Boron nitride pressureless sintering method and device

Abstract

The invention relates to a boron nitride pressureless sintering method and device applied to the technical field of boron nitride pressureless sintering. The pressureless sintering method comprises the following steps: S1, preparing raw materials; s2, forming; s3, performing pretreatment; s4, carrying out pressureless sintering; s5, cooling and post-processing; s6, performance testing; the pressureless sintering device comprises a shell, a cooling circulation treatment assembly and an intelligent controller, the sintering module controls a heating element to preheat a furnace body, the detection module controls a furnace temperature thermocouple to monitor temperature data in the furnace, and when the temperature in the furnace reaches the set temperature, the sintering module reduces the power of the heating element; the circulating sucking pump and the circulating ventilating pump are controlled to operate to achieve the circulating heat preservation effect, the detection module controls the thermocouple piece to monitor the temperature of the workpiece, after sintering is completed, the cooling circulating module controls the two-way air pump to suck hot air in the air cavity into the heat preservation chamber to be stored, preparation is made for next sintering, and the furnace body is circularly cooled. Loss of heating elements in the preheating stage is reduced, and efficiency is improved.

Description

Technical Field

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

[0002] The pressureless sintering device is simple and easy to industrialize. It is the most basic sintering method. This method is not only simple and easy, but also suitable for the firing of objects of different shapes and sizes. The temperature system is easy to control and is widely used in the sintering of nanoceramics. It is mainly achieved by selecting the sintering system to achieve densification of the green body under the premise of minimum grain growth. Because in the sintering process, the activation energy of particle coarsening, green body densification and grain growth are different, that is, particle coarsening, green body densification and grain growth are mainly carried out in different temperature ranges. By utilizing this relationship, the sintering temperature can be controlled to obtain sintering conditions with a high densification rate and slow grain growth. The control of the sintering system mainly controls the speed of heating and cooling, the holding time and the maximum temperature.

[0003] In pressureless sintering, since only the temperature system is a controllable factor, it is relatively difficult to control the sintering of materials. The densification process is seriously affected by factors such as powder properties and green billet density.

[0004] The invention patent with publication number CN113375454A discloses a water circulation cooling system for a vacuum sintering furnace, including a box body and a furnace body, wherein a mounting plate is horizontally fixedly connected to the bottom of the furnace body, and the mounting plate is horizontally mounted on the top of the box body by bolts, a heating chamber is horizontally mounted inside the furnace body, and a water tank is horizontally mounted inside the box body, a cooling mechanism for cooling the heating chamber is provided inside the furnace body, and a first C-type tube and a second C-type tube are respectively connected at both ends of the top of the water tank, cooling fins are horizontally mounted on the surfaces of the first C-type tube and the second C-type tube located in the box body, and there are multiple cooling fins evenly distributed on the surfaces of the first C-type tube and the second C-type tube, and a blowing mechanism for blowing air to the cooling 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 blockage and leakage, high maintenance cost, and excessive temperature can easily cause the cooling water to boil and create the risk of steam explosion, poor safety. When the furnace body is used again, it is necessary to reheat the cooled furnace body to the specified temperature, which consumes a lot of energy and increases production costs.

[0006] Application Contents

[0007] In view of the above-mentioned prior art, the technical problem to be solved by the present invention is that at the current stage, the cooling circulation technology used in pressureless sintering mostly adopts condensed water circulation to control the rapid cooling of the furnace body, which is prone to blockage and leakage, high maintenance cost, and excessive temperature can easily lead to boiling of cooling water and create the risk of steam explosion, poor safety, and when the furnace body is used again, it is necessary to reheat the cooled furnace body to the specified temperature, which consumes a lot of energy and increases production costs.

[0008] In order to solve the above problems, the present invention provides a boron nitride pressureless sintering device, including a shell, a cooling cycle processing component and an intelligent controller. A furnace body is arranged in the shell, the furnace body is a hollow structure, a plurality of air cavities are arranged around the inner cavity of the furnace body, a furnace temperature thermocouple is arranged on the inner wall of the furnace body, a multi-layer fixed plate and a heating plate matched with the fixed plate are arranged in the furnace body, each fixed plate is provided with a thermocouple sheet, each heating plate is evenly provided with a heating element, and a buzzer is arranged on the shell;

[0009] The cooling cycle treatment component includes a treatment chamber and a filter chamber, an air box and a heat preservation chamber are arranged in the treatment chamber, an air storage chamber is arranged in the air box, an air extraction pipe is connected through the bottom of the filter chamber, the other end of the air extraction pipe is respectively connected with the air storage chamber and the heat preservation chamber through a multi-way pipe, a circulating air extraction pump is arranged at the connection between the air storage chamber 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 chamber, the other end of the ventilation pipe is connected with the inner cavity of the filter chamber, and 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 circulation module and an alarm module. The sintering module is electrically connected to the heating element, the detection module and the cooling circulation module respectively. The detection module is electrically connected to the furnace temperature thermocouple, the thermocouple sheet and the cooling circulation module respectively. The cooling circulation module is electrically connected to the circulating exhaust 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 element to slowly preheat the furnace body, and 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 vacuum pump and the circulating ventilation pump to achieve the circulating insulation effect. The detection module controls the thermocouple to monitor the workpiece temperature in real time. If the set value is reached, the sintering module controls the heating element to turn off, and the cooling circulation module controls the two-way air pump to draw the hot gas in the air cavity into the insulation chamber for storage, and controls the circulating vacuum pump and the circulating ventilation pump to circulate and cool the furnace body. While achieving rapid cooling, it also prepares for the next sintering preheating, reduces the loss of the heating element in the preheating stage, and improves efficiency.

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

[0013] As a further improvement of the present application, the insulation chamber adopts insulation material, and a temperature sensor and a pressure sensor are arranged in the insulation chamber. The temperature sensor is arranged at the connection between the insulation chamber and the exhaust pipe, and an inflation pipe connected to the air storage chamber is arranged on the air box. An air valve switch is arranged at the connection between the input end of the inflation pipe and the air box, and 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 bin, a plurality of air holes are arranged on the filter in a surrounding manner, the air holes are connected to the exhaust pipe, an air pressure sensor is provided at the connection between the air holes and the exhaust pipe, a partition is provided on the top of the filter bin, the filter bin is fixedly connected to the furnace body through the partition, and the detection module is electrically connected to the air pressure sensor.

[0015] As a further improvement and supplement to the present application, a temperature sensor and a pressure sensor are provided in the insulation chamber, the temperature sensor is provided at the connection between the insulation chamber and the exhaust pipe, and 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 chamber is formed between the inner wall of the shell and the outer wall of the furnace body, a plurality of fixing rods are arranged between the shell and the furnace body, a vacuum pump is arranged on the shell, an input end of the vacuum pump is connected with the vacuum chamber through a vacuum tube, and the sintering module is electrically connected with the vacuum pump.

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

[0018] As another improved supplement of the present application, a switchable furnace door is arranged on the shell, a rubber gasket is arranged on the furnace door, and an O-type rubber sealing ring matching with the rubber gasket is arranged on the furnace body.

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

[0020] S1. Raw material preparation: Use high-purity hexagonal boron nitride powder as raw material, add sintering aids according to the set value to promote sintering, and mix the materials to obtain raw material powder;

[0021] S2. Molding: First, the raw material powder is loaded into a stainless steel mold and cold pressed by bidirectional pressure to form a preliminary green body. By applying uniform pressure to the green body in a high-pressure liquid or gas environment, a compact preform is obtained;

[0022] S3. Pretreatment: Pre-sintering the preform, placing the preform in a furnace, preheating at a relatively low temperature, removing moisture and volatiles from the raw materials, and performing a partial reaction in air or a protective atmosphere to obtain a pretreated green body;

[0023] S4. Pressureless sintering: The main sintering stage is carried out without external pressure. The pretreated green body is placed in a pressureless sintering device, and the sintering atmosphere is controlled by inert gas to reduce the oxidation of boron nitride and maintain its chemical purity and properties;

[0024] S5. Cooling and post-processing: After sintering in step S4 is completed, slowly cool to reduce thermal stress and crack generation, and perform post-processing steps of cutting, grinding and polishing according to the settings to achieve the desired size and surface finish;

[0025] S6. Performance test: After sintering, the boron nitride ceramics are subjected to performance tests such as density, hardness, thermal conductivity and electrical insulation to ensure that they meet the application requirements.

[0026] To sum up, during sintering, the sintering module controls the heating element to slowly preheat the furnace body, and 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 controls the circulation exhaust pump and the circulation ventilation pump to operate to achieve a circulation effect. When the thermocouple detects that the workpiece temperature has reached the set value, the circulation exhaust pump and the circulation ventilation pump are turned off and the power of the heating element is increased to make the temperature reach the peak value and maintain the temperature in the furnace until the temperature monitored by the thermocouple reaches the set value. At the end of sintering, the sintering module controls the heating element to turn off, and the cooling circulation module controls the two-way air pump to draw the hot gas in the air cavity into the insulation chamber for storage, and controls the circulation exhaust pump and the circulation ventilation pump to circulate and cool the furnace body. While achieving rapid cooling, the hot gas can also be effectively preserved. In the next pressureless sintering process, hot gas is introduced to reduce the loss of the heating element in the preheating stage, reduce costs, and reduce the preheating time and improve efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic structural diagram of a sintering device according to the first and second embodiments of the present application;

[0028] Figure 2 It is a side sectional view of the sintering device of the first and second embodiments of the present application;

[0029] Figure 3This is a cross-sectional structural diagram of a sintering device according to the first and second embodiments of the present application;

[0030] Figure 4 This is a schematic diagram of the connection structure between the filter bin and the furnace body of the first and second embodiments of the present application;

[0031] Figure 5 This is a schematic diagram of the structure of the filtration chamber and the processing chamber of the first and second embodiments of the present application;

[0032] Figure 6 It is a side sectional view of the internal structure of the air box of the first and second embodiments of the present application;

[0033] Figure 7 This is a control flow chart of the intelligent controller of the first embodiment of the present application;

[0034] Figure 8 This is a schematic diagram of the structure of the sliding telescopic assembly of the first and second embodiments of the present application;

[0035] Fig. 9 This is a control flow chart of the intelligent controller of the second embodiment of the present application.

[0036] Description of the numbers in the figure:

[0037] 1. Shell; 2. Cooling cycle processing component; 3. Intelligent controller; 11. Furnace body; 12. Air cavity; 13. Buzzer; 101. Furnace temperature thermocouple; 102. Fixing plate; 103. Heating plate; 104. Thermocouple sheet; 105. Heating element; 106. Vacuum chamber; 107. Fixing rod; 108. Vacuum pump; 109. Vacuum tube; 110. Furnace door; 111. Rubber gasket; 112. Rubber sealing ring; 113. Sliding groove; 114. Telescopic member; 1 15. Sliding rod; 201. Processing chamber; 202. Filter chamber; 203. Air box; 204. Insulation chamber; 205. Exhaust pipe; 206. Circulating exhaust pump; 207. Two-way air pump; 208. Air storage chamber; 209. Cooling component; 210. Temperature sensor; 211. Inflating pipe; 212. Air valve switch; 213. Filter; 214. Air pressure sensor; 215. Partition; 216. Ventilation pipe; 217. Circulating ventilation pump; 218. Pressure sensor. DETAILED DESCRIPTION

[0038] Two implementation modes of the present application are described in detail below with reference to the accompanying drawings.

[0039] The first implementation method:

[0040] Figure 1-Figure 7A boron nitride pressureless sintering device is shown, comprising a shell 1, a cooling circulation processing component 2 and an intelligent controller 3. A furnace body 11 is arranged in the shell 1. The furnace body 11 is a hollow structure. A plurality of air cavities 12 are arranged around the inner cavity of the furnace body 11. The furnace body 11 can be kept warm by filling the air cavities 12. At the same time, cold air can be filled into the air cavities 12 by circulation, so as to achieve the effect of rapidly 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 send a temperature signal to the intelligent controller 3. The device 3 transmits data. A multi-layer fixed plate 102 and a heating plate 103 matched with the fixed plate 102 are arranged in the furnace body 11. A thermocouple sheet 104 is arranged on each fixed plate 102 to monitor the temperature of the workpiece in real time. The temperature change in the furnace is analyzed and accurately controlled by the intelligent controller 3 to improve the production quality of the workpiece. A heating element 105 is evenly arranged on each heating plate 103 to evenly heat the workpiece and improve the quality. A buzzer 13 is arranged on the housing 1. In case of emergency, an alarm is issued in real time to remind the maintenance personnel.

[0041] The cooling cycle processing assembly 2 includes a processing chamber 201 and a filtering chamber 202. The processing chamber 201 is provided with an air box 203 and a heat preservation chamber 204. The air box 203 is provided with an air storage chamber 208 for storing inert gas and cooling it in the air box 203. An exhaust pipe 205 is connected to the bottom of the filtering chamber 202. The other end of the exhaust pipe 205 is connected to the air storage chamber 208 and the heat preservation chamber 204 through a multi-way pipe. The inert gas in the air cavity 12 is controlled to flow between the air storage chamber 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 hot gas, which is convenient for the next sintering and shortening the time. The heating time of the furnace body 11 is shortened, and the loss of the heating element 105 is reduced to improve the efficiency. A circulating air pump 206 is provided at the connection between the gas storage chamber 208 and the air extraction pipe 205, and a two-way air pump 207 is provided at the connection between the insulation chamber 204 and the air extraction pipe 205. A ventilation pipe 216 is connected to the gas storage chamber 208, and the other end of the ventilation pipe 216 is connected to the inner cavity of the filter bin 202. A circulating air pump 217 is installed on the ventilation pipe 216. By controlling the circulating air pump 206, the two-way air pump 207 and the circulating air pump 217, the sintering process is cooled quickly, the temperature is maintained, and the hot gas is preserved, thereby improving the sintering efficiency.

[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 and loading and unloading of the sintering device. The detection module is electrically connected to the furnace temperature thermocouple 101, the thermocouple sheet 104 and the cooling cycle module respectively. The detection module is used to monitor the temperature in the furnace and the workpiece temperature in real time and analyze the data. The cooling cycle module is electrically connected to the circulating vacuum 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 cool it quickly. 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 maintenance personnel.

[0043] Therefore, 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, monitors the temperature of the furnace body 11 in real time, and transmits data to the intelligent controller 3 until the temperature in the furnace reaches the set value (the preheating temperature of the workpiece detected by the furnace temperature thermocouple 101 preset in the detection module reaches the standard value), the sintering module reduces the power of the heating element 105, and at the same time controls the circulation exhaust pump 206 and the circulation ventilation pump 217 to achieve the effect of circulating hot and cold gases, maintains the temperature in the furnace, and maintains it until the thermocouple piece 104 monitors that the workpiece temperature reaches the preheating value (the preheating temperature of the workpiece detected by the thermocouple piece 104 preset in the detection module reaches the standard value), controls the circulation exhaust pump 206 and the circulation ventilation pump 217 to close and increase the power of the heating element 105, so that the temperature in the furnace rises to the peak value (the preheating temperature of the workpiece detected by the thermocouple piece 104 preset in the detection module reaches the standard value), controls the circulation exhaust pump 206 and the circulation ventilation pump 217 to close and increase the power of the heating element 105, so that the temperature in the furnace rises to the peak value (the preheating temperature of the workpiece detected by the thermocouple piece 104 preset in the detection module). The block is preset with a furnace temperature thermocouple 101 detecting a stable sintering temperature value of the workpiece), and controls the circulating exhaust pump 206, the circulating ventilation pump 217 and the heating element 105 to help maintain the temperature in the furnace until the workpiece temperature monitored by the thermocouple sheet 104 reaches the completion value (the workpiece sintering stable temperature value detected by the thermocouple sheet 104 is preset in the detection module), and it is determined that the pressureless sintering of the workpiece is completed, the sintering module controls the heating element 105 to be turned off, and the cooling circulation module controls the two-way air pump 207 to draw the hot gas in the air cavity 12 into the insulation chamber 204 for storage. After the hot gas is drawn in, the circulating exhaust pump 206 and the circulating ventilation pump 217 are controlled to quickly cool the furnace body 11. While achieving rapid cooling, the hot gas can also be effectively preserved. In the next pressureless 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] See also Figure 6 and Figure 7A cooling assembly 209 is provided in the gas box 203, and the cooling circulation module is electrically connected to the cooling assembly 209. The inert gas stored in the gas storage chamber 208 is cooled by the cooling assembly 209, so as to maintain the temperature in the furnace and cool it quickly.

[0045] The cooling component 209 is a common component in the art that uses a compressor to quickly cool the gas. It compresses the gas through a built-in compressor to dissipate heat to the outside, thereby achieving the purpose of lowering the internal gas temperature. It is an existing technology well known to people in the art and is not within the protection scope of the technical solution of this application. This application will not elaborate on its specific structure and working principle.

[0046] See also Figure 2 and Figure 6 The insulation chamber 204 uses insulation materials to insulate the hot inert gas stored in the insulation chamber 204. The gas box 203 is provided with a gas filling pipe 211 connected to the gas storage chamber 208. The connection between the input end of the gas filling pipe 211 and the gas box 203 is provided with a gas valve switch 212 to replenish and replace the internal inert gas.

[0047] See also Figure 2 , Figure 4 and Figure 7 A filter 213 is provided at the bottom of the inner cavity of the filter bin 202, and a plurality of air holes are arranged on the filter 213 in a surrounding manner. The gas in the air cavity 12 is filtered through the filter 213 to prevent deterioration and pollution in the inert gas. The air hole is connected to the exhaust pipe 205, and an air pressure sensor 214 is provided at the connection between the air hole and the exhaust pipe 205 to monitor the air pressure in the filter 213 in real time and compare it with the air pressure under normal operating conditions. If the air pressure difference is too large (greater than the pressure difference range of blockage detected by the air pressure sensor 214 preset in the detection module), the alarm module controls the buzzer 13 to sound an alarm. A partition 215 is provided on the top of the filter bin 202, and the filter bin 202 is fixedly connected to the furnace body 11 through the partition 215 to separate the furnace body 11 from the filter bin 202, and the detection module is electrically connected to the air pressure sensor 214.

[0048] It can be seen that the present invention is cleverly designed in structure. 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, and the thermocouple sheet 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 pump 206, the circulating ventilation pump 217 and the heating element 105 to help maintain the temperature in the furnace, accurately control the temperature change in the furnace, and after the sintering is completed, the bidirectional air pump 207 is set to pump the hot gas in the air cavity 12 into the insulation chamber 204 for storage, and 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 exhaust pump 206 and the circulating ventilation pump 217 quickly cool the furnace body 11. For this purpose, the cooling component 209 arranged in the air box 203 quickly cools the inert gas during the cooling cycle, further improving the cooling efficiency. The insulation chamber 204 adopts insulation materials to increase the insulation time of the hot inert gas. The set gas valve switch 212 replenishes and replaces the internal inert gas to prevent gas deterioration and pollution. During the sintering and cooling process, the gas in the air cavity 12 is filtered through the filter 213 to prevent the inert gas from being contaminated.

[0049] The second implementation method:

[0050] Figure 2 and Fig. 9 A pressureless sintering device for boron nitride is shown. Different from the first embodiment, a temperature sensor 210 and a pressure sensor 218 are arranged in the insulation chamber 204. The temperature sensor 210 is arranged at the connection between the insulation chamber 204 and the exhaust 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 sucked into the insulation chamber 204 by the exhaust pipe 205 in real time. If the temperature is lower than the set value (the lowest temperature of the collected insulation gas detected by the temperature sensor 210 preset in the detection module), the two-way air pump 207 is turned off and the suction of the hot inert gas is stopped. The pressure sensor 218 monitors the air pressure value of the hot inert gas in the insulation chamber 204 in real time. If the air pressure value is higher than the set value (the air pressure of the storable gas in the insulation chamber 204 detected by the pressure sensor 218 preset in the detection module), the two-way air pump 207 is turned off and the suction of the hot inert gas is stopped.

[0051] See also Figure 1-Figure 3 and Fig. 9 A vacuum chamber 106 is formed between the inner wall of the shell 1 and the outer wall of the furnace body 11. A plurality of fixing rods 107 are arranged between the shell 1 and the furnace body 11. A vacuum pump 108 is arranged on the shell 1. The input end of the vacuum pump 108 is connected with the vacuum chamber 106 through a vacuum tube 109. The sintering module is electrically connected with the vacuum pump 108. The gas in the vacuum chamber 106 is extracted by the vacuum pump 108 to form a vacuum state, thereby achieving a good thermal insulation effect.

[0052] See also Figure 8 and Fig. 9 , each fixed plate 102 is provided with sliding telescopic components on both sides, and each sliding 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 shell 1, and 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 matching the sliding rod 115. The sliding rod 115 is fixed to both sides of the fixed plate 102. The sintering module is electrically connected to the telescopic member 114. When 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 move horizontally 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 loading and unloading process of the sintering workpiece, and the sintering personnel are not easily affected and scalded by the residual heat.

[0053] See also Figure 1-Figure 3 A closable furnace door 110 is provided on the shell 1, a rubber gasket 111 is provided on the furnace door 110, and an O-type rubber sealing ring 112 matching with the rubber gasket 111 is provided on the furnace body 11. During the sintering preparation process, when the furnace door 110 is closed, the rubber gasket 111 and the O-type rubber sealing ring 112 are fixed to achieve a perfect sealing effect.

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

[0055] S1. Raw material preparation: Use high-purity hexagonal boron nitride powder as 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, the raw material powder is loaded into a stainless steel mold and cold pressed by bidirectional pressure to form a preliminary green body. In order to further improve the density and uniformity of the green body, a uniform pressure can be applied to the green body in a high-pressure liquid or gas environment to obtain a compact preform;

[0057] S3 pretreatment: pre-sintering the preform, placing the preform in the furnace 11, preheating at a lower temperature, removing moisture and volatiles from the raw material, and partially reacting in air or a protective atmosphere to obtain a pretreated green body;

[0058] S4. Pressureless sintering: The main sintering stage is carried out without external pressure. The pretreated green body is placed in a pressureless sintering device, and the sintering atmosphere is controlled by inert gas to reduce the oxidation of boron nitride and maintain its chemical purity and properties;

[0059] S5. Cooling and post-processing: After sintering in step S4 is completed, slowly cool to reduce thermal stress and crack generation, and perform post-processing steps of cutting, grinding and polishing according to the settings to achieve the desired size and surface finish;

[0060] S6. Performance test: After sintering, the boron nitride ceramics are subjected to performance tests such as density, hardness, thermal conductivity and electrical insulation to ensure that they meet the application requirements.

[0061] In view of current practical needs, the above-mentioned implementation mode adopted in this application is not limited to the scope of protection. Various changes made within the knowledge scope of technical personnel in this field without departing from the concept of this application still fall within the scope of protection of the present invention.

Claims

1. A boron nitride pressureless sintering device, characterized in that: It comprises a housing (1), a cooling cycle processing component (2) and an intelligent controller (3); A furnace body (11) is arranged in the shell (1), the furnace body (11) is 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 fixed plates (102) and heating plates (103) matched with the fixed plates (102) are arranged in the furnace body (11), a thermocouple sheet (104) is arranged on each of the fixed plates (102), a heating element (105) is evenly arranged on each of the heating plates (103), and a buzzer (13) is arranged on the shell (1); The cooling cycle treatment component (2) comprises a treatment chamber (201) and a filtering chamber (202); an air box (203) and a heat preservation chamber (204) are arranged in the treatment chamber (201); an air storage chamber (208) is arranged in the air box (203); an air extraction pipe (205) is connected to the bottom of the filtering chamber (202); the other end of the air extraction pipe (205) is respectively connected to the air storage chamber (208) and the heat preservation chamber (204) through a multi-way pipe. The air storage chamber (208) and the air extraction pipe (205) are connected, a circulating air extraction pump (206) is provided at the connection between the air storage chamber (208) and the air extraction pipe (205), a bidirectional air pump (207) is provided at the connection between the air preservation chamber (204) and the air extraction pipe (205), a ventilation pipe (216) is connected to the air storage chamber (208), the other end of the ventilation pipe (216) is connected to the inner cavity of the filter chamber (202), and a circulating air extraction pump (217) is installed on the ventilation pipe (216); The intelligent controller (3) is provided with a sintering module, a detection module, a cooling circulation module and an alarm module. The sintering module is electrically connected to the heating element (105), the detection module and the cooling circulation module respectively. The detection module is electrically connected to the furnace temperature thermocouple (101), the thermocouple sheet (104) and the cooling circulation module respectively. The cooling circulation module is electrically connected to the circulating air 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 boron nitride pressureless sintering device according to claim 1, characterized in that: A cooling component (209) is disposed in the air box (203), and the cooling circulation module is electrically connected to the cooling component (209).

3. A boron nitride pressureless sintering device according to claim 2, characterized in that: The heat preservation chamber (204) is made of heat preservation material, the air box (203) is provided with an air filling pipe (211) connected with the air storage chamber (208), and an air valve switch (212) is provided at the connection between the input end of the air filling pipe (211) and the air box (203).

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

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

6. The boron nitride pressureless sintering device according to claim 1, characterized in that: A vacuum chamber (106) is formed between the inner wall of the shell (1) and the outer wall of the furnace body (11); a plurality of fixing rods (107) are arranged between the shell (1) and the furnace body (11); a vacuum pump (108) is arranged on the shell (1); an input end of the vacuum pump (108) is connected to the vacuum chamber (106) via a vacuum tube (109); and the sintering module is electrically connected to the vacuum pump (108).

7. The boron nitride pressureless sintering device according to claim 1, characterized in that: Each of the fixed plates (102) is provided with sliding telescopic components on both sides, and each of the sliding telescopic components comprises 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 shell (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 matching the sliding rod (115); the sliding rod (115) is fixed to both sides of the fixed plate (102); and the sintering module is electrically connected to the telescopic member (114).

8. The boron nitride pressureless sintering device according to claim 1, characterized in that: The shell (1) is provided with a closable furnace door (110), the furnace door (110) is provided with a rubber gasket (111), and the furnace body (11) is provided with an O-type rubber sealing ring (112) matched with the rubber gasket (111).

9. A method for pressureless sintering of boron nitride, which relates to a pressureless sintering device for boron nitride according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Raw material preparation: Use high-purity hexagonal boron nitride powder as raw material, add sintering aids according to the set value to promote sintering, and mix the materials to obtain raw material powder; S2. Molding: First, the raw material powder is loaded into a stainless steel mold and cold pressed by bidirectional pressure to form a preliminary green body. By applying uniform pressure to the green body in a high-pressure liquid or gas environment, a compact preform is obtained; S3 pretreatment: pre-sintering the preform, placing the preform in a furnace (11), preheating at a relatively low temperature, removing moisture and volatiles from the raw material, and performing a partial reaction in air or a protective atmosphere to obtain a pretreated green body; S4. Pressureless sintering: The main sintering stage is carried out without external pressure. The pretreated green body is placed in a pressureless sintering device, and the sintering atmosphere is controlled by inert gas to reduce the oxidation of boron nitride and maintain its chemical purity and properties; S5. Cooling and post-processing: After sintering in step S4 is completed, slowly cool to reduce thermal stress and crack generation, and perform post-processing steps of cutting, grinding and polishing according to the settings to achieve the desired size and surface finish; S6. Performance test: After sintering, the boron nitride ceramics are subjected to performance tests such as density, hardness, thermal conductivity and electrical insulation to ensure that they meet the application requirements.

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