TW202342776A - Titanium material - Google Patents

Abstract

This titanium material is configured such that: in a range from the surface to a position at which the oxygen concentration measured in the thickness direction from the surface by a glow discharge spectroscopic analysis method is 1/3 the maximum value, the average nitrogen concentration and the average carbon concentration are both 14.0 at% or less, and the average hydrogen concentration is 30.0 at% or less; and the difference between the c-axis lattice constant of [alpha]-phase Ti as determined by X-ray diffraction measurement by a parallel beam method in which the angle of incidence on the surface is 0.3 degrees and the c-axis lattice constant of [alpha]-phase Ti as determined by X-ray diffraction measurement by an intensive method at the plate thickness center is 0.015 Å or less.

Description

Titanium

Field of invention The invention relates to a titanium material.

Background of the invention Because titanium exhibits extremely excellent corrosion resistance in atmospheric environments, it is used as a building material such as roofs and exterior walls of buildings. However, titanium materials sometimes change color after long-term use. Discoloration of titanium materials can sometimes be a problem from a design perspective. Therefore, titanium materials that suppress discoloration and have excellent discoloration resistance have been proposed.

For example, Patent Document 1 discloses a titanium material or titanium alloy material with excellent discoloration resistance, characterized in that an oxide film with a thickness of 100 Å or less exists on the surface of the substrate, and the amount of C in the surface oxide film is 30 atomic % or less, and The amount of C in the base surface layer under the oxide film is 30 atomic % or less.

Patent Document 2 discloses titanium that is less likely to discolor in an atmospheric environment and is characterized by having an average carbon concentration of 14 at% or less in a depth range of 100 nm from the surface, and having an oxide film with a thickness of 12 to 40 nm on the outermost surface.

Patent Document 3 discloses a titanium material that is resistant to discoloration and is characterized in that the fluorine content in the oxide film on the surface is 7at% or less.

Patent Document 4 discloses a method for manufacturing a titanium plate, which is characterized in that in order to efficiently manufacture a titanium or titanium alloy plate that is less discolored in a light environment, the titanium plate is cold-rolled using the following lubricant: The lubricant can make the carbon content of the carbon-concentrated layer on the surface of the cold-rolled titanium plate be less than 150 mg/ ^m2 . After that, it is annealed in an oxidizing gas environment, and then immersed in molten salt and nitric fluoric acid aqueous solution. Pickling to remove rust.

Patent Document 5 discloses a titanium or titanium alloy that is less likely to discolor in an atmospheric environment. It is characterized in that the average carbon concentration in a depth range of 100 nm from the surface is 14 at% or less, and it has an oxide film with a thickness of 12 nm or more and 30 nm or less on the surface. Furthermore, the arithmetic mean height (Ra) of the titanium surface is 0.035 μm or less. Prior technical literature

patent documents [Patent Document 1] Japanese Patent Application Publication No. 2000-1729 [Patent Document 2] Japanese Patent Application Publication No. 2002-12962 [Patent Document 3] Japanese Patent Application Publication No. 2002-47589 [Patent Document 4] Japanese Patent Application Publication No. 2002-60984 [Patent Document 5] Japanese Patent Application Publication No. 2005-272870

[Non-patent literature] [Non-patent document 1] Tsutomu Miyashita, "Review of Surface Roughness", Journal of the Society of Precision Engineering, Society of Precision Engineering, Vol.73, No.2, 2007, No. 201- 205 pages

Summary of the invention Invent the problem to be solved In the technologies described in Patent Documents 1 to 5, the deterioration of the discoloration resistance of the titanium material is suppressed by reducing the surface carbon concentration. In addition, conventional discoloration resistance evaluation of titanium materials is based on the color difference after immersing in sulfuric acid with a temperature of 60° C. and a pH of 3 for 14 days, as described in Patent Document 5, for example. However, in recent years, a titanium material with better discoloration resistance than conventional titanium materials has been pursued.

The present invention was completed in view of the above problems, and its object is to provide a titanium material that can continuously suppress discoloration for a long time and has excellent discoloration resistance than conventional titanium materials. An object of the present invention is to provide a titanium material that does not undergo discoloration even if it is immersed for a longer period than the evaluation described in Patent Documents 1 to 5, for example.

Means for Solving the Problems The gist of the present invention based on the above findings is as follows. [1] A titanium material according to an aspect of the present invention, in which the oxygen concentration is measured from the surface toward the thickness direction by glow discharge spectroscopy, starting from the surface to a position where the measured oxygen concentration is 1/3 of the maximum value. The average nitrogen concentration and the average carbon concentration in the range are 14.0 atomic % or less, and the average hydrogen concentration is 30.0 atomic % or less; The difference between the c-axis lattice constant of α-phase Ti and the c-axis lattice constant of α-phase Ti determined by X-ray diffraction measurement at the center of the plate thickness is less than 0.015Å. [2] The titanium material described in [1] above may be provided with an oxide film having a thickness of 30.0 nm or less. [3] The titanium material according to the above [1] or [2], which may be as follows: having a titanium base material and an oxide film disposed on the surface of the titanium base material; when analyzed by X-ray photoelectron spectroscopy, The maximum value of the nitrogen concentration derived from nitride in the oxide film is 2.0 to 10.0 atomic %. When converted by the sputtering speed of _SiO2 , the nitrogen concentration derived from nitride in the oxide film is one of the maximum values. The position exists in the range of 2 to 10 nm from the surface of the oxide film, and the range of 20 nm from the position where the oxygen concentration reaches 1/2 of the maximum value to the titanium substrate side. The concentration of nitrogen derived from the nitride existing in this range is is less than the maximum value of the nitrogen concentration derived from nitride in the oxide film and 7 atomic % or less, and the maximum value of the nitrogen concentration derived from nitride in the oxide film is the nitride-derived concentration in the oxide film The maximum nitrogen concentration is greater than the carbon concentration derived from carbides. [4] The titanium material according to the above [1] or [2], which may be as follows: provided with a titanium base material, and the titanium base material has an arithmetic mean roughness in a roughness curve in a direction in which the arithmetic mean roughness Ra reaches a maximum. The ratio of the degree Ra to the element length RSm, that is, Ra/RSm, is 0.006~0.015, and the root mean square slope RΔq is 0.150~0.280; the kurtosis (kurtosis) Rku of the aforementioned titanium base material is greater than 3, and the aforementioned The skewness (skewness) Rsk of the titanium substrate is greater than -0.5. [5] The titanium material according to the above [3], which may be as follows: In the roughness curve in the direction in which the arithmetic mean roughness Ra of the titanium base material reaches the maximum, the ratio of the arithmetic mean roughness Ra to the element length RSm That is, Ra/RSm is 0.006~0.015, and the root mean square tilt RΔq is 0.150~0.280; the kurtosis Rku of the titanium base material is greater than 3, and the skewness Rsk of the titanium base material is greater than -0.5.

Invention effect According to the present invention, it is possible to provide a titanium material that can continuously suppress discoloration for a longer period of time than conventional titanium materials and has excellent discoloration resistance.

Embodiments of the present invention Form used to implement the invention Hereinafter, a titanium material according to an embodiment of the present invention will be described with reference to the drawings. In addition, the size and ratio of each component in the figure do not represent the actual size and ratio of each component.

In addition, regarding the limited range of numerical values enclosed by "~" described below, the lower limit value and the upper limit value are included in this range. Regarding values marked "less than" and "greater than", these values are not included in the numerical range.

The inventors of the present invention have finally completed the present invention. First, they will describe in detail the innovative insights obtained by the inventors of the present application through review.

Titanium materials have the following structure: an oxide film is arranged on the surface of the titanium base material; the discoloration of titanium materials has been considered to be caused by an increase in the thickness of the oxide film due to acid rain, etc. The carbon concentration near the surface of titanium materials will affect the thickness of the oxide film. Therefore, in the past, titanium materials with the purpose of improving discoloration resistance would limit the carbon concentration on the surface. The inventors of the present invention conducted examinations in order to obtain a titanium material that can suppress discoloration for a longer period of time than conventional materials and has excellent discoloration resistance.

First, the inventors of the present invention measured the oxygen concentration, carbon concentration, and nitrogen concentration from the titanium material surface (in other words, the oxide film surface) toward the thickness direction through glow discharge spectroscopy (hereinafter referred to as "GDS"). It can be understood that titanium has an oxide film, and the position where the oxygen concentration measured by GDS is 1/3 of the maximum value is located near the interface between the oxide film and the titanium base material and on the side of the titanium base material. Hereinafter, the range from the surface of the titanium material in the thickness direction to the position where the oxygen concentration measured by GDS is 1/3 of the maximum value is called the titanium material surface layer portion.

Next, the inventors of the present invention immersed the titanium material in a sulfuric acid aqueous solution with pH 3 and 60° C. for 4 weeks, and evaluated the discoloration resistance based on the color difference before and after immersion. After comparing the titanium material with obvious discoloration before and after impregnation and the titanium material with almost no discoloration, it was found that the carbon concentration and nitrogen concentration measured by GDS were different in the titanium material before impregnation. Specifically, it was found that for the titanium material that changed color significantly after being immersed in a sulfuric acid aqueous solution of pH 3 and 60°C for 4 weeks, in the titanium material before immersion, the inside of the oxide film and the interface between the oxide film and the substrate began to change. Nitrogen and carbon are present near the interface on the substrate side. It has never been considered in the past that the oxide film and the nitrogen present near the interface between the oxide film and the base material on the base material side will affect the discoloration of the titanium material. However, it can be speculated that when titanium materials are continuously exposed to an acid rain environment for a long time, the oxide film and the nitrogen present in its vicinity will become the same starting point as carbon and the oxide film will grow.

Furthermore, the inventors of the present case obtained the insight from the examination results that the nitrogen concentration in and around the oxide film has the same impact on the discoloration resistance of the titanium material as the carbon concentration, and that limiting the nitrogen concentration improves the discoloration resistance. It is also understood that in the range from the surface of the titanium material in the thickness direction to the position where the oxygen concentration measured by GDS is 1/3 of the maximum value, if the average nitrogen concentration and the average carbon concentration are each 14.0 atomic % or less, the titanium The discoloration resistance of the material will be improved than before. The average carbon concentration in the surface layer of titanium materials can be reduced by increasing the annealing temperature or extending the annealing time. The average nitrogen concentration can be reduced by increasing the vacuum degree of heat treatment.

Next, the inventors of the present invention focused on the hydrogen concentration in the surface layer of the titanium material and examined the influence of the hydrogen concentration in the surface layer of the titanium material on the discoloration resistance of the titanium material. It was found that if the average hydrogen concentration in the surface layer of the titanium material is 30.0 atomic % or less, the discoloration resistance will be further improved. In the acid rain environment of the atmosphere, titanium hydride is thermodynamically more unstable than titanium oxide. When the hydrogen concentration in the titanium material increases and the formation of titanium oxide is promoted, the discoloration resistance may decrease. However, it is considered that if the average hydrogen concentration in the surface layer of the titanium material is 30.0 atomic % or less, the titanium hydride will not change into titanium oxide, and a decrease in discoloration resistance can be suppressed.

Next, the inventors of the present invention focused on changes in the crystal structure of Ti on the surface of the titanium material. The inventors of this case discovered that changes in the c-axis of Ti in the α phase of the densest hexagonal crystal will affect the discoloration resistance of titanium materials.

According to the review by the inventors of the present case, it was found that the c-axis lattice constant of the α-phase Ti was determined by X-ray diffraction measurement using the parallel beam method with an incident angle of 0.3 degrees on the surface of the titanium material, and the lattice constant on the plate If the difference between the c-axis lattice constant of α-phase Ti and the thick center (also called the thickness center) is 0.015Å or less, which is determined by X-ray diffraction measurement using the concentration method, the discoloration resistance can be greatly improved. sex. Regarding the above-mentioned X-ray diffraction measurement, the penetration degree of X-rays varies depending on the X-ray diffraction energy. However, by performing the above-mentioned X-ray diffraction measurement on the surface of the titanium material and in the center of the titanium material plate thickness, it can be measured. Find the lattice constant of the c-axis of Ti in each α phase. In this case, the increase in the lattice constant of the c-axis of Ti in the α phase in the surface layer is defined as follows. That is, the lattice constant of the c-axis of α-phase Ti was determined by X-ray diffraction measurement using the parallel beam method with an incident angle of 0.3 degrees on the surface of the titanium material, and X-rays were measured using the concentration method at the center of the plate thickness. The difference between the c-axis lattice constant of α-phase Ti and the two is determined by diffraction measurement is called the increase in the c-axis lattice constant of α-phase Ti in the surface layer portion. The measurement depth in X-ray diffraction measurement using the parallel beam method with an incident angle of 0.3 degrees does not exactly match the thickness direction range of the surface layer measured by GDS, but it can roughly measure the α phase in the surface layer. The increase in the lattice constant of the c-axis of Ti. It is considered that the increase in the c-axis lattice constant of the α-phase Ti in the surface layer of the titanium material is related to oxygen. If oxygen is solidly dissolved in the α-phase Ti in the surface layer of the titanium material, the lattice constant of the c-axis will increase. It can be speculated that if the lattice constant of the c-axis of Ti in the α-phase present on the surface of the titanium material is larger than the c-axis lattice constant of the Ti in the α-phase present in the center of the thickness, then a defect concentration will be generated due to the action of acid rain. With high titanium oxide content, the oxide film will grow easily and the discoloration resistance will deteriorate. The crystal structure of the α-phase Ti in the surface layer of the titanium material is affected by the temperature, time, and vacuum degree of the heat treatment. By increasing the degree of vacuum in the gas environment during heat treatment, the amount of oxygen dissolved in the α-phase Ti in the surface part of the titanium material will be reduced, and the c-axis lattice constant of the α-phase Ti in the surface part of the titanium material will be reduced. The increase will be suppressed. This concludes the explanation of the innovative insights obtained by the inventors of this case through review.

Next, a titanium material according to an embodiment of the present invention will be described with reference to FIG. 1 . FIG. 1 is a schematic enlarged cross-sectional view showing the layer structure of the titanium material of this embodiment. Regarding the titanium material of this embodiment, the oxygen concentration is measured from the surface toward the thickness direction by the glow discharge spectrometry method, and the average nitrogen concentration in the range from the surface to the position where the measured oxygen concentration is 1/3 of the maximum value, and The average carbon concentration is 14.0 atomic % or less, and the average hydrogen concentration is 30.0 atomic % or less; the c-axis of α-phase Ti is determined by X-ray diffraction measurement using the parallel beam method with an incident angle of 0.3 degrees on the aforementioned surface. The difference between the lattice constant and the c-axis lattice constant of Ti in the α phase determined by X-ray diffraction measurement using the concentration method at the center of the plate thickness is 0.015Å or less. The titanium material of this embodiment will be described in detail below.

(titanium material 1) As shown in FIG. 1 , the titanium material 1 of this embodiment is a titanium material in which an oxide film 20 is formed on the surface of a titanium base material 10 . In other words, the titanium material 1 has a titanium base material 10 and an oxide film 20 formed on the surface of the titanium base material 10 . The surface portion 30 is a region starting from the surface of the titanium material 1 (in other words, the surface of the oxide film 20 ) in the thickness direction to a position where the oxygen concentration measured by GDS is 1/3 of the maximum value, and includes the titanium base material 10 part of it.

(titanium base material 10) The titanium base material 10 of the titanium material 1 is pure titanium, industrial pure titanium or titanium alloy. The titanium base material 10 is, for example, pure titanium with a Ti content of 70% by mass or more, industrial pure titanium, or a titanium alloy. Hereinafter, these materials may be collectively referred to as "titanium". The crystal structure of pure titanium is the α phase of the densest hexagonal crystal and does not contain the β phase of the body-centered cubic structure. Industrial pure titanium is mainly composed of α phase, and sometimes contains β phase due to chemical composition, etc. Titanium alloys can be: α-type alloys with only α-phase; or they can be: α+β-type alloys containing β-phase with a body-centered cubic structure. In addition, the titanium base material 10 may be industrial titanium, for example. Examples of industrial titanium used for the titanium base material 10 include various industrial titanium plates and strips described in JIS H 4600:2012, and various industrial titanium rods described in JIS H 4650:2016. If workability is required, industrial pure titanium of JIS Class 1 (for example, JIS H 4600: 2012) with reduced impurities is preferred. Moreover, if strength is required, JIS type 2 to 4 industrial pure titanium can be applied to the titanium base material 10 . Examples of titanium alloys include: JIS 11 to 23 containing trace amounts of precious metal elements such as palladium, platinum, ruthenium, etc., in order to improve corrosion resistance; or JIS 60 containing a larger number of elements, such as Ti-6Al-4V series Alloy, 60E type, 61 type and 61F type, etc. In addition, mainly used in buildings: industrial pure titanium specified in JIS Class 1, its equivalent ASTM Gr.1, or its equivalent.

Regarding titanium alloys mainly composed of α phase, there are, for example, high corrosion resistance alloys (JIS grades 11 to 13, 17, 19 to 22, and ASTM grades 7, 11, 13, 14, 17, Titanium alloys specified in 30 and 31, or titanium alloys containing small amounts of various elements (Ti-Ru-Mm, etc.), Ti-0.5Cu, Ti-1.0Cu, Ti-1.0Cu-0.5Nb, Ti-1.0Cu -1.0Sn-0.35Si-0.25Nb, etc. Mm represents rare earth metal alloy (mischmetal).

Regarding α+β type titanium alloys, there are examples: Ti-3Al-2.5V, Ti-5Al-1Fe, Ti-6Al-4V, etc.

When the titanium base material 10 contains aluminum like the Ti-6Al-4V based alloy, the corrosion resistance may be deteriorated and the discoloration resistance may be adversely affected. Therefore, if the oxide film 20 is to be formed on the surface of the titanium alloy as the titanium base material 10, it is recommended to investigate the influence of the alloy elements on the application in advance and appropriately adjust the composition and thickness of each layer according to the titanium base material 10.

The titanium base material 10 is, for example, industrial pure titanium or titanium alloy, which contains: in mass %: Co: 0% or more and less than 1.0%, Cr: 0% or more and 0.5% or less, Ni: 0% or more and 1.00% or less, Ta: 0% or more and 6.00% or less, Al: 0% or more and 7.0% or less, V: 0% or more and 5.0% or less, S: 0% or more and 0.3% or less, Cu: 0% or more and 1.50% or less, Nb: 0% or more and 0.70% or less, Sn: 0% or more and 1.40% or less, Si: 0% or more and 0.55% or less, Mo: 0% or more and 0.5% or less, W: 0% or more and 0.5% or less, Pd: 0% or more and 0.25%, Ru: 0% or more and 0.15% or less, Rh: 0% or more and 0.15% or less, Os: 0% or more and 0.15% or less, Ir: 0% or more and 0.15% or less, Pt: 0% or more and 0.15% or less, REM: 0% or more and 0.10% or less, C: 0% or more and 0.18% or less, H: 0% or more and 0.015% or less, O: 0% or more and 0.40% or less, N: 0% or more and 0.05% or less, and Fe: 0% or more and 2.50% or less, The remainder consists of Ti and impurities. REM here refers to rare earth elements, specifically selected from Sc, Y, light rare earth elements (La, Ce, Pr, Nd, Pm, Sm, Eu) and heavy rare earth elements (Gd, Tb, Dy, One or more elements in the group consisting of Ho, Er, Tm, Yb, Lu).

In addition, the titanium base material 10 is, for example, industrial pure titanium, which contains: in mass %: C: 0% or more and 0.10% or less, H: 0% or more and 0.015% or less, O: 0% or more and 0.40% or less, N: 0% or more and 0.05% or less, and Fe: 0% or more and 0.50% or less, The remainder consists of Ti and impurities.

In addition, the titanium base material 10 is, for example, a titanium alloy, which contains: in mass %: Co: 0% or more and less than 0.80%, Pd: 0% or more and 0.25% or less, Cr: 0% or more and 0.2% or less, Ru: 0% or more and 0.06% or less, Ni: 0% or more and 0.60% or less, Ta: 0% or more and 6.0% or less, N: 0% or more and 0.05% or less, C: 0% or more and 0.08% or less, H: 0% or more and 0.015% or less, O: 0% or more and 0.35% or less, and Fe: 0% or more and 0.30% or less, The remainder consists of Ti and impurities.

In addition, the titanium base material 10 is, for example, a titanium alloy, which contains: in mass %: Al: 2.0% or more and 7.0% or less, V: 1.0% or more and 5.0% or less, S: 0% or more and 0.3% or less, REM: 0% or more and 0.08% or less, N: 0% or more and 0.05% or less, C: 0% or more and 0.10% or less, H: 0% or more and 0.015% or less, O: 0% or more and 0.35% or less, and Fe: 0% or more and 2.5% or less, The remainder consists of Ti and impurities.

In addition, the titanium base material 10 is, for example, a titanium alloy, which contains: in mass %: Cu: 0.3% or more and 1.50% or less, Nb: 0% or more and 0.70% or less, Sn: 0% or more and 1.40% or less, Si: 0% or more and 0.55% or less, N: 0% or more and 0.05% or less, C: 0% or more and 0.10% or less, H: 0% or more and 0.015% or less, O: 0% or more and 0.15% or less, and Fe: 0% or more and 0.10% or less, The remainder consists of Ti and impurities.

In addition, the titanium base material 10 is, for example, a titanium alloy, which contains: in mass %: V: 0% or more and 0.5% or less, Ni: 0% or more and 1.00% or less, Cr: 0% or more and 0.5% or less, Co: 0% or more and less than 1.0%, Mo: 0% or more and 0.5% or less, W: 0% or more and 0.5% or less, Pd: 0% or more and 0.15% or less, Ru: 0% or more and 0.15% or less, Rh: 0% or more and 0.15% or less, Os: 0% or more and 0.15% or less, Ir: 0% or more and 0.15% or less, Pt: 0% or more and 0.15% or less, REM: 0.001% or more and 0.10% or less, N: 0% or more and 0.03% or less, C: 0% or more and 0.18% or less, H: 0% or more and 0.015% or less, O: 0% or more and 0.35% or less, Fe: 0% or more and 0.30% or less, and The total of Pd, Ru, Rh, Os, Ir and Pt: 0.01% or more and 0.15% or less, The remainder consists of Ti and impurities.

In terms of impurities, they are components that exist in titanium and are not necessarily present in the obtained titanium material regardless of the intention of addition. The term "impurities" is a concept that includes impurities mixed in from raw materials or the manufacturing environment during the industrial production of titanium. Examples of impurities include Cl, Na, Mg, Ca and B. The content of each element of impurities should be less than 0.1 mass%, and the total amount should be less than 0.4 mass%.

The titanium substrate 10 is usually a plate, a strip, a tube, a straight line, or is formed into such a suitably processed shape. The titanium base material 10 can also be in any shape, such as spherical or rectangular parallelepiped.

(Oxide film 20) An oxide film 20 is formed on the surface of the titanium base material 10 . The thickness of the oxide film 20 is not particularly limited, but if it is greater than 30.0 nm, the color development of the titanium material 1 may be affected due to interference of light. Therefore, the thickness of the oxide film 20 is preferably 30.0 nm or less. From the viewpoint of suppressing color development due to interference of light, the thickness of the oxide film 20 is preferably 25.0 nm or less, more preferably 20.0 nm or less. Although the thickness of the oxide film 20 is greater than 0 nm, it may be, for example, 10.0 nm or more. In addition, the discoloration resistance of the titanium material will be improved by ensuring the thickness of the oxide film 20 . Therefore, from the viewpoint of improving discoloration resistance, the thickness of the oxide film 20 on the surface of the titanium material 1 is preferably 12.0 nm or more.

The thickness of the oxide film 20 is measured by GDS. The measurement using GDS is carried out by the following method. The GDS was measured using the JOBIN YVON GD-Profiler2 manufactured by Horiba Manufacturing Co., Ltd. in a constant power mode of 35W. The pressure of the argon gas was set to 600Pa, and the discharge range was set to a diameter of 4mm. The measurement pitch in the measurement based on GDS is 0.5nm. In the measurement performed by GDS, O (oxygen), N (nitrogen), C (carbon), H (hydrogen), and Ti are analyzed from the surface of the titanium material 1. The concentration (atomic %) of each of the above elements is calculated based on the total of the above elements being 100 atomic %. The thickness of the oxide film 20 is calculated from the oxygen concentration measured by GDS. Specifically, the distance in the thickness direction from the surface to the position where the oxygen concentration is halved relative to the maximum value is the thickness of the oxide film 20 . The average nitrogen concentration, average carbon concentration and average hydrogen concentration are the arithmetic average values of the nitrogen concentration, carbon concentration and hydrogen concentration at each measurement point.

The nitrogen concentration derived from nitride in the vicinity of the interface between the titanium base material 10 and the oxide film 20 is preferably less than the maximum value of the nitrogen concentration in the oxide film 20 measured by XPS and 7 atomic % or less. Nitride will be formed on the oxide film 20 through the manufacturing method of the titanium material 1 of this embodiment described later. However, according to this method, the nitride formed near the interface between the titanium base material 10 and the oxide film 20 does not exist or For a very small amount. The nitrogen content of the titanium base material 10, that is, the base material, based on the value obtained by chemical analysis, is about 0.05 to 0.07 mass %, or at most about 0.20 atomic %, which is an impurity level. Since this content is below the solid solution limit of nitrogen in titanium, nitrides are not formed. According to this, if nitride exists near the interface between the titanium base material 10 and the oxide film 20, the nitride is formed by nitrogen diffusing from the surface to the inside during the annealing process in one example of the method for manufacturing the titanium material 1 of this embodiment. By. Therefore, the nitrogen concentration derived from nitrides near the interface between the titanium base material 10 and the oxide film 20 is preferably less than the maximum value of the nitrogen concentration in the oxide film 20 measured by XPS and 7 atomic % or less. If the nitrogen concentration derived from nitrides near the interface between the titanium base material 10 and the oxide film 20 is less than the maximum value of the nitrogen concentration in the oxide film 20 measured by XPS and is 7.0 atomic % or less, the long-term durability of the titanium material 1 will be inhibited. When exposed to acid rain, an oxide film grows and inhibits discoloration. The nitrogen concentration derived from nitride in the vicinity of the interface between the titanium base material 10 and the oxide film 20 is preferably less than the maximum value of the nitrogen concentration in the oxide film 20 and 3.0 atomic % or less. On the other hand, the lower limit of the nitrogen concentration derived from nitride in the vicinity of the interface with the oxide film 20 in the titanium base material 10 is not limited. Therefore, according to an example of the manufacturing method of the titanium material 1 of this embodiment, the lower limit of the nitrogen concentration derived from nitride in the vicinity of the interface with the oxide film 20 in the titanium base material 10 is 0 atomic %. However, if the separation of XPS peaks is considered The resulting situation (not zero) is sometimes around 0.5 atomic %.

In addition, the vicinity of the interface between the titanium base material 10 and the oxide film 20 refers to a range of 20 nm toward the titanium base material side from the interface when measured by XPS. In the diagram measured by XPS described later (for example, FIG. 4 ), the position where the oxygen concentration reaches 1/2 of the maximum value measured by XPS is determined as the aforementioned interface. Therefore, the range from the position where the oxygen concentration reaches 1/2 of the maximum value measured by XPS to 20 nm on the titanium base material side is defined as the vicinity of the interface between the titanium base material 10 and the oxide film 21 . There is a region different from the surface layer portion 30 near the interface with the oxide film 20 in the titanium base material 10 . Although the oxide film 20 can be identified through GDS or XPS, the thickness of the oxide film obtained by each measurement method is often not strictly consistent due to different measurement methods. However, for each measurement method, the position where the oxygen concentration reaches 1/2 of the maximum value is designated as an oxide film. From this point of view, the definition of oxide film is consistent. In this case, when the nitrogen concentration derived from nitride in the vicinity of the interface between the titanium base material 10 and the oxide film 20 is measured, the oxide film is measured by XPS.

The oxide film 20 preferably contains nitrogen derived from nitride. Nitrogen derived from nitride in the oxide film 20 can be measured through X-ray photoelectron spectroscopy (XPS). FIG. 2 is a diagram showing an example of the change in the depth direction of the energy spectrum of the titanium material 1 of this embodiment obtained by X-ray photoelectron spectroscopy. Figure 3 is a diagram showing the following: an example of the depth direction change of the energy spectrum of a general titanium material obtained by X-ray photoelectron spectroscopy. Figure 2(A) and Figure 3(A) show the changes in the depth direction of the N1s energy spectrum, Figure 2(B) and Figure 3(B) show the changes in the depth direction of the C1s energy spectrum, Figure 2(C) and Figure 3 (C) shows the change in the depth direction of the O1s energy spectrum, and Figure 2(D) and Figure 3(D) show the change in the depth direction of the Ti2p energy spectrum. As shown in FIG. 2(C) , in the titanium material 1 of this embodiment, a clear peak derived from nitride may sometimes be recognized at a depth corresponding to the oxide film 20 . On the other hand, as shown in FIG. 3(C) , in general titanium materials, the peak originating from nitride is extremely low. Thus, the titanium material 1 of this embodiment preferably contains a predetermined amount of nitrogen derived from nitride in the oxide film 20 . Next, the nitrogen content derived from nitride in the oxide film 20 will be described in detail. In addition, in the titanium material 1 of this embodiment, as the peak intensity of nitride (Nitride) in Figure 2(C) continues to increase, the peak intensity related to TiN in Figure 2(A) also increases. From this, it can be considered that, The nitride in Figure 2(C) is a nitride derived from titanium.

The nitrogen content derived from nitride in the oxide film 20 (the maximum value of the nitrogen concentration) is preferably 2.0 to 10.0 atomic %. The nitrogen content derived from nitrides in the oxide film 20 refers to the maximum value of the nitrogen concentration derived from nitrides in the oxide film 20 measured by XPS. For uncolored materials, if the oxide film 20 contains 2.0 atomic % or more of nitrogen derived from nitrides, the discoloration resistance will be further improved. Although the reason for this is not necessarily clear, it is considered that the reasons are as follows: if nitride exists in the oxide film 20, the atomic arrangement will be disordered, and the strain distribution in the oxide film 20 will change; or due to changes in conductivity, changes in nanoscale potential distribution, etc. , and the function of shielding ions from penetrating into the oxide film 20 (shielding function) changes. If the nitrogen content derived from nitride in the oxide film 20 is 2.0 atomic % or more, the shielding function can be more reliably improved, and the effect of improving the discoloration resistance can be more reliably achieved. In consideration of manufacturing stability, the nitrogen content derived from nitride in the oxide film 20 is preferably 4.0 atomic % or more. On the other hand, if the nitrogen content derived from nitride in the oxide film 20 exceeds 10.0 atomic %, the shielding function may be reduced and the effect of improving discoloration resistance may not be obtained. However, if the nitrogen content derived from nitride in the oxide film 20 When the nitrogen content is 10.0 atomic % or less, the shielding function can be maintained and the discoloration resistance can be more significantly improved. In consideration of manufacturing stability, the nitrogen content derived from nitride in the oxide film 20 is preferably 8.0 atomic % or less.

In addition, the inventors of the present invention also thought of improving the discoloration resistance by controlling the distribution of nitrogen derived from nitrides in the oxide film 20 . FIG. 4 is a diagram showing an example of the element concentration distribution in the depth direction obtained by X-ray photoelectron spectroscopy of the titanium material 1 of this embodiment (example of the present invention) and the general titanium material (conventional example). The sputtering depth on the horizontal axis in Figure 4 is the depth converted by the sputtering speed of _SiO2 . The example of the present invention shown in FIG. 4 is the element concentration distribution of the titanium material of this embodiment shown in FIG. 2 . The conventional example shown in Figure 4 is the element concentration distribution of a general titanium material (one type of industrial pure titanium) shown in Figure 3.

As shown in FIG. 4 , in the titanium material 1 of this embodiment, the nitrogen concentration derived from nitride exhibits a maximum value at a position where the sputtering depth converted from the sputtering speed of SiO ₂ is 2 to 10 nm. On the other hand, in general titanium materials, the nitrogen concentration is extremely low. Accordingly, the depth at which the nitrogen concentration derived from nitride reaches the maximum in the oxide film 20 is preferably 2 to 10 nm in terms of the sputtering speed of SiO ₂ . In addition, the upper limit of the sputtering depth is preferably 30 nm or more including the range near the interface with the oxide film 20 . In addition, it may be changed according to the thickness of the oxide film 20, but it is preferably about three times or more the thickness of the oxide film 20.

In addition, the inventors of the present invention also investigated the effect of the nitrogen concentration at the depth where the nitrogen concentration derived from nitride reaches the maximum in the oxide film 20 on the discoloration resistance. FIG. 5 is a graph showing the relationship between the maximum concentration of nitrogen derived from nitrides in the oxide film 20 and the color difference ΔE ^* ab before and after the discoloration test.

The color difference ΔE ^* ab is obtained by the following method. Immerse in the pH 3 sulfuric acid aqueous solution at 60°C for 4 weeks, and measure L ^* a ^* b ^* on the surface of the titanium material before and after immersion. The lightness L ^* and chromaticity a ^* and b ^* are calculated according to JIS Z 8730:2009. The difference values ΔL ^* , Δa ^* , and Δb ^* before and after immersion are calculated by the following formula. ΔE ^* ab = [(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ] ^1/2 color difference ΔE ^{* ab The smaller the color difference ΔE *} ab is, the lower the degree of discoloration before and after the test, which means: excellent discoloration resistance .

As shown in FIG. 5 , if the nitrogen concentration in the depth where the nitrogen concentration derived from nitride reaches the maximum in the oxide film 20 is less than 2.0 atomic %, the shielding property will not be improved enough, and the color difference may be greater than 8. On the other hand, if the nitrogen concentration derived from the nitride exceeds 10.0 atomic %, the shielding properties will decrease, and the color difference may exceed 8. In addition, if the nitrogen concentration in the depth where the nitrogen concentration derived from nitride reaches the maximum in the oxide film 20 exceeds 10.0 atomic %, it may become golden or yellow in color. When it turns into a gold or yellow hue, the color tone will change, so it may not be suitable for such applications where the silver color of titanium itself is pursued. This color change is presumably due to the material color of titanium nitride. Therefore, the nitrogen concentration at the depth where the nitrogen concentration derived from nitride reaches the maximum in the oxide film 20 is 2.0 to 10.0 atomic %.

In addition, as shown in FIG. 5 , if the nitrogen concentration at the depth where the nitrogen concentration derived from nitride reaches the maximum in the oxide film 20 is smaller than the carbon concentration derived from carbides at the same depth, the color difference may be greater than 8. As mentioned above, this is considered to be due to the influence on the strain distribution in the oxide film 20 and the influence on the nanoscale potential distribution due to the change in conductivity. Therefore, the nitrogen concentration at the depth where the nitrogen concentration derived from nitrides reaches the maximum in the oxide film 20 is preferably greater than the carbon concentration derived from carbides at the position where the nitrogen concentration derived from nitrides reaches the maximum in the oxide film 20 .

The concentrations of N, C, O, and Ti derived from nitrides, carbides, and oxides in the titanium base material 10 and the oxide film 20 can be calculated by using X-ray photoelectron spectroscopy to analyze the surface of the titanium material with Ar ions. Sputtering is performed. In detail, the analysis conditions are set as follows: X-ray source: mono-AlKα (hν: 1486.6eV), beam diameter: 200 μmΦ (≒ analysis area), detection depth: several nm, acquisition angle: 45°, sputtering conditions: Ar ⁺ , sputtering rate 4.3nm/min. (SiO ₂ conversion value). The SiO ₂ conversion value is the sputtering speed obtained by measuring the thickness of the SiO ₂ film in advance using an ellipsometer and then calculating the sputtering speed under the same measurement conditions using the film. The peak shown at a position with a binding energy of about 393~408eV is measured as the peak of N1s, and the N derived from organic matter is set to about 399~401eV, and the N derived from nitride is set to be about 397±1eV, and the two are separated. By. The peak shown at a position with a binding energy of approximately 280~395eV is measured as the peak of C1s, and the C derived from organic matter is set to approximately 284~289eV, and the C derived from carbide is set to approximately 281.5±1eV to separate the two. By. The peak shown at a position with a binding energy of about 525 to 540 eV was measured as the peak of O1s, and O derived from organic matter was set to about 399 to 401 eV, and O derived from metal oxides was set to about 529.5 to 530.5 eV. The peak shown at the position of binding energy 450 to 470 eV was measured as the peak of Ti2p. The bound energy of the above substances is a general value and may change due to the charge of the measurement sample, etc. As one of the charge correction methods, the following method can be applied: a method of correcting together with the peak position of CC bonding in C derived from organic matter. As for the general practice of using these peaks for analysis, the analysis software MultiPak can be used to analyze the concentration of elements and the concentration according to the chemical state. General procedures are described below. The background is corrected based on Shirley's method. Next, the Gauss-Lorents function is used for compounds, and the Asymmetric function is used for metals to fit the peaks according to the chemical states of each element. Then, the area ratio of the peak originating from each chemical state is multiplied by the element concentration (atomic %) to calculate the concentration (atomic %) by chemical state. This process is used to calculate the nitrogen content derived from nitrides and the carbon content derived from carbides. In addition, the aforementioned element concentration is calculated by calculating the peak area including all peaks related to the element (without separation) for each element detected by XPS, and then dividing the aforementioned peak area by the sensitivity coefficient of each element to convert it into a percentage. The nitrogen content derived from nitride in the oxide film 20 has been described in detail.

(Surface part 30) The discoloration resistance of the titanium material 1 will be improved as the average nitrogen concentration and the average carbon concentration of the surface layer 30 are reduced. From the viewpoint of discoloration resistance, the average nitrogen concentration and the average carbon concentration of the surface layer portion 30 measured from the surface of the titanium material 1 toward the thickness direction by GDS using the above method are 14.0 atomic % or less respectively. The average nitrogen concentration of the surface layer portion 30 of the titanium material 1 is preferably 12.0 atomic % or less, more preferably 10.0 atomic % or less. The average carbon concentration of the surface layer portion 30 of the titanium material 1 is preferably 13.0 atomic % or less, more preferably 12.0 atomic % or less, and more preferably 10.0 atomic % or less. The average nitrogen concentration of the surface layer portion 30 of the titanium material 1 may be 0 atomic % or more than 1.0 atomic %. The average carbon concentration of the surface layer 30 of the titanium material 1 may be 0 atomic % or more than 1.0 atomic %.

The discoloration resistance of the titanium material 1 will be further improved due to the reduction in the average hydrogen concentration of the surface layer 30 . The hydrogen concentration of the surface layer portion 30 of the titanium material 1 is 30.0 atomic % or less, preferably 25.0 atomic % or less, more preferably 20.0 atomic % or less. Titanium is a metal with high affinity for hydrogen, and the hydrogen concentration in the surface layer 30 may be 10.0 atomic % or more.

(Difference in lattice constants of the c-axis of Ti in the α phase in the surface layer portion 30) The crystal structure of the α-phase Ti in the surface layer portion 30 of the titanium material 1 affects the discoloration resistance. Specifically, if the lattice constant of the c-axis of the α-phase Ti in the surface layer portion 30 of the titanium material 1 increases, the discoloration resistance will deteriorate. The increment of the c-axis lattice constant of the α-phase Ti in the surface layer portion 30 of the titanium material 1 is evaluated by the following difference: The c-axis lattice constant of α-phase Ti determined by diffraction measurement, and the c-axis lattice constant of α-phase Ti determined by X-ray diffraction measurement at the center of the plate thickness. The difference between them. From the viewpoint of discoloration resistance, the increment of the c-axis lattice constant of Ti in the α phase in the surface layer portion 30 of the titanium material 1 is 0.015Å or less, preferably 0.010Å or less. The smaller the increment of the lattice constant of the c-axis of Ti in the α phase on the surface of titanium material 1, the better, and it can also be 0Å. When the increment is a negative value, the reason is measurement error, and the increment can be regarded as 0Å.

The lattice constant of the c-axis of Ti in the α phase in the surface layer portion 30 of the titanium material 1 can be obtained by X-ray diffraction measurement using the parallel beam method on the surface of the titanium material. For X-ray diffraction measurement using the parallel beam method, the X-ray diffraction device SmartLab manufactured by Rigaku Co., Ltd. can be used, and the X-ray source is Co-Kα (wavelength λ = 1.7902 Å). Regarding the removal of Kβ rays, a W/Si multilayer mirror is used on the X-ray incident side. The X-ray source load power (tube voltage/tube current) is 5.4kW (40kV/135mA) respectively. The incident angle of X-rays on the sample is 0.3 degrees, and the diffraction angle 2θ is scanned. For measurement, a sample with a size of 25 mm (length) × 50 mm (width) was cut out from the titanium material through machining and used. A beam is irradiated with the sample's 12.5mm (vertical) × 25mm (horizontal) center as the center, and the measurement is performed on the sample surface. In addition, the cut sample may have dirt attached to the surface to be measured, so clean it with acetone or ethanol.

The crystal structure of the α-phase Ti in the center of the titanium plate thickness can be measured by X-ray diffraction using the concentration method. The sample used to analyze the crystal structure of the α-phase Ti in the center of the titanium plate thickness was finished by mechanical grinding and electrolytic polishing so that the center of the titanium plate thickness became the measurement surface for X-ray diffraction measurement. For X-ray diffraction measurement using the concentration method, it is sufficient to use: an X-ray diffraction device used for X-ray diffraction measurement using the parallel beam method; an X-ray source, a filter to remove Kβ rays, and an X-ray source load The power can also be the same as the above-mentioned parallel beam method. The crystal structure of Ti will be the same in the center of the plate thickness, so samples can also be produced from the plate width, rolling direction, etc. In this case, a sample was made from the center part starting from about a quarter of the plate width, and the test was conducted.

The lattice constant of the c-axis of the α phase of Ti on the surface of the titanium material and in the center of the plate thickness was calculated from the diffraction peak of the (0002) plane using software (X'Pert HighScore Plus) manufactured by Spectris Co., Ltd. Even when the titanium base material is of the α+β type, the lattice constant of the c-axis of the α-phase Ti can be calculated from the diffraction peak of the α-phase Ti.

(Ra/RSm: 0.006~0.015) (RΔq: 0.150~0.280) In addition, the inventors of the present case also examined the relationship between the surface properties and the discoloration resistance of the titanium material in detail, and obtained the following insights: Regarding the discoloration resistance of the titanium material, the arithmetic mean roughness Ra of the titanium base material surface and the contour curve element The ratio of the average length RSm, that is, Ra/RSm, and the root mean square slope RΔq of the roughness curve element have an impact on the discoloration resistance.

The arithmetic mean roughness Ra, the average length RSm of the contour curve elements, and the root mean square slope RΔq of the roughness curve elements can be measured by the method in accordance with JIS B 0601:2013. In addition, the kurtosis Rku and skewness Rsk described later can also be measured by methods based on JIS B 0601:2013.

The arithmetic mean roughness Ra of this embodiment is the arithmetic mean roughness Ra specified in JIS B 0601:2013, and is the average of the absolute values of the total coordinate values Zj in the reference length. The arithmetic mean roughness Ra can be calculated by the following formula (1). In addition, the roughness curve that is the basis for calculating the arithmetic mean roughness Ra is determined as follows: a low-pass filter with a cutoff wavelength λc = 0.8 mm is applied to the measured profile curve of the oxide film to obtain the profile curve, and then the profile curve is obtained A high-pass filter with a cutoff wavelength λs = 2.667 μm is applied to the profile curve to obtain a roughness curve. In addition, the reference length of the roughness curve is set to be the same length as the cut-off wavelength λc, which is 0.8mm. λc is a filter used to define the boundary between the roughness component and the waviness component. λs is a filter used to define the boundary between the roughness component and the component with a shorter wavelength.

[Mathematical formula 1]

In the above formula (1), n is the number of measurement points, and Zj is the height of the j-th measurement point in the roughness curve.

The average length RSm of the contour curve elements can be calculated by the following equation (2).

[Mathematical formula 2]

In the above formula (2), m is the number of measurement points, and Xsi is the length of the contour curve element in the reference length.

The root mean square slope RΔq of the roughness curve element can be calculated by the following equation (3).

[Mathematical formula 3]

In the above formula (3), N is the number of measurement points. (dZj/dXj) is the local tilt at the j-th measurement point in the roughness curve, and can be defined by the following equation (4).

[Mathematical formula 4]

In the above formula (4), ΔX is the measurement interval. In this embodiment, the measurement interval ΔX may be determined as follows. That is, the measurement interval ΔX is a value set by the surface roughness shape measuring machine. If the numerical data (data) is obtained when N points are measured when measuring the measurement length L, then the average ΔX will be L/(N based on the measurement interval) -1). For example, when using Tokyo Seiko's SURFCOM 1900DX and software TIMS Ver.9.0.3 to measure a measurement length of 5mm, if 25601 points of digital data are obtained, ΔX will be 5mm/25600 points and average about 0.195μm.

The root-mean-square inclination RΔq of the roughness curve element is a parameter that specifies the inclination angle (local inclination dZ/dX) of the minute range that forms the surface unevenness relative to the reference length X of the roughness curve.

The inventors of this case produced titanium materials by changing Ra/RSm and RΔq, and examined the effects of Ra/RSm and RΔq of the titanium base material on the discoloration resistance. Figure 6 is a graph showing the following: the ratio of the arithmetic mean roughness Ra of the titanium base material to the average length RSm of the contour curve element, that is, Ra/RSm, and the root mean square inclination RΔq of the roughness curve element, and the discoloration resistance. relationship.

As mentioned above, discoloration resistance can be evaluated through color difference ΔE ^* ab and appearance observation. However, for the measurement of the hue L ^* a ^* b ^* used to evaluate the color difference ΔE ^* ab, a sunlight source is installed directly above the titanium plate and light is irradiated from the sunlight source. Therefore, the actual appearance may sometimes differ. Especially in a titanium plate with a large RΔq, even if the color difference ΔE ^* ab is small, discoloration may be visible when observed with the naked eye under sunlight. Accordingly, in terms of evaluation of discoloration resistance, visual observation under sunlight is also important.

"O" in Figure 6 indicates the following conditions: the color difference ΔE ^* ab is 5 or less, and the rate of people who believe that the discoloration is inconspicuous in sensory evaluation with the naked eye is 80% or more; "×" indicates the following conditions : Although the color difference ΔE ^* ab is 5 or less, the rate of people who feel that the discoloration is inconspicuous in sensory evaluation with the naked eye is less than 80%. In this case, regarding this sensory evaluation through naked eye observation, the titanium materials that have not yet been submitted to the accelerated discoloration test of this case and the titanium materials that have been subjected to the accelerated discoloration test of this case were placed side by side on a flat plate in advance, and 10 evaluators evaluated them under the sun. Look and compare from various angles to determine whether there is an angle where discoloration is noticeable to the naked eye. Compare the proportion of people who think discoloration is inconspicuous. In addition, this visual observation assumes the conditions of the roof and walls of an actual building, and is an evaluation method that also takes into account the change in color tone depending on the viewing angle.

As shown in Figure 6, it is understood that for the surface of the titanium material of this embodiment, if the ratio of the arithmetic mean roughness Ra to the average length RSm of the contour curve elements, that is, Ra/RSm, is 0.006 to 0.015, and the roughness curve When the root mean square slope RΔq of the element is 0.150~0.280, the discoloration resistance is excellent even in a higher temperature and acidic environment. This titanium material has excellent discoloration resistance even under high temperature and acidic environments, and can further suppress discoloration over a long period of time.

If Ra/RSm is less than 0.006, the unevenness on the surface of the titanium base material is small, and the intervals between the unevenness are wide. If Ra/RSm is less than 0.006, the surface of the titanium material is relatively smooth. Because of the optical path difference between the light reflected on the oxide film surface and the light reflected on the titanium substrate surface, sometimes the light enhanced by this optical path difference can be recognized. color. That is, titanium materials sometimes change color. It can be considered that if Ra/RSm is 0.006~0.015, the optical path difference between the light reflected by the oxide film surface and the light reflected by the titanium substrate surface will become smaller due to the relatively large tilt of the titanium surface, and there will be no Enhanced light in the visible range, thus inhibiting discoloration. Considering the mechanism of suppressing discoloration, there is no reason to limit the upper limit of Ra/RSm to 0.015. However, industrial production of deep and narrow valley-shaped unevenness exceeding 0.015 is difficult. Therefore, the upper limit of Ra/RSm is preferably 0.015, which can clearly obtain the effects of the present invention.

If RΔq is 0.150 or more, the inclination of the relatively fine unevenness in the oxide film is large. Due to this local inclination, the regular reflection of the light irradiated onto the surface of the titanium base material is suppressed and diffused. Therefore, on the surface of the titanium base material, the intensity of the reflected light in the direction of the reflected light on the surface of the oxide film becomes smaller. As a result, the enhanced light color is difficult to discern. If RΔq is less than 0.150, the above effect will not occur, so discoloration of the titanium material may be seen. On the other hand, if RΔq is greater than 0.280, even if the color difference is as low as 5 or less, there may be an angle at which discoloration becomes conspicuous under sunlight. The reason is considered to be as follows: if RΔq is greater than 0.280, the titanium material is tilted in the direction of regular reflection when viewed obliquely, and the interference color due to the increase in the thickness of the oxide film is enhanced and becomes visible to the naked eye.

If Ra/RSm is 0.006~0.015, and the root mean square slope RΔq of the roughness curve element is 0.150~0.280, then the superposition of the above effects can be obtained, so the discoloration of the titanium material can be further suppressed. In addition, even if the oxide film on the surface of a titanium material having the above-mentioned surface state grows to a thickness of about several tens of nanometers, a change in color tone, that is, discoloration is suppressed. According to this, the titanium base material should have a roughness curve in the direction where the arithmetic mean roughness Ra reaches the maximum. The ratio of the arithmetic mean roughness Ra to the element length RSm, that is, Ra/RSm, should be 0.006~0.015, and the root mean square slope RΔq is 0.150~0.280. The lower limit of Ra/RSm is preferably 0.007. Moreover, RΔq is preferably 0.190 or more. If RΔq reaches 0.190~0.0280, the color difference of the accelerated discoloration test will be less than 6, and higher effects can be obtained.

Regarding the arithmetic mean roughness Ra and the average length RSm of the contour curve elements, as mentioned above, Ra/RSm is preferably 0.006~0.015. However, the arithmetic mean roughness Ra is preferably 0.700~3.0 μm, and the average length RSm of the contour curve elements is preferably 0.006~0.015. Preferably it is 60~300μm. The arithmetic mean roughness Ra is set to 0.700~3.0μm, and the average length RSm of the contour curve element is set to 60~300μm, which can be easily realized industrially through the manufacturing method described below.

[Kurtosis Rku: greater than 3] Kurtosis Rku is an indicator showing the sharpness of the amplitude distribution curve. FIG. 7 is a diagram for explaining the kurtosis Rku. In addition, Figure 7 is shown in Tsutomu Miyashita, "Reviewing Surface Roughness," Journal of the Society of Precision Engineering, Society of Precision Engineering, Vol. 73, No. 2, 2007, page 205. The kurtosis Rku represents the average of the fourth power of Zj in the dimensionless reference length obtained by taking the fourth power of the root mean square height Rq.

[Mathematical formula 5]

Zj is the height of the jth measurement point in the roughness curve. Rq is the root mean square height and can be expressed by the following equation (6).

[Mathematical formula 6]

Kurtosis Rku is an indicator that shows the sharpness of the height distribution; when the kurtosis Rku is 3, as shown in Figure 7, the height distribution is a normal distribution; if the kurtosis Rku is less than 3, the surface will become flat as the value decreases; Peak If Sku is greater than 3, as the value increases, sharp peaks or valleys will appear on the surface of the titanium material.

In the roughness curve in the direction where the arithmetic mean roughness Ra reaches the maximum, the kurtosis Rku of the titanium base material should be greater than 3. When the kurtosis Rku is greater than 3, the unevenness on the surface of the titanium base material is sharp. On the surface with sharp unevenness, the regular reflection components that show interference colors in the light reflected by the surface of the titanium base material can be further suppressed. As a result, even if the thickness of the oxide film increases, the interference color is less likely to become more conspicuous, so the discoloration of the titanium material can be further suppressed.

[Skewness Rsk: greater than -0.5] Skewness Rsk, also known as skewness, is an indicator of the sharpness of surface unevenness. The skewness Rsk represents the cubic average of Z(x) in the reference length that is dimensionless using the cube of the root mean square height Rq, and can be expressed by the following equation (7).

[Mathematical formula 7]

In the above formula (7), N is the number of measurement points, and Zj is the height of the j-th measurement point in the roughness curve.

In the roughness curve, when the length of the valley bottom is greater than the length of the top of the mountain, the skewness Rsk will be greater than 0. In other words, when the skewness Rsk is greater than 0, the average line of the roughness curve has a high proportion of concave portions. That is, the top of the mountain top (convex part) in the roughness curve will be sharp and pointed, and the bottom of the valley (concave part) will become wider. The average line of the roughness curve refers to a curve showing the long wavelength component blocked by the transmission cutoff wavelength λc. On the other hand, when the length of the valley bottom is less than the length of the top of the mountain, the skewness Rsk will be less than 0. In other words, when the skewness Rsk is less than 0, the average line of the roughness curve has a high proportion of concave portions. That is, the top of the mountain top (convex part) in the roughness curve will become wider, and the bottom of the valley (concave part) will be sharp and pointed. When the skewness Rsk is 0, the concave and convex shapes in the roughness curve will be symmetrical relative to the average surface.

In the roughness curve in the direction where the arithmetic mean roughness Ra reaches the maximum, the skewness Rsk of the titanium base material should be greater than -0.5. When the skewness Rsk is greater than -0.5, the top of the mountain top (convex part) in the roughness curve is pointed. Through the top of the mountain (convex part) close to the light source, the light reflected from the surface of the titanium substrate will become easier to scatter. This will further inhibit discoloration. Due to the shielding effect brought by the mountain top (convex part), it becomes difficult to see the interference color, which is the cause of the discoloration. Therefore, it can be inferred that the valley bottom (convex part) far away from the light source is less likely to occur than the mountain top (convex part). influence.

This completes the description of the titanium material of this embodiment. The thickness of the titanium material in this embodiment may be, for example, 0.2 mm or more, or may be 0.3 mm or more. In addition, the thickness of the titanium material in this embodiment is not particularly limited, and may be, for example, 5.0 mm or less, 3.0 mm or less, or 2.0 mm or less.

In the titanium material of this embodiment, the oxygen concentration is measured from the surface toward the thickness direction by the glow discharge spectrometry method, and the average nitrogen concentration in the range from the surface to the position where the measured oxygen concentration is 1/3 of the maximum value is obtained. The average carbon concentration is 14.0 atomic % or less, and the average hydrogen concentration is 30.0 atomic % or less; the c-axis of α-phase Ti is determined by X-ray diffraction measurement on the aforementioned surface using the parallel beam method with an incident angle of 0.3 degrees. The difference between the lattice constant of Ti and the c-axis lattice constant of α-phase Ti determined by X-ray diffraction measurement using the concentration method at the center of the plate thickness is 0.015Å or less. As a result, the titanium material of this embodiment can continuously suppress discoloration over a long period of time and has excellent discoloration resistance compared to conventional titanium materials.

In addition, in the oxide film, the maximum value of the nitrogen concentration derived from nitride when analyzed by X-ray photoelectron spectroscopy is 2.0 to 10.0 atomic %, and when converted by the sputtering speed of _SiO2 , the aforementioned oxide film The maximum concentration of nitrogen derived from nitride exists in the range of 2 to 10 nm from the surface of the oxide film. The concentration of nitrogen derived from nitride that exists near the interface between the titanium base material and the oxide film is: is less than the maximum value of the nitrogen concentration derived from nitride in the oxide film and 7.0 atomic % or less, and the maximum value of the nitrogen concentration derived from nitride in the oxide film is the concentration of nitrogen derived from nitride in the oxide film If the nitrogen concentration reaches the maximum position above the carbon concentration derived from the carbide, the discoloration resistance will be excellent even in a high temperature and acidic environment. Furthermore, titanium materials that are excellent in discoloration resistance even under high temperatures and acidic environments can further suppress discoloration over a long period of time.

(How to manufacture titanium materials) An example of the manufacturing method of the titanium material of this embodiment is demonstrated. However, the titanium material of this embodiment is not limited to the one produced by the manufacturing method described below. In addition, since pure titanium and titanium alloys used in building materials such as exterior materials are mostly in the form of plates, an example of a method of manufacturing plate-shaped titanium materials will be described below.

Titanium materials are manufactured by cold-rolling pure titanium or titanium alloys as raw materials, and then subjecting them to annealing treatment and cooling treatment.

The titanium material used for cold rolling can be produced by known methods. For example, a master alloy to which titanium sponge and alloying elements are added is used as a raw material, and various melting methods such as vacuum arc melting, electron beam melting, or furnace melting such as plasma melting are used to produce products having the above composition. Ingots of pure titanium or titanium alloys. Then, the obtained ingot is divided into pieces as required and hot forged to form flat blanks. Thereafter, the flat blank is hot-rolled to produce a hot-rolled coil of pure titanium or titanium alloy having the above composition. In addition, the flat embryos can also be subjected to pre-processing such as washing and cutting as needed. Furthermore, when a rectangular shape capable of hot rolling is formed by the furnace melting method, it can be subjected to hot rolling without hot forging or the like.

Next, the hot-rolled coil is subjected to cold rolling. Although lubricating oil can be used in cold rolling, the lubricating oil used may cause the carbon concentration on the surface of the titanium material to increase during annealing. Therefore, it is advisable to remove oily components present on the surface of the titanium material through alkaline degreasing, rolling using a matte roller (matte rolling), coil grinder, or grinding before annealing. In addition, when lubricating oil is applied to the surface of the titanium material and cold rolling is performed, the surface of the titanium material will contain carbon due to a mechanochemical reaction. The cold titanium material used for final annealing treatment can also be suitably pickled and annealed.

A final annealing treatment is applied to the titanium material after cold rolling or the titanium material after treatment to remove oily components. Generally speaking, the final annealing treatment is a step of softening the titanium material by reducing the strain introduced by cold rolling into the titanium material, that is, pure titanium or titanium alloy. In the production of the titanium material of this embodiment, the purpose of the steps of the final annealing treatment and the subsequent cooling treatment is to control: the average nitrogen concentration and the average carbon concentration of the titanium material surface layer, the average hydrogen concentration, the titanium material surface layer part The lattice constant of the c-axis of Ti in the α phase, and the thickness of the oxide film. It is considered that by increasing the final annealing treatment temperature, nitrogen and carbon caused by impurities in the surface layer of the titanium material will diffuse in the thickness direction, and the average nitrogen concentration and average carbon concentration in the surface layer of the titanium material will decrease. It is considered that by increasing the vacuum degree of the final annealing treatment, the average hydrogen concentration in the surface layer of the titanium material and the lattice constant of the c-axis of Ti in the α phase in the surface layer of the titanium material will be reduced. Therefore, the final calcining treatment is performed in an inert gas (except nitrogen) gas environment after creating a vacuum gas environment or directly maintained in a vacuum. The heating temperature of the final annealing process and the gas environment of the final annealing process are explained below. The so-called inactive gas here refers to a gas that is inactive for titanium, that is, argon, helium, and neon.

From the viewpoint of reducing the average nitrogen concentration and average carbon concentration in the surface layer of the titanium material, the heating temperature (annealing temperature) of the final annealing treatment is 630°C or more. From the viewpoint of reducing the average carbon concentration in the surface layer of the titanium material, the annealing temperature is preferably 650°C or higher. The upper limit of the annealing temperature is not particularly set, but from the viewpoint of manufacturing cost, it is preferably 750°C or lower. The annealing temperature here refers to the temperature in the heating furnace used for the annealing process, and is measured using a thermocouple installed in the heating furnace. From the viewpoint of reducing the average nitrogen concentration and average carbon concentration in the surface layer of the titanium material, the annealing time is preferably 5 hours or more. The annealing time is preferably more than 10 hours. Since the titanium material maintained in the cold-rolled state can be annealed, the annealing time can also be more than 3 hours. On the other hand, from the viewpoint of productivity, the annealing time is preferably 48 hours or less. In addition, if the annealing time is longer than 10 hours, the crystal grain size may become too coarse, which may cause defects such as a decrease in tensile strength or wrinkles due to processing. Accordingly, from the viewpoint of maintaining tensile strength and the like, the annealing time is preferably 10 hours or less. In addition, the annealing time here refers to the time during which the temperature in the heating furnace containing the titanium material is maintained at the annealing temperature.

The final annealing treatment is performed in a vacuum gas environment, an inert gas environment (except nitrogen), or an inert gas environment in which an inert gas other than nitrogen is introduced after a vacuum gas environment is created. The vacuum degree of the vacuum gas environment is, for example, 1.0×10 ^-2 Pa or less. The inert gas environment should be an inert gas environment, and an Ar gas environment is more suitable. From the viewpoint of suppressing the increase in the lattice constant of the c-axis of the α phase Ti in the surface layer of the titanium material and reducing the average hydrogen concentration and average nitrogen concentration in the surface layer of the titanium material, an inert gas atmosphere is created during the final annealing treatment. The previous vacuum degree should be below 1.0×10 ^-2 Pa. From the viewpoint of reducing the average hydrogen concentration in the surface layer of the titanium material, the degree of vacuum before creating an inert gas atmosphere in the final annealing treatment is preferably 5.0×10 ^-3 Pa or less. Furthermore, regarding the inert gas atmosphere, for example, it is sufficient to create a gas atmosphere containing 99.99% by volume or more of Ar in the heating furnace. The inert gas environment may also be a gas environment containing more than 99.99% by volume of He (helium). It is also possible to create a vacuum gas environment in the heating furnace before starting the heating of the final annealing treatment, and then create an inert gas environment; it is also possible to create a vacuum gas environment in the heating furnace before starting the heating, and to create a vacuum gas environment from the beginning to the beginning of the heating. Before cooling, change the inside of the heating furnace from a vacuum gas environment to an inert gas environment.

In a vacuum gas environment, or in an inert gas gas environment (excluding nitrogen) after creating a vacuum gas environment and introducing an inert gas other than nitrogen, a final annealing treatment is performed at the above-mentioned annealing temperature and annealing time, whereby the titanium is The surface of the material will form a state in which oxygen, nitrogen, carbon, and hydrogen are low. In the final annealing process, the surface of the titanium material is brought into a highly clean surface state, whereby during the subsequent cooling process, it can be exposed to the atmosphere, a nitrogen gas environment, and an inert gas environment containing more than 10% nitrogen. A predetermined amount of nitride is generated in the oxide film through the nitrogen contained in the gas environment. In titanium materials that have been cooled by final annealing and then exposed to the atmosphere, even if they are reheated in a nitrogen-containing gas environment, the intended nitride cannot be generated in the oxide film.

The nitrogen concentration of the annealing gas environment is an inactive gas below 0.005% by volume. In addition, in general industrial pure gas, nitrogen accounts for less than half of the impurities. Therefore, the annealing process in this embodiment using the above-mentioned inert gas has sufficient purity in terms of the gas environment.

The gas environment of the final annealing treatment is maintained below the temperature at which the annealed titanium material does not have tempering color, such as a temperature below 300°C. The annealing gas environment can also be maintained until it cools to room temperature, or the heating furnace can be opened to the atmosphere at a temperature below 300°C.

After the final annealing treatment, the titanium material is cooled. For example, the cooling gas environment can be: when cooling is first started, it is the same gas environment as the annealing gas environment; when the temperature in the heating furnace is below 300°C, it is a gas environment composed of nitrogen and containing 10 volume% of nitrogen. The above mixed gas environment of argon or helium, or the atmosphere.

The cooling rate after the final annealing treatment is not particularly limited. However, in order to keep the amount of nitrogen derived from nitrides present in the oxide film within a predetermined range at the open temperature of 300° C. or lower, it is preferable to proceed under the following conditions. In addition, in order to suppress shape disorder caused by thermal shrinkage of the titanium material during cooling, the cooling rate until opening (until 300°C or lower) is preferably 50°C/min or less, more preferably 30°C/min or less; in addition, , if you want to cool large titanium materials of more than 1 ton, it should be 1℃/minute.

During the cooling after the final annealing treatment, it is advisable to introduce nitrogen gas into the heating furnace when the temperature in the heating furnace reaches a temperature below 300°C or to open the heating furnace to the atmosphere to make the heating furnace contain 10 volumes of nitrogen. % or more nitrogen gas environment. In addition to temperature and gas environment, the amount of nitrogen derived from nitride present in the oxide film also changes with the surface cleanliness of the titanium material. It is believed that the reason is that although trace amounts of carbon, oxygen, hydrogen, and nitrogen present on the surface of the titanium material compete to react on the surface of the titanium material, the amount of reaction between nitrogen and titanium changes depending on which reaction takes place preferentially. The result is that the amount of nitride produced will also change. However, if the temperature when changing the gas environment (when opening) is 300°C or lower, titanium and nitrogen will fully react, and the nitride generated will not be excessive. Therefore, by following the cooling process after the annealing process, the maximum value of the nitrogen concentration derived from nitride existing in the oxide film can be set to 2.0 to 10.0 atomic %. On the other hand, if the temperature when changing the gas environment is less than 200°C, the nitrogen content derived from nitride in the oxide film will be less than 2.0 atomic %. The reason is that if the temperature is low, the reaction between nitrogen and titanium will become slower. The above-mentioned temperature is preferably above 250°C, more preferably above 280°C.

After creating a nitrogen gas environment in the heating furnace, the cooling time until reaching 200°C is preferably 1.5 hours or more, more preferably 2.0 hours or more. After creating a nitrogen gas environment in the heating furnace, the cooling time until reaching 200°C is set to 1.5 hours or more. This allows the maximum value of the nitrogen concentration derived from nitrides in the oxide film to be analyzed by X-ray photoelectron spectroscopy. is 2.0 to 10.0 atomic %, and when converted based on the sputtering speed of SiO ₂ , the position where the nitrogen concentration derived from the nitride in the oxide film reaches the maximum value exists 2 to 10 nm from the surface of the oxide film. range.

In addition, even if the titanium material after the cooling treatment is cold rolled at a reduction rate of 5% or less and the cold rolling includes rolling using a matte roller, the characteristics of the titanium material of this embodiment can still be maintained.

In the manufacturing method of the titanium material of this embodiment, it is preferable to have a grinding step and a rough surface rolling step; the grinding step is to use grinding powder to grind the surface of the titanium material, and the grinding powder has the properties according to JIS R 6001-2:2017 The particle size distribution is below #320; the rough side rolling step is to use a roller with a surface roughness Ra of more than 0.5 μm to roll the titanium material in such a way that the total reduction rate reaches more than 0.10%. The grinding step is performed before the final annealing treatment, and the matte rolling step is performed after the final annealing treatment. Through the above grinding steps and matte rolling steps, the Ra/RSm of the titanium substrate surface will be 0.006~0.015, and the root mean square slope RΔq of the roughness curve element will be 0.150~0.280. The above-mentioned grinding step and matte rolling step will be described below.

[Grinding steps] In this step, the surface of the titanium material is ground using abrasive powder, and the abrasive powder has a particle size distribution of No. 320 or less in accordance with JIS R 6001-2:2017. The means for grinding the surface of the titanium material is not particularly limited, and known means such as brush rollers and coil grinders can be used.

For example, when using a coil grinder, the surface of a coil-shaped titanium material is ground by the following method. Grind the titanium material through a wire grinder and use abrasive belts below #320, such as #320, #240, #100, #80, etc. The grinding powder used in the grinding belt should be #100 or below. In order to obtain a more uniform grinding surface, grinding is sometimes carried out several times with the same number or changing the number.

The titanium material used in the grinding step can be prepared by known methods. For example, a master alloy to which titanium sponge and alloying elements are added is used as a raw material, and various melting methods such as vacuum arc melting, electron beam melting, or furnace melting such as plasma melting are used to produce products having the above composition. Ingots of pure titanium or titanium alloys. Then, the obtained ingot is divided into pieces as required and hot forged to form flat blanks. Thereafter, the flat blank is hot-rolled to produce a hot-rolled coil of pure titanium or titanium alloy having the above composition. The hot-rolled coil is cold-rolled, and the cold-rolled titanium material is ground. The cold-rolled titanium material required for the grinding step can also be suitably annealed. In addition, the flat blanks can also be subjected to pre-processing such as grinding and cutting as needed. In addition, when the furnace smelting method is used to form a rectangular shape that can be hot-rolled, it can be subjected to hot rolling without segmentation, hot forging, etc. The cold rolling conditions are not particularly limited, as long as the desired thickness, characteristics, etc. can be obtained.

[Matte side rolling step] In this step, the titanium material is rolled using a rolling work roll (hereinafter referred to as a roll) with a surface arithmetic mean roughness Ra of 0.5 μm or more. Using the above-mentioned rollers to roll the titanium material to a total reduction rate of 0.10% or more can provide the surface of the titanium material with concavities and convexes that constitute a more local slope. When the arithmetic mean roughness Ra of the surface of the roll is too large, the uneven shape provided in advance by the polishing step may change significantly. Therefore, the arithmetic mean roughness Ra of the surface of the roll is preferably 2.0 μm or less. The surface roughness of the roll can be adjusted through grinding and bead blasting.

In order to provide unevenness that constitutes a local slope, the total reduction rate should be set to 0.10% or more; more preferably, from the perspective of surface placement stability over the entire length of the coil, the total reduction rate should be set to 0.2% or more. On the other hand, in order to prevent the surface roughness formed by the grinding in the previous step from being damaged by cold rolling and causing the desired uneven shape to disappear, it should be set to 1.5% or less. In addition, in order to obtain the surface characteristics of the present invention, one pass of cold rolling is enough. However, considering the fact that the entire length of a long coiled material is finished to have a uniform surface as much as possible, two or more passes are required. Just implement cold rolling. Taking this point into consideration, the total reduction rate is specified. In the case of multiple passes, the total reduction rate is determined as the reduction rate obtained from the difference in plate thickness between the initial stage and the finished plate. [Example]

(Example 1) After the titanium material shown in Table 1 is cold-rolled to a thickness of 0.4 mm, alkali or organic solvents are used to degrease the surface of the titanium material to remove oily components. In this example, JIS type 1 pure titanium (equivalent to ASTM Gr.1), JIS type 2 pure titanium (equivalent to ASTM Gr.2), and JIS type 3 pure titanium (equivalent to ASTM Gr.2) based on JIS H 4600:2012 were used. .3 equivalent), JIS 4 types of pure titanium (equivalent to ASTM Gr.4), JIS 11 titanium alloys (equivalent to ASTM Gr.11, Ti-0.15Pd), JIS 21 titanium alloys (equivalent to ASTM Gr.13, Ti- 0.5Ni-0.05Ru), JIS17 titanium alloys (equivalent to ASTM Gr.7, Ti-0.05Pd), Ti-Ru-Mm, Ti-3Al-2.5V, Ti-5Al-1Fe, and JIS60 titanium alloys ( Equivalent to ASTM Gr.5, Ti-6Al-4V). Mm in Ti-Ru-Mm represents rare earth metal alloy. Thereafter, in Examples 1 to 23 of the present invention, each titanium material was annealed under the conditions shown in Table 1. The opening temperature shown in Table 1 is the temperature when the furnace is opened during the cooling process after each annealing temperature is maintained for each annealing time. The temperature at this time is the temperature in the furnace measured using a thermocouple. In Examples 1 to 13, 19 to 23 and Comparative Examples 1 to 3 of the present invention, heating was started in a vacuum gas environment as shown in the "vacuum degree" in Table 1, and 99.99% by volume or more was used until cooling was started. The Ar gas is introduced into the annealing furnace. Each titanium material is only kept in the furnace at each annealing temperature for each annealing time. During the subsequent cooling process, each annealing gas environment is maintained until the opening temperature shown in Table 1. When the temperature in the furnace drops to the opening temperature, the furnace is Open inside. In Examples 14 and 15 of the present invention, heating was started in an Ar gas environment, and the Ar gas environment was maintained until the furnace was opened. In Examples 16 to 18 of the present invention, heating was started in the vacuum gas environment shown in "vacuum degree" in Table 1, and the vacuum degree was maintained until the furnace was opened. In Comparative Examples 4 and 5, the titanium materials shown in Table 1 were cold rolled to a thickness of 0.4 mm, degreased using an alkali or an organic solvent, and then nitric fluoric acid pickling was performed without final annealing. processing.

[Table 1]

The average nitrogen concentration, average carbon concentration, and average hydrogen concentration in the surface layer are determined by the following method. For O, N, C, H and Ti, GDS is used for analysis. For measurement, JOBIN YVON GD-Profiler2 manufactured by Horiba Manufacturing Co., Ltd. was used. The measurement conditions are as follows: 35W constant power mode, argon gas pressure of 600Pa, and discharge range of 4mm in diameter. In the measurement using GDS, the measurement pitch is 0.5nm. The concentration (atomic %) of each of the above elements is calculated based on the total of the above elements being 100 atomic %. The range from the surface of the titanium material in the thickness direction to the position where the oxygen concentration measured by GDS is 1/3 of the maximum value is defined as the surface layer of the titanium material. The average nitrogen concentration, average carbon concentration and average hydrogen concentration are determined as the arithmetic mean of the values of nitrogen concentration, carbon concentration and hydrogen concentration at each measurement point.

The lattice constant of the c-axis of Ti in the α phase on the surface of the titanium material was determined by X-ray diffraction measurement using the parallel beam method. For X-ray diffraction measurement using the parallel beam method, the X-ray diffraction device SmartLab manufactured by Rigaku Co., Ltd. can be used, and the X-ray source is Co-Kα (wavelength λ = 1.7902 Å). Regarding the removal of Kβ rays, a W/Si multilayer mirror is used on the X-ray incident side. The X-ray source load power (tube voltage/tube current) is 5.4kW (40kV/135mA) respectively. The incident angle of X-rays on the sample is 0.3 degrees, and the diffraction angle 2θ is scanned. Regarding the measurement sample, a titanium material with a thickness of 0.4mm was cut into 25mm (vertical) x 50mm (horizontal) through mechanical processing, and the center position of the surface of the titanium material was measured. In other words, 12.5mm (vertical) x 25mm on the surface of the sample was measured. The position of (horizontal) was irradiated with a beam at the center and measured. In addition, the cut out sample may have dirt attached to the surface to be measured, so it must be cleaned with acetone.

The lattice constant of the c-axis of the α-phase Ti in the center of the titanium plate thickness was measured by X-ray diffraction using the concentration method. The sample used to analyze the crystal structure of the α-phase Ti in the center of the titanium plate thickness was finished by mechanical grinding and electrolytic polishing so that the center of the titanium plate thickness became the measurement surface for X-ray diffraction measurement. X-ray diffraction measurement using the concentration method uses an X-ray diffraction device used in X-ray diffraction measurement using the parallel beam method, an X-ray source, a filter for removing Kβ rays, and an X-ray source. The load power is also set to the same conditions as the above-mentioned parallel beam method.

The lattice constant of the c-axis of the α phase of Ti on the surface of the titanium material and in the center of the plate thickness is calculated from the diffraction peak of the (0002) plane. The difference in the lattice constant of the c-axis of Ti in the α phase on the surface of the titanium material is calculated from the difference between the lattice constant calculated on the surface of the titanium material and the lattice constant calculated in the center of the plate thickness. have to.

The thickness of the oxide film can be determined by GDS and the oxygen concentration measured by the above method. Specifically, the distance in the thickness direction from the surface to the position where the oxygen concentration is halved relative to the maximum value is defined as the oxide film thickness.

The nitrogen content derived from nitride contained in the oxide film is measured by the following method. That is, the nitride-derived nitrogen concentration distribution in the depth direction is measured by the following method, and from the nitrogen concentration distribution, the maximum value in the oxide film is determined as the nitride-derived nitrogen content contained in the oxide film.

The depth direction (film thickness direction) distribution of the nitrogen concentration derived from nitrides and the carbon concentration derived from carbides in the oxide film, and in the vicinity of the interface with the oxide film in the titanium base material (from the interface toward the titanium base material The nitrogen concentration derived from the nitride (20 nm on the side) is measured by the following method. That is, using XPS, Ar ions are sputtered on the surface of the titanium material and the concentration distribution in the depth direction is measured. The element states at each peak position of N1s, C1s, O1s and Ti2p are analyzed to calculate the elements originating from nitrides, carbides and oxides. N, C, O and Ti concentrations. Specifically, it is calculated through the above-mentioned process. The XPS analysis conditions are as follows. ^Device : Quantera SXM made by ULVAC-PHI Rate 4.3nm/min. (SiO ₂ converted value) The SiO ₂ converted value is the sputtering speed calculated by measuring the thickness of the SiO ₂ film in advance using an ellipsometer and then using the film under the same measurement conditions. Sputtering speed.

According to JIS B 0601:2013, various parameters of the surface roughness of the manufactured titanium material (arithmetic mean roughness Ra, average length of the contour curve element RSm, root mean square inclination RΔq of the roughness curve element, peak degree Rku, skewness Rsk). Equipment: Surface roughness and shape measuring machine (SURFCOM 1900DX manufactured by Tokyo Precision Co., Ltd., analysis software: TiMS Ver.9.0.3) Probe: Tokyo Precision Co., Ltd. shape probe (Type: DT43801) Parameter calculation standard: JIS-01 standard Measurement Category: Roughness Measurement Cutoff Category: GAUSSIAN Tilt Correction: Least Squares Straight Line Correction Measuring distance: 5.0mm Cutoff wavelength λc: 0.8mm Measuring range: ±64.0μm Measuring speed: 0.3mm/sec Movement/return speed: 0.6mm/sec Return to setting: normal measurement Pre-drive length: (cutoff wavelength/3)×2 Measurement interval Δx: 0.195μm λs cutoff ratio: 300 λs cutoff wavelength: 2.667μm Pickup category: Standard pickup Polarity: forward rotation

Regarding the measurement position, three points were measured in the direction where Ra reaches the maximum and the average value was calculated. Regarding the direction in which Ra reaches the maximum, if the titanium material is a plate, the direction parallel to the rolling direction is set to 0°, and the direction is 22.5°, 45°, and 90° (the direction perpendicular to the rolling direction). Measure the roughness and determine the direction in which Ra reaches the maximum. If a roller is used to roll a titanium material to make a titanium material, or if a roller embedded with abrasive grains is rotated in the rolling direction to grind the plate surface, Ra will be in the 90° direction perpendicular to the rolling direction. up to maximum.

The titanium materials produced were immersed in a sulfuric acid aqueous solution of pH 3 and 60°C for 4 weeks, and the color difference before and after immersion was calculated. The discoloration resistance was evaluated based on the value of the color difference. If the color difference ΔE is 0 or more and 5 or less, the discoloration resistance is extremely good (A), if it is more than 5 and 10 or less, the discoloration resistance is good (B), and if it is more than 10, it is judged as poor (C). In addition, the color difference ΔE before and after the test is calculated by the following formula. ΔE＝((L＊2-L＊1) ² +(a＊2-a＊1) ² +(b＊2-b＊1) ² )1/2 Here, L＊1, a＊1, b*1 is the color measurement result before the discoloration test, L*2, a*2, and b*2 are the color measurement results after the discoloration test; they are based on the L*a*b* table specified in JIS Z 8729 Those who gain from color. In addition, the measurement of color difference was carried out using CR400 manufactured by KONICA MINOLTA Co., Ltd. under the conditions of a measurement area of 8 mm in diameter and a D65 light source.

In addition, sensory evaluation with the naked eye was performed on each titanium material produced. Regarding the evaluation through naked eye observation, the titanium materials that have not yet been submitted to the accelerated discoloration test of this case and the titanium materials that have been subjected to the accelerated discoloration test of this case were placed side by side on a flat plate in advance, and 10 evaluators observed and compared them from various angles under the sun. , to determine whether there is an angle at which discoloration is visible to the naked eye. When more than 90% of the 10 evaluators judge that the discoloration is inconspicuous, it is rated as A+++; when more than 80% but less than 90% of the 10 evaluators judge that the discoloration is inconspicuous, it is rated as A++; When more than 70% and less than 80% judge that the discoloration is inconspicuous, it is rated as A+; when more than 50% and less than 70% of the 10 evaluators judge that the discoloration is inconspicuous, it is rated as A0; 30% of the 10 evaluators If it is more than 50% and less than 50% determines that the discoloration is inconspicuous, it will be graded as B; if less than 30% of the 10 evaluators determine that the discoloration is inconspicuous, it will be graded as C; if the evaluation is C, it will be graded as unqualified. In addition, this visual observation assumes the conditions of the roof and walls of an actual building, and is an evaluation method that also takes into account the change in color tone depending on the viewing angle. The results are shown in Tables 2 and 3. The bottom lines in Tables 2 and 3 indicate that they are outside the scope of the present invention.

[Table 2]

[table 3]

Regarding Examples 1 to 23 of the present invention, the average nitrogen concentration and the average carbon concentration in the surface layer are both 14.0 atomic % or less, the average hydrogen concentration is 30.0 atomic % or less, and the α phase of Ti on the surface of the titanium material and in the center of the plate thickness is The difference in lattice constants along the c-axis is 0.015Å or less, the color difference evaluation result is B or above, and the sensory evaluation result through the naked eye is B or above. In Comparative Example 1, the degree of vacuum during the annealing treatment was as low as 1.0×10 ^-1 Pa, so the average nitrogen concentration in the surface layer was high. As a result, the titanium material of Comparative Example 1 failed to pass the color difference evaluation results and the sensory evaluation results through the naked eye. Comparative Example 2 has a low annealing temperature and a high average carbon concentration in the surface layer. As a result, the titanium material of Comparative Example 2 failed to pass the color difference evaluation results and the sensory evaluation results through the naked eye. In Comparative Example 3, since the degree of vacuum during the annealing treatment was as low as 8.0×10 ^-2 Pa, it is speculated that the oxygen concentration in the surface layer of the titanium material becomes higher, the lattice constant of the c-axis of the α phase Ti in the surface layer becomes larger, and the crystal structure becomes smaller. The difference in lattice constants becomes larger. As a result, the titanium material of Comparative Example 3 failed to pass the color difference evaluation results and the sensory evaluation results through the naked eye. In Comparative Examples 4 and 5, the average hydrogen concentration in the surface layer portion was high, and the titanium material of Comparative Example 3 was unsatisfactory in both the color difference evaluation results and the sensory evaluation results with the naked eye.

As shown above, the titanium material of this embodiment has excellent discoloration resistance even if it is exposed to a pH 3 sulfuric acid aqueous solution that simulates severe acid rain for a long period of time. The present invention is particularly effective for use in outdoor environments such as roofs and wall panels, and its industrial value is extremely high.

(Example 2) After the titanium material shown in Table 4 is cold-rolled to a thickness of 0.4 mm, alkali or organic solvents are used to degrease the surface of the titanium material to remove oily components. After that, each titanium material was annealed under the conditions shown in Table 4. The opening temperature shown in Table 4 is the temperature when the furnace is opened during the cooling process after each annealing temperature is maintained for each annealing time. The temperature at this time is the temperature in the furnace measured using a thermocouple.

[Table 4]

The same evaluation as in Example 1 was performed on each titanium material produced. The results are shown in Tables 5 and 6.

[table 5]

[Table 6]

As shown in Tables 5 and 6, regarding Examples 24 to 39 of the present invention, the maximum value of the nitrogen concentration derived from nitrides in the oxide films analyzed by X-ray photoelectron spectroscopy was 2.0 to 10.0 atomic %, and When converted to the sputtering speed of SiO ₂ , the maximum value of the nitrogen concentration derived from nitride in the oxide film exists in the range of 2 to 10 nm from the surface of the oxide film, and exists near the interface with the oxide film in the titanium base material. The nitrogen concentration derived from nitride is less than the maximum value of the nitrogen concentration derived from nitride in the oxide film and is 7 atomic % or less, and the maximum value of the nitrogen concentration derived from nitride in the oxide film is the nitrogen derived from the oxide film The nitrogen concentration of the compound reaches the maximum position above the carbon concentration of the carbide. The color difference evaluation results were A, and the sensory evaluation results with the naked eye were all A++, indicating excellent discoloration resistance.

(Example 3) After the titanium material shown in Table 7 is cold rolled to a thickness of 0.4 mm, the grinding step, washing, annealing treatment, and matte side rolling steps are performed in sequence under the conditions shown in Table 7 and Table 8. The "number of grinding passes" shown in Table 7 represents the number of times the titanium material passes through the production line of the coil grinder. The production line of the coil grinder is composed of three grinding and rolling tables equipped with grinding belts. In Examples 40 to 72 of the present invention, each titanium material was finally annealed under the conditions shown in Table 8. The opening temperature shown in Table 8 is the temperature when the furnace is opened during the cooling process after each annealing temperature is maintained for each annealing time. The temperature at this time is the temperature in the furnace measured using a thermocouple. In Examples 40 to 61 and 63 to 72 of the present invention, heating was started in a vacuum gas environment as shown in the "vacuum degree" in Table 8, and 99.99% by volume or more of Ar gas was introduced and retreated until cooling was started. Inside the stove. Each titanium material is only kept in the furnace at each annealing temperature for each annealing time. During the subsequent cooling process, each annealing gas environment is maintained until the opening temperature shown in Table 8. When the temperature in the furnace drops to the opening temperature, the furnace is Open inside. In Example 62 of the present invention, heating was started in the vacuum gas environment shown in "vacuum degree" in Table 8, and the vacuum degree was maintained until the furnace was opened. In Comparative Example 6, the titanium material was cold rolled to a thickness of 0.4 mm, degreased using an alkali or an organic solvent, and then nitric fluoric acid pickling was performed without final annealing.

[Table 7]

[Table 8]

The same evaluation as in Example 1 was performed on each titanium material produced. The results are shown in Tables 9 and 10. The bottom line in Table 9 indicates outside the scope of the present invention.

[Table 9]

[Table 10]

As shown in Tables 7 to 10, if the heat treatment temperature, time and heat treatment gas environment are controlled, as well as the cooling gas environment, it can be achieved that: in the roughness curve in the direction where the arithmetic mean roughness Ra reaches the maximum, the arithmetic mean roughness The ratio of Ra to the element length RSm, that is, Ra/RSm, is 0.006~0.015, and the root mean square slope RΔq is 0.150~0.280. The kurtosis Rku of the titanium base material is greater than 3, and the skewness Rsk of the titanium base material is greater than -0.5, and The evaluation results are even better. Especially in Examples 59 to 61 of the present invention, the average nitrogen concentration and the average carbon concentration in the surface layer are both 14.0 atomic % or less, the average hydrogen concentration is 30.0 atomic % or less, and the α-phase Ti on the surface of the titanium material and in the center of the plate thickness The lattice constant difference of the c-axis is less than 0.015Å, the maximum nitrogen concentration derived from nitride in the oxide film is 2.0~10.0 atomic % when analyzed by X-ray photoelectron spectroscopy, and the sputtering of SiO ₂ When converted in terms of speed, the maximum concentration of nitrogen derived from nitrides in the oxide film exists in the range of 2 to 10 nm from the surface of the oxide film, and the nitride derived concentration exists near the interface with the oxide film in the titanium base material. The nitrogen concentration is less than the maximum value of the nitrogen concentration derived from nitrides in the oxide film and is 7 atomic % or less. The maximum value of the nitrogen concentration derived from nitrides in the oxide film is the maximum value of the nitrogen concentration derived from nitrides in the oxide film. The maximum position is above the carbon concentration derived from carbide. As a result, the color difference evaluation result was A, the sensory evaluation result through the naked eye was A+++, and the discoloration resistance was extremely excellent.

1:Titanium material 10:Titanium base material 20: Oxide film 30: Surface part

FIG. 1 is a schematic enlarged cross-sectional view showing the layer structure of a titanium material according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of the change in the depth direction of the energy spectrum (spectrum) obtained by X-ray photoelectron spectroscopy of the titanium material of the same embodiment. Figure 3 is a diagram showing the following: an example of the depth direction change of the energy spectrum of a general titanium material obtained by X-ray photoelectron spectroscopy. FIG. 4 is a diagram showing an example of the element concentration distribution in the depth direction obtained by X-ray photoelectron spectroscopy for titanium materials of the same embodiment and general titanium materials. Figure 5 is a graph showing the relationship between the maximum concentration of nitride-derived nitrogen in titanium in the oxide film and the color difference ΔE ^* ab before and after the discoloration test. 6 is a diagram showing the following: the ratio of the arithmetic mean roughness Ra to the mean length (mean width of the profile elements) RSm, that is, Ra/RSm, and the root mean square slope RΔq of the roughness curve element, etc. and discoloration resistance. Figure 7 is a schematic diagram illustrating kurtosis Rku.

1:Titanium material

10:Titanium base material

20: Oxide film

30: Surface part

Claims (5)

A titanium material in which the oxygen concentration is measured from the surface toward the thickness direction by glow discharge spectroscopy, and the average nitrogen concentration and the average carbon concentration are measured from the surface to the position where the measured oxygen concentration is 1/3 of the maximum value. respectively below 14.0 atomic %, and the average hydrogen concentration is below 30.0 atomic %; The lattice constant of the c-axis of Ti in the α phase was determined by X-ray diffraction measurement using the parallel beam method with an incident angle of 0.3 degrees on the aforementioned surface, and X-ray diffraction measurement using the concentration method at the center of the plate thickness. The calculated lattice constant of the c-axis of Ti in the α phase is found to be less than 0.015Å. For example, the titanium material of claim 1 has: an oxide film with a thickness of 30.0 nm or less. The titanium material of claim 1 or 2, which has: a titanium base material, and an oxide film disposed on the surface of the titanium base material; when analyzed by X-ray photoelectron spectroscopy, the nitrogen concentration derived from nitride in the aforementioned oxide film is The maximum value is 2.0 to 10.0 atomic %. When converted based on the sputtering speed of SiO ₂ , the position where the nitrogen concentration derived from the nitride shows the maximum value in the oxide film exists 2 to 10 nm from the surface of the oxide film. The range is the range from the position where the oxygen concentration reaches 1/2 of the maximum value to the range of 20 nm from the titanium substrate side. The concentration of nitrogen derived from nitride existing in this range is smaller than the concentration of nitrogen derived from nitride in the aforementioned oxide film. The maximum value of the nitrogen concentration is 7 atomic % or less, and the maximum value of the nitrogen concentration derived from nitrides in the oxide film is derived from carbonization at the position in the oxide film where the nitrogen concentration derived from nitrides reaches the maximum. above the carbon concentration of the substance. For example, the titanium material of claim 1 or 2 has a titanium base material. In the roughness curve of the titanium base material in the direction where the arithmetic mean roughness Ra reaches the maximum, the ratio of the arithmetic mean roughness Ra to the element length RSm is Ra/ RSm is 0.006~0.015, and the root mean square tilt RΔq is 0.150~0.280; The kurtosis Rku of the aforementioned titanium substrate is greater than 3, The skewness Rsk of the aforementioned titanium base material is greater than -0.5. Such as the titanium material of claim 3, wherein in the roughness curve of the direction in which the arithmetic mean roughness Ra reaches the maximum of the titanium base material, the ratio of the arithmetic mean roughness Ra to the element length RSm, that is, Ra/RSm, is 0.006~0.015, and , the root mean square tilt RΔq is 0.150~0.280; The kurtosis Rku of the aforementioned titanium substrate is greater than 3, The skewness Rsk of the aforementioned titanium base material is greater than -0.5.

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