JP2004283855A

JP2004283855A - Forging method

Info

Publication number: JP2004283855A
Application number: JP2003077693A
Authority: JP
Inventors: Junpei Tajima; 淳平田嶋
Original assignee: Sumitomo Metal Industries Ltd
Current assignee: Nippon Steel Corp
Priority date: 2003-03-20
Filing date: 2003-03-20
Publication date: 2004-10-14

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forging method by which the bending of a material to be worked caused in producing a round bar with a free forging including high speed forging can be restrained. <P>SOLUTION: In the forging method, pressing the material A to be worked with anvils from a direction perpendicular to the axis of the material and moving the material in its axial direction are repeated to produce the round bar, wherein in the forging pass in which the cross sectional shape of the material after being pressed becomes round, a manipulator G for holding the material to be worked is always advanced in a direction where the manipulator G is away from the pressing part of the material to be worked (the round groove anvils B) and also, the material to be worked is rotated around its axis. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【産業上の利用分野】
本発明は、高速鍛造を含む自由鍛造により丸棒を製造する際の鍛造方法、特に、被加工材の断面形状が円形となる鍛造パスの際に生じる被加工材の曲がりを抑制することができる鍛造方法に関する。
【０００２】
【従来の技術】
従来、炭素鋼、合金鋼、ステンレス鋼、Ｎｉ基合金等の被加工材を加熱し、自由鍛造（高速鍛造を含む）により丸棒を製造する場合、被加工材の加熱時における偏熱や被加工材を圧下する金敷の摩耗により、圧下後の被加工材の断面形状が円形となる鍛造パスの際に、被加工材に曲がりが生じることが往々にしてあった。これは、被加工材の軸に対して対称の複数の方向から同時に金敷により繰り返し圧下を加える高速鍛造においても例外ではない。そのため、鍛造終了後に曲がりを矯正する工程が必要であった。
【０００３】
高速鍛造法における被加工材の曲がり発生の抑制について、例えば、特許文献１には、被鍛造材を、その一方の端側のマニプレータで把持して逆方の端方向へ移動させつつその被鍛造材の長さ方向の中途まで鍛造した後、その際に生じた曲がりを矯正するために前記一方の端方向へ移動させ、次いで、被鍛造材を逆方端側のマニプレータで把持して再度逆方の端方向へ移動しつつ鍛造を継続することにより曲がりを低減する鍛造方法が開示されている。しかし、この鍛造方法では、曲がりが生じた被鍛造材を曲がりを矯正しながら一旦鍛造開始位置まで移動させ、再度鍛造を行うので、鍛造時間が延長し、生産効率が大幅に低下する。
【０００４】
また、特許文献２には、一方向の鍛造パスと逆方向の鍛造パスとの間で、被鍛造材をその軸の回りに、曲がり方向が軸に実質的に対象になるように（具体的には、平材では１８０°）回転させてから逆方向のパスを行う鍛造方法が開示されている。しかしながら、この方法は、断面が長方形の平材の製造を前提としたもので、丸棒の製造に適用した場合の効果については明らかではない。
【０００５】
【特許文献１】
特開２００１−１０５０７７号公報
【特許文献２】
特開２００１−１０５０７９号公報
【０００６】
【発明が解決しようとする課題】
本発明は、高速鍛造を含む自由鍛造により丸棒を製造する際の鍛造方法であって、特に、圧下後の被加工材の断面形状が円形となる鍛造パスにおいて、鍛造時間を大幅に増加させることなく被加工材に生じる曲がりを抑制し、後工程である曲がり矯正工程を省略することができる鍛造方法を提供することを目的としている。
【０００７】
【課題を解決するための手段】
上記の課題を解決するために、本発明者は、自由鍛造機を用いて、被加工材を円形断面に鍛造するパスにおいて曲がりが生じる過程を詳細に調査した。
【０００８】
図２は、曲がりの発生過程を説明するための図で、（ａ）は被加工材と圧下部の縦断面を模式的に示す図、（ｂ）は（ａ）のＩ−Ｉ矢視図である。図２において、丸溝金敷Ｂは前記被加工材Ａを挟んで対称位置（上下）に設けられた同形で対をなす金敷で、金敷平行部Ｆを有している。
【０００９】
先ず、被加工材Ａをその軸の回りの回転を与えずに丸溝金敷Ｂによる圧下部を通過させる場合、被加工材Ａは、丸溝金敷Ｂによる上下からの圧下と軸方向（図２（ａ）おいて、図面の左から右方向）への移動とが交互に加えられ、鍛造される。被加工材Ａは丸溝金敷Ｂの塑性変形領域Ｃで圧下されるが、図２（ｂ）に示すように、丸溝金敷Ｂと接触しない非接触面Ｄにおいて圧下毎に幅の広がりが生じる。なお、同図中の破線は、前記幅の広がりが生じなかった場合の断面形状を表す。この幅の広がりは、圧下領域外となるすぐ前の圧下終了直前領域Ｅにおいても起こる。このとき、例えば、被加工材Ａに偏熱が生じていると、圧下毎の伸び量が不均一となり、非加工材Ａに曲がりが生じる。
【００１０】
次に、同じく断面が円形をなす被加工材Ａをその軸の回りに回転させながら圧下部を通過させると、被加工材Ａは、丸溝金敷Ｂによる圧下と軸方向への移動とが交互に加えられるので、図２（ａ）に矢印で示すように、スパイラル回転しながら進行し、鍛造される。
【００１１】
この場合は、前記の回転を与えないときと同様に、丸溝金敷Ｂによる鍛造の過程で非接触面Ｄにおいて圧下毎に幅の広がりが生じ、伸び量の不均一に起因する曲がりが生じるが、被加工材Ａはその軸の回りに回転しながら前記矢印で示すように移動しているので、一の圧下により生じた曲がりは次の圧下時に金敷平行部Ｆで矯正され、軽減する。しかし、このとき非接触面Ｄに該当することとなった部分では、再び伸び量が不均一となり、曲がりが生じる。このような曲がりの矯正と発生は、圧下終了直前領域Ｅにおいても起こり、この領域Ｅで生じた曲がりはもはや丸溝金敷Ｂによる矯正は受け得ないので、非加工材Ａに生じた曲がりとして残ることになる。
【００１２】
本発明者は、この曲がりを抑制する方策を検討した結果、被加工材Ａを保持して、その軸の回りに回転（この断面が円形の被加工材の軸の回りの回転を、「自転」ともいう）させるとともに、この回転軸を固定し、かつ被加工材Ａをこの軸方向へ移動させるためのマニプレータを、被加工材Ａを圧下して塑性変形させる丸溝金敷Ｂから遠ざける方向に進行させることにより、すなわち“引き手”にすることにより、前記曲がりを抑制することが可能であることを見いだした。
【００１３】
本発明はこの知見に基づきなされたもので、その要旨は、下記の鍛造方法にある。
【００１４】
『被加工材に対し、その軸に直角の方向からの金敷による圧下と前記軸方向への移動とを繰り返して丸棒を製造する鍛造方法であって、圧下後の被加工の断面形状が円形となる鍛造パスの際、被加工材を保持するマニプレータを常に被加工材圧下部から遠ざける方向に進行させるとともに、被加工材をその軸の回りに回転させる鍛造方法。』
【００１５】
【発明の実施の形態】
以下に、本発明の鍛造方法を詳細に説明する。
【００１６】
本発明の鍛造方法は、先に述べたように、「丸棒を製造する鍛造方法であって、圧下後の被加工の断面形状が円形となる鍛造パスの際、被加工材を保持するマニプレータを常に被加工材圧下部から遠ざける方向に進行させるとともに、被加工材をその軸の回りに回転させる鍛造方法」である。
【００１７】
図１は、本発明の鍛造方法を説明するための図である。図１において、丸溝金敷Ｂの形状および配置は、前記の図２の場合と同じであり、したがって、丸溝金敷Ｂと接触しない非接触面Ｄ（図２（ｂ）参照）において、図２（ｂ）に示したように、圧下毎に幅の広がりが生じる。図２の場合と異なるのは、被加工材Ａを保持して、その軸の回りに回転（つまり、自転）させるとともに、この回転軸を固定するためのマニプレータＧが、図面において圧下部の右側、すなわち被加工材Ａの進行方向端部に取り付けられている点である。
【００１８】
図１に示すように、本発明の鍛造方法では、被加工材Ａを保持するマニプレータＧを常に被加工材圧下部、すなわち丸溝金敷Ｂの位置から遠ざける方向に進行させる（すなわち、鍛造を“引き手”のみで行う）とともに、被加工材をその軸の回りに回転させる。
【００１９】
前記図２に示したように、被加工材Ａの圧下部を通過させた側（図２（ａ）において、丸溝金敷Ｂの右側）がフリーである場合、すなわち、鍛造を“押し手”で行う場合は、先に述べたように、圧下終了直前領域Ｅにおいて生じた曲がりが矯正されずに被加工材Ａの曲がりとして残るのであるが、“引き手”で鍛造を行うと、図１に示したように、曲がりが発生する被加工材Ａの部位（丸溝金敷Ｂの出側近傍）にマニプレータＧによる軸Ｓを固定する力が加わるので、曲がりの発生が抑制されることになる。すなわち、鍛造を“引き手”のみで行い、マニプレータＧに、被加工材を移動させる役割に加え、曲がり防止の役割を担わせるのである。なお、マニプレータＧで保持する側とは反対側については、マニプレータにより保持する必要はないが、被加工材の形状等によっては、マニプレータに、被加工材を移動するための力を加えず、被加工材の端を支持する役割だけをさせてもよい。
【００２０】
この“引き手”のみで鍛造を行うことに加え、被加工材Ａをその軸Ｓの回りに回転させることも、前記曲がりの防止に必須の要件である。前述したように、被加工材Ａが回転しながら移動することによって、丸溝金敷Ｂによる一の圧下により生じた非接触面Ｄ（前記図２参照）における幅の広がり（伸び量）の不均一に起因して生じる曲がりが、次の圧下時に金敷平行部Ｆで矯正され、軽減するからである。
【００２１】
本発明の鍛造方法で、前記のように、被加工材Ａを保持するマニプレータＧを常に被加工材圧下部から遠ざける方向に進行させる（すなわち、鍛造を“引き手”のみで行う）のは、「圧下後の被加工材Ａの断面形状が円形となる鍛造パスの際」である。すなわち、本発明の方法で断面形状が円形の丸棒を製造するに際し、例えば、素材として角材を用い、鍛造の初期の段階で、まだ圧下後の断面形状が円形とはならない場合には、“引き手”、“押し手”のいずれでもよい。圧下後の断面形状が円形とはならない場合は、その後も鍛造が続けられるので、前記圧下後の断面形状が円形となる鍛造パスにおいて“引き手”にすれば、前記の図２（ｂ）に示した非接触面Ｄにおける幅の広がり（伸び量）の不均一により生じる被加工材Ａの曲がりを抑制することができるからである。
【００２２】
このように、本発明の鍛造方法の特徴は、丸棒を製造するに当たり、圧下後の被加工材Ａの断面形状が円形となる鍛造パスの際、被加工材を保持するマニプレータを常に被加工材圧下部から遠ざける方向に進行させ、すなわち鍛造工程において“引き手”のみにし、鍛造中、被加工材を回転させることにある。
【００２３】
前掲の特許文献１に記載の鍛造方法では、「被鍛造材を、一方端側のマニプレータで把持して逆方端方向へ移動させる」こととし、一連の工程のなかで、“押し手”で鍛造を行うことを構成要件の一つとして規定している。また、特許文献２に記載の鍛造方法では、「一方向の鍛造パスと逆方向の鍛造パスとの間で、被鍛造材をその軸の回りに、曲がり方向が軸に実質的に対象になるように回転させてから逆方向のパスを行う」と記載されているのみで、“引き手”で鍛造を行うという記載がなく、さらに、丸棒ではなく平材の製造を前提としたものである。したがって、本発明の鍛造方法は、特許文献１、特許文献２に記載の鍛造方法のいずれとも明確に技術思想を異にするものである。
【００２４】
以上の本発明の鍛造方法についての説明は、自由鍛造の中でも、丸溝金敷Ｂによる上下からの圧下と軸方向への移動とが交互に加えられる鍛造方法により丸棒を製造する場合についての説明である。しかし、本発明の方法は、先に記したように、「被加工材に対し、その軸に直角の方向からの金敷による圧下と前記軸方向への移動とを繰り返して丸棒を製造する鍛造方法」であって、高速鍛造により丸棒を製造する場合に限定されるものではない。「被加工材の軸に直角の方向からの金敷による圧下」は、上下からの圧下に限らず、複数の方向からの圧下でもよいし、一方向からの（例えば、上からのみの）圧下でもよい。また、「金敷による圧下と前記軸方向への移動とを繰り返して」丸棒を製造するのであって、前記の「繰り返し」は必ずしも交互でなくてもよい。したがって、いわゆる従来の自由鍛造による丸棒の製造にも適用することができる。
【００２５】
前記本発明の鍛造方法によれば、鍛造を常に“引き手”で行うという簡易な方法で、自由鍛造（高速鍛造を含む）により丸棒を製造する際に被加工材に生じる曲がりを極めて効果的に抑制することができる。鍛造時間の増加もなく、しかも、後工程である曲がり矯正工程を省略し、ないしは前記矯正工程での所要工数を著しく軽減することができるので、鍛造による丸棒生産の効率を大幅に向上させることが可能になる。
【００２６】
【実施例】
断面形状が正八角形で、断面対辺間の距離が３３７ｍｍ、全長が４０００ｍｍの、ＳＵＳ３１６製またはＳＵＳ３０４製の材料を被加工材とし、これを１２００℃に加熱した後、本発明の鍛造方法により、熱間での半径が１６１．５ｍｍの丸棒に鍛造した場合の曲がりの発生状況を調査した。なお、比較のために、マニプレータを常に丸溝金敷に近づける（すなわち、鍛造を“押し手”で行う）鍛造方法についても同様の調査を行った。
【００２７】
用いた鍛造機は、前記図１に示した構成を有する自由鍛造機で、丸溝金敷Ｂの開き角度が１０５°、金敷平行部Ｆの長さが２００ｍｍ、丸溝金敷Ｂの曲率半径が１６０ｍｍのものである。被加工材の軸の回りの回転角度は、７０°／圧下とした。
【００２８】
調査結果を表１に示す。
【００２９】
【表１】

表１に示した結果から明らかなように、マニプレータを常に丸溝金敷から遠ざける（すなわち、鍛造を“引き手”で行う）本発明の鍛造方法では、鍛造時に発生する被加工材の曲がりは、材質、被加工材の送り量の如何によらず、鍛造を“押し手”で行った比較例に比べて格段に小さく、本発明の方法が曲がりの抑制に極めて有効であることが確認できた。
【００３０】
【発明の効果】
本発明の鍛造方法によれば、自由鍛造（高速鍛造を含む）により丸棒を製造する際に被加工材に生じる曲がりを極めて効果的に抑制することができる。したがって、鍛造による丸棒生産の効率を大幅に向上させることが可能である。
【図面の簡単な説明】
【図１】本発明の鍛造方法を説明するための図である。
【図２】曲がりの発生過程を説明するための図で、（ａ）は被加工材と圧下部の縦断面を模式的に示す図、（ｂ）は（ａ）のＩ−Ｉ矢視図である。
【符号の説明】
Ａ：被加工材
Ｂ：丸溝金敷
Ｃ：塑性変形領域
Ｄ：非接触面
Ｅ：圧下終了直前領域
Ｆ：金敷平行部
Ｇ：マニプレータ[0001]
[Industrial applications]
INDUSTRIAL APPLICABILITY The present invention provides a forging method for manufacturing a round bar by free forging including high-speed forging, and in particular, can suppress bending of a workpiece which occurs during a forging pass in which a workpiece has a circular cross-sectional shape. It relates to a forging method.
[0002]
[Prior art]
Conventionally, when a workpiece such as carbon steel, alloy steel, stainless steel, or a Ni-base alloy is heated and a round bar is manufactured by free forging (including high-speed forging), the heat of the workpiece may be deviated by heat or heat. Due to the wear of the anvil that presses down the work material, the work material often bends during a forging pass in which the cross-sectional shape of the work material after rolling is circular. This is not an exception in a high-speed forging in which a reduction is repeatedly applied simultaneously from a plurality of directions symmetrical to the axis of the workpiece by anvil. Therefore, a step of correcting bending after the forging is completed is required.
[0003]
Regarding the suppression of the occurrence of bending of the workpiece in the high-speed forging method, for example, in Patent Document 1, the forging is performed while the workpiece is gripped by a manipulator on one end side and moved in the opposite end direction. After forging to the middle of the longitudinal direction of the material, it is moved toward the one end in order to correct the bending that occurred at that time, and then the forged material is gripped by the manipulator on the opposite end side and reversely rotated again. A forging method that reduces bending by continuing forging while moving toward one end is disclosed. However, in this forging method, the bent forged material is temporarily moved to the forging start position while correcting the bending, and forging is performed again. Therefore, the forging time is extended, and the production efficiency is significantly reduced.
[0004]
Further, Patent Document 2 discloses that a material to be forged is turned around its axis between a forging pass in one direction and a forging pass in the opposite direction so that the bending direction is substantially symmetric with respect to the axis (specifically, as described in Japanese Patent Application Laid-Open No. H11-157556). Discloses a forging method in which a flat material is rotated by 180 ° and a pass is made in the opposite direction. However, this method is based on the premise of manufacturing a flat material having a rectangular cross section, and the effect when applied to the manufacture of a round bar is not clear.
[0005]
[Patent Document 1]
JP 2001-105077 A [Patent Document 2]
JP 2001-105079 A
[Problems to be solved by the invention]
The present invention is a forging method for producing a round bar by free forging including high-speed forging, and in particular, significantly increases the forging time in a forging pass in which a cross-sectional shape of a workpiece after rolling is circular. It is an object of the present invention to provide a forging method capable of suppressing a bending generated in a workpiece without a bending process, which is a subsequent process.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present inventor has investigated in detail a process in which bending occurs in a pass for forging a workpiece into a circular cross section using a free forging machine.
[0008]
FIGS. 2A and 2B are diagrams for explaining a bending generation process, in which FIG. 2A is a diagram schematically illustrating a longitudinal section of a workpiece and a pressing portion, and FIG. 2B is a view taken along line II of FIG. It is. In FIG. 2, the round groove anvil B is a pair of anvils of the same shape provided at symmetrical positions (up and down) with the workpiece A interposed therebetween, and has an anvil parallel part F.
[0009]
First, when the workpiece A is passed through the reduction by the round grooved anvil B without giving a rotation around its axis, the workpiece A is pressed down from above and below by the circular grooved anvil B and in the axial direction (FIG. 2). In (a), movement from left to right in the drawing) is added alternately and forged. The workpiece A is pressed down in the plastic deformation region C of the round grooved anvil B, but as shown in FIG. . Note that the broken line in the figure represents the cross-sectional shape when the width does not increase. This widening also occurs in the region E just before the end of the reduction immediately before the outside of the reduction region. At this time, for example, if the workpiece A has uneven heat, the amount of elongation for each reduction becomes uneven, and the non-processed material A bends.
[0010]
Next, when the workpiece A, which also has a circular cross section, is caused to pass through the lowering portion while rotating about its axis, the lowering of the workpiece A by the round groove anvil B and the movement in the axial direction alternate. Therefore, as shown by the arrow in FIG. 2A, the forging proceeds while rotating spirally and is forged.
[0011]
In this case, as in the case where the rotation is not applied, in the process of forging with the round groove anvil B, the width expands at each reduction on the non-contact surface D, and bending occurs due to uneven expansion. Since the workpiece A is moving as shown by the arrow while rotating around its axis, the bending caused by one reduction is corrected by the anvil parallel portion F at the next reduction and reduced. However, at this time, in the portion corresponding to the non-contact surface D, the amount of elongation becomes non-uniform again, and bending occurs. The correction and occurrence of such a bending also occur in the region E immediately before the end of the reduction, and the bending generated in this region E can no longer be corrected by the round groove anvil B, and therefore remains as the bending generated in the non-processed material A. Will be.
[0012]
As a result of studying a measure for suppressing the bending, the inventor of the present invention holds the workpiece A and rotates it around its axis (the rotation around the axis of the workpiece having a circular cross section is referred to as “rotation”. ), And a manipulator for fixing the rotating shaft and moving the workpiece A in the axial direction in a direction away from the round groove anvil B for plastically deforming the workpiece A by pressing down the workpiece A. It has been found that the bending can be suppressed by proceeding, that is, by using a "puller".
[0013]
The present invention has been made based on this finding, and its gist lies in the following forging method.
[0014]
"A forging method for manufacturing a round bar by repeatedly rolling down the work material by a metal anvil from a direction perpendicular to the axis and moving in the axial direction, and the cross-sectional shape of the work after the reduction is circular. A forging method in which a manipulator holding a workpiece is always moved in a direction away from the workpiece pressure lower part during a forging pass, and the workpiece is rotated around its axis. 』
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the forging method of the present invention will be described in detail.
[0016]
As described above, the forging method of the present invention is a method for manufacturing a round bar, which is a manipulator that holds a workpiece during a forging pass in which the cross-sectional shape of the workpiece after rolling is circular. A forging method in which the workpiece is always moved in a direction away from the workpiece pressure lower part, and the workpiece is rotated around its axis.
[0017]
FIG. 1 is a diagram for explaining the forging method of the present invention. In FIG. 1, the shape and arrangement of the round groove anvil B are the same as those in FIG. 2 described above, and therefore, on the non-contact surface D that does not come into contact with the round groove anvil B (see FIG. As shown in (b), the width increases with each rolling. 2 is different from the case of FIG. 2 in that a manipulator G for holding the work material A and rotating it around its axis (that is, rotating) and fixing this rotation axis is provided on the right side of the pressing part in the drawing. That is, it is attached to the end of the workpiece A in the traveling direction.
[0018]
As shown in FIG. 1, in the forging method of the present invention, the manipulator G holding the workpiece A always advances in a direction in which the manipulator G holding the workpiece A is moved away from the pressure of the workpiece, ie, the position of the round groove anvil B. The work piece is rotated about its axis together with the "puller").
[0019]
As shown in FIG. 2, when the side of the workpiece A that has passed through the pressing portion (the right side of the round groove anvil B in FIG. 2A) is free, that is, forging is performed by a “push hand”. When the forging is performed, as described above, the bending generated in the region E immediately before the end of the reduction is not corrected and remains as the bending of the workpiece A. As shown in (1), since the force for fixing the shaft S by the manipulator G is applied to the portion of the workpiece A where the bending occurs (near the exit side of the round groove anvil B), the occurrence of the bending is suppressed. . In other words, forging is performed only by the "puller", and the manipulator G plays a role of preventing bending in addition to a role of moving the workpiece. The side opposite to the side held by the manipulator G does not need to be held by the manipulator. However, depending on the shape of the work material, etc., the manipulator is not subjected to a force for moving the work material, Only the role of supporting the end of the workpiece may be performed.
[0020]
In addition to performing forging using only the "pull", rotating the workpiece A about its axis S is also an essential requirement for preventing the bending. As described above, as the workpiece A moves while rotating, the width of the non-contact surface D (the amount of elongation) on the non-contact surface D (see FIG. 2) caused by one reduction by the round groove anvil B is not uniform. This is because the bending caused by the above is corrected by the anvil parallel part F at the time of the next reduction and is reduced.
[0021]
In the forging method of the present invention, as described above, the manipulator G that holds the workpiece A is always advanced in a direction away from the workpiece pressure lowering (that is, forging is performed only with the “puller”). "At the time of a forging pass in which the cross-sectional shape of the workpiece A after the rolling is circular". That is, when manufacturing a round bar having a circular cross-sectional shape by the method of the present invention, for example, when a square bar is used as a material, and in the initial stage of forging, if the cross-sectional shape after reduction is not yet circular, It may be either a "puller" or a "pusher". In the case where the cross-sectional shape after the rolling is not circular, forging is continued thereafter, so that if a "puller" is used in the forging pass in which the cross-sectional shape after the rolling becomes circular, the above-described FIG. This is because it is possible to suppress the bending of the workpiece A caused by the uneven width (elongation) on the non-contact surface D shown.
[0022]
As described above, the feature of the forging method of the present invention is that, when a round bar is manufactured, a manipulator that holds a workpiece is always processed during a forging pass in which a cross-sectional shape of the workpiece A after rolling is circular. It is to proceed in the direction away from the lower part of the material pressure, that is, to use only the "puller" in the forging process, and to rotate the workpiece during forging.
[0023]
In the forging method described in Patent Document 1 described above, “the forged material is gripped by the manipulator on one end side and moved in the opposite end direction”, and in a series of steps, “push hand” is used. Forging is specified as one of the constituent requirements. Also, in the forging method described in Patent Document 2, "the forged material is around the axis between the forging pass in one direction and the forging pass in the opposite direction, and the bending direction is substantially symmetric with respect to the axis. And then perform a pass in the opposite direction ", there is no mention of performing forging with a" puller ", and it is based on the premise of manufacturing flat materials instead of round bars. is there. Therefore, the forging method of the present invention clearly differs in technical idea from any of the forging methods described in Patent Documents 1 and 2.
[0024]
The above description of the forging method of the present invention is directed to a case where a round bar is manufactured by a forging method in which a vertical depression and an axial movement by a circular groove anvil B are alternately applied among free forging. It is. However, as described above, the method of the present invention is based on "a forging process for manufacturing a round bar by repeatedly rolling down the workpiece by anvil from a direction perpendicular to the axis and moving in the axial direction. Method ", and is not limited to the case of producing a round bar by high-speed forging. “Reduction by anvil from a direction perpendicular to the axis of the workpiece” is not limited to reduction from above and below, but may be reduction from multiple directions or reduction from one direction (for example, only from above). Good. In addition, a round bar is manufactured by “repeating the reduction by the anvil and the movement in the axial direction”, and the “repetition” is not necessarily alternated. Therefore, the present invention can be applied to the production of a round bar by so-called conventional free forging.
[0025]
According to the forging method of the present invention, it is a simple method in which forging is always performed with a "puller", and a bend generated in a workpiece when a round bar is manufactured by free forging (including high-speed forging) is extremely effective. Can be suppressed. There is no increase in forging time, and furthermore, the bending correction step as a post-step can be omitted, or the number of steps required in the correction step can be significantly reduced, so that the efficiency of round bar production by forging can be greatly improved. Becomes possible.
[0026]
【Example】
A SUS316 or SUS304 material having a regular octagonal cross section, a distance between opposite sides of 337 mm, and a total length of 4000 mm was used as a workpiece, heated to 1200 ° C., and then heated by a forging method of the present invention. The state of occurrence of bending when forging into a round bar having a radius of 161.5 mm was investigated. For comparison, a similar investigation was performed on a forging method in which the manipulator was always brought close to the round groove anvil (that is, forging was performed with a "push hand").
[0027]
The forging machine used was a free forging machine having the configuration shown in FIG. 1 described above, in which the opening angle of the circular grooved anvil B was 105 °, the length of the parallel anvil parallel part F was 200 mm, and the radius of curvature of the circular grooved anvil B was 160 mm. belongs to. The rotation angle of the workpiece around the axis was 70 ° / down.
[0028]
Table 1 shows the survey results.
[0029]
[Table 1]

As is clear from the results shown in Table 1, in the forging method of the present invention in which the manipulator is always kept away from the anvil of the round groove (that is, forging is performed with a "puller"), the bending of the work material generated at the time of forging is as follows. Regardless of the material and the feed amount of the workpiece, the forging was significantly smaller than the comparative example in which the forging was performed with a "push hand", and it was confirmed that the method of the present invention was extremely effective in suppressing bending. .
[0030]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the forging method of this invention, the bending which arises in a to-be-processed material at the time of manufacturing a round bar by free forging (including high-speed forging) can be suppressed very effectively. Therefore, it is possible to greatly improve the efficiency of round bar production by forging.
[Brief description of the drawings]
FIG. 1 is a view for explaining a forging method of the present invention.
FIGS. 2A and 2B are diagrams for explaining a process of generation of bending, in which FIG. 2A is a diagram schematically illustrating a longitudinal section of a workpiece and a pressing portion, and FIG. It is.
[Explanation of symbols]
A: Workpiece material B: Round groove anvil C: Plastic deformation area D: Non-contact surface E: Area immediately before the end of rolling F: Anvil parallel part G: Manipulator

Claims

A forging method in which a round bar is manufactured by repeatedly rolling down the workpiece with an anvil from a direction perpendicular to its axis and moving in the axial direction, and the cross-sectional shape of the workpiece after the rolling is circular. A forging method characterized in that, during a forging pass, the manipulator holding the workpiece is always moved in a direction away from the workpiece pressure lower part, and the workpiece is rotated around its axis.