Deoxidation treatment method for refractory metal

Abstract

The invention discloses a deoxidation treatment method for refractory metal. The deoxidation treatment method for the refractory metal comprises the following steps that the refractory metal is placed in airflow crushing equipment to be subjected to crushing treatment, and refractory metal powder is obtained; the refractory metal powder is placed in radio frequency plasma equipment to be subjected to high-temperature calcination, the power of the radio frequency plasma spheroidizing equipment is controlled to be 50-100 Kw, the carrier gas flow is 2-15 L / min, the speed of a powder feeder is 10-60 g / min, the length of a heating area of the radio frequency plasma equipment in the moving direction of the refractory metal powder is 0.3-0.7 m, the temperature of the heating area is larger than 4000 K, and the refractory metal powder is subjected to high-temperature calcination. The refractory metal powder is in a molten state, and the refractory metal surface oxide is in a gasified state; and the low-oxygen refractory metal is cooled and recycled in a cooling grading system in the radio frequency plasma equipment, and the low-oxygen refractory metal is formed. By means of the deoxidation treatment method, the deoxidation treatment steps of the refractory metal are greatly simplified, and the deoxidation treatment cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of metal smelting, and in particular relates to a deoxidation treatment method for refractory metals. Background Art

[0002] Refractory metals usually refer to metal materials with a melting point above 2000°C, mainly including metal elements such as niobium, tantalum, molybdenum, tungsten, hafnium, and high melting point alloys based on these elements. This kind of high melting point metal occupies an extremely important position in high temperature and high pressure fields such as aviation, aerospace, nuclear energy, electronics, and metallurgy due to its high melting point, high strength, high hardness, low thermal expansion coefficient, good thermal stability, and corrosion resistance. The high strength, high hardness, low thermal expansion coefficient, good thermal stability, and corrosion resistance of refractory metals largely depend on the oxygen content inside the metal, that is, the lower the oxygen content inside the metal, the higher the strength of the refractory metal.

[0003] At present, in order to reduce the oxygen content of refractory metals, the reduction effect of hydrogen is usually used to react with the oxides on the surface of the refractory metals, followed by dehydrogenation and deoxidation using deoxidizers and halide salts at high temperatures, and finally the byproducts of hydrogen and acid produced in the deoxygenation treatment need to be purified. However, this deoxygenation treatment method has complex steps and high processing costs. Summary of the invention

[0004] In view of this, an object of the present invention is to provide a deoxidation treatment method for refractory metals, aiming to solve the technical problems of the current refractory metal deoxidation treatment steps being complicated and the treatment cost being high.

[0005] To achieve the above object, the present invention provides the following technical solution: a deoxidation treatment method for refractory metals, comprising the following steps:

[0006] Crushing treatment: The refractory metal is placed in a gas flow crushing device for crushing to obtain refractory metal powder;

[0007] High-temperature deoxidation treatment: placing the refractory metal powder in a radio frequency plasma device for high-temperature calcination, the power of the radio frequency plasma spheroidization device is 50-100Kw, the carrier gas flow rate is 2-15L / min, the powder feeder rate is 10-60g / min, the length of the heating area of ​​the radio frequency plasma device along the movement direction of the refractory metal powder is 0.3-0.7m, and the temperature of the heating area is greater than 4000K, so that the refractory metal powder itself is in a molten state and the surface oxide of the refractory metal is in a vaporized state; the refractory metal powder in a molten state and the surface oxide in a vaporized state are driven by the flow of the carrier gas to enter the cooling and grading system in the radio frequency plasma device for cooling and recovery respectively, so as to form a low-oxygen refractory metal.

[0008] Furthermore, in the crushing step: the pressure of the air flow crushing equipment is 0.3-1.0Mpa, and the frequency of the feeder is 3-50Hz.

[0009] Furthermore, the air flow breaking equipment comprises a first classifier and a second classifier, the frequency of the first classifier is 0-80 Hz, and the frequency of the second classifier is 0-80 Hz.

[0010] Furthermore, the crushing step further includes the following steps:

[0011] Measure oxygen and nitrogen content in refractory metals after crushing.

[0012] Furthermore, the particle size of the refractory metal is ≤150 μm.

[0013] Furthermore, the inner ring gas flow rate of the radio frequency plasma equipment is 30-100 L / min, and the outer ring gas flow rate is 60-200 L / min.

[0014] Furthermore, the inner ring gas, the outer ring gas and the carrier gas are all argon.

[0015] Furthermore, the purity of the argon gas is 99%-99.95wt%.

[0016] The beneficial effects of the present invention are as follows: compared with the prior art, a deoxidation treatment method of a refractory metal in the present invention can crush the refractory metal into powder particles with smaller particle size through pre-crushing treatment, so as to obtain a refractory metal powder raw material with a large specific surface area; by placing the crushed refractory metal powder in a radio frequency plasma device for high-temperature calcination, that is, by controlling the power, carrier gas flow rate, powder feeder rotation speed, length and temperature of the heating zone and other parameters of the radio frequency plasma device, and based on the fact that the melting point of the refractory metal oxide is lower than the melting point of the refractory metal itself, and the refractory metal oxide layer is usually concentrated on the surface of the refractory metal exposed to the outside, it is ensured that the refractory metal powder stays in the heating zone of the radio frequency plasma device for a sufficient time, thereby achieving the effect of gasification and separation of impurities such as oxygen and nitrogen on the surface of the refractory metal powder while the refractory metal powder is liquefied as a whole, and then the refractory metal powder in a molten state and the surface oxide in a gasified state are brought into the cooling and grading system in the radio frequency plasma device by the flow of carrier gas for cooling and recovery respectively, thereby achieving deoxidation treatment of the refractory metal. The two-step treatment process of the present application greatly simplifies the steps of deoxidation treatment of refractory metals; through high-temperature calcination treatment, impurities such as oxygen and nitrogen on the surface of refractory metals are effectively gasified and separated without introducing by-products, greatly reducing the treatment cost.

[0017] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art may be taught from the practice of the present invention. The objectives and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0019] Figure 1 A flow chart of a deoxidation treatment method for refractory metals proposed in one embodiment of the present invention;

[0020] Figure 2 This is a crushing morphology diagram of the refractory metal tungsten raw material in Example 1 of the present invention;

[0021] Figure 3 This is a crushing morphology diagram of the refractory metal molybdenum raw material in Example 2 of the present invention;

[0022] Figure 4 This is a crushing morphology diagram of the refractory metal tantalum raw material in Example 2 of the present invention. DETAILED DESCRIPTION

[0023] like Figure 1 As shown, this embodiment provides a deoxidation treatment method for refractory metals, comprising the following steps:

[0024] S01: Crushing treatment: placing the refractory metal in an air flow crushing device for crushing treatment to obtain refractory metal powder;

[0025] S02: High-temperature deoxidation treatment: The refractory metal powder is placed in a radio frequency plasma device for high-temperature calcination. The power of the radio frequency plasma spheroidization device is 50-100Kw, the carrier gas flow rate is 2-15L / min, and the powder feeder rate is 10-60g / min. The length of the heating area of ​​the radio frequency plasma device along the movement direction of the refractory metal powder is 0.3-0.7m, and the temperature of the heating area is greater than 4000K, so that the refractory metal powder itself is in a molten state and the surface oxide of the refractory metal is in a vaporized state; the refractory metal powder in a molten state and the surface oxide in a vaporized state are driven by the flow of carrier gas to enter the cooling and grading system in the radio frequency plasma device for cooling and recovery respectively, so as to form a low-oxygen refractory metal.

[0026] By pre-crushing treatment, the refractory metal can be crushed into powder particles with smaller particle size, so as to obtain refractory metal powder raw material with large specific surface area; by placing the crushed refractory metal powder in a radio frequency plasma device for high-temperature calcination, that is, by controlling the power, carrier gas flow rate, powder feeder rotation speed, length and temperature of the heating zone and other parameters of the radio frequency plasma device, and based on the fact that the melting point of the refractory metal oxide is lower than the melting point of the refractory metal itself, and the refractory metal oxide layer is usually concentrated on the surface of the refractory metal exposed to the outside, it is ensured that the refractory metal powder stays in the heating zone of the radio frequency plasma device for a sufficient time, thereby achieving the effect of gasification and separation of impurities such as oxygen and nitrogen on the surface of the refractory metal powder while the refractory metal powder is liquefied as a whole, and then the refractory metal powder in a molten state and the surface oxide in a gasified state are brought into the cooling and grading system of the radio frequency plasma device by the flow of carrier gas for cooling and recovery respectively, so as to achieve deoxidation treatment of the refractory metal. The two-step treatment process of the present application greatly simplifies the steps of deoxidation treatment of refractory metals; through high-temperature calcination treatment, impurities such as oxygen and nitrogen on the surface of refractory metals are effectively gasified and separated without introducing by-products, greatly reducing the treatment cost.

[0027] In the present application, the length of the heating area of ​​the radio frequency plasma device along the moving direction of the refractory metal powder is 0.3m, 0.4m, 0.5m, 0.6m, 0.7m, etc., which effectively ensures the residence time of the refractory metal powder in the heating area, so that the refractory metal powder is fully melted and the oxygen reduction effect is guaranteed. Specifically, the length of the heating area can be adjusted according to the actual situation of the refractory metal powder melting, and is not limited here.

[0028] In the present application, the temperature of the heating area is greater than 4000 K. Preferably, the temperature of the heating area is 4000-8000 K, specifically, the temperature of the heating area may be 4500 K, 5000 K, 5500 K, 6000 K, 7000 K, 8000 K, etc. The specific temperature of the heating area may be adjusted accordingly with the melting point of the refractory metal itself, and is not limited here.

[0029] In the application, in the crushing process step, the pressure of the air flow crushing equipment is 0.3-1.0Mpa, and the frequency of the feeder is 3-50Hz. By controlling the pressure, the refractory metal powder can obtain more kinetic energy, increase the collision energy, and make the powder particle size finer; by controlling the frequency of the feeder, the speed of material entry is controlled to avoid the material entering too fast, thereby affecting the crushing effect. Specifically, the pressure of the air flow crushing equipment is 0.3Mpa, 0.5Mpa, 0.7Mpa, 0.8Mpa, 1.0Mpa, etc.; the frequency of the feeder is 3Hz, 10Hz, 15Hz, 20Hz, 25Hz, 30Hz, 35Hz, 40Hz, 45Hz, 50Hz, etc. Of course, according to actual conditions and specific needs, the pressure and the frequency of the feeder can also be set to other ranges, which are not limited here.

[0030] Furthermore, the air flow crushing equipment includes a first classifier and a second classifier, the frequency of the first classifier is 0-80Hz, and the frequency of the second classifier is 0-80Hz. Preferably, the frequency of the first classifier is 0Hz, 10Hz, 20Hz, 30Hz, 40Hz, 50Hz, 60Hz, 70Hz, 80Hz, etc.; the frequency of the second classifier is 0Hz, 10Hz, 20Hz, 30Hz, 40Hz, 50Hz, 60Hz, 70Hz, 80Hz, etc. Through the first classifier and the second classifier, the material that meets the specific particle size requirements can be separated through two classifications, that is, when the material crushed by the first classifier is large, the material with a larger particle size can be re-sent to the crushing area by the second classifier for re-crushing, so as to obtain a refractory metal powder with a smaller particle size, and then obtain a refractory metal powder raw material with a large specific surface area. In the present application, if the particle size of the refractory metal powder raw material just meets the requirements, the frequency of the first classifier and the second classifier can be 0 Hz, and no classifier processing is required; of course, in the present application, according to actual conditions and specific needs, the frequency of the first classifier and the second classifier can also be other values, which is not the only limitation here.

[0031] Preferably, the particle size of the refractory metal is ≤150 μm. That is, the particle size of the refractory metal is effectively ensured to meet the requirements of fine particle size through the first classifier and the second classifier, so that the refractory metal powder raw material after crushing has a larger specific surface area.

[0032] Furthermore, the crushing step further includes the following steps:

[0033] Measure oxygen and nitrogen content in refractory metals after crushing.

[0034] In the present application, by measuring the oxygen and nitrogen contents in the refractory metal after the crushing treatment, it is taken into account that the refractory metal may be oxidized during the crushing process, resulting in changes in the oxygen and nitrogen contents that affect the subsequent evaluation of the oxygen reduction effect of the refractory metal, thereby ensuring the accuracy of the test effect comparison.

[0035] Furthermore, the inner ring gas flow rate of the radio frequency plasma device is 30-100 L / min, and the outer ring gas flow rate is 60-200 L / min. By adjusting the flow rates of the inner ring gas and the outer ring gas, the distribution of the refractory metal powder particles in the high temperature flow field can be affected, ensuring smooth gas flow of the radio frequency plasma device.

[0036] Preferably, the inner ring gas, the outer ring gas and the carrier gas are all argon. By selecting argon, a stable inert environment can be provided for the refractory metal powder during the deoxidation process, preventing the metal from being disturbed by the external environment and affecting the deoxidation effect.

[0037] Preferably, the purity of the argon gas is 99%-99.95wt%.

[0038] In order to better demonstrate that the deoxidation treatment method of refractory metals of the present application has a good deoxidation effect, a comparative analysis is now conducted through the following examples:

[0039] Embodiment 1

[0040] The refractory metal tungsten raw material was added to the air flow crushing and grading equipment, and the refractory metal tungsten raw material was crushed and graded in an argon gas environment with a purity of 99.95%, and the air flow crushing and grading equipment was controlled to be at an argon gas station pressure of 0.6Mpa, a feeder frequency of 15Hz, a first classifier frequency of 48Hz, and a second classifier frequency of 60Hz. Subsequently, the oxygen content of the refractory metal tungsten powder after the crushing process was measured to be 430ppm, the nitrogen content was 290ppm, Figure 2 This is the crushing morphology of the refractory metal tungsten raw material;

[0041] The tungsten powder obtained by the air flow crushing and grading equipment is fed into the radio frequency plasma equipment, the power of the radio frequency plasma equipment is controlled to be set to 100kw, the working frequency is set to 2.5MHz, the working gas is argon gas with a purity of 99.95wt%, the carrier gas is 4L / min, the inner ring gas is 60L / min, the outer ring gas is 180L / min, the length of the heating area with a temperature higher than 4000K along the powder movement direction in the radio frequency plasma arc column area is 0.6m, and the deoxidation treatment is carried out under the working environment of the powder feeding rate of 30g / min; then the deoxidized tungsten is obtained through the cooling and grading system in the radio frequency plasma equipment. The oxygen content of the deoxidized tungsten powder measured is 55ppm.

[0042] Embodiment 2

[0043] The refractory metal molybdenum raw material was added to the air flow crushing and grading equipment, and the refractory metal molybdenum raw material was crushed and graded in an argon gas environment with a purity of 99.95%, and the air flow crushing and grading equipment was controlled to be under an argon gas station pressure of 0.5Mpa, a feeder frequency of 18Hz, a first classifier frequency of 30Hz, and a second classifier frequency of 65Hz. Subsequently, the oxygen content of the refractory metal molybdenum powder after the crushing treatment was measured to be 480ppm, the nitrogen content was 290ppm, Figure 3 This is the crushing morphology of the refractory metal molybdenum raw material;

[0044] The molybdenum powder obtained by the air flow crushing and grading equipment is fed into the radio frequency plasma equipment, the power of the radio frequency plasma equipment is controlled to be set to 100kw, the working frequency is set to 2.5MHz, the working gas is argon gas with a purity of 99.95wt%, the carrier gas is 5L / min, the inner ring gas is 80L / min, the outer ring gas is 160L / min, the length of the heating area with a temperature higher than 4000K along the powder movement direction in the radio frequency plasma arc column area is 0.5m, and the deoxidation treatment is carried out under the working environment of the powder feeding rate of 40g / min; then the deoxidized molybdenum is obtained through the cooling and grading system in the radio frequency plasma equipment. The oxygen content of the deoxidized molybdenum powder measured is 90ppm.

[0045] Embodiment 3

[0046] The refractory metal tantalum raw material was added to the air flow crushing and grading equipment, and the refractory metal tantalum raw material was crushed and graded in an argon gas environment with a purity of 99.95%, and the air flow crushing and grading equipment was controlled to be at an argon gas station pressure of 0.7Mpa, a feeder frequency of 20Hz, a first classifier frequency of 15Hz, and a second classifier frequency of 65Hz. Subsequently, the oxygen content of the refractory metal tantalum powder after the crushing process was measured to be 500ppm, the nitrogen content was 335ppm, Figure 4 This is the crushing morphology of the refractory metal tantalum raw material;

[0047] The tantalum powder obtained by the air flow crushing and grading equipment is fed into the radio frequency plasma equipment, the power of the radio frequency plasma equipment is controlled to be set to 100kw, the working frequency is set to 2.5MHz, the working gas is argon gas with a purity of 99.95wt%, the carrier gas is 3L / min, the inner ring gas is 60L / min, the outer ring gas is 180L / min, the length of the heating area with a temperature higher than 4000K along the powder movement direction in the radio frequency plasma arc column area is 0.6m, and the powder feeding rate is 55g / min. Deoxidation treatment is performed under the working environment; then the tantalum after deoxidation is obtained through the cooling and grading system in the radio frequency plasma equipment. The oxygen content of the tantalum powder after deoxidation is measured to be 150ppm.

[0048] Comparative Example

[0049] (1) Place the high-purity tantalum ingot into a stainless steel crucible, hang it into the resistance hydrogenation furnace, evacuate it to below 200 Pa, and then fill it with hydrogen to 1.0*10 5 Pa, then control the pressure not to exceed 2.0*10 5 Pa, the temperature is raised to 700℃, and the temperature is kept for 3 hours. After the temperature is kept, the power is turned off and the temperature is lowered for hydrogenation. During the cooling process, hydrogen is added in time until the tantalum ingot no longer absorbs hydrogen;

[0050] (2) placing the hydrogenated tantalum ingot into a ball mill for crushing to obtain tantalum powder;

[0051] (3) The milled tantalum powder is placed in a crucible and then in a resistance dehydrogenation furnace for dehydrogenation. The argon gas is replaced by vacuum to make the argon gas in the reaction bomb ≥ 0.4Mpa, and the temperature is raised to 800℃ and kept at this temperature for 4 hours for dehydrogenation.

[0052] (4) The dehydrogenated tantalum powder is added to an air flow mill for shaping. The working pressure is 6 kg, the primary frequency is 20 Hz, the secondary frequency is 45 Hz, the air flow shaping time is controlled at 15 h, and the fine powder is sieved to the secondary level.

[0053] (5) The powder after airflow shaping is pickled with a mixture of nitric acid and hydrofluoric acid for 1.5 h.

[0054] (6) The raw powder obtained after pickling is placed in a tantalum crucible and placed in a vacuum heat treatment furnace for vacuum heat treatment at a temperature of 1250° C. for 45 minutes.

[0055] (7) Add magnesium chips with a mass percentage of about 1% to the tantalum powder after vacuum heat treatment. Perform deoxidation treatment in a dehydrogenation furnace. The heating temperature of the dehydrogenation furnace is 800°C, and the insulation time is 4 hours. Then use a mixed acid wash with nitric acid and hydrofluoric acid to remove the metallic magnesium and magnesium oxides, and then add pure water to filter and remove the waste acid liquid. Then dry the low-oxygen tantalum powder. The oxygen content in the tantalum powder after the above deoxidation treatment is 350ppm, and the nitrogen content is 90ppm.

[0056] The oxygen content and nitrogen content of the samples obtained in Examples 1 to 3 and the comparative example were tested by an oxygen, nitrogen and hydrogen analyzer, and the test results are shown in the following table:

[0057] Sample name Oxygen content before treatment (ppm) Oxygen content before treatment (ppm) Embodiment 1 430 55 Embodiment 2 480 90 Embodiment 3 500 150 Comparative Example 500 350

[0058] It can be seen from Examples 1 to 3 that the present application can achieve rapid preparation of low-oxygen refractory metals. By comparing Example 3 with the comparative example, it can be seen that although the refractory metals prepared by the oxidation-reduction, pickling, drying, and screening processes used in the comparative example can achieve a certain degree of oxygen reduction effect, the process flow of this method is complicated, the production cycle is long, impurity elements are easily introduced during the process, and highly polluted pickling waste liquid is produced, and the shortcomings are very obvious. However, the present application quickly completes the deoxidation treatment of refractory metals through a two-step process of air flow crushing combined with plasma oxygen reduction treatment, and the oxygen reduction effect is obvious, and no difficult-to-treat acid-containing waste liquid is produced, and the treatment cost is significantly lower.

[0059] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for deoxidation of refractory metals, characterized in that: The steps include: Crushing treatment: The refractory metal is placed in a gas flow crushing device for crushing to obtain refractory metal powder; High-temperature deoxidation treatment: placing the refractory metal powder in a radio frequency plasma device for high-temperature calcination, the power of the radio frequency plasma spheroidization device is 50-100Kw, the carrier gas flow rate is 2-15L / min, the powder feeder rate is 10-60g / min, the length of the heating area of ​​the radio frequency plasma device along the movement direction of the refractory metal powder is 0.3-0.7m, and the temperature of the heating area is greater than 4000K, so that the refractory metal powder itself is in a molten state and the surface oxide of the refractory metal is in a vaporized state; the refractory metal powder in a molten state and the surface oxide in a vaporized state are driven by the flow of the carrier gas to enter the cooling and grading system in the radio frequency plasma device for cooling and recovery respectively, so as to form a low-oxygen refractory metal.

2. A deoxidation treatment method for refractory metal according to claim 1, characterized in that: In the crushing process step: the pressure of the air flow crushing equipment is 0.3-1.0Mpa, and the frequency of the feeder is 3-50Hz.

3. A deoxidation treatment method for refractory metal according to claim 2, characterized in that: The air flow breaking equipment comprises a first classifier and a second classifier, the frequency of the first classifier is 0-80 Hz, and the frequency of the second classifier is 0-80 Hz.

4. A deoxidation treatment method for refractory metal according to claim 1, characterized in that: The crushing step also includes the following steps: Measure oxygen and nitrogen content in refractory metals after crushing.

5. The deoxidation treatment method for refractory metal according to claim 3, characterized in that: The particle size of the refractory metal is ≤150 μm.

6. The deoxidation treatment method for refractory metal according to claim 1, characterized in that: The inner ring gas flow rate of the radio frequency plasma equipment is 30-100 L / min, and the outer ring gas flow rate is 60-200 L / min.

7. A deoxidation treatment method for refractory metal according to claim 6, characterized in that: The inner ring gas, the outer ring gas and the carrier gas are all argon.

8. A deoxidation treatment method for refractory metal according to claim 7, characterized in that: The purity of the argon gas is 99%-99.95wt%.

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