A vacuum sintering process for preventing distortion of cemented carbide rod

Abstract

The application relates to the technical field of sintering, in particular to a vacuum sintering process for preventing deformation of hard alloy rod materials, which comprises the following steps: S1: preparing hard alloy rod material blanks and carrying out degreasing treatment; S2: carrying out vacuumizing treatment on the degreased rod material blanks; and S3: carrying out sintering treatment on the vacuumized rod material blanks, and the temperature rising rate in the sintering process is controlled. The application dynamically adjusts the temperature rising rate based on the change of the temperature and the temperature rising rate in the sintering process, solves the problem that the product quality and the production efficiency of the hard alloy rod materials are reduced due to the control of the furnace temperature by only using a fixed temperature rising rate, and improves the product quality and the production efficiency of the hard alloy rod materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sintering, in particular to a vacuum sintering process for preventing deformation of hard alloy rod materials. BACKGROUND

[0002] Hard alloy is an alloy material prepared from hard compound and binder metal, which is widely used in the field of tool materials due to its high hardness, good wear resistance, high toughness and other excellent properties. The vacuum sintering process has become the mainstream process for preparing hard alloy due to its high alloy densification and suitable cost. However, the vacuum sintering furnace mainly transfers heat by radiation and conduction, which may cause temperature gradient in the furnace, and thus the sintered alloy may also be bent and deformed. Therefore, it is necessary to optimize the existing sintering process to avoid the bending deformation of hard alloy rod materials.

[0003] The furnace temperature control of the sintering furnace is the key to the production quality of hard alloy rod materials. However, the existing technology usually adjusts the furnace temperature of the sintering furnace by fixing the heating parameters, without fully considering the dynamic influence of the density, composition distribution and other differences of different batches of rod material blanks on the temperature gradient in the furnace. In addition, the accumulation of local thermal stress of the rod material caused by the severity of different temperature gradients is also different. Therefore, controlling the furnace temperature by fixing the heating rate will reduce the finished product quality and production efficiency of the hard alloy rod material. SUMMARY

[0004] In order to solve the above technical problems, the present application provides a vacuum sintering process for preventing deformation of hard alloy rod materials to solve the existing problems.

[0005] The vacuum sintering process for preventing deformation of hard alloy rod materials of the present application adopts the following technical solutions:

[0006] One embodiment of the present application provides a vacuum sintering process for preventing deformation of hard alloy rod materials, which includes the following steps:

[0007] S1: preparing hard alloy rod material blanks and performing degreasing treatment;

[0008] S2: performing vacuumizing treatment on the degreased rod material blanks;

[0009] S3: performing sintering treatment on the vacuumized rod material blanks, and controlling the heating rate during the sintering process, specifically:

[0010] Real-time acquisition of the temperature at each preset height in the sintering furnace during each sintering process, wherein the heights are the top, middle and bottom of the sintering furnace;

[0011] screening a temperature difference significant moment in each sintering process based on a dispersion degree of temperatures at all heights in the sintering furnace at each moment in each sintering process;

[0012] determining a temperature imbalance coefficient of the first temperature rising stage in each sintering process based on a correlation between temperatures between the top and the bottom in the sintering furnace at all moments in the first temperature rising stage in each sintering process, and a number of clustering clusters obtained by clustering all temperature difference significant moments in the first temperature rising stage, and in combination with the furnace temperature deviation factor;

[0013] determining a temperature rising deviation coefficient of the first temperature rising stage in the current sintering process based on a difference between temperature imbalance coefficients of the first temperature rising stage between the current sintering process and all sintering processes in the good cluster and a difference in the temperature rising rate at the middle part of the sintering furnace, so as to regulate the temperature rising rate of the subsequent temperature rising stage in the current sintering process.

[0014] Preferably, the vacuum degree in the vacuumizing process ranges from 0.3 to 0.7 Torr.

[0015] Preferably, the temperature rising time length of the preset first temperature rising stage is controlled to be 55-60 min.

[0016] Preferably, the temperature dropping rate in the sintering process ranges from 11 to 30℃ / min.

[0017] Preferably, the screening of the temperature difference significant moment in each sintering process comprises:

[0018] the dispersion degree of the temperatures at all heights in the sintering furnace at each moment in each sintering process is recorded as a temperature dispersion value of each sintering process;

[0019] the temperature dispersion values at all moments in each sintering process are taken as inputs of a threshold segmentation algorithm, and a segmentation threshold is outputted, and the moment at which the temperature dispersion value is greater than or equal to the segmentation threshold is taken as the temperature difference significant moment in each sintering process.

[0020] Preferably, the expression of the furnace temperature deviation factor of the first temperature rising stage in each sintering process is: ; in the formula, represents the furnace temperature deviation factor of the first temperature rising stage in the i th sintering process; represents a proportion of all temperature difference significant moments in the first temperature rising stage in the i th sintering process in all moments; a mean value of temperature dispersion values of all temperature difference significant moments in the first temperature rising stage of the i-th sintering process.

[0021] Preferably, the method for determining the temperature imbalance coefficient of the first temperature rising stage of each sintering process comprises:

[0022] calculating cross-correlation sequences of temperatures between the middle part and the top part and between the middle part and the bottom part in the sintering furnace at all moments in the first temperature rising stage of each sintering process, taking a time lag corresponding to the maximum value in the cross-correlation sequence between the middle part and the top part as a first time lag, taking a time lag corresponding to the maximum value in the cross-correlation sequence between the middle part and the bottom part as a second time lag, and taking a difference between the first time lag and the second time lag as a time lag difference of the first temperature rising stage of each sintering process;

[0023] taking a product of the time lag difference of the first temperature rising stage of each sintering process and the furnace temperature deviation factor as a temperature imbalance coefficient of the first temperature rising stage of each sintering process.

[0024] Preferably, the clustering of the preset number of sintering processes before the current sintering process to obtain a good cluster comprises:

[0025] obtaining a deformation rate of the bar at the end of each sintering process, clustering the preset number of sintering processes before the current sintering process, wherein a metric distance of the clustering process is set as an absolute value of a difference in deformation rates of the bar between sintering processes, outputting all clusters, calculating a mean value of deformation rates of the bar in all sintering processes in each cluster as a deformation rate mean value, and taking a cluster corresponding to the minimum deformation rate mean value as a good cluster of the current sintering process.

[0026] Preferably, the expression of the temperature rising deviation coefficient of the first temperature rising stage in the current sintering process is: ; in the formula, the temperature rising deviation coefficient of the first temperature rising stage in the current sintering process is represented by the minimum value in differences between the temperature imbalance coefficients of the first temperature rising stage between the current sintering process and all sintering processes in the good cluster is represented by a mean value of differences in temperature rising rates at the middle part of the sintering furnace between the current sintering process and all sintering processes in the good cluster is represented by

[0027] Preferably, the regulation of the temperature rising rate of the subsequent temperature rising stage in the current sintering process comprises:

[0028] the expression of the temperature rising rate of the next temperature rising stage after the first temperature rising stage in the current sintering process is: ; in the formula, ​represents a preset initial heating rate of the next heating stage after the first heating stage in the current sintering process; represents a preset rate adjustment value; represents a temperature rise deviation coefficient of the first heating stage in the current sintering process; norm() represents a normalization function;

[0029] Iterate the above-mentioned heating rate adjustment process of the next heating stage to traverse all heating stages after the first heating stage in the current sintering process, and adjust the heating rate thereof.

[0030] The present application has at least the following beneficial effects:

[0031] The present application first constructs a furnace temperature deviation factor based on the proportion of all temperature difference significant moments in the preset first heating stage in each sintering process, and combines the dispersion degree of the temperature at all heights in the sintering furnace at each temperature difference significant moment in the first heating stage, comprehensively evaluates the frequency and intensity of temperature non-uniformity in the first heating stage, realizes the quantitative characterization of the thermal stress accumulation risk, provides a basis for subsequent dynamic adjustment of the heating rate, and thus helps to effectively prevent deformation of the bar caused by temperature gradient, significantly improves the sintering quality and production efficiency; further, the present application constructs a temperature imbalance coefficient by combining the time lag difference, the furnace temperature deviation factor and the cluster number, accurately quantifies the temperature non-uniformity degree of the sintering furnace in the first heating stage, effectively distinguishes the real thermal stress risk and the impurity interference error, thereby guiding the dynamic optimization of the subsequent heating rate, significantly reducing the risk of bar deformation and improving the sintering quality and production efficiency; finally, the present application constructs a temperature rise deviation coefficient by combining historical good sintering process data, dynamically evaluates the deviation degree of the current sintering process from the historical high-quality state, and intelligently adjusts the heating rate of the subsequent heating stage according to the deviation degree, effectively reduces the risk of thermal stress accumulation caused by temperature gradient, and improves the sintering quality and production efficiency of the hard alloy bar. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0033] Figure 1 A step flow chart of a deformation-preventing hard alloy bar vacuum sintering process is provided for an embodiment of the present application;

[0034] Figure 2 A heating rate adjustment step flow chart is provided for an embodiment of the present application. Detailed Implementation

[0035] To further illustrate the technical means and effects adopted by this application to achieve the intended purpose of the invention, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a vacuum sintering process for preventing deformation of cemented carbide rods proposed in this application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0036] Unless otherwise defined, terms such as “comprising,” “including,” or any other variations thereof are intended to cover a non-exclusive inclusion, such that a circuit structure, article, or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the article or device that includes said element. Furthermore, the term “and / or” as used herein includes any and all combinations of one or more of the associated listed items. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The following detailed description, in conjunction with the accompanying drawings, illustrates a specific scheme of a vacuum sintering process for preventing deformation of cemented carbide rods provided by this application.

[0037] The following describes in detail, with reference to the accompanying drawings, a specific scheme for a vacuum sintering process for preventing deformation of cemented carbide rods provided in this application.

[0038] Example 1

[0039] Example 1 provides a vacuum sintering process for preventing deformation of cemented carbide rods. For details, please refer to [link / reference]. Figure 1 The method includes the following steps:

[0040] S1: Prepare cemented carbide rod blanks and perform degumming treatment.

[0041] The uniformly mixed and well-adhesive-added cemented carbide raw material is fed into an extruder. Cemented carbide billets are prepared according to the billet die and subjected to natural disturbance treatment. Then, the billets are placed in a degumming furnace and degummed by hydrogen gas. After degumming, the billets are naturally cooled to room temperature.

[0042] S2: Vacuum treatment is performed on the degummed bar stock.

[0043] The degummed rod blank is cut to a set length by a diamond grinding machine, then the graphite boat loaded with the rod blank is coated with an anti-sticking coating, and the graphite boat is naturally dried in a ventilated environment. The graphite boat loaded with the rod blank is placed in a vacuum sintering furnace, and vacuumizing is performed. In this embodiment, the vacuum degree in the sintering furnace cavity is 0.3 Torr.

[0044] S3: Sintering treatment is performed on the vacuumized rod blank, and the temperature rising rate in the sintering process is controlled.

[0045] After the vacuumizing operation based on step S2 is completed, sintering operation is performed. First, the temperature of the sintering furnace is raised from room temperature to 600°C. In this embodiment, the temperature rising time is set to 55 min, and the temperature is kept at 600°C for 30 min, then the temperature is raised to 800°C and kept at 800°C for 20 min. Next, the temperature is raised to 1350°C and kept at 1350°C for 30 min. Then, the temperature is lowered to 1250°C at a rate of 11°C / min. When the temperature reaches 1250°C, the temperature is raised to 1450°C and kept at 1450°C for 40 min. Finally, after the temperature keeping at 1450°C is completed, the vacuum sintering furnace is powered off, and the hard alloy rod blank is cooled to room temperature while keeping the vacuum degree, and the sintering of the hard alloy rod is completed.

[0046] The furnace temperature control of the sintering furnace is the key to the production quality of the hard alloy rod. However, the prior art usually controls the furnace temperature of the sintering furnace by fixing the temperature rising rate, without fully considering the dynamic influence of the density, component distribution and other differences of different batches of rod blanks on the temperature gradient in the furnace, and the different degrees of accumulation of local thermal stress of the rod caused by different temperature gradients. Therefore, controlling the furnace temperature by fixing the temperature rising rate will affect the finished product quality of the rod, and easily cause the rod to bend and deform, resulting in poor sintering effect.

[0047] Therefore, to solve the above problems, the present embodiment controls the temperature rising rate in the current sintering process by analyzing the temperature and temperature rising rate changes in the historical sintering process. The temperature rising rate control step flow chart provided by the present embodiment is shown in Figure 2 The specific temperature rising rate control process is as follows:

[0048] S301: The temperature at each preset height in the sintering furnace in each sintering process is acquired in real time, wherein the heights are the top, middle and bottom of the sintering furnace.

[0049] In a vacuum sintering process of a hard alloy rod, the temperature at each preset height in the sintering furnace during each sintering process is collected in real time by three temperature thermocouples, wherein the heights are the top, middle and bottom of the sintering furnace, all temperature data are collected synchronously and in real time, the data collection frequency is set to f, and the collection time is from the start to the end of each sintering process.

[0050] It should be noted that the value of the data collection frequency f is artificially set, and in the present embodiment, the value of the data collection frequency f is 0.2 Hz. In actual application, as other implementation manners, the implementer can also set it himself according to the specific situation, and the present embodiment does not make special limitation.

[0051] It should be noted that the top temperature is the temperature at the center of the top of the sintering furnace, and the middle temperature and the bottom temperature are the temperatures at the center of the middle and the center of the bottom of the sintering furnace respectively.

[0052] S302: Based on the dispersion degree of the temperature at all heights in the sintering furnace at each time during each sintering process, the temperature difference significant moment in each sintering process is screened out; based on the proportion of all temperature difference significant moments in the preset first temperature rising stage during each sintering process, and combined with the dispersion degree of the temperature at all heights in the sintering furnace at each temperature difference significant moment in the first temperature rising stage, the furnace temperature deviation factor of the first temperature rising stage in each sintering process is determined.

[0053] Since the internal graphite heating pipes of the vacuum sintering furnace are uniformly distributed around the sintering furnace, the internal heating temperature of the sintering furnace should be theoretically centrally symmetrically distributed, the temperature at the top and the bottom of the sintering furnace should be consistent, and after a period of time, it finally keeps consistent with the center temperature of the sintering furnace. However, since the vacuum sintering furnace mainly heats by non-contact radiation, it takes time for heat to transfer from the periphery to the center area, and the heat will also be affected by the blockage of the rod blank during the transmission process. The rod blanks under different extrusion batches have differences in internal density and component distribution, which further causes the change of the intensity and duration of the temperature gradient in the furnace.

[0054] The greater the temperature gradient and the longer the duration, the greater the accumulation of local thermal stress of the rod blank in the current sintering process, and the more the subsequent heating rate needs to be adjusted to avoid further affecting the sintering quality of the rod. Therefore, the embodiment screens the temperature difference significant moment in each sintering process based on the dispersion degree of the temperature at all heights in the sintering furnace at each moment in each sintering process; determines the furnace temperature deviation factor of the first heating stage in each sintering process based on the proportion of all temperature difference significant moments in the preset first heating stage in each sintering process, and combines the dispersion degree of the temperature at all heights in the sintering furnace at each temperature difference significant moment in the first heating stage, to evaluate the degree of deviation of the temperature distribution in the sintering furnace from the ideal uniform state, thereby indirectly reflecting the risk of accumulation of thermal stress in the rod, and then adjusting the heating rate to avoid the influence of thermal stress accumulation on the sintering quality of the rod. The specific acquisition process of the furnace temperature deviation factor is as follows:

[0055] In the embodiment, first, the temperature difference significant moment in each sintering process is screened based on the dispersion degree of the temperature at all heights in the sintering furnace at each moment in each sintering process, specifically:

[0056] In the embodiment, the dispersion degree of the temperature at all heights in the sintering furnace at each moment in each sintering process is recorded as the temperature dispersion value of each sintering process. The temperature dispersion value reflects the difference between the top temperature, the bottom temperature and the middle temperature in the sintering furnace at the same moment. The greater the temperature dispersion value, the greater the non-uniformity of the temperature in the sintering furnace at the same moment, which is more likely to cause local thermal stress accumulation in the rod.

[0057] It should be noted that there are many methods for measuring the dispersion degree of a group of data. In the embodiment, the standard deviation of the temperature at all heights in the sintering furnace at each moment in each sintering process is recorded as the dispersion degree of the temperature at all heights in the sintering furnace at each moment in each sintering process. In actual application, the implementer can also use other methods for measuring the dispersion degree of data, such as variance or dispersion coefficient, to measure the dispersion degree of data. The selection of the method for measuring the dispersion degree of data is not limited in the embodiment.

[0058] The temperature dispersion values at all moments in each sintering process are used as the input of the threshold segmentation algorithm, and the segmentation threshold is output. The moment when the temperature dispersion value is greater than or equal to the segmentation threshold is used as the temperature difference significant moment in each sintering process. The temperature difference significant moment reflects the moment when the temperature gradient in the sintering furnace is relatively severe in the first heating stage.

[0059] It should be noted that there are many commonly used threshold segmentation algorithms, and in the present embodiment, Otsu threshold segmentation algorithm is used to screen out the temperature difference significant moment. In actual application process, as other implementation manners, the implementer can also use other threshold segmentation algorithms according to specific circumstances, and the selection of threshold segmentation algorithm is not specially limited in the present embodiment.

[0060] Among them, the Otsu threshold segmentation algorithm is a known technology, and the specific process of obtaining the temperature difference significant moment will not be repeated.

[0061] Further, the present embodiment determines the furnace temperature deviation factor of the first temperature rising stage in each sintering process based on the proportion of all temperature difference significant moments in the preset first temperature rising stage and the dispersion degree of the temperature at all heights in the sintering furnace at each temperature difference significant moment in the first temperature rising stage, and the expression is:

[0062] As an implementation manner, in the present embodiment, the furnace temperature deviation factor of the first temperature rising stage in the i th sintering process is The expression is: ; in the formula, represents the proportion of all temperature difference significant moments in the first temperature rising stage in the i th sintering process in all moments; represents the average value of the temperature dispersion value of all temperature difference significant moments in the first temperature rising stage in the i th sintering process.

[0063] It should be noted that in the present embodiment, the stage between the temperature rising from room temperature to 600 DEG C in the sintering furnace and the moment when the temperature at 600 DEG C is maintained is taken as the first temperature rising stage in each sintering process.

[0064] According to the furnace temperature deviation factor of the first temperature rising stage in each sintering process, it can be understood that the furnace temperature deviation factor reflects the influence degree of the non-uniformity of the internal temperature of the sintering furnace in the first temperature rising stage. If the proportion of all temperature difference significant moments in the first temperature rising stage in the i th sintering process in all moments is larger, it means that the non-uniformity of the internal temperature of the sintering furnace in the first temperature rising stage in the i th sintering process occurs more frequently, and the corresponding first furnace temperature deviation factor is relatively larger, which means that the non-uniformity of the internal temperature of the sintering furnace in the first temperature rising stage in the i th sintering process is more severe and the duration is longer, and the deviation degree of the sintering furnace temperature in the normal temperature rising stage may be larger, so it is more necessary to adjust the temperature rising rate in the subsequent sintering process to a larger extent to alleviate the local stress concentration problem caused by the temperature gradient and reduce the risk of deformation of the bar;

[0065] Conversely, if the proportion of all temperature difference significant moments in all moments in the first temperature rising stage in the i-th sintering process is smaller, it means that the temperature inhomogeneity in the sintering furnace in the first temperature rising stage in the i-th sintering process is less significant, the corresponding first furnace temperature deviation factor is relatively smaller, which means that in the first temperature rising stage in the i-th sintering process, the temperature distribution in the sintering furnace is relatively uniform and stable, and the deviation degree from the sintering furnace temperature in the ideal uniform state is smaller, so the adjustment range of the temperature rising rate in the subsequent sintering process can be relatively small, and even the preset temperature rising rate can be maintained for sintering, which helps to improve the production efficiency and shorten the sintering cycle while ensuring the sintering quality.

[0066] So far, by constructing the furnace temperature deviation factor, the frequency and intensity of the temperature inhomogeneity in the sintering furnace in the first temperature rising stage are comprehensively evaluated, the quantitative characterization of the thermal stress accumulation risk is realized, and the basis for subsequent dynamic adjustment of the temperature rising rate is provided, thereby helping to effectively prevent the deformation of the bar caused by the temperature gradient and significantly improve the sintering quality and production efficiency.

[0067] S303: Determine the temperature imbalance coefficient of the first temperature rising stage in each sintering process based on the correlation between the temperatures of the top and bottom in the sintering furnace at all moments in the first temperature rising stage in each sintering process, the number of clustering clusters obtained by clustering all temperature difference significant moments in the first temperature rising stage, and the furnace temperature deviation factor.

[0068] Since the sintering quality of the hard alloy bar is also affected by factors such as sintering particles and water vapor dust in the sintering furnace, and the precipitation time, precipitation degree and moving direction of the particles and water vapor dust are irregular, the temperature data collected at a certain moment at the top, bottom or center of the sintering furnace may fluctuate instantaneously, thereby causing a large difference between the temperatures at the three positions under the condition of temperature uniformity, and further causing a large temperature dispersion value at that moment. Therefore, there will be errors in the evaluation of temperature uniformity by only using the temperature deviation factor, so in this embodiment, the temperature imbalance coefficient of the first temperature rising stage in each sintering process is determined based on the correlation between the temperatures of the top and bottom in the sintering furnace at all moments in the first temperature rising stage in each sintering process, the number of clustering clusters obtained by clustering all temperature difference significant moments in the first temperature rising stage, and the furnace temperature deviation factor, so as to more accurately judge the uniformity of the furnace temperature in the temperature rising stage. The specific process is as follows:

[0069] If the top and bottom are not consistent in the degree of obstruction by the rod when transferring heat to the central area, it will also cause the temperature of the top, bottom and central area to be out of sync, and then cause the temperature in the furnace to be uneven. Although the instantaneous temperature difference caused by the different pace may be small, the continuous different pace of heating will also produce uneven thermal stress.

[0070] Based on the above analysis, in this embodiment, the maximum value corresponding time lag in the cross-correlation sequence between the temperature of the middle part and the top is recorded as the first time lag, the maximum value corresponding time lag in the cross-correlation sequence between the temperature of the middle part and the bottom is recorded as the second time lag, and the difference between the first time lag and the second time lag is recorded as the time lag difference of the first heating stage in each sintering process, which reflects whether the influence of the top and bottom on the central temperature is consistent. The greater the time lag difference, the more inconsistent the influence, and the more out of sync the heat transfer of the top and bottom to the central area in time.

[0071] It should be noted that the process of obtaining the cross-correlation sequence is a known technology, and each element in the cross-correlation sequence represents the cross-correlation coefficient between the temperature of the middle part and the top and bottom at different time lags, wherein the value of time lag k ranges from 0 to m-1. In this embodiment, the value of m is 180, and k is sequentially increased by 1.

[0072] It should be understood that there are many methods for measuring the difference between data. In this embodiment, the absolute value of the difference between the first time lag and the second time lag is used to determine the difference between the data. For example, in this embodiment, the absolute value of the difference between the first time lag and the second time lag is used as the difference between the first time lag and the second time lag. In actual application, as an alternative, the implementer can also use the square or ratio of the difference to measure the difference between the data. The selection of the method for measuring the difference between the data is not limited in this embodiment.

[0073] It should be noted that, except for special instructions, the method for measuring the difference between data in this embodiment is the method of taking the absolute value of the difference.

[0074] In addition, in the heating stage, the temperature of the top and bottom in the furnace is relatively consistent at the beginning of heating, and both have a difference with the temperature of the central position. With the conduction of heat, the temperature in the furnace gradually becomes uniform, and the temperature dispersion value should also gradually decrease. Therefore, if the sintering process of the rod is not affected by impurities such as precipitated particles and water vapor, the temperature dispersion value should change from large to small and then tend to be stable, so all the temperature difference significant moments should have high clustering.

[0075] Therefore, based on the above analysis, the embodiment will cluster the number of clusters of all temperature difference significant moments in the first temperature rising stage, denoted as the clustering number;

[0076] It should be noted that there are many commonly used clustering algorithms, and the k-means clustering algorithm is used in the embodiment to cluster the temperature difference significant moments, wherein the measurement distance is set as the time interval between the temperature difference significant moments, the elbow rule is used to obtain the number of clusters, and all clusters are output.

[0077] Among them, the k-means clustering algorithm and the elbow rule are both known technologies, and the specific process of clustering the temperature difference significant moments by using the k-means clustering algorithm and the specific process of determining the number of clusters by using the elbow rule are not repeated.

[0078] It should be noted that the number of clusters can reflect whether all temperature difference significant moments have high aggregation, the greater the clustering number, the worse the aggregation, the more dispersed the distribution of temperature difference significant moments, and thus the greater the possibility that the collected temperature is affected by precipitated particles or water vapor, and further, the greater the error of the calculated furnace temperature deviation factor; on the contrary, the smaller the clustering number, the smaller the error disturbance of the furnace temperature deviation factor during calculation, and the more accurate the reflected furnace temperature non-uniformity.

[0079] Further, the embodiment takes the product of the time lag difference of the first temperature rising stage in each sintering process and the furnace temperature deviation factor divided by the number of clusters as the temperature imbalance coefficient of the first temperature rising stage in each sintering process.

[0080] According to the temperature imbalance coefficient of the first temperature rising stage in each sintering process, it can be understood that the temperature imbalance coefficient is used to characterize the degree of non-uniformity of the sintering furnace temperature in the first temperature rising stage of the sintering process. If the time lag difference of the first temperature rising stage in the current sintering process is larger, it means that the heat transfer from the top and bottom of the sintering furnace to the middle part of the sintering furnace is seriously out of sync in time, and there is a significant delay in the heat transfer between the upper and lower parts of the sintering furnace, which may cause uneven heating of the upper and lower parts of the bar, and the corresponding temperature imbalance coefficient is larger. At the same time, if the furnace temperature deviation factor of the first temperature rising stage in the current sintering process is larger, it means that the temperature non-uniformity phenomenon in the sintering furnace is frequent and severe, so the corresponding temperature imbalance coefficient is also larger. In addition, if the cluster number of the first temperature rising stage in the current sintering process is smaller, it means that the temperature difference significant moment distribution is highly clustered, indicating that the temperature non-uniformity phenomenon is real, rather than impurity interference, so the corresponding temperature imbalance coefficient is larger. If the temperature imbalance coefficient is large, it reflects that the degree of non-uniformity of the furnace temperature is larger and is not disturbed by a larger impurity error, and the measurement of the non-uniformity of the furnace temperature is more accurate, so the degree of thermal stress accumulated by the bar blank in the first temperature rising stage may be larger, and a larger degree of adjustment of the temperature rising rate is needed in the subsequent temperature rising stage.

[0081] On the contrary, if the time lag difference of the first temperature rising stage in the current sintering process is smaller, it means that the heat transfer from the top and bottom of the sintering furnace to the middle part is relatively synchronous in time, and the upper and lower parts of the furnace are evenly heated, and the corresponding temperature imbalance coefficient is smaller. At the same time, if the furnace temperature deviation factor of the first temperature rising stage in the current sintering process is smaller, it means that the temperature non-uniformity phenomenon in the sintering furnace occurs less frequently and weakly, and the temperature distribution is relatively stable, so the corresponding temperature imbalance coefficient is also smaller. In addition, if the cluster number of the first temperature rising stage in the current sintering process is larger, it means that the temperature difference significant moment distribution is relatively dispersed, indicating that the temperature non-uniformity phenomenon may be affected by impurity interference or occasional factors, and the measurement of the temperature imbalance is less reliable, so the corresponding temperature imbalance coefficient is smaller. If the temperature imbalance coefficient is small, it reflects that the degree of non-uniformity of the furnace temperature is lighter or there is a larger measurement error, and the measurement reliability of the non-uniformity of the furnace temperature is lower, so the risk of thermal stress accumulated by the bar blank in the first temperature rising stage is smaller, and the adjustment amplitude of the temperature rising rate in the subsequent temperature rising stage can be appropriately reduced, or even the original temperature rising rate can be maintained, which helps to improve the production efficiency while ensuring the sintering quality.

[0082] So far, by constructing the temperature imbalance coefficient by combining the time lag difference, the furnace temperature deviation factor and the cluster number, the temperature non-uniformity degree of the sintering furnace in the first temperature rising stage is accurately quantified, the real thermal stress risk and the impurity interference error are effectively distinguished, thereby guiding the dynamic optimization of the subsequent temperature rising rate, significantly reducing the risk of bar deformation and improving the sintering quality and production efficiency.

[0083] S304: Based on the difference between the temperature imbalance coefficient of the first temperature rising stage between the current sintering process and all the sintering processes in the good cluster and the difference of the temperature rising rate at the middle part of the sintering furnace, the temperature rising deviation coefficient of the first temperature rising stage in the current sintering process is determined to regulate the temperature rising rate of the subsequent temperature rising stage in the current sintering process. In this embodiment, the sintering process data with smaller rod deformation rate in the historical sintering process is combined to optimize and adjust the current sintering process, and the specific process is as follows:

[0084] Firstly, the preset number of sintering processes before the current sintering process are taken as the input of the clustering algorithm, wherein the measurement distance of the clustering process is set as the absolute value of the difference of the rod deformation rate between the sintering processes, the elbow rule is used to determine the number of clusters, all clusters are output, the mean value of the rod deformation rate of all the sintering processes in each cluster is calculated and recorded as the deformation rate mean value, and the cluster corresponding to the minimum deformation rate mean value is taken as the good cluster of the current sintering process.

[0085] It should be noted that the preset number is artificially set, and in this embodiment, the preset number is 200. In actual application, the implementer can also set it according to the specific situation, and this embodiment does not make special limitation.

[0086] In this embodiment, the k-means clustering algorithm is used to cluster the sintering processes, and in actual application, the implementer can also set it according to the specific situation, and this embodiment does not make special limitation.

[0087] Further, based on the difference between the temperature imbalance coefficient of the first temperature rising stage between the current sintering process and all the sintering processes in the good cluster and the difference of the temperature rising rate at the middle part of the sintering furnace, the temperature rising deviation coefficient of the first temperature rising stage in the current sintering process is determined, and the specific process is as follows:

[0088] As an implementation manner, in this embodiment, the expression of the temperature rising deviation coefficient of the first temperature rising stage in the current sintering process is as follows: In the formula, min represents the minimum value in the difference between the temperature imbalance coefficient of the first temperature rising stage between the current sintering process and all the sintering processes in the good cluster; mean represents the mean value of the difference of the temperature rising rate at the middle part of the sintering furnace between the current sintering process and all the sintering processes in the good cluster.

[0089] Wherein, the calculation method of the temperature rising rate is a known technology, and the specific calculation process is not described here.

[0090] ​​Based on the temperature rise deviation coefficient during the first heating stage of the current sintering process, it can be understood that the temperature rise deviation coefficient reflects the degree of deviation between the current sintering process and historically successful sintering processes during the first heating stage. The larger the minimum difference in temperature imbalance coefficients between the current sintering process and all subsequent sintering processes within the successful cluster, the greater the difference between the current sintering process's temperature imbalance coefficient and that of historically successful sintering processes. This indicates a significant deviation of the current furnace temperature uniformity from historically excellent levels, a high risk of thermal stress, and a correspondingly larger temperature rise deviation coefficient. Simultaneously, if the current... The greater the average difference in heating rate at the center of the sintering furnace between the sintering process and all sintering processes in the good sintering cluster, the more significant the difference between the current sintering process's heating rate and the average of the good sintering process. The heating strategy may be too fast or too slow, which can easily lead to thermal stress problems, and the corresponding temperature rise deviation coefficient is larger. The larger the temperature rise deviation coefficient, the greater the possibility that the bar has accumulated thermal stress in the first heating stage of the current sintering process. Therefore, in the subsequent heating stages, it is more necessary to adjust the heating rate to a greater extent to alleviate the stress concentration problem caused by uneven furnace temperature and reduce the risk of bar bending deformation.

[0091] Conversely, if the minimum difference in temperature imbalance coefficient between the current sintering process and all subsequent sintering processes in the good cluster during the first heating stage is smaller, it indicates that the temperature imbalance coefficient of the current sintering process is close to that of a historical good sintering process, the current furnace temperature uniformity is well controlled, the risk of thermal stress is low, and the corresponding temperature rise deviation coefficient is smaller. At the same time, if the average difference in heating rate at the middle of the sintering furnace between the current sintering process and all subsequent sintering processes in the good cluster is smaller, it indicates that the heating rate of the current sintering process is highly consistent with the average of the good sintering process, the heating strategy is reasonable, and it is not easy to cause thermal stress problems, and the corresponding temperature rise deviation coefficient is smaller. The smaller the temperature rise deviation coefficient, the less likely the bars will accumulate thermal stress in the first heating stage of the current sintering process. In this case, the adjustment range of the heating rate can be appropriately reduced in subsequent heating stages, or even the original heating rate can be maintained, which helps to improve production efficiency while ensuring sintering quality.

[0092] Furthermore, this embodiment uses the temperature rise deviation coefficient of the first heating stage in the current sintering process to regulate the heating rate of subsequent heating stages in the current sintering process, specifically as follows:

[0093] As one implementation method, in this embodiment, the heating rate of the next heating stage after the first heating stage in the current sintering process is... The expression is: In the formula, This indicates the preset initial heating rate for the next heating stage after the first heating stage in the current sintering process; This indicates the preset rate adjustment value; represents the temperature rise deviation coefficient of the first temperature rise stage in the current sintering process; norm() represents a normalization function.

[0094] According to the above regulation process of the next temperature rise stage, the temperature rise rate is iterated and regulated for all temperature rise stages after the first temperature rise stage in the current sintering process.

[0095] It should be noted that the preset initial temperature rise rate of the next temperature rise stage after the first temperature rise stage in the current sintering process, i.e., the initial temperature rise rate during the process of rising the temperature to 800℃, is in the range of 8-13℃ / min, and in the embodiment, the value is 10℃ / min, the initial temperature rise rate during the process of rising the temperature to 1350℃ is in the range of 6.5-7.5℃ / min, and in the embodiment, the value is 7℃ / min, and the initial temperature rise rate during the process of rising the temperature from 1250℃ to 1450℃ is in the range of 2-3℃ / min, and in the embodiment, the value is 2.5℃ / min.

[0096] In addition, it should be noted that the preset rate adjustment value is also artificially set, and in the embodiment, the value of the preset rate adjustment value is 5, and in actual application, the implementer can also set it by himself according to the specific situation, and the embodiment does not have special limitations.

[0097] So far, the embodiment combines historical good sintering process data to build a temperature rise deviation coefficient to dynamically evaluate the deviation degree of the current sintering process from the historical high-quality state, and intelligently adjust the temperature rise rate of the subsequent temperature rise stage, effectively reducing the risk of thermal stress accumulation caused by temperature gradient, and significantly improving the sintering quality and production efficiency of the hard alloy rod.

[0098] Embodiment 2

[0099] The vacuum sintering process of the hard alloy rod provided in Embodiment 2 prevents deformation, and specifically, please refer to Figure 1 The method comprises the following steps:

[0100] S1: preparing a hard alloy rod blank and performing a degreasing treatment.

[0101] S2: performing a vacuumizing treatment on the degreased rod blank. In the embodiment, the vacuum degree in the sintering furnace cavity is 0.5 Torr, and the remaining operations are the same as in Embodiment 1.

[0102] S3: performing a sintering treatment on the vacuumized rod blank, and regulating the temperature rise rate during the sintering process.

[0103] In the embodiment, the value of the cooling rate is 15℃ / min, and the remaining operations are the same as in Embodiment 1.

[0104] Embodiment 3

[0105] Embodiment 3 provides a vacuum sintering process for preventing deformation of a cemented carbide rod, in particular, refer to Figure 1 The method comprises the following steps:

[0106] S1: preparing a cemented carbide rod blank and performing a degreasing treatment.

[0107] S2: performing a vacuum extraction treatment on the degreased rod blank. In this embodiment, the vacuum degree of the sintering furnace cavity is 0.7 Torr, and the remaining operations are the same as those of Embodiment 1.

[0108] S3: performing a sintering treatment on the vacuum-extracted rod blank, and controlling the temperature rising rate during sintering.

[0109] In this embodiment, the value of the cooling rate is 15℃ / min, and the remaining operations are the same as those of Embodiment 1.

[0110] It should be noted that the above sequence of the embodiments of the present application is only for description, and does not represent the advantages and disadvantages of the embodiments. Moreover, the above describes specific embodiments of the present specification. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multi-task processing and parallel processing are possible or can be advantageous.

[0111] Each embodiment in the present specification is described in a progressive manner, and the same or similar parts between each embodiment can be referred to each other. Each embodiment focuses on the difference from other embodiments.

[0112] The above-described embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; modifying the technical solutions described in the above embodiments, or equivalently replacing some technical features, without changing the essence of the corresponding technical solutions, falls within the scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A process for vacuum sintering of cemented carbide rod material without distortion, c h a r a c t e r i s e d in that, The process comprises the following steps: S1: preparing a hard alloy rod blank and performing a degreasing treatment; S2: performing a vacuum extraction treatment on the degreased rod blank; S3: performing a sintering treatment on the vacuum-extracted rod blank, and controlling the temperature rising rate during the sintering process, specifically: real-time acquisition of the temperature at each preset height in the sintering furnace during each sintering process, wherein the heights are the top, middle and bottom of the sintering furnace; taking the dispersion degree of the temperature at all heights in the sintering furnace at each time during each sintering process as the temperature dispersion value of each sintering process, taking the temperature dispersion value at all times during each sintering process as the input of the threshold segmentation algorithm, outputting the segmentation threshold, taking the time when the temperature dispersion value is greater than or equal to the segmentation threshold as the significant temperature difference moment during each sintering process; based on the proportion of all significant temperature difference moments in the preset first temperature rising stage during each sintering process, and combining the dispersion degree of the temperature at all heights in the sintering furnace at each significant temperature difference moment in the first temperature rising stage, the furnace temperature deviation factor of the first temperature rising stage during each sintering process is determined; based on the correlation between the temperatures in the middle part and the top and bottom of the sintering furnace at all times during the first temperature rising stage in each sintering process, and the number of clustering clusters obtained by clustering all significant temperature difference moments in the first temperature rising stage, and combining the furnace temperature deviation factor, the temperature imbalance coefficient of the first temperature rising stage during each sintering process is determined; based on the difference between the temperature imbalance coefficients of the first temperature rising stage and the difference in the temperature rising rate of the middle part of the sintering furnace between the current sintering process and all sintering processes in the good cluster, the temperature rising deviation coefficient of the first temperature rising stage in the current sintering process is determined to control the temperature rising rate of the subsequent temperature rising stage in the current sintering process; The expression of the furnace temperature deviation factor in the first temperature rising stage of each sintering process is: ; in the formula, represents the furnace temperature deviation factor in the first temperature rising stage of the i th sintering process; represents the proportion of all temperature difference significant moments in all moments in the first temperature rising stage of the i th sintering process; represents the average value of temperature dispersion values of all temperature difference significant moments in the first temperature rising stage of the i th sintering process; the temperature dispersion value is the dispersion degree of temperatures at all heights in the sintering furnace at each moment in each sintering process. the determination method of the temperature imbalance coefficient of the first temperature rising stage during each sintering process is: calculating the cross-correlation sequence of the temperatures in the middle part and the top and bottom of the sintering furnace at all times during the first temperature rising stage in each sintering process, taking the time lag corresponding to the maximum value in the cross-correlation sequence of the temperatures between the middle part and the top as the first time lag, taking the time lag corresponding to the maximum value in the cross-correlation sequence of the temperatures between the middle part and the bottom as the second time lag, taking the difference between the first time lag and the second time lag as the time lag difference of the first temperature rising stage in each sintering process; taking the number of clustering clusters obtained by clustering all significant temperature difference moments in the first temperature rising stage as the clustering number, taking the product of the time lag difference of the first temperature rising stage in each sintering process and the furnace temperature deviation factor divided by the clustering number as the temperature imbalance coefficient of the first temperature rising stage in each sintering process; The expression of the temperature rise deviation coefficient of the first temperature rise stage in the current sintering process is: ; in the formula, represents the temperature rise deviation coefficient of the first temperature rise stage in the current sintering process; represents the minimum value in the difference between the temperature imbalance coefficient of the first temperature rise stage in the current sintering process and all secondary sintering processes in the good cluster; represents the average value of the difference in the temperature rise rate at the middle part of the sintering furnace between the current sintering process and all secondary sintering processes in the good cluster; the control of the temperature rising rate of the subsequent temperature rising stage in the current sintering process comprises: a preset initial heating rate of a next heating stage after the first heating stage in the current sintering process is expressed as: ; in the formula, represents a preset initial heating rate of a next heating stage after the first heating stage in the current sintering process; represents a preset rate adjustment value; represents a temperature rise deviation coefficient of the first heating stage in the current sintering process; norm() represents a normalization function; iterating the above control process of the next temperature rising stage, and traversing all temperature rising stages after the first temperature rising stage in the current sintering process to control the temperature rising rate.

2. A process for vacuum sintering of cemented carbide rod material to prevent distortion according to claim 1, c h a r a c t e r i s e d i n that The vacuum degree during the vacuum extraction process is 0.3-0.7 Torr.

3. A process for vacuum sintering of cemented carbide rod material to prevent distortion according to claim 1, c h a r a c t e r i s e d i n that The temperature rising time of the preset first temperature rising stage is controlled to be 55-60 min.

4. A process for vacuum sintering of cemented carbide rod material to prevent distortion according to claim 1, c h a r a c t e r i s e d i n that The cooling rate of the cooling stage in the sintering process is 11-30℃ / min.

5. A process for the vacuum sintering of cemented carbide rod material to prevent distortion as claimed in claim 1, c h a r a c t e r i s e d i n that The good cluster obtained by clustering the preset number of sintering processes before the current sintering process includes: The deformation rate of the bar at the end of each sintering process is obtained, and the preset number of sintering processes before the current sintering process is clustered, wherein the metric distance of the clustering process is set as the absolute value of the difference between the deformation rates of the bars in the sintering processes, all clusters are output, the average of the deformation rates of the bars in all sintering processes in each cluster is calculated and recorded as the average deformation rate, and the cluster corresponding to the minimum average deformation rate is taken as the good cluster of the current sintering process.

Images