Diamond tool cold-press sintering reducing atmosphere self-adaptive control method and system

Abstract

The application relates to the technical field of adaptive control, and discloses a diamond tool cold pressure sintering reducing atmosphere adaptive control method and system. The method comprises the following steps: calculating reducing process prediction data according to green compact physical property parameters, performing target backstepping type optimization operation on a hydrogen concentration instruction with a predicted pore closure critical point as a time endpoint, and delivering the hydrogen concentration instruction to a hydrogen flow controller; confirming the pore closure critical point in real time through a shrinkage acceleration inflection point and generating an event trigger signal; in response to the event trigger signal, step switching the furnace atmosphere and pulse injecting hydrocarbon gas; and using thermal cracking products to form a blocking layer at residual microchannel orifices, so that a reducing internal microclimate is sealed in a closed pore. The application improves the synchronization accuracy of a reducing atmosphere control timing and a green compact real pore structure state, and the protection reliability of diamond particles in the whole sintering high-temperature holding process.

Description

Technical Field

[0001] This application relates to the field of adaptive control technology, and in particular to an adaptive control method and system for reducing atmosphere in cold pressing and sintering of diamond tools. Background Technology

[0002] Cold pressing sintering of diamond tools is a manufacturing process in which diamond abrasive grains are mixed with iron-based, copper-based, cobalt-based, and other metal binder powders, cold-pressed into shape, and then placed in a continuous sintering furnace to complete pressureless sintering and densification under a reducing atmosphere. In existing solutions, the control of the reducing atmosphere in the sintering furnace generally adopts a steady-state control scheme with oxygen partial pressure probes or dew point sensors as feedback elements. By preset a fixed hydrogen-nitrogen mixing ratio or adjusting the hydrogen flow rate according to the real-time deviation of the gas concentration in the furnace, the atmosphere in the furnace is maintained near the set redox equilibrium point. This ensures that the iron-based, copper-based, and other oxides in the metal binder powder are fully reduced during the heating process, while preventing the diamond particles from undergoing graphitization transformation due to contact with the oxidizing atmosphere at high temperatures.

[0003] However, the control scheme described above only controls the steady-state concentration of the macroscopic external atmosphere in the furnace. The timing of atmosphere switching depends on a preset fixed temperature node, which is completely decoupled from the actual pore structure inside the compact. Due to differences in powder oxygen content, cold-pressing density, and axial characteristic dimensions among different batches of compacts, the actual temperature range for the transition from open to closed pores can differ by 50 to 150 degrees Celsius. For some batches, the fixed temperature node results in atmosphere switching before the pores are closed, leading to insufficient reduction of internal oxides. For other batches, the pores have been closed for a long time, but hydrogen is still being supplied continuously. Excess hydrogen in the high-temperature section undergoes a decarburization reaction with the solid carbon on the outer surface of the compact, causing a decrease in the carbon potential of the binder. A more fundamental flaw is that the existing scheme is completely unaware of the physical fact that the protective effect of the external atmosphere on the diamond particles inside the compact is essentially lost after the pores are closed. The correlation between external atmosphere control and the microclimate inside the closed pores is completely ignored.

[0004] Because existing solutions cannot perceive the real-time evolution of the compact's pore structure, the decoupling between the atmosphere switching timing and the actual physical state of the compact cannot be solved by simply adjusting a fixed temperature node. This leads to two progressive technical problems: First, how to perceive the critical moment when the compact's pores change from open to closed during sintering, and use this moment as a dynamic anchor point for atmosphere switching, so that the switching timing is precisely synchronized with the actual pore closure state of each batch of compacts; Second, simply switching to an inert atmosphere at the critical moment is not enough to ensure that diamond particles are effectively protected throughout the subsequent high-temperature insulation process, because if the remaining microchannels are not completely closed after the switch, the external inert atmosphere may still penetrate and dilute the reducing atmosphere already established in the closed pores. This raises the technical problem of how to actively seal the reducing microclimate already established inside the compact at the critical point of pore closure, so that diamond particles can achieve self-protection within the closed pores. Summary of the Invention

[0005] This application provides an adaptive control method and system for the reducing atmosphere in the cold pressing and sintering of diamond tools. It solves the problems in existing solutions, such as the sintering atmosphere switching timing relying on a fixed temperature node, decoupling from the actual pore closure state of the compact leading to insufficient internal oxide reduction and the risk of decarburization at high temperatures, and the lack of active sealing mechanisms when the external atmosphere fails to protect diamond particles after pore closure. Compared to existing solutions, this application improves the synchronization accuracy between the reducing atmosphere control timing and the actual pore structure state of the compact by real-time identification of the pore closure critical point using the compact shrinkage acceleration inflection point and triggering a step-switching of the atmosphere and a linkage operation with hydrocarbon gas blocking. This enhances the reliability of diamond particle protection throughout the high-temperature holding process during sintering.

[0006] In a first aspect, this application provides an adaptive control method for the reducing atmosphere of cold pressing sintering of diamond tools, the adaptive control method for the reducing atmosphere of cold pressing sintering of diamond tools comprising: Step S1: Calculate the reduction process prediction data based on the powder oxygen content, cold pressing density, and axial characteristic dimensions of the compact. Step S2: Based on the predicted data of the reduction process, with the predicted pore closure critical point as the time endpoint, perform a target backward optimization calculation on the hydrogen gas integral to obtain the hydrogen concentration command, and send the hydrogen concentration command to the hydrogen flow controller to dynamically adjust the hydrogen-nitrogen mixing ratio in the furnace. Step S3: Collect the axial shrinkage of the compact, filter and perform second-order difference processing on the axial shrinkage to obtain the shrinkage acceleration, and confirm the inflection point when the shrinkage acceleration changes from positive to negative and the amplitude exceeds the noise threshold as the critical point of pore closure, and generate an event trigger signal. Step S4: In response to the event trigger signal, a step switching command is issued to the hydrogen flow controller and the nitrogen flow controller respectively to switch the furnace atmosphere from hydrogen-containing reducing mixed gas to inert protective gas. After the switching is completed, hydrocarbon gas is pulsedly injected into the furnace. The hydrocarbon gas thermal decomposition products form a sealing layer at the pore opening of the residual microchannel of the pressed billet, and the reducing internal microclimate established in the sealed hole of the pressed billet at the critical point of pore closure is sealed in the sealed hole.

[0007] Secondly, this application provides an adaptive control system for the reducing atmosphere of cold pressing sintering of diamond tools, the adaptive control system for the reducing atmosphere of cold pressing sintering of diamond tools comprising: The calculation module is used to calculate the reduction process prediction data based on the powder oxygen content, cold pressing density and axial characteristic dimensions of the compact; The adjustment module is used to perform a target-based backward optimization calculation on the hydrogen gas integral number based on the predicted data of the reduction process, with the predicted pore closure critical point as the time endpoint, to obtain a hydrogen concentration command, and to send the hydrogen concentration command to the hydrogen flow controller to dynamically adjust the hydrogen-nitrogen mixing ratio in the furnace. The generation module is used to collect the axial shrinkage of the compact, filter and perform second-order difference processing on the axial shrinkage to obtain the shrinkage acceleration, and identify the inflection point when the shrinkage acceleration changes from positive to negative and the amplitude exceeds the noise threshold as the critical point of pore closure, and generate an event trigger signal. The switching module is used to respond to the event trigger signal and send step switching commands to the hydrogen flow controller and nitrogen flow controller respectively to switch the furnace atmosphere from hydrogen-containing reducing mixed gas to inert protective gas. After the switching is completed, hydrocarbon gas is pulsedly injected into the furnace. The thermal decomposition products of the hydrocarbon gas form a sealing layer at the pore opening of the residual microchannel of the pressed billet, and the reducing internal microclimate established in the sealed hole of the pressed billet at the critical point of pore closure is sealed in the sealed hole.

[0008] Thirdly, a diamond tool cold pressing sintering reducing atmosphere adaptive control device is provided, comprising: a memory and at least one processor, wherein the memory stores instructions; the at least one processor invokes the instructions in the memory to cause the diamond tool cold pressing sintering reducing atmosphere adaptive control device to execute the aforementioned diamond tool cold pressing sintering reducing atmosphere adaptive control method.

[0009] Fourthly, a computer-readable storage medium is provided, wherein instructions are stored therein, which, when executed on a computer, cause the computer to perform the aforementioned adaptive control method for the reducing atmosphere of cold pressing sintering of diamond tools.

[0010] The technical solution provided in this application uses three physical property parameters—powder oxygen content, cold-pressed density, and axial characteristic dimensions—of the pressed billet as the calculation input for the reduction process prediction data. It incorporates the objectively existing physical property differences between batches into the feedforward calculation stage of atmosphere control. This ensures that the generation of hydrogen concentration commands no longer depends on the current steady-state deviation of the gas concentration in the furnace, but is based on a quantitative prediction of the reduction kinetics process inside the pressed billet of this batch. Using the predicted pore closure critical point as the time endpoint, a target-driven backward optimization calculation is performed, ensuring that the hydrogen concentration command output in each control sampling cycle matches the current remaining reduction amount and the remaining time window. This dynamically adjusts the hydrogen-nitrogen mixing ratio in the furnace to a level precisely meeting the reduction completion target before the pore closure critical point arrives. This avoids insufficient reduction caused by the hydrogen concentration remaining at a conservative set value for a long time, and also avoids the risk of decarburization in the high-temperature section caused by continuously high hydrogen concentrations, achieving a dynamic balance between reduction efficiency and atmosphere safety.

[0011] The shrinkage acceleration is obtained by filtering and second-order differential processing of the axial shrinkage of the compact. The inflection point when the shrinkage acceleration changes from positive to negative and the amplitude exceeds the noise threshold is used to confirm the pore closure critical point and generate an event trigger signal. The determination of the atmosphere switching timing is changed from a preset fixed temperature node to the real-time physical state of the evolution of the internal pore structure of the compact, so that the switching action is precisely synchronized with the actual pore closure process of each batch of compacts. After the event trigger signal is triggered, step switching commands are issued to the hydrogen flow controller and nitrogen flow controller respectively to complete the switching of the atmosphere from hydrogen-containing reducing mixture to inert protective gas. After the switching is completed, hydrocarbon gas is pulsedly injected, utilizing carbon The hydrogen gas thermal decomposition products form a sealing layer at the microchannel pores of the compact, sealing the reducing internal microclimate established within the compact's sealed pores at the critical point of pore closure. This ensures that the diamond particles remain in a self-protective reducing environment within the sealed pores throughout the subsequent high-temperature insulation process, eliminating the need for a continuous external supply of hydrogen. This fundamentally solves the essential defect in existing technologies where the external atmosphere fails to protect the internal diamond particles after pore closure. Simultaneously, the dynamic calculation mechanism of the noise threshold in the shrinkage acceleration inflection point criterion allows the critical point identification results to adapt to changes in noise levels under different batches of sintering furnace conditions, ensuring the consistency and reliability of the event trigger signal across batches. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1This is a schematic diagram of an embodiment of the adaptive control method for reducing atmosphere in cold pressing and sintering of diamond tools in this application. Figure 2 This is a schematic diagram illustrating the convergence process of batch-to-batch updating of the reduction kinetic parameters using recursive least squares operation in an embodiment of this application. Detailed Implementation

[0014] This application provides an adaptive control method and system for the reducing atmosphere in the cold pressing sintering of diamond tools. The terms "first," "second," "third," "fourth," etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in a sequence other than that illustrated or described herein. Furthermore, the terms "comprising" or "having" and any variations thereof are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0015] For ease of understanding, the specific process of the embodiments of this application is described below. Please refer to [link / reference]. Figure 1 One embodiment of the adaptive control method for the reducing atmosphere in the cold pressing and sintering of diamond tools in this application includes: Step S1: Calculate the reduction process prediction data based on the powder oxygen content, cold pressing density, and axial characteristic dimensions of the compact. Specifically, the reduction process prediction data refers to the cumulative reduction rate sequence calculated at each time point within each temperature range of the sintering heating curve, based on three physical property parameters: powder oxygen content, cold-pressed density, and axial characteristic dimension of the compact. Powder oxygen content reflects the total amount of oxides to be reduced in the metal binder powder; cold-pressed density determines the cross-sectional area of ​​the hydrogen mass transfer channels in the compact's pore network; and axial characteristic dimension determines the maximum path length for hydrogen diffusion from the compact's outer surface to its interior. These three parameters jointly constrain the actual reduction rate of hydrogen inside the compact; the absence of any one of these parameters makes it impossible to accurately predict the reduction process of the internal oxides.

[0016] Step S2: Based on the reduction process prediction data, with the predicted pore closure critical point as the time endpoint, perform a target backward optimization calculation on the hydrogen gas integral to obtain the hydrogen concentration command, and send the hydrogen concentration command to the hydrogen flow controller to dynamically adjust the hydrogen-nitrogen mixing ratio in the furnace. Specifically, the target-driven backward optimization calculation refers to using the predicted pore closure critical point as the time endpoint. Within each control sampling cycle, the remaining reduction amount is calculated based on the difference between the current cumulative reduction rate and the target reduction rate. Then, combined with the remaining time window from the current time to the pore closure critical point, the minimum hydrogen gas integral required to complete the reduction before the pore closure critical point is calculated backward. This minimum hydrogen gas integral, after being constrained by upper and lower limits, becomes the hydrogen concentration command. The lower limit of the hydrogen gas integral is set at 5 vol% to maintain the minimum reduction capacity in the furnace; the upper limit is set at 30 vol% to prevent excessively high hydrogen concentration in the high-temperature section from causing decarburization reaction on the outer surface of the pressed billet. The hydrogen concentration command, after conversion, is sent as an analog signal to the hydrogen flow controller. The nitrogen flow controller simultaneously receives the difference compensation command, and the two work together to maintain a constant total flow rate in the furnace.

[0017] Step S3: Collect the axial shrinkage of the compact, filter and perform second-order difference processing on the axial shrinkage to obtain the shrinkage acceleration. The inflection point when the shrinkage acceleration changes from positive to negative and the amplitude exceeds the noise threshold is identified as the critical point of pore closure, and an event trigger signal is generated. Specifically, shrinkage acceleration refers to the second time derivative of the axial shrinkage of the compact, reflecting the changing trend of the compact densification rate. During the open-pore stage, the sintering neck continues to grow, densification accelerates, and the shrinkage acceleration is positive. When a large number of open pores transform into closed pores, the pore shrinkage resistance increases sharply, the densification rate increases abruptly, and the shrinkage acceleration changes from positive to negative, showing an inflection point. The noise threshold is set to three times the standard deviation of the shrinkage acceleration sequence during the initial heating stage. This is used to distinguish the true pore closure critical point signal from the false inflection point caused by measurement noise. Only when the shrinkage acceleration amplitude exceeds this noise threshold and continuously meets the criterion of changing from positive to negative within three consecutive sampling periods can it be confirmed as a pore closure critical point, generating an event trigger signal.

[0018] Step S4: Respond to the event trigger signal and send a step switching command to the hydrogen flow controller and nitrogen flow controller respectively to switch the furnace atmosphere from hydrogen-containing reducing mixed gas to inert protective gas. After the switching is completed, inject hydrocarbon gas into the furnace in a pulse. Use the hydrocarbon gas thermal decomposition products to form a sealing layer at the microchannel orifice of the compaction blank to seal the reducing internal microclimate established in the compaction blank at the critical point of pore closure.

[0019] Specifically, the reducing internal microclimate refers to the gaseous environment sealed within the compact's closed pores at the critical point of pore closure. This gaseous environment consists of a high hydrogen partial pressure and low water vapor partial pressure atmosphere established in the furnace before sealing, continuously providing reducing protection to the diamond particle surface. The hydrocarbon gas pulse injection rate is 0.25 vol% of the total furnace flow rate, with an injection duration not exceeding 34 seconds. This range ensures that the deposition of carbon from thermal decomposition products at the residual microchannel pore openings is sufficient to form a sealing layer, while avoiding excessive hydrocarbon gas that could lead to an abnormal increase in the carbon potential on the compact surface. When the step switching command is executed, the hydrogen flow rate linearly decreases to zero within 6 seconds according to a preset decreasing slope, with nitrogen flow rate compensating synchronously. The positive pressure in the furnace is maintained within the range of 300 to 500 Pa to prevent external air from flowing back into the furnace due to insufficient positive pressure and disrupting the sealed reducing internal microclimate.

[0020] In one specific embodiment, step S1 includes: The oxygen content of this batch of metal binder powder was determined by hydrogen loss method. The density of the cold-pressed compact was measured using the Archimedes drainage method. Based on the powder oxygen content and density measurement results, the cold-pressed density and relative compact density were calculated. Based on the relative compact density and axial characteristic dimensions, the effective cross-sectional area and maximum diffusion path length of the gas mass transfer channel for hydrogen in the compact pore network are calculated to obtain the corrected value of hydrogen permeation rate. Substituting the powder oxygen content, relative compact density, and hydrogen permeation rate correction values ​​into the reduction kinetic equation, and using the sintering heating curve as the time axis, the cumulative reduction rate corresponding to each temperature range is integrated step by step to obtain the reduction process prediction data.

[0021] Specifically, the relative compact density is calculated by dividing the cold-pressed density measured by the Archimedes displacement method by the theoretical density, which is calculated by weighting the mass fractions of each component in the metal binder formulation. The resulting dimensionless ratio reflects the degree of pore filling in the compact, typically ranging from 0.72 to 0.85. The effective cross-sectional area of ​​the gas mass transfer channel refers to the effective flow area occupied by interconnected pores per unit cross-section when hydrogen permeates axially through the compact's pore network. Its value is derived from the relative compact density; the lower the relative compact density, the more interconnected pores, the larger the effective cross-sectional area, and the lower the hydrogen permeation resistance. The maximum diffusion path length is taken as half the axial characteristic dimension of the compact, i.e., the maximum distance hydrogen needs to travel from the outer surface of the compact to its geometric center. This value is based on the assumption of symmetrical mass transfer, where hydrogen permeates simultaneously from both ends. The hydrogen permeation rate correction value combines two parameters: the effective cross-sectional area of ​​the gas mass transfer channel and the maximum diffusion path length. It corrects the apparent rate constant in the reduction kinetic equation so that the reduction rate output by the equation reflects the actual mass transfer capacity of hydrogen under the geometric and pore structure conditions of this batch of compacts, rather than relying solely on the theoretical value of temperature and hydrogen concentration.

[0022] The cumulative reduction rate refers to the ratio of the mass of oxides that have been reduced inside the compact to the total mass of oxides corresponding to the oxygen content of the powder from the start of sintering to a certain moment, with a value ranging from 0 to 1. Substituting the powder oxygen content, relative compact density, and hydrogen permeation rate correction value into the reduction kinetic equation, and using the time step of each temperature segment specified in the sintering heating curve as the integration step, the reduction rate increment for each temperature segment is calculated based on the current temperature and hydrogen concentration. These increments are then accumulated sequentially to obtain the cumulative reduction rate sequence corresponding to each moment. This sequence is the predicted data for the reduction process. The time step for each temperature segment in the sintering heating curve is 30 seconds, consistent with the control sampling period, ensuring that the temporal resolution of the predicted data matches the frequency of subsequent hydrogen concentration commands. The target reduction rate is set to 0.95, meaning that the reduction ratio of oxides inside the compact is not less than 95% at the critical point of pore closure. A reduction ratio below this means that after the pores are closed, the remaining unreduced oxides will be permanently sealed in the pores and cannot be further reduced by external hydrogen.

[0023] In one specific embodiment, step S2 includes: Based on the reduction process prediction data, the cumulative reduction rate of each temperature segment in the sintering heating curve is verified segment by segment, and the moment when the cumulative reduction rate first reaches the target reduction rate is identified as the predicted pore closure critical point. Using the pore closure critical point as the time endpoint, the cumulative reduction rate gap within the remaining time window from the current time to the pore closure critical point is calculated to obtain the remaining reduction amount; Based on the remaining reduction amount and the remaining time window, the minimum requirement value of hydrogen gas integral is optimized by reverse calculation, and upper and lower limits of hydrogen gas integral are imposed on the minimum requirement value to obtain the hydrogen concentration command. The hydrogen concentration command is converted into a hydrogen mass flow rate value and sent to the hydrogen flow controller. The difference between the total flow rate in the furnace and the hydrogen mass flow rate value is simultaneously sent to the nitrogen flow controller, thus completing the dynamic adjustment of the hydrogen-nitrogen mixing ratio in the furnace.

[0024] Specifically, the predicted pore closure critical point refers to the moment when the cumulative reduction rate value in the cumulative reduction rate sequence of the reduction process prediction data first reaches the target reduction rate of 0.95, recorded as the predicted pore closure critical point for that batch of compacts. This moment represents the time when the reduction degree of the oxides inside the compact is expected to reach 95% under the current hydrogen concentration command. The significance of using this point as the end point is that after the pores are closed, external hydrogen can no longer penetrate into the compact, so the reduction work must be completed before this point. The remaining time window refers to the length of time between the current sampling time of the control system and the predicted pore closure critical point. This value gradually shortens with each sampling cycle and is updated every 30 seconds. The cumulative reduction rate gap is the difference between the target reduction rate of 0.95 and the actual cumulative reduction rate completed at the current time. It reflects the proportion of the reduction amount that still needs to be completed within the remaining time window to the total reduction task. This difference is the remaining reduction amount.

[0025] The specific process of the target-oriented backward optimization calculation is as follows: divide the remaining reduction amount by the remaining time window to obtain the incremental reduction rate required per unit time. Then, substitute this incremental rate into the relationship between the rate constant and the hydrogen gas integral in the reduction kinetic equation to solve for the minimum hydrogen gas integral required to meet the reduction rate. This value is the minimum required hydrogen gas integral for this sampling period. The lower limit of the hydrogen gas integral is set at 5 vol%, because below this value, the hydrogen partial pressure in the furnace is insufficient to maintain an effective reduction reaction for iron-based and copper-based oxides. The upper limit is set at 30 vol%, because above this value, in the sintering temperature range exceeding 750 degrees Celsius, excessively high hydrogen partial pressure will trigger a decarburization reaction between hydrogen and solid carbon on the outer surface of the compact, leading to a decrease in the carbon potential of the binder. The output value after being truncated by the upper and lower limits is the hydrogen concentration command. The hydrogen concentration command multiplied by the total flow rate in the furnace yields the hydrogen mass flow rate. The total flow rate in the furnace minus the hydrogen mass flow rate yields the nitrogen flow rate. Both are simultaneously sent to the hydrogen flow controller and the nitrogen flow controller in the form of analog signals ranging from 4 to 20 mA. The two controllers work together to adjust the hydrogen-nitrogen mixing ratio in the furnace according to the command while keeping the total flow rate constant.

[0026] In one specific embodiment, step S3 includes: The axial shrinkage of the compact is obtained by symmetrically collecting the axial displacement of both ends of the compact using a laser displacement sensor and taking the average value of the displacement of both ends. Savitzky-Golay polynomial filtering is applied to the axial contraction sequence to obtain a denoised contraction sequence. Five-point central difference operation is performed on the denoised shrinkage sequence to obtain the first-order shrinkage rate and shrinkage acceleration. Substituting the first-order contraction rate and contraction acceleration into the critical point criterion: if the first-order contraction rate is negative, the contraction acceleration changes from positive to negative, and the amplitude of the contraction acceleration exceeds three times the sequence standard deviation of the contraction acceleration in the initial stage of heating, and these conditions are simultaneously met within three consecutive sampling periods, this is used as the confirmation condition for the pore closure critical point. The furnace temperature value corresponding to the confirmation time is recorded, and an event trigger signal is generated.

[0027] Specifically, laser displacement sensors are symmetrically arranged on both ends of the compact along its axial direction, with a resolution of no less than 0.5 micrometers and a sampling frequency of no less than 10 Hz. The reason for averaging the displacements at both ends is to eliminate the unilateral warping error caused by uneven heating during sintering, so that the axial shrinkage truly reflects the overall densification degree of the compact. The Savitzky-Golay polynomial filter has a window length of 21 sampling points, corresponding to a time window of 2.1 seconds, and a polynomial order of 4. This parameter combination suppresses high-frequency noise caused by vibration and thermal convection in the sintering furnace while retaining the local curvature change information of the axial shrinkage curve during the pore closure transition stage. If the window is too long, it will smooth out the true critical inflection point characteristics; if the order is too low, it will be unable to accurately fit the nonlinear local morphology of the shrinkage curve. The five-point central difference operation takes the two denoised shrinkage values ​​before and after the current time as the center, sums them with a fixed difference coefficient, and divides them by the sampling time step to obtain the first-order shrinkage rate. The same five-point central difference operation with the same difference coefficient is applied again to the first-order shrinkage rate sequence to obtain the shrinkage acceleration. This operation method has higher numerical stability than the two-point difference and reduces the amplification effect of noise in the differentiation process.

[0028] In the critical point criterion, the noise threshold is taken as three times the standard deviation of the shrinkage acceleration sequence during the initial heating stage (from room temperature to 200 degrees Celsius). During this stage, the compact has not yet undergone substantial densification, and fluctuations in shrinkage acceleration originate entirely from sensor noise and thermal drift. Using three times the standard deviation as the threshold is based on the statistical basis that 99.7% of the noise data falls within this range under the assumption of a normal distribution. Changes in shrinkage acceleration exceeding this threshold can be considered genuine structural signals rather than noise. It is required that three consecutive sampling periods (i.e., three consecutive 90 seconds) simultaneously satisfy three conditions: a negative first-order shrinkage rate, a shrinkage acceleration changing from positive to negative, and an amplitude exceeding the noise threshold. This is because satisfying the conditions in a single sampling period carries the risk of occasional noise triggering; consistently satisfying them for three consecutive periods reduces the probability of false triggering to a negligible level. The condition of a negative first-order shrinkage rate is used to exclude the axial elongation stage of the compact due to thermal expansion during the initial heating stage, ensuring that the judgment window is activated only when the compact is in a substantial shrinkage state. The furnace temperature value corresponding to the confirmation moment is read in real time by thermocouple and recorded synchronously with the event trigger signal. This furnace temperature value is written into the batch database and stored together with the oxygen content, cold-pressed density and axial characteristic dimensions of the powder in this batch. It is used for the accumulation and correction of the cross-batch pore closure critical point prediction database.

[0029] In one specific embodiment, step S4, in response to the event trigger signal, sends step switching commands to the hydrogen flow controller and nitrogen flow controller respectively, switching the furnace atmosphere from a hydrogen-containing reducing mixture to an inert protective gas, including: In response to the event trigger signal, a hydrogen flow zeroing command is sent to the hydrogen flow controller, and the output value of the hydrogen flow controller is linearly reduced according to the preset deceleration slope to obtain the hydrogen flow zeroing timing. Based on the hydrogen flow rate zeroing time sequence, a nitrogen compensation flow command is synchronously sent to the nitrogen flow controller. The difference between the total flow rate in the furnace and the current hydrogen flow rate is calculated time by time to obtain the nitrogen compensation flow value. The nitrogen compensation flow value is then sent to the nitrogen flow controller for execution, so that the total flow rate in the furnace remains constant during the switching process. The furnace pressure value collected by the furnace pressure sensor is monitored in real time. The furnace pressure value is compared with the preset positive pressure threshold to obtain the pressure deviation value. Based on the pressure deviation value, the nitrogen compensation flow value is corrected in a closed loop to complete the step switching from hydrogen-containing reduction mixture to inert protective gas.

[0030] Specifically, the preset rate of decrease refers to the decrease per second of the hydrogen flow controller output value after the hydrogen flow rate zeroing command is triggered. It is calculated by dividing the current output value of the hydrogen flow controller at the moment the event trigger signal is issued by 6 seconds, requiring the hydrogen flow rate to linearly decrease to zero within 6 seconds. The selection of 6 seconds is based on the fact that a rate of rapid decrease in hydrogen flow rate below this duration would cause negative pressure fluctuations in the furnace pressure at the moment of switching, posing a risk of external air backflow into the furnace; while a time above 10 seconds would result in excessively long hydrogen presence during the switching process, offering no substantial protection in the high-temperature section after pore closure and posing a risk of decarbonization. 6 seconds represents an engineering value that satisfies both furnace pressure stability and timely switching requirements. The hydrogen flow rate zeroing sequence refers to the sequence of hydrogen flow output values ​​corresponding to each control step within the 6-second switching window. This sequence is generated starting from the current hydrogen flow rate value, ending at zero, and decreasing at equal intervals according to the preset rate of decrease. The control step size is consistent with the sampling period, taking 1 second.

[0031] The nitrogen compensation flow rate is calculated within each control step by subtracting the actual output value of the hydrogen flow controller at the current moment from the total furnace flow rate. The difference between the two is the compensation flow rate that the nitrogen flow controller needs to output at that moment. This difference increases linearly with the linear decrease in hydrogen flow rate, ensuring that the sum of the two always equals the total furnace flow rate, and the total volumetric flow rate of the gas in the furnace remains constant throughout the switching process. The preset positive pressure threshold is 350 Pa. This value is based on the fact that when the positive pressure in the furnace is below 200 Pa, there is a risk of external air seeping in due to incomplete furnace sealing, and when it is above 500 Pa, the pressure on the furnace seals exceeds the design range. 350 Pa is the median value of the safe positive pressure range. The furnace pressure sensor has a range of 0 to 2000 Pa, an accuracy of ±5 Pa, and a sampling interval of 1 second. The pressure deviation value is the difference between the real-time reading of the furnace pressure sensor and the preset positive pressure threshold of 350 Pa. A positive difference indicates that the furnace pressure is too high, and the nitrogen compensation flow rate should be reduced accordingly; a negative difference indicates that the furnace pressure is too low, and the nitrogen compensation flow rate should be increased accordingly. The closed-loop correction value of the nitrogen compensation flow rate is obtained by multiplying the pressure deviation value by a proportional coefficient of 0.02 standard liters per minute per Pa. The corrected nitrogen compensation flow rate value is then reissued to the nitrogen flow controller for execution, forming a pressure closed-loop control loop with furnace pressure as the feedback quantity and nitrogen flow rate as the adjustment quantity, until the hydrogen flow rate zeroing sequence is completed and the furnace atmosphere is completely switched to inert protective gas.

[0032] In one specific embodiment, step S4 involves pulsed injection of hydrocarbon gas into the furnace after the switching is completed, utilizing the hydrocarbon gas thermal decomposition products to form a sealing layer at the microchannel orifices of the pressed billet, including: Starting from the moment the step switching is completed, the total orifice area of ​​the residual microchannels in the compact is calculated based on the cold pressing density and axial characteristic dimensions to obtain the amount of hydrocarbon gas required for sealing. Based on the amount of hydrocarbon gas required for plugging, a pulse injection command is sent to the hydrocarbon gas flow controller to inject hydrocarbon gas into the furnace with a preset volume fraction. The injection duration is determined according to the ratio of the amount of hydrocarbon gas required for plugging to the total flow rate in the furnace, thus obtaining the hydrocarbon gas pulse injection sequence. The injection is performed according to the hydrocarbon gas pulse injection sequence. The hydrocarbon gas undergoes thermal decomposition reaction at the sintering temperature. The deposition process of the thermal decomposition products at the residual microchannel orifice of the compact is correlated with the pulse injection sequence to obtain a sealing layer covering the residual microchannel orifice. After the hydrocarbon gas pulse injection sequence ends, a zeroing command is sent to the hydrocarbon gas flow controller.

[0033] Specifically, residual microchannels refer to pore channels in the compact's pore network that are not completely closed at the critical point of pore closure and still maintain a weak connection with the external furnace atmosphere. Their pore size typically ranges from submicron to several micrometers. The total pore area refers to the sum of the cross-sectional areas of all residual microchannel openings on the outer surface of the compact. It is calculated by multiplying the open porosity corresponding to the cold-pressed density by the outer surface area of ​​the compact, and then multiplying by the residual open pore ratio correction factor corresponding to the critical point of pore closure. This correction factor is set to 0.08, based on the empirical rule in sintering densification theory that the residual open porosity accounts for approximately 8% of the initial open porosity when the transformation from open to closed pores is complete. The calculation process for the amount of hydrocarbon gas required for plugging is as follows: multiply the total orifice area by the average depth of the residual microchannel (taken as 0.02 times the axial characteristic dimension) to obtain the total volume of the residual microchannel, and then divide by the carbon production rate of hydrocarbon gas thermal decomposition (taken as 0.74 for the carbon mass fraction produced by the thermal decomposition of methane at 700 to 900 degrees Celsius), to obtain the amount of hydrocarbon gas required to cover all the orifices of the residual microchannel.

[0034] The preset volume fraction of hydrocarbon gas is 0.25 vol%. This value is based on the fact that below 0.1 vol%, the amount of carbon produced by pyrolysis per unit time is insufficient to effectively seal the residual microchannel orifices within 34 seconds, while above 0.5 vol%, excessive pyrolysis carbon will deposit over a large area on the outer surface of the compact, leading to an abnormal increase in the carbon potential of the outer binder and affecting the phase composition of the metal binder. 0.25 vol% is the midpoint of the feasible engineering range between these two values. The injection time is determined by dividing the amount of hydrocarbon gas required for sealing by the product of the total flow rate in the furnace and the preset volume fraction. That is, the injection time equals the amount of hydrocarbon gas required for sealing divided by the actual volumetric flow rate of hydrocarbon gas injected per unit time. This calculation result usually falls within the range of 20 to 40 seconds. Hydrocarbon gases undergo thermal decomposition at sintering temperatures of 700 to 900 degrees Celsius, generating nanoscale pyrolytic carbon particles. These pyrolytic carbon particles preferentially accumulate and deposit at the pores of the smallest residual microchannels, forming a sealing layer 100 to 300 nanometers thick. This physically blocks gas exchange between the external furnace atmosphere and the reducing microclimate inside the sealed pores of the pressed billet. The pulse injection sequence is terminated when the cumulative injection time reaches the calculated injection duration. Upon reaching this duration, a zero-reset command is sent to the hydrocarbon gas flow controller, reducing the hydrocarbon gas flow rate to zero within 2 seconds, and restoring the furnace atmosphere to a pure nitrogen protective state.

[0035] In one specific embodiment, step S4, which involves sealing the reductive internal microclimate established within the sealed cavity of the compact at the critical point of pore closure, includes: Using the integral number of hydrogen gas and the partial pressure of water vapor in the furnace at the critical point of pore closure as a benchmark, the partial pressure of hydrogen gas and the partial pressure of water vapor in the closed pore are calculated to obtain the initial atmosphere parameters of the reducing internal microclimate. Based on the formation of the sealing layer, the sealing status of the residual microchannel orifice is confirmed. The sealing status is correlated with the initial atmosphere parameters and recorded to obtain the sealing confirmation record of the reducing internal microclimate inside the sealed orifice. The sealing confirmation record, along with the powder oxygen content, cold-pressed density, and axial characteristic dimensions of this batch, are written into the batch database. The cumulative reduction rate prediction deviation in the reduction process prediction data is calculated to obtain the batch prediction error. The batch prediction error is then input into the recursive least squares operation to update the rate constant and reaction order in the reduction kinetic equation, resulting in the updated reduction kinetic parameters.

[0036] Specifically, the reducing internal microclimate refers to the gas composition state sealed within the closed pores of the compact at the critical point of pore closure. Its core characteristic is the combination of high hydrogen partial pressure and low water vapor partial pressure. This combination protects the carbon potential on the surface of diamond particles, preventing graphitization transformation of diamond due to contact with an oxidizing atmosphere during subsequent high-temperature holding stages. The initial atmosphere parameters are calculated by multiplying the partial hydrogen gas volume in the furnace at the critical point of pore closure by the absolute pressure of the furnace to obtain the hydrogen partial pressure within the closed pores; and by multiplying the volume fraction of water vapor in the exhaust gas at the furnace tail at the critical point of pore closure by the absolute pressure of the furnace to obtain the water vapor partial pressure within the closed pores. These two parameters together constitute the initial atmosphere parameters. When the water vapor partial pressure is below 500 Pa, the corresponding dew point is below -30 degrees Celsius. Under this condition, the thermodynamic direction of the reduction reaction of iron-based and copper-based oxides is positive, indicating that the sealed atmosphere has an effective reducing protective capability. The confirmation of the sealing status is based on the fact that after the hydrocarbon gas pulse injection sequence is completed, the water vapor partial pressure in the tail gas does not show an upward trend in two consecutive sampling cycles, indicating that the residual microchannel has been sealed by the sealing layer and the gas exchange channel between the external furnace atmosphere and the atmosphere inside the sealing hole has been disconnected.

[0037] The sealing confirmation record is a batch record entry that packages the sealing status confirmation conclusion, initial atmosphere parameters (hydrogen partial pressure and water vapor partial pressure), and furnace temperature at the critical point of pore closure. This entry, along with the batch's powder oxygen content, cold-pressed density, and axial characteristic dimensions, is written into the batch database to form a complete batch process record. The batch prediction error is calculated as the difference between the measured residual oxygen content determined by X-ray fluorescence spectrometry after the compact is removed from the furnace and the predicted residual oxygen content at the critical point of pore closure in the reduction process prediction data. This difference reflects the direction and magnitude of the prediction deviation of the reduction kinetic equation under the current batch conditions. The recursive least squares operation uses the batch prediction error as the observed residual, and the rate constant and reaction order as parameters to be updated. The forgetting factor is set to 0.97, which gives higher weight to recent batch data, enabling the model parameters to track the systematic drift of oxygen content caused by switching between different powder batches. The updated rate constant is constrained to the reciprocal of 0.05 to 0.80 seconds, and the updated reaction order is constrained to the range of 0.30 to 1.50. Both constraints are set based on the physically feasible range of solid-gas reduction reaction kinetics. Update results that exceed the constraint range are truncated to the boundary value and anomalies are recorded in the batch log. The updated rate constant and reaction order are the updated reduction kinetic parameters, which replace the original parameter values ​​when initializing the reduction kinetic equations in the next batch.

[0038] Figure 2 This is a schematic diagram illustrating the convergence process of batch-to-batch updating of the reduction kinetic parameters using recursive least squares operation in an embodiment of this application. Figure 2 The figure illustrates the convergence process of recursive least squares operation in updating the rate constant k and reaction order n in the reduction kinetic equation across 30 consecutive sintering batches. The upper figure shows that the estimated value of the rate constant k gradually approaches the batch data-driven convergence interval from the initial literature value of 0.18 in the first batch. After the batch database is activated in the 10th batch, the update step size narrows and the estimated value tends to stabilize. The gray-filled area represents the confidence band centered on the current estimated value. The lower figure shows that the estimated value of the reaction order n exhibits a bounded fluctuation convergence trend around the true value of 0.54 throughout the entire batch range. The fluctuation amplitude gradually compresses with the accumulation of batches. Both figures jointly verify that when the forgetting factor is 0.97, the recursive least squares operation can still maintain the adaptive correction ability of the parameter estimated value to continuously approach the true value under different powder batch oxygen content drift conditions.

[0039] The adaptive control method for reducing atmosphere in the cold pressing sintering of diamond tools in this application has been described above. The adaptive control system for reducing atmosphere in the cold pressing sintering of diamond tools in this application is described below. One embodiment of the adaptive control system for reducing atmosphere in the cold pressing sintering of diamond tools in this application includes: The calculation module is used to calculate the reduction process prediction data based on the powder oxygen content, cold pressing density and axial characteristic dimensions of the compact; The adjustment module is used to perform a target-based backward optimization calculation on the hydrogen gas integral number based on the predicted data of the reduction process, with the predicted pore closure critical point as the time endpoint, to obtain a hydrogen concentration command, and to send the hydrogen concentration command to the hydrogen flow controller to dynamically adjust the hydrogen-nitrogen mixing ratio in the furnace. The generation module is used to collect the axial shrinkage of the compact, filter and perform second-order difference processing on the axial shrinkage to obtain the shrinkage acceleration, and identify the inflection point when the shrinkage acceleration changes from positive to negative and the amplitude exceeds the noise threshold as the critical point of pore closure, and generate an event trigger signal. The switching module is used to respond to the event trigger signal and send step switching commands to the hydrogen flow controller and nitrogen flow controller respectively to switch the furnace atmosphere from hydrogen-containing reducing mixed gas to inert protective gas. After the switching is completed, hydrocarbon gas is pulsedly injected into the furnace. The thermal decomposition products of the hydrocarbon gas form a sealing layer at the pore opening of the residual microchannel of the pressed billet, and the reducing internal microclimate established in the sealed hole of the pressed billet at the critical point of pore closure is sealed in the sealed hole.

[0040] This invention also provides an adaptive control device for the reducing atmosphere of cold pressing sintering of diamond tools, which can be a server. The adaptive control device includes a processor, memory, display screen, input device, network interface, and database connected via a system bus. The processor, designed as a computer, provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system, computer programs, and a database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The database stores the data corresponding to this embodiment. The network interface communicates with external terminals via a network connection. When the computer program is executed by the processor, it implements the above-described method.

[0041] The present invention also provides a computer-readable storage medium, which can be a non-volatile computer-readable storage medium or a volatile computer-readable storage medium, wherein the computer-readable storage medium stores instructions that, when the instructions are executed on a computer, cause the computer to perform the steps of the adaptive control method for the reducing atmosphere of the diamond tool cold pressing sintering.

[0042] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0043] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the existing solution, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a diamond tool cold pressing sintering reduction atmosphere adaptive control device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0044] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An adaptive control method for the reducing atmosphere during cold pressing and sintering of diamond tools, characterized in that, The method includes: Step S1: Calculate the reduction process prediction data based on the powder oxygen content, cold pressing density, and axial characteristic dimensions of the compact. Step S2: Based on the predicted data of the reduction process, with the predicted pore closure critical point as the time endpoint, perform a target backward optimization calculation on the hydrogen gas integral to obtain the hydrogen concentration command, and send the hydrogen concentration command to the hydrogen flow controller to dynamically adjust the hydrogen-nitrogen mixing ratio in the furnace. Step S3: Collect the axial shrinkage of the compact, filter and perform second-order difference processing on the axial shrinkage to obtain the shrinkage acceleration, and confirm the inflection point when the shrinkage acceleration changes from positive to negative and the amplitude exceeds the noise threshold as the critical point of pore closure, and generate an event trigger signal. Step S4: In response to the event trigger signal, a step switching command is issued to the hydrogen flow controller and the nitrogen flow controller respectively to switch the furnace atmosphere from hydrogen-containing reducing mixed gas to inert protective gas. After the switching is completed, hydrocarbon gas is pulsedly injected into the furnace. The hydrocarbon gas thermal decomposition products form a sealing layer at the pore opening of the residual microchannel of the pressed billet, and the reducing internal microclimate established in the sealed hole of the pressed billet at the critical point of pore closure is sealed in the sealed hole.

2. The adaptive control method for reducing atmosphere in cold pressing and sintering of diamond tools according to claim 1, characterized in that, Step S1 includes: The oxygen content of this batch of metal binder powder was determined by hydrogen loss assay. The density of the cold-pressed compact was measured using the Archimedes drainage method. Based on the oxygen content of the powder and the density measurement results, the cold-pressed density and relative compact density of the compact were calculated. Based on the relative compact density and the axial characteristic dimension, the effective cross-sectional area and maximum diffusion path length of the gas mass transfer channel of hydrogen in the compact pore network are calculated to obtain the corrected value of hydrogen permeation rate. Substituting the powder oxygen content, the relative compact density, and the hydrogen permeation rate correction value into the reduction kinetic equation, and using the sintering heating curve as the time axis, the cumulative reduction rate corresponding to each temperature segment is integrated step by step to obtain the reduction process prediction data.

3. The adaptive control method for reducing atmosphere in cold pressing and sintering of diamond tools according to claim 1, characterized in that, Step S2 includes: Based on the predicted reduction process data, the cumulative reduction rate of each temperature segment in the sintering heating curve is verified segment by segment, and the moment when the cumulative reduction rate first reaches the target reduction rate is confirmed as the predicted pore closure critical point. Using the pore closure critical point as the time endpoint, the cumulative reduction rate gap within the remaining time window from the current time to the pore closure critical point is calculated to obtain the remaining reduction amount; Based on the remaining reduction amount and the remaining time window, a target backward optimization calculation is performed on the minimum required value of hydrogen gas integral, and upper and lower limits of hydrogen gas integral are imposed on the minimum required value to obtain the hydrogen concentration command. The hydrogen concentration command is converted into a hydrogen mass flow rate value and sent to the hydrogen flow controller. The difference between the total flow rate in the furnace and the hydrogen mass flow rate value is simultaneously sent to the nitrogen flow controller to complete the dynamic adjustment of the hydrogen-nitrogen mixing ratio in the furnace.

4. The adaptive control method for reducing atmosphere in cold pressing and sintering of diamond tools according to claim 1, characterized in that, Step S3 includes: The axial shrinkage of the compact is obtained by symmetrically collecting the axial displacement of both ends of the compact using a laser displacement sensor and taking the average value of the displacement of both ends. The axial contraction sequence is subjected to Savitzky-Golay polynomial filtering to obtain a denoised contraction sequence. Perform a five-point central difference operation on the denoised shrinkage sequence to obtain the first-order shrinkage rate and the shrinkage acceleration; Substituting the first-order contraction rate and the contraction acceleration into the critical point criterion: if the first-order contraction rate is negative, the contraction acceleration changes from positive to negative, and the amplitude of the contraction acceleration exceeds three times the sequence standard deviation of the contraction acceleration in the initial stage of heating, and these conditions are simultaneously met within three consecutive sampling periods, this is used as the confirmation condition for the pore closure critical point. The furnace temperature value corresponding to the confirmation time is recorded, and the event trigger signal is generated.

5. The adaptive control method for reducing atmosphere in cold pressing and sintering of diamond tools according to claim 1, characterized in that, In step S4, in response to the event trigger signal, a step switching command is issued to the hydrogen flow controller and the nitrogen flow controller respectively to switch the furnace atmosphere from a hydrogen-containing reducing mixture to an inert protective gas, including: In response to the event trigger signal, a hydrogen flow rate zeroing command is sent to the hydrogen flow controller, and the output value of the hydrogen flow controller is linearly reduced according to a preset deceleration slope to obtain the hydrogen flow rate zeroing timing sequence. Based on the hydrogen flow rate zeroing timing, a nitrogen compensation flow command is synchronously sent to the nitrogen flow controller. The difference between the total flow rate in the furnace and the current hydrogen flow rate is calculated hourly to obtain the nitrogen compensation flow value. The nitrogen compensation flow value is then sent to the nitrogen flow controller for execution, so that the total flow rate in the furnace remains constant during the switching process. The furnace pressure value collected by the furnace pressure sensor is monitored in real time. The furnace pressure value is compared with a preset positive pressure threshold to obtain a pressure deviation value. Based on the pressure deviation value, the nitrogen compensation flow value is corrected in a closed loop to complete the step switching from hydrogen-containing reduction mixture to inert protective gas.

6. The adaptive control method for reducing atmosphere in cold pressing and sintering of diamond tools according to claim 5, characterized in that, In step S4, after the switching is completed, hydrocarbon gas is pulsedly injected into the furnace. The thermal decomposition products of the hydrocarbon gas form a sealing layer at the pores of the residual microchannels in the pressed billet, including: Starting from the moment when the step switching is completed, the total orifice area of ​​the residual microchannels in the compact is calculated based on the cold pressing density and the axial characteristic dimension, so as to obtain the amount of hydrocarbon gas injected for sealing. Based on the amount of hydrocarbon gas required for sealing, a pulse injection command is sent to the hydrocarbon gas flow controller to inject hydrocarbon gas into the furnace with a preset volume fraction. The injection duration is determined according to the ratio of the amount of hydrocarbon gas required for sealing to the total flow rate in the furnace, thus obtaining the hydrocarbon gas pulse injection sequence. The injection is performed according to the specified hydrocarbon gas pulse injection sequence. The hydrocarbon gas undergoes a thermal decomposition reaction at the sintering temperature. The deposition process of the thermal decomposition products at the residual microchannel orifice of the compact is correlated with the pulse injection sequence to obtain the sealing layer covering the residual microchannel orifice. After the hydrocarbon gas pulse injection sequence ends, a zeroing command is issued to the hydrocarbon gas flow controller.

7. The adaptive control method for reducing atmosphere in cold pressing and sintering of diamond tools according to claim 6, characterized in that, Step S4 involves sealing the reductive internal microclimate established within the sealed cavity of the compact at the critical point of pore closure within the sealed cavity, including: Using the partial pressure of hydrogen gas and water vapor in the furnace at the critical point of pore closure as a benchmark, the partial pressure of hydrogen gas and water vapor in the closed pore are calculated to obtain the initial atmosphere parameters of the reducing internal microclimate. Based on the formation of the sealing layer, the sealing status of the residual microchannel orifice is confirmed, and the sealing status is correlated with the initial atmosphere parameters to obtain a sealing confirmation record of the reducing internal microclimate inside the sealed orifice. The sealing confirmation record, along with the powder oxygen content, cold-pressed density, and axial characteristic dimensions of this batch, are written into the batch database. The cumulative reduction rate prediction deviation in the reduction process prediction data is calculated to obtain the batch prediction error. The batch prediction error is then input into the recursive least squares operation to update the rate constant and reaction order in the reduction kinetic equation, resulting in updated reduction kinetic parameters.

8. An adaptive control system for the reducing atmosphere of cold pressing and sintering of diamond tools, characterized in that, For implementing the adaptive control method for the reducing atmosphere of cold pressing sintering of diamond tools as described in any one of claims 1-7, the adaptive control system for the reducing atmosphere of cold pressing sintering of diamond tools comprises: The calculation module is used to calculate the reduction process prediction data based on the powder oxygen content, cold pressing density and axial characteristic dimensions of the compact; The adjustment module is used to perform a target-based backward optimization calculation on the hydrogen gas integral number based on the predicted data of the reduction process, with the predicted pore closure critical point as the time endpoint, to obtain a hydrogen concentration command, and to send the hydrogen concentration command to the hydrogen flow controller to dynamically adjust the hydrogen-nitrogen mixing ratio in the furnace. The generation module is used to collect the axial shrinkage of the compact, filter and perform second-order difference processing on the axial shrinkage to obtain the shrinkage acceleration, and identify the inflection point when the shrinkage acceleration changes from positive to negative and the amplitude exceeds the noise threshold as the critical point of pore closure, and generate an event trigger signal. The switching module is used to respond to the event trigger signal and send step switching commands to the hydrogen flow controller and nitrogen flow controller respectively to switch the furnace atmosphere from hydrogen-containing reducing mixed gas to inert protective gas. After the switching is completed, hydrocarbon gas is pulsedly injected into the furnace. The thermal decomposition products of the hydrocarbon gas form a sealing layer at the pore opening of the residual microchannel of the pressed billet, and the reducing internal microclimate established in the sealed hole of the pressed billet at the critical point of pore closure is sealed in the sealed hole.

9. An adaptive control device for the reducing atmosphere of cold pressing and sintering of diamond tools, characterized in that, The method includes a memory and a processor, the memory storing a computer program that can run on the processor, and the processor executing the computer program to implement the adaptive control method for reducing atmosphere in cold pressing sintering of diamond tools according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is run by the processor, it causes the processor to execute the adaptive control method for reducing atmosphere in cold pressing sintering of diamond tools as described in any one of claims 1 to 7.

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