Device and method for preparing low-O / N / C ultra-high-purity metal tungsten through electron beam hydrogen reduction drop melting

Abstract

The invention discloses a device and method for preparing low-O / N / C ultra-high-purity metal tungsten through electron beam hydrogen reduction drop melting. The device comprises a furnace body, an electron beam gun I, an electron beam gun II and a cooling water pipeline. A collecting container is arranged in the furnace body; a water-cooling copper mold is wrapped outside the collecting container; a hydrogen conveying device is arranged above the water-cooling copper mold; a horizontal feeding mechanism is horizontally arranged above the hydrogen conveying device; according to the method, the content of impurities such as Fe, Si, Ni, Na, K, Ba, U and Th in metal is greatly reduced, gas impurities such as O, N and C are deeply removed, the removal rate of the impurities such as K, Na and As after single-time drop melting is larger than 90%, the sum of the content of O, N and C is smaller than 10 ppm, and the purity of tungsten is larger than 6 N (the purity is 99.9999%).

Description

Technical Field

[0001] The present invention belongs to the field of metallurgical technology, and mainly relates to an apparatus and method for preparing low O / N / C ultra-high purity metallic tungsten by electron beam hydrogen reduction drip melting. Background Art

[0002] High-purity tungsten (with a purity of 99.999% or higher) has characteristics such as low resistivity, high thermal conductivity, good high-temperature stability, and strong resistance to electron migration, making it used as a sputtering target in high-end integrated circuits. Since the purity of the tungsten thin film depends on the purity of the tungsten target, when the O content is too high, it is easy to cause film defects and circuit short circuits; too high contents of C and Mo will increase the resistivity of the film and affect the electron migration rate. Therefore, the impurities in the target need to be strictly controlled.

[0003] At present, high-purity tungsten in China is mainly purified by chemical methods and powder metallurgy. Due to reasons such as oxygen and nitrogen adsorbed on the powder surface and the C infiltration reaction of the graphite mold during the hot isostatic pressing process, the improvement of the purity of metallic tungsten is restricted. Although the trace elements in the 5N-grade tungsten powder batch-prepared by an enterprise in China can be effectively controlled (purity above 5N, excluding gas impurities), the content of the difficult-to-separate element Mo can be controlled at 0.08 ppmw, but there are still relatively high contents of O, N, and C remaining in the powder, with their contents being 247, 23, and 29 ppmw respectively. These impurities will be inherited into the tungsten ingot blank during the powder metallurgy process and then affect the performance of the product in applications. There are certain difficulties in removing impurities such as oxygen, nitrogen, and carbon in high-purity tungsten. The traditional hydrometallurgical process cannot solve problems such as high gas impurity content and inability to meet the temperature and vacuum requirements for purifying tungsten. Although electron beam melting has the characteristics of high temperature and high vacuum and can meet the melting requirements, the effect of deep carbon removal is not ideal. For this reason, an apparatus and method for preparing low O / N / C ultra-high purity metallic tungsten by electron beam hydrogen reduction drip melting are proposed. Summary of the Invention

[0004] To solve the above-mentioned existing technical problems, a device and method for preparing low O / N / C ultra-high purity metallic tungsten by electron beam hydrogen reduction drip melting are provided. The present invention mainly utilizes the high temperature and high vacuum environment during the electron beam melting process to promote the volatilization and removal of impurities with low saturated vapor pressures such as Fe, Si, Ni, and Na; on this basis, high-purity H2 is introduced for deep removal of O, N, and C gas impurities, while effectively reducing the oxygen potential in the furnace and effectively avoiding the re-dissolution of oxygen; in addition, the drip melting process is used to realize the simultaneous melting and solidification, and the high-temperature region of the melt separates the melt from the vacuum, preventing the re-dissolution of oxygen. The metallic tungsten ingot prepared by the technical solution of this application can not only greatly reduce the contents of impurities such as Fe, Si, Ni, Na, K, Ba, U, and Th in metallic tungsten, but also deeply remove O, N, and C gas impurities. The removal rates of impurities such as K, Na, and As after single drip melting are greater than 90%, the sum of the contents of O, N, and C is less than 10 ppm, and the purity of tungsten is greater than 6N (99.9999%), which is an effective method for preparing low O / N / C ultra-high purity and high-density metallic tungsten ingots.

[0005] According to one aspect of the present invention, a device for preparing low O / N / C ultra-high purity metallic tungsten by electron beam hydrogen reduction drip melting is provided. The device includes a furnace body, an electron beam gun I, and an electron beam gun II;

[0006] A collection container is provided inside the furnace body;

[0007] Cooling water pipelines are provided around the furnace body;

[0008] The outside of the collection container is wrapped with a water-cooled copper mold;

[0009] The water-cooled copper mold communicates with the cooling water pipelines;

[0010] A hydrogen delivery device is provided above the water-cooled copper mold;

[0011] A horizontal feeding mechanism is provided horizontally above the hydrogen delivery device;

[0012] A rotary ingot pulling mechanism is provided in the cavity formed by the collection container, the cooling water pipelines, and the water-cooled copper mold.

[0013] Optionally, a pump is provided on one side of the upper part of the furnace body, and an observation port is provided on the other side of the upper part;

[0014] Cooling water inlets and cooling water outlets are respectively provided on both sides of the bottom of the furnace body;

[0015] The electron beam gun I heats the collection container;

[0016] The electron beam gun II heats the hydrogen transmitted by the horizontal feeding mechanism and the hydrogen delivery device;

[0017] The collection container is a crucible;

[0018] The pump includes a mechanical pump, a Roots pump, and a diffusion pump.

[0019] According to another aspect of the present invention, there is provided a method for preparing ultra-high purity tungsten metal with low O / N / C by electron beam hydrogen reduction and drop melting, which at least includes the following steps:

[0020] Step 1: Place the tungsten metal raw material containing gas impurities and metal impurity elements in the horizontal feeding mechanism of the device, introduce hydrogen through the hydrogen transfer device, preheat the crucible with electron beam gun I, and preheat the horizontal feeding mechanism and the hydrogen transfer device with electron beam gun II;

[0021] Step 2: The hydrogen introduced in Step 1 reacts with the tungsten metal raw material for melting to form a molten pool and metal droplets, and then vacuum cooling is carried out to obtain ultra-high purity tungsten metal with low O / N / C.

[0022] Optionally, the metal impurity elements in Step 1 are selected from at least one of Fe, Si, Ni, Na, K, Ba, U, and Th;

[0023] The gas impurity elements in Step 1 are selected from at least one of O, N, C, and H.

[0024] Optionally, the tungsten metal raw material is in rod shape. When the tungsten metal raw material is in powder form, it needs to be subjected to cold isostatic pressing treatment, sintering treatment, polishing, and cleaning to obtain a rod-shaped metal raw material.

[0025] Optionally, the conditions of the cold isostatic pressing treatment are as follows:

[0026] The cold isostatic pressing pressure is 50 - 300 Mpa;

[0027] The cold isostatic pressing time is 1 - 30 min.

[0028] Optionally, the conditions of the sintering treatment are as follows:

[0029] The sintering temperature is 1500 - 2200 °C;

[0030] The sintering time is 2 - 40 h.

[0031] Optionally, the feeding speed of hydrogen is 0.2 - 0.5 L / min.

[0032] Optionally, the melting power for preheating is 5 - 50 kW.

[0033] The vacuum degree for preheating is 5×10 -3 ~5×10 -2 Pa;

[0034] The preheating temperature is 1500 - 2000 °C.

[0035] Optionally, the smelting conditions are as follows:

[0036] The smelting temperature is 3800 - 4500 °C;

[0037] The smelting power is 50 - 80 kW;

[0038] The ingot pulling speed during smelting is 1.7 - 2 mm / min;

[0039] The smelting time is 20 - 60 min;

[0040] The vacuum degree during smelting is 2.5×10 -3 ~5×10 -3 Pa.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] 1) In the technical solution of the present invention, during smelting, the ingot pulling speed of the rotary ingot pulling mechanism is adjusted to regulate the position of the crucible, so as to keep the distance between the raw material and the molten pool unchanged, achieving the effects of reducing the depth of the molten pool, shortening the distance of impurity transmission, and strengthening impurity removal.

[0043] 2) The tungsten metal prepared by the technical solution of the present invention can not only greatly reduce the contents of impurities such as Fe, Si, Ni, Na, K, Ba, U, and Th in tungsten metal, but also deeply remove gas impurities such as O, N, and C. The removal rates of impurities such as K, Na, and As after single-drop melting are greater than 90%, the sum of the contents of O, N, and C is less than 10 ppm, and the purity of tungsten is greater than 6N (purity is 99.9999%), which is an effective method for preparing ultra-high purity and high-density tungsten metal with low O / N / C. Description of the Drawings

[0044] Figure 1 It is a device diagram for removing oxygen, nitrogen, and carbon in high-purity metal adopted in the embodiment of the present invention;

[0045] Among them, 1. Molten pool; 2. Water-cooled copper mold; 3. Observation window; 4. Rotary ingot pulling mechanism; 5. Cooling water inlet; 6. Electron beam gun II; 7. Horizontal feeding mechanism; 8. Hydrogen delivery device; 9. Pump; 10. Cooling water pipeline; 11. Cooling water outlet. 12. Electron beam gun I; 13. Raw material rod; 14. Furnace body; 15. Crucible. Detailed Embodiments

[0046] The following describes the present application in detail with reference to the embodiments, but the present invention is not limited to these embodiments.

[0047] Unless otherwise specified, the raw materials and reagents in the embodiments of the present invention are all purchased through commercial channels.

[0048] Glow discharge mass spectrometry (GDMS) was used to determine the total elemental content of the raw materials in Example 1 and the low O / N / C ultra-high purity metal tungsten.

[0049] A carbon-sulfur analyzer and an oxygen-nitrogen-hydrogen analyzer were used to determine the contents of O, N, and C elements in the raw materials and the low O / N / C ultra-high purity metal in Examples 1 to 3.

[0050] As Figure 1 shown, the present application provides a device for removing oxygen, nitrogen, and carbon from high-purity metals. The device includes a furnace body 14, an electron beam gun I (12), and an electron beam gun II (6); cooling water pipelines 10 are provided around the furnace body 14; a crucible 15 is provided inside the furnace body 14; cooling water inlets 5 and cooling water outlets 11 are respectively provided on both sides of the bottom of the furnace body 14; a pump 9 is provided on one side of the upper part of the furnace body 14, and an observation port 3 is provided on the other side of the upper part; the outside of the crucible 15 is wrapped with a water-cooled copper mold 2; the water-cooled copper mold 2 is connected to the cooling water pipeline 10; a rotary ingot-pulling mechanism 4 is provided in the cavity formed by the crucible 15, the cooling water pipeline 10, and the water-cooled copper mold 2 (when in use, when the molten droplets enter the crucible 15, the position of the crucible 15 is adjusted by the rotary ingot-pulling mechanism 4 to keep the distance between the raw material rod 13 and the molten pool 1 unchanged); a hydrogen delivery device 8 is provided above the water-cooled copper mold 2; a horizontal feeding mechanism 7 is provided horizontally above the hydrogen delivery device 8; the electron beam gun I heats the crucible 15; the electron beam gun II heats the raw material rod 13 and the hydrogen delivered by the hydrogen delivery device 8; the pump 9 includes a mechanical pump, a Roots pump, and a diffusion pump.

[0051] Example 1

[0052] This example uses the Figure 1 shown device for removing oxygen, nitrogen, and carbon from high-purity tungsten for testing. A tungsten rod (purity 99.99%, O content 36.9 ppmw, N content 70.1 ppmw, C content 68.7 ppmw) is used as the raw material to be purified and placed in the horizontal feeding mechanism 7. The cooling water in the cooling water pipeline 10 is turned on to maintain the circulating cooling of the water-cooled copper mold 2; then the mechanical pump is started to make the vacuum degree in the furnace body 14 reach 500 Pa, and then the Roots pump is started to reduce the vacuum degree in the furnace body 14 to 1 Pa. Finally, the diffusion pump is started to make the vacuum degree in the furnace body 14 reach 2.5×10 -3 Pa; the electron beam gun body II and the electron beam gun I are pumped to the target vacuum state (3×10 -3In step (Pa), hydrogen is introduced through the hydrogen transfer device 8 at a flow rate of 0.5 L / min. Then, the electron beam gun I is started to preheat the crucible 15 (temperature: 1500 °C), and the electron beam gun II is used to preheat the tungsten rod and the hydrogen delivery device 8 (temperature: 2000 °C), with a preheating power of 20 kW.

[0053] After preheating, the tungsten rod and the introduced hydrogen undergo a smelting reaction under the action of the electron beam gun II (i.e., the electron beam gun II melts the tungsten rod raw material to form molten droplets, and the molten droplets react with hydrogen during the dropping process for smelting). During the smelting process, the drawing speed of the rotary ingot drawing mechanism 4 is controlled at 1.7 mm / min (adjust the position of the crucible 15 to keep the distance between the raw material rod 13 and the molten pool 1 unchanged), the smelting power is 80 kW, the smelting reaction temperature is 3800 °C, forming a tungsten metal molten pool and molten droplets. After 30 min of the smelting reaction, the rotary ingot drawing mechanism 4 is adjusted to slowly lower the crucible 15, the electron beam gun I and the electron beam gun II are turned off, and vacuum cooling is carried out to obtain a cylindrical high-purity tungsten ingot. Repeat the above operations to obtain low O / N / C ultra-high-purity metallic tungsten (secondary melting and casting). The test results of the element contents after secondary melting and casting are shown in Table 1.

[0054] Table 1 Test results of the element contents after melting and casting in Example 1 are shown in Table 1

[0055] Raw material / ppmw O N C Mg AI Ca Ti Cr Mn Fe Ni Mo Ta 36.9 70.1 68.7 6 5 12 15 7 16 9 4 1 2 Secondary melting and casting 1.76 1.6 4.1 0.03 0.04 0.06 0.09 0.01 0.16 0.06 0.01 0.06 0.09

[0056] Example 2

[0057] The difference between this example and Example 1 is that tungsten powder (purity: 99.99%, O content: 81.5 ppmw, N content: 75.3 ppmw, C content: 45.6 ppmw) is used as the raw material. The raw material needs to be cold isostatically pressed, with a cold isostatic pressure of 150 Mpa and a cold isostatic time of 5 min; then the raw material is sintered, with a sintering temperature of 2000 °C and a sintering time of 30 min; then polishing, cleaning, and drying are carried out, and finally the raw material tungsten rod to be purified is obtained.

[0058] Before smelting, the vacuum degree of the furnace body 14 is controlled at 2.5×10 -3 Pa by the pump 9, and the vacuum degrees of the gun chambers of the electron beam gun 6 and the electron beam gun 12 are 3×10 -3 Pa; then hydrogen is introduced through the hydrogen transfer device 8 at a flow rate of 0.5 L / min; then the electron beam gun I is used to preheat the crucible 15 (1500 °C), and the electron beam gun II is used to preheat the tungsten rod and the hydrogen delivery device 8 (temperature: 2000 °C), with a preheating power of 20 kW for the electron beam gun.

[0059] After the preheating is completed, the tungsten rod and the introduced hydrogen undergo a smelting reaction under the action of the electron beam gun II (that is, the electron beam gun II melts the tungsten rod raw material to form molten droplets, and the molten droplets react with hydrogen during the dropping process for smelting). During the smelting process, the ingot pulling speed of the ingot pulling rotation mechanism 4 is controlled at 2 mm / min, the smelting power of the electron beam gun II is 70 kW, the smelting reaction time is 30 min, and the smelting reaction temperature is 3800 °C. Repeat the above operations to obtain low O / N / C ultra-high purity metallic tungsten. The test results of the O, N, and C contents show that the content of O is 2.62 ppmw, the content of N is 1.7 ppmw, and the content of C is 5.6 ppmw.

[0060] Example 3

[0061] The difference between this example and Examples 1 and 2 is that tantalum metal (with a purity of 99.99%, an O content of 45 ppmw, an N content of 70 ppmw, and a C content of 35 ppmw) is used as the raw material to obtain low O / N / C ultra-high purity metallic tantalum. The test results of the O, N, and C contents show that the content of O is 2.1 ppmw, the content of N is 1.3 ppmw, and the content of C is 5.8 ppmw.

[0062] As described above, these are only several embodiments of the present invention and do not impose any form of limitation on the present invention. Although the present invention is disclosed with preferred embodiments as above, it is not intended to limit the present invention. Any person skilled in the art, without departing from the technical solution of the present invention, makes some changes or modifications using the disclosed technical content, which are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. An apparatus for preparing ultra-high purity metallic tungsten with low O / N / C by electron beam hydrogen reduction and drop melting, characterized in that, The device includes a furnace body, an electron beam gun I, and an electron beam gun II; A collection container is provided inside the furnace body; Cooling water pipelines are provided around the furnace body; The outside of the collection container is wrapped with a water-cooled copper mold; The water-cooled copper mold communicates with the cooling water pipelines; A hydrogen delivery device is provided above the water-cooled copper mold; A horizontal feeding mechanism is provided horizontally above the hydrogen delivery device; A rotating ingot pulling mechanism is provided in the cavity formed by the collection container, the cooling water pipelines, and the water-cooled copper mold.

2. The device according to claim 1, characterized in that One side of the upper part of the furnace body is provided with a pump, and the other side of the upper part is provided with an observation port; Cooling water inlets and cooling water outlets are respectively provided on both sides of the bottom of the furnace body; The electron beam gun I heats the collection container; The electron beam gun II heats the hydrogen transmitted by the horizontal feeding mechanism and the hydrogen delivery device; The collection container is a crucible; The pump includes a mechanical pump, a Roots pump, and a diffusion pump.

3. A method for preparing low-O / N / C ultra-high purity metallic tungsten by electron beam hydrogen reduction and drop melting, characterized in that, At least includes the following steps: Step 1: Place the metal tungsten raw material containing gas impurities and metal impurity elements in the horizontal feeding mechanism of the device, introduce hydrogen through the hydrogen delivery device, preheat the crucible with the electron beam gun I, and preheat the horizontal feeding mechanism and the hydrogen delivery device with the electron beam gun II; Step 2: The hydrogen introduced in Step 1 reacts with the metal tungsten raw material to carry out melting, forming a molten pool and metal droplets, and vacuum cooling to obtain low O / N / C ultra-high purity metal tungsten; The device is the device according to any one of claims 1 or 2.

4. The method according to claim 3, characterized in that, The metal impurity elements in Step 1 are selected from at least one of Fe, Si, Ni, Na, K, Ba, U, and Th; The gas impurity elements in Step 1 are selected from at least one of O, N, C, and H.

5. The method according to claim 3, characterized in that, The metal tungsten raw material in Step 1 is in a rod shape. When the metal tungsten raw material is in powder form, it needs to be subjected to cold isostatic pressing treatment, sintering treatment, polishing, and cleaning to obtain a metal rod-shaped raw material.

6. The method according to claim 5, wherein The conditions of the cold isostatic pressing treatment are as follows: The cold isostatic pressing pressure is 50 - 300 Mpa; The cold isostatic pressing time is 1 - 30 min.

7. The method according to claim 5, characterized in that, The conditions of the sintering treatment are as follows: The sintering temperature is 1500 - 2200 °C; The sintering time is 2 - 40 h.

8. The method according to claim 3, wherein The feeding speed of the hydrogen is 0.2 - 0.5 L / min.

9. The method according to claim 3, wherein The melting power of the preheating is 5 - 50 kW; The degree of vacuum for preheating is 5×10 -3 ~5×10 -2 Pa; The preheating temperature is 1500 - 2000 °C.

10. The method according to claim 3, characterized in that, The conditions of the melting are as follows: The melting temperature is 3800 - 4500 °C; The melting power is 50 - 80 kW; The ingot pulling speed of the melting is 1.7 - 2 mm / min; The melting time is 20 - 60 min; The vacuum degree of the smelting is 2.5×10 -3 ~5×10 -3 Pa.

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