JP2006334607A - Forging method for hard-to-work material - Google Patents

Forging method for hard-to-work material Download PDF

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JP2006334607A
JP2006334607A JP2005159221A JP2005159221A JP2006334607A JP 2006334607 A JP2006334607 A JP 2006334607A JP 2005159221 A JP2005159221 A JP 2005159221A JP 2005159221 A JP2005159221 A JP 2005159221A JP 2006334607 A JP2006334607 A JP 2006334607A
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forging
temperature
workpiece
ratio
work
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Junpei Tajima
Masaaki Terunuma
正明 照沼
淳平 田嶋
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Sumitomo Metal Ind Ltd
住友金属工業株式会社
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a forging method capable forging a hard-to-work material to be worked in 5-30 forging ratio by heating once without causing any defect such as crack. <P>SOLUTION: This forging method for hard-to-work material is characterized in that when a workpiece to be the hard-to-work material of 1,000-4,000kg is forged under condition in 5-30 forging ratio, the workpiece is heated to the temperature range of t-T defined below, then is forged within 20 min. Further, it is desirable that the rolling reduction per one pass is ≤120 mm. Wherein, t is the temperature where the draw ratio is 80% of the maximum draw ratio in the lower temperature zone than the temperature being the maximum draw ratio in the high temperature tensile strength test of the workpiece and T is the temperature where the draw ratio is 50% of the maximum draw ratio in the higher temperature zone than the temperature being the maximum draw ratio in the high temperature tensile strength test of the workpiece. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、難加工材の熱間自由鍛造による鍛造方法に関し、さらに詳しくは、難加工性の材料を被加工材とし、1回の加熱で断面形状が円形または多角形の棒材またはビレットを加工できる難加工材の鍛造方法に関するものである。   The present invention relates to a forging method by hot free forging of difficult-to-work materials. More specifically, a difficult-to-work material is used as a work material, and a rod or billet having a circular or polygonal cross-section is formed by one heating. The present invention relates to a forging method for difficult-to-process materials.
熱間加工性が劣る難加工材を熱間自由鍛造によって塑性加工する場合に、その加工過程において被加工材の温度が低下すると、加工後の外表面に割れ等の欠陥が生じ易い。このため、難加工材の熱間自由鍛造に際しては、加熱条件や加工状況に十分に留意し、被加工材の外表面に欠陥が生じるおそれがある場合には、鍛造加工を中断し、加工途中の被加工材を再度加熱し、充分に加工温度を確保した後、鍛造加工を行う必要がある。このため、難加工材の熱間自由鍛造では、多くの作業工数を要し加工効率を低下させるとともに、鍛造加工の歩留りも著しく悪化させることになる。   When a difficult-to-work material with poor hot workability is subjected to plastic working by hot free forging, if the temperature of the work material decreases during the working process, defects such as cracks are likely to occur on the outer surface after processing. For this reason, in hot free forging of difficult-to-process materials, pay sufficient attention to heating conditions and processing conditions, and if there is a risk of defects on the outer surface of the workpiece, the forging process is interrupted and It is necessary to perform forging after heating the workpiece again to ensure a sufficient processing temperature. For this reason, in hot free forging of difficult-to-process materials, a large number of work steps are required, the processing efficiency is lowered, and the yield of the forging process is remarkably deteriorated.
このため、従来から、難加工材の鍛造方法に関して種々の提案がなされている。例えば、特許文献1には、難加工材のインゴットをビレットに加工する熱間鍛造を行う方法として、鍛造の前段階でインゴットを鍛造に必要な温度範囲で加熱し、次いで鍛造の段階でインゴットを加熱して鍛造に必要な下限温度以上の温度に保持しながら鍛造する難加工材の製造方法が提案されている。   For this reason, various proposals have conventionally been made regarding methods for forging difficult-to-work materials. For example, in Patent Document 1, as a method of performing hot forging in which an ingot of a difficult-to-process material is processed into a billet, the ingot is heated in a temperature range necessary for forging at a stage before forging, and then the ingot is formed at the forging stage. There has been proposed a method of manufacturing difficult-to-process materials that are forged while being heated and maintained at a temperature equal to or higher than the lower limit temperature required for forging.
しかし、特許文献1で提案の製造方法では、インゴットを鍛造に必要な温度範囲に保持するため、インゴットを加熱する手段としてガスバーナなどを用いることとし、鍛造加工部の移動にともない加熱部の移動および簡易的加熱に有効であるとしていが、補助的な熱供給装置の設置は鍛造設備の構造を複雑なものとし、さらに熱供給するための費用も発生することになる。   However, in the manufacturing method proposed in Patent Document 1, in order to keep the ingot in a temperature range necessary for forging, a gas burner or the like is used as a means for heating the ingot. Although it is effective for simple heating, the installation of the auxiliary heat supply device complicates the structure of the forging facility and further incurs costs for supplying heat.
また、特許文献2では、鋼塊や鋼材などの被加工材を熱間で自由鍛造する際に発生する表面欠陥を抑制する鍛造方法として、被加工材の圧下位置を規定して鍛造することにより、熱間自由鍛造における被加工材の幅中央部の組織を微細化し、幅中央部の割れを防止する方法が開示されている。
特許文献2の鍛造方法では、被加工材の表面組織を微細化し表面欠陥を抑制することにより、被加工材の熱間加工性を向上させることが可能になるが、被加工材の温度低下にともなう欠陥発生については検討がなされていない。このため、被加工材が難加工材である場合に、被加工材の温度低下にともなう割れ等の欠陥発生が顕著となり、発生した欠陥を取除くための工数が増加し、鍛造加工の作業効率を低下させると同時に、鍛造加工の歩留りを極端に悪化させることになる。
Moreover, in patent document 2, as a forging method which suppresses the surface defect which generate | occur | produces when workpieces, such as a steel ingot and steel materials, are hot forged, by forging by specifying the reduction position of a workpiece In addition, a method for refining the structure of the width center portion of the workpiece in hot free forging and preventing cracking in the width center portion is disclosed.
In the forging method of Patent Document 2, it is possible to improve the hot workability of the workpiece by reducing the surface texture of the workpiece and suppressing surface defects. The accompanying defect generation has not been studied. For this reason, when the workpiece is difficult to process, the occurrence of defects such as cracks due to a decrease in the temperature of the workpiece becomes prominent, the man-hour for removing the generated defects increases, and the work efficiency of forging processing At the same time, the yield of forging is extremely deteriorated.
特開平10−193027号公報JP-A-10-193027 特開2002−160036号公報JP 2002-160036 A
通常、難加工材を熱間自由鍛造によって塑性加工する場合、1パス当りの圧下量が大きくなると、外表面に割れ等の欠陥が生じるおそれがあるため、鍛造加工のスケジュールでは圧下量を小さくする傾向がある。圧下量を小さくスケジュールした場合には、仕上寸法までに鍛造加工するのに時間を要し、結果として被加工材の温度が低下し、熱間加工性が悪くなり被加工材表面に欠陥が生じ易くなる。このため、十分な鍛造比(鍛造前断面積/鍛造後断面積)を確保することができず、特に難加工材を加工する場合には、加熱回数や鍛造回数が増加し、熱間鍛造における総加工時間が増大することになる。   Normally, when plastically processing difficult-to-process materials by hot free forging, if the amount of reduction per pass increases, defects such as cracks may occur on the outer surface, so the amount of reduction is reduced in the forging schedule. Tend. If the reduction amount is scheduled to be small, it takes time to forge to the finished size, resulting in a decrease in the temperature of the workpiece, resulting in poor hot workability and defects on the workpiece surface. It becomes easy. For this reason, a sufficient forging ratio (cross-sectional area before forging / cross-sectional area after forging) cannot be ensured, and particularly when processing difficult-to-work materials, the number of heating times and the number of forgings are increased. Total machining time will increase.
まず、熱間自由鍛造による加工時間について、最近では、自由鍛造機として高エネルギー高速加工による高速鍛造機が広く適用されている。この高速鍛造機によれば、エネルギーの制御が簡単で再現性が良好であるだけでなく、大きな特長として加工時間が短いことが挙げられ、しかも、これにともなって熱間自由鍛造の際に、工具から被加工材への伝達熱量が少なくなり、被加工材の温度低下を少なくすることができる。したがって、熱間自由鍛造での加工時間の短縮や被加工材の温度低下の抑制の観点から、自由鍛造機として高速鍛造機が広く適用されることになる。   First, regarding the processing time by hot free forging, recently, high speed forging machines by high energy high speed processing have been widely applied as free forging machines. According to this high-speed forging machine, not only energy control is easy and reproducibility is good, but a major feature is that processing time is short, and with this, during hot free forging, The amount of heat transferred from the tool to the workpiece can be reduced, and the temperature drop of the workpiece can be reduced. Therefore, a high-speed forging machine is widely applied as a free forging machine from the viewpoint of shortening the processing time in hot free forging and suppressing the temperature drop of the workpiece.
次に、高速鍛造機等による1回の加熱で加工可能な鍛造比に関し、種々の検討結果から、鍛造比が5未満と小さい場合には、鍛造加工にともなう割れ等の欠陥を発生することがないが、鍛造比が5以上になると、加熱温度や加工時間等との関係で欠陥が発生する場合がある。一方、鍛造比が30を超えるようになると、鍛造加工度が過大となり加熱温度の管理に拘わらず鍛造加工にともなう割れ等の欠陥発生が増大する。このようなことから、難加工材を熱間自由鍛造によって塑性加工する場合に、1回の加熱で加工可能な鍛造比として5〜30とするのが目安となる。   Next, regarding the forging ratio that can be processed by one-time heating by a high-speed forging machine or the like, from various examination results, if the forging ratio is as small as less than 5, defects such as cracks associated with forging may occur. However, if the forging ratio is 5 or more, defects may occur due to the heating temperature, processing time, or the like. On the other hand, when the forging ratio exceeds 30, the degree of forging becomes excessive, and the occurrence of defects such as cracks associated with forging increases regardless of the control of the heating temperature. For this reason, when plastically processing a difficult-to-work material by hot free forging, a forging ratio that can be processed by one heating is set to 5 to 30.
さらに、従来において高速鍛造機等の熱間自由鍛造によって難加工材を塑性加工する場合に、鍛造加工性の評価項目として被加工材の重量、加熱温度、加熱炉の抽出から所定形状に鍛造終了までの加工時間、または1パスでの圧下量等の個別条件に着目していた。このため、被加工材の加工表面に発生する割れ等の欠陥に関する有効な検討がなされておらず、難加工材に発生した不良や欠陥を除去するために多くの工数をかけたり、難加工材に発生する欠陥を防止するために加熱回数を増加する等の個別の対策に終始していた。   Furthermore, when plastically processing difficult-to-work materials by hot free forging such as with a high-speed forging machine in the past, forging into a predetermined shape is completed based on the weight of the work material, heating temperature, and extraction of the heating furnace as evaluation items for forgeability Focusing on the individual conditions such as the machining time up to or the amount of reduction in one pass. For this reason, effective examination about defects, such as a crack which occurs on the processing surface of a work material, has not been made, and it takes a lot of man-hours to remove defects and defects generated on difficult-to-work materials, or difficult-to-work materials. In order to prevent defects that occur in the process, individual measures such as increasing the number of times of heating were used.
本発明は、このような状況に鑑みてなされたものであり、高速鍛造機等の自由鍛造機の適用に対応し、被加工材の重量、加熱温度、加熱炉の抽出から鍛造終了までの加工時間、さらに1パス当たりの圧下量を総合的に管理することによって、1回の加熱により難加工性の被加工材を鍛造比5〜30で鍛造加工する場合であっても、割れ等の欠陥を発生させることがない鍛造方法を提供することを目的としている。   The present invention has been made in view of such a situation, and corresponds to the application of a free forging machine such as a high-speed forging machine, processing from the weight of the workpiece, the heating temperature, extraction of the heating furnace to the end of forging. Even when forging a difficult-to-work material with a forging ratio of 5 to 30 by one heating by comprehensively managing the time and the amount of reduction per pass, defects such as cracks It aims at providing the forging method which does not generate | occur | produce.
本発明者らは、上記の課題を解決するため、難加工材を高速鍛造機等の自由鍛造機を用いて熱間加工する場合に、被加工材の重量、加熱温度、加熱炉の抽出から鍛造終了までの加工時間、および1パス当たりの圧下量が表面欠陥の発生に及ぼす影響について調査した。この調査結果に基づいて、それぞれの影響を定性的に示すと、下記の(a)〜(d)式を得ることができる。   In order to solve the above-mentioned problems, the present inventors, when hot-working difficult-to-work materials using a free forging machine such as a high-speed forging machine, from the weight of the workpiece, heating temperature, extraction of the heating furnace The effects of the processing time until the end of forging and the amount of reduction per pass on the occurrence of surface defects were investigated. If each influence is shown qualitatively based on this investigation result, the following formulas (a) to (d) can be obtained.
欠陥発生を防止するには、下記(a)、(b)式で示される鍛造に要する加工時間Hを短くすることが必要である。加工時間Hを短縮するには、ハンドリング時間Hhを短くし、平均圧下量Rを大きくし、被加工材の重量Wを小さくし、鍛造比Kを小さくするのがよい。   In order to prevent the occurrence of defects, it is necessary to shorten the processing time H required for forging represented by the following formulas (a) and (b). In order to shorten the processing time H, it is preferable to shorten the handling time Hh, increase the average reduction amount R, decrease the weight W of the workpiece, and decrease the forging ratio K.
H=Hf+Hh ・・・ (a)
ただし、Hf:鍛造加工時間、Hh:ハンドリング時間
Hf=f(1/R,W,K) ・・・ (b)
ただし、R:平均圧下量、W:被加工材の重量、K:鍛造比
さらに、欠陥発生を防止するのに有効なのは、熱間加工性に適正な温度範囲に被加工材を保持して鍛造加工を行うことである。ある鍛造加工の過程における被加工材温度Tは、下記(c)式によって示される。
H = Hf + Hh (a)
However, Hf: Forging time, Hh: Handling time Hf = f (1 / R, W, K) (b)
However, R: average reduction amount, W: weight of workpiece, K: forging ratio Furthermore, it is effective to prevent the occurrence of defects by holding the workpiece in a temperature range appropriate for hot workability and forging. It is to process. A workpiece temperature T in a certain forging process is expressed by the following equation (c).
T=Ti+f(H,1/W)+f(ΣR,1/W) ・・・ (c)
ただし、Ti:被加工材加熱温度、ΣR:それまで鍛造加工された圧下量の和
上記(c)式で示す被加工材温度Tは、高いほどよいが、被加工材の高温引張特性に応じて、一定の制限があることが明らかになった。
T = Ti + f (H, 1 / W) + f (ΣR, 1 / W) (c)
However, Ti: work material heating temperature, ΣR: sum of the amount of reduction that has been forged until then, the higher the work material temperature T shown in the above formula (c), the better, but depending on the high temperature tensile properties of the work material It became clear that there were certain restrictions.
さらに、欠陥発生を防止する限界圧下量Rmaxは、下記(d)式で示すように、被加工材温度Tおよびその時点での鍛造比Kにより規定される。すなわち、被加工材温度Tは、被加工材の高温強度に応じる制限を満たしていれば高いほどよく、鍛造比か大きいほど組織改善がなされ、限界圧下量Rmaxは大きくなる。   Further, the critical reduction amount Rmax for preventing the occurrence of defects is defined by the workpiece temperature T and the forging ratio K at that time, as shown by the following equation (d). That is, the higher the workpiece temperature T that satisfies the restriction depending on the high-temperature strength of the workpiece, the better. The larger the forging ratio, the better the structure, and the greater the critical reduction amount Rmax.
Rmax=f(T,K) ・・・ (d)
ただし、T:被加工材温度、K:鍛造比
上記(a)〜(d)式の関係から、加工時間Hは短いほどよく、被加工材重量Wは一定の範囲で管理する必要があり、被加工材温度Tは一定の制限を満たす限りにおいて高いほどよく、さらに、圧下量Rは大きいほどよいが、限界圧下量Rmaxによって制限するのが望ましい場合がある。
Rmax = f (T, K) (d)
However, T: work material temperature, K: forging ratio From the relationship of the above formulas (a) to (d), it is better that the processing time H is shorter, and the work material weight W needs to be managed within a certain range. It is better that the workpiece temperature T is higher as long as a certain limit is satisfied, and further, the larger the reduction amount R is better, but it may be desirable to limit it by the limit reduction amount Rmax.
すなわち、難加工材を1回の加熱で鍛造加工するに際し、被加工材の高温引張特性に応じて、鍛造加工の過程で被加工材の温度を熱間加工性に適合する温度範囲に保持できるように、被加工材の重量、加熱温度、加工時間、さらに圧下量を管理することによって、割れ等の欠陥を発生させることなく、鍛造比5〜30で鍛造加工できることを知見した。   That is, when forging a difficult-to-process material by a single heating, the temperature of the work material can be maintained in a temperature range suitable for hot workability during the forging process according to the high temperature tensile properties of the work material. Thus, it has been found that forging can be performed at a forging ratio of 5 to 30 without generating defects such as cracks by controlling the weight of the workpiece, the heating temperature, the processing time, and the reduction amount.
本発明は、上記の知見に基づいて完成されたものであり、下記(1)、(2)の難加工材の鍛造方法を要旨としている。
(1)難加工性の被加工材の重量を1000〜4000kgとし鍛造比5〜30で鍛造加工するに際し、前記被加工材を下記で規定するt〜Tの温度範囲に加熱したのち、20分以内の加工時間で鍛造することを特徴とする難加工材の鍛造方法である。
The present invention has been completed on the basis of the above findings, and the gist of the forging methods of difficult-to-work materials (1) and (2) below.
(1) When forging is performed at a forging ratio of 5 to 30 with a weight of difficult-to-work material to be 1000 to 4000 kg, the workpiece is heated to a temperature range of t to T specified below, and then 20 minutes. It is a forging method of a difficult-to-process material characterized by forging with a processing time within.
t:被加工材の高温引張試験で絞り率が最大となる温度より低い温度域で、絞り率が最
大絞り率の80%となる温度
T:被加工材の高温引張試験で絞り率が最大となる温度より高い温度域で、絞り率が最
大絞り率の50%となる温度
(2)上記(1)の難加工材の鍛造方法では、1パス当たりの圧下量を120mm以下とするのが望ましい。
t: Temperature at which the drawing ratio becomes 80% of the maximum drawing ratio in a temperature range lower than the temperature at which the drawing ratio becomes maximum in the high temperature tensile test of the workpiece T: Maximum drawing ratio in the high temperature tensile test of the workpiece The temperature at which the drawing ratio becomes 50% of the maximum drawing ratio in a temperature range higher than the temperature at which the above becomes (2) In the forging method of difficult-to-work materials (1) above, the reduction amount per pass is 120 mm or less. Is desirable.
本発明の難加工材の鍛造方法によれば、被加工材の高温引張特性に応じて、鍛造加工の過程で被加工材の温度を熱間加工性に適合する温度範囲に保持できるように、被加工材の重量、加熱温度、加工時間、さらに圧下量を管理することにより、難加工材を1回の加熱で割れ等の欠陥を発生させることなく、鍛造比5〜30で鍛造できる。これにより、難加工材の熱間自由鍛造であっても高効率で、かつ高い歩留まりで行うことができる。   According to the forging method of the difficult-to-work material of the present invention, according to the high temperature tensile properties of the work material, so that the temperature of the work material can be maintained in the temperature range suitable for hot workability during the forging process, By controlling the weight of the workpiece, the heating temperature, the processing time, and the amount of reduction, the difficult-to-process material can be forged at a forging ratio of 5 to 30 without generating defects such as cracks by one heating. Thereby, even hot free forging of difficult-to-process materials can be performed with high efficiency and high yield.
本発明が対象とする難加工材として、JIS規格のNCF600、NCF690、NCF800およびNCF825、並びにASTM規格のUNS N06250およびN06255等であって、著しく熱間加工性を劣化させる共晶炭化物やσ相、ラーベス相、χ(カイ)相等の金属間化合物が析出しないNi含有量が30%以上の合金材を例示することができる。   As difficult-to-work materials targeted by the present invention, JIS standard NCF600, NCF690, NCF800 and NCF825, ASTM standards UNS N06250 and N06255, etc., eutectic carbide and σ phase, which significantly deteriorate hot workability An alloy material having an Ni content of 30% or more in which intermetallic compounds such as Laves phase and χ (chi) phase do not precipitate can be exemplified.
本発明の製造方法では、被加工材の重量を1000〜4000kgとする。これは、本発明者らの実験結果に基づくものであり、被加工材の重量が小さいと被加工材の単位体積に対する表面積が大きくなる。このため、鍛造加工中における被加工材の大気放熱および加工工具への抜熱が大きくなり、被加工材の温度が急激に低下することから、被加工材表面に割れ等の欠陥が発生し易くなる。これらを防止するため、被加工材重量の下限を1000kgとする。   In the manufacturing method of the present invention, the weight of the workpiece is 1000 to 4000 kg. This is based on the results of experiments conducted by the present inventors. When the weight of the workpiece is small, the surface area per unit volume of the workpiece is increased. For this reason, during the forging process, the heat release to the atmosphere of the work material and the heat removal from the work tool increase, and the temperature of the work material decreases rapidly, so that defects such as cracks are likely to occur on the work material surface. Become. In order to prevent these, the lower limit of the workpiece weight is set to 1000 kg.
一方、被加工材の重量が大きいと鍛造加工初期の温度低下は緩やかであるが、鍛造加工による単位表面積当たりの入熱量が少なくなる。このため、鍛造加工後期になると被加工材の表面への加工熱の付与が少ないまま、大気へ放熱する時間が長くなることから、被加工材の温度は急激に低下し、被加工材の表面に割れ等の欠陥が発生する。このため、被加工材重量の上限を4000kgとする。   On the other hand, when the weight of the workpiece is large, the temperature drop at the initial stage of forging is moderate, but the amount of heat input per unit surface area due to forging is reduced. For this reason, in the latter stage of forging, the time for heat release to the atmosphere is increased while the processing heat is not applied to the surface of the workpiece, so the temperature of the workpiece is drastically reduced, and the surface of the workpiece is reduced. Defects such as cracks occur. For this reason, the upper limit of the workpiece weight is set to 4000 kg.
前述の通り、本発明の鍛造方法では、1回の加熱で加工可能な鍛造比(鍛造前断面積/鍛造後断面積)を5〜30とする。鍛造比が5未満と小さい場合には、鍛造加工にともなう欠陥を発生することがないが、鍛造比の低下にともない加工時間が非常に長くなり生産性が低下するばかりか、温度低下により再加熱する回数も増えエネルギーロスとなる。   As described above, in the forging method of the present invention, the forging ratio (cross-sectional area before forging / cross-sectional area after forging) that can be processed by one heating is set to 5 to 30. When the forging ratio is less than 5, defects due to forging will not occur. However, as the forging ratio decreases, the processing time becomes very long and productivity decreases, and reheating due to a decrease in temperature. The number of times to increase increases energy loss.
一方、鍛造比が30を超えるようになると、鍛造加工度が過大となり加熱温度の管理に拘わらず、鍛造加工にともなう割れ等の欠陥発生が増大する。このようなことから、1回の加熱で加工可能な鍛造比を5〜30とする。   On the other hand, when the forging ratio exceeds 30, the degree of forging becomes excessive, and the occurrence of defects such as cracks associated with forging increases regardless of the control of the heating temperature. Therefore, the forging ratio that can be processed by one heating is set to 5-30.
本発明で採用する被加工材の加熱温度に関し、その加熱温度が高すぎる場合には、被加工材の粒界が予融解(pre−melting)するために、被加工材の延性は急激に低下し、鍛造加工初期において被加工材の表面に欠陥が発生する。また、被加工材の加熱温度が低すぎる場合には、延性が低下することから、鍛造加工後期に被加工材の表面に欠陥が発生する。   Regarding the heating temperature of the workpiece used in the present invention, when the heating temperature is too high, the grain boundary of the workpiece is pre-melted, and the ductility of the workpiece is rapidly reduced. In the initial stage of forging, defects are generated on the surface of the workpiece. In addition, when the heating temperature of the workpiece is too low, the ductility is lowered, so that a defect is generated on the surface of the workpiece in the later stage of the forging process.
そこで、発明者らが実験を繰り返して加熱温度を検討した結果、1回の加熱で鍛造比5〜30の条件のもとで、割れ等の欠陥を発生することなく鍛造するための加熱温度は、被加工材の引張変形特性によって異なることが明らかになる。しかも、この加工温度は、被加工材の粒界に予融解(pre−melting)を生ずることもなく、被加工材の低温加熱による延性低下を発生することがない。   Therefore, as a result of examining the heating temperature by repeating the experiment, the heating temperature for forging without generating defects such as cracks under the condition of a forging ratio of 5 to 30 by one heating is as follows. It becomes clear that it varies depending on the tensile deformation characteristics of the workpiece. Moreover, this processing temperature does not cause pre-melting at the grain boundaries of the workpiece, and does not cause a decrease in ductility due to low temperature heating of the workpiece.
具体的には、各種の温度で被加工材(鍛造前の素材)の高温引張試験を行い、最大絞り率Pとなる試験温度PTとした場合に、PTより低い温度域で絞り率が最大絞り率Pの80%となる温度tと、PTより高い温度域で絞り率が最大絞り率Pの50%となる温度Tとを測定する。この測定結果に基づいて、被加工材を上記t〜Tの温度範囲に加熱する必要がある。   Specifically, when a high-temperature tensile test is performed on a workpiece (raw material before forging) at various temperatures to obtain a test temperature PT at which the maximum draw ratio P is obtained, the maximum draw ratio is obtained in a temperature range lower than PT. A temperature t at which the rate P becomes 80% and a temperature T at which the drawing rate becomes 50% of the maximum drawing rate P in a temperature range higher than PT are measured. Based on this measurement result, it is necessary to heat the workpiece to the temperature range of t to T described above.
すなわち、本発明の鍛造方法では、被加工材を上記t〜Tの温度範囲に加熱したのち、鍛造することによって、粒界の予融解(pre−melting)による延性の低下や、低温加熱での延性の低下を防止でき、安定して被加工材の表面に割れ等の欠陥を発生させることがない。   That is, in the forging method of the present invention, the work material is heated to the temperature range of t to T, and then forged, thereby reducing ductility due to pre-melting of grain boundaries and low temperature heating. A drop in ductility can be prevented and defects such as cracks are not stably generated on the surface of the workpiece.
高温引張試験における被加工材の引張性質は、加熱温度および歪み速度の影響を受けることから、本発明で適用する高温引張試験法はJIS G0567に基づくものとした。JIS G0567に基づく試験法とは、試験片を試験温度に10〜15min保持した後、歪み速度0.3%/minの引張試験を行い、最大絞り率P、そのときの試験温度PTとし、試験温度PTより低い温度領域で絞り率が最大絞り率Pの80%となる下限加熱温度t、および試験温度PTより高い温度領域で絞り率が最大絞り率Pの50%となる上限加熱温度Tを定めた。   Since the tensile properties of the workpiece in the high temperature tensile test are affected by the heating temperature and strain rate, the high temperature tensile test method applied in the present invention is based on JIS G0567. The test method based on JIS G0567 means that after holding a test piece at a test temperature for 10 to 15 minutes, a tensile test at a strain rate of 0.3% / min is performed to obtain a maximum drawing ratio P and a test temperature PT at that time. A lower limit heating temperature t at which the drawing ratio becomes 80% of the maximum drawing ratio P in a temperature region lower than the temperature PT, and an upper limit heating temperature T at which the drawing ratio becomes 50% of the maximum drawing ratio P in a temperature region higher than the test temperature PT. Determined.
発明者らの検討によれば、被加工材を加熱炉から抽出し所定の形状に鍛造するまでの加工時間が20分を超えるようになると、被加工材の温度低下にともない延性が低下し、被加工材表面に欠陥が発生し易くなる。このため、本発明の鍛造方法では、前記(a)式に示すように、鍛造加工時間およびハンドリング時間からなる加工時間を20分以内にする必要がある。   According to the study by the inventors, when the processing time until the workpiece is extracted from the heating furnace and forged into a predetermined shape exceeds 20 minutes, the ductility decreases as the temperature of the workpiece decreases. Defects are likely to occur on the workpiece surface. For this reason, in the forging method of this invention, as shown to said (a) type | formula, it is necessary to make the processing time which consists of a forging time and handling time within 20 minutes.
さらに、本発明の鍛造方法では、1パス当たりの最大圧下量を規定するのが望ましい。被加工材への1パス当たりの圧下量が大きい場合には、被加工材表層における歪み量が大きくなり、表面に割れ等の欠陥が発生し易くなる。発明者らの検討結果によれば、安定して被加工材の表面に割れ等の欠陥を発生させないためには、1パス当たりの圧下量を120mm以下にするのが望ましい。   Furthermore, in the forging method of the present invention, it is desirable to define the maximum reduction amount per pass. When the reduction amount per pass to the workpiece is large, the amount of strain on the surface layer of the workpiece is increased, and defects such as cracks are likely to occur on the surface. According to the results of investigations by the inventors, it is desirable that the amount of reduction per pass is 120 mm or less in order not to cause defects such as cracks on the surface of the workpiece stably.
本発明の鍛造方法の効果を確認するため、供試加工材として難加工材である合金A、合金Bおよび合金C、並びに比較材のSUS316鋼を準備した。準備した供試加工材からJIS G0567に準じて引張試験片を採取し、種々の温度に加熱して10分間保持し歪み速度0.3%/minの高温引張試験を実施した。   In order to confirm the effect of the forging method of the present invention, alloy A, alloy B and alloy C, which are difficult to process, and SUS316 steel as a comparative material were prepared as test materials. Tensile test specimens were collected from the prepared workpieces to be tested in accordance with JIS G0567, heated to various temperatures, held for 10 minutes, and subjected to a high-temperature tensile test with a strain rate of 0.3% / min.
高温引張試験後の引張試験片の破断面から絞り率を求め、高温引張試験で最大絞り率Pが得られる試験温度PTを定め、試験温度PTより低い温度領域で絞り率が最大絞り率Pの80%となる温度t、および試験温度PTより高い温度領域で絞り率が最大絞り率Pの50%となる温度Tを求めた。高温引張試験結果から得られたPT、tおよびTを表1に示した。   The drawing ratio is obtained from the fracture surface of the tensile test piece after the high-temperature tensile test, the test temperature PT at which the maximum drawing ratio P is obtained in the high-temperature tensile test is determined, and the drawing ratio is the maximum drawing ratio P in the temperature region lower than the test temperature PT. A temperature t at which the drawing ratio is 80% and a temperature T at which the drawing ratio is 50% of the maximum drawing ratio P in a temperature range higher than the test temperature PT were obtained. Table 1 shows PT, t, and T obtained from the results of the high-temperature tensile test.
合金Aは、ASTM規格UNS N06255相当材とした。合金Aの高温引張試験によれば、最大絞り率Pは95%であり、そのときの試験温度PTは1230℃であった。試験温度PTの1230℃より低い温度領域で絞り率76%(P:95%×80%)となる温度tは1130℃であり、試験温度PTの1230℃より高い温度領域で絞り率47.5%(P:95%×50%)となる温度Tは1270℃であった。   Alloy A was a material equivalent to ASTM standard UNS N06255. According to the high temperature tensile test of Alloy A, the maximum drawing ratio P was 95%, and the test temperature PT at that time was 1230 ° C. The temperature t at which the drawing rate is 76% (P: 95% × 80%) in the temperature range lower than 1230 ° C. of the test temperature PT is 1130 ° C., and the drawing rate is 47.5 in the temperature range higher than 1230 ° C. of the test temperature PT. % T (P: 95% × 50%) was 1270 ° C.
合金Bは、JIS規格NCF800相当材とした。合金Bの高温引張試験によれば、最大絞り率Pは95%であり、そのときの試験温度PTは1200℃であった。試験温度PTの1200℃より低い温度領域で絞り率76%(P:95%×80%)となる温度tは1100℃であり、試験温度PTの1200℃より高い温度領域で絞り率47.5%(P:95%×50%)となる温度Tは1270℃であった。   Alloy B was a JIS standard NCF800 equivalent material. According to the high temperature tensile test of Alloy B, the maximum drawing ratio P was 95%, and the test temperature PT at that time was 1200 ° C. The temperature t at which the drawing rate is 76% (P: 95% × 80%) in the temperature region lower than 1200 ° C. of the test temperature PT is 1100 ° C., and the drawing rate is 47.5 in the temperature region higher than 1200 ° C. of the test temperature PT. % T (P: 95% × 50%) was 1270 ° C.
合金Cは、JIS規格NCF825相当材とした。合金Bの高温引張試験によれば、最大絞り率Pは93%であり、そのときの試験温度PTは1250℃であった。試験温度PTの1250℃より低い温度領域で絞り率74.4%(P:93%×80%)となる温度tは1095℃であり、試験温度PTの1250℃より高い温度領域で絞り率46.5%(P:93%×50%)となる温度Tは1295℃であった。   Alloy C was a JIS standard NCF825 equivalent material. According to the high temperature tensile test of Alloy B, the maximum drawing ratio P was 93%, and the test temperature PT at that time was 1250 ° C. The temperature t at which the drawing rate is 74.4% (P: 93% × 80%) in the temperature range lower than 1250 ° C. of the test temperature PT is 1095 ° C., and the drawing rate is 46 in the temperature range higher than 1250 ° C. of the test temperature PT. The temperature T to be 5% (P: 93% × 50%) was 1295 ° C.
比較材としてSUS316鋼を用いた。SUS316鋼の高温引張試験によれば、最大絞り率Pは94%であり、そのときの試験温度PTは1200℃であった。試験温度PTの1200℃より低い温度領域で絞り率75%(P:94%×80%)となる温度tは850℃であり、PTの1200℃より高い温度領域で絞り率47%(P:94%×50%)となる温度Tは1300℃であった。   SUS316 steel was used as a comparative material. According to the high temperature tensile test of SUS316 steel, the maximum drawing ratio P was 94%, and the test temperature PT at that time was 1200 ° C. The temperature t at which the drawing rate is 75% (P: 94% × 80%) in the temperature range lower than 1200 ° C. of the test temperature PT is 850 ° C., and the drawing rate is 47% in the temperature range higher than 1200 ° C. of PT (P: 94% × 50%) was a temperature T of 1300 ° C.
表1に示す供試加工材を用いて、高速鍛造機による鍛造試験を行った。試験条件は供試加工材の重量、加熱温度、鍛造に要する加工時間、最大圧下量、および鍛造比(鍛造前断面積/鍛造後断面積)を変化させ、鍛造後の欠陥発生状況を観察した。鍛造試験の結果を表2〜表4に示す。欠陥発生状況は、鍛造後の供試加工材の表面に割れ等の欠陥が発生している場合に「有」とし、それ以外は「無」とした。   A forging test using a high-speed forging machine was performed using the test workpieces shown in Table 1. The test conditions varied the weight of the test workpiece, the heating temperature, the processing time required for forging, the maximum reduction amount, and the forging ratio (cross-sectional area before forging / cross-sectional area after forging), and observed the occurrence of defects after forging. . Tables 2 to 4 show the results of the forging test. The defect occurrence status was “Yes” when a defect such as a crack occurred on the surface of the test workpiece after forging, and “No” otherwise.
表4に示すように、比較材であるSUS316鋼を供試加工材とする場合(試験No.39〜43)には、本発明で規定する条件を外れる場合であっても割れ等の欠陥の発生がなかった。一方、表2〜表4に示すように、本発明が対象とする難加工材である合金A、合金Bおよび合金Cでは、供試加工材の重量、加熱温度、および加工時間のいずれかが本発明で規定する条件を外れる場合、または鍛造比が大きくなり本発明で規定する条件を外れる場合に割れ等の欠陥が発生した。   As shown in Table 4, when SUS316 steel, which is a comparative material, is used as a test material (test Nos. 39 to 43), defects such as cracks are observed even when the conditions specified in the present invention are not satisfied. There was no outbreak. On the other hand, as shown in Tables 2 to 4, in Alloy A, Alloy B, and Alloy C, which are difficult-to-work materials targeted by the present invention, any one of the weight of the test material, the heating temperature, and the processing time is Defects such as cracks occurred when the conditions specified in the present invention were not satisfied, or when the forging ratio was increased and the conditions specified by the present invention were not satisfied.
表2〜表4に示すように、本発明が対象とする難加工材である合金A、合金Bおよび合金Cであっても、本発明で規定する条件で鍛造する場合には、割れ等の欠陥は発生しなかった。さらに、鍛造比が小さい場合には、供試加工材の重量、加熱温度、および加工時間のいずれかが本発明で規定する条件を外れても欠陥は発生しなかったが(例えば、試験No.16)、加工時間が長くなり生産性が悪化した。また、本発明で規定する条件で鍛造する場合であっても、最大圧下量が130mmと大きくなると、割れ等の欠陥が発生する場合があり、圧下量を120mm以下にするのが望ましいことが分かる。   As shown in Tables 2 to 4, even when alloy A, alloy B and alloy C, which are difficult-to-work materials targeted by the present invention, are forged under the conditions specified in the present invention, such as cracks Defects did not occur. Further, when the forging ratio was small, no defect was generated even when any of the weight of the test material, the heating temperature, and the processing time deviated from the conditions specified in the present invention (for example, test no. 16) The processing time became longer and the productivity deteriorated. In addition, even when forging under the conditions specified in the present invention, if the maximum reduction amount is as large as 130 mm, defects such as cracks may occur, and it is understood that the reduction amount is desirably 120 mm or less. .
本発明の難加工材の鍛造方法によれば、被加工材の高温引張特性に応じて、鍛造加工の過程で被加工材の温度を熱間加工性に適合する温度範囲に保持できるように、被加工材の重量、加熱温度、加工時間、さらに圧下量を管理することにより、難加工材を1回の加熱で割れ等の欠陥を発生させることなく、鍛造比5〜30で鍛造できる。これにより、難加工材の熱間自由鍛造であっても高効率で、かつ高い歩留まりで行うことができるので、難加工材の熱間自由鍛造法として広く採用することができる。
According to the forging method of the difficult-to-work material of the present invention, according to the high temperature tensile properties of the work material, so that the temperature of the work material can be maintained in the temperature range suitable for hot workability during the forging process, By controlling the weight of the workpiece, the heating temperature, the processing time, and the amount of reduction, the difficult-to-process material can be forged at a forging ratio of 5 to 30 without generating defects such as cracks by one heating. As a result, even hot free forging of difficult-to-work materials can be performed with high efficiency and high yield, so that it can be widely adopted as a hot free forging method for difficult-to-work materials.

Claims (2)

  1. 難加工性の被加工材の重量を1000〜4000kgとし鍛造比5〜30で鍛造加工するに際し、前記被加工材を下記で規定するt〜Tの温度範囲に加熱したのち、20分以内の加工時間で鍛造することを特徴とする難加工材の鍛造方法。
    t:被加工材の高温引張試験で絞り率が最大となる温度より低い温度域で、絞り率が最
    大絞り率の80%となる温度
    T:被加工材の高温引張試験で絞り率が最大となる温度より高い温度域で、絞り率が最
    大絞り率の50%となる温度
    When forging is performed at a forging ratio of 5 to 30 with a weight of the difficult-to-work material to be set to 1000 to 4000 kg, the workpiece is heated to a temperature range of t to T specified below and then processed within 20 minutes. A method for forging difficult-to-process materials characterized by forging in time.
    t: Temperature at which the drawing ratio becomes 80% of the maximum drawing ratio in a temperature range lower than the temperature at which the drawing ratio becomes maximum in the high temperature tensile test of the workpiece T: Maximum drawing ratio in the high temperature tensile test of the workpiece The temperature at which the drawing ratio is 50% of the maximum drawing ratio in the temperature range higher than
  2. 1パス当たりの圧下量を120mm以下として鍛造することを特徴とする請求項1に記載の難加工材の鍛造方法。
    The forging method of a difficult-to-work material according to claim 1, wherein forging is performed with a reduction amount per pass of 120 mm or less.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5861699B2 (en) * 2011-04-25 2016-02-16 日立金属株式会社 Manufacturing method of stepped forging

Citations (3)

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JPH0711404A (en) * 1993-06-29 1995-01-13 Sumitomo Metal Ind Ltd Production of ni-base alloy having intergranular fracture resistance
JPH1157924A (en) * 1997-08-27 1999-03-02 Sumitomo Metal Ind Ltd Round groove anvil and method for hot-forging round steel billet by using the anvil
JP2002322548A (en) * 2001-04-24 2002-11-08 Daido Steel Co Ltd METHOD FOR PRODUCING Nb-CONTAINING Ni-BASED HEAT RESISTANT SUPERALLOY AND METHOD FOR IMPROVING NOTCH RUPTURE RESISTANCE THEREOF

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0711404A (en) * 1993-06-29 1995-01-13 Sumitomo Metal Ind Ltd Production of ni-base alloy having intergranular fracture resistance
JPH1157924A (en) * 1997-08-27 1999-03-02 Sumitomo Metal Ind Ltd Round groove anvil and method for hot-forging round steel billet by using the anvil
JP2002322548A (en) * 2001-04-24 2002-11-08 Daido Steel Co Ltd METHOD FOR PRODUCING Nb-CONTAINING Ni-BASED HEAT RESISTANT SUPERALLOY AND METHOD FOR IMPROVING NOTCH RUPTURE RESISTANCE THEREOF

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5861699B2 (en) * 2011-04-25 2016-02-16 日立金属株式会社 Manufacturing method of stepped forging

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