Vacuum split nitriding furnace for processing silicon carbide powder and method thereof

Abstract

The invention relates to the technical field of nitriding furnaces, in particular to a vacuum split nitriding furnace for silicon carbide powder processing and a method thereof.The vacuum split nitriding furnace comprises a nitriding furnace body and a condenser, and the nitriding furnace is externally connected with the condenser and a circulating pump, so that when the pressure in the nitriding furnace is stable, the nitriding furnace is cooled; nitrogen-containing gas is driven by the circulating pump to circularly flow between the nitriding furnace and the condenser and is matched with a real-time gas supplementing mechanism, so that nitrogen and silicon powder can fully react, high-temperature gas is cooled by the condenser and then pumped into the nitriding furnace through the circulating pump, the circulating pump and a pipeline system can be protected, and the service life of the nitriding furnace is prolonged. And gas-phase by-products can be removed, gas circulation in the nitriding furnace can be ensured, and the problems that tail gas of an existing nitriding furnace is not recycled, and gas flow is not smooth are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of nitriding furnaces, and more particularly to a vacuum split nitriding furnace and method for processing silicon carbide powder. Background Art

[0002] Silicon carbide (SiC) powder is widely used in fields such as ceramics, refractories, semiconductors, and composite materials due to its excellent high-temperature stability, high hardness, corrosion resistance, and good thermal conductivity. However, in some application scenarios, the surface properties of silicon carbide powder need to be further optimized. For example, by coating a layer of silicon nitride (Si3N4) on its surface to improve its oxidation resistance, enhance high-temperature stability, or improve the interfacial bonding properties with other materials.

[0003] Currently, the nitriding treatment of silicon carbide powder is usually carried out in a high-temperature nitriding furnace under a nitrogen or ammonia atmosphere. That is, the surface of silicon carbide powder reacts with nitrogen to form silicon nitride under a high-temperature nitrogen atmosphere. This process is usually carried out in a nitriding furnace, and in the prior art, a molybdenum wire electric furnace or a molybdenum disilicide rod electric furnace is mostly used as a heating device. The furnace chamber needs to be strictly sealed, filled with silicon carbide powder, and nitrogen gas is introduced. The reaction temperature is usually controlled at 970 - 1000 °C. As the temperature rises, the reaction rate accelerates, and finally silicon nitride is formed. However, the existing nitriding furnaces still have the following technical problems: Tail gas is not recycled: The tail gas generated during the reaction is usually directly discharged into the atmosphere, which may not only cause environmental pollution, but also the residual nitrogen in the tail gas is not effectively recycled, resulting in waste of resources. Poor gas flow: If the gas flow in the furnace is uneven or fails to fully contact with the silicon carbide powder, it will lead to incomplete nitriding reaction of the silicon powder or uneven local reaction, affecting the quality and performance of the final product. Summary of the Invention

[0004] In view of the problems existing in the prior art, a vacuum split nitriding furnace and method for processing silicon carbide powder are provided. By connecting an external condenser and a circulation pump to the nitriding furnace, when the pressure in the nitriding furnace is stable, the nitrogen-containing gas is driven to circulate between the nitriding furnace and the condenser by the circulation pump, and with a real-time gas replenishment mechanism, the nitrogen can react fully with the silicon powder. Moreover, the high-temperature gas is cooled by the condenser and then pumped into the nitriding furnace by the circulation pump, which can protect the circulation pump and the pipeline system, remove gaseous by-products, and ensure the gas circulation in the nitriding furnace, solving the problems of non-recycling of tail gas and poor gas flow in the existing nitriding furnaces.

[0005] To solve the problems of the prior art, the present invention provides a vacuum split nitriding furnace for processing silicon carbide powder, which includes a nitriding furnace body and a condenser. A nitrogen-containing gas inlet, a vacuum pumping port, a circulating gas outlet and a circulating gas inlet are arranged on the nitriding furnace body, and the gas in the nitriding furnace body circulates between the nitriding furnace body and the condenser; the nitriding furnace body includes a furnace body and a hearth arranged in the furnace body. Brackets arranged at equal intervals in the vertical direction are arranged in the hearth, trays are arranged at equal intervals on the brackets, and an air cavity communicated with the nitrogen-containing gas inlet and the circulating gas inlet is arranged at the inner bottom of the tray. The top end of the air cavity is rectangularly arrayed with air holes, and the nitrogen-containing gas passes through the silicon powder placed in the tray through the air holes; a side cavity communicated with the nitrogen-containing gas inlet and the circulating gas inlet is formed between the movable plate and the side surface of the air cavity. When the pressure in the side cavity is greater than the abutting pressure of the movable plate against the air holes, the movable plate moves downward relative to the air holes.

[0006] Preferably, plug columns are rectangularly arrayed at the top end of the movable plate, and plug heads capable of fitting with the air holes are arranged at the top ends of the plug columns. A pressure cavity communicated with the side cavity is formed between the top end of the movable plate and the top end of the air cavity.

[0007] Preferably, an elastic reset element is arranged between the bottom end of the movable plate and the bottom end of the air cavity. When the pressure in the side cavity is greater than the elastic force of the elastic reset element, the movable plate moves downward relative to the air holes.

[0008] Preferably, a nitrogen-containing gas shunt pipe rack communicated with the nitrogen-containing gas inlet is arranged in the nitriding furnace body, and a circulating gas shunt pipe rack communicated with the circulating gas inlet is also arranged in the nitriding furnace body. A nitrogen-containing gas pipe capable of communicating with the nitrogen-containing gas shunt pipe rack is arranged on the bracket, and the nitrogen-containing gas pipe is communicated with the air cavity; a circulating gas pipe capable of communicating with the circulating gas inlet is also arranged on the bracket, and the circulating gas pipe is communicated with the air cavity.

[0009] Preferably, a first one-way conduction element is arranged at the connection between the nitrogen-containing gas pipe and the air cavity, and a second one-way conduction element is arranged at the connection between the circulating gas pipe and the air cavity.

[0010] Preferably, the first one-way conduction element and the second one-way conduction element have the same structure. The first one-way conduction element includes a valve seat, a valve block and a valve bead. The valve seat is arranged in the bracket and a conical port communicated with the nitrogen-containing gas pipe is arranged at the top of the valve seat. The valve block is slidably arranged in the valve seat. The valve block has an inclined groove and a valve cylinder penetrating through the valve seat and capable of communicating with the air cavity. A positioning ring and an elastic buffer element are arranged on the outside of the valve cylinder located in the valve seat. The elastic buffer element is located between the positioning ring and the inner wall of the bracket, and the valve bead is located in the inclined groove and elastically abuts against the conical port.

[0011] Preferably, one end of the valve cylinder penetrates through the bracket and forms an abutting cone head, and a fitting air port capable of fitting with the abutting cone head is arranged on the side surface of the tray. The fitting air port is communicated with the air cavity.

[0012] A vacuum split nitriding method for processing silicon carbide powder, using a vacuum split nitriding furnace for processing silicon carbide powder, includes the following steps: Step 1, evacuate the nitriding furnace body through the evacuation hole; Step 2, inject nitrogen-containing gas into the nitriding furnace body through the nitrogen-containing gas inlet; Step 3, stop gas injection after the pressure in the nitriding furnace body reaches the specified pressure, start the circulation pump, and make the gas circulate between the nitriding furnace body and the condenser; Step 4, heat up the nitriding furnace body to nitride and form the silicon carbide powder.

[0013] The beneficial effects of this application compared with the prior art are: By setting a circulation pump and a condenser in this application, the nitrogen-containing gas continuously circulates between the nitriding furnace and the condenser, which not only improves the utilization rate of nitrogen, reduces gas waste, but also enhances the reaction sufficiency between nitrogen and silicon powder, thereby significantly improving the nitriding reaction efficiency.

[0014] In this application, the high-temperature gas generated during the nitriding process is cooled by the condenser and then recycled, avoiding direct exhaust of tail gas, effectively reducing the overflow of gas-phase by-products during the nitriding reaction process, reducing environmental pollution, and realizing green and clean production.

[0015] In this application, the high-temperature tail gas is cooled by the condenser before entering the circulation pump, greatly reducing the gas temperature, effectively protecting the circulation pump and pipeline system from erosion by high-temperature gas, thereby extending the service life of the equipment and enhancing the reliability and safety of system operation.

[0016] This application also effectively improves the uniformity of gas distribution in the silicon powder through the design of the gas cavity and air holes, thereby accelerating the nitriding reaction process, reducing the nitriding time, and ensuring the uniformity and stability of the reaction. It enables the gas to penetrate the entire silicon powder layer more evenly, avoiding the limitation that the gas only contacts the surface layer in the traditional system and reducing unnecessary gas waste. The uniform air flow and clear gas channels reduce the high-temperature aggregation or system failures caused by unstable air flow, improving the safety of the nitriding process and the service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of a vacuum split nitriding furnace for processing silicon carbide powder according to the present invention.

[0018] Figure 2 is a perspective view of the nitriding furnace body in a vacuum split nitriding furnace for processing silicon carbide powder according to the present invention.

[0019] Figure 3It is a cross-sectional view of the nitriding furnace body in a vacuum split nitriding furnace for processing silicon carbide powder according to the present invention.

[0020] Figure 4 is Figure 3 The partial enlarged view of part A.

[0021] Figure 5 It is a schematic diagram when introducing nitrogen-containing gas in a vacuum split nitriding furnace for processing silicon carbide powder according to the present invention.

[0022] Figure 6 It is a schematic diagram of the internal structure of a vacuum split nitriding furnace for processing silicon carbide powder according to the present invention.

[0023] Figure 7 It is a schematic diagram of the bracket and the tray in a vacuum split nitriding furnace for processing silicon carbide powder according to the present invention.

[0024] Figure 8 It is a three-dimensional exploded view of the bracket and the tray in a vacuum split nitriding furnace for processing silicon carbide powder according to the present invention.

[0025] Figure 9 It is a three-dimensional view of the first one-way conduction component in a vacuum split nitriding furnace for processing silicon carbide powder according to the present invention.

[0026] Figure 10 It is a three-dimensional exploded view of the second one-way conduction component in a vacuum split nitriding furnace for processing silicon carbide powder according to the present invention.

[0027] The reference numerals in the figure are: 1, nitriding furnace body; 111, nitrogen-containing gas inlet; 112, vacuum pumping port; 113, circulating gas outlet; 114, circulating gas inlet; 12, furnace body; 13, furnace chamber; 131, positioning block; 14, bracket; 141, sliding plate; 142, nitrogen-containing gas pipe; 143, circulating gas pipe; 15, tray; 152, air hole; 153, fitting gas port; 16, movable plate; 161, side cavity; 162, plug column; 163, plug head; 164, pressure cavity; 17, elastic reset element; 181, nitrogen-containing gas shunt pipe rack; 182, circulating gas shunt pipe rack; 183, first one-way conduction component; 1831, valve seat; 1832, valve block; 1833, valve bead; 1834, valve cylinder; 1835, positioning ring; 1836, elastic buffer element; 184, second one-way conduction component; 2, condenser; 21, superheated gas inlet; 22, low-temperature gas outlet; 3, first circulation pipe; 4, second circulation pipe; 5, circulation pump. Detailed implementation manners

[0028] In order to further understand the features, technical means, specific purposes and functions achieved by the present invention, the present invention will be further described in detail below with reference to the drawings and specific implementation manners.

[0029] As Figure 1 、 Figure 2 and Figure 3 shown, a vacuum split nitriding furnace for silicon carbide powder processing includes a nitriding furnace body 1 and a condenser 2. The nitriding furnace body 1 is provided with a nitrogen-containing gas inlet 111, a vacuum pumping port 112, a circulating gas outlet 113 and a circulating gas inlet 114. The condenser 2 has a superheated gas inlet 21 and a low-temperature gas outlet 22. A first circulation pipe 3 is provided between the circulating gas outlet 113 and the superheated gas inlet 21. A second circulation pipe 4 is provided between the low-temperature gas outlet 22 and the circulating gas inlet 114. A circulation pump 5 is provided on the second circulation pipe 4. The circulation pump 5 is used to guide the low-temperature gas discharged from the condenser 2 to re-flow into the nitriding furnace body. After the nitriding furnace body 1 is evacuated, nitrogen-containing gas is injected into the nitriding furnace body 1 through the nitrogen-containing gas inlet 111. When the internal pressure of the nitriding furnace body 1 reaches the set value, the injection of nitrogen-containing gas is stopped, and the circulation pump 5 is started for gas circulation.

[0030] A vacuum split nitriding furnace system for silicon carbide powder processing includes a nitriding furnace body 1, a condenser 2, a circulation pump 5, a first circulation pipe 3 and a second circulation pipe 4. It has functions of gas circulation, heat recovery and real-time air replenishment, aiming to improve nitriding efficiency, protect equipment and realize tail gas utilization.

[0031] The structural configuration is as follows: Nitriding furnace body 1: It is provided with a nitrogen-containing gas inlet 111, a vacuum pumping port 112, a circulating gas outlet, a circulating gas inlet, and a pressure sensor (pressure gauge) is provided inside for real-time monitoring of the pressure inside the furnace.

[0032] Condenser 2: It has a high-temperature gas inlet and a low-temperature gas outlet 22, and is used for cooling the superheated tail gas generated during the nitriding process to realize the condensation of gas-phase by-products and gas reuse.

[0033] Circulation pipeline system: The first circulation pipe 3 connects the circulating gas outlet 113 of the nitriding furnace body 1 and the superheated gas inlet 21 of the condenser 2.

[0034] The second circulation pipe 4 connects the low-temperature gas outlet 22 of the condenser 2 and the circulating gas inlet 114 of the nitriding furnace body 1.

[0035] The circulation pump 5 is arranged in the second circulation pipe 4 and is used to push the cooled gas to re-flow into the nitriding furnace to form a closed-loop gas flow system.

[0036] Working process and control mechanism: Vacuum pumping and gas filling: After the system is started, the nitriding furnace body 1 is first evacuated through the vacuum port 112 to remove the residual air in the furnace; then nitrogen-containing gas (such as a mixture of nitrogen or ammonia gas) is injected through the nitrogen-containing gas inlet 111.

[0037] Pressure monitoring and gas replenishment control: When the pressure in the furnace reaches the set value, the gas filling automatically stops. The pressure gauge installed in the furnace detects the air pressure in real time. When the air pressure is lower than the set threshold, the system automatically replenishes gas through the nitrogen-containing gas inlet 111 to implement a real-time gas replenishment mechanism to maintain the reaction stability.

[0038] Gas circulation and thermal management: The high-temperature nitrogen-containing tail gas generated during the nitriding process is introduced into the condenser 2 through the first circulation pipe 3.

[0039] The condenser 2 cools the high-temperature tail gas. On the one hand, it condenses by-products (such as nitrogen oxides and volatile impurities), and on the other hand, it reduces the gas temperature to protect the circulation pump 5 and the pipeline.

[0040] The cooled low-temperature gas is pushed by the circulation pump 5 through the second circulation pipe 4 and returns to the nitriding furnace to realize the recycling of the gas.

[0041] As Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 shown, the nitriding furnace body 1 includes a furnace body 12 and a hearth 13 arranged in the furnace body 12. In the hearth 13, brackets 14 are arranged at equal intervals in the vertical direction. On the brackets 14, trays 15 are arranged at equal intervals. At the inner bottom of the tray 15, there is an air cavity communicated with the nitrogen-containing gas inlet 111 and the circulating gas inlet 114. At the top end of the air cavity, air holes 152 are arranged in a rectangular array. The nitrogen-containing gas passes through the silicon powder placed in the tray 15 through the air holes 152.

[0042] By arranging the air cavity and the air holes 152 at the bottom of the tray 15, the nitrogen-containing gas can be evenly distributed to each part of the tray 15 through the air holes 152 in the air cavity, thus avoiding the problem that the gas in the traditional nitriding furnace only contacts the surface of the silicon powder. Such a design can ensure that the gas can effectively penetrate the entire silicon powder layer, realize the full reaction of the gas and the silicon powder, and improve the nitriding efficiency.

[0043] During the nitriding process, the nitriding reaction of the silicon powder not only occurs on the surface, but can penetrate deep into the interior of the silicon powder. The design of the air cavity and the air holes 152 ensures that the nitrogen-containing gas can pass through the silicon powder layer more evenly, avoiding the problems of uneven gas flow and incomplete local reaction in the traditional method, and significantly improving the reaction uniformity and the nitriding effect of the silicon powder.

[0044] Due to the uniform arrangement of the air holes 152, the gas can flow stably when passing through the tray 15, avoiding the problem of local overheating caused by overly concentrated air flow or too fast flow rate. In addition, the design of the air cavity also provides a larger flow space for the gas, further improving the stability of the system and reducing the risk of unstable reactions or equipment failures that may be caused by uneven air flow distribution.

[0045] Sliding plates 141 are provided on both sides of the bracket 14, and sliding grooves that cooperate with the sliding plates 141 are provided in the furnace chamber 13. The bracket 14 is pushed into the sliding grooves through the sliding plates 141. A positioning block 131 that can elastically abut against the top end of the sliding plate 141 is provided at the top end of the sliding groove. Chamfers are provided on both sides of the bottom end of the positioning block 131, and a groove that can be fitted with the bottom end of the positioning block 131 is provided at the top end of the sliding plate 141. When the sliding plate 141 is pushed into the sliding groove and reaches the designated position, the positioning block 131 is fitted with the groove.

[0046] Chamfer designs are provided on both sides of the bottom end of the positioning block 131, and a groove that precisely fits with the bottom end of the positioning block 131 is provided at the top end of the sliding plate 141. This mechanical fitting locking design effectively prevents the bracket 14 from moving due to gas pressure or vibration during the pressurization process. The mutual cooperation of the positioning block 131 and the groove ensures the stability of the bracket 14 during the entire working process and avoids process instability problems caused by loosening or displacement of the bracket 14.

[0047] The positioning block 131 abuts against the top end of the sliding plate 141 through an elastic element. When the sliding plate 141 is pushed into the designated position, the elastic positioning block 131 will automatically elastically snap into the groove to achieve automatic locking without additional mechanical intervention.

[0048] During the nitriding process, the change in the gas pressure inside the furnace chamber 13 will have a certain impact on the bracket 14. The fitting design of the positioning block 131 and the groove effectively prevents the movement of the bracket 14. Even in a high-pressure environment, the bracket 14 can maintain a stable position, thus ensuring the stability of the nitriding process and the consistency of the reaction. This design can reduce the risk of uneven gas distribution and incomplete reactions caused by the displacement of the bracket 14.

[0049] As Figure 4 and Figure 5 shown, a movable plate 16 that can abut against the bottom of the air hole 152 is provided in the air cavity. A side cavity 161 that communicates with the nitrogen-containing gas inlet 111 and the circulating gas inlet 114 is formed between the movable plate 16 and the side surface of the air cavity. When the pressure in the side cavity 161 is greater than the abutting pressure of the movable plate 16 against the air hole 152, the movable plate 16 moves downward relative to the air hole 152.

[0050] During the silicon powder loading stage, since the movable plate 16 is in the upper position and closely adheres to the bottom of the air hole 152, effectively closing the air hole 152 channel, a physical barrier is formed to prevent the silicon powder from falling through the air hole 152 into the lower air cavity, avoiding blocking the channel or polluting the interior of the air cavity.

[0051] The air pressure in the side cavity 161 is dynamically controlled by being connected to the nitrogen-containing gas inlet 111 and the circulating gas inlet 114. When entering the reaction stage, the gas starts to be injected and the pressure in the side cavity 161 increases. The air pressure drives the movable plate 16 to overcome its own elastic resistance and move downward to release the seal, realizing the automatic opening of the air flow channel. The nitrogen-containing gas can smoothly flow into the tray 15 through the air hole 152.

[0052] After the air flow terminates, the movable plate 16 can automatically return to the original abutting position, blocking the possibility of dust, residues, or unreacted silicon powder falling back into the air cavity, further reducing the maintenance frequency and risk, and enhancing the continuous working ability of the equipment.

[0053] As Figure 4 and Figure 5 shown, the top of the movable plate 16 has a rectangular array of plug columns 162. The top of the plug column 162 is provided with a plug head 163 that can be fitted with the air hole 152. A pressure cavity 164 communicating with the side cavity 161 is formed between the top of the movable plate 16 and the top of the air cavity.

[0054] During the feeding process, the precise fitting of the plug head 163 with the air hole 152 effectively prevents silicon powder particles from entering the air hole 152, thus avoiding the risk of blocking the air hole 152. The particle sizes of the silicon powder are different, and it is easy to form blockage points due to friction or accumulation between particles. The design of the plug head 163 can ensure that the air hole 152 always remains unblocked.

[0055] The pressure cavity 164 is connected to the side cavity 161 to adjust the position of the movable plate 16 by using the change of air flow or air pressure. If it is necessary to release the air flow or perform subsequent reaction steps, the air pressure in the side cavity 161 will push the movable plate 16, and then push the plug head 163 away from the air hole 152 to open the air flow channel. By utilizing the change of air pressure, the sealing state of the plug head 163 can be automatically released when needed, ensuring the smooth air flow and the normal progress of the reaction.

[0056] As Figure 4 and Figure 5 shown, an elastic reset element 17 is provided between the bottom of the movable plate 16 and the bottom of the air cavity. When the pressure in the side cavity 161 is greater than the elastic force of the elastic reset element 17, the movable plate 16 moves downward relative to the air hole 152.

[0057] An elastic reset element 17 is provided between the bottom end of the movable plate 16 and the bottom end of the air cavity, usually a spring or a similar elastic element, which can generate a certain reset force on the movable plate 16 when the pressure in the side cavity 161 changes.

[0058] This design ensures that the movable plate 16 can move flexibly under the action of external pressure, and when the pressure disappears or returns to normal, the elastic reset element 17 can restore the movable plate 16 to its original position.

[0059] When the pressure in the side cavity 161 is greater than the elastic force of the elastic reset element 17, the movable plate 16 will move downward relative to the air hole 152, pushing the plug 163 out of the air hole 152 and opening the air flow channel. This downward movement enables the air hole 152 to remain open when needed, ensuring the smooth flow of air and the progress of the reaction.

[0060] Conversely, if the pressure in the side cavity 161 decreases, the elastic reset element 17 will bring the movable plate 16 back to its original position through its elastic force, so that the plug 163 is re-engaged with the air hole 152, closing the air hole 152 to prevent excessive air flow or silicon powder from entering the air hole 152.

[0061] As Figure 3 、 Figure 6 and Figure 7 shown, a nitrogen-containing gas shunt pipe rack 181 communicating with the nitrogen-containing gas inlet 111 is provided in the nitriding furnace body 1, and a circulating gas shunt pipe rack 182 communicating with the circulating gas inlet 114 is also provided in the nitriding furnace body 1. A nitrogen-containing gas pipe 142 capable of communicating with the nitrogen-containing gas shunt pipe rack 181 is provided on the bracket 14, and the nitrogen-containing gas pipe 142 communicates with the air cavity; a circulating gas pipe 143 capable of communicating with the circulating gas inlet 114 is also provided on the bracket 14, and the circulating gas pipe 143 communicates with the air cavity.

[0062] Nitrogen-containing gas shunt system: nitrogen-containing gas inlet 111 → nitrogen-containing gas shunt pipe rack 181 → nitrogen-containing gas pipe 142 → air cavity. This channel constitutes the fresh nitrogen source supply line of the entire system. The role of the shunt pipe rack is to evenly distribute the nitrogen gas entering from the inlet into multiple nitrogen-containing gas pipes 142, and these pipes are then respectively connected to the corresponding air cavities to provide independent and stable nitrogen source supply for each reaction unit. It can achieve multi-channel parallel gas supply and improve nitriding uniformity.

[0063] Circulating gas shunt system: circulating gas inlet 114 → circulating gas shunt pipe rack 182 → circulating gas pipe 143 → air cavity. This system constitutes the gas loop circulation part. The used gas re-enters the furnace body 12 through a certain method (such as through purification or heat exchange), and enters each air cavity through the circulating gas shunt pipe rack 182 to achieve resource reuse and system heat balance adjustment. It realizes a closed cycle and saves gas resources.

[0064] As Figure 3 shown, a first one-way conduction member 183 is provided at the connection between the nitrogen-containing gas pipe 142 and the gas chamber, and a second one-way conduction member 184 is provided at the connection between the circulating gas pipe 143 and the gas chamber.

[0065] The first one-way conduction member 183 is located at the connection between the nitrogen-containing gas pipe 142 and the gas chamber, and its main function is to prevent the nitrogen-containing gas from flowing backward when the circulating gas is flowing. During normal operation, the nitrogen-containing gas enters the gas chamber through this conduction member, but when the pressure in the gas chamber changes or the circulating gas flows, the conduction member will close to prevent external gas from flowing backward into the nitrogen-containing gas pipe 142, ensuring the one-way fluidity of gas distribution.

[0066] The second one-way conduction member 184 is located at the connection between the circulating gas pipe 143 and the gas chamber, and its function is to prevent the circulating gas from flowing backward when nitrogen-containing gas is injected. That is, during the injection of nitrogen-containing gas, the second one-way conduction member 184 will automatically close to prevent the newly injected nitrogen-containing gas from entering the circulating pipeline, ensuring the complete independence of the two gas systems.

[0067] As Figure 4 、 Figure 9 and Figure 10 shown, the structures of the first one-way conduction member 183 and the second one-way conduction member 184 are the same. The first one-way conduction member 183 includes a valve seat 1831, a valve block 1832 and a valve bead 1833. The valve seat 1831 is arranged in the bracket 14 and a tapered opening communicating with the nitrogen-containing gas pipe 142 is provided at its top. The valve block 1832 is slidably arranged in the valve seat 1831. The gate block has an inclined groove and a valve cylinder 1834 penetrating through the valve seat 1831 and capable of communicating with the gas chamber. A positioning ring 1835 and an elastic buffer element 1836 are provided on the outside of the valve cylinder 1834 located in the valve seat 1831. The elastic buffer element 1836 is located between the positioning ring 1835 and the inner wall of the bracket 14. The valve bead 1833 is located in the inclined groove and elastically abuts against the tapered opening.

[0068] When the gas pressure flowing in the nitrogen-containing gas pipe 142 reaches a certain value, the pressure at the top of the valve bead 1833 increases accordingly, and then the valve bead 1833 is urged to slide downward along the path of the inclined groove of the valve block 1832. At this time, the sealing contact point between the valve bead 1833 and the valve seat 1831 is broken through, resulting in the formation of a channel between the nitrogen-containing gas pipe 142 and the valve seat 1831, thereby realizing gas communication.

[0069] Since the valve bead 1833 is placed in the inclined groove of the valve block 1832, the sliding of the valve block 1832 will be accompanied by the movement of the valve bead 1833. Specifically, when the valve bead 1833 moves downward, the valve block 1832 can overcome the elastic force provided by the elastic buffer element 1836 (usually a spring or a similar flexible element), and then push the valve block 1832 downward while connecting with the valve seat 1831, thereby guiding the opening of the channel between the valve barrel 1834 and the air cavity, forming an effective connection between the nitrogen-containing gas pipe 142 and the air cavity.

[0070] During this process, the change in the pressure in the air cavity also affects the actions of the valve block 1832 and the valve bead 1833. When the air pressure in the air cavity increases, the action of the valve block 1832 will automatically reverse, re-closing the channel. At this time, the valve bead 1833 will return to its original position due to its structure and elastic design, and re-seal the contact with the conical opening, preventing any reverse flow of gas and avoiding the backflow of gas into the air cavity through the nitrogen-containing gas pipe 142.

[0071] As Figure 4 、 Figure 9 and Figure 10 shown, one end of the valve barrel 1834 penetrates through the bracket 14 and forms a butt conical head, and the side surface of the tray 15 is provided with a fitting air port 153 that can be fitted with the butt conical head, and the fitting air port 153 communicates with the air cavity.

[0072] The fitting air port 153 communicates with the air cavity, so that the gas inside the valve barrel 1834 can be smoothly guided to the air cavity, realizing the closed-loop path of the high-pressure gas entering the air cavity from the nitrogen-containing gas pipe 142 through the conduction structure. The conical surface contact between the butt conical head and the fitting air port 153 can remain stable under the impact of multi-directional airflows, preventing the tray 15 from displacing or shaking in the horizontal or vertical direction due to sudden airflow pressure.

[0073] A vacuum split nitriding method for processing silicon carbide powder, using a vacuum split nitriding furnace for processing silicon carbide powder, includes the following steps: Step 1, evacuate the nitriding furnace body 1 through the vacuum hole; Step 2, inject nitrogen-containing gas into the nitriding furnace body 1 through the nitrogen-containing gas inlet 111; Step 3, stop injecting gas after the pressure in the nitriding furnace body 1 reaches the specified pressure, start the circulation pump 5, and make the gas circulate between the nitriding furnace body 1 and the condenser 2; Step 4, heat up the nitriding furnace body 1 to nitride and form the silicon carbide powder.

[0074] The above embodiments merely represent one or several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the appended claims.

Claims

1. A vacuum split nitriding furnace for processing silicon carbide powder, characterized in that, It includes a nitriding furnace body and a condenser. A nitrogen-containing gas inlet, a vacuum pumping port, a circulating gas outlet and a circulating gas inlet are provided on the nitriding furnace body. The gas in the nitriding furnace body circulates between the nitriding furnace body and the condenser; The nitriding furnace body includes a furnace body and a hearth arranged in the furnace body. Brackets arranged at equal intervals in the vertical direction are provided in the hearth. Trays are provided at equal intervals on the brackets. An air cavity communicated with the nitrogen-containing gas inlet and the circulating gas inlet is provided at the inner bottom of the tray. Air holes are arranged in a rectangular array at the top end of the air cavity. The nitrogen-containing gas passes through the silicon powder placed in the tray through the air holes; An activity plate capable of abutting against the bottom of the air hole is arranged in the air cavity. A side cavity communicated with the nitrogen-containing gas inlet and the circulating gas inlet is formed between the activity plate and the side surface of the air cavity. When the pressure in the side cavity is greater than the abutting pressure of the activity plate against the air hole, the activity plate moves downward relative to the air hole.

2. The vacuum split nitriding furnace for processing silicon carbide powder according to claim 1, wherein, Plug columns are arranged in a rectangular array at the top end of the activity plate. A plug head capable of fitting with the air hole is arranged at the top end of the plug column. A pressure cavity communicated with the side cavity is formed between the top end of the activity plate and the top end of the air cavity.

3. A vacuum split nitriding furnace for processing silicon carbide powder according to claim 1 or 2, characterized in that, An elastic reset element is arranged between the bottom end of the activity plate and the bottom end of the air cavity. When the pressure in the side cavity is greater than the elastic force of the elastic reset element, the activity plate moves downward relative to the air hole.

4. A vacuum split nitriding furnace for processing silicon carbide powder according to claim 1 or 2, characterized in that, A nitrogen-containing gas shunt pipe rack communicated with the nitrogen-containing gas inlet is arranged in the nitriding furnace body. A circulating gas shunt pipe rack communicated with the circulating gas inlet is also arranged in the nitriding furnace body. A nitrogen-containing gas pipe capable of communicating with the nitrogen-containing gas shunt pipe rack is arranged on the bracket. The nitrogen-containing gas pipe is communicated with the air cavity; A circulating gas pipe capable of communicating with the circulating gas inlet is also arranged on the bracket. The circulating gas pipe is communicated with the air cavity.

5. The vacuum split nitriding furnace for processing silicon carbide powder according to claim 4, characterized in that, A first one-way conduction part is arranged at the connection of the nitrogen-containing gas pipe and the air cavity. A second one-way conduction part is arranged at the connection of the circulating gas pipe and the air cavity.

6. A vacuum split nitriding furnace for processing silicon carbide powder according to claim 5, characterized in that, The structures of the first one-way conduction part and the second one-way conduction part are the same. The first one-way conduction part includes a valve seat, a valve block and a valve bead. The valve seat is arranged in the bracket and a conical port communicated with the nitrogen-containing gas pipe is arranged at its top. The valve block is slidably arranged in the valve seat. The valve block has an inclined groove and a valve cylinder penetrating through the valve seat and capable of communicating with the air cavity. A positioning ring and an elastic buffer element are arranged on the outside of the valve seat of the valve cylinder. The elastic buffer element is located between the positioning ring and the inner wall of the bracket. The valve bead is located in the inclined groove and elastically abuts against the conical port.

7. A vacuum split nitriding furnace for processing silicon carbide powder according to claim 1 or 2, characterized in that, One end of the valve cylinder penetrates through the bracket and forms an abutting cone head. A fitting air port capable of fitting with the abutting cone head is arranged on the side surface of the tray. The fitting air port is communicated with the air cavity.

8. A vacuum separate nitriding method for processing silicon carbide powder, characterized in that, Adopt a vacuum split nitriding furnace for processing silicon carbide powder as described in claim 1 or 2, including the following steps: Step 1, evacuate the nitriding furnace body through the vacuum pumping hole; Step 2, inject nitrogen-containing gas into the nitriding furnace body through the nitrogen-containing gas inlet; Step 3, stop injecting gas after the pressure in the nitriding furnace body reaches the specified pressure, start the circulating pump, and make the gas circulate between the nitriding furnace body and the condenser; Step 4, heat up the nitriding furnace body to nitride and form the silicon carbide powder.

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