Method for producing titanium or titanium alloy

Abstract

In the method for producing titanium or a titanium alloy, titanium or a titanium alloy having an oxygen concentration of 0.1 mass% (1000 mass ppm) or less is produced by melting and reacting titanium or a titanium alloy with a rare earth metal and a rare earth metal halide salt.

Description

Technical Field

[0001] This invention relates to a method for manufacturing titanium or titanium alloys.

[0002] This application claims priority based on Japanese Patent Application No. 2023-117129 filed with the Japan Patent Office on July 18, 2023, the contents of which are hereby incorporated. Background Technology

[0003] Titanium (Ti) and titanium-based alloys (titanium alloys) possess the highest specific strength and excellent corrosion resistance among metallic materials. Although titanium resources are inexhaustible, the main reason why titanium and titanium alloys have not been widely adopted is that titanium has a strong affinity for oxygen, making it difficult to smelt, melt, and cast, resulting in high manufacturing costs for titanium products.

[0004] The current mainstream method is to process titanium ore (TiO2, FeTiO2) in a carbon-containing reducing atmosphere. x The titanium is chlorinated to form an oxygen-free chloride (TiCl4), which is then reduced with metallic magnesium (Mg) to produce titanium with a low oxygen concentration of less than 0.05% by mass (500 mass ppm). Current titanium manufacturing processes, namely chlorination smelting, are costly and environmentally burdensome, generating large amounts of CO2 gas. To achieve mass production of titanium, it is urgent to develop groundbreaking new smelting processes.

[0005] However, an efficient method has not yet been established to remove oxygen from titanium ore and metallic titanium to a low concentration (below 500 mass ppm) without the use of chlorides, thus the mass production of titanium has not yet been achieved.

[0006] For example, to directly convert titanium oxide (TiO2) into metallic titanium, the reduction reaction of titanium oxide with aluminum (Al) and magnesium is considered. However, the crude titanium alloy (ATR-Ti) obtained by reducing titanium oxide with aluminum, or the crude titanium (MTR-Ti) obtained by reducing titanium oxide with magnesium, contains a large amount of oxygen impurities and cannot be directly used as a structural material for industrial applications.

[0007] The inventors of this invention have developed the following technique: by reacting rare earth metals such as yttrium (Y) and rare earth metal chlorides with oxygen present in solid titanium at about 1000°C for 24 to 48 hours, oxygen in titanium is directly removed, and titanium with an extremely low oxygen concentration of less than 0.01% by mass (100 mass ppm) can be produced (see Non-Patent Literature 1).

[0008] According to the method described in Non-Patent Document 1, even with thin waste only a few millimeters thick, oxygen can be efficiently removed, thus enabling the recycling of titanium waste with high oxygen concentrations. However, since oxygen diffusion in solid titanium is the rate-limiting stage of the process, there is a problem that the reaction time required to remove oxygen from the solid titanium is too long, and it cannot be applied to materials such as larger titanium ingots.

[0009] Furthermore, when using the method described in Non-Patent Document 1 for titanium alloy ingots containing large amounts of oxygen, such as ATR-Ti and MTR-Ti, removing the oxygen present inside the ingot takes a considerable amount of time. Therefore, it is not possible to use the method described in Non-Patent Document 1 to mass-produce low-oxygen-concentration titanium for structural material applications from ATR-Ti and MTR-Ti.

[0010] To remove oxygen directly from large titanium ingots or titanium alloy ingots in a short time, it is more ideal to process molten titanium or titanium alloys.

[0011] For the melting of titanium, heating methods such as high-frequency induction heating, plasma arc melting, and electron beam melting are effective. Especially when using high-frequency induction heating, the molten metal is thoroughly mixed, thus producing homogeneous titanium or titanium alloys. However, because molten titanium exhibits extremely high reactivity with oxygen, directly removing oxygen impurities from molten titanium or molten titanium alloys during the melting process is not easy.

[0012] For example, it is known that when melting titanium using a cold crucible-type suspension melting apparatus, one of the high-frequency induction heating devices, a method is used to remove oxygen from titanium by adding rare earth metals and calcium fluoride (see Patent Document 1). According to the method described in Patent Document 1, by adding the rare earth metal cerium (Ce) or a mixture of rare earth metals, i.e., mixed rare earth metals (Misch metal), to the molten titanium, the oxygen in the molten titanium can be reduced to 0.5% by mass (5000 mass ppm). However, using the method described in Patent Document 1, it is not possible to remove oxygen to the oxygen concentration level required for structural material applications, i.e., 0.1 to 0.2% by mass (1000 to 2000 mass ppm).

[0013] Furthermore, even when using the method described in Patent Document 1 on molten titanium alloys such as ATR-Ti and MTR-Ti, it is impossible to remove oxygen to 0.1 to 0.2% by mass (1000 to 2000 mass ppm). Therefore, it is impossible to use the method described in Patent Document 1 to manufacture low-oxygen-concentration titanium for structural material applications from ATR-Ti and MTR-Ti.

[0014] Furthermore, it is known that when melting Ti-46Al-8Nb alloy using a cold crucible-type melting apparatus, one of the high-frequency induction heating devices, oxygen is removed from the alloy by adding the rare earth metal yttrium (Y) and calcium fluoride (see Non-Patent Document 2). According to the method described in Non-Patent Document 2, oxygen in the molten Ti-46Al-8Nb alloy can be removed to 0.08% by mass (800 mass ppm). However, titanium alloys containing large amounts of aluminum are thermodynamically easy to deoxygenate, and the method described in Non-Patent Document 2 cannot remove oxygen from pure titanium or titanium alloy melts with low aluminum concentrations to the oxygen concentration level required for structural material applications, i.e., 0.1–0.2% by mass (1000–2000 mass ppm).

[0015] Furthermore, methods for removing oxygen from titanium-aluminum alloys containing 40% by mass or more aluminum are known, employing methods such as electric arc melting, plasma arc melting, and induction melting based on a water-cooled copper container. (See Patent Document 2). According to the method described in Patent Document 2, oxygen in the molten titanium-aluminum alloy can be removed to 0.022% by mass (220 mass ppm). However, the method described in Patent Document 2 is only effective for titanium-aluminum alloys with an aluminum concentration of 40% by mass or more. For titanium-aluminum alloys with an aluminum concentration of less than 40% by mass and a titanium content of 60% by mass or more, it is impossible to remove oxygen to a concentration below 0.6% by mass (6000 mass ppm).

[0016] Existing technical documents

[0017] Patent documents

[0018] Patent Document 1: Japanese Patent No. 2949222

[0019] Patent Document 2: Japanese Patent Application Publication No. 2016-135907

[0020] Non-patent literature

[0021] Non-patent literature 1: "Ultimate Deoxidation Method of Titanium Utilizing Y / YOCl / YCl3 Equilibrium", Akihiro Iizuka, Takanari Ouchi, and Toru H. Okabe: Metall. Mater. Trans. B, vol. 51 (2020) pp. 433-442. DOI: 10.1007 / s11663-019-01742-6)

[0022] Non-Patent Literature 2: “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) Summary of the Invention

[0023] The problem that the invention aims to solve

[0024] This invention was made in view of the above-mentioned problems, and its purpose is to provide a method for producing titanium or titanium alloy with low oxygen concentration by directly removing oxygen impurities from molten titanium or titanium alloy to a low concentration of less than 0.1% by mass (1000 mass ppm).

[0025] Methods for solving problems

[0026] (1) One aspect of the present invention provides a method for manufacturing titanium or titanium alloy, wherein titanium (Ti) or titanium alloy is melted together with rare earth metals and rare earth metal halide salts and reacted to produce titanium or titanium alloy with an oxygen concentration of less than 0.1% by mass (1000 mass ppm).

[0027] (2) One aspect of the present invention provides a method for manufacturing titanium or titanium alloys, which utilizes the deoxidizing ability of rare earth metals to react with the formation of rare earth metal oxyhalides to directly remove oxygen impurities in molten titanium or molten titanium alloys, thereby producing titanium or titanium alloys with low oxygen concentration.

[0028] (3) In the manufacturing method of (1) or (2), the titanium alloy may also be an alloy with a titanium concentration of 65% by mass or more.

[0029] (4) In any of the manufacturing methods in (1) to (3), one or more rare earth metals selected from yttrium (Y), cerium (Ce), and lanthanum (La) and one or more rare earth metal halide salts selected from yttrium fluoride (YF3), cerium fluoride (CeF3), and lanthanum fluoride (LaF3) may be used.

[0030] (5) In any of the manufacturing methods in (1) to (4), in addition to rare earth metals and rare earth metal halide salts, a flux of metal halide salts may also be used.

[0031] (6) In any of the manufacturing methods in (1) to (5), titanium or titanium alloy containing a large amount of oxygen impurities, which is produced by reducing titanium oxide with aluminum (Al) or magnesium (Mg), can also be used as titanium raw material.

[0032] (7) In any of the manufacturing methods in (1) to (5), titanium or titanium alloy containing a large amount of oxygen impurities, which is produced by reducing titanium oxide with rare earth metals or rare earth metal alloys, can also be used as titanium raw material.

[0033] (8) In any of the manufacturing methods in (1) to (5), titanium or titanium alloy waste can also be used as titanium raw material.

[0034] (9) In any of the manufacturing methods in (1), (4), and (5), in addition to the rare earth metal and the rare earth metal halide salt, a metal halide salt that lowers the melting point of the halide salt melt is used to melt the titanium and the titanium alloy.

[0035] (10) In any of the manufacturing methods in (1) to (9), the amount of rare earth metal added can be adjusted to control the oxygen concentration in titanium.

[0036] (11) In any of the manufacturing methods in (1) to (8), titanium and titanium alloys together with rare earth metals and rare earth metal halide salts may be melted in an inert atmosphere using a melting device selected from a high-frequency induction heating device, a plasma arc melting device, and an electron beam melting device.

[0037] (12) In the manufacturing method of (11), a cold crucible induction melting furnace may also be used as the high-frequency induction heating device, and a heat-resistant adhesive may be applied to the slit of the crucible in the cold crucible induction melting furnace to prevent the rare earth metal halide salt from adhering to the crucible.

[0038] Invention Effects

[0039] According to one aspect of the invention, a method is provided for directly removing oxygen impurities from molten titanium or titanium alloy, thereby producing titanium or titanium alloy with low oxygen concentration. Attached Figure Description

[0040] Figure 1 This is a process diagram illustrating the method for producing titanium or titanium alloys from titanium oxide according to the embodiments.

[0041] Figure 2 This is an example of a process diagram of a method for directly manufacturing low-oxygen-concentration titanium or titanium alloy from titanium or titanium alloy scrap, as described in the embodiments.

[0042] Figure 3It is a pseudo-binary phase diagram of Y2O3-YF3.

[0043] Figure 4 This is the isothermal chemical potential diagram of yttrium-oxygen-fluorine at 1727℃.

[0044] Figure 5 The thermodynamic relationship between equilibrium oxygen partial pressure and equilibrium oxygen concentration in titanium is shown in various deoxidation reaction systems.

[0045] Figure 6 The equilibrium oxygen concentration in titanium is shown in each deoxidation reaction system in the titanium-oxygen binary phase diagram.

[0046] Figure 7 This is an overall diagram of the titanium or titanium alloy melting apparatus involved in the embodiments.

[0047] Figure 8 This is a schematic cross-sectional view of a metal sample obtained by cooling after melting in a cold crucible induction melting furnace.

[0048] Figure 9 The image shows a titanium sample in a water-cooled copper crucible obtained by directly removing oxygen from molten titanium and cooling it to solidify in Example 1 of Table 1.

[0049] Figure 10 The image shows a side view of a titanium sample taken from a water-cooled copper crucible after oxygen was directly removed from the molten titanium using a cold crucible induction melting furnace in Example 1 of Table 1, followed by cooling and solidification.

[0050] Figure 11 In Example 1 of Table 1, the following was photographed. Figure 10 A photograph of the upper surface of the titanium sample shown.

[0051] Figure 12 In Example 1 of Table 1, photographs were taken of analytical titanium sample pieces cut from the obtained titanium sample.

[0052] Figure 13 In Example 2 of Table 1, photographs were taken of analytical titanium sample pieces cut from the obtained titanium sample.

[0053] Figure 14 In Example 8 of Table 1, photographs were taken of analytical titanium sample pieces cut from the obtained titanium sample.

[0054] Figure 15 The results are obtained by X-ray diffraction analysis of the yttrium fluoride (YF3) flux used in the deoxidation of titanium samples.

[0055] Figure 16 The results are obtained by X-ray diffraction analysis of the yttrium fluoride (YF3) flux used in the deoxidation of titanium samples.

[0056] Figure 17 This is a scanning electron microscope image of the yttrium fluoride (YF3) flux used in the deoxidation of titanium samples.

[0057] Figure 18 This is an example of a conceptual diagram of a novel titanium smelting method that directly produces titanium or titanium alloys from titanium oxide using the manufacturing method described in the above embodiments. Detailed Implementation

[0058] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0059] The basic content of the manufacturing method of this embodiment is as follows: oxygen-containing titanium or titanium alloy obtained by melting using a high-frequency induction device as a melting device is reacted with rare earth metals and rare earth metal halide salts to generate rare earth metal oxyhalides, and the oxygen in the molten titanium or titanium alloy is directly removed to a low concentration to produce titanium or titanium alloy with low oxygen concentration.

[0060] Figure 1 This is a process diagram illustrating the method for manufacturing titanium or titanium alloys from titanium oxide according to the embodiments. Figure 1 As shown, the manufacturing method of titanium or titanium alloy of the present invention mainly includes three stages of processes (first process S11 to third process S13).

[0061] First step S11: First, titanium oxide is reduced using aluminum, magnesium, etc., to produce titanium or titanium alloys. Titanium oxide can be made from titanium ore or produced from titanium ore. In this first step, by adding calcium fluoride (CaF2) or similar reaction aids (fluxes), the products of the reduction reaction, namely aluminum oxide and magnesium oxide, can be absorbed into the reaction aids. Metal halide salts other than calcium fluoride can also be used as fluxes.

[0062] Second step S12: Since the titanium or titanium alloy obtained through the first step contains a large amount of oxygen impurities, the impurity-containing titanium or titanium alloy is melted next, and rare earth metals and reaction aids are added to remove the oxygen. In the second step, rare earth metal halide salts are added as reaction aids to convert the products of the above reaction, i.e., rare earth metal oxides, into rare earth metal oxyhalides. Alternatively, metal halide salts that lower the melting point of the halide salt melt can also be used.

[0063] Third step S13: Finally, the molten titanium or titanium alloy with low oxygen concentration obtained through the second step is cast and rolled.

[0064] Fourth step S14: The reaction products of the second step S12, namely rare earth metal oxyhalides, can be reused as rare earth metals used in the second step S12 through the rare earth metal separation and recovery process.

[0065] Figure 2 This is a process diagram illustrating a manufacturing method according to other embodiments. Figure 2 This is an example of a process diagram for manufacturing low-oxygen-concentration titanium or titanium alloy directly from titanium or titanium alloy scrap. Figure 2 The manufacturing method shown includes the first step S21 to the third step S23.

[0066] In the first step S21, rare earth metals and reaction aids containing rare earth metal halide salts are added to the waste titanium or titanium alloy to remove oxygen.

[0067] In the second process S22, the molten titanium or titanium alloy with low oxygen concentration obtained in the first process S21 is cast and rolled.

[0068] In the third step S23, rare earth metals are recovered from the rare earth metal oxyhalides generated in the first step S21 and recycled as rare earth metals used in the first step S21.

[0069] like Figure 2 As shown, using the titanium or titanium alloy manufacturing method of this embodiment, even from waste containing a large amount of oxygen impurities, it is possible to directly manufacture titanium or titanium alloys with low oxygen concentration.

[0070] The following describes the principle of a deoxidation method using a rare earth metal oxyhalide generation reaction based on an embodiment, which directly produces low-oxygen-concentration titanium or titanium alloy from molten titanium or titanium alloy.

[0071] The oxygen removal method for removing oxygen from molten titanium or titanium alloys involved in the embodiments is characterized in that oxygen-containing titanium or titanium alloys, rare earth metals and rare earth metal halide salts are melted in an inert atmosphere using a high-frequency induction device such as a cold crucible induction melting furnace, and held for about 10 to 20 minutes, so that the oxygen (O) in the molten titanium or titanium alloy reacts with rare earth metals (RE (Y, La, Ce, etc.)) and rare earth metal halide salts (REX3 (REF3, etc.)) (refer to formula (1)).

[0072] O(Ti) + 2 / 3 RE(l) + 1 / 3 REX3(l) → REOX(s)…(1)

[0073] RE: Rare earth metal elements such as Y, La, and Ce

[0074] X: Halogen elements such as Cl and F

[0075] In the oxygen removal process for removing oxygen from molten titanium or titanium alloys as described in this embodiment, rare earth metal halide salts are added to generate rare earth metal oxyhalides (REOX) through the reaction of formula (1). It should be noted that the core of the manufacturing method in this embodiment, namely the deoxidation reaction of titanium, utilizes the deoxidation ability of rare earth metals and the generation reaction of rare earth metal oxyhalides. As long as rare earth metal oxyhalides can be generated, the method of using rare earth metal halide salt REX3 is not limited. For example, by keeping rare earth metals and metal halide salts such as CaF2, which are stable at high temperatures, under conditions for generating rare earth metal oxyhalides, rare earth metal oxyhalides can also be generated in situ to deoxidize titanium.

[0076] As a representative example of rare earth metals and their halide salts involved in the implementation method, the deoxidation limit in the deoxidation reaction of molten titanium using yttrium (Y) and fluoride was studied based on thermodynamic principles. When yttrium and yttrium fluoride (YF3) are used in formula (1), yttrium fluoride oxyfluoride (YOF) is generated, and the equilibrium of yttrium / yttrium fluoride oxyfluoride (Y / YOF / YF3 equilibrium) is established.

[0077] Figure 3 This is the phase diagram of the pseudo-binary Y2O3-YF3 system (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 lines in the diagram represent the temperature conditions of this embodiment. At high temperatures exceeding the melting point of titanium, yttrium fluoride (YF3)... x O y F z The yttrium oxide (Y₂O₃) phase can thermodynamically coexist with the YF₃ phase, while the yttrium oxide (Y₂O₃) phase cannot. Therefore, in systems where YF₃ is in excess, the deoxidation product of titanium using yttrium is yttrium fluoride (Y₂O₃). x O y F z ), to carry out the deoxygenation reaction of formula (1).

[0078] Figure 4 This is the isothermal chemical potential diagram of yttrium-oxygen-fluorine at 1727℃. The circles in the diagram indicate the conditions of this embodiment, under the condition that the Y / YOF / YF3 equilibrium is met, to remove oxygen impurities from titanium or titanium alloys.

[0079] Figure 5The thermodynamic relationship between equilibrium oxygen partial pressure and equilibrium oxygen concentration in titanium is shown in various deoxidation reaction systems. The elliptical region in the figure represents the Y / YOF / YF3 equilibrium and temperature, which are the main conditions for this embodiment. It can be seen that by utilizing the Y / YOF / YF3 equilibrium, the oxygen in titanium can theoretically be reduced to 0.01% by mass (100 mass ppm).

[0080] Figure 6 The equilibrium oxygen concentration in titanium under various deoxidation reaction systems is shown in the titanium-oxygen binary phase diagram. According to the attached figure, based on thermodynamic theory, it can be predicted that titanium with an oxygen concentration of less than 0.1% by mass (1000 mass ppm) can be obtained by utilizing the Y / YOF / YF3 equilibrium.

[0081] In this embodiment, it was found that the formation reaction of rare earth metal oxyhalides (REOX) could, in principle, directly remove oxygen impurities from molten titanium. However, the thermodynamic stability of rare earth metal oxyhalides (REOX) at high temperatures remains unclear, and the above calculations and predictions have significant uncertainties. Since the actual deoxidation limit of titanium needs to be determined experimentally, its effectiveness is demonstrated in the examples described later.

[0082] In the method described in Patent Document 1, no rare earth metal halide salts are added. In this case, rare earth metal oxides (RE2O3) are generated through the reaction of oxygen in titanium and titanium alloys with rare earth metals. On the other hand, in this embodiment where rare earth metal halide salts (REX3) are added, the rare earth metal oxides react with the rare earth metal halide salts to make the rare earth metal oxides chemically and thermodynamically unstable, generating rare earth metal oxyhalides (REOX). Thus, in this embodiment, since the chemical activity (activity) of the rare earth metal oxides is reduced, it is possible to manufacture titanium or titanium alloys with high chemical and thermodynamic deoxidation ability and lower oxygen concentration.

[0083] In the manufacturing method described in the embodiments, the titanium or titanium alloy containing oxygen impurities used as the titanium raw material in the deoxidation process can be not only ATR-Ti or MTR-Ti, but also titanium waste generated during the cutting process of titanium ingots or titanium waste contained in waste products. Alternatively, titanium or titanium alloys containing a large amount of oxygen impurities, which are produced by reducing titanium oxide using rare earth metals or rare earth metal alloys, can also be used as the titanium raw material. Titanium alloys contain alloying elements such as aluminum and vanadium.

[0084] In the manufacturing method of this embodiment, the titanium alloy used as raw material can be an alloy with a titanium mass concentration of 65% or more. Titanium alloys with high titanium mass concentrations are difficult to remove oxygen impurities from, and existing refining methods cannot produce titanium alloys with low oxygen concentrations. However, according to the manufacturing method of this embodiment, even when using a titanium alloy containing 65% or more titanium as raw material, oxygen impurities can be directly removed from the molten titanium alloy, enabling the production of titanium alloys with low oxygen concentrations.

[0085] Regarding the rare earth metals used in the deoxidation reaction of the manufacturing method described in the embodiments, it is preferable to use one or more selected from yttrium (Y), lanthanum (La), and cerium (Ce). Alternatively, a mixture of these metals, i.e., a mixed rare earth metal, may be added. Other rare earth metals besides those mentioned above may also be used. However, in recent years, with the increase in the production of neodymium (Nd), holmium (Dy), terbium (Tb), etc., which are used as raw materials for magnets, the supply of Y, La, and Ce, which are produced as byproducts, has become insufficient. Therefore, from the perspective of economic rationality and resource utilization, byproduct rare earth metals such as yttrium, lanthanum, and cerium are preferred.

[0086] Regarding the rare earth metal halide salts used in the deoxidation reaction of the manufacturing method described in the embodiments, fluorides of Y, La, Ce, etc., can be used. These rare earth metal fluorides are stable in a liquid state even at high temperatures above 1700°C where titanium or titanium alloys are molten, and are therefore preferred. The rare earth metal constituting the rare earth metal halide salt and the rare earth metal added as a titanium raw material can also be different types of rare earth metals. For example, cerium fluoride (CeF3) and yttrium (Y) can be used in combination.

[0087] [Example]

[0088] The present invention will be further described in detail below through embodiments. However, the present invention is not limited to the following embodiments.

[0089] Figure 7 This is an overall diagram of the titanium or titanium alloy melting apparatus involved in the embodiments.

[0090] Figure 7The melting apparatus shown is a type of high-frequency induction heating apparatus, namely a cold crucible induction melting furnace. The cold crucible induction melting furnace 10 of this embodiment includes a crucible 1, an induction coil 3 disposed around the outer periphery of the crucible 1, and a water-cooling mechanism 4 for cooling the crucible 1. The crucible 1 is a bottomed cylindrical heat-resistant container with an opening at the top and a bottom wall at the bottom. Multiple slits (not shown) extending vertically are provided on the side wall of the crucible 1. The induction coil 3 is configured to surround the lower outer periphery of the crucible 1. A high-frequency power supply (not shown) is connected to the induction coil 3. A heat-resistant adhesive 2 is applied to the slits on the inner surface of the crucible 1. By applying the heat-resistant adhesive 2, adhesion between the metal sample and flux inside the crucible 1 and the inner wall surface of the crucible 1 can be suppressed. This makes it easy to remove the deoxidized metal sample. In this embodiment, the heat-resistant adhesive 2 is applied from the lower end of the slit upwards along the slit. The upper end of the applied heat-resistant adhesive 2 is located higher than the setting range of the induction coil 3.

[0091] Figure 8 This is a cross-sectional schematic diagram of a metal sample obtained by cooling after melting in a cold crucible induction melting furnace. Metal sample 5 is located at the bottom center of crucible 1, and flux 6 is located between metal sample 5 and the inner wall of crucible 1.

[0092] The cooled titanium block was cut into small pieces for quantitative determination of the concentrations of oxygen, nitrogen, and rare earth metals.

[0093] The oxygen and nitrogen concentrations of the titanium metal samples obtained after melting and cooling are shown in Table 1 along with the melting experimental conditions.

[0094] [Table 1]

[0095]

[0096] In this embodiment, a yttrium oxide-based heat-resistant adhesive is applied to the slit of a water-cooled copper crucible (62 mm inner diameter, 130 mm depth) inside a cold crucible induction melting furnace. After applying the heat-resistant adhesive, 350 g of titanium (Ti), 2-65 g of yttrium (Y), and 110 g of yttrium fluoride (YF3) are loaded into the water-cooled copper crucible.

[0097] In some experiments, to achieve an initial oxygen concentration of 1% by mass (10,000 mass ppm) in the titanium, 9g of titanium oxide (TiO2) was added. The sample was heated under an argon atmosphere, and after visual confirmation that it had completely melted, the temperature was maintained for 10–20 minutes. Afterward, the furnace power was reduced and the sample was air-cooled before being removed.

[0098] Figure 9 The image shows a photograph of a titanium sample obtained in a water-cooled copper crucible after oxygen was directly removed from molten titanium and cooled and solidified using a cold crucible induction melting furnace, as described in Example 1 of Table 1.

[0099] Figure 10 as well as Figure 11 The image shows the appearance of a titanium sample taken from a water-cooled copper crucible after oxygen was removed directly from molten titanium using a cold crucible induction melting furnace in Example 1 of Table 1, followed by cooling and solidification.

[0100] Figure 12 The photographs are taken from the analytical titanium sample pieces cut from the obtained titanium sample in Example 1 of Table 1.

[0101] Figure 13 The photographs are taken from the analytical titanium sample pieces cut from the obtained titanium sample in Example 2 of Table 1.

[0102] Figure 14 The photographs are taken from the analytical titanium sample pieces cut from the obtained titanium sample in Example 8 of Table 1.

[0103] When titanium was melted under the conditions of Example 1 in Table 1, metal samples with extremely low oxygen concentrations of 0.011% to 0.023% by mass (110 to 230 mass ppm) were obtained. Figure 12 As shown in the analysis of the sample, the oxygen concentration decreased to 0.02% by mass (200 mass ppm) throughout the entire sample, yielding a result highly consistent with thermodynamic predictions. Furthermore, it is evident that deoxidation was uniformly achieved throughout the entire sample. At this point, the nitrogen concentration in the metal sample was 0.012% to 0.015% by mass (120 to 150 mass ppm), and the yttrium concentration was approximately 2% by mass. Generally, even using methods such as chlorination to produce high-purity titanium via chloride production, it is difficult to obtain titanium with oxygen concentrations below 0.02% by mass (200 mass ppm), making this experimental result particularly noteworthy.

[0104] When titanium was melted under the conditions of Example 2 in Table 1, a metal sample with a low oxygen concentration of approximately 0.06% by mass (600 mass ppm) was obtained. Figure 13 As shown in the analysis of the sample, the oxygen concentration decreased to 0.06% by mass (600 mass ppm) throughout the entire sample. At this point, the yttrium concentration in the metallic sample was below 1% by mass. It is clear that yttrium incorporation into titanium can be suppressed, and oxygen can be removed to a concentration of approximately 0.1% by mass (1000 mass ppm).

[0105] When titanium was melted under the conditions of Examples 3, 4, and 5 in Table 1, metal samples with an oxygen concentration of less than 0.1% by mass (1000 massppm) were obtained.

[0106] As shown in the melting experiments of Examples 6, 7, 8, 10, and 11 in Table 1, even in experiments where titanium oxide (TiO2) was intentionally added to set the initial oxygen concentration in titanium to 1% by mass (10,000 mass ppm), the oxygen in the molten titanium was removed to 0.1% by mass (1,000 mass ppm). According to... Figure 14 As can be seen from the analysis of the sample areas shown, in Example 8 of Table 1, the oxygen concentration in the overall sample area was reduced to approximately 0.1% by mass (1000 mass ppm). It is particularly noteworthy that even with the deliberate addition of a large amount of oxide to the titanium sample, the oxygen impurities can be reduced to 0.1% by mass (1000 mass ppm) using the method described above.

[0107] As shown in the melting experiments of Examples 9-11 in Table 1, even when the rare earth metals were changed to lanthanum (La) and cerium (Ce), it was confirmed that titanium with the same low oxygen concentration as when yttrium (Y) was used was obtained.

[0108] On the other hand, as shown in the melting experiments of the comparative examples in Table 1, it is not possible to obtain metal samples with a low oxygen concentration of less than 0.1% by mass (1000 mass ppm) without using rare earth metal halide salts for deoxidation treatment.

[0109] Figure 15 as well as Figure 16 The X-ray diffraction results of the yttrium fluoride (YF3) flux used in the deoxidation of titanium samples are shown. Yttrium fluoride (YF3) was confirmed to have formed in the flux after the experiment. x O y F z ), but yttrium oxide (Y2O3) was not detected.

[0110] Figure 17 These are scanning electron microscope images of the yttrium fluoride flux used in the deoxidation of titanium samples. Table 2 shows... Figure 17 The results of energy-dispersive X-ray spectroscopy analysis at various points are shown in the scanning electron microscope images. In the flux after the experiment, metallic yttrium (Y), yttrium fluoride, and yttrium fluoride phases were detected, but yttrium oxide phase was not detected. These results indicate that, under the conditions of the embodiment, oxygen in titanium is removed by the reaction shown in formula (1).

[0111] [Table 2]

[0112]

[0113] Based on the above results, it can be concluded that titanium with low oxygen concentration can be produced by removing oxygen from ATR-Ti and MTR-Ti, which have high oxygen concentrations. Furthermore, the recycling of titanium waste can be achieved by removing oxygen from titanium waste with high oxygen concentrations. After all experiments, the nitrogen concentration in the metal samples was approximately 0.02% by mass (200 mass ppm), and even if nitrogen was introduced due to the addition of rare earth metals or fluxes, the amount was negligible.

[0114] It is clear that by adjusting the yttrium concentration, i.e. the amount of rare earth metals added, the oxygen concentration in titanium can be controlled to a low value.

[0115] As can be clearly seen from the above embodiments, the manufacturing method of titanium or titanium alloy using the above embodiments can directly manufacture titanium or titanium alloy with a low oxygen concentration of less than 0.1% by mass (1000 mass ppm), which is not achievable in existing melting technology, without the use of chloride.

[0116] Figure 18 This is an example of a conceptual diagram of a novel titanium smelting method that directly produces titanium or titanium alloys from titanium oxide (TiO2) using the manufacturing method described in the above embodiments.

[0117] like Figure 18 As shown, in the novel smelting method, a first device 101 for reducing titanium oxide, a second device 102 for deoxidizing titanium, and a third device 103 for casting titanium with low oxygen concentration are connected and used in sequence.

[0118] The first apparatus 101 includes a reaction vessel 101a, a titanium discharge section 101b, and a waste discharge section 101c. The second apparatus 102 includes a reaction vessel 102a, a titanium discharge section 102b, and a waste discharge section 102c. The third apparatus 103 includes a casting mold 103a.

[0119] In the reaction vessel 101a of the first apparatus 101, titanium ore or titanium oxide, aluminum (Al), magnesium (Mg) and other metal reducing agents, and calcium oxide (CaO) and other fluxing agents are loaded. The titanium ore or titanium oxide in the reaction vessel 101a is reduced by the metal reducing agents to generate titanium with a high oxygen concentration.

[0120] The titanium discharge section 101b of the first apparatus 101 is a pipe extending from the side of the reaction vessel 101a to the reaction vessel 102a of the second apparatus 102. The front end of the titanium discharge section 101b opens at the opening of the reaction vessel 102a. 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.

[0121] The waste discharge section 101c of the first device 101 is a pipe extending outward from the upper side of the reaction vessel 101a. The waste generated in the first device 101 is discharged and recycled to the outside of the reaction vessel 101a through the waste discharge section 101c.

[0122] In the reaction vessel 102a of the second apparatus 102, molten titanium, rare earth metals such as yttrium (Y), lanthanum (La), and cerium (Ce), as well as rare earth metal halide salts such as yttrium fluoride (YF3), supplied from the first apparatus 101, with a high oxygen concentration, are loaded together. In the reaction vessel 102a, oxygen impurities are removed from the molten titanium using a rare earth metal oxyhalide formation reaction, resulting in titanium with a low oxygen concentration.

[0123] The titanium discharge section 102b of the second device 102 is a pipe extending from the side of the reaction vessel 102a to the mold 103a of the third device 103. The front end of the titanium discharge section 102b opens into the opening of the mold 103a. Molten titanium with a low oxygen concentration produced in the second device 102 is supplied to the mold 103a of the third device 103 through the titanium discharge section 102b.

[0124] The waste discharge section 102c of the second device 102 is a pipe extending outward from the upper side of the reaction vessel 102a. The waste generated in the second device 102 is discharged and recycled to the outside of the reaction vessel 102a through the waste discharge section 102c.

[0125] The casting performed by the third device 103 enables the production of titanium ingots with low oxygen concentration from molten titanium with low oxygen concentration.

[0126] use Figure 18 The novel smelting method shown can directly produce low-oxygen-concentration titanium or titanium alloys from titanium oxide without the need for chlorides.

[0127] Figure Labels

[0128] 1…Water-cooled copper crucible; 2…Slit and heat-resistant adhesive; 3…Induction coil; 4…Water-cooling mechanism; 5…Metal sample; 6…Fluid; S11, S21…First process; S12, S22…Second process; S13, S23…Third process; S14…Fourth process.

Claims

1. A method for manufacturing titanium or titanium alloy, wherein, Titanium (Ti) or titanium alloys are melted together with rare earth metals and rare earth metal halide salts and reacted to produce titanium or titanium alloys with an oxygen concentration of less than 0.1% by mass (1000 mass ppm).

2. A method for manufacturing titanium or titanium alloy, wherein, By utilizing the deoxidizing ability of rare earth metals and the reaction that generates rare earth metal oxyhalides, oxygen impurities in molten titanium or molten titanium alloys can be directly removed, producing titanium or titanium alloys with low oxygen concentration.

3. The method for manufacturing titanium or titanium alloy according to claim 1 or 2, wherein, The titanium alloy is an alloy with a titanium mass concentration of 65% or more.

4. The method for manufacturing titanium or titanium alloy according to claim 1 or 2, wherein, It uses one or more rare earth metals selected from yttrium (Y), cerium (Ce), and lanthanum (La) and one or more rare earth metal halide salts selected from yttrium fluoride (YF3), cerium fluoride (CeF3), and lanthanum fluoride (LaF3).

5. The method for manufacturing titanium or titanium alloy according to claim 1 or 2, wherein, In addition to rare earth metals and rare earth metal halide salts, fluxes of metal halide salts are also used.

6. The method for manufacturing titanium or titanium alloy according to claim 1 or 2, wherein, Titanium or titanium alloys containing a large amount of oxygen impurities, produced by reducing titanium oxide with aluminum (Al) or magnesium (Mg), are used as titanium raw materials.

7. The method for manufacturing titanium or titanium alloy according to claim 1 or 2, wherein, Titanium or titanium alloys containing a large amount of oxygen impurities, produced by reducing titanium oxide with rare earth metals or rare earth metal alloys, are used as titanium raw materials.

8. The method for manufacturing titanium or titanium alloy according to claim 1 or 2, wherein, Waste titanium or titanium alloys is used as titanium raw material.

9. The method for manufacturing titanium or titanium alloy according to claim 1, wherein, In addition to the rare earth metals and the rare earth metal halide salts, metal halide salts that lower the melting point of the halide salt melt are also used to melt titanium and titanium alloys.

10. The method for manufacturing titanium or titanium alloy according to claim 1 or 2, wherein, Adjust the amount of rare earth metals added to control the oxygen concentration in titanium.

11. The method for manufacturing titanium or titanium alloy according to claim 1 or 2, wherein, Rare earth metals and rare earth metal halide salts, along with titanium and titanium alloys, are melted together in an inert atmosphere using a melting apparatus selected from high-frequency induction heating devices, plasma arc melting devices, and electron beam melting devices.

12. The method for manufacturing titanium or titanium alloy according to claim 11, wherein, A cold crucible induction melting furnace is used as the high-frequency induction heating device. A heat-resistant adhesive is applied to the slits of the crucible in the cold crucible induction melting furnace to prevent the rare earth metal halide salt from adhering to the crucible.

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