JP2005007402A - Forging method - Google Patents
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【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炭素鋼、合金鋼、ステンレス鋼、Ｎｉ基合金鋼等の被加工材を加熱し、丸棒を製造する際の鍛造方法に関する。
【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、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称になるように（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、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。
【０００４】
また、特許文献２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。しかしながら、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。
【０００５】
【特許文献１】
特開２００１−１０５０７９号公報
【特許文献２】
特開２００１−１０５０７７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、すなわちこの円形断面の被加工材の軸の回りに回転させながら鍛造するパスにおいて、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３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３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】
被加工材Ａを丸溝金敷Ｂによる圧下部を通過させる場合、被加工材Ａは、図３（ａ）に示すように、丸溝金敷Ｂによる上下からの圧下を加えられ、丸溝金敷Ｂの塑性変形領域Ｃで圧下されるが、図３（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に水平方向の曲がりが生じる。
【００１０】
しかし、被加工材を円形断面に鍛造するパスにおいては、被加工材Ａは、軸方向（図３（ａ）おいて、図面の左から右方向）への移動と被加工材の軸の回りの回転（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）が加えられるので、図３（ａ）に矢印で示すように、スパイラル回転しながら進行し、圧下部を通過して鍛造される。したがって、その前の段階での圧下により生じた水平方向の曲がり（「Ｘ方向の曲がり」であり、以下、単に「曲がり」ともいう）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が繰り返されるが、金敷平行部Ｆで曲がりを完全に矯正できない場合、圧下毎に被加工材Ａには曲がりが重畳され、当該パスで曲がりを矯正することができず、曲がり矯正工程が必要となる。
【００１１】
本発明者は、この曲がりを抑制する方策を検討した結果、丸溝金敷の溝底部曲率半径（以下、単に「丸溝金敷の曲率半径」ともいう）を当該パス終了後の被加工材Ａの断面半径より小さくすると、当該パス終了後の被加工材Ａに残存する曲がりを大幅に低減できることを見いだした。
【００１２】
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（１）および（２）の鍛造方法にある。
【００１３】
（１）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、圧下後の被加工材の断面形状が円形となる鍛造パスの際、下記▲１▼式を満たす丸溝金敷を用いて鍛造する鍛造方法。
【００１４】
（被加工材の仕上断面半径）＞（丸溝金敷の溝底部曲率半径） ・・▲１▼
前記被加工材の仕上断面半径と丸溝金敷の曲率半径との差が８ｍｍ未満であれば、被加工材の仕上断面の真円度（＝最大直径−最小直径）が小さく、断面が円形ないしは円形に近い形状をなすので望ましい。
【００１５】
ここで、「被加工材の仕上断面半径」とは、被加工材を円形断面に鍛造するパス、すなわち、被加工材を自転させながら鍛造するパスを終了した後の被加工材Ａの断面半径をいう。以下、単に「被加工材の断面半径」ともいう。
【００１６】
（２）被加工材に対し、その軸に直角の２方向から一対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、圧下後の被加工材の断面形状が円形となる鍛造パスの際、被加工材と４面で接触する金敷を用いて鍛造する鍛造方法。
【００１７】
【発明の実施の形態】
以下に、本発明の鍛造方法（前記（１）に記載の方法、および（２）に記載の方法）を詳細に説明する。
前記（１）に記載の鍛造方法は、「丸棒を製造する鍛造方法であって、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、
（被加工材の断面半径）＞（丸溝金敷の曲率半径） ・・▲１▼
を満たす丸溝金敷を用いて鍛造する鍛造方法」である。
【００１８】
このように、丸溝金敷の曲率半径を被加工材Ａの仕上断面半径より小さくするのは、以下の理由による。
【００１９】
図１は曲率半径が被加工材Ａの断面半径より小さい丸溝金敷を用いて鍛造した場合の、また、図２は曲率半径が被加工材Ａの断面半径より大きい丸溝金敷を用いて鍛造した場合の丸溝金敷の平行部の縦断面図である。
【００２０】
図２に示すように、丸溝金敷Ｂの溝底部の曲率半径Ｇが被加工材Ａの断面半径Ｈより大きい、すなわち、前記▲１▼式を満足しない丸溝金敷Ｂを用いて鍛造する場合は、被加工材Ａを丸溝金敷Ｂで塑性加工する領域は平行部ＦにおいてＩ５およびＩ６の２面となる。この場合、力は被加工材Ａに対して上下方向から作用するだけで、Ｘ方向の曲がりを矯正するＸ方向の力は働かず、曲がりを矯正することはできない。
【００２１】
これに対して、図１に示すように、前記▲１▼式を満足する丸溝金敷Ｂを用いて鍛造する場合は、被加工材Ａを丸溝金敷Ｂで塑性加工する領域は平行部ＦにおいてＩ１、Ｉ２、Ｉ３およびＩ４の４面となる。この場合は、被加工材Ａに対して水平方向（Ｘ方向）の分力、すなわち、Ｘ方向の曲がりを矯正する力が作用するので、曲がりを効果的に矯正することが可能となる。
【００２２】
ただし、前記被加工材の断面半径Ｈと丸溝金敷の曲率半径Ｇとの差が大きすぎると、被加工材Ａの真円度（＝最大直径−最小直径）が大きくなり、断面が円形ないしは円形に近い形状の丸棒が得られない。したがって、後述する実施例に示すように、被加工材の断面半径Ｈと丸溝金敷の曲率半径Ｇとの差が８ｍｍ未満、すなわち、下記▲２▼式を満たす丸溝金敷を用いて鍛造するのが望ましい。
【００２３】
０ｍｍ＜（被加工材の断面半径）−（丸溝金敷の曲率半径）＜８ｍｍ ・・▲２▼
次に、前記（２）に記載の鍛造方法は、「被加工材に対し、その軸に直角の２方向から一対の金敷による圧下を加えて、丸棒を製造する鍛造方法であって、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、被加工材と４面で接触する金敷を用いて鍛造する鍛造方法」である。
【００２４】
「２方向から一対の金敷による圧下を加えて、被加工材と４面で接触する金敷」といえば、具体的には、前記図１に示した曲率半径Ｇが被加工材Ａの断面半径Ｈより小さい丸溝金敷が該当するが、必ずしもこのような丸溝金敷に限らない。被加工材と４面で接触する金敷であれば、被加工材の上部および下部近辺において４面で接触するということは通常は考えにくく、被加工材の上部および下部からはある程度離れた、被加工材にＸ方向の分力が作用するような面で接触することになるので、Ｘ方向の曲がりを矯正する力が働く。
【００２５】
このような２つの（一対の）金敷を用いて鍛造すれば、例えば、水平に対して４５°傾斜した方向およびその反対方向からの圧下と、水平に対して−４５°傾斜した方向およびその反対方向からの圧下、すなわち合計４方向からの圧下を加える方式の鍛造と、曲がりの抑制に関しては同等の効果が期待できる。
【００２６】
本発明の鍛造方法において、前述したように、▲１▼式を満たす丸溝金敷を用いて鍛造し、または被加工材と４面で接触する丸溝金敷を用いて鍛造するのは、「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、丸溝金敷は必ずしも▲１▼式を満たす必要はないし、被加工材と４面で接触する金敷を用いなくてもよい。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前記の条件を満たす丸溝金敷等を用いれば、前記の図３（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。
【００２７】
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２方向から一対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、横からの圧下でもよい。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。
【００２８】
前記本発明の鍛造方法によれば、曲率半径が被加工材Ａの仕上断面半径より小さい丸溝金敷を用いて鍛造するか、または、被加工材と４面で接触する金敷を用いて２方向から一対の金敷による圧下を加えて鍛造する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。これにより、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。
【００２９】
【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、前記▲１▼式を満足しない丸溝金敷Ｂを用いる鍛造方法についても同様の調査を行った。
【００３０】
用いた鍛造機は、前記図３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、被加工材の送り量は２５ｍｍ／圧下、被加工材の軸の回りの回転角度は、７０°／圧下とした。丸溝金敷Ｂとしては、曲率半径が１６３．０ｍｍから１５１．５ｍｍの範囲の４種類の金敷を用いた。
【００３１】
調査結果を表１に示す。
【００３２】
【表１】
表１に示した結果から明らかなように、丸溝金敷の曲率半径が被加工材の仕上断面半径（この場合は、１６１．５ｍｍ）より小さい丸溝金敷Ｂを用いて鍛造した本発明例Ｎｏ．３〜Ｎｏ．６では、曲がりの発生を大幅に抑制することができた。ただし、本発明例Ｎｏ．６では、被加工材Ａの真円度がやや大きかった。真円度を考慮すれば、被加工材の仕上断面半径と丸溝金敷の曲率半径との差を８ｍｍ未満とするのが望ましい。
【００３４】
一方、丸溝金敷の曲率半径が被加工材の仕上断面半径より大きい丸溝金敷Ｂを用いて鍛造した比較例Ｎｏ．１および２では、曲がりが発生し、評価は不良（×印）であった。
【００３５】
【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】曲率半径が被加工材Ａの仕上断面半径より小さい丸溝金敷を用いて鍛造した場合の丸溝金敷の平行部の縦断面図である。
【図２】曲率半径が被加工材Ａの仕上断面半径より大きい丸溝金敷を用いて鍛造した場合の丸溝金敷の平行部の縦断面図である。
【図３】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
Ｆ：金敷平行部
Ｇ：丸溝金敷の曲率半径
Ｈ：被加工材の断面半径[0001]
[Industrial application fields]
The present invention relates to a forging method for manufacturing a round bar by heating a workpiece such as carbon steel, alloy steel, stainless steel, or Ni-base alloy steel by free forging including high-speed forging.
[0002]
[Prior art]
Conventionally, when a work piece such as carbon steel, alloy steel, stainless steel, or Ni-based alloy is heated and a round bar is manufactured by free forging (including high-speed forging), the heat bias and the heat Due to the wear of an anvil that squeezes the work material, the work material often bends during a forging pass in which the cross-sectional shape of the work material after the squeezing is circular. This is no exception even in high-speed forging in which rolling reduction is repeatedly performed by anvil simultaneously from a plurality of directions symmetrical to the axis of the workpiece. For this reason, a process for correcting the bending after the forging 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 material is bent around its axis between the forging pass in one direction and the forging pass in the opposite direction. A forging method is disclosed in which a pass in the reverse direction is performed after rotating so that is substantially symmetric with respect to the axis (specifically, 180 ° for a flat member). However, this method is premised on the production of a flat material having a rectangular cross section, and the effect when applied to the production of a round bar is not clear.
[0004]
Further, in Patent Document 2, a forged material is gripped by a manipulator on one end side and moved in the opposite end direction, and then forged to the middle in the length direction of the forged material. By moving in the one end direction to correct the bending generated in the process, and then holding the forging material with the manipulator on the opposite end side and continuing the forging while moving again in the opposite end direction. A forging method that reduces bending is disclosed. However, in this forging method, the forged material in which bending has occurred is once moved to the forging start position while correcting the bending, and forging is performed again, so that the forging time is extended, and the production efficiency is greatly reduced.
[0005]
[Patent Document 1]
JP 2001-105079 A [Patent Document 2]
Japanese Patent Laid-Open No. 2001-105077
[Problems to be solved by the invention]
The present invention relates to a forging method for manufacturing a round bar by free forging including high-speed forging, and in particular, a forging pass in which a cross-sectional shape of a work material after reduction is circular, that is, a work material having this circular cross section. In a pass forging while rotating around the axis of the forging, a forging method is provided that can suppress the bending that occurs in the work piece without significantly increasing the forging time and can omit the bending correction process that is a subsequent process. The purpose is that.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present inventor has investigated in detail a process in which bending occurs in a pass forging a workpiece into a circular cross section using a free forging machine.
[0008]
FIGS. 3A and 3B are diagrams for explaining a process of occurrence of bending, in which FIG. 3A is a diagram schematically showing a longitudinal section of a workpiece and an indented portion, and FIG. 3B is a view taken along the line II in FIG. It is. In FIG. 3, the round groove anvil B is an anvil with a pair of the same shape provided at symmetrical positions (up and down) across the workpiece A, and has an anvil parallel part F.
[0009]
When the work material A is passed through the indented portion of the round groove anvil B, the work material A is subjected to a downward pressure by the round groove anvil B as shown in FIG. In the non-contact surface D that does not come into contact with the round groove anvil B, as shown in FIG. In addition, the broken line in the same figure represents the cross-sectional shape when the said breadth does not arise. At this time, for example, if heat deviation occurs in the workpiece A, the amount of elongation at each reduction becomes non-uniform, and the non-work A is bent in the horizontal direction.
[0010]
However, in the pass for forging the workpiece into a circular cross section, the workpiece A moves in the axial direction (from left to right in the drawing in FIG. 3A) and around the axis of the workpiece. (This rotation around the axis of the work piece having a circular cross section is also referred to as “rotation”), as shown by the arrow in FIG. Forged through the lower part. Accordingly, the horizontal bend ("X direction bend", hereinafter simply referred to as "bend") caused by the reduction in the previous stage is corrected and reduced by the anvil parallel part F at the next reduction. . However, in the portion that corresponds to the non-contact surface D at this time, the amount of elongation becomes non-uniform again, and bending occurs. Such correction and generation of bending are repeated, but if the bending cannot be completely corrected by the anvil parallel part F, the bending is superimposed on the workpiece A at each reduction, and the bending can be corrected by the pass. Therefore, a bending correction process is required.
[0011]
As a result of studying measures for suppressing this bending, the present inventor has determined the groove bottom radius of curvature of the round groove anvil (hereinafter also simply referred to as “the radius of curvature of the round groove anvil”) of the workpiece A after the end of the pass. It has been found that if the radius is smaller than the cross-sectional radius, the bending remaining on the workpiece A after completion of the pass can be greatly reduced.
[0012]
The present invention has been made based on this finding, and the gist thereof is the following forging methods (1) and (2).
[0013]
(1) A forging method in which a round bar is manufactured by repeatedly rolling down an anvil from a direction perpendicular to the axis of the workpiece and moving in the axial direction, and a cross section of the workpiece after the reduction A forging method in which forging is performed using a round groove anvil that satisfies the following formula (1) during a forging pass having a circular shape.
[0014]
(Finished section radius of workpiece)> (Groove bottom radius of curvature of round groove anvil) ・ ・ ▲ 1 ▼
If the difference between the finished section radius of the workpiece and the radius of curvature of the round groove anvil is less than 8 mm, the roundness (= maximum diameter-minimum diameter) of the finished section of the workpiece is small and the section is circular or This is desirable because it has a nearly circular shape.
[0015]
Here, the “finish cross-sectional radius of the work material” means the cross-sectional radius of the work material A after finishing the pass for forging the work material into a circular cross section, that is, the pass for forging while rotating the work material. Say. Hereinafter, it is also simply referred to as “cross-sectional radius of the workpiece”.
[0016]
(2) A forging method in which a round bar is manufactured by repeatedly reducing a workpiece with two pairs of anvils from two directions perpendicular to the axis and moving in the axial direction. A forging method in which forging is performed by using an anvil that is in contact with a workpiece on four sides during a forging pass in which the cross-sectional shape of the material is circular.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the forging method of the present invention (the method described in (1) above and the method described in (2)) will be described in detail.
The forging method described in the above (1) is “a forging method for producing a round bar, in the case of a forging pass in which the cross-sectional shape of the workpiece after reduction is circular,
(Cross-section radius of workpiece)> (Curve radius of round groove anvil) ・ ・ ▲ 1 ▼
Is a forging method in which forging is performed using a round groove anvil that satisfies the above.
[0018]
Thus, the reason why the radius of curvature of the round groove anvil is made smaller than the finishing section radius of the workpiece A is as follows.
[0019]
FIG. 1 shows a case where forging is performed using a round groove anvil with a radius of curvature smaller than the cross-sectional radius of the workpiece A. FIG. 2 shows a forging using a round groove anvil with a radius of curvature larger than the cross-sectional radius of the workpiece A. It is a longitudinal cross-sectional view of the parallel part of a round groove anvil at the time of doing.
[0020]
As shown in FIG. 2, forging using a round groove anvil B in which the curvature radius G of the groove bottom portion of the round groove anvil B is larger than the cross-sectional radius H of the workpiece A, that is, the above formula (1) is not satisfied. In the parallel part F, the region where the workpiece A is plastically processed with the round groove anvil B is two surfaces I 5 and I 6 . In this case, the force only acts on the workpiece A from above and below, the X-direction force for correcting the X-direction bending does not work, and the bending cannot be corrected.
[0021]
On the other hand, as shown in FIG. 1, in the case of forging using the round groove anvil B that satisfies the formula (1), the region where the workpiece A is plastically processed with the round groove anvil B is the parallel portion F. In FIG. 4, there are four faces I 1 , I 2 , I 3 and I 4 . In this case, since a component force in the horizontal direction (X direction), that is, a force for correcting the bending in the X direction is applied to the workpiece A, the bending can be effectively corrected.
[0022]
However, if the difference between the cross-sectional radius H of the workpiece and the radius of curvature G of the round groove anvil is too large, the roundness (= maximum diameter-minimum diameter) of the workpiece A increases and the cross-section is circular or A round bar with a nearly circular shape cannot be obtained. Therefore, as shown in an example described later, forging is performed using a round groove anvil in which the difference between the cross-sectional radius H of the workpiece and the curvature radius G of the round groove anvil is less than 8 mm, that is, the following equation (2) is satisfied. Is desirable.
[0023]
0 mm <(section radius of workpiece) − (curvature radius of round groove anvil) <8 mm ・ ・ ▲ 2 ▼
Next, the forging method described in the above (2) is “a forging method for manufacturing a round bar by applying a pair of anvils to a workpiece from two directions perpendicular to the axis thereof. In the forging method in which the cross-sectional shape of the subsequent workpiece is circular, the forging is performed using an anvil that is in contact with the workpiece on four sides.
[0024]
Specifically, the curvature radius G shown in FIG. 1 is the cross-sectional radius H of the workpiece A. Smaller round groove anvils are applicable, but are not necessarily limited to such round groove anvils. With an anvil that is in contact with the workpiece on four sides, it is usually difficult to think that it is in contact with the four sides in the vicinity of the upper and lower parts of the workpiece, and the workpiece is somewhat distant from the upper and lower parts of the workpiece. Since the workpiece is brought into contact with the surface where the component force in the X direction acts, the force for correcting the bending in the X direction works.
[0025]
Forging using such two (a pair of) anvils, for example, rolling in a direction inclined by 45 ° with respect to the horizontal and the opposite direction, and a direction inclined by -45 ° with respect to the horizontal and vice versa. The same effect can be expected with respect to the forging of the method of applying the reduction from the direction, that is, the reduction from the total of four directions, and the bending.
[0026]
In the forging method of the present invention, as described above, forging using a round groove anvil satisfying the formula (1), or forging using a round groove anvil that contacts the workpiece on four sides, This is “at the time of a forging pass in which the cross-sectional shape of the subsequent workpiece A is circular”. That is, when a round bar having a circular cross-sectional shape is manufactured by the method of the present invention, for example, when a square bar is used as a raw material and the cross-sectional shape after reduction is not yet circular at the initial stage of forging, The groove anvil does not necessarily satisfy the expression (1), and an anvil that contacts the workpiece on four sides may not be used. If the cross-sectional shape after the reduction is not circular, forging is continued after that, and if the round groove anvil that satisfies the above conditions is used in the forging pass where the cross-sectional shape after the reduction is circular, This is because it is possible to suppress the bending of the workpiece A caused by the non-uniformity of the width expansion (elongation amount) on the non-contact surface D shown in 3 (b).
[0027]
The description of the forging method of the present invention described above is an explanation of the case where a round bar is manufactured by a forging method in which rolling from the top and bottom by the round groove anvil B and movement in the axial direction are alternately applied among free forging. It is. However, as described above, the method according to the present invention “manufactures a round bar by repeatedly rolling down a workpiece with two pairs of anvils and moving in the axial direction from two directions perpendicular to the axis. The forging method is not limited to the case of manufacturing a round bar by high-speed forging. “The reduction by the anvil from the direction perpendicular to the axis of the workpiece” is not limited to the reduction from the top and bottom, but may be the reduction from the side. In addition, the round bar is manufactured by “repeating the pressing by the anvil and the movement in the axial direction”, and the “repetition” does not necessarily have to be alternated. Therefore, the present invention can also be applied to the production of round bars by so-called conventional free forging.
[0028]
According to the forging method of the present invention, forging is performed using a round groove anvil having a radius of curvature smaller than the finishing cross-sectional radius of the workpiece A, or two directions using an anvil that contacts the workpiece on four sides. From the simple method of forging by applying a reduction by a pair of anvils, it is possible to very effectively suppress the bending that occurs in the workpiece when a round bar is manufactured by free forging (including high-speed forging). As a result, the bending correction process, which is a subsequent process, can be omitted, or the required man-hours in the correction process can be significantly reduced, so that the efficiency of production of round bars by forging can be greatly improved.
[0029]
【Example】
A material made of SUS316 or SUS304 having a regular octagonal cross section, a distance between opposite sides of the cross section of 337 mm, and a total length of 4000 mm is used as a work material, heated to 1200 ° C., and then heated by the forging method of the present invention. The state of occurrence of bending when forged into a round bar having a radius of 161.5 mm was investigated. For comparison, the same investigation was conducted for the forging method using the round groove anvil B that does not satisfy the above-mentioned formula (1).
[0030]
The forging machine used is a free forging machine having the configuration shown in FIG. 3, the opening angle of the round groove anvil B is 105 °, the length of the anvil parallel part F is 200 mm, and the feed amount of the workpiece is 25 mm / The reduction and rotation angle around the axis of the workpiece was 70 ° / reduction. As the round groove anvil B, four kinds of anvils having a radius of curvature ranging from 163.0 mm to 151.5 mm were used.
[0031]
The survey results are shown in Table 1.
[0032]
[Table 1]
As is apparent from the results shown in Table 1, Example No. of the present invention forged using a round groove anvil B having a radius of curvature of the round groove anvil smaller than the finishing cross-section radius of the workpiece (in this case, 161.5 mm). . 3-No. In 6, it was possible to greatly suppress the occurrence of bending. However, Invention Example No. In No. 6, the roundness of the workpiece A was slightly large. In consideration of roundness, it is desirable that the difference between the finishing cross-section radius of the workpiece and the radius of curvature of the round groove anvil be less than 8 mm.
[0034]
On the other hand, Comparative Example No. forged using a round groove anvil B in which the radius of curvature of the round groove anvil is larger than the finishing section radius of the workpiece. In 1 and 2, bending occurred and the evaluation was poor (x mark).
[0035]
【The invention's effect】
According to the forging method of the present invention, it is possible to extremely effectively suppress bending that occurs in a workpiece when a round bar is manufactured by free forging (including high-speed forging). Therefore, it is possible to greatly improve the efficiency of production of round bars by forging.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a parallel portion of a round groove anvil when forged with a round groove anvil having a radius of curvature smaller than the finishing cross section radius of a workpiece A;
FIG. 2 is a longitudinal sectional view of a parallel portion of a round groove anvil when forged using a round groove anvil having a radius of curvature larger than the finishing cross section radius of the workpiece A;
FIGS. 3A and 3B are diagrams for explaining a process of occurrence of bending, in which FIG. 3A is a diagram schematically showing a longitudinal section of a workpiece and an indented portion, and FIG. 3B is a view taken along the line II in FIG. It is.
[Explanation of symbols]
A: Work material B: Round groove anvil C: Plastic deformation region D: Non-contact surface F: Anvil parallel part G: Curvature radius of round groove anvil H: Section radius of work material
Claims (3)
（被加工材の仕上断面半径）＞（丸溝金敷の溝底部曲率半径） ・・▲１▼A forging method in which a round bar is manufactured by repeatedly rolling down an anvil from a direction perpendicular to the axis of the workpiece and moving in the axial direction, and the cross-sectional shape of the workpiece after rolling is circular A forging method characterized by forging using a round groove anvil that satisfies the following formula (1) during the forging pass.
(Finish section radius of workpiece)> (Groove bottom radius of curvature of round groove anvil) ・ ・ ▲ 1 ▼
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| JP2003171244A JP2005007402A (en) | 2003-06-16 | 2003-06-16 | Forging method |
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| JP2005007402A true JP2005007402A (en) | 2005-01-13 |
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| CN111036823A (en) * | 2019-12-26 | 2020-04-21 | 中钢集团邢台机械轧辊有限公司 | Device and method for controlling diameter size of shaft forging |
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