Method for preparing low-oxygen titanium through stepping coupling type deoxidation

Abstract

The invention provides a method for preparing low-oxygen titanium through stepping coupling type deoxidation, which comprises the following steps: under a protective atmosphere, taking mixed molten salt at least comprising ionic metal chloride and rare earth chloride as an electrolyte, taking titanium-containing waste as an anode, adding elemental rare earth into the electrolyte, applying voltage, and then carrying out primary electrolysis, after electrolysis is finished, titanium with the first oxygen content is obtained on the cathode; the titanium with the first oxygen content is continuously soaked in the mixed molten salt under the protective atmosphere for a thermochemical deoxidation reaction, and titanium with the second oxygen content is obtained after the reaction is finished; and taking the titanium with the second oxygen content as a cathode, applying voltage and then carrying out secondary electrolysis, and obtaining the metal titanium with the low oxygen content on the cathode after the secondary electrolysis is finished. By means of the method, oxygen in titanium can be controlled to be 500 ppm or below.

Description

Technical Field

[0001] The invention relates to the field of titanium preparation, and more particularly to a method for preparing low-oxygen titanium by step-coupled deoxidation. Background Art

[0002] The presence of oxygen in titanium usually impairs the properties of sintering and the final product, such as strength and toughness. There are many deoxidation processes, such as calcium-based deoxidation processes, etc. However, many current deoxidation processes cannot fully deoxidize titanium. Summary of the invention

[0003] In view of the deficiencies in the prior art, one of the purposes of the present invention is to solve one or more problems in the prior art. For example, one of the purposes of the present invention is to provide a method for preparing low-oxygen titanium by step-coupled deoxidation.

[0004] In order to achieve the above-mentioned purpose, the present invention provides a method for preparing low-oxygen titanium by step-coupled deoxidation, which can include the following steps: under a protective atmosphere, using a mixed molten salt including at least ionic metal chloride and rare earth chloride as an electrolyte, titanium-containing waste as an anode, and adding a single rare earth to the electrolyte, applying a voltage and performing a first electrolysis, and obtaining titanium with a first oxygen content on the cathode after the electrolysis; continuously immersing the titanium with the first oxygen content in the molten salt under a protective atmosphere for a thermochemical deoxidation reaction, and obtaining titanium with a second oxygen content after the reaction; using the titanium with the second oxygen content as the cathode, applying a voltage and performing a second electrolysis, and obtaining metallic titanium with a low oxygen content on the cathode after the second electrolysis.

[0005] Furthermore, the voltage applied in the first electrolysis may be 2.8V to 3.2V, the temperature may be 850°C to 1000°C, and the electrolysis time may be 12h to 36h.

[0006] Further, continuously immersing the titanium having the first oxygen content in the molten salt under the protective atmosphere may include immersing the titanium having the first oxygen content in the molten salt at a temperature of 750° C. to 800° C. for 40 h to 55 h.

[0007] Furthermore, the voltage applied in the second electrolysis may be 2.8V to 3.2V, the temperature may be 850°C to 1000°C, and the electrolysis time may be 6h to 12h.

[0008] Furthermore, the ionic metal chloride may be one or a combination of potassium chloride and sodium chloride.

[0009] Furthermore, the rare earth chloride may be any one of rare earth metal Sc chloride, Y chloride, La chloride, Ce chloride, Tm chloride, Ho chloride, Sm chloride, Gd chloride, Dy chloride, Lu chloride and Pr chloride.

[0010] Furthermore, the first electrolysis may include placing the titanium-containing waste in a graphite crucible connected to a graphite rod, and performing molten salt electrolysis with the graphite rod as an anode and the molybdenum rod as a cathode.

[0011] Furthermore, the second electrolysis can use a graphite rod as an anode.

[0012] Furthermore, the method may also include pre-electrolyzing the mixed molten salt at a voltage of 2.8V to 3.2V and a temperature of 850°C to 1000°C before the first electrolysis.

[0013] Furthermore, the titanium-containing waste may be titanium alloy TC4 and / or titanium alloy TA10.

[0014] Compared with the prior art, the beneficial effects of the present invention include at least: the present invention reduces titanium and then deeply deoxidizes it through a step-coupling method of first electrolytic reduction and deoxidation-thermochemical deoxidation-second electrolytic deoxidation, so that the oxygen in metallic titanium can be controlled at 500 ppm or less. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other objects and features of the present invention will become more apparent through the following description in conjunction with the accompanying drawings, in which:

[0016] Figure 1 Schematic diagram of the device for preparing low-oxygen titanium by step-coupled deoxidation.

[0017] Description of reference numerals:

[0018] 1-large crucible, 2-small crucible; 3-waste titanium material; 4-first anode; 5-cathode; 6-mixed molten salt; 7-elemental rare earth; 8-cathode product; 9-second anode. DETAILED DESCRIPTION

[0019] Hereinafter, a method for preparing low-oxygen titanium by step-coupled deoxidation according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.

[0020] Specifically, the present invention reduces titanium and then deeply deoxidizes it through a step-coupling method of first electrolytic reduction and deoxidation-thermochemical deoxidation-second electrolytic deoxidation, so that the oxygen content in titanium can reach 300 ppm or even below.

[0021] During the first electrolysis process, the titanium in the anode waste titanium material is ionized and dissolved in the molten salt to form titanium ions, which undergo a reduction reaction at the cathode to generate metallic titanium that may have a high oxygen content. Since the molten salt contains rare earth chlorides and elemental rare earths, the rare earth chlorides and elemental rare earths will react with the oxygen in the cathode titanium product to further remove oxygen from the metallic titanium. The reactions at the anode and cathode can be:

[0022] Anode: Ti→Ti n+ +ne - (1) Cathode: Ti n+ +ne - →Ti (2)

[0023] Other reactions that can occur in the electrolysis system include:

[0024] 3[O] inTi +2RE(s,l)→RE2O3(s,l) (3)

[0025] RE2O3(s,l)+RECl3(l)→3REOCl(s) (4)

[0026] 3[O] inTi +2RE(s,l)+RECl3(l)→3REOCl(s) (5)

[0027] Among them, in the above reaction formula, [O] inTi It represents oxygen contained in metallic titanium; RE represents rare earth metal element.

[0028] After the first electrolysis, a thermochemical deoxidation process is carried out. The cathode titanium product obtained after the first electrolysis is continuously immersed in an electrolyte containing rare earth chlorides and elemental rare earths. On the one hand, the RE metal part contained in the electrolyte will dissolve in the molten salt, and after contacting with the cathode titanium product, a redox reaction will continue to occur. The generated rare earth oxide will then react with RECl3 in the molten salt to generate REOCl. The continuous reaction of RE2O3 can cause the chemical equilibrium of the reaction to move to the right, promoting the deoxidation of the cathode titanium product by the rare earth metal; at the same time, the RE metal can directly react with the cathode titanium product and RECl3 in the molten salt, and can also further deoxidize the cathode titanium product. Since the cathode titanium product after the first electrolysis continues to undergo a thermochemical deoxidation reaction with the rare earth element and rare earth chloride in the molten salt, it can further remove oxygen from the cathode product titanium and control the oxygen content at a low level. The reactions that occur may include:

[0029] 3[O] inTi +2RE(s,l)→RE2O3(s,l) (6)

[0030] RE2O3(s,l)+RECl3(l)→3REOCl(s) (7)

[0031] 3[O] inTi +2RE(s,l)+RECl3(l)→3REOCl(s) (8)

[0032] After the thermochemical deoxidation is completed, the cathode titanium product is subjected to a second electrolytic deoxidation. The second electrolysis uses the titanium product after thermochemical deoxidation as the cathode, the graphite rod as the anode, and the electrolyte remains unchanged. The time of the second electrolysis can be controlled at 6h to 12h, which can be less than the first electrolytic deoxidation time. By electrolyzing the cathode product titanium again, the oxygen content in the product metal titanium can be further reduced to below 300ppm. The reactions occurring at the anode and cathode may include:

[0033] Anode: C(s)+nO 2- →CO n (g)+2ne - (9) Cathode: [O] inTi +ne - →nO 2- (10)

[0034] Other reactions that can occur in the electrolysis system include:

[0035] 3[O] inTi +2RE(s,l)→RE2O3(s,l) (11)

[0036] RE2O3(s,l)+RECl3(l)→3REOCl(s) (12)

[0037] 3[O] inTi +2RE(s,l)+RECl3(l)→3REOCl(s) (13)

[0038] The present invention provides a method for preparing low-oxygen titanium by step-coupled deoxidation. In some embodiments, the method for preparing low-oxygen titanium may include the following steps:

[0039] Step S01, first electrolysis reaction. The reaction device is as follows Figure 1As shown, a large crucible 1 is used as a reaction container, and the material of the large crucible 1 can be a ceramic crucible. A small crucible 2 is used to load titanium-containing waste 3, and the material of the small crucible 2 can be graphite. The small crucible 2 is connected to the first anode 4, and the first anode 4 can be graphite. The cathode 5 can be a molybdenum rod. A mixed molten salt 6 including at least ionic metal chloride and rare earth chloride is used as an electrolyte. The mixed molten salt 6 contains a single rare earth 7. Under a protective atmosphere, for example, an argon protective atmosphere, the cathode 5 and the first anode 4 are connected to a power supply for electrolysis. The titanium in the anode waste titanium material is ionized and deposited on the cathode, and the above-mentioned reactions (1) and (2) occur, and the rare earth single substance and rare earth chloride are used in the electrolyte for deoxidation, and the above-mentioned reactions (3) to (5) occur, and the cathode product 8-metal titanium with a first oxygen content is obtained.

[0040] Step S02, thermochemical deoxidation. In the electrolysis system of step S01, under a protective atmosphere, titanium with a first oxygen content is continuously immersed in a mixed molten salt under a protective atmosphere for thermochemical deoxidation. The reactions that occur may include the above-mentioned reaction formulas (6), (7) and (8). The cathode titanium is continuously deoxidized by rare earth elements and rare earth chlorides, and titanium with a second oxygen content is obtained after the reaction is completed.

[0041] Step S03, second electrolytic deoxidation. Keeping the electrolyte unchanged, under a protective atmosphere, the titanium with the second oxygen content obtained in step S02 is used as the cathode, and the second anode 9 is used as the anode. After applying voltage, a second electrolysis is performed. After the second electrolysis is completed, metallic titanium with a low oxygen content is obtained on the cathode. The reactions that occur may include the above reaction formulas (9) to (13). Among them, the second anode 9 may be graphite.

[0042] In some embodiments, the voltage applied for the first electrolysis can be 2.8V to 3.2V, the temperature can be 850°C to 1000°C, and the electrolysis time can be 12h to 36h. Under the above voltage, temperature and electrolysis time, it can be ensured that the titanium in the anode is reduced to metallic titanium to the maximum extent and the molten salt will not be ionized. For example, in some embodiments, the voltage applied for the first electrolysis can be 2.9V to 3.1V, the temperature can be 880°C to 950°C, and the electrolysis time can be 14h to 32h; for another example, the applied voltage can be 3.0V, the temperature can be 900°C to 930°C, and the electrolysis time can be 18h to 25h.

[0043] In some embodiments, the molten salt temperature of the thermochemical deoxidation process in step S02 can be 750°C to 800°C, and the thermochemical deoxidation process can last for 40h to 55h. The thermochemical deoxidation temperature is set lower than the temperature of the first electrolysis, which can achieve a better deoxidation effect of titanium. For example, the temperature of the thermochemical deoxidation can be 770°C to 790°C, and the duration can be 45h to 50h.

[0044] In some embodiments, the voltage of the second electrolysis can be 2.8V to 3.2V, the temperature can be 850°C to 1000°C, and the electrolysis time can be 6h to 12h. Under the voltage, temperature and electrolysis time of the above-mentioned second electrolysis, the metal titanium after thermochemical deoxidation can be further deoxidized. The time is controlled within 12h, which can reduce energy consumption while ensuring the deoxidation effect. For example, the voltage of the second electrolysis can be 2.9V to 3.1V, the temperature can be 880°C to 950°C, and the electrolysis time can be 7h to 10h. For another example, the voltage of the second electrolysis can be 3.0V, the temperature can be 900°C to 930°C, and the electrolysis time can be 8h to 9h.

[0045] In some embodiments, the ionic metal chloride can be one or a combination of potassium chloride and sodium chloride. The rare earth chloride can be any one of the rare earth metal chlorides of Sc, Y, La, Ce, Tm, Ho, Sm, Gd, Dy, Lu and Pr. The ratio of the ionic metal chloride to the rare earth chloride and the amount added can be actually proportioned and added according to the amount of titanium required in the reaction system.

[0046] In some embodiments, the molten salt may be pretreated before the first electrolysis. For example, the molten salt may be dried before pre-electrolysis. The drying temperature may be 300°C to 500°C, and the drying time may be 20h to 30h. The pre-electrolysis may be pre-electrolysis of the mixed molten salt at a voltage of 2.8V to 3.2V and a temperature of 850°C to 1000°C. The anode of the pre-electrolysis may be a graphite rod, and the cathode may be a molybdenum rod.

[0047] In some embodiments, the titanium-containing waste material may be titanium alloy TC4 and / or titanium alloy TA10. Of course, the titanium-containing waste material of the present invention is not limited thereto, and may be any alloy or other material containing titanium. In order to facilitate molten salt electrolysis, the waste titanium material may be melted into titanium ingots by a suspension smelting furnace and then subjected to molten salt electrolysis.

[0048] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with specific examples, but the content of the present invention is not limited to the following examples.

[0049] Example 1

[0050] A method for preparing low-oxygen titanium by step-coupled deoxidation may include the following steps:

[0051] Step 1: melt the waste titanium material of TC4 / TA10 alloy into titanium ingots through a suspension melting furnace.

[0052] Step 2: Mix potassium chloride, sodium chloride and yttrium chloride in a ratio of 1:3:6, dry at 200°C for 24 hours, and then heat to 400°C and dry for 24 hours. After drying, take out and perform pre-electrolysis for 3 hours in an argon atmosphere at a temperature of 850°C and a voltage of 2.9V.

[0053] Step 3, after the pre-electrolysis is completed, the first electrolysis is carried out in an argon atmosphere at a voltage of 2.9 V and a temperature of 850°C. The electrolysis apparatus is as follows: Figure 1 As shown, the molten titanium ingot is placed in a small crucible as an anode, a molybdenum rod is used as a cathode, and the bottom of the large crucible is filled with metal yttrium. The electrolysis ends after 48 hours, and the cathode obtains metal titanium with a first oxygen content.

[0054] Step 4: After the first electrolysis is completed, the temperature is lowered to 800° C. The metal titanium with the first oxygen content is kept in the electrolyte melt for 48 hours, and the cathode product is thermochemically deoxidized by yttrium chloride and Y (yttrium).

[0055] Step 5: After the thermochemical deoxidation is completed, the temperature is raised to 850°C, and the second electrolysis is started for deep deoxidation, with the graphite rod as the anode and the molybdenum rod with the electrolysis product as the cathode. The oxide on the surface of the cathode product is ionized, and the oxygen ions are captured by yttrium chloride and Y, and the electrolysis time is controlled to be 6 hours.

[0056] Step 6: After the second electrolysis, the cathode metal titanium is taken out and washed with water, acid washed and vacuum dried at 60° C. to obtain low-oxygen metal titanium. The oxygen content in the titanium is 295 ppm as measured by LECO (TC-400).

[0057] Example 2

[0058] A method for preparing low-oxygen titanium by step-coupled deoxidation may include the following steps:

[0059] Step 1: melt the scrap titanium material of TA10 alloy into titanium ingots through a suspension melting furnace.

[0060] Step 2: Mix potassium chloride, sodium chloride and lanthanum chloride in a ratio of 1.2:3.3:5.5, dry at 200°C for 24 hours, and then heat to 400°C and dry for 24 hours. After drying, take out and perform pre-electrolysis for 3 hours in an argon atmosphere at a temperature of 850°C and a voltage of 2.9V.

[0061] Step 3, after the pre-electrolysis is completed, the first electrolysis is carried out in an argon atmosphere at a voltage of 3.1 V and a temperature of 980° C. The electrolysis apparatus is as follows: Figure 1 As shown, the molten titanium ingot is placed in a small crucible as an anode, a molybdenum rod is used as a cathode, and the bottom of the large crucible is filled with metal lanthanum. After 40 hours of electrolysis, the cathode obtains metal titanium with a first oxygen content.

[0062] Step 4: After the first electrolysis is completed, the temperature is lowered to 780° C. The metal titanium with the first oxygen content is kept in the electrolyte melt for 52 hours, and the cathode product is thermochemically deoxidized by lanthanum chloride and La (lanthanum).

[0063] Step 5: After the thermochemical deoxidation is completed, the temperature is raised to 980°C, and the second electrolysis is started for deep deoxidation, with the graphite rod as the anode and the molybdenum rod with the electrolysis product as the cathode. The oxide on the surface of the cathode product is ionized, and the oxygen ions are captured by lanthanum chloride and lanthanum, and the electrolysis time is controlled to be 10 hours.

[0064] Step 6: After the second electrolysis, the cathode metal titanium is taken out and washed with water, acid washed and vacuum dried at 60° C. to obtain low-oxygen metal titanium. The oxygen content in the titanium is 289 ppm as measured by LECO (TC-400).

[0065] Comparative Example 1

[0066] Compared with Example 1, the thermochemical deoxidation process in step 4 was not performed in this comparative example, and the other processes were the same as those in Example 1. The oxygen content of the prepared product, titanium metal, was 9050 ppm as measured by LECO (TC-400).

[0067] Comparative Example 2

[0068] Compared with Example 1, the second electrolytic deoxidation process in step 5 was not performed in this comparative example, and the other processes were the same as those in Example 1. The oxygen content of the prepared product, titanium metal, was measured by LECO (TC-400) and was 6850 ppm.

[0069] Although the present invention has been described above by combining with exemplary embodiments, it will be apparent to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined in the claims.

Claims

1. A method for preparing low-oxygen titanium by step-coupled deoxidation, characterized in that: The following steps are involved: Under a protective atmosphere, a mixed molten salt including at least ionic metal chloride and rare earth chloride is used as an electrolyte, a titanium-containing waste is used as an anode, and a single rare earth is added to the electrolyte, and a voltage is applied to perform a first electrolysis, and titanium with a first oxygen content is obtained on the cathode after the electrolysis is completed; The titanium with the first oxygen content is continuously immersed in a mixed molten salt under a protective atmosphere to perform a thermochemical deoxidation reaction, and titanium with a second oxygen content is obtained after the reaction is completed; The titanium with the second oxygen content is used as the cathode, and a voltage is applied to perform a second electrolysis, and metallic titanium with a low oxygen content is obtained on the cathode after the second electrolysis is completed.

2. The method for preparing low-oxygen titanium by step-coupling deoxidation according to claim 1, characterized in that: The voltage applied in the first electrolysis is 2.8V to 3.2V, the temperature is 850°C to 1000°C, and the electrolysis time is 12h to 36h.

3. A method for preparing low-oxygen titanium by step-coupled deoxidation according to claim 1 or 2, characterized in that: Continuously immersing the titanium with the first oxygen content in the mixed molten salt under the protective atmosphere includes immersing the titanium with the first oxygen content in the mixed molten salt at a temperature of 750° C. to 800° C. for 40 hours to 55 hours.

4. A method for preparing low-oxygen titanium by step-coupled deoxidation according to claim 1 or 2, characterized in that: The voltage applied in the second electrolysis is 2.8V~3.2V, the temperature is 850℃~1000℃, and the electrolysis time is 6h~12h.

5. A method for preparing low-oxygen titanium by step-coupled deoxidation according to claim 1 or 2, characterized in that: The ionic metal chloride is one or a combination of potassium chloride and sodium chloride; The rare earth chloride is any one of chloride of rare earth metal Sc, chloride of Y, chloride of La, chloride of Ce, chloride of Tm, chloride of Ho, chloride of Sm, chloride of Gd, chloride of Dy, chloride of Lu and chloride of Pr.

6. A method for preparing low-oxygen titanium by step-coupled deoxidation according to claim 1 or 2, characterized in that: The first electrolysis includes placing the titanium-containing waste in a graphite crucible connected to a graphite rod, and performing molten salt electrolysis with the graphite rod as an anode and a molybdenum rod as a cathode.

7. A method for preparing low-oxygen titanium by step-coupled deoxidation according to claim 1 or 2, characterized in that: The second electrolysis uses a graphite rod as the anode.

8. A method for preparing low-oxygen titanium by step-coupled deoxidation according to claim 1 or 2, characterized in that: The method also includes pre-electrolyzing the mixed molten salt at a voltage of 2.8V to 3.2V and a temperature of 850°C to 1000°C before the first electrolysis.

9. A method for preparing low-oxygen titanium by step-coupled deoxidation according to claim 1 or 2, characterized in that: The titanium-containing waste is titanium alloy TC4 and / or titanium alloy TA10.

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