Titanium material, chemical device component, and chemical device

Abstract

A titanium material according to one aspect of the present invention contains 0.100-0.300% by mass of C, and contains compound particles containing titanium and carbon and having an average diameter of 400 nm or less. In a titanium material according to one aspect of the present invention, it is preferable that an A value, which is an index value for the ratio of TiC to Ti2C in compound particles containing titanium and carbon, is 0.10 or more. The titanium material according to one aspect of the present invention preferably contains Ti3C2. Another aspect of the present invention relates to a chemical device component comprising the titanium material according to the present embodiment. Another aspect of the present invention relates to a chemical device comprising the chemical device component of the present embodiment.

Description

Technical Field

[0001] The invention relates to a titanium material, a chemical device component and a chemical device. Background Art

[0002] Industrial pure titanium exhibits excellent corrosion resistance even in seawater, where general-purpose stainless steel such as SUS304 corrodes. Taking advantage of this high corrosion resistance, industrial pure titanium is used in seawater desalination equipment, etc.

[0003] On the other hand, industrial pure titanium is sometimes used as a material for chemical equipment parts in an environment with a corrosiveness equal to or higher than that of seawater, such as hydrochloric acid. In such an environment, industrial pure titanium may also corrode significantly.

[0004] In anticipation of use in such severely corrosive environments, corrosion-resistant titanium alloys have been developed that have corrosion resistance superior to that of industrial pure titanium in highly corrosive environments.

[0005] Patent Document 1 discloses an alloy to which a platinum group element such as Pd is added. Patent Document 2 and Non-Patent Document 1 disclose alloys to which an intermetallic compound is precipitated in addition to the addition of a platinum group element.

[0006] However, these titanium alloys use rare elements such as Pd, which increases the cost of the billet. Therefore, there is a technical problem of improving the economical corrosion resistance of titanium without using expensive rare elements. For this reason, some solutions have been proposed for titanium alloys that do not require the use of rare elements but utilize common elements.

[0007] Patent document 3 discloses a technical solution for improving the corrosion resistance and strength of Ti by adding C. Non-patent document 2 describes a technology for producing steel with carbides having an average particle diameter of several hundred nm or less by adding trace amounts of elements that easily form carbides, such as Ti, Cr, V, and Nb, to steel. Non-patent document 3 describes a technology for precipitating carbides (TiC) having an average particle diameter of several hundred nm or less on the surface of industrial pure titanium.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: International Publication No. 2007 / 077645

[0011] Patent Document 2: Japanese Patent Application Publication No. 2012-012636

[0012] Patent Document 3: Japanese Patent Publication No. 2009-509038

[0013] Non-patent literature

[0014] Non-patent document 1: "Iron and Steel", vol.80, No.4 (1994), P353-358

[0015] Non-patent document 2: Journal of the Japan Society of Metals, vol. 81, No. 10 (2017), P447-457

[0016] Non-patent document 3: "Iron and Steel", vol.104, No.5 (2018), P264-273 Summary of the invention

[0017] Problem that the invention aims to solve

[0018] However, if Figure 2A As shown in FIG. 2 of Patent Document 3, the titanium material described in Patent Document 3 has compound particles containing titanium and carbon with an average diameter of several μm or more precipitated. When the diameter of the compound particles containing titanium and carbon is as large as several μm or more, the compound particles containing titanium and carbon themselves, or the interface between the compound particles containing titanium and carbon and the parent phase, easily become the starting point of cracks. Therefore, the titanium material described in Patent Document 3 has technical problems in ductility (total elongation), processability and strength-ductility balance. The ductility of the titanium material described in Patent Document 3 is less than 30%. In contrast, the general-purpose plates of industrial titanium used in heat exchangers and equipment components require a total elongation of more than 30%. On this basis, in order to form the general-purpose plates of industrial titanium into component shapes, processability such as bending is required. Furthermore, in these uses, in order to pursue lightweight and miniaturization, an excellent balance of strength and ductility is required, and the product of tensile strength and total elongation is required to be 15000 MPa·% or more under the premise of a total elongation of more than 30%. The titanium material of Patent Document 3 is insufficient in ductility (total elongation), which is problematic in practical application to heat exchangers and chemical equipment components.

[0019] When a titanium material is heat treated so that compound particles containing titanium and carbon with a large average diameter that are likely to become crack starting points are not formed, the technical problems of ductility, workability and strength-ductility balance are sometimes solved. Figure 3B As shown in the figure, there is a technical problem of local corrosion in titanium materials. The occurrence of local corrosion not only significantly deteriorates the corrosion resistance and increases the corrosion rate, but also induces stress corrosion cracking starting from the local corrosion that occurs. Therefore, titanium materials that are prone to local corrosion sometimes have poor resistance to stress corrosion cracking. In addition, in titanium materials with insufficient corrosion resistance, in addition to local corrosion and stress corrosion cracking, sometimes corrosion caused by general corrosion becomes a problem.

[0020] In order to solve this technical problem, in addition to reducing the average diameter of the formed compound particles containing titanium and carbon to less than several hundred nanometers, the formed compound particles containing titanium and carbon need to fully exert the effect of improving corrosion resistance. However, there is no technology in the existing titanium materials that meets these requirements.

[0021] For example, although Non-Patent Document 2 describes a technique for producing steel having carbides precipitated with an average particle diameter of less than several hundred nm by adding trace amounts of elements such as Ti, Cr, V, and Nb that easily form carbides to steel, titanium materials cannot be produced by the same method because Ti atoms that easily form carbides exist everywhere in titanium materials.

[0022] As mentioned above, although Non-Patent Document 3 records a technology for forming compound particles containing titanium and carbon with an average diameter of less than several hundred nanometers on the surface of industrial pure titanium, in reality, the compound particles containing titanium and carbon are only formed on the surface, and the same method cannot be used to form compound particles containing titanium and carbon with an average diameter of less than several hundred nanometers in a metallic titanium block.

[0023] The technical problem of the present invention is to provide a titanium material, a chemical device component, and a chemical device having high ductility, workability, a balance between strength and ductility, and improved corrosion resistance, localized corrosion resistance, and stress corrosion cracking resistance.

[0024] Solutions for solving problems

[0025] The gist of the present invention is as follows.

[0026] (1) A titanium material according to one aspect of the present invention contains, in terms of mass%, C: 0.100 to 0.300%, N: 0.000 to 0.030%, Si: 0.000 to 0.100%, Fe: 0.000 to 0.300%, S: 0.0300% or less, P: 0.0300% or less, H: 0.000 to 0.015%, O: 0.000 to 0.250%, B: 0.000 to 0.300%, A l: 0.000~0.500%, Ca: 0.000~0.200%, Sc: 0.000~0.100%, V: 0.000~0.500%, Co: 0.000~0.600%, Ni: 0.000~0.400%, Zn: 0.000~0.300%, Ga: 0.000~0.200%, Ge: 0.000~0.200%, Y: 0.000~0.300% , Nb: 0.000~0.150%, Mo: 0.000~0.250%, Ag: 0.000~0.100%, Cd: 0.000~0.200%, In: 0.000~0.10 0%, Sb: 0.000~0.100%, Bi: 0.000~0.180%, Hf: 0.000~0.300%, Ta: 0.000~0.300%, W: 0.000~0.6 00%, Re: 0.000~0.300%, Au: 0.000~0.100%, one or more of Pt, Pd, Ru, Ir, Rh and Os: the total is 0.000~0.200%, and one or more of Mn, Cu, Cr, Sn and Zr: the total is 0.00~0.20%, the balance is Ti and impurities, and contains compound particles containing titanium and carbon with an average diameter of less than 400nm.

[0027] (2) In the titanium material described in (1) above, preferably, the contents of S are 0.0001 to 0.0300% and P are 0.0001 to 0.0300% in terms of mass %.

[0028] (3) In the titanium material described in (1) or (2) above, it is preferred that the A value calculated by substituting the analysis results of the compound particles containing titanium and carbon by X-ray diffraction into the following formula is 0.10 or more.

[0029] A=I Ti2C / (1.3I TiC +I Ti2C )

[0030] I TiC ={∑(I TiC(hkl) / R TiC(hkl) )} / n

[0031] I Ti2C={∑(I Ti2C(hkl) / R Ti2C(hkl) )} / n

[0032] Among them, I TiC is a representative value of the integrated intensity of TiC, which is one of the compound particles containing titanium and carbon, and I Ti2C It's Ti 2 Representative value of the integrated intensity of C, Ti 2 C is one of the compound particles comprising titanium and carbon, TiC(hkl) is the integrated intensity measured at each Miller index of the TiC, I Ti2C(hkl) It is the Ti 2 The integrated intensity measured at each Miller index of C, R TiC(hkl) is the coefficient corresponding to each Miller index of TiC, R Ti2C(hkl) is related to the Ti 2 The coefficients corresponding to each Miller index of C, n is 5, R TiC(hkl) and R Ti2C(hkl) The corresponding relationship with each Miller index is shown in the following table.

[0033] [Table 1]

[0034] Miller Index <![CDATA[R TiC(hkl) ]]> <![CDATA[R Ti2C(hkl) ]]> (111) 0.94 (200) 1.00 (220) 0.46 (311) 0.22 (222) 0.14 (111) 0.12 (222) 1.00 (400) 0.70 (440) 0.33 (620) 0.22

[0035] (4) The titanium material described in any one of (1) to (3) above preferably contains Ti 3 C 2 .

[0036] (5) A chemical device component according to another aspect of the present invention includes the titanium material according to any one of (1) to (4) above.

[0037] (6) Another aspect of the present invention provides a chemical device including the chemical device component described in (5) above.

[0038] Effects of the Invention

[0039] According to the present invention, it is possible to provide a titanium material having excellent ductility, workability, strength-ductility balance, corrosion resistance, localized corrosion resistance, and stress corrosion cracking resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is an example of a metallographic structure photograph of a titanium material manufactured by the manufacturing method involved in this embodiment.

[0041] Figure 2A This is an example of a metallographic photograph of a titanium material produced using a conventional production method. The black contrasting portion is TiC. Figure 2A Cited from Patent Document 3.

[0042] Figure 2B This is an example of a metallographic photograph of a titanium material produced using a conventional production method. The black contrasting portion is TiC.

[0043] Figure 3A This is an example of a surface SEM image of a titanium material manufactured by the manufacturing method according to the present embodiment after a corrosion resistance test in a hydrochloric acid aqueous solution.

[0044] Figure 3B This is an example of a surface SEM image of a titanium material manufactured by a conventional manufacturing method after a corrosion resistance test in a hydrochloric acid aqueous solution. The arrows indicate pitting.

[0045] Figure 4 It is a schematic diagram illustrating the annealing method of the titanium material according to the present embodiment.

[0046] Figure 5 This is a graph showing the relationship between the average diameter of compound particles containing titanium and carbon and the balance between strength and ductility.

[0047] Figure 6 This is a graph showing the relationship between the average diameter of compound particles containing titanium and carbon and the total elongation.

[0048] Figure 7 represents the A value (Ti in the formed compound particles containing titanium and carbon) 2 A graph showing the relationship between the ratio of C (index value) and corrosion resistance. DETAILED DESCRIPTION

[0049] (1. Overview of Titanium Material According to the Embodiment)

[0050] In order to solve the above technical problems, the present inventors studied the relationship between the formation size of compound particles containing titanium and carbon and the ductility, workability, strength-ductility balance, corrosion resistance, localized corrosion resistance and stress corrosion cracking resistance of titanium materials.

[0051] As a result, the present inventors have found that the following aspects are mainly effective in improving the ductility, workability, strength-ductility balance, corrosion resistance, localized corrosion resistance, and stress corrosion cracking resistance of titanium materials.

[0052] (1) setting the C content to 0.10 to 0.30%; and

[0053] (2) The average diameter of the compound particles containing titanium and carbon formed in the titanium material is set to 400 nm or less.

[0054] Figure 1 This is an example of a metallographic structure photograph of a titanium material manufactured by the manufacturing method involved in this embodiment. Figure 2A and Figure 2BEach of these is an example of a metallographic structure photograph of a titanium material manufactured using an existing manufacturing method. Figure 2A These are figures cited from Patent Document 3. In these photographs, the black contrasting parts are TiC. Figure 3A This is an example of a surface SEM image of the titanium material according to the present embodiment after the corrosion resistance test in a hydrochloric acid aqueous solution. Figure 3B This is an example of a surface SEM image of a conventional titanium material after a corrosion resistance test in a hydrochloric acid aqueous solution. Local corrosion occurs on the surface of the conventional titanium material. Figure 3B The part with an arrow in the middle is a local corrosion occurrence part. It can be seen from this that the titanium material involved in this embodiment has greatly improved corrosion resistance and local corrosion resistance. The inventors have confirmed that the titanium material involved in this embodiment is also very excellent in other characteristics.

[0055] Furthermore, the present inventors have found that in order to further improve various properties, it is preferable to combine TiC and Ti in the compound particles containing titanium and carbon. 2 The index value of the ratio of C (the A value described later) is set to 0.10 or more. On this basis, the present inventors have also found that it is more preferable to include Ti in the compound particles containing titanium and carbon. 3 C 2 .

[0056] In the titanium material according to the present embodiment, the compound particles containing titanium and carbon play an important role in achieving excellent ductility, workability, strength-ductility balance, corrosion resistance, local corrosion resistance, and stress corrosion cracking resistance. In the titanium material according to the present embodiment, as long as the size of the compound particles containing titanium and carbon is within the above range, the type of the compound particles is not particularly limited. For the above reasons, it is more desirable that Ti 2 C. Ti 3 C 2 .

[0057] Furthermore, the present inventors have found that by cold working a C-containing titanium alloy at a working degree of 10% or more and then subjecting it to a specific heat treatment, the average diameter of compound particles containing titanium and carbon formed in the titanium material can be reduced to 400 nm or less.

[0058] The heat treatment applied in an example of the manufacturing method of the titanium material involved in the present embodiment is described. The titanium material involved in the present embodiment is obtained by, for example, cold working a titanium material semi-finished product containing C at a working degree of 10% or more and then performing heat treatment. In the heat treatment, the residence time and holding time at a relatively low temperature of 200 to 590°C are ensured to be longer than those of the conventional heat treatment.

[0059] In the above temperature range, due to the insufficient diffusion rate of titanium and the elements contained in the titanium material, recrystallization and phase transformation cannot be fully carried out. Therefore, the above temperature range is not used in the prior art. However, the present inventors have found that by cold working a titanium semi-finished product containing a specified amount of C, and then performing a heat treatment in the above temperature range at a specific average heating rate or heating before heat treatment, small compound particles containing titanium and carbon are formed, and then the compound particles containing titanium and carbon are made into Ti as a metastable phase. 2 C. Ti 3 C 2 .

[0060] There are several types of compound particles containing titanium and carbon, but Ti 2 C and Ti 3 C 2 Compared with TiC, it is a metastable phase that is not stable in terms of thermodynamic equilibrium theory and mechanics. In order to make the average diameter of the compound particles containing titanium and carbon less than 400nm, the residence time and holding time at 200-590℃ are ensured to be longer than before. However, during this thermal history, TiC is also formed. 2 C or Ti 3 C 2 At this time, the Ti 2 C and Ti 3 C 2 Compared with TiC, the particle growth rate is slow, so the average particle diameter can be less than 400nm. Although part of the phase is transformed into TiC by subsequent heating and holding at 600-850℃, the Ti before the phase transformation 2 C. Ti 3 C 2 The average particle diameter is small, and even after the phase transformation into TiC, the average particle diameter can be 400 nm or less.

[0061] Furthermore, the present inventors have found that when the titanium material having the above characteristics is used as a chemical device component or as one of the materials of a chemical device, it exhibits excellent contact resistance, hydrogen overvoltage, and oxygen overvoltage.

[0062] (2. Specific aspects of the titanium material according to the present embodiment)

[0063] Next, the specific scheme of the titanium material involved in this embodiment is described. It should be noted that the characteristics of the titanium material involved in this embodiment are mainly the chemical composition of the titanium material and the state of the compound particles containing titanium and carbon contained in the titanium material. Therefore, the shape of the titanium material is not particularly limited. When the titanium material is made into a titanium plate, a titanium foil, a titanium strip or a titanium coil, for example, its plate thickness is preferably made into 0.1 to 6.0 mm, but other plate thicknesses can also be appropriately adopted. The titanium material can also have other shapes such as rods. When the titanium material is made into a rod-shaped wire, for example, its diameter is preferably made into 1 to 10 mm, but other diameters can also be appropriately adopted. When the titanium material is made into a tubular shape, for example, its diameter is preferably made into 10 to 300 mm, but other diameters can also be appropriately adopted. Titanium materials whose chemical composition and the state of the compound particles containing titanium and carbon are within the range described below are regarded as titanium materials involved in this embodiment. The titanium material involved in this embodiment has improved corrosion resistance, so it is easy to form oxides and hydrates that act as a protective layer on the surface of the titanium material. In addition, the titanium material according to this embodiment may react with sulfuric acid contained in the environment during use in a corrosive environment to form sulfides on the surface. Even if such a protective layer or sulfides are formed on the surface, it is still considered to be the titanium material according to this embodiment.

[0064] (2.1. Chemical Composition of Titanium Material According to the Embodiment)

[0065] First, the chemical composition of the titanium material of the present embodiment will be described. In the following description of the chemical composition, "mass %" is abbreviated as "%".

[0066] <C: 0.100~0.300%>

[0067] In the present embodiment, C plays an important role in improving ductility, workability, strength-ductility balance, corrosion resistance, local corrosion resistance, and stress corrosion cracking resistance. As the C content increases, corrosion resistance, local corrosion resistance, and stress corrosion cracking resistance improve. The effect of improving corrosion resistance brought about by containing C is significantly manifested when it is 0.100% or more. The C content is preferably 0.280% or less, and more preferably 0.250% or less.

[0068] On the other hand, as described later, a portion of C contained in the titanium material involved in the present embodiment exists in the form of compound particles containing titanium and carbon. In the case of forming compound particles containing titanium and carbon, when the C content is too much, compound particles containing titanium and carbon are excessively formed, which will have an adverse effect on ductility, workability and strength-ductility balance. Therefore, the C content is set to 0.300% or less. It should be noted that the C content is preferably 0.120% or more, and more preferably 0.150% or more.

[0069] <N: 0.000~0.030%>

[0070] N has the effect of improving strength, but in the titanium material involved in this embodiment, strength is ensured by other means. Therefore, the lower limit of the N content can be 0.000%. The lower limit of the N content can be set to 0.005%, and more preferably 0.010%.

[0071] On the other hand, as the N content increases, ductility and toughness deteriorate. In addition, N is an intrusive solid solution element, the same as C, which plays an important role in improving corrosion resistance in the titanium material involved in this embodiment. Therefore, an increase in the N content may cause a decrease in the solid solution content of C, or may have an adverse effect on the formation behavior of compound particles containing titanium and carbon. Therefore, the N content is set to 0.030% or less. The N content is preferably 0.025% or less, and more preferably 0.020% or less.

[0072] <Si: 0.000~0.100%>

[0073] Si is a relatively cheap element and is an effective element for improving heat resistance (oxidation resistance, high temperature strength). However, in the titanium material involved in this embodiment, strength is ensured by other means. Therefore, the lower limit of the Si content can be 0.000%. The lower limit of the Si content is more preferably 0.003%, and the upper limit of the Si content is more preferably 0.080%.

[0074] On the other hand, when the Si content is too high, the precipitation of Si compounds may be promoted. In addition, since Si is mixed into the compound particles containing titanium and carbon, the formation behavior of the compound particles may be adversely affected. In particular, the amount of compound particles containing titanium and carbon may be excessive. In this case, the ductility and toughness of the titanium material deteriorate. Therefore, the Si content is set to 0.100% or less. The upper limit of the Si content is more preferably 0.080%, 0.060% or 0.040%.

[0075] <Fe: 0.000~0.300%>

[0076] Fe has the effect of improving strength, but in the titanium material involved in this embodiment, strength is ensured by other means. Therefore, the lower limit of the Fe content can be 0.000%. It should be noted that the lower limit of the Fe content is preferably 0.020%, and more preferably 0.030%.

[0077] On the other hand, as the Fe content increases, the ductility and toughness of the titanium material deteriorate. In addition, since a large amount of Fe is distributed near the compound particles containing titanium and carbon, it may have an adverse effect on the formation behavior of the compound particles. In particular, the amount of compound particles containing titanium and carbon may be excessive. Therefore, the Fe content is set to 0.300% or less. The upper limit of the Fe content is preferably 0.250%, more preferably 0.200%. The Fe content can be set to less than 0.100% or less than 0.080%.

[0078] <S: 0.0000~0.0300%>

[0079] S is not essential in the titanium material involved in the present embodiment. Therefore, the lower limit of the S content can be 0.0000%. However, S has the effect of improving strength. In addition, S is an element effective in improving interface contact resistance. For example, when the titanium material involved in the present embodiment is included in chemical device parts and chemical devices, etc., and a passivation film is grown after being used in an aqueous solution for a long time, the S contained in the titanium material has a greater effect of suppressing the increase in interface contact resistance. By suppressing the increase in the interface contact resistance of the titanium material used as a constituent material of a chemical device part or a chemical device, the chemical device parts and chemical devices can operate with less energy loss. In order to obtain this effect, the lower limit content of S is preferably 0.0001%, more preferably 0.0005%, and further preferably 0.0010%.

[0080] On the other hand, as the S content increases, ductility and toughness deteriorate. In addition, since S is mixed into the compound particles containing titanium and carbon, the formation behavior of the compound particles may be adversely affected. In particular, the amount of compound particles containing titanium and carbon may be excessive. Therefore, the S content is set to 0.0300% or less. It should be noted that the upper limit content of S is preferably 0.0250%, and more preferably 0.0200%.

[0081] <P: 0.0000~0.0300%>

[0082] P is not essential in the titanium material involved in the present embodiment. Therefore, the lower limit of the P content can be 0.0000%. However, P is an element effective in improving strength. In addition, P is an element effective in improving interface contact resistance. For example, when the titanium material involved in the present embodiment is included in chemical device parts and chemical devices, etc., and a passivation film is grown after being used in an aqueous solution for a long time, the P contained in the titanium material has a greater effect of suppressing the increase in interface contact resistance. By suppressing the increase in the interface contact resistance of the titanium material used as a constituent material of chemical device parts and chemical devices, etc., the chemical device parts and chemical devices, etc. can operate with less energy loss. Therefore, the lower limit content of P is preferably 0.0001%, more preferably 0.0005%, and further preferably 0.0010%.

[0083] On the other hand, as the P content increases, ductility and toughness deteriorate. In addition, since P is mixed into the compound particles containing titanium and carbon, the formation behavior of the compound particles may be adversely affected. In particular, the amount of compound particles containing titanium and carbon may be excessive. Therefore, the P content is set to 0.0300% or less. It should be noted that the upper limit content of P is preferably 0.0250%, and more preferably 0.0200%.

[0084] <H: 0.000~0.015% or less>

[0085] H is an element that forms titanium hydride and deteriorates the ductility and toughness of the blank. Therefore, the less the H content, the better. Therefore, the H content can be 0.000%. In addition, the H content is limited to less than 0.015%. The upper limit of H content is preferably 0.013% or 0.010%. In the case of obtaining such a low-H titanium material, commercially available sponge titanium can be used as a smelting raw material. In the case of obtaining a titanium material with even lower H, high-purity titanium can be used as a smelting raw material.

[0086] However, commercially available titanium sponges also have various grades, and excessive use of high-purity titanium sponges increases costs. In the titanium material of this embodiment, the H content is preferably 0.001% or more from the perspective of cost. The lower limit of the H content is more preferably 0.005%.

[0087] <O: 0.000~0.250% or less>

[0088] O is an element effective in improving strength, but is not necessary in the titanium material involved in the present embodiment. In addition, as the O content increases, the ductility and toughness of the titanium material deteriorate. In addition, O is an intrusive solid solution element, the same as C, which plays an important role in improving corrosion resistance in the titanium material involved in the present embodiment. Therefore, the increase in the O content may cause the solid solution content of C to decrease, or may have an adverse effect on the formation behavior of the compound particles containing titanium and carbon. In particular, the amount of compound particles containing titanium and carbon may be excessive. Therefore, the O content can be 0.000%. In addition, the O content is set to less than 0.250%. The upper limit content of O is preferably 0.200%, and more preferably 0.180%.

[0089] When obtaining a titanium alloy with a low O content, high-purity sponge titanium can be used among commercially available sponge titanium. When obtaining a titanium material with a lower O content, high-purity titanium can be used as a smelting raw material.

[0090] However, if high-purity titanium sponge is excessively used, the cost increases. In the titanium material according to the present embodiment, the lower limit of the content of O is preferably 0.020%, and more preferably 0.030%.

[0091] <B: 0.000~0.300%>

[0092] B has the effect of improving strength, but in the titanium material involved in this embodiment, strength is ensured by other means. Therefore, the lower limit of the B content can be 0.000%. The lower limit of the B content can be set to 0.005%, and more preferably set to 0.010%. On the other hand, as the B content increases, the ductility and toughness of the titanium material deteriorate. In addition, B is an intrusive solid solution element, the same as C, which plays an important role in improving corrosion resistance in the titanium material involved in this embodiment. Therefore, an increase in the B content may cause a decrease in the solid solution content of C, or may have an adverse effect on the formation behavior of compound particles containing titanium and carbon. Therefore, the B content is set to less than 0.300%. The B content is preferably less than 0.100, and more preferably less than 0.050%.

[0093] <Al: 0.000~0.500%>

[0094] Al has the effect of improving strength, but in the titanium material involved in this embodiment, strength is ensured by other means. Therefore, the lower limit of the Al content can be 0.000%. It should be noted that the lower limit of the Al content is preferably 0.010%, and more preferably 0.020%. On the other hand, as the Al content increases, the ductility and toughness of the titanium material deteriorate. Therefore, the Al content is set to 0.000-0.500%. It should be noted that the upper limit of the Al content is preferably 0.350%, and more preferably 0.200%.

[0095] <Ca: 0.000~0.200%>

[0096] Ca has the effect of improving local corrosion resistance and stress corrosion cracking resistance, but in the titanium material involved in this embodiment, local corrosion resistance and stress corrosion cracking resistance are ensured by other means. Therefore, the lower limit of the Ca content can be 0.000%. It should be noted that the lower limit of the Ca content is preferably 0.002%, and more preferably 0.005%. On the other hand, as the Ca content increases, the ductility and toughness of the titanium material deteriorate. Therefore, the Ca content is set to 0.000-0.200%. It should be noted that the upper limit of the Ca content is preferably 0.100%, and more preferably 0.040%.

[0097] <Sc: 0.000~0.100%>

[0098] Sc has the effect of improving local corrosion resistance and stress corrosion cracking resistance, but in the titanium material involved in this embodiment, local corrosion resistance and stress corrosion cracking resistance are ensured by other means. Therefore, the lower limit of the Sc content can be 0.000%. It should be noted that the lower limit of Sc is preferably 0.001%, and more preferably 0.003%. On the other hand, as the Sc content increases, the ductility and toughness of the titanium material deteriorate. Therefore, the Sc content is set to 0.000-0.100%. It should be noted that the upper limit of Sc is preferably 0.060%, and more preferably 0.030%.

[0099] <V: 0.000~0.500%>

[0100] V has the effect of improving strength, but in the titanium material involved in this embodiment, strength is ensured by other means. Therefore, the lower limit of the V content can be 0.000%. It should be noted that the lower limit of the V content is preferably 0.010%, and more preferably 0.020%. On the other hand, V is a strong β-stabilizing element. If the V content is too much, it is difficult to obtain a structure with α phase as the main body. Therefore, the V content is set to less than 0.500%. The upper limit of the V content is preferably 0.200%, and more preferably 0.100%.

[0101] <Co: 0.000~0.600%>

[0102] Co has the effect of improving corrosion resistance and local corrosion resistance, but in the titanium material involved in this embodiment, corrosion resistance and local corrosion resistance are ensured by other means. Therefore, the lower limit of the Co content can be 0.000%. It should be noted that the lower limit of Co is preferably 0.010%, and more preferably 0.020%. On the other hand, Co is an element that can form a compound with Ti. If the amount of Co is too much, a compound of Co and Ti is formed, and the ductility and processability of the titanium material are poor. Therefore, the content of Co is set to less than 0.600%. The upper limit of Co is preferably 0.100%, and more preferably 0.050%.

[0103] <Ni: 0.000~0.400%>

[0104] Ni has the effect of improving corrosion resistance and local corrosion resistance, but in the titanium material involved in this embodiment, corrosion resistance and local corrosion resistance are ensured by other means. Therefore, the lower limit of the Ni content can be 0.000%. It should be noted that the lower limit of Ni content is preferably 0.002%, and more preferably 0.005%. On the other hand, Ni is an element that can form a compound with Ti. If the amount of Ni is too much, a compound of Ni and Ti is formed, and the ductility and processability of the titanium material are poor. Therefore, the Ni content is set to less than 0.400%. The upper limit of Ni content is preferably 0.200%, and more preferably 0.150%.

[0105] <Zn: 0.000~0.300%>

[0106] Zn has the effect of improving local corrosion resistance, but in the titanium material involved in this embodiment, local corrosion resistance is ensured by other means. Therefore, the lower limit of the Zn content can be 0.000%. It should be noted that the lower limit of the Zn content is preferably 0.001%, and more preferably 0.002%. On the other hand, as the Zn content increases, the ductility and toughness of the titanium material deteriorate. Therefore, the Zn content is set to 0.000-0.300%. It should be noted that the upper limit of the Zn content is preferably 0.150%, and more preferably 0.050%.

[0107] <Ga: 0.000~0.200%>

[0108] Ga has the effect of improving local corrosion resistance, but in the titanium material involved in this embodiment, local corrosion resistance is ensured by other means. Therefore, the lower limit of the Ga content can be 0.000%. It should be noted that the lower limit of Ga content is preferably 0.001%, and more preferably 0.005%. On the other hand, as the Ga content increases, the ductility and toughness of the titanium material deteriorate. Therefore, the Ga content is set to 0.000-0.200%. It should be noted that the upper limit of Ga content is preferably 0.100%, and more preferably 0.050%.

[0109] <Ge: 0.000~0.200%>

[0110] Ge has the effect of improving local corrosion resistance, but in the titanium material involved in this embodiment, local corrosion resistance is ensured by other means. Therefore, the lower limit of the Ge content can be 0.000%. It should be noted that the lower limit of the Ge content is preferably 0.001%, and more preferably 0.005%. On the other hand, as the Ge content increases, the ductility and toughness of the titanium material deteriorate. Therefore, the Ge content is set to 0.000-0.200%. It should be noted that the upper limit of the Ge content is preferably 0.100%, and more preferably 0.050%.

[0111] <Y: 0.000~0.300%>

[0112] Y has the effect of improving local corrosion resistance and stress corrosion cracking resistance, but in the titanium material involved in this embodiment, local corrosion resistance and stress corrosion cracking resistance are ensured by other means. Therefore, the lower limit of the Y content can be 0.000%. It should be noted that the lower limit of the Y content is preferably 0.001%, and more preferably 0.002%. On the other hand, as the Y content increases, the ductility and toughness of the titanium material deteriorate. Therefore, the Y content is set to 0.000-0.300%. It should be noted that the upper limit of the Y content is preferably 0.120%, and more preferably 0.060%.

[0113] <Nb: 0.000~0.150%>

[0114] Nb has the effect of improving corrosion resistance, but in the titanium material involved in this embodiment, corrosion resistance is ensured by other means. Therefore, the lower limit of the Nb content can be 0.000%. It should be noted that the lower limit of the Nb content is preferably 0.050%, and more preferably 0.070%. On the other hand, as the Nb content increases, the ductility of the titanium material deteriorates. Therefore, the Nb content is set to 0.000-0.150%. It should be noted that the upper limit of the Nb content is preferably 0.130%, and more preferably 0.100%.

[0115] <Mo: 0.000~0.250%>

[0116] Mo has the effect of improving strength, but in the titanium material involved in this embodiment, strength is ensured by other means. Therefore, the lower limit of the Mo content can be 0.000%. It should be noted that the lower limit of Mo is preferably 0.005%, and more preferably 0.010%. On the other hand, as the Mo content increases, the ductility of the titanium material deteriorates. Therefore, the Mo content is set to 0.250% or less. The upper limit of Mo is preferably 0.200%, and more preferably 0.100%.

[0117] <Ag: 0.000~0.100%>

[0118] Ag has the effect of improving local corrosion resistance, but in the titanium material involved in this embodiment, local corrosion resistance is ensured by other means. Therefore, the lower limit of the Ag content can be 0.000%. It should be noted that the lower limit of the Ag content is preferably 0.010%, and more preferably 0.015%. On the other hand, as the Ag content increases, the ductility of the titanium material deteriorates. Therefore, the Ag content is set to 0.000-0.100%. It should be noted that the upper limit of the Ag content is preferably 0.080%, and more preferably 0.060%.

[0119] <Cd: 0.000~0.200%>

[0120] Cd has the effect of improving local corrosion resistance, but in the titanium material involved in this embodiment, local corrosion resistance is ensured by other means. Therefore, the lower limit of the Cd content can be 0.000%. It should be noted that the lower limit of the Cd content is preferably 0.005%, and more preferably 0.010%. On the other hand, as the Cd content increases, the ductility of the titanium material deteriorates. Therefore, the Cd content is set to 0.000-0.200%. It should be noted that the upper limit of the Cd content is preferably 0.120%, and more preferably 0.080%.

[0121] <In: 0.000~0.100%>

[0122] In has the effect of improving local corrosion resistance, but in the titanium material involved in this embodiment, local corrosion resistance is ensured by other means. Therefore, the lower limit of the In content can be 0.000%. It should be noted that the lower limit of the In content is preferably 0.005%, and more preferably 0.008%. On the other hand, as the In content increases, the ductility of the titanium material deteriorates. Therefore, the In content is set to 0.000-0.100%. It should be noted that the upper limit of the In content is preferably 0.070%, and more preferably 0.050%.

[0123] <Sb: 0.000~0.100%>

[0124] Sb has the effect of improving local corrosion resistance, but in the titanium material involved in this embodiment, local corrosion resistance is ensured by other means. Therefore, the lower limit of the Sb content can be 0.000%. It should be noted that the lower limit of the Sb content is preferably 0.002%, and more preferably 0.005%. On the other hand, as the Sb content increases, the ductility of the titanium material deteriorates. Therefore, the Sb content is set to 0.000-0.100%. It should be noted that the upper limit of the Sb content is preferably 0.060%, and more preferably 0.050%.

[0125] <Bi: 0.000~0.180%>

[0126] Bi has the effect of improving local corrosion resistance, but in the titanium material involved in this embodiment, local corrosion resistance is ensured by other means. Therefore, the lower limit of the Bi content can be 0.000%. It should be noted that the lower limit of Bi is preferably 0.002%, and more preferably 0.005%. On the other hand, as the Bi content increases, the ductility of the titanium material deteriorates. Therefore, the Bi content is set to 0.000-0.180%. It should be noted that the upper limit of Bi is preferably 0.150%, and more preferably 0.080%.

[0127] <Hf: 0.000~0.300%>

[0128] Hf has the effect of improving corrosion resistance, but in the titanium material involved in this embodiment, corrosion resistance is ensured by other means. Therefore, the lower limit of the Hf content can be 0.000%. It should be noted that the lower limit of the Hf content is preferably 0.002%, and more preferably 0.004%. On the other hand, as the Hf content increases, the ductility of the titanium material deteriorates. Therefore, the Hf content is set to 0.000-0.300%. It should be noted that the upper limit of the Hf content is preferably 0.240%, and more preferably 0.140%.

[0129] <Ta:0.000~0.300%>

[0130] Ta has the effect of improving corrosion resistance, but in the titanium material involved in this embodiment, corrosion resistance is ensured by other means. Therefore, the lower limit of the Ta content can be 0.000%. It should be noted that the lower limit of Ta content is preferably 0.020%, and more preferably 0.050%. On the other hand, as the Ta content increases, the ductility of the titanium material deteriorates. Therefore, the Ta content is set to 0.000-0.300%. It should be noted that the upper limit of Ta content is preferably 0.250%, and more preferably 0.220%.

[0131] <W: 0.000~0.600%>

[0132] W has the effect of improving corrosion resistance, but in the titanium material involved in this embodiment, corrosion resistance is ensured by other means. Therefore, the lower limit of the W content can be 0.000%. It should be noted that the lower limit of the W content is preferably 0.050%, and more preferably 0.080%. On the other hand, as the W content increases, ductility deteriorates. Therefore, the W content is set to 0.000-0.600%. It should be noted that the upper limit of the W content is preferably 0.500%, and more preferably 0.450%.

[0133] <Re:0.000~0.300%>

[0134] Re has the effect of improving corrosion resistance, local corrosion resistance and stress corrosion cracking resistance, but in the titanium material involved in this embodiment, strength is ensured by other means. Therefore, the lower limit of the Re content can be 0.000%. It should be noted that the lower limit of Re is preferably 0.001%, and more preferably 0.002%. On the other hand, as the Re content increases, the ductility of the titanium material deteriorates. Therefore, the Re content is set to 0.000-0.300%. It should be noted that the upper limit of Re is preferably 0.100%, and more preferably 0.050%.

[0135] <Au: 0.000~0.100%>

[0136] Au has the effect of improving corrosion resistance, local corrosion resistance and stress corrosion cracking resistance, but in the titanium material involved in this embodiment, strength is ensured by other means. Therefore, the lower limit of the Au content can be 0.000%. It should be noted that the lower limit of the total Au content is preferably 0.005%, and more preferably 0.010%. On the other hand, as the Au content increases, the ductility of the titanium material deteriorates. Therefore, the Au content is set to 0.000-0.100%. It should be noted that the preferred upper limit of the Au content is 0.080%, and more preferably 0.040%.

[0137] <One or more of Pt, Pd, Ru, Ir, Rh and Os: the total is 0.000 to 0.200%>

[0138] Pt, Pd, Ru, Ir, Rh and Os have the effect of improving corrosion resistance, local corrosion resistance and stress corrosion cracking resistance, but in the titanium material involved in this embodiment, strength is ensured by other means. Therefore, the lower limit of the total content of Pt, Pd, Ru, Ir, Rh and Os can be 0.000%. It should be noted that the lower limit of the total content of Pt, Pd, Ru, Ir, Rh and Os is preferably 0.002%, and more preferably 0.004%. On the other hand, if the total content of Pt, Pd, Ru, Ir, Rh and Os is too much, the ductility of the titanium material deteriorates. Therefore, the total content of Pt, Pd, Ru, Ir, Rh and Os is set to less than 0.200%. The upper limit of the total content of Pt, Pd, Ru, Ir, Rh and Os is preferably 0.080%, and more preferably 0.060%.

[0139] <Total content of Mn, Cu, Cr, Sn and Zr: 0.00 to 0.20%>

[0140] In titanium materials that do not contain C, the effects of Mn, Cu, Cr, Sn, and Zr on improving corrosion resistance, localized corrosion resistance, and stress corrosion cracking resistance are weak. However, the present inventors have found that by adding a trace amount of one or more of Mn, Cu, Cr, Sn, and Zr to a titanium material containing 0.10 to 0.30% of C, and then performing cold working at a reduction rate of 10% or more, and then performing heat treatment in the modes A, B, and C described below, the effects of improving corrosion resistance, localized corrosion resistance, and stress corrosion cracking resistance can be further exerted. As in the titanium material involved in the present embodiment, in a titanium material containing C, containing one or more of Mn, Cu, Cr, Sn, and Zr in a total amount of 0.01% or more, the passivation film with titanium oxide as the main constituent material can be made more difficult to melt, and the effects of further improving corrosion resistance, localized corrosion resistance, and stress corrosion cracking resistance can be obtained.

[0141] In the titanium material involved in this embodiment, Mn, Cu, Cr, Sn and Zr are not essential, and the total content of Mn, Cu, Cr, Sn and Zr can be 0.00% or less than 0.01%. However, when the total content of Mn, Cu, Cr, Sn and Zr is 0.01% or more, the corrosion resistance, local corrosion resistance and stress corrosion cracking resistance can be further improved. Therefore, when one or more of Mn, Cu, Cr, Sn and Zr are contained, the lower limit of the total content of these elements can be set to 0.01%, 0.02% or 0.05%.

[0142] However, if the total content of Mn, Cu, Cr, Sn and Zr is too high, there is a risk of forming Ti 2 Cu and other metals are not required for the titanium material of this embodiment, and thus are not desirable. Therefore, the upper limit of the total content of Mn, Cu, Cr, Sn and Zr is set to 0.20% or less. The upper limit of the preferred total content of Mn, Cu, Cr, Sn and Zr is preferably 0.10%, and more preferably 0.08%. It should be noted that Mn, Cu, Cr, Sn and Zr can be contained alone or in combination of two or more.

[0143] The balance of the chemical composition of the titanium material involved in this embodiment is Ti and impurities. Impurities refer to components mixed into the titanium material due to various factors in the raw materials or manufacturing process when the titanium material is manufactured industrially, and are acceptable within the range that does not adversely affect the titanium material involved in this embodiment.

[0144] (2.2. Metallographic Structure of Titanium Material According to the Present Embodiment)

[0145] Next, the metallographic structure of the titanium material according to the present embodiment will be described.

[0146] <Average diameter of the compound particles containing titanium and carbon contained in the titanium material: 400 nm or less>

[0147] The titanium material according to the present embodiment contains particles such as inclusions and precipitates containing titanium and carbon as main components.

[0148] Generally speaking, particles contained in titanium materials improve the strength of titanium materials, but reduce the ductility and workability of titanium materials. Therefore, in the prior art, titanium materials that use compound particles containing titanium and carbon to ensure strength do not necessarily have sufficient ductility.

[0149] However, in the titanium material according to the present embodiment, the average diameter of the compound particles containing titanium and carbon is set to 400 nm or less, thereby achieving both high strength and high ductility and workability of the titanium material, thereby achieving an excellent balance between strength and ductility.

[0150] In addition, the compound particles containing titanium and carbon improve the corrosion resistance of the titanium material. However, when the size of the compound particles containing titanium and carbon is not appropriate, the improvement of local corrosion resistance and stress corrosion cracking resistance is insufficient. Therefore, in this embodiment, the average diameter of the compound particles containing titanium and carbon is controlled.

[0151] In addition, the smaller the average diameter of the compound particles containing titanium and carbon, the greater the effect of improving the ductility, processability, strength-ductility balance and local corrosion resistance of the titanium material. If the mismatch between the parent phase and the interface of the compound particles containing titanium and carbon is large, the interface may become the starting point of cracks and local corrosion during titanium material processing. However, by reducing the average diameter of the compound particles containing titanium and carbon, cracks and local corrosion at the interface of the parent phase and the compound particles containing titanium and carbon are suppressed. When the average diameter of the compound particles containing titanium and carbon is less than 400nm, this effect is significantly exerted.

[0152] It should be noted that the preferred lower limit of the average diameter of the compound particles containing titanium and carbon is 1 nm, more preferably 2 nm. The preferred upper limit of the average diameter of the compound particles containing titanium and carbon is 200 nm, more preferably 150 nm, further preferably 100 nm, and further preferably 10 nm.

[0153] In the titanium material according to the present embodiment, as long as the average diameter of the compound particles containing titanium and carbon is within the above range, the other metallographic structures are not particularly limited.

[0154] <Maximum diameter of particles: preferably 5 μm (5000 nm) or less>

[0155] As long as the average diameter of the compound particles containing titanium and carbon is within the above range, the titanium material may contain coarse particles. The "particles" refer to the compound particles containing titanium and carbon.

[0156] On the other hand, by suppressing the formation of coarse particles and making the maximum particle size of particles contained in the titanium material 5 μm or less, the mechanical properties of the titanium material are further improved. Therefore, the maximum particle size of particles contained in the titanium material can be set to 5 μm or less.

[0157] <Type and ratio of compound particles containing titanium and carbon: preferably Ti 2 The index value A of the ratio of C is 0.10 or more>

[0158] In the titanium material involved in this embodiment, the type of main carbide constituting the compound particles containing titanium and carbon is not particularly limited. When the average diameter of the compound particles containing titanium and carbon is 400nm or less, good properties can be obtained regardless of the type of carbide contained in the particles.

[0159] It is generally believed that various carbides that can be formed in titanium materials are mainly TiC. On the other hand, in order to further improve various properties of titanium materials, Ti is preferred. 2 Therefore, in the titanium material according to the present embodiment, the value of A calculated by the following formula can be used to define Ti: 2 The amount of C.

[0160] A=I Ti2C / (1.3I TiC +I Ti2C )

[0161] I TiC ={∑(I TiC(hkl) / R TiC(hkl) )} / n

[0162] I Ti2C ={∑(I Ti2C(hkl) / R Ti2C(hkl) )} / n

[0163] Among them, I TiC is a representative value of the integrated intensity of TiC, which is one of the compound particles containing titanium and carbon, and I Ti2C It's Ti 2 Representative value of the integrated intensity of C, Ti 2 C is one of the compound particles comprising titanium and carbon, TiC(hkl) is the integrated intensity measured at each Miller index of the TiC, I Ti2C(hkl) It is the Ti 2 The integrated intensity measured at each Miller index of C, R TiC(hkl) is the coefficient corresponding to each Miller index of TiC, R Ti2C(hkl) is related to the Ti 2 The coefficients corresponding to each Miller index of C, n is 5. TiC(hkl) and R Ti2C(hkl) The corresponding relationship with each Miller index is as follows.

[0164] [Table 2]

[0165] Miller Index <![CDATA[R TiC(hkl) ]]> <![CDATA[R Ti2C(hkl) ]]> (111) 0.94 (200) 1.00 (220) 0.46 (311) 0.22 (222) 0.14 (111) 0.12 (222) 1.00 (400) 0.70 (440) 0.33 (620) 0.22

[0166] The A value is the ratio of TiC to Ti in the compound particles containing titanium and carbon formed in the titanium material. 2 The specific method for measuring the A value is described below.

[0167] In the titanium material according to the present embodiment, the type of carbide is not limited, so the A value can be 0. In this case, it is estimated that the compound particles containing titanium and carbon contain almost no Ti. 2 C. On the other hand, it is preferred to generate Ti in the titanium material 2 C, and A value is set to be 0.10 or more. 2 Compared with TiC, C is a metastable phase that is unstable both in thermodynamic equilibrium theory and in mechanics. 2 C has a lower critical shear stress than TiC. 2 Titanium materials containing TiC (or compound particles containing titanium and carbon) are prone to plastic deformation. It is usually difficult to achieve both strength, ductility and processability in titanium materials that have formed TiC (or compound particles containing titanium and carbon). 2 C, the strength of the titanium material can be improved without impairing ductility and workability. Therefore, the A value is preferably set to 0.10 or more. 2 The ratio of C to TiC can further improve the ductility and workability of the titanium material, and can also further improve the strength-ductility balance.

[0168] On this basis, Ti is formed in terms of corrosion resistance, local corrosion resistance and stress corrosion cracking resistance. 2 C titanium is also more excellent. This is because Ti 2 C has a higher cathode reaction promoting ability than TiC, which can not only promote the compound particles containing titanium and carbon, but also promote the potential increase of the titanium material containing the compound particles. Titanium material has a wide passivation area in the high potential area. Therefore, by increasing the potential of the titanium material itself, passivation is promoted, and better corrosion resistance is exerted. That is, by increasing the TiC by 0.10 or more, the A value is increased. 2 The proportion of C further promotes the passivation of titanium, and improves the corrosion resistance, local corrosion resistance and stress corrosion cracking resistance.

[0169] When the A value is 0.10 or more, these effects can be significantly obtained. The lower limit of the A value is preferably 0.40, more preferably 0.60, and further preferably 0.80.

[0170] <Type of compound particles containing titanium and carbon: more preferably containing Ti 3 C 2 >

[0171] From the composition of Ti 3 C 2 The energy state of the electrons in the C atoms is different from that in TiC and Ti 2 C. Titanium contains Ti 3 C2 , which can further improve the interface contact resistance, hydrogen overvoltage and oxygen overvoltage of the titanium material. Therefore, the titanium material involved in this embodiment preferably contains Ti 3 C 2 .

[0172] Ti 3 C 2 Compared with TiC, it is a metastable phase that is unstable both in thermodynamic equilibrium theory and in mechanics. 3 C 2 The critical shear stress of TiC is lower than that of TiC. 3 C 2 Titanium is easy to plastically deform. It is usually difficult to achieve both strength, ductility and processability in titanium. However, when titanium is made to form a Ti that is easy to plastically deform 3 C 2 When the titanium material contains Ti, the strength can be improved without damaging the ductility and workability. 2 C 3 , can further improve the ductility and processability such as elongation, and can further improve the balance of strength and ductility. 2 C is similar.

[0173] On this basis, Ti 3 C 2 The effect of improving the interface contact resistance, hydrogen overvoltage and oxygen overvoltage of titanium is greater than that of Ti 2 C. Formed Ti 3 C 2 Titanium is more excellent. This is because Ti 3 C 2 The electrical conductivity, hydrogen production and oxygen production capacity of titanium are higher than those of other compound particles containing titanium and carbon, such as TiC. Of course, titanium can also contain Ti 2 C and Ti 3 C 2 Most preferably, the A value in the titanium material is 0.10 or more, and the titanium material contains Ti 3 C 2 .

[0174] Ti with an average diameter of less than 400nm 2 C and Ti 3 C 2 The critical shear stress of TiC is lower than that of TiC. 2 C and Ti 3 C 2 , it is possible to obtain titanium materials with better corrosion resistance as described below, and higher levels of ductility such as high elongation, processability, and strength-ductility balance.

[0175] An example of the method for controlling the compound particles containing titanium and carbon as described above is described below. 2 The proportion of C and Ti in the compound particles 3 C 2 The presence or absence of the metastable Ti is affected by the heat treatment mode and heat treatment conditions. Specifically, the morphology of these compound particles depends on the residence time and holding time at a relatively low temperature of 200 to 590°C. 2 C or Ti 3 C 2 The longer the residence time and holding time at 200-590°C, the greater the Ti content in the final billet. 2 The larger the proportion of C, the more Ti can be formed. 3 C 2 . After that, the temperature is raised and maintained at 600-850℃. 2 C and Ti 3 C 2 A portion of the phase is transformed into TiC, but by extending the residence time and holding time at 200 to 590°C, the TiC and TiC in the formed compound particles containing titanium and carbon can be separated. 2 The index value of the C ratio is 0.10 or more, and Ti 3 C 2 .

[0176] In terms of corrosion resistance, local corrosion resistance, and stress corrosion cracking resistance, Ti 2 C and Ti 3 C 2 The titanium material with TiC is obviously better than the titanium material with TiC. 2 C and Ti 3 C 2 It has a higher cathode reaction promoting ability than TiC, which not only promotes the compound particles containing titanium and carbon, but also promotes the potential increase of the titanium material containing the compound particles. Titanium has a wide passivation area in the high potential area. Therefore, by increasing the TiC and TiC in the formed compound particles containing titanium and carbon, 2 C ratio index value, passivation is promoted, and corrosion resistance, local corrosion resistance, and stress corrosion cracking resistance can be improved. 3 C 2 These characteristics can be further improved.

[0177] It should be noted that, just as various compounds exist within an arbitrary composition ratio range, the Ti in the titanium material according to the present embodiment 2 C and Ti 3 C 2In the present invention, Ti atoms and C atoms may not have a stoichiometric composition. 2 Ti carbides whose diffraction angle (2θ) determined by the lattice structure of C coincides with the diffraction peak in X-ray diffraction measurement are considered to be Ti 2 C. The ratio of Ti atoms to C atoms in carbides is not exactly 2:1. For example, carbides containing atomic vacancies are also considered Ti as long as they meet the above requirements. 2 C. In addition, Ti 3 C 2 The (spectral intensity at 282.0 eV) / (spectral intensity at 281.5 eV) of the C1s orbital is used as the spectral intensity of Ti 3 C 2 The unit of the spectrum intensity is counts / second. When the average value of (spectrum intensity at 282.0 eV) / (spectrum intensity at 281.5 eV) measured at three locations is 0.60 or more, it is judged that the titanium material contains Ti. 3 C 2 .

[0178] The ratio of Ti atoms to C atoms in carbides is not exactly 3:2. For example, carbides containing atomic vacancies are also considered Ti as long as they meet the above requirements. 3 C 2 .

[0179] The volume ratio of the compound particles containing titanium and carbon in the titanium material is not particularly limited, but at least the ratio of the total X-ray diffraction peak integrated intensity of the compound particles containing titanium and carbon to the X-ray diffraction peak integrated intensity of the α phase is 0.01 or more.

[0180] The titanium material involved in the present embodiment has a metallographic structure with α phase as the main body due to the above-mentioned chemical composition. In addition to the α phase, the metallographic structure may also include a β phase. For example, the proportion of the β phase in the titanium material can be set to less than 1Vol%. In addition, the proportion of the total amount of α phase and compound particles containing titanium and carbon in the titanium material can be set to more than 96Vol%. Due to the use environment of the titanium material, titanium hydride is sometimes formed in the titanium material. The titanium material involved in the present embodiment is also allowed to contain titanium hydride. For example, the proportion of the amount of titanium hydride in the titanium material can be set to less than 3Vol%. It should be noted that "Vol%" refers to the volume ratio.

[0181] (2.3. Method for evaluating the metallographic structure of the titanium material according to the present embodiment)

[0182] It should be noted that the metallographic structure of the titanium material in this embodiment can be determined by the following method.

[0183] <Method for determining average diameter of compound particles containing titanium and carbon>

[0184] The average diameter of the compound particles containing titanium and carbon can be measured by observing the cross section of the titanium material using SEM and TEM. The data used is different depending on the size of the average diameter of the compound particles containing titanium and carbon. First, the average diameter of the compound particles containing titanium and carbon is measured using SEM. When the result of SEM observation is that the average diameter of the compound particles containing titanium and carbon is 400nm or more, the SEM data is used. When the average diameter of the compound particles containing titanium and carbon obtained using SEM is less than 400nm, further measurement using TEM is performed and TEM data is used.

[0185] In SEM observation, two observation planes are first determined. The two cross sections are set as an arbitrary cross section parallel to the plate thickness direction of the titanium material (cross section 1) and a cross section (cross section 2) that satisfies the relationship of being parallel to the plate thickness direction of the titanium material and perpendicular to cross section 1. For example, when cross section 1 is the L cross section of the titanium material, cross section 2 is the T cross section of the titanium material. The L cross section is a cross section parallel to the rolling direction of the titanium material and perpendicular to the rolling surface, and the T cross section is a cross section perpendicular to the rolling direction of the titanium material and perpendicular to the rolling surface.

[0186] After the cross section 1 and the cross section 2 are mirror-polished, the surface obtained by grinding the cross section with a liquid containing colloidal silica as a grinding fluid is observed. These cross sections are observed with a scanning electron microscope at a magnification of 1000 times, 3000 times, 5000 times and 10000 times. Then, the average diameter is determined by the magnification of the image containing more than 5 and less than 20 particles in the observation field. If particles containing more than 5 and less than 20 are observed at two or more magnifications, the observation result at a higher magnification is adopted.

[0187] Observe 5 fields of view in section 1 at the adopted magnification, and also observe 5 fields of view in section 2. The total number of observed fields of view is 10. Then, calculate the average diameter of the particles in the 10 fields of view respectively. When the particles are observed to be elliptical, the average value of the major axis length and the minor axis length of the particles is regarded as the diameter of the particles. Then, calculate the arithmetic mean of the average diameters of the particles calculated in the 10 fields of view respectively. Take it as the average diameter of the particles contained in the titanium material. It should be noted that when the average diameter of the particles is calculated by observing with a scanning electron microscope, particles with a diameter less than 100nm are excluded from the observation object. When the particles are observed to be elliptical, particles with a major axis length less than 100nm are excluded from the observation object.

[0188] The particles were also subjected to point analysis using EDS equipped with a scanning electron microscope. On this basis, XRD (X-ray diffraction) analysis was also performed. The conditions for X-ray diffraction were as follows.

[0189] Characteristic X-ray: CoKα ray

[0190] Voltage: 30kV

[0191] Current: 100mA

[0192] ·Measurement range: 10°≤2θ≤110°

[0193] Step length: 0.04°

[0194] ·Determination method: θ-2θ method

[0195] Based on the position of the X-ray diffraction peak, the α phase, β phase, and Ti 2 C and TiC. Phases with diffraction peak intensity equal to or weaker than the background were considered undetected.

[0196] Particles satisfying the following two conditions are regarded as compound particles containing titanium and carbon.

[0197] (1) As a result of point analysis using SEM-EDS, both Ti and C were detected.

[0198] (2) The results of XRD analysis showed that TiC and Ti 2 One or both of C.

[0199] When it is confirmed that all particles visually recognized in the above SEM observation contain both Ti and C, the average diameter of the particles calculated by the above SEM observation is regarded as the average diameter of the compound particles containing Ti and C. When part or all of the particles visually recognized in the above SEM observation do not contain one or both of Ti and C, the average diameter is measured again only for the particles containing both Ti and C.

[0200] In TEM observation, two observation planes are first determined. The two cross sections are an arbitrary cross section parallel to the plate thickness direction of the titanium material (cross section 1) and a cross section parallel to the plate thickness direction of the titanium material and perpendicular to the cross section 1 (cross section 2).

[0201] Samples were collected from cross sections 1 and 2 by FIB processing and used for TEM observation. The samples were observed with a transmission electron microscope at magnifications of 5000, 20000, 50000, 100000, and 300000, and the average diameter was determined at a magnification that allowed pixels containing 5 or more and 20 or less particles to be obtained in the observation field.

[0202] Observe 5 fields of view in section 1 and 5 fields of view in section 2 at the adopted magnification. The total number of observed fields of view is 10. Then, calculate the average diameter of the particles in the 10 fields of view respectively. When the particles are observed to be elliptical, the average value of the major axis length and the minor axis length of the particles is regarded as the diameter of the particles. Then, calculate the arithmetic mean of the average diameters of the particles calculated in the 10 fields of view respectively. Take it as the average diameter of the particles contained in the titanium material. It should be noted that when the average diameter of the particles is calculated by observation using a transmission electron microscope, particles with a diameter less than 1nm are excluded from the observation object. When the particles are observed to be elliptical, particles with a major axis length less than 1nm are excluded from the observation object.

[0203] It should be noted that the particles were also subjected to point analysis using EDS equipped with a transmission electron microscope, and XRD analysis was also performed under the above conditions. Particles that satisfy the following two conditions are considered to be compound particles containing titanium and carbon.

[0204] (1) As a result of point analysis using TEM-EDS, both Ti and C were detected.

[0205] (2) The results of XRD analysis showed that TiC and Ti 2 One or both of C.

[0206] According to this confirmation operation, it can be determined whether the particles contain Ti and C. When it is confirmed that all the particles visually identified in the above TEM observation contain both Ti and C, the average diameter of the particles calculated by the above TEM observation is regarded as the average diameter of the compound particles containing Ti and C. When part or all of the particles visually identified in the above TEM observation do not contain one or both of Ti and C, only the particles containing both Ti and C are taken as the object and the average diameter is measured again. On this basis, it can also be confirmed that the crystal structure has carbide by the electron beam diffraction pattern or the fast Fourier transform pattern of the transmission electron microscope.

[0207] <Method for specifying A value>

[0208] The A value is determined by X-ray diffraction of Ti 2 The integrated intensities of the diffraction peaks of C and TiC were calculated.

[0209] An example of a method for calculating the A value is described below. TiC uses five diffraction planes: (111)(200)(220)(311)(222). 2 The five diffraction surfaces (111)(222)(400)(440)(620) in C are made of Ti 2C (222). It should be noted that the values ​​in parentheses are the Miller indices (hkl) of the crystal. The A value is calculated according to Formula 3, Formula 4, and Formula 5 using the measured integrated intensity in the 2θ range and the following coefficients.

[0210] [Table 3]

[0211] Miller Index <![CDATA[R TiC(hkl) ]]> <![CDATA[R Ti2C ( hkl )]]> (111) 0.94 (200) 1.00 (220) 0.46 (311) 0.22 (222) 0.14 (111) 0.12 (222) 1.00 (400) 0.70 (440) 0.33 (620) 0.22

[0212] First, substitute the integrated intensity and coefficient of the diffraction surface into the following formula to calculate I TiC and I Ti2C .

[0213] [Mathematical formula 3]

[0214] I TiC ={∑(I TiC(hkl) / R TiC(hkl) )} / n

[0215] Among them, I TiC(hkl) is the measured integrated intensity, R TiC(hkl) is the above coefficient, n=5.

[0216] [Formula 4]

[0217] I Ti2C ={∑(I Ti2C(hkl) / R Ti2C(hkl)} / n

[0218] Among them, I Ti2C(hkl) is the measured integrated intensity, R Ti2C(hkl) is the above coefficient, n=5.

[0219] Next, using the calculated I TiC and I Ti2C , calculate the A value according to the following formula.

[0220] [Formula 5]

[0221] A=I Ti2C / (1.3I TiC +I Ti2C )

[0222] <Ti 3 C 2 How to determine >

[0223] Ti 3 C 2The presence or absence is confirmed by XPS. The X-ray used is set to Al Kα ray. The diameter of the analysis area is set to 10μmφ. First, the measurement sample is sputtered to a depth of 20nm. This removes surface contamination and oxides of the measurement sample. Next, a narrow scan spectral analysis is performed on the measurement sample in the range of 280.00 to 284.00eV. The narrow scan is performed with a measurement interval with a binding energy of less than 0.05eV. The number of measurements at each measurement point is 3 times, and the average data of the 3 measurements is calculated. The spectral intensities of 282.00eV and 281.50eV in the calculated data are used as the judgment of Ti 3 C 2 Specifically, (spectral intensity at 282.00 eV) / (spectral intensity at 281.50 eV) is used as the criterion for judging the presence or absence of Ti. 3 C 2 The unit of the spectrum intensity is counts / second. When the average value of (spectrum intensity at 282.00 eV) / (spectrum intensity at 281.50 eV) measured at three locations is 0.60 or more, it is judged that the titanium material contains Ti. 3 C 2 .

[0224] (3. An Example of a Method for Manufacturing a Titanium Material According to the Embodiment)

[0225] Next, a preferred manufacturing method of the titanium material involved in the present embodiment is described. According to the manufacturing method, a titanium material having the above-mentioned characteristics can be obtained. However, in the titanium material involved in the present embodiment, its manufacturing method is not particularly limited. Even if the titanium material is obtained under manufacturing conditions different from those described below, as long as its chemical composition and the average diameter of the compound particles containing titanium and carbon are within the above range, it is the titanium material involved in the present embodiment. In the following description, "s" means seconds.

[0226] An example of a preferred method for producing a titanium material according to the present embodiment includes the following steps:

[0227] (S1) a step of melting an ingot, a slab, a billet, or a bloom having the same chemical composition as the titanium material according to the present embodiment;

[0228] (S2) a process of performing initial rolling or hot forging on the ingot, slab, billet or bloom to obtain a semi-finished product;

[0229] (S3) a step of hot-processing the semi-finished product obtained in the above step S2 to obtain a hot-processed material;

[0230] (S4) performing intermediate annealing on the hot-worked material as required;

[0231] (S5) a step of cold working the hot worked material to obtain a cold worked material; and

[0232] (S6) A step of performing additional annealing on the cold-worked material.

[0233] In the case where the shape of the ingot, slab, billet or bloom does not hinder the implementation of (S3), the step of performing initial rolling or hot forging on the ingot, slab, billet or bloom described in (S2) may also be omitted. Steps S5 and S6 may be repeated multiple times. Steps S3 to S6 are performed under the conditions shown in the following table. Before and after these steps, surface finishing by grinding and cutting may also be performed. Before and after these steps, sandblasting and pickling treatment may also be performed as needed.

[0234] (Smelting S1)

[0235] (initial rolling or hot forging S2)

[0236] First, ingots or slabs within the above-mentioned composition range are melted. Billets or blooms may also be melted as needed. The melting method is not particularly limited. Various known melting methods such as vacuum arc melting, electron beam melting, and plasma melting may be used. Next, the ingot or slab is subjected to initial rolling or hot forging. In the case where the shape of the ingot or slab or billet or bloom does not hinder the implementation of hot working (S3), initial rolling and hot forging may be omitted. The method of initial rolling or hot forging is not particularly limited. Surface finishing by grinding and cutting may also be performed before and after these steps.

[0237] (Hot working S3)

[0238] The semi-finished product or ingot or slab or billet or bloom of initial rolling or hot forging is hot worked to obtain a hot rolled material. The hot working temperature and the hot working rate are not particularly limited. On the other hand, by properly controlling the cooling rate after hot working, a state in which the titanium material at the mid-stage of manufacturing contains fewer compound particles of titanium and carbon can be obtained. By forming a state in which the compound particles containing titanium and carbon are fewer at the mid-stage of manufacturing, it is easy to increase the compound particles containing titanium and carbon in the final product, which is desirable. Specifically, in order to be in this state, the cooling rate of the hot rolled material after hot working is set to be above 0.1°C / sec.

[0239] (Intermediate annealing S4)

[0240] By performing intermediate annealing on the hot-rolled material after hot working instead of limiting the cooling rate after hot working, it is also possible to achieve a state in which there are fewer compound particles containing titanium and carbon in the middle stage of manufacturing. When intermediate annealing is performed after hot working, the intermediate annealing is performed in the range of 600 to 850°C. Intermediate annealing can also be performed under normal conditions of the average heating rate, holding time, and cooling rate in the annealing after hot working. On the other hand, the holding time can be maintained for more than 10 seconds within the range of 600 to 850°C. It can be performed at an average heating rate of more than 0.1°C / s and less than 100°C / s, and a cooling rate of more than 1°C / s and less than 100°C / s. In particular, in order to increase Ti 3 C 2 It is effective to set the holding time in the intermediate annealing after hot working to 50s or more. It should be noted that the average heating rate in the intermediate annealing refers to the value obtained by dividing the difference between room temperature and the holding temperature by the time required for heating from room temperature to the holding temperature.

[0241] (Cold Working S5)

[0242] Next, the hot-worked material or the hot-worked material subjected to intermediate annealing is cold-worked to obtain a cold-worked material having a final desired shape. In the cold working, the degree of cold working is set to 10% or more. The technical significance of the degree of cold working is described below.

[0243] It should be noted that the "cold working degree" refers to the working degree calculated based on the change rate of the size of the titanium material after cold working and final heat treatment relative to the size of the hot-worked material or the hot-worked material subjected to intermediate annealing. That is, the cold working degree refers to the total working degree from the end of hot working S3 or the end of intermediate annealing S4 after hot working to the end of additional annealing S6 described later. Cold working performed for shape correction after the end of additional annealing S6 is not included in the working degree of cold working.

[0244] (Additional annealing S6)

[0245] For cold-worked materials, for example Figure 5 Additional annealing of any of the thermal curves of the four modes A, B, C1 and C2 shown. Mode A includes heat treatment II performed at a high temperature. Modes B, C1 and C2 include heat treatment I performed at a low temperature and heat treatment II performed at a high temperature. Through these heat treatments, a titanium material that satisfies the above-mentioned metallographic structure can be obtained. First, heat treatment I and heat treatment II are described, and then their combined modes A, B, C1 and C2 are described. However, the heat treatment mode shown below is only a preferred example of the manufacturing method of the titanium material involved in this embodiment. Even if the titanium material is obtained by a method other than the heat treatment mode shown below, as long as the above-mentioned requirements are met, it can be regarded as the titanium material involved in this embodiment.

[0246] <Heat Treatment I>

[0247] In the heat treatment I, the residence time or holding time at 200 to 590° C. is prolonged to form compound particles containing titanium and carbon having an average diameter of 400 nm or less.

[0248] <Heat Treatment II>

[0249] In the heat treatment II, additional annealing is performed in a temperature range of 600 to 850° C. The cooling rate after the heat treatment II is not particularly limited. The cooling rate after the heat treatment II is 0.001° C. / s or more. More preferably, it is 0.005° C. / s or more and 100° C. / s or less.

[0250] It should be noted that, in the case of heat treatment I, the average heating rate before heat treatment II is not limited. However, in the case of not performing heat treatment I, that is, in the case of heat treatment of mode A described later, it is preferred that the average heating rate between 200 and 590°C, which is at least equivalent to heat treatment I, is 1°C / s or less. The average heating rate between 200 and 590°C is further preferably 0.001°C / s or more and 0.800°C / s or less. It should be noted that the average heating rate in mode A refers to the value obtained by dividing the difference between 200°C and 590°C by the time required to heat from 200°C to 590°C. When the holding temperature is lower than 590°C, the average heating rate is the value obtained by dividing the difference between 200°C and the holding temperature by the time required to heat from 200°C to the holding temperature.

[0251] The key points of these thermal curves are as follows:

[0252] (1) Ti is formed by adjusting the average heating rate in mode A or maintaining the heat treatment I in modes B and C at a relatively low temperature. 2 C or Ti 3 C 2 ;

[0253] (2) Recrystallization of α by subsequent heat treatment II.

[0254] It should be noted that in this embodiment, once Ti is formed 2 C and Ti 3 C 2 , from Ti 2 C to TiC or from Ti 3 C 2 The phase transformation to TiC is slow. 2 C or Ti 3 C 2 It will not completely transform into TiC due to heat treatment II.

[0255] The average temperature increase rate and holding time of heat treatment I and heat treatment II differ depending on the heat history model adopted. The following is an explanation of each condition.

[0256] <<Mode A>>

[0257] Pattern A is a thermal curve in which heat treatment I is omitted and the average heating rate before the holding temperature of heat treatment II is slowed down. It should be noted that the average heating rate in pattern A is the value obtained by dividing the difference between 200°C and 590°C by the time required to heat from 200°C to 590°C.

[0258] When heat treatment is performed in mode A after cold working, the average heating rate of heat treatment II (maintaining the lower limit temperature of 600°C and the upper limit temperature of 850°C) at 200 to 590°C is set to 1°C / s or less, and the holding time is set to 10 seconds or more. It is more preferred that the holding time of heat treatment II in mode A is 30 seconds or more.

[0259] Figure 4 The upper part of FIG. 1 shows an example of a heat treatment mode according to mode A. In mode A, heat treatment I is omitted. By slowing down the average heating rate in heat treatment II, the residence time at 200 to 590°C is extended. Therefore, the key point of the heat treatment in mode A is to form compound particles containing titanium and carbon with an average diameter of less than 400nm, and TiC and Ti in the compound particles containing titanium and carbon are separated. 2 The index value of the ratio of C is 0.10 or more. The reaching temperature after heating in the heat treatment II of mode A is set to 600-850°C. By maintaining at this temperature, the following metallographic structure can be obtained: comprising grains composed of α phase (hereinafter referred to as α grains) and compound particles containing titanium and carbon formed with an average diameter of 400nm or less, and the A value is 0.10 or more.

[0260] In mode A, when the average heating rate at 200 to 590°C is too fast before the holding temperature of heat treatment II is reached, the residence time in the same temperature range becomes shorter, and Ti 2 C or Ti 3 C 2 It cannot be fully formed and does not meet the A value. In addition, when the average heating rate at 200 to 590°C before the holding temperature of heat treatment II is reached is too fast, the Ti 2 C or Ti 3 C 2 TiC is formed and grows in the stage where it has not yet been formed, and the average diameter of the compound particles containing titanium and carbon increases.

[0261] In mode A, if the holding time of heat treatment II is too short, the recrystallization of α is insufficient. Therefore, the average heating rate at 200 to 590°C before the holding temperature of heat treatment II is reached is slowed down to less than 1°C / s, and the holding time of heat treatment II is set to more than 10s.

[0262] In mode A, the processing rate in the cold working before the additional annealing is set to 10% or more. The processing rate is more preferably 15% or more. 2 C and Ti 3 C 2 The increase in the number of particles.

[0263] <<Mode B>>

[0264] Pattern B is a thermal curve in which heat treatment I and heat treatment II are performed continuously. When heat treatment is performed by pattern B after cold working, the holding time in heat treatment I (maintaining the lower limit temperature at 200°C and the upper limit temperature at 590°C) is set to 100 seconds or more, and the holding time in heat treatment II (maintaining the lower limit temperature at 600°C and the upper limit temperature at 850°C) is set to 10 seconds or more.

[0265] exist Figure 4 In the heat curve of mode B shown in the middle of the example, two stages of heat treatment are performed. In the first stage of heat treatment (heat treatment I) of mode B, the temperature is maintained in the range of 200 to 590°C. As a result, compound particles containing titanium and carbon with an average diameter of less than 400nm are formed, and TiC and Ti in the compound particles containing titanium and carbon are further separated. 2 The index value of the ratio of C is 0.10 or more.

[0266] Then, the second stage heat treatment (heat treatment II) is continuously performed. In heat treatment II in mode B, the temperature is maintained in the range of 600°C to 850°C to eliminate the strain and non-recrystallized grains remaining after heat treatment I.

[0267] By performing such two-step heat treatment, a metallographic structure including α grains and compound particles containing titanium and carbon having an average diameter of 400 nm or less and an A value of 0.10 or more can be obtained.

[0268] When the holding time in the heat treatment I of mode B is too short, Ti 2 C and Ti 3 C 2 The holding time in heat treatment I is preferably 300 s or more, more preferably 1000 s or more. In addition, the holding time in heat treatment II of mode B is set to 1 s or more. It is preferably 30 s or more, more preferably 1000 s or more.

[0269] <<Mode C1, Mode C2>>

[0270] In the case of heat treatment by mode C after cold working, the titanium alloy of the present embodiment can be manufactured by two manufacturing condition ranges illustrated. These two modes are subdivided into mode C1 and mode C2. In either case, both heat treatment I and heat treatment II are performed, similar to mode B. However, unlike mode B in which the heat treatment I is heated again after completion, in modes C1 and C2, the titanium material is temporarily cooled after completion of heat treatment I and then heated again.

[0271] exist Figure 4 In mode C (i.e., modes C1 and C2) illustrated in the lower part of , unlike mode B, cooling is performed after the first stage heat treatment (heat treatment I), and then the second stage heat treatment (heat treatment II) is performed. Between heat treatment I and heat treatment II, not only cooling but also cold rolling and other processing can be performed. In mode C1, the holding temperature of heat treatment I is in the range of 200 to 590°C, and the holding temperature of heat treatment II is in the range of 600 to 850°C. The holding temperature of heat treatment II in mode C2 is in the range of 600 to 850°C, and the temperature range of heat treatment I is not particularly limited. Through the heat treatment of mode C, compound particles containing titanium and carbon having an average diameter of less than 400nm can be formed, as in mode B, and the TiC and TiC in the compound particles containing titanium and carbon are 2 The index value of the ratio of C is 0.10 or more.

[0272] It should be noted that, according to the treatment performed between heat treatment I and heat treatment II, the average diameter of the compound particles containing titanium and carbon can be made smaller than that of mode A and mode B, and the TiC and TiC in the compound particles containing titanium and carbon can be made smaller. 2 The index value of the ratio of C is larger. 3 C 2 It can be formed by any of the heat treatment modes A to C, but in order to form more Ti 3 C 2 , it is effective to implement heat treatment by mode C and to perform cold working immediately before the final heat treatment.

[0273] For example, when a set of pattern C processes is performed, heat treatment II is the final heat treatment. Therefore, it is effective to perform cold working between heat treatment I and heat treatment II. If the cold working degree before the final heat treatment is too large, it will promote the removal of Ti. 3 C 2 Therefore, the cold working degree before the final heat treatment is preferably 70% or less.

[0274] When heat treatment is performed by mode C1, the holding time in heat treatment I (maintaining the lower limit temperature at 200°C and the upper limit temperature at 590°C) is set to 100 seconds or more, and the holding time in heat treatment II (maintaining the lower limit temperature at 600°C and the upper limit temperature at 850°C) is set to 10 seconds or more. When heat treatment is performed by mode C1, it is not necessary to limit the average temperature increase rate before the holding temperature of heat treatment I is reached and the average temperature increase rate before the holding temperature of heat treatment II is reached.

[0275] When heat treatment is performed by mode C2, the holding time in heat treatment I is set to 30 seconds or more, the average heating rate between 200 and 590°C (200 to the holding temperature when the holding temperature is lower than 590°C) before the holding temperature of heat treatment II is reached is set to 1°C / s or less, and the holding time in heat treatment II is set to 10 seconds or more. When heat treatment is performed by mode C2, the average heating rate before the holding temperature of heat treatment I is reached does not need to be limited.

[0276] For example, as manufacturing equipment for implementing the manufacturing method of the titanium material involved in the present embodiment, mode A and mode B are methods using an intermittent annealing furnace, and mode C (both C1 and C2) is a method using a continuous annealing furnace in more than one heat treatment. In C1, continuous annealing is used for both heat treatment I and heat treatment II. In C2, only a continuous annealing furnace is used for heat treatment I, and an intermittent annealing furnace is used for heat treatment II. In mode C1, cooling and cold rolling are not necessary after heat treatment I (before heat treatment II). Both mode C1 and mode C2 can implement cold rolling after heat treatment I (before heat treatment II), or they may not implement cold rolling.

[0277] The difference between mode C1 and mode C2 lies in the holding time of heat treatment I and the average temperature increase rate before the holding temperature of heat treatment II is reached.

[0278] In mode C1, the holding time of heat treatment I is longer than that of mode C2. On the other hand, in mode C1, the average heating rate of heat treatment II is not limited. Mode C1 is to form Ti by simultaneously holding heat treatment I and heating up before the holding temperature of heat treatment II is reached. 2 Conditions of C can shorten the holding time of heat treatment I. Therefore, the holding time of heat treatment I may be 30 seconds or longer. That is, according to mode C1, the time required for manufacturing the titanium material can be shortened.

[0279] In mode C2, the holding time of heat treatment I is shorter than that of mode C1. In addition, in mode C2, the average heating rate before the holding temperature of heat treatment II is reached is maintained at less than 1°C / s. Mode C2 is to form Ti during the holding of heat treatment I. 2 C and Ti 3 C 2And Ti is also formed during the heating process of heat treatment II 2 C and Ti 3 C 2 Therefore, the time of the heat treatment I in mode C2 can be shorter than that in mode C1.

[0280] In addition, when performing heat treatment in two steps as in Mode B and Mode C, heat treatment I to heat treatment II are counted as one set, and this may be repeated in a plurality of sets.

[0281] It should be noted that the cooling rate after heat treatment I and heat treatment II in modes A, B, and C is not limited, and the heat treatment atmosphere is not limited. 2 、N 2 With H 2 Annealing can be carried out in an atmosphere of a mixed gas or the like.

[0282] In addition, after the additional annealing of Modes A, B, and C, the titanium material may be descaled and corrected in shape using a tension leveler, etc., as required. However, as mentioned above, the processing rate in the cold working after the additional annealing is not included in the cold working rate of the above-mentioned cold working process.

[0283] Through the method described above, the average diameter of the compound particles containing titanium and carbon in the titanium material of this embodiment is controlled to be below 400nm, which can improve ductility, processability, strength-ductility balance, corrosion resistance, local corrosion resistance, and stress corrosion cracking resistance.

[0284] (4. Chemical device component and chemical device according to the present embodiment)

[0285] A chemical device component and a chemical device according to an embodiment of the present invention will be described.

[0286] The present inventors have found that the titanium material of the present embodiment achieves low interface contact resistance, low hydrogen overvoltage, and low oxygen overvoltage, and therefore has excellent energy efficiency as a constituent material of a chemical device component or a chemical device. Therefore, the chemical device component of the present embodiment includes the titanium material of the present embodiment. The chemical device of the present embodiment includes the chemical device component of the present embodiment. However, of course, not all chemical device components and chemical devices need to be manufactured from titanium materials having the above characteristics.

[0287] In the following, bipolar plates, gas diffusion layers, and electrodes are used as chemical device components, and PEM (Proton Exchange Membrane) electrolyzer is used as a chemical device. However, the following description does not limit the use of the titanium material of this embodiment and the use of the chemical device components. In addition, the following description does not limit the chemical device involved in this embodiment to a specific chemical device.

[0288] A PEM electrolyser is a chemical device that produces hydrogen at the cathode and oxygen at the anode.

[0289] The bipolar plate, also known as the separator, is a component that separates the electrolyte in the electrolytic cell. The bipolar plate also serves to form a flow path for the generated hydrogen and oxygen. In addition to high sulfuric acid corrosion resistance, the bipolar plate also requires low interfacial contact resistance. The gas diffusion layer is a component used to effectively separate the generated hydrogen and oxygen from the electrode. In addition to high sulfuric acid corrosion resistance, it also requires low interfacial contact resistance. The components that generate hydrogen and oxygen are also called electrodes and current collectors. In addition to high sulfuric acid corrosion resistance, they also require low interfacial contact resistance, low hydrogen overvoltage, and low oxygen overvoltage.

[0290] In order to make the bipolar plates, gas diffusion layers and electrodes exert these characteristics, coatings containing Pt and Ir have been used in the past. On the other hand, by using the titanium material of this embodiment as the constituent material of the bipolar plates, gas diffusion layers and electrodes, low interface contact resistance, low hydrogen overvoltage and low oxygen overvoltage can be achieved without coatings containing Pt and Ir.

[0291] The bipolar plate is formed into a shape suitable for forming a flow path for hydrogen and oxygen. In the chemical device component according to the present embodiment, the forming method is not limited. For example, the bipolar plate can be formed by mechanical pressing, hydraulic forming, etc.

[0292] The gas diffusion layer needs to effectively diffuse the generated gas, and therefore requires pores or spaces having the same function. In the chemical device component involved in this embodiment, the method of forming the pores or spaces is not limited. For example, the gas diffusion layer can be formed by a method of forming a titanium material into a mesh shape by lath processing or laser processing and combining them; or a method of forming a titanium material into a fiber shape by a coil cutting method, etc., and sintering the titanium fiber to form a porous body.

[0293] It should be noted that, when a porous body is formed by sintering titanium fibers, any of the treatments in Modes A, B, and C described in the preferred method for manufacturing the titanium material according to the present embodiment may be performed as a treatment during the formation of the sintered body. Thus, a porous body can be formed from the titanium material having compound particles containing titanium and carbon according to the present embodiment.

[0294] The electrode is similar to the gas diffusion layer, and can be made by, for example, processing titanium into a mesh by lath processing or laser processing. It should be noted that the electrode can also be combined with an ion exchange membrane to form a MEA (Membrane Electrode Assembly) or a zero-gap electrode.

[0295] Example

[0296] The present invention is further specifically described with reference to the following examples. The present invention is not limited to the following examples, and can be implemented with appropriate modifications within the scope of the present invention, and such modifications are also included in the technical scope of the present invention.

[0297] Titanium ingots with chemical compositions shown in Tables 4A, 4B, 4C and 4D were cast by electron beam melting using titanium sponge, scrap and smelting raw materials containing specified additive elements. It should be noted that in Table 1, the symbol "-" indicates the content of elements not intentionally added to the titanium ingot.

[0298] [Table 4A]

[0299]

[0300] [Table 4B]

[0301]

[0302] [Table 4C]

[0303]

[0304] [Table 4D]

[0305]

[0306] After the cast titanium ingot is heated at a heating temperature of 750°C to 1000°C, it is forged and hot rolled to obtain a hot rolled plate with a thickness of 5.0 mm. After the hot rolled plate is descaled, intermediate plate annealing (hot rolled plate annealing), cold rolling and additional annealing are performed under the conditions shown in Table 5A, Table 5B and Table 5C. It should be noted that the additional annealing is performed in an Ar atmosphere. It should be noted that the manufacturing conditions not disclosed in the table are as follows.

[0307] Cooling temperature control after hot rolling: None

[0308] Average heating rate from room temperature to the holding temperature of intermediate annealing (hot rolled sheet annealing): 0.1°C / s or more and 100°C / s or less

[0309] ·Intermediate annealing (hot rolled sheet annealing) holding time: more than 10s

[0310] · Cooling rate after holding of intermediate annealing (hot rolled sheet annealing): 0.1°C / s or more and 50°C / s or less

[0311] [Table 5A]

[0312]

[0313] [Table 5B]

[0314]

[0315] It should be noted that in Nos. 32, 34 to 37, and 64 in Table 5B, cold working was performed between the heat treatment I and the heat treatment II.

[0316] [Table 5C]

[0317]

[0318] Test pieces were made from the produced titanium plates, and metallographic structure, workability, ductility, strength-ductility balance, corrosion resistance, localized corrosion resistance, stress corrosion cracking resistance, interface contact resistance, hydrogen overvoltage, and oxygen overvoltage were investigated.

[0319] The metallographic structure investigation refers to the investigations 1 to 5 listed below.

[0320] 1. Determination of the average diameter of particles containing titanium and carbon

[0321] 2. Determination of A value

[0322] 3. Confirm Ti 3 C 2 The presence or absence

[0323] 4. Determination of maximum particle diameter

[0324] 5. Ratio of the X-ray peak integrated intensity of the compound particles containing titanium and carbon to the X-ray peak integrated intensity of the α phase

[0325] Survey 1, Survey 2, and Survey 3 were conducted by the above-mentioned method. The methods of Survey 4 and Survey 5 are described below.

[0326] The maximum particle diameter of the compound particles containing titanium and carbon is measured by observing the cross section of the titanium material using SEM and TEM. The data used differs depending on the size of the maximum particle diameter of the compound particles containing titanium and carbon.

[0327] First, the average diameter of the compound particles containing titanium and carbon was measured using SEM. When the maximum diameter of the compound particles containing titanium and carbon was 400 nm or more as a result of SEM observation, the SEM data was used. When the average diameter of the compound particles containing titanium and carbon obtained using SEM was less than 400 nm, a further measurement using TEM was performed, and the TEM data was used.

[0328] In SEM observation, two observation planes are first determined. The two cross sections are set as an arbitrary cross section parallel to the plate thickness direction of the titanium material (cross section 1) and a cross section (cross section 2) that satisfies the relationship of being parallel to the plate thickness direction of the titanium material and perpendicular to cross section 1. For example, when cross section 1 is the L cross section of the titanium material, cross section 2 is the T cross section of the titanium material. The L cross section is a cross section parallel to the rolling direction of the titanium material and perpendicular to the rolling surface, and the T cross section is a cross section perpendicular to the rolling direction of the titanium material and perpendicular to the rolling surface.

[0329] Section 1 and section 2 are mirror-polished. Then, the cross section is further polished with a liquid containing colloidal silica as a grinding liquid. The surface thus obtained is subjected to SEM observation. These cross sections are observed with a scanning electron microscope at magnifications of 100 times, 500 times, 1000 times, 3000 times, 5000 times and 10000 times. Then, the maximum particle diameter is determined by the magnification at which an image containing more than 5 and less than 20 particles can be obtained in the observation field. If particles containing more than 5 and less than 20 are observed at two or more magnifications, the observation result at a lower magnification is adopted.

[0330] Five fields of view are observed in section 1 and five fields of view are also observed in section 2 at the adopted magnification. The total number of observed fields of view is 10 fields of view. Then, the maximum particle diameter in each of the 10 fields of view is calculated. When the particle is observed to be elliptical, the arithmetic mean of the length of the major axis diameter and the length of the minor axis diameter of the particle is regarded as the diameter of the particle.

[0331] The largest value among the 10 calculated maximum particle diameters was used as the maximum particle diameter. When the measured value of the maximum particle diameter was 400 nm or more, the data obtained by SEM observation was used.

[0332] The particles were also subjected to point analysis using EDS equipped with a scanning electron microscope. Particles containing both Ti and C were detected and were considered to be compound particles containing titanium and carbon.

[0333] In TEM observation, two observation planes are also determined first. The two cross sections are set as the above-mentioned arbitrary cross section (cross section 1) parallel to the thickness direction of the titanium material and the cross section (cross section 2) that satisfies the relationship parallel to the thickness direction of the titanium material and perpendicular to cross section 1. Samples are collected from cross section 1 and cross section 2 by FIB processing and used for TEM observation. Observe with a transmission electron microscope at magnifications of 1000 times, 5000 times, 20000 times, 50000 times, 100000 times, and 300000 times. The maximum particle diameter is determined by the magnification at which an image containing more than 5 and less than 20 particles can be obtained in the observation field. If particles containing more than 5 and less than 20 particles are observed at more than two magnifications, the observation results at a lower magnification are used.

[0334] Five fields of view are observed in the cross section 1 at the adopted magnification, and five fields of view are also observed in the cross section 2. The total number of observed fields of view is 10 fields of view. Then, the maximum particle diameter of the particles in the 10 fields of view is calculated respectively. When the particles are observed to be elliptical, the arithmetic mean of the length of the major axis diameter and the length of the minor axis diameter of the particles is regarded as the diameter of the particles.

[0335] Then, the largest value among the 10 largest particle diameters calculated in the 10 fields of view was used as the maximum particle diameter. When the maximum particle diameter was less than 400 nm, TEM data was used.

[0336] The particles were also subjected to point analysis using EDS equipped with a transmission electron microscope. Particles in which both Ti and C were detected were considered to be compound particles containing titanium and carbon. On this basis, the particles can also be confirmed to have a carbide crystal structure through the electron beam diffraction pattern or fast Fourier transform pattern of the transmission electron microscope.

[0337] The ratio of the integrated intensity of the X-ray diffraction peak of the compound particles containing titanium and carbon to the integrated intensity of the X-ray diffraction peak of the α phase is calculated by the following method.

[0338] First, the Ti 2 The integrated intensity of the diffraction peaks of C, TiC and α phase was measured. From the measured integrated intensity of the X-ray diffraction peaks, five diffraction planes corresponding to each crystal structure were selected. Specifically, five diffraction planes (111)(200)(220)(311)(222) were selected for TiC, 2Select 5 diffraction planes of (111)(222)(400)(440)(620) in C, and select 5 diffraction planes of (002)(101)(102)(110)(103) in α phase. It should be noted that the values ​​in brackets are the Miller indices (hkl) of the crystal. The integrated intensities of these X-ray diffraction peaks are added and divided by the following formula to calculate the ratio of the integrated intensity of the X-ray diffraction peaks of the compound particles containing titanium and carbon to the integrated intensity of the X-ray diffraction peaks of the α phase, i.e., the B value. It should be noted that when no diffraction peaks corresponding to the above-mentioned Miller indices are observed, zero is substituted into each term of Formula 6 to calculate the B value.

[0339] [Mathematical formula 6]

[0340] B=(1.3I TiC +I Ti2C ) / I α

[0341] I TiC ={∑(I TiC(hkl) / R TiC(hkl ))} / n

[0342] I Ti2C ={∑(I Ti2C(hkl) / R Ti2C(hkl) )} / n

[0343] I α ={∑(I α(hkl) / R α(hkl) )} / n

[0344] Among them, I TiC is a representative value of the integrated intensity of TiC, which is one of the compound particles containing titanium and carbon, and I Ti2C It's Ti 2 The representative value of the integrated intensity of C, Ti 2 C is one of the compound particles comprising titanium and carbon, α It is the representative value of the integrated intensity of the α phase. TiC(hkl) is the integrated intensity measured at each Miller index of the TiC, I Ti2C(hkl) It is the Ti 2 The integrated intensity measured at each Miller index of C, I α is the integrated intensity measured at the α phase. R TiC(hkl) is the coefficient corresponding to each Miller index of TiC, R Ti2C(hkl) is related to the Ti 2 The coefficients corresponding to each Miller index of C, R α(hkl) is the coefficient corresponding to each Miller index of the α phase. n is 5. R TiC(hkl) , R Ti2C(hkl) and Rα(hkl) The corresponding relationship with each Miller index is as follows.

[0345] [Table 6]

[0346] Miller Index <![CDATA[R TiC(hkl) ]]> <![CDATA[R Ti2C(hkl) ]]> <![CDATA[R α(hkl) ]]> (111) 0.94 (200) 1.00 (220) 0.46 (311) 0.22 (222) 0.14 (111) 0.12 (222) 1.00 (400) 0.70 (440) 0.33 (620) 0.22 (002) 0.36 (101) 0.99 (102) 0.22 (110) 0.22 (103) 0.21

[0347] The workability of the test piece was tested according to the press bending method described in JIS Z 2248:2014 "Methods for bending test of metal materials". The bending angle was set to 105° for the test. The appearance of the test piece after the bending test was observed with the naked eye, and the test piece without cracks and other defects was judged as good workability. The test piece with cracks and other defects was judged as poor workability.

[0348] Ductility and strength-ductility balance are evaluated by performing a tensile test in accordance with JIS Z 2241:2011 "Methods for tensile testing of metallic materials". According to the tensile test, the tensile strength (TS) and the elongation at break (EL%) are measured. The elongation at break is measured by butting the broken test pieces together. The elongation at break is used as an indicator of ductility. The product of the tensile strength and the elongation at break is used as an indicator of the strength-ductility balance. In the tensile test conducted in this embodiment, the shape of the test piece is JIS 13B, and the strain rate after the yield strength measurement is controlled to (0.002±0.0004)s by the crosshead displacement. -1 .

[0349] Titanium materials having a tensile strength (TS) and elongation at break (EL%) of 15,000 MPa·% or more are evaluated as having an excellent balance between strength and ductility. It should be noted that the product of tensile strength (TS) and elongation at break (EL%) is more preferably 16,000 MPa·% or more, 17,000 MPa·% or more, 18,000 MPa·% or more, or 19,000 MPa·% or more.

[0350] The corrosion resistance of the test piece was evaluated by both the sulfuric acid immersion test and the hydrochloric acid immersion test. For one example, two test pieces were prepared, one of which was immersed in a 2 mass % hydrochloric acid aqueous solution and the other was immersed in a 4 mass % sulfuric acid aqueous solution. In all tests, the aqueous solution temperature was set to 80°C and the immersion time was set to 240h. The weight of the test piece was measured immediately before and after the immersion test. Then, the corrosion rate was calculated based on the following formula.

[0351] (Weight loss from corrosion (g)) = (Weight before test (g)) - (Weight after test (g))

[0352] (Corrosion rate (mm / year)) = 36.5 × 10 × (Corrosion weight loss (g)) ÷ 4.506 ÷ (Test piece surface area (cm2 ))

[0353] It should be noted that "36.5" in the above formula is a coefficient for converting the time unit from day to year, and is a value obtained by the following formula.

[0354] 365 (days) × 24 (hours / day) ÷ test time (hours)

[0355] "10" in the above formula is a coefficient for converting the length unit from cm to mm.

[0356] The "4.506" in the above formula is a coefficient related to weight and volume.

[0357] In both the sulfuric acid immersion test and the hydrochloric acid immersion test, test pieces having a corrosion rate of 0.10 mm / year or less were judged to exhibit sufficient corrosion resistance.

[0358] Localized corrosion resistance was evaluated in two ways.

[0359] The first local corrosion resistance evaluation was performed by observing the surface of the test piece after the above corrosion resistance evaluation test with an electron microscope at a magnification of 50 to 5000 times to confirm the presence or absence of pitting. The test piece with pitting of 20 μm or more in diameter was judged as unqualified for corrosion resistance.

[0360] The second local corrosion resistance evaluation is carried out by the crevice corrosion test method described in ASTM G78-15. In the crevice corrosion test method, a crevice forming fixture is installed on the test piece to form multiple crevice between the test piece and the fixture. Then, the crevice forming fixture is removed after the immersion test to confirm whether there is corrosion in the crevice. The test time is set to 720h, the test temperature is set to 80°C, and the types of test solutions are set to 2 mass% hydrochloric acid aqueous solution and 25% NaCl aqueous solution. The test piece after the test is observed under an optical microscope. Etching at a depth of more than 20μm is judged as crevice corrosion. The test piece where crevice corrosion occurred was evaluated as unqualified for local corrosion resistance. In addition, in the test piece where crevice corrosion occurred, the probability of crevice corrosion was determined based on the ratio of the total number of sites where crevice corrosion was formed to the number of sites where crevice corrosion occurred.

[0361] The stress corrosion cracking resistance was evaluated according to Method A "42% magnesium chloride stress corrosion cracking test method" described in JIS G 0576:2001 "Stress corrosion cracking test method for stainless steel". This evaluation method is for stainless steel, but can also be used as an evaluation method for titanium.

[0362] The U-bending test according to method A was carried out for up to 240 hours, and the macro crack occurrence time was measured. The macro crack occurrence time refers to the time required from the start of the test until the cracks are observed with a magnifying glass. The magnification of the magnifying glass was set to 5 to 15 times. Two test solutions were used. One is a 42% magnesium chloride aqueous solution used in method A of JIS G 0576:2001. The other is a 2 mass % hydrochloric acid aqueous solution. These tests were carried out at a test temperature of 80°C. The macro crack occurrence time is recorded in the table. For samples that did not crack after 240 hours, the macro crack occurrence time was recorded as "more than 240".

[0363] The steps of the method for measuring the interface contact resistance are as follows.

[0364] First, prepare two sheets of 20 mm x 20 mm carbon paper and measure the resistance of each sheet of carbon paper in the following steps. Clamp the top and bottom of a sheet of carbon paper with copper-plated conductors. The contact area between the conductor and the carbon paper is set to 20 mm x 20 mm. A 4.00 A (1.00 A / cm 2 ) current and measure the resistance between the conductors at this time. The resistance values ​​measured on the two pieces of carbon paper are respectively taken as the resistance value 1 (mΩ / cm 2 )、Resistance value 2(mΩ / cm 2 ).

[0365] Next, prepare a disc-shaped test piece with a diameter of 15 mm. Clamp the top and bottom of the test piece with 20 mm × 20 mm carbon paper. After clamping with carbon paper, clamp it with copper-plated conductors. The contact area between the conductor and the carbon paper is set to 20 mm × 20 mm. A current of 1.76 A (1.00 A / cm 2 ) current, and measure the resistance value between the conductors at this time as the resistance value 3 (mΩ / cm 2 ).

[0366] Substitute the measured resistance values ​​1, 2, and 3 into the following formula to calculate the interface contact resistance. Interface contact resistance (mΩ / cm 2 ) = {resistance value 3 - (resistance value 1 + resistance value 2) / 2} / 2

[0367] The steps of the method for determining hydrogen overvoltage are as follows.

[0368] A 0.5 M sulfuric acid aqueous solution was flowed through the test piece at 80°C. 2 The cathode current is 5 minutes, and the potential is measured. The test piece is a disc with a diameter of 15 mm. The test area is 1 cm 2 The reference electrode is a saturated silver / silver chloride electrode. The counter electrode is a platinum plate.

[0369] The potential when the current is passed at the above current density for 5 minutes is measured. The hydrogen overvoltage is calculated by substituting the measured potential into the following formula. It should be noted that the hydrogen overvoltage is an absolute value.

[0370] Hydrogen overvoltage (V) = |[measured potential (V)] + 0.199|

[0371] The steps of the method for measuring oxygen overvoltage are as follows.

[0372] In a 0.5M sulfuric acid aqueous solution at 80°C, a flow of +0.5A / cm 2 The test piece is a disc with a diameter of 15 mm. The test area is 1 cm 2 The reference electrode is a saturated silver / silver chloride electrode. The counter electrode is a platinum plate.

[0373] The potential when the current is passed at the above current density for 5 minutes is measured. The oxygen overvoltage is calculated by substituting the measured potential into the following formula. It should be noted that the oxygen overvoltage is an absolute value.

[0374] Oxygen overvoltage (V) = |[measured potential (V)] + 0.199-1.230|

[0375] After measuring the oxygen overvoltage, the interface contact resistance was measured in the same procedure as above.

[0376] The results of the organizational survey are shown in Table 7A, Table 7B and Table 7C. The results of the survey on processability, ductility, strength-ductility balance, corrosion resistance, local corrosion resistance, and stress corrosion cracking resistance are shown in Table 8A, Table 8B and Table 8C. The results of the survey on interface contact resistance, hydrogen overvoltage, and oxygen overvoltage are shown in Table 9A, Table 9B and Table 9C. It should be noted that the evaluation results disclosed in Table 8A to Table 9C are the effects obtained by the chemical composition disclosed in Table 4A to Table 4C and the metallographic structures disclosed in Table 7A to Table 7C and Table 8A to Table 8C.

[0377] [Table 7A]

[0378]

[0379] [Table 7B]

[0380]

[0381] [Table 7C]

[0382]

[0383] [Table 8A]

[0384]

[0385] [Table 8B]

[0386]

[0387] [Table 8C]

[0388]

[0389] [Table 9A]

[0390]

[0391] [Table 9B]

[0392]

[0393] [Table 9C]

[0394]

[0395] The chemical compositions of Invention Examples 1 to 64 and the average diameters of the compound particles containing titanium and carbon are within a specified range. It should be noted that these invention examples have a metallographic structure containing compound particles containing titanium and carbon and an α-phase.

[0396] These invention examples are excellent in ductility, workability, strength-ductility balance, corrosion resistance, pitting corrosion resistance, and stress corrosion cracking resistance.

[0397] On the other hand, in Comparative Examples 65 to 90 where one or both of the chemical composition and the average diameter of the compound particles containing titanium and carbon are outside the specified range, one or more of ductility, workability, strength-ductility balance, corrosion resistance, pitting corrosion resistance, and stress corrosion cracking resistance are insufficient. It should be noted that in these comparative examples, Comparative Example 76 has a metallographic structure of a single α-phase, and Comparative Example 83 has a metallographic structure containing intermetallic compounds. The other comparative examples have a metallographic structure containing compound particles containing titanium and carbon and an α-phase.

[0398] The chemical composition of Comparative Example 65 is within the specified range, but the average diameter of the compound particles is too large. It is presumed that this is because the additional annealing is based on Mode A, heat treatment I is not performed, and on the other hand, the average heating rate in heat treatment II is too fast.

[0399] The chemical composition of Comparative Example 66 is within the specified range, but the average diameter of the compound particles is too large. It is presumed that this is because the cold working degree is insufficient in the cold working before the additional annealing.

[0400] The chemical composition of Comparative Example 67 is within the specified range, but the average diameter of the compound particles is too large. It is presumed that this is because the cooling temperature control after hot rolling is not performed and the intermediate annealing temperature is insufficient.

[0401] The chemical composition of Comparative Example 68 was within the prescribed range, but the average diameter of the compound particles was too large. This is presumably because the intermediate annealing temperature was too high.

[0402] The chemical composition of Comparative Example 69 was within the prescribed range, but the average diameter of the compound particles was too large. This is presumably because the holding temperature in the heat treatment II was insufficient.

[0403] The chemical composition of Comparative Example 70 was within the prescribed range, but the average diameter of the compound particles was too large. This is presumably because the retention time in the heat treatment II was insufficient.

[0404] The chemical composition of Comparative Example 71 was within the prescribed range, but the average diameter of the compound particles was too large. This is presumably because the retention time in the heat treatment II was insufficient.

[0405] The chemical composition of Comparative Example 72 was within the prescribed range, but the average diameter of the compound particles was too large. This is presumably because the holding temperature in the heat treatment I was too low.

[0406] The chemical composition of Comparative Example 73 was within the prescribed range, but the average diameter of the compound particles was too large. This is presumably because the average heating rate and holding temperature in heat treatment I were too high.

[0407] The chemical composition of Comparative Example 74 was within the prescribed range, but the average diameter of the compound particles was too large. This is presumably because the retention time in the heat treatment I was too short.

[0408] The chemical composition of Comparative Example 75 was within the prescribed range, but the average diameter of the compound particles was too large. This is presumably because the retention time in the heat treatment II was insufficient.

[0409] Comparative Example 76 has an insufficient C content. Therefore, in Comparative Example 76, compound particles containing Ti and carbon are not generated.

[0410] Comparative Example 77 has an excessively high C content. Therefore, in Comparative Example 77, the average diameter of the compound particles containing Ti and carbon is too large.

[0411] The Fe content of Comparative Example 78 was too high. Therefore, in Comparative Example 78, the average diameter of the compound particles containing Ti and carbon was too large.

[0412] The S content of Comparative Example 79 is too high. Therefore, in Comparative Example 79, the average diameter of the compound particles containing Ti and carbon is too large.

[0413] The P content of Comparative Example 80 was too high. Therefore, in Comparative Example 80, the average diameter of the compound particles containing Ti and carbon was too large.

[0414] The Si content of Comparative Example 81 was too high. Therefore, in Comparative Example 81, the average diameter of the compound particles containing Ti and carbon was too large.

[0415] Comparative Example 82 has an excessively high content of O. Therefore, in Comparative Example 82, the average diameter of the compound particles containing Ti and carbon is too large.

[0416] The total content of Mn, Cu, Cr, Sn, and Zr was too high in Comparative Example 83. Therefore, in Comparative Example 83, an intermetallic compound was formed.

[0417] Although the chemical composition of Comparative Example 84 was within the prescribed range, the average diameter of the compound particles containing Ti and carbon was too large. This is presumably because the degree of cold working was insufficient in the cold working before the additional annealing.

[0418] Although the chemical composition of Comparative Example 85 was within the prescribed range, the average diameter of the compound particles containing Ti and carbon was too large. This is presumably because cold working was not performed in the cold working before the additional annealing.

[0419] The chemical composition of Comparative Example 86 was within the prescribed range, but the average diameter of the compound particles containing Ti and carbon was too large. This is presumably because the holding temperature in the heat treatment II was insufficient.

[0420] The chemical composition of Comparative Example 87 was within the prescribed range, but the average diameter of the compound particles containing Ti and carbon was too large. This is presumably because the holding temperature in the heat treatment II was insufficient.

[0421] In Comparative Example 88, since the holding time in heat treatment I is 80 seconds, the additional annealing corresponds to mode C2. The chemical composition of Comparative Example 88 is within the specified range, but the average diameter of the compound particles containing Ti and carbon is too large. Although Comparative Example 88 uses a salt bath for heating, the average heating rate in heat treatment II is too fast. Therefore, it is estimated that the compound particles containing Ti and carbon are too large.

[0422] The chemical composition of Comparative Example 89 was within the prescribed range, but the average diameter of the compound particles containing Ti and carbon was too large. This is presumably because the holding temperature in the heat treatment I was too low.

[0423] The chemical composition of Comparative Example 90 was within the prescribed range, but the average diameter of the compound particles containing Ti and carbon was too large. This is presumably because the heating rate and the soaking temperature in the heat treatment II were insufficient.

[0424] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to these examples. Obviously, a person skilled in the art with common knowledge in the field to which the present invention belongs can think of various variations or modifications within the scope of the technical concept described in the claims, and understand that these also belong to the technical scope of the present invention.

Claims

1. A titanium material, characterized in that it contains, by mass%, Si: 0.000 to 0.100%, C：0.100～0.300％、 N：0.000～0.030％、 Fe: 0.000 to 0.300%, S: 0.0300% or less, P: 0.0300% or less, Ca: 0.000 to 0.200%, H：0.000～0.015％、 O：0.000～0.250％、 B：0.000～0.300％、 Al：0.000～0.500％、 Sc: 0.000 to 0.100%, Co: 0.000 to 0.600%, V：0.000～0.500％、 Ni: 0.000 to 0.400%, Zn: 0.000 to 0.300%, Ga: 0.000 to 0.200%, Ge: 0.000 to 0.200%, Nb: 0.000 to 0.150%, Y：0.000～0.300％、 Mo: 0.000 to 0.250%, Ag: 0.000 to 0.100%, Cd: 0.000 to 0.200%, In: 0.000 to 0.100%, Sb: 0.000 to 0.100%, Bi: 0.000 to 0.180%, Hf: 0.000 to 0.300%, Ta: 0.000 to 0.300%, Re: 0.000 to 0.300%, W：0.000～0.600％、 Au: 0.000 to 0.100%, one or more of Pt, Pd, Ru, Ir, Rh, and Os: the total is 0.000 to 0.200%, and one or more of Mn, Cu, Cr, Sn, and Zr: the total is 0.00 to 0.20%, the balance is Ti and impurities, and contains titanium and carbon compound particles with an average diameter of 400 nm or less.

2. The titanium material according to claim 1, characterized in that, by mass%, it is S: 0.0001 to 0.0300%, and 3. The titanium material according to claim 1, characterized in that the A value calculated by substituting the analysis result of the titanium and carbon compound particles using X-ray diffraction into the following formula is 0.10 or more, P：0.0001～0.0300％。 where, n is 5, 4. The titanium material according to claim 1, A=I Ti2C / (1.3I TiC +I Ti2C ) I TiC ={∑(I TiC(hkl) / R TiC(hkl) )} / n I Ti2C ={∑(I Ti2C(hkl) / R Ti2C(hkl) )} / n characterized in that, I TiC is a representative value of the integrated intensity of TiC, which is one of the compound particles containing titanium and carbon, I Ti2C It's Ti 2 Representative value of the integrated intensity of C, Ti 2 C is one of the compound particles comprising titanium and carbon, I TiC(hkl) is the integrated intensity measured at each Miller index of the TiC, I Ti2C(hkl) It is the Ti 2 The integrated intensity measured at each Miller index of C, R TiC(hkl) is the coefficient corresponding to each Miller index of TiC, R Ti2C(hkl) is related to the Ti 2 The coefficients corresponding to each Miller index of C are, 5. A chemical device component comprising the titanium material according to any one of claims 1 to 4. R TiC(hkl) and R Ti2C(hkl) The corresponding relationship with each Miller index is shown in the following table. 。 6. A chemical device comprising the chemical device component according to claim 5. ​ Contains Ti 3 C 2 . ​ ​

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