Cubic press for artificial diamond and cavity temperature heating method

Abstract

The invention relates to the technical field of cubic presses, and discloses a cubic press for artificial diamond and a cavity temperature heating method.The cubic press comprises six pressure-bearing beams and a main holding-up hammer hydraulically sliding and stretching out and drawing back along the pressure-bearing beams; the head section of the main holding-up hammer is provided with a hydraulic sliding telescopic auxiliary holding-up hammer, and the head end of the auxiliary holding-up hammer protrudes out of the end face of the head end of the main holding-up hammer; when the main holding-up hammer is closed, the auxiliary holding-up hammers are in a contraction state, a gap is formed between every two adjacent auxiliary holding-up hammers, and the auxiliary holding-up hammers stretch out to apply pressure in a diamond synthesis stage; in the cooling stage after synthesis, the auxiliary holding-up hammers are closed; according to the cubic press, the auxiliary anvil capable of independently hydraulically stretching out and drawing back is arranged on the main anvil, and a staged cavity temperature heating and cooling pressure relief process is matched, so that the problems of non-uniform pressure, anvil cracking, blasting and the like caused by volume shrinkage of an existing cubic press in the diamond synthesis process are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of six-sided top press technology, specifically to a six-sided top press for synthetic diamonds and a cavity temperature heating method. Background Technology

[0002] The six-sided top press is a key piece of equipment that applies ultra-high pressure and high temperature to the central cavity simultaneously from six directions (X, Y, Z axes). It mainly adopts a hinged structure and uses six hydraulic top hammers to push synchronously, creating a high-pressure and high-temperature environment of thousands of degrees Celsius inside the cavity. It is the core equipment for producing superhard materials such as synthetic diamonds, lab-grown diamonds, and cubic boron nitride, and is also widely used in scientific research fields such as high-pressure physics.

[0003] The working principle of the six-sided top press is that six top hammers apply vertical pressure from the six faces of a pyrophyllite cube. The small bevels around the hammer faces form triangular sealing edges on the cube's edges. Pyrophyllite exhibits good fluidity under high pressure, maintaining a relatively balanced pressure field within the cavity. The flow of pyrophyllite under high pressure also exhibits a certain viscosity. Through the wedge-shaped structure and friction of the sealing edges, the pyrophyllite seals the material within the cavity formed by the top hammers. The sealing edges formed by the pyrophyllite act like wedges inserted into gaps. During the pressure holding phase, the compressive force on the small bevels of the top hammers is far greater than the pressure on the hammer faces.

[0004] Diamond synthesis involves increasing pressure to the required value and raising the temperature. As graphite transforms into diamond, density gradually increases and volume gradually decreases; for this transformation to continue continuously, the pressure within the chamber must be maintained above 5 GPa. Current methods include: some use a high-expansion, low-thermal-conductivity material as a liner, utilizing the expansion of dolomite to compensate for the volume shrinkage during diamond synthesis; others utilize the fluidity of pyrophyllite at the sealing edge to advance the hammer. However, by the time diamond synthesis conditions are met, the sealing edge has already formed, and the advancement of the hammer inevitably results in greater pressure at the sealing edge. The fluidity of pyrophyllite makes the sealing edge thinner, hindering the hammer's advance. The pressure at the sealing edge is far greater than the threshold that the pyrophyllite crystal structure can withstand, causing the sealing edge material to undergo a phase transition under high pressure, resulting in decreased fluidity. This leads to the pressure at the sealing edge being higher than the internal pressure of the chamber. The hammer needs to advance a greater distance, resulting in a large pressure difference between the hammer's center and the small inclined surface of the sealing edge. This pressure difference easily causes the hammer to bulge inward, resulting in increased tensile stress along the hammer surface. When the tensile stress exceeds the threshold that the top hammer can withstand, cracks will appear on the hammer surface, and even cause explosions. As the synthesis proceeds, the significant volume shrinkage causes the internal pressure to gradually decrease, with even lower pressure at the center of the top hammer surface. When the synthesis is complete, the pressure difference between the center of the top hammer surface and the sealing edge is already large. During the cooling process, the material shrinks further, increasing the tensile stress on the top hammer surface. This causes the pressure unevenness on the top hammer surface to exceed the top hammer threshold, resulting in cracking of the top hammer. Summary of the Invention

[0005] The purpose of this invention is to solve at least one of the problems in the prior art and to provide a six-sided press for synthetic diamonds and a cavity temperature heating method.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A six-sided press for synthetic diamond includes six pressure beams and a main ejector hammer that slides and extends hydraulically along the pressure beams; the head section of the main ejector hammer is provided with a secondary ejector hammer that slides and extends hydraulically, the head end of the secondary ejector hammer protruding from the head end face of the main ejector hammer; when the main ejector hammer closes the mold, the secondary ejector hammer is in a retracted state and there is a gap between adjacent secondary ejector hammers; during the diamond synthesis stage, the secondary ejector hammer extends to apply pressure; during the cooling stage after synthesis, the secondary ejector hammer closes.

[0007] Furthermore, the pressure-bearing beam is provided with a first oil cavity, the inner end of the main top hammer extends into the first oil cavity and is connected to a first piston part, and the two ends of the first oil cavity are respectively connected to a first oil passage and a second oil passage.

[0008] Furthermore, the main top hammer is provided with a second oil chamber, the inner end of the auxiliary top hammer extends into the second oil chamber and is connected to a second piston part, and the two ends of the second oil chamber are respectively connected to a third oil passage and a fourth oil passage.

[0009] Furthermore, the first oil chamber is provided with an oil pipe connected to the third oil passage, and the main top hammer is provided with an oil delivery hole communicating with the second oil chamber. The oil pipe extends into the oil delivery hole and slides to seal with the inner wall of the oil delivery hole.

[0010] Furthermore, a boss is provided at the center of the end face of the main ejector hammer, and the secondary ejector hammer slides through the center of the boss. When the main ejector hammer is closed, the end of the secondary ejector hammer is attached to the outer side of the boss, and the contact surface is parallel to the end face of the main ejector hammer.

[0011] Furthermore, the center of the boss is provided with an annular stepped groove, and the side of the secondary top hammer head facing the annular stepped groove is provided with an annular step that cooperates with the annular stepped groove.

[0012] Furthermore, each of the main top hammers is equipped with a cooling channel.

[0013] This invention also provides the following technical solutions: A method for heating the cavity temperature of a six-sided press for synthetic diamond, the method comprising the following steps: Step 1, Heating Preparation: Select two auxiliary hammers that are positioned opposite each other from the six auxiliary hammers as conductive hammers; Step 2, Mold Closure and Pressurization: Control the six main ejector hammers to close the mold synchronously on six axes, pressurize in stages to the preset synthesis pressure of 5-8 GPa, and maintain the pressure until the pressure fluctuation is ≤ ±0.1 MPa, thus completing the sealing and pressure stabilization of the synthesis cavity; Step 3, graded gradient heating: Start the low-voltage, high-current power supply and use a segmented heating mode to heat the inner cavity; Step 4: Cooling and depressurization: After the isothermal growth is completed, the temperature is reduced in a step-by-step power reduction mode. In the first stage, the temperature is reduced to 50% of the target power at a rate of 50-80 kW / min for 3-5 minutes. In the second stage, the temperature is reduced to 0 kW at a rate of 30-50 kW / min for 2-10 minutes. During the cooling process, the pressure is depressurized simultaneously, and the temperature and pressure of the chamber decrease synchronously. Step 5: After depressurization is completed, the top hammer returns, the composite block is removed, and the composite cavity is cleaned.

[0014] Furthermore, step three includes the following steps: Preheating section: The heating power is linearly increased at a rate of 50-100kW / min for 3-8 minutes to raise the temperature of the synthesis chamber to 800-1000℃; Rapid heating phase: Adjust the heating rate to 100-200kW / min and continue for 2-5 minutes to raise the chamber temperature to the target growth temperature of 1350-1450℃; Constant temperature growth section: The heating power is dynamically adjusted to keep the cavity temperature stable within the target temperature range and control the temperature of the main top hammer to ≤80℃.

[0015] Furthermore, in step four, the depressurization rate is controlled to be 0.5-1.0 GPa / min.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention effectively solves the problems of uneven pressure, hammer cracking, and blowout caused by volume shrinkage during diamond synthesis in existing six-sided presses by setting an independently hydraulically retractable auxiliary hammer on the main hammer, combined with a phased cavity temperature heating, cooling and depressurization process. This invention compensates for volume shrinkage and balances the internal pressure of the cavity; during the diamond synthesis stage, the secondary top hammer extends to apply pressure, which can compensate for the volume shrinkage generated during the conversion of graphite to diamond in real time, avoid the internal pressure of the cavity from dropping due to volume reduction, and always keep the cavity pressure stable at the synthesis requirement value above 5GPa, ensuring the continuous progress of the diamond conversion reaction. During the cooling stage of this invention, the secondary top hammer further closes to compensate for the secondary shrinkage of the material after cooling, significantly reducing the pressure difference between the top hammer surface and the sealing edge, thereby reducing the tensile stress caused by uneven pressure on the top hammer from the root and preventing the top hammer from cracking or deforming. When the main ejector hammer closes the mold, the secondary ejector hammer is in a retracted state and there is a gap between adjacent secondary ejector hammers, so as to avoid the secondary ejector hammers from causing additional pressure on the sealing edge. Compared with the traditional method of compensating for volume shrinkage by relying on the fluidity of pyrophyllite, this invention does not require the main hammer to continuously advance and squeeze the sealing edge, thus preventing the sealing edge from undergoing a phase change and deteriorating fluidity due to pressure exceeding the pyrophyllite crystal's tolerance threshold. At the same time, it avoids the sealing edge from becoming thinner due to excessive squeezing, thereby improving the stability and service life of the sealing edge and reducing the risk of blasting. The protrusion at the end of the main hammer head of this invention cooperates with the annular step of the secondary hammer to achieve precise limiting of the extension and retraction of the secondary hammer, and the contact surface is parallel to the end face of the main hammer head, ensuring uniform force transmission when the secondary hammer applies pressure; before the phase change fluidity of the pyrophyllite sealing edge deteriorates, it can prevent material from entering between the main hammer and the secondary hammer. The main and auxiliary top hammers of this invention are hydraulically driven through independent oil chambers and oil channels, with precise motion control and good synchronization, which is suitable for the pressurization requirements of six-axis synchronous mold closing. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the external structure of the present invention.

[0018] Figure 2 This is a side view of the top hammer of the present invention.

[0019] Figure 3 This is a schematic diagram of the internal structure of the top hammer of the present invention.

[0020] Figure 4 This is an enlarged schematic diagram of the central part of the present invention.

[0021] Figure 5 This is a schematic diagram of the secondary top hammer in the closed state according to the present invention.

[0022] Figure 6 This is a schematic diagram of the non-conductive top hammer of the present invention.

[0023] Figure 7 This is a schematic diagram of the conductive top hammer of the present invention.

[0024] Figure 8 This is a schematic diagram of the external structure of the non-conductive top hammer of the present invention.

[0025] In the diagram: 1. Pressure-bearing beam; 2. Main jacking hammer; 3. Secondary jacking hammer; 4. First piston section; 5. First oil chamber; 6. First oil passage; 7. Second oil passage; 8. Second piston section; 9. Second oil chamber; 10. Third oil passage; 11. Oil pipe; 12. Oil delivery hole; 13. Fourth oil passage; 14. Boss; 15. Annular stepped groove; 16. Annular step; 17. Cooling channel; 18. Secondary chamber; 19. Insulating plate; 20. Power transmission line. Detailed Implementation

[0026] The present invention will now be described in further detail. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention; that is, the described embodiments are merely some, not all, of the embodiments of the present invention.

[0027] Specific embodiments of the six-sided press and cavity temperature heating method for synthetic diamond provided by the present invention: Please see Figures 1-8 A six-sided jacking press for synthetic diamonds includes six bearing beams 1, a main jacking hammer 2 that cooperates with the bearing beams 1, and an auxiliary jacking hammer 3 located at the head of the main jacking hammer 2. The connection and cooperation details of each component are as follows: The hydraulic drive structure of the main hammer 2: A first oil chamber 5 is provided inside the pressure beam 1. The inner end of the main hammer 2 extends into the first oil chamber 5 and is fixedly connected to the first piston part 4. The two ends of the first oil chamber 5 are respectively connected to the first oil passage 6 and the second oil passage 7. The first oil passage 6 and the second oil passage 7 extend to the outside of the pressure beam 1 to form a joint and connect with the external hydraulic system. By alternately inputting hydraulic oil into the first oil passage 6 and the second oil passage 7, the first piston part 4 is pushed to slide in the first oil chamber, so as to realize the hydraulic sliding extension and retraction of the main hammer 2 along the pressure beam 1. The six main hammers 2 can realize six-axis synchronous action.

[0028] The hydraulic drive structure of the auxiliary hammer 3: The main hammer 2 has a second oil chamber 9 inside. The inner end of the auxiliary hammer 3 extends into the second oil chamber 9 and is fixedly connected to the second piston part 8. The two ends of the second oil chamber 9 are respectively connected to the third oil passage 10 and the fourth oil passage 13. The third oil passage 10 and the fourth oil passage 13 extend to the outside of the pressure beam 1 and the outside of the main hammer 2 to form a joint, and are connected to the external hydraulic system through the joint. The first oil chamber 5 is provided with an oil pipe 11 connected to the third oil passage 10. The main hammer 2 has an oil supply hole 12 connecting the first oil chamber 5 and the second oil chamber 9. The oil pipe 11 extends into the oil supply hole 12 and is slidably sealed with the inner wall of the oil supply hole 12 to prevent the first oil chamber 5 and the second oil chamber 9 from communicating. This ensures that during the extension and retraction of the main hammer 2, the hydraulic oil can be stably delivered to the second oil chamber 9 through the oil pipe 11 and the oil supply hole 12, so as to realize the hydraulic sliding extension and retraction of the auxiliary hammer 3 independently of the main hammer 2. The head end of the auxiliary hammer 3 protrudes from the head end face of the main hammer 2.

[0029] The main ejector hammer 2 has an integrally formed boss 14 at the center of its head end face, and the secondary ejector hammer 3 slides through the central through hole of the boss 14. An annular stepped groove 15 is provided at the central through hole of the boss 14, and a matching annular step 16 is provided on the side of the secondary ejector hammer 3 facing the annular stepped groove 15. When the main ejector hammer 2 is closed, the head end of the secondary ejector hammer 3 is attached to the outer side of the boss 14, and the contact surface of the two is parallel to the head end face of the main ejector hammer 2, ensuring the uniformity of force transmission when the secondary ejector hammer 3 applies pressure. The hydraulic action makes the secondary ejector hammer 3 and the main ejector hammer 2 actively and tightly fit together, and before the phase transformation fluidity of the pyrophyllite sealing edge deteriorates, it can prevent material from entering between the main ejector hammer 2 and the secondary ejector hammer 3.

[0030] Each main hammer 2 has a cooling channel 17 inside, through which cooling water or cooling gas can be introduced to achieve real-time heat dissipation of the main hammer 2 and control the working temperature of the hammer to ≤80℃. Two auxiliary hammers 3 are selected and arranged opposite each other as conductive hammers. The main hammer 2 outside the conductive hammers has a secondary cavity 18. The auxiliary hammers 3 pass through the secondary cavity 18. The auxiliary hammers 3 as conductive hammers are divided into two parts, which are connected by an insulating plate 19 and correspond to the secondary cavity 18. The head section of the two parts of the auxiliary hammers 3 as conductive hammers is connected to a power transmission line 20. The power transmission line 20 is connected to a low-voltage high-current power supply, forming a current loop through the two conductive hammers to achieve electric heating of the synthesis cavity. The main hammer 2 has an insulating layer on the outside. In some embodiments, the main hammer 2 in contact with the conductive part of the auxiliary hammer 3 has an insulating tube inside to achieve insulation of the conductive hammer.

[0031] During the mold closing stage, the secondary ejector hammer 3 is in a contracted state, with gaps between adjacent secondary ejector hammers 3. The six main ejector hammers 2 close the mold synchronously on six axes, and the cavity is sealed by forming a sealing edge through pyrophyllite. During the diamond synthesis stage, the secondary ejector hammers 3 extend and apply pressure to the center of the cavity to compensate for the volume shrinkage of graphite conversion. During the cooling stage after synthesis, the secondary ejector hammers 3 close further to compensate for the volume shrinkage of the material after cooling.

[0032] Initial standby: The six pressure beams 1 are in their initial extended state. The main top hammer 2 is hydraulically controlled by the first oil chamber 5 and is retracted into the inner side of the pressure beam 1 without extending towards the central composite cavity. The auxiliary top hammer 3 is hydraulically controlled by the second oil chamber 9, and the head of the auxiliary top hammer 3 is attached to the head protrusion 14 of the main top hammer 2. All six main top hammers 2 and auxiliary top hammers 3 are in a non-contact state, with a cavity space reserved in the center for placing raw materials. The various oil passages and cooling channels 17 of the equipment are in a ready-to-work state.

[0033] Mold sealing; Hydraulic oil is input into the first oil chamber 5 inside the pressure beam 1 through the first oil passage 6 and the second oil passage 7, pushing the first piston part 4 to drive the six main ejector hammers 2 to extend synchronously towards the center along the pressure beam 1, realizing six-axis synchronous mold closing; during the mold closing process, the oil entering and exiting the second oil chamber 9 keeps the auxiliary ejector hammers 3 in a retracted state, and a preset gap is maintained between adjacent auxiliary ejector hammers 3 to avoid the auxiliary ejector hammers 3 interfering with the mold closing action of the main ejector hammers 2, and at the same time to prevent additional extrusion on the pyrophyllite sealing edge; the head ends of the six main ejector hammers 2 are in contact with the six sides of the pyrophyllite cube, and the pyrophyllite forms a wedge-shaped sealing edge through the bevel of the hammer surface, completing the initial sealing of the composite cavity. During this stage, the main ejector hammers 2 are continuously pressurized in stages to the preset pressure threshold.

[0034] Synthetic pressure compensation: During the diamond synthesis stage, hydraulic oil is input into the second oil chamber 9 inside the main top hammer 2 through the third oil passage 10 and the fourth oil passage 13, which pushes the second piston part 8 to drive the auxiliary top hammer 3 to extend outward from the boss 14. The head of the auxiliary top hammer 3 extends towards the center of the synthesis chamber to apply pressure. During the synthesis process, as the volume shrinks due to the conversion of graphite into diamond, the auxiliary top hammer 3 continues to extend slightly to compensate for the changes in the volume of the chamber in real time, and always keeps the internal pressure of the chamber above 5GPa to ensure that the synthesis reaction continues. During this stage, the main top hammer 2 maintains a pressure-holding state, and the cooling channel 17 continuously dissipates heat.

[0035] Cooling and closing compensation: After the isothermal growth of diamond is completed, the cooling stage begins. The heating power decreases in stages, and the cavity temperature decreases synchronously. The material undergoes secondary volume shrinkage due to the cooling. The hydraulic system continues to drive the secondary top hammer 3 to further close towards the center of the cavity, compensating for the volume shrinkage caused by the cooling and significantly reducing the pressure difference between the center of the main top hammer 2 and the sealing edge, thus avoiding tensile stress caused by uneven pressure on the top hammer. During the cooling process, the main top hammer 2 simultaneously begins to depressurize in stages, with the depressurization rate controlled at 0.5-1.0 GPa / min. The secondary top hammer 3 remains in a closed compensating state until the cavity temperature drops to near room temperature and the pressure drops to near atmospheric pressure.

[0036] Depressurization return reset: After the temperature and pressure of the cavity reach the required level for depressurization, the hydraulic oil is reversed and input into the first oil chamber 5, pushing the first piston 4 to cause the six main top hammers 2 to retract a section along the pressure beam 1. Figure 5 As shown; then the hydraulic oil is input in reverse into the second oil chamber 9, pushing the second piston part 8 to drive the head of the auxiliary top hammer 3 to move towards the boss 14 of the main top hammer 2 until it returns to the contracted state that fits against the outer side of the boss 14; after the auxiliary top hammer 3 is reset, the hydraulic oil is input in reverse into the first oil chamber 5, pushing the first piston part 4 to drive the six main top hammers 2 to retract, and the auxiliary top hammers 3 are reset synchronously, completing the top hammer return stroke and disengaging from contact with the pyrophyllite and the composite block.

[0037] The cavity temperature heating method is implemented based on the cavity temperature heating method of the six-sided press described above. The following steps must be strictly followed, and all process parameters must be controlled within the specified range to ensure the temperature and pressure requirements for diamond synthesis: Step 1: Heating preparation; Connect the conductive top hammer to the low-voltage, high-current power supply via the transmission line 20, and insulate the other top hammers. Check whether the pyrophyllite, graphite raw materials, etc. in the synthesis chamber are placed in place, and check whether each oil passage, hydraulic system, and cooling channel 17 are operating normally.

[0038] Step 2: Mold closing and pressure application; The six main top hammers 2 are controlled by a hydraulic system to achieve six-axis synchronous mold closing. Pressure is applied to the synthesis cavity in a staged pressurization manner until the cavity pressure reaches the preset synthesis pressure of 5-8 GPa. After pressurization, the pressure is maintained until the fluctuation value of the cavity pressure is ≤ ±0.1 MPa, ensuring that the synthesis cavity has a good sealing effect and the internal pressure of the cavity is in a stable state, providing a basic pressure environment for diamond synthesis.

[0039] Step 3: Graded gradient heating; The low-voltage high-current power supply is started, and the current forms a circuit through the two conductive top hammers. The synthesis cavity is electrically heated by a segmented heating mode. The heating process is divided into three stages. The cavity temperature and top hammer temperature are monitored in real time by the temperature detection module throughout the process. The cooling channel 17 of the main top hammer 2 is continuously circulated with cooling medium to control the temperature of the main top hammer 2 to ≤80℃. Preheating stage: The heating power is linearly increased at a rate of 50-100kW / min. This stage lasts for 3-8 minutes, so that the temperature of the synthesis chamber can be steadily increased to 800-1000℃, completing the preheating of the raw materials and avoiding uneven heating of the raw materials due to direct high temperature.

[0040] Rapid heating stage: Adjust the heating power heating rate to 100-200kW / min. This stage lasts for 2-5 minutes, rapidly raising the temperature of the synthesis chamber to the target diamond growth temperature of 1350-1450℃, quickly entering the optimal temperature environment for crystal growth.

[0041] Constant temperature growth stage: Based on real-time data from the temperature detection module, the heating power is dynamically fine-tuned (power fine-tuning range ≤5kW / min) to stabilize the temperature of the synthesis chamber within the target range of 1350-1450℃. The duration of this stage is set according to the growth requirements of synthetic diamond. During this period, the internal pressure of the chamber is always maintained at ≥5GPa. The auxiliary top hammer 3 extends in real time to compensate for volume shrinkage, ensuring the continuous growth of diamond crystals.

[0042] Step 4: Cooling and depressurizing; After the isothermal diamond growth stage is completed, a stepped power reduction mode is used to cool the cavity, while simultaneously performing a synchronous depressurization operation to achieve a synchronous decrease in cavity temperature and pressure. Specific parameters are controlled as follows: The first stage of cooling: The heating power is reduced to 50% of the target growth power at a rate of 50-80kW / min. This stage lasts for 3-5 minutes. The cavity temperature decreases steadily with the power and there are no sudden changes.

[0043] The second stage of cooling: adjust the power reduction rate to 30-50kW / min and continue to reduce it to 0kW. This stage lasts for 2-10 minutes until the cavity temperature drops to near room temperature.

[0044] Synchronous pressure relief: The pressure relief program is started at the same time as the cooling begins, and the pressure relief rate of the cavity is controlled at 0.5-1.0 GPa / min to ensure that the temperature and pressure changes of the cavity are synchronized during the cooling process. In addition, the auxiliary top hammer 3 continues to close during the cooling stage to compensate for the cavity volume change caused by the material cooling and shrinkage, and to prevent the pressure difference from being too large.

[0045] Step 5: Remove the finished product and clean the cavity; After the pressure in the chamber is completely released and the temperature drops to room temperature, the main top hammer 2 and the auxiliary top hammer 3 are controlled by the hydraulic system to retract and complete the top hammer return stroke, opening the synthesis chamber and taking out the diamond synthesis block; thoroughly clean the pyrophyllite residue, raw material debris, etc. in the synthesis chamber, check whether the hammer surface of the top hammer is damaged, and whether the cooling channel 17 and the oil channel are unobstructed, in order to prepare for the next diamond synthesis.

[0046] The six-sided top press of the present invention can be adapted to the synthesis requirements of synthetic diamonds of different specifications. Only the preset synthesis pressure, constant temperature growth time and heating and cooling rate of each stage need to be adjusted according to the size of the diamond crystal. The rest of the structure and process steps do not need to be significantly adjusted. The hammer surface of the top hammer is made of high-strength wear-resistant alloy material, which can withstand the working environment of high pressure and high temperature. With the heat dissipation effect of the cooling channel 17, the replacement cycle of the top hammer is effectively extended.

[0047] This invention precisely controls temperature and pressure to improve the quality of diamond synthesis. It employs a graded gradient heating and stepwise power reduction cooling process, combined with synchronous adjustment of pressure and temperature, to ensure a smooth transition of the synthesis chamber temperature from preheating to isothermal growth. The temperature does not change abruptly during the cooling process, and the temperature and pressure in the chamber change synchronously, avoiding diamond crystal growth defects caused by asynchronous temperature and pressure changes. During the isothermal stage, the heating power is dynamically fine-tuned, while the temperature of the main top hammer 2 is controlled to be ≤80℃. This ensures the optimal temperature environment for diamond growth and prevents damage to the top hammer due to high temperature, thereby improving the yield and crystal quality of synthetic diamonds.

[0048] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still make modifications to the technical solutions described in the foregoing embodiments without creative effort, or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A six-sided jacking press for synthetic diamonds, comprising six bearing beams (1) and a main jacking hammer (2) that hydraulically slides and extends along the bearing beams (1); characterized in that, The main ejector hammer (2) has a hydraulically sliding and telescopic secondary ejector hammer (3) at its head section. The head end of the secondary ejector hammer (3) protrudes from the head end face of the main ejector hammer (2). When the main ejector hammer (2) closes the mold, the secondary ejector hammer (3) is in a contracted state and there is a gap between adjacent secondary ejector hammers (3). During the diamond synthesis stage, the secondary ejector hammer (3) extends to apply pressure. During the cooling stage after synthesis, the secondary ejector hammer (3) closes.

2. The six-sided press for synthetic diamonds according to claim 1, characterized in that, The pressure beam (1) is provided with a first oil chamber (5), the inner end of the main top hammer (2) extends into the first oil chamber (5) and is connected to a first piston part (4), and the two ends of the first oil chamber (5) are respectively connected to a first oil passage (6) and a second oil passage (7).

3. The six-sided press for synthetic diamonds according to claim 2, characterized in that, The main top hammer (2) is provided with a second oil chamber (9), the inner end of the auxiliary top hammer (3) extends into the second oil chamber (9) and is connected to a second piston part (8), and the two ends of the second oil chamber (9) are respectively connected to a third oil passage (10) and a fourth oil passage (13).

4. The six-sided press for synthetic diamonds according to claim 3, characterized in that, The first oil chamber (5) is provided with an oil pipe (11) connected to the third oil passage (10), and the main top hammer (2) is provided with an oil delivery hole (12) connected to the second oil chamber (9). The oil pipe (11) extends into the oil delivery hole (12) and slides and seals with the inner wall of the oil delivery hole (12).

5. The six-sided press for synthetic diamonds according to claim 1, characterized in that, The main ejector hammer (2) has a boss (14) at the center of its head end face. The secondary ejector hammer (3) slides through the center of the boss (14). When the main ejector hammer (2) closes the mold, the head end of the secondary ejector hammer (3) is attached to the outer side of the boss (14), and the contact surface is parallel to the head end face of the main ejector hammer (2).

6. The six-sided press for synthetic diamonds according to claim 5, characterized in that, The boss (14) has an annular stepped groove (15) at its center, and the head end of the auxiliary hammer (3) has an annular step (16) that cooperates with the annular stepped groove (15) on the side facing the annular stepped groove (15).

7. The six-sided press for synthetic diamonds according to claim 1, characterized in that, The main top hammer (2) is equipped with a cooling channel (17).

8. The cavity temperature heating method for a six-sided press for synthetic diamond according to any one of claims 1-7, characterized in that, The cavity temperature heating method includes the following steps: Step 1, Heating preparation: Select two of the six auxiliary top hammers (3) that are set opposite to each other as conductive top hammers; Step 2, Mold Closure and Pressurization: Control the six main ejector hammers (2) to close the mold synchronously on six axes, pressurize in stages to the preset synthesis pressure of 5-8 GPa, and maintain the pressure until the pressure fluctuation is ≤ ±0.1 MPa, thus completing the sealing and pressure stabilization of the synthesis cavity; Step 3, graded gradient heating: Start the low-voltage, high-current power supply and use a segmented heating mode to heat the inner cavity; Step 4: Cooling and depressurization: After the isothermal growth is completed, the temperature is reduced in a step-by-step power reduction mode. In the first stage, the temperature is reduced to 50% of the target power at a rate of 50-80 kW / min for 3-5 minutes. In the second stage, the temperature is reduced to 0 kW at a rate of 30-50 kW / min for 2-10 minutes. During the cooling process, the pressure is depressurized simultaneously, and the temperature and pressure of the chamber decrease synchronously. Step 5: After depressurization is completed, the top hammer returns, the composite block is removed, and the composite cavity is cleaned.

9. The cavity temperature heating method for a six-sided press for synthetic diamonds according to claim 8, characterized in that, Step three includes the following steps: Preheating section: The heating power is linearly increased at a rate of 50-100kW / min for 3-8 minutes to raise the temperature of the synthesis chamber to 800-1000℃; Rapid heating phase: Adjust the heating rate to 100-200kW / min and continue for 2-5 minutes to raise the chamber temperature to the target growth temperature of 1350-1450℃; Constant temperature growth section: dynamically adjust the heating power to keep the cavity temperature stable within the target temperature and control the temperature of the main hammer (2) to ≤80℃.

10. The cavity temperature heating method for a six-sided press for synthetic diamonds according to claim 8, characterized in that, In step four, the depressurization rate is controlled to be 0.5-1.0 GPa / min.

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