that tries to open the seam gap due to springback acts on the welded part after welding the seam gap that has an excessively large opening amount, so that welding defects are likely to occur. If the force is too large, welding is performed. The part breaks.
そこで、プレスベンド後のオープン管のシームギャップ部の開き量を小さくするための技術が、特許文献1〜4に開示されている。特許文献1では、パンチ先端部とパンチ支持体との結合部を回転自由とすることにより、パンチ支持体の幅を小さくして、オープン管のシームギャップ部の開き量を小さくする技術が開示されている。特許文献2では、パンチの移動方向と直交する方向への板材の移動を制限する間隔保持手段を設け、板幅端部がパンチ支持体に接触することなく、最終曲げ加工において大きな加圧をしてオープン管のシームギャップ部の開き量を小さくする技術が開示されている。特許文献3では、最終圧下工程後の板幅端部とパンチ支持体との隙間を測定し、その隙間を極力小さくすることでオープン管のシームギャップ部の開き量を小さくする技術が開示されている。さらに、特許文献4では、最終曲げ工程の圧下時に板幅端間の間隔が所定の値となった時点を基準に、最終工程のパンチによる圧下量を定めることにより、それまでのプレスベンド成形工程で生じた形状の差によらず、オープン管のシームギャップ部の開き量を小さくする技術が開示されている。 Therefore, Patent Documents 1 to 4 disclose techniques for reducing the opening amount of the seam gap portion of the open pipe after press bending. Patent Document 1 discloses a technique in which the width of the punch support is reduced and the opening amount of the seam gap portion of the open pipe is reduced by allowing the joint portion between the punch tip portion and the punch support to rotate freely. ing. In Patent Document 2, an interval holding means for restricting the movement of the plate material in a direction orthogonal to the movement direction of the punch is provided, and a large pressure is applied in the final bending process without the plate width end contacting the punch support. A technique for reducing the opening amount of the seam gap portion of an open pipe is disclosed. Patent Document 3 discloses a technique of measuring the gap between the plate width end portion and the punch support after the final reduction step and reducing the gap as much as possible to reduce the opening amount of the seam gap portion of the open pipe. There is. Further, in Patent Document 4, the press bend forming step up to that point is determined by determining the reduction amount by the punch in the final process based on the time when the interval between the plate width ends becomes a predetermined value at the time of reduction in the final bending process. Disclosed is a technique for reducing the opening amount of the seam gap portion of the open pipe regardless of the difference in shape caused in.
しかし、特許文献1〜4に開示された技術では、オープン管のシームギャップ部の開き量をパンチ支持体の幅より小さくすることができない。そこで、プレスベンド成形後のオープン管にさらに加工を加えてシームギャップ部の開き量を小さくする技術が、特許文献5〜9に開示されている。特許文献5では、プレスベンド後の鋼管に対して熱間ロール成形を行うことで、少ない荷重で成形する技術が開示されている。特許文献6には、スライドに装着した押圧材の傾きまたは歪の検出を可能とする歪検出器を配設するとともに、歪検出器の傾きまたは歪の検出に対応して押圧材を傾動可能または平行移動可能に配設し、成形材料をパイプ状にプレス成形するときに、押圧材の傾斜量または歪量に対して、その歪量が小さくなるように押圧材を傾斜または平行移動してプレス成形する技術が開示されている。特許文献7には、漸次成形される板材に進入する上側工具の長手方向軸線により規定される中央に関して、それぞれ左右で板材の内面に作用する少なくとも1回の曲げステップで、他の曲げステップに比べて僅かな成形を行うことによって、非円形のプリフォームを備えるスリット管を形成し、その後、外側から非円形のプリフォームにその都度適当に、中央の両側の予め僅かに成形された領域において作用する押し付け力を加えることにより、完成したスリット管を成形する技術が開示されている。さらに、特許文献8には、少なくとも2つのパイプ曲率に曲げられた部分の間に平坦な部分がある成形体に、少なくとも1か所の平坦な部分にのみ塑性変形を与えて所定の曲率にして、スリット部が閉じたパイプを成形する技術が開示されている。さらに、特許文献9には、他の領域に比較しごく僅かな曲率を付与した軽加工部を設けるか、もしくは、曲げ加工を省略した未加工部を設けるかした成形体を圧下してオープン管とする際に、軽加工部もしくは未加工部を拘束することなしに、押圧力を付加することで、スリット部を閉じたパイプを成形する方法が開示されている。また、その押圧の際には、開放部を上方に向けたU字姿勢で成形体が金型に保持され、成形体の最下端で支持することが推奨されている。 However, in the techniques disclosed in Patent Documents 1 to 4, the opening amount of the seam gap portion of the open pipe cannot be made smaller than the width of the punch support. Therefore, Patent Documents 5 to 9 disclose a technique for further processing the open pipe after press bend molding to reduce the opening amount of the seam gap portion. Patent Document 5 discloses a technique for forming a steel pipe after press bending with a small load by performing hot roll forming. In Patent Document 6, a strain detector capable of detecting the inclination or strain of the pressing material mounted on the slide is provided, and the pressing material can be tilted in response to the detection of the inclination or strain of the strain detector. When the molding material is press-formed into a pipe shape by arranging it so as to be able to move in parallel, the pressing material is tilted or moved in parallel so that the amount of strain is smaller than the amount of inclination or strain of the pressing material. The molding technique is disclosed. In Patent Document 7, at least one bending step acting on the inner surface of the plate material on the left and right sides with respect to the center defined by the longitudinal axis of the upper tool entering the plate material to be gradually formed, as compared with other bending steps. By performing a slight molding, a slit tube with a non-circular preform is formed, which then acts on the non-circular preform from the outside, each time appropriately, in the pre-slightly molded regions on both sides of the center. A technique for forming a completed slit tube by applying a pressing force is disclosed. Further, in Patent Document 8, a molded product having a flat portion between portions bent to at least two pipe curvatures is subjected to plastic deformation at least one flat portion to obtain a predetermined curvature. , A technique for forming a pipe with a closed slit portion is disclosed. Further, in Patent Document 9, a molded body is provided with a lightly machined portion having a very slight curvature as compared with other regions, or an unprocessed portion without bending is provided, and a molded body is reduced to form an open pipe. Disclosed is a method of forming a pipe in which a slit portion is closed by applying a pressing force without restraining a lightly processed portion or an unprocessed portion. Further, at the time of pressing, it is recommended that the molded body is held by the mold in a U-shaped posture with the open portion facing upward, and is supported by the lowermost end of the molded body.
特許文献10及び11では、Oプレス金型の内面の径と製品管の外径と異なる製品径のUOE管の製造技術が開示されている。特許文献10にて開示している金型は、上下ダイの内面が横長円形の一部だけを切り欠いた形状であり、その金型の作用を説明する、特許文献10の図3(a)及び図4(a)では、Oプレス金型の内面全体にO管が接触している。また、特許文献11では、製品外径よりも大きな半径の円弧が内面に形成され、端面を予め研削しておきギャップを充分に大きくした金型を用い、金型内に材料を充満させて所定の圧縮を行った後、この成形したパイプを略90[°]回転し、再度Oプレスを行うことによって円形に成形する方法が開示されている。このときの第1回目のOプレス工程でも、金型全面に鋼管が密着した状態となっている。 Patent Documents 10 and 11 disclose a technique for manufacturing a UOE pipe having a product diameter different from the inner diameter of the O-press die and the outer diameter of the product pipe. The mold disclosed in Patent Document 10 has a shape in which the inner surface of the upper and lower dies is cut out only in a part of a horizontally oblong circle, and the operation of the mold is described in FIG. 3 (a) of Patent Document 10. In FIG. 4A, the O-tube is in contact with the entire inner surface of the O-press die. Further, in Patent Document 11, an arc having a radius larger than the outer diameter of the product is formed on the inner surface, and a mold is used in which the end face is ground in advance and the gap is sufficiently large, and the mold is filled with a material to determine the predetermined value. A method of forming a circular shape by rotating the formed pipe by about 90 [°] and performing O-press again is disclosed. Even in the first O-pressing process at this time, the steel pipe is in close contact with the entire surface of the mold.
特開2004−82219号公報Japanese Unexamined Patent Publication No. 2004-82219 特開2011−56524号公報Japanese Unexamined Patent Publication No. 2011-56524 国際公開第2014/188468号International Publication No. 2014/188468 国際公開第2014/192043号International Publication No. 2014/192043 特開2005−324255号公報Japanese Unexamined Patent Publication No. 2005-324255 特開2005−21907号公報Japanese Unexamined Patent Publication No. 2005-21907 特開2012−250285号公報Japanese Unexamined Patent Publication No. 2012-250285 米国特許第4149399号明細書U.S. Pat. No. 4,149,399 国際公開第2016/084607号International Publication No. 2016/08467 特開2003−39115号公報Japanese Unexamined Patent Publication No. 2003-39115 特開2002−178026号公報JP-A-2002-178026
しかしながら、特許文献5に開示された技術では、加熱にかかる熱エネルギーの消費量を含めると製造コストの著しい上昇を招くという問題がある。また、この技術は、強度や靱性、溶接性を兼備するために加工熱処理プロセスを経て製造された板材を用いる場合に、その特性を損なうおそれもある。特許文献6〜8に開示された技術では、成形材料あるいは非円形のプリフォームを左右それぞれ別々に成形しているため、変形量が左右で異なった場合、溶接部分となるシームギャップ部あるいはスリット部に、段差(目違い)が形成されてしまうことが懸念される。また、これら技術では、1回で所望の形状にまで変形させようとすると局部に変形が集中し、鋼管の真円度を悪化させてしまうおそれがあることから、複数回にわたる変形が不可欠であり効率的な成形を行うにも限界がある。また、特許文献9に開示された技術では、下金型の半径がパイプ外径よりも大きいため、U字姿勢の成形体の最下端で曲げ戻しが行われ、ギャップ部が開くような変形が生じるため、スリット部の間隔を小さくできない場合がある。また、特許文献10及び11に開示された技術では、金型全面にO管が密着した状態でのプレス加工であるため、上述したように高いプレス力を必要とすることから、大掛かりなプレス機を使用せざるを得ない状況にあることは変わらない。 However, the technique disclosed in Patent Document 5 has a problem that the manufacturing cost is significantly increased when the consumption of heat energy required for heating is included. In addition, this technique may impair the characteristics of a plate material manufactured through a processing heat treatment process in order to have strength, toughness, and weldability. In the techniques disclosed in Patent Documents 6 to 8, since the molding material or the non-circular preform is molded separately on the left and right, if the deformation amount is different on the left and right, the seam gap portion or the slit portion which becomes the welded portion is formed. In addition, there is a concern that a step (mismatch) will be formed. Further, in these techniques, if it is attempted to deform to a desired shape at one time, the deformation may be concentrated locally and the roundness of the steel pipe may be deteriorated. Therefore, it is indispensable to perform the deformation multiple times. There is a limit to efficient molding. Further, in the technique disclosed in Patent Document 9, since the radius of the lower mold is larger than the outer diameter of the pipe, bending back is performed at the lowermost end of the U-shaped molded body, and the deformation is such that the gap portion is opened. Therefore, it may not be possible to reduce the distance between the slit portions. Further, in the techniques disclosed in Patent Documents 10 and 11, since the pressing process is performed in a state where the O-tube is in close contact with the entire surface of the mold, a high pressing force is required as described above, so that a large-scale pressing machine is required. There is no change in the situation where we have no choice but to use.
本発明は、上記課題に鑑みてなされたものであって、その目的は、真円度の高い鋼管を効率的に成形することができる鋼管の製造方法及びプレス金型を提供することである。 The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a steel pipe and a press die capable of efficiently forming a steel pipe having a high roundness.
上述した課題を解決し、目的を達成するために、本発明に係る鋼管の製造方法は、幅方向両端部に端曲げ加工が施された板材に、その幅方向に沿って3回以上の曲げ加工を施してU字状断面をなす成形体を成形し、次いで、該成形体にプレス加工を施すことにより、その長手方向にシームギャップ部を有する管体であるオープン管とした後、該シームギャップ部を接合して鋼管とする鋼管の製造方法であって、前記端曲げ加工前の前記板材の幅を板幅Wとしたとき、前記成形体は、板幅端部からW/4だけ離れた部位を中心に、他の領域に比較して小さな曲率を付与した軽加工部、または、曲げ加工を省略した未加工部を有し、前記オープン管の形状が、前記U字状断面の最下部を中心に前記板幅Wの20[%]以上の範囲と、前記板幅端から前記板幅Wの10[%]以上の範囲とが、前記鋼管の外径と同径または略同径の円弧に内接する形状となるように、プレス加工することを特徴とするものである。 In order to solve the above-mentioned problems and achieve the object, the method for manufacturing a steel pipe according to the present invention is to bend a plate material having end bending processing at both ends in the width direction three times or more along the width direction. A molded body having a U-shaped cross section is formed by processing, and then the molded body is pressed to obtain an open pipe having a seam gap in the longitudinal direction thereof, and then the seam is formed. In a method for manufacturing a steel pipe in which gaps are joined to form a steel pipe, when the width of the plate material before the end bending process is the plate width W, the molded body is separated from the plate width end by W / 4. It has a lightly machined part that is given a small curvature compared to other areas, or an unprocessed part that omits bending, and the shape of the open pipe is the maximum of the U-shaped cross section. The range of 20 [%] or more of the plate width W and the range of 10 [%] or more of the plate width W from the plate width end are the same diameter or substantially the same diameter as the outer diameter of the steel pipe centering on the lower part. It is characterized in that it is pressed so as to have a shape inscribed in the arc of.
また、本発明に係る鋼管の製造方法は、上記の発明において、前記鋼管の外径と同径または略同径の円弧に内接する前記U字状断面の最下部を中心に前記板幅Wの20[%]以上の範囲をAとし、前記鋼管の外径と同径または略同径の円弧に内接する板幅両端から前記板幅Wの10[%]以上の範囲の合計をBとしたとき、式(1)を満たすことを特徴とするものである。
2|A−B|/(A+B)<0.4 ・・・(1)
ここで、|A−B|は、A−Bの絶対値を示す。
Further, in the above-described invention, the method for manufacturing a steel pipe according to the present invention has a plate width W centered on the lowermost portion of the U-shaped cross section inscribed in an arc having the same or substantially the same diameter as the outer diameter of the steel pipe. The range of 20 [%] or more was defined as A, and the total of the range of 10 [%] or more of the plate width W from both ends of the plate width inscribed in an arc having the same or substantially the same diameter as the outer diameter of the steel pipe was defined as B. When, it is characterized in that the equation (1) is satisfied.
2 | AB | / (A + B) <0.4 ... (1)
Here, | AB | indicates the absolute value of AB.
また、本発明に係る鋼管の製造方法は、上記の発明において、一対の金型のうちの一方の金型と前記成形体のU字開放側とが対向するように他方の金型に該成形体を載置して、該一対の金型で該成形体を挟み込んで該成形体にプレス加工を施すにあたり、前記他方の金型は、前記他方の金型に前記成形体を載置した状態で、前記U字状断面の最下部を中心に、前記鋼管の外径と同径または略同径の円弧に内接する形状となる範囲を除いて前記成形体が接触せず、プレス加工が完了した状態で、前記他方の金型の一部に前記オープン管に接触しない加工面を備えており、前記一方の金型は、前記他方の金型に前記成形体を載置した状態で、前記成形体が接触せず、プレス加工が完了した状態で、前記一方の金型の一部に前記オープン管に接触しない加工面を備えたことを特徴とするものである。 Further, in the method for manufacturing a steel pipe according to the present invention, in the above invention, one of the pair of dies is molded into the other die so that the U-shaped open side of the molded body faces each other. When the body is placed and the molded body is sandwiched between the pair of dies and the molded body is pressed, the other mold is in a state where the molded body is placed on the other mold. Then, the press processing is completed without contacting the molded body except for a range in which the shape is inscribed in an arc having the same or substantially the same diameter as the outer diameter of the steel pipe, centering on the lowermost portion of the U-shaped cross section. In this state, a part of the other mold is provided with a processed surface that does not come into contact with the open tube, and the one mold has the molded body placed on the other mold. It is characterized in that a part of the one die is provided with a processed surface that does not come into contact with the open tube in a state where the molded body does not come into contact and the press processing is completed.
また、本発明に係る鋼管の製造方法は、上記の発明において、前記鋼管の外半径に相当する半径に対して±3.5[%]の範囲にある円弧部の半径を有する金型を用いてプレス加工を実施することを特徴とするものである。 Further, in the method for manufacturing a steel pipe according to the present invention, in the above invention, a mold having a radius of an arc portion within a range of ± 3.5 [%] with respect to a radius corresponding to the outer radius of the steel pipe is used. It is characterized in that it is pressed.
また、本発明に係る鋼管の製造方法は、上記の発明において、前記成形体のプレス加工に際して、前記成形体のプレス加工に用いるプレス金型の中心と、前記成形体の幅方向の中心とが一致していることを特徴とするものである。 Further, in the method for manufacturing a steel pipe according to the present invention, in the above invention, when the molded body is pressed, the center of the press die used for the press working of the molded body and the center in the width direction of the molded body are formed. It is characterized by being in agreement.
また、本発明に係る鋼管の製造方法は、上記の発明において、前記成形体は、U字開放側を上方に向けたU字姿勢に保持されることを特徴とするものである。 Further, the method for manufacturing a steel pipe according to the present invention is characterized in that, in the above invention, the molded body is held in a U-shaped posture with the U-shaped open side facing upward.
また、本発明に係るプレス金型は、上記の発明の鋼管の製造方法において使用するプレス金型であって、前記プレス金型は、前記成形体を挟持する一対の押圧体からなり、各金型の前記成形体と接触し得る面には、各金型の加工中心と一致する位置に円弧中心が位置するように、前記鋼管の外半径に相当する半径に対して±3.5[%]の範囲にある半径の円弧部が形成されており、各金型における前記円弧部の中心角が70度以上であり、両金型の前記中心角の角度の合計が360度未満であることを特徴とするものである。 Further, the press die according to the present invention is a press die used in the method for manufacturing a steel pipe of the above invention, and the press die is composed of a pair of pressing bodies that sandwich the molded body, and each die. ± 3.5 [%] with respect to the radius corresponding to the outer radius of the steel pipe so that the arc center is located at a position corresponding to the processing center of each mold on the surface of the mold that can come into contact with the molded body. ] Is formed, the central angle of the arc portion in each mold is 70 degrees or more, and the total angle of the central angles of both molds is less than 360 degrees. It is characterized by.
また、本発明に係るプレス金型は、上記の発明において、両金型の前記中心角の角度が同じであることを特徴とするものである。 Further, the press die according to the present invention is characterized in that, in the above invention, the angles of the central angles of both dies are the same.
また、本発明に係るプレス金型は、上記の発明において、各金型は、前記円弧部の円弧方向両端にそれぞれつながった、直線部、または、該円弧部よりも曲率が小さい小曲率円弧部を有することを特徴とするものである。 Further, in the above invention, the press die according to the present invention is a straight line portion connected to both ends of the arc portion in the arc direction, or a small curvature arc portion having a curvature smaller than that of the arc portion. It is characterized by having.
また、本発明に係る鋼管の製造方法は、上記の発明の鋼管の製造方法において、上記の発明のプレス金型を用いることを特徴とするものである。 Further, the method for manufacturing a steel pipe according to the present invention is characterized in that the press die of the above invention is used in the method for manufacturing a steel pipe of the above invention.
本発明に係る鋼管の製造方法及びプレス金型においては、真円度の高い鋼管を効率的に成形することができるという効果を奏する。 In the steel pipe manufacturing method and the press die according to the present invention, there is an effect that a steel pipe having a high roundness can be efficiently formed.
図1は、実施形態に係るプレスベンド方式でU字状断面をなす成形体を成形するのに用いるダイ及びパンチなどの外観斜視図である。FIG. 1 is an external perspective view of a die, a punch, and the like used to form a molded body having a U-shaped cross section by the press bend method according to the embodiment. 図2は、プレスベンド方式によりU字状断面をなす成形体を成形する手順を示す図である。FIG. 2 is a diagram showing a procedure for molding a molded body having a U-shaped cross section by a press bend method. 図3は、U字状断面をなす成形体の断面図である。FIG. 3 is a cross-sectional view of a molded body having a U-shaped cross section. 図4は、成形体にOプレスを施してオープン管を成形する工程を模式的に示した図である。FIG. 4 is a diagram schematically showing a process of forming an open tube by applying O-press to a molded body. 図5は、上金型及び下金型の円弧部と直線部と中心角とについての説明図である。FIG. 5 is an explanatory view of an arc portion, a straight portion, and a central angle of the upper mold and the lower mold. 図6は、オープン管のシームギャップ部の開き量と拘束範囲との関係を、プレス荷重と合わせて示したグラフである。FIG. 6 is a graph showing the relationship between the opening amount of the seam gap portion of the open pipe and the restraint range together with the press load. 図7は、拘束範囲が0度の上金型及び下金型を用いてオープン管を成形した際の変形状況を模式的に示した図である。FIG. 7 is a diagram schematically showing a deformation state when an open tube is formed by using an upper mold and a lower mold having a restraint range of 0 degrees. 図8は、拘束範囲と、オープン管のシームギャップ部を溶接で閉じたときの拡管前における鋼管の真円度との関係を示すグラフである。FIG. 8 is a graph showing the relationship between the restraint range and the roundness of the steel pipe before the pipe expansion when the seam gap portion of the open pipe is closed by welding. 図9は、拘束範囲とプレス荷重との関係を示すグラフである。FIG. 9 is a graph showing the relationship between the restraint range and the press load. 図10は、上金型及び下金型の個々の拘束範囲を変化させた場合におけるオープン管のシームギャップ部の開き量の結果を示すグラフである。FIG. 10 is a graph showing the result of the opening amount of the seam gap portion of the open pipe when the individual restraint ranges of the upper mold and the lower mold are changed. 図11は、上金型及び下金型の個々の拘束範囲を変化させた場合における、オープン管のシームギャップ部を溶接で閉じて成形された拡管前の鋼管の真円度の結果を示すグラフである。FIG. 11 is a graph showing the result of the roundness of the steel pipe before expansion, which is formed by closing the seam gap portion of the open pipe by welding when the individual restraint ranges of the upper mold and the lower mold are changed. Is. 図12は、上金型及び下金型の個々の拘束範囲を変化させた場合におけるプレス荷重の結果を示すグラフである。FIG. 12 is a graph showing the result of the press load when the individual restraint ranges of the upper die and the lower die are changed. 図13は、上金型の拘束範囲と下金型の拘束範囲とを同一として、プレスベンド後の成形体の軽加工部もしくは未加工部の長さを変化させた場合におけるシームギャップ部の開き量の結果を示すグラフである。FIG. 13 shows the opening of the seam gap portion when the length of the lightly processed portion or the unprocessed portion of the molded body after press bending is changed while the restraint range of the upper mold and the restraint range of the lower mold are the same. It is a graph which shows the result of the quantity. 図14は、上金型の拘束範囲と下金型の拘束範囲とを同一として、プレスベンド後の成形体の軽加工部もしくは未加工部の長さを変化させた場合における拡管前の鋼管の真円度の結果を示すグラフである。FIG. 14 shows the steel pipe before expansion when the length of the lightly processed portion or the unprocessed portion of the molded body after press bending is changed while the restraint range of the upper mold and the restraint range of the lower mold are the same. It is a graph which shows the result of roundness. 図15は、上金型の拘束範囲と下金型の拘束範囲とを同一として、プレスベンド後の成形体の軽加工部もしくは未加工部の長さを変えた場合におけるプレス荷重の結果を示すグラフである。FIG. 15 shows the result of the press load when the restraint range of the upper mold and the restraint range of the lower mold are the same and the lengths of the lightly processed portion or the unprocessed portion of the molded body after press bending are changed. It is a graph. 図16は、上金型及び下金型の円弧部の半径を変化させた場合におけるオープン管のシームギャップ部の開き量の結果を示すグラフである。FIG. 16 is a graph showing the result of the opening amount of the seam gap portion of the open pipe when the radii of the arc portions of the upper mold and the lower mold are changed. 図17は、上金型及び下金型の円弧部の半径を変化させた場合におけるプレス荷重の結果を示すグラフである。FIG. 17 is a graph showing the result of the press load when the radius of the arc portion of the upper die and the lower die is changed.
以下に、本発明に係る鋼管の製造方法、及び、その鋼管の製造方法に使用されるプレス金型の一実施形態について説明する。図1は、本実施形態に係るプレスベンド方式でU字状断面をなす成形体を成形するのに用いるダイ1及びパンチ2などの外観斜視図である。ダイ1は、複数の搬送ローラ3によって形成された、板材Sの搬送経路内に配置されており、板材Sを板材搬送方向に沿って2箇所で支持する左右一対の棒状部材1a,1bで構成されている。また、棒状部材1a,1bの板材搬送方向における間隔eは、最終的に成形される鋼管のサイズに応じて変更可能となっている。 Hereinafter, a method for manufacturing a steel pipe according to the present invention and an embodiment of a press die used in the method for manufacturing the steel pipe will be described. FIG. 1 is an external perspective view of a die 1 and a punch 2 used for molding a molded body having a U-shaped cross section by the press bend method according to the present embodiment. The die 1 is arranged in a transport path of the plate material S formed by a plurality of transport rollers 3, and is composed of a pair of left and right rod-shaped members 1a and 1b that support the plate material S at two locations along the plate material transport direction. Has been done. Further, the interval e of the rod-shaped members 1a and 1b in the plate material transport direction can be changed according to the size of the steel pipe to be finally formed.
パンチ2は、ダイ1に対して近接及び離隔する向きに移動可能となっており、板材Sを押圧する下向き凸状のパンチ先端部2aと、このパンチ先端部2aの背面(上端面)に同一の幅をもってつながり、パンチ先端部2aを支持するパンチ支持体2bとから構成されている。パンチ支持体2bは、上端部が図示しない駆動手段に連結されており、その駆動手段によってパンチ先端部2aに押圧力を付与することができるものである。 The punch 2 is movable in the direction of approaching and separating from the die 1, and is the same as the downwardly convex punch tip 2a that presses the plate material S and the back surface (upper end surface) of the punch tip 2a. It is composed of a punch support 2b that is connected by the width of the punch and supports the punch tip 2a. The upper end of the punch support 2b is connected to a driving means (not shown), and the driving means can apply a pressing force to the punch tip 2a.
図2に、プレスベンド方式によりU字状断面をなす成形体Sを成形する手順を示す。なお、この手順は、予め端曲げ加工を施した板材Sに対して、図2の左列の上から下、次いで、図2の中央列の上から下、最後に図2の右列の順で、曲げ加工及び板材Sの送りを実施する場合の一例を具体的に示したものである。また、図2中のパンチ2や板材Sにそれぞれ付されている矢印は、各段階でのパンチ2や板材Sの移動方向を示している。Figure 2 shows a procedure for molding the molded body S 1 forming a U-shaped cross section by pressing bend method. In this procedure, for the plate material S that has been subjected to the edge bending process in advance, the order is from top to bottom in the left column of FIG. 2, then from top to bottom in the center row of FIG. 2, and finally in the right column of FIG. In the above, an example in the case of performing bending processing and feeding of the plate material S is specifically shown. Further, the arrows attached to the punch 2 and the plate material S in FIG. 2 indicate the moving directions of the punch 2 and the plate material S at each stage.
板材Sを出発材料として、この板材Sを管状に成形するには、まず、板材Sに端曲げ加工を施しておく。この端曲げ加工は、ダイ1及びパンチ2を用いて板材Sに曲げ加工を施す場合に比べて、相対的に曲げ難い板幅端部について行われるものであり、この端曲げ加工により板材Sの板幅端部に端曲げ加工部を設けておくことで、端曲げ加工部を設けない場合よりも、高い真円度の確保された鋼管が得やすくなる。なお、鋼管の真円度とは、鋼管の断面形状がどれだけ円に近いかを表す指標であり、鋼管の全周において近似円弧からの変動量の最大と最小との差を、鋼管径で除した率で示される値である。例えば、外直径Dの鋼管の任意の管長位置で管を周方向に、8等分、12等分、16等分、あるいは24等分して対向する位置での外直径を測定し、それらのうちの最大径と最小径とをそれぞれDmax、Dminとした場合に、真円度[%]は{(Dmax−Dmin)/D}×100で定義される。真円度が0に近いほど、鋼管の断面形状が完全な円に近い形状となる。In order to form the plate material S into a tubular shape using the plate material S as a starting material, first, the plate material S is subjected to edge bending. This end bending process is performed on the plate width end portion, which is relatively difficult to bend as compared with the case where the plate material S is bent using the die 1 and the punch 2, and the end bending process of the plate material S By providing the end bending portion at the plate width end portion, it becomes easier to obtain a steel pipe with a high roundness as compared with the case where the end bending portion is not provided. The roundness of the steel pipe is an index showing how close the cross-sectional shape of the steel pipe is to a circle, and the difference between the maximum and minimum amount of fluctuation from the approximate arc on the entire circumference of the steel pipe is calculated by the steel pipe diameter. It is a value indicated by the divided rate. For example, at an arbitrary pipe length position of a steel pipe having an outer diameter D, the pipe is divided into 8 equal parts, 12 equal parts, 16 equal parts, or 24 equal parts in the circumferential direction, and the outer diameters at opposite positions are measured. When the maximum diameter and the minimum diameter are D max and D min , respectively, the roundness [%] is defined by {(D max −D min ) / D} × 100. The closer the roundness is to 0, the closer the cross-sectional shape of the steel pipe is to a perfect circle.
端曲げ加工部が設けられた板材Sは、図1に示したダイ1の上に載置され、板材Sを所定の送り量で間欠的に送られつつ、図2に示す手順で、板材Sの幅方向に沿って3回以上の曲げ加工が施され、全体としてU字状断面をなす成形体Sに成形される。The plate material S provided with the edge bending portion is placed on the die 1 shown in FIG. 1, and while the plate material S is intermittently fed at a predetermined feed amount, the plate material S is performed by the procedure shown in FIG. along the width direction it is 3 times or more the bending undergone a is formed into the molded body S 1 forming a U-shaped cross section as a whole.
図3は、U字状断面をなす成形体Sの断面図である。端曲げ加工前の板材Sの幅を板幅Wとしたとき、図3に示すように、成形体Sの一部分、特に板幅端からそれぞれW/4だけ離れた部位であるW/4部を中心に、曲げ加工を省略した未加工部Pが設けられている。この未加工部Pは、板材Sの送りを大きくしてパンチ2による押圧を省略することにより設けることができる。なお、成形体Sの一部分、特に板幅端からそれぞれW/4部を中心に、未加工部Pではなく、他の部分よりも曲率が小さな(他の部分と比較して、ごく僅かな曲率を付与した)軽加工部を設けても良い。その場合には、以下の説明において「未加工部P」を「軽加工部」に適宜読み替えれば良い。軽加工部は、パンチ2によって付加される押圧量を他の部分よりも小さくして圧下することにより設けることができる。Figure 3 is a cross-sectional view of a shaped body S 1 forming a U-shaped cross section. When the width of the plate material S before the edge bending process is the plate width W, as shown in FIG. 3, a part of the molded body S 1 , particularly the W / 4 portion which is a portion separated by W / 4 from the plate width end, respectively. An unprocessed portion P in which bending is omitted is provided around the center. The unprocessed portion P can be provided by increasing the feed of the plate material S and omitting the pressing by the punch 2. Incidentally, a portion of the molded body S 1, in particular about respective from strip width end W / 4 parts of the unprocessed portion P without curvature than the other portion in comparison with a small (other portions, very small A lightly machined portion (with a curvature) may be provided. In that case, "unprocessed portion P" may be appropriately read as "lightly processed portion" in the following description. The lightly machined portion can be provided by reducing the amount of pressing applied by the punch 2 to be smaller than that of other portions.
また、図1及び図2に示したパンチ2の形状は、パンチ先端部2aの板材搬送方向における幅と、パンチ支持体2bの板材搬送方向における幅とを同じにしたI字形状のものであるが、パンチ2の形状としては、これに限るものでない。例えば、パンチ2として、パンチ先端部2aの板材搬送方向における幅を、パンチ支持体2bの板材搬送方向における幅よりも大きくした、略逆T字形状のものを用いることもできる。パンチ支持体2bの板材搬送方向における幅が同じ場合、略逆T字形状のパンチ2を用いたほうが、I字形状のパンチ2を用いる場合に比べて、1回の押圧で、板材Sに対してより大きな面積を押圧することができ、押圧回数の低減を図ることが可能となる。 Further, the shape of the punch 2 shown in FIGS. 1 and 2 is an I-shape in which the width of the punch tip portion 2a in the plate material transport direction and the width of the punch support 2b in the plate material transport direction are the same. However, the shape of the punch 2 is not limited to this. For example, as the punch 2, a punch 2 having a substantially inverted T shape in which the width of the punch tip portion 2a in the plate material transport direction is larger than the width of the punch support 2b in the plate material transport direction can also be used. When the widths of the punch supports 2b in the plate material transport direction are the same, it is better to use the substantially inverted T-shaped punch 2 than to use the I-shaped punch 2 with respect to the plate material S with one pressing. Therefore, a larger area can be pressed, and the number of times of pressing can be reduced.
板材Sに対してプレスベンド方式により曲げ加工を施し、U字状断面をなす成形体Sを成形したら、図4に示すような一対の金型である上金型4及び下金型5からなるプレス金型を用いて成形体SをO字状にプレス加工するOプレスを施すことで、周方向で互いに向き合った板幅端部間にシームギャップ部Gを有する管体であるオープン管Sを成形する。Subjected to bending by the press bending method with respect to the plate material S, After shaping the shaped bodies S 1 forming a U-shaped cross-section, the upper mold 4 and the lower mold 5 are a pair of molds as shown in FIG. 4 comprising a molded body S 1 using a press mold to O-shape by performing O press pressing, between the plate width end portions which face each other in the circumferential direction is a tubular body having a seam gap G open pipe to form the S 2.
次に、図4を用いて、成形体SにOプレスを施してオープン管Sを成形する手順について説明する。まず、図4(a)に示すように、上金型4と成形体SのU字開放側とが対向するように(成形体SのU字開放側が上方を向くように)、下金型5に成形体Sを設置して、上金型4と下金型5とで成形体Sを挟み込む。また、成形体Sのプレス加工に際しては、プレス金型の加工中心と、成形体Sの幅方向の中心とを一致させるようにしている。これにより、成形体S1のU字開放側において、板幅端部を左右均等に押圧することが可能となる。Next, a procedure for forming the open tube S 2 by applying an O-press to the molded body S 1 will be described with reference to FIG. First, as shown in FIGS. 4 (a), (as U-shaped open side of the molded body S 1 is directed upward) upper mold 4 and the molded body S 1 of the U-shape so that the open side faces, bottom The molded body S 1 is installed in the mold 5, and the molded body S 1 is sandwiched between the upper mold 4 and the lower mold 5. Further, when pressing of the molded body S 1 is designed so as to coincide with the processing center of the press die, and a center in the width direction of the molded body S 1. As a result, the plate width end portion can be pressed evenly on the left and right sides of the U-shaped open side of the molded body S1.
なお、図5に示すように、上金型4及び下金型5の成形体Sと接触し得る面には、成形する鋼管の外径と同径または略同径であって中心角θの円弧部4a,5aが形成されており、この範囲が鋼管の外径と同径または略同径の円弧に内接する形状にプレス加工される。例えば、中心角θが360度の場合が、板幅の100[%]が前記内接する形状にプレス加工される場合に相当することになる。なお、以後、円弧部4a,5aの中心角θを拘束範囲と称し、その角度を360度で除した値が、鋼管の外径と同径または略同径の円弧に内接する形状となるようにプレス加工される範囲となる。円弧部4aは、上金型4の加工中心Op4と一致する位置に円弧中心が位置しており、円弧部5aは、下金型5の加工中心Op5と一致する位置に円弧中心が位置している。また、上金型4は、円弧部4aの円弧方向両端にそれぞれつながった直線部4b,4bを有しており、下金型5は、円弧部5aの円弧方向両端にそれぞれつながった直線部5b,5bを有している。なお、上金型4及び下金型5においては、直線部4b,4b,5b,5bに替えて、円弧部4a,5aよりも曲率が小さい小曲率円弧部を有するようにしてもよい。なお、本発明において、最終的に得られる鋼管の対称性を高める観点から、円弧部4a,5aにつながった直線部4b,4b,5b,5bまたは小曲率円弧部は、加工中心Op4,Op5に対して、すなわち、円弧部4a,5aの中心に対して対称であることが好ましい。また、鋼管の外半径に相当する半径に対して±3.5[%]の範囲にある円弧部の半径を有する金型を用いてプレス加工を実施することが好ましい。その理由については、後述する。As shown in FIG. 5, the surface that may contact the shaped body S 1 of the upper mold 4 and the lower mold 5, the center angle θ a outer diameter and the same diameter or substantially the same diameter of the steel pipe to be molded Arc portions 4a and 5a are formed, and this range is pressed into a shape inscribed in an arc having the same or substantially the same diameter as the outer diameter of the steel pipe. For example, the case where the central angle θ is 360 degrees corresponds to the case where 100 [%] of the plate width is pressed into the inscribed shape. Hereinafter, the central angles θ of the arc portions 4a and 5a will be referred to as a restraint range, and the value obtained by dividing the angle by 360 degrees will be inscribed in an arc having the same or substantially the same diameter as the outer diameter of the steel pipe. It will be in the range to be pressed. Arc portion 4a is arc center to a position which coincides with the processing center O p4 of the upper mold 4 is positioned, the arc portion 5a, arc center is located at a position which coincides with the processing center O p5 of the lower die 5 doing. Further, the upper mold 4 has straight portions 4b 1 and 4b 2 connected to both ends of the arc portion 4a in the arc direction, and the lower mold 5 has straight portions connected to both ends of the arc portion 5a in the arc direction, respectively. It has parts 5b 1 and 5b 2 . The upper mold 4 and the lower mold 5 have a small curvature arc portion having a smaller curvature than the arc portions 4a and 5a instead of the straight portions 4b 1 , 4b 2 , 5b 1 , 5b 2. May be good. In the present invention, from the viewpoint of enhancing the symmetry of the finally obtained steel pipe, the straight portions 4b 1 , 4b 2 , 5b 1 , 5b 2 or the small curvature arc portion connected to the arc portions 4a, 5a is the processing center. It is preferable that it is symmetrical with respect to Op4 and Op5 , that is, with respect to the centers of the arc portions 4a and 5a. Further, it is preferable to perform press working using a die having an arc portion radius within a range of ± 3.5 [%] with respect to a radius corresponding to the outer radius of the steel pipe. The reason will be described later.
次に、上金型4と下金型5とで挟み込まれた成形体Sを、図4(b)に示すように上金型4で圧下してOプレスを施す。このとき、成形体Sにおける上金型4及び下金型5の円弧部4a,5aと対向する部分は、上金型4及び下金型5によって拘束されるが、成形体Sの未加工部Pは、上金型4及び下金型5によって拘束されない。そのため、上金型4及び下金型5によって成形体Sの全周が拘束される場合に必要とされる押圧力よりも小さな押圧力で、図4(c)に示すようなオープン管Sを成形することができる。Next, the molded body S 1 sandwiched by the upper mold 4 and the lower die 5, subjected to O pressing and rolling in the upper mold 4, as shown in Figure 4 (b). At this time, the circular arc portion 4a, 5a and opposite portions of the upper mold 4 and the lower mold 5 in the molding member S 1 is constrained by upper mold 4 and the lower mold 5, non-molded body S 1 The processed portion P is not constrained by the upper mold 4 and the lower mold 5. Therefore, with a small pressing force than the pressing force required when the entire circumference of the shaped body S 1 is constrained by the upper mold 4 and the lower mold 5, open pipe S as shown in FIG. 4 (c) 2 can be molded.
そして、本実施形態に係る鋼管の製造方法においては、上金型4と下金型5とからなるプレス金型によって、オープン管Sの形状が、U字状断面の最下部を中心に板幅Wの20[%]以上(中心角θが70度以上に相当)の範囲と、板幅端から板幅Wの10[%]以上(中心角θが35度以上に相当)の範囲とが、鋼管の外径と同径または略同径の円弧に内接する形状となるように、成形体Sをプレス加工する。Then, in the manufacturing method of a steel pipe according to the present embodiment, a press die composed of upper mold 4 and the lower die 5 which, the shape of the open pipe S 2, the plate around the bottom of the U-shaped cross section A range of 20 [%] or more of the width W (corresponding to a central angle θ of 70 degrees or more) and a range of 10 [%] or more of the plate width W (corresponding to a central angle θ of 35 degrees or more) from the plate width end. but as a shape inscribed in a circular arc of the outer diameter and the same diameter or substantially the same diameter of the steel tube, the molded body S 1 pressing.
そして、本実施形態においては、最終的に得られる鋼管形状を向上させる観点から、オープン管Sが金型に内接する範囲が、上金型4側と下金型5側とで、略同じ大きさであることが好ましい。すなわち、鋼管の外径と同径または略同径の円弧に内接するU字状断面の最下部を中心に板幅Wの20[%]以上の範囲をAとし、鋼管の外径と同径または略同径の円弧に内接する板幅両端から板幅Wの10[%]以上の範囲の合計をBとしたとき、式(1)を満たすことが好ましい。
2|A−B|/(A+B)<0.4 ・・・(1)
ここで、|A−B|は、A−Bの絶対値を示す。
また、式(1)の意味については、後で詳述する。
Then, in the present embodiment, from the viewpoint of improving the shape of the steel pipe finally obtained, the range in which the open pipe S 2 is inscribed in the mold is substantially the same on the upper mold 4 side and the lower mold 5 side. The size is preferable. That is, A is a range of 20 [%] or more of the plate width W centered on the lowermost part of the U-shaped cross section inscribed in an arc having the same or substantially the same diameter as the outer diameter of the steel pipe, and has the same diameter as the outer diameter of the steel pipe. Alternatively, it is preferable that the equation (1) is satisfied, where B is the sum of the range of 10 [%] or more of the plate width W from both ends of the plate width inscribed in an arc having substantially the same diameter.
2 | AB | / (A + B) <0.4 ... (1)
Here, | AB | indicates the absolute value of AB.
The meaning of the equation (1) will be described in detail later.
本実施形態に係る鋼管の製造方法においては、オープン管Sを、所定の範囲で確実に金型に内接させ、良好な形状を得るためには、図5に示すように、プレス加工が施される前の成形体Sは、U字状断面内において、板幅中央部であるW/2部における接線TLと、W/4部における接線TL21,TL22とのなす角θ11,θ12が35度以上90度未満であることが好ましい。さらに、プレス加工が施される前の成形体Sは、板幅端部における接線TL31,TL32と、W/4部における接線TL21,TL22とのなす角θ21,θ22が35度以上90度未満であることが好ましい。また、上金型4側と下金型5側とで内接する範囲を同じにするためには、接線TLと接線TL21,TL22とのなす角θ11,θ12の和と、接線TL31,TL32と接線TL21,TL22とのなす角θ21,θ22の和と、が略同じであることが好ましい。In the method for producing a steel pipe according to the present embodiment, the open pipe S 2, certainly is inscribed in a mold in a predetermined range, in order to obtain a good shape, as shown in FIG. 5, the press working moldings S 1 before being subjected, in a U-shaped cross section, the tangent TL 1 in W / 2 parts is a plate width central portion, the angle between the tangent line TL 21, TL 22 in W / 4 parts θ It is preferable that 11 , θ 12 is 35 degrees or more and less than 90 degrees. Further, in the molded body S 1 before being pressed, the angles θ 21 and θ 22 formed by the tangents TL 31 and TL 32 at the plate width end and the tangents TL 21 and TL 22 at the W / 4 portion are formed. It is preferably 35 degrees or more and less than 90 degrees. Further, in order to make the inscribed range on the upper mold 4 side and the lower mold 5 side the same, the sum of the angles θ 11 and θ 12 formed by the tangent line TL 1 and the tangent lines TL 21 and TL 22 and the tangent line. It is preferable that the sum of the angles θ 21 and θ 22 formed by the TL 31 and TL 32 and the tangents TL 21 and TL 22 is substantially the same.
なお、これらの角度については、以下の理由により、U字状の成形体Sに曲げ加工する設備や、U字状の成形体Sをオープン管Sに加工する際の金型の形状を勘案して定める必要がある。これらの角度が大きすぎると、板幅端間の距離が小さくなる。その距離が、U字状の成形体Sに曲げ加工する際のパンチ支持体2bの幅より小さくなると、U字状の成形体Sを得ることができなくなる。一方、これらの角度が小さすぎると、U字状の成形体Sの板幅端間の距離が大きくなるので、U字状の成形体Sを金型に載置した際に、板幅端が上金型4の開口部よりも大きくなり、加工力を付与できなくなる。また、左右の未加工部Pの間の距離が大きくなり過ぎ、下金型5に正しく載置されなくなる。It should be noted that these angles, following the reasons, mold shape during processing equipment and for bending the molded body S 1 of the U-shaped, the shaped body S 1 of U-shape open pipe S 2 It is necessary to determine in consideration of. If these angles are too large, the distance between the plate width ends will be small. The distance is, the smaller than the width of the punch support 2b when bending the molded body S 1 of the U-shape, making it impossible to obtain a molded product S 1 of the U-shape. On the other hand, if these angles are too small, the distance between the plate width ends of the U-shaped body S 1 is increased, when the molded body S 1 of the U-shaped is placed in a mold, the plate width The end becomes larger than the opening of the upper mold 4, and the processing force cannot be applied. Further, the distance between the left and right unprocessed portions P becomes too large, and the lower mold 5 cannot be placed correctly.
また、一対の金型のうちの一方の金型である上金型4と成形体SのU字開放側とが対向するように他方の金型である下金型5に成形体Sを載置して、上金型4と下金型5とにより成形体Sを挟み込んで成形体Sにプレス加工を施すにあたり、上金型4と下金型5とは、次のような加工面を備えている。すなわち、下金型5は、下金型5に成形体Sを載置した状態で、U字状断面の最下部を中心に、板幅Wの20[%]以上(中心角θが70度以上に相当)の範囲を除いて成形体Sが接触せず、プレス加工が完了した状態で、下金型5の一部にオープン管Sに接触しない加工面を備えている。また、上金型4は、下金型5に成形体Sを載置した状態で、成形体Sが接触せず、プレス加工が完了した状態で、上金型4の一部にオープン管Sに接触しない加工面を備えている。Further, the molded body S 1 to the lower mold 5, which is the other die so that one of the upper mold 4 is a mold with U-shaped open side of the molded body S 1 is opposite of the pair of molds the is placed, in the molded body S 1 by sandwiching the molded product S 1 by the upper mold 4 and the lower die 5 Upon performing press working, the upper mold 4 and the lower die 5, as follows It has a machined surface. That is, the lower mold 5, in a state of placing the molded bodies S 1 to the lower mold 5, around the bottom of the U-shaped cross-section, 20% or more in the plate width W (center angle θ is 70 A part of the lower die 5 is provided with a processed surface that does not come into contact with the open tube S 2 in a state where the molded body S 1 does not come into contact with the molded body S 1 except for the range of (corresponding to a degree or more). Further, the upper die 4 is opened in a part of the upper die 4 in a state where the molded body S 1 is placed on the lower die 5 and the molded body S 1 does not come into contact with the lower die 5 and the press working is completed. and a working surface that does not contact the tube S 2.
そして、本実施形態においては、成形体Sのプレス加工に際して、成形体Sのプレス加工に用いるプレス金型の中心と、成形体Sの幅方向の中心とが一致していることが好ましい。これは、成形体Sの幅方向の中心に対して対称な力を加えることが、最終的に得られる鋼管の形状精度向上に寄与するからである。Then, in the present embodiment, when pressing of the molded body S 1, that the center of the press die used for press working of the compact S 1, and the center in the width direction of the molded body S 1 is match preferable. This is because the addition of symmetric force relative to the center in the width direction of the molded body S 1, it contributes to the shape accuracy of the finally obtained steel pipes.
そして、本実施形態においては、成形体Sは、U字開放側を上方に向けたU字姿勢に保持されることが好ましい。これは、一つには、この姿勢でプレス加工するほうが、作業がしやすいからである。また、別の理由としては、仮にU字開放側を下方に向けた場合には、成形体Sの自重が成形体Sの板幅端部に加わるため、板幅端部に、あるいは、金型に擦り疵をつける可能性があるので、それを避けるためである。Then, in the present embodiment, the molded body S 1 is preferably held in a U-posture with its U-shaped open side upwards. This is partly because it is easier to work by pressing in this position. As another reason, if the case with its U-shaped open side downward, since the own weight of the molded body S 1 is applied to the plate width end portions of the molded article S 1, or the plate width ends, This is to avoid scratches on the mold as it may be scratched.
ここで、本実施形態においては、上金型4及び下金型5を用いて成形体SにOプレスを施してオープン管Sを成形する際、成形体Sにおける未加工部Pの中心から板幅端部に向かってW/4だけ離れた部位に押圧力が付加されるようにしているが、その理由は以下の通りである。すなわち、成形体Sの全体が円形になったときの曲げモーメントは、押圧部から中心角が角度φだけ離れた位置では、M=F・r・cosφ(F:押圧力、r:円の半径)となり、押圧部から90度離れた位置で最大となり、変形も最大となる。そこで、未加工部Pの中心から90度すなわち全周の1/4離れた位置に押圧力を付加することで、未加工部Pが効果的に変形することになる。このとき、曲げモーメントは、押圧力を付加する位置から90度離れた位置が最大で、この位置から離れると小さくなっていく。そのため、未加工部Pに十分な塑性変形が生じるためには、未加工部Pの中心から板幅端部に向かってW/4±0.07Wだけ離れた部位に押圧力を付加するのが好ましい。In the present embodiment, when forming the open pipe S 2 is subjected to O press the molded body S 1 with upper mold 4 and the lower mold 5, the raw portion P in the molding material S 1 The pressing force is applied to a portion separated by W / 4 from the center toward the end of the plate width, and the reason is as follows. That is, the bending moment when the whole of the molded body S 1 is becomes circular, the position where the central angle away by an angle φ from the pressing unit, M = F · r · cosφ (F: pressing force, r: circle Radius), the maximum at a position 90 degrees away from the pressing portion, and the maximum deformation. Therefore, by applying a pressing force at a position 90 degrees from the center of the unprocessed portion P, that is, a position separated by 1/4 of the entire circumference, the unprocessed portion P is effectively deformed. At this time, the bending moment is maximum at a position 90 degrees away from the position where the pressing force is applied, and becomes smaller as the distance from this position is increased. Therefore, in order for the unprocessed portion P to undergo sufficient plastic deformation, it is necessary to apply a pressing force to a portion separated by W / 4 ± 0.07 W from the center of the unprocessed portion P toward the end of the plate width. preferable.
また、本実施形態においては、未加工部Pの中心を、板幅端からW/4だけ離れた位置を含む部位に設けることにしたが、その理由は以下の通りである。すなわち、上述したように、押圧力は未加工部Pの中心から板幅端部に向かってW/4だけ離れた部位に付加することが望ましいが、成形体Sをオープン管Sとする段階で、成形体Sの形状は変化するので、上金型4と成形体Sとの接触位置が変わり押圧力を付加する位置も変化する。未加工部Pを、成形体Sにおける板幅端からW/4だけ離れた位置を含む部位に設けた場合は、押圧力を付加する部分は常に成形体Sの板幅端部となり、未加工部Pが最も変形するようになる。このようにすることで、押圧位置を変えることなく、1回の押圧で未加工部Pに変形を与えることができる。また、未加工部Pを、押圧力を付加する位置すなわち成形体Sの板幅端からW/4±0.07Wの範囲に設けるのが好ましい。Further, in the present embodiment, the center of the unprocessed portion P is provided at a portion including a position separated by W / 4 from the plate width end, and the reason is as follows. That is, as described above, it is desirable that the pressing force is applied to a portion separated by W / 4 from the center of the unprocessed portion P toward the plate width end portion, but the molded body S 1 is an open tube S 2 . in step, the shape of the molded body S 1 changes, also changes the position for adding the contact position changes the pressing force of the upper mold 4 and the molded body S 1. When the unprocessed portion P is provided at a portion of the molded body S 1 including a position separated by W / 4 from the plate width end, the portion to which the pressing force is applied is always the plate width end of the molded body S 1 . The unprocessed portion P is most deformed. By doing so, the raw portion P can be deformed by one pressing without changing the pressing position. Further, the raw portion P, preferably provided from the position i.e. the plate width ends of the molded body S 1 adds a pressing force in the range of W / 4 ± 0.07W.
また、図4(a)及び図4(b)のような押圧の初期の段階では、板幅端部が上金型4に接するので、未加工部Pは成形体Sの板幅端からW/4だけ離れた部位を含む部位に設けることが好ましい。Further, the pressing early stages such as shown in FIG. 4 (a) and 4 (b), since the plate width end portions are in contact with the upper mold 4, the unprocessed portion P from the plate width ends of the molded body S 1 It is preferable to provide it in a portion including a portion separated by W / 4.
図6は、オープン管Sのシームギャップ部Gの開き量と拘束範囲との関係を、プレス荷重と合わせて示したグラフである。なお、図6に示す開き量と拘束範囲との関係、及び、プレス荷重は、オープン管Sの両端部を溶接後に拡管率1[%]の拡管による形状矯正を行って、引張強度630[MPa]、外径660.4[mm]、管厚40.0[mm]の鋼管を成形する際におけるものである。6, the relationship between the restraint range and amount of opening of the seam gap G of the open pipe S 2, is a graph showing together with the press load. The relationship between the opening amount and the restraining range shown in FIG. 6, and the press load, the both end portions of the open pipe S 2 performs expanded tube straightening by the expansion ratio 1 [%] after welding, the tensile strength 630 [ MPa], outer diameter 660.4 [mm], pipe thickness 40.0 [mm] when forming a steel pipe.
プレスベンド後の成形体Sは、その両側の板幅端からそれぞれW/4の部分に長さW/12の未加工部Pを設け、板幅中央部における接線と、板幅端からW/4だけ離れた部位であるW/4部における接線とのなす角θ11,θ12が75度、板幅端部における接線と、W/4部における接線とのなす角θ21,θ22が75度の形状とした。この成形体Sを拘束範囲が同じ上金型4と下金型5とで挟持した場合のものである。また、押圧量は、オープン管SのW/2の部分を結んだ距離が、拡管前の直径と等しくなるようにしている(Oプレスでの圧下量は、縦径が拡管前の径と一致するようにしている)。図6から、拘束範囲が大きいほど、オープン管Sのシームギャップ部Gの開き量が小さくなることがわかる。Moldings S 1 after pressing the bend, the raw portion P of length W / 12 provided from both sides of the plate width end in a portion of the respective W / 4, and the tangent at plate width central portion, W from the plate width end The angles θ 11 and θ 12 formed by the tangent at the W / 4 part, which is a part separated by 4/4, are 75 degrees, and the angles θ 21 and θ 22 formed by the tangent at the plate width end and the tangent at the W / 4 part. Has a shape of 75 degrees. This is a case where the molded body S 1 is sandwiched between the upper mold 4 and the lower mold 5 having the same restraint range. Further, the pressing amount is set so that the distance connecting the W / 2 portions of the open pipe S 2 is equal to the diameter before the pipe expansion (the vertical diameter of the reduction amount in the O press is the diameter before the pipe expansion. I try to match). 6, the larger the constraint range, it can be seen that the amount of opening of the seam gap G of the open pipe S 2 becomes small.
図7は、拘束範囲が0度の上金型4及び下金型5を用いてオープン管Sを成形した際の変形状況を模式的に示した図である。上金型4及び下金型5の拘束範囲が0度のときには、上金型4が成形体Sの両端部のみと接触し、下金型5が成形体Sの板幅中央部のみで接触するように、円弧部4a,5aを鋼管外径の1.16倍の直径を有する円弧とした場合である。図7(a)に示すように、成形体Sの断面を時計に見立てたときに6時部分のみが下金型5と接触するように、下金型5の円弧部5aの径が鋼管径よりも大きな径となっている。そのため、図7(b)に示すように、Oプレス中には成形体Sの6時部分及びその近傍に、下金型5の円弧部5aになじむような曲げ戻しが生じ、曲率半径が鋼管径よりも大きくなる。そのため、Oプレス後では、図7(c)に示すようなオープン管Sのシームギャップ部Gの開き量が、成形体Sの3時部分及び9時部分でのスプリングバックと合わせて大きなものとなる。Figure 7 is a diagram schematically showing a modified situation when the constraint range was molded open pipe S 2 with the upper mold 4 and the lower mold 5 of 0 degrees. When the restraint range of the upper mold 4 and the lower mold 5 is 0 degrees, the upper mold 4 contacts only both ends of the molded body S 1 , and the lower mold 5 only contacts the central portion of the plate width of the molded body S 1. This is a case where the arcuate portions 4a and 5a are formed into arcs having a diameter 1.16 times the outer diameter of the steel pipe so as to make contact with each other. As shown in FIG. 7 (a), the cross section of the shaped body S 1 so that only the 6 o'clock portion when regarded in a clockwise is in contact with the lower mold 5, the diameter of the circular arc portion 5a of the lower die 5 steel The diameter is larger than the diameter. Therefore, as shown in FIG. 7 (b), 6 o'clock portion and the vicinity thereof of the molding S 1 is in O press, occurs bent back as fit in the circular arc portion 5a of the lower die 5, the radius of curvature It is larger than the steel pipe diameter. Large Therefore, after the O press, the opening amount of the seam gap G of the open pipe S 2 as shown in FIG. 7 (c), in conjunction with spring back at the 3 o'clock parts and 9:00 parts of the molded body S 1 It becomes a thing.
図8は、拘束範囲と、オープン管Sのシームギャップ部Gを溶接で閉じたときの拡管前における鋼管の真円度との関係を示すグラフである。図8から、拘束範囲が60度の場合には、拘束範囲が0度の場合よりも真円度が悪くなっているが、拘束範囲を大きくすると真円度は良くなり、拘束範囲が70度以上の場合では拘束範囲が0度の場合よりも真円度が良くなることがわかる。また、拘束範囲が100度〜110度で最も真円度が良くなっているのがわかる。Figure 8 is a graph showing the constrained range, the relationship between the roundness of the steel pipe before pipe expansion when closing the weld seam gap portion G of the open pipe S 2. From FIG. 8, when the restraint range is 60 degrees, the roundness is worse than when the restraint range is 0 degrees, but when the restraint range is increased, the roundness is improved and the restraint range is 70 degrees. It can be seen that in the above cases, the roundness is better than when the restraint range is 0 degrees. Further, it can be seen that the roundness is the best when the restraint range is 100 to 110 degrees.
図9は、拘束範囲とプレス荷重との関係を示すグラフである。図9から、拘束範囲が大きくなるとプレス荷重が大きくなるのがわかる。そのため、拘束範囲を大きくすると、オープン管Sのシームギャップ部Gの開き量は小さくなるが、プレス荷重が大きくなる分、プレス設備が大型化するので、所望の開き量が得られる範囲で拘束範囲を小さくするのが望ましい。例えば、プレス荷重を、上金型4及び下金型5で成形体Sの全周を拘束する上金型4及び下金型5の個々の拘束範囲が180度の場合の90[%]以下とするには、拘束範囲を150度以下とすればよい。FIG. 9 is a graph showing the relationship between the restraint range and the press load. From FIG. 9, it can be seen that the press load increases as the restraint range increases. For that reason, increasing the constraint range, restraint in an amount ranging opening of the seam gap G of the open pipe S 2 becomes small, minute the pressing load increases, the pressing equipment is increased in size, the desired opening amount is obtained It is desirable to reduce the range. For example, the press load, 90 [%] when the individual restraint range of the upper die 4 and the lower mold 5 for restraining the entire periphery of the shaped body S 1 in the upper mold 4 and the lower mold 5 is 180 degrees In order to make the following, the restraint range may be 150 degrees or less.
図10は、上金型4及び下金型5の個々の拘束範囲を変化させた場合におけるオープン管Sのシームギャップ部Gの開き量の結果を示すグラフである。図11は、上金型4及び下金型5の個々の拘束範囲を変化させた場合における、オープン管Sのシームギャップ部Gを溶接で閉じて成形された拡管前の鋼管の真円度の結果を示すグラフである。図12は、上金型4及び下金型5の個々の拘束範囲を変化させた場合におけるプレス荷重の結果を示すグラフである。なお、図10〜図12においては、図6、図8及び図9と同様の引張強度630[MPa]、外径660.4[mm]、管厚40.0[mm]の鋼管を対象としており、横軸は上金型4及び下金型5の拘束範囲の平均値であり、下金型5の拘束範囲毎にグラフ中のシンボルを変えている。図中で、例えば、「下60度」とは、下金型5における拘束範囲が60度であることを意味する。Figure 10 is a graph showing the results of the amount of opening of the seam gap G of the open pipe S 2 with changes in individual restraining range of the upper die 4 and the lower mold 5. 11, the upper mold 4 and with changes in individual restraining range of the lower die 5, roundness of the steel pipe before pipe expansion molded by closing the seam gap portion G of the open pipe S 2 by welding It is a graph which shows the result of. FIG. 12 is a graph showing the result of the press load when the individual restraint ranges of the upper die 4 and the lower die 5 are changed. In FIGS. 10 to 12, steel pipes having a tensile strength of 630 [MPa], an outer diameter of 660.4 [mm], and a pipe thickness of 40.0 [mm] similar to those in FIGS. 6, 8 and 9 are targeted. The horizontal axis is the average value of the restraint ranges of the upper mold 4 and the lower mold 5, and the symbols in the graph are changed for each restraint range of the lower mold 5. In the figure, for example, "lower 60 degrees" means that the restraint range in the lower mold 5 is 60 degrees.
図10から、上金型4及び下金型5の個々の拘束範囲によらず、上金型4及び下金型5の拘束範囲の平均値が大きくなると、オープン管Sのシームギャップ部Gの開き量は小さくなっていることがわかる。また、図11から、上金型4と下金型5とのいずれかの拘束範囲が60度未満の場合には、鋼管の真円度が悪くなっていることがわかる。そのため、上金型4及び下金型5の個々の拘束範囲は、上金型4と下金型5とで必ずしも等しくする必要はないが、鋼管の真円度が良好な形状を得るためには、上金型4及び下金型5の拘束範囲を、どちらも60度を超える拘束範囲とするのが望ましい。また、図12から、上金型4及び下金型5の拘束範囲の平均値が大きいほど、プレス荷重は大きくなることがわかる。そのため、許容できるプレス荷重の上限値を設定した場合には、そのプレス荷重の上限値に応じて、適用可能な上金型4及び下金型5の拘束範囲の平均値の範囲が決まる。From Figure 10, regardless of the individual restraint range of the upper die 4 and the lower mold 5, the average value of the constraint range of the upper die 4 and the lower mold 5 is large, the open pipe S 2 seam gap G It can be seen that the opening amount of is small. Further, from FIG. 11, it can be seen that when the restraint range of either the upper mold 4 or the lower mold 5 is less than 60 degrees, the roundness of the steel pipe is deteriorated. Therefore, the individual restraint ranges of the upper mold 4 and the lower mold 5 do not necessarily have to be the same for the upper mold 4 and the lower mold 5, but in order to obtain a shape in which the roundness of the steel pipe is good. It is desirable that the restraint range of the upper mold 4 and the lower mold 5 is set to a restraint range exceeding 60 degrees for both. Further, from FIG. 12, it can be seen that the larger the average value of the restraint ranges of the upper die 4 and the lower die 5, the larger the press load. Therefore, when the upper limit value of the allowable press load is set, the range of the average value of the applicable restraint ranges of the upper die 4 and the lower die 5 is determined according to the upper limit value of the press load.
また、図11において、上下の拘束範囲の差が30度であり、その差が上下の拘束範囲の平均値の29[%]である、上90度/下90度、上90度/下120度、上120度/下90度のものでは、溶接後の拡管前における真円度が1.5[%]以下と非常に優れている。一方、上下拘束範囲の差は30度であるが、その差が上下拘束範囲の平均値の40[%]と大きい、上90度/下60度のものは、溶接後の拡管前における真円度が2.0[%]と若干悪くなっている。このように、上下の拘束範囲の差を小さくすることで、良好な形状を得ることができる。すなわち、本発明においては、上下の拘束範囲の差を上下拘束範囲の平均値の40[%]未満とすることが好ましく、30[%]以下とすることがさらに好ましい。また、上下の拘束範囲の差を30度未満とすることが好ましい。この上下の拘束範囲の差と上下拘束範囲の平均値との関係を言い換えれば、鋼管の外径と同径または略同径の円弧に内接するU字状断面の最下部を中心に板幅Wの20[%]以上の範囲をAとし、鋼管の外径と同径または略同径の円弧に内接する板幅両端から板幅Wの10[%]以上の範囲の合計をBとしたとき、式(1)を満たすことが好ましい。
2|A−B|/(A+B)<0.4 ・・・(1)
ここで、|A−B|は、A−Bの絶対値を示す。
Further, in FIG. 11, the difference between the upper and lower restraint ranges is 30 degrees, and the difference is 29 [%] of the average value of the upper and lower restraint ranges, 90 degrees above / 90 degrees below, and 90 degrees above / 120 below. At 120 degrees above / 90 degrees below, the roundness after welding and before pipe expansion is very excellent at 1.5 [%] or less. On the other hand, the difference in the vertical restraint range is 30 degrees, but the difference is as large as 40 [%] of the average value of the vertical restraint range, and the one with 90 degrees above / 60 degrees below is a perfect circle after welding and before pipe expansion. The degree is slightly worse at 2.0 [%]. By reducing the difference between the upper and lower restraint ranges in this way, a good shape can be obtained. That is, in the present invention, the difference between the upper and lower restraint ranges is preferably less than 40 [%] of the average value of the upper and lower restraint ranges, and more preferably 30 [%] or less. Further, it is preferable that the difference between the upper and lower restraint ranges is less than 30 degrees. In other words, the relationship between the difference between the upper and lower restraint ranges and the average value of the upper and lower restraint ranges is that the plate width W is centered on the bottom of the U-shaped cross section inscribed in an arc having the same or substantially the same diameter as the outer diameter of the steel pipe. When the range of 20 [%] or more is defined as A, and the total of the range of 10 [%] or more of the plate width W from both ends of the plate width inscribed in an arc having the same or substantially the same diameter as the outer diameter of the steel pipe is defined as B. , It is preferable to satisfy the formula (1).
2 | AB | / (A + B) <0.4 ... (1)
Here, | AB | indicates the absolute value of AB.
図13は、上金型4の拘束範囲と下金型5の拘束範囲とを同一として、プレスベンド後の成形体Sの未加工部Pの長さLを変化させた場合におけるシームギャップ部Gの開き量の結果を示すグラフである。図14は、上金型4の拘束範囲と下金型5の拘束範囲とを同一として、プレスベンド後の成形体Sの未加工部Pの長さLを変化させた場合における拡管前の鋼管の真円度の結果を示すグラフである。図15は、上金型4の拘束範囲と下金型5の拘束範囲とを同一として、プレスベンド後の成形体Sの未加工部Pの長さLを変えた場合におけるプレス荷重の結果を示すグラフである。なお、図13〜図15において、板幅中央部における接線と、板幅端からW/4だけ離れた部位であるW/4部における接線とのなす角をθ11,θ12、板幅端部における接線と、W/4部における接線とのなす角をθ21,θ22としたとき、これらの角度は全て等しい値とし、それぞれ未加工部Pの幅に応じて変化させている。また、横軸は、上金型4の拘束範囲と下金型5の拘束範囲との平均値である。13, as the same a restricting range of constraint range and a lower mold 5 of the upper mold 4, the seam gaps in the case of changing the length L of the unprocessed portion P of the molded article S 1 after the pressing bend It is a graph which shows the result of the opening amount of G. 14, as the same a restricting range of constraint range and a lower mold 5 of the upper mold 4, before pipe expansion in the case of changing the length L of the unprocessed portion P of the molded article S 1 after the pressing Bend It is a graph which shows the result of the roundness of a steel pipe. 15, as the same a restricting range of constraint range and a lower mold 5 of the upper mold 4, the result of the press load in case of changing the length L of the unprocessed portion P of the molded article S 1 after the pressing Bend It is a graph which shows. In FIGS. 13 to 15, the angles formed by the tangent line at the center of the plate width and the tangent line at the W / 4 portion, which is a portion separated by W / 4 from the plate width end, are θ 11 , θ 12 , and the plate width end. When the angles formed by the tangent line in the portion and the tangent line in the W / 4 portion are set to θ 21 and θ 22 , these angles are all set to the same value and are changed according to the width of the unprocessed portion P, respectively. The horizontal axis is the average value of the restraint range of the upper mold 4 and the restraint range of the lower mold 5.
図13から、成形体Sの未加工部Pの長さLや接線のなす角θ11,θ12,θ21,θ22の角度によらず、上金型4の拘束範囲と下金型5の拘束範囲との平均値が大きくなるほど、シームギャップ部Gの開き量は小さくなっており、また、上金型4の拘束範囲と下金型5の拘束範囲との平均値が同じ場合には、前記長さLが長く、接線のなす角θ11,θ12,θ21,θ22の角度が小さいほど開き量が小さくなっていることがわかる。また、図14及び図15から、上金型4の拘束範囲と下金型5の拘束範囲との平均値が同じ場合には、鋼管の真円度及びプレス荷重に、成形体Sの未加工部Pの長さLや接線のなす角θ11,θ12,θ21,θ22の角度による差異はほとんどみられないことがわかる。このように、上金型4の拘束範囲と下金型5の拘束範囲との平均値が同じ場合には、成形体Sの未加工部Pの長さLを長く、接線のなす角θ11,θ12,θ21,θ22の角度を小さくすることで、鋼管の真円度やプレス荷重の差異を前記長さLによって生じさせることなく、オープン管Sのシームギャップ部Gの開き量を小さくすることが可能となる。From Figure 13, the unprocessed portion P of the length L and the tangent of the angle theta 11 of the molded body S 1, θ 12, θ 21 , regardless of the angle of theta 22, lower die and constraining the range of the upper die 4 The larger the average value with the restraint range of 5, the smaller the opening amount of the seam gap portion G, and when the average value between the restraint range of the upper mold 4 and the restraint range of the lower mold 5 is the same. It can be seen that the longer the length L and the smaller the angles of the angles θ 11 , θ 12 , θ 21 and θ 22 formed by the tangents, the smaller the opening amount. Further, it is seen from FIGS. 14 and 15, when the average value of the constraint range of the constraint range and a lower mold 5 of the upper mold 4 are the same, the roundness and the press load of the steel pipe, the molded body S 1 It can be seen that there is almost no difference depending on the length L of the machined portion P and the angles of the tangents θ 11 , θ 12 , θ 21 and θ 22 . Thus, when the average value of the constraint range of the constraint range and a lower mold 5 of the upper mold 4 are the same, the length L of the unprocessed portion P of the molded body S 1 long, tangential angle of θ 11, θ 12, θ 21, by reducing the angle of theta 22, without causing the difference in roundness and the press load of the steel pipe by the length L, a open open pipe S 2 of the seam gap G It is possible to reduce the amount.
図16は、上金型4及び下金型5の円弧部半径を変化させた場合におけるオープン管Sのシームギャップ部Gの開き量の結果を示すグラフである。図17は、上金型4及び下金型5の円弧部半径を変化させた場合におけるプレス荷重の結果を示すグラフである。なお、図16及び図17においては、上金型4及び下金型5の円弧部4a,5aの中心角を45度とし、円弧部4a,5aの半径である円弧部半径を変えて、引張強度630MPa、外径660.4[mm]、管厚40.0[mm」の鋼管を、縦径が拡管前の径と一致するようにOプレスで圧下した場合を示している。また、図16及び図17の横軸は、円弧部半径と鋼管外半径(鋼管外径に相当する半径)との比であり、円弧部半径が鋼管外半径よりも大きい場合は1.0より大きくなり、円弧部半径が鋼管外半径よりも小さい場合は1.0よりも小さくなる。Figure 16 is a graph showing the results of the amount of opening of the seam gap G of the open pipe S 2 in the case of changing the arcuate portion radius of the upper die 4 and the lower mold 5. FIG. 17 is a graph showing the result of the press load when the arc portion radii of the upper die 4 and the lower die 5 are changed. In FIGS. 16 and 17, the central angles of the arc portions 4a and 5a of the upper mold 4 and the lower mold 5 are set to 45 degrees, and the arc portion radius which is the radius of the arc portions 4a and 5a is changed to pull. It shows a case where a steel pipe having a strength of 630 MPa, an outer diameter of 660.4 [mm], and a pipe thickness of 40.0 [mm] is pressed down by an O-press so that the vertical diameter matches the diameter before the pipe expansion. Further, the horizontal axis of FIGS. 16 and 17 is the ratio of the radius of the arc portion to the radius of the outer diameter of the steel pipe (radius corresponding to the outer diameter of the steel pipe), and is greater than 1.0 when the radius of the arc portion is larger than the outer radius of the steel pipe. When the radius of the arc portion is smaller than the outer radius of the steel pipe, it becomes smaller than 1.0.
図16に示すように、上金型4及び下金型5の円弧部半径が鋼管外半径と等しい(図16の横軸が1.0)ときには、シームギャップ部Gの開き量が最も小さくなっている。一方、上金型4及び下金型5の円弧部半径が鋼管外半径よりも大きくなると、図7で示したように成形体Sの6時部分及びその近傍に曲げ戻し変形が生じるため、上金型4及び下金型5の円弧部半径が大きくなるにしたがって、シームギャップ部Gの開き量が大きくなっている。また、上金型4及び下金型5の円弧部半径が鋼管外半径よりも小さくなると、上金型4及び下金型5の円弧部4a,5aが終了した部分で曲げ戻し変形が生じるため、円弧部半径が小さくなるにしたがって、シームギャップ部Gの開き量が大きくなっている。このように、上金型4及び下金型5の円弧部半径が鋼管外半径と同じ場合が最も望ましいが、上金型4及び下金型5の円弧部半径が鋼管外半径に相当する半径±3.5[%]のときには、シームギャップ部Gの開き量が40[mm]以下に抑えられている。As shown in FIG. 16, when the arc portion radius of the upper mold 4 and the lower mold 5 is equal to the outer radius of the steel pipe (the horizontal axis of FIG. 16 is 1.0), the opening amount of the seam gap portion G becomes the smallest. ing. Meanwhile, since the upper die 4 and the arcuate portion radius of the lower die 5 is greater than the steel pipe outer radius, deformation bent back at six portions and the vicinity thereof of the molding S 1 as shown in FIG. 7 occurs, As the radius of the arc portion of the upper mold 4 and the lower mold 5 increases, the opening amount of the seam gap portion G increases. Further, when the arc portion radius of the upper mold 4 and the lower mold 5 is smaller than the outer radius of the steel pipe, bending back deformation occurs at the portion where the arc portions 4a and 5a of the upper mold 4 and the lower mold 5 are completed. As the radius of the arc portion becomes smaller, the opening amount of the seam gap portion G becomes larger. As described above, it is most desirable that the arc portion radius of the upper mold 4 and the lower mold 5 is the same as the steel pipe outer radius, but the arc portion radius of the upper mold 4 and the lower mold 5 corresponds to the steel pipe outer radius. When ± 3.5 [%], the opening amount of the seam gap portion G is suppressed to 40 [mm] or less.
しかしながら、図17からわかるように、プレス荷重は、円弧部半径が小さくなるにしたがって大きくなっており、特に円弧部半径が小さい場合には、プレス機の荷重も考慮してその半径を決める必要がある。 However, as can be seen from FIG. 17, the press load increases as the radius of the arc portion decreases, and especially when the radius of the arc portion is small, it is necessary to determine the radius in consideration of the load of the press machine. is there.
[実施例1]
エッジミラーを用いて開先を設けて、板幅Wを1928[mm]に加工した、長さ1000[mm]、板厚40[mm]、引張強度635[MPa]の鋼板に、端曲げを行った後、プレスベンド加工を行った成形体Sを準備した。次に、この成形体Sに対し、様々な拘束範囲の上金型4及び下金型5を用いて、30[MN]のプレス機によりOプレスを行うことで、成形体A,Bを成形した。表1及び表2に、成形体A,Bの形状を示す。なお、表1及び表2の「No.」における最初のアルファベットA,Bは、成形体の形状(成形体A,B)を示しており、そのアルファベットA,Bの後の数字は、上金型4及び下金型5の拘束範囲の組み合わせを示している。
[Example 1]
Edge bending is performed on a steel plate having a length of 1000 [mm], a plate thickness of 40 [mm], and a tensile strength of 635 [MPa], which is processed to a plate width W of 1928 [mm] by providing a groove using an edge mirror. after was prepared molded body S 1 subjected to press bending process. Next, with respect to the molded body S 1, with the upper mold 4 and the lower mold 5 of the various constraint range, by performing the O pressing by a press machine 30 [MN], moldings A, B Molded. Tables 1 and 2 show the shapes of the molded bodies A and B. The first letters A and B in "No." in Tables 1 and 2 indicate the shape of the molded body (molded bodies A and B), and the numbers after the letters A and B are the upper metal. The combination of the restraint ranges of the mold 4 and the lower mold 5 is shown.
表1には、条件Aとして板幅端からW/4部を中心に160[mm](W/12)の幅で未加工部を設け、板幅端部における接線と、W/4部における接線とのなす角θ21,θ22が65度、板幅中央部における接線と、W/4部における接線とのなす角θ11,θ12が73度とした成形体Aを示している。表2には、条件Bとして板幅端からW/4部を中心に321[mm](W/6)の幅(条件Aの2倍の幅)で未加工部を設け、板幅端部における接線と、W/4部における接線とのなす角θ21,θ22が59度、板幅中央部における接線と、W/4部における接線とのなす角θ11,θ12が61度とした成形体Bを示している。なお、成形体A,Bは、板幅端部の中央と板幅1/2を結ぶ直線に対して対称であり、表1及び表2には、その板幅1/2の部分の値を示している。また、Oプレス時における圧下量は、W/2部の外面側と板幅端部の外面側との距離が654[mm]となる圧下量とした。In Table 1, as a condition A, an unprocessed portion having a width of 160 [mm] (W / 12) centered on the W / 4 portion from the plate width end is provided, and a tangent line at the plate width end and a W / 4 portion are provided. The molded body A is shown in which the angles θ 21 and θ 22 formed by the tangents are 65 degrees, and the angles θ 11 and θ 12 formed by the tangents at the center of the plate width and the tangent at the W / 4 portion are 73 degrees. In Table 2, as condition B, an unprocessed portion is provided with a width of 321 [mm] (W / 6) (twice the width of condition A) centering on the W / 4 portion from the plate width end, and the plate width end portion is provided. The angles θ 21 and θ 22 formed by the tangent line in the W / 4 part and the tangent line in the W / 4 part are 59 degrees, and the angles θ 11 and θ 12 formed by the tangent line in the center of the plate width and the tangent line in the W / 4 part are 61 degrees. The molded body B is shown. The molded bodies A and B are symmetrical with respect to the straight line connecting the center of the plate width end portion and the plate width 1/2, and the values of the plate width 1/2 portion are shown in Tables 1 and 2. Shown. The reduction amount at the time of O-press was set so that the distance between the outer surface side of the W / 2 portion and the outer surface side of the plate width end portion was 654 [mm].
そして、成形体A,BのOプレス後のオープン管Sの開き量を測定した後に、オープン管Sのシームギャップ部Gを溶接して外径654[mm]の鋼管を成形した後、その直径を周方向に22.5度のピッチで8カ所測定し、前記直径の最大と最小との差を求めた。表1及び表2に、金型形状(拘束範囲)、プレス荷重、開き量、及び、真円度も合わせて示す。このときの真円度は、最大と最小の差を鋼管外径(前記直径の全測定値の平均値)で除した数字である。Then, after measuring the opening amount of the open pipe S 2 after O-pressing the molded bodies A and B, the seam gap portion G of the open pipe S 2 is welded to form a steel pipe having an outer diameter of 654 [mm]. The diameter was measured at eight points at a pitch of 22.5 degrees in the circumferential direction, and the difference between the maximum and minimum diameters was determined. Tables 1 and 2 also show the mold shape (constraint range), press load, opening amount, and roundness. The roundness at this time is a number obtained by dividing the difference between the maximum and the minimum by the outer diameter of the steel pipe (the average value of all the measured values of the diameter).
なお、本実施例で使用した溶接機では、Oプレス後の開き量が40[mm]を超えているものは、その開きを閉じることができず、別のプレス機で開きを閉じた状態で管軸方向の両端及び中央を仮溶接した後、シームギャップ部Gの全長の本溶接を行った。また、真円度については、拡管前で2.5[%]を合格の目安とした。これは、拡管前の真円度が2.5[%]以下であれば、拡管後の真円度を1.0[%]以下という良好な値にすることができるからである。 In the welding machine used in this embodiment, if the opening amount after O-pressing exceeds 40 [mm], the opening cannot be closed, and the opening is closed by another press. After provisionally welding both ends and the center in the pipe axis direction, the entire length of the seam gap portion G was main welded. Regarding the roundness, 2.5 [%] was used as a guideline for passing before the pipe expansion. This is because if the roundness before tube expansion is 2.5 [%] or less, the roundness after tube expansion can be a good value of 1.0 [%] or less.
本発明例の範囲である、表1のNo.A1〜A7,A9,A10、表2のNo.B1〜B7,B9,B10では、開き量が小さく、真円度も良好である。特に、拘束範囲が90度〜110度のものは、拡管を行わなくても真円度が1.0[%]以下となっている。また、拘束範囲の平均値が小さくなるほど、プレス荷重が小さくなっている。 No. 1 in Table 1, which is the scope of the examples of the present invention. A1 to A7, A9, A10, No. in Table 2. In B1 to B7, B9, and B10, the opening amount is small and the roundness is also good. In particular, when the restraint range is 90 degrees to 110 degrees, the roundness is 1.0 [%] or less even if the pipe is not expanded. Further, the smaller the average value of the restraint range, the smaller the press load.
これに対し、上金型4及び下金型5の拘束範囲が60度と90度との組み合わせになっている、表1のNo.A8,A11、表2のNo.B8,B11では、開き量は小さいが、真円度が悪くなっている。また、拘束範囲の平均値が60度以下になっている、表1のNo.A12〜A16、表2のNo.B12〜B16では、開き量が大きく、特に、表1のNo.A15,A16、表2のNo.B16では、シームギャップ部Gを溶接した後の溶接部分が破断したために真円度の測定はできなかった。 On the other hand, the restraint range of the upper mold 4 and the lower mold 5 is a combination of 60 degrees and 90 degrees. A8, A11, No. in Table 2. In B8 and B11, the opening amount is small, but the roundness is poor. In addition, No. 1 in Table 1 in which the average value of the restraint range is 60 degrees or less. A12 to A16, No. in Table 2. In B12 to B16, the opening amount is large, and in particular, No. 1 in Table 1. A15, A16, No. in Table 2. In B16, the roundness could not be measured because the welded portion after welding the seam gap portion G was broken.
また、未加工部の幅が成形体Aよりも大きい成形体Bを用いたものでは、成形体Aを用いたものと比べて、プレス荷重及び真円度は略同じであったが、開き量が小さくなっている。 Further, in the case where the molded body B having a width of the unprocessed portion larger than that of the molded body A was used, the press load and the roundness were substantially the same as those using the molded body A, but the opening amount. Is getting smaller.
以上、本発明を適用した実施形態について説明したが、本実施形態による本発明の開示の一部をなす記述及び図面により本発明は限定されることはない。すなわち、本実施形態に基づいて当業者等によりなされる他の実施形態、実施例及び運用技術等は全て本発明の範疇に含まれる。 Although the embodiment to which the present invention is applied has been described above, the present invention is not limited by the description and the drawings which form a part of the disclosure of the present invention according to the present embodiment. That is, all other embodiments, examples, operational techniques, and the like made by those skilled in the art based on the present embodiment are included in the scope of the present invention.
[実施例2]
エッジミラーを用いて開先を設けて板幅1639[mm]に加工した、長さ1000[mm]、板厚31.8[mm]、引張強度779[MPa]の鋼板に、端曲げを行った後、プレスベンド加工を行った成形体Sを準備した。次に、この成形体Sに対し、様々な拘束範囲の上金型4及び下金型5を用いて、30[MN]のプレス機によりOプレスを行うことで、成形体A,Bを成形した。表3及び表4に、成形体A,Bの形状を示す。なお、表3及び表4の「No.」における最初のアルファベットA,Bは、成形体の形状(成形体A,B)を示しており、そのアルファベットA,Bの後の数字は、上金型4及び下金型5の拘束範囲の組み合わせを示している。
[Example 2]
Edge bending is performed on a steel sheet having a length of 1000 [mm], a plate thickness of 31.8 [mm], and a tensile strength of 779 [MPa], which is processed to a plate width of 1639 [mm] by providing a groove using an edge mirror. after was prepared molded body S 1 subjected to press bending process. Next, with respect to the molded body S 1, with the upper mold 4 and the lower mold 5 of the various constraint range, by performing the O pressing by a press machine 30 [MN], moldings A, B Molded. Tables 3 and 4 show the shapes of the molded bodies A and B. The first letters A and B in "No." in Tables 3 and 4 indicate the shape of the molded body (molded bodies A and B), and the numbers after the alphabets A and B are the upper metal. The combination of the restraint ranges of the mold 4 and the lower mold 5 is shown.
表3には、条件Aとして板幅端からW/4部を中心に137[mm](W/12)の幅で未加工部を設け、板幅端部における接線と、W/4部における接線とのなす角θ21,θ22が65度、板幅中央部における接線と、W/4部における接線とのなす角θ11,θ12が72度とした成形体Aを示している。表4には、条件Bとして板幅端からW/4を中心に273[mm](W/6)の幅(条件Aの2倍の幅)で未加工部を設け、板幅端部における接線と、W/4部における接線とのなす角θ21,θ22が59度、板幅中央における接線と、W/4部における接線とのなす角θ11,θ12が61度とした成形体Bを示している。なお、成形体A,Bは、板幅端部の中央と板幅1/2を結ぶ直線に対して対称であり、表3及び表4には、その板幅1/2の部分の値を示している。また、Oプレス時における圧下量は、W/2部の外面側と板幅端部の外面側との距離が553[mm]となる圧下量とした。In Table 3, as a condition A, an unprocessed portion having a width of 137 [mm] (W / 12) centered on the W / 4 portion from the plate width end is provided, and a tangent line at the plate width end and a W / 4 portion are provided. The molded body A is shown in which the angles θ 21 and θ 22 formed by the tangents are 65 degrees, and the angles θ 11 and θ 12 formed by the tangents at the center of the plate width and the tangent at the W / 4 portion are 72 degrees. In Table 4, as condition B, an unprocessed portion is provided with a width of 273 [mm] (W / 6) (twice the width of condition A) centered on W / 4 from the plate width end, and the plate width end is provided. Molding where the angles θ 21 and θ 22 between the tangent and the tangent at the W / 4 part are 59 degrees, and the angles θ 11 and θ 12 between the tangent at the center of the plate width and the tangent at the W / 4 part are 61 degrees. Shows body B. The molded bodies A and B are symmetrical with respect to the straight line connecting the center of the plate width end portion and the plate width 1/2, and Tables 3 and 4 show the values of the plate width 1/2 portion. Shown. Further, the reduction amount at the time of O-press was set so that the distance between the outer surface side of the W / 2 portion and the outer surface side of the plate width end portion was 553 [mm].
そして、成形体A,BのOプレス後のオープン管Sの開き量を測定した後に、オープン管Sのシームギャップ部Gを溶接して外径553[mm]の鋼管を成形した後、その直径を周方向に22.5度のピッチで8カ所測定し、前記直径の最大と最小との差を求めた。表3及び表4に、金型形状(拘束範囲)、プレス荷重、開き量、及び、真円度も合わせて示す。このときの真円度は、最大と最小の差を鋼管外径で除した数字である。Then, after measuring the opening amount of the open pipe S 2 after O-pressing the molded bodies A and B, the seam gap portion G of the open pipe S 2 is welded to form a steel pipe having an outer diameter of 553 [mm]. The diameter was measured at eight points at a pitch of 22.5 degrees in the circumferential direction, and the difference between the maximum and minimum diameters was determined. Tables 3 and 4 also show the mold shape (constraint range), press load, opening amount, and roundness. The roundness at this time is a number obtained by dividing the difference between the maximum and the minimum by the outer diameter of the steel pipe.
なお、本実施例で使用した溶接機では、Oプレス後の開き量が40[mm]を超えているものは、その開きを閉じることができず、別のプレス機で開きを閉じた状態で管軸方向の両端及び中央を仮溶接した後、シームギャップ部Gの全長の本溶接を行った。また、真円度については、拡管を行うことで1.0[%]以下になる拡管前で2.5[%]を合格の目安とした。 In the welding machine used in this embodiment, if the opening amount after O-pressing exceeds 40 [mm], the opening cannot be closed, and the opening is closed by another press. After provisionally welding both ends and the center in the pipe axis direction, the entire length of the seam gap portion G was main-welded. As for the roundness, 2.5 [%] was used as a guideline for passing before the pipe was expanded to 1.0 [%] or less by expanding the pipe.
本発明例の範囲である、表3のNo.A1〜A7,A9,A10、表4のNo.B1〜B7,B9,B10では、開き量が小さく、真円度も良好である。特に、拘束範囲が90度〜110度のものは、拡管を行わなくても真円度が1.0[%]以下となっている。また、拘束範囲の平均値が小さくなるほど、プレス荷重が小さくなっている。 No. 3 in Table 3, which is the scope of the examples of the present invention. A1 to A7, A9, A10, No. in Table 4. In B1 to B7, B9, and B10, the opening amount is small and the roundness is also good. In particular, when the restraint range is 90 degrees to 110 degrees, the roundness is 1.0 [%] or less even if the pipe is not expanded. Further, the smaller the average value of the restraint range, the smaller the press load.
これに対し、上金型4及び下金型5の拘束範囲が60度と90度との組み合わせになっている、表3のNo.A8,A11、表4のNo.B8,B11では、開き量は小さいが、真円度が悪くなっている。また、拘束範囲の平均値が60度以下になっている、表3のNo.A12〜A16、表4のNo.B12〜B16では、開き量が大きく、特に、表3のNo.A15,A16、表4のNo.B16では、シームギャップ部Gを溶接した後の溶接部分が破断したために真円度の測定はできなかった。 On the other hand, the restraint range of the upper mold 4 and the lower mold 5 is a combination of 60 degrees and 90 degrees. A8, A11, No. in Table 4. In B8 and B11, the opening amount is small, but the roundness is poor. In addition, No. 1 in Table 3 in which the average value of the restraint range is 60 degrees or less. A12 to A16, No. in Table 4. In B12 to B16, the opening amount is large, and in particular, No. A15, A16, No. in Table 4. In B16, the roundness could not be measured because the welded portion after welding the seam gap portion G was broken.
また、未加工部の幅が成形体Aよりも大きい成形体Bを用いたものでは、成形体Aを用いたものと比べて、プレス荷重及び真円度は略同じであったが、開き量が小さくなっている。 Further, in the case where the molded body B having a width of the unprocessed portion larger than that of the molded body A was used, the press load and the roundness were substantially the same as those using the molded body A, but the opening amount. Is getting smaller.
[実施例3]
エッジミラーを用いて開先を設けて板幅2687[mm]に加工した、長さ1000[mm]、板厚50.8[mm]、引張強度779[MPa]の鋼板に、端曲げを行った後、プレスベンド加工を行った成形体Sを準備した。次に、この成形体Sに対し、様々な拘束範囲の上金型4及び下金型5を用いて、30[MN]のプレス機によりOプレスを行うことで、成形体A,Bを成形した。表5及び表6に、成形体A,Bの形状を示す。なお、表5及び表6の「No.」における最初のアルファベットA,Bは、成形体の形状(成形体A,B)を示しており、そのアルファベットA,Bの後の数字は、上金型4及び下金型5の拘束範囲の組み合わせを示している。
[Example 3]
Edge bending is performed on a steel sheet having a length of 1000 [mm], a plate thickness of 50.8 [mm], and a tensile strength of 779 [MPa], which is processed to a plate width of 2687 [mm] by providing a groove using an edge mirror. after was prepared molded body S 1 subjected to press bending process. Next, with respect to the molded body S 1, with the upper mold 4 and the lower mold 5 of the various constraint range, by performing the O pressing by a press machine 30 [MN], moldings A, B Molded. Tables 5 and 6 show the shapes of the molded bodies A and B. The first letters A and B in "No." in Tables 5 and 6 indicate the shape of the molded body (molded bodies A and B), and the numbers after the alphabets A and B are the upper metal. The combination of the restraint ranges of the mold 4 and the lower mold 5 is shown.
表5には、条件Aとして板幅端からW/4部を中心に224[mm](W/12)の幅で未加工部を設け、板幅端部における接線と、W/4部における接線とのなす角θ21,θ22が73度、板幅中央部における接線と、W/4部における接線とのなす角θ11,θ12が72度とした成形体Aを示している。表6には、条件Bとして板幅端からW/4を中心に448[mm](W/6)の幅(条件Aの2倍の幅)で未加工部を設け、板幅端部における接線と、W/4部における接線とのなす角θ21,θ22が58度、板幅中央部における接線と、W/4部における接線とのなす角θ11,θ12が59度とした成形体Bを示している。なお、成形体A,Bは、板幅端部の中央と板幅1/2を結ぶ直線に対して対称であり、表5及び表6には、その板幅1/2の部分の値を示している。また、Oプレス時における圧下量は、W/2部の外面側と板幅端部の外面側との距離が905[mm]となる圧下量とした。In Table 5, as a condition A, an unprocessed portion having a width of 224 [mm] (W / 12) centered on the W / 4 portion from the plate width end is provided, and a tangent line at the plate width end and a W / 4 portion are provided. The molded body A is shown in which the angles θ 21 and θ 22 formed by the tangents are 73 degrees, and the angles θ 11 and θ 12 formed by the tangents at the center of the plate width and the tangent at the W / 4 portion are 72 degrees. In Table 6, as condition B, an unprocessed portion is provided with a width of 448 [mm] (W / 6) (twice the width of condition A) centered on W / 4 from the plate width end, and the plate width end is provided. The angles θ 21 and θ 22 between the tangent and the tangent at the W / 4 part are 58 degrees, and the angles θ 11 and θ 12 between the tangent at the center of the plate width and the tangent at the W / 4 part are 59 degrees. The molded body B is shown. The molded bodies A and B are symmetrical with respect to the straight line connecting the center of the plate width end portion and the plate width 1/2, and Tables 5 and 6 show the values of the plate width 1/2 portion. Shown. Further, the reduction amount at the time of O-press was set so that the distance between the outer surface side of the W / 2 portion and the outer surface side of the plate width end portion was 905 [mm].
そして、成形体A,BのOプレス後のオープン管Sの開き量を測定した後に、オープン管Sのシームギャップ部Gを溶接して外径905[mm]の鋼管を成形した後、その直径を周方向に22.5度のピッチで8カ所測定し、前記直径の最大と最小との差を求めた。表5及び表6に、金型形状(拘束範囲)、プレス荷重、開き量、及び、真円度も合わせて示す。このときの真円度は、最大と最小の差を鋼管外径で除した数字である。Then, after measuring the opening amount of the open pipe S 2 after O-pressing the molded bodies A and B, the seam gap portion G of the open pipe S 2 is welded to form a steel pipe having an outer diameter of 905 [mm]. The diameter was measured at eight points at a pitch of 22.5 degrees in the circumferential direction, and the difference between the maximum and minimum diameters was determined. Tables 5 and 6 also show the mold shape (constraint range), press load, opening amount, and roundness. The roundness at this time is a number obtained by dividing the difference between the maximum and the minimum by the outer diameter of the steel pipe.
なお、本実施例で使用した溶接機では、Oプレス後の開き量が40[mm]を超えているものは、その開きを閉じることができず、別のプレス機で開きを閉じた状態で管軸方向の両端及び中央を仮溶接した後、シームギャップ部Gの全長の本溶接を行った。また、真円度については、拡管を行うことで1.0[%]以下になる拡管前で2.5[%]を合格の目安とした。 In the welding machine used in this embodiment, if the opening amount after O-pressing exceeds 40 [mm], the opening cannot be closed, and the opening is closed by another press. After provisionally welding both ends and the center in the pipe axis direction, the entire length of the seam gap portion G was main welded. As for the roundness, 2.5 [%] was used as a guideline for passing before the pipe was expanded to 1.0 [%] or less by expanding the pipe.
本発明例の範囲である、表5のNo.A1〜A7,A9,A10、表6のNo.B1〜B7,B9,B10では、開き量が小さく、真円度も良好である。特に、拘束範囲が90度〜110度のものは、拡管を行わなくても真円度が1.0[%]以下となっている。また、拘束範囲の平均値が小さくなるほど、プレス荷重が小さくなっている。 No. 1 in Table 5, which is the scope of the examples of the present invention. A1 to A7, A9, A10, No. in Table 6. In B1 to B7, B9, and B10, the opening amount is small and the roundness is also good. In particular, when the restraint range is 90 degrees to 110 degrees, the roundness is 1.0 [%] or less even if the pipe is not expanded. Further, the smaller the average value of the restraint range, the smaller the press load.
これに対し、上金型4及び下金型5の拘束範囲が60度と90度との組み合わせになっている、表5のNo.A8,A11、表6のNo.B8,B11では、開き量は小さいが、真円度が悪くなっている。また、拘束範囲の平均値が60度以下になっている、表5のNo.A12〜A16、表6のNo.B12〜B16では、開き量が大きく、特に、表5のNo.A15,A16、表6のNo.B16では、シームギャップ部Gを溶接した後の溶接部分が破断したために真円度の測定はできなかった。 On the other hand, the restraint range of the upper mold 4 and the lower mold 5 is a combination of 60 degrees and 90 degrees. A8, A11, No. in Table 6. In B8 and B11, the opening amount is small, but the roundness is poor. In addition, No. 1 in Table 5 in which the average value of the restraint range is 60 degrees or less. A12 to A16, No. in Table 6. In B12 to B16, the opening amount is large, and in particular, No. A15, A16, No. in Table 6. In B16, the roundness could not be measured because the welded portion after welding the seam gap portion G was broken.
また、未加工部の幅が成形体Aよりも大きい成形体Bを用いたものでは、成形体Aを用いたものと比べて、プレス荷重及び真円度は略同じであったが、開き量が小さくなっている。 Further, in the case where the molded body B having a width of the unprocessed portion larger than that of the molded body A was used, the press load and the roundness were substantially the same as those using the molded body A, but the opening amount. Is getting smaller.
[実施例4]
目標外径621[mm]〜687[mm]の鋼管を製造するために、エッジミラーを用いて開先を設けて板幅1826〜2032[mm]に加工した、長さ1000[mm]、板厚40[mm]、引張強度635[MPa]の鋼板に、端曲げを行った後、プレスベンド加工を行った成形体Sを準備した。次に、この成形体Sに対し、円弧部半径327mm、拘束範囲45度の様々な上金型4及び下金型5を用いて、30[MN]のプレス機によりOプレスを行い、成形体D1〜D11を成形した。表7に成形体D1〜D11の成形条件を示す。成形体D1〜D11には、初期の板幅Wに応じて、板幅端からW/4部を中心にW/12の幅で未加工部を設け、板幅端部における接線と、W/4部における接線とのなす角θ21,θ22を75度とし、板幅中央部における接線と、W/4部における接線とのなす角θ11,θ12を75度とした。また、OプレスではW/2部の外面側と板幅端部の外面側との距離が、表7に示すように初期の板幅Wに対応した値となるように圧下した。また、表7に、Oプレス圧下後の鋼管の外径を示す。
[Example 4]
In order to manufacture a steel pipe with a target outer diameter of 621 [mm] to 687 [mm], a plate with a length of 1000 [mm] and a plate width of 1826 to 2032 [mm] was processed by providing a groove using an edge mirror. thickness 40 [mm], the steel sheet of the tensile strength 635 [MPa], after bending an end were prepared molded body S 1 subjected to press bending process. Next, with respect to the molded body S 1, arcuate portion radius 327 mm, using a variety of upper mold 4 and the lower mold 5 of the restraint range 45 degrees, perform O pressing by a press machine 30 [MN], molding The bodies D1 to D11 were molded. Table 7 shows the molding conditions of the molded bodies D1 to D11. The molded bodies D1 to D11 are provided with an unprocessed portion having a width of W / 12 centered on the W / 4 portion from the plate width end according to the initial plate width W, and the tangent line at the plate width end portion and W / The angles θ 21 and θ 22 formed by the tangents in the four parts were set to 75 degrees, and the angles θ 11 and θ 12 formed by the tangents in the central part of the plate width and the tangents in the W / 4 part were set to 75 degrees. Further, in the O press, the distance between the outer surface side of the W / 2 portion and the outer surface side of the plate width end portion was reduced so as to be a value corresponding to the initial plate width W as shown in Table 7. Table 7 shows the outer diameter of the steel pipe after O-press reduction.
そして、これら成形体D1〜D11のOプレス後のオープン管Sの開き量を測定した。表7に、その結果としてプレス荷重及び開き量も合わせて示す。Then, to measure the amount of opening of the open pipe S 2 after O press these moldings D1 to D11. Table 7 also shows the press load and opening amount as a result.
円弧部半径と鋼管の外半径との比が1.00である、表7のNo.D6の開き量が最も小さく、鋼管外半径が小さくまたは大きくなると、開き量が大きくなっている。また、実施例1で使用した溶接機で閉じることができる開き量40[mm]以下となるのは、表7のNo.D2〜D10であり、円弧部半径と鋼管の外半径との比が0.96〜1.04となる。また、実施例1において溶接部破断が生じなかった開き量50[mm]となるのも、表7のNo.D2〜D10であり、円弧部半径と鋼管の外半径との比が0.96〜1.04となる。 The ratio of the arc portion radius to the outer radius of the steel pipe is 1.00. When the opening amount of D6 is the smallest and the outer radius of the steel pipe is small or large, the opening amount is large. Further, the opening amount of 40 [mm] or less that can be closed by the welding machine used in Example 1 is No. 1 in Table 7. It is D2 to D10, and the ratio of the radius of the arc portion to the outer radius of the steel pipe is 0.96 to 1.04. Further, the opening amount of 50 [mm] in which the welded portion was not broken in Example 1 was also found in No. 7 of Table 7. It is D2 to D10, and the ratio of the radius of the arc portion to the outer radius of the steel pipe is 0.96 to 1.04.
なお、シームギャップ部Gを溶接して閉じることのできる開き量や、溶接部破断が生じない開き量は、溶接設備や溶接方法により異なるが、上金型4及び下金型5の円弧部半径の目安は鋼管外半径の0.96〜1.04となる。 The opening amount that can be closed by welding the seam gap portion G and the opening amount that does not cause the welded portion to break differ depending on the welding equipment and the welding method, but the radius of the arc portion of the upper mold 4 and the lower mold 5 The guideline for is 0.96 to 1.04 of the outer radius of the steel pipe.
本発明によれば、真円度の高い鋼管を効率的に成形することができる鋼管の製造方法及びプレス金型を提供することができる。 According to the present invention, it is possible to provide a method for manufacturing a steel pipe and a press die capable of efficiently forming a steel pipe having a high roundness.
1 ダイ
1a 棒状部材
1b 棒状部材
2 パンチ
2a パンチ先端部
2b パンチ支持体
3 搬送ローラ
4 上金型
4a 円弧部
4b直線部または小曲率円弧部
4b直線部または小曲率円弧部
5 下金型
5a 円弧部
5b直線部または小曲率円弧部
5b直線部または小曲率円弧部
1 Die 1a Rod-shaped member 1b Rod-shaped member 2 Punch 2a Punch tip 2b Punch support 3 Conveying roller 4 Upper mold 4a Arc part 4b 1 Straight part or small curvature arc part 4b 2 Straight part or small curvature arc part 5 Lower mold 5a Arc part 5b 1 Straight line part or small curvature arc part 5b 2 Straight part or small curvature arc part
上述した課題を解決し、目的を達成するために、本発明に係る鋼管の製造方法は、幅方向両端部に端曲げ加工が施された板材に、その幅方向に沿って3回以上の曲げ加工を施してU字状断面をなす成形体を成形し、次いで、該成形体にプレス加工を施すことにより、その長手方向にシームギャップ部を有する管体であるオープン管とした後、該シームギャップ部を接合して鋼管とする鋼管の製造方法であって、前記端曲げ加工前の前記板材の幅を板幅Wとしたとき、前記成形体は、板幅端からW/4だけ離れた部位を中心に、他の領域に比較して小さな曲率を付与した軽加工部、または、曲げ加工を省略した未加工部を有し、前記オープン管の形状が、前記U字状断面の最下部を中心に前記板幅Wの20[%]以上の範囲と、前記板幅端から前記板幅Wの10[%]以上の範囲とが、前記鋼管の外径と同径または略同径の円弧に内接する形状となるように、前記鋼管の外半径に相当する半径に対して±3.5[%]の範囲にある円弧部の半径を有する金型を用いてプレス加工を実施することを特徴とするものである。 In order to solve the above-mentioned problems and achieve the object, the method for manufacturing a steel pipe according to the present invention is to bend a plate material having end bending processed at both ends in the width direction three times or more along the width direction. A molded body having a U-shaped cross section is formed by processing, and then the molded body is pressed to obtain an open pipe having a seam gap in the longitudinal direction thereof, and then the seam is formed. a method of manufacturing a steel pipe and steel pipe by joining gap, when the width of the plate before bending said end a plate width W, the shaped body is spaced et W / 4 or the plate width end It has a lightly machined part that is given a small curvature compared to other areas, or an unprocessed part that omits bending, and the shape of the open pipe is the maximum of the U-shaped cross section. The range of 20 [%] or more of the plate width W centering on the lower portion and the range of 10 [%] or more of the plate width W from the plate width end are the same diameter or substantially the same diameter as the outer diameter of the steel pipe. Pressing is performed using a mold having an arc portion radius within a range of ± 3.5 [%] with respect to a radius corresponding to the outer radius of the steel pipe so as to have a shape inscribed in the arc. It is characterized by that.
また、本発明に係るプレス金型は、上記の発明の鋼管の製造方法において使用するプレス金型であって、前記プレス金型は、前記成形体を挟持する一対の金型からなり、各金型の前記成形体と接触し得る面には、各金型の加工中心と一致する位置に円弧中心が位置するように、前記鋼管の外半径に相当する半径に対して±3.5[%]の範囲にある半径の円弧部が形成されており、各金型における前記円弧部の中心角が70度以上であり、両金型の前記中心角の角度の合計が360度未満であることを特徴とするものである。 Further, the press die according to the present invention is a press die used in the method for manufacturing a steel pipe of the above invention, and the press die is composed of a pair of dies that sandwich the molded body, and each die. ± 3.5 [%] of the radius corresponding to the outer radius of the steel pipe so that the arc center is located at a position corresponding to the processing center of each mold on the surface of the mold that can come into contact with the molded body. ] Is formed, the central angle of the arc portion in each mold is 70 degrees or more, and the total angle of the central angles of both molds is less than 360 degrees. It is characterized by.

Claims (10)

  1. 幅方向両端部に端曲げ加工が施された板材に、その幅方向に沿って3回以上の曲げ加工を施してU字状断面をなす成形体を成形し、次いで、該成形体にプレス加工を施すことにより、その長手方向にシームギャップ部を有する管体であるオープン管とした後、該シームギャップ部を接合して鋼管とする鋼管の製造方法であって、
    前記端曲げ加工前の前記板材の幅を板幅Wとしたとき、
    前記成形体は、板幅端部からW/4だけ離れた部位を中心に、他の領域に比較して小さな曲率を付与した軽加工部、または、曲げ加工を省略した未加工部を有し、
    前記オープン管の形状が、前記U字状断面の最下部を中心に前記板幅Wの20[%]以上の範囲と、前記板幅端から前記板幅Wの10[%]以上の範囲とが、前記鋼管の外径と同径または略同径の円弧に内接する形状となるように、
    プレス加工することを特徴とする鋼管の製造方法。
    A plate material whose ends have been bent at both ends in the width direction is bent three times or more along the width direction to form a molded body having a U-shaped cross section, and then the molded body is pressed. This is a method for manufacturing a steel pipe, which is a pipe body having a seam gap portion in the longitudinal direction thereof to form an open pipe, and then the seam gap portion is joined to form a steel pipe.
    When the width of the plate material before the edge bending process is the plate width W,
    The molded body has a lightly machined portion having a small curvature as compared with other regions or an unprocessed portion in which bending is omitted, centering on a portion separated by W / 4 from the plate width end. ,
    The shape of the open pipe includes a range of 20 [%] or more of the plate width W centering on the lowermost portion of the U-shaped cross section and a range of 10 [%] or more of the plate width W from the plate width end. Is inscribed in an arc having the same or substantially the same diameter as the outer diameter of the steel pipe.
    A method for manufacturing a steel pipe, which is characterized by being pressed.
  2. 前記鋼管の外径と同径または略同径の円弧に内接する前記U字状断面の最下部を中心に前記板幅Wの20[%]以上の範囲をAとし、前記鋼管の外径と同径または略同径の円弧に内接する板幅両端から前記板幅Wの10[%]以上の範囲の合計をBとしたとき、式(1)を満たすことを特徴とする請求項1に記載の鋼管の製造方法。
    2|A−B|/(A+B)<0.4 ・・・(1)
    ここで、|A−B|は、A−Bの絶対値を示す。
    A is a range of 20 [%] or more of the plate width W centered on the lowermost part of the U-shaped cross section inscribed in an arc having the same or substantially the same diameter as the outer diameter of the steel pipe. The first aspect of claim 1 is that the equation (1) is satisfied, where B is the sum of the range of 10 [%] or more of the plate width W from both ends of the plate width inscribed in an arc having the same diameter or substantially the same diameter. The method for manufacturing a steel pipe according to the description.
    2 | AB | / (A + B) <0.4 ... (1)
    Here, | AB | indicates the absolute value of AB.
  3. 一対の金型のうちの一方の金型と前記成形体のU字開放側とが対向するように他方の金型に該成形体を載置して、該一対の金型で該成形体を挟み込んで該成形体にプレス加工を施すにあたり、
    前記他方の金型は、
    前記他方の金型に前記成形体を載置した状態で、前記U字状断面の最下部を中心に、前記鋼管の外径と同径または略同径の円弧に内接する形状となる範囲を除いて前記成形体が接触せず、
    プレス加工が完了した状態で、前記他方の金型の一部に前記オープン管に接触しない加工面を備えており、
    前記一方の金型は、
    前記他方の金型に前記成形体を載置した状態で、前記成形体が接触せず、
    プレス加工が完了した状態で、前記一方の金型の一部に前記オープン管に接触しない加工面を備えたことを特徴とする請求項1または2に記載の鋼管の製造方法。
    The molded product is placed on the other mold so that one of the pair of molds and the U-shaped open side of the molded product face each other, and the molded product is mounted on the pair of molds. When sandwiching and pressing the molded product,
    The other mold is
    With the molded body placed on the other mold, the range of the shape that is inscribed in an arc with the same or substantially the same diameter as the outer diameter of the steel pipe is centered on the lowermost part of the U-shaped cross section. Except that the molded body does not come into contact,
    When the press working is completed, a part of the other die is provided with a machined surface that does not come into contact with the open pipe.
    One of the molds is
    In the state where the molded body was placed on the other mold, the molded body did not come into contact with each other.
    The method for manufacturing a steel pipe according to claim 1 or 2, wherein when the press working is completed, a part of the one die is provided with a machined surface that does not come into contact with the open pipe.
  4. 前記鋼管の外半径に相当する半径に対して±3.5[%]の範囲にある円弧部の半径を有する金型を用いてプレス加工を実施することを特徴とする請求項1乃至3のいずれか1項に記載の鋼管の製造方法。 Claims 1 to 3, wherein the press working is performed using a die having a radius of an arc portion in a range of ± 3.5 [%] with respect to a radius corresponding to the outer radius of the steel pipe. The method for manufacturing a steel pipe according to any one item.
  5. 前記成形体のプレス加工に際して、前記成形体のプレス加工に用いるプレス金型の中心と、前記成形体の幅方向の中心とが一致していることを特徴とする請求項1乃至4のいずれか1項に記載の鋼管の製造方法。 Any of claims 1 to 4, wherein when the molded product is pressed, the center of the press die used for the press working of the molded product coincides with the center in the width direction of the molded product. The method for manufacturing a steel pipe according to item 1.
  6. 前記成形体は、U字開放側を上方に向けたU字姿勢に保持されることを特徴とする請求項1乃至5のいずれか1項に記載の鋼管の製造方法。 The method for manufacturing a steel pipe according to any one of claims 1 to 5, wherein the molded body is held in a U-shaped posture with the U-shaped open side facing upward.
  7. 請求項1乃至6のいずれか1項に記載の鋼管の製造方法において使用するプレス金型であって、
    前記プレス金型は、前記成形体を挟持する一対の押圧体からなり、各金型の前記成形体と接触し得る面には、各金型の加工中心と一致する位置に円弧中心が位置するように、前記鋼管の外半径に相当する半径に対して±3.5[%]の範囲にある半径の円弧部が形成されており、
    各金型における前記円弧部の中心角が70度以上であり、両金型の前記中心角の角度の合計が360度未満であることを特徴とするプレス金型。
    A press die used in the method for manufacturing a steel pipe according to any one of claims 1 to 6.
    The press die is composed of a pair of pressing bodies that sandwich the molded body, and an arc center is located at a position corresponding to the processing center of each die on a surface of each die that can come into contact with the molded body. As described above, an arc portion having a radius within a range of ± 3.5 [%] is formed with respect to the radius corresponding to the outer radius of the steel pipe.
    A press die characterized in that the central angle of the arc portion in each die is 70 degrees or more, and the total angle of the central angles of both dies is less than 360 degrees.
  8. 両金型の前記中心角の角度が同じであることを特徴とする請求項7に記載のプレス金型。 The press die according to claim 7, wherein the central angles of both dies are the same.
  9. 各金型は、前記円弧部の円弧方向両端にそれぞれつながった、直線部、または、該円弧部よりも曲率が小さい小曲率円弧部を有することを特徴とする請求項7または8に記載のプレス金型。 The press according to claim 7 or 8, wherein each die has a straight portion or a small curvature arc portion having a curvature smaller than that of the arc portion, which is connected to both ends of the arc portion in the arc direction. Mold.
  10. 請求項7乃至9のいずれか1項に記載のプレス金型を用いることを特徴とする、請求項1乃至6のいずれか1項に記載の鋼管の製造方法。 The method for manufacturing a steel pipe according to any one of claims 1 to 6, wherein the press die according to any one of claims 7 to 9 is used.
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