Metal powder metallurgy sintering furnace and sintering method thereof

Abstract

The present application relates to the technical field of metal powder manufacturing, in particular to a metal powder metallurgy sintering furnace and a sintering method thereof, which comprises the following steps: feeding a blank into a sintering furnace for pre-sintering to obtain a pre-sintered blank; heating the pre-sintered blank to a preset sintering temperature and then keeping warm, and after keeping warm for a first preset time, a sintered blank is obtained; when it is determined that the preparation of the sintered blank is at risk of being unqualified according to a sintering distortion representation value, it is determined whether the preparation of the sintered blank is qualified according to a distortion peak value of the risk sintered blank; when it is determined that the preparation of the sintered blank is unqualified according to the sintering distortion representation value, a treatment strategy for the unqualified preparation of the sintered blank is determined according to a densification deviation representation value of the sintered blank; the sintered blank meeting the preset standard is kept warm for a second preset time, and the to-be-remedied blank is kept warm for a remediation warm-keeping time; after the warm-keeping is completed, unified cooling is performed to obtain a sintered product, thereby improving the sintering efficiency of the sintering furnace.

Description

Technical Field

[0001] This invention relates to the field of metal powder manufacturing technology, specifically to a metal powder metallurgy sintering furnace and its sintering method. Background Technology

[0002] The sintering process of powder metallurgy materials is the core step that determines the performance of the final product, and the sintering furnace is the key equipment for realizing this process. During the sintering process, the pre-pressed powder compact is heated at high temperature in the sintering furnace, and physical and chemical changes such as diffusion, bonding, and densification occur between the powder particles, ultimately forming metal parts with the required mechanical properties and physicochemical characteristics.

[0003] The sintering process has a decisive impact on the quality of the finished product. Improper sintering control can easily lead to problems such as high porosity, abnormal grain growth, and uneven microstructure, severely affecting the product's strength, toughness, wear resistance, and corrosion resistance. Good sintering control, on the other hand, ensures the product's density, improving its overall mechanical properties and service life.

[0004] However, existing sintering furnaces still have shortcomings in controlling the sintering process. Because the sintering process takes place in a high-temperature, enclosed furnace, it cannot be directly observed in real time, resulting in a significant lag in process control and making it difficult to dynamically adjust based on the real-time status of the products during sintering. Once a process deviation occurs, it is often only discovered after sintering is complete, at which point internal defects have already formed irreversibly, leading to batch scrap and wasting materials and energy. Summary of the Invention

[0005] Therefore, the present invention provides a metal powder metallurgy sintering furnace and its sintering method to overcome the problem that the existing technology does not consider the influence of the dynamic changes of the product during the sintering process on the forming quality of the sintered parts, resulting in poor sintering efficiency of the sintering furnace.

[0006] To achieve the above objectives, a first aspect of the present invention provides a sintering method for a metal powder metallurgy sintering furnace, comprising: The blank is fed into the sintering furnace for pre-sintering to obtain a pre-sintered blank. The initial point cloud data of several sampling points uniformly distributed on the upper surface of several pre-sintered blanks is obtained by scanning. The pre-fired blank is heated to a preset sintering temperature and then held at that temperature for a first preset time to obtain the sintered blank. Real-time point cloud data of each sampling point on the upper surface of several sintered billets are obtained by scanning, and the sintering distortion characterization value of the sintered billet is obtained based on the initial point cloud data and the real-time point cloud data. When it is determined that the preparation of the sintered blank is at risk of being unqualified based on the sintering distortion characterization value, the preparation of the sintered blank is then determined a second time based on the distortion peak value of the risky sintered blank. When the sintering blank is determined to be unqualified based on the sintering distortion characterization value, the processing strategy for the unqualified sintering blank is determined based on the densification deviation characterization value of the sintering blank. The processing strategy is to mark the sintering blank as a blank to be remedied or to immediately terminate the sintering process of the sintering blank. The sintered blanks that meet the preset standards are kept at the temperature for a second preset time, and the blanks to be repaired are kept at the temperature for a repair time. After the temperature is kept at the temperature, they are cooled to obtain sintered products.

[0007] Preferably, the process of determining whether the preparation of the sintered blank is qualified based on the sintering distortion characterization value of the sintered blank includes: The sintering distortion characterization value is compared with the first preset sintering distortion characterization value and the second preset sintering distortion characterization value, respectively. If the sintering distortion characterization value is less than the first preset sintering distortion characterization value, then the preparation of the sintered blank is deemed qualified. If the sintering distortion characterization value is greater than or equal to the first preset sintering distortion characterization value and less than the second preset sintering distortion characterization value, it is determined that the preparation of the sintered blank has a risk of being unqualified, and the preparation of the sintered blank is determined a second time based on the distortion peak value of the risky sintered blank. Wherein, the first preset sintering distortion characterization value is less than the second preset sintering distortion characterization value.

[0008] Preferably, the process for obtaining the sintering distortion characterization values ​​of the sintered blank includes: The initial height value of each sampling point on the upper surface of each pre-fired billet is obtained based on the initial point cloud data; The real-time height value of each sampling point on the upper surface of each sintered billet is obtained based on the real-time point cloud data. The difference between the real-time height value and the corresponding initial height value is denoted as the height change. The mean square value of the height change is obtained by squaring the height change at each sampling point, summing all the squared values ​​and dividing the sum by the total number of sampling points. The root mean square root of the height change is taken to obtain the morphological error root mean square of the sintered blank. The root mean square of the morphological errors of all sintered blanks is added together and then divided by the total number of sintered blanks to obtain the sintering distortion characterization value.

[0009] Preferably, based on the comparison result that the sintering distortion characterization value of the sintered blank is greater than or equal to the second preset sintering distortion characterization value, the preparation of the sintered blank is determined to be unqualified, and the processing strategy when the preparation of the sintered blank is unqualified is determined based on the densification deviation characterization value of the sintered blank.

[0010] Preferably, the process of determining whether the preparation of the sintered blank is qualified based on the distortion peak value of the risk sintered blank includes: If the distortion peak value is less than the preset distortion peak value, the sintered blank is deemed to be of qualified preparation. If the distortion peak value is greater than or equal to the preset distortion peak value, the preparation of the sintered billet is determined to be unqualified, and the temperature of the furnace area corresponding to the risky sintered billet is increased according to the difference between the distortion peak value and the preset distortion peak value. Among them, sintered blanks with root mean square error of morphology greater than or equal to the preset root mean square error of morphology are denoted as risky sintered blanks.

[0011] Preferably, the process for obtaining the distortion peak value of the risky sintered billet includes: The upper surface projection plane of the risk sintered blank is divided into several sub-regions of equal area; Extract the height change of all sampling points in the sub-region, and square the height change of each sampling point to obtain the square value of each sampling point. The mean square value of the height change of the sub-region is obtained by summing all the square values ​​and dividing by the total number of sampling points in the sub-region. The local distortion value of the sub-region is obtained by taking the square root of the mean square value of the height change. The maximum value of the local distortion value of all sub-regions is taken and recorded as the distortion peak value of the risky sintered billet.

[0012] Preferably, the process of determining the handling strategy when the sintered blank is found to be defective based on the densification deviation characterization value of the sintered blank includes: If the densification deviation characterization value is less than the preset densification deviation characterization value, the sintered blank is marked as a blank to be remedied that requires extended heat preservation, and heat preservation is carried out according to the remedied heat preservation time determined by the difference between the densification deviation characterization value and the preset densification deviation characterization value. If the densification deviation characterization value is greater than or equal to the preset densification deviation characterization value, the sintering process of the sintered blank is immediately terminated.

[0013] Preferably, several methods are provided for determining the duration of the remedial insulation, among which... If the densification excess value is less than the first preset densification excess value, then the remedial heat preservation time is the product of the first adjustment coefficient and the second preset time. If the densification excess value is greater than or equal to the first preset densification excess value and less than the second preset densification excess value, then the remedial heat preservation time is the product of the second adjustment coefficient and the second preset time. If the densification excess value is greater than or equal to the second preset densification excess value, then the remedial heat preservation time is the product of the third adjustment coefficient and the second preset time. The densification excess value is the difference between the densification deviation characterization value and the preset densification deviation characterization value.

[0014] Preferably, the process for obtaining the densification deviation characterization value of the sintered blank includes: For the initial height value of each sampling point on the upper surface of a single pre-fired billet, calculate the arithmetic mean of the height values ​​of all sampling points, and use it as the initial reference height of the pre-fired billet; During the heat preservation process for the first preset time, the upper surface of each sintered billet is scanned at a preset frequency to collect three-dimensional point cloud data at the corresponding time, and the arithmetic mean of the height values ​​of all sampling points at each time is calculated to obtain the real-time average height at the corresponding time. The percentage obtained by dividing the difference between the initial reference height and the real-time average height by the initial reference height is recorded as the shrinkage rate at the corresponding time. By arranging the shrinkage rates at all times in chronological order, the shrinkage rate-time variation curve of the sintered blank is obtained. The first derivative of the shrinkage rate-time variation curve with respect to time is obtained to obtain the densification acceleration-time variation curve. Extract the densification acceleration corresponding to the moment when the heat preservation is carried out to the first preset time from the densification acceleration-time change curve, and take it as the instantaneous densification acceleration of the sintered blank; Calculate the absolute value of the difference between the instantaneous densification acceleration and the preset acceleration, and record the ratio of the absolute value of the difference to the preset acceleration as the densification deviation characterization value of the sintered blank.

[0015] A second aspect of the present invention provides a metal powder metallurgy sintering furnace suitable for the above-described sintering method, comprising: The pre-sintering module is used to pre-sinter the preform to obtain a pre-sintered preform; The sintering furnace main module is connected to the pre-sintering module. It has a heating section, a heat preservation section and a cooling section connected sequentially along the material conveying direction. The heat preservation section is divided into several independent furnace temperature control zones along the material conveying direction. The data acquisition module is connected to the pre-sintering module and the sintering furnace main body module respectively, and is used to scan and acquire the initial point cloud data of the upper surface of the pre-sintered billet, and to scan and acquire the three-dimensional point cloud data of the upper surface of the sintered billet at a preset frequency during the heat preservation process, including the real-time point cloud data at the end of the first preset heat preservation time. The data processing module, which is connected to the data acquisition module, is used to obtain the sintering distortion characterization value of the sintered billet and the distortion peak value of the risk sintered billet based on the initial point cloud data and the real-time point cloud data, and to obtain the densification deviation characterization value of the sintered billet based on the three-dimensional point cloud data and the initial point cloud data. A control module, which is connected to the data processing module, is used to determine whether the preparation of the sintered blank is qualified based on the sintering distortion characterization value of the sintered blank, and to make a secondary determination on whether the preparation of the sintered blank is qualified based on the distortion peak value of the risk sintered blank. A strategy determination module, which is connected to the control module, is used to determine the processing strategy when the sintered blank is unqualified based on the densification deviation characterization value of the sintered blank. The processing strategy is to mark the sintered blank as a blank to be remedied or to immediately terminate the sintering process of the sintered blank.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: by collecting point cloud data after pre-sintering and after the first preset holding time, the present invention calculates the sintering distortion characterization value that can quantify the degree of overall morphological distortion of the sintered billet, thereby realizing real-time monitoring of the morphological changes of the billet during the sintering process; by establishing a graded qualification judgment mechanism and differentiated processing strategy, the present invention achieves precise control and timely intervention of the quality status during the sintering process; at the same time, by matching corresponding control methods for sintered billets in different states, a closed-loop control of the entire process from data acquisition and state identification to process control is formed, thereby improving the sintering efficiency of the sintering furnace.

[0017] Furthermore, by comparing the initial height value with the real-time height value and combining the derivation of the mean square value and the root mean square of the morphology error, this invention forms a method that can objectively and comprehensively reflect the overall distortion degree of the sintered billet in the whole furnace, transforming complex morphological changes into intuitive quantitative indicators, thereby providing a reliable data basis for subsequent state determination.

[0018] Furthermore, this invention classifies the preparation state of sintered billets into three levels—qualified, risky, and unqualified—by setting two threshold values: a first preset sintering distortion characterization value and a second preset sintering distortion characterization value, thus forming a clear three-level classification system. This classification method avoids the coarseness of judging with a single threshold and provides a clear basis for subsequent differentiated processing, enabling sintered billets in a critical state to be accurately identified and preventing them from being directly passed over or scrapped due to misjudgment, thereby improving the reliability of the judgment.

[0019] Furthermore, this invention performs a secondary determination of the distortion peak value of the risk sintered blank. For risk sintered blanks with smaller distortion peak values, they are reclassified as qualified. For risk sintered blanks with larger distortion peak values, heat preservation temperature compensation is performed, thereby avoiding the problem that the overall average value may mask serious local anomalies.

[0020] Furthermore, this invention adopts a graded processing strategy for unqualified sintered blanks, marking slightly unqualified sintered blanks as blanks to be remedied and performing heat preservation remediation, and immediately terminating the sintering process for severely unqualified sintered blanks, thereby achieving differentiated treatment of unqualified sintered blanks. Attached Figure Description

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0022] Figure 1 This is a flowchart of the sintering method of the metal powder metallurgy sintering furnace according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating how to determine whether the preparation of a sintered blank is qualified based on the sintering distortion characterization value of the sintered blank, according to an embodiment of the present invention. Figure 3 This is a flowchart illustrating the processing strategy for unqualified sintered blanks based on the densification deviation characterization value of the sintered blanks according to an embodiment of the present invention. Figure 4 This is a schematic diagram of the module connection of a metal powder metallurgy sintering furnace applicable to the sintering method in an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that the data in this embodiment are all derived from a comprehensive analysis and evaluation of historical test data and corresponding historical test results from the three months prior to this test. Those skilled in the art will understand that the method described in this invention can determine the above-mentioned parameters in the following ways: selecting the value with the highest proportion based on the data distribution as the preset standard parameter; using weighted summation to obtain the value as the preset standard parameter; substituting each historical data point into a specific formula and using the value obtained by that formula as the preset standard parameter; or other selection methods, as long as the method described in this invention can clearly define different specific situations in the single-item judgment process through the obtained values.

[0025] Please see Figure 1 As shown, the first aspect of this embodiment provides a sintering method for a metal powder metallurgy sintering furnace, comprising: Step S1: The gear-shaped blank formed by iron-based powder metallurgy is fed into a sintering furnace for pre-sintering at a temperature of 800℃ and a holding time of 40 minutes to obtain a pre-sintered blank. The upper surface of all pre-sintered blanks in the furnace is scanned using a three-dimensional laser contour sensor array. The sampling points are uniformly distributed in a grid with a grid density of 5 points / mm. 2 The initial three-dimensional coordinates of each sampling point on the upper surface of each pre-fired billet are obtained to form initial point cloud data; Step S2: The pre-fired billet is heated to the preset sintering temperature of 1280°C at a heating rate of 5°C / min, and then placed in the heat-holding section for heat-holding. The heat-holding section is divided into 5 independent furnace temperature control zones along the material conveying direction, and the temperature of each zone can be independently adjusted. After the first preset heat-holding time of 30 minutes, the sintered billet is obtained. Step S3: Scan and acquire real-time point cloud data of each sampling point on the upper surface of several sintered billets, and obtain the sintering distortion characterization value of the sintered billet based on the initial point cloud data and the real-time point cloud data. Step S4: When it is determined that the preparation of the sintered blank is at risk of being unqualified based on the sintering distortion characterization value, the preparation of the sintered blank is determined for the second time based on the distortion peak value of the risky sintered blank. Step S5: When the sintering blank is determined to be unqualified based on the sintering distortion characterization value, the processing strategy for the unqualified sintering blank is determined based on the densification deviation characterization value of the sintering blank. The processing strategy is to mark the sintering blank as a blank to be remedied or to immediately terminate the sintering process of the sintering blank. Step S6: Continue to heat the sintered blank that meets the preset standard for a second preset time of 60 minutes to heat the blank to be repaired for the repair time; after the heat preservation is completed, uniformly enter the cooling section and cool to room temperature at a cooling rate of 3℃ / min to obtain the sintered product.

[0026] Specifically, please refer to Figure 2 As shown, the process of determining whether the preparation of the sintered blank is qualified based on the sintering distortion characterization value of the sintered blank includes: The sintering distortion characterization value is compared with the first preset sintering distortion characterization value of 0.04 mm and the second preset sintering distortion characterization value of 0.15 mm, respectively. If the sintering distortion characterization value is less than the first preset sintering distortion characterization value, then the preparation of the sintered blank is deemed qualified. If the sintering distortion characterization value is greater than or equal to the first preset sintering distortion characterization value and less than the second preset sintering distortion characterization value, it is determined that the preparation of the sintered blank has a risk of being unqualified, and the preparation of the sintered blank is determined a second time based on the distortion peak value of the risky sintered blank. Based on the comparison result that the sintering distortion characterization value of the sintered blank is greater than or equal to the second preset sintering distortion characterization value, it is determined that the preparation of the sintered blank is unqualified, and the processing strategy when the preparation of the sintered blank is unqualified is determined based on the densification deviation characterization value of the sintered blank.

[0027] Wherein, the first preset sintering distortion characterization value is less than the second preset sintering distortion characterization value.

[0028] Specifically, the sintering distortion characterization value represents the degree of overall morphological distortion of the sintered billet during the sintering process. When the sintering distortion characterization value is less than the first preset sintering distortion characterization value, it indicates that the overall morphological distortion of the sintered billet is slight and within the acceptable range. It can be directly judged as qualified and no intervention is required. The subsequent sintering can continue according to the original process. When the sintering distortion characterization value is greater than or equal to the first preset sintering distortion characterization value and less than the second preset sintering distortion characterization value, it indicates that the overall morphological distortion of the sintered billet has exceeded the acceptable range, but has not yet reached an unacceptable level. It is in a critical state between qualified and unqualified. At this point, the overall distortion value alone cannot determine whether there are serious local problems with the sintered blank (it may be a slight distortion that is uniform throughout, or it may be a serious local distortion that raises the average value). Therefore, it is determined that there is a risk of its preparation being unqualified, and the distortion peak value of the risky sintered blank needs to be introduced for secondary judgment. When the sintering distortion characterization value is greater than or equal to the second preset sintering distortion characterization value, it indicates that the overall morphological distortion degree of the sintered blank has seriously exceeded the standard, and it is directly judged as unqualified. Based on the densification deviation characterization value of the sintered blank, a specific processing strategy is further determined. This not only avoids the misjudgment that may be caused by a single threshold judgment, but also provides a clear basis for subsequent differentiated processing, improving the accuracy of sintering process control.

[0029] Specifically, the first preset sintering distortion characterization value ranges from [0.03 mm to 0.08 mm], and the second preset sintering distortion characterization value ranges from [0.12 mm to 0.20 mm]. Preferably, the first preset sintering distortion characterization value is 0.04 mm and the second preset sintering distortion characterization value is 0.15 mm.

[0030] Specifically, the process of obtaining the sintering distortion characterization values ​​of the sintered blank includes: Based on the initial point cloud data, the Z-axis coordinates of each sampling point on the upper surface of each pre-fired billet are extracted using industrial-grade point cloud processing software such as Halcon, and the Z-axis coordinates are used as the initial height value of each sampling point. Based on the real-time point cloud data, the same point cloud processing software is used to extract the Z-axis coordinate of the corresponding sampling point on the upper surface of each sintered billet (which corresponds one-to-one with the sampling point in the initial point cloud data to ensure consistent position), and the Z-axis coordinate is used as the real-time height value of each sampling point. The difference between the real-time height value and the corresponding initial height value is denoted as the height change. The mean square value of the height change is obtained by squaring the height change at each sampling point, summing all the squared values ​​and dividing the sum by the total number of sampling points. The root mean square root of the height change is taken to obtain the morphological error root mean square of the sintered blank. The root mean square of the morphological errors of all sintered blanks is added together and then divided by the total number of sintered blanks to obtain the sintering distortion characterization value.

[0031] Specifically, the process of determining whether the preparation of the sintered blank is qualified based on the distortion peak value of the risk sintered blank includes: If the distortion peak value is less than the preset distortion peak value of 0.09 mm, the sintered blank is deemed to be qualified for preparation. If the distortion peak value is greater than or equal to the preset distortion peak value, the preparation of the sintered billet is determined to be unqualified, and the temperature of the furnace area corresponding to the risky sintered billet is increased according to the difference between the distortion peak value and the preset distortion peak value. Among them, sintered blanks with root mean square morphology error greater than or equal to the preset root mean square morphology error of 0.05 mm are designated as risky sintered blanks.

[0032] Specifically, the risky sintered blank may ultimately pass due to slight, uniform distortion, or it may have defects due to severe local distortion that raises the average value. A distortion peak value is introduced for secondary assessment. This distortion peak value characterizes the degree of distortion in the most severely affected local area of ​​the risky sintered blank. Unlike the overall average level reflected by the root mean square error of morphology, the distortion peak value focuses on extreme local conditions. When the distortion peak value is greater than or equal to a preset distortion peak value, it indicates that there is a local area on the risky sintered blank where the degree of distortion exceeds the acceptable range. In this case, abnormal shrinkage or expansion in this local area will lead to stress concentration, which, without intervention, will develop into irreversible defects such as warping and cracking during subsequent heat preservation. Therefore, the preparation of this sintered blank is deemed unqualified, and the temperature of the furnace region corresponding to the risky sintered blank is increased. Through local temperature compensation, the material diffusion of the risky sintered blank is homogenized, internal stress is relieved, and further development of defects is inhibited.

[0033] Specifically, the preset distortion peak value is 0.09 mm. In this embodiment, 50 gear parts that passed the inspection after sintering were selected, and their distortion peak values ​​were calculated at one-third of the time during the heat preservation stage of the sintering process. The 95th percentile was found to be 0.07 mm, and the 99th percentile was 0.08 mm. Therefore, setting the preset distortion peak value to 0.09 mm can cover more than 95% of the qualified products.

[0034] Specifically, the process of obtaining the distortion peak value of the risky sintered billet includes: The upper surface projection plane of the risk sintered blank is divided into several sub-regions of equal area. In this embodiment, the upper surface of the risk sintered blank is 50mm×50mm in size, and it is divided into 4 square sub-regions of equal area. The size of each sub-region is 25mm×25mm, ensuring that each sub-region contains several evenly distributed sampling points. Extract the height change of all sampling points in the sub-region, and square the height change of each sampling point to obtain the square value of each sampling point. The mean square value of the height change of the sub-region is obtained by summing all the square values ​​and dividing by the total number of sampling points in the sub-region. The local distortion value of the sub-region is obtained by taking the square root of the mean square value of the height change. The maximum value of the local distortion value of all sub-regions is taken and recorded as the distortion peak value of the risky sintered billet.

[0035] Specifically, please refer to Figure 3 As shown, the process of determining the handling strategy when the sintered blank fails to meet the preparation standards based on the densification deviation characterization value of the sintered blank includes: If the densification deviation characterization value is less than the preset densification deviation characterization value of 0.45, the sintered blank is marked as a blank to be remedied that requires extended heat preservation, and heat preservation is carried out according to the remedied heat preservation time determined by the difference between the densification deviation characterization value and the preset densification deviation characterization value. If the densification deviation characterization value is greater than or equal to the preset densification deviation characterization value, the sintering process of the sintered blank is immediately terminated.

[0036] Specifically, the densification deviation characterization value is used to quantify the degree of abnormality in the densification process of unqualified sintered blanks. When the densification deviation characterization value is less than the preset value, it indicates that although the densification process is abnormal, it has not yet gone out of control, and the microstructure still has room for adjustment. It is marked as a blank to be repaired, and the repair holding time is extended to promote material diffusion and eliminate defects. When the densification deviation characterization value is greater than or equal to the preset value, it indicates that the densification process has seriously deviated from the normal track, and continued sintering will form irreversible defects. Therefore, its sintering process is terminated immediately to avoid ineffective energy consumption.

[0037] In this embodiment, the preset densification deviation characterization value is 0.45, but the above value is not limited to this, and those skilled in the art can adjust the value according to actual needs.

[0038] Specifically, several methods are provided for determining the duration of the remedial insulation, among which, If the densification excess value is less than the first preset densification excess value of 0.15, then the remedial heat preservation time is the product of the first adjustment coefficient 1.04 and the second preset time. If the densification excess value is greater than or equal to the first preset densification excess value and less than the second preset densification excess value of 0.35, then the remedial heat preservation time is the product of the second adjustment coefficient 1.06 and the second preset time. If the densification excess value is greater than or equal to the second preset densification excess value, then the remedial heat preservation time is the product of the third adjustment coefficient 1.08 and the second preset time. The densification excess value is the difference between the densification deviation characterization value and the preset densification deviation characterization value.

[0039] Specifically, the process of obtaining the densification deviation characterization value of the sintered blank includes: For the initial height value of each sampling point on the upper surface of a single pre-fired billet, calculate the arithmetic mean of the height values ​​of all sampling points, and use it as the initial reference height of the pre-fired billet; During the heat preservation process for the first preset time, the upper surface of each sintered billet is scanned at a preset frequency of 1 time / minute to collect three-dimensional point cloud data at the corresponding time, and the arithmetic mean of the height values ​​of all sampling points at each time is calculated to obtain the real-time average height at the corresponding time. The percentage obtained by dividing the difference between the initial reference height and the real-time average height by the initial reference height is recorded as the shrinkage rate at the corresponding time. The shrinkage rates at all times were arranged in chronological order, and the shrinkage rate-time variation curve of the sintered blank was obtained using Origin software. The first derivative of the shrinkage rate-time variation curve with respect to time is obtained to obtain the densification acceleration-time variation curve. Extract the densification acceleration corresponding to the moment when the heat preservation is carried out to the first preset time from the densification acceleration-time change curve, and take it as the instantaneous densification acceleration of the sintered blank; Calculate the absolute value of the difference between the instantaneous densification acceleration and the preset acceleration, and record the ratio of the absolute value of the difference to the preset acceleration as the densification deviation characterization value of the sintered blank.

[0040] Please see Figure 4 As shown, in a second aspect of this embodiment, a metal powder metallurgy sintering furnace suitable for the above-described sintering method is provided, comprising: The pre-sintering module is used to pre-sinter the blank to obtain a pre-fired blank; in this embodiment, a continuous mesh belt pre-firing furnace is used, the pre-firing temperature is 600-700℃, and the pre-firing time is 50-70 minutes. In this embodiment, the sintering furnace as a whole adopts a continuous mesh belt sintering furnace, and the pre-sintering module is the pre-sintering section of the continuous mesh belt sintering furnace.

[0041] The main module of the sintering furnace, which is connected to the pre-sintering module, is the section located behind the pre-sintering module in the continuous mesh belt sintering furnace. Its feed end is directly connected to the discharge end of the pre-sintering module along the mesh belt conveying direction. It contains a heating section, a heat preservation section and a cooling section connected sequentially along the material conveying direction. The heat preservation section is divided into 5 independent furnace temperature control zones along the material conveying direction. Each zone is equipped with an independent heating element and thermocouple, which can achieve a temperature control accuracy of ±2℃. The data acquisition module, connected to both the pre-sintering module and the sintering furnace main body module, includes five sets of high-temperature protective three-dimensional laser contour sensors installed above the quartz glass observation window at the top of the furnace. These sensors are used to scan and acquire initial point cloud data of the upper surface of the pre-sintered billet, and to scan and acquire three-dimensional point cloud data of the upper surface of the sintered billet at a preset frequency (1 time / minute in this embodiment) during the heat preservation process, including real-time point cloud data at the end of the first preset heat preservation time. The data processing module, which is connected to the data acquisition module, is used to obtain the sintering distortion characterization value of the sintered billet and the distortion peak value of the risk sintered billet based on the initial point cloud data and the real-time point cloud data, and to obtain the densification deviation characterization value of the sintered billet based on the three-dimensional point cloud data and the initial point cloud data. A control module, which is connected to the data processing module, is used to determine whether the preparation of the sintered blank is qualified based on the sintering distortion characterization value of the sintered blank, and to make a secondary determination on whether the preparation of the sintered blank is qualified based on the distortion peak value of the risk sintered blank. A strategy determination module, which is connected to the control module, is used to determine the processing strategy when the sintered blank is unqualified based on the densification deviation characterization value of the sintered blank. The processing strategy is to mark the sintered blank as a blank to be remedied or to immediately terminate the sintering process of the sintered blank.

[0042] Specifically, there are no restrictions on the specific structure of the data processing module, control module, and strategy determination module. They themselves and their units can be composed of logic components, including field-programmable components, computers, or microprocessors in computers.

[0043] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. 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 sintering method for a metal powder metallurgy sintering furnace, characterized in that, include: The blank is fed into the sintering furnace for pre-sintering to obtain a pre-sintered blank. The initial point cloud data of several sampling points uniformly distributed on the upper surface of several pre-sintered blanks is obtained by scanning. The pre-fired blank is heated to a preset sintering temperature and then held at that temperature for a first preset time to obtain the sintered blank. Real-time point cloud data of each sampling point on the upper surface of several sintered billets are obtained by scanning, and the sintering distortion characterization value of the sintered billet is obtained based on the initial point cloud data and the real-time point cloud data. When it is determined that the preparation of the sintered blank is at risk of being unqualified based on the sintering distortion characterization value, the preparation of the sintered blank is then determined a second time based on the distortion peak value of the risky sintered blank. When the sintering blank is determined to be unqualified based on the sintering distortion characterization value, the processing strategy for the unqualified sintering blank is determined based on the densification deviation characterization value of the sintering blank. The processing strategy is to mark the sintering blank as a blank to be remedied or to immediately terminate the sintering process of the sintering blank. The sintered billet that meets the preset standard is kept at the temperature for a second preset time, and the billet to be repaired is kept at the temperature for a repair time. After the heat preservation is completed, the products are cooled to obtain sintered products.

2. The sintering method of the metal powder metallurgy sintering furnace according to claim 1, characterized in that, The process of determining whether the preparation of the sintered blank is qualified based on the sintering distortion characterization value of the sintered blank includes: The sintering distortion characterization value is compared with the first preset sintering distortion characterization value and the second preset sintering distortion characterization value, respectively. If the sintering distortion characterization value is less than the first preset sintering distortion characterization value, then the preparation of the sintered blank is deemed qualified. If the sintering distortion characterization value is greater than or equal to the first preset sintering distortion characterization value and less than the second preset sintering distortion characterization value, it is determined that the preparation of the sintered blank has a risk of being unqualified, and the preparation of the sintered blank is determined a second time based on the distortion peak value of the risky sintered blank. Wherein, the first preset sintering distortion characterization value is less than the second preset sintering distortion characterization value.

3. The sintering method of the metal powder metallurgy sintering furnace according to claim 2, characterized in that, The process of obtaining the sintering distortion characterization value of the sintered billet includes: The initial height value of each sampling point on the upper surface of each pre-fired billet is obtained based on the initial point cloud data; The real-time height value of each sampling point on the upper surface of each sintered billet is obtained based on the real-time point cloud data. The difference between the real-time height value and the corresponding initial height value is denoted as the height change. The mean square value of the height change is obtained by squaring the height change at each sampling point, summing all the squared values ​​and dividing the sum by the total number of sampling points. The root mean square root of the height change is taken to obtain the morphological error root mean square of the sintered blank. The root mean square of the morphological errors of all sintered blanks is added together and then divided by the total number of sintered blanks to obtain the sintering distortion characterization value.

4. The sintering method of the metal powder metallurgy sintering furnace according to claim 3, characterized in that, Based on the comparison result that the sintering distortion characterization value of the sintered blank is greater than or equal to the second preset sintering distortion characterization value, it is determined that the preparation of the sintered blank is unqualified, and the processing strategy when the preparation of the sintered blank is unqualified is determined based on the densification deviation characterization value of the sintered blank.

5. The sintering method of the metal powder metallurgy sintering furnace according to claim 4, characterized in that, The process of determining whether the preparation of the sintered blank is qualified based on the distortion peak value of the risk sintered blank includes: If the distortion peak value is less than the preset distortion peak value, the sintered blank is deemed to be of qualified preparation. If the distortion peak value is greater than or equal to the preset distortion peak value, the preparation of the sintered billet is determined to be unqualified, and the temperature of the furnace area corresponding to the risky sintered billet is increased according to the difference between the distortion peak value and the preset distortion peak value. Among them, sintered blanks with root mean square error of morphology greater than or equal to the preset root mean square error of morphology are denoted as risky sintered blanks.

6. The sintering method of the metal powder metallurgy sintering furnace according to claim 5, characterized in that, The process of obtaining the distortion peak value of the risky sintered billet includes: The upper surface projection plane of the risk sintered blank is divided into several sub-regions of equal area; Extract the height change of all sampling points in the sub-region, and square the height change of each sampling point to obtain the square value of each sampling point. The mean square value of the height change of the sub-region is obtained by summing all the square values ​​and dividing by the total number of sampling points in the sub-region. The local distortion value of the sub-region is obtained by taking the square root of the mean square value of the height change. The maximum value of the local distortion value of all sub-regions is taken and recorded as the distortion peak value of the risky sintered billet.

7. The sintering method of the metal powder metallurgy sintering furnace according to claim 6, characterized in that, The process of determining the handling strategy when the sintered blank fails to meet the densification deviation characterization value includes: If the densification deviation characterization value is less than the preset densification deviation characterization value, the sintered blank is marked as a blank to be remedied that requires extended heat preservation, and heat preservation is carried out according to the remedied heat preservation time determined by the difference between the densification deviation characterization value and the preset densification deviation characterization value. If the densification deviation characterization value is greater than or equal to the preset densification deviation characterization value, the sintering process of the sintered blank is immediately terminated.

8. The sintering method of the metal powder metallurgy sintering furnace according to claim 7, characterized in that, Several methods are provided for determining the duration of the remedial insulation, among which, If the densification excess value is less than the first preset densification excess value, then the remedial heat preservation time is the product of the first adjustment coefficient and the second preset time. If the densification excess value is greater than or equal to the first preset densification excess value and less than the second preset densification excess value, then the remedial heat preservation time is the product of the second adjustment coefficient and the second preset time. If the densification excess value is greater than or equal to the second preset densification excess value, then the remedial heat preservation time is the product of the third adjustment coefficient and the second preset time. The densification excess value is the difference between the densification deviation characterization value and the preset densification deviation characterization value.

9. The sintering method of the metal powder metallurgy sintering furnace according to claim 8, characterized in that, The process of obtaining the densification deviation characterization value of the sintered blank includes: For the initial height value of each sampling point on the upper surface of a single pre-fired billet, calculate the arithmetic mean of the height values ​​of all sampling points, and use it as the initial reference height of the pre-fired billet; During the heat preservation process for the first preset time, the upper surface of each sintered billet is scanned at a preset frequency to collect three-dimensional point cloud data at the corresponding time, and the arithmetic mean of the height values ​​of all sampling points at each time is calculated to obtain the real-time average height at the corresponding time. The percentage obtained by dividing the difference between the initial reference height and the real-time average height by the initial reference height is recorded as the shrinkage rate at the corresponding time. By arranging the shrinkage rates at all times in chronological order, the shrinkage rate-time variation curve of the sintered blank is obtained. The first derivative of the shrinkage rate-time variation curve with respect to time is obtained to obtain the densification acceleration-time variation curve. Extract the densification acceleration corresponding to the moment when the heat preservation is carried out to the first preset time from the densification acceleration-time change curve, and take it as the instantaneous densification acceleration of the sintered blank; Calculate the absolute value of the difference between the instantaneous densification acceleration and the preset acceleration, and record the ratio of the absolute value of the difference to the preset acceleration as the densification deviation characterization value of the sintered blank.

10. A metal powder metallurgy sintering furnace suitable for the sintering method according to any one of claims 1-9, characterized in that, include: The pre-sintering module is used to pre-sinter the preform to obtain a pre-sintered preform; The sintering furnace main module is connected to the pre-sintering module. It has a heating section, a heat preservation section and a cooling section connected sequentially along the material conveying direction. The heat preservation section is divided into several independent furnace temperature control zones along the material conveying direction. The data acquisition module is connected to the pre-sintering module and the sintering furnace main body module respectively, and is used to scan and acquire the initial point cloud data of the upper surface of the pre-sintered billet, and to scan and acquire the three-dimensional point cloud data of the upper surface of the sintered billet at a preset frequency during the heat preservation process, including the real-time point cloud data at the end of the first preset heat preservation time. The data processing module, which is connected to the data acquisition module, is used to obtain the sintering distortion characterization value of the sintered billet and the distortion peak value of the risk sintered billet based on the initial point cloud data and the real-time point cloud data, and to obtain the densification deviation characterization value of the sintered billet based on the three-dimensional point cloud data and the initial point cloud data. A control module, which is connected to the data processing module, is used to determine whether the preparation of the sintered blank is qualified based on the sintering distortion characterization value of the sintered blank, and to make a secondary determination on whether the preparation of the sintered blank is qualified based on the distortion peak value of the risk sintered blank. A strategy determination module, which is connected to the control module, is used to determine the processing strategy when the sintered blank is unqualified based on the densification deviation characterization value of the sintered blank. The processing strategy is to mark the sintered blank as a blank to be remedied or to immediately terminate the sintering process of the sintered blank.

Images