A method and device for pressureless sintering of boron nitride

Abstract

The present invention relates to a method and device for pressureless sintering of boron nitride applied to the technical field of pressureless sintering of boron nitride. The pressureless sintering method comprises the following steps: S1. Raw material preparation; S2. Molding; S3. Pretreatment; S4. Pressureless sintering; S5. Cooling and post-treatment; S6. Performance testing. The pressureless sintering device comprises a housing, a cooling circulation treatment component and an intelligent controller. The sintering module controls the heating element to preheat the furnace body. The detection module controls the furnace temperature thermocouple to monitor the temperature data in the furnace. When the temperature in the furnace reaches the set temperature, the sintering module reduces the power of the heating element and controls the operation of the circulating air extraction pump and the circulating air supply pump to achieve the function of circulating heat preservation. The detection module controls the thermocouple piece to monitor the temperature of the workpiece. After sintering is completed, the cooling circulation module controls the two-way air pump to extract the hot gas in the air cavity into the heat preservation chamber for storage, preparing for the next sintering, and circulating to cool the furnace body, reducing the loss of the heating element in the preheating stage and improving the efficiency.

Description

Technical Field

[0001] The present invention relates to a sintering method, in particular to a pressureless sintering method and device for boron nitride applied in the technical field of boron nitride pressureless sintering. Background Art

[0002] The pressureless sintering device is simple and easy for industrial production. It is the most basic sintering method. This method is not only simple and feasible, but also applicable to the firing of objects with different shapes and sizes. The temperature regime is easy to control and is widely used in the sintering of nano-ceramics. It mainly achieves the densification of the green body with the least grain growth through the selection of the sintering regime. Because during the sintering process, the activation energies of particle coarsening, green body densification, and grain growth have different dependencies, that is, particle coarsening, green body densification, and grain growth mainly occur in different temperature ranges. By using this relationship, sintering conditions with a large densification rate and slow grain growth can be obtained through the control of the sintering temperature. The control of the sintering regime mainly involves controlling the heating and cooling rates, holding time, and maximum temperature, etc.

[0003] In pressureless sintering, since only the temperature regime is a controllable factor, the control of material sintering is relatively difficult, and the densification process is severely affected by factors such as powder properties and green body density.

[0004] The invention patent with the publication number CN113375454A discloses a water circulation cooling system for a vacuum sintering furnace, including a box body and a furnace body. The bottom of the furnace body is horizontally fixedly connected with a mounting plate, and the mounting plate is horizontally installed on the top of the box body through bolts. A heating chamber is horizontally installed inside the furnace body, and a water tank is horizontally installed inside the box body. A cooling mechanism for cooling the heating chamber is provided inside the furnace body. The two ends of the top of the water tank are respectively communicated with a first C-shaped pipe and a second C-shaped pipe. Radiating fins are horizontally installed on the surfaces of the first C-shaped pipe and the second C-shaped pipe located inside the box body, and there are multiple radiating fins and they are evenly distributed on the surfaces of the first C-shaped pipe and the second C-shaped pipe. A blowing mechanism for blowing air on the radiating fins is provided inside the box body.

[0005] However, at present, the cooling cycle technology used in pressureless sintering mostly adopts condensed water circulation to control the rapid cooling of the furnace body, which is prone to problems such as blockage and leakage, with high maintenance costs. Moreover, when the temperature is too high, it is easy to cause the cooling water to boil and pose a risk of steam explosion, with poor safety. When the furnace body is used again, it is necessary to reheat the cooled furnace body to the specified temperature, consuming a large amount of energy and increasing production costs.

[0006] Application Content

[0007] In view of the above-mentioned prior art, the technical problem to be solved by the present invention is that at present, the cooling cycle technology used in pressureless sintering mostly adopts the condensation water circulation to control the rapid cooling of the furnace body, which is easy to cause problems such as blockage and leakage, with high maintenance costs. Moreover, when the temperature is too high, it is easy to cause the cooling water to boil and pose a risk of steam explosion, with poor safety. When the furnace body is used again, it is necessary to reheat the cooled furnace body to the specified temperature, consuming a large amount of energy and increasing production costs.

[0008] To solve the above problems, the present invention provides a boron nitride pressureless sintering device, which includes a housing, a cooling cycle processing component and an intelligent controller. A furnace body is arranged inside the housing. The furnace body is of a hollow structure. A plurality of air cavities are arranged in a surrounding manner in the inner cavity of the furnace body. A furnace temperature thermocouple is arranged on the inner wall of the furnace body. A plurality of fixed plates and heating plates cooperating with the fixed plates are arranged inside the furnace body. A thermocouple piece is arranged on each fixed plate, and heating elements are evenly arranged on each heating plate. A buzzer is arranged on the housing;

[0009] The cooling cycle processing component includes a processing chamber and a filtering chamber. An air box and a heat preservation chamber are arranged inside the processing chamber. An air storage cavity is arranged inside the air box. An air extraction pipe penetrates and is connected to the bottom of the filtering chamber. The other end of the air extraction pipe is respectively connected to the air storage cavity and the heat preservation chamber through a multi-way pipe. A circulating air extraction pump is arranged at the connection between the air storage cavity and the air extraction pipe. A two-way air pump is arranged at the connection between the heat preservation chamber and the air extraction pipe. A ventilation pipe is connected to the air storage cavity. The other end of the ventilation pipe is connected to the inner cavity of the filtering chamber. A circulating ventilation pump is installed on the ventilation pipe;

[0010] The intelligent controller is provided with a sintering module, a detection module, a cooling cycle module and an alarm module. The sintering module is electrically connected to the heating elements, the detection module and the cooling cycle module respectively. The detection module is electrically connected to the furnace temperature thermocouple, the thermocouple piece and the cooling cycle module respectively. The cooling cycle module is electrically connected to the circulating air extraction pump, the two-way air pump and the circulating ventilation pump respectively. The alarm module is electrically connected to the detection module and the buzzer respectively.

[0011] In the above-mentioned boron nitride pressureless sintering device, the sintering module controls the heating elements to slowly preheat the furnace body. The detection module controls the furnace temperature thermocouple to continuously monitor the temperature data inside the furnace body. When the temperature inside the furnace reaches the set temperature, the sintering module reduces the power of the heating elements, and at the same time controls the operation of the circulating air extraction pump and the circulating ventilation pump to achieve the function of circulating heat preservation. The detection module controls the thermocouple piece to continuously monitor the temperature of the workpiece. If the set value is reached, the sintering module controls the heating elements to turn off. The cooling cycle module controls the two-way air pump to pump the hot gas in the air cavity into the heat preservation chamber for storage, and controls the circulating air extraction pump and the circulating ventilation pump to circulate and cool the furnace body. While achieving rapid cooling, it also prepares for the preheating of the next sintering, reduces the loss of the heating elements in the preheating stage, and improves the efficiency.

[0012] As a further improvement of the present application, a cooling component is provided inside the air box, and the cooling circulation module is electrically connected to the cooling component.

[0013] As a further improvement of the present application, the heat preservation chamber is made of heat preservation materials, and a temperature sensor and a pressure sensor are provided inside the heat preservation chamber. The temperature sensor is arranged at the connection between the heat preservation chamber and the air extraction pipe. An inflation pipe communicating with the gas storage cavity is provided on the air box, and a gas valve switch is arranged at the connection between the input end of the inflation pipe and the air box. The detection module is electrically connected to the temperature sensor and the pressure sensor respectively.

[0014] As a further improvement of the present application, a filter is provided at the bottom of the inner cavity of the filter chamber. A plurality of air holes are circumferentially formed on the filter, and the air holes are communicated with the air extraction pipe. A pressure sensor is arranged at the connection between the air holes and the air extraction pipe. A partition is provided at the top of the filter chamber, and the filter chamber is fixedly connected to the furnace body through the partition. The detection module is electrically connected to the pressure sensor.

[0015] As a supplement to the further improvement of the present application, a temperature sensor and a pressure sensor are provided inside the heat preservation chamber. The temperature sensor is arranged at the connection between the heat preservation chamber and the air extraction pipe. The detection module is electrically connected to the temperature sensor and the pressure sensor respectively.

[0016] As another improvement of the present application, a vacuum cavity is formed between the inner wall of the housing and the outer wall of the furnace body. A plurality of fixing rods are arranged between the housing and the furnace body. A vacuum pump is provided on the housing, and the input end of the vacuum pump is communicated with the vacuum cavity through a vacuum pipe. The sintering module is electrically connected to the vacuum pump.

[0017] As a supplement to another improvement of the present application, sliding telescopic components are provided on both sides of each fixing plate. Each sliding telescopic component includes a sliding groove, a telescopic member and a sliding rod. The sliding groove is fixed on the inner wall of the housing. The telescopic member is arranged on the sliding groove, and a threaded structure matching the sliding rod is arranged at the output end of the telescopic member. The sliding rod is fixed on both sides of the fixing plate. The sintering module is electrically connected to the telescopic member.

[0018] As a supplement to another improvement of the present application, a switchable furnace door is provided on the housing. A rubber gasket is provided on the furnace door, and an O-shaped rubber sealing ring matching the rubber gasket is provided on the furnace body.

[0019] A method for pressureless sintering of boron nitride includes the following steps:

[0020] S1. Raw material preparation: Using high-purity hexagonal boron nitride powder as the raw material, adding a sintering aid according to a set value to promote sintering, and mixing the materials to obtain raw material powder;

[0021] S2. Shaping: First, load the raw material powder into a stainless-steel mold and perform cold pressing by means of bi-directional pressing to form a preliminary green body. Apply uniform pressure to the green body in a high-pressure liquid or gas environment to obtain a dense preform;

[0022] S3. Pretreatment: Pre-sinter the preform. Place the preform in a furnace body and pre-heat it at a relatively low temperature to remove moisture and volatile substances in the raw materials. At the same time, conduct partial reactions in air or a protective atmosphere to obtain a pre-treated green body;

[0023] S4. Pressureless sintering: The main sintering stage is carried out under the condition of no external pressure. Place the pre-treated preform in a pressureless sintering device, use an inert gas to control the sintering atmosphere, reduce the oxidation of boron nitride, and maintain its chemical purity and performance;

[0024] S5. Cooling and post-treatment: After the sintering in step S4 is completed, cool it slowly to reduce thermal stress and reduce crack generation. According to the setting, perform post-treatment steps such as cutting, grinding, and polishing to achieve the required dimensions and surface finish;

[0025] S6. Performance testing: Conduct performance tests on the sintered boron nitride ceramic, such as density, hardness, thermal conductivity, and electrical insulation, to ensure that it meets the application requirements.

[0026] In summary, during sintering, the sintering module controls the heating element to pre-heat the furnace body slowly. The detection module controls the furnace temperature thermocouple to monitor the temperature data in the furnace body in real time. When the temperature in the furnace reaches the set temperature, the sintering module reduces the power of the heating element and at the same time controls the operation of the circulating air extraction pump and the circulating air supply pump to achieve a circulating effect. When the thermocouple detects that the temperature of the workpiece reaches the set value, turn off the circulating air extraction pump and the circulating air supply pump and increase the power of the heating element to make the temperature reach the peak and maintain the temperature in the furnace until the thermocouple detects that the temperature reaches the set value; at the end of sintering, the sintering module controls the heating element to turn off. The cooling circulation module controls the bi-directional air pump to pump the hot gas in the air chamber into the heat preservation chamber for storage, and controls the circulating air extraction pump and the circulating air supply pump to circulate and cool the furnace body. While achieving rapid cooling, it can also effectively store the hot gas. During the next pressureless sintering process, introduce the hot gas, reduce the loss of the heating element in the pre-heating stage, reduce costs, and at the same time reduce the pre-heating time and improve efficiency. Description of the Drawings

[0027] Figure 1 Structural schematic diagram of the sintering device for the first and second embodiments of the present application;

[0028] Figure 2 Side sectional view of the sintering device for the first and second embodiments of the present application;

[0029] Figure 3Cross-sectional structure analysis diagram of the sintering equipment for the first and second embodiments of the present application;

[0030] Figure 4 Schematic diagram of the connection structure between the filter bin and the furnace body for the first and second embodiments of the present application;

[0031] Figure 5 Schematic diagram of the filter bin and the processing bin structures for the first and second embodiments of the present application;

[0032] Figure 6 Side cross-sectional analysis diagram of the internal structure of the air box for the first and second embodiments of the present application;

[0033] Figure 7 Intelligent controller control flow chart for the first embodiment of the present application;

[0034] Figure 8 Schematic diagram of the sliding and telescoping component structure for the first and second embodiments of the present application;

[0035] Figure 9 Intelligent controller control flow chart for the second embodiment of the present application.

[0036] Description of the reference numerals in the figure:

[0037] 1. Housing; 2. Cooling cycle processing component; 3. Intelligent controller; 11. Furnace body; 12. Air cavity; 13. Buzzer; 101. Furnace temperature thermocouple; 102. Fixed plate; 103. Heating plate; 104. Thermocouple piece; 105. Heating element; 106. Vacuum cavity; 107. Fixed rod; 108. Vacuum pump; 109. Vacuum tube; 110. Furnace door; 111. Rubber gasket; 112. Rubber sealing ring; 113. Sliding groove; 114. Telescoping member; 115. Sliding rod; 201. Processing bin; 202. Filter bin; 203. Air box; 204. Insulation chamber; 205. Exhaust pipe; 206. Circulating exhaust pump; 207. Bidirectional air pump; 208. Air storage cavity; 209. Cooling component; 210. Temperature sensor; 211. Inflation pipe; 212. Air valve switch; 213. Filter; 214. Air pressure sensor; 215. Partition board; 216. Vent pipe; 217. Circulating ventilation pump; 218. Pressure sensor. Specific embodiments

[0038] The following provides a detailed description of the two embodiments of the present application in conjunction with the accompanying drawings.

[0039] The first embodiment:

[0040] Figures 1 - 7Disclosed is a boron nitride pressureless sintering device, including a housing 1, a cooling circulation processing component 2 and an intelligent controller 3. A furnace body 11 is arranged inside the housing 1. The furnace body 11 is of a hollow structure. A plurality of air cavities 12 are arranged in a surrounding manner in the inner cavity of the furnace body 11. By inflating the air cavities 12, heat preservation of the furnace body 11 can be achieved. At the same time, cold air can also be circulated and filled into the air cavities 12 to achieve the effect of quickly cooling the furnace body 11. A furnace temperature thermocouple 101 is arranged on the inner wall of the furnace body 11 to monitor the temperature of the furnace body 11 in real time and transmit data to the intelligent controller 3. A plurality of fixed plates 102 and heating plates 103 matched with the fixed plates 102 are arranged inside the furnace body 11. A thermocouple sheet 104 is arranged on each fixed plate 102 to monitor the workpiece temperature in real time. The intelligent controller 3 analyzes and precisely controls the temperature change in the furnace to improve the production quality of the workpiece. Heating elements 105 are evenly arranged on each heating plate 103 to uniformly heat the workpiece and improve the quality. A buzzer 13 is arranged on the housing 1. In case of an emergency, an alarm is issued in real time to remind the maintenance personnel;

[0041] The cooling circulation processing component 2 includes a processing chamber 201 and a filtering chamber 202. An air box 203 and a heat preservation chamber 204 are arranged inside the processing chamber 201. An air storage cavity 208 is arranged inside the air box 203 for storing inert gas and cooling in the air box 203. A suction pipe 205 penetrates and is connected to the bottom of the filtering chamber 202. The other end of the suction pipe 205 is respectively connected to the air storage cavity 208 and the heat preservation chamber 204 through a multi-way pipe to control the flow of the inert gas in the air cavity 12 between the air storage cavity 208 and the heat preservation chamber 204 during the sintering process, so as to achieve the effect of controlling the temperature of the furnace body 11 and storing the hot gas, facilitating shortening the heating time of the furnace body 11 during the next sintering, reducing the loss of the heating element 105 at the same time, and improving the efficiency. A circulating air suction pump 206 is arranged at the connection between the air storage cavity 208 and the suction pipe 205. A two-way air pump 207 is arranged at the connection between the heat preservation chamber 204 and the suction pipe 205. A ventilation pipe 216 is connected to the air storage cavity 208. The other end of the ventilation pipe 216 is connected to the inner cavity of the filtering chamber 202. A circulating ventilation pump 217 is installed on the ventilation pipe 216 to play a role in quickly cooling, maintaining the temperature, storing the hot gas and improving the sintering efficiency during the sintering process by controlling the circulating air suction pump 206, the two-way air pump 207 and the circulating ventilation pump 217;

[0042] The intelligent controller 3 is provided with a sintering module, a detection module, a cooling cycle module and an alarm module. The sintering module is electrically connected to the heating element 105, the detection module and the cooling cycle module respectively. The sintering module is used to control the sintering process of the sintering device and the loading and unloading of materials. The detection module is electrically connected to the furnace temperature thermocouple 101, the thermocouple piece 104 and the cooling cycle module respectively. The detection module is used to monitor the temperature inside the furnace and the temperature of the workpiece in real time and analyze the data. The cooling cycle module is electrically connected to the circulating air extraction pump 206, the two-way air pump 207 and the circulating ventilation pump 217 respectively. The cooling cycle module is used to control the sintering device to maintain the temperature of the furnace body 11 and rapidly cool it. The alarm module is electrically connected to the detection module and the buzzer 13 respectively. The alarm module is used to issue an alarm in real time when an emergency occurs to remind the maintenance personnel.

[0043] Thus, during sintering, the sintering module controls the heating element 105 to slowly preheat the furnace body 11. The detection module controls the furnace temperature thermocouple 101 to monitor the temperature of the furnace body 11 in real time and transmit data to the intelligent controller 3 until the temperature inside the furnace reaches the set value (the preset standard value of the workpiece preheating temperature detected by the furnace temperature thermocouple 101 in the detection module). The sintering module reduces the power of the heating element 105 and at the same time controls the circulating air extraction pump 206 and the circulating ventilation pump 217 to operate to achieve the effect of circulating and transporting hot and cold gases and maintain the temperature inside the furnace until the thermocouple piece 104 monitors that the workpiece temperature reaches the preheating value (the preset standard value of the workpiece preheating temperature detected by the thermocouple piece 104 in the detection module). Then it controls the circulating air extraction pump 206 and the circulating ventilation pump 217 to close and increases the power of the heating element 105 to raise the temperature inside the furnace to the peak value (the preset standard value of the workpiece sintering stable temperature detected by the furnace temperature thermocouple 101 in the detection module), and controls the circulating air extraction pump 206, the circulating ventilation pump 217 and the heating element 105 to assist in maintaining the temperature inside the furnace until the thermocouple piece 104 monitors that the workpiece temperature reaches the completion value (the preset standard value of the workpiece sintering stable temperature detected by the thermocouple piece 104 in the detection module), and determines that the non-pressure sintering of the workpiece is completed. The sintering module controls the heating element 105 to turn off. The cooling cycle module controls the two-way air pump 207 to pump the hot gas in the air chamber 12 into the heat preservation chamber 204 for storage. After pumping, it controls the circulating air extraction pump 206 and the circulating ventilation pump 217 to rapidly cool the furnace body 11. While achieving rapid cooling, it can also effectively store the hot gas. In the next non-pressure sintering process, the hot gas is introduced to reduce the loss of the heating element 105 in the preheating stage, reduce costs, and at the same time reduce the preheating time and improve efficiency.

[0044] Please refer to Figure 6 and Figure 7, a cooling component 209 is arranged in the air box 203. The cooling circulation module is electrically connected to the cooling component 209. The inert gas stored in the gas storage cavity 208 is cooled by the arranged cooling component 209, which is used for the circulation mechanism to maintain the temperature in the furnace and rapidly cool down.

[0045] The cooling component 209 is a common component in the art for rapidly cooling gas by a compressor. It compresses the gas through a built-in compressor to dissipate heat to the outside, so as to achieve the purpose of reducing the temperature of the internal gas. It is a well-known prior art to those skilled in the art and is not within the protection scope of the technical solution of this application. The specific structure and working principle thereof will not be elaborated herein.

[0046] Please refer to Figure 2 and Figure 6 , the heat preservation chamber 204 is made of heat preservation materials to keep the thermally inert gas stored in the heat preservation chamber 204 warm. An inflation pipe 211 communicating with the gas storage cavity 208 is arranged on the air box 203. A gas valve switch 212 is arranged at the connection between the input end of the inflation pipe 211 and the air box 203, and the internal inert gas is supplemented and replaced.

[0047] Please refer to Figure 2 、 Figure 4 and Figure 7 , a filter 213 is arranged at the bottom of the inner cavity of the filter chamber 202. A plurality of air holes are circumferentially formed on the filter 213. The gas in the air cavity 12 is filtered by the filter 213 to prevent deterioration and pollution in the inert gas. The air holes are communicated with the air extraction pipe 205. A pressure sensor 214 is arranged at the connection between the air holes and the air extraction pipe 205 to monitor the air pressure in the filter 213 in real time and compare it with the air pressure in the normal operation state. If the pressure difference is too large (greater than the pressure difference range detected by the pressure sensor 214 preset in the detection module when it is blocked), the alarm module controls the buzzer 13 to give an alarm. A partition plate 215 is arranged at the top of the filter chamber 202. The filter chamber 202 is fixedly connected to the furnace body 11 through the partition plate 215 to separate the furnace body 11 from the filter chamber 202. The detection module is electrically connected to the pressure sensor 214.

[0048] It can be seen from this that the ingenious structural design of the present invention lies in that during the sintering process, the detection module controls the furnace temperature thermocouple 101 to monitor the temperature of the furnace body 11 in real time, the thermocouple piece 104 monitors the workpiece temperature in real time, and transmits data to the intelligent controller 3. The intelligent controller 3 analyzes and controls the circulating air extraction pump 206, the circulating air supply pump 217 and the heating element 105 to assist in maintaining the temperature in the furnace, accurately controlling the temperature change in the furnace. And after the sintering is completed, the set two-way air pump 207 pumps the hot gas in the air cavity 12 into the heat preservation chamber 204 for storage. The stored hot gas is introduced into the air cavity 12 during the second sintering process, reducing the loss of the heating element 105, reducing costs and improving efficiency. At the same time, the circulating air extraction pump 206 and the circulating air supply pump 217 rapidly cool the furnace body 11. For this purpose, the cooling component 209 arranged in the air box 203 rapidly cools the inert gas during the cooling cycle, further improving the cooling efficiency. The heat preservation chamber 204 uses heat preservation materials to increase the heat preservation time of the hot inert gas. The set air valve switch 212 prevents gas deterioration and pollution by supplementing and replacing the internal inert gas. During the sintering and cooling processes, the gas in the air cavity 12 is filtered through the filter 213 to prevent the inert gas from being polluted.

[0049] The second embodiment:

[0050] Figure 2 and Figure 9 shows a boron nitride pressureless sintering device. Different from the first embodiment, a temperature sensor 210 and a pressure sensor 218 are arranged in the heat preservation chamber 204. The temperature sensor 210 is arranged at the connection between the heat preservation chamber 204 and the air extraction pipe 205. The detection module is electrically connected to the temperature sensor 210 and the pressure sensor 218 respectively. The temperature sensor 210 monitors the temperature of the hot inert gas pumped into the heat preservation chamber 204 by the air extraction pipe 205 in real time. If the temperature is lower than the set value (the lowest temperature for collecting heat preservation gas detected by the temperature sensor 210 preset in the detection module), the two-way air pump 207 is closed and the pumping of the hot inert gas is stopped. The pressure sensor 218 monitors the air pressure value of the hot inert gas in the heat preservation chamber 204 in real time. If the air pressure value is higher than the set value (the air pressure that the heat preservation chamber 204 can store gas detected by the pressure sensor 218 preset in the detection module), the two-way air pump 207 is closed and the pumping of the hot inert gas is stopped.

[0051] Please refer to Figures 1 - 3 and Figure 9 , a vacuum cavity 106 is formed between the inner wall of the housing 1 and the outer wall of the furnace body 11. A plurality of fixing rods 107 are arranged between the housing 1 and the furnace body 11. A vacuum pump 108 is arranged on the housing 1. The input end of the vacuum pump 108 is connected to the vacuum cavity 106 through a vacuum pipe 109. The sintering module is electrically connected to the vacuum pump 108. The gas in the vacuum cavity 106 is pumped out by the vacuum pump 108 to form a vacuum state, achieving a good heat preservation effect.

[0052] Please refer to Figure 8 and Figure 9 Figure 9 , on both sides of each fixing plate 102, there are sliding and telescopic components arranged. Each sliding and telescopic component includes a sliding groove 113, a telescopic member 114, and a sliding rod 115. The sliding groove 113 is fixed to the inner wall of the housing 1. The telescopic member 114 is arranged on the sliding groove 113. The output end of the telescopic member 114 is provided with a threaded structure that cooperates with the sliding rod 115. The sliding rod 115 is fixed to both sides of the fixing plate 102. The sintering module is electrically connected to the telescopic member 114. During unloading and loading, the sintering module controls the output end of the telescopic member 114 to rotate. The telescopic member 114 drives the sliding rod 115 to perform horizontal movement through the threaded linkage structure arranged on the output end of the telescopic member 114 and the sliding rod 115, which can automatically control the process of loading and unloading sintered workpieces, and sintering personnel are not easily affected by and scalded by the residual heat.

[0053] Please refer to Figures 1 - 3 Figures 1 - 3 , on the housing 1, there is a switchable furnace door 110. A rubber gasket 111 is arranged on the furnace door 110. An O-ring rubber seal 112 that cooperates with the rubber gasket 111 is arranged on the furnace body 11. During the sintering preparation process, when the furnace door 110 is closed, the rubber gasket 111 and the O-ring rubber seal 112 are fixed together to achieve a perfect sealing effect.

[0054] A boron nitride pressureless sintering method, which relates to a boron nitride pressureless sintering device provided above, includes the following steps:

[0055] S1. Raw material preparation: Use high-purity hexagonal boron nitride powder as the raw material, add sintering aids according to the set value to promote sintering, and mix the materials to obtain raw material powder;

[0056] S2. Molding: First, load the raw material powder into a stainless steel mold, and perform cold pressing through a two-way pressing method to form a preliminary green body. In order to further improve the density and uniformity of the green body, uniform pressure can be applied to the green body in a high-pressure liquid or gas environment to obtain a dense preform;

[0057] S3. Pretreatment: Perform pre-sintering on the preform. Put the preform into the furnace body 11, and preheat it at a lower temperature to remove moisture and volatiles in the raw material. At the same time, perform partial reactions in air or a protective atmosphere to obtain a pre-treated green body;

[0058] S4. Pressureless sintering: The main sintering stage is carried out under the condition of no external pressure. Place the pre-treated preform in a pressureless sintering device, use an inert gas to control the sintering atmosphere, reduce the oxidation of boron nitride, and maintain its chemical purity and performance;

[0059] S5. Cooling and Post-treatment: After the sintering in step S4 is completed, it is slowly cooled to reduce thermal stress and crack generation. Then, cutting, grinding, and polishing post-treatment steps are carried out according to the settings to achieve the required dimensions and surface finish.

[0060] S6. Performance Testing: The sintered boron nitride ceramic is subjected to performance tests such as density, hardness, thermal conductivity, and electrical insulation to ensure that it meets the application requirements.

[0061] Combined with the current actual requirements, the above-mentioned implementation methods adopted in this application, the protection scope is not limited to this. Within the scope of knowledge possessed by those skilled in the art, various changes made without departing from the concept of this application still fall within the protection scope of the present invention.

Claims

1. A boron nitride pressureless sintering device, characterized in that, It includes a housing (1), a cooling cycle processing component (2), and an intelligent controller (3); A furnace body (11) is arranged inside the housing (1). The furnace body (11) is of a hollow structure. A plurality of air cavities (12) are arranged in a surrounding manner in the inner cavity of the furnace body (11). A furnace temperature thermocouple (101) is arranged on the inner wall of the furnace body (11). A plurality of fixing plates (102) and heating plates (103) cooperating with the fixing plates (102) are arranged inside the furnace body (11). A thermocouple piece (104) is arranged on each fixing plate (102). Heating elements (105) are evenly arranged on each heating plate (103). A buzzer (13) is arranged on the housing (1); The cooling cycle processing component (2) includes a processing chamber (201) and a filtering chamber (202). An air box (203) and a heat preservation chamber (204) are arranged inside the processing chamber (201). An air storage cavity (208) is arranged inside the air box (203). An air extraction pipe (205) is connected through the bottom of the filtering chamber (202). The other end of the air extraction pipe (205) is respectively communicated with the air storage cavity (208) and the heat preservation chamber (204) through a multi-way pipe, controlling the flow of the inert gas in the air cavity (12) between the air storage cavity (208) and the heat preservation chamber (204) during the sintering process. A circulating air extraction pump (206) is arranged at the connection of the air storage cavity (208) and the air extraction pipe (205). A two-way air pump (207) is arranged at the connection of the heat preservation chamber (204) and the air extraction pipe (205). A ventilation pipe (216) is connected to the air storage cavity (208). The other end of the ventilation pipe (216) is communicated with the inner cavity of the filtering chamber (202). A circulating ventilation pump (217) is installed on the ventilation pipe (216); The intelligent controller (3) is provided with a sintering module, a detection module, a cooling cycle module, and an alarm module. The sintering module is electrically connected to the heating elements (105), the detection module, and the cooling cycle module respectively. The detection module is electrically connected to the furnace temperature thermocouple (101), the thermocouple pieces (104), and the cooling cycle module respectively. The cooling cycle module is electrically connected to the circulating air extraction pump (206), the two-way air pump (207), and the circulating ventilation pump (217) respectively. The alarm module is electrically connected to the detection module and the buzzer (13) respectively.

2. The pressureless sintering device for boron nitride according to claim 1, wherein: A cooling component (209) is arranged inside the air box (203). The cooling cycle module is electrically connected to the cooling component (209).

3. The pressureless sintering device for boron nitride according to claim 2, characterized in that: The heat preservation chamber (204) is made of heat preservation materials. An inflation pipe (211) communicated with the air storage cavity (208) is arranged on the air box (203). An air valve switch (212) is arranged at the connection of the input end of the inflation pipe (211) and the air box (203).

4. The pressureless sintering device for boron nitride according to claim 1, wherein: At the bottom of the inner cavity of the filter chamber (202), a filter (213) is provided. A plurality of air holes are circumferentially formed on the filter (213). The air holes are communicated with the air extraction pipe (205). A pressure sensor (214) is provided at the connection between the air holes and the air extraction pipe (205). At the top of the filter chamber (202), a partition plate (215) is provided. The filter chamber (202) is fixedly connected to the furnace body (11) through the partition plate (215). The detection module is electrically connected to the pressure sensor (214).

5. The pressureless sintering device for boron nitride according to claim 3, characterized in that: A temperature sensor (210) and a pressure sensor (218) are provided in the heat preservation chamber (204). The temperature sensor (210) is provided at the connection between the heat preservation chamber (204) and the air extraction pipe (205). The detection module is electrically connected to the temperature sensor (210) and the pressure sensor (218) respectively.

6. The pressureless sintering device for boron nitride according to claim 1, wherein: A vacuum chamber (106) is formed between the inner wall of the housing (1) and the outer wall of the furnace body (11). A plurality of fixing rods (107) are provided between the housing (1) and the furnace body (11). A vacuum pump (108) is provided on the housing (1). The input end of the vacuum pump (108) is communicated with the vacuum chamber (106) through a vacuum pipe (109). The sintering module is electrically connected to the vacuum pump (108).

7. A boron nitride pressureless sintering device according to claim 1, characterized in that: On both sides of each fixing plate (102), a sliding and telescoping assembly is provided. Each sliding and telescoping assembly includes a sliding groove (113), a telescoping member (114), and a sliding rod (115). The sliding groove (113) is fixed to the inner wall of the housing (1). The telescoping member (114) is provided on the sliding groove (113). The output end of the telescoping member (114) is provided with a threaded structure that cooperates with the sliding rod (115). The sliding rod (115) is fixed to both sides of the fixing plate (102). The sintering module is electrically connected to the telescoping member (114).

8. A boron nitride pressureless sintering device according to claim 1, characterized in that: A switchable furnace door (110) is provided on the housing (1). A rubber gasket (111) is provided on the furnace door (110). An O-ring rubber seal (112) that cooperates with the rubber gasket (111) is provided on the furnace body (11).

9. A method for pressureless sintering of boron nitride, which relates to a device for pressureless sintering of boron nitride according to any one of claims 1-8, and is characterized in that: Including the following steps: S1. Raw material preparation: Using high-purity hexagonal boron nitride powder as the raw material, adding a sintering aid according to a set value to promote sintering, and mixing the materials to obtain raw material powder; S2. Forming: First, load the raw material powder into a stainless steel mold, and perform cold pressing by means of bidirectional pressing to form a preliminary green body. By applying uniform pressure to the green body in a high-pressure liquid or gas environment, a dense preform is obtained; S3. Pretreatment: Pre-sinter the preform. Place the preform in the furnace body (11) and preheat it at a lower temperature to remove moisture and volatiles in the raw materials. At the same time, perform partial reactions in air or a protective atmosphere to obtain a pre-treated green body; S4. Pressureless sintering: The main sintering stage is carried out under the condition of no external pressure. Place the pre-treated preform in a pressureless sintering device, and use an inert gas to control the sintering atmosphere to reduce the oxidation of boron nitride and maintain its chemical purity and performance; S5. Cooling and Post-treatment: After the sintering in step S4 is completed, it is slowly cooled to reduce thermal stress and crack generation. Cutting, grinding, and polishing post-treatment steps are carried out according to the settings to achieve the required dimensions and surface finish; S6. Performance Testing: The sintered boron nitride ceramic is subjected to performance tests of density, hardness, thermal conductivity, and electrical insulation to ensure that it meets the application requirements.

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