Titanium material, processed article, and product

Abstract

Provided is a titanium material comprising a titanium base material and a film that is formed on the titanium base material, wherein the film includes at least one substance selected from titanium nitride and titanium oxide, and the chemical composition at a 0.1 μm depth position from the surface of the titanium material has a carbon content of more than 0.5 mass% but less than 10.0 mass%.

Description

Titanium materials, processed products, and products

[0001] The present invention relates to titanium materials, workpieces, and products.

[0002] Press forming is a common method for forming metal materials by pressing a material against a die and applying pressure. Adhesion between the material and the die can be a problem during press forming. Adhesion can lead to poor lubrication and reduced formability. It can also cause scratches on the surface of the material and shorten the life of the die. Therefore, there is a need for technology to suppress adhesion between the material and the die during press forming.

[0003] Commercially pure titanium or titanium alloys (hereinafter simply referred to as "titanium material") are materials that are prone to adhesion, i.e., have low lubricity. For this reason, when titanium material is press-formed, a chemical called a film-type solid lubricant is usually applied to the surface. This improves lubricity and suppresses adhesion. However, when a film-type solid lubricant is used, additional steps are required to dry the surface after application and to clean the surface after press-forming. This results in increased manufacturing costs. In light of this background, the invention described in Patent Document 1 has developed a titanium material that is resistant to adhesion and has good lubricity. The titanium material disclosed in Patent Document 1 contains TiO, which has good lubricity. ２ A film of this is formed on the surface.

[0004] Japanese Patent Application Laid-Open No. 2020-183551

[0005] Coatings containing titanium oxide and / or titanium nitride (hereinafter also referred to as "ceramic coatings") can be formed relatively easily by heat treatment or the like, taking advantage of the highly reactive properties of titanium. However, because ceramic coatings are very hard, they wear down the mold during press molding, necessitating frequent mold replacement. This results in a problem of high manufacturing costs. From this perspective, there is still room for improvement in the titanium material disclosed in Patent Document 1.

[0006] In light of the above, an object of the present invention is to provide a titanium material, a processed product, and a finished product that can suppress die wear while improving lubricity.

[0007] The present invention has been made to solve the above-mentioned problems, and the gist of the present invention is the following titanium material, processed product, and product.

[0008] (1) A titanium material comprising a titanium base material and a coating formed on the titanium base material, wherein the coating contains one or more selected from titanium nitrides and titanium oxides, and the titanium material has a chemical composition at a depth of 0.1 μm from the surface thereof of the titanium material of more than 0.5 mass % and less than 10.0 mass % C.

[0009] (2) The titanium material according to (1) above, wherein the coating has a deemed shear strength of less than 800.0 MPa.

[0010] (3) The titanium material is a titanium plate, and an electron probe microanalyzer is used to perform 500 line analyses at 0.4 μm intervals in a predetermined direction on the surface of the titanium plate, and 500 line analyses at 0.4 μm intervals in a direction perpendicular to the predetermined direction on the surface, and the measured concentrations (mass%) of C, N, and O are [C], [N], and [O], respectively. Among all the measurement points, the average value of 36[C] + 3.6[N] is 90 or more, the percentage of the number of measurement points where the value of 36[C] + 3.6[N] is 20 or less is 35% or less, and the percentage of the number of measurement points where [O] / [C] is 0.2 or less is 35% or less, and for each line analysis, a distribution line of [O] is created, and when the number of intersections between the distribution line and a line showing a concentration 0.2 times the average value of [C] is measured, the average number of intersections in the 500 line analyses is 20 to 150. The titanium material according to (1) or (2) above.

[0011] (4) The titanium material according to (3) above, wherein the ratio of the number of measurement points at which [O] / [C] is 2.0 or less is 90% or more.

[0012] (5) A processed titanium product comprising a titanium base material and a coating formed on the titanium base material, wherein the coating contains at least one selected from titanium nitride and titanium oxide, and the chemical composition at a depth of 0.1 μm from the surface of the processed titanium product is C: more than 0.5 mass % and less than 10.0 mass %.

[0013] (6) The processed titanium material according to (5) above, wherein the coating has a deemed shear strength of less than 800.0 MPa.

[0014] (7) The processed product is a processed product of a titanium plate, and when 500 line analyses are performed at 0.4 μm intervals in a predetermined direction on the surface of the processed product using an electron probe microanalyzer, and 500 line analyses are performed at 0.4 μm intervals in a direction perpendicular to the predetermined direction on the surface, and the measured concentrations (mass%) of C, N, and O are [C], [N], and [O], respectively, the average value of 36[C] + 3.6[N] at all measurement points is 90 or more, the percentage of the number of measurement points where the value of 36[C] + 3.6[N] is 20 or less is 35% or less, and the percentage of the number of measurement points where [O] / [C] is 0.2 or less is 35% or less, and when a distribution line of [O] is created for each line analysis and the number of intersections between the distribution line and a line showing a concentration 0.2 times the average value of [C] is measured, the average number of intersections in the 500 line analyses is 20 to 150. A processed titanium material according to (5) or (6) above.

[0015] (8) A processed titanium material according to (7) above, in which the ratio of the number of measurement points where [O] / [C] is 2.0 or less is 90% or more.

[0016] (9) The processed product according to any one of (5) to (8) above, which is an expanded metal.

[0017] (10) A product comprising the titanium material according to any one of (1) to (4) above and / or the processed product according to any one of (5) to (8) above.

[0018] (11) The product according to (10) above, which is a solid polymer water electrolysis device.

[0019] According to the present invention, it is possible to obtain a titanium material, a processed product, and a finished product that can suppress die wear while improving lubricity.

[0020] FIG. 1A is a diagram illustrating a method for measuring deemed shear strength, showing an enlarged view of the surface layer and cutting edge of a titanium material. FIG. 1B is a schematic diagram illustrating a method for measuring and calculating deemed shear strength λ. FIG. 2A is a diagram illustrating a method for measuring [C], [N], and [O], showing the relationship between the titanium plate and the measurement area. FIG. 2B is a diagram illustrating a method for measuring [C], [N], and [O], showing an enlarged view of the measurement area. FIG. 2C is a diagram illustrating a method for measuring [C], [N], and [O], showing an enlarged view of areas A and B enclosed by dashed lines in FIG. 2B. FIG. 3 is a graph showing the relationship between the value of [O] / [C] and the cumulative relative frequency. FIG. 4A is a graph showing the relationship between the measurement position and the concentration distribution of each element. FIG. 4B is a graph showing the relationship between the measurement position and the concentration distribution of each element. FIG. 5 is a side view showing the measurement of penetration resistance.

[0021] The present inventors have conducted extensive research to obtain a titanium material that can suppress die wear while improving lubricity, and have obtained the following findings.

[0022] From the viewpoint of enhancing the lubricity of titanium materials, it is effective to form a ceramic coating on a titanium base material. However, because ceramic coatings are hard, they can damage the die during press forming, resulting in a reduced die life. Therefore, the present inventors investigated a method for suppressing die wear during press forming while ensuring the lubricity of titanium materials. As a result, they came to the conclusion that even if a hard ceramic coating is formed, die wear can be suppressed if the ceramic coating is easily destroyed by the frictional force generated between the titanium material surface and the die surface during press forming.

[0023] As a result of further investigations, the inventors discovered that by incorporating a certain amount of C into the titanium nitride and / or titanium oxide contained in the ceramic coating, the ceramic coating becomes more easily destroyed during press forming. Thus, by forming a ceramic coating with C dissolved in the titanium substrate, it is possible to increase lubricity during press forming while suppressing die wear.

[0024] The present invention was made based on the above findings. Each requirement of the titanium material according to one embodiment of the present invention will be described in detail below.

[0025] 1. Structure of the Titanium Material The titanium material of this embodiment comprises a titanium base material and a coating formed on the titanium base material. In this embodiment, the titanium material includes, for example, a titanium plate. The thickness of the titanium plate is preferably 0.3 to 4.5 mm, and more preferably 2.0 mm or less, when used as a processed product such as expanded metal, or when used as a product such as a solid polymer water electrolysis device including a titanium material or a processed product.

[0026] 2. Titanium Base Material The type of titanium base material in this embodiment is not particularly limited. Examples of titanium base materials include commercially pure titanium and titanium alloys.

[0027] Commercially pure titanium is specified by JIS, ASTM, etc., and typically has a Ti content of 99% by mass or more. Typical examples of commercially pure titanium include commercially pure titanium types 1 to 4 specified in JIS H 4600:2012, or ASTM / ASME Grades 1 to 4. Typical impurity elements in commercially pure titanium are C, H, O, N, and Fe. The contents of these elements in the above-mentioned commercially pure titanium are: 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 contained in an amount of 0.1% by mass or less each and 0.4% by mass or less in total, as long as they do not deteriorate performance such as mechanical properties.

[0028] Titanium alloys are generally 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 highly corrosion-resistant alloys (titanium alloys specified in JIS H 4600:2012 as grades 11 to 13, 17, and 19 to 22, as well as ASTM grades 7, 11, 13, 14, 17, 30, and 31, and titanium alloys containing small amounts of various elements), Ti-0.5Cu, Ti-1.0Cu, Ti-1.0Cu-0.5Nb, and Ti-1.0Cu-1.0Sn-0.3Si-0.25Nb. In all cases, the C content is 0.08 mass% or less, the H content is 0.015 mass% or less, the O content is 0.40 mass% or less, and the N content is 0.05 mass% or less. Furthermore, 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), which are not included in the elements and main additive elements described in the above-mentioned standards, may be contained in a range of 0.1 mass% or less each, and 0.4 mass% or less in total, as long as they do not deteriorate performance such as mechanical properties.

[0029] Examples of α+β titanium alloys include Ti-3Al-2.5V, Ti-5Al-1Fe, and Ti-6Al-4V. Examples of β 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. All of these alloys contain 0.08% by mass or less of C, 0.015% by mass or less of H, 0.40% by mass or less of O, and 0.05% by mass or less of N. Furthermore, 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), which are not included in the elements and main additive elements described in the above-mentioned standards, may be contained in an amount of 0.1% by mass or less each, and 0.4% by mass or less in total, as long as they do not deteriorate performance such as mechanical properties.

[0030] 3. Coating 3-1. Coating Composition The coating of the titanium material of this embodiment contains one or more selected from titanium nitride and titanium oxide. The balance may be an impurity phase. The coating of the titanium material of this embodiment may also contain titanium carbide. That is, the coating of the titanium material of this embodiment may contain one or more selected from titanium nitride and titanium oxide, with the balance being titanium carbide and / or an impurity phase. There are no particular limitations on the respective proportions of titanium nitride, titanium oxide, and titanium carbide present.

[0031] The presence of a ceramic coating containing titanium nitride and / or titanium oxide on a titanium base material can suppress adhesion of the titanium material to the die during press working and increase the lubricity of the titanium material.

[0032] The titanium nitride, titanium oxide, and titanium carbide contained in the coating are identified using the following method. Using the thin-film X-ray diffraction function of an X-ray diffractometer, a Cu tube is used, and the angle of incidence is 1°. If the peak specific to titanium nitride is 150% or more of the background intensity in the obtained X-ray diffraction pattern, it is determined that the coating contains titanium nitride. In this case, the diffraction peak is separated into Kα1 and Kα2, and the integrated intensity of the Kα1 diffraction peak is used. The same method is used for determining titanium oxide and titanium carbide. Peaks that are less than 150% of the background intensity are determined to be impurity phases.

[0033] 3-2. Chemical Composition of the Coating The chemical composition of the coating of the titanium material of this embodiment will be described. As described above, in order to dissolve C in the ceramic coating, the chemical composition of the titanium material of this embodiment at a depth of 0.1 μm from the surface (hereinafter simply referred to as the "0.1 μm depth position") is more than 0.5 mass % and less than 10.0 mass % C.

[0034] Whether or not a coating is easily destroyed during press working depends on the characteristics of the surface layer of the titanium material. Therefore, in the present invention, we focus on the chemical composition of the coating at a depth of 0.1 μm.

[0035] By setting the C content at a depth of 0.1 μm to more than 0.5 mass%, the ceramic coating becomes easily fractured during press forming. While the reason why the ceramic coating becomes easily fractured is unclear, it is believed that the ductility, brittleness, and work hardening index of the coating, as well as the simple hardness of the coating, play a role. Furthermore, by setting the C content at a depth of 0.1 μm to less than 10.0 mass%, the formation of extremely hard TiC can be suppressed. Therefore, the C content at a depth of 0.1 μm is greater than 0.5 mass% and less than 10.0 mass%.

[0036] The C content at a depth of 0.1 μm is preferably 1.0 mass% or more, more preferably 2.0 mass% or more, even more preferably 2.5 mass% or more, even more preferably 3.0 mass% or more, and even more preferably 3.5 mass% or more. The C content at a depth of 0.1 μm is preferably 9.0 mass% or less, more preferably 8.5 mass% or less, even more preferably 7.0 mass% or less, and even more preferably 6.5 mass% or less.

[0037] At a depth of 0.1 μm, the remainder other than C is preferably Ti, O, N, and impurities. The O content at a depth of 0.1 μm is not particularly limited and can be 0 to 40.0 mass%. However, from the viewpoint of making the coating more susceptible to destruction, the O content at a depth of 0.1 μm is preferably 0 mass% or more and less than 6.4 mass%. For the same reason, it is preferable that the C content be higher than the O content at a depth of 0.1 μm. The N content at a depth of 0.1 μm is not particularly limited, but is preferably 0.1 to 21.5 mass%, and more preferably 7.7 to 13.5 mass%.

[0038] Impurities include elements contained in the titanium base material, and it is believed that the total amount of impurity elements is within a range that does not impair the target characteristics of the present invention, provided that the total amount is 0.4 mass % or less.

[0039] Furthermore, from the viewpoint of suppressing an increase in the assumed shear strength in the depth direction of the coating, the C content at a depth of 0.5 μm from the surface of the titanium material (hereinafter simply referred to as the "0.5 μm depth position") is preferably 0.1 to 3.5 mass%. The C content at the 0.5 μm depth position is more preferably 0.2 mass% or more, even more preferably 0.3 mass% or more, and even more preferably 0.4 mass% or more. The O content at the 0.5 μm depth position is preferably 0.5 to 5.3 mass%, and more preferably 1.9 mass% or less. The N content at the 0.5 μm depth position is preferably 0.1 to 20.0 mass%, and more preferably 2.5 mass% or more.

[0040] The chemical composition of the coating is measured by the following method: Glow discharge optical emission spectrometry (GD-OES). ＋ The measurement was performed under the conditions specified in the Oxide RF method. The discharge conditions were a constant power mode of 35 W, an Ar pressure of 600 Pa, and a measurement area of ​​a 4 mm diameter planar area. The content (mass%) of each element, Ti, Fe, O, C, and N, was measured from the surface of the titanium material to a depth of 10 μm at a measurement pitch of approximately 1 nm. In this case, if the base material is a titanium alloy, in addition to Ti, Fe, O, C, and N, other elements present in the titanium alloy at 0.1% or more were also measured, and the total content of all measured elements was calculated to be 100%.

[0041] Next, using the sample after measurement, the depth removed by sputtering in the above measurement is measured with a surface roughness meter. The depth value corresponding to the content automatically output by the GD-OES is calibrated with the depth measured with the surface roughness meter. Next, based on the data of the calibrated depth and the corresponding content, the average content at 0.01 μm (10 nm) intervals is calculated. For example, the average content value within the range of 0.005 μm or more and less than 0.015 μm is taken as the content at a depth of 0.01 μm. The average content value of each element within the range of 0.095 μm or more and less than 0.105 μm is taken as the C, O, and N content at a depth of 0.1 μm, respectively, and the average content value of each element within the range of 0.495 μm or more and less than 0.505 μm is taken as the C, O, and N content at a depth of 0.5 μm, respectively.

[0042] 3-3. Coating Thickness In the present invention, the thickness of the coating is not particularly limited. However, the coating thickness is preferably greater than 100 nm and less than 1000 nm. By making the coating thickness greater than 100 nm, adhesion between the titanium material and the mold can be suppressed. Furthermore, by making the coating thickness less than 1000 nm, the ductility of the coating can be ensured. Furthermore, even if strain is introduced into the surface layer of the titanium material due to bending deformation, torsional deformation, etc. during press forming, necking and fracture of the titanium material caused by cracking of the coating can be suppressed, thereby ensuring the formability of the titanium material. The coating thickness is preferably greater than 150 nm or greater than 200 nm, and preferably less than 900 nm, less than 800 nm, or less than 600 nm.

[0043] The coating thickness is measured using the following method. The data on the O and N contents at 0.01 μm (10 nm) intervals from the surface of the titanium material to a depth of 10 μm obtained as described above is used to measure the coating thickness. Specifically, based on the data, the O or N peak with the highest maximum value observed from the surface of the titanium material to a depth of 10 μm is selected. The depth position deeper than the peak of the selected element, where the content is half of the peak, is determined as the boundary between the titanium base material and the coating. The distance in the depth direction from the surface of the titanium material to this boundary is determined as the coating thickness.

[0044] 4. Deemed Shear Strength In the titanium material of this embodiment, as described above, adjusting the composition of the coating makes the ceramic coating more likely to break during press forming. Here, the deemed shear strength can be used as an indicator of whether the ceramic coating is easily broken or not. In the present invention, the deemed shear strength represents the strength against shear stress in an extremely fine region, measured using a SAICAS NN-05 model manufactured by Daipla Wintes Co., Ltd. In other words, a low deemed shear strength of the ceramic coating means that the ceramic coating is more likely to break due to the frictional force generated between the titanium material surface and the mold surface during press forming.

[0045] In the titanium material of this embodiment, the deemed shear strength of the coating is not particularly limited. However, if the deemed shear strength of the coating is less than 800.0 MPa, die wear during press forming can be more reliably suppressed. Therefore, it is preferable that the deemed shear strength of the coating be less than 800.0 MPa. Here, measurements by the present inventors have shown that the deemed shear strength of JIS Class 1 commercially pure titanium is 800.0 MPa or higher. Furthermore, since the above-mentioned titanium alloys have a higher alloy element content than pure titanium and therefore higher tensile strength, it is believed that the deemed shear strength will be 800.0 MPa or higher. Therefore, in the present invention, a deemed shear strength of less than 800.0 MPa means that the deemed shear strength of the coating is lower than the deemed shear strength of the titanium base material, and the presence of the coating means that die wear can be suppressed. The deemed shear strength of the coating is more preferably less than 600.0 MPa, even more preferably less than 400.0 MPa, and even more preferably less than 200.0 MPa. There is no particular lower limit for the deemed shear strength of the coating, but if the deemed shear strength is too low, the lubricity may actually decrease, so it is preferably 40.0 MPa or more, and more preferably 50.0 MPa or more.

[0046] The deemed shear strength is measured by the following method. FIG. 1A is a diagram illustrating a method for measuring deemed shear strength using a SAICAS NN-05, showing an enlarged view of the surface layer of titanium material 1 and cutting edge 2. FIG. 1B is a schematic diagram illustrating a method for measuring and calculating deemed shear strength λ. In FIGS. 1A and 1B, the cutting direction of cutting edge 2 is indicated by an arrow. As shown in FIG. 1A, titanium material 1 and cutting edge 2 are used to measure deemed shear strength. Cutting edge 2 is a diamond cutting edge with a cutting width of 0.114 mm, and has a rake angle A of 20° and a clearance angle B of 10°. The speed at which cutting edge 2 cuts the surface layer of titanium material 1 in the cutting direction is set to 100 nm / s horizontally and 10 nm / s vertically.

[0047] First, the method for measuring the apparent shear strength will be described. As shown in FIG. 1B , titanium material 1 has a coating 5 on a titanium substrate 4. Cutting blade 2 cuts titanium material 1 from its surface 6 at the aforementioned speed. The cut titanium material 1 is removed as chips 3. The cutting depth d (m) and the horizontal force Fh (N) applied to cutting blade 2 by cutting are measured using equipment (not shown). While cutting blade 2 is cutting the coating 5, the horizontal force Fh applied to cutting blade 2 increases as cutting depth d increases. In other words, there is a positive correlation between cutting depth d and Fh. As cutting blade 2 approaches titanium substrate 4 from coating 5 and then reaches titanium substrate 4, the horizontal force Fh gradually changes due to the difference in material between coating 5 and titanium substrate 4. In this manner, data on the horizontal force Fh versus cutting depth d is obtained.

[0048] Next, we will explain how to calculate the assumed shear strength using the analytical software provided with SAICAS. As described above, let t be the thickness of the coating 5 measured by GD-OES. We focus on the region from the surface 6, from 1 / 10t depth position P1 to 7 / 10t depth position P2, excluding the surface layer of the titanium material 1 and the region close to the titanium base material 4. In this region, it is believed that there is a positive correlation between the cutting depth d and the horizontal force Fh. Then, ΔFh / Δd is calculated using the following equation (I): ΔFh / Δd = (Fh2 - Fh1) / (7 / 10t - 1 / 10t) (I) where Fh1 and Fh2 are the horizontal forces (N) applied to the cutting edge at P1 and P2, respectively.

[0049] The value of ΔFh / Δd thus obtained is substituted into the following equation (II) derived from Merchant's principle of least work to calculate the deemed shear strength λ: λ = ΔFh / (2 × w × Δd × cotφ) (II) where φ is the shear angle (see Figure 1A) and is assumed to be 45° in the calculation of the deemed shear strength λ. Also, w is the blade width, into which 0.114 mm is substituted.

[0050] 5. Conductivity When the titanium material according to this embodiment is a titanium plate and is used in products such as a solid polymer water electrolysis device, it is desirable for the titanium material to have excellent thermal conductivity and electrical conductivity (hereinafter, collectively referred to as "conductivity").

[0051] The titanium plate of this embodiment has excellent conductivity because it has a ceramic coating on the titanium base material. However, because the ceramic coating is very hard, cracks may occur in the ceramic coating during press forming, etc. If cracks occur, voids may form on the surface of the titanium plate, reducing the area for heat and electricity transmission, which may degrade conductivity.

[0052] Furthermore, the newly formed surface in the voids is oxidized by oxygen in the atmosphere, such as the air, and a passive film mainly composed of titanium oxide, which has low conductivity, is formed on the newly formed surface. Therefore, when voids form, even if pressure is applied to press the titanium plate against another conductive material or substance, and the newly formed surface of the titanium plate comes into contact with the other conductive material or substance, conductivity may not be ensured.

[0053] Therefore, the present inventors have investigated methods for suppressing the occurrence of cracks during press forming of titanium plates and the like and for ensuring conductivity.

[0054] It was found that titanium carbide is about 10 times more effective at improving conductivity than titanium nitride. Therefore, it is effective to concentrate C in the surface layer of the titanium plate. This reduces the area on the surface of the titanium plate where the C content is extremely low. In this way, by controlling the chemical composition of the surface layer of the titanium plate, the conductivity of the titanium plate can be ensured.

[0055] However, even if the chemical composition of the titanium plate surface layer is controlled in this way, the C-enriched areas are more brittle than other areas, and there is a risk that cracks will occur in the ceramic coating starting from the C-enriched areas during press forming, etc. As a result of further investigation, it was found that by incorporating O into the C-enriched areas, it is possible to suppress the occurrence of cracks in the ceramic coating without significantly reducing conductivity, and by controlling the distribution of the C and O-enriched areas as described below.

[0056] If C and O are concentrated uniformly on the surface layer of a titanium plate, there is a risk of cracks occurring on the surface of the titanium plate during press forming, etc. As a result of various studies, it was discovered that the occurrence of cracks can be suppressed by distributing regions where C and O are concentrated in an island pattern on the surface of the titanium plate in advance.

[0057] In the present invention, whether or not regions where C and O are concentrated are distributed in an island pattern on the surface of the titanium plate is evaluated using the chemical composition of the titanium plate surface measured using an electron probe microanalyzer (EPMA) as an index.

[0058] Specifically, 500 line analyses were performed at 0.4 μm intervals in a predetermined direction on the surface of the titanium plate. Furthermore, 500 line analyses were performed at 0.4 μm intervals in a direction perpendicular to the predetermined direction on the surface of the titanium plate. The measured concentrations (mass%) of C, N, and O are designated as [C], [N], and [O], respectively. The measurement method will now be described.

[0059] 2A to 2D are diagrams illustrating the measurement method for [C], [N], and [O]. Fig. 2A shows the relationship between titanium plate 11 and measurement area 12, Fig. 2B is an enlarged view of measurement area 12, and Fig. 2C is an enlarged view of areas A and B enclosed by dashed lines in Fig. 2B. In Fig. 2C, measurement points 13 are indicated by black dots, and a virtual line 14 used for line analysis is indicated by a dashed two-dot line.

[0060] 2B, the left-right direction D1 and the up-down direction D2 on the paper surface are indicated by arrows. The left-right direction D1 and the up-down direction D2 are orthogonal to each other. In this embodiment, the left-right direction D1 corresponds to a "predetermined direction," and the up-down direction D2 corresponds to a "direction orthogonal to the predetermined direction."

[0061] 2A, first, the position and size of measurement area 12 are determined on the surface of titanium plate 11. Measurement area 12 is located on the surface of titanium plate 11, near the center in the rolling direction of titanium plate 11, and near the center in the width direction of titanium plate 11. Measurement area 12 may be 200 μm × 200 μm in size so that all measurement points described below are included.

[0062] Next, the chemical composition of the titanium plate surface was measured using a field emission electron microanalyzer (FE-EPMA). As shown in Figures 2B and 2C, [C], [N], and [O] were measured in the measurement area 12 along the imaginary line 14a connecting the measurement points 13a and 13b. Measurements were performed at 500 points in the left-right direction D1, with the measurement points 13 spaced 0.4 μm apart.

[0063] Then, [C], [N], and [O] are similarly measured along imaginary line 14b connecting measurement point 13c and measurement point 13d. Imaginary line 14b is spaced 0.4 μm from imaginary line 14a. Similarly, measurements are continued until the number of imaginary lines 14 in the vertical direction D2 reaches 500, with the spacing between each imaginary line 14 being 0.4 μm. In this manner, data on [C], [N], and [O] are obtained at a total of 250,000 measurement points 13, 500 in the horizontal direction D1 and 500 in the vertical direction D2.

[0064] The quantitative determination of [C], [N], and [O] in the titanium plate is performed by comparison with the measurement results using a standard sample. Specifically, [C] is quantified by comparison with the measurement results using 100% C (graphite), and the background is the C intensity measured on the mirror surface of pure Ti with a purity of 99.9%. [N] is quantified by comparison with the measurement results using TiN. However, in the measurement of [N], the measured value cannot simply be taken as the N intensity. This is because the TiLι (iota) line of Ti overlaps with the NKα line of N. Therefore, the intensity ratio between the TiKα line and the TiLι line is determined in advance by measuring the TiKα line and the TiLι line on the mirror surface of pure Ti with a purity of 99.9%. Subsequently, when measuring [N] in the titanium plate and TiN, the intensity of the TiKα line is measured, and the intensity of the TiLι line is calculated from the measured value and the above-mentioned intensity ratio. Then, the intensity of the NKα ray is calculated by subtracting the calculated intensity of the TiLι ray from the measured value of the N intensity, and the amount of [N] is quantified based on the obtained intensity. ２ O ３ ) and the background is the O intensity measured on a mirror surface of pure Ti with a purity of 99.9%.

[0065] Average value of 36[C] + 3.6[N] at all measurement points: 90 or more. The value of 36[C] + 3.6[N] is calculated at each of the above measurement points, and the average value is calculated for all measurement points, a total of 250,000 points. If this value is less than 90, the concentration of titanium carbide and titanium nitride may be insufficient, making it difficult to obtain good conductivity. Therefore, if excellent conductivity is desired, the average value of 36[C] + 3.6[N] at all measurement points is preferably 90 or more. The average value of 36[C] + 3.6[N] at all measurement points is more preferably 100 or more, even more preferably 110 or more, and even more preferably 120 or more. There is no need to set an upper limit to the average value of 36[C] + 3.6[N] at all measurement points, but 250 is the upper limit that can be manufactured.

[0066] Proportion of measurement points where the 36[C] + 3.6[N] value is 20 or less: 35% or less. The number of measurement points where the 36[C] + 3.6[N] value is 20 or less at each of the above measurement points is counted, and the proportion of these measurement points relative to the total of 250,000 measurement points is calculated. If this proportion exceeds 35%, there will be areas on the titanium plate surface where the concentration of titanium carbide and titanium nitride is extremely low, resulting in reduced conductivity at these locations, which may prevent the titanium plate from achieving good conductivity. Therefore, it is preferable that the proportion of measurement points where the 36[C] + 3.6[N] value is 20 or less be 35% or less. It is more preferable that the proportion of measurement points where the 36[C] + 3.6[N] value is 20 or less be 30% or less. The percentage of the number of measurement points where the value of 36[C] + 3.6[N] is 20 or less is preferably as low as possible, so there is no need to set a lower limit; it may be 0% or 0.01% or more.

[0067] The proportion of measurement points where [O] / [C] is 0.2 or less: 35% or less. Fig. 3 is a graph showing the relationship between the [O] / [C] value and the cumulative relative frequency. The horizontal axis shows the [O] / [C] value, and the vertical axis shows the cumulative relative frequency at each measurement point for each [O] / [C] value.

[0068] Measurement points where [O] / [C] is 0.2 or less have a higher [C] than [O], making them more brittle and likely to become crack initiation points. When the number of measurement points where [O] / [C] is 0.2 or less exceeds 35% of all measurement points, i.e., in the example shown by the dashed line in Figure 3, cracks may occur on the surface of the titanium plate and develop into large cracks. Therefore, as in the example shown by the solid line in Figure 3, it is preferable that the number of measurement points where [O] / [C] is 0.2 or less is 35% or less. It is more preferable that the number of measurement points where [O] / [C] is 0.2 or less is 30% or less. Furthermore, it is preferable that the number of measurement points where [O] / [C] is 0.1 or less is 20% or less. The lower the percentage of the number of measurement points where [O] / [C] is 0.2 or less and the lower the percentage of the number of measurement points where [O] / [C] is 0.1 or less, the better. Therefore, there is no need to set a lower limit; they may be 0% or 1% or more.

[0069] On the other hand, by setting [O] / [C] to 2.0 or less, it is possible to contain C and O in an appropriate ratio in the surface layer of the titanium plate, and to suppress the occurrence of cracks and a decrease in conductivity due to excessive O concentration. Therefore, as shown by the solid line in Figure 3, it is preferable that the number ratio of measurement points where [O] / [C] is 2.0 or less is 90% or more. The higher the number ratio of measurement points where [O] / [C] is 2.0 or less, the better, so there is no need to set an upper limit, and it can be 100%.

[0070] Furthermore, by setting the maximum value of [O] / [C] to 7.0 or less, it is possible to suppress a decrease in conductivity due to excessive concentration of O. Therefore, the maximum value of [O] / [C] is preferably set to 7.0 or less, and more preferably set to 4.0 or less.

[0071] Number of intersections between the [O] distribution line and the line indicating a concentration 0.2 times the average value of [C]: 20 to 150. Figures 4A and 4B are graphs showing the relationship between measurement position and the concentration distribution of each element. In Figures 4A and 4B, the horizontal axis represents the position in the left-right direction D1 on the virtual line 14 (see Figure 2B), and the vertical axis represents [C] and [O] at each position. Note that Figures 4A and 4B each show an example of the 500 virtual lines 14 described above. In Figures 4A and 4B, [C] is represented by a dashed line and [O] by a solid line. Also, in Figures 4A and 4B, the dashed line represents the concentration 0.2 times the average value of [C]. Note that for convenience of explanation, the concentration distribution of [N] is omitted.

[0072] The number of intersections between the straight line P shown in Figures 4A and 4B and the distribution line [O] is measured. For example, in the example shown in Figure 4A, there were 53 intersections, and in the example shown in Figure 4B, there were 209 intersections. This measurement is performed for all 500 virtual lines 14, and the average number of intersections is calculated. For example, in the example shown in Figure 4A, there were 62 intersections, and in the example shown in Figure 4B, there were 208 intersections.

[0073] As mentioned above, if O is uniformly concentrated on the surface layer of the titanium plate, cracks may occur in the ceramic coating during forming. Therefore, it is necessary that the O-concentrated areas are appropriately dispersed on the surface of the titanium plate. That is, as in the example shown in Figure 4A, it is preferable that areas with low [O] and areas with high [O] are appropriately repeated, and that the [O] peaks are measured at an appropriate frequency.

[0074] If the average value obtained as described above is less than 20, the width of the [O] peak will be too wide or the number of [O] peaks will be too small. As a result, the region where [O] is high or the region where [O] is low will be too wide, respectively, and in either case, cracks may occur. On the other hand, if the average value exceeds 150, the width of the [O] peak will be too narrow or the number of [O] peaks will be too large. As a result, O will be distributed almost uniformly, and cracks may occur. Therefore, it is preferable that the number of intersections between the [O] distribution line and the line representing a concentration 0.2 times the average value of [C] be 20 to 150. It is more preferable that the number of intersections between the [O] distribution line and the line representing a concentration 0.2 times the average value of [C] be 100 or less.

[0075] 6. Processed Products The titanium material according to this embodiment has excellent lubricity and can suppress die wear, so it can be used as a processed product after various processes. That is, the processed product is obtained by processing the titanium material described above. Examples of processing methods include press processing and shear processing. Examples of processed titanium products include expanded metal.

[0076] The composition of the coating on the processed product preferably satisfies the specifications for the composition of the coating on the titanium material described above. Similarly, the deemed shear strength of the coating on the processed product preferably satisfies the specifications for the deemed shear strength of the coating on the titanium material described above. The reasons why it is preferable to satisfy these specifications are the same as those explained for the titanium material, so further explanation will be omitted. However, the measurement of the coating composition and deemed shear strength is performed using a smooth surface on which testing can be performed. Titanium material or processed titanium material products may be used to make products such as solid polymer water electrolysis devices.

[0077] 7. Manufacturing Method The manufacturing method of the titanium material of this embodiment is not particularly limited. For example, the titanium material can be stably manufactured by the following manufacturing method.

[0078] 7-1. Preparation Step In the preparation step, a material for hot rolling is prepared. This material may be commercially pure titanium or a titanium alloy, and the type is not particularly limited. The material for hot rolling may be produced according to a conventional method. For example, an ingot of titanium material may be produced by arc melting or the like, and then hot forged to produce the material for hot rolling.

[0079] The above-mentioned hot rolling material is hot rolled to produce a hot rolled material. The conditions for hot rolling are not particularly limited. They may be appropriately adjusted depending on the desired properties. The obtained hot rolled material may be subjected to a heat treatment as appropriate.

[0080] 7-2. Descaling Process In the descaling process, oxide scale formed by hot rolling, heat treatment, etc. is removed. The method and conditions for descaling are not particularly limited. For example, shot blasting followed by pickling or mechanical grinding may be performed. As will be described later, from the viewpoint of facilitating the retention of cold-rolling oil and promoting the concentration of C in the hot-rolled material, it is preferable to provide appropriate irregularities on the surface of the hot-rolled material after descaling or to grind it with a P80 grinding belt. The irregularities provided on the surface of the hot-rolled material preferably have an arithmetic mean roughness Ra of 1.0 to 5.5.

[0081] 7-3. Cold Rolling Process In the cold rolling process, after removing the scale, the hot-rolled material is cold-rolled to produce a cold-rolled material. During cold rolling, a cold-rolling oil containing C is used. In the method for producing a titanium material of this embodiment, for example, mineral oil or soluble oil can be used as the cold-rolling oil. By using mineral oil or soluble oil, a mechanochemical reaction occurs during cold rolling. As a result, C is supersaturated and dissolved in the surface layer of the hot-rolled material. Note that commercially available cold-rolling oils can be used. To further promote the mechanochemical reaction, it is preferable to use mineral oil rather than soluble oil.

[0082] Cold rolling is typically performed using a Sendzimir rolling mill. In a Sendzimir rolling mill, a titanium material is rolled by passing it back and forth between a pair of work rolls multiple times. Here, passing a titanium material through the work rolls of the rolling mill is called a pass. Therefore, in cold rolling, the target thickness is typically controlled through multiple passes. In other words, cold rolling is a process that involves multiple passes.

[0083] In the method for producing a titanium material according to this embodiment, the average reduction rate in cold rolling is set to 5 to 19%. By setting the average reduction rate to 5 to 19%, it is possible to promote the mechanochemical reaction while suppressing the occurrence of surface defects. To further promote the mechanochemical reaction, the average reduction rate is preferably set to more than 5%, and more preferably to more than 7%.

[0084] The average rolling reduction mentioned above is the average value of the rolling reductions of the passes obtained by the following formula (ii): Rolling reduction (%) = (h1 - h2) / h1 x 100 (ii) where the symbols in the formula (ii) above are defined as follows: h1 (mm): thickness of the titanium material before the pass h2 (mm): thickness of the titanium material after the pass

[0085] In the washing process, the cold-rolling oil adhering to the surface of the cold-rolled material is washed away after cold rolling. The detergent used for washing is an alkaline detergent containing NaOH and KOH (Pakuna DST-58-L manufactured by Yuken Industry Co., Ltd.), with a concentration of 2.5 to 5.0 vol%.

[0086] Among these, the cold-rolled material is preferably cleaned by diluting the alkaline detergent with water to 2.5 vol% and heating it to 65°C followed by spraying (cleaning method A), or by diluting the alkaline detergent with water to 5.0 vol% and heating it to 65°C followed by spraying (cleaning method B). Here, an oxide film is inevitably formed on the surface of the cold-rolled material. It is believed that the dissolved carbon in the surface layer of the cold-rolled material reduces the oxide film, allowing nitrogen to penetrate into the surface layer of the cold-rolled material and facilitate the formation of titanium nitride. In cleaning method A, the cold-rolling oil adhering to the surface of the cold-rolled material is not completely removed and remains on the surface of the cold-rolled material. The dissolved carbon in the cold-rolling oil is used to reduce the oxide film, so the dissolved carbon in the surface layer of the cold-rolled material is not consumed. Therefore, cleaning method A is more preferable. After cleaning, the cold-rolled material is preferably washed with hot water at 65°C for 2 to 5 minutes and then dried with a dryer.

[0087] When it is desired to distribute regions where C and O are concentrated in an island pattern on the surface of the titanium plate in advance in order to suppress the occurrence of cracks in the ceramic coating and ensure conductivity, it is preferable to wash the cold-rolled material with hot water, remove any water droplets remaining on the surface of the cold-rolled material with a rubber roller, and then dry the material with a dryer.

[0088] After cleaning, the surface layer is not removed by acid treatment, grinding, or the like, because this removes the C that has adhered to and concentrated on the surface of the cold-rolled material during the cold rolling process.

[0089] In the coating formation step, the titanium material is obtained by heating and maintaining the material in a predetermined atmosphere to form the coating according to the present invention. The atmosphere may be air, but a nitrogen atmosphere is preferable to an oxidizing atmosphere, and nitrogen gas is more preferable.

[0090] When forming a coating in the atmosphere, it is preferable to hold the cold-rolled material in the atmosphere at a temperature range of 550 to 650°C for 30 to 900 seconds, which allows the formation of a coating with a thickness that satisfies both the lubricity and formability of the titanium material.

[0091] When forming a coating in a nitrogen gas atmosphere, it is preferable to use nitrogen gas with a purity of 5N or higher, with a nitrogen partial pressure of 1 atm or higher and a dew point of -55°C or lower. In such an atmosphere, it is preferable to hold the cold-rolled material at a holding temperature of 800 to 880°C for a holding time of 15 to 900 seconds. By holding the temperature at 800°C or higher, titanium nitride formation predominates, reducing the O content in the coating that hardens the coating. By holding the temperature at 880°C or lower, the formation of TiN, a hard titanium nitride, can be suppressed. The holding temperature is more preferably 815°C or higher, 830°C or higher, or 845°C or higher. Furthermore, by holding the time at 15 seconds or longer, a coating thick enough to ensure the lubricity of the titanium material is formed. By holding the time at 900 seconds or shorter, the coating is prevented from becoming too thick and formability can be ensured. There is no particular upper limit on the partial pressure of the nitrogen gas. Due to the nature of annealing equipment, the nitrogen partial pressure is usually 10 atm or less.

[0092] 7-6. Processed Product Manufacturing Process In the processed product manufacturing process, the titanium material obtained as described above is processed to obtain a processed product. The processing method is not particularly limited. For example, pressing or shearing may be performed. Examples of processed products obtained by pressing, shearing, etc. include expanded metal. Furthermore, products such as solid polymer water electrolysis devices may be manufactured using the titanium material or the processed product.

[0093] The titanium material according to this embodiment will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0094] The types of titanium materials shown in Table 1 were prepared. These titanium materials were manufactured through processes such as hot rolling. Note that "JIS Class 1" refers to Class 1 commercially pure titanium as specified in JIS H 4600:2012, and "JIS Class 2" refers to Class 2 commercially pure titanium as specified in JIS H 4600:2012.

[0095] These titanium materials were subjected to a cold rolling process, a cleaning process, and a coating process under the conditions shown in Table 1 to obtain titanium plates with the thicknesses shown in Table 1. In Table 1, "AP" in the "Descaling Process" column indicates that the plate was subjected to pickling after shot blasting. In Table 1, "A" in the "Cleaning Method" column of the "Cleaning Process" column indicates the above-mentioned "Cleaning Method A," and "B" indicates the above-mentioned "Cleaning Method B." "Pickling" refers to pickling using a 55% by mass HF aqueous solution and 64% by mass HNO . ３ The aqueous solutions were mixed to 1.3 vol% and 8 vol% hydrofluoric and nitric acids, respectively, and heated to 40°C to remove approximately 50 μm of the surface of one side of the titanium plate. "Hot water washing time" refers to the time spent washing with hot water at 65°C.

[0096] In addition, "air annealing and pickling" in Table 1 refers to air annealing in which the titanium plate is held in air at 800°C for 3 minutes, and then the plate is subjected to pickling in an aqueous solution of 55% by mass of HF and 64% by mass of HNO. ３ The aqueous solutions of nitric acid and fluorohydrogen were mixed to 1.3 vol% and 8 vol%, respectively, and heated to 40°C, and pickling was performed to remove approximately 50 μm from one side of the titanium plate. "Ion plating" in Table 1 means that titanium was used as the evaporation material, the differential pressure was 400 V, and ion plating was performed in an oxygen atmosphere of 0.1 Pa for Test No. 24 and in a nitrogen atmosphere of 0.1 Pa for Test No. 23. "Anodic oxidation" in Table 1 means that ion plating was performed in a 5 vol% H atmosphere at room temperature. ２ SO ４ This means that a titanium plate was immersed in the solution and anodization was carried out with an applied voltage of 80V.

[0097]

[0098] For each of the titanium plates obtained as described above, the titanium nitride contained in the coating was identified, the chemical composition of the coating was measured, the coating thickness was measured, the deemed shear strength was measured, and the lubricity was evaluated. The deemed shear strength was measured using the method described above.

[0099] <Identification of Titanium Nitride, Titanium Oxide, and Titanium Carbide Contained in the Coating> The titanium nitride, titanium oxide, and titanium carbide contained in the coating were identified by the following method. The thin film X-ray diffraction function of an EMPYREAN X-ray diffractometer manufactured by Spectris Inc. (Malvern Panalytical) was used, with a Cu tube and an incident angle of 1°. From the obtained X-ray diffraction pattern, if the peak specific to titanium nitride was 150% or more of the background intensity, it was determined that the coating contained titanium nitride. The same determination was made for titanium oxide and titanium carbide. Peaks less than 150% of the background intensity were determined to be impurity phases.

[0100] <Measurement of Chemical Composition of Film> The chemical composition of the film was measured by the following method. The chemical composition of the film was measured by GD-OES using a GDS850A model manufactured by LECO Corporation. The analysis software used for the measurement was QDP v4.90. The sputtering was performed using Ar ＋ The other measurement conditions were in accordance with the Oxide RF method. The discharge conditions were a constant power mode of 35 W, an Ar pressure of 600 Pa, and a measurement area of ​​a flat area with a diameter of 4 mm. The contents (mass%) of the elements Ti, Fe, O, C, and N were measured from the surface of the titanium material to a depth of 10 μm at a measurement pitch of approximately 1 nm.

[0101] Next, using the measured sample, the depth removed by the sputtering in the above measurement was measured with a surface roughness meter. The depth value corresponding to the content automatically output by the GD-OES was calibrated with the depth measured with the surface roughness meter. Next, based on the data of the calibrated depth and the corresponding content, the average content value at 0.01 μm (10 nm) intervals was calculated. That is, the average content value of each element in the range of 0.095 μm or more and less than 0.105 μm was taken as the C, O, and N content at a depth of 0.1 μm, and the average content value of each element in the range of 0.495 μm or more and less than 0.505 μm was taken as the C, O, and N content at a depth of 0.5 μm.

[0102] <Measurement of Coating Thickness> The coating thickness was measured by the following method. Based on the data on the O and N contents at 0.01 μm (10 nm) intervals from the surface of the titanium plate to a depth of 10 μm obtained as described above, the O and N peaks with the highest maximum values ​​observed from the surface of the titanium plate to a depth of 10 μm were selected. Then, deeper than the peak depth of the selected element, the depth position closest to the surface where the content was half of the peak was defined as the boundary between the titanium base material and the coating, and the distance in the depth direction from the surface of the titanium material to this boundary was defined as the coating thickness.

[0103] <Evaluation of Lubricity> The lubricity of the titanium plate was evaluated by the average coefficient of friction. The average coefficient of friction was measured using the following method. A pin-on-disk friction and wear tester was used to slide a pin on the surface of the titanium material without lubrication, and a friction and wear test was performed. The test was performed under conditions of a surface pressure of 1 MPa, a speed of 0.1 m / min, and a sliding distance of 200 mm. The pin used in the test was made of high-carbon chromium bearing steel SUJ2 specified in Japanese Industrial Standards JIS G 4805:2019, and had a smooth surface with a diameter of 3.5 mm and an arithmetic mean roughness Ra of 0.12.

[0104] <Evaluation of Mold Wear> Although it is clear that materials with low assumed shear strength and high lubricity reduce mold wear, to confirm this, mold wear was examined for several titanium plates. First, 100 test pieces were cut out from each of the titanium plates of Test Nos. 3, 4, 7, 8, 14, 26, 30, and 33. An extension test was then performed, and the degree of mold wear was evaluated based on the state of defects on the mold and test pieces. In the extension test, a cylindrical flat-head punch made of SKD61, measuring φ40 mm and r4 mm, was used to fix the test piece with a beaded die to suppress the inflow of material, and pressing was performed, stopping at an extension height of 5 mm. Continuous pressing was performed using 100 test pieces for each test number, and the r portion of the mold after 100 consecutive pressings was visually inspected. If clear scratches were found on the mold, it was rated D; if there were no scratches but marks like rubbing on the mold were found, it was rated C; if there were no scratches but there was a change in gloss, it was rated B; and if no change was found, it was rated A.

[0105] The results are summarized in Table 2 below.

[0106]

[0107] Furthermore, the [C], [N], and [O] on the surface of several titanium plates were measured using the method described above. The conductivity of each titanium plate was also evaluated by electrical conductivity as described below. Since both electricity and heat are conducted by electrons, the higher the electrical conductivity, the higher the thermal conductivity. The conductivity of each titanium plate after processing, simulating press forming, was also evaluated.

[0108] <Evaluation of Electrical Conductivity> The evaluation of electrical conductivity was carried out by the following method. Electrical conductivity was evaluated by penetration resistance. FIG. 5 is a side view when measuring penetration resistance. First, a test piece 21 measuring 1.5 cm x 1.5 cm was taken from the above-mentioned titanium plate without changing the plate thickness. Then, both sides of the test piece 21 were sandwiched between 1 cm x 1 cm conductive carbon sheets 22, and further sandwiched between 2 cm x 2 cm platinum electrodes 23. For the conductive carbon sheets, carbon paper TGP-H-090 manufactured by Toray Industries, Inc. was used. In this state, a pressure of 10 kgf / cm was applied. ２ The electric resistance α was measured with a load of 1.0 MPa and a current of 1 A.

[0109] The carbon conductive sheet 22 alone was sandwiched between the platinum electrodes in advance, and a pressure of 10 kgf / cm ２ The electrical resistance β was measured with a load of 1000 kJ / cm2 and a current of 1 A. This electrical resistance β is the electrical resistance between the electrode and the conductive sheet. The penetration resistance of the titanium plate was determined by subtracting the electrical resistance β from the electrical resistance α. The penetration resistance of Test No. 35 was used as the reference penetration resistance, and the value obtained by dividing the penetration resistance of each test piece by the reference penetration resistance is shown in Table 3 as the relative penetration resistance. The lower this relative penetration resistance, the higher the conductivity.

[0110] In addition, each test piece was subjected to a process simulating press forming, and the penetration resistance was measured. First, from each titanium plate obtained as described above, a tensile test piece was prepared, having a parallel portion with a width of 20 mm and a length of 60 mm, a gauge length of 50 mm in the parallel portion, and a shoulder and a grip portion at both ends, so that the cold rolling direction was parallel to the tensile direction. Then, the tensile test piece was pulled from both ends by the grip portion, and the pulling was stopped when the gauge length of the parallel portion was elongated by 15%. Then, a test piece with a thickness of 1.5 cm x 1.5 cm was taken from the center of the parallel portion, and the penetration resistance was measured by the method described above. Then, the penetration resistance of Test No. 35 before processing was taken as the reference penetration resistance, and the value obtained by dividing the penetration resistance of each test piece by the reference penetration resistance was shown in Table 3 as the relative penetration resistance.

[0111]

[0112] In the invention examples, Test Nos. 1 to 25, the preferred manufacturing conditions were satisfied, and therefore the requirements of the present invention were met, resulting in good lubrication. Furthermore, because the assumed shear strength was low, it was possible to suppress mold wear, as confirmed in particular in Test Nos. 3, 4, 7, 8, and 14. Furthermore, as can be seen from a comparison of Test Nos. 3 and 4, for example, when water droplets were removed using a rubber roller in the cleaning process, the occurrence of cracks was suppressed by previously distributing regions where C and O were concentrated on the titanium plate surface in an island-like pattern, resulting in excellent electrical conductivity.

[0113] On the other hand, in Comparative Examples Test Nos. 26 to 35, the preferred manufacturing conditions of the present invention were not satisfied, and therefore the requirements of the present invention were not satisfied. Although the lubricity was good, the deemed shear strength was high, and die wear could not be suppressed, as confirmed in particular in Test Nos. 19, 22, and 25. Furthermore, in Comparative Example Test No. 27, no coating was formed, and therefore the lubricity was reduced.

[0114] In Test Nos. 26 and 27, air annealing and pickling were performed after the cleaning process. In Test No. 28, pickling was performed during the cleaning process. In these examples, the C dissolved in the cold working process was removed by pickling, so C could not be dissolved in the coating, and the deemed shear strength was 800.0 MPa or higher. In Test Nos. 29 and 30, two or more of the more preferable conditions were not adopted in the manufacturing process of the titanium material. As a result, a sufficient amount of C could not be dissolved in the coating, and the deemed shear strength was 800.0 MPa or higher.

[0115] In Test No. 31, cleaning was not performed after the cold rolling process. As a result, the C content in the coating became excessive, resulting in the formation of TiC and an assumed shear strength of 800.0 MPa or more. In Test Nos. 32 and 33, air annealing and pickling were performed, and then a coating was formed by ion plating. As a result, a coating containing titanium oxide or titanium nitride was formed, but the C that had been dissolved in the cold rolling process was removed by pickling, making it impossible to dissolve C in the coating, resulting in an assumed shear strength of 800.0 MPa or more.

[0116] In Test No. 34, air annealing and pickling were performed, followed by anodizing to form a coating. As a result, a coating containing titanium oxide was formed, but the C that had been dissolved by cold rolling was removed by pickling, so C could not be dissolved in the coating, and the deemed shear strength was 800.0 MPa or more. In Comparative Example No. 35, the coating formation step was not performed, so no coating was formed, the deemed shear strength was 800.0 MPa or more, and the lubricity was also reduced.

[0117] According to the present invention, it is possible to obtain a titanium material, a processed product, and a finished product that can suppress die wear while improving lubricity.

[0118] REFERENCE SIGNS LIST 1 titanium material 2 cutting edge 3 chips 4 titanium base material 5 coating 6 surface 11 titanium plate 12 measurement area 13 measurement point 14 imaginary line 21 test piece 22 conductive sheet 23 electrode

Claims

1. A titanium material comprising a titanium base material and a coating formed on the titanium base material, wherein the coating contains one or more selected from titanium nitride and titanium oxide, and the chemical composition at a depth of 0.1 μm from the surface of the titanium material is C: more than 0.5 mass % and less than 10.0 mass %.

2. The titanium material according to claim 1, wherein the coating has a deemed shear strength of less than 800.0 MPa.

3. The titanium material is a titanium plate, and an electron probe microanalyzer is used to perform 500 line analyses at 0.4 μm intervals in a predetermined direction on the surface of the titanium plate, and 500 line analyses at 0.4 μm intervals in a direction perpendicular to the predetermined direction on the surface, and the measured concentrations of C, N, and O (mass%) are [C], [N], and [O], respectively. Among all the measurement points, the average value of 36[C] + 3.6[N] is 90 or more, the percentage of the number of measurement points where the value of 36[C] + 3.6[N] is 20 or less is 35% or less, and the percentage of the number of measurement points where [O] / [C] is 0.2 or less is 35% or less, and a distribution line of [O] is created for each line analysis, and when the number of intersections between the distribution line and a line showing a concentration 0.2 times the average value of [C] is measured, the average number of intersections among the 500 line analyses is 20 to 150. The titanium material according to claim 1 or 2.

4. The titanium material according to claim 3, wherein the percentage of measurement points where [O] / [C] is 2.0 or less is 90% or more.

5. A titanium processed product comprising a titanium base material and a coating formed on the titanium base material, wherein the coating contains one or more selected from titanium nitride and titanium oxide, and the chemical composition at a depth of 0.1 μm from the surface of the processed product is C: more than 0.5 mass % and less than 10.0 mass %.

6. The processed titanium material according to claim 5, wherein the coating has a deemed shear strength of less than 800.0 MPa.

7. The processed product is a titanium plate processed product, and an electron probe microanalyzer is used to perform 500 line analyses at 0.4 μm intervals in a predetermined direction on the surface of the processed product, and 500 line analyses at 0.4 μm intervals in a direction perpendicular to the predetermined direction on the surface, and the measured concentrations of C, N, and O (mass%) are [C], [N], and [O], respectively. Among all the measurement points, the average value of 36[C] + 3.6[N] is 90 or more, the percentage of the number of measurement points where the value of 36[C] + 3.6[N] is 20 or less is 35% or less, and the percentage of the number of measurement points where [O] / [C] is 0.2 or less is 35% or less, and a distribution line of [O] is created for each line analysis, and when the number of intersections between the distribution line and a line showing a concentration 0.2 times the average value of [C] is measured, the average number of intersections among the 500 line analyses is 20 to 150.

7. A processed titanium material according to claim 5 or 6.

8. A processed titanium product according to claim 7, in which the percentage of measurement points where [O] / [C] is 2.0 or less is 90% or more.

9. The processed product according to any one of claims 5 to 8, which is an expanded metal.

10. A product comprising the titanium material according to any one of claims 1 to 4 and / or the processed product according to any one of claims 5 to 8.

11. The product according to claim 10, which is a solid polymer water electrolysis device.

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