JP2009215601A - Titanium alloy sheet having high strength and excellent in formability - Google Patents
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本発明は、強度と成形性に優れたチタン合金板に関するものである。 The present invention relates to a titanium alloy plate excellent in strength and formability.
Ti−6Al−4Vに代表される高強度α+β型チタン合金は、軽量、高強度、高耐食性に加え、溶接性、超塑性、拡散接合性などの利用加工諸特性を有することから、航空機産業を中心に多用されてきた。これらの特性を更に活用すべく、近年では、ゴルフ用品をはじめとしたスポーツ用品にも使用されるようになってきており、自動車部品、土木建築用素材、各種工具類などの民生品分野や、深海やエネルギー開発用途などへの適用拡大も進んでいる。しかし、α+β型チタン合金の著しく高い製造コストがその適用拡大の妨げとなっており、これら民生品分野等への更なる適用拡大を促進するには、上記した諸特性を阻害することなく、且つ安価なチタン合金が開発されることであり、その開発が待ち望まれている。 High strength α + β type titanium alloys represented by Ti-6Al-4V have various processing characteristics such as weldability, superplasticity and diffusion bonding properties in addition to lightweight, high strength and high corrosion resistance. Has been heavily used in the center. In order to further utilize these characteristics, in recent years it has come to be used for sports equipment such as golf equipment, such as consumer products such as automobile parts, civil engineering materials, various tools, Application to deep seas and energy development applications is also expanding. However, the remarkably high production cost of α + β type titanium alloy has hindered its application expansion, and in order to promote further application expansion to the field of consumer products, etc., without impairing the above-mentioned characteristics and An inexpensive titanium alloy is to be developed, and its development is awaited.
これら高強度α+β型チタン合金の製造コストが高くなる理由としては次の2点を挙げることができる。Vなどの高価なβ相安定化元素を使用していること。α相安定化元素として使用しているAlが、熱間での変形抵抗を著しく高め、熱間加工性を損ねるため、加工しにくく、また割れなどの欠陥を生じやすいということ。以上の2点である。 The following two points can be cited as the reasons why the production cost of these high-strength α + β-type titanium alloys increases. Expensive β-phase stabilizing elements such as V are used. Al used as an α-phase stabilizing element remarkably increases hot deformation resistance and impairs hot workability, so that it is difficult to work and easily causes defects such as cracks. These are the above two points.
特に、Alの添加は、主要製品である合金板を製造する際に製造コストが高くなる大きな要因となっており、圧延途中で再加熱を必要としたり、合金板の端部に割れを生じて材料歩留まりが低下したりするといった問題が発生する要因となっていた。 In particular, the addition of Al is a major factor that increases the manufacturing cost when manufacturing the main product alloy plate, and requires reheating during rolling, or cracks at the end of the alloy plate. This has been a cause of problems such as a decrease in material yield.
このような状況下で、近年、低コストチタン合金が種々提案されている。それらの中でも、Ti−Fe−O−N系高強度チタン合金は、β相安定化元素として、安価なFeを採用し、α相安定化元素として、熱間加工性を低下させるAlに替えて、熱間での加工性を損なわず且つ安価な酸素や窒素を採用していることから、従来のα+β型チタン合金に比べて、相当な低コスト化が期待されている。 Under such circumstances, various low-cost titanium alloys have been proposed in recent years. Among them, Ti-Fe-O-N-based high-strength titanium alloys adopt inexpensive Fe as the β-phase stabilizing element, and replace Al as the α-phase stabilizing element, which reduces hot workability. In view of the fact that inexpensive oxygen and nitrogen are used without impairing hot workability, a considerable cost reduction is expected as compared with conventional α + β type titanium alloys.
しかしながら、このTi−Fe−O−N系高強度チタン合金は、通常の一方向圧延により板を製造した場合、極端な板面内材質異方性が生じ、板の圧延方向すなわち長さ方向の特性は優れるものの、その幅方向の延性が極端に乏しくなってしまうという問題を兼ね備えていた。 However, when this Ti—Fe—O—N-based high-strength titanium alloy is produced by normal unidirectional rolling, extreme in-plane material anisotropy occurs, and the rolling direction of the plate, that is, the lengthwise direction, Although it has excellent characteristics, it also has the problem that the ductility in the width direction becomes extremely poor.
この問題を解消するための改善案として一度だけ圧延方向に対して垂直方向に圧延を行い、その面内異方性を小さくすることで、長さ方向、幅方向ともに高強度・高延性のTi−Fe−O−N系高強度チタン合金を得られることが、特許文献1に開示されている。しかしながら、このようなクロス圧延を実機に適用することはコスト増を招くことになり、実質的な改善とはなっていない。従って、実機へ適用してもコスト増を招かず低コストで面内異方性が小さい上に、高強度で成形性に優れたチタン合金板が開発されることが待ち望まれている。 As an improvement plan to solve this problem, rolling in the direction perpendicular to the rolling direction only once, and reducing the in-plane anisotropy, high strength and high ductility in both the length and width directions Patent Document 1 discloses that a —Fe—O—N high-strength titanium alloy can be obtained. However, applying such cross rolling to an actual machine causes an increase in cost, and is not a substantial improvement. Accordingly, there is a long-awaited development of a titanium alloy plate that is low in cost, has low in-plane anisotropy, and has high strength and excellent formability even when applied to an actual machine.
本発明は、上記従来の問題を解決せんとしてなされたもので、高強度で成形性に優れる上に、且つ安価なチタン合金板を提供することを課題とするものである。 The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a titanium alloy plate that is high in strength, excellent in formability, and inexpensive.
請求項1記載の発明は、Fe:1.0質量%以下、O:0.1〜0.5質量%を含み、残部がTiおよび不可避的不純物であるチタン合金板であって、FeとOの含有量の関係が、−0.4[Fe]+0.15<[O]<−0.4[Fe]+0.5という要件を満たし、更に、α相の平均アスペクト比が5以下、圧延方向の全伸びが20%以上であることを特徴とする高強度で成形性に優れたチタン合金板である。但し、前式で[ ]は、各元素の含有量(質量%)を示す。 The invention according to claim 1 is a titanium alloy plate containing Fe: 1.0 mass% or less, O: 0.1-0.5 mass%, the balance being Ti and inevitable impurities, wherein Fe and O The relation of the content of the steel satisfies the requirement of −0.4 [Fe] +0.15 <[O] <− 0.4 [Fe] +0.5, and the average aspect ratio of the α phase is 5 or less. A titanium alloy plate having high strength and excellent formability, characterized in that the total elongation in the direction is 20% or more. However, in the above formula, [] indicates the content (% by mass) of each element.
請求項2記載の発明は、α相の平均結晶粒径の標準偏差が30%以下である請求項1記載の高強度で成形性に優れたチタン合金板である。 The invention according to claim 2 is the titanium alloy plate having high strength and excellent formability according to claim 1, wherein the standard deviation of the average crystal grain size of the α phase is 30% or less.
本発明によると、高強度で成形性に優れる上に、且つ安価なチタン合金板を得ることができ、従来からの航空機産業ばかりでなく、スポーツ用品、自動車部品、土木建築用素材、各種工具類などの民生品分野や、深海やエネルギー開発用途など多方面への適用拡大を更に促進することができる。 According to the present invention, it is possible to obtain a titanium alloy plate that has high strength and excellent formability and is inexpensive, and not only the conventional aircraft industry, but also sports equipment, automobile parts, civil engineering and building materials, and various tools. It is possible to further promote the expansion of applications in various fields such as consumer products such as deep sea and energy development.
本発明者らは、FeとOの含有量が、チタン合金板の強度と成形性に与える影響を実験により調査し、鋭意研究を進めることで、Feの含有量が多くなりすぎるとr値(深絞り性)が減少して成形性が低下し、Oの含有量が多くなりすぎると伸び特性が低下することを見出した。 The present inventors investigated the influence of the contents of Fe and O on the strength and formability of the titanium alloy plate by experiment, and by conducting earnest research, the r value ( It has been found that when the deep drawability is reduced, the moldability is lowered, and when the O content is excessively increased, the elongation characteristics are lowered.
また、α相の平均アスペクト比と、圧延方向の全伸び、更にはα相の平均粒径の標準偏差を規定することで、高強度と優れた成形性を確保することができることも見出した。 It has also been found that high strength and excellent formability can be secured by defining the average aspect ratio of the α phase, the total elongation in the rolling direction, and the standard deviation of the average particle size of the α phase.
本発明のチタン合金板は、Feの含有量が1.0質量%以下であって、Oの含有量は0.1〜0.5質量%である。また、FeとOの含有量の関係は、−0.4[Fe]+0.15<[O]<−0.4[Fe]+0.5という要件を満たす必要がある。 In the titanium alloy plate of the present invention, the Fe content is 1.0% by mass or less, and the O content is 0.1 to 0.5% by mass. Further, the relationship between the contents of Fe and O needs to satisfy the requirement of −0.4 [Fe] +0.15 <[O] <− 0.4 [Fe] +0.5.
Feはβ相安定化元素として安価な元素である。このFeの含有量が1.0質量%を超えると、r値が小さくなりすぎ成形性が低下する。Oはα相安定化元素として安価な元素である。また、不純物として不可避的に混入する元素でもある。このOの含有量が、0.5質量%を超えると、伸びが小さくなりすぎ成形性が低下する。また、Oの含有量が、0.1質量%未満であると強度レベルが低下してしまう。従って、Feの含有量は1.0質量%以下、Oの含有量は0.1〜0.5質量%の範囲とする。 Fe is an inexpensive element as a β-phase stabilizing element. If the Fe content exceeds 1.0% by mass, the r value becomes too small and the formability is lowered. O is an inexpensive element as an α-phase stabilizing element. It is also an element inevitably mixed as an impurity. When the content of O exceeds 0.5% by mass, the elongation becomes too small and the moldability deteriorates. Moreover, an intensity | strength level will fall that content of O is less than 0.1 mass%. Therefore, the Fe content is 1.0% by mass or less, and the O content is 0.1 to 0.5% by mass.
また、FeとOの含有量の関係が、−0.4[Fe]+0.15<[O]という要件を満たさない場合、強度レベルが低下してしまう。逆に、[O]<−0.4[Fe]+0.5という要件を満たさない場合、伸びが小さくなりすぎ成形性が低下する。従って、FeとOの含有量が、−0.4[Fe]+0.15<[O]<−0.4[Fe]+0.5という関係を満たすことを要件とする(前記したFe、Oの含有量を含め、図1の点線で囲む範囲)。尚、Oの質量%([O])は、−0.4[Fe]+0.3未満であることがより望ましい(前記したFe、Oの含有量を含め、図1の実線で囲む範囲)。 Further, when the relationship between the contents of Fe and O does not satisfy the requirement of −0.4 [Fe] +0.15 <[O], the strength level is lowered. On the other hand, when the requirement of [O] <− 0.4 [Fe] +0.5 is not satisfied, the elongation becomes too small and the moldability deteriorates. Therefore, it is a requirement that the contents of Fe and O satisfy the relationship of −0.4 [Fe] +0.15 <[O] <− 0.4 [Fe] +0.5 (the above-described Fe, O The range enclosed by the dotted line in FIG. In addition, it is more desirable that the mass% ([O]) of O is less than −0.4 [Fe] +0.3 (a range surrounded by the solid line in FIG. 1 including the contents of Fe and O described above). .
本発明のチタン合金板のFeとO以外の残部は、Tiおよび不可避的不純物であり、その不可避的不純物としては、原料、資材、製造設備等の状況によって持ち込まれるNi、Cr、H、C、Nといった元素の混入が許容され得る。その含有量を例示すると、Ni、Crは総量で0.05質量%以下、H、C、Nは総量で数十質量ppm程度である。上記したようにOも不純物として不可避的に混入する元素ではあるが、本発明のチタン合金板における、O以外の不可避的不純物の総含有量は、おおよそ0.05質量%である。 The balance other than Fe and O of the titanium alloy plate of the present invention is Ti and unavoidable impurities, and as the unavoidable impurities, Ni, Cr, H, C, which are brought in depending on the situation of raw materials, materials, manufacturing equipment, etc. Incorporation of elements such as N can be tolerated. When the content is illustrated, Ni and Cr are 0.05 mass% or less in total amount, and H, C, and N are about several dozen mass ppm in total amount. As described above, O is an element inevitably mixed as an impurity, but the total content of unavoidable impurities other than O in the titanium alloy plate of the present invention is approximately 0.05% by mass.
α相の平均アスペクト比は5以下とする。α相の平均アスペクト比が5を超えると、延性が低下し、成形性が低下する。尚、α相の平均アスペクト比は、3以下とすることがより好ましい。また、2以下とすることが更に好ましい。 The average aspect ratio of the α phase is 5 or less. When the average aspect ratio of the α phase exceeds 5, the ductility is lowered and the moldability is lowered. The average aspect ratio of the α phase is more preferably 3 or less. Moreover, it is more preferable to set it as 2 or less.
α相の平均結晶粒径の標準偏差は30%以下とすることが好ましい。α相の平均結晶粒径の標準偏差が30%を超えると、α相の結晶粒径の平均値と比較して大きな結晶粒の数が多くなりすぎ、成形性が低下する。尚、α相の平均結晶粒径の標準偏差は、20%以下とすることがより好ましい。また、15%以下とすることが更に好ましい。 The standard deviation of the average crystal grain size of the α phase is preferably 30% or less. When the standard deviation of the average crystal grain size of the α phase exceeds 30%, the number of large crystal grains becomes too large as compared with the average value of the crystal grain size of the α phase, and the formability deteriorates. The standard deviation of the average crystal grain size of the α phase is more preferably 20% or less. Further, it is more preferably 15% or less.
チタン合金板の圧延方向の全伸びは20%以上とする。チタン合金板の圧延方向の全伸びが20%未満であると、所望とする優れた成形性が得られなくなる。 The total elongation in the rolling direction of the titanium alloy plate is 20% or more. If the total elongation in the rolling direction of the titanium alloy plate is less than 20%, desired excellent formability cannot be obtained.
次に、本発明のチタン合金板の製造条件について説明する。チタン合金板は、通常は、鋳造→分塊圧延→熱間圧延→中間焼鈍→冷間圧延→最終焼鈍という工程を経て、また、各工程間に随時ブラスト、酸洗処理という工程を挿入して製造される。本発明者らは、その成分組成や各製造工程の設定条件によって得られるチタン合金板の物性や組織状態は変わるが、個々の工程毎に条件を厳密に設定することは必ずしも適切ではなく、一連の製造工程として関連付けて総合的に条件を選択してチタン合金板の製造条件を決定すべきであると考えた。 Next, manufacturing conditions for the titanium alloy plate of the present invention will be described. Titanium alloy sheets are usually subjected to the steps of casting-> batch rolling-> hot rolling-> intermediate annealing-> cold rolling-> final annealing, and blasting and pickling treatments are inserted as needed between each step. Manufactured. Although the present inventors change the physical properties and structure of the titanium alloy plate obtained depending on the component composition and the setting conditions of each manufacturing process, it is not always appropriate to set the conditions strictly for each individual process. It was considered that the manufacturing conditions of the titanium alloy plate should be determined by selecting the conditions comprehensively in relation to the manufacturing process.
本発明者らは、前記した成分組成のチタン合金を用いて加工する条件として、以下の条件を採用すれば、本発明の高強度で成形性に優れたチタン合金板を製造することができることを、実験、研究により確認した。 The present inventors can manufacture a titanium alloy plate having high strength and excellent formability according to the present invention by adopting the following conditions as conditions for processing using a titanium alloy having the above-described component composition. Confirmed by experiments and research.
条件の一つ目は、冷間圧延の圧延率を50%以上とすることである。冷間圧延の圧延率が50%未満であると、最終焼鈍後のα相の平均粒径の標準偏差が大きくなりすぎ、成形性が劣化する。 The first condition is that the cold rolling reduction rate is 50% or more. If the rolling rate of cold rolling is less than 50%, the standard deviation of the average particle diameter of the α phase after the final annealing becomes too large, and the formability deteriorates.
二つ目の条件は、最終焼鈍の昇温速度を5℃/s以上とすることである。最終焼鈍の昇温速度が5℃/s未満であると、圧延方向伸びが低下すると共に、α相の平均粒径の標準偏差も大きくなりすぎる。 The second condition is that the temperature increase rate of the final annealing is 5 ° C./s or more. If the temperature increase rate of the final annealing is less than 5 ° C./s, the elongation in the rolling direction is lowered and the standard deviation of the average particle diameter of the α phase is too large.
また、三つ目の条件は、最終焼鈍温度を700℃以上、ベータ変態点温度(Tβ)までとすることである。最終焼鈍温度が700℃未満であると、圧延方向伸びが低下し、一方、最終焼鈍温度がTβを超えると、α相の平均アスペクト比が5より大きくなると共に、α相の平均結晶粒径の標準偏差も大きくなる。 The third condition is that the final annealing temperature is 700 ° C. or higher and the beta transformation point temperature (Tβ). When the final annealing temperature is less than 700 ° C., the elongation in the rolling direction is lowered. On the other hand, when the final annealing temperature exceeds Tβ, the average aspect ratio of the α phase is larger than 5, and the average grain size of the α phase The standard deviation also increases.
最後の条件は、最終焼鈍の冷却速度を5℃/s以上とすることである。最終焼鈍の冷却速度が5℃/s未満であると、冷却時に針状組織が発達しすぎるため、α相の平均アスペクト比が5より大きくなってしまう。 The last condition is that the cooling rate of the final annealing is 5 ° C./s or more. If the cooling rate of the final annealing is less than 5 ° C./s, the needle-like structure develops too much during cooling, and the average aspect ratio of the α phase becomes larger than 5.
以上の4条件を適切に組み合わせてチタン合金板を製造することで、本発明の高強度で成形性に優れたチタン合金板を製造することができる。 By producing a titanium alloy plate by appropriately combining the above four conditions, a titanium alloy plate having high strength and excellent formability according to the present invention can be produced.
以上説明した本発明に係るチタン合金板は、本来の優れた耐食性はもとより高い機械的強度に加え、優れた成形性を備えているので、プレート式熱交換器の構成材のほか、燃料電池のセパレーター、携帯電話機、モバイルパソコン、カメラ等のボディ、眼鏡フレーム等、高度な成形性が要求される用途にも広く適用することができる。 Since the titanium alloy plate according to the present invention described above has excellent formability in addition to the original excellent corrosion resistance, it has excellent formability. Therefore, in addition to the components of the plate heat exchanger, The present invention can be widely applied to applications requiring high formability, such as separators, mobile phones, mobile personal computers, camera bodies, and eyeglass frames.
以下実施例を挙げて本発明をより具体的に説明するが、本発明はもとより下記実施例によって制限を受けるものではなく、本発明の趣旨に適合し得る範囲で適宜変更を加えて実施することも可能であり、それらは何れも本発明の技術的範囲に含まれる。 Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, but may be implemented with appropriate modifications within a range that can be adapted to the gist of the present invention. These are all included in the technical scope of the present invention.
本実施例では、まず、CCIM(コールドクルーシブル誘導加熱法)溶解により表1に示す各成分組成のチタン合金でなる鋳塊を鋳造した。その鋳塊を分塊圧延し、以下、熱間圧延→中間焼鈍→冷間圧延→最終焼鈍という工程を経て厚み0.3mmのチタン合金板を製造した。高強度で成形性に優れたチタン合金板を製造するために必要とした前記4つの製造条件を満足することで、本発明のチタン合金板を製造することができるが、各発明例、比較例毎に、それら4つの製造条件をどのように設定したかを表1に示す。 In this example, first, ingots made of titanium alloys having respective component compositions shown in Table 1 were cast by CCIM (cold crucible induction heating method) melting. The ingot was subjected to split rolling, and a titanium alloy plate having a thickness of 0.3 mm was manufactured through steps of hot rolling → intermediate annealing → cold rolling → final annealing. The titanium alloy plate of the present invention can be manufactured by satisfying the above four manufacturing conditions required for manufacturing a titanium alloy plate having high strength and excellent formability. Table 1 shows how these four manufacturing conditions were set for each.
製造した各チタン合金板の金属組織の観察・測定と、強度および成形性の評価を夫々下記の要領で行った。 Observation and measurement of the metal structure of each manufactured titanium alloy plate, and evaluation of strength and formability were performed as follows.
<α相の平均アスペクト比、α相の平均結晶粒径、α相の平均結晶粒径の標準偏差の測定>
本実施例では、上記各パラメータの測定を、電界放出型走査顕微鏡(Field Emission Scanning Electron Microscope:FESEM)に、後方錯乱電子回析像(Electron Back Scattering(Scattered) Pattern:EBSP)システムを搭載した結晶方位解析法で行った。この測定方法を用いたのは、EBSP法は他の測定方法と比較して高分解能であり、高精度な測定ができるためである。まず、以下測定原理について説明する。
<Measurement of average aspect ratio of α phase, average crystal grain size of α phase, standard deviation of average crystal grain size of α phase>
In the present example, the measurement of each of the above parameters is carried on a field emission scanning electron microscope (FESEM) equipped with an electron back scattering (scattered) pattern (EBSP) system. The orientation analysis method was used. This measurement method was used because the EBSP method has higher resolution than other measurement methods and can perform measurement with high accuracy. First, the measurement principle will be described below.
EBSP法は、FESEMの鏡筒内にセットした試料に電子線を照射してスクリーン上にEBSPを投影する。これを高感度カメラで撮影して、コンピュータに画像として取り込む。コンピュータでは、この画像を解析して、既知の結晶系を用いたシミュレーションによるパターンとの比較によって、結晶の方位が決定される。算出された結晶の方位は3次元オイラー角として、位置座標(x、y)などと共に記録される。このプロセスが全測定点に対して自動的に行われるので、測定終了時には数万〜数十万点の結晶方位データを得ることができる。 In the EBSP method, an electron beam is irradiated onto a sample set in a lens barrel of FESEM to project EBSP on a screen. This is taken with a high-sensitivity camera and captured as an image on a computer. In the computer, the orientation of the crystal is determined by analyzing this image and comparing it with a pattern obtained by simulation using a known crystal system. The calculated crystal orientation is recorded as a three-dimensional Euler angle together with position coordinates (x, y) and the like. Since this process is automatically performed for all measurement points, tens of thousands to hundreds of thousands of crystal orientation data can be obtained at the end of measurement.
このように、EBSP法には、X線回析法や透過電子顕微鏡を用いた電子線回析法よりも、観察視野が広く、数百個以上の多数の結晶粒に対する、平均結晶粒径、平均結晶粒径の標準偏差、平均アスペクト比に関する情報を、数時間以内で得ることができる利点がある。また、結晶粒毎の測定ではなく、指定した領域を一定間隔で走査して測定するために、測定領域全体を網羅した上記多数の測定ポイントに関する、上記各情報を得ることができる利点もある。尚、これらFESEMにEBSPシステムを搭載した結晶方位解析法の詳細は、神戸製鋼技報/Vol.52 No.2(Sep.2002)P66−70などに詳細に記載されている。 Thus, the EBSP method has a wider field of view than the X-ray diffraction method or the electron diffraction method using a transmission electron microscope, and the average crystal grain size for a large number of crystal grains of several hundred or more, There is an advantage that information on the standard deviation of the average grain size and the average aspect ratio can be obtained within several hours. In addition, since the specified region is scanned at a fixed interval instead of the measurement for each crystal grain, there is an advantage that each of the above-mentioned information regarding the above-described many measurement points covering the entire measurement region can be obtained. Details of the crystal orientation analysis method in which the EBSP system is mounted on these FESEMs are described in Kobe Steel Technical Report / Vol. 52 no. 2 (Sep. 2002) P66-70 and the like.
ここで、通常のチタン合金の場合、主に、α相(HCP)、β相(BCC)に示す如きCube方位、Goss方位、Brass方位、Copper方位、S方位等と呼ばれる多くの方位因子からなる集合組織を形成し、それらに応じた結晶面が存在する。 Here, in the case of a normal titanium alloy, mainly composed of many orientation factors called Cube orientation, Goss orientation, Brass orientation, Copper orientation, S orientation, etc. as shown in α phase (HCP) and β phase (BCC). A texture is formed and there is a crystal plane corresponding to them.
本発明においては、基本的に、各結晶面から±15°以内の方位のずれのものは同一の結晶面(方位因子)に属するものとする。また、隣り合う結晶粒の方位差が5°以上の結晶粒の境界を結晶粒界と定義する。 In the present invention, basically, deviations of orientation within ± 15 ° from each crystal face belong to the same crystal face (orientation factor). Further, a boundary between crystal grains in which the orientation difference between adjacent crystal grains is 5 ° or more is defined as a crystal grain boundary.
得られたチタン合金板の平均結晶径を測定した。これらの測定については、前記したように、FESEMにEBSPシステムを搭載した結晶方位解析法を用いて、チタン合金板の表面に平行な面であり、且つ、板厚方向の1/4t部の集合組織を測定して行った。具体的には、チタン合金板の圧延面表面を機械研磨し、更にバフ研磨に次いで電解研磨を行い、表面を調整した試料を準備した。その後、日本電子社製FESEM(JEOL JSM 5410)を用いて、EBSPによる結晶方位測定並びに結晶粒径測定を行った。測定領域は300μm×300μmの領域であり、測定ステップ間隔0.5μmとした。EBSP測定・解析システムは、EBSP:TSL社製(OIM)を用いた。 The average crystal diameter of the obtained titanium alloy plate was measured. For these measurements, as described above, using the crystal orientation analysis method in which the EBSP system is mounted on the FESEM, the surface is parallel to the surface of the titanium alloy plate and is a set of 1/4 t portions in the plate thickness direction. This was done by measuring the tissue. Specifically, the surface of the rolled surface of the titanium alloy plate was mechanically polished, followed by buffing and then electrolytic polishing to prepare a sample whose surface was adjusted. Thereafter, crystal orientation measurement and crystal grain size measurement by EBSP were performed using FESEM (JEOL JSM 5410) manufactured by JEOL Ltd. The measurement area was an area of 300 μm × 300 μm, and the measurement step interval was 0.5 μm. As the EBSP measurement / analysis system, EBSP: manufactured by TSL (OIM) was used.
上記の手法により測定範囲内のα、βの全結晶の方位を個別に同定し、各粒子の結晶粒径は円相当径を採用した。上記平均結晶粒径と平均結晶粒径の標準偏差は、以下に示す各数式から求めだした。すなわち、測定した結晶粒の数をn、夫々の測定した結晶粒径をxとしたときに、平均結晶粒径は、(Σx)/nという数式から、平均結晶粒径の標準偏差は、〔nΣx2−(Σx)2〕/〔n/(n−1)1/2〕という数式から求めた。また、各α相の長軸長さaおよび短軸長さbを求め、α相の平均アスペクト比は、Σ(a/b)/nという数式から求めた。 The orientations of all the crystals of α and β within the measurement range were individually identified by the above method, and the equivalent circle diameter was adopted as the crystal grain size of each particle. The average crystal grain size and the standard deviation of the average crystal grain size were obtained from the following formulas. That is, when the number of measured crystal grains is n and each measured crystal grain size is x, the average crystal grain size is expressed by the formula (Σx) / n, and the standard deviation of the average crystal grain size is [ nΣx 2 − (Σx) 2 ] / [n / (n−1) 1/2 ]. Further, the major axis length a and minor axis length b of each α phase were obtained, and the average aspect ratio of the α phase was obtained from the mathematical formula Σ (a / b) / n.
<強度、全伸びの測定>
得られた各チタン合金板からJISZ2201に規定される13号試験片を作製し、この試験片について、圧延方向の引張強度(TS)、圧延方向の全伸び、並びにr値(深絞り性)を測定した。このとき、試験速度(引張試験での歪み速度)は、0.2%耐力までを0.5%/min、それ以降を10%/minとした。
<Measurement of strength and total elongation>
A No. 13 test piece defined in JISZ2201 is prepared from each titanium alloy plate obtained, and the tensile strength (TS) in the rolling direction, the total elongation in the rolling direction, and the r value (deep drawability) are measured for this test piece. It was measured. At this time, the test speed (strain speed in the tensile test) was 0.5% / min up to 0.2% proof stress, and 10% / min thereafter.
この試験で得られた圧延方向の引張強度(TS)が、500MPa以上のものを高強度であると評価した。尚、r値は成形性に影響を与える因子であるが、ここでは、1.0以上のものを深絞り性に優れるとも判断した。(因みに、試験結果では全てr値は1.0以上となった。) When the tensile strength (TS) in the rolling direction obtained in this test was 500 MPa or more, it was evaluated as high strength. In addition, although r value is a factor which affects a moldability, it was also judged here that the thing of 1.0 or more is excellent in deep drawability. (By the way, in all the test results, the r value was 1.0 or more.)
<成形性(エリクセン値)の測定>
本実施例の試験では、成形性の評価にエリクセン試験を採用した。得られた各チタン合金板からJISZ2247に規定される2号試験片を作製し、この試験片について、JISZ2247の規定に準拠するエリクセン試験を実施し、エリクセン値を測定した。このとき、試験速度(エリクセン試験でのプレス速度すなわちプレス工具の変位速度)は、5mm/minとした。
<Measurement of formability (Ericsen value)>
In the test of this example, the Eriksen test was adopted for the evaluation of moldability. The No. 2 test piece prescribed | regulated to JISZ2247 was produced from each obtained titanium alloy plate, the Eriksen test based on the prescription | regulation of JISZ2247 was implemented about this test piece, and the Eriksen value was measured. At this time, the test speed (press speed in the Eriksen test, that is, the displacement speed of the press tool) was set to 5 mm / min.
この試験で得られたエリクセン値が、7.5以上のものを成形性に優れると評価した。 Those having an Erichsen value of 7.5 or more obtained in this test were evaluated as having excellent moldability.
以上の試験結果を表1に示す。 The test results are shown in Table 1.
試料No.2は、Feの含有量が請求項1で定めた上限に近い0.80質量%のもの、試料No.3は、Feの含有量が極めて低い0.02質量%のもの、試料No.4は、Oの含有量が請求項1で定めた上限に近い0.45質量%のもの、試料No.5は、Oの含有量が請求項1で定めた下限に近い0.11質量%のものである。 Sample No. No. 2 is a sample having a Fe content of 0.80% by mass, which is close to the upper limit defined in claim 1; 3 is 0.02% by mass with a very low Fe content. No. 4 is 0.45% by mass, the sample No. 0, whose O content is close to the upper limit defined in claim 1. No. 5 is 0.11 mass% in which the O content is close to the lower limit defined in claim 1.
また、試料No.6は、製造条件のうち冷間圧延の圧延率が下限の50%のもの、試料No.7は、製造条件のうち最終焼鈍の昇温速度が下限の5℃/sのもの、試料No.8は、製造条件のうち最終焼鈍温度が下限の700℃のもの、試料No.9は、製造条件のうち最終焼鈍の冷却速度が下限の5℃/sのものである。 Sample No. No. 6 has a lower rolling reduction ratio of 50% in the production conditions, sample No. No. 7 is the one in which the temperature increase rate of final annealing is 5 ° C./s, which is the lower limit among the production conditions. No. 8 has a final annealing temperature of 700 ° C., which is the lower limit among the production conditions. No. 9 is the 5 ° C./s lower limit of the cooling rate of the final annealing among the production conditions.
また、試料No.1と試料No.10は、それらの条件が上下限から離れた中間のものであり、特に試料No.10は、それらの条件がベストと考える条件のものである。 Sample No. 1 and sample no. No. 10 is an intermediate one in which these conditions depart from the upper and lower limits. 10 is a condition where those conditions are considered to be the best.
上記したように、これら試料No.1〜10は、本発明で規定する要件を全て満たすものであり、試験で得られた圧延方向の引張強度(TS)は、全て500MPa以上、エリクセン値は、全て7.5以上である。すなわち、本発明で規定する要件を満たすチタン合金板は、高強度で且つ成形性に優れたものであることが分かる。 As described above, these sample Nos. 1-10 satisfy | fills all the requirements prescribed | regulated by this invention, the tensile strength (TS) of the rolling direction obtained by the test is all 500 MPa or more, and the Erichsen values are all 7.5 or more. That is, it can be seen that a titanium alloy plate that satisfies the requirements defined in the present invention has high strength and excellent formability.
一方、試料No.11は、Feの含有量が請求項1で定めた上限を超える1.00質%のもの、試料No.12は、Oの含有量は請求項1で定めた上限の0.50質量%ではあるが、[O]<−0.4[Fe]+0.5という要件を外し、Oの含有量が多すぎるもの、試料No.13は、Oの含有量は請求項1で定めた下限以上の0.11質量%のではあるが、−0.4[Fe]+0.15<[O] という要件を外し、Oの含有量が少なすぎるものである。 On the other hand, sample No. No. 11 is a 1.00% by mass sample whose Fe content exceeds the upper limit defined in claim 1; No. 12, the O content is 0.50% by mass of the upper limit defined in claim 1, but the requirement of [O] <− 0.4 [Fe] +0.5 is removed, and the O content is large. Too much, sample no. 13, O content is 0.11% by mass above the lower limit defined in claim 1, but the requirement of −0.4 [Fe] +0.15 <[O] is removed, and the content of O Is too little.
また、試料No.14は、製造条件のうち冷間圧延の圧延率が下限未満の45%のもの、試料No.15は、製造条件のうち最終焼鈍の昇温速度が下限未満の3℃/sのもの、試料No.16は、製造条件のうち最終焼鈍温度が下限未満の650℃のもの、試料No.17は、製造条件のうち最終焼鈍温度が上限を超える900℃のもの、試料No.18は、製造条件のうち最終焼鈍の冷却速度が下限未満の3℃/sのものである。 Sample No. No. 14 is 45% of the production conditions where the rolling rate of the cold rolling is less than the lower limit. No. 15 is the one of 3 ° C./s with the heating rate of the final annealing less than the lower limit among the production conditions. No. 16 is one having a final annealing temperature of less than the lower limit of 650 ° C. among the production conditions. 17 is 900 ° C. whose final annealing temperature exceeds the upper limit among the production conditions. 18 is a thing of 3 degrees C / s whose cooling rate of the last annealing is less than a minimum among manufacturing conditions.
すなわち、これら試料No.11〜18は、本発明で規定する要件の何れかから外れるものであり、試験で得られた圧延方向の引張強度(TS)が500MPa未満であるか、エリクセン値が7.5未満である。すなわち、本発明で規定する要件から外れるチタン合金板は、高強度で且つ成形性に優れたものとはいえないことが分かる。 That is, these sample Nos. 11 to 18 deviate from any of the requirements defined in the present invention, and the tensile strength (TS) in the rolling direction obtained in the test is less than 500 MPa, or the Erichsen value is less than 7.5. That is, it can be seen that a titanium alloy plate that deviates from the requirements defined in the present invention cannot be said to have high strength and excellent formability.
Claims (2)
FeとOの含有量の関係が、−0.4[Fe]+0.15<[O]<−0.4[Fe]+0.5という要件を満たし、
更に、α相の平均アスペクト比が5以下、圧延方向の全伸びが20%以上であることを特徴とする高強度で成形性に優れたチタン合金板。
但し、上式で[ ]は、各元素の含有量(質量%)を示す。 Fe: 1.0% by mass or less, O: 0.1 to 0.5% by mass, the balance being Ti and inevitable impurities titanium alloy plate,
The relation between the contents of Fe and O satisfies the requirement of −0.4 [Fe] +0.15 <[O] <− 0.4 [Fe] +0.5,
Furthermore, the titanium alloy plate having high strength and excellent formability, characterized in that the average aspect ratio of the α phase is 5 or less and the total elongation in the rolling direction is 20% or more.
However, in the above formula, [] indicates the content (% by mass) of each element.
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