Titanium materials, processed products, and building components

Abstract

To provide a titanium material, a processed product, and a building member excellent in discoloration resistance. [Solution] A titanium material comprising a titanium base material and a film formed on the titanium base material, wherein when the surface of the titanium material is measured by X-ray photoelectron spectroscopy, the peak intensity ratio I = I 4+ / I b is 1.5 or more, and a lightness index L * , a chromaticness index a * , and a chromaticness index b * respectively satisfy 55≦L * ≦75, 1.0≦a * ≦2.0, and 4.0≦b * ≦8.0, and in a cross-section of the titanium material, when the chemical composition in a range of 20 nm from the surface of the film in the thickness direction of the titanium material is measured using an energy dispersive X-ray spectrometer provided in a spherical aberration-corrected scanning transmission electron microscope, the Ca content is 1.0 atomic % or more. The present disclosure relates to the titanium material, a processed product, and a building member.

Description

[Technical Field]

[0001] This invention relates to titanium materials, processed products, and building components. [Background technology]

[0002] Titanium is covered with an oxide film on its surface, giving it excellent corrosion resistance in the atmosphere. Furthermore, its beautiful silvery-white color makes it suitable for use in building walls, roofs, and other applications where aesthetic appeal is important. However, prolonged exposure to acidic environments such as acid rain can cause discoloration, posing a problem from an aesthetic standpoint. This discoloration is known to be caused by interference colors resulting from the thickening of the oxide film on the titanium surface in acidic environments.

[0003] Therefore, titanium materials have been developed that exhibit excellent discoloration resistance by suppressing the growth of oxide films in acidic environments, making them suitable for applications such as building walls and roofs (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2023 / 170979 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, while titanium does not discolor when used for walls, roofs, etc., it sometimes discolors when used under eaves, etc. Therefore, the inventors investigated the cause of discoloration of titanium, taking into account the areas where discoloration was observed and the usage environment.

[0006] As a result, it was hypothesized that the discoloration of the titanium material was caused by a more severely acidic environment in areas such as under eaves and exterior walls that are not directly exposed to rain, compared to walls and roofs. Specifically, in areas such as under eaves and exterior walls that are not directly exposed to rain, the surface of the titanium material undergoes repeated cycles of drying and wetting in short periods. Therefore, it is thought that acidic substances in the atmosphere easily concentrate on the surface of the titanium material, resulting in a severely acidic environment. Furthermore, since the acidic substances concentrated on the surface of the titanium material are not washed away by rain, it is thought that the severely acidic environment persisted.

[0007] Therefore, there is a need for a titanium material that can suppress the growth of oxide films even in such a harsh acidic environment, and as a result suppress discoloration.

[0008] Based on the above, the present invention aims to provide titanium materials, processed products, and building components that exhibit excellent discoloration resistance. [Means for solving the problem]

[0009] This invention was made to solve the above problems and is characterized by the following titanium material, processed product, and building component.

[0010] (1) A titanium material comprising a titanium base material and a coating formed on the titanium base material, When measurements are performed on the surface of the titanium material by X-ray photoelectron spectroscopy, the peak intensity ratio I, defined by the following equation (i), is 1.5 or greater. Lightness index L on the aforementioned surface * , Chromanetics Index a * , and the Chromatics Index b * However, each satisfies equations (ii), (iii), and (iv) below, When the chemical composition of the cross-section of the titanium material, within a 20 nm range from the surface of the coating in the thickness direction of the titanium material, is measured using an energy-dispersive X-ray spectrometer equipped on a spherical aberration-corrected scanning transmission electron microscope, the Ca content is 1.0 atomic percent or more. Titanium material. I=I 4+ / Ib ···(i) 55≦L * ≦75 ···(ii) 1.0≦a * ≦2.0 ···(iii) 4.0≦b * ≦8.0 ···(iv) Provided that, the meaning of each symbol in the above formula (i) is as follows. I 4+ : Ti 4+ 2p of Ti derived from -O bond 3 / 2 photoelectron intensity of the peak I b : average value of photoelectron intensity within a binding energy range of 450 to 480 eV

[0011] (2) When the thickness of the coating film is defined as t in a cross-section of the titanium material, and the crystal structure is analyzed in the depth direction of the titanium material from a depth position of 1 / 2t to a depth position of t using a field emission transmission electron microscope, rutile-type titanium oxide is detected. The titanium material according to (1) above.

[0012] (3) The thickness t of the coating film is 2 to 30 nm. The titanium material according to (1) or (2) above.

[0013] (4) The chemical composition of the surface layer of the titanium material, in atomic%, is:[] C: 10.0% or less, F: 10.0% or less, N: 10.0% or less. The titanium material according to any one of (1) to (3) above.

[0014] (5) A processed product comprising the titanium material according to any of (1) to (4) above.

[0015] (6) A building member comprising the titanium material according to any of (1) to (5) above. Effects of the Invention

[0016] According to the present invention, titanium materials, processed products, and building components with excellent discoloration resistance can be obtained. [Modes for carrying out the invention]

[0017] The inventors of this invention have diligently studied how to obtain a titanium material that suppresses the growth of oxide films and has excellent discoloration resistance, and have obtained the following findings.

[0018] It is known that the native oxide film formed on the surface of titanium materials, which grows easily in acidic environments, is formed of amorphous titanium oxide. Therefore, the inventors focused on the crystalline structure of titanium oxide in the oxide film and investigated a method to suppress the growth of the oxide film.

[0019] In the aforementioned natural oxide film, it was found that the valency of titanium in the oxide was lower than 4, and that it contained many oxygen vacancies. It is thought that the presence of these oxygen vacancies leads to electron transfer between the solution and the titanium material when exposed to an acidic environment, causing titanium ions to dissolve. As a result, the dissolved titanium ions are oxidized in the acidic solution to form titanium oxide, which is thought to contribute to the growth of the oxide film. Therefore, maintaining the valency of the titanium constituting the oxide film close to 4 is effective in suppressing the growth of the oxide film.

[0020] Furthermore, we found that by making the crystalline structure of the oxide film rutile-type, the transfer of electrons between the acidic solution and the titanium material can be efficiently suppressed, and as a result, the elution of titanium ions can be suppressed. In this invention, whether or not rutile-type titanium oxide has been obtained is determined by the Ca content. As will be described later, rutile-type titanium oxide is obtained by utilizing Ca, and the Ca content helps to confirm the presence of rutile-type titanium oxide.

[0021] This invention is based on the above findings. The requirements for the titanium material of this invention will be described in detail below.

[0022] 1. Titanium material In the present invention, the titanium material includes, for example, a titanium plate. The thickness of the titanium plate is not particularly limited. For example, when the titanium material is used as the exterior wall of a building, the plate thickness is preferably 0.1 to 2.0 mm.

[0023] 2. Titanium base material The type of base material for the titanium material according to the present invention is not particularly limited. Examples of base materials include industrial-grade pure titanium and titanium alloys.

[0024] Industrial-grade pure titanium is defined by standards such as JIS and ASTM, and typically has a Ti content of 99% by mass or more. Typical impurity elements in industrial-grade pure titanium are C, H, O, N, and Fe. Examples of general industrial-grade pure titanium include industrial-grade pure titanium types 1 to 4 as defined in JIS H 4600:2012, or ASTM / ASME Grade 1 to 4. In the above-mentioned industrial-grade pure titanium, the content of the above elements is C: 0.08% by mass or less, H: 0.015% by mass or less, O: 0.40% by mass or less, N: 0.05% by mass or less, and Fe: 0.50% by mass or less. Other elements such as Al, V, Si, Cr, Ni, Zr, Cu, Nb, Mo, Mn, Sn, Ta, Pd, Pt, Ru, B, Au, Ag, Hf, and REM (rare earth elements) may be included in amounts of 0.1 mass% or less for each element and 0.4 mass% or less in total, as long as they do not degrade the mechanical properties or other performance characteristics.

[0025] Furthermore, titanium alloys are typically alloys containing 70% or more by mass of Ti. Examples of titanium alloys include α-type titanium alloys, α+β-type titanium alloys, and β-type titanium alloys. Examples of α-type titanium alloys include high corrosion-resistant alloys (titanium alloys specified in JIS H 4600:2012, types 11-13, 17, 19-22, and ASTM standards Grade 7, 11, 13, 14, 17, 30, and 31, as well as titanium alloys containing small amounts of various other elements), Ti-0.5Cu, Ti-1.0Cu, Ti-1.0Cu-0.5Nb, and Ti-1.0Cu-1.0Sn-0.3Si-0.25Nb.

[0026] In the following explanation, alloy names written as "Ti-1.0Cu" followed by "-" + "number" + "element name" indicate an alloy based on Ti, containing the element represented by "element name" in the mass percentage represented by "number". For example, Ti-1.0Cu-0.5Nb alloy contains 1.0 mass% Cu and 0.5 mass% Nb, with the remainder being Ti and impurities. The mass percentage values ​​are representative values ​​and have a likelihood of approximately ±2 in the smallest digit of the mass percentage. However, this does not apply to alloys for which the component range is specified in JIS and ASTM.

[0027] Typical impurity elements in titanium alloys are C, H, O, N, and Fe. In the titanium alloys mentioned above, the content of these elements is C: 0.08 mass% or less, H: 0.015 mass% or less, O: 0.40 mass% or less, and N: 0.05 mass% or less. In addition, other elements such as Al, V, Si, Cr, Ni, Zr, Cu, Nb, Mo, Mn, Sn, Ta, Pd, Pt, Ru, B, Au, Ag, Hf, and REM (rare earth elements) that are not included in the elements and major additive elements listed in the above standards may be included in amounts of 0.1 mass% or less each and 0.4 mass% or less in total, as long as they do not degrade the performance such as mechanical properties.

[0028] Examples of α+β type titanium alloys include Ti-3Al-2.5V, Ti-5Al-1Fe, and Ti-6Al-4V. Examples of β type titanium alloys include Ti-11.5Mo-6Zr-4.5Sn, Ti-8V-3Al-6Cr-4Mo-4Zr, Ti-13V-11Cr-3Al, Ti-15V-3Al-3Cr-3Sn, Ti-20V-4Al-1Sn, and Ti-22V-4Al.

[0029] Typical impurity elements in α+β type titanium alloys are C, H, O, N, and Fe. In the α+β type titanium alloys described above, the content of these elements is C: 0.08 mass% or less, H: 0.015 mass% or less, O: 0.40 mass% or less, and N: 0.05 mass% or less. In addition, other elements such as Al, V, Si, Cr, Ni, Zr, Cu, Nb, Mo, Mn, Sn, Ta, Pd, Pt, Ru, B, Au, Ag, Hf, and REM (rare earth elements) that are not included in the elements and major additive elements described in the above standards may be included in amounts of 0.1 mass% or less each and 0.4 mass% or less in total, as long as they do not degrade the performance such as mechanical properties.

[0030] 3. Peak intensity ratio I When X-ray photoelectron spectroscopy (XPS) is performed on the surface of the titanium material according to the present invention, the peak intensity ratio I, defined by the following equation (i), is 1.5 or higher. If the peak intensity ratio I is less than 1.5, there are few tetravalent titanium ions, and oxygen vacancies occur in the oxide film. As a result, the oxide film grows and the discoloration resistance deteriorates. I=I 4+ / I b ...(i) However, the meaning of each symbol in equation (i) above is as follows: I 4+ :Ti with bond energies in the range of 458.0 to 459.9 eV 4+ -Ti 2p derived from O bond 3 / 2 Maximum photoelectron intensity I b : Average value of photoelectron intensity in the binding energy range of 450-480 eV

[0031] A higher peak intensity ratio I is better, and there is no particular upper limit. In the manufacturing method described later, the maximum value of the peak intensity ratio I will be 10.0, 9.0, or 8.0.

[0032] The peak intensity ratio I is measured and calculated by the following method: XPS measurement is performed on the central part of the titanium surface under the conditions described below to obtain an XPS spectrum. In the obtained XPS spectrum, the average value of the photoelectron intensity in the bond energy range of 450 to 480 eV is determined, and I is calculated. b Let's assume that.

[0033] Furthermore, the 2p of Ti due to the bonding of titanium ions with oxygen. 3 / 2 The peak is observed at different bond energies depending on the valence of the titanium ion, for example, around the following bond energies. TiO(Ti 2+ -O bond):454.1~455.4eV Ti2O3(Ti 3+ -O bond):455.5~457.9eV TiO2(Ti 4+ -O bond):458.0~459.9eV

[0034] XPS spectra at binding energies of 450-480 eV are measured, and the valence of the titanium ion is determined from the binding energy at which the maximum photoelectron intensity is obtained. If the maximum value exists in the range of valence 4, that maximum value is defined as I 4+ The peak intensity ratio I is then determined. Note that the maximum value of the photoelectron intensity I is also determined. 4+ As such, the maximum value of the photoelectron intensity, including the so-called background, of the peak located in the bond energy range where the valency is determined to be 4 is adopted. Furthermore, when the surface of the titanium material according to the present invention is observed as described above, Ti 4+ The peak of Ti is the highest. 2+ and Ti 3+ The peak is barely detectable. 4+ In addition to the peak of Ti 2+ and / or Ti 3+ Even if a peak is detected, Ti 4+ When the peak of Ti is at its highest, 4+ Peak photoelectron intensity I 4+ Substitute the above equation (i) to obtain the peak intensity ratio I.

[0035] Furthermore, the measurement conditions for the XPS spectrum are set as follows. Here, MultiPak Ver9.9.2 is used as the peak pattern analysis software. Measurement device: ULVAC-PHI VersaProbeIII X-ray source: mono-AlKα (hν:1486.6eV) Beam diameter: 200 μmΦ Beam angle: 15° Energy shift correction: Au 4f 7 / 2 (83.95 eV) Measurement interval: 0.1 eV

[0036] 4.Color The titanium material according to the present invention does not produce interference colors in its oxide film and has a metallic color, i.e., a silvery-white color. Therefore, on the surface of the titanium material according to the present invention, the lightness index L * , Chromanetics Index a * , and the Chromatics Index b * Each satisfies equations (ii), (iii), and (iv) below. L * a * , and b * However, if each satisfies equations (ii) to (iv) below, it will exhibit a silvery-white color. 55 ≤ L * ≤75 ···(ii) 1.0 ≤ a * ≤2.0 ···(iii) 4.0 ≤ b * ≤8.0 ···(iv)

[0037] The color of titanium material is measured by the following method: At the center of the surface of the titanium material (measurement point A), the L color tone, which represents the color tone specified in JIS Z 8781-4:2013, is measured. * a * , and b * The three values ​​are measured using a Konica Minolta CR-200b colorimeter under light source C. Then, the same L values ​​are measured at the edge of the titanium surface (measurement point B) and at a position symmetric to measurement point B with respect to measurement point A (measurement point C). *a * , and b * The three values ​​are measured. In this invention, L at measurement point A, measurement point B, and measurement point C * a * , and b * The value of L can be obtained from this value. * The average value of a * The mean value of, and b * The average values ​​of each satisfy equations (ii) to (iv) above.

[0038] 5.Ca content In the cross-section of the titanium material according to the present invention, the Ca content, measured using an energy-dispersive X-ray spectrometer attached to a spherical aberration-corrected scanning transmission electron microscope, is 1.0 atomic percent or more when the chemical composition in the 20 nm range from the surface of the coating in the thickness direction of the titanium material is measured. If the Ca content is less than 1.0 atomic percent, the crystallinity of the oxide film cannot be improved, and rutile-type titanium oxide cannot be obtained. As a result, the oxide film grows, and the discoloration resistance deteriorates.

[0039] While a higher Ca content is preferable, it may affect the color and design of the titanium material, so a Ca content of 20.0 atomic percent or less is preferable.

[0040] The Ca content is measured by the following method. First, a thin film sample is prepared using focused ion beam (FIB) spectroscopy in the central part of the titanium material, so that the cross-section serves as the observation surface. The conditions for preparing the thin film sample are set as follows. Thin film sample preparation system: FIB SEM NB5000 (manufactured by Hitachi High-Technologies) Acceleration voltage during thin film processing: 40kV (however, 2kV during finishing). Temperature during thin film sample preparation: Room temperature (25°C) Mesh used: Made with Mo Protective film: C(e-depо)

[0041] Next, using an energy-dispersive X-ray spectroscopy (EDS) instrument equipped with a spherical aberration-corrected scanning transmission electron microscope (Cs-STEM), the Ca content is measured at 1 nm intervals from the surface of the titanium material up to a position of 20 nm in the thickness direction. Then, the maximum value of the Ca content in the range from the surface of the titanium material up to 20 nm in the thickness direction is determined.

[0042] Such measurements are performed at a total of 10 locations, moving the measurement position 1 μm increments parallel to the surface of the titanium material. The maximum value of the Ca content at each measurement location is then determined, and the average value across the 10 locations is calculated. In this invention, a Ca content of 1.0 atomic percent or more means that the average value is 1.0 atomic percent or more.

[0043] The measurement conditions for Cs-STEM-EDS are set as follows: Measurement device: JEM ARM200F [NEOARM] (manufactured by JEOL) Acceleration voltage during observation: 200kV EDS analyzer: JED 2300T (manufactured by JEOL) Acceleration voltage during analysis: 200kV Electron probe diameter: approximately 0.1 nm

[0044] 6. Film thickness In the titanium material of the present invention, the thickness t of the coating is preferably 2 to 30 nm. By setting the thickness t of the coating within this range, discoloration of the titanium material due to the coating can be suppressed, and a silvery-white color can be achieved.

[0045] The film thickness is measured by the following method. Similar to the method for measuring Ca content, the O content is measured at 1 nm intervals from the surface of the titanium material to a position 50 nm in the thickness direction using Cs-STEM-EDS. Generally, the O content tends to decrease from the surface of the titanium material toward the thickness direction. Therefore, the length from the surface of the titanium material to the depth position where the O content first becomes half of its maximum value is defined as the film thickness.

[0046] This measurement is performed at a total of 10 locations, moving the measurement position 1 μm increments parallel to the surface of the titanium material. The thickness of the film at each measurement location is then determined, and the average value across the 10 locations is calculated. In this invention, a film thickness t of 2 to 30 nm means that the average value is 2 to 30 nm.

[0047] 7. Rutile-type titanium dioxide In the cross-section of the titanium material of the present invention, it is preferable that rutile-type titanium oxide is detected when the crystal structure is analyzed using a field emission transmission electron microscope from a depth of 1 / 2t to a depth of t, with the film thickness being t, starting from the outermost surface. The presence of rutile-type titanium oxide efficiently suppresses the transfer of electrons between the acidic solution and the titanium material, thereby further suppressing the elution of titanium ions and improving discoloration resistance.

[0048] The identification of rutile-type titanium oxide is performed using the following method. First, as described above, a thin film sample is prepared by the FIB method so that the cross-section of the central part of the titanium material becomes the observation surface. Next, using a field emission transmission electron microscope (FE-TEM), under the conditions described later, the crystal structure is measured every 1 nm in the thickness direction from a depth of 1 / 2t to a depth of t, starting from the outermost surface (depth position 0, where the surface of the titanium material is the starting point). That is, for the region of thickness 1 / 2t on the base material side of the film with thickness t, the crystal structure is measured every 1 nm in the thickness direction from a depth of 1 / 2t to a depth of t.

[0049] These measurements are performed at a total of 10 locations, moving the measurement position 1 μm increments parallel to the surface of the titanium material. Then, using the analysis software described later, the number of measurement locations where the rutile-type titanium oxide pattern can be confirmed is counted: one location if the film thickness is between 2 nm and 4 nm, and two or more locations if the film thickness is 4 nm or more. Rutile-type titanium oxide is considered to have been detected if eight or more such measurement locations are found.

[0050] The measurement conditions for FE-TEM are set as follows: Measurement device: JEM 2100F (manufactured by JEOL) Acceleration voltage during observation: 200kV Electron diffraction pattern analysis software: ReciPro Electron probe diameter: approximately 0.5 nm

[0051] 8. Content of C, F, and N in the surface layer of titanium material The content of C, F, and N in the surface layer of the titanium material of the present invention is preferably limited to the following ranges, respectively. Note that elements other than C, F, and N may also be present in the surface layer of the titanium material. Furthermore, C and F in the surface layer of the titanium material may exist individually or as compounds with titanium, hydrogen, oxygen, etc., and the content described below includes cases where they are present as these compounds. In the following explanation of the content of C, F, and N, "%" indicates atomic percent.

[0052] C: 10.0% or less F: 10.0% or less When the carbon (C) and phosphorus (F) content in the surface layer of titanium material is excessive, an oxide film is likely to grow. This is because C and F, as well as compounds containing C and F, reduce the effectiveness of the oxide film, making it easier for titanium ions to dissolve. Furthermore, C and F form compounds within the oxide film. Since these compounds are easily soluble in acidic environments, titanium ions dissolve, and the oxide film grows. Moreover, accelerated oxide film growth can reduce adhesion and lead to deterioration of the oxide film. Therefore, it is preferable that the C and F content be 10.0% or less, respectively.

[0053] A carbon (C) content of 8.0% or less is more preferable, and an fluorine (F) content of 9.0% or less is more preferable. Lower C and F content is preferable in the surface layer of the titanium material. While there are no particular lower limits on the C and F content, for manufacturing purposes, the actual C and F content should be 1.0% or more, each.

[0054] N: 10.0% or less If the nitrogen content in the surface layer of the titanium material is excessive, it becomes difficult to form a dense film using the manufacturing method of the material of the present invention. As a result, there is a risk that the elution of titanium ions cannot be suppressed due to cracking or peeling of the film. For this reason, an nitrogen content of 10.0% or less is preferable. An nitrogen content of 8.0% or less is more preferable. There is no particular lower limit to the nitrogen content, but in terms of manufacturing, the actual nitrogen content is 0.1%.

[0055] The chemical composition of the titanium surface layer is measured by the following method. Using a JOBIN YVON GD-Profiler 2 manufactured by Horiba, Ltd., the chemical composition of the titanium surface layer is measured by glow discharge optical emission spectrometry (GD-OES). In this instrument, the discharge conditions are set to a constant power mode of 35W, the Ar pressure to 600Pa, the discharge area to φ4mm, and the measurement pitch to 1nm. Then, the chemical composition is analyzed while sputtering in the depth direction from the surface of the titanium to a depth of 50nm, and profiles of the C, F, and N content in the depth direction (hereinafter simply referred to as "profiles") are obtained.

[0056] Using the sample after measurement, the depth removed by sputtering as described above is measured and confirmed with a surface roughness meter. Then, the content values ​​for each depth, automatically output by the device, are calibrated using the depths measured with the surface roughness meter. Furthermore, the measurement results on the outermost surface of the titanium material are susceptible to contamination such as attached organic matter. For this reason, in this invention, regions less than 2 nm from the surface of the titanium material are excluded. From the profiles of C, F, and N content measured continuously in the depth direction of the titanium material in this way, the maximum values ​​in the region from 2 to 50 nm from the surface of the titanium material are determined and used as the C, F, and N content, respectively.

[0057] 9.Processed products The titanium material according to the present invention has excellent discoloration resistance. Therefore, it can be used as a processed product after various processing steps. That is, the processed product is obtained by processing and / or welding the titanium material described above. The processing method is not particularly limited, but examples include bending and folding. Examples of processed products include angle materials, pipe materials, folded and / or welded panel materials.

[0058] The processed product shall satisfy the above-mentioned specifications regarding peak intensity ratio I, color, Ca content, film thickness, rutile-type titanium oxide, and chemical composition of the titanium surface layer. However, the measurement of these requirements in the processed product shall be carried out by taking a sample from the smooth, unprocessed portion of the processed product.

[0059] 10. Building materials The titanium material or processed products described above may also be used as building components. In other words, building components are made by processing and / or welding the titanium material or processed products described above. Examples of building components include exterior wall materials, roofing materials, and rain gutter materials.

[0060] The building components must satisfy the above-mentioned specifications regarding peak intensity ratio I, color, Ca content, film thickness, rutile-type titanium oxide, and chemical composition of the titanium surface. However, the measurement of these requirements for building components shall be carried out by taking samples from the smooth and unprocessed parts of the building components.

[0061] 11. Manufacturing method The method for manufacturing the titanium material of the present invention is not particularly limited. For example, it can be manufactured stably by the following manufacturing method.

[0062] <Preparation process> In the preparation process, the raw materials are prepared. These materials can be industrial-grade pure titanium and titanium alloys, and the type is not particularly limited. For example, the industrial-grade pure titanium and titanium alloys exemplified above as titanium base materials may be used. The raw materials should be manufactured according to conventional methods. For example, a titanium ingot can be produced by arc melting, and then hot-forged to create the raw material.

[0063] The above material is subjected to hot rolling to produce a hot-rolled material. The conditions for hot rolling are not particularly limited. They can be adjusted as appropriate according to the desired properties. The obtained hot-rolled material may be subjected to heat treatment as appropriate.

[0064] Subsequently, the oxide scale formed by hot rolling, heat treatment, etc., is removed. The method and conditions for scale removal are not particularly limited. For example, shot blasting followed by pickling or mechanical grinding may be performed.

[0065] When pickling is performed, the composition of the pickling solution is not particularly limited. However, if it is desired to reduce the fluorine (F) content on the surface of the titanium material, it is preferable to reduce the concentration of hydrofluoric acid in the pickling solution. By reducing the concentration of hydrofluoric acid in the pickling solution, it is possible to suppress the retention of F as Ti fluoride on the surface of the titanium material and reduce the F content on the surface of the titanium material.

[0066] After hot rolling, heat treatment, and descaling, the hot-rolled material is subjected to cold rolling to produce cold-rolled material. The conditions for cold rolling are not particularly limited; they can be adjusted as appropriate according to the desired dimensions.

[0067] When cold rolling is performed, the composition of the cold rolling oil is not particularly limited. If it is desired to reduce the carbon content on the surface of the titanium material, it is preferable to reduce the reduction ratio during cold rolling in addition to performing the annealing process described later. By reducing the reduction ratio in addition to performing the annealing process, it is possible to suppress the remaining carbon as Ti carbides on the surface of the titanium material, and the carbon content on the surface of the titanium material can be reduced to 10% or less. The reduction ratio during cold rolling is preferably less than 10%, more preferably 5% or less, and preferably 1% or more.

[0068] <Washing process> The cleaning process comprises an alkaline cleaning process and a water rinsing process. In the alkaline cleaning process, the cold-rolled material is exposed to an alkaline aqueous solution to wash away the cold-rolling oil adhering to its surface. The type of alkaline aqueous solution is not particularly limited. Any commonly used alkaline aqueous solution may be used; for example, Pakuna DST-58-L manufactured by Yuken Kogyo Co., Ltd. may be used. Furthermore, the alkaline cleaning method may be immersion in the alkaline aqueous solution or spraying. In the case of spraying, the immersion time should be the same as the spraying time. The immersion or spraying time is preferably 1 minute or more and 10 minutes or less. If it is 1 minute or more, the cold-rolling oil adhering to the surface of the cold-rolled material can be sufficiently washed away. Furthermore, the upper limit of the immersion or spraying time is preferably 10 minutes or less from the viewpoint of efficient manufacturability.

[0069] In the water washing process, the cold-rolled material after the alkaline washing process is washed with a water washing solution. The water washing solution in this application is prepared by adjusting the Ca ion concentration to 1.0 to 20 mg / L and the chloride ion concentration to 0.02 mg / L or less with respect to deionized water. If the Ca ion concentration in the water washing solution is less than 1.0 mg / L, rutile-type titanium oxide cannot be formed in the annealing process described later. The higher the Ca ion concentration, the more advantageous it is for the formation of rutile-type titanium oxide in the annealing process. However, if the Ca ion concentration and chloride ion concentration in the water washing solution are excessive, Ca(OH)2, chlorides, etc. will accumulate on the surface of the titanium material in a plate-like manner, causing uneven patterns on the surface of the titanium material and degrading its discoloration resistance. Therefore, the Ca ion concentration in the water washing solution should be 1.0 to 20 mg / L and the chloride ion concentration should be 0.02 mg / L or less.

[0070] A lower chloride ion concentration is preferable. However, it is difficult to excessively reduce chloride ions, and the lower limit of the chloride ion concentration is 0.001 mg / L. Regarding elements other than Ca ions and chloride ions in the washing solution, impurities of the type and content corresponding to A1 as described in JIS K 0557:1998 may be included, within a range that does not affect the effects of the present invention.

[0071] Other conditions in the washing process are not particularly limited. The temperature of the washing solution should be 5 to 50°C, and the immersion time in the washing solution should be 0.5 to 5 minutes. The washing method may be immersion in the washing solution or spraying. In the case of spraying, the immersion time should be the same as the spraying time.

[0072] Furthermore, no surface layer removal such as pickling or grinding is performed after washing. This is because the calcium that has adhered to and concentrated on the surface of the cold-rolled material is removed during the water washing process.

[0073] Furthermore, generally, solutions containing Ca ions are not used in the alkaline cleaning and rinsing processes. This is because if solutions containing Ca ions are used in the alkaline cleaning and rinsing processes, the Ca will solidify on the surface of the titanium material, causing whitening or mottling in the final product. Generally, the alkaline cleaning process uses an alkaline aqueous solution containing sodium hydroxide, potassium hydroxide, sodium carbonate, sodium phosphate, and trace amounts of surfactant. In the rinsing process, ion-exchanged water is used, from which ions such as Ca and Mg contained in the factory water have been removed.

[0074] <Annealing process> In the annealing process, the material is maintained at a temperature of 400°C or higher in a predetermined atmosphere. Furthermore, by performing the annealing process, the carbon remaining on the surface can be diffused into the interior of the titanium material, thereby reducing the carbon content on the surface.

[0075] In the washing process, washing is performed using a washing solution with adjusted Ca ion and chloride ion concentrations, ensuring that an appropriate amount of CaCl2 remains on the surface of the cold-rolled material. Furthermore, titanium combines with oxygen in the atmosphere to form amorphous titanium oxide containing oxygen vacancies. By annealing this cold-rolled material under the above conditions, the valency of the titanium constituting the oxide film can be brought close to valency 4. Additionally, by setting the annealing temperature to 600°C or higher, the crystalline structure of titanium oxide can undergo a phase transition from amorphous to rutile. Therefore, an annealing temperature of 600°C or higher is preferable.

[0076] Furthermore, the annealing atmosphere is a vacuum with a dew point of -20°C or lower, and 1.0 × 10⁻⁶ -4 The annealing process should be performed under a vacuum of Pa or less, or in an atmosphere with an inert gas such as Ar at a concentration of 99% or higher. If annealing is performed in an atmosphere with a high oxygen concentration, the oxide film will grow rapidly, causing interference colors and making it impossible to maintain the metallic color. Also, if annealing is performed in an atmosphere with a high nitrogen concentration, such as air, TiN will form on the surface of the titanium material, resulting in a brownish color and making it impossible to maintain the metallic color. Furthermore, the formation of TiN inhibits the formation of titanium oxide, resulting in the formation of low-valent titanium oxide.

[0077] There is no particular upper limit to the annealing temperature, but from the viewpoint of manufacturability, it is preferable to keep it below 900°C. There is also no particular limit to the holding time at the annealing temperature. It should be the time until the entire cold-rolled material reaches the annealing temperature; for example, the annealing time may be 0.5 to 72 hours.

[0078] To reduce the nitrogen content on the surface of titanium material, it is preferable to further reduce the nitrogen content in the annealing atmosphere, increase the vacuum level in the annealing atmosphere, or cool the material before exposing it to a nitrogen atmosphere. By implementing these conditions, it is possible to suppress the retention of nitrogen as Ti nitride on the surface of the titanium material and reduce the nitrogen content on the surface of the titanium material.

[0079] Furthermore, by applying an annealing process, the carbon remaining on the surface due to cold rolling can be diffused into the interior of the titanium material, thereby reducing the carbon content on the surface.

[0080] <Cooling process> In the cooling process, after the annealing process, furnace cooling or gas cooling with an inert gas such as Ar is performed. When the temperature of the titanium material reaches 50-200°C, the cooling is stopped, and the atmosphere is switched to a high-oxygen atmosphere and held for 5-60 minutes at that temperature.

[0081] If the atmosphere switching temperature is below 50°C, the surface of the titanium material cannot be sufficiently oxidized, resulting in a state with many oxygen deficiencies. As a result, sufficient tetravalent titanium oxide cannot be obtained. Furthermore, if the atmosphere switching temperature exceeds 200°C, the oxide film grows rapidly, making it impossible to obtain sufficient tetravalent titanium oxide. In addition, the metallic color cannot be maintained. Moreover, the nitrogen contained in the cooling atmosphere forms nitrides with the titanium, increasing the nitrogen content on the surface.

[0082] In this invention, a high-oxygen atmosphere refers to an atmosphere adjusted to have an oxygen concentration of 10% or more. Components other than oxygen may be inert gases such as Ar. If the oxygen concentration is less than 10%, sufficient oxidation cannot be achieved, and the mixture will remain oxygen-deficient. As a result, sufficient titanium oxide with a valency of tetravalent cannot be obtained. While theoretically, effects can be obtained even when the oxygen concentration is raised to 100%, the effect saturates at 30%. Therefore, an upper limit of 30% for the oxygen concentration is preferable.

[0083] In such a high-oxygen atmosphere, if the holding time is less than 5 minutes, sufficient oxidation cannot be achieved, and the material remains in a state with many oxygen deficiencies. As a result, sufficient titanium oxide with a valency of 4 cannot be obtained. On the other hand, if the holding time exceeds 60 minutes, the oxide film grows excessively, and sufficient titanium oxide with a valency of 4 cannot be obtained. Furthermore, the metallic color cannot be maintained.

[0084] Although the description above describes the case where a cooling process is performed immediately after the annealing process, it is also possible to cool the material to room temperature after the annealing process, heat it to 50-200°C, and hold it in a high-oxygen atmosphere for 5-60 minutes.

[0085] Furthermore, by controlling the cooling conditions as described above, it is possible to cool the rutile-type titanium oxide while maintaining the rutile-type titanium oxide formed during the annealing process. Specifically, it is possible to suppress the bonding of Ti in the rutile-type titanium oxide with elements other than O, such as C and / or N, during cooling. In addition, it is possible to suppress the diffusion of O in the rutile-type titanium oxide into the interior of the titanium material during cooling, resulting in the formation of low-valence Ti ions.

[0086] <Processed product manufacturing process> In the manufacturing process for processed products, the titanium material obtained as described above is processed and / or welded to obtain processed products. The processing method is not particularly limited. Examples include bending and folding. Furthermore, the titanium material or processed products are processed and / or welded to obtain building components. The processing method is not particularly limited.

[0087] The titanium material according to the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [Examples]

[0088] The types of cold-rolled titanium materials shown in Table 1 were prepared. These titanium materials were manufactured through processes such as hot rolling and cold rolling. "CP1" refers to Type 1 industrial pure titanium as defined in JIS H 4600:2012, "CP2" refers to Type 2 industrial pure titanium as defined in JIS H 4600:2012, and "CP3" refers to Type 3 industrial pure titanium as defined in JIS H 4600:2012. The reduction ratio when cold rolling was performed was set to less than 10%.

[0089] From these cold-rolled materials, 70mm x 70mm x 0.3mmt samples were cut out and subjected to an alkaline cleaning process using Pakuna DST-58-L manufactured by Yuken Kogyo Co., Ltd., followed by a water rinsing process under the conditions shown in Table 1, and then an annealing and cooling process under the conditions shown in Table 1 to obtain titanium plates for Tests No. 1 to 17. In Test No. 1, the annealing process was not performed. In Test No. 4, pickling was performed using a pickling solution containing hydrofluoric acid. In Test No. 5, annealing was performed in a low vacuum atmosphere. In Test No. 21, the atmosphere was switched in the high-temperature range. In all tests except No. 1, the annealing time was 48 hours.

[0090] [Table 1]

[0091] For each titanium plate obtained as described above, the peak intensity ratio I, color, Ca content, film thickness, rutile-type titanium oxide, and the chemical composition of the titanium plate surface were measured. Furthermore, the discoloration resistance was evaluated.

[0092] <Peak intensity ratio I> The peak intensity ratio I was measured and calculated using the following method. XPS measurements were performed on the central part of the titanium plate surface under the conditions described later, and an XPS spectrum was obtained. From the obtained XPS spectrum, the average value of the photoelectron intensity in the binding energy range of 450-480 eV was determined, and I was calculated. b This was done. Furthermore, from the obtained XPS spectrum, as described above, Ti 4+ The peak photoelectron intensity of I is determined, 4+ This is how I was obtained. b and I 4+ Substituting this into equation (i) above, the peak intensity ratio I was obtained.

[0093] Furthermore, the measurement conditions for the XPS spectrum were set as follows. MultiPak Ver9.9.2 was used as the peak pattern analysis software. Measurement device: ULVAC-PHI VersaProbeIII X-ray source: mono-AlKα (hν:1486.6eV) Beam diameter: 200 μmΦ Beam angle: 15° Energy shift correction: Au 4f 7 / 2 (83.95 eV) Measurement interval: 0.1 eV

[0094] <Color> The color of the titanium plate was measured using the following method: At the center of the titanium plate surface (measurement point A), the L color tone, as defined in JIS Z 8781-4:2013, was measured. * a * , and b * The three values ​​were measured using a Konica Minolta CR-200b colorimeter under light source C. The same measurements were then taken at the edge of the titanium plate surface (measurement point B) and at a position symmetrical to measurement point B with respect to measurement point A (measurement point C). * a * , and b * Three values ​​were measured: L at measurement point A, measurement point B, and measurement point C. * a * , and b *obtained from the values of L * average value of a * average value of, and b * average value of are shown in Table 2. And, when the average value of L * average value of a * average value of, and b * average value of satisfy formula (ii), formula (iii), and formula (iv), respectively, the evaluation was rated as ○. Furthermore, when one or more of the average value of L * average value of a * average value of, and b * average value of do not satisfy formulas (ii) to (iv), the evaluation was rated as ×.

[0095] <Ca content> Ca content was measured by the following method. First, at the center portion of a titanium plate, a thin film sample was prepared by the FIB method such that a cross section becomes the observation surface. The conditions for preparing the thin film sample were set as follows. Thin film sample preparation apparatus: FIB SEM NB5000 (manufactured by Hitachi High-Technologies) Acceleration voltage during thin film processing: 40 kV (provided that it was set to 2 kV during finishing) Temperature during thin film sample preparation: normal temperature (25°C) Mesh used: made of Mo Protective film: C(e-depо)

[0096] Next, using an EDS device equipped in a Cs-STEM, Ca content was measured at a 1 nm pitch from the surface of the titanium plate to a position of 20 nm in the thickness direction. Then, the maximum value of Ca content in the range from the surface of the titanium plate to 20 nm in the thickness direction was obtained.

[0097] Such measurement was performed at a total of 10 locations by moving the measurement position 1 μm at a time parallel to the surface of the titanium plate. Then, the maximum value of Ca content at each measurement position was obtained, and the average value at the 10 locations was obtained. The measurement conditions by Cs-STEM-EDS were set as follows. Measurement apparatus: JEM ARM200F [NEOARM] (manufactured by JEOL Ltd.) Acceleration voltage during observation: 200 kV EDS analyzer: JED 2300T (manufactured by JEOL) Acceleration voltage during analysis: 200kV Electron probe diameter: approximately 0.1 nm

[0098] <Coating thickness> The thickness of the coating was measured using the following method. Similar to the method for measuring Ca content, the O content was measured using Cs-STEM-EDS at 1 nm intervals from the surface of the titanium plate to a depth of 20 nm. The thickness of the coating was defined as the length from the surface of the titanium plate to the depth where the O content first reached half of its maximum value. This measurement was performed at a total of 10 locations, moving the measurement position 1 μm increments parallel to the surface of the titanium plate. The thickness of the coating at each measurement location was then determined, and the average value across the 10 locations was calculated.

[0099] <Presence or absence of rutile-type titanium dioxide> The rutile-type titanium oxide was identified using the following method. First, as described above, a thin film sample was prepared by the FIB method so that the cross-section of the central part of the titanium plate would be the observation surface. Next, using FE-TEM, under the conditions described later, the crystal structure was measured at 1 nm intervals from a depth of 1 / 2t starting from the outermost surface to a depth of t, as described above.

[0100] These measurements were performed at a total of 10 locations, moving the measurement position 1 μm increments parallel to the surface of the titanium plate. Then, using the analysis software described later, the number of measurement locations where the rutile-type titanium oxide pattern could be confirmed was counted: one location if the film thickness was between 2 nm and 4 nm, and two or more locations if the film thickness was 4 nm or more. Rutile-type titanium oxide was evaluated as having been detected if eight or more such measurement locations were found.

[0101] The measurement conditions for FE-TEM are set as follows: Measurement device: JEM 2100F (manufactured by JEOL) Acceleration voltage during observation: 200kV Electron diffraction pattern analysis software: ReciPro Electron probe diameter: approximately 0.5 nm

[0102] <Chemical composition of the surface layer of the titanium plate> The chemical composition of the titanium plate surface was measured using the following method. A JOBIN YVON GD-Profiler 2 manufactured by Horiba, Ltd. was used to measure the chemical composition of the titanium plate surface by GD-OES. In this apparatus, the discharge conditions were set to a constant power mode of 35W, an Ar pressure of 600Pa, a discharge area of ​​φ4mm, and a measurement pitch of 1nm. The chemical composition was then analyzed by sputtering in the depth direction from the surface of the titanium plate to a depth of 50nm, and profiles of C, F, and N content were obtained.

[0103] Using the sample after measurement, the depth removed by sputtering as described above was measured and confirmed using a surface roughness meter. The content values ​​for each depth, automatically output by the instrument, were then calibrated using the depths measured by the surface roughness meter. Furthermore, the measurement results on the outermost surface of the titanium plate are susceptible to contamination such as attached organic matter. Therefore, regions less than 2 nm from the surface of the titanium plate were excluded. From the profiles of C, F, and N content measured continuously in the depth direction of the titanium plate in this way, the maximum values ​​in the region from 2 to 50 nm from the surface of the titanium plate were determined and used as the C, F, and N content, respectively.

[0104] <Evaluation of colorfastness> The discoloration resistance of the titanium plate was evaluated as follows. A test piece measuring 50 mm in length, 25 mm in width, and 0.3 mm in thickness was cut from the above titanium plate, and an accelerated discoloration test was conducted. The accelerated discoloration test simulated an environment where acid rain dries and intensifies, and involved immersing the plate in a sulfuric acid aqueous solution adjusted to pH 3 and 80°C for 23 hours, followed by drying in a constant temperature bath at 80°C for 1 hour. This process was repeated for 14 days. The L of the titanium plate surface before and after the test was measured. * a * b * Measure the color difference ΔE * We found ab. ΔE * Samples in which ab does not exceed 8.0 are used as examples of the present invention, and ΔE * Samples with ab values ​​of 7.0 or less were classified as having good colorfastness (○), while samples with ab values ​​between 7.0 and 8.0 were classified as having fair colorfastness (△).

[0105] Color difference ΔE * ab represents the L value among the three values L, a, b representing the color tone specified in JIS Z 8781-4:2013 * , a * , b * , where ΔL is the difference before and after the discoloration acceleration test * , Δa * , Δb * , it is expressed as √{(ΔL * ) 2 +(Δa * ) 2 +(Δb * ) 2}. A larger color difference value indicates greater discoloration before and after the test. The measurement was performed using a Konica Minolta CR-200b color difference meter with light source C.

[0106] The results are summarized in Table 2.

[0107]

Table 2

[0108] As shown in Table 2, Test Nos. 2, 6 to 8, and 13 to 20, which satisfy all the requirements of the present invention, exhibited excellent discoloration resistance. On the other hand, Test Nos. 1, 3 to 5, 9 to 12, 21, and 22, which do not satisfy one or more requirements of the present invention, exhibited poor discoloration resistance.

[0109] Specifically, in Test No. 1, since the Ca ion concentration in the washing solution in the water washing step was low, the Ca content in the surface layer of the titanium plate decreased. In addition, since the annealing step was not performed, sufficient titanium oxide with tetravalent titanium was not obtained. As a result, the discoloration resistance deteriorated.

[0110] In Test No. 3, the chloride ion concentration in the washing solution during the washing process was high, while the Ca ion concentration was low. As a result, the Ca content at a depth of 20 nm from the surface was less than 1.0 atomic percent. Consequently, the discoloration resistance deteriorated. It should be noted that while the Ca ion concentration in the washing solution during the washing process was 0 mg / L, Ca was present at a depth of 20 nm from the surface, with a Ca content of 0.2 atomic percent. This suggests that the Ca was either present in the titanium material or was introduced during processes other than the washing process.

[0111] In Test No. 4, the chloride ion concentration in the washing solution during the washing process was high. As a result, uneven patterns occurred on the titanium surface, the desired design could not be maintained due to deviations from the specified color, and the discoloration resistance deteriorated. In Test No. 9, the annealing process was performed in an atmospheric environment. As a result, sufficient titanium oxide with a valency of 4 was not obtained. Consequently, the metallic color could not be maintained due to deviations from the specified color, and the discoloration resistance deteriorated.

[0112] In Test No. 10, the atmosphere switching temperature during the cooling process was below 50°C. As a result, sufficient oxidation was not achieved, and insufficient titanium oxide with a valence of 4 was obtained. Consequently, the discoloration resistance deteriorated. In Test No. 11, the holding time in a high-oxygen atmosphere was less than 5 minutes. As a result, sufficient oxidation was not achieved, and insufficient titanium oxide with a valence of 4 was obtained. Consequently, the discoloration resistance deteriorated.

[0113] In test No. 12, the holding time in a high-oxygen atmosphere exceeded 60 minutes. As a result, sufficient oxidation was not achieved, and a sufficient amount of titanium oxide with a valency of 4 was not obtained. Consequently, the discoloration resistance deteriorated. Furthermore, the metallic color could not be maintained, and the color specifications were not met.

[0114] In Test No. 21, the atmosphere switching temperature during the cooling process exceeded 200°C. Therefore, sufficient oxidation was not achieved, and a sufficient amount of titanium oxide with a valency of 4 was not obtained. As a result, the discoloration resistance deteriorated. Furthermore, the metallic color could not be maintained, and the color requirements were not met.

[0115] In test No. 22, the atmosphere was switched to one with an oxygen concentration of less than 5%. As a result, sufficient oxidation could not be achieved, and a sufficient amount of titanium oxide with a valency of 4 was not obtained. Consequently, the discoloration resistance deteriorated. [Industrial applicability]

[0116] According to the present invention, titanium materials, processed products, and building components with excellent discoloration resistance can be obtained.

Claims

1. A titanium material comprising a titanium base material and a coating formed on the titanium base material, When measurements are performed on the surface of the titanium material by X-ray photoelectron spectroscopy, the peak intensity ratio I, defined by the following equation (i), is 1.5 or greater. Lightness index L on the aforementioned surface ＊ , Chromanetics Index a ＊ , and the Chromatics Index b ＊ However, each satisfies equations (ii), (iii), and (iv) below, When the chemical composition of the titanium material in the cross-section, within a range of 20 nm from the surface of the coating in the thickness direction of the titanium material, is measured using an energy-dispersive X-ray spectrometer equipped on a spherical aberration-corrected scanning transmission electron microscope, the Ca content is 1.0 atomic percent or more. Titanium material. I=I ４＋ / I ｂ ・・・(i) 55≦L ＊ ≦75 ・・・(ii) 1.0≦a ＊ ≦2.0 ・・・(iii) 4.0≦b ＊ ≦8.0 ・・・(iv) However, the meaning of each symbol in equation (i) above is as follows: I ４＋ : I ４＋ : Ti ４＋ 2p of Ti derived from -O bond ３／２ photoelectron intensity of the peak I ｂ : Average value of photoelectron intensity in the binding energy range of 450–480 eV

2. When the thickness of the coating in the cross-section of the titanium material is denoted as t, and the crystal structure is analyzed in the depth direction of the titanium material from a depth of 1 / 2t to a depth of t using a field emission transmission electron microscope, rutile-type titanium oxide is detected. The titanium material according to claim 1.

3. The thickness t of the aforementioned film is 2 to 30 nm. The titanium material according to claim 2.

4. The chemical composition of the surface layer of the aforementioned titanium material is, in atomic percent, C: 10.0% or less, F: 10.0% or less, N: 10.0% or less. The titanium material according to claim 1.

5. The chemical composition of the surface layer of the aforementioned titanium material is, in atomic percent, C: 10.0% or less, F: 10.0% or less, N: 10.0% or less. The titanium material according to claim 2.

6. The chemical composition of the surface layer of the aforementioned titanium material is, in atomic percent, C: 10.0% or less, F: 10.0% or less, N: 10.0% or less. The titanium material according to claim 3.

7. A processed product containing the titanium material described in claims 1 to 6.

8. A building component comprising the titanium material described in claims 1 to 6.

9. A building component including the processed product described in claim 7.

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