JP5625646B2 - Titanium plate excellent in rigidity in the rolling width direction and method for producing the same - Google Patents
Titanium plate excellent in rigidity in the rolling width direction and method for producing the same Download PDFInfo
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本発明は、チタン製のパイプ（特に長尺もの）やプレート式熱交換器に適した、圧延幅方向の剛性に優れたチタン板及びその製造方法に関するものである。 The present invention relates to a titanium plate suitable for titanium pipes (especially long ones) and plate heat exchangers and excellent in rigidity in the rolling width direction, and a method for producing the same.
チタン・チタン合金は、軽量、高強度、高耐食性といった特徴を有している。そのため、近年、この特徴を活用すべく、エネルギー・化学プラント、自動車、建材に加え、眼鏡やゴルフ用途をはじめとした民生品分野への適用拡大が進められている。 Titanium / titanium alloys have features such as light weight, high strength, and high corrosion resistance. Therefore, in recent years, in order to utilize this feature, in addition to energy / chemical plants, automobiles, and building materials, the application has been expanded to consumer products such as glasses and golf.
しかしながら、チタン・チタン合金を構造材料として使用する場合、ヤング率（剛性）が低いという問題がある。構造材料として広く用いられている鋼のヤング率は約２１０ＧＰａであるのに対し、チタンの常温におけるヤング率は、α相が主である工業用純チタンやα型チタン合金、α相とβ相からなるα＋β型チタン合金では、約１００〜１２０ＧＰａ、β相が主であるβ型チタン合金では約７０〜９０ＧＰａであり、鋼の約半分と非常に小さい。 However, when titanium / titanium alloy is used as a structural material, there is a problem that Young's modulus (rigidity) is low. The Young's modulus of steel, which is widely used as a structural material, is about 210 GPa, whereas the Young's modulus of titanium at room temperature is that of industrial pure titanium and α-type titanium alloys, mainly α-phase, α-phase and β-phase. The α + β-type titanium alloy made of the material is about 100 to 120 GPa, and the β-type titanium alloy mainly containing the β phase is about 70 to 90 GPa, which is as small as about half of steel.
そのため、チタン・チタン合金を構造材料として用いる場合、この剛性の低さを補うために、例えば、長尺な製品（薄板、パイプ）などでは、断面形状を大きく（太くしたり、厚くしたり）する必要がある。そのため、チタンの特徴の一つである軽量化の効果が得にくくなる。 Therefore, when titanium / titanium alloy is used as a structural material, for example, long products (thin plates, pipes) have a larger cross-sectional shape (thicker or thicker) in order to compensate for this low rigidity. There is a need to. For this reason, it is difficult to obtain the light weight effect which is one of the characteristics of titanium.
また、チタンにおいて、純チタンでは強度が不足する場合、より高強度を得るためＡｌ，Ｆｅ，Ｍｏ，Ｖ，Ｎｂといった元素を添加する。しかしながら、これら元素を添加すると、強度は上昇するが、（１）必要以上に高強度化すると延性が低下してしまい、成形性を損ねる、（２）Ｍｏ，Ｖ，Ｍｏといった比較的高価な添加元素を使用することによるコストが上昇する、（３）固溶強化元素であるＡｌを添加することによる熱間加工性の低下、といった問題がある。 In addition, in the case where the strength of titanium is insufficient with pure titanium, elements such as Al, Fe, Mo, V, and Nb are added to obtain higher strength. However, when these elements are added, the strength is increased, but (1) if the strength is increased more than necessary, the ductility is lowered and the formability is impaired. (2) Relatively expensive additions such as Mo, V, and Mo. There are problems such as an increase in cost due to the use of elements and a decrease in hot workability due to the addition of Al, which is a solid solution strengthening element.
このような状況下、近年、ヤング率を高めたチタン合金や低合金系のチタン合金、さらには集合組織を制御することにより特性を向上させたチタンが種々提案されている。特許文献１の面内異方性の小さいＴｉ−Ｆｅ−Ｏ−Ｎ系高強度チタン合金板、特許文献２のＦｅ：０．８％以上・２．５％以下およびＯ：０．０６％以下を含有し、残部がＴｉおよび不可避の不純物である曲げ性および張出性に優れたチタン合金板、特許文献３の一方向の圧延により得られた圧延板により構成され、その主圧延方向がゴルフフェースの横方向になるようにすることを特徴とするα＋β型チタン合金、特許文献４のＡｌ，Ｖ，Ｍｏなど合金化元素を添加することなく、優れた耐衝撃特性を有するチタン板がある。 Under such circumstances, various titanium alloys having a high Young's modulus, low alloy titanium alloys, and titanium having improved characteristics by controlling the texture have been proposed in recent years. Ti-Fe-ON-based high-strength titanium alloy plate with small in-plane anisotropy of Patent Document 1, Fe: 0.8% to 2.5% and O: 0.06% or less of Patent Document 2 In which the balance is Ti and an inevitable impurity, a titanium alloy plate excellent in bendability and stretchability, and a rolled plate obtained by rolling in one direction of Patent Document 3, the main rolling direction of which is golf There is an α + β-type titanium alloy characterized by being in the lateral direction of the face, and a titanium plate having excellent impact resistance characteristics without adding alloying elements such as Al, V, Mo of Patent Document 4.
チタン合金において、圧延幅方向への剛性に優れていれば、例えば圧延幅方向を長尺な製品（薄板、パイプ）の長手方向となるように成形することで、従来よりも断面形状を小さくしても、長手方向の剛性を確保することが可能である。
面内異方性の小さいＴｉ−Ｆｅ−Ｏ−Ｎ系高強度チタン合金板（特許文献１参照）は、安価な添加元素のみで構成されており低コストであり、且つ、固溶強化元素であるＡｌを使用していないため、特に、熱間加工性に優れている。しかしながら、クロス圧延等により内面異方性を低減させているため、圧延幅方向のヤング率は高くない。
If the titanium alloy has excellent rigidity in the rolling width direction, the cross-sectional shape can be made smaller than before by, for example, forming the rolling width direction to be the longitudinal direction of a long product (thin plate, pipe). However, it is possible to ensure the rigidity in the longitudinal direction.
A Ti—Fe—O—N-based high-strength titanium alloy plate with a small in-plane anisotropy (see Patent Document 1) is composed of only inexpensive additive elements, is low in cost, and is a solid solution strengthening element. Since some Al is not used, it is particularly excellent in hot workability. However, since the internal anisotropy is reduced by cross rolling or the like, the Young's modulus in the rolling width direction is not high.
Ｆｅ：０．８％以上・２．５％以下およびＯ：０．０６％以下を含有し、残部がＴｉおよび不可避の不純物である曲げ性および張出性に優れたチタン合金板は（特許文献２参照）、添加元素にＦｅやＯといった比較的安価な元素を使用しており非常に低コストであり、且つ、形成性に優れている。しかしながら、上記チタン合金同様に内面異方性が低いことから、圧延幅方向のヤング率は高くないと考えられる。また、Ｆｅを０．８〜２．５％も添加しており、偏析による材質の変化も懸念される。 A titanium alloy plate containing Fe: 0.8% to 2.5% and O: 0.06% or less, with the balance being Ti and inevitable impurities and excellent bendability and stretchability (Patent Documents) 2), a relatively inexpensive element such as Fe or O is used as the additive element, which is very low cost and excellent in formability. However, it is considered that the Young's modulus in the rolling width direction is not high because the internal anisotropy is low like the titanium alloy. Further, Fe is added in an amount of 0.8 to 2.5%, and there is a concern that the material changes due to segregation.
一方向の圧延により得られた圧延板により構成され、その主圧延方向がゴルフフェースの横方向になるようにすることを特徴とするα＋β型チタン合金（特許文献３参照）は、チタンの異方性を利用しており、圧延幅方向のヤング率がもっとも高い。しかしながら、Ｍｏ，Ｖ等の高価な金属を含むα＋β型チタン合金からなることから、製造コストが非常に高い、また、添加元素の偏析も懸念される。 An α + β type titanium alloy (see Patent Document 3), which is composed of a rolled plate obtained by rolling in one direction and whose main rolling direction is the lateral direction of the golf face, is an anisotropic of titanium. The Young's modulus in the rolling width direction is the highest. However, since it is made of an α + β type titanium alloy containing an expensive metal such as Mo or V, the production cost is very high, and there is a concern about segregation of additive elements.
Ａｌ，Ｖ，Ｍｏなど合金化元素を添加することなく、優れた耐衝撃特性を有するチタン板（特許文献４参照）は、Ｆｅ，Ｃｒ，Ｎｉとった比較的安価な添加元素を使用することにより低コストとし、且つ、集合組織を制御することにより耐衝撃特性を向上させている。しかしながら、９０°直交する少なくとも２方向にて圧延をしているため、内面異方性が小さくなる集合組織を形成しており、圧延幅方向へのヤング率は高くないと考えられる。 A titanium plate having excellent impact resistance without adding alloying elements such as Al, V, and Mo (see Patent Document 4) can be obtained by using relatively inexpensive additive elements such as Fe, Cr, and Ni. The impact resistance is improved by reducing the cost and controlling the texture. However, since rolling is performed in at least two directions orthogonal to 90 °, a texture is formed in which the internal anisotropy is small, and it is considered that the Young's modulus in the rolling width direction is not high.
本発明者は、低合金系にすることでコストの上昇や冷間加工性の低下を抑制しつつ、チタン板の圧延幅方向のヤング率を高めたチタン合金について、鋭意研究を重ねた。その結果、添加元素の含有量を調整するとともに、金属組織の集合組織においてα相の（０００１）面の法線と圧延面の法線とがなす角度を制御することで、圧延幅方向のヤング率を高めることができる知見を得た。 This inventor repeated earnest research about the titanium alloy which raised the Young's modulus of the rolling width direction of a titanium plate, suppressing the raise in cost and the fall of cold workability by using a low alloy system. As a result, by adjusting the content of additive elements and controlling the angle formed by the normal of the (0001) plane of the α phase and the normal of the rolled surface in the texture of the metal structure, the Young in the rolling width direction is controlled. The knowledge which can raise the rate was obtained.
上記課題を解決するために本発明の要旨は、以下の通りである。
（１）Ｆｅ、Ｃｒ、Ｎｉの１種以上を総含有量［％Ｆｅ］＋［％Ｃｒ］＋［％Ｎｉ］で０．２５０質量％以上０．７５０質量％以下、Ｏ、Ｎ、Ｃの１種以上を総含有量［％Ｏ］＋［％Ｎ］＋［％Ｃ］で０．０３０質量％以上０．４００質量％以下、且つ、Ｃの含有量を０．０５質量％以下とし、残部がＴｉ及び不可避的な不純物からなるチタン板であって、
圧延面の法線方向をＮＤ方向、圧延方向をＲＤ方向、圧延幅方向をＴＤ方向とし、α相の（０００１）面の法線方向をＣ軸方位として、Ｃ軸方位がＮＤ方向となす角度をθ、Ｃ軸方位とＮＤ方向を含む面がＮＤ方向とＴＤ方向を含む面となす角度をφとし、
圧延面より法線方向からのα相の（０００１）面極点図において、角度θが４０°未満である結晶粒の総面積をＡとし、角度θが７０°以上１１０°以下で角度φが±２０°の範囲内である結晶粒の総面積をＢとし、面積比Ｂ／Ａが１以上であることを特徴とする圧延幅方向の剛性に優れたチタン板。
（２）上記面積比Ｂ／Ａが３以上であることを特徴とする上記（１）に記載の圧延幅方向の剛性に優れたチタン板。
（３）さらに、Ｎｂ，Ｖ，Ｍｏ，Ｃｕのうち１種以上をそれぞれ０．２質量％以上１．５質量％以下含有する、上記（１）又は（２）に記載の圧延幅方向の剛性に優れたチタン板。
（４）さらに、Ｓｉを０．２質量％以上１．０質量％以下含有する、上記（１）〜（３）の何れか１項に記載の圧延幅方向の剛性に優れたチタン板。
（５）熱間圧延素材をβ変態点＋２０〜１２０℃に加熱した後、β変態点−７０℃以上の温度域にて圧下率５０％以上で一方向に熱間圧延することを特徴とする、上記（１）〜（４）の何れか１項に記載の圧延幅方向の剛性に優れたチタン熱延板の製造方法。
（６）熱間圧延素材をβ変態点＋２０〜１２０℃に加熱した後、β変態点−７０℃以上の温度域にて圧下率５０％以上で一方向に熱間圧延し、更に、一方向の熱間圧延した板をそのまま又は焼鈍した後、熱間圧延と同じ方向へ圧下率４０％以下で冷間圧延し、その後に焼鈍する冷間圧延・焼鈍工程を、少なくとも一回以上実施することを特徴とする、上記（１）〜（４）の何れか１項に記載の圧延幅方向の剛性に優れたチタン冷延板の製造方法。
（７）上記（１）〜（４）の何れか１項に記載のチタン板を用いて、板のＴＤ方向がパイプの長手方向となるように成形し、溶接することを特徴とするチタン製パイプの製造方法。
In order to solve the above problems, the gist of the present invention is as follows.
(1) One or more of Fe, Cr, and Ni in a total content of [% Fe] + [% Cr] + [% Ni] of 0.250 mass% or more and 0.750 mass% or less, O, N, and C One or more types with a total content [% O] + [% N] + [% C] of 0.030% by mass to 0.400% by mass, and the C content is 0.05% by mass or less, The balance is a titanium plate made of Ti and inevitable impurities,
The normal direction of the rolling surface is the ND direction, the rolling direction is the RD direction, the rolling width direction is the TD direction, the normal direction of the (0001) plane of the α phase is the C axis direction, and the C axis direction is the angle with the ND direction. Is θ, and the angle between the plane including the C axis direction and the ND direction and the plane including the ND direction and the TD direction is φ,
In the (0001) plane pole figure of the α phase from the normal direction to the rolled surface, the total area of crystal grains having an angle θ of less than 40 ° is A, the angle θ is 70 ° to 110 °, and the angle φ is ± A titanium plate excellent in rigidity in the rolling width direction, characterized in that the total area of crystal grains within a range of 20 ° is B and the area ratio B / A is 1 or more.
(2) The titanium plate having excellent rigidity in the rolling width direction according to (1), wherein the area ratio B / A is 3 or more.
(3) Further, the rigidity in the rolling width direction according to (1) or (2) above, wherein one or more of Nb, V, Mo, and Cu are contained in an amount of 0.2% by mass to 1.5% by mass, respectively. Excellent titanium plate.
(4) The titanium plate having excellent rigidity in the rolling width direction according to any one of (1) to (3), further including Si in an amount of 0.2% by mass to 1.0% by mass.
(5) The hot-rolled material is heated to a β transformation point +20 to 120 ° C., and then hot-rolled in one direction at a reduction rate of 50% or more in a temperature range of β transformation point −70 ° C. or more. The manufacturing method of the titanium hot-rolled sheet excellent in the rigidity of the rolling width direction of any one of said (1)-(4).
(6) After the hot-rolled material is heated to the β transformation point +20 to 120 ° C., it is hot-rolled in one direction at a reduction rate of 50% or more in the temperature range of the β transformation point −70 ° C. or more, and further in one direction. After performing the hot-rolled sheet as it is or after annealing, it is cold-rolled in the same direction as hot rolling at a reduction of 40% or less, and then the cold-rolling / annealing process is performed at least once. The manufacturing method of the titanium cold-rolled sheet excellent in the rigidity of the rolling width direction of any one of said (1)-(4) characterized by these.
(7) Using the titanium plate according to any one of (1) to (4) above, the titanium plate is formed and welded so that the TD direction of the plate is the longitudinal direction of the pipe. Pipe manufacturing method.
本発明によって、冷間加工性の低下やコストの上昇を抑制したまま、圧延幅方向の剛性に優れたチタン合金を提供できるため、産業上の効果は計り知れない。 According to the present invention, it is possible to provide a titanium alloy having excellent rigidity in the rolling width direction while suppressing a decrease in cold workability and an increase in cost, and thus industrial effects are immeasurable.
以下に、本発明について詳しく説明する。以降、添加元素の含有量は「質量％」で示す。 The present invention is described in detail below. Hereinafter, the content of the additive element is indicated by “mass%”.
本発明の材料指標について説明する。チタンに限らず金属材料において結晶構造の向き（結晶方位）によりヤング率は大きく変化する。通常、構造材料として用いられる金属材料は、多結晶体からなっており、その集合組織がヤング率に大きく影響する。そこで、本発明者は、この集合組織を制御することにより、圧延幅方向のヤング率を高めることを指標とした。また、添加元素を多量に添加した高合金系としてしまうと、製造コストの上昇や、熱間、冷間での製造性・成形性が劣化してしまうため、低合金系であることを指標とした。 The material index of the present invention will be described. The Young's modulus varies greatly depending on the direction of crystal structure (crystal orientation) not only in titanium but also in metal materials. Usually, a metal material used as a structural material is made of a polycrystal, and its texture greatly affects the Young's modulus. Therefore, the present inventor made an index to increase the Young's modulus in the rolling width direction by controlling the texture. In addition, if a high alloy system is added with a large amount of additive elements, the manufacturing cost will increase, and hot and cold manufacturability and formability will deteriorate. did.
［集合組織］
ヤング率はその材料や結晶構造ごとのみならず、結晶方位分布（集合組織）により変化する。常温におけるチタンの金属組織はＨＣＰ（Hexagonal Close Packed Structure）構造であるα相からなる。このＨＣＰ構造において、六角柱底面に対し法線方向と平行方向ではヤング率が異なることが知られており、平行方向に比べ法線方向の方がヤング率は高い。例えば、単結晶の場合、六角柱底面に対し法線方向に試料を切り出せば、六角柱底面に対し平行方向に切出した場合よりもヤング率の高い素材が得られる。
[Organization]
The Young's modulus varies not only with the material and crystal structure, but also with the crystal orientation distribution (texture). The metal structure of titanium at room temperature consists of an α phase having an HCP (Hexagonal Close Packed Structure) structure. In this HCP structure, it is known that the Young's modulus is different between the normal direction and the parallel direction with respect to the hexagonal column bottom surface, and the Young's modulus is higher in the normal direction than in the parallel direction. For example, in the case of a single crystal, if a sample is cut in a normal direction with respect to the hexagonal column bottom surface, a material having a higher Young's modulus can be obtained than when a sample is cut in a direction parallel to the hexagonal column bottom surface.
しかしながら、通常、構造材料として用いられるチタンは多結晶体からなる。そのため、多結晶材料では集合組織が、ヤング率に大きく影響する。ここで、集合組織とは、多結晶材において、ある特定の結晶方位に結晶粒が集中的に配向した状態である。各々の結晶粒が有する結晶方位がランダム、すなわち集合組織がランダムな場合、ヤング率は全ての平均値を取ることとなり、通常のチタン材料と同等となる。しかし、集合組織がある一定方向に集積した場合、単結晶に近いヤング率の特性を示すこととなる。つまり、六角柱底面の法線方向が圧延幅方向に対し平行した方向に集合組織が集積すれば、圧延幅方向のヤング率を高めることが出来る。ここで、α相の六角柱底面の法線方向は、α相の（０００１）面の法線方向と言い換えることができる。α相の（０００１）面の法線方向をここでは「Ｃ軸方位」と呼ぶ。 However, usually, titanium used as a structural material is made of a polycrystal. Therefore, in a polycrystalline material, the texture greatly affects the Young's modulus. Here, the texture is a state in which polycrystalline grains are concentrated in a specific crystal orientation in a polycrystalline material. When the crystal orientation of each crystal grain is random, that is, when the texture is random, the Young's modulus takes all average values, which is equivalent to a normal titanium material. However, when the texture is accumulated in a certain direction, a Young's modulus characteristic close to that of a single crystal is exhibited. That is, if the texture is accumulated in a direction in which the normal direction of the hexagonal column bottom surface is parallel to the rolling width direction, the Young's modulus in the rolling width direction can be increased. Here, the normal direction of the bottom surface of the hexagonal prism of the α phase can be rephrased as the normal direction of the (0001) plane of the α phase. The normal direction of the (0001) plane of the α phase is referred to herein as “C-axis orientation”.
そこで、まず、集合組織の指標を検討した。その結果、圧延面の法線方向からのα相の（０００１）面極点図における、ある結晶方位を有する結晶粒の面積比を用いることが、集合組織の指標として用いるのに比較的容易であることを見出した。ここで、圧延面の法線方向をＮＤ（Nominal Direction）方向、圧延方向をＲＤ（Rolling Direction）方向、圧延幅方向をＴＤ（Transverse Direcion）方向とする。そして、圧延面より法線方向からのα相の（０００１）面極点図において、結晶粒のＣ軸方位を球極座標（θ、φ）で表す。即ち、図２（ａ）に示すように、Ｃ軸方位がＮＤ方向となす角度をθ、Ｃ軸方位とＮＤ方向を含む面１１がＮＤ方向とＴＤ方向を含む面１２となす角度をφとする。ここにおいて、図２（ｂ）のハッチング部に示すように、Ｃ軸方位とＮＤ方向とのなす角度θが４０°未満である結晶粒の総面積をＡとする。また、図２（ｃ）のハッチング部に示すように、Ｃ軸方位とＮＤ方向とのなす角度θが７０°以上１１０°以下であって、前記角度φが±２０°の範囲内の結晶粒の総面積をＢとする。このとき、面積比Ｂ／Ａが１以上になると、圧延方向や厚み方向に比べ、圧延幅方向のヤング率が高くなることを見出した。好ましくは、上記面積比Ｂ／Ａが３以上である。 Therefore, we first examined the index of texture. As a result, it is relatively easy to use the area ratio of the crystal grains having a certain crystal orientation in the (0001) plane pole figure of the α phase from the normal direction of the rolled surface as an index of the texture. I found out. Here, the normal direction of the rolling surface is the ND (Nominal Direction) direction, the rolling direction is the RD (Rolling Direction) direction, and the rolling width direction is the TD (Transverse Direcion) direction. And in the (0001) plane pole figure of (alpha) phase from a normal line direction from a rolling surface, the C-axis orientation of a crystal grain is represented by a spherical pole coordinate ((theta), (phi)). That is, as shown in FIG. 2A, the angle formed by the C-axis azimuth with the ND direction is θ, and the angle formed by the surface 11 including the C-axis azimuth and the ND direction with the surface 12 including the ND and TD directions is φ. To do. Here, as shown in the hatched portion in FIG. 2B, the total area of crystal grains in which the angle θ between the C-axis orientation and the ND direction is less than 40 ° is A. In addition, as shown in the hatched portion of FIG. 2C, an angle θ formed between the C-axis orientation and the ND direction is 70 ° or more and 110 ° or less, and the angle φ is within a range of ± 20 °. Let B be the total area. At this time, it was found that when the area ratio B / A was 1 or more, the Young's modulus in the rolling width direction was higher than that in the rolling direction or the thickness direction. Preferably, the area ratio B / A is 3 or more.
一般に、集合組織を測定する方法としては、Ｘ線回折法やＥＢＳＰ（Electron Back Scattered Diffraction Pattern）等がある。本発明では、集合組織の指標として、特定結晶方位を有する結晶粒の面積比を用いていることから、それに最も適したＥＢＳＰ法により測定すると好ましい。このＥＢＳＰ法は、試料に電子ビームを照射し、反射電子により得られる菊池パターンを高感度カメラで撮影し、菊池パターンを解析することにより、各結晶粒の結晶方位を容易に測定することが出来る手法である。この手法は、数百μｍから数ｍｍ範囲を測定することが出来、観察視野が非常に広く、また、測定時間が数分から数十分程度で測定可能である。そのため、広範囲にわたる結晶方位や結晶粒径等を得ることができる。なお、本発明の集合組織については、Ｘ線回折法でも容易に測定することが出来る。 In general, methods for measuring texture include X-ray diffraction, EBSP (Electron Back Scattered Diffraction Pattern), and the like. In the present invention, since the area ratio of crystal grains having a specific crystal orientation is used as the texture index, it is preferable to measure by the EBSP method most suitable for it. This EBSP method can easily measure the crystal orientation of each crystal grain by irradiating a sample with an electron beam, photographing a Kikuchi pattern obtained by reflected electrons with a high sensitivity camera, and analyzing the Kikuchi pattern. It is a technique. This method can measure a range of several hundred μm to several mm, has a very wide observation field, and can be measured with a measurement time of several minutes to several tens of minutes. Therefore, a wide range of crystal orientations and crystal grain sizes can be obtained. Note that the texture of the present invention can be easily measured by X-ray diffraction.
図１に圧延面の法線方向からのＥＢＳＰ測定結果の一例を示す。図１−１（ａ）はＥＢＳＰ測定結果であり、図１−２（ｂ）はＣ軸方位とＮＤ方向とのなす角度θが４０°未満である結晶粒の存在領域を示し、図１−２（ｃ）はＣ軸方位とＮＤ方向とのなす角度θが７０°以上１１０°以下であって、Ｃ軸方位とＮＤ方向を含む面１１がＮＤ方向とＴＤ方向を含む面１２となす角度φが±２０°の範囲内の結晶粒の存在領域を示す。図１−２（ｂ）（ｃ）のいずれも、黒く塗り潰された領域が対象外の結晶領域であり、グレー又は白色の領域が対象とする結晶の存在領域である。図に示すように、ＥＢＳＰでは付属する解析ソフトを使用することにより、簡単に圧延面より法線方向からの（０００１）面極点図において、角度θが４０°未満である結晶粒および、角度θが７０°以上１１０°以下であって角度φが±２０°の範囲内の結晶粒に分離することが出来る。このデータを画像解析することにより、特定の結晶方位を有する結晶粒の総面積を求めることができ、面積比Ｂ／Ａを容易に求めることが出来る。 FIG. 1 shows an example of the EBSP measurement result from the normal direction of the rolled surface. 1-1 (a) shows the EBSP measurement results, and FIG. 1-2 (b) shows the existence region of crystal grains in which the angle θ formed between the C-axis orientation and the ND direction is less than 40 °. 2 (c) is an angle θ between the C axis azimuth and the ND direction is 70 ° or more and 110 ° or less, and an angle formed by the surface 11 including the C axis azimuth and the ND direction with the surface 12 including the ND direction and the TD direction. A region where crystal grains exist within a range of φ of ± 20 ° is shown. In each of FIGS. 1-2 (b) and (c), the blacked out region is a non-target crystal region, and the gray or white region is a target crystal existing region. As shown in the figure, in EBSP, by using the attached analysis software, in the (0001) plane pole figure from the normal direction from the rolling surface, the crystal grains having an angle θ of less than 40 ° and the angle θ Can be separated into crystal grains in a range of 70 ° to 110 ° and an angle φ of ± 20 °. By analyzing the image of this data, the total area of crystal grains having a specific crystal orientation can be obtained, and the area ratio B / A can be easily obtained.
［Ｆｅ、Ｎｉ、Ｃｒの添加量］
上述したように集合組織を制御し、圧延幅方向のヤング率を高めるためには、β単相域もしくはα＋βの２相高温域に加熱し、β相の割合が多くなる温度領域で熱間圧延を行う必要がある。工業用純チタンはＦｅやＯといった不純物元素を有しており、β変態点近傍で僅かに２相領域が存在するものの、その温度範囲は非常に狭く、狙いとする集合組織を得ることは難しい。そこで本発明では、α＋βの２相領域を広げることにより、目的とする集合組織を形成しやすくするため、β変態点近傍でα＋βの２相領域を広げる効果があり、且つ、比較的安価な元素であるＦｅ、Ｃｒ、Ｎｉの１種以上を用いることとした。添加元素量が少なすぎるとα＋βの２相領域が狭くなり、目的とする集合組織が得られなくなることから、これら元素の総含有量［％Ｆｅ］＋［％Ｃｒ］＋［％Ｎｉ］の下限を０．２５％とした。α＋βの２相領域を安定的に得るためには、好ましくは０．２８７％であり、更に好ましくは０．２９０％である。一方、添加量が多くなりすぎると偏析の問題や、強度が必要以上に高くなり、成形性が低下することから好ましくない。そこで、本発明ではこれら元素の総添加量の上限を０．７５％とした。安定的な成形性を得るためには好ましくは、０．６１５％であり、更に好ましくは０．６１０％である。なお、Ｆｅ、Ｎｉ、Ｃｒは金属チタンもしくはスポンジチタンを製造する際の反応容器等から混入する不可避的不純物であり、通常用いられる原料と製造方法を適用した場合、不可避不純物としてこれら元素をそれぞれ０．００１〜０．００２％程度含有している。また例え、高純度化したチタンを原料として用いても含有が避けられない。高純度純チタンにおいてもこれらの元素を約０．０００１％程度含有していることから、実質的な含有量の下限値は、いずれも０．０００１％以上である。
[Fe, Ni, Cr addition amount]
As described above, in order to control the texture and increase the Young's modulus in the rolling width direction, the steel is heated to a β single phase region or a two-phase high temperature region of α + β, and hot rolled in a temperature region where the proportion of β phase increases. Need to do. Industrial pure titanium has impurity elements such as Fe and O, and although there are only two phase regions near the β transformation point, its temperature range is very narrow, and it is difficult to obtain the target texture. . Therefore, in the present invention, by expanding the α + β two-phase region, the target texture can be easily formed. Therefore, there is an effect of expanding the α + β two-phase region in the vicinity of the β transformation point, and a relatively inexpensive element. One or more of Fe, Cr, and Ni that are: If the amount of the added element is too small, the two-phase region of α + β becomes narrow and the target texture cannot be obtained. Therefore, the lower limit of the total content [% Fe] + [% Cr] + [% Ni] of these elements Was 0.25%. In order to stably obtain the α + β two-phase region, the content is preferably 0.287%, and more preferably 0.290%. On the other hand, if the amount added is too large, the problem of segregation, the strength becomes higher than necessary, and the moldability is lowered, which is not preferable. Therefore, in the present invention, the upper limit of the total amount of these elements is set to 0.75%. In order to obtain stable moldability, the content is preferably 0.615%, and more preferably 0.610%. Fe, Ni, and Cr are unavoidable impurities mixed from a reaction vessel or the like when producing titanium metal or sponge titanium, and when the commonly used raw materials and production methods are applied, these elements are each 0 as unavoidable impurities. About 0.001 to 0.002%. For example, the use of highly purified titanium as a raw material is inevitable. High purity pure titanium also contains about 0.0001% of these elements, so the lower limit of the substantial content is 0.0001% or more.
［Ｏ、Ｎ、Ｃの添加量］
Ｏ，Ｎ，Ｃは主に不純物として混入する元素である。これら元素の含有量が増加することで強度を高めことができる。また、上記元素と同様にα＋βの２相粒領域を大きくすることが出来る。これらの効果を得るためには、これら元素の総含有量［％Ｏ］＋［％Ｎ］＋［％Ｃ］で０．０３０％以上含有する必要があることから、これを下限とした。しかしながら、総含有量で０．４００％を超えると、上記元素と同様に強度が必要以上に高くなり、成形性が著しく低下するので好ましくない。よって本発明では、上限を０．４００％とした。好ましくは、０．３００％であり、更に好ましくは０．２５０％である。チタン製造の原料によって不可避不純物のみでＯ、Ｎ、Ｃの総含有量が上記本発明範囲に入る場合には、積極的にこれら元素を添加する必要はない。また、不可避不純物のみでは上記本発明範囲に入らない場合には、Ｏ、Ｎ、Ｃのうち１元素以上を添加することによって本発明範囲とすればよい。なお、Ｃについては少量であっても室温延性、冷間加工性、熱間加工性を低下させてしまう場合があり、Ｃが０．０５％未満であれば、問題ないレベルであることを見出し、本発明ではこれを上限とした。また、Ｏ，Ｎ，Ｃは、上記Ｆｅ，Ｃｒ，Ｎｉ同様、いずれもスポンジチタンを製造する上で不可避的不純物であり、含有が避けられない。従って、実質的な含有量の下限値は、それぞれ、Ｏで０．００５％以上、Ｎで０．００１％以上、Ｃで０．００１％以上である。
[Addition amounts of O, N and C]
O, N, and C are elements mainly mixed as impurities. The strength can be increased by increasing the content of these elements. Further, similarly to the above element, the α + β two-phase grain region can be enlarged. In order to acquire these effects, since it is necessary to contain 0.030% or more in total content [% O] + [% N] + [% C] of these elements, this was made into the minimum. However, if the total content exceeds 0.400%, the strength becomes unnecessarily high as in the case of the above elements, and the moldability is remarkably deteriorated. Therefore, in the present invention, the upper limit was made 0.400%. Preferably, it is 0.300%, more preferably 0.250%. When the total content of O, N, and C falls within the scope of the present invention with only inevitable impurities depending on the raw material for titanium production, it is not necessary to positively add these elements. Further, when the inevitable impurities alone do not fall within the scope of the present invention, one or more elements of O, N, and C may be added to make the scope of the present invention. It should be noted that even if the amount of C is small, room temperature ductility, cold workability, and hot workability may be deteriorated. If C is less than 0.05%, it is found that there is no problem level. In the present invention, this is the upper limit. Further, O, N, and C are unavoidable impurities for producing sponge titanium, as in the case of Fe, Cr, and Ni. Therefore, the lower limit value of the substantial content is 0.005% or more for O, 0.001% or more for N, and 0.001% or more for C, respectively.
［β安定化元素］
β安定化元素であるＮｂ、Ｖ、Ｍｏ、Ｃｕは上述のＦｅ、Ｃｒ、Ｎｉと同様にα＋βの２相領域を広げる効果がある。これら元素を含有させる場合、含有量が少ないと効果が得られないことから、下限をそれぞれ０．２％とした。しかし添加量が多くなりすぎると、上述の元素同様に強度が高くなり、成形性が低下することや凝固偏析の影響が大きくなるため、上限をそれぞれ１．５％とした。
[Β-stabilizing element]
The β-stabilizing elements Nb, V, Mo, and Cu have the effect of expanding the α + β two-phase region in the same manner as the above-described Fe, Cr, and Ni. When these elements are contained, the effect cannot be obtained if the content is small, so the lower limit was set to 0.2%. However, if the amount added is too large, the strength increases as in the case of the above-described elements, and the moldability deteriorates and the influence of solidification segregation increases, so the upper limit was made 1.5%.
［Ｓｉ］
Ｓｉは多量に含有すると室温延性、冷間加工性、熱間加工性を低下させてしまう場合がある。しかしながら、Ｓｉを適量添加することにより、α＋βの２相領域でシリサイド析出物を残存させることができ、目標とする集合組織を形成しやすくなる。Ｓｉの効果を得るためには必要に応じて０．２％以上添加する。しかしながら、Ｓｉを１．０％以上添加すると、冷間加工性が急激に劣化することから、これを上限とした。
[Si]
If Si is contained in a large amount, room temperature ductility, cold workability, and hot workability may be deteriorated. However, by adding an appropriate amount of Si, silicide precipitates can remain in the α + β two-phase region, and a target texture can be easily formed. In order to obtain the effect of Si, 0.2% or more is added as necessary. However, if Si is added in an amount of 1.0% or more, the cold workability deteriorates rapidly, so this was made the upper limit.
［熱間圧延］
上述したように目的とする集合組織を得るためには、β相単相領域もしくはα＋β相の高温領域で多くの圧下率で熱延をする必要がある。β単相もしくはα＋β高温領域であるβ変態点−７０℃以上までに圧下率５０％以上で、且つ、一方向の熱間圧延を行えば、目的とする集合組織を得ることができる。さらに好ましくは、７０％以上の圧下率である。なお、圧下率とは、圧延前と圧延後の厚みの差を圧延前の素材厚みで割った値である。この圧下率５０％までをβ変態点−７０℃以上の温度で行うためには、熱間圧延時にβ変態点＋２０℃以上まで加熱すれば問題ないことから、これを下限とした。一方、高温に加熱しすぎると、熱間加熱時に結晶粒径が大きくなり過ぎたり、スラブ表面の酸化が著しく進行することから、上限をβ変態点＋１２０℃とした。なお、β変態点については示唆熱分析等で求めることが出来る。
[Hot rolling]
As described above, in order to obtain the target texture, it is necessary to perform hot rolling at a large reduction rate in a β-phase single phase region or a high temperature region of α + β phase. The target texture can be obtained by carrying out hot rolling in one direction with a reduction rate of 50% or more up to a β transformation point of −70 ° C. or higher in the β single phase or α + β high temperature region. More preferably, the rolling reduction is 70% or more. The rolling reduction is a value obtained by dividing the difference in thickness before and after rolling by the thickness of the material before rolling. In order to perform the rolling reduction of up to 50% at a temperature of β transformation point of −70 ° C. or higher, there is no problem if heating is performed to the β transformation point of + 20 ° C. or higher during hot rolling. On the other hand, if the temperature is too high, the crystal grain size becomes too large during hot heating and the slab surface oxidation proceeds remarkably, so the upper limit was made β transformation point + 120 ° C. The β transformation point can be obtained by suggestion thermal analysis or the like.
［冷間圧延］
板を製造する場合、必要に応じて焼鈍により歪を取り除いた後、冷間圧延により板厚を調整する必要がある。熱間圧延と同一方向に冷間圧延をする場合、圧下率が大きくなると、α相の集合組織が、ＨＣＰの（０００１）面の法線方向がＮＤ方向からＴＤ方向に３０°方向傾いた位置に変化する。そのため、上記の面積比Ｂ／Ａが１より小さくなり、圧延幅方向のヤング率が低下する。冷延時の圧下率について検討した結果、４０％以下の圧下率であれば、上記の面積比Ｂ／Ａを１以上にすることができ、圧延幅方向のヤング率を高めることが出来る。さらに好ましくは、３０％以下の圧下率である。なお、４０％以上の圧下率が必要な場合は、その都度、焼鈍工程を追加すれば、集合組織の変化を抑制することが出来る。
[Cold rolling]
When manufacturing a plate, it is necessary to adjust the plate thickness by cold rolling after removing the strain by annealing as necessary. When cold rolling is performed in the same direction as hot rolling, when the rolling reduction increases, the α phase texture is a position where the normal direction of the (0001) plane of HCP is inclined by 30 ° from the ND direction to the TD direction. To change. Therefore, said area ratio B / A becomes smaller than 1, and the Young's modulus in the rolling width direction decreases. As a result of examining the rolling reduction during cold rolling, if the rolling reduction is 40% or less, the area ratio B / A can be set to 1 or more, and the Young's modulus in the rolling width direction can be increased. More preferably, the rolling reduction is 30% or less. In addition, when the rolling reduction of 40% or more is required, if an annealing process is added each time, the change of a texture can be suppressed.
［パイプの製造方法］
上述したように、チタン・チタン合金は剛性が低く、それを補うために長尺な製品（薄板、パイプ）などでは、剛性を補うために断面形状を大きくする必要がある。しかし、本発明のチタン合金は、圧延幅方向への剛性に優れている。従って、圧延幅方向をパイプの長手方向となるように成形することで、従来よりも断面形状を小さくしても、長手方向の剛性を確保することが可能である。なお、パイプのみに限らず、剛性を確保した方向を圧延幅方向になるように成形することで、他形状の製品においても、剛性を確保することが出来る。
[Pipe manufacturing method]
As described above, titanium / titanium alloy has low rigidity, and a long product (thin plate, pipe) or the like needs to have a large cross-sectional shape in order to supplement rigidity. However, the titanium alloy of the present invention is excellent in rigidity in the rolling width direction. Accordingly, by forming the rolling width direction to be the longitudinal direction of the pipe, it is possible to ensure the rigidity in the longitudinal direction even if the cross-sectional shape is made smaller than before. In addition, not only a pipe but the shape which ensured rigidity became the rolling width direction, and it can also ensure rigidity also in products of other shapes.
表１に本発明のチタン合金の組成およびβ変態温度を示す。各成分系について真空アーク溶解によりチタン合金インゴットを作製した。ここにおいて、本発明例Ｎｏ．１〜６については高純度の原料を用いて溶解を行った。そして、Ｆｅ、Ｃｒ、Ｎｉについては、Ｎｏ．１〜３は３元素とも添加、Ｎｏ．４はＦｅのみ、Ｎｏ．５はＣｒのみ、Ｎｏ．６はＮｉのみを積極的に添加している。Ｏ、Ｎ、Ｃについては、Ｎｏ．１はＮ、Ｃを添加、Ｎｏ．２はＯ、Ｃを添加、Ｎｏ．３はＯ、Ｎを添加、Ｎｏ．４〜６はＯ、Ｎ、Ｃを添加している。本発明例Ｎｏ．７〜１１については通常の原料を用いて溶解を行ったものであり、これらのうちで不可避不純物レベルにあるのはＮｏ．９のＣｒ、及びＮｏ．１１のＮｉである。Ｎｏ．１〜１１において、「−」と表示されている元素は積極的に添加していないことを示す。 Table 1 shows the composition and β transformation temperature of the titanium alloy of the present invention. Titanium alloy ingots were prepared for each component system by vacuum arc melting. Here, the present invention example No. About 1-6, it melt | dissolved using the raw material of high purity. And about Fe, Cr, and Ni, no. 1 to 3 are added for all three elements. 4 is Fe only. No. 5 is Cr only. 6 is actively adding only Ni. For O, N and C, no. No. 1 added N, C; No. 2 added O and C, No. 2 No. 3 added O and N. In 4-6, O, N, and C are added. Invention Example No. About 7-11, it melt | dissolved using a normal raw material, and it is No. which is in an inevitable impurity level among these. 9 Cr, and No. 9 11 Ni. No. 1 to 11 indicate that the element indicated by “−” is not actively added.
これらインゴットを熱間鍛造し、熱延用素材を作製した。この素材をβ変態点＋２０℃〜＋１２０℃の温度に大気雰囲気で加熱した後、熱間圧延した。なお、熱延時の温度は放射温度計により測定し、β変態点−７０℃になった時の圧下率は圧延のロール間の距離により測定した。熱間圧延時の加熱温度、β変態点−７０℃になった時の圧下率、及び熱間圧延後の熱延板についての圧延方向及び圧延幅方向のヤング率を表２に示す。この熱間圧延条件では表２のＮｏ．１２〜２２のいずれのチタン合金においても、β変態点−７０℃の時点での圧下率は５０％以上である。一方、表２のＮｏ．２３は、熱間圧延において、熱間加熱温度がβ変態点−２０℃より低く、それに伴い、β変態点−７０℃の時点での圧下率は５０％未満である。
These ingots were hot forged to produce hot rolling materials. This material was heated in the air atmosphere to a β transformation point + 20 ° C. to + 120 ° C., and then hot-rolled. The temperature at the time of hot rolling was measured by a radiation thermometer, and the rolling reduction when the β transformation point was −70 ° C. was measured by the distance between rolling rolls. Table 2 shows the heating temperature at the time of hot rolling, the reduction ratio when the β transformation point is -70 ° C, and the Young's modulus in the rolling direction and the rolling width direction of the hot-rolled sheet after hot rolling. In this hot rolling condition, No. 2 in Table 2 was obtained. In any of the titanium alloys of 12 to 22, the rolling reduction at the time of the β transformation point of −70 ° C. is 50% or more. On the other hand, no. No. 23, in hot rolling, the hot heating temperature is lower than the β transformation point −20 ° C., and accordingly, the rolling reduction at the time of the β transformation point −70 ° C. is less than 50%.
また、表２の熱間圧延後の素材を用いて、冷間圧延を実施した。一回当たりの最大圧下率、焼鈍回数、冷間加工後の圧延方向及び圧延幅方向のヤング率を表３に示す。表３のＮｏ．２３〜３４のいずれのチタン合金も、冷間圧延条件において、一回当たりの最大圧下率は４０％以下である。一方、表３のＮｏ．３５は、冷間圧延において、一回当たりの圧下率が４０％超である。表２及び表３において、本発明範囲から外れる数値にアンダーラインを付している。 Moreover, cold rolling was implemented using the raw material after hot rolling of Table 2. Table 3 shows the maximum rolling reduction per time, the number of annealing times, the Young's modulus in the rolling direction and the rolling width direction after cold working. No. in Table 3 In any of the titanium alloys 23 to 34, the maximum rolling reduction per one time is 40% or less under the cold rolling conditions. On the other hand, no. No. 35 has a rolling reduction rate of more than 40% per time in cold rolling. In Tables 2 and 3, numerical values outside the scope of the present invention are underlined.
ＥＢＳＰ測定用の試料については、圧延方向に対し平行方向断面を切り出した後、この断面を機械研磨し鏡面にした後、コロイダルシリカを用いて研磨した。その後、ＦＥ−ＳＥＭ（Field Emission-Scanning Electron Microscope）／ＥＢＳＰを用いて結晶方位解析を実施した。なお、ＥＢＳＰ測定については、試料の平均的な情報を得るため、試料ごとに１０視野以上を測定し、その平均値を用いた。 About the sample for EBSP measurement, after cutting out a cross section in a direction parallel to the rolling direction, this cross section was mechanically polished to a mirror surface, and then polished using colloidal silica. Then, crystal orientation analysis was performed using FE-SEM (Field Emission-Scanning Electron Microscope) / EBSP. In addition, about EBSP measurement, in order to obtain the average information of a sample, 10 or more visual fields were measured for every sample, and the average value was used.
また、圧延幅方向および圧延方向のヤング率については、各々の方向から試験片を切り出し、共振法もしくは歪ゲージを付与した引張試験により測定した。 In addition, the Young's modulus in the rolling width direction and the rolling direction were measured by a tensile test with a test piece cut out from each direction and provided with a resonance method or a strain gauge.
表２の実施例Ｎｏ．１２〜１７は、本発明の請求項１の合金成分であり、熱間圧延条件も本発明の請求範囲内である。したがって、上記の面積比Ｂ／Ａがいずれも１以上と高い値を示している。それに伴い、ヤング率も圧延方向が約１１５ＧＰａであるのに対し、圧延幅方向のそれはいずれも１２５ＧＰａ以上であり、非常に高い。 Example No. in Table 2 12-17 are the alloy components of Claim 1 of this invention, and hot rolling conditions are also in the claim of this invention. Accordingly, the area ratio B / A has a high value of 1 or more. Along with this, the Young's modulus is about 115 GPa in the rolling direction, while it is 125 GPa or more in the rolling width direction, which is very high.
また、表２の実施例Ｎｏ．１８〜２１は、本発明の請求項３の合金成分であり、熱間圧延条件も本発明の請求範囲内である。したがって、面積比Ｂ／Ａがいずれも１以上と高い値を示している。それに伴い、ヤング率も圧延方向が約１１５ＧＰａであるのに対し、圧延幅方向のそれはいずれも１２５ＧＰａ以上であり、上記成分系同様に非常に高い。 In addition, in Example 2 of Table 2, 18-21 are the alloy components of Claim 3 of this invention, and hot rolling conditions are also in the claim of this invention. Accordingly, the area ratio B / A is a high value of 1 or more. Accordingly, the Young's modulus is about 115 GPa in the rolling direction, whereas it is 125 GPa or more in the rolling width direction, which is very high as in the above component system.
さらに、表２の実施例Ｎｏ．２２は、本発明の請求項４の合金成分であり、熱間圧延条件も本発明の請求範囲内である。したがって、面積比Ｂ／Ａがいずれも１以上と高い値を示している。それに伴い、ヤング率も圧延方向が約１１５ＧＰａであるのに対し、圧延幅方向のそれはいずれも１２５ＧＰａ以上であり、上記成分系同様に非常に高い。 Furthermore, Example No. 22 is an alloy component of claim 4 of the present invention, and the hot rolling conditions are also within the scope of the present invention. Accordingly, the area ratio B / A is a high value of 1 or more. Accordingly, the Young's modulus is about 115 GPa in the rolling direction, whereas it is 125 GPa or more in the rolling width direction, which is very high as in the above component system.
一方で、表２の比較例のＮｏ．２３は、成分系は本発明範囲内であるものの、熱間圧延時の加熱温度がβ変態点＋２０℃よりも低い。それに伴い、熱間圧延においてβ変態点−７０℃の時点での圧下率は５０％よりも少ない。そのため、面積比Ｂ／Ａの値が１未満となり、冷延後において圧延方向と圧延幅方向のヤング率は約１１５ＧＰａとほぼ同等となってしまい、圧延幅方向のヤング率が高くない。 On the other hand, No. of the comparative example of Table 2. No. 23, although the component system is within the scope of the present invention, the heating temperature during hot rolling is lower than the β transformation point + 20 ° C. Accordingly, the rolling reduction at the time of β transformation point −70 ° C. in hot rolling is less than 50%. Therefore, the value of the area ratio B / A is less than 1, and the Young's modulus in the rolling direction and the rolling width direction becomes substantially equal to about 115 GPa after cold rolling, and the Young's modulus in the rolling width direction is not high.
また、表３に示す冷間圧延後では、表３の実施例Ｎｏ．２３〜３４は、いずれも請求項６に示すように一回当たりの圧下率が４０％以下である。したがって、面積比Ｂ／Ａがいずれも１以上と高い値を示している。それに伴い、ヤング率も圧延方向のヤング率は約１１５ＧＰａであるのに対し、圧延幅方向のヤング率は１２５ＧＰａ以上と非常に高い。 In addition, after the cold rolling shown in Table 3, Example No. As for all 23-34, as shown in Claim 6, the rolling reduction per time is 40% or less. Accordingly, the area ratio B / A is a high value of 1 or more. Accordingly, the Young's modulus in the rolling direction is about 115 GPa, whereas the Young's modulus in the rolling width direction is as high as 125 GPa or more.
一方で、表３の比較例のＮｏ．３５は、熱間圧延は本発明の請求範囲内であるものの、その後の冷間圧延において、最大冷延率が９０％と高い。したがって、面積比Ｂ／Ａが１未満となっており、圧延方向と圧延幅方向のヤング率は約１１５ＧＰａとほぼ同等となってしまい、圧延幅方向のヤング率が高くない。 On the other hand, No. of the comparative example of Table 3. No. 35, although hot rolling is within the scope of the present invention, in the subsequent cold rolling, the maximum cold rolling rate is as high as 90%. Therefore, the area ratio B / A is less than 1, and the Young's modulus in the rolling direction and the rolling width direction is substantially equal to about 115 GPa, and the Young's modulus in the rolling width direction is not high.
本発明は、圧延幅方向の剛性に優れており、また、低合金系とすることで、低コストで、且つ、成形性に優れていることから、チタン製のパイプ（特に長尺もの）やプレート式熱交換器に利用することに適しており、これら部材へのチタン適用の際に厚みの低減やスプリングバックの低減に寄与する。 Since the present invention is excellent in rigidity in the rolling width direction, and is made of a low alloy system, it is low in cost and excellent in formability, so that a titanium pipe (especially a long one) or It is suitable for use in plate heat exchangers and contributes to thickness reduction and springback reduction when titanium is applied to these members.
Claims (7)
圧延面の法線方向をＮＤ方向、圧延方向をＲＤ方向、圧延幅方向をＴＤ方向とし、α相の（０００１）面の法線方向をＣ軸方位として、Ｃ軸方位がＮＤ方向となす角度をθ、Ｃ軸方位とＮＤ方向を含む面がＮＤ方向とＴＤ方向を含む面となす角度をφとし、
圧延面より法線方向からのα相の（０００１）面極点図において、角度θが４０°未満である結晶粒の総面積をＡとし、角度θが７０°以上１１０°以下で角度φが±２０°の範囲内である結晶粒の総面積をＢとし、面積比Ｂ／Ａが１以上であることを特徴とする圧延幅方向の剛性に優れたチタン板。 One or more of Fe, Cr, and Ni in a total content of [% Fe] + [% Cr] + [% Ni] of 0.250% to 0.750% by mass, and one or more of O, N, and C The total content [% O] + [% N] + [% C] is 0.030 mass% or more and 0.400 mass% or less, the C content is 0.05 mass% or less, and the balance is Ti. And a titanium plate made of inevitable impurities,
The normal direction of the rolling surface is the ND direction, the rolling direction is the RD direction, the rolling width direction is the TD direction, the normal direction of the (0001) plane of the α phase is the C axis direction, and the C axis direction is the angle with the ND direction. Is θ, and the angle between the plane including the C axis direction and the ND direction and the plane including the ND direction and the TD direction is φ,
In the (0001) plane pole figure of the α phase from the normal direction to the rolled surface, the total area of crystal grains having an angle θ of less than 40 ° is A, the angle θ is 70 ° to 110 °, and the angle φ is ± A titanium plate excellent in rigidity in the rolling width direction, characterized in that the total area of crystal grains within a range of 20 ° is B and the area ratio B / A is 1 or more.
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