Method for manufacturing titanium electrodeposits

Abstract

To provide a method for manufacturing a titanium electrodeposit with excellent productivity.SOLUTION: There is provided a method for manufacturing titanium deposits, the method comprising using an electrode having an anode containing a conductive crude titanium-based material containing titanium, aluminum and oxygen and a cathode in a chloride bath as a molten salt bath and depositing a refined titanium-based material on the cathode to obtain an electrodeposit. In the electrodeposition step, the chloride bath contains 30 mol% or more of magnesium chloride and 1 mol% or more of lower titanium chloride. An anode current amount in the electrodeposition process is more than twice the anode current amount determined in a molten salt electrolysis test under the same conditions except that the chloride bath does not contain lower titanium chloride.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present invention relates to a method for producing a titanium electrodeposit.

Background Art

[0002] Typically, the production of metallic titanium is carried out by the Kroll process in which titanium ore, carbon, and chlorine gas are reacted to produce titanium tetrachloride, and the titanium tetrachloride is reduced with metallic magnesium to obtain a sponge titanium mass. However, this method requires a large number of steps, starting from titanium ore as a raw material, performing processes such as chlorination and reduction, and also performing processes such as crushing of the sponge titanium mass and electrolysis of magnesium chloride by-produced during reduction.

[0003] In recent years, as a smelting method other than the Kroll process, a technique for producing a titanium alloy by electrolytic refining using molten salt electrolysis is known. For example, Patent Document 1 discloses a method for producing a titanium-aluminum master alloy by heat-treating titanium ore, aluminum, and calcium fluoride as raw materials and electrolytically refining the obtained titanium product (hereinafter referred to as a crude titanium-based material). Further, Patent Document 2 discloses a method for producing a titanium-aluminum master alloy by electrolytically refining a crude titanium-based material as a raw material.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In both Patent Documents 1 and 2, crude titanium-based material is used as a raw material, and a titanium-aluminum matrix alloy is deposited on the surface of the cathode. However, there is a demand to produce metallic titanium by electrolytic refining using molten salt electrolysis. If metallic titanium can be produced by electrolytic refining using molten salt electrolysis, this production method could be a different method for smelting metallic titanium from the Kroll process. Such a new method for smelting metallic titanium is preferably superior in productivity.

[0006] Therefore, in one embodiment of the present invention, the objective is to provide a method for producing titanium electrodeposits with good productivity. [Means for solving the problem]

[0007] The inventors of the present invention conducted diligent studies to solve the above problems and found that in the electrodeposition process, if the chloride bath contains a predetermined amount of magnesium chloride and a predetermined amount of lower titanium chloride, and the anode current in the electrodeposition process is more than twice the anode current obtained in a molten salt electrolysis test under identical conditions except that the chloride bath does not contain lower titanium chloride, the productivity of titanium electrodeposits can be improved, and the inventors have created the invention exemplified below.

[0008] [1] A method for producing titanium electrodeposits by electrolytic refining using molten salt electrolysis, The process includes an electrodeposition step in which a refined titanium-based material is deposited on the cathode using an electrode having an anode and a cathode containing a conductive crude titanium-based material containing titanium, aluminum, and oxygen in a chloride bath as a molten salt bath, thereby obtaining an electrodeposited product. In the electrodeposition step, the chloride bath contains 30 mol% or more of magnesium chloride and 1 mol% or more of lower titanium chloride. A method for producing titanium electrodeposits, wherein the amount of current at the anode in the electrodeposition step is more than twice the amount of current at the anode determined in a molten salt electrolysis test under identical conditions except that the chloride bath does not contain lower titanium chloride. [2] The method for producing a titanium electrodeposited product according to [1], wherein the bath temperature of the chloride bath in the electrodeposition step is 750°C or higher and 950°C or lower. [3] The method for producing a titanium electrodeposited product according to [1] or [2], wherein the anode in the electrodeposition step further comprises a conductive container having the crude titanium-based material disposed inside, being insoluble in the chloride bath, and having through holes. [4] The method for producing a titanium electrodeposit according to any one of [1] to [3], wherein the titanium electrodeposit produced has an aluminum content of 5000 ppm by mass or less. [Effects of the Invention]

[0009] According to one embodiment of the present invention, a method for producing titanium electrodeposits with good productivity can be provided. [Brief explanation of the drawing]

[0010] [Figure 1A] This is a schematic diagram illustrating the electrodeposition process in the method for producing titanium electrodeposits according to the present invention. [Figure 1B] This is a schematic diagram illustrating the electrodeposition process in the method for producing titanium electrodeposits according to the present invention. [Figure 1C] This is a schematic diagram illustrating the electrodeposition process in the method for producing titanium electrodeposits according to the present invention. [Figure 1D] This is a schematic diagram illustrating the electrodeposition process in the method for producing titanium electrodeposits according to the present invention. [Figure 2] Figure 1A is an end view of XX. [Modes for carrying out the invention]

[0011] The present invention is not limited to the embodiments described below, and components can be modified and embodied without departing from the gist thereof. Further, various inventions can be formed by appropriately combining a plurality of components disclosed in each embodiment. For example, an invention may be formed by deleting some components from all the components shown in the embodiment. In the drawings, there are also members shown schematically to assist in understanding the embodiments included in the invention, and the illustrated sizes, positional relationships, etc. may not always be accurate.

[0012] [Method for Producing Titanium Electrodeposit] One embodiment of the method for producing a titanium electrodeposit according to the present invention is a method for producing a titanium electrodeposit by electrolytic purification using molten salt electrolysis, and includes an electrodeposition step. In the electrodeposition step, a chloride bath as a molten salt bath contains 30 mol% or more of magnesium chloride and 1 mol% or more of lower titanium chloride. Further, the current amount of the anode in the electrodeposition step is more than twice the current amount of the anode obtained in a molten salt electrolysis test under the same conditions except that the chloride bath does not contain lower titanium chloride. In the production of the titanium electrodeposit, the electrodeposition step is the main step, and in addition, an electrodeposition auxiliary step for optionally performing electrodeposition may be further included. Before the electrodeposition step and the electrodeposition auxiliary step, an extraction step described later may be further included. In this specification, "the same conditions except that the chloride bath does not contain lower titanium chloride" means that the bath composition, bath temperature, electrode distance, voltage, etc. excluding lower titanium chloride are the same. Therefore, an additional molten salt electrolysis test is performed under the same conditions except that the chloride bath does not contain lower titanium chloride, and the current amount of the anode obtained in this test is compared with the current amount of the anode measured in the electrodeposition step to determine whether the current amount of the anode in the electrodeposition step is more than twice the current amount obtained in the molten salt electrolysis test.

[0013] First, the present inventor intensively studied and succeeded in depositing a refined titanium-based material with a relatively reduced aluminum content on the surface of the cathode when using a crude titanium-based material as an anode raw material in electrolytic purification using molten salt electrolysis by incorporating a predetermined amount of magnesium chloride into the chloride bath. As a result, it became possible to produce metallic titanium by molten salt electrolysis in a smaller number of times.

[0014] Next, the present inventor studied the productivity of titanium electrodeposits. When the crude titanium-based material as the anode raw material is consumed in electrolytic purification, it becomes a residue (hereinafter also referred to as "anode residue") having a lower titanium content and higher aluminum and oxygen contents than the crude titanium-based material. As the crude titanium-based material increases in aluminum and oxygen contents with consumption, its specific resistance increases. If the specific resistance of the crude titanium-based material increases, the production amount of titanium electrodeposits per unit power consumption tends to decrease. Therefore, in view of the behavior of the crude titanium-based material in electrolytic purification, the present inventor came to think that increasing the consumption amount of the crude titanium-based material per unit time would result in increased productivity of titanium electrodeposits. Furthermore, since an increase in the current amount at the anode is related to the promotion of titanium elution from the anode, the present inventor came to think that increasing the current amount of the anode would increase the productivity of titanium electrodeposits per unit time.

[0015] Based on such an idea, the present inventor further studied and added a predetermined amount of lower titanium chloride in addition to magnesium chloride to the chloride bath in the electrodeposition step, and made the current amount of the anode in the electrodeposition step more than twice the current amount of the anode obtained in a molten salt electrolysis test under the same conditions except that the chloride bath does not contain lower titanium chloride, and as a result, obtained the finding that the productivity of titanium electrodeposits is increased.

[0016] In other words, it was found that using a chloride bath containing a predetermined amount of magnesium chloride and a predetermined amount of lower titanium chloride makes it easier for current to flow, thereby improving the productivity of titanium electrodeposition. The mechanism by which the productivity of titanium electrodeposition is improved is presumed to be as follows: Electrolytic refining proceeds through the elution of titanium ions from the anode to the chloride bath, the movement of titanium ions in the chloride bath, and the electrodeposition of titanium by the reduction of titanium ions at the cathode. Since the current in the chloride bath is created by the movement of titanium ions, only a very small amount of current can flow in a chloride bath where titanium ions are absent or the titanium ion concentration is low. In such a situation, if a high voltage is applied in order to make the current flow, decomposition reactions of the components of the chloride bath or elution of components of the container acting as the anode may occur. When these phenomena occur, the apparent current increases, but since the current is flowing due to reactions other than the intended electrolytic refining, the efficiency of producing electrodeposited titanium also decreases. Furthermore, contamination of the electrodeposited titanium with impurities may also occur. Therefore, in the present invention, by supplying a predetermined amount of lower titanium chloride to the chloride bath, even if the voltage is the same whether or not the chloride bath contains lower titanium chloride, a large current can be generated with high production efficiency. Furthermore, since titanium tetrachloride is more volatile than lower titanium chloride, lower titanium chloride is more suitable for inclusion in the chloride bath. Also, since the valency of titanium ions represents the number of electrons required for reduction to titanium electrodeposition at the cathode, lower titanium chloride is advantageous from a productivity standpoint. The following are examples of preferred embodiments for each process.

[0017] <Extraction process> First, a crude titanium-based material is prepared in the extraction process. Below, an example of the preparation of the crude titanium-based material used in the electrodeposition process described later will be explained. The extraction process can be appropriately applied to the content disclosed in Patent Document 1, etc. That is, the crude titanium-based material can be manufactured based on known methods, and the crude titanium-based material can be appropriately obtained and used. The extraction process will also be explained in detail below.

[0018] The extraction process involves heating a chemical blend containing titanium ore with titanium oxide, aluminum, and a separating agent, for example, in a heating device, to obtain a crude titanium-based material. The reaction at this time is complex, but generally, it is thought that a reaction such as 3TiO2 + 4Al → 3Ti + 2Al2O3 occurs. Here, Ti corresponds to the crude titanium-based material. In Ti, Al and O may be present in levels ranging from those corresponding to unavoidable impurities to those described later, but it is electrically conductive. Aluminum may be present in the anodic residue obtained in the electrodeposition process described later, and this can be used in the extraction process, but usually, separately prepared aluminum is mixed into the chemical blend. The crude titanium-based material obtained in the extraction process has relatively high conductivity and can be used in the electrodeposition process described later. After the above heat treatment, from the viewpoint of removing impurities, it is preferable to remove slag etc. adhering to the surface of the crude titanium-based material by post-treatment (for example, blast treatment). The titanium oxide content in the titanium ore is not limited, but is, for example, 50% by mass or more, for example, 80% by mass or more, or for example, 90% by mass or more. Upgraded titanium ore may also be used.

[0019] (Separating agent) The separating agent is included in the chemical blend for the purpose of separating the crude titanium-based material from the by-product, slag, during the extraction process. Therefore, any substance that can separate the crude titanium-based material from the slag during the extraction process is considered a separating agent. For example, the separating agent preferably contains one or more selected from calcium fluoride, aluminum fluoride, potassium fluoride, magnesium fluoride, calcium oxide, calcium chloride, and sodium fluoride, and more preferably contains calcium fluoride. The separating agent may also be calcium fluoride alone.

[0020] (Content of each chemical blend) To prepare the above chemical blend, the molar ratio of titanium, aluminum, and separating agent should be adjusted so that, for example, titanium oxide:aluminum:separating agent = 3:4 to 7:2 to 6.

[0021] (heating device) The heating device is a device for producing crude titanium-based material by heat treatment. Examples of heating devices include high-frequency induction heating devices. Such a high-frequency induction heating device may include, for example, a carbon crucible, a solenoid-shaped induction heating coil on the outer wall of the crucible, and a high-frequency power supply connected to the induction heating coil. Since the chemical blend in the crucible contains a conductive metal, it is considered that high-speed heating is possible.

[0022] (Heat treatment conditions) Regarding the heat treatment conditions, for example, the temperature inside the container is set to, for example, 1500°C or higher and 1800°C or lower under an inert gas (e.g., Ar gas) atmosphere. Furthermore, the material of the inner wall of the container can be, from the viewpoint of heat resistance, carbon or ceramics, for example.

[0023] (Composition of crude titanium-based material obtained in the extraction process) The crude titanium-based material obtained in the extraction process has, for example, a titanium content of 50% by mass or more and 80% by mass or less, an aluminum content of 3% by mass or more and 40% by mass or less, and an oxygen content of 0.2% by mass or more and 20% by mass or less. The crude titanium-based material obtained in this extraction process has high aluminum and oxygen content, but it is well purified in the electrodeposition process described later, reducing the aluminum and oxygen content to become a refined titanium-based material. The titanium content mentioned above has a lower limit, for example, of 60% by mass or more. Furthermore, the aluminum content is, for example, 5% by mass or more as a lower limit. On the other hand, the aluminum content is, for example, 30% by mass or less, or 20% by mass or less as an upper limit. Furthermore, the oxygen content can be set at a lower limit of, for example, 3% by mass or more, 5% by mass or more, or 8% by mass or more. On the other hand, the oxygen content can be set at an upper limit of, for example, 15% by mass or less, or 10% by mass or less. In this invention, even with crude titanium-based materials that have high aluminum and oxygen content, it is possible to obtain metallic titanium with low levels of such impurities and high purity. The method for measuring the impurity content of each component in the crude titanium-based material is as follows: First, a sample is prepared by taking a portion from the crude titanium-based material. The impurity content of each component in this sample can then be measured using ICP emission spectrometry (e.g., PS3520UVDDII, manufactured by Hitachi) for the metal components and inert gas fusion-infrared absorption spectrometry (e.g., TC-436AR, manufactured by LECO) for the oxygen components.

[0024] (specific resistance) The resistivity of the crude titanium-based material produced in the extraction process should be set at an upper limit of, for example, 8 × 10⁻⁶, from the perspective of properly carrying out electrolytic refining. -5 The resistivity may be Ω·m or less. Furthermore, the crude titanium-based material is conductive and only needs to be able to conduct electricity to a reasonable degree, so the lower limit of the resistivity is not particularly limited, but if we were to give an example, it would be 1 × 10⁻⁶ -8 It may be greater than or equal to Ω·m, for example, 5 × 10 -8 It may be greater than or equal to Ω·m, for example, 1 × 10⁻⁶ -7 The resistivity may be Ω·m or greater. As an example of the measurement method, a sample taken from a crude titanium-based material is cut into 10 mm square blocks, and the resistivity of the cut sample is measured at room temperature using a two-terminal measurement method (for example, using a low-resistivity meter 3566-RY (manufactured by Tsuruga Electric Co., Ltd.)).

[0025] <Electrodeposition process> The electrodeposition process uses an electrode comprising an anode and a cathode, both containing a conductive crude titanium-based material containing titanium, aluminum, and oxygen, in a chloride bath as a molten salt bath. The refined titanium-based material is deposited on the surface of the cathode to obtain a titanium electrodeposit. This refines the crude titanium-based material, resulting in a refined titanium-based material with a higher titanium content than the crude titanium-based material. Typically, the electrodeposition process is set to apply a voltage within a specific range between the anode and cathode. This is to prevent impurities originating from the molten salt bath from contaminating the refined titanium-based material.

[0026] Furthermore, in the electrodeposition process, the chloride bath contains 30 mol% or more of magnesium chloride and 1 mol% or more of lower titanium chloride. This allows for the deposition of a refined titanium-based material with reduced impurity content (especially aluminum content) on the cathode surface (electrolytic surface) compared to crude titanium-based material. Moreover, the anode current in the electrodeposition process is more than twice that of the anode current obtained in a molten salt electrolysis test under identical conditions except that the chloride bath does not contain lower titanium chloride, thereby improving the productivity of titanium electrodeposits. In one embodiment, the start time for measuring the anode current is 600 seconds after the application of voltage between the anode and cathode, and the end time for measuring the anode current is the time when the application of voltage between the anode and cathode is stopped.

[0027] (electrolyzer) In one embodiment, various electrolytic devices can be used. An example of an electrolytic device 100 shown in Figure 1A is a batch type, comprising a sealed container-shaped electrolytic cell 110 for storing the chloride bath Bf, electrodes including an anode 120 and a cathode 130 immersed in the chloride bath Bf, and a power supply (not shown) connected to the anode 120 and cathode 130 via conductive wires to supply current to the anode 120 and cathode 130. Although not shown, the electrolytic device 100 is normally openable for installing or removing the anode and cathode. Also, although not shown, the electrolytic device 100 is equipped with openings for supplying and exhausting gas to create an inert gas atmosphere in the space above the chloride bath Bf. Also, although not shown, the electrolytic device 100 is equipped with heaters at appropriate locations to maintain the molten state of the chloride bath Bf by heating. The material of the electrolytic cell 110 is not particularly limited as long as it has heat resistance and corrosion resistance. Furthermore, electrodes may also contain bipolar elements.

[0028] (Chloride bath) In the electrolytic refining process of electrodeposition, a chloride bath Bf containing 30 mol% or more magnesium chloride is used to produce metallic titanium by reducing not only the oxygen content but also the aluminum content. Using a chloride bath with a higher magnesium chloride content tends to enhance the effect of reducing the aluminum content. The chloride bath Bf containing the above-mentioned predetermined amount of magnesium chloride is effective in reducing the aluminum and oxygen content in the titanium electrodeposit. The magnesium chloride content is preferably 30 mol% or more, more preferably 50 mol% or more, even more preferably 80 mol% or more, even more preferably 85 mol% or more, and even more preferably 90 mol% or more. The chloride bath Bf may further contain, along with magnesium chloride, one or more metal chlorides selected from lithium chloride (LiCl), sodium chloride (NaCl), potassium chloride (KCl), rubidium chloride (RbCl), cesium chloride (CsCl), beryllium chloride (BeCl2), calcium chloride (CaCl2), strontium chloride (SrCl2), and barium chloride (BaCl2), and the metal chloride may be further contained in amounts of, for example, 70 mol% or less, 50 mol% or less, 20 mol% or less, 15 mol% or less, or 10 mol% or less. However, the chloride bath Bf may also be composed of magnesium chloride and lower titanium chloride. Note that the bath temperature required to maintain the chloride bath Bf in a molten state may vary depending on its composition. Furthermore, the content of lower titanium chloride is 1 mol% or more, from the viewpoint of promoting the deposition of the purified titanium-based material 123 on the surface of the cathode 130. The lower limit of the content of lower titanium chloride is, for example, 2 mol% or more, and also, for example, 3 mol% or more. Also, the upper limit of the content of lower titanium chloride is, for example, 50 mol% or less, for example, 30 mol% or less, for example, 20 mol% or less, for example, 15 mol% or less, for example, 13 mol% or less, and for example, 10 mol% or less, taking into account the saturation amount for the chloride bath Bf. Examples of lower titanium chloride include titanium dichloride and titanium trichloride. Lower titanium chloride can be produced by contacting titanium tetrachloride with titanium scrap or sponge titanium. The specific type and content of the chlorides described above can be appropriately determined by considering the composition of the titanium electrodeposition and the bath temperature during the operation of the electrolytic device. The molar content is measured by ICP emission spectrometry and atomic absorption spectrometry. Here, the molar content is calculated as follows: After solidifying a sample of molten salt taken from the chloride bath Bf, the molar content of each metal ion in the chloride bath Bf is calculated by performing ICP emission spectrometry and atomic absorption spectrometry on the components of the sample. If the chloride bath contains MgCl2, NaCl, KCl, CaCl2, LiCl, TiCl2, and TiCl3, the total content of metal ions (Mm) is determined by adding up the content of magnesium ions, sodium ions, potassium ions, calcium ions, lithium ions, and titanium ions, using atomic absorption spectrometry for Na, K, and Li, and ICP emission spectrometry for the others. The molar content of each component contained in the chloride bath Bf can be calculated by dividing the content of the metal ion of that component by the total content of that metal ion (Mm) and expressing it as a percentage. Based on the metal ion content contained in the chloride bath as described above, the chloride content is determined.

[0029] (anode) Since crude titanium-based material 121 is used as the anode raw material, it is preferable to store the crude titanium-based material in a conductive container 122 to constitute the anode 120. The container 122 can be handled as the anode 120 based on its external shape. The shape of the anode 120 is not particularly limited, but examples include a rod shape, a long strip shape for use while moving, a plate shape or cylindrical shape, a cylinder or other columnar shape, or a lump shape. The shape of the crude titanium-based material 121 is also not particularly limited, but examples include granular or lump shapes. When using the granular crude titanium-based material 121, it is preferable to store the crude titanium-based material 121 in the container 122 before use. The number of anodes 120 may be one or more, depending on the number of cathodes 130.

[0030] For example, the container 122 may be suspended in the chloride bath Bf, or, although not shown in the drawing, a base (not shown) supporting the container 122 from below may be erected on the bottom surface of the electrolytic cell 110. The shape of the base can be appropriately determined in consideration of the shape of the container 122. If the bottom wall of the container 122 is an annular bottomed cylinder, the base may be cylindrical to match the shape of the container 122, or multiple columnar bases may be arranged at equal intervals. Furthermore, the base only needs to be insulating so as not to conduct electricity with the container 122 during electrolytic refining, so ceramics are preferable, and among them, refractory bricks are more preferable from the viewpoint of insolubility with the chloride bath.

[0031] (container) Container 122 is used to store the crude titanium-based material 121 and the anode residues 124 and 127 after electrodeposition, and is electrically conductive. The shape of container 122 is not particularly limited and may correspond to the shape of the anode (crude titanium-based material 121 and the anode residues 124 and 127 after electrodeposition). For example, a basket-type container 122 with through holes can be used. As an example, container 122 has the appearance of a bottomed cylinder and comprises an annular bottom wall 122a, an inner wall 122b extending upward from the bottom wall 122a, and an outer wall 122c extending upward from the bottom wall 122a, with an opening formed at the top. Container 122 only needs to have at least a through hole 122d in the inner wall 122b facing the cathode 130, and may further have a through hole 122d in the outer wall 122c. The inner wall 122b and the outer wall 122c may more preferably have a plurality of through holes 122d. The arrangement of the plurality of through holes 122d is not particularly limited and may be in a grid pattern or a staggered pattern. Furthermore, assuming that the crude titanium-based material 121 can be held inside the container 122, the bottom wall 122a may also have through holes 122d. From the viewpoint of performing electrolytic refining while reducing power consumption, the resistivity of the container 122 is set to an upper limit of, for example, 1 × 10⁻⁶. -4 It is sufficient if the resistivity is Ω·m or less. Furthermore, the container 122 is conductive and only needs to be able to conduct electricity to a reasonable degree, so the lower limit of the resistivity is not particularly limited, but if we were to give an example, it would be 1 × 10⁻⁶ -8 A resistance of Ω·m or greater is acceptable. As an example of a measurement method, the resistivity is measured at room temperature by measuring the resistance of a sample cut to a predetermined size using a two-terminal measurement method (low resistance meter 3566-RY, manufactured by Tsuruga Electric Co., Ltd.). The material of the container 122 can be any material that is insoluble in the chloride bath, such as nickel, nickel-based alloys (e.g., Hastelloy), iron, and carbon. Containers 122 made of these materials hardly dissolve into the chloride bath Bf during electrolytic refining, and mainly the crude titanium-based material 121 inside the container 122 dissolves. Of these materials, nickel, nickel-based alloys (e.g., Hastelloy), and iron are preferred for the container 122 from the viewpoint of impact resistance, with nickel being more preferred. Furthermore, if the container 122 is made of steel, nickel plating may be formed by applying a plating treatment to the surface of the steel.

[0032] (cathode) Furthermore, the cathode 130 may be, for example, rod-shaped, and at least a portion of the surface of the cathode 130 on which the refined titanium-based material is deposited may be curved. The shape of the cathode 130 is not particularly limited, and examples include long strip-shaped, plate-shaped, cylindrical, columnar, or other columnar or block-shaped cathodes that are used while being moved. The number of cathodes 130 may be one or more, depending on the number of anodes 120. The material of the cathode 130 is not particularly limited. For example, the cathode 130 may have at least 90% by mass or more of at least one material selected from the group consisting of titanium, molybdenum, glassy carbon, and tungsten on its surface. The surface of the cathode 130 may also be made of titanium.

[0033] The distance between the anode 120 and the cathode 130 is not particularly limited, but for example, it is 20 mm or more and 700 mm or less. Also, for example, if a cylindrical, rod-shaped, or columnar cathode 130 is used and the anode 120 is placed on the outside thereof, the anode 120 may also be cylindrical. In this case, since the cylindrical anode 120 surrounds the cathode 130, the area on which the refined titanium-based material 123 is generated can be increased. Alternatively, a rod-shaped or columnar cathode 130 with a fixed axis position that is rotatable may be used, and a plate-shaped anode 120 with an arc-shaped cross-section may be used at the opposing part. Even in this case, the opposing parts of the anode 120 and cathode 130 can maintain approximately the same distance between the electrodes. Using such a cathode 130 allows for the deposition of titanium electrodeposits on the surface of the cathode 130 while the cathode 130 is rotated or otherwise operated, contributing to the miniaturization of the equipment during continuous production.

[0034] <Electrodeposition auxiliary process> The electrodeposition auxiliary step is preferably included before and / or after the aforementioned electrodeposition step, with the aim of further increasing the purity of titanium. Since the electrodeposited material is purified in molten salt electrolysis, the molten salt bath used in the electrodeposition auxiliary step is not particularly limited from this viewpoint. For example, the chloride bath mentioned above may be used, or a molten salt bath further containing fluoride, bromide, iodide, etc., or a molten salt bath that is a fluoride bath, bromide bath, or iodide bath may be used. In the electrodeposition auxiliary step, as an example, the electrolytic apparatus used in the aforementioned electrodeposition step can be used. The conditions for the electrodes in the electrodeposition auxiliary step can be set in the same way as in the aforementioned electrodeposition step or as appropriate, so a detailed explanation is omitted.

[0035] Furthermore, the chloride bath Bf used in the electrodeposition auxiliary step may further contain lower titanium chloride. The content of said lower titanium chloride can be adjusted as appropriate.

[0036] When performing the electrodeposition auxiliary process, it may be performed only once, but performing it multiple times more reliably reduces the aluminum and / or oxygen content, resulting in a high-purity refined titanium-based material. The number of electrodeposition auxiliary processes can be appropriately determined considering manufacturing costs and man-hours. For example, the electrodeposition auxiliary process may be performed a total of 1 to 5 times, a total of 2 to 5 times, or a total of 2 to 3 times. Furthermore, when performing the electrodeposition auxiliary process multiple times, the molten salt bath used in each electrodeposition auxiliary process may be the same or different.

[0037] Next, an example of manufacturing titanium electrodeposits by carrying out the electrodeposition process and the electrodeposition auxiliary process in that order will be explained using Figures 1A to 1D and Figure 2. Each conductive wire shown in Figures 1A to 1D can be connected to a power supply (not shown), and the control mechanism (not shown) of the power supply can appropriately switch the conductive wires EL that supply current according to each anode and cathode. Please note that the container shape shown in the diagram is merely an example and is not the only possible shape.

[0038] The electrodeposition process involves electrolytic refining in a chloride bath Bf using an electrode containing the aforementioned predetermined crude titanium-based material to obtain a purified titanium-based material. For example, in the electrodeposition process, as shown in Figure 1A, a nickel container 122 and an anode 120 containing crude titanium-based material 121 within the container 122, and a titanium cathode 130 are placed in a chloride bath Bf, respectively. Next, a voltage is applied by a control mechanism via conductive wires EL connected to the container 122 and cathode 130 to energize the crude titanium-based material 121 contained in the container 122 and the cathode 130, thereby performing electrolytic refining. At this time, considering the components of the chloride bath Bf, the voltage is set so as not to reduce the efficiency of producing the refined titanium-based material 123 due to the decomposition of the chloride bath Bf and to prevent the contamination of the refined titanium-based material with impurities originating from the chloride bath Bf. Therefore, in most cases, a voltage within a certain range is applied. Although the drawing shows the crude titanium-based material 121 stored in container 122, for example, multiple containers may be used, with the crude titanium-based material 121 of the anode 120 stored in separate containers.

[0039] (Bath temperature for chloride baths) The temperature of the chloride bath Bf can be appropriately adjusted depending on the components in the chloride bath Bf. That is, the temperature of the chloride bath Bf should be appropriately determined from the viewpoint of maintaining a molten state in the chloride bath and avoiding energy loss due to excessive heating. In this case, it is also possible to appropriately determine the temperature of the chloride bath Bf by referring to the melting point of each metal chloride. The temperature of the chloride bath Bf is preferably 750°C or higher and 950°C or lower, preferably 750°C or higher and 900°C or lower, and preferably 750°C or higher and 850°C or lower. Within this temperature range, a relatively large amount of magnesium chloride can be included in the chloride bath Bf. Furthermore, lower titanium chloride can be well included in the chloride bath, and electrolytic refining can be carried out without requiring excessive heating.

[0040] The atmosphere inside the electrolytic cell 110 is controlled to an inert gas atmosphere, such as argon, in order to suppress the increase in the impurity content of the titanium electrodeposit due to the incorporation of moisture from the atmosphere.

[0041] Next, as shown in Figure 1B, as the crude titanium-based material 121 containing titanium, which has a higher ionization tendency than nickel, and aluminum is dissolved into the chloride bath Bf, the crude titanium-based material 121 is consumed, and a refined titanium-based material 123 with reduced impurity content is deposited on the surface of the cathode 130. At this time, the crude titanium-based material 121 in the container 122 becomes the anode residue 124 due to electrolytic refining. Then, in order to terminate the electrolytic refining, the control mechanism stops the application of voltage between the anode 120 and the cathode 130.

[0042] The refined titanium-based material 123 deposited on the surface of the cathode 130 removed from the electrolytic cell 110 can be recovered by removing it with a cutting tool or the like. In this case, the refined titanium-based material 123 may be washed and dried, or vacuum separation may be performed. This treatment may be performed on the refined titanium-based material 123 together with the cathode 130, or after it has been recovered from the cathode 130. As an example, the cathode 130 is removed from the electrolytic cell 110, and the cathode 130 and the refined titanium-based material 123 are cleaned with acid and / or water to dissolve and remove any molten salt components adhering to them. Next, the refined titanium-based material 123 is peeled off the surface of the cathode 130 using a cutting tool or the like. Then, the refined titanium-based material 123 is placed in a container such as a crucible and vacuum-dried to evaporate any moisture. As an example, the cathode 130 is removed from the electrolytic cell 110 and subjected to vacuum separation treatment. In the vacuum separation treatment, the molten salt components are removed by evaporation. The refined titanium-based material 123 has reduced aluminum and oxygen content compared to the crude titanium-based material 121. Because the aluminum content of the refined titanium-based material 123 is appropriately reduced, it can be handled as a titanium electrodeposit. Furthermore, if molten salt electrolysis is performed to further reduce the impurity content, the refined titanium-based material 123 can be used as the crude titanium-based material 121 in the next electrolytic refining process.

[0043] <Electrodeposition auxiliary process> In the electrodeposition auxiliary step, for example, after the aforementioned electrodeposition step, the refined titanium-based material 123 is electrolytically purified in a chloride bath Bf using an electrode containing the crude titanium-based material. This further purifies the refined titanium-based material 123 obtained in the electrodeposition step, resulting in a titanium electrodeposited product 126 with an even lower impurity content. In other words, when the electrodeposition auxiliary step is repeated, the previously obtained refined titanium-based material 123 is used as the electrode in subsequent electrodeposition auxiliary steps. For example, as shown in Figure 1C, an anode 125 containing a refined titanium-based material 123 and a nickel container 122 containing the refined titanium-based material 123, and a titanium cathode 130 are placed in a chloride bath Bf. Next, a voltage is applied between the container 122 and the cathode 130 by a control mechanism via a conductive wire EL connected to the container 122 and the cathode 130, thereby energizing the refined titanium-based material 123 stored in the container 122 and the cathode 130 to perform electrolytic refining. At this time, a voltage within a certain range is set. Note that the cathode 130 may be the same cathode 130 used in the electrodeposition process, or it may be replaced with a new cathode.

[0044] In this embodiment, a chloride bath Bf is also used in the electrodeposition auxiliary step. Alternatively, a molten salt bath other than the chloride bath Bf may be used in the electrodeposition auxiliary step; for example, a molten salt bath containing fluoride, bromide, or iodide can be used. The composition of these can be adjusted as appropriate. The temperature of the molten salt bath should be set appropriately considering the composition of the molten salt bath, etc.

[0045] Next, as shown in Figure 1D, as the titanium-containing anode 125 is dissolved into the chloride bath Bf, the purified titanium-based material 123 is consumed, and a titanium electrodeposited material 126 with reduced impurity content is formed on the surface of the cathode 130. At this time, the purified titanium-based material 123 in the container 122 becomes the anode residue 127 due to electrolytic purification. Then, to terminate the electrolytic purification, the control mechanism stops the application of voltage between the anode 125 and the cathode 130.

[0046] The titanium electrodeposit 126 formed on the surface of the cathode 130 removed from the electrolytic cell 110 is recovered by peeling it off with a cutting tool or the like. Alternatively, the titanium electrodeposit 126 may be subjected to the washing, drying, or vacuum separation processes described in the electrodeposition step. Furthermore, washing and drying may be performed together with the cathode 130, or after recovery from the cathode 130. This results in a titanium electrodeposited material 126 with further reduced aluminum and oxygen content.

[0047] (Composition of titanium electrodeposits, etc.) Titanium electrodeposits are produced by carrying out the above-described method for producing titanium electrodeposits. While it is preferable that the titanium electrodeposits are free of impurities, they may contain a certain amount of impurities. Examples of impurities are given below. In the titanium electrodeposit produced by the said titanium electrodeposit manufacturing method, it is preferable that the aluminum content is at least 5,000 ppm by mass or less. For example, the titanium electrodeposit preferably consists of an aluminum content of 5,000 ppm by mass or less, an oxygen content of 20,000 ppm by mass or less, and the remainder being titanium and unavoidable impurities. These unavoidable impurities are often impurities derived from the ore or components derived from the chloride bath. The aluminum content is limited to, for example, 5000 ppm by mass or less, 2500 ppm by mass or less, 500 ppm by mass or less, 300 ppm by mass or less, and 200 ppm by mass or less as upper limits. On the other hand, the aluminum content is limited to, for example, 30 ppm by mass or more, 50 ppm by mass or more, and 80 ppm by mass or more as lower limits. The above oxygen content has upper limits, for example, 20,000 ppm by mass or less, 12,000 ppm by mass or less, 1,000 ppm by mass or less, 800 ppm by mass or less, and 600 ppm by mass or less. On the other hand, the above oxygen content has lower limits, for example, 80 ppm by mass or more, 110 ppm by mass or more, 150 ppm by mass or more, and 300 ppm by mass or more. Comparing the impurity content described above with the case where only the electrodeposition process is performed, and the case where both the electrodeposition process and the electrodeposition auxiliary process are performed, the impurity content tends to decrease even further when both the electrodeposition process and the electrodeposition auxiliary process are performed. The method for measuring the impurity content of each component in the titanium electrodeposit is the same as the method for measuring the impurity content of each component in the crude titanium-based material described above. [Examples]

[0048] The present invention will be specifically described based on examples and comparative examples. The following descriptions of examples and comparative examples are merely experimental examples intended to facilitate understanding of the technical content of the present invention, and the technical scope of the present invention is not limited by these examples.

[0049] [Preparation of crude titanium-based material (extraction process)] A chemical blend containing titanium ore with titanium oxide, aluminum, and calcium fluoride as a separating agent was heat-treated according to a known method, and then post-treated to produce a crude titanium-based material.

[0050] The composition of the sample taken from the crude titanium-based material was measured using the method described above. As a result, the titanium content of the crude titanium-based material was 70% by mass or more, the aluminum content was 9% by mass, and the oxygen content was 13% by mass. Furthermore, the resistivity of the measurement sample taken from the crude titanium-based material was measured using the method described above. As a result, the resistivity of the crude titanium-based material was 5 × 10⁻⁶. -5 It was Ω·m.

[0051] For the crude titanium-based material mentioned above, five sets were collected in granular form so that the mass of each anode was 200g.

[0052] [Manufacturing of refined titanium-based materials (electrodeposition process)] [Example 1] Next, an electrolytic apparatus 100 having the configuration shown in Figures 1A, 1B, and 2 was prepared. The electrolytic apparatus 100 included a sealed container-shaped electrolytic cell 110 for storing a chloride bath Bf, an anode 120 immersed in the chloride bath Bf and containing a crude titanium-based material 121 and a nickel basket-shaped container 122 containing the crude titanium-based material 121, a titanium cathode 130, and a power supply (not shown) connected to the anode 120 and the titanium cathode 130 via a conductive wire EL to supply current to the anode 120 and the titanium cathode 130. The container 122 has a bottomed cylindrical shape and comprises an annular bottom wall 122a, an inner wall 122b extending upward from the bottom wall 122a, and an outer wall 122c extending upward from the bottom wall 122a. An opening is formed at the top, and multiple through holes 122d are formed in the inner wall 122b and the outer wall 122c of the container 122. The power supply was connected to a control mechanism (not shown). Although not illustrated, the electrolytic cell 110 was designed to have an openable and closable top. Therefore, by closing the top of the electrolytic cell 110, the ingress of outside air during the electrodeposition process can be suppressed. The dimensions and shape of the bath portion of the electrolytic cell 110 of the electrolytic device 100 were 100 mmΦ × 200 mm depth. Next, magnesium chloride was added to the electrolytic cell 110 of the electrolytic device 100, and dissolved while controlling the bath temperature as shown in Table 1 to prepare the chloride bath Bf. Subsequently, titanium tetrachloride was brought into contact with the sponge titanium obtained by the Chlor method to supply lower titanium chloride to the chloride bath Bf and prepare the bath composition shown in Table 1. In Table 1, "TiCl2" means lower titanium chloride. Furthermore, in Example 1 and Example 2 described later, compared with Comparative Example 1 described later, the chloride bath Bf was prepared by adding lower titanium chloride to magnesium chloride, and the bath temperature and voltage of the chloride bath Bf were the same. Therefore, Comparative Example 1 corresponds to the case where a "molten salt electrolysis test under the same conditions as Examples 1 and 2, except that the chloride bath does not contain lower titanium chloride" was performed.

[0053] Next, crude titanium-based material 121 is placed in container 122 as the anode raw material (resistivity: 5 × 10 -5It was housed within Ω·m). A titanium cylinder measuring 10mmΦ × 300mm in length was prepared as the cathode 130. In other words, there was one container 122 and one cathode 130. The container 122 and cathode 130 were positioned with the conductive wire EL connected so that their heights were approximately parallel to the depth of the chloride bath Bf. Since the cathode 130 was longer than the depth of the chloride bath Bf, it was used with a portion of it positioned above the bath surface.

[0054] A voltage was applied between the anode 120 and the cathode 130 by a control mechanism, and molten salt electrolysis was performed in a chloride bath Bf. One hour after the start of voltage application, the voltage application was stopped by the control mechanism. The current was measured at the start and end of the measurement of the current in the anode 120 according to the method described above. As shown in Figure 1B, purified titanium-based material 123 was obtained by depositing it over the entire surface of the cathode 130. The other electrolytic purification conditions are shown below. <Conditions for electrolytic refining> Inside the electrolytic cell: Ar gas atmosphere Interelectrode distance: 50mm

[0055] After the voltage application was stopped, the container 122 and cathode 130 were removed from the electrolytic cell 110, and the container 122, the anode residue 124 inside the container 122, the cathode 130, and the refined titanium-based material 123 were washed with water to remove any adhering molten salt components. Next, the refined titanium-based material 123 was peeled off and recovered from the cathode 130 using a cutting tool. After recovery, the moisture contained in the refined titanium-based material 123 was evaporated by vacuum drying.

[0056] After vacuum drying, the mass of the refined titanium-based material 123 was measured. The aluminum content of the refined titanium-based material 123 was measured using the method described above. The results are shown in Table 1. The oxygen content of the refined titanium-based material 123 was approximately 0.8% by mass.

[0057] [Examples 2-3, Comparative Examples 1-3] In Examples 2 and 3, molten salt electrolysis was performed in the same manner as in Example 1, except that the bath composition and bath temperature were changed as shown in Table 1. Subsequently, the mass and aluminum content of the refined titanium-based material 123 were measured, as in Example 1. The results are shown in Table 1. The oxygen content of the refined titanium-based material 123 in Examples 2 and 3 was approximately 0.8% by mass. Furthermore, the oxygen content of the refined titanium-based material 123 in Comparative Examples 1 to 3 described later was approximately 7% by mass. In Comparative Example 1, molten salt electrolysis was performed in the same manner as in Example 1, except that the bath composition was changed as shown in Table 1. However, since Comparative Example 1 used a lower current than Example 1, the voltage application was stopped 5 hours after the start of voltage application. For comparison with Example 1, the current values ​​shown in Table 1 were confirmed up to 1 hour of the electrolytic refining operation time. After that, the mass and aluminum content of the refined titanium-based material 123 were measured, as in Example 1. The results are shown in Table 1. Comparative Example 1 corresponds to the case where a molten salt electrolysis test was performed under the same conditions as Examples 1 and 2, except that the chloride bath did not contain lower titanium chloride. In Comparative Example 2, molten salt electrolysis was performed in the same manner as in Example 1, except that the bath composition was changed as shown in Table 1. However, since Comparative Example 2 used a lower current than Example 1, the voltage application was stopped 6 hours after the start of voltage application. For comparison with Example 1, the current values ​​shown in Table 1 were confirmed up to 1 hour of electrolytic refining operation. Subsequently, the mass and aluminum content of the refined titanium-based material 123 were measured, as in Example 1. The results are shown in Table 1. In Comparative Example 3, molten salt electrolysis was performed in the same manner as in Example 3, except that the bath composition was changed as shown in Table 1. However, since Comparative Example 3 used a lower current than Example 3, the voltage application was stopped 6 hours after the start of voltage application. For comparison with Example 3, the current values ​​shown in Table 1 were confirmed up to 1 hour of electrolytic refining operation. After that, the mass and aluminum content of the refined titanium-based material 123 were measured, as in Example 3. The results are shown in Table 1. For Comparative Examples 1-3, the weights of the refined titanium-based materials shown in Table 1 were obtained after 5-6 hours of operation for each comparative example.

[0058] [Table 1]

[0059] (Discussion based on examples) Examples 1-3 had a high anode current, resulting in better titanium electrodeposition productivity compared to Comparative Examples 1-3. It is presumed that the chloride baths in Examples 1-3 contained lower titanium chloride, which contributed to the increased productivity. Furthermore, Comparative Example 1 showed superior results in aluminum purification compared to Comparative Example 2. It was considered that the use of magnesium chloride is effective in reducing the aluminum content in the titanium electrodeposition. Comparing Examples 1-2 with Comparative Example 1, the difference in molten salt electrolysis conditions is the presence or absence of lower titanium chloride in the molten salt bath. In Examples 1-2, the chloride bath contained a predetermined amount of lower titanium chloride, resulting in more than double the anode current and improved productivity of titanium electrodeposition. Furthermore, the effect of reducing the aluminum content in the titanium electrodeposition was also good. Example 1 had a higher lower titanium chloride content than Example 2, and Example 3 had a higher lower titanium chloride content than Example 1. The lower titanium chloride content in the chloride bath affects the productivity of titanium electrodeposition, and it is considered that the effect of reducing aluminum content by magnesium chloride is well maintained even when lower titanium chloride is present in the chloride bath. Comparing Example 3 and Comparative Example 3, the difference in the conditions for molten salt electrolysis is the presence or absence of lower titanium chloride in the molten salt bath. In Example 3, the chloride bath contained a predetermined amount of lower titanium chloride, resulting in more than double the anode current and improving the productivity of titanium electrodeposition. Furthermore, it also showed a good effect in reducing the aluminum content in the titanium electrodeposition. On the other hand, comparing Examples 1-3 with Comparative Examples 1-3, the titanium content of the refined titanium-based materials in Comparative Examples 1-3 was lower. This is because the oxygen content of the refined titanium-based materials in Examples 1-3 was approximately 0.8% by mass, while the oxygen content of the refined titanium-based materials in Comparative Examples 1-3 was approximately 7% by mass, suggesting that the oxygen content of the refined titanium-based materials in Comparative Examples 1-3 was higher. Furthermore, Comparative Examples 1-3 did not contain a predetermined amount of lower titanium chloride in the chloride bath compared to Examples 1-3, resulting in finer titanium particles obtained from the recovery of the refined titanium-based materials. In other words, the specific surface area of ​​the refined titanium-based materials recovered in Comparative Examples 1-3 was larger than that of Examples 1-3, indicating a higher oxygen content. [Explanation of Symbols]

[0060] 100 Electrolyzer 110 Electrolytic cell 120, 125 anode 121 Crude titanium-based materials 122 Container 122a Bottom wall 122b Inside wall 122c outer wall 122d through hole 123 Refined Titanium-Based Materials 124, 127 Anode residue 126 Titanium Electrodeposition 130 Cathode Bf Chloride Bath EL conductive wire

Claims

1. A method for producing titanium electrodeposits by electrolytic refining using molten salt electrolysis, The process includes an electrodeposition step in which a refined titanium-based material is deposited on the cathode using an electrode having an anode and a cathode containing a conductive crude titanium-based material containing titanium, aluminum, and oxygen in a chloride bath as a molten salt bath, thereby obtaining an electrodeposited product. In the electrodeposition step, the chloride bath contains 30 mol% or more of magnesium chloride and 1 mol% or more of lower titanium chloride. A method for producing titanium electrodeposits, wherein the amount of current at the anode in the electrodeposition step is more than twice the amount of current at the anode determined in a molten salt electrolysis test under identical conditions except that the chloride bath does not contain lower titanium chloride.

2. The method for producing a titanium electrodeposited product according to claim 1, wherein the bath temperature of the chloride bath in the electrodeposition step is 750°C or higher and 950°C or lower.

3. The method for producing a titanium electrodeposited product according to claim 1, wherein the anode in the electrodeposition step further includes a conductive container having the crude titanium-based material disposed inside, being insoluble in the chloride bath, and having through holes.

4. A method for producing a titanium electrodeposit according to any one of claims 1 to 3, wherein the titanium electrodeposit produced has an aluminum content of 5,000 ppm by mass or less.

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