WO2023210033A1 - Titanium alloy plate and method for producing same - Google Patents

Titanium alloy plate and method for producing same Download PDF

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WO2023210033A1
WO2023210033A1 PCT/JP2022/028491 JP2022028491W WO2023210033A1 WO 2023210033 A1 WO2023210033 A1 WO 2023210033A1 JP 2022028491 W JP2022028491 W JP 2022028491W WO 2023210033 A1 WO2023210033 A1 WO 2023210033A1
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titanium alloy
alloy plate
temperature
plate according
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PCT/JP2022/028491
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French (fr)
Japanese (ja)
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知徳 國枝
良樹 小池
元気 塚本
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日本製鉄株式会社
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C14/00—Alloys based on titanium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
    • C22F1/18—High-melting or refractory metals or alloys based thereon

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  • the present invention relates to a titanium alloy plate and a method for manufacturing the same.
  • This application claims priority based on Japanese Patent Application No. 2022-073153 filed in Japan on April 27, 2022, the contents of which are incorporated herein.
  • Titanium alloys are used as lightweight, high-strength materials in fields such as aircraft, automobiles, and consumer products such as golf clubs.
  • the commonly used titanium alloys are ⁇ + ⁇ type titanium alloys, which are mainly composed of ⁇ and ⁇ phases, such as Ti-6Al-4V alloy, Ti-6Al-2Sn-4Zr-2Mo alloy, Ti-5Al-1Fe alloy and the like are known.
  • titanium alloys are often used for golf clubs, especially for drivers.
  • the characteristics required of titanium alloys used in golf clubs are high strength and low specific gravity in order to increase capacity (light weight), and high young strength so that even if the wall thickness is made thinner, it is possible to avoid repulsion regulations. rate.
  • the strength (particularly 0.2% PS) and Young's modulus in the width direction are generally required as the above-mentioned strength and Young's modulus. Processability is also required when processing into golf clubs.
  • Patent Document 1 states that in terms of mass %, Al: 7.1 to 10%, Fe: 0.1 to 3.0%, C: 0.5% or less, O: 0 A high specific strength ⁇ + ⁇ type titanium alloy is disclosed, which contains N: 0.05 to 0.5%, N: 0.5% or less, and the balance is Ti and unavoidable impurities.
  • Patent Document 1 by replacing V, which is a ⁇ -stabilizing element, with Fe, and adding Al, which is an ⁇ -stabilizing element and has a light specific gravity, high specific strength and cost reduction of a high specific strength ⁇ + ⁇ type titanium alloy is achieved. It is said that it is possible to However, since the alloy of Patent Document 1 has a high Al content, it has high deformation resistance under hot conditions, and there is a possibility that productivity may be reduced due to the formation of an ordered phase (Ti 3 Al) during the manufacturing process. This may be due to low manufacturability (difficult to manufacture coils).
  • the Ti-5Al-1Fe alloy does not contain expensive V, and provides mechanical properties equivalent to or better than the Ti-6Al-4V alloy.
  • Patent Document 2 describes an ⁇ + ⁇ type alloy consisting of 1.4% or more and less than 2.1% Fe, 4.4% or more and less than 5.5% Al, and the balance titanium and impurities.
  • a titanium alloy is disclosed.
  • the texture etc. are not specified, and it is considered that the titanium alloy does not necessarily satisfy the properties in the width direction required for golf applications.
  • Patent Document 3 discloses a titanium alloy plate that has high strength and high Young's modulus in one direction within the plate surface, excellent fatigue properties and/or impact toughness, and good hot workability. ing.
  • the tensile strength and Young's modulus in the width direction of the sheet are increased by developing a texture called transverse-texture in which the c-axis of the titanium ⁇ phase is strongly oriented in the width direction of the sheet.
  • the strength is obtained in a state where the hot-rolled sheet is not annealed and strain remains, so if hot working is subsequently performed during processing into a product, the strength will be significantly reduced. There was a case.
  • the Ti-6Al-2Sn-4Zr-2Mo alloy needs to contain a large amount of elements heavier than Ti (having a larger atomic weight) such as Sn, Zr, and Mo, which increases the specific gravity and makes it impossible to reduce the weight. There is.
  • an object of the present invention is to provide a titanium alloy plate having high strength, high Young's modulus, low specific gravity, and high workability.
  • the titanium alloy plate is a hot-rolled plate with a thickness of more than 2.5 mm.
  • the present inventors investigated the strength (0.2% PS (0.2% proof stress)), Young's modulus, specific gravity, and workability of an ⁇ + ⁇ type titanium alloy that does not require expensive elements such as V. . As a result, it was found that high strength, high Young's modulus, low specific gravity, and high workability can be obtained by controlling the chemical composition, texture, etc. within appropriate ranges.
  • the present invention was completed based on the above findings, and the gist thereof is as follows.
  • the titanium alloy plate according to one embodiment of the present invention has a chemical composition in mass %: Al: 5.0 to 6.6%, Fe: 0.7 to 2.3%, Si: 0.20 ⁇ 0.30%, O: 0.10 ⁇ 0.20%, C: less than 0.050%, N: 0.050% or less, Ni: 0% or more and less than 0.15%, Cr: 0% or more and 0 less than .25%, Mn: 0% or more and less than 0.25%, and the remainder: Ti and impurities, in the chemical composition, Al content in mass % is [%Al], Fe content is [% When the Si content is [%Si] and the O content is [%O], the following formulas (1) and (2) are satisfied, and the crystal orientation of the ⁇ phase is according to Bunge's notation method.
  • the maximum accumulated orientation indicated by the crystal orientation distribution function f(g) is ⁇ 1: 0 ⁇ 30°, ⁇ : 60 ⁇ 90°, ⁇ 2: 0 ⁇ 60°, the maximum integration degree of the maximum integration direction is 10.0 or more, and ⁇ 1: 70 to 90°, ⁇ : 70 to 90°, ⁇ 2: 0 to 60°, and ⁇ 1: 70 to 90°. °, ⁇ : 10-30°, ⁇ 2: 0-60°, the maximum integration degree is 2.5 or less, and YR in the board width direction is 0.99 or less.
  • the titanium alloy plate according to [1] above has a 0.2% proof stress in the plate width direction at 25°C of 1000 MPa or more, a Young's modulus in the plate width direction of 135 GPa or more, and a specific gravity of 4. It may be less than .45g/ cm3 .
  • the titanium alloy plate according to any one of [1] to [3] above has a band structure having an aspect ratio of more than 3.0 and extending in the longitudinal direction of the plate, and the area ratio of the band structure is It may be 70% or more.
  • the titanium alloy plate according to any one of [1] to [3] above may have a YR in the plate width direction of 0.85 or more and 0.97 or less.
  • YR in the plate width direction may be 0.85 or more and 0.97 or less.
  • the titanium alloy plate according to [1] or [2] above may have a thickness of more than 2.5 mm.
  • the titanium alloy plate according to [3] above may have a thickness of more than 2.5 mm.
  • the titanium alloy plate described in [4] above may have a thickness of more than 2.5 mm.
  • the titanium alloy plate described in [5] above may have a thickness of more than 2.5 mm.
  • the titanium alloy plate described in [6] above may have a thickness of more than 2.5 mm.
  • a method for producing a titanium alloy plate according to another aspect of the present invention is the method for producing a titanium alloy plate according to [1], wherein the chemical composition is Al: 5.0 to 6% by mass. .6%, Fe: 0.7-2.3%, Si: 0.20-0.30%, O: 0.10-0.20%, C: less than 0.050%, N: 0.050 % or less, Ni: 0% or more and less than 0.15%, Cr: 0% or more and less than 0.25%, Mn: 0% or more and less than 0.25%, remainder: Ti and impurities.Heat the titanium material to the heating temperature.
  • the chemical composition is Al: 5.0 to 6% by mass. .6%, Fe: 0.7-2.3%, Si: 0.20-0.30%, O: 0.10-0.20%, C: less than 0.050%, N: 0.050 % or less, Ni: 0% or more and less than 0.15%, Cr: 0% or more and less than 0.25%, Mn: 0% or more and less than 0.25%,
  • the heating temperature is T ⁇ °C or more and (T ⁇ +150) °C or less, where T ⁇ is the ⁇ transformation point temperature in °C, and in the hot rolling step, the rolling reduction is 85% or more, the finishing temperature is (T ⁇ -170) °C or more and (T ⁇ -100) °C or less, and in the annealing step, the annealing temperature T in the annealing is 600 °C or more and T ⁇ or less.
  • the annealing temperature T and the holding time t in units of seconds at the annealing temperature satisfy the following formula (3). (T+273.15) ⁇ (Log 10 (t)+20) ⁇ 27000...Formula (3) [13]
  • the annealing temperature T in the annealing is 600°C or more and T ⁇ or less
  • the holding time t in units of seconds at the temperature may satisfy the following formula (3'). 22000 ⁇ (T+273.15) ⁇ (Log 10 (t)+20) ⁇ 27000...Equation (3')
  • an ⁇ + ⁇ type titanium alloy plate having high strength, high Young's modulus, low specific gravity, and high workability, and a method for manufacturing the same.
  • This titanium alloy plate is suitable for use in golf clubs.
  • FIG. 2 is an explanatory diagram for explaining the crystal orientation of ⁇ -phase crystal grains of a titanium alloy plate according to Euler angles according to Bunge's notation method. It is an example of the crystal orientation distribution function calculated
  • titanium alloy plate according to one embodiment of the present invention (titanium alloy plate according to this embodiment) will be described.
  • the titanium alloy plate according to this embodiment has a chemical composition in mass %: Al: 5.0 to 6.6%, Fe: 0.7 to 2.3%, Si: 0.20 to 0.30%.
  • Al 5.0-6.6%
  • Al is an element with high solid solution strengthening ability, and is an element effective in increasing strength at room temperature. Furthermore, Al is a lighter element than Ti, and contributes to lowering the specific gravity.
  • the Al content is set to 5.0% or more.
  • the Al content is preferably 5.2% or more, more preferably 5.3% or more, even more preferably 5.4% or more.
  • the Al content exceeds 6.6%, the alloy plate may become brittle and break during rolling or transportation, and the ⁇ phase may locally become excessively solid solution strengthened due to solidification segregation. Hard areas are formed and the toughness is reduced. Therefore, the Al content is set to 6.6% or less.
  • the Al content is preferably 6.5% or less, more preferably 6.3% or less, even more preferably 6.0% or less.
  • Fe 0.7-2.3%
  • Fe is inexpensive, it is an element with high solid solution strengthening ability. Therefore, it is an effective element for increasing strength at room temperature at low cost.
  • Fe is a ⁇ -stabilizing element and has the effect of widening the high-temperature two-phase temperature range, which is necessary to obtain the T-texture that is developed to increase the Young's modulus and strength in the sheet width direction, which will be described later. It is.
  • the Fe content is set to 0.7% or more.
  • the Fe content is preferably 0.9% or more, more preferably 1.2% or more.
  • Fe is an element that is extremely susceptible to solidification and segregation. Therefore, as the content increases, variations in performance will increase, and fatigue strength will decrease depending on the location.
  • the Fe content is set to 2.3% or less.
  • the Fe content is preferably 2.1% or less, more preferably 1.9% or less.
  • Si 0.20-0.30%
  • Si is a ⁇ stabilizing element, it is also an element that dissolves in solid solution in the ⁇ phase and exhibits a high solid solution strengthening ability. As mentioned above, it is difficult to contain more than 2.3% Fe due to segregation problems. Therefore, in the titanium alloy plate according to this embodiment, the strength is further increased by solid solution strengthening of Si. Si has a tendency to segregate in the opposite direction to O, as described below, and is also less likely to solidify and segregate than O. Therefore, high strength (0.2% PS) can be obtained by containing an appropriate amount of Si at the same time as O. . If the Si content is less than 0.20%, sufficient effects cannot be obtained, so the Si content is set to 0.20% or more.
  • the Si content is set to 0.30% or less.
  • O 0.10-0.20%
  • O is an effective element for increasing strength.
  • the O content is set to 0.10% or more.
  • the effect is great when it is contained simultaneously with Si.
  • the ductility and workability may decrease, or the steel may become more likely to break during hot-rolled sheet production, resulting in a decrease in manufacturability.
  • O coexists with Al, it promotes the formation of Ti 3 Al.
  • Ti 3 Al causes a significant decrease in ductility and workability at room temperature.
  • O is an interstitial element, and as the content increases, the specific gravity increases, so it is necessary to adjust the equations (1) and (2) described below. Based on these, the O content is set to 0.20% or less.
  • C and N are elements that reduce the ductility and workability of the titanium alloy plate. Therefore, the C content is set to less than 0.050%, and the N content is set to 0.050% or less.
  • C and N like O, are elements that contribute to high strength, but in the titanium alloy plate according to this embodiment, C and N are not essential because the strength is improved by O. From the viewpoint of ductility and workability, it is preferable that the C content and N content are low, and 0% is also acceptable, but C and N may be mixed in as impurities from the raw material titanium sponge, scrap, and alloying element raw materials. Therefore, the C content may be set to 0.0001% or more, and the N content may be set to 0.0001% or more.
  • the remainder of the chemical composition of the titanium alloy plate according to this embodiment may be Ti and impurities.
  • impurities include H, Cl, Na, Mg, Ca, and B that are mixed in during the refining process, and Zr, Sn, Mo, Nb, Ta, and V that are mixed in from scraps, etc., but are not limited to these. I can't do it.
  • the level of impurities is acceptable if the content of each element is 0.1% or less and the total amount is 0.5% or less.
  • H content is 150 ppm or less.
  • B will form coarse precipitates within the ingot.
  • the B content is preferably 0.01% or less.
  • Ni, Cr, and Mn may be contained in the following range in place of a part of the remaining portion.
  • the lower limit is 0%. Further, it is also allowed to be contained as an impurity.
  • Ni less than 0.15%
  • Ni is an element that improves tensile strength and workability. Therefore, it may be included.
  • the Ni content is preferably 0.01% or more.
  • the Ni content is set to less than 0.15%.
  • the Ni content is preferably 0.14% or less, more preferably 0.11% or less.
  • Cr Less than 0.25% Cr is an element that improves tensile strength and workability. Therefore, it may be included. In order to obtain these effects, the Cr content is preferably 0.01% or more. On the other hand, if the Cr content is 0.25% or more, an intermetallic compound TiCr2 , which is an equilibrium phase, is generated, which may deteriorate the fatigue strength and ductility at room temperature of the titanium alloy plate. Therefore, when Cr is included, the Cr content should be less than 0.25%. The Cr content is preferably 0.24% or less, more preferably 0.21% or less.
  • Mn less than 0.25%
  • Mn is an element that improves tensile strength and workability. Therefore, it may be included.
  • the Mn content is preferably 0.01% or more.
  • the Mn content is preferably 0.24% or less, more preferably 0.20% or less.
  • the Al content in mass % is [%Al]
  • the Fe content is [%Fe]
  • the Si content is [%Fe].
  • %Si] and the O content is [%O], it is necessary to satisfy the following formulas (1) and (2).
  • T-texture is a texture formed when an unrecrystallized ⁇ phase that has undergone rolling deformation transforms into an ⁇ phase. T-texture improves strength such as 0.2% PS and tensile strength in the sheet width direction, and Young's modulus.
  • the maximum accumulation orientation shown by the crystal orientation distribution function f(g) is ⁇ 1: 0 to 30°, If it is in the range of ⁇ : 60 to 90 degrees, ⁇ 2: 0 to 60 degrees (hereinafter sometimes referred to as region 1), and the maximum degree of accumulation in the maximum accumulation direction is 10.0 or more, T-texture has developed. It is an organization that has If the maximum degree of integration in region 1 is less than 10.0, strength such as tensile strength in the width direction and Young's modulus will not increase sufficiently.
  • the upper limit of the maximum integration degree of region 1 is not limited, but may be 40.0 or less, or 30.0 or less.
  • the crystal orientation distribution function f(g) The range of ⁇ 1: 70 to 90°, ⁇ : 70 to 90°, ⁇ 2: 0 to 60° and the range of ⁇ 1: 70 to 90°, ⁇ : 10 to 30°, ⁇ 2: 0 to 60° (hereinafter (sometimes referred to as region 2), the maximum integration degree is 2.5 or less.
  • the maximum integration degree of region 2 is more than 2.5 ( ⁇ 1: 70-90°, ⁇ : 70-90°, ⁇ 2: 0-60° or ⁇ 1: 70-90°, ⁇ : 10-30 ⁇ 2: If the maximum integration degree exceeds 2.5 even in the range of 0 to 60°, the workability decreases. Furthermore, as the degree of integration in region 2 increases, the degree of integration in region 1 decreases, leading to a decrease in strength in the width direction and Young's modulus.
  • a high degree of integration in region 2 means that many textures are formed in which the C-axis of hcp is oriented in the longitudinal direction of the titanium alloy plate.
  • FIG. 1 is an explanatory diagram for explaining the crystal orientation of ⁇ -phase crystal grains of a titanium alloy plate using Euler angles according to Bunge's notation method.
  • sample coordinate system three coordinate axes, RD (rolling direction), TD (plate width direction), and ND (normal line direction to the rolling surface), which are perpendicular to each other, are shown.
  • RD rolling direction
  • TD plate width direction
  • ND normal line direction to the rolling surface
  • the respective coordinate axes are arranged so that the origin of each coordinate system coincides, and the hexagonal prism indicating hcp is shown so that the center of the (0001) plane of hcp, which is the alpha phase of titanium, coincides with the origin.
  • the X-axis coincides with the [10-10] direction of the ⁇ phase
  • the Y-axis coincides with the [-12-10] direction
  • the Z-axis coincides with the [0001] direction (C-axis direction).
  • the crystal orientation is uniquely determined using the three angles ⁇ 1, ⁇ , and ⁇ 2.
  • These three angles ⁇ 1, ⁇ , and ⁇ 2 are called Euler angles according to Bunge's notation.
  • the Euler angle according to Bunge's notation method defines the crystal orientation (C-axis direction, etc.) of the ⁇ -phase crystal grains of the titanium alloy plate.
  • ⁇ 1 is the intersection line between the RD-TD plane (rolling plane) of the sample coordinate system and the [10-10]-[-12-10] plane of the crystal coordinate system, and the RD (rolling plane) of the sample coordinate system. direction).
  • ⁇ is the angle between the ND (normal direction to the rolling surface) of the sample coordinate system and the [0001] direction (normal direction to the (0001) plane) of the crystal coordinate system.
  • ⁇ 2 is the intersection line between the RD-TD plane (rolled surface) of the sample coordinate system and the [10-10]-[-12-10] plane of the crystal coordinate system, and the [10-10] direction of the crystal coordinate system. is the angle formed by
  • the maximum accumulation direction and maximum accumulation degree can be determined as follows.
  • a cross section (L cross section) perpendicular to the width direction of the titanium alloy plate is chemically polished at the central position in the width direction (TD), and crystal orientation analysis is performed using backscattered electron diffraction (EBSD).
  • EBSD backscattered electron diffraction
  • this L cross section is wet-polished using emery paper, and then the surface is mirror-polished using colloidal silica to give a mirror surface.
  • a rectangular area is defined in the thickness direction excluding 1000 ⁇ m from each of the front and back surfaces in the board thickness direction, and in a range of 1000 ⁇ m in the board longitudinal direction ((total board thickness - front and back surfaces 1000 ⁇ m) x 1000 ⁇ m).
  • a crystal orientation distribution function f(g) (ODF) is calculated using OIM Analysis TM software (Ver. 8.1.0) manufactured by TSL Solutions.
  • the crystal orientation distribution function f(g) is calculated by setting the expansion index to 16 and the Gauss half width to 5° in texture analysis using the spherical harmonic function method of the EBSD method.
  • ODF is a distribution function that represents a three-dimensional distribution of measured crystal orientations plotted in a three-dimensional space (Euler space) of ⁇ 1- ⁇ - ⁇ 2.
  • FIG. 2 is an example of the crystal orientation distribution function f(g) obtained by the electron beam backscatter diffraction method of the titanium alloy plate according to the present embodiment.
  • the Euler space is horizontally sliced every 5 degrees in the angle ⁇ 2 direction, and the obtained cross sections are arranged.
  • the maximum accumulation direction and maximum accumulation degree are determined based on the L cross section at the center position in the sheet width direction, but the texture of the titanium alloy sheet is Since it is substantially uniform, the maximum accumulation direction and maximum degree of accumulation may be determined based on the L cross section at any board width position excluding the edge portion. However, since the edge portion is often trimmed when the product board is made, in that case, the maximum accumulation direction and maximum integration degree may be determined based on the L cross section at an arbitrary board width position of the product board. If the presence or absence of trim is unknown, it may be determined at a position more than 50 mm from the end.
  • the strain (dislocation) in the hot rolled sheet is small.
  • a method for estimating the residual amount of strain (dislocation density) there is a method of estimating the dislocation density from the half-width of a diffraction peak obtained by X-ray diffraction (XRD). The larger the half width of the diffraction peak, the larger the amount of residual strain.
  • the half width of the diffraction peak is more preferably 0.17° or less, and even more preferably 0.12° or less.
  • the surface of the titanium alloy plate is wet-polished using emery paper, and then mirror-polished using colloidal silica to give a mirror surface.
  • XRD measurement is performed on the surface of a titanium alloy plate made into a mirror surface.
  • the XRD measurement is carried out using CuK ⁇ as a radiation source in the range of 2 ⁇ from 50.0° to 55.0° at a measurement pitch of 0.01° and a measurement speed of 2°/min.
  • the half width is calculated by Rigaku's integrated powder X-ray analysis software PDXL using X-ray diffraction data measured by Rigaku's Smartlab.
  • the titanium alloy plate according to the present embodiment has a band structure 1 having an aspect ratio of more than 3.0 and extending in the longitudinal direction of the plate (rolling direction), and the area ratio of the band structure 1 is 70% or more. is preferred.
  • the band structure 1 referred to here is, for example, a structure extending in the longitudinal direction of the plate as shown in the optical microscope photograph of FIG. Specifically, it refers to crystal grains having an aspect ratio expressed by the long axis/short axis of the crystal grains of more than 3.0.
  • the area ratio of the band structure 1 is 70% or more. More preferably, it is 75% or more, and still more preferably 80% or more. Further, all crystal grains may have a band structure, and the upper limit is 100%.
  • the area ratio of the band structure is determined by the following method. A cross section of each sample cut perpendicular to the width direction of the plate at the center of the plate width is wet-polished using emery paper, and then the surface is polished to a mirror surface using colloidal silica.
  • the EBSD method was applied to a rectangular area in the thickness direction excluding 1000 ⁇ m from the front and back surfaces of the mirror-finished cross section and 1000 ⁇ m in the longitudinal direction of the sheet, with a step of 1 ⁇ m and approximately 5 fields of view.
  • the ratio is calculated, and the portion of crystal grains having an aspect ratio of more than 3.0 is regarded as a band structure, and its area ratio is calculated.
  • the titanium alloy plate according to the present embodiment has high strength, high Young's modulus, low specific gravity, and high workability by controlling the chemical composition, texture, and microstructure.
  • the titanium alloy plate according to this embodiment aims to satisfy the following as indicators of strength, Young's modulus, specific gravity, and workability.
  • excellent workability can be obtained by controlling the texture.
  • YR (0.2% PS/TS (tensile strength)) is high, workability may deteriorate depending on the type of processing.
  • processing at high temperatures improves workability, but heating reduces strength, which is not preferable.
  • YR is more than 0.99, there is no work hardening allowance during processing, and breakage is likely to occur, resulting in reduced workability.
  • YR in the plate width direction is set to 0.99 (99%) or less. Furthermore, when workability in the sheet width direction is required, it is preferable that YR in the sheet width direction is 0.98 or less. YR in the plate width direction is more preferably 0.97 or less, still more preferably 0.95 or less, and still more preferably 0.93 or less. YR changes depending on the amount of residual strain and other factors, but since the amount of strain has a large effect, it is preferable to reduce the amount of strain when reducing YR. On the other hand, when YR is less than 0.85, it is suggested that the targeted texture cannot be formed. Therefore, the goal is for YR to be 0.85 or more.
  • 0.2% PS in the plate width direction at room temperature 1000 MPa or more
  • titanium alloy plates for golf clubs are required to have higher strength than before in order to further reduce weight. It is required that 0.2% PS in the direction is 1000 MPa or more. Therefore, in the titanium alloy plate according to the present embodiment, the target is that the 0.2% PS in the plate width direction at room temperature is 1000 MPa or more.
  • the 0.2% PS in the width direction of the titanium alloy plate at room temperature is preferably 1010 MPa or more, more preferably 1030 MPa or more.
  • the higher the 0.2% PS the better, but if it is too high, the risk of fracture of the alloy plate increases from the viewpoint of notch sensitivity.
  • the 0.2% PS in the plate width direction at room temperature is preferably 1200 MPa or less. More preferably, it is 1150 MPa or less.
  • the reason for increasing the PS by 0.2% in the width direction is that in golf applications, the vertical direction of the face has a large effect on repulsion, and normally titanium alloy plates are designed so that the width direction is the vertical direction of the face. This is because it is processed into In this embodiment, the room temperature is 25°C.
  • PS and TS in the board width direction are measured in accordance with JIS Z 2241:2011.
  • a No. 13B tensile test piece (parallel part width 12.5 mm, gauge distance 50 mm) specified in JIS Z 2241:2011 was used so that the tensile direction was in the width direction of the titanium alloy plate.
  • a tensile test is performed at a strain rate of 0.5%/min for measurement.
  • Young's Modulus in Plate Width Direction 135 GPa or More
  • the Young's modulus in the sheet width direction is 135 GPa or more, the repulsion regulation is satisfied, so the Young's modulus is set as a target of 135 GPa or more.
  • a more preferable target is 137 GPa or higher.
  • the higher the Young's modulus the better, so there is no need to limit the upper limit, but from the viewpoint of structure control and chemical composition, the practical upper limit is about 150 GPa.
  • the Young's modulus in the width direction of the plate can be increased by controlling the texture and forming a band structure.
  • the Young's modulus in the sheet width direction is determined by the following method.
  • a No. 13B tensile test piece (parallel part width 12.5 mm, gauge distance 50 mm) specified in JIS Z 2241:2011 was prepared so that the tensile direction was in the width direction of the titanium alloy plate, and a strain gauge was used. At a strain rate of 10.0%/min, loading and unloading were repeated 5 times in the stress range from 100 MPa to half of 0.2% PS, the slope was determined, and the maximum and minimum values were removed. Let the average value of the times be Young's modulus.
  • Specific gravity 4.45 g/cm 3 or less If the specific gravity of a titanium alloy plate for golf clubs becomes too high, it will not be possible to reduce the weight of the face even if the strength is increased. Therefore, from the viewpoint of weight reduction, specific gravity is important.
  • the target specific gravity is 4.45 g/cm 3 or less.
  • the lower limit is substantially 4.38/cm 3 .
  • the specific gravity may be measured by a dry method using a gas or a wet method using a liquid.
  • a dry method specifically, AccuPycII manufactured by Micromeritics is used.
  • the container size is 1 to 100 cm 3 , and any container may be used depending on the sample size.
  • Inert gases such as N 2 , Ar, and He gas are used as the gas.
  • the thickness of the titanium alloy plate according to this embodiment is not limited. When considering application to a golf club, it is, for example, more than 2.5 mm. Preferably it is 3.0 mm or more. On the other hand, if it exceeds 6.0 mm, the load in processes such as annealing the hot rolled sheet or unwinding after pickling may become too large, so it may be set to 6.0 mm or less.
  • the titanium alloy plate according to the present embodiment has the above-mentioned characteristics, the effect can be obtained, so the manufacturing method is not limited. However, a manufacturing method including the steps described below is preferable because stable manufacturing can be achieved. That is, the titanium alloy plate according to this embodiment, (I) Chemical composition in mass%: Al: 5.0 to 6.6%, Fe: 0.7 to 2.3%, Si: 0.20 to 0.30%, O: 0.10 to 0.20%, C: less than 0.050%, N: 0.050% or less, Ni: 0% or more and less than 0.15%, Cr: 0% or more and less than 0.25%, Mn: 0% or more and less than 0.25%.
  • Chemical composition in mass% Al: 5.0 to 6.6%, Fe: 0.7 to 2.3%, Si: 0.20 to 0.30%, O: 0.10 to 0.20%, C: less than 0.050%, N: 0.050% or less, Ni: 0% or more and less than 0.15%, Cr: 0% or more and less than 0.25%, Mn: 0% or
  • a heating step of heating a titanium material consisting of Ti and impurities to a heating temperature (II) a hot rolling step of hot rolling the titanium material in one direction after the heating step to obtain a hot rolled sheet; (III) a winding step of cooling the hot rolled sheet after the hot rolling step to a winding temperature of 400° C. or lower at an average cooling rate of 8° C./s or higher and winding it at the winding temperature; (IV) an annealing step of annealing the hot rolled sheet after the winding step; It can be manufactured by a manufacturing method including. Preferred conditions for each step will be explained. Known conditions can be applied to steps and conditions that are not explained.
  • the chemical composition in mass% is Al: 5.0 to 6.6%, Fe: 0.7 to 2.3%, Si: 0.20 to 0.30%, O: 0.10 ⁇ 0.20%, C: less than 0.050%, N: 0.050% or less, Ni: 0% or more and less than 0.15%, Cr: 0% or more and less than 0.25%, Mn: 0% or more and 0
  • a titanium material such as a titanium alloy slab consisting of less than .25% and the remainder: Ti and impurities is heated to a heating temperature.
  • the heating temperature is at least T ⁇ °C and at most (T ⁇ +150) °C, where T ⁇ is the ⁇ transformation point temperature in °C.
  • the heating temperature is less than T ⁇ °C, the titanium material will be rolled down in a state where the ratio of ⁇ phase is high, and the rolling down will be insufficient when the ratio of ⁇ phase is high. Therefore, T-texture is not sufficiently developed. Furthermore, if the reduction rate is low when the proportion of the ⁇ phase is high, it may be difficult to form a band structure. Therefore, when increasing the ratio of the band structure, the heating temperature is preferably (T ⁇ +20°C) or higher. On the other hand, if the heating temperature exceeds (T ⁇ +150°C), there is a very high possibility that the ⁇ phase will recrystallize during rolling.
  • T-texture is difficult to develop because variant selection does not occur during phase transformation from ⁇ phase to ⁇ phase. Furthermore, the surface of the titanium material becomes more intensely oxidized, and the surface of the hot-rolled sheet is more likely to be bald or scratched after hot rolling.
  • the ⁇ -transform temperature T ⁇ means the boundary temperature at which the ⁇ -phase starts to be generated when the titanium alloy is cooled from the ⁇ -phase single-phase region.
  • T ⁇ can be obtained from the phase diagram.
  • the phase diagram can be obtained by, for example, the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) method. Specifically, a phase diagram of a titanium alloy was obtained by the CALPHAD method using Thermo-Calc, an integrated thermodynamic calculation system from Thermo-Calc Software AB, and a predetermined database (TI3), and T ⁇ was calculated. can do.
  • the titanium material after the heating process is hot rolled in one direction to obtain a hot rolled plate.
  • the rolling reduction ratio is 85% or more
  • the finishing temperature is (T ⁇ -170)°C or more and (T ⁇ -100)°C or less. It is known that a T-texture can be formed in a hot-rolled titanium alloy sheet by heating it to the ⁇ region or the ⁇ + ⁇ two-phase high temperature region just below the ⁇ transformation point, and then hot rolling it to the ⁇ + ⁇ region (for example, Publication No. 2012-149283).
  • JP-A No. 2012-149283 states that a reduction of 85% or more is required up to 900° C. in the ⁇ + ⁇ two-phase high temperature range.
  • 900°C in the two-phase region is a very high temperature, and furthermore, when heating to the ⁇ region or just below the ⁇ transformation point, the temperature in the center of the plate is higher, and it also depends on the alloy type. Since the temperature difference between the steel and the ⁇ -transus point may be large, if the holding time is too long, the strain accumulated during hot rolling may cause recrystallization.
  • the hot rolling completion temperature (finishing temperature) is set to a temperature of (T ⁇ -170) °C or higher and (T ⁇ -100) °C or lower, and the post-process is carried out under predetermined conditions. It was found that a predetermined texture can be obtained by doing this. If the finishing temperature is less than (T ⁇ -170)°C, the texture will develop in the range of ⁇ 1: 70 to 90°, ⁇ : 10 to 30°, and ⁇ 2: 0 to 60°, which will not meet the above aim. The texture in the area (region 1) does not develop, and the strength and Young's modulus in the width direction of the plate do not improve sufficiently.
  • the hot-rolled sheet after the hot rolling step is cooled to a winding temperature of 400° C. or lower at an average cooling rate of 8.0° C./s or higher, and then wound at that temperature (winding temperature). If the coiling temperature (cooling stop temperature) is over 400°C, the plate will be cooled in a coiled form, that is, the shape will be frozen due to the solid solution of Al, O, etc. mentioned above, or the precipitation of compounds. This may make it difficult to unwind after that, making it impossible to manufacture plates or coils.
  • the winding temperature is preferably 300°C or lower, more preferably 100°C or lower.
  • the average cooling rate to the coiling temperature is less than 8.0° C./s, the predetermined texture will not develop sufficiently.
  • the average cooling rate is preferably 10.0°C/s or more, more preferably 12.0°C/s or more, even more preferably 15.0°C/s or more.
  • cooling is preferably controlled by water cooling, oil cooling, gas spraying, or the like.
  • As the atmosphere it is preferable to use an inert gas that is expected to suppress oxidation, but when descaling is performed, air can be used.
  • the hot rolled sheet after the winding step is annealed.
  • the hot-rolled sheet that has gone through the above steps has not only processing strain but also residual transformation strain. Therefore, although the strength is high, the workability in the sheet width direction is extremely low. Therefore, in the method for manufacturing a titanium alloy plate according to the present embodiment, strain is removed by annealing the hot-rolled plate (hot-rolled plate annealing).
  • the annealing temperature T (°C) is set to 600°C or higher, and the annealing temperature T in °C and the holding time t in seconds at the annealing temperature are as follows. Annealing is performed so that formula (3) is satisfied.
  • the annealing temperature T is preferably (T ⁇ ⁇ 50)° C. or lower.
  • the holding time t at the annealing temperature is the time when the annealing temperature is ⁇ 20° C., and includes the time during which the temperature is fluctuating as long as it is within that temperature range.
  • the temperature of the titanium material, etc. explained in the above manufacturing process is the surface temperature, and is measured by a radiation thermometer after each process is performed.
  • the emissivity of the radiation thermometer is a value calibrated to match the temperature measured using a contact thermocouple on the slab immediately after it comes out of the heating furnace. It is also possible to use a contact thermometer instead of a radiation thermometer. Measurements are taken multiple times without changing the manufacturing equipment, taking into account fluctuations due to seasonal factors, etc., and if it is confirmed that the target temperature has been achieved as the actual value, we will not take any special measures such as equipment changes or significant deterioration. If no circumstances arise, the measurement may be omitted.
  • titanium alloy ingots which are the raw materials for the titanium alloy plates shown in Table 1, A to M, and RT to T, are manufactured by vacuum arc remelting (VAR), and then are bloomed or forged to a thickness of 150 mm. A slab of ⁇ 200 mm x 1000 mm width x 5000 mm length was produced.
  • a titanium alloy ingot which is the material of the titanium alloy plate shown in N in Table 1, is manufactured by electron beam remelting (EBR), and then it is made into 160 mm thick x 1000 mm wide x length by blooming rolling or forging. A 5000mm slab was produced.
  • a titanium alloy ingot which is the raw material for the titanium alloy plate shown in O in Table 1, by plasma arc melting (PAR), it is made into a material with a thickness of 160 mm x width of 800 mm x length of 5000 mm by blooming rolling or forging.
  • PAR plasma arc melting
  • a titanium alloy slab serving as a material for the titanium alloy plate shown in P in Table 1 was manufactured using EBR to have a thickness of 160 mm x width of 800 mm x length of 5000 mm.
  • a titanium alloy slab serving as a material for the titanium alloy plate shown in Q in Table 1 was manufactured using PAM to have a thickness of 160 mm x width of 800 mm x length of 5000 mm. After manufacture, both slabs were milled on their surfaces and sides.
  • Approximately 5 fields of view were measured at a step of 1 ⁇ m in an area in the thickness direction excluding 1000 ⁇ m from the front and back surfaces of the plate, and in a range of 1000 ⁇ m in the longitudinal direction of the plate, and the data was analyzed using OIM Analysis TM manufactured by TSL Solutions.
  • the ODF was calculated using software (Ver. 8.1.0), and from this ODF, the peak position of the degree of accumulation and the maximum degree of accumulation were calculated.
  • the ODF was calculated using a texture analysis using the spherical harmonic function method of the EBSD method, with an expansion index of 16 and a Gauss half width of 5°.
  • the symmetry of rolling deformation was taken into account and calculations were performed to ensure line symmetry in each of the plate thickness direction, rolling direction, and plate width direction.
  • the maximum accumulation orientation indicated by the crystal orientation distribution function f(g) is ⁇ 1 : 0 to 30°, ⁇ : 60 to 90°, ⁇ 2: 0 to 60°.
  • the 0.2% PS (0.2% proof stress), tensile strength (TS), YR, and Young's modulus in the width direction of the obtained titanium alloy plate were determined.
  • 0.2% PS and tensile strength were measured in accordance with JIS Z 2241:2011. Specifically, a No. 13B tensile test piece (parallel part width 12.5 mm, gauge distance 50 mm) specified in JIS Z 2241:2011 was used so that the tensile direction was in the width direction of the titanium alloy plate. A tensile test was performed at 25° C. and a strain rate of 0.5%/min. Further, YR was calculated from this 0.2% PS and tensile strength.
  • the Young's modulus in the sheet width direction was determined by the following method.
  • a No. 13B tensile test piece (parallel part width 12.5 mm, gauge distance 50 mm) specified in JIS Z 2241:2011 was prepared so that the tensile direction was in the width direction of the titanium alloy plate, and a strain gauge was used. At a strain rate of 10.0%/min, loading and unloading are repeated 5 times in the stress range from 100 MPa to half of the 0.2% proof stress, and the slope is determined. At that time, the maximum and minimum values are The average value of the three times removed was taken as the Young's modulus.
  • the surface of the titanium alloy plate was wet-polished using emery paper, and then mirror-polished using colloidal silica to give a mirror-like surface. XRD measurement was performed on the surface of the titanium alloy plate which was made into a mirror surface.
  • the XRD measurement was carried out using CuK ⁇ as a radiation source in the range of 2 ⁇ from 50.0° to 55.0° at a measurement pitch of 0.01° and a measurement speed of 2°/min.
  • the half width was calculated by Rigaku's integrated powder X-ray analysis software PDXL using X-ray diffraction data measured by Rigaku's Smartlab.
  • the area ratio of the band structure of the obtained titanium alloy plate was determined.
  • the band structure area ratio is determined by wet polishing a cross section cut perpendicular to the width direction of the plate at the center of the plate width using emery paper, and then polishing the surface to a mirror surface using colloidal silica.
  • Crystal orientation analysis was performed using the EBSD method on a rectangular area of the cross section excluding 1000 ⁇ m from the front and back sides in the plate thickness direction x 1000 ⁇ m in the longitudinal direction of the plate, with a step of 1 ⁇ m and about 5 fields of view.
  • the aspect ratio was calculated for each grain, and the area ratio of crystal grains having an aspect ratio of more than 3.0 was calculated and obtained.
  • the specific gravity of the obtained titanium alloy plate was measured by a dry method using gas. At that time, measurements were made using AccuPycII manufactured by Micromeritics, with a container size of 1 cm 3 or 10 cm 3 and using N 2 gas as the gas.
  • the hot-rolled sheet after the annealing process (the hot-rolled sheet after the winding process since only Comparative Example 9 was not annealed) was cut by 100 to 150 ⁇ m using shot blasting and nitric-hydrofluoric acid solution to oxidize the surface.
  • cold rolling was performed for the purpose of quantitatively evaluating the workability (cold workability) of the hot rolled sheet, and cracks on the surface and side surfaces (edge cracks) were evaluated.
  • a case where surface and edge cracking occurred at a rolling reduction of 38% or less during cold rolling was evaluated as NG, and a case where no cracking occurred was evaluated as OK (high workability).
  • YR is low, as well as the evaluation of cold workability described above. Therefore, on the premise that the cold workability was OK, it was determined that if YR was 0.97 or less, the workability would be better (workability including YR in the table is Ex). Even if the cold workability is OK, if YR is over 0.97, it is judged as GOOD.

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Abstract

This titanium alloy plate has a prescribed chemical composition and, representing the crystal orientation of the α phase using the Euler angles g = {φ1, Φ, φ2} according to Bunge notation, the maximum accumulation orientation expressed by the crystal orientation distribution function f(g) is in the range φ1 : 0- 30°, Φ : 60-90°, and φ2 : 0-60°; the maximum degree of accumulation in said maximum accumulation orientation is at least 10.0; the maximum degree of accumulation in the ranges of φ1 : 70-90°, Φ : 70-90°, and φ2 : 0-60° and φ1 : 70-90°, Φ : 10-30°, and φ2 : 0-60° is not more than 2.5; and YR in the plate width direction is not more than 0.99.

Description

チタン合金板およびその製造方法Titanium alloy plate and its manufacturing method
　本発明は、チタン合金板およびその製造方法に関する。
　本願は、２０２２年０４月２７日に、日本に出願された特願２０２２－０７３１５３号に基づき優先権を主張し、その内容をここに援用する。 The present invention relates to a titanium alloy plate and a method for manufacturing the same.
This application claims priority based on Japanese Patent Application No. 2022-073153 filed in Japan on April 27, 2022, the contents of which are incorporated herein.
　チタン合金は、軽量高強度の材料として、航空機、自動車、ゴルフクラブ等の民生品などの分野で使用されている。チタン合金の中で汎用的に使われる合金は、主としてα相とβ相から構成されるα+β型チタン合金であり、Ｔｉ－６Ａｌ－４Ｖ合金、Ｔｉ－６Ａｌ－２Ｓｎ－４Ｚｒ－２Ｍｏ合金、Ｔｉ－５Ａｌ－１Ｆｅ合金などが知られている。 Titanium alloys are used as lightweight, high-strength materials in fields such as aircraft, automobiles, and consumer products such as golf clubs. The commonly used titanium alloys are α+β type titanium alloys, which are mainly composed of α and β phases, such as Ti-6Al-4V alloy, Ti-6Al-2Sn-4Zr-2Mo alloy, Ti-5Al-1Fe alloy and the like are known.
　上記の用途のうち、ゴルフクラブ用途では、特にドライバーにチタン合金が多く使用されている。ゴルフクラブに用いられるチタン合金に求められる特性は、大容量化（軽量化）のために高強度かつ低比重であること、さらに薄肉化しても反発規制を回避することが可能なように高ヤング率であることである。ゴルフ用途ではフェースの縦方向が反発力などに大きく影響するため、上述した強度やヤング率として、一般に、板幅方向の、強度（特に０．２％ＰＳ）及びヤング率が求められる。また、ゴルフクラブへの加工の際の、加工性も求められる。 Of the above uses, titanium alloys are often used for golf clubs, especially for drivers. The characteristics required of titanium alloys used in golf clubs are high strength and low specific gravity in order to increase capacity (light weight), and high young strength so that even if the wall thickness is made thinner, it is possible to avoid repulsion regulations. rate. In golf applications, since the longitudinal direction of the face greatly affects repulsion and the like, the strength (particularly 0.2% PS) and Young's modulus in the width direction are generally required as the above-mentioned strength and Young's modulus. Processability is also required when processing into golf clubs.
　ゴルフクラブ用途を考慮した場合、Ｔｉ－６Ａｌ―４Ｖ合金は、高価な元素であるＶを４％程度含有する必要があるので、好ましくない。そのため、Ｖを含まずに同等の特性を得られるチタン合金が求められている。
　このような課題に対し、例えば、特許文献１には、質量％で、Ａｌ：７．１～１０％、Ｆｅ：０．１～３．０％、Ｃ：０．５％以下、Ｏ：０．０５～０．５％、Ｎ：０．５％以下を含み、残部がＴｉ及び不可避的不純物からなる高比強度α＋β型チタン合金が開示されている。特許文献１では、β安定化元素であるＶをＦｅに置換し、比重が軽くα安定化元素であるＡｌを添加することにより、高比強度α＋β型チタン合金の高比強度化及び低廉化を図ることができるとされている。
　しかしながら、特許文献１の合金では、Ａｌの含有量が高いため、熱間での変形抵抗が高いことや、製造過程で規則相(Ｔｉ３Ａｌ)の形成による製造性低下の可能性等、コイル製造性が低い（コイルの製造が難しい）ことが考えられる。 When considering golf club applications, the Ti-6Al-4V alloy is not preferred because it needs to contain about 4% of V, which is an expensive element. Therefore, there is a need for a titanium alloy that does not contain V and can obtain the same characteristics.
To deal with such problems, for example, Patent Document 1 states that in terms of mass %, Al: 7.1 to 10%, Fe: 0.1 to 3.0%, C: 0.5% or less, O: 0 A high specific strength α+β type titanium alloy is disclosed, which contains N: 0.05 to 0.5%, N: 0.5% or less, and the balance is Ti and unavoidable impurities. In Patent Document 1, by replacing V, which is a β-stabilizing element, with Fe, and adding Al, which is an α-stabilizing element and has a light specific gravity, high specific strength and cost reduction of a high specific strength α+β type titanium alloy is achieved. It is said that it is possible to
However, since the alloy of Patent Document 1 has a high Al content, it has high deformation resistance under hot conditions, and there is a possibility that productivity may be reduced due to the formation of an ordered phase (Ti 3 Al) during the manufacturing process. This may be due to low manufacturability (difficult to manufacture coils).
　また、Ｔｉ－５Ａｌ－１Ｆｅ合金は、高価なＶを含有せず、Ｔｉ－６Ａｌ－４Ｖ合金と同等以上の機械的特性が得られる。
　Ｔｉ－５Ａｌ－１Ｆｅ合金として、例えば、特許文献２には、１．４％以上２．１％未満のＦｅ、４．４％以上５．５％未満のＡｌ、残部チタンおよび不純物からなるα＋β型チタン合金が開示されている。
　しかしながら、特許文献２のチタン合金では、集合組織等は規定されておらず、ゴルフ用途で必要とされる板幅方向の特性を必ずしも満足しないと考えられる。 Furthermore, the Ti-5Al-1Fe alloy does not contain expensive V, and provides mechanical properties equivalent to or better than the Ti-6Al-4V alloy.
As a Ti-5Al-1Fe alloy, for example, Patent Document 2 describes an α+β type alloy consisting of 1.4% or more and less than 2.1% Fe, 4.4% or more and less than 5.5% Al, and the balance titanium and impurities. A titanium alloy is disclosed.
However, in the titanium alloy of Patent Document 2, the texture etc. are not specified, and it is considered that the titanium alloy does not necessarily satisfy the properties in the width direction required for golf applications.
　また、特許文献３には、板面内の一方向で高強度、高ヤング率を有し、疲労特性および／または衝撃靭性に優れると共に、良好な熱間加工性を有するチタン合金板が開示されている。特許文献３では、チタンα相のｃ軸が板幅方向に強く配向したＴｒａｎｓｖｅｒｓｅ－ｔｅｘｔｕｒｅと呼ばれる集合組織を発達させることにより、板幅方向の引張強さおよびヤング率を高めている。
　しかしながら、特許文献３では、熱延板の焼鈍を行っておらずひずみが残存した状態での強度のため、その後、製品への加工の際に熱間加工を行うと強度が大きく低下してしまう場合があった。さらに、Ａｌ含有量が５．５％以下かつＦｅ含有量が１．３％以下のため、上記、製品加工後に強度が得られない場合があった。一方で、室温で加工する際にも、ひずみの残存によってＹＲが大きく、加工性が劣る場合もあった。 Furthermore, Patent Document 3 discloses a titanium alloy plate that has high strength and high Young's modulus in one direction within the plate surface, excellent fatigue properties and/or impact toughness, and good hot workability. ing. In Patent Document 3, the tensile strength and Young's modulus in the width direction of the sheet are increased by developing a texture called transverse-texture in which the c-axis of the titanium α phase is strongly oriented in the width direction of the sheet.
However, in Patent Document 3, the strength is obtained in a state where the hot-rolled sheet is not annealed and strain remains, so if hot working is subsequently performed during processing into a product, the strength will be significantly reduced. There was a case. Furthermore, since the Al content was 5.5% or less and the Fe content was 1.3% or less, strength could not be obtained after the above-mentioned product processing. On the other hand, even when processed at room temperature, YR was large due to residual strain, and processability was sometimes poor.
　また、Ｔｉ－６Ａｌ－２Ｓｎ－４Ｚｒ－２Ｍｏ合金には、Ｓｎ、Ｚｒ、ＭｏなどのＴｉよりも重い（原子量の大きい）元素を多く含む必要があるので、比重が高くなり、軽量化できないという課題がある。 In addition, the Ti-6Al-2Sn-4Zr-2Mo alloy needs to contain a large amount of elements heavier than Ti (having a larger atomic weight) such as Sn, Zr, and Mo, which increases the specific gravity and makes it impossible to reduce the weight. There is.
日本国特開２００７－２３９０３０号公報Japanese Patent Application Publication No. 2007-239030 日本国特開平７－６２４７４号公報Japanese Patent Application Publication No. 7-62474 日本国特開２０１４－２２４３０１号公報Japanese Patent Application Publication No. 2014-224301
　上述の通り、従来のチタン合金では、近年ゴルフクラブ用途に好適なチタン合金に要求される、高強度、高ヤング率、低比重、かつ高加工性を同時に満足することはできない。
　そのため、本発明は、高強度、高ヤング率、低比重、かつ高加工性を有する、チタン合金板を提供することを課題とする。ゴルフクラブ用途を考慮する場合、チタン合金板は、板厚が２．５ｍｍ超の熱延板を対象とする。 As mentioned above, conventional titanium alloys cannot simultaneously satisfy the requirements of high strength, high Young's modulus, low specific gravity, and high workability, which are recently required of titanium alloys suitable for golf club applications.
Therefore, an object of the present invention is to provide a titanium alloy plate having high strength, high Young's modulus, low specific gravity, and high workability. When considering golf club use, the titanium alloy plate is a hot-rolled plate with a thickness of more than 2.5 mm.
　本発明者らは、Ｖ等の高価な元素を必須としないα＋β型チタン合金において、強度（０．２％ＰＳ（０．２％耐力））、ヤング率、比重、加工性について検討を行った。
　その結果、化学組成及び集合組織等を適切な範囲に制御することで、高強度、高ヤング率、低比重、かつ高加工性が得られることが分かった。
　本発明は上記知見に基づき完成されたものであり、その要旨は、以下の通りである。
［１］本発明の一態様に係るチタン合金板は、化学組成が、質量％で、Ａｌ：５．０～６．６％、Ｆｅ：０．７～２．３％、Ｓｉ：０．２０～０．３０％、Ｏ：０．１０～０．２０％、Ｃ：０．０５０％未満、Ｎ：０．０５０％以下、Ｎｉ：０％以上０．１５％未満、Ｃｒ：０％以上０．２５％未満、Ｍｎ：０％以上０．２５％未満、及び残部：Ｔｉ及び不純物からなり、前記化学組成における、質量％での、Ａｌ含有量を［％Ａｌ］、Ｆｅ含有量を［％Ｆｅ］、Ｓｉ含有量を［％Ｓｉ］、Ｏ含有量を［％Ｏ］としたとき、以下の式（１）及び式（２）を満足し、α相の結晶方位をＢｕｎｇｅの表記方法によるオイラー角ｇ＝｛φ１，Φ，φ２｝で表した場合に、結晶方位分布関数ｆ（ｇ）により示される最大集積方位がφ１：０～３０°、Φ：６０～９０°、φ２：０～６０°の範囲にあり、前記最大集積方位の最大集積度が１０．０以上で、かつ、φ１：７０～９０°、Φ：７０～９０°、φ２：０～６０°及びφ１：７０～９０°、Φ：１０～３０°、φ２：０～６０°の範囲の最大集積度が２．５以下であり、板幅方向のＹＲが０．９９以下である。
１１．５＜［％Ａｌ］＋２×［％Ｆｅ］＋８×［％Ｓｉ］＋１８×［％Ｏ］＜１５．５・・・（１）
－４．５＜［％Ｆｅ］－０．９×［％Ａｌ］＋１．３×［％Ｏ］＋１．８×［％Ｓｉ］＜－２．４・・・（２）
［２］上記［１］に記載のチタン合金板は、２５℃における前記板幅方向の０．２％耐力が１０００ＭＰａ以上であり、前記板幅方向のヤング率が１３５ＧＰａ以上であり、比重が４．４５ｇ／ｃｍ３以下であってもよい。
［３］上記［１］または［２］に記載のチタン合金板は、ＣｕＫαを線源とするＸ線回折法によって検出される２θ＝５３．３±１°における回折ピークの半値幅が０．２０°以下であってもよい。
［４］上記［１］～［３］のいずれかに記載のチタン合金板は、アスペクト比が３．０超かつ板長手方向に伸長した、バンド組織を有し、前記バンド組織の面積率が７０％以上であってもよい。

［５］上記［１］～［３］のいずれかに記載のチタン合金板は、前記板幅方向のＹＲが０．８５以上、０．９７以下であってもよい。
［６］上記［４］に記載のチタン合金板は、前記板幅方向のＹＲが０．８５以上、０．９７以下であってもよい。
［７］上記［１］または［２］に記載のチタン合金板は、板厚が２．５ｍｍ超であってもよい。
［８］上記［３］に記載のチタン合金板は、板厚が２．５ｍｍ超であってもよい。
［９］上記［４］に記載のチタン合金板は、板厚が２．５ｍｍ超であってもよい。
［１０］上記［５］に記載のチタン合金板は、板厚が２．５ｍｍ超であってもよい。
［１１］上記［６］に記載のチタン合金板は、板厚が２．５ｍｍ超であってもよい。
［１２］本発明の別の態様に係るチタン合金板の製造方法は、［１］に記載のチタン合金板の製造方法であって、化学組成が、質量％で、Ａｌ：５．０～６．６％、Ｆｅ：０．７～２．３％、Ｓｉ：０．２０～０．３０％、Ｏ：０．１０～０．２０％、Ｃ：０．０５０％未満、Ｎ：０．０５０％以下、Ｎｉ：０％以上０．１５％未満、Ｃｒ：０％以上０．２５％未満、Ｍｎ：０％以上０．２５％未満、残部：Ｔｉ及び不純物からなるチタン素材を加熱温度まで加熱する加熱工程と、前記加熱工程後の前記チタン素材を一方向に熱間圧延して熱延板を得る熱間圧延工程と、前記熱間圧延工程後の前記熱延板を、４００℃以下の巻取温度まで８．０℃／ｓ以上の速度で冷却して、前記巻取温度で巻き取る巻取工程と、前記巻き取り工程後の前記熱延板に対して焼鈍を行う焼鈍工程と、を有し、前記加熱工程では、前記加熱温度が、単位℃でのβ変態点温度をＴβとしたとき、Ｔβ℃以上、（Ｔβ＋１５０）℃以下であり、前記熱間圧延工程では、圧下率が８５％以上であり、仕上温度が（Ｔβ－１７０）℃以上（Ｔβ－１００）℃以下であり、前記焼鈍工程では、前記焼鈍における焼鈍温度Ｔが６００℃以上Ｔβ以下であり、かつ、前記焼鈍温度Ｔと、前記焼鈍温度における単位秒での保持時間ｔとが、下記式（３）を満足する。
　（Ｔ＋２７３．１５）×（Ｌｏｇ１０（ｔ）＋２０）＜２７０００　…式（３）
［１３］上記［１２］に記載のチタン合金板の製造方法は、前記焼鈍工程では、前記焼鈍における前記焼鈍温度Ｔが６００℃以上Ｔβ以下であり、かつ、前記焼鈍温度Ｔと、前記焼鈍温度における単位秒での前記保持時間ｔとが、下記式（３’）を満足してもよい。
　２２０００≦（Ｔ＋２７３．１５）×（Ｌｏｇ１０（ｔ）＋２０）＜２７０００　…式（３’） The present inventors investigated the strength (0.2% PS (0.2% proof stress)), Young's modulus, specific gravity, and workability of an α+β type titanium alloy that does not require expensive elements such as V. .
As a result, it was found that high strength, high Young's modulus, low specific gravity, and high workability can be obtained by controlling the chemical composition, texture, etc. within appropriate ranges.
The present invention was completed based on the above findings, and the gist thereof is as follows.
[1] The titanium alloy plate according to one embodiment of the present invention has a chemical composition in mass %: Al: 5.0 to 6.6%, Fe: 0.7 to 2.3%, Si: 0.20 ~0.30%, O: 0.10~0.20%, C: less than 0.050%, N: 0.050% or less, Ni: 0% or more and less than 0.15%, Cr: 0% or more and 0 less than .25%, Mn: 0% or more and less than 0.25%, and the remainder: Ti and impurities, in the chemical composition, Al content in mass % is [%Al], Fe content is [% When the Si content is [%Si] and the O content is [%O], the following formulas (1) and (2) are satisfied, and the crystal orientation of the α phase is according to Bunge's notation method. When expressed as Euler angle g = {φ1, φ, φ2}, the maximum accumulated orientation indicated by the crystal orientation distribution function f(g) is φ1: 0~30°, Φ: 60~90°, φ2: 0~ 60°, the maximum integration degree of the maximum integration direction is 10.0 or more, and φ1: 70 to 90°, φ: 70 to 90°, φ2: 0 to 60°, and φ1: 70 to 90°. °, Φ: 10-30°, Φ2: 0-60°, the maximum integration degree is 2.5 or less, and YR in the board width direction is 0.99 or less.
11.5<[%Al]+2×[%Fe]+8×[%Si]+18×[%O]<15.5...(1)
-4.5<[%Fe]-0.9×[%Al]+1.3×[%O]+1.8×[%Si]<-2.4...(2)
[2] The titanium alloy plate according to [1] above has a 0.2% proof stress in the plate width direction at 25°C of 1000 MPa or more, a Young's modulus in the plate width direction of 135 GPa or more, and a specific gravity of 4. It may be less than .45g/ cm3 .
[3] The titanium alloy plate according to [1] or [2] above has a half width of a diffraction peak at 2θ=53.3±1° detected by X-ray diffraction using CuKα as a radiation source of 0. The angle may be 20° or less.
[4] The titanium alloy plate according to any one of [1] to [3] above has a band structure having an aspect ratio of more than 3.0 and extending in the longitudinal direction of the plate, and the area ratio of the band structure is It may be 70% or more.

[5] The titanium alloy plate according to any one of [1] to [3] above may have a YR in the plate width direction of 0.85 or more and 0.97 or less.
[6] In the titanium alloy plate according to [4] above, YR in the plate width direction may be 0.85 or more and 0.97 or less.
[7] The titanium alloy plate according to [1] or [2] above may have a thickness of more than 2.5 mm.
[8] The titanium alloy plate according to [3] above may have a thickness of more than 2.5 mm.
[9] The titanium alloy plate described in [4] above may have a thickness of more than 2.5 mm.
[10] The titanium alloy plate described in [5] above may have a thickness of more than 2.5 mm.
[11] The titanium alloy plate described in [6] above may have a thickness of more than 2.5 mm.
[12] A method for producing a titanium alloy plate according to another aspect of the present invention is the method for producing a titanium alloy plate according to [1], wherein the chemical composition is Al: 5.0 to 6% by mass. .6%, Fe: 0.7-2.3%, Si: 0.20-0.30%, O: 0.10-0.20%, C: less than 0.050%, N: 0.050 % or less, Ni: 0% or more and less than 0.15%, Cr: 0% or more and less than 0.25%, Mn: 0% or more and less than 0.25%, remainder: Ti and impurities.Heat the titanium material to the heating temperature. a heating step of hot-rolling the titanium material in one direction after the heating step to obtain a hot-rolled sheet, and rolling the hot-rolled sheet after the hot-rolling step at a temperature of 400°C or less. a winding step of cooling to a winding temperature at a rate of 8.0° C./s or more and winding at the winding temperature; an annealing step of annealing the hot rolled sheet after the winding step; In the heating step, the heating temperature is T β °C or more and (T β +150) °C or less, where T β is the β transformation point temperature in °C, and in the hot rolling step, , the rolling reduction is 85% or more, the finishing temperature is (T β -170) °C or more and (T β -100) °C or less, and in the annealing step, the annealing temperature T in the annealing is 600 °C or more and T β or less. And, the annealing temperature T and the holding time t in units of seconds at the annealing temperature satisfy the following formula (3).
(T+273.15)×(Log 10 (t)+20)<27000...Formula (3)
[13] In the method for manufacturing a titanium alloy plate according to [12] above, in the annealing step, the annealing temperature T in the annealing is 600°C or more and Tβ or less, and the annealing temperature T and the annealing The holding time t in units of seconds at the temperature may satisfy the following formula (3').
22000≦(T+273.15)×(Log 10 (t)+20)<27000...Equation (3')
　本発明の上記態様によれば、α＋β型チタン合金板であって、高強度、高ヤング率、低比重、かつ高加工性を有するチタン合金板及びその製造方法を提供することができる。
　このチタン合金板は、ゴルフクラブ用途に好適である。 According to the above aspect of the present invention, it is possible to provide an α+β type titanium alloy plate having high strength, high Young's modulus, low specific gravity, and high workability, and a method for manufacturing the same.
This titanium alloy plate is suitable for use in golf clubs.
Ｂｕｎｇｅの表記方法によるオイラー角によるチタン合金板のα相結晶粒の結晶方位を説明するための説明図である。FIG. 2 is an explanatory diagram for explaining the crystal orientation of α-phase crystal grains of a titanium alloy plate according to Euler angles according to Bunge's notation method. 本開示の一実施形態に係るチタン合金板の電子線後方散乱回折法により求められた結晶方位分布関数の一例である。It is an example of the crystal orientation distribution function calculated|required by the electron beam backscatter diffraction method of the titanium alloy plate based on one embodiment of this disclosure. バンド組織の一例を示す光学顕微鏡写真（倍率２００倍）である。It is an optical micrograph (200x magnification) showing an example of a band structure.
　本発明の一実施形態に係るチタン合金板（本実施形態に係るチタン合金板）について説明する。
　本実施形態に係るチタン合金板は、化学組成が、質量％で、Ａｌ：５．０～６．６％、Ｆｅ：０．７～２．３％、Ｓｉ：０．２０～０．３０％、Ｏ：０．１０～０．２０％、Ｃ：０．０５０％未満、Ｎ：０．０５０％以下、Ｎｉ：０％以上０．１５％未満、Ｃｒ：０％以上０．２５％未満、Ｍｎ：０％以上０．２５％未満、残部：Ｔｉ及び不純物からなり、
　前記化学組成における、質量％での、Ａｌ含有量を［％Ａｌ］、Ｆｅ含有量を［％Ｆｅ］、Ｓｉ含有量を［％Ｓｉ］、Ｏ含有量を［％Ｏ］としたとき、１１．５＜［％Ａｌ］＋２×［％Ｆｅ］＋８×［％Ｓｉ］＋１８×［％Ｏ］＜１５．５、及び、－４．５＜［％Ｆｅ］－０．９×［％Ａｌ］＋１．３×［％Ｏ］＋１．８×［％Ｓｉ］＜－２．４を満足し、
　α相の結晶方位をＢｕｎｇｅの表記方法によるオイラー角ｇ＝｛φ１，Φ，φ２｝で表した場合に、結晶方位分布関数ｆ（ｇ）により示される最大集積方位がφ１：０～３０°、Φ：６０～９０°、φ２：０～６０°の範囲にあり、
　前記最大集積方位の最大集積度が１０．０以上で、かつ、
　φ１：７０～９０°、Φ：７０～９０°、φ２：０～６０°及びφ１：７０～９０°、Φ：１０～３０°、φ２：０～６０°の範囲の最大集積度が２．５以下であり、
　板幅方向のＹＲが０．９９以下である。 A titanium alloy plate according to one embodiment of the present invention (titanium alloy plate according to this embodiment) will be described.
The titanium alloy plate according to this embodiment has a chemical composition in mass %: Al: 5.0 to 6.6%, Fe: 0.7 to 2.3%, Si: 0.20 to 0.30%. , O: 0.10 to 0.20%, C: less than 0.050%, N: 0.050% or less, Ni: 0% or more and less than 0.15%, Cr: 0% or more and less than 0.25%, Mn: 0% or more and less than 0.25%, remainder: consisting of Ti and impurities,
In the chemical composition, when the Al content is [%Al], the Fe content is [%Fe], the Si content is [%Si], and the O content is [%O] in mass %, 11 .5<[%Al]+2×[%Fe]+8×[%Si]+18×[%O]<15.5, and -4.5<[%Fe]-0.9×[%Al] +1.3×[%O]+1.8×[%Si]<-2.4,
When the crystal orientation of the α phase is expressed by the Euler angle g = {φ1, Φ, φ2} according to Bunge's notation, the maximum accumulation orientation shown by the crystal orientation distribution function f(g) is φ1: 0 to 30°, Φ: in the range of 60 to 90°, φ2: in the range of 0 to 60°,
The maximum degree of accumulation in the maximum accumulation direction is 10.0 or more, and
The maximum integration degree in the range of φ1: 70-90°, φ: 70-90°, φ2: 0-60° and φ1: 70-90°, φ: 10-30°, φ2: 0-60° is 2. 5 or less,
YR in the board width direction is 0.99 or less.
＜化学組成＞
　本実施形態に係るチタン合金板の化学組成について説明する。以下の合金元素の含有量の説明において特に断りのない限り、「％」との表記は「質量％」を表わすものとする。 <Chemical composition>
The chemical composition of the titanium alloy plate according to this embodiment will be explained. In the following description of the content of alloying elements, unless otherwise specified, the notation "%" represents "mass %".
Ａｌ：５．０～６．６％
　Ａｌは固溶強化能の高い元素であり、室温での強度の上昇に有効な元素である。また、ＡｌはＴｉよりも軽い元素であり、比重の低下に寄与する。所定の室温での強度（特に０．２％ＰＳ（０．２％耐力））の確保及び低比重化のため、Ａｌ含有量を５．０％以上とする。Ａｌ含有量は、好ましくは５．２％以上、より好ましくは５．３％以上、さらに好ましくは５．４％以上である。
　一方、Ａｌ含有量が６．６％を超えると、合金板が脆化して圧延、搬送の際に破断するおそれがあるとともに、凝固偏析などにより局所的にα相が過度に固溶強化されて硬い領域が生成し、靱性が低下する。そのため、Ａｌ含有量を６．６％以下とする。Ａｌ含有量は、好ましくは６．５％以下、より好ましくは６．３％以下、さらに好ましくは６．０％以下である。 Al: 5.0-6.6%
Al is an element with high solid solution strengthening ability, and is an element effective in increasing strength at room temperature. Furthermore, Al is a lighter element than Ti, and contributes to lowering the specific gravity. In order to ensure strength (particularly 0.2% PS (0.2% yield strength)) at a predetermined room temperature and to reduce specific gravity, the Al content is set to 5.0% or more. The Al content is preferably 5.2% or more, more preferably 5.3% or more, even more preferably 5.4% or more.
On the other hand, if the Al content exceeds 6.6%, the alloy plate may become brittle and break during rolling or transportation, and the α phase may locally become excessively solid solution strengthened due to solidification segregation. Hard areas are formed and the toughness is reduced. Therefore, the Al content is set to 6.6% or less. The Al content is preferably 6.5% or less, more preferably 6.3% or less, even more preferably 6.0% or less.
Ｆｅ：０．７～２．３％
　Ｆｅは安価であるが、固溶強化能の高い元素である。そのため、安価に室温での強度を高めるために有効な元素である。また、Ｆｅは、β安定化元素であり、後述する板幅方向のヤング率と強度とを高めるために発達させるＴ－ｔｅｘｔｕｒｅを得るために必要な、高温２相温度域を広げる効果を有する元素である。
　これらの効果を得るため、Ｆｅ含有量を０．７％以上とする。Ｆｅ含有量は、好ましくは０．９％以上であり、より好ましくは１．２％以上である。
　一方、Ｆｅは非常に凝固偏析し易い元素である。そのため、含有量が多くなると性能のばらつきが大きくなり、場所によっては疲労強度が低下する。さらに、ＦｅはＴｉよりも重いため入れすぎると比重が上昇する。そのため、Ｆｅ含有量を２．３％以下とする。Ｆｅ含有量は、好ましくは２．１％以下、より好ましくは１．９％以下である。 Fe: 0.7-2.3%
Although Fe is inexpensive, it is an element with high solid solution strengthening ability. Therefore, it is an effective element for increasing strength at room temperature at low cost. In addition, Fe is a β-stabilizing element and has the effect of widening the high-temperature two-phase temperature range, which is necessary to obtain the T-texture that is developed to increase the Young's modulus and strength in the sheet width direction, which will be described later. It is.
In order to obtain these effects, the Fe content is set to 0.7% or more. The Fe content is preferably 0.9% or more, more preferably 1.2% or more.
On the other hand, Fe is an element that is extremely susceptible to solidification and segregation. Therefore, as the content increases, variations in performance will increase, and fatigue strength will decrease depending on the location. Furthermore, since Fe is heavier than Ti, if it is added too much, the specific gravity will increase. Therefore, the Fe content is set to 2.3% or less. The Fe content is preferably 2.1% or less, more preferably 1.9% or less.
Ｓｉ：０．２０～０．３０％
　Ｓｉはβ安定化元素であるが、α相中にも固溶し高い固溶強化能を示す元素である。上記のようにＦｅは偏析の問題から２．３％超含有させることは難しい。そのため、本実施形態に係るチタン合金板では、Ｓｉの固溶強化によって更なる高強度化を図る。Ｓｉは下記のＯと逆の偏析傾向にあり、さらにＯ程には凝固偏析し難いことから、適正量のＳｉをＯと同時に含有させることにより、高い強度（０．２％ＰＳ）が得られる。Ｓｉ含有量が０．２０％未満では十分な効果が得られないので、Ｓｉ含有量を０．２０％以上とする。
　一方、Ｓｉ含有量が多いとシリサイドと言われる金属間化合物が形成され、疲労強度が低下したり、圧延時に割れが生じやすくなったりする場合がある。また、偏析によって板厚方向の特性差が多くなる場合がある。そのため、Ｓｉ含有量を０．３０％以下とする。 Si: 0.20-0.30%
Although Si is a β stabilizing element, it is also an element that dissolves in solid solution in the α phase and exhibits a high solid solution strengthening ability. As mentioned above, it is difficult to contain more than 2.3% Fe due to segregation problems. Therefore, in the titanium alloy plate according to this embodiment, the strength is further increased by solid solution strengthening of Si. Si has a tendency to segregate in the opposite direction to O, as described below, and is also less likely to solidify and segregate than O. Therefore, high strength (0.2% PS) can be obtained by containing an appropriate amount of Si at the same time as O. . If the Si content is less than 0.20%, sufficient effects cannot be obtained, so the Si content is set to 0.20% or more.
On the other hand, if the Si content is high, an intermetallic compound called silicide is formed, which may reduce fatigue strength or cause cracks to easily occur during rolling. Furthermore, due to segregation, differences in properties in the thickness direction may increase. Therefore, the Si content is set to 0.30% or less.
Ｏ：０．１０～０．２０％
　Ｏは高強度化に有効な元素である。この効果を得るため、Ｏ含有量を０．１０％以上とする。上述の通り、Ｓｉと同時に含有させることでその効果は大きい。
　一方、Ｏ含有量が多くなると、延性や加工性が低下したり、熱延板製造時に破断し易くなって製造性が低下したりする場合がある。特に、ＯはＡｌと共存するとＴｉ３Ａｌの形成を促進する。Ｔｉ３Ａｌの形成は室温での延性や加工性が大幅に低下する原因となる。また、Ｏは侵入型元素であり、含有量が多くなると比重が上昇するため、後述する式（１）や式（２）の調整が必要となる。これらより、Ｏ含有量を０．２０％以下とする。 O: 0.10-0.20%
O is an effective element for increasing strength. In order to obtain this effect, the O content is set to 0.10% or more. As mentioned above, the effect is great when it is contained simultaneously with Si.
On the other hand, if the O content increases, the ductility and workability may decrease, or the steel may become more likely to break during hot-rolled sheet production, resulting in a decrease in manufacturability. In particular, when O coexists with Al, it promotes the formation of Ti 3 Al. The formation of Ti 3 Al causes a significant decrease in ductility and workability at room temperature. Further, O is an interstitial element, and as the content increases, the specific gravity increases, so it is necessary to adjust the equations (1) and (2) described below. Based on these, the O content is set to 0.20% or less.
Ｃ：０．０５０％未満
Ｎ：０．０５０％以下
　Ｃ及びＮは、チタン合金板の延性や加工性を低下させる元素である。そのため、Ｃ含有量を０．０５０％未満、Ｎ含有量を０．０５０％以下とする。
　Ｃ及びＮは、Ｏと同様に高強度化に寄与する元素であるものの、本実施形態に係るチタン合金板ではＯによって強度の向上を図るため、Ｃ、Ｎは必須ではない。
　延性や加工性の観点からは、Ｃ含有量及びＮ含有量は少ない方が好ましく、０％でもよいが、Ｃ及びＮは原料のスポンジチタン、スクラップ、合金元素原料から不純物として混入することがあるので、Ｃ含有量を０．０００１％以上、Ｎ含有量を０．０００１％以上としてもよい。 C: less than 0.050% N: 0.050% or less C and N are elements that reduce the ductility and workability of the titanium alloy plate. Therefore, the C content is set to less than 0.050%, and the N content is set to 0.050% or less.
C and N, like O, are elements that contribute to high strength, but in the titanium alloy plate according to this embodiment, C and N are not essential because the strength is improved by O.
From the viewpoint of ductility and workability, it is preferable that the C content and N content are low, and 0% is also acceptable, but C and N may be mixed in as impurities from the raw material titanium sponge, scrap, and alloying element raw materials. Therefore, the C content may be set to 0.0001% or more, and the N content may be set to 0.0001% or more.
　残部：Ｔｉ及び不純物
　本実施形態に係るチタン合金板の化学組成の残部は、Ｔｉおよび不純物であってよい。不純物とは、例示すれば、精錬工程等で混入するＨ、Ｃｌ、Ｎａ、Ｍｇ、Ｃａ、Ｂおよびスクラップ等から混入するＺｒ、Ｓｎ、Ｍｏ、Ｎｂ、Ｔａ、Ｖであるが、これらには限られない。不純物は、各元素の含有量が０．１％以下、かつ総量で０．５％以下であれば問題無いレベルである。また、Ｈ含有量は、１５０ｐｐｍ以下であることが好ましい。Ｂは、鋳塊内で粗大な析出物となる懸念がある。そのため、不純物として含有される場合でも、Ｂ含有量は極力抑制することが好ましい。本実施形態に係るチタン合金板では、Ｂ含有量を０．０１％以下とすることが好ましい。
　ただし、本実施形態に係るチタン合金板では、強度や加工性を向上させるため、残部の一部に代えて、Ｎｉ、Ｃｒ、Ｍｎを以下の範囲で含有量してもよい。ただし、これらの元素は含まれなくてもよい（任意元素である）ので、下限は０％である。また、不純物として含有されることも許容される。 Remainder: Ti and Impurities The remainder of the chemical composition of the titanium alloy plate according to this embodiment may be Ti and impurities. Examples of impurities include H, Cl, Na, Mg, Ca, and B that are mixed in during the refining process, and Zr, Sn, Mo, Nb, Ta, and V that are mixed in from scraps, etc., but are not limited to these. I can't do it. The level of impurities is acceptable if the content of each element is 0.1% or less and the total amount is 0.5% or less. Moreover, it is preferable that H content is 150 ppm or less. There is a concern that B will form coarse precipitates within the ingot. Therefore, even when B is contained as an impurity, it is preferable to suppress the B content as much as possible. In the titanium alloy plate according to this embodiment, the B content is preferably 0.01% or less.
However, in the titanium alloy plate according to the present embodiment, in order to improve strength and workability, Ni, Cr, and Mn may be contained in the following range in place of a part of the remaining portion. However, since these elements do not need to be included (they are optional elements), the lower limit is 0%. Further, it is also allowed to be contained as an impurity.
Ｎｉ：０．１５％未満
　Ｎｉは、引張強さおよび加工性を向上させる元素である。そのため、含有させてもよい。これらの効果を得る場合、Ｎｉ含有量は０．０１％以上であることが好ましい。
　一方、Ｎｉ含有量が０．１５％以上であると、平衡相である金属間化合物Ｔｉ２Ｎｉが生成し、チタン合金板の疲労強度および室温での延性が劣化する場合がある。よって、含有させる場合、Ｎｉ含有量は、０．１５％未満とする。Ｎｉ含有量は、好ましくは０．１４％以下、より好ましくは０．１１％以下である。 Ni: less than 0.15% Ni is an element that improves tensile strength and workability. Therefore, it may be included. In order to obtain these effects, the Ni content is preferably 0.01% or more.
On the other hand, if the Ni content is 0.15% or more, an intermetallic compound Ti 2 Ni, which is an equilibrium phase, is generated, which may deteriorate the fatigue strength and ductility at room temperature of the titanium alloy plate. Therefore, when included, the Ni content is set to less than 0.15%. The Ni content is preferably 0.14% or less, more preferably 0.11% or less.
Ｃｒ：０．２５％未満
　Ｃｒは、引張強さおよび加工性を向上させる元素である。そのため、含有させてもよい。これらの効果を得る場合、Ｃｒ含有量は０．０１％以上であることが好ましい。
　一方、Ｃｒ含有量が０．２５％以上であると、平衡相である金属間化合物ＴｉＣｒ２が生成し、チタン合金板の疲労強度および室温での延性が劣化する場合がある。よって、含有させる場合、Ｃｒ含有量は０．２５％未満とする。Ｃｒ含有量は、好ましくは、０．２４％以下、より好ましくは０．２１％以下である。 Cr: Less than 0.25% Cr is an element that improves tensile strength and workability. Therefore, it may be included. In order to obtain these effects, the Cr content is preferably 0.01% or more.
On the other hand, if the Cr content is 0.25% or more, an intermetallic compound TiCr2 , which is an equilibrium phase, is generated, which may deteriorate the fatigue strength and ductility at room temperature of the titanium alloy plate. Therefore, when Cr is included, the Cr content should be less than 0.25%. The Cr content is preferably 0.24% or less, more preferably 0.21% or less.
Ｍｎ：０．２５％未満
　Ｍｎは、引張強さおよび加工性を向上させる元素である。そのため、含有させてもよい。これらの効果を得る場合、Ｍｎ含有量は０．０１％以上であることが好ましい。
　一方、Ｍｎ含有量が０．２５％以上であると、平衡相である金属間化合物ＴｉＭｎが生成し、チタン合金板の疲労強度および室温での延性が劣化する場合がある。よって、含有させる場合、Ｍｎ含有量は０．２５％未満とする。Ｍｎ含有量は、好ましくは０．２４％以下、より好ましくは０．２０％以下である。 Mn: less than 0.25% Mn is an element that improves tensile strength and workability. Therefore, it may be included. In order to obtain these effects, the Mn content is preferably 0.01% or more.
On the other hand, if the Mn content is 0.25% or more, an intermetallic compound TiMn, which is an equilibrium phase, is generated, and the fatigue strength and ductility at room temperature of the titanium alloy plate may deteriorate. Therefore, when Mn is included, the Mn content should be less than 0.25%. The Mn content is preferably 0.24% or less, more preferably 0.20% or less.
　本実施形態に係るチタン合金板では、各元素が上記の範囲を満足した上で、質量％での、Ａｌ含有量を［％Ａｌ］、Ｆｅ含有量を［％Ｆｅ］、Ｓｉ含有量を［％Ｓｉ］、Ｏ含有量を［％Ｏ］としたとき、以下の式（１）及び式（２）を満足する必要がある。
１１．５＜［％Ａｌ］＋２×［％Ｆｅ］＋８×［％Ｓｉ］＋１８×［％Ｏ］＜１５．５・・・（１）
－４．５＜［％Ｆｅ］－０．９×［％Ａｌ］＋１．３×［％Ｏ］＋１．８×［％Ｓｉ］＜－２．４・・・（２）
　式（１）の中辺の値が、１１．５以下である、または、式（２）の中辺の値が、－４．５以下であると、十分な０．２％ＰＳが得られない。
　一方、式（１）の中辺の値が、１５．５以上である、または、式（２）の中辺の値が、－２．４以上であると、比重が高くなる。
　式（１）の中辺の値は、好ましくは１２．０以上、１５．０以下である。 In the titanium alloy plate according to the present embodiment, after each element satisfies the above range, the Al content in mass % is [%Al], the Fe content is [%Fe], and the Si content is [%Fe]. %Si] and the O content is [%O], it is necessary to satisfy the following formulas (1) and (2).
11.5<[%Al]+2×[%Fe]+8×[%Si]+18×[%O]<15.5...(1)
-4.5<[%Fe]-0.9×[%Al]+1.3×[%O]+1.8×[%Si]<-2.4...(2)
If the value of the middle side of equation (1) is 11.5 or less, or if the value of the middle side of equation (2) is -4.5 or less, sufficient 0.2% PS can be obtained. do not have.
On the other hand, when the value of the middle side of equation (1) is 15.5 or more, or the value of the middle side of equation (2) is -2.4 or more, the specific gravity becomes high.
The value of the middle side of formula (1) is preferably 12.0 or more and 15.0 or less.
＜集合組織＞
　チタン合金は、β域またはβ相割合の高いα＋β高温域の温度で、一方向に熱間圧延を行うと、β相からα相への相変態時に、バリアント選択則により板幅方向にｈｃｐのＣ軸が配向した集合組織（Ｔ－ｔｅｘｔｕｒｅ）を形成する。Ｔ－ｔｅｘｔｕｒｅは、圧延変形を受けた未再結晶のβ相がα相に変態する際に形成する集合組織である。Ｔ－ｔｅｘｔｕｒｅは、板幅方向の、０．２％ＰＳや引張強さなどの強度、及びヤング率を向上させる。
　α相の結晶方位をＢｕｎｇｅの表記方法によるオイラー角ｇ＝｛φ１，Φ，φ２｝で表した場合に、結晶方位分布関数ｆ（ｇ）により示される最大集積方位がφ１：０～３０°、Φ：６０～９０°、φ２：０～６０°の範囲（以下領域１と言う場合がある）にあり、前記最大集積方位の最大集積度が１０．０以上であれば、Ｔ－ｔｅｘｔｕｒｅが発達した組織である。
　領域１の最大集積度が、１０．０未満であると、板幅方向の引張強さなどの強度及びヤング率が十分に上昇しない。
　領域１の最大集積度の上限は限定されないが、４０．０以下、または３０．０以下であってもよい。 <Collective tissue>
When a titanium alloy is hot-rolled in one direction at a temperature in the β range or α+β high temperature range with a high β phase ratio, during the phase transformation from the β phase to the α phase, the hcp increases in the sheet width direction due to the variant selection rule. A texture (T-texture) in which the C-axis is oriented is formed. T-texture is a texture formed when an unrecrystallized β phase that has undergone rolling deformation transforms into an α phase. T-texture improves strength such as 0.2% PS and tensile strength in the sheet width direction, and Young's modulus.
When the crystal orientation of the α phase is expressed by the Euler angle g = {φ1, Φ, φ2} according to Bunge's notation, the maximum accumulation orientation shown by the crystal orientation distribution function f(g) is φ1: 0 to 30°, If it is in the range of Φ: 60 to 90 degrees, φ2: 0 to 60 degrees (hereinafter sometimes referred to as region 1), and the maximum degree of accumulation in the maximum accumulation direction is 10.0 or more, T-texture has developed. It is an organization that has
If the maximum degree of integration in region 1 is less than 10.0, strength such as tensile strength in the width direction and Young's modulus will not increase sufficiently.
The upper limit of the maximum integration degree of region 1 is not limited, but may be 40.0 or less, or 30.0 or less.
　また、本実施形態に係るチタン合金板では、さらに、α相の結晶方位をＢｕｎｇｅの表記方法によるオイラー角ｇ＝｛φ１，Φ，φ２｝で表した場合に、結晶方位分布関数ｆ（ｇ）により示されるφ１：７０～９０°、Φ：７０～９０°、φ２：０～６０°の範囲及びφ１：７０～９０°、Φ：１０～３０°、φ２：０～６０°の範囲（以下領域２と言う場合がある）の、最大集積度が２．５以下である。
　領域２の最大集積度が２．５超であると（φ１：７０～９０°、Φ：７０～９０°、φ２：０～６０°の範囲またはφ１：７０～９０°、Φ：１０～３０°、φ２：０～６０°の範囲のいずれかでも最大集積度が２．５超であると）加工性が低下する。また、領域２の集積度が高くなると、領域１の集積度は低くなるので、板幅方向の強度やヤング率の低下につながる。領域２の集積度が高いことは、チタン合金板の板長手方向にｈｃｐのＣ軸が配向した集合組織が多く形成されていることを意味する。 Furthermore, in the titanium alloy plate according to the present embodiment, when the crystal orientation of the α phase is expressed by the Euler angle g={φ1, φ, φ2} according to Bunge's notation method, the crystal orientation distribution function f(g) The range of φ1: 70 to 90°, φ: 70 to 90°, φ2: 0 to 60° and the range of φ1: 70 to 90°, Φ: 10 to 30°, φ2: 0 to 60° (hereinafter (sometimes referred to as region 2), the maximum integration degree is 2.5 or less.
If the maximum integration degree of region 2 is more than 2.5 (φ1: 70-90°, Φ: 70-90°, φ2: 0-60° or φ1: 70-90°, Φ: 10-30 φ2: If the maximum integration degree exceeds 2.5 even in the range of 0 to 60°, the workability decreases. Furthermore, as the degree of integration in region 2 increases, the degree of integration in region 1 decreases, leading to a decrease in strength in the width direction and Young's modulus. A high degree of integration in region 2 means that many textures are formed in which the C-axis of hcp is oriented in the longitudinal direction of the titanium alloy plate.
　ここで、図１を参照して、Ｂｕｎｇｅの表記方法によるオイラー角ｇ＝｛φ１，Φ，φ２｝を説明する。図１は、Ｂｕｎｇｅの表記方法によるオイラー角によるチタン合金板のα相結晶粒の結晶方位を説明するための説明図である。試料座標系として、互いに直交する関係にある、ＲＤ（圧延方向）、ＴＤ（板幅方向）およびＮＤ（圧延面の法線方向）の３本の座標軸が示されている。また、結晶座標系として、互いに直交する関係にあるＸ軸、Ｙ軸およびＺ軸の３本の座標軸が示されている。そして、各座標系の原点が一致するようにそれぞれの座標軸が配置されており、ｈｃｐを示す六角柱がチタンのα相であるｈｃｐの（０００１）面の中心が原点と一致するように示されている。図１では、Ｘ軸は、α相の［１０－１０］方向と一致し、Ｙ軸は、［－１２－１０］方向と一致し、Ｚ軸は［０００１］方向（Ｃ軸方向）と一致する。 Here, the Euler angle g={φ1, φ, φ2} according to Bunge's notation will be explained with reference to FIG. FIG. 1 is an explanatory diagram for explaining the crystal orientation of α-phase crystal grains of a titanium alloy plate using Euler angles according to Bunge's notation method. As the sample coordinate system, three coordinate axes, RD (rolling direction), TD (plate width direction), and ND (normal line direction to the rolling surface), which are perpendicular to each other, are shown. Furthermore, as a crystal coordinate system, three coordinate axes, the X-axis, Y-axis, and Z-axis, which are orthogonal to each other are shown. The respective coordinate axes are arranged so that the origin of each coordinate system coincides, and the hexagonal prism indicating hcp is shown so that the center of the (0001) plane of hcp, which is the alpha phase of titanium, coincides with the origin. ing. In Figure 1, the X-axis coincides with the [10-10] direction of the α phase, the Y-axis coincides with the [-12-10] direction, and the Z-axis coincides with the [0001] direction (C-axis direction). do.
　Ｂｕｎｇｅの表記方法では、試料座標系のＲＤ、ＴＤ、ＮＤと結晶座標系のＸ軸、Ｙ軸、Ｚ軸とがそれぞれ一致した状態をまず考える。そこから、結晶座標系をＺ軸回りに角度φ１だけ回転させ、φ１回転後のＸ軸（図１の状態）回りに角度Φだけ回転させる。最後にΦ度回転の後のＺ軸回りに角度φ２だけ回転させる。これらのφ１、Φ、φ２の３つの角度によって、結晶または結晶座標系は、試料座標系に対して特定の傾いた状態が表される。すなわち、φ１、Φ、φ２の３つの角度を用いて、結晶方位は一義的に定められる。これら３つの角度φ１、Φ、φ２を、Ｂｕｎｇｅの表記方法によるオイラー角という。このＢｕｎｇｅの表記方法によるオイラー角により、チタン合金板のα相結晶粒の結晶方位（Ｃ軸方向など）を規定する。 In Bunge's notation method, first consider a state in which the RD, TD, and ND of the sample coordinate system are aligned with the X, Y, and Z axes of the crystal coordinate system, respectively. From there, the crystal coordinate system is rotated by an angle φ1 around the Z-axis, and then rotated by an angle Φ around the X-axis (the state shown in FIG. 1) after the φ1 rotation. Finally, after rotation by Φ degrees, it is rotated by an angle of φ2 around the Z axis. These three angles φ1, φ, and φ2 represent a specific tilted state of the crystal or the crystal coordinate system with respect to the sample coordinate system. That is, the crystal orientation is uniquely determined using the three angles φ1, φ, and φ2. These three angles φ1, φ, and φ2 are called Euler angles according to Bunge's notation. The Euler angle according to Bunge's notation method defines the crystal orientation (C-axis direction, etc.) of the α-phase crystal grains of the titanium alloy plate.
　図１では、φ１は、試料座標系のＲＤ－ＴＤ平面（圧延平面）と結晶座標系の［１０－１０］－［－１２－１０］平面との交線と、試料座標系のＲＤ（圧延方向）とがなす角度である。Φは、試料座標系のＮＤ（圧延面の法線方向）と、結晶座標系の［０００１］方向（（０００１）面の法線方向）とがなす角度である。φ２は、試料座標系のＲＤ－ＴＤ平面（圧延面）と結晶座標系の［１０－１０］－［－１２－１０］平面との交線と、結晶座標系の［１０－１０］方向とがなす角度である。 In Figure 1, φ1 is the intersection line between the RD-TD plane (rolling plane) of the sample coordinate system and the [10-10]-[-12-10] plane of the crystal coordinate system, and the RD (rolling plane) of the sample coordinate system. direction). Φ is the angle between the ND (normal direction to the rolling surface) of the sample coordinate system and the [0001] direction (normal direction to the (0001) plane) of the crystal coordinate system. φ2 is the intersection line between the RD-TD plane (rolled surface) of the sample coordinate system and the [10-10]-[-12-10] plane of the crystal coordinate system, and the [10-10] direction of the crystal coordinate system. is the angle formed by
　最大集積方位および最大集積度は、以下のようにして求めることができる。
　チタン合金板を幅方向（ＴＤ）中央位置で、板幅方向に垂直な断面（Ｌ断面）を化学研磨して後方散乱電子線回折（ＥＢＳＤ）法を用いて結晶方位解析を行う。
　具体的には、このＬ断面を、エメリー紙を用いて湿式研磨した後、当該表面を、コロイダルシリカを用いて鏡面研磨して鏡面とする。この鏡面にした面について、板厚方向の表裏面からそれぞれ１０００μｍを除いた厚さ方向の範囲、かつ板長手方向に１０００μｍの範囲（（全板厚―表裏面１０００μｍ）×１０００μｍ）の矩形の領域に対し、ステップ１μｍで５視野程度測定する。ただし、板厚が２．５ｍｍ未満の場合は、板厚方向の測定範囲は、板厚中央部を中心として板厚の３０％の範囲とする。
　得られたデータについて、ＴＳＬソリューションズ製のＯＩＭ　ＡｎａｌｙｓｉｓＴＭソフトウェア（Ｖｅｒ．８．１．０）を用いて結晶方位分布関数ｆ（ｇ）（ＯＤＦ；Ｏｒｉａｎｔａｔｉｏｎ　Ｄｉｓｕｔｒｉｂｕｔｉｏｎ　Ｆｕｎｃｔｉｏｎ）を算出する。結晶方位分布関数ｆ（ｇ）は、ＥＢＳＤ法の球面調和関数法を用いたＴｅｘｔｕｒｅ解析において、展開指数を１６とし、ガウス半値幅を５°として算出する。その際に、圧延変形の対称性を考慮し、板厚方向、圧延方向、板幅方向それぞれに対して線対称となるように、計算を行う。
　ＯＤＦは、測定された結晶方位がφ１－Φ－φ２の３次元空間（オイラー空間）にプロットされた三次元分布を分布関数で表したものである。図２は、本実施形態に係るチタン合金板の電子線後方散乱回折法により求められた結晶方位分布関数ｆ（ｇ）の一例である。図２では、オイラー空間を二次元で表示するために、オイラー空間を角度φ２方向に５°ごとに水平にスライスし、得られた断面を並べられている。このＯＤＦにより、最大集積方位および最大集積度を算出することができる。図２では、φ１＝０°、Φ＝９０°、φ２＝３０°（点Ａ）において、最大集積方位が確認され、最大集積度は、３６．１である。上記では、板幅方向中央位置でのＬ断面を基に最大集積方位および最大集積度を求めているが、チタン合金板の集合組織は、板幅方向において、端部（エッジ部）を除いて略均一であるので、エッジ部を除く任意の板幅位置におけるＬ断面を基に最大集積方位および最大集積度を求めてもよい。ただし、エッジ部は製品板となる際にトリムされることが多いので、その場合には製品板の任意の板幅位置におけるＬ断面を基に最大集積方位および最大集積度を求めてもよい。トリムの有無が不明な場合には、端部から５０ｍｍ超の位置で求めればよい。 The maximum accumulation direction and maximum accumulation degree can be determined as follows.
A cross section (L cross section) perpendicular to the width direction of the titanium alloy plate is chemically polished at the central position in the width direction (TD), and crystal orientation analysis is performed using backscattered electron diffraction (EBSD).
Specifically, this L cross section is wet-polished using emery paper, and then the surface is mirror-polished using colloidal silica to give a mirror surface. Regarding this mirror-finished surface, a rectangular area is defined in the thickness direction excluding 1000 μm from each of the front and back surfaces in the board thickness direction, and in a range of 1000 μm in the board longitudinal direction ((total board thickness - front and back surfaces 1000 μm) x 1000 μm). On the other hand, about 5 fields of view are measured at a step of 1 μm. However, if the plate thickness is less than 2.5 mm, the measurement range in the plate thickness direction is a range of 30% of the plate thickness centered on the center of the plate thickness.
For the obtained data, a crystal orientation distribution function f(g) (ODF) is calculated using OIM Analysis TM software (Ver. 8.1.0) manufactured by TSL Solutions. The crystal orientation distribution function f(g) is calculated by setting the expansion index to 16 and the Gauss half width to 5° in texture analysis using the spherical harmonic function method of the EBSD method. At this time, the symmetry of rolling deformation is taken into account and calculations are performed so that the rolling deformation is symmetrical in each of the thickness direction, rolling direction, and width direction.
ODF is a distribution function that represents a three-dimensional distribution of measured crystal orientations plotted in a three-dimensional space (Euler space) of φ1-φ-φ2. FIG. 2 is an example of the crystal orientation distribution function f(g) obtained by the electron beam backscatter diffraction method of the titanium alloy plate according to the present embodiment. In FIG. 2, in order to display the Euler space in two dimensions, the Euler space is horizontally sliced every 5 degrees in the angle φ2 direction, and the obtained cross sections are arranged. With this ODF, the maximum accumulation direction and maximum accumulation degree can be calculated. In FIG. 2, the maximum integration direction is confirmed at φ1=0°, φ=90°, and φ2=30° (point A), and the maximum integration degree is 36.1. In the above, the maximum accumulation direction and maximum accumulation degree are determined based on the L cross section at the center position in the sheet width direction, but the texture of the titanium alloy sheet is Since it is substantially uniform, the maximum accumulation direction and maximum degree of accumulation may be determined based on the L cross section at any board width position excluding the edge portion. However, since the edge portion is often trimmed when the product board is made, in that case, the maximum accumulation direction and maximum integration degree may be determined based on the L cross section at an arbitrary board width position of the product board. If the presence or absence of trim is unknown, it may be determined at a position more than 50 mm from the end.
＜２θ＝５３．３±１°における回折ピークの半値幅＞
　チタン合金板では、その製造過程において熱延後に水冷を施すと、熱延により蓄積した転位が残存したり、β相からα相へ変態した際のひずみが残存したりする。このようなひずみは熱延板の強度を上昇させるものの、その後の加工等で熱を加えた際に、強度低下を招くことが懸念される。また、ひずみが残存することで、その後の加工の際に製品が変形する場合がある。また、ひずみが残存していると加工の際の加工硬化代が少なくなるので、ＹＲが高くなり加工性が低下する。そのため、加工時の変形を抑制するとともに、加工条件によらず高強度を得るとともに、ＹＲを低くするためには、熱延板のひずみ（転位）は少ない方が望ましい。
　ひずみの残存量（転位密度）を見積もる手法として、Ｘ線回折法（ＸＲＤ；Ｘ－Ｒａｙ　Ｄｉｆｆｒａｃｔｉｏｎ）により得られる回折ピークの半値幅から転位密度を見積もる方法がある。回折ピークの半値幅が大きいほど残存ひずみ量が多い。本実施形態に係るチタン合金板では、ＣｕＫαを線源とするＸ線回折法によって検出される２θ＝５３．３±１°の位置に表れる（１０－１２）面の回折ピークの半値幅によって、ひずみの残存量を評価する。本実施形態に係るチタン合金板では、ＣｕＫαを線源とするＸ線回折法によって検出される２θ＝５３．３±１°における回折ピークの半値幅が０．２０°以下であることが好ましい。上記回折ピークの半値幅は、より好ましくは０．１７°以下、さらに好ましくは０．１２°以下である。
　上記回折ピークの半値幅は、低い方が好ましいが、安定した相状態であっても転位はある程度存在し、完全に除去することは困難であることから、実質的な下限は０．０５°である。 <Half width of diffraction peak at 2θ=53.3±1°>
When a titanium alloy plate is water-cooled after hot rolling in the manufacturing process, dislocations accumulated during hot rolling may remain, or strains caused by transformation from β phase to α phase may remain. Although such strain increases the strength of the hot-rolled sheet, there is a concern that it may lead to a decrease in strength when heat is applied during subsequent processing. Furthermore, residual strain may cause the product to deform during subsequent processing. Furthermore, if strain remains, the work hardening allowance during processing will be reduced, resulting in a higher YR and lower workability. Therefore, in order to suppress deformation during processing, obtain high strength regardless of processing conditions, and lower YR, it is desirable that the strain (dislocation) in the hot rolled sheet is small.
As a method for estimating the residual amount of strain (dislocation density), there is a method of estimating the dislocation density from the half-width of a diffraction peak obtained by X-ray diffraction (XRD). The larger the half width of the diffraction peak, the larger the amount of residual strain. In the titanium alloy plate according to this embodiment, the half-value width of the diffraction peak of the (10-12) plane that appears at the position of 2θ = 53.3 ± 1° detected by X-ray diffraction using CuKα as a radiation source, Evaluate the amount of residual strain. In the titanium alloy plate according to the present embodiment, it is preferable that the half width of the diffraction peak at 2θ=53.3±1° detected by X-ray diffraction using CuKα as a radiation source is 0.20° or less. The half width of the diffraction peak is more preferably 0.17° or less, and even more preferably 0.12° or less.
The lower the half-width of the diffraction peak is, the better, but since dislocations exist to some extent even in a stable phase state and it is difficult to completely remove them, the practical lower limit is 0.05°. be.
　上記半値幅の測定に際しては、チタン合金板の表面を、エメリー紙を用いて湿式研磨した後、当該表面を、コロイダルシリカを用いて鏡面研磨して鏡面とする。鏡面としたチタン合金板の表面についてＸＲＤ測定を実施する。ＸＲＤ測定はＣｕＫαを線源とし、２θが５０．０°から５５．０°までの範囲を測定ピッチ０．０１°、測定速度２°／分で実施する。半値幅はＲｉｇａｋｕ製Ｓｍａｒｔｌａｂにより測定されたＸ線回折データを用い、Ｒｉｇａｋｕ製統合粉末Ｘ線解析ソフトウェアＰＤＸＬにより算出する。 When measuring the half-width, the surface of the titanium alloy plate is wet-polished using emery paper, and then mirror-polished using colloidal silica to give a mirror surface. XRD measurement is performed on the surface of a titanium alloy plate made into a mirror surface. The XRD measurement is carried out using CuKα as a radiation source in the range of 2θ from 50.0° to 55.0° at a measurement pitch of 0.01° and a measurement speed of 2°/min. The half width is calculated by Rigaku's integrated powder X-ray analysis software PDXL using X-ray diffraction data measured by Rigaku's Smartlab.
＜ミクロ組織＞
　本実施形態に係るチタン合金板は、アスペクト比が３．０超であり板長手方向（圧延方向）に伸長したバンド組織１を有し、当該バンド組織１の面積率が７０％以上であることが好ましい。ここで言うバンド組織１とは、例えば、図３の光学顕微鏡写真に示すような、板長手方向に伸長した組織である。具体的には、結晶粒の長軸／短軸で表されるアスペクト比が３．０超の結晶粒のことを言う。
　チタン合金では、変態点直下のα＋β域やβ域の温度で熱間圧延を行うと、板長手方向に伸長したバンド組織１が形成される。バンド組織１は、板厚方向に対して垂直な結晶粒界を多く有しているので、このバンド組織１を形成することで、板幅方向の強度やヤング率が高くなる。
　そのため、本実施形態に係るチタン合金板では、バンド組織１の面積率が７０％以上であることが好ましい。より好ましくは、７５％以上、更に好ましくは８０％以上である。また、すべての結晶粒がバンド組織でもよく、上限は１００％である。 <Microstructure>
The titanium alloy plate according to the present embodiment has a band structure 1 having an aspect ratio of more than 3.0 and extending in the longitudinal direction of the plate (rolling direction), and the area ratio of the band structure 1 is 70% or more. is preferred. The band structure 1 referred to here is, for example, a structure extending in the longitudinal direction of the plate as shown in the optical microscope photograph of FIG. Specifically, it refers to crystal grains having an aspect ratio expressed by the long axis/short axis of the crystal grains of more than 3.0.
When a titanium alloy is hot rolled at a temperature in the α+β range or β range just below the transformation point, a band structure 1 extending in the longitudinal direction of the plate is formed. Since the band structure 1 has many grain boundaries perpendicular to the sheet thickness direction, the strength and Young's modulus in the sheet width direction are increased by forming this band structure 1.
Therefore, in the titanium alloy plate according to this embodiment, it is preferable that the area ratio of the band structure 1 is 70% or more. More preferably, it is 75% or more, and still more preferably 80% or more. Further, all crystal grains may have a band structure, and the upper limit is 100%.
　バンド組織の面積率は、以下の方法で求める。
　各試料を板幅中央の位置で板幅方向に対し垂直に切断した断面を、エメリー紙を用いて湿式研磨した後、当該表面を、コロイダルシリカを用いて鏡面研磨して鏡面とする。その鏡面とした断面の板厚方向の表裏面からそれぞれ１０００μｍを除いた厚さ方向の範囲、かつ板長手方向に１０００μｍの範囲の矩形の領域を、ステップ１μｍで５視野程度を対象に、ＥＢＳＤ法による結晶方位解析を行い、旧β粒界に相当する方位差が１５°以上である大傾角粒界を粒界し、その粒界で囲まれた範囲を結晶粒として、結晶粒のそれぞれについてアスペクト比を算出し、アスペクト比が３．０超の結晶粒の部分をバンド組織と見なし、その面積率を算出する。 The area ratio of the band structure is determined by the following method.
A cross section of each sample cut perpendicular to the width direction of the plate at the center of the plate width is wet-polished using emery paper, and then the surface is polished to a mirror surface using colloidal silica. The EBSD method was applied to a rectangular area in the thickness direction excluding 1000 μm from the front and back surfaces of the mirror-finished cross section and 1000 μm in the longitudinal direction of the sheet, with a step of 1 μm and approximately 5 fields of view. By performing crystal orientation analysis using The ratio is calculated, and the portion of crystal grains having an aspect ratio of more than 3.0 is regarded as a band structure, and its area ratio is calculated.
＜特性＞
　本実施形態に係るチタン合金板は、上述のように、化学組成、集合組織、ミクロ組織を制御することで、高強度、高ヤング率、低比重、かつ高加工性を有する。
　近年のゴルフクラブ用途のチタン合金板への要求を考慮し、本実施形態に係るチタン合金板では、強度、ヤング率、比重、加工性の指標として、以下を満足することを目標とする。 <Characteristics>
As described above, the titanium alloy plate according to the present embodiment has high strength, high Young's modulus, low specific gravity, and high workability by controlling the chemical composition, texture, and microstructure.
Considering recent demands for titanium alloy plates for golf clubs, the titanium alloy plate according to this embodiment aims to satisfy the following as indicators of strength, Young's modulus, specific gravity, and workability.
板幅方向のＹＲ（０．２％ＰＳ／ＴＳ）：０．９９以下
　本実施形態に係るチタン合金板では、集合組織の制御によって、優れた加工性が得られる。しかしながら、その場合でもＹＲ（０．２％ＰＳ／ＴＳ（引張強さ））が高いと、加工の種類によっては加工性が低下する。通常は冷間圧延で加工されるチタン合金板については、高温で加工すれば加工性は改善するが、加熱により強度が低下するので、好ましくない。
　具体的には、上記集合組織を有したとしても、ＹＲが０．９９超であると、加工の際の加工硬化代がなく、破断が生じやすくなり、加工性が低下する。そのため、本実施形態に係るチタン合金板では、板幅方向のＹＲを０．９９（９９％）以下とする。
　さらに板幅方向の加工性が求められる場合には、板幅方向のＹＲが０．９８以下であることが好ましい。板幅方向のＹＲは、より好ましくは０．９７以下であり、さらに好ましくは０．９５以下であり、一層好ましくは０．９３以下である。
　ＹＲは、残存ひずみの量やその他の要因によって変化するが、ひずみ量の影響が大きいので、ＹＲを低下させる場合には、ひずみ量を低下させることが好ましい。
　一方、ＹＲが０．８５未満である場合には、狙いとする集合組織を形成出来ていないことが示唆される。そのため、ＹＲは０．８５以上であることを目標とする。 YR in the sheet width direction (0.2% PS/TS): 0.99 or less In the titanium alloy sheet according to the present embodiment, excellent workability can be obtained by controlling the texture. However, even in that case, if YR (0.2% PS/TS (tensile strength)) is high, workability may deteriorate depending on the type of processing. For titanium alloy plates that are normally processed by cold rolling, processing at high temperatures improves workability, but heating reduces strength, which is not preferable.
Specifically, even if it has the above-mentioned texture, if YR is more than 0.99, there is no work hardening allowance during processing, and breakage is likely to occur, resulting in reduced workability. Therefore, in the titanium alloy plate according to this embodiment, YR in the plate width direction is set to 0.99 (99%) or less.
Furthermore, when workability in the sheet width direction is required, it is preferable that YR in the sheet width direction is 0.98 or less. YR in the plate width direction is more preferably 0.97 or less, still more preferably 0.95 or less, and still more preferably 0.93 or less.
YR changes depending on the amount of residual strain and other factors, but since the amount of strain has a large effect, it is preferable to reduce the amount of strain when reducing YR.
On the other hand, when YR is less than 0.85, it is suggested that the targeted texture cannot be formed. Therefore, the goal is for YR to be 0.85 or more.
室温での板幅方向の０．２％ＰＳ：１０００ＭＰａ以上
　近年、ゴルフクラブ用途のチタン合金板には、更なる軽量化のため従来よりも高強度が要求されており、具体的には板幅方向の０．２％ＰＳが１０００ＭＰａ以上であることが要求されている。そのため、本実施形態に係るチタン合金板では、室温における板幅方向の０．２％ＰＳが１０００ＭＰａ以上であることを目標とする。
　チタン合金板の室温での板幅方向の０．２％ＰＳは、好ましくは１０１０ＭＰａ以上、より好ましくは１０３０ＭＰａ以上である。
　一方で、上記０．２％ＰＳは高い方が良いが、高すぎると切り欠き感受性の観点から合金板の破断のリスクが高まる。そのため、室温での板幅方向の０．２％ＰＳは１２００ＭＰａ以下であることが好ましい。より好ましくは、１１５０ＭＰａ以下である。
　板幅方向の０．２％ＰＳを高める理由としては、ゴルフ用途ではフェースの縦方向が反発力などに大きく影響し、通常は、チタン合金板は、板幅方向がフェースの縦方向となるように加工されるためである。
　本実施形態において、室温は２５℃とする。 0.2% PS in the plate width direction at room temperature: 1000 MPa or more In recent years, titanium alloy plates for golf clubs are required to have higher strength than before in order to further reduce weight. It is required that 0.2% PS in the direction is 1000 MPa or more. Therefore, in the titanium alloy plate according to the present embodiment, the target is that the 0.2% PS in the plate width direction at room temperature is 1000 MPa or more.
The 0.2% PS in the width direction of the titanium alloy plate at room temperature is preferably 1010 MPa or more, more preferably 1030 MPa or more.
On the other hand, the higher the 0.2% PS, the better, but if it is too high, the risk of fracture of the alloy plate increases from the viewpoint of notch sensitivity. Therefore, the 0.2% PS in the plate width direction at room temperature is preferably 1200 MPa or less. More preferably, it is 1150 MPa or less.
The reason for increasing the PS by 0.2% in the width direction is that in golf applications, the vertical direction of the face has a large effect on repulsion, and normally titanium alloy plates are designed so that the width direction is the vertical direction of the face. This is because it is processed into
In this embodiment, the room temperature is 25°C.
　板幅方向の０．２％ＰＳ及びＴＳについては、ＪＩＳ　Ｚ　２２４１：２０１１に準拠して測定する。
　具体的には、引張方向が、チタン合金板の板幅方向になるようにＪＩＳ　Ｚ　２２４１：２０１１に規定される１３Ｂ号引張試験片（平行部の幅１２．５ｍｍ、標点間距離５０ｍｍ）を作製し、ひずみ速度０．５％／ｍｉｎで引張試験を行い測定する。 0.2% PS and TS in the board width direction are measured in accordance with JIS Z 2241:2011.
Specifically, a No. 13B tensile test piece (parallel part width 12.5 mm, gauge distance 50 mm) specified in JIS Z 2241:2011 was used so that the tensile direction was in the width direction of the titanium alloy plate. A tensile test is performed at a strain rate of 0.5%/min for measurement.
板幅方向のヤング率：１３５ＧＰａ以上
　上述したように、近年、ゴルフクラブには反発規制があり、その観点から、ゴルフクラブ用途のチタン合金板には、高ヤング率化が求められている。板幅方向のヤング率が１３５ＧＰａ以上であれば反発規制を満たすことから、ヤング率が１３５ＧＰａ以上であることを目標とする。より好ましい目標は、１３７ＧＰａ以上である。
　一方、ヤング率は高ければ高いほど良いので上限を限定する必要はないが、組織制御や化学組成の観点から、実質的な上限は１５０ＧＰａ程度である。
　チタン合金板においては、集合組織制御やバンド組織の形成により板幅方向のヤング率を高めることができる。 Young's Modulus in Plate Width Direction: 135 GPa or More As mentioned above, in recent years, golf clubs have been subject to repulsion regulations, and from that perspective, titanium alloy plates for use in golf clubs are required to have a high Young's modulus. If the Young's modulus in the sheet width direction is 135 GPa or more, the repulsion regulation is satisfied, so the Young's modulus is set as a target of 135 GPa or more. A more preferable target is 137 GPa or higher.
On the other hand, the higher the Young's modulus, the better, so there is no need to limit the upper limit, but from the viewpoint of structure control and chemical composition, the practical upper limit is about 150 GPa.
In a titanium alloy plate, the Young's modulus in the width direction of the plate can be increased by controlling the texture and forming a band structure.
　板幅方向のヤング率は、以下の方法で求める。
　引張方向が、チタン合金板の板幅方向になるようにＪＩＳ　Ｚ　２２４１：２０１１に規定される１３Ｂ号引張試験片（平行部の幅１２．５ｍｍ、標点間距離５０ｍｍ）を作製し、歪ゲージを張り付けてひずみ速度１０．０％／ｍｉｎで、１００ＭＰａから０．２％ＰＳの半分までの応力範囲で負荷－除荷を５回繰り返し、その傾きを求め、最大値と最小値を除いた３回の平均値をヤング率とする。 The Young's modulus in the sheet width direction is determined by the following method.
A No. 13B tensile test piece (parallel part width 12.5 mm, gauge distance 50 mm) specified in JIS Z 2241:2011 was prepared so that the tensile direction was in the width direction of the titanium alloy plate, and a strain gauge was used. At a strain rate of 10.0%/min, loading and unloading were repeated 5 times in the stress range from 100 MPa to half of 0.2% PS, the slope was determined, and the maximum and minimum values were removed. Let the average value of the times be Young's modulus.
比重：４．４５ｇ／ｃｍ３以下
　ゴルフクラブ用途のチタン合金板は、比重が重くなりすぎると強度を高くしてもフェースを軽量化できなくなる。そのため、軽量化の観点から、比重が重要である。本実施形態に係るチタン合金板では、軽量化の観点から、比重は４．４５ｇ／ｃｍ３以下であることを目標とする。比重は低い方が好ましいが、化学組成の観点から、実質的には、４．３８／ｃｍ３が下限となる。 Specific gravity: 4.45 g/cm 3 or less If the specific gravity of a titanium alloy plate for golf clubs becomes too high, it will not be possible to reduce the weight of the face even if the strength is increased. Therefore, from the viewpoint of weight reduction, specific gravity is important. In the titanium alloy plate according to this embodiment, from the viewpoint of weight reduction, the target specific gravity is 4.45 g/cm 3 or less. Although a lower specific gravity is preferable, from the viewpoint of chemical composition, the lower limit is substantially 4.38/cm 3 .
　比重は、気体ガスを用いた乾式もしくは液体を用いた湿式で測定すればよい。
　乾式の方法については、具体的には、Ｍｉｃｒｏｍｅｒｉｔｉｃｓ社製のＡｃｃｕＰｙｃＩＩを用いる。容器サイズは１～１００ｃｍ３であり、サンプルサイズに合わせて任意のものを使用すればよい。気体には不活性ガスであるＮ２、Ａｒ、Ｈｅガスを用いる。 The specific gravity may be measured by a dry method using a gas or a wet method using a liquid.
As for the dry method, specifically, AccuPycII manufactured by Micromeritics is used. The container size is 1 to 100 cm 3 , and any container may be used depending on the sample size. Inert gases such as N 2 , Ar, and He gas are used as the gas.
＜板厚＞
　本実施形態に係るチタン合金板の板厚は限定されない。
　ゴルフクラブへの適用を考慮した場合、例えば２．５ｍｍ超である。好ましくは３．０ｍｍ以上である。
　一方、６．０ｍｍ超では、熱延板の焼鈍や酸洗後の巻き戻しなどの工程での荷重が大きくなりすぎる場合があるので、６．０ｍｍ以下としてもよい。 <Plate thickness>
The thickness of the titanium alloy plate according to this embodiment is not limited.
When considering application to a golf club, it is, for example, more than 2.5 mm. Preferably it is 3.0 mm or more.
On the other hand, if it exceeds 6.0 mm, the load in processes such as annealing the hot rolled sheet or unwinding after pickling may become too large, so it may be set to 6.0 mm or less.
＜製造方法＞
　本実施形態に係るチタン合金板は、上記の特徴を有していればその効果が得られるので、製造方法については限定されない。しかしながら、以下に示す工程を含む製造方法であれば安定して製造できるので好ましい。
　すなわち、本実施形態に係るチタン合金板は、
（Ｉ）化学組成が、質量％で、Ａｌ：５．０～６．６％、Ｆｅ：０．７～２．３％、Ｓｉ：０．２０～０．３０％、Ｏ：０．１０～０．２０％、Ｃ：０．０５０％未満、Ｎ：０．０５０％以下、Ｎｉ：０％以上０．１５％未満、Ｃｒ：０％以上０．２５％未満、Ｍｎ：０％以上０．２５％未満、および残部：Ｔｉ及び不純物からなるチタン素材を加熱温度まで加熱する加熱工程と、
（ＩＩ）前記加熱工程後の前記チタン素材を一方向に熱間圧延して熱延板を得る熱間圧延工程と、
（ＩＩＩ）前記熱間圧延工程後の前記熱延板を、４００℃以下の巻取温度まで８℃／ｓ以上の平均冷却速度で冷却して前記巻取温度で巻き取る巻取工程と、
（ＩＶ）前記巻取工程後の前記熱延板に対して焼鈍を行う焼鈍工程と、
を含む、製造方法によって製造できる。
　各工程について好ましい条件を説明する。説明しない工程、条件については公知の条件を適用できる。 <Manufacturing method>
Since the titanium alloy plate according to the present embodiment has the above-mentioned characteristics, the effect can be obtained, so the manufacturing method is not limited. However, a manufacturing method including the steps described below is preferable because stable manufacturing can be achieved.
That is, the titanium alloy plate according to this embodiment,
(I) Chemical composition in mass%: Al: 5.0 to 6.6%, Fe: 0.7 to 2.3%, Si: 0.20 to 0.30%, O: 0.10 to 0.20%, C: less than 0.050%, N: 0.050% or less, Ni: 0% or more and less than 0.15%, Cr: 0% or more and less than 0.25%, Mn: 0% or more and less than 0.25%. Less than 25% and the remainder: a heating step of heating a titanium material consisting of Ti and impurities to a heating temperature;
(II) a hot rolling step of hot rolling the titanium material in one direction after the heating step to obtain a hot rolled sheet;
(III) a winding step of cooling the hot rolled sheet after the hot rolling step to a winding temperature of 400° C. or lower at an average cooling rate of 8° C./s or higher and winding it at the winding temperature;
(IV) an annealing step of annealing the hot rolled sheet after the winding step;
It can be manufactured by a manufacturing method including.
Preferred conditions for each step will be explained. Known conditions can be applied to steps and conditions that are not explained.
［加熱工程］
　加熱工程では、化学組成が、質量％で、Ａｌ：５．０～６．６％、Ｆｅ：０．７～２．３％、Ｓｉ：０．２０～０．３０％、Ｏ：０．１０～０．２０％、Ｃ：０．０５０％未満、Ｎ：０．０５０％以下、Ｎｉ：０％以上０．１５％未満、Ｃｒ：０％以上０．２５％未満、Ｍｎ：０％以上０．２５％未満、残部：Ｔｉ及び不純物からなるチタン合金スラブなどのチタン素材を加熱温度まで加熱する。
　加熱温度は、単位℃でのβ変態点温度をＴβとしたとき、Ｔβ℃以上、（Ｔβ＋１５０）℃以下とする。
　加熱温度がＴβ℃未満の場合、α相の割合が高い状態でチタン素材が圧下されることになり、β相の割合が高い状態での圧下が不十分となる。そのため、Ｔ－ｔｅｘｔｕｒｅが十分に発達しない。
　また、β相の割合が高い状態での圧下率が低いと、バンド組織を形成し難くなる場合がある。そのため、バンド組織の割合を高める場合、加熱温度は、好ましくは（Ｔβ＋２０℃）以上である。
　一方、加熱温度が（Ｔβ＋１５０℃）を超えると、圧延中にβ相が再結晶する可能性が非常に高くなる。この場合、β相からα相への相変態時にバリアント選択が生じないため、Ｔ－ｔｅｘｔｕｒｅは発達し難い。さらには、チタン素材の表面の酸化が激しくなり、熱間圧延後に熱延板表面にヘゲやキズを生じ易くなる。 [Heating process]
In the heating step, the chemical composition in mass% is Al: 5.0 to 6.6%, Fe: 0.7 to 2.3%, Si: 0.20 to 0.30%, O: 0.10 ~0.20%, C: less than 0.050%, N: 0.050% or less, Ni: 0% or more and less than 0.15%, Cr: 0% or more and less than 0.25%, Mn: 0% or more and 0 A titanium material such as a titanium alloy slab consisting of less than .25% and the remainder: Ti and impurities is heated to a heating temperature.
The heating temperature is at least T β °C and at most (T β +150) °C, where T β is the β transformation point temperature in °C.
If the heating temperature is less than T β °C, the titanium material will be rolled down in a state where the ratio of α phase is high, and the rolling down will be insufficient when the ratio of β phase is high. Therefore, T-texture is not sufficiently developed.
Furthermore, if the reduction rate is low when the proportion of the β phase is high, it may be difficult to form a band structure. Therefore, when increasing the ratio of the band structure, the heating temperature is preferably (T β +20°C) or higher.
On the other hand, if the heating temperature exceeds (T β +150°C), there is a very high possibility that the β phase will recrystallize during rolling. In this case, T-texture is difficult to develop because variant selection does not occur during phase transformation from β phase to α phase. Furthermore, the surface of the titanium material becomes more intensely oxidized, and the surface of the hot-rolled sheet is more likely to be bald or scratched after hot rolling.
　本実施形態において、β変態点温度Ｔβは、チタン合金をβ相単相域から冷却した際にα相が生成し始める境界温度を意味する。Ｔβは、状態図から取得することができる。状態図は、例えばＣＡＬＰＨＡＤ（Ｃｏｍｐｕｔｅｒ　Ｃｏｕｐｌｉｎｇ　ｏｆ　Ｐｈａｓｅ　Ｄｉａｇｒａｍｓ　ａｎｄ　Ｔｈｅｒｍｏｃｈｅｍｉｓｔｒｙ）法により取得することができる。具体的には、Ｔｈｅｒｍｏ－Ｃａｌｃ　Ｓｏｔｗａｒｅ　ＡＢ社の統合型熱力学計算システムであるＴｈｅｒｍｏ－Ｃａｌｃおよび所定のデータベース（ＴＩ３）を用いてＣＡＬＰＨＡＤ法により、チタン合金の状態図を取得し、Ｔβを算出することができる。 In this embodiment, the β-transform temperature T β means the boundary temperature at which the α-phase starts to be generated when the titanium alloy is cooled from the β-phase single-phase region. T β can be obtained from the phase diagram. The phase diagram can be obtained by, for example, the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) method. Specifically, a phase diagram of a titanium alloy was obtained by the CALPHAD method using Thermo-Calc, an integrated thermodynamic calculation system from Thermo-Calc Software AB, and a predetermined database (TI3), and T β was calculated. can do.
［熱間圧延工程］
　熱間圧延工程では、加熱工程後のチタン素材を一方向に熱間圧延して熱延板を得る。その際、圧下率は８５％以上、仕上温度が（Ｔβ－１７０）℃以上（Ｔβ－１００）℃以下とする。
　チタン合金の熱延板において、β域やβ変態点直下のα＋β二相高温域に加熱し、α＋β域にかけて熱延することでＴ－ｔｅｘｔｕｒｅを形成させることができることは知られている（例えば特開２０１２－１４９２８３号公報）。
　しかしながら、本発明者らが検討した結果、必ずしも上記の条件では本実施形態に係るチタン合金板の集合組織は必ずしも得られないことが判明した。
　また、特開２０１２－１４９２８３号では、α＋β二相高温域の９００℃までに８５％以上の圧下が必要であるとされている。しかしながら、二相域の９００℃は非常に高い温度であり、さらに、β域やβ変態点直下まで加熱していると、板厚中央部はより高い温度となっていること、さらに合金種によってはβ変態点との温度差が大きい場合があることから、保持時間が長くなると熱延により蓄積したひずみにより再結晶してしまうことがある。
　本発明者らが検討した結果、熱間圧延完了温度（仕上温度）を、（Ｔβ－１７０）℃以上（Ｔβ－１００）℃以下の温度とした上で、後工程を所定の条件で行うことで、所定の集合組織を得ることができることが分かった。
　仕上温度が、（Ｔβ－１７０）℃未満であると、φ１：７０～９０°、Φ：１０～３０°、φ２：０～６０°の範囲に集合組織が発達するため、上述の狙いの範囲（領域１）の集合組織が発達せず板幅方向の強度やヤング率が十分に向上しない。また、室温での加工性も低下する。
　一方、仕上温度が（Ｔβ－１００）℃超となると、φ１：７０～９０°、Φ：７０～９０°、φ２：０～６０°の集合組織が発達する。そのため、狙いの集合組織が発達せずに目標の特性が得られなくなる。 [Hot rolling process]
In the hot rolling process, the titanium material after the heating process is hot rolled in one direction to obtain a hot rolled plate. At this time, the rolling reduction ratio is 85% or more, and the finishing temperature is (T β -170)°C or more and (T β -100)°C or less.
It is known that a T-texture can be formed in a hot-rolled titanium alloy sheet by heating it to the β region or the α+β two-phase high temperature region just below the β transformation point, and then hot rolling it to the α+β region (for example, Publication No. 2012-149283).
However, as a result of studies conducted by the present inventors, it has been found that the texture of the titanium alloy plate according to the present embodiment cannot necessarily be obtained under the above conditions.
Furthermore, JP-A No. 2012-149283 states that a reduction of 85% or more is required up to 900° C. in the α+β two-phase high temperature range. However, 900°C in the two-phase region is a very high temperature, and furthermore, when heating to the β region or just below the β transformation point, the temperature in the center of the plate is higher, and it also depends on the alloy type. Since the temperature difference between the steel and the β-transus point may be large, if the holding time is too long, the strain accumulated during hot rolling may cause recrystallization.
As a result of studies by the present inventors, the hot rolling completion temperature (finishing temperature) is set to a temperature of (T β -170) °C or higher and (T β -100) °C or lower, and the post-process is carried out under predetermined conditions. It was found that a predetermined texture can be obtained by doing this.
If the finishing temperature is less than (T β -170)°C, the texture will develop in the range of φ1: 70 to 90°, φ: 10 to 30°, and φ2: 0 to 60°, which will not meet the above aim. The texture in the area (region 1) does not develop, and the strength and Young's modulus in the width direction of the plate do not improve sufficiently. Furthermore, the processability at room temperature is also reduced.
On the other hand, when the finishing temperature exceeds (T β -100)°C, textures of φ1: 70 to 90°, φ: 70 to 90°, and φ2: 0 to 60° develop. Therefore, the target texture will not develop and the target properties will not be obtained.
［巻取工程］
　巻取工程では、熱間圧延工程後の熱延板を、４００℃以下の巻取温度まで８．０℃／ｓ以上の平均冷却速度で冷却してその温度（巻取温度）で巻き取る。
　巻取温度（冷却停止温度）が４００℃超であると、板がコイル状で冷却される、すなわち、前述したＡｌ、Ｏなどの固溶、或いは、化合物の析出などの影響により形が凍結されてしまい、その後の巻き戻しが困難となり、板やコイルが製造できない場合がある。巻取温度は、好ましくは３００℃以下、より好ましくは１００℃以下である。
　一方、巻取温度までの平均冷却速度が８．０℃／ｓ未満であると、所定の集合組織が十分に発達しない。平均冷却速度は、好ましくは１０．０℃／ｓ以上、より好ましくは１２．０℃／ｓ以上、さらに好ましくは１５．０℃／ｓ以上である。上記冷却速度を得るため、冷却は水冷や油冷、或いは、ガス吹き付けなどで制御することが好ましい。雰囲気は酸化の抑制が期待される不活性ガスの使用が好ましいが、脱スケールを行う場合、大気も可能である。 [Winding process]
In the winding step, the hot-rolled sheet after the hot rolling step is cooled to a winding temperature of 400° C. or lower at an average cooling rate of 8.0° C./s or higher, and then wound at that temperature (winding temperature).
If the coiling temperature (cooling stop temperature) is over 400°C, the plate will be cooled in a coiled form, that is, the shape will be frozen due to the solid solution of Al, O, etc. mentioned above, or the precipitation of compounds. This may make it difficult to unwind after that, making it impossible to manufacture plates or coils. The winding temperature is preferably 300°C or lower, more preferably 100°C or lower.
On the other hand, if the average cooling rate to the coiling temperature is less than 8.0° C./s, the predetermined texture will not develop sufficiently. The average cooling rate is preferably 10.0°C/s or more, more preferably 12.0°C/s or more, even more preferably 15.0°C/s or more. In order to obtain the above cooling rate, cooling is preferably controlled by water cooling, oil cooling, gas spraying, or the like. As the atmosphere, it is preferable to use an inert gas that is expected to suppress oxidation, but when descaling is performed, air can be used.
［焼鈍工程］
　焼鈍工程では、巻取工程後の熱延板に対して焼鈍を行う。
　上述の工程を経た熱延板は、加工ひずみだけでなく、変態ひずみが残存している。
　そのため、強度は高いものの、板幅方向の加工性が著しく低い。したがって、本実施形態に係るチタン合金板の製造方法では、熱延板での焼鈍（熱延板焼鈍）によるひずみ除去を行う。
　ひずみを除去するとともに、ＹＲを低くするため、焼鈍温度Ｔ（℃）は６００℃以上とし、かつ、単位℃での焼鈍温度Ｔと、焼鈍温度における単位秒での保持時間ｔとが、以下の式（３）を満たすように焼鈍を行う。
　焼鈍温度Ｔが６００℃未満では、ひずみが十分に除去されない。一方、（Ｔ＋２７３．１５）×（Ｌｏｇ１０（ｔ）＋２０）が２７０００超では、相変態を生じたり、必要以上に結晶粒が粗大化したりして、所定の集合組織が得られない。
　（Ｔ＋２７３．１５）×（Ｌｏｇ１０（ｔ）＋２０）＜２７０００　…式（３）
　ＹＲをさらに低く、例えば０．９７以下にする場合、焼鈍温度Ｔ（℃）は６００℃以上とし、かつ、単位℃での焼鈍温度Ｔと、焼鈍温度における単位秒での保持時間ｔとが、以下の式（３’）を満たすように焼鈍を行うことが好ましい。
　２２０００≦（Ｔ＋２７３．１５）×（Ｌｏｇ１０（ｔ）＋２０）＜２７０００　…式（３’）
　すなわち、（Ｔ＋２７３．１５）×（Ｌｏｇ１０（ｔ）＋２０）は、好ましくは、２２０００以上である。（Ｔ＋２７３．１５）×（Ｌｏｇ１０（ｔ）＋２０）は、より好ましくは２３０００以上である。
　一方、β域まで加熱されると、β→α変態を生じ針状組織となる。このような組織では、集合組織が変化してしまい、板幅方向の強度やヤング率が低くなる。そのため、焼鈍温度ＴはＴβ以下とする。
　また、Ｔβ（β変態点温度）（℃）直下でもバイモーダル組織（等軸組織と針状組織の混在組織）となることが懸念される。そのため、好ましくは、焼鈍温度Ｔは、（Ｔβ－５０）℃以下である。
　ここで、焼鈍温度における保持時間ｔとは、焼鈍温度±２０℃の時間であり、その温度範囲内であれば温度が変動している時間も含む。 [Annealing process]
In the annealing step, the hot rolled sheet after the winding step is annealed.
The hot-rolled sheet that has gone through the above steps has not only processing strain but also residual transformation strain.
Therefore, although the strength is high, the workability in the sheet width direction is extremely low. Therefore, in the method for manufacturing a titanium alloy plate according to the present embodiment, strain is removed by annealing the hot-rolled plate (hot-rolled plate annealing).
In order to remove strain and lower YR, the annealing temperature T (°C) is set to 600°C or higher, and the annealing temperature T in °C and the holding time t in seconds at the annealing temperature are as follows. Annealing is performed so that formula (3) is satisfied.
If the annealing temperature T is less than 600°C, strain will not be removed sufficiently. On the other hand, if (T+273.15)×(Log 10 (t)+20) exceeds 27,000, phase transformation occurs or crystal grains become coarser than necessary, making it impossible to obtain the desired texture.
(T+273.15)×(Log 10 (t)+20)<27000...Formula (3)
When YR is lowered, for example, 0.97 or less, the annealing temperature T (°C) is 600°C or higher, and the annealing temperature T in units of °C and the holding time t in units of seconds at the annealing temperature are It is preferable to perform annealing so that the following formula (3') is satisfied.
22000≦(T+273.15)×(Log 10 (t)+20)<27000...Equation (3')
That is, (T+273.15)×(Log 10 (t)+20) is preferably 22,000 or more. (T+273.15)×(Log 10 (t)+20) is more preferably 23,000 or more.
On the other hand, when heated to the β region, β→α transformation occurs, resulting in an acicular structure. In such a structure, the texture changes and the strength and Young's modulus in the sheet width direction decrease. Therefore, the annealing temperature T is set to be equal to or lower than Tβ .
Furthermore, there is a concern that a bimodal structure (a mixed structure of an equiaxed structure and an acicular structure) may occur even just below T β (β transformation point temperature) (° C.). Therefore, the annealing temperature T is preferably (T β −50)° C. or lower.
Here, the holding time t at the annealing temperature is the time when the annealing temperature is ±20° C., and includes the time during which the temperature is fluctuating as long as it is within that temperature range.
　上記製造工程で説明したチタン素材等の温度は、表面温度であり、放射温度計により各工程が実施された後に測定する。放射温度計の放射率には、加熱炉から出てきた直後のスラブに対して、接触式の熱電対を用いて測定した温度と一致するように校正した値を用いる。放射温度計に換えて、接触式の温度計を用いることも可能である。
　製造装置が変更されること無く、複数回の測定を行い、季節要因などによる変動も考慮し、それらの実績値として目標温度の達成が確認された場合、装置の変更や大幅な劣化など特段の事情が生じなければ、測定を省略しても良い。 The temperature of the titanium material, etc. explained in the above manufacturing process is the surface temperature, and is measured by a radiation thermometer after each process is performed. The emissivity of the radiation thermometer is a value calibrated to match the temperature measured using a contact thermocouple on the slab immediately after it comes out of the heating furnace. It is also possible to use a contact thermometer instead of a radiation thermometer.
Measurements are taken multiple times without changing the manufacturing equipment, taking into account fluctuations due to seasonal factors, etc., and if it is confirmed that the target temperature has been achieved as the actual value, we will not take any special measures such as equipment changes or significant deterioration. If no circumstances arise, the measurement may be omitted.
　以下に、実施例を示しながら、本開示の実施形態について、具体的に説明する。以下に示す実施例は、あくまでも一例であって、下記の例に限定されるものではない。 Hereinafter, embodiments of the present disclosure will be specifically described while showing examples. The examples shown below are merely examples, and the invention is not limited to the following examples.
　まず、表１のＡ～Ｍ、Ｒ～Ｔに示すチタン合金板の素材となるチタン合金インゴットを真空アーク溶解（ＶＡＲ：Ｖａｃｕｕｍ　Ａｒｃ　Ｒｅｍｅｌｔｉｎｇ）にて製造した後、分塊圧延または鍛造により厚さ１５０～２００ｍｍ×幅１０００ｍｍ×長さ５０００ｍｍのスラブを製造した。
　また、表１のＮに示すチタン合金板の素材となるチタン合金インゴットを電子ビーム溶解（ＥＢＲ：Ｅｌｅｃｔｒｏｎ　Ｂｅａｍ　Ｒｅｍｅｌｔｉｎｇ）にて製造した後、分塊圧延または鍛造により厚さ１６０ｍｍ×幅１０００ｍｍ×長さ５０００ｍｍのスラブを製造した。
　表１のＯに示すチタン合金板の素材となるチタン合金インゴットをプラズマアーク溶解（ＰＡＲ：Ｐｌａｓｍａ　Ａｒｃ　Ｍｅｌｔｉｎｇ）にて製造した後、分塊圧延または鍛造により厚さ１６０ｍｍ×幅８００ｍｍ×長さ５０００ｍｍのスラブを製造した。
　表１のＰに示すチタン合金板の素材となるチタン合金スラブをＥＢＲにて厚さ１６０ｍｍ×幅８００ｍｍ×長さ５０００ｍｍで製造したスラブを製造した。
　表１のＱに示すチタン合金板の素材となるチタン合金スラブをＰＡＭにて厚さ１６０ｍｍ×幅８００ｍｍ×長さ５０００ｍｍで製造したスラブを製造した。
　いずれのスラブも製造後、表面及び側面をフライス切削した。 First, titanium alloy ingots, which are the raw materials for the titanium alloy plates shown in Table 1, A to M, and RT to T, are manufactured by vacuum arc remelting (VAR), and then are bloomed or forged to a thickness of 150 mm. A slab of ~200 mm x 1000 mm width x 5000 mm length was produced.
In addition, a titanium alloy ingot, which is the material of the titanium alloy plate shown in N in Table 1, is manufactured by electron beam remelting (EBR), and then it is made into 160 mm thick x 1000 mm wide x length by blooming rolling or forging. A 5000mm slab was produced.
After manufacturing a titanium alloy ingot, which is the raw material for the titanium alloy plate shown in O in Table 1, by plasma arc melting (PAR), it is made into a material with a thickness of 160 mm x width of 800 mm x length of 5000 mm by blooming rolling or forging. Manufactured slabs.
A titanium alloy slab serving as a material for the titanium alloy plate shown in P in Table 1 was manufactured using EBR to have a thickness of 160 mm x width of 800 mm x length of 5000 mm.
A titanium alloy slab serving as a material for the titanium alloy plate shown in Q in Table 1 was manufactured using PAM to have a thickness of 160 mm x width of 800 mm x length of 5000 mm.
After manufacture, both slabs were milled on their surfaces and sides.
　スラブの化学組成について、Ａｌ、Ｆｅ、Ｓｉ、Ｎｉ、Ｃｒ、ＭｎをＩＣＰ発光分光分析により測定した。ＯおよびＮについては、酸素・窒素同時分析装置を用い、不活性ガス溶融、熱伝導度・赤外線吸収法により測定した。Ｃについては、炭素硫黄同時分析装置を用い、赤外線吸収法により測定した。製造されたそれぞれの熱延板の化学組成は、表１に示したチタン合金スラブの化学組成と等しいものであった。また、表１に示したチタン素材Ａ～Ｔについて、Ｔｈｅｒｍｏ－Ｃａｌｃ　Ｓｏｔｗａｒｅ　ＡＢ社の統合型熱力学計算システムであるＴｈｅｒｍｏ－Ｃａｌｃおよび所定のデータベース（ＴＩ３）を用いてＣＡＬＰＨＡＤ法により、チタン合金の状態図を取得し、β変態点温度Ｔβを算出した。 Regarding the chemical composition of the slab, Al, Fe, Si, Ni, Cr, and Mn were measured by ICP emission spectrometry. O and N were measured using an oxygen/nitrogen simultaneous analyzer, inert gas melting, thermal conductivity/infrared absorption method. C was measured by infrared absorption method using a carbon-sulfur simultaneous analyzer. The chemical composition of each of the manufactured hot rolled sheets was the same as that of the titanium alloy slab shown in Table 1. In addition, for the titanium materials A to T shown in Table 1, the state of the titanium alloy was determined by the CALPHAD method using Thermo-Calc, an integrated thermodynamic calculation system from Thermo-Calc Software AB, and a predetermined database (TI3). The figure was obtained and the β transformation point temperature T β was calculated.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　次に、これらのスラブに対して、表２に示す条件で、加熱し、一方向に熱間圧延を行い、冷却して巻き取り、焼鈍を行ってチタン合金板を得た。巻取温度は、その後の巻き戻しや展開などが可能となるように１００℃以下とした。ただし、比較例７のみは５００℃で迅速に巻き取りを実施した。
　比較例１、４、７はいずれもチタン合金板の巻き戻しが困難となり、破断した。そのため、以降の工程を中止し（焼鈍に供さず）、後述する特性の評価も実施しなかった。 Next, these slabs were heated under the conditions shown in Table 2, hot-rolled in one direction, cooled, wound, and annealed to obtain titanium alloy plates. The winding temperature was set to 100° C. or less to enable subsequent unwinding and unfolding. However, only in Comparative Example 7, winding was performed quickly at 500°C.
In Comparative Examples 1, 4, and 7, it became difficult to unwind the titanium alloy plate, and the plate broke. Therefore, the subsequent steps were discontinued (no annealing was performed), and the characteristics described below were not evaluated.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　得られたチタン合金板（上述の通り、比較例１、４、７を除く。以下同様。）から、チタン合金板の集積度が最大となる方位および領域１及び領域２での最大集積度を求めた。測定に際しては、チタン合金板の板幅方向（ＴＤ）の中央位置で、板幅方向に垂直な断面を、エメリー紙を用いて湿式研磨した後、当該表面を、コロイダルシリカを用いて鏡面研磨して鏡面とし、ＥＢＳＤを用いて結晶方位解析を行った。
　板厚方向の表裏面からそれぞれ１０００μｍを除いた厚さ方向の範囲、かつ板長手方向に１０００μｍの範囲の領域を、ステップ１μｍで５視野程度測定し、そのデータについて、ＴＳＬソリューションズ製のＯＩＭ　ＡｎａｌｙｓｉｓＴＭソフトウェア（Ｖｅｒ．８．１．０）を用いてＯＤＦを算出し、このＯＤＦから、集積度のピーク位置および最大集積度を算出した。
　ＯＤＦは、ＥＢＳＤ法の球面調和関数法を用いたＴｅｘｔｕｒｅ解析において、展開指数を１６とし、ガウス半値幅を５°として算出した。その際に、圧延変形の対称性を考慮し、板厚方向、圧延方向、板幅方向それぞれに対して線対称となるように、計算を行った。
　いずれの場合にも、α相の結晶方位をＢｕｎｇｅの表記方法によるオイラー角ｇ＝｛φ１，Φ，φ２｝で表した場合に、結晶方位分布関数ｆ（ｇ）により示される最大集積方位がφ１：０～３０°、Φ：６０～９０°、φ２：０～６０°の範囲にあった。 From the obtained titanium alloy plate (as mentioned above, excluding Comparative Examples 1, 4, and 7; the same applies hereinafter), determine the direction in which the degree of integration of the titanium alloy plate is maximum and the maximum degree of integration in region 1 and region 2. I asked for it. For measurement, a cross section perpendicular to the width direction (TD) of the titanium alloy plate was wet-polished using emery paper at the central position in the width direction (TD) of the titanium alloy plate, and then the surface was mirror-polished using colloidal silica. The crystal orientation was analyzed using EBSD.
Approximately 5 fields of view were measured at a step of 1 μm in an area in the thickness direction excluding 1000 μm from the front and back surfaces of the plate, and in a range of 1000 μm in the longitudinal direction of the plate, and the data was analyzed using OIM Analysis TM manufactured by TSL Solutions. The ODF was calculated using software (Ver. 8.1.0), and from this ODF, the peak position of the degree of accumulation and the maximum degree of accumulation were calculated.
The ODF was calculated using a texture analysis using the spherical harmonic function method of the EBSD method, with an expansion index of 16 and a Gauss half width of 5°. At that time, the symmetry of rolling deformation was taken into account and calculations were performed to ensure line symmetry in each of the plate thickness direction, rolling direction, and plate width direction.
In either case, when the crystal orientation of the α phase is expressed by the Euler angle g = {φ1, Φ, φ2} according to Bunge's notation, the maximum accumulation orientation indicated by the crystal orientation distribution function f(g) is φ1 : 0 to 30°, Φ: 60 to 90°, φ2: 0 to 60°.
　また、得られたチタン合金板の、板幅方向の０．２％ＰＳ（０．２％耐力）、引張強さ（ＴＳ）、ＹＲ、ヤング率を求めた。 Additionally, the 0.2% PS (0.2% proof stress), tensile strength (TS), YR, and Young's modulus in the width direction of the obtained titanium alloy plate were determined.
　０．２％ＰＳ及び引張強さは、ＪＩＳ　Ｚ　２２４１：２０１１に準拠して測定した。具体的には、引張方向が、チタン合金板の板幅方向になるようにＪＩＳ　Ｚ　２２４１：２０１１に規定される１３Ｂ号引張試験片（平行部の幅１２．５ｍｍ、標点間距離５０ｍｍ）を作製し、２５℃で、ひずみ速度０．５％／ｍｉｎで引張試験を行い測定した。
　また、この０．２％ＰＳ及び引張強さからＹＲを算出した。 0.2% PS and tensile strength were measured in accordance with JIS Z 2241:2011. Specifically, a No. 13B tensile test piece (parallel part width 12.5 mm, gauge distance 50 mm) specified in JIS Z 2241:2011 was used so that the tensile direction was in the width direction of the titanium alloy plate. A tensile test was performed at 25° C. and a strain rate of 0.5%/min.
Further, YR was calculated from this 0.2% PS and tensile strength.
　板幅方向のヤング率は、以下の方法で求めた。
　引張方向が、チタン合金板の板幅方向になるようにＪＩＳ　Ｚ　２２４１：２０１１に規定される１３Ｂ号引張試験片（平行部の幅１２．５ｍｍ、標点間距離５０ｍｍ）を作製し、歪ゲージを張り付けてひずみ速度１０．０％／ｍｉｎで、１００ＭＰａから０．２％耐力の半分までの応力範囲で負荷－除荷を５回繰り返し、その傾きを求め、その際、最大値と最小値を除いた３回の平均値をヤング率とした。 The Young's modulus in the sheet width direction was determined by the following method.
A No. 13B tensile test piece (parallel part width 12.5 mm, gauge distance 50 mm) specified in JIS Z 2241:2011 was prepared so that the tensile direction was in the width direction of the titanium alloy plate, and a strain gauge was used. At a strain rate of 10.0%/min, loading and unloading are repeated 5 times in the stress range from 100 MPa to half of the 0.2% proof stress, and the slope is determined. At that time, the maximum and minimum values are The average value of the three times removed was taken as the Young's modulus.
　また、得られたチタン合金板の、ＣｕＫαを線源とするＸ線回折法によって検出される２θ＝５３．３±１°における回折ピーク（（１０－１２）ピーク）の半値幅ＣｕＫαを線源とするＸＲＤによって検出される２θ＝５３．３±１°の位置に表れる（１０－１２）面の回折ピーク半値幅を算出した。
　具体的には、チタン合金板の表面を、エメリー紙を用いて湿式研磨した後、当該表面を、コロイダルシリカを用いて鏡面研磨して鏡面とした。鏡面としたチタン合金板の表面についてＸＲＤ測定を実施した。ＸＲＤ測定はＣｕＫαを線源とし、２θが５０．０°から５５．０°までの範囲を測定ピッチ０．０１°、測定速度２°／分で実施した。半値幅はＲｉｇａｋｕ製Ｓｍａｒｔｌａｂにより測定されたＸ線回折データを用い、Ｒｉｇａｋｕ製統合粉末Ｘ線解析ソフトウェアＰＤＸＬにより算出した。 In addition, the half-value width CuKα of the diffraction peak ((10-12) peak) at 2θ = 53.3 ± 1° detected by the X-ray diffraction method using CuKα as the radiation source of the obtained titanium alloy plate was calculated as the radiation source. The half-value width of the diffraction peak of the (10-12) plane appearing at the position of 2θ=53.3±1° detected by XRD was calculated.
Specifically, the surface of the titanium alloy plate was wet-polished using emery paper, and then mirror-polished using colloidal silica to give a mirror-like surface. XRD measurement was performed on the surface of the titanium alloy plate which was made into a mirror surface. The XRD measurement was carried out using CuKα as a radiation source in the range of 2θ from 50.0° to 55.0° at a measurement pitch of 0.01° and a measurement speed of 2°/min. The half width was calculated by Rigaku's integrated powder X-ray analysis software PDXL using X-ray diffraction data measured by Rigaku's Smartlab.
　また、得られたチタン合金板の、バンド組織の面積率を求めた。
　バンド組織面積率は、板幅中央の位置で板幅方向に対し垂直に切断した断面を、エメリー紙を用いて湿式研磨した後、当該表面を、コロイダルシリカを用いて鏡面研磨して鏡面とし、その断面の板厚方向に表裏面からそれぞれ１０００μｍを除いた範囲×板長手方向に１０００μｍの範囲の矩形の領域を、ステップ１μｍで５視野程度を対象に、ＥＢＳＤ法による結晶方位解析を行い、結晶粒のそれぞれについてアスペクト比を算出し、アスペクト比が３．０超の結晶粒の面積率を算出し、得た。 In addition, the area ratio of the band structure of the obtained titanium alloy plate was determined.
The band structure area ratio is determined by wet polishing a cross section cut perpendicular to the width direction of the plate at the center of the plate width using emery paper, and then polishing the surface to a mirror surface using colloidal silica. Crystal orientation analysis was performed using the EBSD method on a rectangular area of the cross section excluding 1000 μm from the front and back sides in the plate thickness direction x 1000 μm in the longitudinal direction of the plate, with a step of 1 μm and about 5 fields of view. The aspect ratio was calculated for each grain, and the area ratio of crystal grains having an aspect ratio of more than 3.0 was calculated and obtained.
　また、得られたチタン合金板の、比重を、気体ガスを用いた乾式で測定した。その際、Ｍｉｃｒｏｍｅｒｉｔｉｃｓ社製のＡｃｃｕＰｙｃＩＩを用いて、容器サイズ１ｃｍ３もしくは１０ｃｍ３とし、気体にＮ２ガスを用いて測定した。 Further, the specific gravity of the obtained titanium alloy plate was measured by a dry method using gas. At that time, measurements were made using AccuPycII manufactured by Micromeritics, with a container size of 1 cm 3 or 10 cm 3 and using N 2 gas as the gas.
　得られたチタン合金板の、加工性の評価として、まず、冷間圧延による評価を実施した。
　具体的には焼鈍工程後の熱延板（比較例９のみ焼鈍を行っていないので巻取工程後の熱延板）をショットブラストおよび硝ふっ酸溶液で１００～１５０μｍ溶削して表面の酸化相を除去したのち、熱延板の加工性（冷間加工性）を定量的に評価する目的で冷間圧延を行い、表面および側面の割れ（耳割れ）を評価した。冷間圧延にて圧下率が３８％以下で表面および耳割れが発生した場合をＮＧ、しなかった場合をＯＫ（高加工性）として評価した。 To evaluate the workability of the obtained titanium alloy plate, first, cold rolling was performed.
Specifically, the hot-rolled sheet after the annealing process (the hot-rolled sheet after the winding process since only Comparative Example 9 was not annealed) was cut by 100 to 150 μm using shot blasting and nitric-hydrofluoric acid solution to oxidize the surface. After removing the phase, cold rolling was performed for the purpose of quantitatively evaluating the workability (cold workability) of the hot rolled sheet, and cracks on the surface and side surfaces (edge cracks) were evaluated. A case where surface and edge cracking occurred at a rolling reduction of 38% or less during cold rolling was evaluated as NG, and a case where no cracking occurred was evaluated as OK (high workability).
　また、上述の通り、様々な加工を考慮した場合、上記の冷間加工性の評価とともに、ＹＲが低い方が好ましい。そのため、冷間加工性がＯＫであることを前提として、ＹＲが０．９７以下であれば、より加工性に優れると判断した（表中ＹＲも加味した加工性がＥｘ）。冷間加工性がＯＫであっても、ＹＲが０．９７超である場合は、ＧＯＯＤとした。 Furthermore, as described above, when various processing is taken into consideration, it is preferable that YR is low, as well as the evaluation of cold workability described above. Therefore, on the premise that the cold workability was OK, it was determined that if YR was 0.97 or less, the workability would be better (workability including YR in the table is Ex). Even if the cold workability is OK, if YR is over 0.97, it is judged as GOOD.
　これらの結果を表３に示す。 These results are shown in Table 3.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　表１～３から分かるように、発明例１～１５では、化学組成、集合組織が本発明範囲内であり、２５℃における板幅方向の０．２％耐力が１０００ＭＰａ以上であり、板幅方向のヤング率が１３５ＧＰａ以上であり、比重が４．４５ｇ／ｃｍ３以下であり、ＹＲが０．９９以下であり、高強度、高ヤング率、低比重、かつ高加工性を有する。
　これに対し、比較例２、３、５、６、８～１２では、化学組成、集合組織の少なくとも一方が本発明範囲外であり、０．２％耐力、ヤング率、比重のいずれかが目標を達成していない。
　比較例１、４、７は、途中で合金板が破断し、所定のチタン合金板が得られなかった。 As can be seen from Tables 1 to 3, in Invention Examples 1 to 15, the chemical composition and texture are within the range of the present invention, and the 0.2% proof stress in the sheet width direction at 25°C is 1000 MPa or more. Young's modulus is 135 GPa or more, specific gravity is 4.45 g/cm 3 or less, YR is 0.99 or less, and has high strength, high Young's modulus, low specific gravity, and high workability.
On the other hand, in Comparative Examples 2, 3, 5, 6, 8 to 12, at least one of the chemical composition and texture is outside the scope of the present invention, and one of the 0.2% proof stress, Young's modulus, and specific gravity is the target. have not been achieved.
In Comparative Examples 1, 4, and 7, the alloy plates were broken on the way, and the desired titanium alloy plates could not be obtained.
　１　　バンド組織
　２　　等軸部 1 Band structure 2 Equiaxed part

Claims (13)

  1. 　化学組成が、質量％で、
    Ａｌ：５．０～６．６％、
    Ｆｅ：０．７～２．３％、
    Ｓｉ：０．２０～０．３０％、
    Ｏ：０．１０～０．２０％、
    Ｃ：０．０５０％未満、
    Ｎ：０．０５０％以下、
    Ｎｉ：０％以上０．１５％未満、
    Ｃｒ：０％以上０．２５％未満、
    Ｍｎ：０％以上０．２５％未満、及び
    残部：Ｔｉ及び不純物
    からなり、
    　前記化学組成における、質量％での、Ａｌ含有量を［％Ａｌ］、Ｆｅ含有量を［％Ｆｅ］、Ｓｉ含有量を［％Ｓｉ］、Ｏ含有量を［％Ｏ］としたとき、以下の式（１）及び式（２）を満足し、
    　α相の結晶方位をＢｕｎｇｅの表記方法によるオイラー角ｇ＝｛φ１，Φ，φ２｝で表した場合に、結晶方位分布関数ｆ（ｇ）により示される最大集積方位がφ１：０～３０°、Φ：６０～９０°、φ２：０～６０°の範囲にあり、
    　前記最大集積方位の最大集積度が１０．０以上で、かつ、
    　φ１：７０～９０°、Φ：７０～９０°、φ２：０～６０°及びφ１：７０～９０°、Φ：１０～３０°、φ２：０～６０°の範囲の最大集積度が２．５以下であり、
    　板幅方向のＹＲが０．９９以下である、
    ことを特徴とする、チタン合金板。
    １１．５＜［％Ａｌ］＋２×［％Ｆｅ］＋８×［％Ｓｉ］＋１８×［％Ｏ］＜１５．５・・・（１）
    －４．５＜［％Ｆｅ］－０．９×［％Ａｌ］＋１．３×［％Ｏ］＋１．８×［％Ｓｉ］＜－２．４・・・（２）     The chemical composition is in mass%,
    Al: 5.0-6.6%,
    Fe: 0.7-2.3%,
    Si: 0.20-0.30%,
    O: 0.10-0.20%,
    C: less than 0.050%,
    N: 0.050% or less,
    Ni: 0% or more and less than 0.15%,
    Cr: 0% or more and less than 0.25%,
    Mn: 0% or more and less than 0.25%, and the remainder: Ti and impurities,
    In the chemical composition, when the Al content in mass % is [%Al], the Fe content is [%Fe], the Si content is [%Si], and the O content is [%O], the following is satisfies equations (1) and (2),
    When the crystal orientation of the α phase is expressed by the Euler angle g = {φ1, Φ, φ2} according to Bunge's notation, the maximum accumulation orientation shown by the crystal orientation distribution function f(g) is φ1: 0 to 30°, Φ: in the range of 60 to 90°, φ2: in the range of 0 to 60°,
    The maximum degree of accumulation in the maximum accumulation direction is 10.0 or more, and
    The maximum integration degree in the range of φ1: 70-90°, φ: 70-90°, φ2: 0-60° and φ1: 70-90°, φ: 10-30°, φ2: 0-60° is 2. 5 or less,
    YR in the board width direction is 0.99 or less,
    A titanium alloy plate characterized by:
    11.5<[%Al]+2×[%Fe]+8×[%Si]+18×[%O]<15.5...(1)
    -4.5<[%Fe]-0.9×[%Al]+1.3×[%O]+1.8×[%Si]<-2.4...(2)
  2. 　２５℃における前記板幅方向の０．２％耐力が１０００ＭＰａ以上であり、
    　前記板幅方向のヤング率が１３５ＧＰａ以上であり、
    　比重が４．４５ｇ／ｃｍ３以下である、
    ことを特徴とする、請求項１に記載のチタン合金板。     The 0.2% yield strength in the plate width direction at 25°C is 1000 MPa or more,
    The Young's modulus in the plate width direction is 135 GPa or more,
    Specific gravity is 4.45 g/cm 3 or less,
    The titanium alloy plate according to claim 1, characterized in that:
  3. 　ＣｕＫαを線源とするＸ線回折法によって検出される２θ＝５３．３±１°における回折ピークの半値幅が０．２０°以下である、
    ことを特徴とする、請求項１または２に記載のチタン合金板。     The half width of the diffraction peak at 2θ = 53.3 ± 1° detected by X-ray diffraction using CuKα as a radiation source is 0.20° or less,
    The titanium alloy plate according to claim 1 or 2, characterized in that:
  4. 　アスペクト比が３．０超かつ板長手方向に伸長した、バンド組織を有し、
    　前記バンド組織の面積率が７０％以上である、
    ことを特徴とする、請求項３に記載のチタン合金板。     Having a band structure with an aspect ratio of more than 3.0 and extending in the longitudinal direction of the plate,
    The area ratio of the band structure is 70% or more,
    The titanium alloy plate according to claim 3, characterized in that:
  5. 　前記板幅方向のＹＲが０．８５以上、０．９７以下である
    ことを特徴とする、請求項３に記載のチタン合金板。     The titanium alloy plate according to claim 3, wherein YR in the width direction of the plate is 0.85 or more and 0.97 or less.
  6. 　前記板幅方向のＹＲが０．８５以上、０．９７以下である
    ことを特徴とする、請求項４に記載のチタン合金板。     The titanium alloy plate according to claim 4, wherein YR in the width direction of the plate is 0.85 or more and 0.97 or less.
  7. 　板厚が２．５ｍｍ超である
    ことを特徴とする請求項１または２に記載のチタン合金板。     The titanium alloy plate according to claim 1 or 2, characterized in that the plate thickness is more than 2.5 mm.
  8. 　板厚が２．５ｍｍ超である
    ことを特徴とする請求項３に記載のチタン合金板。     The titanium alloy plate according to claim 3, characterized in that the plate thickness is more than 2.5 mm.
  9. 　板厚が２．５ｍｍ超である
    ことを特徴とする請求項４に記載のチタン合金板。     The titanium alloy plate according to claim 4, characterized in that the plate thickness is more than 2.5 mm.
  10. 　板厚が２．５ｍｍ超である
    ことを特徴とする請求項５に記載のチタン合金板。     The titanium alloy plate according to claim 5, characterized in that the plate thickness is more than 2.5 mm.
  11. 　板厚が２．５ｍｍ超である
    ことを特徴とする請求項６に記載のチタン合金板。     The titanium alloy plate according to claim 6, characterized in that the plate thickness is more than 2.5 mm.
  12. 　請求項１に記載のチタン合金板の製造方法であって、
    　化学組成が、質量％で、Ａｌ：５．０～６．６％、Ｆｅ：０．７～２．３％、Ｓｉ：０．２０～０．３０％、Ｏ：０．１０～０．２０％、Ｃ：０．０５０％未満、Ｎ：０．０５０％以下、Ｎｉ：０％以上０．１５％未満、Ｃｒ：０％以上０．２５％未満、Ｍｎ：０％以上０．２５％未満、残部：Ｔｉ及び不純物からなるチタン素材を加熱温度まで加熱する加熱工程と
    、
    　前記加熱工程後の前記チタン素材を一方向に熱間圧延して熱延板を得る熱間圧延工程と、
    　前記熱間圧延工程後の前記熱延板を、４００℃以下の巻取温度まで８．０℃／ｓ以上の速度で冷却して、前記巻取温度で巻き取る巻取工程と、
    　前記巻き取り工程後の前記熱延板に対して焼鈍を行う焼鈍工程と、
    を有し、
    　前記加熱工程では、前記加熱温度が、単位℃でのβ変態点温度をＴβとしたとき、Ｔβ℃以上、（Ｔβ＋１５０）℃以下であり、
    　前記熱間圧延工程では、圧下率が８５％以上であり、仕上温度が（Ｔβ－１７０）℃以上（Ｔβ－１００）℃以下であり、
    　前記焼鈍工程では、前記焼鈍における焼鈍温度Ｔが６００℃以上Ｔβ以下であり、かつ、前記焼鈍温度Ｔと、前記焼鈍温度における単位秒での保持時間ｔとが、下記式（３）を満足する、
    ことを特徴とする、チタン合金板の製造方法。
    　（Ｔ＋２７３．１５）×（Ｌｏｇ１０（ｔ）＋２０）＜２７０００　…式（３）     A method for manufacturing a titanium alloy plate according to claim 1, comprising:
    The chemical composition is in mass%, Al: 5.0 to 6.6%, Fe: 0.7 to 2.3%, Si: 0.20 to 0.30%, O: 0.10 to 0.20 %, C: less than 0.050%, N: 0.050% or less, Ni: 0% or more and less than 0.15%, Cr: 0% or more and less than 0.25%, Mn: 0% or more and less than 0.25%. , the remainder: a heating step of heating a titanium material consisting of Ti and impurities to a heating temperature;
    a hot rolling step of hot rolling the titanium material in one direction after the heating step to obtain a hot rolled sheet;
    A winding step of cooling the hot rolled sheet after the hot rolling step at a rate of 8.0° C./s or more to a winding temperature of 400° C. or lower and winding it at the winding temperature;
    an annealing step of annealing the hot rolled sheet after the winding step;
    has
    In the heating step, the heating temperature is T β °C or more and (T β +150) °C or less, where T β is the β transformation point temperature in °C,
    In the hot rolling process, the rolling reduction is 85% or more, and the finishing temperature is (T β -170) °C or more and (T β -100) °C or less,
    In the annealing step, the annealing temperature T in the annealing is 600° C. or more and T β or less, and the annealing temperature T and the holding time t in seconds at the annealing temperature satisfy the following formula (3). do,
    A method for manufacturing a titanium alloy plate, characterized by:
    (T+273.15)×(Log 10 (t)+20)<27000...Formula (3)
  13. 　前記焼鈍工程では、前記焼鈍における前記焼鈍温度Ｔが６００℃以上Ｔβ以下であり、かつ、前記焼鈍温度Ｔと、前記焼鈍温度における単位秒での前記保持時間ｔとが、下記式（３’）を満足する、
    ことを特徴とする、請求項１２に記載のチタン合金板の製造方法。
    　２２０００≦（Ｔ＋２７３．１５）×（Ｌｏｇ１０（ｔ）＋２０）＜２７０００　…式（３’）     In the annealing step, the annealing temperature T in the annealing is 600° C. or more and T β or less, and the annealing temperature T and the holding time t in units of seconds at the annealing temperature are expressed by the following formula (3' ),
    13. The method for manufacturing a titanium alloy plate according to claim 12.
    22000≦(T+273.15)×(Log 10 (t)+20)<27000...Equation (3')
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Publication number Priority date Publication date Assignee Title
WO2016084243A1 (en) * 2014-11-28 2016-06-02 新日鐵住金株式会社 Titanium alloy with high strength and high young's modulus and excellent fatigue characteristics and impact toughness
WO2020101008A1 (en) * 2018-11-15 2020-05-22 日本製鉄株式会社 Titanium alloy wire rod and method for manufacturing titanium alloy wire rod
JP2021080489A (en) * 2019-11-14 2021-05-27 日本製鉄株式会社 Titanium alloy thin plate and manufacturing method of titanium alloy thin plate

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* Cited by examiner, † Cited by third party
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WO2016084243A1 (en) * 2014-11-28 2016-06-02 新日鐵住金株式会社 Titanium alloy with high strength and high young's modulus and excellent fatigue characteristics and impact toughness
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