Exfoliation method for refined titanium-based material and manufacturing method for titanium or titanium alloy

Abstract

To provide an exfoliation method for a refined titanium-based material that can efficiently exfoliate a refined titanium-based material from a titanium-deposited cathode and suppress the impact of the exfoliation of the refined titanium-based material on the cathode, and a manufacturing method for titanium or titanium alloy.SOLUTION: A method for exfoliating a refined titanium-based material 3 deposited to a cathode 2 by electrolytic refining of crude titanium-based material in a molten salt bath from the cathode 2, uses an exfoliation blade 11 having a body part 12 with a cathode receiving recess 12a that can receive the cathode 2 inside and a cutting edge part 13 provided at an opening 12b of the cathode receiving recess 12a to move the titanium-deposited cathode 1 towards the exfoliation blade 11, so that the refining titanium-based material 3 of the titanium-deposited cathode 1 is made to bite into the cutting edge part 13, and the cathode 2, from which the refined titanium-based material 3 has been separated by the bite of the cutting edge part 13, is inserted into the cathode receiving recess 12a, and thus, the refined titanium-based material 3 is exfoliated off from the cathode 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This invention relates to a method for peeling a refined titanium-based material from a titanium-attached cathode obtained by depositing a refined titanium-based material on a cathode through electrolytic refining of a crude titanium-based material in a molten salt bath, and to a method for producing titanium or a titanium alloy using the same. [Background technology]

[0002] Titanium (pure titanium) and titanium alloys are generally produced from titanium metal sponge, an intermediate product obtained from titanium ore in a process based on the Kroll process suitable for mass production.

[0003] This method requires the production of titanium tetrachloride by chlorinating titanium ore, the subsequent purification of titanium tetrachloride, and the reduction of titanium tetrachloride by metallic magnesium, as well as the crushing of sponge titanium lumps and the electrolysis of magnesium chloride produced by the reduction, and therefore involves many batch processes, making it difficult to say that titanium and titanium alloys can be produced efficiently and at low cost. In addition, coke (carbon) is used in the reaction to produce titanium tetrachloride, which results in the emission of carbon dioxide, a greenhouse gas that contributes to global warming.

[0004] In contrast, electrolytic refining using a molten salt bath (also called "molten salt electrolytic refining") makes it easier to produce conductive titanium and titanium alloys with relatively few impurities than the Kroll process-based method, and since it does not use coke, it may contribute to the realization of carbon neutrality. Examples of this type of technology are described in Patent Documents 1 and 2.

[0005] Patent Document 1 describes a method for extracting a titanium product from titanium ore, comprising the steps of: mixing a chemical blend containing titanium ore and a reducing agent, the ratio of the titanium ore to the reducing agent 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 an increasing rate of 1°C to 50°C / min; maintaining the chemical blend at a reaction temperature of 1500 to 1800°C for a time period between 5 and 30 minutes; cooling the chemical blend to a temperature lower than 1670°C; and separating the titanium product from the residual slag; placing the titanium product in a reaction vessel having an anode, a cathode and an electrolyte; heating the reaction vessel to a temperature of 600°C to 900°C to produce a molten mixture (in an electrolysis chamber) and applying an electrical differential between the anode and the cathode to deposit titanium ions on the cathode; and terminating the electrical differential and cooling the molten mixture to produce a refined titanium product, the refined titanium product having a surface area (specific surface area) of at least 0.1 m. 2 / g." A similar method is described in Patent Document 2.

[0006] In molten salt electrolytic refining, an anode containing a crude titanium-based material and a cathode are immersed in a molten salt bath, and a voltage is applied between the anode and the cathode, thereby dissolving Ti from the crude titanium-based material in the anode and precipitating a refined titanium-based material on the cathode. The titanium-adhered cathode obtained by precipitating the refined titanium-based material on the cathode in this way requires an operation to peel off the refined titanium-based material from the cathode.

[0007] Although this is a technology mainly related to the electrolytic refining of copper by performing aqueous solution electrolysis, Patent Document 3 describes "a method for stripping electrodeposited metal, in which electrodeposited metal is stripped from a cathode plate on whose surface the metal has been electrodeposited by electrolytic smelting, characterized in that, prior to a stripping step in which a chisel is inserted between the electrodeposited metal and the cathode plate to strip the metal, a forming step is provided in which an upper side of the electrodeposited metal is bent outward to open a gap between the electrodeposited metal and the cathode plate, thereby ensuring a gap for easy insertion of the chisel." [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 2015-507696 [Patent Document 2] Special Publication No. 2019-533081 [Patent Document 3] JP 2008-231501 A Summary of the Invention [Problem to be solved by the invention]

[0009] In order to separate the refined titanium-based material from the cathode with titanium attached thereto obtained by molten salt electrolytic refining, it is possible to perform cutting processing on the cathode with a milling cutter, planer, scraper, etc., and separate the refined titanium-based material attached to the surface of the cathode from the cathode. However, such cutting processing requires a certain amount of time, and is therefore not desirable from the viewpoint of increasing the production efficiency of titanium or titanium alloys.

[0010] In addition, when molten salt electrolytic refining is performed using a plate-shaped cathode, the titanium-attached cathode may have a refined titanium-based material attached to two surfaces, one surface and the other surface on the back side of the cathode. In this case, after cutting one surface of the titanium-attached cathode and peeling off the refined titanium-based material attached thereto, the rigidity of the titanium-attached cathode decreases due to the absence of the refined titanium-based material on the one surface side, so that when cutting the other surface side, bending deformation may easily occur, especially in a thin cathode. A cathode that has undergone bending deformation becomes difficult to use repeatedly in subsequent molten salt electrolytic refining. For mass production, a large number of cathodes may be placed in an electrolytic cell in which molten salt electrolytic refining is performed, and it may be desirable to make the thickness of the cathode somewhat thin due to restrictions on the placement space. The problem of bending deformation of the cathode during cutting as described above may occur not only when the cathode is plate-shaped but also when a cathode is rod-shaped such as a round bar or other shape and parts of its surface are cut sequentially. One way to avoid this is to cut little by little over a long period of time so as not to apply a large load, but this is an inefficient method.

[0011] The object of the present invention is to provide a method for stripping a purified titanium-based material, which can efficiently strip the purified titanium-based material from the cathode of a titanium-adhering cathode and can suppress the effect of the stripping of the purified titanium-based material on the cathode, and a method for producing titanium or a titanium alloy. [Means for solving the problem]

[0012] As a result of intensive research, the inventors have devised the use of a stripping blade for stripping the refined titanium-based material from the titanium-adhering cathode, which has a main body portion formed with a cathode receiving recess on the inside into which the cathode of the titanium-adhering cathode can be inserted, and a cutting edge portion provided at the opening of the cathode receiving recess. By moving the titanium-adhering cathode toward the stripping blade, the cutting edge portion bites into the refined titanium-based material around the cathode (at the boundary with the cathode or a portion close thereto), and the refined titanium-based material is separated from the cathode, while the separated cathode is inserted inside the cathode receiving recess. At this time, as the refined titanium-based material attached to the periphery of the cathode is simultaneously separated, the cathode receives external forces from all directions from the stripping blade surrounding the cathode toward the cathode, but these external forces act as opposing symmetrical forces to cancel each other out. This suppresses the occurrence of bending deformation of the cathode due to a decrease in rigidity, such as when cutting the plate-shaped cathode described above to peel off the purified titanium-based material from one surface of the cathode and then peeling off the purified titanium-based material from the other surface.

[0013] The method for peeling a refined titanium-based material of this invention is a method for peeling a refined titanium-based material from a titanium-adhering cathode obtained by electrolytic refining of a crude titanium-based material in a molten salt bath, where the refined titanium-based material is precipitated on the cathode. A peeling blade is used as the peeling blade, the peeling blade having a main body portion formed with a cathode receiving recess into which the cathode can be inserted, and a cutting edge portion provided at the opening of the cathode receiving recess. The titanium-adhering cathode is moved toward the peeling blade, causing the refined titanium-based material of the titanium-adhering cathode to bite into the cutting edge portion, while the cathode from which the refined titanium-based material has been separated by the biting of the cutting edge portion is inserted into the inside of the cathode receiving recess, and the refined titanium-based material is peeled off from the cathode.

[0014] In the above peeling method, it is preferable that the opening of the cathode receiving recess has a shape similar to that of the cathode in a cross section perpendicular to a direction in which the cathode is inserted into the cathode receiving recess.

[0015] In the above-mentioned peeling method, it is preferable that the cathode includes a main portion and a tip guide portion that is provided on the tip side of the main portion in the insertion direction of the cathode into the cathode receiving recess, is made of a poorly conductive material or a non-conductive material, and guides the insertion of the main portion into the cathode receiving recess.

[0016] In the above peeling method, it is preferable that the tip guide portion has a width that narrows smoothly or stepwise toward the tip side in a cross section along the insertion direction.

[0017] At least a surface of the main portion may consist of titanium or a titanium alloy, molybdenum or a molybdenum alloy, iron or an iron alloy, or nickel or a nickel alloy.

[0018] In the above peeling method, it is preferable that, in a cross section along the insertion direction of the cathode into the cathode receiving recess, the cutting edge portion of the peeling blade has a width that gradually decreases toward the opening of the cathode receiving recess, at least in a portion along the insertion direction.

[0019] In the above-described peeling method, the cathode is rod-shaped, and the refined titanium-based material is adhered to the periphery of the rod-shaped cathode using the titanium-adhering cathode, and by inserting the cathode into the cathode receiving recess of the peeling blade, the refined titanium-based material adhered to the periphery of the cathode can be peeled off from the cathode.

[0020] In the above-described peeling method, the cathode is plate-shaped, and the refined titanium-based material is adhered to at least two opposing surfaces of the plate-shaped cathode in the titanium-adhering cathode, and by inserting the cathode into the cathode receiving recess of the peeling blade, the refined titanium-based material adhered to at least the two surfaces of the cathode can be peeled off from the cathode.

[0021] In the above-described stripping method, the plurality of titanium-deposited cathodes are moved together toward the plurality of stripping blades, and the refined titanium-based material can be stripped from each of the titanium-deposited cathodes.

[0022] The method for producing titanium or a titanium alloy of the present invention includes an electrolysis step in which electrolytic refining is performed in a molten salt bath to dissolve Ti from the crude titanium-based material of the anode and deposit a refined titanium-based material on the cathode, and a stripping step in which the refined titanium-based material is stripped from the cathode with the titanium-adhered cathode obtained in the electrolysis step by using the stripping method for refined titanium-based material described above.

[0023] The above-mentioned manufacturing method preferably includes, after the peeling step, a heating and separating step of heating the purified titanium-based material to separate the molten salt residue from the purified titanium-based material. Effect of the Invention

[0024] According to the present invention, it is possible to efficiently peel off the refined titanium-based material from the cathode of the titanium-adhered cathode, and to suppress the influence of the peeling of the refined titanium-based material on the cathode. [Brief description of the drawings]

[0025] [Figure 1] FIG. 2 is a cross-sectional view taken along the insertion direction of the cathode into the cathode receiving recess of the stripping blade, showing the operation of the titanium-adhering cathode or cathode in the method for stripping purified titanium-based material according to one embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view showing an operation subsequent to that shown in FIG. 1; [Diagram 3] 3 is a cross-sectional view showing the operation following that shown in FIG. 2. [Figure 4] FIG. 2 is a cross-sectional view showing a state of an electrolysis step in a method for producing titanium or a titanium alloy according to one embodiment of the present invention. [Diagram 5] 5 is a cross-sectional view showing the titanium-deposited cathode being pulled out of the molten salt bath after the electrolysis step in FIG. 4. FIG. [Figure 6]FIG. 6 is a cross-sectional view showing a state before the refined titanium-based material is peeled off from the titanium-attached cathode in the peeling step following FIG. 5. [Figure 7] 7 is a cross-sectional view showing a state immediately after peeling in a peeling step following FIG. 6. [Figure 8] 8 is a cross-sectional view showing a state after peeling in a peeling step following FIG. 7. [Figure 9] 9(a) is a cross-sectional view of the titanium-deposited cathode taken along line aa in FIG. 1, and FIG. 9(b) is a plan view of the stripping blade taken along line bb in FIG. [Figure 10] 10(a) and 10(b) are respectively a cross-sectional view and a plan view similar to FIG. 9, showing another example of a titanium-deposited cathode and a peeling blade. [Figure 11] 11(a) and 11(b) are respectively a cross-sectional view and a plan view similar to FIG. 9, showing still another example of a titanium-deposited cathode and a peeling blade. [Figure 12] 12(a) to (d) are cross-sectional views showing the tip guide portion of the cathode and other aspects. [Figure 13] 13(a) to (c) are cross-sectional views showing other embodiments of the peeling blade. [Figure 14] FIG. 2 is a perspective view showing an example of a specific structure of a cathode and its surrounding area. [Figure 15] FIG. 13 is a perspective view showing another example of a specific structure of the cathode and its surrounding portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the drawings are merely schematic illustrations of an embodiment for ease of understanding, and the dimensions, shapes, numbers of members, and other aspects of the various parts in the drawings may be changed as appropriate.

[0027] In the method for stripping a purified titanium-based material according to one embodiment of the present invention, a titanium-adhering cathode 1 as exemplified in Fig. 1 can be used. The titanium-adhering cathode 1 is obtained by precipitating a purified titanium-based material 3 on a cathode 2 by electrolytic refining of a crude titanium-based material in a molten salt bath Bm, as described later, and includes the cathode 2 and the purified titanium-based material 3 attached to the surface of the cathode 2 so as to cover the surface. The stripping method of this embodiment is a method for stripping the purified titanium-based material 3 of such a titanium-adhering cathode 1 from the cathode 2. In Fig. 1, the cathode 2 is connected to a rod member 2i, and this rod member 2i plays the role of both a holding rod and a current-carrying rod, which will be described later.

[0028] Here, for example, a peeling blade 11 as shown in Fig. 1 can be used. The peeling blade 11 has a main body portion 12 on the inside thereof, which has a cathode receiving recess 12a into which a cathode 2 constituting a part of the titanium-deposited cathode 1 can be inserted, and a cutting edge portion 13 provided around an opening 12b of the cathode receiving recess 12a.

[0029] When the purified titanium-based material 3 of the titanium-attached cathode 1 is peeled off from the cathode 2, the titanium-attached cathode 1 is moved toward the peeling blade 11 as shown by the arrow in FIG. 1. When the titanium-attached cathode 1 approaches and comes into contact with the peeling blade 11, the purified titanium-based material 3 is bitten into the cutting edge portion 13 of the peeling blade 11 around the cathode 2 of the titanium-attached cathode 1. When the titanium-attached cathode 1 is further moved, the purified titanium-based material 3 is gradually separated from the cathode 2 by the biting as shown in FIG. 2, and the cathode 2 is inserted into the inside of the cathode receiving recess 12a of the peeling blade 11. In this way, the purified titanium-based material 3 can be peeled off from the cathode 2 of the titanium-attached cathode 1. After the purified titanium-based material 3 is peeled off, the cathode 2 can be moved away from the peeling blade 11 as shown in FIG. 3, and pulled out from the inside of the cathode receiving recess 12a.

[0030] The stripping method of this embodiment can be used in the stripping step in the production method of titanium or titanium alloys including molten salt electrolytic refining. The production method of titanium or titanium alloys includes an electrolysis step and a stripping step. In addition, an extraction step before the electrolysis step and / or a heating separation step after the stripping step may be performed. Each step will be described in detail below.

[0031] (extraction process) In the extraction process, TiO2, TiO, TiO 2-x A mixture of titanium raw material such as titanium ore containing titanium oxide (0≦x<2) and a reducing agent containing mainly aluminum (Al) is heated and reacted in slag. At this time, a slag generating assistant may be mixed.

[0032] The titanium raw material used in the extraction process may be any material that contains oxygen-containing titanium compounds such as titanium oxide, and typically includes titanium ore. Examples of titanium ore include natural rutile, upgraded ilmenite (UGI) or upgraded slag (UGS) that has been subjected to leaching or other upgrading treatments as necessary, and the like. The content of TiO2 in the titanium ore used as the titanium raw material may be, for example, 50 mass% or more, typically 80 mass% or more, and particularly 90 mass% or more.

[0033] The slag formation aid is used to facilitate the formation of slag after heating and to facilitate separation. Specifically, the slag formation aid is preferably one or more selected from calcium fluoride, aluminum fluoride, potassium fluoride, magnesium fluoride, calcium chloride, calcium oxide, magnesium oxide, and sodium fluoride. Among them, calcium fluoride (CaF2) is particularly suitable because it provides excellent slag formation and separation of the crude titanium-based material from the mixture.

[0034] When Al is used as the main reducing agent, the reducing agent may contain substantially only Al, or may further contain Ca, Na, Mg, Cu, Si, Fe, etc.

[0035] For example, the mixture may be prepared by adjusting the molar ratio of TiO2:Al:CaF2 to 3:1-8:2-6.

[0036] The temperature at which the mixture is heated may be, for example, 1500°C to 3000°C. The reaction at this time is complex, but generally, it is thought that a reaction such as 3TiO2+4Al→3Ti+2Al2O3 occurs. Here, Ti on the right side is a solid solution of a certain amount of Al and O, which corresponds to the crude titanium-based material. This crude titanium-based material may contain small amounts of impurities in the ore, such as Fe, Si, V, Cr, Ni, and Mn.

[0037] After the mixture is heated to a molten slag state, the crude titanium-based material (liquid or solid) and the slag are separated due to density differences, and the crude titanium-based material (Ti in the above reaction formula) can be extracted. Since this type of extraction process does not contain C (carbon) in the reaction system, no CO2 (carbon dioxide) is generated, and the titanium or titanium alloy produced by the subsequent electrolysis and stripping processes is smelted without using C. For this reason, it can be said that the smelting method described here contributes to the realization of carbon neutrality.

[0038] The crude titanium-based material obtained in the extraction step using Al as the main reducing agent contains Ti, Al, and O, and may have, for example, a Ti content of 50% by mass to 80% by mass, an Al content of 0.1% by mass to 30% by mass, and an O content of 0.3% by mass to 20% by mass. Typically, the Ti content of the crude titanium-based material may be 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, in the crude titanium-based material, Al and O in Ti may be contained in a content less than the above content, which may correspond to unavoidable impurities. The crude titanium-based material may contain very small amounts of Al and O. In addition, it may contain a small amount of unavoidable impurities such as impurities derived from ore.

[0039] The crude titanium-based material has electrical conductivity and can be used for electrolytic refining by being included in the anode in the electrolytic process described below. The resistivity of the crude titanium-based material measured at room temperature is, for example, 1×10 -8 Ω m~1×10 -4 Ω m, typically 1×10 -7 Ω·m~5×10 -5 Ω m.

[0040] (Electrolysis process) In the electrolysis step, the crude titanium-based material is used to carry out molten salt electrorefining. In the molten salt electrorefining, a voltage is applied between electrodes including an anode and a cathode, which are immersed in a molten salt bath in an electrolytic cell. At this time, an anode containing the crude titanium-based material is used. When a voltage is applied between the electrodes, Ti is dissolved from the crude titanium-based material of the anode, and is electrodeposited on the cathode to precipitate a refined titanium-based material.

[0041] The anode is not particularly limited as long as it contains a crude titanium-based material. For example, a plate-like crude titanium-based material obtained by casting or the like after the extraction step can be used as the anode as it is. Alternatively, a granular or powdery crude titanium-based material may be placed in a cage-like container having a large number of through holes and capable of passing electricity, and used as the anode. The cage-like container may have a plate-like, cylindrical, or other external 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 a large number of through holes.

[0042] The cathode (main part 2e in the case where a tip guide part 2f described later is included) can have at least its surface made of titanium or a titanium alloy, and can be, for example, a titanium plate or a titanium rod entirely made of titanium. Alternatively, at least the surface of the cathode can be made of molybdenum or a molybdenum alloy, iron or an iron alloy (such as low carbon steel), or nickel or a nickel alloy. When a material with high electrical resistance such as titanium or a titanium alloy is used as the material for the cathode, the electrical resistance of the entire cathode can be reduced by making the inside of the cathode out of copper, which has low electrical resistance, and making the surface out of titanium or a titanium alloy. Note that although it is possible to arrange a bipolar electrode between the anode and the cathode, a bipolar electrode is not necessary.

[0043] The molten salt bath may be a chloride bath mainly containing metal chlorides, for example, alkali metal chlorides and / or alkaline earth metal chlorides, for example, 70 mol% or more, further 90 mol% or more, and further 95 mol% or more. Such chloride baths are preferred because they are less corrosive, have a lower environmental impact, and are less expensive than fluoride baths, bromide baths, and iodide baths. In particular, when a chloride bath containing magnesium chloride (MgCl2) is used, a purified titanium-based material can be obtained in which not only the oxygen content but also the aluminum content is sufficiently reduced. The magnesium chloride content in the chloride bath is preferably 10 mol% or more, further 30 mol% or more, further 50 mol% or more, further 80 mol% or more, and particularly 95 mol% or more.

[0044] 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 (BeCl2), calcium chloride (CaCl2), strontium chloride (SrCl2), and barium chloride (BaCl2), for example, in an amount of 90 mol% or less, further 70 mol% or less, further 50 mol% or less, further 20 mol% or less, or further 5 mol% or less.

[0045] Furthermore, the molten salt bath may contain lower titanium chlorides having a smaller Ti valence than titanium tetrachloride, specifically titanium dichloride (TiCl2) or titanium trichloride (TiCl3), if necessary. 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, and may be 10 mol% or more, and is preferably 20 mol% or less.

[0046] 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 a further reduced aluminum content is obtained, which is suitable for titanium production. In the chloride bath, the titanium dichloride may be partially converted to titanium trichloride by a disproportionation reaction.

[0047] The content of metal chlorides and metal ions in the molten salt bath can be measured by ICP emission spectrometry or atomic absorption spectrometry. The content of Ti ions is calculated as a percentage of the total content of metal ions in the molten salt bath.

[0048] During molten salt electrolytic refining, for example, the temperature of the molten salt bath is set to 450°C to 900°C, and the current density at the cathode is set to 0.01A / cm 2 ~3A / cm 2 The current density is calculated using the formula: Current density (A / cm 2 ) = Current (A) ÷ Macroscopic electrodeposition area (cm 2 ) can be used to calculate the electrochemical potential. The electrodes may be used to pass a current continuously or may pass a pulsed current in which a current-on period and a current-off period 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.

[0049] The molten salt electrorefining can be repeated multiple times to further refine the purified titanium-based material obtained thereby. When molten salt electrorefining is performed multiple times, in the next molten salt electrorefining, the purified titanium-based material deposited on the cathode in the previous molten salt electrorefining is used as a crude titanium-based material for the anode containing the crude titanium-based material. In this way, in the next molten salt electrorefining, a purified titanium-based material from which impurities have been further removed is deposited on the cathode. By performing molten salt electrorefining multiple times, it is also possible to produce high-purity titanium that is almost free of impurities.

[0050] As an example, the electrolysis process may be performed in a state where the electrolytic cell 21 and the cathode containment vessel 31 are connected as shown in FIG. 4. In the illustrated example, a molten salt bath Bm in which molten salt is stored is provided inside the electrolytic cell 21, and a plurality of anodes 22 and cathodes 2 are immersed and arranged in the molten salt bath Bm. Here, the number of cathodes 2 is five, but the number of cathodes 2 can be appropriately determined, and the number of anodes 22 can be a corresponding number (two, three, four, six, seven, eight, or more). The cathode containment vessel 31 has a lower opening airtightly connected to an upper opening of the electrolytic cell 21. The electrolytic cell 21 and the cathode containment vessel 31 each have an opening provided with an opening that can be separated into upper and lower portions in a sealed state (e.g., a pair of gate valves).

[0051] As an example, the cathode 2 is provided at the lower end of the rod member 2i. As described above, the rod member 2i is a member that serves as both a holding rod and a current-carrying rod. The rod member 2i is provided in a manner that it extends in the vertical direction penetrating the cathode containment vessel 31, and is connected to the lift plate 32 at the upper side outside the cathode containment vessel 31. In other words, the cathode 2 is arranged in a manner that it is suspended from the lift plate 32 via the rod member 2i. This allows the cathode 2 and the rod member 2i to be raised and lowered together with the lift plate 32, and in accordance with this operation, the cathode 2 can move between the inside of the cathode containment vessel 31 and the inside of the electrolytic cell 21 through an opening on the lower side of the cathode containment vessel 31.

[0052] The cathode 2 may be held by being connected to a lift plate by one or more rod members 2i as shown in Fig. 14(a). In Fig. 14(a), one rod member 2i having high strength from room temperature to high temperature and functioning as a holding rod and a current-carrying rod is attached to the cylindrical cathode 2, but the rod member 2i may be divided into a holding rod and a current-carrying rod, and one or more holding rods 2g (two in Fig. 14(b)) and one or more current-carrying rods 2h (one in Fig. 14(b)) may be attached. In the embodiment shown in Fig. 14(b), it is preferable that the holding rod 2g has high strength from room temperature to high temperature and has a higher electric resistance than the cathode 2. The holding rod 2g, which has a large electrical resistance, generates heat when current flows through it, increasing power consumption. However, because current flows mainly through the current-carrying rod 2h due to its large electrical resistance, heat generation due to current flow through the holding rod 2g is unlikely to occur, and the increase in power costs due to the heat generation can be suppressed.

[0053] 15(a) and (b), a plate-shaped, rectangular prism-shaped, or block-shaped cathode 2 is shown. Such a cathode 2 can be fitted with one or more rod members 2i functioning as a holding rod and a current-carrying rod as shown in Fig. 15(a), and can also be fitted with one or more holding rods 2g and one or more current-carrying rods 2h as shown in Fig. 15(b).

[0054] When the rod member 2i or the holding rod 2g and the current-carrying rod 2h are provided as described above, a bus bar electrically connected to the cathode 2 and movable together with the lift plate 32 can be provided outside the electrolytic cell. The lift plate 32 shown in the figure may also function as a bus bar when the rod member 2i is used. Alternatively, when the holding rod 2g and the current-carrying rod 2h are provided as separate members, the current-carrying rod 2h can be connected to a bus bar (not shown), and the holding rod 2g can be connected to the lift plate 32. The anode 22 may be suspended or fixed on a pedestal or the like. The rod member 2i, the holding rod 2g, and the current-carrying rod 2h are usually not inserted into the molten salt bath Bm, but are located above the bath surface of the molten salt bath Bm.

[0055] Fig. 4 shows the state when the molten salt electrorefining in the electrolysis step is completed. During the molten salt electrorefining, the opening and closing mechanisms 23, 33 are opened while the electrolytic cell 21 and the cathode storage vessel 31 are connected, and the lift plate 32 is lowered to position each cathode 2 between adjacent anodes 22 inside the electrolytic cell 21. Although not shown, the anode 22 and the cathode 2 are each connected to a power source, and when a voltage is applied between the anode 22 and the cathode 2, as described above, Ti in the crude titanium-based material contained in the anode 22 dissolves and the refined titanium-based material 3 is precipitated on the cathode 2 as shown in Fig. 4, and a titanium-attached cathode 1 is obtained.

[0056] After the molten salt electrolytic refining is completed, as shown in Fig. 5, the titanium-attached cathode 1 is raised together with the lift plate 32 and stored inside the cathode containment vessel 31, and the opening and closing mechanisms 23, 33 are closed to ensure airtightness inside the cathode containment vessel 31 and the electrolytic cell 21. The inside of each of the cathode containment vessel 31 and the electrolytic cell 21 is preferably filled with an inert gas atmosphere such as argon gas or helium gas. Thereafter, the connection between the cathode containment vessel 31 and the electrolytic cell 21 is released. Then, the cathode containment vessel 31 is used to carry out the peeling step described below. The electrolytic cell 21 can be used for molten salt electrolytic refining that may be carried out separately thereafter.

[0057] (Peeling process) In the peeling step, the cathode storage container 31 is moved from above the electrolytic cell 21 to above the blade arrangement container 41 as shown in FIG. 6, and is connected to the blade arrangement container 41, and the opening and closing mechanisms 33, 43 are opened. The blade arrangement container 41 has peeling blades 11 arranged therein in a number corresponding to the number of titanium-deposited cathodes 1, facing the titanium-deposited cathodes 1 inside the cathode storage container 31 in a connected state with the cathode storage container 31. However, the number of peeling blades 11 arranged in the blade arrangement container 41 does not necessarily have to be the same as the number of titanium-deposited cathodes 1 in the cathode storage container 31, and may be greater than the number of titanium-deposited cathodes 1 in the cathode storage container 31, for example. In this case, the peeling step can be performed using the blade arrangement container 41 for various cathode storage containers 31 having titanium-deposited cathodes 1 in a number equal to or less than the number of peeling blades 11 in the blade arrangement container 41.

[0058] In order to suppress absorption of oxygen, nitrogen, and moisture from the atmosphere by the new titanium surface that is generated on the purified titanium-based material 3 after peeling in the peeling process, it is desirable to make the inside of the cathode containment vessel 31 and the blade arrangement vessel 41 an inert gas atmosphere.

[0059] Next, the titanium-deposited cathode 1 is lowered by the lift plate 32, and the titanium-deposited cathode 1 is moved toward the stripping blade 11 along the direction in which the cathode 2 is inserted into the cathode receiving recess 12a of the stripping blade 11. Then, as shown in FIG. 7, the refined titanium-based material 3 of the titanium-deposited cathode 1 is bitten into the cutting edge portion 13 of the stripping blade 11 from the tip side and gradually separated from the cathode 2. At this time, the stripping blade 11 is bitten into the boundary portion between the cathode 2 and the refined titanium-based material 3 of the titanium-deposited cathode 1, or into a portion slightly away from the cathode 2 from the boundary portion (a position where a very small part of the refined titanium-based material 3 remains on the cathode 2 after stripping). At the same time, the cathode 2 of the titanium-deposited cathode 1 is inserted into the cathode receiving recess 12a of the stripping blade 11 from the tip side from which the refined titanium-based material 3 was separated. As described above, when the cathode 2 is held by the rod member 2i, when the titanium-adhered cathode 1 is moved toward the peeling blade 11 and the refined titanium-based material 3 of the titanium-adhered cathode 1 is peeled off while the cathode 2 is inserted into the cathode receiving recess 12a of the peeling blade 11, the high-strength rod member 2i is not easily deformed even when a force is applied from the peeling blade 11, so that the entire cathode 2 can be easily inserted into the cathode receiving recess 12a in an appropriate posture.

[0060] At this time, if the cathode 2 is in the form of a flat plate or the like with a rectangular cross section perpendicular to the longitudinal direction as shown in Fig. 9(a), the purified titanium-based material 3 attached to both of the two surfaces, one surface 2a and the other back surface 2b, is bitten into the cutting edge portion 13 of the peeling blade 11 and peeled off and separated from the cathode 2. At this time, the cathode 2 receives an external force directed inward in the thickness direction (left and right direction in Fig. 9(a)) from the peeling blade 11 via the purified titanium-based material 3 on the surfaces 2a and 2b, but since the external force on the one surface 2a side and the external force on the other surface 2b side act symmetrically in opposing directions and balance each other, bending deformation of the cathode 2 is unlikely to occur. When the purified titanium-based material 3 is also attached to the end faces 2c, 2d of the cathode 2 in the width direction (the vertical direction in Figure 9(a)), depending on the dimensions and shape of the peeling blade 11, it may be possible to peel off the purified titanium-based material 3 all at once over the entire circumference of the cathode 2, including the end faces 2c, 2d and the surfaces 2a, 2b.

[0061] The cathode receiving recess 12a of the peeling blade 11 is shaped so that the cathode 2 can be inserted inside. In this example, the cathode receiving recess 12a of the peeling blade 11 is a flat space with dimensions slightly larger than the cathode 2 so that the flat cathode 2 can be inserted, as shown in Fig. 9(b). When the opening 12b of the cathode receiving recess 12a is shaped similarly to the cathode 2 when viewed in a cross section perpendicular to the insertion direction of the cathode 2 into the cathode receiving recess 12a, the refined titanium-based material 3 around the cathode 2 can be easily peeled off well over the entire circumference. However, it is possible to adjust as necessary, for example, by making the dimensional increment in the width direction of the flat plate slightly larger than the dimensional increment in the thickness direction, and they do not necessarily need to be similar.

[0062] Alternatively, as shown in Fig. 10(a), when the cathode 2 is rod-shaped or cylindrical with a cross section perpendicular to the longitudinal direction being nearly circular, the titanium-adhering cathode 1 may have the purified titanium-based material 3 adhered to the entire circumference of the surface 2a, which is the outer circumferential surface of the cathode 2. When the titanium-adhering cathode 1 is moved toward the peeling blade 11 and the cathode 2 is inserted into a cathode receiving recess 12a, which is a cylindrical space with dimensions slightly larger than the cathode 2, as shown in Fig. 10(b), the purified titanium-based material 3 can be peeled off from the cathode 2 over the entire circumference of the surface 2a. In this case, an external force directed radially inward acts on the cathode 2 over the entire circumference from the peeling blade 11, but bending deformation is suppressed because the symmetrical external forces opposing each other across the cathode 2 cancel each other out.

[0063] The same applies to the case where the cathode 2 and the opening 12b of the cathode receiving recess 12a are rod-shaped or cylindrical with an oval or elliptical cross section perpendicular to the longitudinal direction as shown in Figures 11(a) and 11(b). The rod-shaped or cylindrical cathode 2 and the opening 12b of the cathode receiving recess 12a as shown in Figures 10 and 11 can also be made to have a similar shape as described for the flat cathode 2 and cathode receiving recess 12a in Figure 9, but they may also be made to have a non-similar shape depending on various conditions, etc.

[0064] In the peeling by cutting described above, the thickness of the purified titanium-based material on the cathode gradually decreases as the cutting progresses, and the rigidity as a whole gradually decreases. In contrast, in this embodiment, it is possible to peel almost the entire purified titanium-based material 3 from the cathode 2 at once by a single action of moving the titanium-adhered cathode 1 toward the peeling blade 11. Therefore, in this embodiment, deformation of the cathode 2 caused by the peeling of the purified titanium-based material 3 is more effectively suppressed, and the cathode 2 can be used repeatedly in the production of titanium or titanium alloys multiple times.

[0065] In this embodiment, a lifting plate 32 is provided to lift and lower the titanium-deposited cathode 1. Therefore, in the peeling step, it is preferable from the viewpoint of simplifying the equipment to move the titanium-deposited cathode 1 using the lifting plate 32 rather than the peeling blade 11. However, the same effect can be obtained by moving the peeling blade 11, although this requires a difficult structural technique.

[0066] After the purified titanium-based material 3 has been peeled off from the cathode 2 by the peeling blade 11, the cathode 2 from which the purified titanium-based material 3 has been separated can be moved away from the peeling blade 11, as shown in Figure 8, and each opening and closing mechanism 33, 43 can be closed.

[0067] As shown in Figs. 12(a)-(d), the cathode 2 preferably includes a main portion 2e having surfaces 2a and 2b (surface 2a in the case of a cylindrical cathode 2 as shown in Figs. 10 and 11) to which the purified titanium-based material 3 adheres, and a tip guide portion 2f provided on the tip side of the main portion 2e in the insertion direction into the cathode receiving recess 12a (lower side in Fig. 12) and guiding the insertion of the main portion 2e into the cathode receiving recess 12a. The tip guide portion 2f is made of a poorly conductive material or a non-conductive material (semiconductor material or insulator material), and the poorly conductive material can be, for example, a material whose electrical resistance value measured at room temperature is 100 times (unit: Ω·m) or more that of titanium. In this case, in the molten salt electrolytic refining in the above electrolysis step, the purified titanium-based material 3 adheres to the main portion 2e but does not substantially adhere to the tip guide portion 2f. The reason for adopting the electrical resistance value measured at room temperature is as follows. This is because, while it is difficult to measure the electrical resistance value of a poorly-conductive material under high-temperature conditions, it is possible to roughly predict the electrical resistance of a poorly-conductive material under high-temperature conditions based on the results of measurements at room temperature.

[0068] In the cathode 2 having the tip guide portion 2f provided on the tip side of the main portion 2e, when the titanium-adhering cathode 1 is moved toward the peeling blade 11, the tip guide portion 2f, to which the refined titanium-based material 3 is not adhered, guides the insertion of the main portion 2e into the cathode receiving recess 12a, so that the cathode 2 can be smoothly inserted into the cathode receiving recess 12a. This makes it even easier to peel the refined titanium-based material 3 from the cathode 2.

[0069] As shown in Figs. 12(a) to (c), the tip guide portion 2f may be tapered with a width that narrows toward the tip side in a cross section along the insertion direction. More specifically, the tip guide portion 2f shown in Fig. 12(a) has a shape that has a width that gradually decreases linearly and smoothly toward the tip side in a cross section along the insertion direction. The tip guide portion 2f in Fig. 12(b) also has a width that gradually decreases smoothly toward the tip side, but the gradual decrease is in the form of an outwardly convex curve. The tip guide portion 2f shown in Fig. 12(c) has a width that gradually narrows in a step-like manner toward the tip side. The width referred to here corresponds to the diameter in the case of a rod-shaped or cylindrical cathode 2.

[0070] 12(d), the tip guide portion 2f may have a constant width narrower than the main portion 2e without tapering toward the tip side. Either tip guide portion 2f can realize smooth insertion of the main portion 2e into the cathode receiving recess 12a.

[0071] Note that tip guide portion 2f may have at least a portion of its cross section along the insertion direction that is narrower than main portion 2e at least on the tip side, for example, the shapes shown in Figures 12(a) to (d), and other cross sections may have the same width as main portion 2e. If at least a portion of tip guide portion 2f has a tapered cross section, main portion 2e can be guided inside cathode receiving recess 12a.

[0072] If the material of the tip guide portion 2f has a sufficiently larger electrical resistance than the material of the main portion 2e of the cathode 2 described above, adhesion of the refined titanium-based material 3 during the molten salt electrolytic refining in the electrolysis step is suppressed, and the tip guide portion 2f can function to effectively guide the main portion 2e to the inside of the cathode receiving recess 12a in the peeling step. The tip guide portion 2f may be made of ceramics, for example, Al2O3, MgO, CaO, Si3N4, Y2O3, or Zr2O3.

[0073] The illustrated peeling blade 11 has a tapered portion 14 in which the width of the outer contour gradually decreases from the middle of the main body portion 12 through the cutting edge portion 13 to the opening 12b of the cathode receiving recess 12a in a cross section along the insertion direction. The region of the tapered portion 14 can be appropriately changed, such as being provided only in the portion close to the cutting edge portion 13 as shown in FIG. 13(a). Although not shown, it is also possible to make a peeling blade in which the tapered portion is provided over the entire insertion direction. Also, although not shown, the tapered portion can be changed in angle with respect to the insertion direction in multiple stages in the middle of the insertion direction. The size of the region of the tapered portion 14 of each peeling blade 11 can be determined taking into consideration the number of cathodes 2 used in one molten salt electrolytic refining, the number of peeling blades 11 to be placed inside the blade placement container 41, the size of the internal space of the electrolytic cell 21 and the blade placement container 41, etc.

[0074] The width of the cathode receiving recess 12a of the stripping blade 11 may be constant throughout the insertion direction, or may be gradually tapered toward the opening 12b in part or in whole on the opening 12b side in the insertion direction, as shown in Figures 13(a) and 13(b). The width of the cathode receiving recess 12a may also increase or decrease in the insertion direction so that its inner surface has a wave shape or the like when viewed in the insertion direction, as shown in Figure 13(c).

[0075] The material of the peeling blade 11 is not particularly limited, but may be the same as that of the crushing shear used to crush sponge titanium chunks in the production of titanium or titanium alloys using the Kroll process. Specific examples include wear-resistant steel, tool steel, and cemented carbide.

[0076] The peeling blade 11 can be fixed and disposed inside the blade arrangement container 41. On the other hand, the peeling blade 11 can also be attached to the blade arrangement container 41 so that it can move passively slightly due to the action of an external force when the titanium-adhering cathode 1 comes into contact with the blade 11, without being completely fixed to the inner surface of the blade arrangement container 41. For example, if an elastic member such as a spring is interposed between the peeling blade 11 and the inner surface of the blade arrangement container 41, when the peeling blade 11 peels the purified titanium-based material 3 of the titanium-adhering cathode 1 from the cathode 2, and the cathode 2 is further extracted from the peeling blade 11, the peeling blade 11 moves due to spring back, and the purified titanium-based material 3 falls from the peeling blade 11. Alternatively, it is also possible to provide a vibration mechanism (not shown) on the peeling blade 11 and drop the purified titanium-based material 3 from the peeling blade 11 by the driving force of the vibration mechanism. As will be described later, when performing high-temperature treatment, the peeling blade 11 may be coated with heat-resistant ceramics so as not to react with the purified titanium-based material 3.

[0077] In the illustrated embodiment, the titanium-attached cathode 1 is disposed above the peeling blade 11 in the vertical direction, and the titanium-attached cathode 1 is moved downward to contact the peeling blade 11. However, the positional relationship or arrangement between the peeling blade 11 and the titanium-attached cathode 1, and the direction in which the titanium-attached cathode 1 is moved are not limited to this. The purified titanium-based material 3 can be peeled off by the peeling blade 11 as long as the positional relationship and direction allow the cathode 2 to be inserted inside the cathode receiving recess 12a. For example, the peeling blade 11 and the titanium-attached cathode 1 may be disposed in a direction inclined or horizontal to the vertical direction, and the titanium-attached cathode 1 may be moved along that direction. In this case, the purified titanium-based material 3 that is separated from the cathode 2 and left around the peeling blade 11 is likely to fall off the peeling blade 11 due to its own weight.

[0078] By the above-mentioned peeling step, the purified titanium-based material 3 peeled from the cathode 2 is obtained around or near the peeling blade 11 or below the peeling blade 11 inside the blade arrangement container 41. Then, if necessary, the following heating and separation step can be performed in the blade arrangement container 41.

[0079] (Heating separation process) The purified titanium-based material 3 obtained inside the blade arrangement container 41 after the above-mentioned peeling step may have residues of the molten salt attached thereto, which are derived from the above-mentioned molten salt bath Bm used in the preceding electrolysis step. In order to remove these, a heating and separating step can be carried out after the peeling step.

[0080] In the thermal separation step, as described above, the residual molten salt is removed by heating from the purified titanium-based material 3. For example, the thermal separation step can be performed by thermal melting separation or high-temperature reduced pressure separation.

[0081] In the above-mentioned heat melt separation, melt dripping occurs. For example, the molten salt remaining in the purified titanium-based material 3 can be melted and dripped and removed under a slightly reduced pressure, normal pressure or pressurized environment. Taking into consideration the components contained in the molten salt bath Bm, heat melt separation may be performed by heating to, for example, about 500°C to 900°C. In addition, in order to suppress an increase in the oxygen content and nitrogen content of the purified titanium-based material 3, it is preferable to use an inert gas atmosphere such as argon gas for heat melt separation. In addition, if a slight reduction in pressure is applied, the melting point of the molten salt residue decreases and the viscosity decreases, making it easier to remove the molten salt residue from the purified titanium-based material 3.

[0082] In the above-mentioned high-temperature vacuum separation, vaporization occurs. For example, the molten salt remaining in the purified titanium-based material 3 is vaporized and removed under high vacuum conditions (preferably vacuum conditions). Taking into consideration the components contained in the molten salt bath Bm, the high-temperature vacuum separation may be performed by heating to, for example, about 750°C to 1200°C.

[0083] Depending on the molten salt remaining in the purified titanium-based material 3 and the temperature conditions, in the thermal separation step, thermal melting separation and high-temperature reduced pressure separation may be carried out simultaneously.

[0084] In addition to or instead of the heat separation step, the purified titanium-based material 3 may be washed with water or the like to remove the molten salt residue. Washing with water may wash away a significant amount of the molten salt residue, making it impossible to reuse the material, and this may increase the production cost.

[0085] In the thermal separation step, the blade arrangement container 41 used in the peeling step can be used continuously. Specifically, in the case of high-temperature reduced pressure separation, the opening and closing mechanism 43 of the blade arrangement container 41 is closed to ensure airtightness inside, and the communication port 42 provided in the blade arrangement container 41 is connected to a pressure reducing device including a condenser (not shown) to open the communication port 42. In this state, the purified titanium-based material 3 inside the blade arrangement container 41 is heated by a heating device such as a heater or induction heating device (not shown), while the inside of the blade arrangement container 41 is made into a reduced pressure atmosphere by the pressure reducing device. Depending on the conditions of the thermal separation step, it is also possible to introduce an inert gas into the blade arrangement container 41 through the communication port 42. Then, inside the blade arrangement container 41, the residue of the molten salt melts, drips or evaporates and is separated from the purified titanium-based material 3, and the molten material generated thereby is removed to the lower side, or the gas generated thereby is sent to the condenser through the communication port 42. When the molten salt residue is separated from the purified titanium-based material by melt dripping, the molten material can be removed by flowing it over the inclined bottom surface of the blade arrangement vessel (not shown), and at this time, if necessary, a comb-shaped or other sieve (made of ceramics or ceramic-coated steel or the like) that blocks the purified titanium-based material may be provided to prevent the purified titanium-based material from being removed as well. In this way, the molten salt residue from the purified titanium-based material 3 can be separated.

[0086] The heating temperature inside the blade arrangement container 41 in the thermal separation step may be, for example, 500°C to 1200°C, 500°C to 900°C, 750°C to 1200°C, or 850°C to 1200°C. When heated at 850°C to 1200°C, the bath components are easily evaporated due to the high temperature, and the molten salt residue is easily removed from the purified titanium-based material 3. Note that, at temperatures below 900°C and even below 800°C, the higher the temperature, the lower the viscosity of the bath components, making it easier to separate the bath components from the purified titanium-based material 3. It is desirable to set this heating temperature to an appropriate temperature in consideration of the material of the peeling blade 11 inside the blade arrangement container 41 and other conditions. When the peeling blade 11 is coated with heat-resistant ceramics, it becomes possible to heat the inside of the blade arrangement container 41 to a relatively high temperature.

[0087] In order to suppress the eutectic reaction between the peeling blade 11 and the purified titanium-based material 3 caused by heating in the thermal separation step, it is preferable to coat the outer surface and inner surface of the peeling blade 11 (the inner surface refers to the surface of the cathode receiving recess 12a) with a material that is unlikely to react with the purified titanium-based material 3. The coating does not necessarily have to be applied to the entire peeling blade 11, but may be applied from the base end portion of the peeling blade 11 to the cutting edge portion 13. In addition, the heating process can be efficiently performed by using induction heating in addition to heating with a heater. Examples of coating materials that meet the above requirements include SiC, Al2O3, MgSi2, MgO, CaO, Si3N4, Y2O3, and Zr2O3. This makes it possible to heat at a relatively high temperature in the thermal separation step, and in addition to MgCl2, it is possible to satisfactorily separate the residues of molten salts such as NaCl, KCl, and TiCl2, which are more difficult to evaporate than MgCl2.

[0088] In the manner described above, titanium or a titanium alloy can be produced as the purified titanium-based material 3. When producing titanium, the titanium finally obtained has an aluminum content of, for example, 0.1 mass% or less, preferably 0.01 mass% or less, and an oxygen 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 producing a titanium alloy, the titanium alloy finally obtained may have an aluminum content of, for example, 3 mass% or less, preferably 2 mass% or less, and an oxygen content of, for example, 0.3 mass% or less, preferably 0.15 mass% or less. [Explanation of symbols]

[0089] 1 Titanium-adhered cathode 2 cathode 2a, 2b surface 2c, 2d end face 2e Main part 2f Tip guide 2g holding rod 2h Electric current rod 2i Rod material 3. Refined titanium-based materials 11 Peeling blade 12 Main body part 12a Cathode receiving recess 12b opening 13 Blade tip 14 Tapered section 21 Electrolytic cell 22 Anode 23, 33, 43 Opening and closing mechanism 31 Cathode Containment Vessel 32 Lifting plate 41 Blade placement container 42 Communication port Bm molten salt bath

Claims

1. A method for removing a purified titanium-based material from a titanium-attached cathode obtained by electrolytically refining a crude titanium-based material in a molten salt bath and precipitating the purified titanium-based material on the cathode, comprising the steps of: A peeling blade is used, the peeling blade having a body portion having a cathode receiving recess formed therein, into which the cathode can be inserted, and a cutting edge portion provided at an opening of the cathode receiving recess, A method for peeling a purified titanium-based material, comprising the steps of: moving the titanium-adhering cathode toward the peeling blade, causing the purified titanium-based material of the titanium-adhering cathode to bite into the cutting edge portion; inserting the cathode from which the purified titanium-based material has been separated by the biting of the cutting edge portion into the inside of the cathode receiving recess; and peeling the purified titanium-based material from the cathode.

2. 2. The method for stripping a purified titanium-based material according to claim 1, wherein the opening of the cathode-receiving recess has a shape similar to that of the cathode in a cross section perpendicular to a direction in which the cathode is inserted into the cathode-receiving recess.

3. 2. The method for stripping a purified titanium-based material according to claim 1, wherein the cathode comprises a main portion and a tip guide portion that is provided on a tip side of the main portion in a direction in which the cathode is inserted into the cathode receiving recess, and that is made of a poorly conductive material or a non-conductive material and that guides insertion of the main portion into the cathode receiving recess.

4. 4. The method for peeling off a purified titanium-based material according to claim 3, wherein the tip guide portion has a width that narrows smoothly or stepwise toward the tip side in a cross section along the insertion direction.

5. 4. The method for stripping a refined titanium-based material according to claim 3, wherein at least the surface of the main portion is made of titanium or a titanium alloy, molybdenum or a molybdenum alloy, iron or an iron alloy, or nickel or a nickel alloy.

6. 2. The method for stripping a purified titanium-based material according to claim 1, wherein the cutting edge portion of the stripping blade has a width that gradually decreases toward an opening of the cathode receiving recess in at least a portion along the insertion direction of the cathode into the cathode receiving recess.

7. The cathode is rod-shaped, and the purified titanium-based material is adhered to the periphery of the rod-shaped cathode in the titanium-adhering cathode, 2. The method for stripping a purified titanium-based material according to claim 1, wherein the purified titanium-based material adhering to the periphery of the cathode is stripped from the cathode by inserting the cathode into the cathode receiving recess of the stripping blade.

8. The cathode is plate-shaped, and the purified titanium-based material is attached to at least two surfaces of the plate-shaped cathode that face in opposite directions, in the titanium-deposited cathode.

2. The method for stripping a purified titanium-based material according to claim 1, wherein the purified titanium-based material adhering to at least the two surfaces of the cathode is stripped from the cathode by inserting the cathode into the cathode-receiving recess of the stripping blade.

9. 2. The method for stripping a purified titanium-based material according to claim 1, further comprising moving a plurality of said titanium-deposited cathodes together toward a plurality of said stripping blades to strip the purified titanium-based material from the cathode of each of said titanium-deposited cathodes.

10. 1. A method for producing titanium or a titanium alloy, comprising the steps of: an electrolysis step in which electrolytic refining is performed in a molten salt bath to dissolve Ti from the crude titanium-based material on the anode and deposit a refined titanium-based material on the cathode; a peeling step of peeling the purified titanium-based material from the cathode obtained in the electrolysis step by using the method for peeling a purified titanium-based material according to any one of claims 1 to 9; A method for producing titanium or a titanium alloy comprising the steps of:

11. The method for producing titanium or a titanium alloy according to claim 10, further comprising, after the peeling step, a heating and separating step of heating the purified titanium-based material and separating the molten salt residue from the purified titanium-based material.

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