Method for producing titanium or titanium alloy, container, and device

Abstract

Disclosed is a method for producing titanium or a titanium alloy, with which titanium or a titanium alloy having an oxygen concentration of 0.15 mass% (1,500 mass ppm) or less is produced by melting, casting, or sintering titanium (Ti) or a titanium alloy using a container that contains a rare earth metal oxyhalide salt as a main component. With the method for producing titanium or a titanium alloy, titanium or a titanium alloy having a low oxygen concentration is produced by melting, casting, or sintering titanium or a titanium alloy using a container of a rare earth metal oxyhalide, to which a rare earth metal and a rare earth metal halide salt are added as auxiliary agents, so as to directly remove impurity oxygen in the titanium or the titanium alloy by utilizing a generation reaction of a rare earth metal oxyhalide salt.

Description

Methods for manufacturing titanium or titanium alloys, containers, and apparatus

[0001] The present invention relates to a method for producing titanium or titanium alloys, and to a container and apparatus for metal manufacturing. This application claims priority under Japanese Patent Application No. 2024-232354, filed in Japan on December 27, 2024, the contents of which are incorporated herein by reference.

[0002] Titanium (Ti) and titanium alloys possess the highest specific strength and outstanding corrosion resistance among metallic materials. Despite being an inexhaustible resource, the main reason why titanium and titanium alloys are not widely used is that titanium has a high affinity for oxygen, making smelting, melting, and casting difficult, and resulting in high manufacturing costs for titanium products.

[0003] Currently, when melting titanium or titanium alloys, heating methods such as high-frequency induction heating devices, plasma arc melting devices, and electron beam melting devices are used. These melting methods require the use of water-cooled copper melting vessels that are chemically and physically inert and do not react with molten titanium or molten titanium alloys. This is because molten titanium is highly reactive, and if a container made of oxides or other materials is used, the molten titanium will react with the oxides in the container material, increasing the concentration of impurities such as oxygen in the molten titanium or molten titanium alloy, making it unsuitable for use as a titanium product.

[0004] Industrially, it is necessary to manufacture titanium or titanium alloys with an oxygen concentration of 0.4 mass% (4000 mass ppm) or less regarding impurity oxygen. However, when titanium or titanium alloys are melted using containers containing oxides, the oxygen concentration in the titanium often exceeds 0.4 mass%, resulting in titanium products that are outside of specifications.

[0005] In the past, Y ２ O ３Attempts have been made to use refractories such as CaO, graphite, and BN as melting vessels for titanium or titanium alloys, but these are rarely used industrially because they increase the concentration of impurities in the titanium or titanium alloy. However, in casting processes where titanium solidifies quickly, refractories such as oxides are sometimes used as vessel materials. The surface of titanium or titanium alloys cast using these refractories is contaminated with oxygen, carbon, nitrogen, and boron derived from the refractory components, and the surface layer needs to be removed.

[0006] Because molten titanium exhibits extremely high reactivity with oxygen, it is not easy to directly remove impurity oxygen from molten titanium or molten titanium alloys. In the past, attempts have been made to directly remove oxygen from molten titanium or molten titanium alloys during the melting process.

[0007] For example, a method is known for removing oxygen from titanium by adding rare earth metals and calcium fluoride when melting titanium using a cold crucible type levitation melting apparatus, which is a type of high-frequency induction heating apparatus (see Patent Document 1). According to the method described in Patent Document 1, by adding cerium (Ce), a rare earth metal, or mischmetal, a mixture of rare earth metals, to molten titanium, oxygen can be removed from molten titanium down to 0.5 mass% (5000 mass ppm). However, the method described in Patent Document 1 could not remove oxygen down to the oxygen concentration level of 0.1 to 0.2 mass% (1000 to 2000 mass ppm) required for structural material applications. Therefore, it is impossible to directly produce low-oxygen-concentration titanium for structural material applications from titanium or titanium alloys with high oxygen concentrations using the method described in Patent Document 1.

[0008] Furthermore, a method is known for removing oxygen from titanium alloys by adding the rare earth metal yttrium (Y) and calcium fluoride when melting Ti-46Al-8Nb alloys using a cold crucible type melting apparatus, which is a type of high-frequency induction heating apparatus (see Non-Patent Literature 1). According to the method described in Non-Patent Literature 1, oxygen can be removed from molten Ti-46Al-8Nb alloys down to 0.08 mass% (800 mass ppm). However, titanium alloys containing a large amount of aluminum are thermodynamically easier to remove oxygen from, and the method described in Non-Patent Literature 1 could not remove oxygen from molten pure titanium or titanium alloys with low aluminum concentrations down to the oxygen concentration level of 0.1 to 0.2 mass% (1000 to 2000 mass ppm) required for structural material applications.

[0009] Furthermore, a method for removing oxygen from a titanium-aluminum alloy containing 40% by mass or more of aluminum is known, by melting the alloy using an arc melting method, plasma arc melting method, or induction melting method with a water-cooled copper container (see Patent Document 2). According to the method described in Patent Document 2, oxygen can be removed from the molten titanium-aluminum alloy to a concentration of 0.022% by mass (220 mass ppm). However, the method described in Patent Document 2 is only effective for titanium-aluminum alloys containing 40% by mass or more of aluminum, and could not remove oxygen to a concentration of 0.6% by mass (6000 mass ppm) or less for titanium-aluminum alloys with an aluminum concentration of 40% by mass or less and containing 60% by mass or more of titanium.

[0010] In response to the above situation, the present inventors have developed a new technology to efficiently remove oxygen impurities directly from molten titanium (Patent Document 3 and Non-Patent Document 2). This method involves melting titanium using a cold crucible type melting apparatus, which is a type of heating device, and then adding rare earth metals such as yttrium (Y) and yttrium fluoride (YF). ３By adding rare earth metal halide salts such as yttrium oxyfluoride (YOF) and utilizing the reaction that produces rare earth metal oxyhalide salts such as yttrium oxyfluoride (YOF), it is possible to directly remove impurity oxygen from molten titanium to an oxygen concentration of 0.1 mass% (1000 mass ppm) or less. Under certain conditions, it has been successful to remove oxygen from titanium to an extremely low oxygen concentration of 0.02 mass% (200 mass ppm).

[0011] In summary, according to the methods described in Patent Document 3 and Non-Patent Document 2, rare earth metals such as yttrium (Y) and yttrium fluoride (YF) ３ By using rare earth metal halide salts such as ), it is possible to remove oxygen from titanium to an extremely low oxygen concentration of about 0.02 mass% (200 mass ppm).

[0012] However, all of the methods described in the aforementioned literature require the use of a water-cooled copper crucible as the container for holding the molten titanium. In this case, a complex cooling system is required, resulting in low thermal efficiency and low production efficiency in both the melting and casting processes.

[0013] If titanium or titanium alloys could be melted and cast using containers other than water-cooled copper crucibles, a complex cooling system would become unnecessary, improving not only the efficiency of the melting and casting processes but also the thermal efficiency, thus further streamlining the production of titanium and titanium alloys.

[0014] As mentioned above, in the past, Y ２ O ３ Attempts have been made to use refractories such as CaO, graphite, and BN as melting vessels for titanium and titanium alloys, but this increases the concentration of impurities in the titanium and titanium alloys. On the other hand, as is clear from the results of demonstration in Patent Document 3 and Non-Patent Document 2, rare earth metal oxyhalide salts such as YOF can thermodynamically coexist with molten titanium at low oxygen concentrations. In other words, rare earth metal oxyhalide salts such as YOF may be usable as melting vessel materials for titanium at low oxygen concentrations.

[0015] For example, a method is known in which rare earth metal oxyfluoride salts such as LaOF are used as linings for containers and ceramic crucibles for melting titanium, zirconium (Zr), and their alloys (see Patent Document 4). According to the method described in Patent Document 4, oxyfluoride salts of rare earth metals such as yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd), or mixtures of oxyfluoride salts and fluoride salts, can be used as reaction vessels. While the method described in Patent Document 4 can melt titanium without damaging the melting vessel or introducing oxygen into the titanium, it has not been reported that titanium with an oxygen concentration lower than 0.15 mass% (1500 mass ppm) can be produced. Furthermore, since the method described in Patent Document 4 cannot reduce the oxygen concentration in the molten titanium, it is not possible to directly produce low-oxygen-concentration titanium from high-oxygen-concentration molten titanium.

[0016] Furthermore, a method is known in which rare earth metal oxyfluoride salts such as CeOF are used as mold materials for titanium and zirconium (see Patent Document 5). According to the method described in Patent Document 5, oxyfluoride salts of rare earth metals such as yttrium (Y), lanthanum (La), and cerium (Ce) can be used as mold shells. In the method described in Patent Document 5, titanium can be dissolved without damaging the melting vessel or introducing oxygen into the titanium, but the lower limit of the oxygen concentration of the manufactured titanium is unknown. Also, since the oxygen concentration in the molten titanium cannot be reduced in the method described in Patent Document 5, it is not possible to directly produce low-oxygen-concentration titanium from high-oxygen-concentration molten titanium.

[0017] In summary, according to the methods described in Patent Documents 4 and 5, titanium or titanium alloys can be melted and cast using containers and reinforcing materials mainly composed of rare earth metal oxyhalide salts.

[0018] However, it is unclear whether titanium with an oxygen concentration lower than 0.15 mass% (1500 mass ppm) can be produced using containers and reinforcing materials mainly composed of rare earth metal oxyhalide salts. Furthermore, there is no technology to directly produce titanium or titanium alloys with a low oxygen concentration by removing oxygen from molten high-oxygen-concentration titanium or titanium alloys using containers other than water-cooled copper crucibles.

[0019] Japanese Patent Publication No. 2949222, Japanese Patent Publication No. 6392179, Japanese Patent Application No. 2023-117129, European Patent Application Publication No. 0372180, U.S. Patent No. 4057433

[0020] 'Direct oxygen removal from titanium aluminide scraps by yttrium reduction', Li-na Jiao, Qi-sheng Feng, Shi-yu He, Bao-hua Duan, Zhi-he Dou, Chong-he Li, and Xiong-gang Lu: Trans. Nonferrous Met. Soc. China, vol. 32 (2022) pp. 2428-2437. DOI: 10.1016 / S1003-6326(22)65958-2'Direct production of low-oxygen-concentration titanium from molten titanium', Toru H. Okabe, Gen Kamimura, Takashi Ikeda, and Takanari Ouchi: Nature Commun., vol. 15 (2024) 5015. DOI: 10.1038 / s41467-024-49085-4

[0021] This invention has been made in view of the above problems, and one of its objectives is to provide a method for producing titanium or titanium alloys with a low oxygen concentration that improves efficiency without complicating the apparatus. This invention also aims to provide a container used for melting, casting, or sintering metal raw materials, which can produce high-purity metal with a low oxygen concentration. This invention also aims to provide an apparatus that can melt, cast, or sinter metal raw materials using the above container to produce metal with a low oxygen concentration.

[0022] (1) According to one aspect of the present invention, a method for producing titanium or a titanium alloy is provided, in which a metal raw material containing titanium (Ti) or a titanium alloy is melted, cast, or sintered using a container having a component mainly composed of a rare earth metal oxyhalide salt in at least the part that comes into contact with the metal raw material, thereby producing titanium or a titanium alloy with an oxygen concentration of 0.15 mass% (1500 mass ppm) or less. According to the above aspect, since it is not necessary to install a cooling system for a water-cooled copper crucible, titanium or a titanium alloy with a low oxygen concentration can be produced with high thermal efficiency.

[0023] (2) According to one aspect of the present invention, a method for producing titanium or a titanium alloy is provided, which involves melting, casting, or sintering titanium or a titanium alloy using a container having a component mainly composed of a rare earth metal oxyhalide salt, to which rare earth metals and rare earth metal halide salts are added as auxiliary agents at least in the part that comes into contact with the metal raw material, thereby utilizing the reaction of rare earth metal oxyhalide salt formation to directly remove impurity oxygen from titanium or a titanium alloy and produce titanium or a titanium alloy with a low oxygen concentration. According to the above aspect, by using a rare earth metal oxyhalide salt that is inert to titanium as the container material and installing rare earth metals and rare earth metal halide salts as auxiliary agents in the container material or in the system, titanium or a titanium alloy with a low oxygen concentration can be produced.

[0024] (3) In the method for producing titanium or a titanium alloy according to (1) or (2), one or more rare earth metal oxyfluoride salts selected from scandium oxyfluoride (ScOF), yttrium oxyfluoride (YOF), lanthanum oxyfluoride (LaOF), cerium oxyfluoride (CeOF), praseodymium oxyfluoride (PrOF), and neodymium oxyfluoride (NdOF) can also be used.

[0025] (4) In the method for producing titanium or a titanium alloy according to any one of (1) to (3), one or more rare earth metals selected from scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd) can also be used.

[0026] (5) In the method for producing titanium or a titanium alloy according to any one of (1) to (4), scandium fluoride (ScF ３ ), yttrium fluoride (YF ３ ), lanthanum fluoride (LaF ３ ), cerium fluoride (CeF ３ ), praseodymium fluoride (PrF ３ ), and neodymium fluoride (NdF ３ ) can also be used.

[0027] (6) In the method for producing titanium or a titanium alloy according to any one of (1) to (5), in addition to the rare earth metal and the rare earth metal halide salt, a metal halide salt can also be used as an auxiliary agent.

[0028] (7) In the method for producing titanium or a titanium alloy according to any one of (1) to (6), a step of forming a material in which a rare earth metal halide salt and a rare earth oxide are mixed with a binder into a container or an inner lining material of the container to produce a formed container or a formed inner lining material, and accommodating a metal raw material containing titanium or a titanium alloy in the formed container or another container in which the formed inner lining material is disposed, and synthesizing a rare earth metal oxyhalide salt in situ from the formed container or the formed inner lining material during the heating of the metal raw material.

[0029] (8) In any one of the methods for producing titanium or a titanium alloy according to (1) to (7), a container in which the member mainly composed of the rare earth metal oxyhalide salt is reinforced from the outside with a high melting point metal may also be used.

[0030] (9) In any one of the methods for producing titanium or a titanium alloy described in (1) to (8), the oxygen concentration in titanium can also be controlled by adjusting the amount of the rare earth metal and the rare earth metal halide salt added to a component mainly composed of a rare earth metal oxyhalide salt.

[0031] (10) In any one of the methods for manufacturing titanium or a titanium alloy described in (1) to (9), titanium or a titanium alloy may also be melted, cast, or sintered in the container using a melting apparatus selected from a resistance heating apparatus, a high-frequency induction heating apparatus, a plasma arc melting apparatus, and an electron beam melting apparatus.

[0032] (11) According to one aspect of the present invention, there is a container used in an apparatus for producing a metal or alloy by melting, casting, or sintering a metal raw material, the container having a component mainly composed of a rare earth metal oxyhalide salt to which a rare earth metal and a rare earth metal halide are added as auxiliary agents, at least in the part that comes into contact with the metal raw material.

[0033] (12) According to one aspect of the present invention, an apparatus is provided comprising the container described in (11) and a heating mechanism, for melting, casting, or sintering a metal raw material using the container.

[0034] According to one aspect of the present invention, a method is provided for producing titanium or titanium alloys with high purity and extremely low oxygen concentration by melting, casting, and sintering titanium or titanium alloys without using complex equipment. According to one aspect of the present invention, a container used for melting, casting, or sintering metal raw materials is provided, which is capable of producing metals with high purity and low oxygen concentration. According to one aspect of the present invention, an apparatus is provided that can melt, cast, or sinter metal raw materials using the above-mentioned container to produce metals with low oxygen concentration.

[0035] Figure 1 shows Y ２ O ３ -YF ３This is a pseudo-binary phase diagram. Figure 2 is an isothermal phase diagram of the yttrium-oxygen-fluorine ternary system at 1727°C. Figure 3 is a schematic diagram of the process for manufacturing a molded body of raw material powder for a rare earth metal oxyhalide crucible. Figure 4 is a photograph of the process for manufacturing a molded body of raw material powder for a rare earth metal oxyhalide crucible. Figure 5 is a schematic diagram of the heating and sintering process for the molded body of raw material powder for a rare earth metal oxyhalide crucible. Figure 6 is an example of a photograph of the heating and sintering process for the molded body of raw material powder for a rare earth metal oxyhalide crucible. Figure 7 is a photograph of the rare earth metal oxyhalide crucible obtained after heating and sintering in Example x of Table 2. Figure 8 is a photograph of the rare earth metal oxyhalide crucible obtained after heating and sintering in Example y of Table 2. Figure 9 is the result of powder X-ray diffraction measurement of the sample powder obtained by crushing the rare earth metal oxyhalide crucible obtained after heating and sintering. Figure 10A is a photograph of titanium and yttrium before heating in a yttrium oxyfluoride crucible. Figure 10B is an example of the temperature profile during heating in the yttrium oxyfluoride crucible shown in Figure 10A. Figure 10C is a photograph of titanium and yttrium after heating in the yttrium oxyfluoride crucible shown in Figure 10A. Figure 11 shows the mole fraction of Y ２ O ３ : YF ３Figure 12 shows photographs of titanium and yttrium being heated in a YOF crucible of an example prepared with raw materials in a mixing ratio of 0.5:0.5. Figure 12 is an example of a conceptual diagram of a method for melting titanium and titanium alloys by reinforcing a rare earth metal oxyhalide crucible from the outside using a high-melting-point metal crucible as a reinforcing material. Figure 13 is an example of a conceptual diagram of a method for melting titanium and titanium alloys by lining a reaction vessel during continuous deoxidation treatment or by placing it in a sleeve shape between a water-cooled copper crucible and a crucible when casting ingots. Figure 14 is an explanatory diagram of an experiment to prepare a rare earth metal oxyhalide crucible using a binder. Figure 15 is a cross-sectional view of a titanium manufacturing apparatus using a molybdenum susceptor. Figure 16 is an explanatory diagram showing a titanium manufacturing method using the manufacturing apparatus shown in Figure 15. Figure 17 is a graph showing the temperature profile of a deoxidation experiment. Figure 18 is a cross-sectional view of a titanium manufacturing apparatus using a carbon susceptor. Figure 19 is an explanatory diagram showing a titanium manufacturing method using the manufacturing apparatus shown in Figure 18. Figure 20 is a graph showing the temperature profile of the deoxidation experiment. Figure 21 is a conceptual diagram of a method for producing solid titanium with a low yttrium concentration by melting and solidifying a titanium yttrium alloy using a rare earth metal oxyhalide crucible. Figure 22 shows the Ti-Y-O molten phase and solid Y at 2000 K (1727 °C). ２ O ３ Phase, or liquid YF ３ and solid Y ４ O ３ F ６ This figure shows the thermodynamic relationship between yttrium (Y) and oxygen concentration in a state where the two phases coexist.

[0036] Embodiments of the present invention will be described below with reference to the drawings.

[0037] This embodiment describes a rare earth metal oxyhalide crucible, which is a container for melting, casting, and sintering titanium or titanium alloys. Table 1 shows the constituent materials and characteristics of the rare earth metal oxyhalide crucible of this embodiment. As shown in Table 1, the main structural material of the rare earth metal oxyhalide crucible is a rare earth metal oxyhalide salt (RE ｘ O ｙ X ｚ) is the formula. Here, RE is a rare earth element (Sc, Y, La, Ce, Pr, Nd...). Among REs, the use of Y, La, and Ce is particularly desirable. X is a halogen element such as Cl or F. As the rare earth metal oxyhalide salt, for example, one or more rare earth metal oxyhalide salts selected from scandium oxyfluoride (ScOF), yttrium oxyfluoride (YOF), lanthanum oxyfluoride (LaOF), cerium oxyfluoride (CeOF), praseodymium oxyfluoride (PrOF), and neodymium oxyfluoride (NdOF) can be used. In order to improve and control the strength and deoxidation performance (oxygen removal rate) of the crucible, REF ３ CaF ２ Rare earth metal halide salts and metal halide salt additives are mixed into the main structural material. Examples of these additives include scandium fluoride (ScF ３ ), yttrium fluoride (YF ３ ), lanthanum fluoride (LaF ３ ), cerium fluoride (CeF ３ ), praseodymium fluoride (PrF ３ ), neodymium fluoride (NdF ３ One or more rare earth metal fluoride salts selected from the following can be used. In addition, deoxidizing agents such as powdered RE metals and RE alloys are mixed in as auxiliary agents. The RE metal auxiliary or RE alloy auxiliary may be placed on the outside of the crucible. As rare earth metals used as deoxidizing agents, one or more rare earth metals selected from, for example, scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd) can be used. The oxygen concentration in titanium can be controlled by adjusting the amount of additives such as rare earth metals, rare earth alloys, rare earth metal halide salts, and metal halide salts.

[0038] The shape of the rare earth metal oxyhalide crucible is not particularly limited and can be any shape depending on the application. Furthermore, the crucible is not limited to being made entirely of a material mainly composed of rare earth metal oxyhalide salts; only a part of the crucible (container) may be made of a material mainly composed of rare earth metal oxyhalide salts. As will be described in detail later, a container made of a high-melting-point metal may be fitted with a lining made of a material mainly composed of rare earth metal oxyhalide salts. In other words, as long as there is a component mainly composed of rare earth metal oxyhalide salts in the part that comes into contact with the metal raw material (titanium or titanium alloy), it can function as the rare earth metal oxyhalide crucible described above. In a configuration that combines a component mainly composed of rare earth metal oxyhalide salts with a container made of a high-melting-point metal, the container made of the high-melting-point metal functions as a reinforcing material for the crucible.

[0039]

[0040] Figure 1 shows Y ２ O ３ -YF ３ This is a pseudo-binary phase diagram (Source: 'Phase diagram study and thermodynamic assessment of the Y2O3-YF3 system', Seungjoo Baek and In-Ho Jung: J. Eur. Ceram. Soc., vol. 42 (2022) pp. 5079-5092. DOI: 10.1016 / j.jeurceramsoc.2022.05.005). The dashed line in Figure 1 represents 1727°C, at which temperature titanium, with a melting point of 1668°C, melts. At 1727°C, YOF and Y ７ O ６ F ９ , Y ４ O ３ F ６ Yttrium oxyfluoride (Y ｘ O ｙ F ｚ The phase exists as a solid. ｘ O ｙ F ｚThe solid phase can thermodynamically coexist with titanium in a high-temperature state, whether solid or liquid, and there is no mutual solubility. That is, Y ｘ O ｙ F ｚ A container made of solid phase can hold solid or liquid titanium at high temperatures. Furthermore, at temperatures above 1150°C, YF ３ Phase melts, Y ４ O ３ F ６ Yttrium oxyfluoride (Y ｘ O ｙ F ｚ ) can coexist with the solid phase. On the other hand, yttrium oxide (Y ２ O ３ ) The solid phase, in terms of equilibrium theory, is YF ３ It cannot coexist with the liquid phase. That is, yttrium oxyfluoride (Y ｘ O ｙ F ｚ ) The solid phase is the main component, with a small amount of YF ３ It can be seen that compound sintered bodies containing a liquid phase can be used as containers for holding solid or liquid titanium at high temperatures. Furthermore, Y ｘ O ｙ F ｚ YF ３ The phase can thermodynamically coexist with metallic yttrium. That is, yttrium oxyfluoride (Y ｘ O ｙ F ｚ ) The solid phase is the main component, with a small amount of YF ３ By using a compound sintered body containing a liquid phase and a metallic yttrium phase as a container, solid or liquid titanium at high temperatures can be deoxidized.

[0041] Figure 2 is an isothermal phase diagram of the yttrium-oxygen-fluorine ternary system at 1727°C. The figure shows Y-Y ４ O ３ F ６ -YF ３ An enlarged view of the three-phase equilibrium region and a typical composition range of the yttrium oxyfluoride crucible are shown. As shown in the figure, the rare earth metal oxyhalide crucible of this embodiment, in the case of the yttrium system, contains yttrium oxyfluoride (Y ｘ O ｙ Fｚ ), a compound sintered body having a solid phase as a main component and containing a small amount of YF ３ and a liquid phase or metallic yttrium.

[0042] When a powdery RE metal or RE alloy is mixed with a main structural material or an auxiliary agent, the RE metal functions as a deoxidizer for titanium. For example, in the case of the yttrium system, when YF ３ is present in excess, the deoxidation product in the deoxidation of titanium is yttrium oxyfluoride (Y ｘ O ｙ F ｚ ). Generalizing for RE, the deoxidation reaction of titanium shown in formula (1) proceeds. O (in Ti) + 2 / 3 RE (l) + 1 / 3 REX ３ (l) → REOX (s) … (1) RE: Rare earth metal elements such as Y, La, Ce X: Halogen elements such as Cl, F

[0043] In this embodiment, by the above deoxidation reaction, the oxygen concentration of titanium or a titanium alloy can be reduced to 0.15% by mass (1500 mass ppm) or less. According to the method for producing titanium or a titanium alloy of this embodiment, as a container for melting, casting, or sintering titanium or a titanium alloy, a container (rare earth metal oxyhalide crucible) made of a material obtained by adding a rare earth metal and a rare earth metal halide as auxiliary agents to a rare earth metal oxyhalide salt is used. Therefore, unlike the case of using a conventional water-cooled copper crucible, there is no need to install a complicated water-cooling system, and a titanium or titanium alloy with a low oxygen concentration can be produced with a simple device.

[0044] At a high temperature of about 1727 °C, since the mobility of oxide ions (O ｘ O ｙ F ｚ (+YF ３ ) in is large, it is also possible to arrange a deoxidizer metal such as yttrium outside the container (rare earth metal oxyhalide crucible) to deoxidize titanium or a titanium alloy in the container.

[0045] ​​Regarding the rare earth metals used in the deoxidation reaction of titanium or titanium alloys in the embodiments, rare earth metals such as Y, La, and Ce can be used. The rare earth metal halide salts that constitute the crucible for the rare earth metal used as the deoxidizer may be different types of rare earth metals from each other. For example, cerium fluoride (CeF ３ ), and yttrium (Y) may be used in combination. Further, calcium fluoride (CaF ２ ) etc. may be added to the above fluorides to adjust the mobility of oxide ions in the crucible, the sinterability and strength of the crucible, etc.

[0046] For the production of titanium or titanium alloys, a melting device selected from a resistance heating device, a high-frequency induction heating device, a plasma arc melting device, and an electron beam melting device can be used.

[0047] In addition, the oxyhalide crucible of the embodiment described above can be used not only for melting and casting titanium, but also for a titanium alloy melting crucible for producing titanium powder used for, for example, additive manufacturing. Specifically, as an example, the oxyhalide crucible of the embodiment can be used as a titanium alloy melting crucible for gas atomization.

[0048] Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the following examples.

[0049] (Example 1) Table 2 shows typical mixing ratios of the raw materials (rare earth oxides and rare earth metal halide salts) of the rare earth metal oxyhalide crucible of the embodiment. After mixing the raw material powders in Table 2, when a binder (adhesive) such as a collodion solution is added to the powder mixture, the powder can be easily formed. In Example x, yttrium oxide (Y ２ O ３ ) powder and yttrium fluoride (YF ３The raw material powder, which was mixed with the powder, was molded using the method shown in Figure 3. In Example y, the raw material powder, which was mixed with a binder in the ratios shown in Table 2, was molded using the method shown in Figure 4. The resulting powder molded bodies (green) of Examples x and y were subjected to a sintering process at 1100 to 1300°C using the high-frequency induction furnace shown in Figure 5.

[0050]

[0051] Figures 3 and 4 show an example of a method for producing molded bodies of raw material powders for rare earth metal oxyhalide crucibles. The raw material powders for the rare earth metal oxyhalide crucibles were molded using a method that is almost identical to the commonly used method for producing oxide crucibles from powder raw materials.

[0052] Figure 5 shows an example of a high-frequency induction furnace used for heating and sintering molded bodies of raw material powders for rare earth metal oxyhalide crucibles. In Examples x (without binder) and y (with binder), the high-frequency induction furnace shown in Figure 5 was used to gradually raise the temperature from room temperature to a predetermined temperature under an argon gas atmosphere, and the molded bodies of raw material powders were heated and held at the predetermined temperature to produce rare earth metal oxyhalide crucibles. Figure 6 shows an example of a photograph of the heating and sintering process of the molded bodies of raw material powders for rare earth metal oxyhalide crucibles.

[0053] Figures 7 and 8 are photographs of rare earth metal oxyhalide crucibles obtained after heating and sintering. Figure 7 is a photograph of a rare earth metal oxyhalide crucible obtained after heating and sintering in Example x, where the raw materials were prepared with the mixing ratios shown in Table 2. A dense crucible with sufficient mechanical strength was obtained. Figure 8 is a photograph of a rare earth metal oxyhalide crucible obtained after heating and sintering in Example y, where the raw materials were prepared with the mixing ratios and binder additions shown in Table 2. A dense crucible with sufficient mechanical strength was obtained.

[0054] Figure 9 shows the results of powder X-ray diffraction measurements of the sample powder obtained by pulverizing the rare earth metal oxyhalide crucible obtained after heating and sintering at the mixing ratios shown in Table 2. As expected from Table 2, through heating and sintering, yttrium oxide (Y) ２ O ３ ) and yttrium fluoride (YF ３ ) from yttrium oxyfluoride (Y７ O ６ F ９ It has been shown that ) was produced. Also, yttrium oxide (Y ２ O ３ The peak of ) disappeared, while yttrium fluoride (YF ３ The peak of ) remained.

[0055] Figures 10A-C show photographs of titanium and yttrium being heated in a yttrium oxyfluoride crucible prepared using the raw materials in the mixing ratios shown in Table 2, along with an example of the temperature profile during heating. ３ The crucible was then inductively heated with yttrium and titanium. Under these conditions, the yttrium melted, but the titanium did not. After cooling, no cracks or deformation were observed in the crucible. By optimizing the induction heating conditions or using a susceptor, it may be possible to melt titanium as well.

[0056] Figure 11 shows the mole fraction Y ２ O ３ : YF ３ These are photographs of the YOF crucible, prepared using raw materials in a 0.5:0.5 mixing ratio, before and after heating titanium and yttrium. The left side of Figure 11 shows the crucible before heating, and the right side shows the crucible after the titanium has melted. Titanium was placed in the prepared crucible and induction heated. Under these conditions, the titanium melted. After cooling, no cracks or deformation were observed in the crucible.

[0057] As can be seen from the results in Figures 10 and 11, the rare earth metal oxyhalide crucible of the present invention maintained sufficient mechanical strength, with no change in the shape of the crucible before and after heating while retaining titanium and yttrium.

[0058] In the above embodiment, titanium was melted using a crucible after sintering, but the sintering of the crucible and the melting of titanium may be carried out continuously. In this case, Y ２ O ３ YF ３The powder is mixed with a binder and molded to produce a molded container (powder molded body). After charging titanium (metal raw material) into the molded container, the molded container containing the titanium is induction heated. First, the molded container is heated and sintered, synthesizing a yttrium oxyfluoride crucible (rare earth metal oxyhalide crucible). Subsequently, by heating above the melting point of titanium, the titanium can be melted in the yttrium oxyfluoride crucible that was formed.

[0059] (Example 2) When melting a large amount of metal in a large container, as shown in Figures 12 and 13, a high-melting-point metal can be used as a reinforcing material to reinforce the rare-earth metal oxyhalide crucible from the outside, and titanium or titanium alloy can be melted.

[0060] Figure 12 shows an apparatus comprising a container with a container-shaped reinforcing material made of a high-melting-point metal such as molybdenum (Mo), tantalum (Ta), or tungsten (W) placed on the outside of a rare-earth metal oxyhalide crucible (YOF crucible). The container with the reinforcing material is placed inside a heating heater (heating mechanism) to melt the titanium placed inside the rare-earth metal oxyhalide crucible. By placing the reinforcing material, it is possible to suppress the collapse of the rare-earth metal oxyhalide crucible even when it is enlarged.

[0061] Figure 13 shows an example of an apparatus for directly producing titanium or titanium alloys from titanium oxide. In the apparatus shown in Figure 13, TiO ２ A first apparatus 101 for reduction, a second apparatus 102 for deoxidation of Ti, and a third apparatus 103 for casting low-oxygen titanium are connected in sequence and used.

[0062] The first apparatus 101 includes a reaction vessel 101a, a titanium discharge section 101b, and a slag discharge section 101c. The second apparatus 102 includes a reaction vessel 102a, a titanium discharge section 102b, and a slag discharge section 102c. The third apparatus 103 includes a mold 103a. The reaction vessels 101a and 102a are provided with a heating mechanism (not shown).

[0063] In the reaction vessel 101a of the first apparatus 101, titanium ore or titanium oxide, a metal reducing agent such as aluminum (Al) or magnesium (Mg), and a flux such as calcium oxide (CaO) are charged. The titanium ore or titanium oxide in the reaction vessel 101a is reduced by the metal reducing agent, and titanium with a high oxygen concentration is produced. The titanium discharge section 101b of the first apparatus 101 is a pipe that extends from the side of the reaction vessel 101a to the reaction vessel 102a of the second apparatus 102. The tip of the titanium discharge section 101b opens above the opening of the reaction vessel 102a. The molten titanium with a high oxygen concentration produced in the first apparatus 101 is supplied to the reaction vessel 102a of the second apparatus 102 through the titanium discharge section 101b. The slag discharge section 101c of the first apparatus 101 is a pipe that extends outward from the upper side of the reaction vessel 101a. The slag generated in the first apparatus 101 is discharged to the outside of the reaction vessel 101a through the slag discharge section 101c and recovered.

[0064] In the reaction vessel 102a of the second apparatus 102, a lining material 102d is installed in the area that comes into contact with the molten titanium. The lining material 102d is a component made of a material containing rare earth metals and rare earth metal halide salts, with rare earth metal halide salts such as YOF as the main component. The lining material 102d can be made by mixing a material of rare earth metal halide salts and rare earth oxides with a binder, molding it into the shape of a lining material for the vessel, and then sintering the molded lining material. In this case, the lining material 102d may be formed inside the reaction vessel 102a. Molten titanium with a high oxygen concentration supplied from the first apparatus 101 is charged into the reaction vessel 102a of the second apparatus 102. Along with the molten titanium, rare earth metals such as yttrium (Y), lanthanum (La), and cerium (Ce), and yttrium fluoride (YF) ３Rare earth metal halide salts such as ) may be charged. Inside the reaction vessel 102a, impurity oxygen is removed from molten titanium by utilizing the rare earth metal oxyhalide formation reaction, and titanium with a low oxygen concentration is produced. The titanium discharge section 102b of the second apparatus 102 is a pipe that extends from the side of the reaction vessel 102a to the mold 103a of the third apparatus 103. The tip of the titanium discharge section 102b opens above the opening of the mold 103a. The molten titanium with a low oxygen concentration produced in the second apparatus 102 is supplied to the mold 103a of the third apparatus 103 through the titanium discharge section 102b. The slag discharge section of the second apparatus 102 is a pipe that extends outward from the upper side of the reaction vessel 102a. The slag produced in the second apparatus 102 is discharged to the outside of the reaction vessel 102a through the slag discharge section 102c and recovered.

[0065] Casting in the third apparatus 103 allows for obtaining titanium ingots with a low oxygen concentration from molten titanium with a low oxygen concentration. The mold 103a of the third apparatus 103 may be lined with the same lining material as the lining material 102d of the second apparatus 102. This suppresses the increase in oxygen concentration caused by the mold 103a.

[0066] (Example 3) In this example, a rare earth metal oxyhalide crucible was prepared using a binder. Using the prepared rare earth gold oxyhalide crucible, titanium production experiments were conducted using a molybdenum susceptor and a carbon susceptor.

[0067] [Crucible Fabrication Using a Binder] Figure 14 is an explanatory diagram of an experiment in fabricating a rare earth metal oxyhalide crucible using a binder. The table in Figure 14 lists the type and content of the binder, the molding method, and the sintering method. The graph in Figure 14 shows the temperature profile during the sintering process. The photograph on the right side of Figure 14 shows the rare earth metal oxyhalide crucible after sintering.

[0068] First, the raw material powders shown in Table 2 (yttrium oxide (Y ２ O ３ ) powder and yttrium fluoride (YF ３4% by mass of polyvinyl alcohol (PVA) was added to the powder and mixed, and a bottomed cylindrical molded body with an open top was made using a resin mold. Next, the molded body was sintered according to the temperature profile shown in Figure 14 to obtain a rare earth metal oxyhalide crucible. As shown in Figure 14, the binder was removed by holding the crucible at 400°C in the initial stages of the sintering process, and after the binder was sufficiently removed, the temperature was raised to 1400°C and held for 6 hours to sinter the crucible.

[0069] As shown in the photograph on the right side of Figure 14, a dense vase with sufficient mechanical strength was obtained by adding a binder to the raw material powder, molding it, and then sintering it.

[0070] [Titanium Manufacturing Using a Molybdenum Susceptor] Figure 15 is a cross-sectional view of a titanium manufacturing apparatus using a molybdenum susceptor. The titanium manufacturing apparatus shown in Figure 15 comprises a Mo crucible (molybdenum susceptor) that houses a YOF crucible (rare earth metal oxyhalide crucible), a carbon felt for insulation that covers the Mo crucible from the outside, a quartz tube that surrounds the carbon felt from the outside, and a high-frequency coil (heating heater) arranged around the quartz tube. A protective tube is inserted through the carbon felt and the top surface of the Mo crucible, and a thermocouple for measuring the temperature inside the Mo crucible is placed inside the protective tube.

[0071] Figure 16 is an explanatory diagram showing a titanium manufacturing method using the manufacturing apparatus shown in Figure 15. As shown in Figure 16, first, a YOF crucible, titanium (Ti), and yttrium (Y) are prepared. Next, titanium (Ti) and yttrium (Y) are placed in the YOF crucible, and then yttrium fluoride (YF ３The raw material was packed into a YOF crucible. Next, the YOF crucible containing the raw material was placed in a Mo crucible (molybdenum susceptor). Then, the Mo crucible was covered with carbon felt and placed inside a quartz tube, and deoxidation of titanium (Ti) was performed by heating it by applying current to a high-frequency coil. Figure 17 is a graph showing the temperature profile of the deoxidation experiment. The temperature inside the Mo crucible was raised to about 1700°C, held for 15 minutes, and then the heating was stopped and it was cooled. Figure 16 shows the molten sample. The photograph on the far right of Figure 16 is the deoxidized titanium removed from the YOF crucible. By using a Mo crucible (molybdenum susceptor), deoxidized solid titanium could be obtained.

[0072] [Titanium Manufacturing Using a Carbon Susceptor] Figure 18 is a cross-sectional view of a titanium manufacturing apparatus using a carbon susceptor. The titanium manufacturing apparatus shown in Figure 18 comprises a carbon crucible (carbon susceptor) that houses a YOF crucible (rare earth metal oxyhalide crucible), a carbon cap that closes the upper opening of the carbon crucible, a carbon felt for insulation that covers the carbon crucible and carbon cap from the outside, a quartz tube that surrounds the carbon felt from the outside, and a high-frequency coil (heating heater) arranged around the quartz tube. A protective tube is inserted through the carbon felt and the upper surface of the carbon cap, and a thermocouple for measuring the temperature inside the carbon crucible is placed inside the protective tube.

[0073] Figure 19 is an explanatory diagram showing a titanium manufacturing method using the manufacturing apparatus shown in Figure 18. As shown in Figure 19, first, a YOF crucible is used, and titanium (Ti), yttrium (Y), and yttrium fluoride (YF) are used. ３ Prepare the following: Next, place titanium (Ti) and yttrium (Y) into a YOF crucible, then add yttrium fluoride (YF ３The raw material was packed into a YOF crucible. Next, the YOF crucible containing the raw material was placed in a carbon crucible (carbon susceptor), and a carbon cap was attached to the carbon crucible. Then, the carbon crucible and carbon cap were covered with carbon felt, placed inside a quartz tube, and deoxidized titanium (Ti) was performed by heating it by applying current to a high-frequency coil. Figure 20 is a graph showing the temperature profile of the deoxidation experiment. The temperature inside the Mo crucible was raised to about 1700°C, held for 15 minutes, and then the heating was stopped and it was cooled. Figure 19 shows the molten sample. The photograph on the far right of Figure 19 is the deoxidized titanium removed from the YOF crucible. By using a carbon crucible (carbon susceptor), deoxidized solid titanium could be obtained.

[0074] (Example 4) Figure 21 is a conceptual diagram of a method for producing solid titanium with a low yttrium concentration by melting and solidifying a titanium yttrium alloy using a rare earth metal oxyhalide crucible. In Figure 21, solid Y ｘ O ｙ F ｚ A rare-earth metal oxyhalide crucible contains liquid titanium-yttrium alloy. The rare-earth metal oxyhalide crucible is configured to allow localized cooling of its lower right section. Cooling allows for the solidification of titanium in the lower right section inside the rare-earth metal oxyhalide crucible.

[0075] Figure 22 shows the Ti-Y-O molten phase and solid Y at 2000 K (1727 °C). ２ O ３ Phase, or liquid YF ３ and solid Y ４ O ３ F ６ This figure shows the thermodynamic relationship between yttrium (Y) and oxygen concentration in a state where two phases coexist. Source: G. Kamimura, T. Ouchi, and TH Okabe, JOM 77, 6887 (2025). https: / / doi.org / 10.1007 / s11837-024-07022-2

[0076] As shown in Figure 22, solid Y ｘ Oｙ F ｚ Using a rare earth metal oxyhalide crucible, liquid YF ３ It can be seen that, according to equilibrium theory, titanium with a concentration of 0.1 mass% (1000 mass ppm) or less can be obtained by dissolving titanium using a flux and yttrium as a deoxidizing agent. Furthermore, as shown in Figure 21, if the liquid titanium with a low oxygen concentration obtained by dissolution is cooled, the yttrium in the titanium can be removed by segregation. This is because the deoxidizing agent yttrium does not dissolve in solid titanium. Therefore, when dissolving titanium using an oxyhalide crucible, it can be seen that titanium with low oxygen concentration and low rare earth metal concentration can be produced by selecting the dissolution and cooling conditions.

Claims

1. A method for producing titanium or a titanium alloy, comprising melting, casting, or sintering a metal raw material containing titanium (Ti) or a titanium alloy using a container having a component mainly composed of a rare earth metal oxyhalide salt in at least the part in contact with the metal raw material, thereby producing titanium or a titanium alloy with an oxygen concentration of 0.15% by mass (1500 mass ppm) or less.

2. A method for producing titanium or a titanium alloy, comprising melting, casting, or sintering titanium or a titanium alloy using a container having a component mainly composed of rare earth metal oxyhalide salts, to which rare earth metals and rare earth metal halide salts are added as auxiliary agents at least in the part that comes into contact with the metal raw material, thereby utilizing the reaction of rare earth metal oxyhalide salt formation to directly remove impurity oxygen from titanium or a titanium alloy and produce titanium or a titanium alloy with a low oxygen concentration.

3. A method for producing titanium or a titanium alloy according to any one of claims 1 to 2, comprising using one or more rare earth metal oxyfluoride salts selected from scandium oxyfluoride (ScOF), yttrium oxyfluoride (YOF), lanthanum oxyfluoride (LaOF), cerium oxyfluoride (CeOF), praseodymium oxyfluoride (ProOF), and neodymium oxyfluoride (NdOF).

4. A method for producing titanium or a titanium alloy according to any one of claims 1 to 2, using one or more rare earth metals selected from scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd).

5. Scandium fluoride (ScF ３ ), yttrium fluoride (YF ３ ), lanthanum fluoride (LaF ３ ), cerium fluoride (CeF ３ ), praseodymium fluoride (PrF ３ ), neodymium fluoride (NdF ３ A method for producing titanium or a titanium alloy according to any one of claims 1 to 2, comprising using one or more rare earth metal fluoride salts selected from the following:

6. A method for producing titanium or a titanium alloy according to any one of claims 1 to 2, wherein, in addition to a rare earth metal and a rare earth metal halide salt, a metal halide salt is used as an auxiliary agent.

7. A method for producing titanium or a titanium alloy according to any one of claims 1 to 2, comprising the steps of: producing a molded container or molded lining by molding a material obtained by mixing a rare earth metal halide salt and a rare earth oxide together with a binder into the shape of a container or a lining material for a container; and containing a metal raw material containing titanium or a titanium alloy in a separate container in which the molded container or the molded lining material is placed, and in this case forming a rare earth metal oxyhalide salt from the molded container or the molded lining material while the metal raw material is being heated.

8. A method for producing titanium or a titanium alloy according to any one of claims 1 to 2, wherein a container is used in which the member mainly composed of the rare earth metal oxyhalide salt is reinforced from the outside with a high melting point metal.

9. A method for producing titanium or a titanium alloy according to claim 2, wherein the oxygen concentration in titanium is controlled by adjusting the amount of the rare earth metal and the rare earth metal halide salt added to a member mainly composed of the rare earth metal oxyhalide salt.

10. A method for producing titanium or a titanium alloy according to any one of claims 1 to 2, wherein titanium or a titanium alloy is melted, cast, or sintered in the container using a melting apparatus selected from a resistance heating apparatus, a high-frequency induction heating apparatus, a plasma arc melting apparatus, and an electron beam melting apparatus.

11. A container used in an apparatus for producing metals or alloys by melting, casting, or sintering metal raw materials, wherein at least the part that comes into contact with the metal raw materials has a component mainly composed of a rare earth metal oxyhalide salt to which rare earth metals and rare earth metal halides are added as auxiliary agents.

12. An apparatus comprising the container described in claim 11 and a heating mechanism, for melting, casting, or sintering a metal raw material using the container.

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