JP2006183104A - High-strength titanium alloy having excellent cold workability - Google Patents
High-strength titanium alloy having excellent cold workability Download PDFInfo
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- 229910001069 Ti alloy Inorganic materials 0.000 title claims abstract description 44
- 230000032683 aging Effects 0.000 claims abstract description 49
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 18
- 238000004519 manufacturing process Methods 0.000 claims abstract description 12
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 12
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 8
- 229910052718 tin Inorganic materials 0.000 claims abstract description 6
- 239000010936 titanium Substances 0.000 claims abstract description 6
- 239000012535 impurity Substances 0.000 claims abstract description 4
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 3
- 229910045601 alloy Inorganic materials 0.000 claims description 70
- 239000000956 alloy Substances 0.000 claims description 70
- 238000001816 cooling Methods 0.000 claims description 19
- 229910052782 aluminium Inorganic materials 0.000 claims description 14
- 238000010438 heat treatment Methods 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 11
- 230000009466 transformation Effects 0.000 claims description 10
- 229910052804 chromium Inorganic materials 0.000 claims description 6
- 229910052715 tantalum Inorganic materials 0.000 claims description 4
- 229910052719 titanium Inorganic materials 0.000 claims description 3
- 239000000203 mixture Substances 0.000 abstract description 6
- 229910052750 molybdenum Inorganic materials 0.000 abstract description 6
- 239000002131 composite material Substances 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 35
- 230000000694 effects Effects 0.000 description 21
- 230000000087 stabilizing effect Effects 0.000 description 15
- 238000012360 testing method Methods 0.000 description 10
- 239000000463 material Substances 0.000 description 9
- 238000002844 melting Methods 0.000 description 7
- 230000008018 melting Effects 0.000 description 7
- 238000005482 strain hardening Methods 0.000 description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- 239000013078 crystal Substances 0.000 description 5
- 239000001301 oxygen Substances 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- 238000005096 rolling process Methods 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 238000005242 forging Methods 0.000 description 4
- 230000005484 gravity Effects 0.000 description 4
- 239000002244 precipitate Substances 0.000 description 4
- 230000006641 stabilisation Effects 0.000 description 4
- 238000011105 stabilization Methods 0.000 description 4
- 239000011733 molybdenum Substances 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- 239000013585 weight reducing agent Substances 0.000 description 3
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 2
- 229910000883 Ti6Al4V Inorganic materials 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000005097 cold rolling Methods 0.000 description 2
- 235000009508 confectionery Nutrition 0.000 description 2
- 238000005098 hot rolling Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 210000000988 bone and bone Anatomy 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 150000002751 molybdenum Chemical class 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
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Abstract
Description
本発明は、溶体化処理された状態で従来のβ型チタン合金と同程度の冷間加工性を有しつつ、時効処理後の強度を向上させたチタン合金に関するものである。 The present invention relates to a titanium alloy that has a cold workability comparable to that of a conventional β-type titanium alloy in a solution-treated state and has improved strength after aging treatment.
チタン合金は比強度（強度／比重）が高く、耐食性に優れるという特徴より、従来から航空機用材料として使用されてきている。近年、自動車用部品、医療用機器、ゴルフクラブヘッド、腕時計ケースおよびバンド、眼鏡フレームなどの一般民生用途にもその需要が広がってきている。代表的なチタン合金としてα＋β型チタン合金であるＴｉ−６Ａｌ−４Ｖ合金が広く使用されている。しかしながら、このチタン合金は冷間加工性が極めて悪く、また引張強度も１２００ＭＰａ程度である。このためより複雑形状への加工および機械構造物への適用拡大のために、冷間加工性に優れ、かつより高強度であって部品の軽量化を可能とするチタン合金が要求されるようになってきている。 Titanium alloys have been conventionally used as aircraft materials because of their high specific strength (strength / specific gravity) and excellent corrosion resistance. In recent years, the demand has expanded to general consumer applications such as automobile parts, medical equipment, golf club heads, watch cases and bands, and spectacle frames. As a typical titanium alloy, a Ti-6Al-4V alloy which is an α + β type titanium alloy is widely used. However, this titanium alloy has extremely poor cold workability and has a tensile strength of about 1200 MPa. For this reason, in order to process into more complex shapes and expand the application to machine structures, titanium alloys that are superior in cold workability and have higher strength and can reduce the weight of parts are required. It has become to.
また、最近では、ヘッドにＴｉ合金を用いたゴルフクラブにより、非力のプレイヤーでも飛距離を向上させようという試みが活発に行われている。飛距離を向上させるためには、クラブヘッドのフェース部にボールが当たった瞬間にフェース部のたわみが大きくなって、蓄えられる弾性エネルギーが大きいことが必要であると言われている（例えば、非特許文献１参照）。すなわち、蓄えられた弾性エネルギーが復元力となってボールを跳ね返すと考えられるからである。 Also, recently, attempts have been actively made to improve the flight distance even by a less powerful player by using a golf club using a Ti alloy for the head. In order to improve the flight distance, it is said that the deflection of the face portion becomes large at the moment when the ball hits the face portion of the club head, and the stored elastic energy is required to be large (for example, non- Patent Document 1). That is, it is considered that the stored elastic energy becomes a restoring force and rebounds the ball.
この際、フェース部のたわみが大きくなっても塑性変形を起こさないようにするには、低剛性のＴｉ合金を選択し、より大きな歪まで塑性変形しないようにする方法と、時効処理により低剛性は得られにくくなるが、従来の合金では得られないレベルの高強度として、前記と同様に高歪まで塑性変形しないようにする２通りの方法が考えられる。この場合、当然後者の時効処理を行う場合の方が、フェース部の板厚をより薄くすることが可能になり、ヘッドを大きくして、スイートスポットを大きくすることができるというメリットがある。 At this time, in order not to cause plastic deformation even when the deflection of the face portion increases, a low rigidity Ti alloy is selected, and a method of preventing plastic deformation to a larger strain and low rigidity by aging treatment. However, as described above, there are two methods for preventing the plastic deformation up to a high strain as described above, as a high strength that cannot be obtained by conventional alloys. In this case, of course, the latter aging treatment has an advantage that the plate thickness of the face portion can be made thinner, the head can be enlarged, and the sweet spot can be enlarged.
このような高強度化への要求に対し、従来は、冷間加工性が良く、時効処理することにより比較的高い強度が得られる体心立方晶の結晶構造を持つβ型チタン合金が用いられており、例えばＴｉ−１５Ｖ−３Ｃｒ−３Ｓｎ−３Ａｌ、Ｔｉ−３Ａｌ−８Ｖ−６Ｃｒ−４Ｍｏ−４Ｚｒなどのβ型チタン合金が使用されていた。さらにこれら従来のβ型チタン合金の冷間加工性、引張強度を改良するために、新規合金が特許文献において公開されている。例えば特許文献１には、重量％で１５〜２５％のＶ、２．５〜５％のＡｌ、０．５〜４％のＳｎ、０．１２％以下の酸素を含有するチタン合金が開示されている。また、特許文献２には、重量％で１０〜２５％未満のＶ、０．２５％以下の酸素を含有するチタン合金、及び該合金に２〜５％のＡｌ、２〜５％のＣｒ、２〜４％のＳｎの内から選択される１種または２種以上を含有する合金あるいはさらにこれらのチタン合金に０．００２〜０．０１３％の水素を含有する合金が開示されている。 In response to such demands for high strength, β-type titanium alloys having a body-centered cubic crystal structure, which has good cold workability and can obtain relatively high strength by aging treatment, have been used. For example, β-type titanium alloys such as Ti-15V-3Cr-3Sn-3Al and Ti-3Al-8V-6Cr-4Mo-4Zr have been used. Furthermore, in order to improve the cold workability and tensile strength of these conventional β-type titanium alloys, new alloys have been disclosed in the patent literature. For example, Patent Document 1 discloses a titanium alloy containing 15 to 25% by weight of V, 2.5 to 5% Al, 0.5 to 4% Sn, and 0.12% or less oxygen. ing. Patent Document 2 discloses that a titanium alloy containing 10 to less than 25% by weight of V, 0.25% or less oxygen, and 2 to 5% Al, 2 to 5% Cr, An alloy containing one or more selected from 2 to 4% of Sn or an alloy containing 0.002 to 0.013% hydrogen in these titanium alloys is disclosed.
しかしながら、前記した合金には次の問題がある。
前記した合金のうち、従来合金であるＴｉ−１５Ｖ−３Ｃｒ−３Ｓｎ−３Ａｌ及びＴｉ−３Ａｌ−８Ｖ−６Ｃｒ−４Ｍｏ−４Ｚｒ等のβ型チタン合金は、時効処理を行って高強度化を図っても、得られる引張強度は１３００〜１３５０ＭＰａ程度であり、前記したＴｉ−６Ａｌ−４Ｖ合金と比較して大きな高強度化を図ることができず、ゴルフクラブヘッドのフェース部に用いた場合でも薄肉化に限界があり、軽量化等の高強度化による効果を十分に得られないという問題がある。
However, the above-described alloy has the following problems.
Among the above-mentioned alloys, β-type titanium alloys such as Ti-15V-3Cr-3Sn-3Al and Ti-3Al-8V-6Cr-4Mo-4Zr, which are conventional alloys, are subjected to aging treatment to increase the strength. However, the obtained tensile strength is about 1300 to 1350 MPa, and it is not possible to increase the strength as compared with the Ti-6Al-4V alloy described above, and even when used for the face part of a golf club head, the thickness is reduced. However, there is a problem that the effect of increasing strength such as weight reduction cannot be obtained sufficiently.
また、特許文献１には、時効処理により１２０ｋｇｆ／ｍｍ２（１１７６ＭＰａ）以上の引張強度が得られるチタン合金について記載されているが、この文献に記載の実施例を参照すると、得られる引張強度は最大でも１４０ｋｇｆ／ｍｍ２（１３７２ＭＰａ）であり、従来チタン合金であるＴｉ−１５Ｖ−３Ｃｒ−３Ｓｎ−３Ａｌの時効処理後の引張強度と大きな差異がなく、同様に軽量化効果を十分に得ることができないという問題がある。 Patent Document 1 describes a titanium alloy that can obtain a tensile strength of 120 kgf / mm 2 (1176 MPa) or more by aging treatment. With reference to the examples described in this document, the obtained tensile strength is The maximum is 140 kgf / mm 2 (1372 MPa), and there is no significant difference from the tensile strength after aging treatment of Ti-15V-3Cr-3Sn-3Al, which is a conventional titanium alloy, and a sufficient weight reduction effect can be obtained similarly. There is a problem that you can not.
さらに、特許文献２においては、実施例にＴｉ−１７Ｖ−３Ｃｒ合金にＡｌを１〜６％添加した際の時効処理後の引張強度が図で記載されているが、α相安定化元素であって、強度向上に効果があるとされているＡｌを６％添加した場合においても、その値は約１３５０ＭＰａであり、特許文献１と同様に従来合金と比較して明確に高強度化効果が得られるレベルの高強度を達成できていないという問題がある。また、冷間加工性については。ＴｉにＶを５〜３０％添加した合金についてしか開示されておらず、Ｔｉ−１７Ｖ−３Ｃｒ合金にＡｌを１〜６％添加して高強度化を図った合金については冷間加工性について何ら検討がされていない。 Furthermore, in Patent Document 2, the tensile strength after aging treatment when 1 to 6% of Al is added to the Ti-17V-3Cr alloy in the examples is shown in the figure, but it is an α-phase stabilizing element. Even when 6% Al, which is said to be effective in improving the strength, is added, the value is about 1350 MPa, and the effect of increasing the strength is clearly obtained as compared with the conventional alloy as in Patent Document 1. There is a problem that a high strength of a certain level cannot be achieved. Also about cold workability. Only an alloy in which 5 to 30% of V is added to Ti is disclosed, and what is known about cold workability for an alloy in which 1 to 6% of Al is added to a Ti-17V-3Cr alloy to increase the strength. It has not been examined.
本発明は、溶体化処理された状態で従来のβ型チタン合金と同程度の冷間加工性を有しつつ、時効処理にて１５００ＭＰａ以上の高強度が得られるチタン合金を提供することを目的とするものであり、特にゴルフクラブヘッドのフェース部に用いた場合には、フェース部を大幅に薄くすることが可能となり、飛距離向上が可能なクラブの製造に適している新規なチタン合金を提供可能にすることを目的とする。 An object of the present invention is to provide a titanium alloy that has a cold workability comparable to that of a conventional β-type titanium alloy in a solution-treated state and can obtain a high strength of 1500 MPa or more by aging treatment. In particular, when used in the face part of a golf club head, a new titanium alloy suitable for manufacturing a club capable of greatly reducing the face part and improving the flight distance can be obtained. The purpose is to make it available.
本発明者らは前記した課題を解決するために、溶体化処理された状態で冷間加工性が優れ、かつ時効処理で高強度が得られ、さらに量産設備（溶解、鍛造、圧延など）で製造が可能な成分範囲を見出すために鋭意研究を行った結果、次の知見を得て本発明を完成したものである。 In order to solve the above-mentioned problems, the present inventors have excellent cold workability in a solution-treated state, high strength is obtained by aging treatment, and mass production facilities (melting, forging, rolling, etc.) As a result of intensive studies to find a component range that can be produced, the present invention has been completed with the following knowledge.
一般に、β型チタン合金はチタンにＭｏ、Ｖ、Ｃｒ等のβ相安定化元素を添加することにより、溶体化処理後においてβ相単相の組織が得られることを特徴としている。また、このβ相は結晶構造が体心立方晶であり、比較的冷間加工しやすい組織である。このようなβ相単相材に時効処理を施すと、α相が析出してくるため、高強度化を図ることができる。また、α相安定化元素であるＡｌ、Ｓｎ、酸素等を添加すると、析出するα相が強化されるため、より強度を高めることが可能となる。つまりβ型チタン合金において溶体化処理後に良好な冷間加工性を確保するためには、溶体化処理時にβ相単相組織を得ることが必要であり、さらにその後の時効処理で高強度を得るためにはより多くのα相を均質かつ微細に析出させることが必要となる。もちろん、時効処理前の冷間加工の有無、時効処理条件により析出するα相の形態が異なるため、強度、延性共に高いレベルの特性が得られるようにするため、時効処理条件を最適化する必要がある。 In general, β-type titanium alloys are characterized in that a β-phase single-phase structure can be obtained after solution treatment by adding a β-phase stabilizing element such as Mo, V, or Cr to titanium. Further, this β phase has a body-centered cubic crystal structure and is a structure that is relatively easy to cold work. When such a β-phase single-phase material is subjected to an aging treatment, the α-phase is precipitated, so that high strength can be achieved. Further, when Al, Sn, oxygen, or the like, which is an α-phase stabilizing element, is added, the precipitated α-phase is strengthened, so that the strength can be further increased. In other words, in order to ensure good cold workability after solution treatment in a β-type titanium alloy, it is necessary to obtain a β-phase single phase structure during solution treatment, and high strength is obtained by subsequent aging treatment. For this purpose, it is necessary to deposit more α phase uniformly and finely. Of course, it is necessary to optimize the aging treatment conditions in order to obtain high-level properties in both strength and ductility because the form of the α-phase that precipitates depends on the presence or absence of cold working before aging treatment and the aging treatment conditions. There is.
しかしながら、溶体化処理後にβ相単相の組織を得るためにβ相安定化元素の添加量を増量していくと、β相が安定化しすぎて時効処理時にα相が析出しにくくなり、析出させるためにより長時間の時効処理が必要となる。一方、β相安定化元素の添加量を少なくしたり、α相安定化元素の添加量を増量すると、時効処理後のα相の析出は促進されるが、溶体化処理後にα相が析出しやすくなって、溶体化処理後にβ相単相の組織が得られにくくなり、冷間加工性が低下するばかりでなく、熱間加工途中で粗大なα相が析出し易くなり熱間加工性も低下する。 However, if the amount of the β-phase stabilizing element added is increased in order to obtain a β-phase single phase structure after the solution treatment, the β-phase is too stabilized and the α-phase is less likely to precipitate during the aging treatment. A longer aging treatment is required for this to occur. On the other hand, if the addition amount of the β phase stabilizing element is decreased or the addition amount of the α phase stabilizing element is increased, precipitation of the α phase after the aging treatment is promoted, but the α phase is precipitated after the solution treatment. As a result, it becomes difficult to obtain a β-phase single phase structure after solution treatment, and not only the cold workability is lowered, but also a coarse α phase is likely to precipitate during hot working, and the hot workability is also improved. descend.
これらβ相安定化元素とα相安定化元素を添加した場合のチタン合金の相安定性に対する各元素の影響の目安として、β相安定化元素の影響についてはモリブデン当量（Ｍｏｅｑ）によって示すことができ、α相安定化元素の影響についてはアルミニウム当量（Ａｌｅｑ）で整理することができる。以下、その式を記載する。
Ｍｏｅｑ（質量％）＝Ｍｏ＋Ｖ／１．５＋Ｎｂ／３．５＋Ｔａ／５＋１．２５×Ｃｒ＋１．２５×Ｎｉ＋１．７×Ｍｎ＋１．７×Ｃｏ＋２．５×Ｆｅ＋Ｗ／２．５
Ａｌｅｑ（質量％）＝Ａｌ＋Ｓｎ／３＋Ｚｒ／６＋１０×Ｏ
As an indication of the influence of each element on the phase stability of the titanium alloy when these β-phase stabilizing element and α-phase stabilizing element are added, the influence of the β-phase stabilizing element can be expressed by molybdenum equivalent (Moeq). In addition, the influence of the α-phase stabilizing element can be arranged by aluminum equivalent (Aleq). The formula is described below.
Moeq (mass%) = Mo + V / 1.5 + Nb / 3.5 + Ta / 5 + 1.25 × Cr + 1.25 × Ni + 1.7 × Mn + 1.7 × Co + 2.5 × Fe + W / 2.5
Aleq (mass%) = Al + Sn / 3 + Zr / 6 + 10 × O
従って、β型チタン合金におけるβ相の安定性について、α安定化元素の影響を考慮すると、モリブデン当量（Ｍｏｅｑ）からアルミニウム当量（Ａｌｅｑ）を差し引いた値で示すことができる。この値を新しい定義によるＭｏｅｑとした。すなわち、
Ｍｏｅｑ（質量％）＝（Ｍｏ＋Ｖ／１．５＋Ｎｂ／３．５＋Ｔａ／５＋１．２５×Ｃｒ＋１．２５×Ｎｉ＋１．７×Ｍｎ＋１．７×Ｃｏ＋２．５×Ｆｅ＋Ｗ／２．５）−（Ａｌ＋Ｓｎ／３＋Ｚｒ／６＋１０×Ｏ）となる。
Accordingly, the stability of the β phase in the β-type titanium alloy can be expressed by a value obtained by subtracting the aluminum equivalent (Aleq) from the molybdenum equivalent (Moeq) in consideration of the influence of the α-stabilizing element. This value was defined as Moeq according to the new definition. That is,
Moeq (mass%) = (Mo + V / 1.5 + Nb / 3.5 + Ta / 5 + 1.25 × Cr + 1.25 × Ni + 1.7 × Mn + 1.7 × Co + 2.5 × Fe + W / 2.5) − (Al + Sn / 3 + Zr / 6 + 10) × O).
従来のβ型チタン合金の成分を上記式に当てはめると、Ｍｏｅｑはおおよそ８〜２０質量％となる。例えば酸素含有量が０．１質量％のＴｉ−１５Ｖ−３Ｃｒ−３Ｓｎ−３Ａｌ合金におけるＭｏｅｑの値は、８．７５質量％となり、同酸素量を含有するＴｉ−３Ａｌ−８Ｖ−６Ｃｒ−４Ｍｏ−４Ｚｒ合金のＭｏｅｑの値は、１２．１７質量％となる。 When the components of the conventional β-type titanium alloy are applied to the above formula, Moeq is approximately 8 to 20% by mass. For example, the value of Moeq in a Ti-15V-3Cr-3Sn-3Al alloy having an oxygen content of 0.1% by mass is 8.75% by mass, and Ti-3Al-8V-6Cr-4Mo— containing the same oxygen content. The Moeq value of the 4Zr alloy is 12.17% by mass.
本発明者等は、溶体化処理後の冷間加工性と、時効処理後に得られる引張強度、弾性限強度について、このモリブデン当量（Ｍｏｅｑ）の値で整理することによって、新合金の開発を進めた結果、本発明を完成したものである。すなわち、前記した新しい定義に基づくＭｏｅｑを従来のβ型チタン合金より低い２〜８質量％の範囲にすることにより、時効処理後のα相の析出量を多くさせることで高強度化をはかり、かつ溶体化処理状態で従来β型チタン合金とほぼ同等の冷間加工性を有する成分組成を見出したものである。 The present inventors proceeded with the development of a new alloy by organizing the cold workability after solution treatment and the tensile strength and elastic limit strength obtained after aging treatment by the value of this molybdenum equivalent (Moeq). As a result, the present invention has been completed. That is, by making Moeq based on the above-mentioned new definition in the range of 2 to 8% by mass lower than that of the conventional β-type titanium alloy, the strength is increased by increasing the precipitation amount of the α phase after the aging treatment, In addition, a component composition having a cold workability substantially equal to that of a conventional β-type titanium alloy in a solution treatment state has been found.
以上の検討により得られた請求項１記載の新合金は、質量％で、Ｎｂ：２５％以下、Ｖ：１５％以下の１種又は２種（但しＮｂ＋Ｖ≧３．０％、Ｎｂ、Ｖの複合添加時のＶは１０％未満）、Ｍｏ：３〜１７％、Ｚｒ：７．１〜３０％、Ｓｎ：０．５％〜５％、Ｏ：０．３０％以下を含有し、かつ下記（１）式からなるＭｏｅｑが２〜８％であり、残部がＴｉ及び不可避的不純物元素からなり、時効処理により引張強度が１５００ＭＰａ以上としたことを特徴とする冷間加工性に優れた高強度チタン合金である。
Ｍｏｅｑ（質量％）＝（Ｍｏ＋Ｖ／１．５＋Ｎｂ／３．５＋Ｔａ／５＋１．２５×Ｃｒ＋１．２５×Ｎｉ＋１．７×Ｍｎ＋１．７×Ｃｏ＋２．５×Ｆｅ＋Ｗ／２．５）−（Ａｌ＋Ｓｎ／３＋Ｚｒ／６＋１０×Ｏ） ・・・（１）
The new alloy according to claim 1 obtained by the above-described study is, in mass%, Nb: 25% or less, V: 15% or less, one or two of them (provided that Nb + V ≧ 3.0%, Nb, V V is less than 10% at the time of compound addition), Mo: 3 to 17%, Zr: 7.1 to 30%, Sn: 0.5% to 5%, O: 0.30% or less, and High strength with excellent cold workability, characterized in that the Moeq consisting of (1) is 2 to 8%, the balance is made of Ti and inevitable impurity elements, and the tensile strength is 1500 MPa or more by aging treatment Titanium alloy.
Moeq (mass%) = (Mo + V / 1.5 + Nb / 3.5 + Ta / 5 + 1.25 × Cr + 1.25 × Ni + 1.7 × Mn + 1.7 × Co + 2.5 × Fe + W / 2.5) − (Al + Sn / 3 + Zr / 6 + 10) × O) (1)
次に請求項１からなる本発明によるチタン合金の各成分範囲の限定理由について説明する。
Ｎｂ：２５％以下、Ｖ：１５％以下の１種又は２種（但しＮｂ＋Ｖ≧３．０％、Ｎｂ、Ｖの複合添加時のＶは１０％未満）
Ｎｂ、Ｖは、本発明にとって最も重要な元素であり、溶体化処理後の冷間加工性を改善するために不可欠となる元素である。従って、その効果を得るためには、最低でもＮｂ、Ｖの合計含有率が３．０％以上である必要がある。特にＮｂは冷間加工性を改善させる効果が大きいため、いずれか一方を選択するのであれば、Ｎｂ単独添加の方がより好ましい。しかしながら、多量に添加すると焼結での製造であれば良いが、溶製法による製造では、性能の均一なインゴットを製造することが困難となり、安定した性能が得られなくなるため、上限をＮｂは２５％、Ｖは１５％とした。また、Ｎｂ、Ｖを複合添加した場合には、同様の理由によりＶの上限を１０％未満とする必要がある。
Next, the reasons for limiting the respective component ranges of the titanium alloy according to the present invention will be described.
Nb: 25% or less, V: 15% or less 1 type or 2 types (however, Nb + V ≧ 3.0%, V in combined addition of Nb and V is less than 10%)
Nb and V are the most important elements for the present invention and are indispensable for improving the cold workability after the solution treatment. Therefore, in order to obtain the effect, at least the total content of Nb and V needs to be 3.0% or more. In particular, since Nb has a large effect of improving the cold workability, if either one is selected, it is more preferable to add Nb alone. However, if it is added in a large amount, it may be produced by sintering. However, in the production by the melting method, it becomes difficult to produce an ingot having uniform performance, and stable performance cannot be obtained. % And V were 15%. When Nb and V are added in combination, the upper limit of V needs to be less than 10% for the same reason.
なお、Ｎｂ、Ｖは添加量が増加すると比重が高くなる傾向にあり、軽量化効果が小さくなる可能性がある。また、前記した通り多量に添加すると、溶製法による製造が困難になるという問題もある。従って、製造性及び比重を重視する場合には、ＮｂとＶの合計含有率を３０％未満とすることが望ましい。 Note that Nb and V tend to increase in specific gravity as the addition amount increases, and the lightening effect may be reduced. In addition, when added in a large amount as described above, there is a problem that it is difficult to produce by a melting method. Therefore, when importance is placed on manufacturability and specific gravity, it is desirable that the total content of Nb and V is less than 30%.
Ｍｏ：３〜１７％
Ｍｏは最もβ相安定化能が高い元素であり、溶体化処理後にβ相単相組織を得るために不可欠な元素である。さらにＭｏはβ相に固溶し強度を向上させる作用を有しているが、Ｍｏ含有量が３％以下ではβ相安定化能が不足し、溶体化処理後もα相が析出し易くなり冷間加工性が低下する。また、Ｍｏ含有量が１７％を超えるとβ相の安定化度が高くなりすぎ、時効処理時のα相の析出能が低下し本発明で意図するところの高強度を得ることが難しくなる。従って、Ｍｏ含有量の範囲は３〜１７％とする必要がある。
Mo: 3 to 17%
Mo is an element having the highest β-phase stabilizing ability, and is an indispensable element for obtaining a β-phase single-phase structure after the solution treatment. Furthermore, Mo has the effect of improving the strength by solid solution in the β phase, but if the Mo content is 3% or less, the β phase stabilization ability is insufficient, and the α phase is likely to precipitate even after the solution treatment. Cold workability decreases. On the other hand, if the Mo content exceeds 17%, the degree of stabilization of the β phase becomes too high, and the precipitation ability of the α phase during the aging treatment decreases, making it difficult to obtain the high strength intended in the present invention. Therefore, the Mo content range needs to be 3 to 17%.
Ｚｒ：７．１〜３０％
Ｚｒはα相とβ相の両相に固溶して強度を向上させる作用を有しており、さらに結晶粒を微細化させる作用がある。これにより結晶粒が粗大化せず良好な冷間加工性が得られる。この効果を十分に得るためにはＺｒ含有量は７．１％以上とする必要がある。しかし、Ｚｒ含有量が多くなり過ぎると、結晶粒の細粒化効果が飽和するばかりでなく、熱間加工性、冷間加工性が劣化してくるので、Ｚｒ含有量の上限は３０％以下、より望ましくは２５％未満とするのが良い。
Zr: 7.1-30%
Zr has the effect of improving the strength by forming a solid solution in both the α phase and the β phase, and further has the effect of refining crystal grains. Thereby, the crystal grain does not become coarse and good cold workability is obtained. In order to sufficiently obtain this effect, the Zr content needs to be 7.1% or more. However, if the Zr content becomes too large, not only the grain refinement effect is saturated, but also the hot workability and cold workability deteriorate, so the upper limit of the Zr content is 30% or less. More desirably, the content is less than 25%.
Ｓｎ：０．５〜５％
Ｓｎは時効処理時のα相の析出を促進する作用があり、またＭｏ、Ａｌほど強い強化作用を有していないため、冷間加工性の悪影響を最小限に抑えつつ、強度を向上させるために有効な元素である。この効果はＳｎ含有量０．５％以下では乏しく、５％を超えると冷間加工性が劣化してくる。従って、Ｓｎ含有量は０．５〜５％とする必要がある。
Sn: 0.5-5%
Sn has the effect of promoting the precipitation of α phase during the aging treatment, and does not have the strong strengthening effect as Mo and Al, so that the strength is improved while minimizing the adverse effects of cold workability. Is an effective element. This effect is poor when the Sn content is 0.5% or less, and when it exceeds 5%, the cold workability deteriorates. Therefore, Sn content needs to be 0.5 to 5%.
Ｏ：０．３０％以下
Ｏは添加すると高強度化できることが知られているが、一方で添加量が増加するほど冷間加工性が低下するという問題がある。従って、優れた冷間加工性を重視する本発明ではできるだけ量を抑制することが望ましい。しかしながら、Ｏは製造時に不可避に混入する不純物元素であるため、極端に上限値を低くすると製造が困難となる。従って、本発明では製造性を考慮して０．３０％以下の範囲での含有を許容することとした。
O: 0.30% or less It is known that when O is added, the strength can be increased, but on the other hand, there is a problem that the cold workability decreases as the addition amount increases. Therefore, it is desirable to suppress the amount as much as possible in the present invention in which excellent cold workability is important. However, since O is an impurity element that is inevitably mixed during production, production becomes difficult if the upper limit value is extremely lowered. Therefore, in the present invention, the content in the range of 0.30% or less is allowed in consideration of manufacturability.
Ｍｏｅｑ：２〜８％
前記した通り、β相安定化元素が多くなると溶体化処理後に容易にβ相単相の組織が得られるが、時効処理によってα相を十分に析出させて高強度化を図ることが難しくなる。また、α相安定化元素が多くなると、時効処理によるα相の析出が容易となる一方で、溶体化処理後にβ相単相の組織を得ることが難しくなって、冷間加工性が低下する。Ｍｏｅｑを２〜８％にするという条件は、このα相安定化元素とβ相安定化元素の添加量のバランスを適正とし、溶体化処理後に必要な冷間加工性を維持しつつ時効処理により１５００ＭＰａ以上の引張強度を得ようとするための必要条件である。従って、Ｍｏｅｑを２〜８％の範囲内とすることにより、現場で大量生産可能な冷間加工性を有しつつ、高強度化が可能となるものである。
Moeq: 2-8%
As described above, when the β-phase stabilizing element is increased, a β-phase single phase structure can be easily obtained after the solution treatment, but it is difficult to sufficiently increase the strength by precipitating the α phase by aging treatment. In addition, when the α-phase stabilizing element is increased, the α-phase is easily precipitated by the aging treatment, but it becomes difficult to obtain a β-phase single phase structure after the solution treatment, and the cold workability is lowered. . The condition that Moeq is 2 to 8% is that the balance of the addition amount of the α-phase stabilizing element and the β-phase stabilizing element is appropriate, and the aging treatment is performed while maintaining the cold workability necessary after the solution treatment. This is a necessary condition for obtaining a tensile strength of 1500 MPa or more. Therefore, by setting Moeq in the range of 2 to 8%, it is possible to increase the strength while having cold workability that can be mass-produced on site.
次に請求項２の合金の成分範囲限定理由について説明する。
請求項２の発明は、請求項１記載の合金に加えて、さらに、Ａｌ、Ｔａ、Ｃｒのうち１種又は２種以上を含有する合金であって、その含有量は、質量％で、これら全体で２５％以下であり、かつＡｌが５％以下、Ｔａが２０％以下、Ｃｒが５％以下であり、時効処理により引張強度を１５００ＭＰａ以上としたことを特徴とする冷間加工性に優れた高強度チタン合金である。
以下、各元素の組成範囲の限定理由について説明する。
Next, the reason for limiting the component range of the alloy of claim 2 will be described.
The invention of claim 2 is an alloy containing one or more of Al, Ta, and Cr in addition to the alloy of claim 1, and the content thereof is mass%. Excellent cold workability, characterized in that the total is 25% or less, Al is 5% or less, Ta is 20% or less, Cr is 5% or less, and the tensile strength is 1500 MPa or more by aging treatment. High strength titanium alloy.
Hereinafter, the reasons for limiting the composition range of each element will be described.
Ａｌ：５％以下
Ａｌはα安定化元素であって析出するα相を強化する作用があり、時効処理後の強度向上に有効な元素である。しかし、Ａｌ含有量が５％を超えると冷間加工性が極端に低下するため、強度と冷間加工性の兼ね合いを考慮するとＡｌ含有量の上限は５％以下とする必要がある。
Al: 5% or less Al is an α-stabilizing element, has an action of strengthening the precipitated α-phase, and is an element effective for improving the strength after aging treatment. However, when the Al content exceeds 5%, the cold workability is extremely lowered. Therefore, in consideration of the balance between strength and cold workability, the upper limit of the Al content needs to be 5% or less.
Ｔａ：２０％以下
Ｔａはβ安定化元素であって溶体化処理後の冷間加工性を向上させる作用がある。しかしながら、Ｔａを２０％を超えて添加してもその添加効果が飽和し、コスト高となるため、その量の上限を２０％とした。
Ta: 20% or less Ta is a β-stabilizing element and has an effect of improving cold workability after solution treatment. However, even if Ta is added in excess of 20%, the effect of the addition is saturated and the cost is increased. Therefore, the upper limit of the amount is set to 20%.
但し、Ｔａは冷間加工性向上に効果を有するものの、多量に添加すると溶製法での製造が難しくなるとともにコストが高くなる。従って、製造性とコストを考慮すると、Ｔａ以外の元素を優先的に利用し、Ｔａは無添加とするか、又は添加する場合でもできるだけ少量とするのがより好ましい。 However, Ta has an effect on improving the cold workability, but if it is added in a large amount, it becomes difficult to produce by the melting method and the cost is increased. Therefore, in consideration of manufacturability and cost, it is more preferable to use elements other than Ta preferentially and to add Ta as little as possible even when it is not added or added.
Ｃｒ：５％以下
Ｃｒはβ安定化元素であってβ相に固溶し強度を向上させる作用を有しているが、Ｃｒ含有量が多くなり過ぎると延性が低下し、本発明で意図するところの優れた冷間加工性が得られなくなるため、上限を５％以下とした。
Ａｌ、Ｔａ、Ｃｒの合計含有率が２５％以下
Ａｌ、Ｃｒは冷間加工性を低下させる元素であり、Ｔａは前記した通り、多量に含有させようとすると溶製法での製造が困難となる元素である。従って、良好な製造性を確保するためには、これらの合計含有率を２５％以下とする必要がある。
Cr: 5% or less Cr is a β-stabilizing element and has the effect of improving the strength by solid solution in the β-phase, but if the Cr content is excessively increased, the ductility is lowered and is intended in the present invention. However, since excellent cold workability cannot be obtained, the upper limit was made 5% or less.
The total content of Al, Ta, and Cr is 25% or less. Al and Cr are elements that lower the cold workability. As described above, if Ta is contained in a large amount, it becomes difficult to manufacture by a melting method. It is an element. Therefore, in order to ensure good manufacturability, the total content of these needs to be 25% or less.
なお、Ｎｂ、Ｖに加えＴａも添加量が増加すると比重が増加する傾向にあり軽量化効果が小さくなる傾向にあるとともに、これらの３元素が多くなりすぎると、溶製法での製造が難しくなるため、それを防止するために、前記３種類の元素の合計含有率を３０％未満とするのが好ましい。 In addition to Nb and V, when Ta is added, the specific gravity tends to increase and the effect of weight reduction tends to decrease. When these three elements are excessive, production by the melting method becomes difficult. Therefore, in order to prevent this, the total content of the three kinds of elements is preferably less than 30%.
以上説明した請求項１、２の成分範囲の合金とすることにより、溶体化処理後においては、冷間加工性に優れ、後述の時効処理後において、１５００ＭＰａ以上の極めて高強度のチタン合金を得ることができる。 By using the alloy in the component range of claims 1 and 2 as described above, it is excellent in cold workability after solution treatment, and an extremely high strength titanium alloy of 1500 MPa or more is obtained after aging treatment described later. be able to.
次に請求項３の発明について説明する。
請求項３の発明は、前記した請求項１又は２に記載の成分からなるチタン合金を、β変態点からβ変態点＋１００℃の温度域（６００〜９００℃程度、β変態点は成分により異なる。）で加熱保持し、０．５℃／秒以上の冷却速度で室温まで冷却する溶体化処理を行った後、再度α＋βの二相域まで加熱及び保持し、室温まで冷却するという時効処理を施すことを特徴とする冷間加工性に優れた高強度チタン合金の製造方法である。
Next, the invention of claim 3 will be described.
According to a third aspect of the present invention, in the titanium alloy comprising the component according to the first or second aspect, the temperature range from the β transformation point to the β transformation point + 100 ° C. (about 600 to 900 ° C., the β transformation point varies depending on the component. )), Followed by solution treatment for cooling to room temperature at a cooling rate of 0.5 ° C./second or more, and then heating and holding again to the α + β two-phase region, followed by cooling to room temperature. It is the manufacturing method of the high strength titanium alloy excellent in the cold workability characterized by performing.
ここで、溶体化処理後に優れた冷間加工性を得るには、溶体化処理にてβ相単相組織であることが求められる。β相単相組織は材料をβ変態点以上に加熱して、組織をβ相単相状態にし、α相を析出させない程度に速く室温まで冷却することによって得ることができる。但し、加熱温度が上昇すると、β相の結晶粒が粗大化し、それが原因となって冷間加工性が低下するため、加熱温度の上限はβ変態点＋１００℃とし、β相単相の組織が得られる範囲内で、できるだけ低めの温度に設定することにした。また保持時間は、製品中心部まで確実にβ相単相組織が得られるようにするため、中心部がβ相単相の温度域まで十分に加熱されるように時間を設定する必要がある。従って、製品の大きさも含めて加熱保持時間を適切に設定する必要がある。 Here, in order to obtain excellent cold workability after the solution treatment, it is required to have a β-phase single-phase structure in the solution treatment. A β-phase single-phase structure can be obtained by heating the material to the β transformation point or higher to bring the structure into a β-phase single-phase state, and quickly cooling to room temperature so as not to precipitate the α-phase. However, when the heating temperature rises, the β-phase crystal grains become coarse, which causes the cold workability to deteriorate. Therefore, the upper limit of the heating temperature is the β transformation point + 100 ° C., and the β-phase single phase structure The temperature was set as low as possible within the range where In addition, the holding time needs to be set so that the central portion is sufficiently heated to the temperature range of the β-phase single phase in order to ensure that the β-phase single-phase structure is obtained up to the center of the product. Therefore, it is necessary to appropriately set the heating and holding time including the size of the product.
β相単相の温度域からの冷却速度は速くするほど好ましいが、冷却途中でα相が析出せず室温でβ相単相が得られる冷却速度であれば良く、少なくとも０．５℃／秒以上の冷却速度である必要がある。但しＭｏｅｑが下限値に近い場合には、５℃／秒以上とする必要がある場合もあるので、成分にあわせて冷却速度を調整する必要がある。また、β相単相組織を得る方法として、圧延や鍛造後に再度室温から加熱して熱処理するのではなく、熱間鍛造、熱間圧延等の熱間加工の最終工程をβ変態点以上の温度で終了させ、０．５℃／秒以上の冷却速度によって冷却することによっても溶体化処理を行うことができ、より効率的にβ相単相組織を得ることができる。 The cooling rate from the temperature range of the β-phase single phase is preferably as high as possible, but it may be any cooling rate at which the α-phase does not precipitate during the cooling and the β-phase single phase is obtained at room temperature, and is at least 0.5 ° C./sec. It is necessary to have the above cooling rate. However, when Moeq is close to the lower limit value, it may be necessary to set the cooling rate to 5 ° C./second or more. Therefore, it is necessary to adjust the cooling rate according to the components. In addition, as a method for obtaining a β-phase single phase structure, heat treatment is not performed again by heating from room temperature after rolling or forging, but the final step of hot working such as hot forging or hot rolling is performed at a temperature equal to or higher than the β transformation point. The solution treatment can be performed also by cooling at a cooling rate of 0.5 ° C./second or more, and a β-phase single-phase structure can be obtained more efficiently.
しかしながら、製品の大きさが大型化した場合には、製造設備の仕様にもよるが、必要な冷却速度が得られず、微量のα相が析出、あるいは成分組成によっては溶体化処理時の冷却過程で準安定相であるαプライム相あるいはαダブルプライム相が析出する可能性がある。これらの相が析出すると冷間加工性が低下するだけでなく、その後の時効処理による高強度化が困難になる。 However, when the size of the product increases, depending on the specifications of the manufacturing equipment, the required cooling rate cannot be obtained, and a small amount of α phase precipitates, or depending on the component composition, cooling during the solution treatment There is a possibility that an α prime phase or α double prime phase which is a metastable phase precipitates during the process. When these phases are precipitated, not only cold workability is lowered, but it is difficult to increase the strength by subsequent aging treatment.
しかし、この場合であってもβ相の体積率が９０％以上であれば、大きく冷間加工性が低下することはなく、ほぼ必要とする加工性を得ることができる（請求項４）。ただし、優れた冷間加工性を得るには、前記したα相、αプライム相、αダブルプライム相が０％であるのが好ましく、β相単相とした方がより望ましい状態であることは言うまでもない。従って、これは製品が大型であって、β相単相の組織を得るのが難しい場合の例外に留めるべきである。 However, even in this case, if the volume fraction of the β phase is 90% or more, the cold workability is not greatly lowered, and the required workability can be obtained (claim 4). However, in order to obtain excellent cold workability, the α phase, α prime phase, and α double prime phase described above are preferably 0%, and it is more desirable to use a β phase single phase. Needless to say. Therefore, this should be an exception when the product is large and it is difficult to obtain a β-phase single phase structure.
溶体化処理された後は、最終部品形状に合わせて必要とする冷間加工が実施され、時効処理により高強度化が図られる。この時効処理は、β変態点以下のα＋β温度域に加熱保持後、冷却することにより行うことができる。さらに具体的に説明すると、本発明の成分組成においては、α＋β温度域とは、３００〜６００℃程度の温度となる。また、保持時間は製品の大きさによって最適条件が変化するが、１〜３０時間程度で実施することができる。また、時効処理は、冷間加工と合わせて実施することが望ましい。すなわち、同一成分の合金の場合、時効処理のみで高強度化を図る場合に比較すると、冷間加工と時効処理を組合わせて実施する方がより高い強度を得ることができるからである。なお、具体的な熱処理条件は、実施する合金の成分組成、冷間加工の内容によって最適条件が異なるため、一意的に決められるものではない。従って、前記した範囲内で適宜条件の最適化を図って熱処理を施すことが必要である。 After the solution treatment, the required cold working is performed according to the final part shape, and the strength is increased by the aging treatment. This aging treatment can be performed by heating and holding in the α + β temperature range below the β transformation point and then cooling. More specifically, in the component composition of the present invention, the α + β temperature range is a temperature of about 300 to 600 ° C. The holding time varies depending on the size of the product, but it can be carried out in about 1 to 30 hours. In addition, it is desirable that the aging treatment is performed together with the cold working. That is, in the case of an alloy having the same component, higher strength can be obtained by combining cold working and aging treatment than in the case of increasing strength only by aging treatment. Specific heat treatment conditions are not uniquely determined because optimum conditions differ depending on the composition of the alloy to be implemented and the content of cold working. Therefore, it is necessary to perform heat treatment by optimizing the conditions as appropriate within the above-mentioned range.
以上説明したように、本発明合金は、成分の最適化を図るとともに、冷間加工と時効処理を組合わせることによって、溶体化処理後に優れた冷間加工性を確保しつつ極めて高い引張強度を得ることができるので、数多くの種類の装身具、携帯品（めがねフレーム、ゴルフクラブフェース、腕時計、ピアス、指輪、ネクタイピン、ブローチ、カフスボタン、携帯電話、ベルトのバックル、様々な鍵、ライター、各種筆記用具（ボールペン等）、キーホルダ、ネックレス、ブレスレット、イアリング、ハンドバッグや財布等の金具）や、人工骨等の医療分野へ適用が可能である。 As described above, the alloy of the present invention has an extremely high tensile strength while ensuring excellent cold workability after solution treatment by combining cold working and aging treatment while optimizing the components. So many kinds of accessories, portable items (eyeglass frames, golf club faces, watches, earrings, rings, tie pins, brooches, cufflinks, mobile phones, belt buckles, various keys, lighters, various The present invention can be applied to medical fields such as writing instruments (ballpoint pens, etc.), key holders, necklaces, bracelets, earrings, fittings such as handbags and wallets, and artificial bones.
特に、本発明合金は極めて高い強度を有しているため、ゴルフクラブヘッドのフェース部に用いた場合、従来合金を使用する場合に比べ薄くすることができるため、ヘッドを大型化してスイートスポットの大きいクラブを容易に製造することができる。また、薄くすることによってボールが当たった瞬間のたわみが大きくなり、ボールを跳ね返す力が増して飛距離が改善されるとともに、極めて高強度であるため耐久性にも優れており、優れたクラブを製造することができるという利点を有する。 In particular, since the alloy of the present invention has extremely high strength, when used in the face part of a golf club head, it can be made thinner than in the case of using a conventional alloy. Large clubs can be manufactured easily. Also, thinning increases the deflection at the moment the ball hits, increases the force to rebound the ball and improves the flight distance, and it is extremely strong, so it has excellent durability, and an excellent club It has the advantage that it can be manufactured.
次に本発明の高強度チタン合金の特徴を実施例により明らかにする。表１に実施例として使用した供試材の化学成分を示す。この表に記載の合金のうち、Ｎｏ．１〜１３が本発明の請求範囲内の合金であり、Ｎｏ．１〜６が請求項１に該当する合金、Ｎｏ．７〜１３が請求項２に該当する合金である。また、Ｎｏ．１４〜２５は、いずれかの条件が本発明の範囲外である比較合金であり、Ｎｏ．２６、２７は、それぞれ従来合金であるＴｉ−１５Ｖ−３Ｃｒ−３Ａｌ合金、Ｔｉ−３Ａｌ−８Ｖ−６Ｃｒ−４Ｍｏ−４Ｚｒ合金であって、従来合金の中で時効処理により最も高強度が得られることが知られている合金である。 Next, the characteristics of the high-strength titanium alloy of the present invention will be clarified by examples. Table 1 shows chemical components of the test materials used as examples. Of the alloys listed in this table, No. Nos. 1 to 13 are alloys within the scope of the present invention. Nos. 1 to 6 are alloys corresponding to claim 1; 7 to 13 are alloys corresponding to claim 2. No. Nos. 14 to 25 are comparative alloys in which any of the conditions is outside the scope of the present invention. 26 and 27 are Ti-15V-3Cr-3Al alloy and Ti-3Al-8V-6Cr-4Mo-4Zr alloy, respectively, which are conventional alloys, and the highest strength can be obtained by aging treatment among the conventional alloys. Is a known alloy.
これらの供試材は、真空２重アーク溶解により溶製された１０ｋｇのインゴット（直径１２０ｍｍ）を熱間鍛造及び熱間圧延で直径６ｍｍの線材とし、β変態点＋５０℃（温度は供試材により異なる）に１５分加熱保持し、表１に記載された速度で室温まで冷却する溶体化処理を行うことにより準備した。 These test materials are a 10 kg ingot (diameter 120 mm) melted by vacuum double arc melting to be a wire rod 6 mm in diameter by hot forging and hot rolling, β transformation point + 50 ° C. (temperature is the test material) Depending on the temperature) for 15 minutes, and a solution treatment was performed by cooling to room temperature at the rate described in Table 1.
そして、この溶体化処理により冷間加工性の改善が図られた供試材について、必要となる冷間加工性が得られるかどうかを評価するために、表面酸化層を酸洗で除去した後、断面減少率が５０％となる冷間圧延を行い、圧延が割れ、キズ等の欠陥を発生させることなく正常に行うことができるかどうかについて調査した。また、供試材の一部を用いて組織観察を行い、β相単相の組織が得られているかどうかを確認し、得られていない場合には、β相の体積率を測定した。結果を表１に示す。なお、表１において、○は冷間圧延が正常に行うことができたことを意味し、×は、割れ、キズ等が発生し、正常な圧延を行うことができなかったことを意味する。 After the surface oxide layer is removed by pickling in order to evaluate whether or not the required cold workability can be obtained for the test material whose cold workability is improved by this solution treatment. Then, cold rolling with a cross-section reduction rate of 50% was performed, and it was investigated whether the rolling could be performed normally without generating defects such as cracks and scratches. Further, the structure was observed using a part of the test material to confirm whether a β-phase single-phase structure was obtained, and when it was not obtained, the volume fraction of the β-phase was measured. The results are shown in Table 1. In Table 1, “O” means that cold rolling could be performed normally, and “X” means that cracking, scratching, etc. occurred and normal rolling could not be performed.
さらに、強度については、前記した溶体化処理後の直径６ｍｍの線材を用い、それぞれの合金の成分に応じた高強度を得るのに適した温度条件（表１に記載）に加熱して時効処理を行い、時効処理後の引張強度を求めることにより評価した。なお、本発明合金においてα＋β相の二相域とは成分によっても変化するが、前記した通り概ね３００〜６００℃であり、表１に示す温度条件は、比較合金、従来合金の処理温度も含めて、全てこの二相域での温度域に相当している。結果を、前記冷間加工性の結果も合わせて表１に示す。 Furthermore, regarding the strength, an aging treatment is performed by using the wire material having a diameter of 6 mm after the solution treatment as described above and heating to a temperature condition (described in Table 1) suitable for obtaining a high strength according to each alloy component. And evaluated by determining the tensile strength after the aging treatment. In the alloy of the present invention, the α + β phase two-phase region varies depending on the components, but is generally 300 to 600 ° C. as described above. The temperature conditions shown in Table 1 include the processing temperatures of the comparative alloy and the conventional alloy. All correspond to the temperature range in this two-phase region. The results are shown in Table 1 together with the results of the cold workability.
表１から明らかなように、本発明合金であるＮｏ．１〜１３合金は、いずれも溶体化処理後において、断面減少率５０％の冷間圧延を正常に行うことができ、かつ時効処理後において、１５００ＭＰａ以上の高い強度を示すことがわかる。なお、この評価では、溶体化処理した後冷間加工を行うことなく、強度を測定しているが、実際に本発明合金を使用する際には、冷間加工される場合が多くあるため、その場合にはより微細なα相の析出が促進されるため、さらに高い強度を得ることが可能である。 As is apparent from Table 1, No. 1 is an alloy of the present invention. It can be seen that all of the alloys 1 to 13 can normally be cold-rolled with a cross-section reduction rate of 50% after the solution treatment, and exhibit a high strength of 1500 MPa or more after the aging treatment. In this evaluation, the strength is measured without performing cold working after solution treatment, but when actually using the alloy of the present invention, it is often cold worked, In that case, precipitation of a finer α phase is promoted, so that higher strength can be obtained.
それに対し比較合金であるＮｏ．１４〜２５合金は、いずれかの条件が、本発明の条件を満足しないために、引張強度、冷間加工性のいずれかが、本発明合金に比較して劣るものである。具体的には、Ｎｏ．１４、１６、１９合金は、Ｍｏｅｑが２％未満であり、β相安定化能が不足しているため、溶体化処理時に冷却速度を５〜１０℃/秒と比較的速い速度で冷却しても、β相が９０％以上となる組織を得ることができず、冷間加工性及び強度が低下したものであり、Ｎｏ．１５、１７、１８、２０、２１、２３合金は、Ｍｏｅｑが８％を超えており、β相安定化能が高すぎるため、０．５〜１℃/秒という比較的遅い速度で冷却する溶体化処理を行っても、β相単相の組織が得られ、冷間加工性については優れているが、時効処理時に十分な量のα相を得ることが難しくなるため、強度が劣るものである。また、Ｎｏ．２２、２４合金は、冷間加工性を低下する元素（２２合金においては、Ｓｎ、Ａｌ、２４合金においてはＯ）の含有率が高いため、β相単相の組織が得られているものの冷間加工性が劣るものであり、２５合金は、溶体化処理時の冷却速度が遅いことにより、β相の比率が大きく低下したため、冷間加工性、強度の両方が劣るものである。 On the other hand, No. which is a comparative alloy. Since any of the conditions for the 14-25 alloy does not satisfy the conditions of the present invention, either the tensile strength or the cold workability is inferior to the alloy of the present invention. Specifically, no. Alloys 14, 16, and 19 have a Moeq of less than 2% and lack β-phase stabilization ability, so the cooling rate is 5 to 10 ° C./second during solution treatment. However, a structure in which the β phase is 90% or more cannot be obtained, and cold workability and strength are deteriorated. 15,17,18,20,21,23 alloys have a Moeq of over 8% and a β-phase stabilization capability that is too high, so the solution cools at a relatively slow rate of 0.5-1 ° C / sec. Even if the aging treatment is performed, a β-phase single phase structure is obtained and the cold workability is excellent, but it is difficult to obtain a sufficient amount of the α phase during the aging treatment, so the strength is inferior. is there. No. Alloys 22 and 24 have a high content of elements that lower the cold workability (Sn, Al in Alloy 22, and O in Alloy 24), so that a β-phase single-phase structure is obtained. The 25 alloy is inferior in both cold workability and strength because the ratio of the β phase is greatly reduced due to the slow cooling rate during the solution treatment.
さらに、従来合金であるＮｏ．２６、２７合金は、適切な溶体化処理を行うことにより冷間加工性については十分に改善することが可能であるが、時効処理を行っても１５００ＭＰａ以上の強度を得ることができないものである。 Furthermore, the conventional alloy No. Alloys 26 and 27 can sufficiently improve the cold workability by performing an appropriate solution treatment, but they cannot obtain a strength of 1500 MPa or more even if an aging treatment is performed. .
以上説明した評価により、本発明合金が時効処理により従来合金と比較して高い強度が得られることが確認できたので、得られた高強度が実際の部品に適用した際の効果について具体的な評価を行った。評価は、前記実施例のＮｏ．７合金に相当する合金の鋼塊を圧延して製造した薄板を製造し、これをゴルフクラブヘッドのフェース部に使用したゴルフクラブヘッドを製造した。そして、比較用のゴルフクラブとして、従来合金であるＴｉ−１５Ｖ−３Ｃｒ−３Ｓｎ−３Ａｌ合金をフェース部に使用した全く同一形状のヘッドからなるクラブを製造し、このクラブを耐久試験用スイングロボットに取り付け、ヘッドスピードが５０ｍ／秒になるように設定して３０００発の耐久試験を実施した。この際、フェース部の板厚を２段階とし、従来合金を用いたクラブについては、市販されているクラブの平均的な厚さで製造したものと、約１５％厚さを薄くして製造したものの両方を準備し、本発明合金を用いたクラブについては、厚さを薄くして製造したクラブのみを準備して耐久試験を実施した。その結果、従来合金を用いて製造したクラブについては、通常の板厚のクラブについては、試験終了後においても何ら問題はなかったが、板厚を薄くして製造した方のクラブについてはフェース部に亀裂が生じているのが認められた。これに対し、本発明合金を用いて製造したクラブについては、板厚を薄くしているにもかかわらず、試験終了後においても亀裂は認められなかった。 As a result of the evaluation described above, it was confirmed that the alloy of the present invention was able to obtain higher strength than the conventional alloy by aging treatment. Therefore, the effect obtained when the obtained high strength was applied to actual parts was specifically described. Evaluation was performed. The evaluation was made according to No. A thin plate produced by rolling an ingot of an alloy corresponding to Alloy 7 was produced, and a golf club head using this for the face portion of the golf club head was produced. Then, as a comparative golf club, a club having a head having the same shape using a Ti-15V-3Cr-3Sn-3Al alloy, which is a conventional alloy, is manufactured, and this club is used as a swing robot for a durability test. The endurance test of 3000 shots was carried out by setting the head speed to 50 m / sec. At this time, the plate thickness of the face part was made into two stages, and the clubs using the conventional alloy were manufactured with an average thickness of a commercially available club and about 15% thinner. Both of these were prepared, and for the clubs using the alloy of the present invention, only clubs manufactured with a reduced thickness were prepared and subjected to a durability test. As a result, for clubs manufactured using conventional alloys, there was no problem even after the test was completed for clubs with normal plate thickness, but for clubs manufactured with reduced plate thickness, the face portion It was observed that cracks occurred in On the other hand, in the club manufactured using the alloy of the present invention, no crack was observed even after the test was completed, although the plate thickness was reduced.
この結果より、本発明合金を用いることにより従来合金を用いて製造する場合より高い設計応力で部品寸法を決定することが可能になることが確認できた。特にゴルフクラブヘッドのフェース部に用いた場合には、板厚を従来合金を使用した場合と比較して薄くできるため、ヘッドを大きくしてスイートスポットを大きくできるとともに、背景技術の箇所で説明した、ボールが当たった瞬間に蓄積可能な弾性エネルギーを大きくできるという効果が得られるため、ゴルフクラブ用として非常に適した特性を有するものである。 From this result, it has been confirmed that the use of the alloy of the present invention makes it possible to determine the part dimensions with a higher design stress than in the case of manufacturing using a conventional alloy. Especially when used in the face part of a golf club head, the plate thickness can be reduced compared to the case where a conventional alloy is used, so that the sweet spot can be increased by increasing the head, as described in the background section. Since the elastic energy that can be accumulated at the moment of hitting the ball can be increased, it has characteristics that are very suitable for golf clubs.
Claims (4)
Ｍｏｅｑ（質量％）＝（Ｍｏ＋Ｖ／１．５＋Ｎｂ／３．５＋Ｔａ／５＋１．２５×Ｃｒ＋１．２５×Ｎｉ＋１．７×Ｍｎ＋１．７×Ｃｏ＋２．５×Ｆｅ＋Ｗ／２．５）−（Ａｌ＋Ｓｎ／３＋Ｚｒ／６＋１０×Ｏ） ・・・（１） % By mass, Nb: 25% or less, V: 15% or less (Nb + V ≧ 3.0%, V when combined with Nb and V is less than 10%), Mo: 3-17 %, Zr: 7.1 to 30%, Sn: 0.5% to 5%, O: 0.30% or less, and Moeq consisting of the following formula (1) is 2 to 8%, the balance Is a high-strength titanium alloy with excellent cold workability, characterized by comprising Ti and inevitable impurity elements, and having an tensile strength of 1500 MPa or more by aging treatment.
Moeq (mass%) = (Mo + V / 1.5 + Nb / 3.5 + Ta / 5 + 1.25 × Cr + 1.25 × Ni + 1.7 × Mn + 1.7 × Co + 2.5 × Fe + W / 2.5) − (Al + Sn / 3 + Zr / 6 + 10) × O) (1)
The method for producing a high-strength titanium alloy having excellent cold workability according to claim 3, wherein the volume fraction of the β phase after solution treatment is 90% or more.
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