Method for producing metallic titanium or titanium alloy

Abstract

To provide a method for producing metal titanium or a titanium alloy by which the reduction of the content of O in a titanium-based raw material by a deoxidizing agent containing Ca can be achieved with high safety and at a low cost.SOLUTION: The method for producing metal titanium or a titanium alloy according to the present invention is a method for producing, from a titanium-based raw material containing O, metal titanium or a titanium alloy having a lower O content than the titanium-based raw material, the method including a deoxidation step of heating the titanium-based raw material and a deoxidizer containing Ca inside a reaction vessel 1, bringing the deoxidizer into contact with the titanium-based raw material in a molten state, and reducing the O content of the titanium-based raw material by a deoxidation reaction, in the deoxidation step, as the reactor vessel 1, there is used a reactor vessel 1 in which at least a part of an upper wall portion located on the upper side of the titanium based material and the deoxidizer disposed in the reactor vessel 1 is a movable wall portion 3a capable of moving to change the volume of the reactor vessel 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing metallic titanium or a titanium alloy with a low oxygen (O) content by reducing the O content from a titanium-based raw material containing O. [Background technology]

[0002] The production of industrial titanium metal and titanium alloys is generally carried out by producing titanium sponge from titanium ore using a method based on the Kroll process.

[0003] However, this method requires the chlorination of titanium ore, the purification of the resulting titanium tetrachloride, the reduction of titanium tetrachloride with metallic magnesium, and the separation and removal of the by-product magnesium chloride. It also requires the crushing of titanium sponge lumps and the electrolysis of the magnesium chloride produced by the reduction, and therefore involves multiple batch processes. For these reasons, the above method cannot be said to be an efficient and low-cost production method for titanium metal and titanium alloys. Furthermore, the reaction to produce titanium tetrachloride uses coke (carbon), which emits carbon dioxide, a greenhouse gas that contributes to global warming.

[0004] Under these circumstances, as described in Patent Documents 1 and 2, for example, studies have been conducted on reducing titanium oxide with Al to smelt titanium ore.

[0005] More specifically, Patent Document 1 describes a "method for extracting a titanium product from titanium ore, characterized by comprising the steps of: mixing a chemical blend containing titanium ore and a reducing agent, the titanium ore to reducing agent ratio being 0.9 to 2.4, the mass ratio of the titanium oxide component in the titanium ore to the reducing metal in the reducing agent being equivalent to; heating the chemical blend to initiate an extraction reaction, the chemical blend being heated at a rate of 1°C to 50°C / min; maintaining the chemical blend at a reaction temperature of 1500 to 1800°C for between 5 and 30 minutes; cooling the chemical blend to a temperature below 1670°C; and separating the titanium product from residual slag," in which "the titanium ore contains titanium oxide (TiO2) and the reducing agent contains aluminum (Al)." Patent Document 2 also describes a similar method.

[0006] Patent Document 3 aims to "provide a high-purity low-oxygen Ti-Al alloy and a method for producing the same by deoxidizing with Ca, evaporating and removing excess Ca, and by homogeneously melting without contamination in the production of an alloy system mainly composed of Ti-Al," and describes a method for producing a low-oxygen Ti-Al alloy, which involves "melting and retaining a Ti-Al alloy in a calcia crucible in the production of an alloy system mainly composed of Ti-Al, adding a Ca source to the alloy to deoxidize it, and using the resulting material as a melting raw material, melting the material in an inert gas atmosphere or vacuum atmosphere at a reduced pressure below atmospheric pressure by a melting method that does not use a refractory material, and retaining the molten metal to forcibly evaporate and remove Ca." Furthermore, Non-Patent Document 1 discloses a technique for reducing a preform containing titanium ore or UGI (upgraded ilmenite) with metallic calcium vapor. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 2015-507696 [Patent Document 2] Special Publication No. 2019-533081 [Patent Document 3] Japanese Patent Application Publication No. 5-140669 [Non-patent literature]

[0008] [Non-Patent Document 1] Haiyan Zheng et al., "Production of Titanium Powder by the Calciothermic Reduction of Titanium Concentrates or Ore Using the Preform Reduction Process", Materials Transactions, Vol. 48, No. 8 (2007) pp. 2244 to 2251 Summary of the Invention [Problem to be solved by the invention]

[0009] Incidentally, in order to smelt or refine titanium ore, titanium-based scrap, or other titanium-based raw materials containing O to reduce the O content, it is believed that it would be effective to utilize the excellent deoxidizing power of Ca in addition to Al as described in Patent Documents 1 and 2. In addition, Ca is difficult to dissolve in solid Ti, and it is also promising as a deoxidizing agent in that it hardly remains as an impurity in the metallic titanium or titanium alloy obtained after deoxidation.

[0010] To efficiently deoxidize titanium-based raw materials using a deoxidizer containing Ca, it is necessary to bring the deoxidizer into contact with the titanium-based raw materials in a molten state. However, there is a concern that Ca in the deoxidizer, which has a relatively low boiling point, may evaporate when heated to a relatively high temperature during the deoxidation reaction and may not contribute sufficiently to the reaction. To prevent this, it is possible to heat the deoxidizer and titanium-based raw materials in a sealed container, thereby causing the deoxidation reaction while suppressing the evaporation of Ca from the deoxidizer.

[0011] However, when high-temperature heating for the above-mentioned deoxidation is performed in a sealed container, even if Ca evaporation can be suppressed to some extent, even a small amount of Ca evaporates inside the container, generating steam, which significantly increases the internal pressure of the sealed container in the gas phase space, resulting in extremely high pressure inside. The sealed container must be made of a material and structure that can withstand such high-temperature and high-pressure conditions, which reduces design freedom from a safety perspective and requires expensive materials. This increases the costs required for smelting and refining titanium-based raw materials. If the reaction is performed in an atmosphere of flowing inert gas, the pressure increase can be avoided, but the amount of calcium evaporated increases, making it unable to contribute to deoxidation.

[0012] Patent Document 3 does not consider at all how to increase the reaction efficiency between the Ca-containing deoxidizer and the titanium-based raw material, as described above, or the problems that arise from an increase in the internal pressure of the sealed container in that case.Non-Patent Document 1 also does not teach a measure to increase the reaction efficiency by using Ca instead of vapor.

[0013] An object of the present invention is to provide a highly safe and low-cost method for producing metallic titanium or a titanium alloy, which can reduce the O content of titanium-based raw materials using a Ca-containing deoxidizer. [Means for solving the problem]

[0014] The method for producing metallic titanium or a titanium alloy of the present invention is a method for producing metallic titanium or a titanium alloy having a lower O content than a titanium-based raw material containing O, from the titanium-based raw material, and includes a deoxidation step of heating the titanium-based raw material and a Ca-containing deoxidizer inside a reaction vessel, bringing the deoxidizer into contact with the titanium-based raw material in a molten state, and reducing the O content of the titanium-based raw material by a deoxidation reaction, and the reaction vessel used in the deoxidation step is a reaction vessel in which at least a portion of an upper wall located above the titanium-based raw material and the deoxidizer placed inside the reaction vessel is a movable wall that can move to change the volume of the reaction vessel.

[0015] Here, in the deoxidizing step, it is preferable that at least a part of the inner surface of the movable wall portion be brought into contact with the titanium-based raw material and the deoxidizing agent inside the reaction vessel.

[0016] In this case, it is preferable that at least the inner surface of the movable wall portion is made of a calcium-based compound having a melting point of 1950° C. or higher.

[0017] The reaction vessel may also include an exhaust hole for discharging gas components inside the reaction vessel to the outside.

[0018] The titanium-based raw material may include a non-metallic substance.

[0019] The non-metallic material is titanium ore, TiO 2-x (0≦x<1) and CaTiO3.

[0020] The titanium-based raw material may include a titanium metal raw material and / or a titanium alloy raw material.

[0021] In the deoxidation step, it is preferable that a slag generating agent is added to the reaction vessel and heated to cause the deoxidation reaction.

[0022] The slag forming agent preferably contains Ca.

[0023] It is also preferable to use a slag forming agent whose melting point is lower than the boiling point of the deoxidizing agent.

[0024] In the deoxidation step, the reaction vessel containing an induction-heatable conductive material is placed in a high-frequency induction heating furnace, and the deoxidation reaction can be caused to occur in an inert gas atmosphere.

[0025] In the deoxidation step, it is preferable to use a reaction vessel having at least an inner surface made of calcia as the reaction vessel.

[0026] In the deoxidation step, the inside of the reaction vessel can be heated to 900°C to 2000°C.

[0027] The above-described manufacturing method may include an electrolysis step in which, after obtaining a titanium-based material having an O content reduced compared to the titanium-based raw material through the deoxidation reaction in the deoxidation step, the titanium-based material is used as a crude titanium-based material for an anode, and a voltage is applied between the anode and cathode in a molten salt bath to elute Ti from the crude titanium-based material and deposit a refined titanium-based material on the cathode.

[0028] In this case, the electrolysis step is repeated multiple times, and in the multiple electrolysis steps, the refined titanium-based material deposited on the cathode in the previous electrolysis step can be used as the crude titanium-based material in the next electrolysis step. [Effects of the Invention]

[0029] According to the method for producing metallic titanium or a titanium alloy of the present invention, it is possible to reduce the O content of titanium-based raw materials using a deoxidizer containing Ca, with high safety and at low cost. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a cross-sectional view taken along the axial direction showing an example of a reaction vessel that can be used in the deoxidation step of a method for producing metallic titanium or a titanium alloy according to one embodiment of the present invention. FIG. [Figure 2] FIG. 10 is a cross-sectional view along the axial direction showing another example of a reaction vessel. [Figure 3] FIG. 10 is a cross-sectional view along the axial direction showing yet another example of a reaction vessel. [Figure 4] FIG. 10 is a cross-sectional view along the axial direction showing yet another example of a reaction vessel. DETAILED DESCRIPTION OF THE INVENTION

[0031] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A method for producing metallic titanium or a titanium alloy according to one embodiment of the present invention is a method for producing metallic titanium or a titanium alloy having a lower O content than the titanium-based raw material from a titanium-based raw material containing oxygen (O), and includes a deoxidation step in which the titanium-based raw material and a deoxidizer containing calcium (Ca) are heated inside a reaction vessel, and the deoxidizer is brought into contact with the titanium-based raw material in a molten state, reducing the O content of the titanium-based raw material through a deoxidation reaction.

[0032] Here, the reaction vessel described above is a reaction vessel having a movable wall portion, at least a portion of which is located above the titanium-based raw material and deoxidizer disposed inside the reaction vessel, and which can move to change the volume of the reaction vessel. By using a reaction vessel with a movable wall portion, if the internal pressure of the reaction vessel increases too much, the movement of the movable wall portion suppresses the increase in internal pressure, allowing the deoxidation process to be performed without excessively high pressure inside the reaction vessel. This allows the reaction vessel to be made of a material and structure that is not particularly pressure-resistant, making it relatively inexpensive to manufacture. Furthermore, the movable wall portion can reduce the internal pressure of the reaction vessel, allowing the deoxidation reaction to occur more safely. Furthermore, even if the deoxidizer or the like evaporates inside the reaction vessel, its gas components are less likely to be released outside the reaction vessel, which increases the time the deoxidizer remains inside the reaction vessel and increases the proportion of deoxidizer that contributes to the reaction.

[0033] The titanium-based raw material to be subjected to the deoxidation step can be various as long as it contains O. Specific examples include titanium ore and titanium-based scrap. This titanium-based scrap may be generated during the manufacturing process of titanium metal products or titanium alloy products, or during post-consumer use. A titanium alloy product obtained in an extraction process using aluminum (Al) or the like may also be used as the titanium-based raw material in the deoxidation step. If necessary, an electrolysis step may be performed after the deoxidation step. The following description will mainly focus on a case where the extraction step, deoxidation step, and electrolysis step are performed in this order, but this is not limiting. The number of times the deoxidation step and electrolysis step are performed is not particularly limited, and the deoxidation step and / or electrolysis step may be performed once or multiple times. For example, at least one of the deoxidation step and the electrolysis step may be performed multiple times to produce a product with fewer impurities.

[0034] (extraction process) In the extraction process, a mixture of titanium ore containing titanium oxides such as titanium oxide (TiO) and a reducing agent containing Al, etc., is heated. A slag-forming agent may be added at this time. This results in a titanium alloy product containing Al and O.

[0035] Titanium ore contains titanium oxide and may be, for example, subjected to upgrading treatment such as leaching or other treatments as necessary. The TiO content in the titanium ore may be, for example, 50 mass% or more, typically 80 mass% or more, particularly 90 mass% or more, and particularly 95 mass% or more.

[0036] The slag forming agent is used to facilitate the formation of molten slag after heating. Specifically, the slag forming agent is preferably one or more selected from calcium fluoride, potassium fluoride, magnesium fluoride, calcium chloride, magnesium chloride, calcium oxide, and sodium fluoride. Of these, calcium fluoride (CaF2) and calcium oxide (CaO) are particularly preferred because they provide excellent separation of the titanium alloy product from the mixture and have little effect on anything other than the separation.

[0037] The reducing agent may be one that contains substantially only aluminum (Al), or may further contain Ca, Na, Mg, Cu, Si, Fe, etc. For example, the mixture may be prepared by adjusting the molar ratio of TiO2:Al:CaF2 or CaO to 3:4-7:2-6.

[0038] The reactions that occur during the extraction process are complex, but generally, they are thought to be something like 3TiO2 + 4Al → 3Ti + 2Al2O3. However, the Ti in this reaction equation contains a certain amount of Al and O in solid solution, which corresponds to the titanium alloy product.

[0039] The heating temperature may be 1400°C to 2500°C, or 1400°C to 1800°C. After the mixture is heated to a molten state, the titanium alloy product (liquid or solid) and the molten slag are separated due to the difference in density, and the titanium alloy product (Ti in the above reaction formula) can be extracted.

[0040] The titanium alloy product obtained in the extraction step contains Ti, Al, and O, and may have, for example, a Ti content of 50% to 80% by mass, an Al content of 1% to 30% by mass, and an O content of 5% to 20% by mass. In addition, when ores with high impurities are used, the titanium alloy product may contain a few mass% or less of Fe and Si. Typically, the titanium alloy product has a Ti content of 60% by mass or more, an Al content of 20% by mass or less, and an O content of 20% by mass or less. However, the titanium alloy product may contain Al and O in amounts less than the above amounts, at levels that may correspond to unavoidable impurities. In other words, the titanium alloy product may contain only trace amounts of Al and O.

[0041] While the above description has focused on the use of an Al-containing reducing agent in the extraction process, a Ca-containing reducing agent can also be used in the extraction process. In this case, the heating temperature can be set to 900°C to 2000°C, resulting in a titanium alloy product with a relatively reduced O content of, for example, approximately 0.1% to 15% by mass. In addition, similar conditions to those when using an Al-containing reducing agent (such as the ability to use a slag-forming agent) can often be adopted. When using a Ca-containing reducing agent, the slag-forming agent preferably contains calcium fluoride, calcium oxide, or calcium chloride. Titanium alloy products include Ti-Al-O solid-solution alloys (alloys in which Al and O are dissolved in Ti) obtained in an extraction process using an Al-containing reducing agent, and Ti-O solid-solution alloys (alloys in which O is dissolved in Ti) obtained in an extraction process using a Ca-containing reducing agent.

[0042] (Deoxidation process) In the deoxidation step, the titanium-based raw material and the deoxidizer are placed in a reaction vessel and heated inside, so that the deoxidizer is brought into a molten state and into contact with the titanium-based raw material, causing a deoxidation reaction of the titanium-based raw material with the deoxidizer, thereby reducing the O content of the titanium-based raw material.

[0043] The titanium-based raw material to be subjected to the deoxidation step contains Ti and O, and is roughly divided into non-metallic substances and metallic substances, and any material containing at least one of these may be used.

[0044] The non-metallic substance mentioned above means a titanium-containing substance that is not a metal and does not have high electrical conductivity like a metal, such as titanium ore or titanium dioxide (TiO2) or other titanium oxides (TiO 2-x In addition to the above (0≦x<1), examples include titanic acid compounds containing alkali metals and alkaline earth metals (e.g., CaTiO3), titanium oxynitrides, titanium carbonates, etc. Non-metallic substances have a molecular weight of 5×10 at room temperature, for example. -6 They may have high electrical resistivities of Ω·m or more. Furthermore, titanium-based raw materials may contain titanium nitrides, titanium carbides, titanium carbonitrides, etc., as long as they contain substances containing Ti and O. When titanium ore is used, the extraction process and deoxidation process may be carried out simultaneously.

[0045] Examples of the metallic substances include titanium alloy products (Ti-Al-O solid solution alloys and Ti-O solid solution alloys) obtained in the extraction process, titanium-based scrap, and other metallic titanium and titanium alloy raw materials. Specific examples of metallic titanium and titanium alloy raw materials include sponge titanium, melted metallic titanium and titanium alloy products, wrought materials, powders and sintered compacts thereof, and scraps thereof. The metallic titanium raw material may contain a relatively high amount of O (e.g., metallic titanium equivalent to JIS Class 2 or JIS Class 3), which may be subjected to a deoxidation process to reduce the O content (e.g., metallic titanium equivalent to JIS Class 1). The titanium raw material may have a Ti content of 98% by mass or more, while the titanium alloy raw material may have a Ti content of 50% by mass or more, or 60% by mass or more. The titanium-based scrap may include chips (so-called swarf) generated during processes such as grinding and cutting various products. The alloys referred to here as titanium alloy raw materials and the like refer to solid solutions in which multiple metal elements are mixed, and include not only alloys in the narrow sense of the term that have an irregular lattice structure, but also intermetallic compounds that form an ordered lattice structure and solid solutions with a body-centered cubic structure. Specific examples of intermetallic compounds include TiAl, TiAl, and FeTi, and specific examples of solid solutions with a body-centered cubic structure include Nb-Ti.

[0046] The titanium-based raw material preferably contains at least one selected from the group consisting of the above-mentioned metallic substances and non-metallic substances such as titanium ore, titanium oxide, and titanic acid compounds. More typically, the titanium-based raw material contains at least one selected from the group consisting of the above-mentioned metallic substances, titanium ore, TiO 2-x (0≦x<1) and at least one selected from the group consisting of CaTiO3.

[0047] For example, when the titanium-based raw material includes titanium ore, the deoxidation step may correspond to smelting, which is a process for extracting metal from ore. Furthermore, when the titanium-based raw material includes smelting products, titanium-based scrap, or the like, the deoxidation step may correspond to refining, which is a process for removing at least a portion of impurities (here, O) from metal. The deoxidation step may be performed once or multiple times, for example, as smelting and one or more refining steps, or as one or more refining steps without smelting. When the deoxidation step is performed multiple times, the titanium-based material obtained in the previous deoxidation step with a reduced O content can be used as the titanium-based raw material in the next deoxidation step, thereby further reducing the O content. When titanium ore is the target, it may be more desirable to perform multiple deoxidation steps, or one or more deoxidation steps and the electrolysis step described below, in the production of metallic titanium or titanium alloys, rather than performing only one deoxidation step.

[0048] The deoxidizer may be any material containing Ca. Ca has excellent deoxidizing power and is therefore effective in reducing the O content of titanium-based raw materials. On the other hand, Ca is hardly dissolved in solid Ti. Therefore, when cooled after the deoxidation reaction, it first remains in the liquid phase as Ti, which has a high melting point, solidifies, and then, upon further cooling, most of it is thought to form a phase separated from the Ti phase. Even if Ca is incorporated into the Ti phase, it is presumed that such Ca will combine with O that may be present in the Ti phase to form CaO or CaTiO3, etc., and therefore, even if it does dissolve in Ti, the amount will be extremely small. Thus, Ca is useful as a deoxidizer because it is unlikely to be mixed in as an impurity.

[0049] The deoxidizer may contain, for example, metallic calcium and / or a calcium alloy. Examples of calcium alloys include Ca-Mg alloys, Ca-Si alloys, and Ca-Al alloys. If Mg, Si, Al, etc. in the calcium alloy are mixed as impurities into the titanium-based material obtained in the deoxidation step, the content of these impurities can be reduced by the electrolysis step described below. If the electrolysis step is not performed, it is preferable to select metallic calcium as the deoxidizer.

[0050] In addition to the titanium-based raw material and deoxidizer, a slag-forming agent may be added to the reaction vessel before or during heating for the deoxidization reaction. The slag-forming agent promotes the formation of a melt and facilitates the reaction between the titanium-based raw material and the deoxidizer in the liquid phase. When a slag-forming agent is added, it may contain calcium and / or have a melting point lower than the boiling point of the deoxidizer. When such a slag-forming agent is added and heated, it often melts to form molten slag, which penetrates into the gaps between the granular titanium-based raw material and the molten deoxidizer, preventing the passage of the partially volatilized deoxidizer. This suppresses the evaporation of the deoxidizer, further facilitating its contribution to the reaction. Examples of slag-forming agents that can be used include CaF2, CaCl2, CaO, and MgCl2. When the deoxidizer is metallic calcium, CaF2 and CaCl2 are preferred as slag-forming agents with low melting points.

[0051] In the deoxidation process, in order to increase the contact area between the deoxidizer and the titanium-based raw material and improve the reaction efficiency, at least the deoxidizer is molten, and preferably the titanium-based raw material is also molten, so that they can contact each other in the resulting melt. However, deoxidizers containing Ca generally tend to have lower boiling points than the titanium-based raw material. For example, the boiling point of metallic calcium is approximately 1484°C, while the melting point of metallic titanium is approximately 1668°C. When the deoxidizer evaporates, its vapor typically accumulates above the melt, and contacts the titanium-based raw material only at the liquid surface of the melt. Therefore, in the deoxidation process, it is desirable to heat the deoxidizer and titanium-based raw material in a reaction vessel and react them while suppressing evaporation of the deoxidizer.

[0052] Furthermore, if the reaction vessel is sealed, the pressure inside the vessel rapidly increases as the deoxidizer evaporates. To safely perform the deoxidation process without removing the pressure, the reaction vessel must have not only the required heat resistance but also extremely high pressure resistance. A reaction vessel made of materials and with such high heat and pressure resistance is expensive, resulting in increased costs. If the reaction vessel is left open, the Ca vapor of the deoxidizer will continue to be discharged outside the system and will not contribute to deoxidation. In contrast, in this embodiment, a reaction vessel with a movable wall is used in the deoxidation process. The movable wall constitutes at least a portion of the upper wall located above the titanium-based raw material and deoxidizer placed inside the reaction vessel and can be moved to change the volume of the reaction vessel. The movement of the movable wall adjusts the internal pressure of the reaction vessel so that it does not increase too much, allowing safe deoxidation of the titanium-based raw material even if the reaction vessel does not have extremely high pressure resistance. This movable wall can also be considered a lid placed on the opening of the reaction vessel.

[0053] Specific examples of the movable wall portion are shown in Figures 1 to 4. It is preferable that at least a portion of the inner surface of the movable wall portion 3a be in contact with the titanium-based raw material and deoxidizer inside the reaction vessel 1 so that the deoxidizer is less likely to evaporate. This makes it easier for the movable wall portion 3a to be positioned near the molten material formed by melting the deoxidizer. Note that some parts of Figures 1 to 4 are exaggerated for ease of understanding, and the actual dimensions, shape, and other configurations are not limited to those shown. In addition to the titanium-based raw material and deoxidizer, a slag-forming agent may also be added inside the reaction vessel 1.

[0054] 1 to 4 have the same configuration except for the movable wall portion 3a, that is, they have a cylindrical container body 2 with a bottom (a "cylindrical" tube is, for example, a cylinder or a rectangular tube) and a predetermined movable wall portion 3a, and a heater 11 is disposed surrounding the container body 2. The container body 2 has an opening 2a formed on the upper side, which is one side in the axial direction (vertical direction), while the lower side, which is the other side in the axial direction, is sealed at the bottom.

[0055] The reaction vessel 1 shown in Figure 1 is configured to include a movable wall portion 3a in the shape of a disk or other plate, which is arranged inside the opening 2a of the vessel body 2, and an exhaust hole 3b, which is a gap formed in at least a portion between the inner surface of the side wall portion of the vessel body 2 and the outer edge of the movable wall portion 3a.

[0056] When a titanium-based raw material and a deoxidizer are heated inside the reaction vessel 1 shown in FIG. 1 to produce a melt 51 typically containing the titanium-based raw material and the deoxidizer in a molten state, vapor and other gaseous components that may be generated when the deoxidizer evaporates from a portion of the melt 51 can be discharged to the outside through the exhaust holes 3b, thereby preventing an excessive increase in internal pressure. In particular, when the exhaust holes 3b are provided on the outer edge of the movable wall portion 3a as shown in the figure, the deoxidizer vapor travels along the liquid surface before being discharged from the exhaust holes 3b to the outside of the reaction vessel 1. Because this travel distance is somewhat long, the deoxidizer vapor tends to be more easily used for deoxidation during this travel. Additionally or alternatively, the movable wall portion 3a, which changes the volume of the reaction vessel 1 by its movement, can also move in the axial direction of the vessel body 2, thereby reducing the internal pressure. The size, shape, and number of the exhaust holes 3b, as well as the magnitude and amount of force required to move the movable wall portion 3a, can be appropriately set depending on the allowable upper limit of the internal pressure of the reaction vessel 1, etc.

[0057] The exhaust hole 3b can be provided at any location in the reaction vessel 1, but in order to efficiently exhaust gas components that may be generated from the melt 51 and rise, it is provided above the melt 51 as in the illustrated example. Any gas components generated from the melt 51 in the reaction vessel 1 are referred to here as gas components. Note that these gas components may include Ca vapor derived from the deoxidizing agent, as well as gas components such as CaCl2 and CaF2 derived from the slag forming agent, and AlF, AlCl, TiF4, TiCl4 derived from the titanium-based raw material and the slag forming agent.

[0058] The vapor of the deoxidizer generated from the melt 51 is cooled and precipitated on the inner surface of the movable wall portion 3a, and the precipitate may adhere to the inner surface. In this case, since the inner surface is close to the melt 51, the precipitate may melt and be included in the melt 51 again, and may be used for the reaction.

[0059] During heating in the deoxidation step, it is preferable that at least a part of the inner surface of the movable wall portion 3a, particularly almost the entire surface as shown in the figure, be in contact with the melt 51 so as to minimize the generation of a gas phase inside the reaction vessel 1. This further suppresses the evaporation of the deoxidizing agent, thereby achieving a more efficient deoxidation reaction.

[0060] As described above, the inner surface of the movable wall portion 3a may come into contact with the melt 51 and be exposed to high temperatures. For this reason, it is preferable that at least the inner surface of the movable wall portion 3a be made of a heat-resistant calcium-based compound with a melting point of 1950°C or higher. Examples of such calcium-based compounds include CaO, CaS, and CaTiO3. Furthermore, the inner surface of the movable wall portion 3a may dissolve into the melt 51 upon contact with the melt. However, if the inner surface is made of a calcium-based compound, Ca in the calcium-based compound is hardly dissolved in Ti, and therefore is unlikely to become an impurity in the metallic titanium or titanium alloy after deoxidation. When the calcium-based compound dissolves in the melt 51, it can become part of the molten slag together with the slag-forming agent.

[0061] The reaction vessel 1 shown in Figure 2 is similar to that shown in Figure 1, except that the thickness of the movable wall portion 3a is increased. By changing the thickness of the movable wall portion 3a in this way, the magnitude of the force required to move the movable wall portion 3a can be adjusted.

[0062] The reaction vessel 1 shown in Fig. 3 is similar to that shown in Fig. 1, except that a weight 3c is placed on the movable wall portion 3a. The weight 3c can also be used to adjust the difficulty of moving the movable wall portion 3a.

[0063] The reaction vessel 1 shown in Fig. 4 is similar to that shown in Fig. 1, except that a rod 3d for axially moving the movable wall portion 3a is connected to the outer surface of the movable wall portion 3a. The rod 3d may be moved by manual intervention at the discretion of an operator or by applying an external force under automatic control.

[0064] In the deoxidation step, various heating furnaces can be used as the heating furnace for heating the inside of the reaction vessel 1. Examples of such heating furnaces include a high-frequency induction heating furnace, an electro-slug remelting (ESR) furnace, an electric furnace, and a gas furnace.

[0065] Among these, when using a high-frequency induction heating furnace, induction heating utilizes a magnetic field generated by passing current through a coil to directly and / or indirectly heat the titanium-based raw material, deoxidizer, and, if present, slag-forming agent placed inside the aforementioned reaction vessel (such as a crucible). The configuration of the high-frequency induction heating furnace is highly flexible as long as the titanium-based raw material and deoxidizer contain a metal (conductive material) that enables induction heating. However, if the titanium-based raw material and deoxidizer do not contain such a metal, the reaction vessel 1 must be a susceptor (magnetic field-sensitive heating element) or must be equipped with a susceptor inside the reaction vessel 1. Materials such as graphite and graphite coated with calcia or other metals can be used as susceptors. In this case, the reaction vessel 1 can be made of graphite, particularly graphite with a calcia coating on the inner surface. When the reaction vessel 1 is made of water-cooled copper or a water-cooled copper alloy and induction skull melting is performed, the need for a susceptor can be determined based on whether the reaction vessel 1 contains the above-mentioned metal.

[0066] The deoxidation step is preferably carried out by creating an inert gas atmosphere such as argon or helium inside the heating furnace in which the reaction vessel 1 is placed, typically by flowing the inert gas into the heating furnace. This prevents contamination gases such as oxygen and nitrogen from entering the reaction vessel 1, allowing for better deoxidation of the titanium-based raw material.

[0067] When using an electroslag remelting furnace, the electrodes can be either consumable or non-consumable. When using a consumable electrode, for example, the electrode inserted into the crucible contains titanium-based raw materials. Deoxidizers and slag-forming agents are placed in the crucible, and the tip of the electrode is placed inside the crucible to begin heating. In this case, an arc is generated between the tip of the electrode and the crucible by passing a current through the electrode. This heats the deoxidizers and other materials inside the crucible and melts the titanium-based raw materials in the electrode inserted into the reaction vessel 1, starting from the tip. When using a non-consumable electrode that does not contain titanium-based raw materials, no titanium-based raw materials are supplied from the electrode, so the reaction vessel 1 still contains titanium-based raw materials.

[0068] An electric furnace is a heating furnace that heats a crucible by applying radiant heat from a coil heater or by stagnation of atmospheric gas when electricity is applied to the coil heater, while a gas furnace is a furnace that heats a crucible by heat generated by combustion of gas.

[0069] In the deoxidation step, the titanium-based raw material and deoxidizer are preferably heated to 900°C to 2000°C inside the reaction vessel 1, such as the crucible described above. This allows the deoxidization reaction of the titanium-based raw material by the deoxidizer to occur. If the heating temperature is too low, the reaction will take a long time, and if it is too high, there is a concern that the deoxidizer will evaporate and other components and reaction products will gasify.

[0070] After the deoxidation reaction occurs, the deoxidized titanium-based material solidifies and separates from the molten slag containing calcium and other elements, typically by settling downward. This results in a titanium-based material with a reduced O content compared to the titanium-based raw material. If Ca remains unavoidably among the impurities contained in the titanium-based material, this Ca can sometimes be separated and removed by heating and melting the titanium-based material and subsequently cooling it. If the titanium-based material does not undergo the electrolysis process described below, it can be made into metallic titanium or a titanium alloy. Alternatively, an electrolysis process may be performed to further reduce the O content of the titanium-based material and to reduce the content of other impurities (e.g., Al, Mg, Si).

[0071] (Electrolysis process) After obtaining a titanium-based material having an O content reduced compared to the titanium-based raw material through the deoxidation reaction in the above-mentioned deoxidation step, the titanium-based material can be subjected to an electrolysis step as electrolytic refining, as needed.

[0072] In the electrolysis process, titanium-based material is used as anode consumable raw material in the form of crude titanium-based material, and Ti is dissolved from the crude titanium-based material by applying voltage between the anode and cathode immersed in a molten salt bath in an electrolytic cell. The Ti dissolved from the anode consumable raw material crude titanium-based material is electrodeposited on the cathode to become refined titanium-based material.

[0073] The anode consumable material is not particularly limited as long as it contains the above-mentioned titanium-based material. For example, granular or powdered titanium-based material may be placed in a cage-like container with numerous through-holes that can be electrically connected and used as the anode. The cage-like container may have a plate-like or cylindrical outer shape and may be made of nickel, a nickel-based alloy, Hastelloy, or steel coated with nickel or a nickel-based alloy, etc., and may have numerous through-holes. The cathode may have at least a titanium surface, such as a titanium plate or titanium rod made entirely of titanium. It is possible to arrange a bipolar electrode between the anode and cathode, but a bipolar electrode is not necessary.

[0074] The molten salt bath may be a chloride bath containing primarily metal chlorides, such as alkali metal chlorides and / or alkaline earth metal chlorides, at a concentration of, for example, 70 mol% or more, further 90 mol% or more, or even 95 mol% or more. Such chloride baths are preferred over fluoride, bromide, and iodide baths because they are less corrosive, less environmentally hazardous, and less expensive. In particular, when a chloride bath containing magnesium chloride (MgCl) is used, a purified titanium-based material can be obtained in which not only the O content but also the Al content is sufficiently reduced. The magnesium chloride content in the chloride bath is preferably 30 mol% or more, further preferably 50 mol% or more, further preferably 80 mol% or more, further preferably 85 mol% or more, and particularly preferably 95 mol% or more. The chloride bath may contain one or more metal chlorides selected from lithium chloride (LiCl), sodium chloride (NaCl), potassium chloride (KCl), rubidium chloride (RbCl), cesium chloride (CsCl), beryllium chloride (BeCl), calcium chloride (CaCl), strontium chloride (SrCl), and barium chloride (BaCl), for example, in an amount of 70 mol% or less, further 50 mol% or less, further 20 mol% or less, further 10 mol% or less, or even 5 mol% or less.

[0075] Furthermore, the molten salt bath may contain, as necessary, lower titanium chlorides having a Ti valence lower than that of titanium tetrachloride, specifically titanium dichloride (TiCl2) or titanium trichloride (TiCl3). The content of Ti ions in the molten salt bath is preferably 3 mol% or more, more preferably 5 mol% or more, even more preferably 6 mol% or more, or even 10 mol% or more, and is preferably 20 mol% or less.

[0076] In particular, when the molten salt bath is a chloride bath, the chloride bath preferably contains magnesium chloride and titanium dichloride. In this case, a purified titanium-based material with an even lower Al content can be obtained, which is suitable for producing metallic titanium. Note that in the chloride bath, some of the titanium dichloride may become titanium trichloride or titanium tetrachloride due to a disproportionation reaction.

[0077] The content of metal chlorides and metal ions in the molten salt bath can be measured by ICP atomic emission spectrometry or atomic absorption spectrometry. The content of Ti ions can be calculated as a percentage of the total content of metal ions in the molten salt bath.

[0078] The conditions for electrolytic refining are, for example, a molten salt bath temperature of 450°C to 900°C and a current density of 0.01 A / cm at the cathode. 2 ~3A / cm 2 The current density can be calculated using the formula: Current density (A / cm 2 ) = Current (A) ÷ Macroscopic electrodeposition area (cm 2 ) can be calculated. The electrodes may be supplied with a continuous current, or may be supplied with a pulsed current in which current-on periods and current-off periods are alternately repeated, with a current-off period during which the current value is set to zero. The maximum voltage between the electrodes may be, for example, 0.2 V to 3.5 V. During electrolytic refining, the inside of the electrolytic cell is preferably maintained in an inert gas atmosphere such as argon.

[0079] The electrolysis process can be repeated multiple times to further refine the purified titanium-based material obtained thereby. When the electrolysis process is performed multiple times, the purified titanium-based material deposited on the cathode in the previous electrolysis process is used as the crude titanium-based material in the next electrolysis process, and this crude titanium-based material is used as the anode consumable raw material. As a result, in the next electrolysis process, a purified titanium-based material from which impurities have been further removed is deposited on the cathode. By performing the electrolysis process multiple times, it is also possible to produce high-purity metallic titanium that is almost free of impurities.

[0080] However, from the viewpoint of suppressing increases in energy consumption and costs, it is desirable to reduce the number of electrolysis steps. Since the titanium-based material obtained by the aforementioned deoxidation step has a reduced O content, good metallic titanium or titanium alloys can be produced even with a small number of electrolysis steps. However, even when two or more electrolysis steps are performed, the reduced Al and O contents of the purified titanium-based material can reduce power consumption and improve yield.

[0081] When titanium metal is produced as described above, the finally obtained titanium metal has an Al content of, for example, 0.1 mass% or less, preferably 0.01 mass% or less, and an O content of, for example, 0.2 mass% or less, preferably 0.10 mass% or less, and more preferably 0.05 mass% or less. Alternatively, when a titanium alloy is produced, the finally obtained titanium alloy may have an Al content of, for example, 3 mass% or less, preferably 2 mass% or less, and an O content of 0.3 mass% or less, preferably 0.15 mass% or less. [Example]

[0082] Next, the method for producing metallic titanium or titanium alloys of the present invention was experimentally carried out, and its effects were confirmed. The following describes this method, however, for illustrative purposes only and is not intended to be limiting.

[0083] (Test Example 1) Using a high-frequency induction heating furnace, tests were conducted to cause a deoxidation reaction of a titanium-based raw material containing O in a crucible (reaction vessel). The dimensions of the crucible were an inner diameter of 100 mm, a depth of 150 mm, and a wall thickness of 10 mm. In test numbers 2, 4, and 6 to 23, a disk-shaped lid (movable wall portion) as shown in Figure 1, 2, 3, or 4 was placed on the upper side of the crucible, while in test numbers 1, 3, and 5, no lid was placed on the upper side and the crucible was left open.

[0084] During the deoxidation reaction, a flowing Ar atmosphere was maintained inside the high-frequency induction heating furnace. A total of 2500g of titanium-based raw material, deoxidizer, and slag-forming agent mixed in a ratio of 3:3:5 was filled into the crucible and heated. After the reaction was completed, the reaction product was removed, and the slag and residual salt were removed. The oxygen content of the metal part was analyzed and compared with that before the test. The results are shown in Tables 1 and 2.

[0085] [Table 1]

[0086] [Table 2]

[0087] As shown in Tables 1 and 2, for test numbers 1 to 6, the oxygen level did not decrease in test numbers 1 and 3, where no lid was placed, whereas the oxygen level decreased significantly in test numbers 2 and 4, where a lid was placed. In test number 5, a low-temperature test, the oxygen level decreased to 18.7 mass% even without a lid, but in test number 6, where a lid was placed, the oxygen level decreased even further. The CaO lid showed some wear in test number 2, a high-temperature test, but was largely intact.

[0088] Test numbers 7 to 23 show that this method is effective even when titanium-based raw materials other than titanium ore are used, and whether the lid material is CaO, CaS, or TiCaO3. The results of test numbers 7 to 9 show that the deoxidation effect improves as the lid becomes thicker and heavier. Test numbers 7 to 11 show that the same effect as increasing the lid thickness can be obtained by changing the type of lid.

[0089] Comparing test number 12 and test number 8, even though the lid had a small hole in the center and was tightly attached to the inner surface of the crucible (test number 12), the effect was the same as test number 8, which had no central hole and a narrow gap between the lid and the inner surface of the crucible. However, as the central hole became larger, as in test numbers 13 and 14, the effect gradually weakened.

[0090] In test number 15, the lid was not brought into contact with the molten metal, but this result shows that having the lid in contact with the molten metal is more effective.

[0091] In test number 17, there was no gap between the crucible and the inner surface, but the absence of an exhaust hole created a gas phase inside. This shows that in order to obtain a sufficient deoxidation effect, it is better to provide an exhaust hole, as in test number 16.

[0092] Test numbers 18 and 19 show that deoxidizers using Ca-Al alloys or Ca-Si alloys instead of Ca are also effective. Test numbers 20, 21, and 22 show that using other non-metallic titanium raw materials is also effective. Note that TiOC and TiON are O, C, and N contaminants that are generated during the titanium manufacturing and utilization processes and would normally be considered waste.

[0093] Test No. 23 shows that the slag generating agent is effective even if it does not contain calcium. However, other slag generating agents containing calcium are more effective. The slag generating agents used in Test Nos. 6 to 12 and 16 were particularly effective.

[0094] (Test Example 2) Unlike Test Example 1, a high-frequency induction skull melting furnace was sealed to create an Ar atmosphere without argon flowing through it. A water-cooled copper crucible was used as the crucible, and a test was conducted to induce a deoxidation reaction of the titanium-based raw material. The crucible was charged with 2500 g of titanium-based raw material, deoxidizer, and slag-forming agent, mixed in a ratio of 1:3:0 or 0.05:0 of ​​the O concentration in the titanium-based raw material. After the reaction was completed, the reaction product was removed, and the slag and residual salt were removed. The oxygen content of the metal was analyzed and compared with that before the test. The results are shown in Tables 3 and 4.

[0095] The titanium-based raw material used in Tests 24 and 25 was an extract (Ti-Al-O solid solution alloy) obtained by reducing titanium ore using a slag-forming agent consisting of Al and CaO. Tests 26 and 27 used the Ti-O solid solution alloy obtained in Test 2, from which slag and residual salts had been removed. Test 28 used the alloy obtained in Test 6. Tests 29 to 32 used scrap titanium or titanium alloy products, such as cutting chips or thin plate chips.

[0096] [Table 3]

[0097] [Table 4]

[0098] As shown in Tables 3 and 4, there was almost no reduction in oxygen in test numbers 24 and 26, where no lid was placed, but there was a significant reduction in oxygen in test numbers 25 and 27, where a lid was placed. The CaO lid showed some wear despite being a high-temperature test, but was largely intact. The oxygen reduction effect was also confirmed in test numbers 28 to 32.

[0099] (Test Example 3) Unlike Test Example 2, an electroslag remelting furnace was used, and a water-cooled copper crucible with an inner diameter of 50 mm and a depth of 200 mm was used to conduct a test to induce a deoxidation reaction of a titanium-based raw material. Here, the electroslag remelting furnace was sealed and an Ar atmosphere was created. The heating temperature was measured by measuring the temperature on the surface of the molten metal pool.

[0100] In this test, a titanium alloy rod was used as a consumable electrode, inserted from above so that its tip was in the slag. The deoxidizer and slag former were mixed so that the ratio of deoxidizer to slag former = (O concentration in titanium alloy rod × 3) to (titanium alloy rod × 0.5), assuming the titanium alloy rod to be melted as 1. A total of 1510 g was inserted into a water-cooled copper crucible. An arc was generated between the rod electrode and the water-cooled copper, which separated the molten metal from the slag, causing the metal to deposit and solidify in the crucible. The molten titanium alloy rod weighed approximately 2000 g. After the test, the metal was removed and its oxygen content was analyzed and compared with that before the test. The final metal weighed approximately 2000 g. The results are shown in Tables 5 and 6. Note that "time" in Table 6 refers to the time from the start to the end of melting.

[0101] [Table 5]

[0102] [Table 6]

[0103] Tables 5 and 6 show that the deoxidation reaction was effective.

[0104] (Test Example 4) The titanium-based materials obtained in the above test numbers 25, 28, 29, and 30 were used as the crude titanium-based material on the anode side, and molten salt electrolytic refining was carried out.

[0105] More specifically, in test numbers 34 to 39, the titanium-based material obtained in test numbers 25 and 28 was crushed into granules and placed in a nickel cage-shaped container with numerous through-holes to form the anode. In test numbers 40 to 45, as in test numbers 29 and 30, the molten material was poured into a plate-shaped crucible and used as an electrode. The composition of the molten salt bath is shown in Table 7. In addition, 4 mol% to 6 mol% of TiCl2 was added. However, it is believed that a portion of this (5 to 15%) became TiCl3.

[0106] In all of test numbers 34 to 45, a titanium plate was used as the cathode, circulating (flowing) Ar was used in the test vessel, and when performing electrolytic refining, a voltage was applied between the anode and cathode to dissolve the crude titanium-based material from the anode and deposit a refined titanium-based material on the cathode.

[0107] After electrolytic refining was completed, the cathode was removed, and the titanium metal or titanium alloy deposited on the cathode was collected and washed with dilute hydrochloric acid, then with water, and then air-dried at about 50°C. The aluminum content, oxygen content, and iron content of the titanium metal or titanium alloy were measured. The results are shown in Table 7.

[0108] [Table 7]

[0109] In all cases, electrolytic refining reduced O, and also significantly reduced Fe (a typical example of an impurity other than O and Al). In the extract obtained from test number 25, which contains Al, the Al content was also significantly reduced by electrolytic refining.

[0110] (Test Example 5) The titanium-based materials of Test Nos. 36 and 38 obtained by the first electrolytic refining were used as the crude titanium-based material on the anode side to carry out a second molten salt electrolytic refining.

[0111] The method and conditions for molten salt electrorefining were basically the same as in Test Example 4, but the titanium-based materials obtained in Test Nos. 36 and 38 were pulverized into granules, which were then placed in a nickel cage-like container with numerous through-holes and used as the anode.

[0112] In both test numbers 46 and 47, the cathode was a titanium plate, circulating (flowing) Ar was used in the test vessel, and when performing electrolytic refining, a voltage was applied between the anode and cathode to dissolve the crude titanium-based material from the anode and deposit a refined titanium-based material on the cathode.

[0113] After electrolytic refining was completed, the cathode was removed, and the titanium metal or titanium alloy deposited on the cathode was collected and washed with dilute hydrochloric acid, then with water, and then air-dried at about 50°C. The aluminum content, oxygen content, and iron content of the titanium metal or titanium alloy were measured. The results are shown in Table 8.

[0114] [Table 8]

[0115] In both cases, the O content was further reduced by electrolytic refining, and the extract obtained in test number 36, which contained Al, also had Al further reduced by the second electrolytic refining in test number 46. [Explanation of symbols]

[0116] 1 reaction vessel 2 Container body 2a opening 3a Movable wall section 3b Exhaust hole 3c weight 3d rod 11 Heater 51 Melt

Claims

1. A method for producing metallic titanium or a titanium alloy having a lower O content than a titanium-based raw material containing O, from the titanium-based raw material, comprising the steps of: a deoxidation step of heating the titanium-based raw material and a deoxidizer containing Ca in a reaction vessel, bringing the deoxidizer into contact with the titanium-based raw material in a molten state, and reducing the O content of the titanium-based raw material by a deoxidation reaction; A method for producing metallic titanium or a titanium alloy, wherein the reaction vessel used in the deoxidation step is a reaction vessel in which at least a portion of an upper wall portion located above the titanium-based raw material and the deoxidizing agent placed inside the reaction vessel is a movable wall portion that can move to change the volume of the reaction vessel.

2. 2. The method for producing metallic titanium or a titanium alloy according to claim 1, wherein in the deoxidizing step, at least a portion of the inner surface of the movable wall portion is brought into contact with the titanium-based raw material and the deoxidizing agent inside the reaction vessel.

3. 3. The method for producing metallic titanium or a titanium alloy according to claim 2, wherein at least the inner surface of the movable wall portion is made of a calcium-based compound having a melting point of 1950°C or higher.

4. 2. The method for producing metallic titanium or a titanium alloy according to claim 1, wherein the reaction vessel includes an exhaust hole for discharging gas components inside the reaction vessel to the outside.

5. The method for producing titanium metal or a titanium alloy according to claim 1, wherein the titanium-based raw material includes a non-metallic substance.

6. The non-metallic substance is titanium ore, TiO 2-x (0≦x<1), and CaTiO 3 The method for producing metallic titanium or a titanium alloy according to claim 5, wherein the titanium or titanium alloy contains at least one selected from the group consisting of:

7. 2. The method for producing titanium metal or a titanium alloy according to claim 1, wherein the titanium-based raw material comprises a titanium metal raw material and / or a titanium alloy raw material.

8. 2. The method for producing metallic titanium or a titanium alloy according to claim 1, wherein in the deoxidation step, a slag generating agent is added to the reaction vessel and heated to cause the deoxidation reaction.

9. 9. The method for producing metallic titanium or a titanium alloy according to claim 8, wherein the slag forming agent contains Ca.

10. 10. The method for producing metallic titanium or a titanium alloy according to claim 9, wherein the slag forming agent has a melting point lower than the boiling point of the deoxidizing agent.

11. 2. The method for producing metallic titanium or a titanium alloy according to claim 1, wherein, in the deoxidation step, the reaction vessel containing an induction-heatable conductive material is placed in a high-frequency induction heating furnace, and the deoxidation reaction is caused to occur in an inert gas atmosphere.

12. 12. The method for producing metallic titanium or a titanium alloy according to claim 11, wherein the reaction vessel used in the deoxidation step has at least an inner surface made of calcia.

13. 2. The method for producing metallic titanium or a titanium alloy according to claim 1, wherein the inside of the reaction vessel is heated to 900°C to 2000°C in the deoxidation step.

14. In the deoxidation step, a titanium-based material having an O content reduced compared to the titanium-based raw material is obtained by the deoxidation reaction, and then 14. The method for producing metallic titanium or a titanium alloy according to claim 1, comprising an electrolysis step of using the titanium-based material as an anode crude titanium-based material and applying a voltage between the anode and a cathode in a molten salt bath to elute Ti from the crude titanium-based material and deposit a refined titanium-based material on the cathode.

15. 15. The method for producing metallic titanium or a titanium alloy according to claim 14, wherein the electrolysis step is repeated a plurality of times, and in the plurality of electrolysis steps, the purified titanium-based material deposited on the cathode in the previous electrolysis step is used as the crude titanium-based material in the next electrolysis step.

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