High-power plasma generator for spheroidizing ceramic powder

Abstract

The high-power plasma generator comprises a cathode assembly and an anode assembly, the cathode assembly comprises a cathode, the front end of the cathode is connected with a working gas pipeline, the front end of the working gas pipeline is provided with a working gas inlet, and the outer side wall of the working gas pipeline is fixedly connected with a cathode binding post; the anode assembly comprises an anode, the front end of the anode is connected with a mixed gas pipeline, the mixed gas pipeline sleeves the working gas pipeline, a mixed gas passage is formed between the mixed gas pipeline and the working gas pipeline, the front end of the mixed gas pipeline is provided with a mixed gas inlet, and the outer side wall of the mixed gas pipeline is fixedly connected with an anode binding post; the anode is of a hollow cylindrical structure, the interior of the anode is of a step structure, the inner diameters are different, and the whole anode is composed of a step front end and a step rear end. The plasma generator provided by the utility model has the characteristics of high working voltage and high energy utilization rate, the temperature of the generated plasma is low, and the ceramic cannot be bonded in the spheroidizing process.

Description

Technical Field

[0001] The utility model belongs to the technical field of plasma and relates to a high-power plasma generator used for spheroidizing ceramic powder. Background Art

[0002] With the rapid development of integrated circuits, new energy and other fields, high-end spherical ceramic powders with excellent mechanical properties have received more and more attention. At present, spherical ceramic powders are generally prepared by ball milling, flame melting and plasma spheroidization. The surface of the ceramic spherical powder prepared by the ball milling method is rough and agglomerated seriously. The surface finish of the spherical ceramic powder prepared by the flame melting method is poor and easy to carbonize, which is not suitable for the preparation of high-end spherical ceramic powders. The spherical ceramic powder prepared by the plasma spheroidization method has the advantages of good powder dispersibility, high purity and high sphericity, which is suitable for the preparation of high-end ceramic powders. However, due to the high plasma temperature and the low temperature required for ceramic spheroidization, it is easy to cause bonding during the ceramic spheroidization process, and the heat generated by the plasma generator cannot be effectively utilized. The existing high-power plasma generator is a generator with high current and low voltage (current greater than 800A and voltage less than 100V). High current will aggravate the ablation of the plasma electrode, and impurities are easily introduced when the powder is spheroidized, which affects the large-scale application of ceramic powder prepared by the plasma spheroidization method. Utility Model Content

[0003] The utility model aims to provide a high-power plasma generator for spheroidizing ceramic powder, which has the characteristics of high operating voltage and high energy utilization rate.

[0004] The technical scheme adopted by the utility model is a high-power plasma generator for spheroidizing ceramic powder, comprising a cathode assembly and an anode assembly, wherein the cathode assembly comprises a cathode, the front end of the cathode is connected to a working gas pipeline, the front end of the working gas pipeline is provided with a working gas inlet, and the outer side wall of the working gas pipeline is fixedly connected with a cathode terminal; the anode assembly comprises an anode, the front end of the anode is connected to a mixed gas pipeline, the mixed gas pipeline is sleeved outside the working gas pipeline, a mixed gas passage is formed between the two, the front end of the mixed gas pipeline is provided with a mixed gas inlet, the interior of the working gas pipeline is the working gas passage, and the outer side wall of the mixed gas pipeline is fixedly connected with an anode terminal; the anode is a hollow cylindrical structure, the interior of which is a stepped structure, the inner diameters are different, and the whole is composed of a stepped front end and a stepped rear end.

[0005] The utility model is also characterized in that:

[0006] The cathode has a hollow cylindrical front end, a solid cone in the middle, and a solid semi-ellipsoidal rear end. A plurality of cathode airflow channels are provided in the solid cone in the middle of the cathode, and the cathode airflow channels are tangent to the inner surface of the hollow cylinder at the front end of the cathode.

[0007] The number of cathode air flow channels is 2-8 and they are evenly distributed in the circumferential direction. The sum of the cross-sectional areas of the cathode air flow channels is 0.3-0.6 times the cross-sectional area of ​​the working gas passage.

[0008] The cathode air flow channel is a through hole with an elliptical cross section. The inner diameter of each part is consistent, and the distance between the center of the elliptical cross section of each part and the cathode axis is consistent; the angle between the center of the ellipse at the inlet and outlet of the cathode air flow channel and the cathode axis is 5-35°.

[0009] The front end of the anode step is connected to the cathode air flow channel of the cathode, and the interior of this part is a conical surface, and the conical surface has the same angle as the conical surface of the cathode solid cone; behind the conical surface is a straight section, and the length of the straight section is 8-25 times its inner diameter; the length of the rear end of the step is 1 / 10-1 / 5 of the length of the front straight section, and the inner diameter is 1.2-2 times the inner diameter of the front straight section; an anode air flow channel is opened at the front end of the anode step, and the anode air flow channel is tangent to the inner surface of the hollow cylinder of the mixed gas pipeline.

[0010] The number of the anode gas flow channels is 3-12 and they are evenly distributed in the circumferential direction. The sum of the cross-sectional areas of the anode gas flow channels is 0.4-0.8 times the cross-sectional area of ​​the mixed gas passage.

[0011] The anode air flow channel is a through hole with an elliptical cross section. The inner diameter of each part is consistent, and the distance between the center of the elliptical cross section of each part and the anode axis is consistent; the angle between the center of the ellipse at the inlet and outlet of the anode air flow channel and the anode axis is 1-10°.

[0012] An injection port for ceramic powder to be spheroidized is arranged at the rear step of the anode, and the outlet of the injection port is behind the plasma arc root.

[0013] The beneficial effects of the utility model are:

[0014] (1) The utility model plasma generator is provided with a working gas pipeline and a mixed gas pipeline, and adopts a gas cooling method instead of a traditional liquid circulation cooling method. The working gas is not only used for ionization to generate plasma, but also for cooling the cathode; after the mixed gas passes through the pipeline, it is not only used to cool the anode, but also directly introduced into the discharge channel of the plasma generator to mix with the generated plasma, thereby reducing the temperature of the plasma generated by the plasma generator and making it suitable for the temperature requirements required for ceramic spheroidization; in addition, the gas cooling method avoids the waste caused by the energy taken away by the liquid during cooling (during liquid cooling, the heat taken away by the liquid cannot be used, and the cooling liquid needs to be cooled by means such as a chiller);

[0015] (2) The anode of the plasma generator of the utility model has a stepped structure, and the rear end of the step is relatively long, which can effectively increase the working voltage of the plasma generator;

[0016] (3) The anode and cathode gas flow channels of the plasma generator of the utility model are arranged to rotate at a certain angle along the circumferential direction, so that the working gas for cooling the cathode and the mixed gas for cooling the anode can adopt a swirl intake method, which can not only further increase the working voltage of the plasma generator, but also make the arc root of the plasma rotate, avoid the arc root from staying for a long time, reduce the ablation of the electrode, and improve the spheroidization quality of the powder;

[0017] (4) The plasma generator of the utility model has a simple structure and high reliability, and is suitable for the spheroidization of high-end ceramic powders. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the utility model plasma generator;

[0019] Figure 2 It is a structural schematic diagram of the cathode air flow channel in the plasma generator of the utility model;

[0020] Figure 3 It is a schematic diagram of the rotation angle of the cathode airflow channel in the plasma generator of the utility model;

[0021] Figure 4 It is a schematic diagram of the rotation angle of the anode gas flow channel in the plasma generator of the utility model.

[0022] In the figure, 1. working gas pipeline, 2. cathode terminal, 3. anode terminal, 4. mixed gas pipeline, 5. cathode air flow channel, 6. cathode, 7. anode air flow channel, 8. anode, 9. injection port of ceramic powder to be spheroidized, 10. working gas inlet, 11. mixed gas inlet, 12. working gas passage, 13. mixed gas passage, 14. plasma, 15. cathode top. DETAILED DESCRIPTION

[0023] The utility model is described in detail below with reference to the accompanying drawings and specific implementation modes.

[0024] Example 1

[0025] The utility model is a high-power plasma generator for spheroidizing ceramic powder, and its structure is as follows Figure 1As shown, it includes a cathode assembly and an anode assembly, the cathode assembly includes a cathode 6, the front end of the cathode 6 is connected to a working gas pipeline 1, the front end of the working gas pipeline 1 is provided with a working gas inlet 10, and the outer wall of the working gas pipeline 1 is fixedly connected with a cathode terminal 2; the anode assembly includes an anode 8, the front end of the anode 8 is connected to a mixed gas pipeline 4, the mixed gas pipeline 4 is sleeved outside the working gas pipeline 1, and a mixed gas passage 13 is formed between the two, the front end of the mixed gas pipeline 4 is provided with a mixed gas inlet 11, and the outer wall of the mixed gas pipeline 4 is fixedly connected with an anode terminal 3; the anode 8 is a hollow cylindrical structure, the interior of which is a stepped structure with different inner diameters, and the whole is composed of a stepped front end and a stepped rear end, and its material is tungsten alloy, copper alloy, molybdenum alloy or copper.

[0026] Example 2

[0027] On the basis of Example 1, the front end of the cathode 6 is set to be a hollow cylinder, the middle is a solid cone, and the rear end is a solid semi-ellipsoidal structure; a plurality of cathode gas flow channels 5 are opened in the solid cone portion in the middle of the cathode 6, and the cathode gas flow channels 5 are tangent to the inner surface of the hollow cylinder at the front end of the cathode 6. The number of cathode gas flow channels 5 is 2-8, and they are evenly distributed in the circumferential direction, and the sum of the cross-sectional areas of the cathode gas flow channels 5 is 0.3-0.6 times the cross-sectional area of ​​the working gas passage 12.

[0028] Example 3

[0029] The utility model is a high-power plasma generator for spheroidizing ceramic powder, and its structure is as follows Figure 1 As shown, it includes a cathode assembly and an anode assembly, the cathode assembly includes a cathode 6, the front end of the cathode 6 is connected to a working gas pipeline 1, the two can be connected by threads, the working gas pipeline 1 can be made of conductive metals such as stainless steel, copper alloy, aluminum alloy, titanium alloy, etc., preferably stainless steel; the front end of the working gas pipeline 1 is provided with a working gas inlet 10, and the inside of the working gas pipeline 1 is a working gas passage 12. The outer wall of the working gas pipeline 1 is welded or threaded with a cathode terminal 2, and the cathode terminal 2 can be made of conductive metals such as stainless steel, tungsten alloy, copper alloy, titanium alloy, etc., preferably stainless steel.

[0030] The cathode 6 can be made of a highly conductive and thermally conductive material such as tungsten alloy or copper alloy, preferably tungsten alloy. The front end of the cathode 6 is a hollow cylinder, the middle is a solid cone, and the rear end (i.e., the cathode top 15) is a solid semi-ellipsoidal structure; Figure 1 and Figure 2 As shown, a plurality of cathode gas flow channels 5 are opened in the solid cone portion in the middle of the cathode 6. The cathode gas flow channels 5 are through holes, which are tangent to the inner surface of the hollow cylinder at the front end of the cathode 6. The cross section thereof is elliptical, and the inner diameter of each portion is consistent. The center of the elliptical cross section of each portion is at the same distance from the axis of the cathode 6, as shown in FIG. Figure 3As shown, the whole is rotated clockwise or counterclockwise in the circumferential direction at an angle of α, where α is 5-35°, which means that the angle between the center of the ellipse at the entrance and exit of the channel and the axis of the cathode 6 is 5-35° (for ease of understanding, Figure 1 The complete cathode gas flow channel 5 is drawn in the figure, but in fact only a part of the cathode gas flow channel 5 can be seen in the figure, not all of it). The existence of the angle can cause the gas to rotate after passing through the channel, thereby causing the plasma to rotate, thereby improving the working voltage and stability of the plasma generator. The number of cathode gas flow channels 5 is 2-8, and they are evenly distributed in the circumferential direction. The sum of the cross-sectional areas of the cathode gas flow channels 5 is 0.3-0.6 times the cross-sectional area of ​​the working gas passage 12.

[0031] The anode assembly includes an anode 8, and the anode 8 can be made of a highly conductive and thermally conductive material such as tungsten alloy, copper alloy, molybdenum alloy, and red copper, preferably red copper. The front end of the anode 8 is connected to a mixed gas pipeline 4, and the two can be connected by threads. The mixed gas pipeline 4 can be made of conductive metals such as stainless steel, copper alloy, aluminum alloy, and titanium alloy, preferably stainless steel. The mixed gas pipeline 4 is arranged outside the working gas pipeline 1 through flanges and bolts, and the channel formed between the two is a mixed gas passage 13. A mixed gas inlet 11 is provided at the front end of the mixed gas pipeline 4, and the outer wall of the mixed gas pipeline 4 is welded or threaded with an anode terminal 3. The anode terminal 3 can be made of conductive metals such as stainless steel, tungsten alloy, copper alloy, and titanium alloy, preferably stainless steel.

[0032] The anode 8 is a hollow cylindrical structure, and its interior is a stepped structure with different inner diameters. The whole is composed of a front end of the step and a rear end of the step, and the inner diameter of the front end is smaller than that of the rear end. The front end of the step is connected to the cathode gas flow channel 5 of the cathode 6, and the interior of this part is a conical surface, and the conical surface is consistent with the conical surface angle of the solid cone of the cathode 6; behind the conical surface is a straight section, and the length of the straight section is 8-25 times its inner diameter. The length of the rear end of the step is 1 / 10-1 / 5 of the length of the front straight section, and the inner diameter is 1.2-2 times the inner diameter of the front straight section. The presence of the step can fix the plasma arc root at the rear end step, effectively increasing the working voltage of the plasma generator.

[0033] A plurality of anode gas flow channels 7 are provided at the front end of the anode 8 step. The anode gas flow channels 7 are through holes, which are tangent to the inner surface of the hollow cylinder of the mixed gas pipeline 4. The anode gas flow channels 7 have a similar structure to the cathode gas flow channels 5, and have an elliptical cross section. The inner diameter of each part is consistent, and the center of the elliptical cross section of each part is consistent with the distance from the axis of the anode 8, such as Figure 4 As shown, the whole rotates clockwise or counterclockwise in the circumferential direction at an angle of β, where β is 1-10°, which means that the angle between the center of the ellipse at the inlet and outlet of the channel and the axis of the anode 8 is 1-10° (for ease of understanding, Figure 1The complete anode gas flow channel 7 is drawn in the figure, but in fact only a part of the anode gas flow channel 7 can be seen in the figure, not all of it). The existence of the angle can make the arc root of the plasma rotate, avoid the arc root from staying for a long time, reduce the ablation of the electrode, and improve the spheroidization quality of the powder. The number of anode gas flow channels 7 is 3-12, and they are evenly distributed in the circumferential direction. The sum of the cross-sectional areas of the anode gas flow channels 7 is 0.4-0.8 times the cross-sectional area of ​​the mixed gas passage 13.

[0034] An injection port 9 for ceramic powder to be spheroidized is arranged at the rear step of the anode 8 , and the outlet of the injection port is after the arc root of the plasma 14 .

[0035] The power of the plasma generator of the utility model is 10-300kW, the current is 50-500A, and the voltage is 200-600V. The working medium used is a mixture of nitrogen, helium, and hydrogen / argon. The working gas pressure range is 0.3-0.6MPa, and the flow range is 2m 3 / h-40m 3 / h, the mixed gas pressure range is 0.3-0.6MPa, and the flow range is 2m 3 / h-100m 3 / h.

[0036] The specific steps of generating plasma by the plasma generator of the utility model are as follows:

[0037] Step 1: inject the working gas into the working gas passage 12 through the working gas inlet 10 at a pressure of 0.3-0.6 MPa and a flow rate of 2 m 3 / h-4m 3 / h working gas;

[0038] Step 2: Start the plasma generator at a low power (e.g., 20 kW). After the plasma generator is working stably, inject the mixed gas passage 13 with a pressure of 0.3-0.6 MPa and a flow rate of 2 m / s through the mixed gas inlet 11. 3 / h-4m 3 / h of mixed gas;

[0039] Step 3, during operation, adjusting the power of the plasma generator to the power required for spheroidizing the ceramic powder, and at the same time adjusting the working gas flow rate to match the power of the plasma generator, and then adjusting the mixed gas flow rate to reduce the temperature of the plasma region, thereby matching the temperature required for plasma spheroidizing the ceramic powder;

[0040] Step 4: When shutting down, first stop the plasma generator, and then adjust the working gas flow rate and the mixed gas flow rate simultaneously until they are zero.

Claims

1. A high-power plasma generator for spheroidizing ceramic powders, characterized in that: The invention comprises a cathode assembly and an anode assembly, wherein the cathode assembly comprises a cathode (6), the front end of the cathode (6) is connected to a working gas pipeline (1), the front end of the working gas pipeline (1) is provided with a working gas inlet (10), the interior of the working gas pipeline (1) is a working gas passage (12), and the outer wall of the working gas pipeline (1) is fixedly connected to a cathode terminal (2); the anode assembly comprises an anode (8), the front end of the anode (8) is connected to a mixed gas pipeline (4), the mixed gas pipeline (4) is sleeved outside the working gas pipeline (1), and a mixed gas passage (13) is formed between the two, the front end of the mixed gas pipeline (4) is provided with a mixed gas inlet (11), and the outer wall of the mixed gas pipeline (4) is fixedly connected to an anode terminal (3); the anode (8) is a hollow cylindrical structure, the interior of which is a stepped structure, the inner diameters are different, and the whole is composed of a stepped front end and a stepped rear end.

2. The high-power plasma generator for spheroidizing ceramic powder according to claim 1, characterized in that: The cathode (6) has a front end in the shape of a hollow cylinder, a middle in the shape of a solid cone, and a rear end in the shape of a solid semi-ellipsoidal structure; a plurality of cathode air flow channels (5) are provided in the solid cone portion in the middle of the cathode (6), and the cathode air flow channels (5) are tangent to the inner surface of the hollow cylinder at the front end of the cathode (6).

3. The high-power plasma generator for spheroidizing ceramic powder according to claim 2, characterized in that: The number of the cathode air flow channels (5) is 2-8 and they are evenly distributed in the circumferential direction. The sum of the cross-sectional areas of the cathode air flow channels (5) is 0.3-0.6 times the cross-sectional area of ​​the working gas passage (12).

4. The high-power plasma generator for spheroidizing ceramic powder according to claim 2, characterized in that: The cathode air flow channel (5) is a through hole, and its cross section is elliptical. The inner diameter of each part is consistent, and the distance between the center of the elliptical cross section of each part and the axis of the cathode (6) is consistent; the angle between the center of the ellipse at the inlet and outlet of the cathode air flow channel (5) and the axis of the cathode (6) is 5-35°.

5. The high-power plasma generator for spheroidizing ceramic powder according to claim 2, characterized in that: The front end of the step of the anode (8) is connected to the cathode gas flow channel (5) of the cathode (6), and the interior of this part is a conical surface, and the angle of the conical surface is consistent with the conical surface of the solid cone of the cathode (6); behind the conical surface is a straight section, and the length of the straight section is 8-25 times its inner diameter; the length of the rear end of the step is 1 / 10-1 / 5 of the length of the front straight section, and the inner diameter is 1.2-2 times the inner diameter of the front straight section; an anode gas flow channel (7) is opened at the front end of the step of the anode (8), and the anode gas flow channel (7) is tangent to the inner surface of the hollow cylinder of the mixed gas pipeline (4).

6. The high-power plasma generator for spheroidizing ceramic powder according to claim 5, characterized in that: The number of the anode gas flow channels (7) is 3-12 and they are evenly distributed in the circumferential direction. The sum of the cross-sectional areas of the anode gas flow channels (7) is 0.4-0.8 times the cross-sectional area of ​​the mixed gas passage (13).

7. The high-power plasma generator for spheroidizing ceramic powder according to claim 5, characterized in that: The anode gas flow channel (7) is a through hole, and its cross section is elliptical. The inner diameter of each part is consistent, and the distance between the center of the elliptical cross section of each part and the axis of the anode (8) is consistent; the angle between the center of the ellipse at the inlet and outlet of the anode gas flow channel (7) and the axis of the anode (8) is 1-10°.

8. The high-power plasma generator for spheroidizing ceramic powder according to claim 1, characterized in that: An injection port (9) for ceramic powder to be spheroidized is arranged at the rear step of the anode (8), and the outlet of the injection port is behind the plasma arc root.

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