Annealing collaborative control method and system for vacuum heat treatment of cold working die steel

Abstract

The present application relates to the technical field of vacuum heat treatment of cold-working die steel, and specifically to an annealing coordinated control method and system for vacuum heat treatment of cold-working die steel, the method comprising: determining a vacuum degree change factor based on the change of vacuum degree measurement values ​​at all acquisition moments between the end of vacuuming and each acquisition moment, and determining a heat transfer influence factor based on the difference in vacuum degree measurement values ​​between adjacent acquisition moments, and the difference between the temperature measurement value and the temperature of the workpiece surface; determining a tissue transformation influence factor based on the difference in vacuum degree measurement values ​​between adjacent acquisition moments and the difference in heat transfer influence factors; and controlling the annealing of vacuum heat treatment of cold-working die steel based on the heat transfer influence factor and the tissue transformation influence factor. The present application aims to control the annealing temperature and holding time of vacuum heat treatment of cold-working die steel to improve the performance of cold-working die steel.

Description

Technical Field

[0001] The present application relates to the technical field of vacuum heat treatment of cold working die steel, and in particular to an annealing coordinated control method and system for vacuum heat treatment of cold working die steel. Background Art

[0002] Cold working die steel is a steel used to make molds that deform or form metals in a cold state. It has high hardness and strength, good wear resistance and good toughness. Annealing is a metal heat treatment process that aims to reduce the hardness of the material, improve the cutting performance of the material, eliminate the residual stress inside the material, and refine the grain. Annealing in a vacuum environment can prevent the metal from reacting with oxygen, nitrogen and other gases in the air during heating, such as oxidation and decarburization. Both temperature and time have a significant impact on the annealing process, and their coordinated control can improve the performance of die steel.

[0003] The traditional annealing process is based on experiments to determine the fixed temperature and time for different time periods. However, when performing vacuum heat treatment, it does not take into account the problem that the vacuum pump of the vacuum furnace may have a decrease in the pumping rate after long-term operation, resulting in changes in the vacuum degree. Due to the change in vacuum degree, the organizational transformation and incomplete spheroidization occur at a fixed temperature and time, which reduces the performance of the cold working die steel. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide an annealing coordinated control method and system for vacuum heat treatment of cold working die steel. The technical solutions adopted are as follows:

[0005] In a first aspect, an embodiment of the present application provides an annealing coordinated control method for vacuum heat treatment of cold working die steel, the method comprising the following steps:

[0006] After the vacuuming is completed in the vacuum heat treatment annealing process of cold-working die steel, the vacuum degree and temperature measurement values ​​in the vacuum furnace and the surface temperature of the workpiece are obtained at each stage and each acquisition time;

[0007] Based on the extreme changes in the vacuum degree measurement values ​​at all collection moments between the end of vacuuming and each collection moment in each stage, the vacuum degree change amplitude at each collection moment in each stage is determined, and the vacuum degree change factor at each collection moment in each stage is determined in combination with the average change rate of the vacuum degree measurement values ​​between the end of vacuuming and each collection moment in each stage, and the number of times the vacuum degree measurement values ​​exceed the preset value;

[0008] Based on the difference in the vacuum degree measurement value between each acquisition moment and the previous acquisition moment, and the preset ideal thermal conductivity coefficient, the thermal conductivity correction coefficient at each acquisition moment in each stage is determined, and the thermal conductivity index at each acquisition moment in each stage is determined in combination with the difference between the temperature measurement value at each acquisition moment and the temperature of the workpiece surface; based on the thermal conductivity index and the vacuum degree variation factor, the heat transfer influence factor at each acquisition moment in each stage is determined;

[0009] Based on the difference in the vacuum degree measurement value and the difference in the heat transfer influencing factor between each acquisition moment and the previous acquisition moment, the tissue transformation influencing factor at each acquisition moment in each stage is determined;

[0010] Based on the heat transfer influencing factor and the organizational transformation influencing factor, the annealing temperature adjustment value and the holding time adjustment value at each sampling moment in each stage are determined to control the annealing of the vacuum heat treatment of the cold working die steel.

[0011] Preferably, the variation range of the vacuum degree at each collection moment in each stage is the range of the vacuum degree measurement values ​​at all collection moments between the vacuuming end moment and each collection moment in each stage.

[0012] Preferably, the method for determining the vacuum degree variation factor at each acquisition moment in each stage is:

[0013] The number of times that the vacuum degree measurement value exceeds the preset value between the end of vacuuming and each sampling time in each stage is recorded as the vacuum degree change frequency at each sampling time in each stage;

[0014] The normalized value of the absolute value of the multiplication of the average change rate of the vacuum degree measurement value between the end of vacuuming and each collection time in each stage, the vacuum degree change amplitude, and the vacuum degree change frequency is used as the vacuum degree change factor at each collection time in each stage.

[0015] Preferably, the expression of the heat conduction correction coefficient at each acquisition moment in each stage is: ; In the formula, represents the heat conduction correction coefficient at the jth acquisition moment in stage i; Indicates the preset ideal heat transfer coefficient; represents the difference in vacuum degree measurement between the jth acquisition moment and the previous acquisition moment in stage i; , Respectively represent the preset first value and the preset second value; wherein .

[0016] Preferably, the expression of the heat conduction index at each acquisition moment in each stage is: ; In the formula, represents the heat transfer index at the jth acquisition moment in stage i; , They represent the temperature measurement value and the temperature of the workpiece surface at the jth acquisition moment in stage i, respectively; , denote the preset firing rate and the preset Stefan-Boltzmann constant, respectively.

[0017] Preferably, the heat transfer influence factor at each acquisition moment in each stage is a normalized value of the product of the heat conduction index and the vacuum degree variation factor at each acquisition moment in each stage.

[0018] Preferably, the expression of the tissue transformation influencing factor at each acquisition moment in each stage is: ; In the formula, represents the organizational transformation influencing factor at the jth acquisition moment under stage i; It represents the difference of heat transfer influence factor between the jth acquisition moment and the previous acquisition moment in stage i; , They represent the preset basic diffusion coefficient and the preset third value respectively; norm[ ] represents the normalization function; exp( ) represents the exponential function with the natural constant as the base.

[0019] Preferably, the method for determining the annealing temperature adjustment value and the holding time adjustment value at each collection moment in each stage is:

[0020] The expression of the annealing temperature adjustment value at the jth acquisition time in stage i is: ; In the formula, represents the preset initial annealing temperature of stage i; represents the heat transfer impact factor at the jth acquisition moment under stage i; represents the organizational transformation influencing factor at the jth acquisition moment under stage i; , Respectively represent the preset first and second adjustment factors;

[0021] The expression of the holding time adjustment value at the jth collection moment in stage i is: ; In the formula, Indicates the preset initial holding time of stage i; , Respectively represent the preset third and fourth adjustment factors.

[0022] Preferably, the process of controlling the annealing of the cold working die steel vacuum heat treatment is:

[0023] The insulation time of the cold-working mold steel at each sampling moment in each stage is obtained, and the error between the temperature measurement value and the annealing temperature adjustment value at each sampling moment in each stage, as well as the error between the insulation time and the insulation time adjustment value at each sampling moment are used as the input of the PID controller, and the temperature control signal and time control signal are output to regulate the temperature and insulation time at the corresponding sampling moment respectively.

[0024] In the second aspect, an embodiment of the present application also provides an annealing collaborative control system for vacuum heat treatment of cold working die steel, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, the steps of any one of the above-mentioned annealing collaborative control methods for vacuum heat treatment of cold working die steel are implemented.

[0025] This application has at least the following beneficial effects:

[0026] The present application constructs a vacuum degree variation factor by the change of the vacuum degree measurement value between the end of vacuuming and each acquisition time in each stage. The vacuum degree variation factor can reflect the influence of the vacuum degree change on the annealing process, and helps to adjust the annealing temperature and holding time when the vacuum degree changes, so as to maintain the stability of the annealing process, thereby improving the performance of the cold-working die steel; the present application corrects the thermal conductivity coefficient based on the vacuum degree measurement values ​​at adjacent moments, and constructs a thermal conductivity correction coefficient. The thermal conductivity correction coefficient can correct the change of the thermal conductivity coefficient caused by the vacuum degree, thereby more accurately reflecting the change of thermal conductivity, and helps to more accurately control the temperature and time in the annealing process, thereby improving the performance of the cold-working die steel; the present application is based on the vacuum degree variation factor and the thermal conductivity correction coefficient, as well as the temperature measurement value in the vacuum furnace at each acquisition time. The difference between the measured value and the temperature of the workpiece surface is used to construct a heat transfer influence factor, which has the beneficial effect of more comprehensively reflecting the changes in heat transfer by comprehensively considering the influence of vacuum changes on heat conduction and thermal radiation, thereby more accurately adjusting the temperature and time in the annealing process; the present application constructs a tissue transformation influence factor by comprehensively considering the differences in vacuum measurement values ​​between adjacent moments and the differences in heat transfer influence factors, which has the beneficial effect of more accurately adjusting the temperature and time in the annealing process to maintain the stability of material properties; the present application analyzes the influence of vacuum on annealing temperature and holding time, and coordinately controls the temperature and time in the annealing process to avoid incomplete tissue transformation and spheroidization, thereby improving the performance of cold working die steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 A flowchart of the steps of an annealing coordinated control method for vacuum heat treatment of cold working die steel provided in one embodiment of the present application;

[0029] Figure 2 A schematic diagram of a heat transfer influencing factor extraction process provided by one embodiment of the present application;

[0030] Figure 3 A schematic diagram of the annealing temperature and holding time adjustment process provided for one embodiment of the present application. DETAILED DESCRIPTION

[0031] In order to further explain the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following, in combination with the accompanying drawings and preferred embodiments, describes in detail the annealing coordinated control method and system for vacuum heat treatment of cold-working die steel proposed in the present application, its specific implementation method, structure, features and effects. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0032] Unless defined otherwise, 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 belongs.

[0033] The specific scheme of the annealing coordinated control method and system for vacuum heat treatment of cold working die steel provided by the present application is described in detail below with reference to the accompanying drawings.

[0034] See also Figure 1 , which shows a flowchart of the steps of an annealing coordinated control method for vacuum heat treatment of cold working die steel provided by an embodiment of the present application, the method comprising the following steps:

[0035] Step S1: After the vacuuming in the vacuum heat treatment annealing process of cold-working die steel ends, the vacuum degree measurement value and the temperature measurement value in the vacuum furnace at each stage and each acquisition time, as well as the temperature of the workpiece surface are obtained.

[0036] This embodiment takes a high-carbon, high-chromium cold-working die steel as an example. It has the advantages of high hardenability, high hardenability, high wear resistance and small heat treatment deformation. However, due to its high carbon content and chromium content, network eutectic carbides are easily generated during the solidification process. Spheroidizing annealing is mainly used to obtain a pearlite structure with uniform carbide distribution.

[0037] The annealing process of the cold working die steel mainly includes five steps: first, loading the furnace, cleaning the surface of the workpiece to be annealed to prevent contamination of the vacuum system and uneven heating; second, vacuuming, starting the vacuum pump to pump the vacuum furnace to a high vacuum to achieve Pa, to avoid oxidation and decarburization reactions of the workpiece during annealing; third, heating, controlling the heating rate until the set temperature is reached; fourth, heat preservation, heat preservation at the set temperature to make the internal structure of the workpiece uniform, and the carbides fully dissolved and evenly distributed; fifth, cooling, using the furnace slow cooling method to control the cooling rate, so that the austenite transforms to pearlite during the slow cooling process, and promotes the spheroidization of carbides.

[0038] In order to prevent the material from oxidizing at high temperatures, the annealing process may need to be carried out in a vacuum furnace, and the three stages of the annealing process: austenitization stage, organizational transformation stage (austenite to pearlite transformation), organizational spheroidization stage, are usually after the end of vacuuming to ensure that the material is not oxidized during the entire annealing process, thereby obtaining the ideal microstructure and performance.

[0039] Therefore, a vacuum sensor is installed at the top and bottom of the workpiece placement position in the furnace of the vacuum furnace, as well as a vacuum sensor is installed at the vacuum pump inlet and the furnace door seal to monitor the vacuum changes in the vacuum furnace in real time. After the vacuum pumping is completed in the vacuum heat treatment annealing process of the cold working die steel, the vacuum degrees of all vacuum sensors in the vacuum furnace at each collection time in each stage are obtained, and the average of all vacuum measurement values ​​at each collection time is used as the vacuum measurement value at each collection time.

[0040] The furnace wall of the vacuum furnace is evenly divided into three layers: upper, middle and lower. Three temperature sensors are installed at the same height of each layer. The distances between temperature sensors in the same layer are equal, that is, they are installed at the three-division points of the ring to monitor the temperature changes in the vacuum furnace in real time. The average of the temperature values ​​of all temperature sensors at each acquisition time in each stage is used as the temperature measurement value at each acquisition time in each stage, and a temperature sensor is installed at a preset distance above the workpiece to measure the surface temperature of the workpiece at each acquisition time in each stage.

[0041] The acquisition frequency of all vacuum sensors and all temperature sensors is set to f.

[0042] It should be noted that the values ​​of the preset distance and the acquisition frequency f are manually set. In this embodiment, the value of the preset distance is 10 cm, and the value of the acquisition frequency f is 10 Hz. The implementer can also set them according to the specific situation. This embodiment does not impose any special restrictions.

[0043] Step S2: Based on the extreme changes in the vacuum degree measurement values ​​at all collection moments between the end of vacuum pumping and each collection moment in each stage, determine the vacuum degree change amplitude at each collection moment in each stage, and combine the average change rate of the vacuum degree measurement values ​​between the end of vacuum pumping and each collection moment in each stage, and the number of times the vacuum degree measurement values ​​exceed the preset value, determine the vacuum degree change factor at each collection moment in each stage.

[0044] In the annealing process of vacuum heat treatment, annealing is performed in a vacuum environment, which can prevent the metal from reacting with oxygen, nitrogen and other gases in the air during heating, such as oxidation and decarburization. The vacuum degree will affect the temperature and time of annealing. The higher the vacuum degree, the lower the content of oxidizing gases such as oxygen in the vacuum furnace, which allows the metal material to avoid oxidation reactions at a lower temperature, so the annealing temperature can be lowered. Since there is no air obstruction, heat can be transferred to the surface and inside of the metal faster, so under the same heating power, the higher the vacuum degree, the faster the heating speed, so the insulation time can be shortened.

[0045] The vacuum environment is obtained by the vacuum pump of the vacuum furnace. As the use time increases, the vacuum pump may experience fluctuations in the exhaust power after long-term operation, resulting in unstable vacuum degree in the vacuum furnace and failure to maintain the ideal high vacuum state. At this time, it is necessary to adjust the temperature and holding time during the annealing process according to the changes in the vacuum degree in the vacuum furnace to avoid affecting the quality of the metal material.

[0046] If the temperature is too low during the annealing process, the internal structure transformation of the metal material cannot be fully carried out, and the residual stress inside the material cannot be effectively eliminated. In the subsequent use process, deformation may occur due to the release of residual stress; if the temperature is too high, the grains will grow abnormally, which will significantly reduce the strength and toughness of the material. If the holding time is too short during the annealing process, the internal structure transformation of the material is uneven, which may lead to inconsistent performance of various parts of the material, affecting the overall quality and performance; if the holding time is too long, it will lead to a long production cycle, reduce economic benefits, and may also cause abnormal grain growth.

[0047] Therefore, the vacuum degree change in the vacuum furnace is measured by the vacuum degree sensor installed in the vacuum furnace, and the vacuum degree change factor is calculated in real time according to the measured vacuum degree time series to determine the degree of change of the vacuum degree during the annealing process, specifically:

[0048] (1) The range of the vacuum degree measurement values ​​at all sampling moments between the end of vacuuming and each sampling moment in each stage is taken as the vacuum degree variation amplitude at each sampling moment in each stage;

[0049] (2) Further, the number of times the vacuum degree measurement value exceeds the preset value between the end of vacuuming and each sampling time in each stage is recorded as the vacuum degree change frequency at each sampling time in each stage;

[0050] (3) Furthermore, the normalized value of the absolute value of the product of the average change rate of the vacuum degree measurement value between the end of vacuum extraction and each sampling time in each stage, the vacuum degree change amplitude, and the vacuum degree change frequency is used as the vacuum degree change factor at each sampling time in each stage.

[0051] Among them, the calculation step of the average change rate is a well-known technology, specifically, the ratio of the absolute value of the difference between the vacuum degree measurement value at the end of vacuuming and the vacuum degree measurement value between each collection time in each stage to the time interval between the end of vacuuming and the corresponding collection time.

[0052] According to the frequency of vacuum degree change at each acquisition moment in each stage, it can be understood that the larger the vacuum degree change amplitude, the larger the range of vacuum degree change, and the greater the impact on the annealing process, and the larger the vacuum degree change frequency and the average change rate, the more frequent the vacuum degree change, and the greater the impact on the annealing process. Therefore, if the vacuum degree change amplitude is larger, the vacuum degree change frequency is higher, and the average change rate is larger, the vacuum degree change factor is larger, indicating that the change of vacuum degree during the annealing process has a greater impact on the annealing process. In order to ensure the performance of the metal material, it is more necessary to adjust the annealing temperature and holding time;

[0053] On the contrary, the smaller the vacuum degree change amplitude, the smaller the range of vacuum degree change, and the smaller the impact on the annealing process. The smaller the vacuum degree change frequency and the average change rate, the slower the vacuum degree changes and the smaller the impact on the annealing process. Therefore, if the vacuum degree change amplitude is smaller, the vacuum degree change frequency is lower, and the average change rate is smaller, the vacuum degree change factor is smaller, which means that the vacuum degree is more stable during the annealing process and less adjustment is needed.

[0054] Step S3: Based on the difference in the vacuum degree measurement value between each acquisition moment and the previous acquisition moment, the heat conduction correction coefficient at each acquisition moment in each stage is determined, and combined with the difference between the temperature measurement value at each acquisition moment and the temperature of the workpiece surface, the heat conduction index at each acquisition moment in each stage is determined; based on the heat conduction index and the vacuum degree variation factor, the heat transfer influence factor at each acquisition moment in each stage is determined.

[0055] The change of vacuum degree will affect the density and movement state of gas molecules in the vacuum furnace, and then change the thermal conductivity coefficient. When the vacuum degree is lower, the gas molecules are more, the heat conduction is stronger, and the temperature should be lowered; when the vacuum degree increases, the heat conduction becomes weaker because the medium for heat transfer becomes less. If the vacuum degree changes more, the heat conduction intensity will also change greatly, requiring a smaller range of changes in annealing temperature and time; conversely, if the vacuum degree changes less, the heat conduction intensity will change less, requiring a larger range of changes in annealing temperature and time.

[0056] In a high vacuum environment, since gas molecules are very scarce, traditional convection heat transfer is almost non-existent, so radiation heat transfer dominates. And as the vacuum fluctuates, the absorption and scattering of radiation by gas molecules changes. When the vacuum is lower, there are more gas molecules, which enhances the absorption and scattering of radiation, resulting in a decrease in the efficiency of radiation heat transfer, and then a decrease in the radiation heat flux density. Therefore, the annealing temperature should be increased to ensure that the material can reach the required temperature and complete the organizational transformation. And when the vacuum changes greatly, in order to maintain the stability of the process, the range of change of annealing temperature and time should be larger.

[0057] Therefore, according to the heat conduction formula, the heat conduction coefficient is corrected using the calculated vacuum degree change factor to determine the degree of influence of vacuum degree change on heat transfer during annealing. Specifically:

[0058] (1) Based on the difference in the vacuum degree measurement value between each acquisition moment and the previous acquisition moment, the heat conduction correction coefficient at each acquisition moment in each stage is determined, specifically:

[0059] Heat conduction correction coefficient at the jth acquisition time in stage i The expression is: ; In the formula, Indicates the preset ideal heat transfer coefficient; represents the difference in vacuum degree measurement between the jth acquisition moment and the previous acquisition moment in stage i; , Respectively represent the preset first value and the preset second value; wherein .

[0060] It should be noted that the preset ideal thermal conductivity coefficient The values ​​of the preset first value a and the preset second value b are both artificially set. In this embodiment, the preset ideal thermal conductivity coefficient The value is 0.05 The preset value of the first value a is 0.2, and the preset value of the second value b is 0.1. The implementer can also set it according to the specific situation. This embodiment does not impose any special restrictions.

[0061] According to the heat conduction correction coefficient at each acquisition moment in each stage, it can be understood that the greater the difference in the vacuum measurement values ​​between adjacent acquisition moments, the greater the change in the vacuum degree, the greater the change in the heat conduction coefficient, and the larger the corresponding heat conduction correction coefficient, the smaller the change range of the annealing temperature and the holding time should be; conversely, the smaller the difference in the vacuum measurement values ​​between adjacent acquisition moments, the smaller the change in the vacuum degree, the smaller the change in the heat conduction coefficient, and the larger the corresponding heat conduction correction coefficient.

[0062] The thermal conductivity coefficient is a well-known technology, and its specific concept principle and calculation steps are not described in detail.

[0063] (2) Further, based on the heat conduction correction coefficient at each acquisition time in each stage and the difference between the temperature measurement value at each acquisition time and the temperature of the workpiece surface, the heat conduction index at each acquisition time in each stage is determined, specifically:

[0064] Thermal conductivity index at the jth acquisition time in stage i The expression is: ; In the formula, , They represent the temperature measurement value and the temperature of the workpiece surface at the jth acquisition moment in stage i, respectively; , denote the preset firing rate and the preset Stefan-Boltzmann constant, respectively.

[0065] It should be noted that the preset emissivity and the default Stefan-Boltzmann constant The values ​​of are all set manually. In this embodiment, the preset emissivity The value of is 0.6, and the Stefan-Boltzmann constant is preset The value of ; The implementer can also set it according to the specific situation, and this embodiment does not impose any special restrictions.

[0066] According to the thermal conductivity index at each acquisition moment in each stage, it can be understood that the greater the difference between the temperature measurement value in the vacuum furnace and the temperature on the workpiece surface, and the smaller the heat conduction correction coefficient, the greater the thermal conductivity index, which means that the range of change of the annealing temperature and the holding time should be greater; conversely, the smaller the difference between the temperature measurement value in the vacuum furnace and the temperature on the workpiece surface, and the larger the heat conduction correction coefficient, the smaller the thermal conductivity index, which means that the range of change of the annealing temperature and the holding time should be smaller.

[0067] Among them, the Stefan-Boltzmann constant is a well-known technology, and its specific related concepts are not repeated here.

[0068] (3) Further, based on the thermal conductivity index and the vacuum degree variation factor, the heat transfer influence factor at each acquisition moment in each stage is determined, specifically:

[0069] The heat transfer influence factor at each acquisition moment in each stage is the normalized value of the product of the heat conduction index and the vacuum degree variation factor at each acquisition moment in each stage.

[0070] According to the heat transfer influence factor at each acquisition moment in each stage, it can be understood that if the vacuum degree change factor is larger and the heat transfer index is larger, the obtained heat transfer influence factor is larger, which means that the influence of the vacuum degree change on the heat transfer in the furnace during the annealing process is greater, and the range of change of the annealing temperature and the holding time is larger; on the contrary, if the vacuum degree change factor is smaller and the heat transfer index is smaller, the obtained heat transfer influence factor is smaller, which means that the influence of the vacuum degree change on the heat transfer during the annealing process is smaller, and the range of change of the temperature and the holding time is smaller.

[0071] Preferably, the heat transfer influencing factor extraction process schematic diagram provided in this embodiment is as follows Figure 2 shown.

[0072] Step S4: Determine the tissue transformation influencing factor at each acquisition moment in each stage based on the difference in the vacuum degree measurement value and the difference in the heat transfer influencing factor between each acquisition moment and the previous acquisition moment.

[0073] When the vacuum degree changes and the heat transfer is affected, it will cause the pressure in the vacuum furnace to change, thereby changing the phase change temperature of the workpiece, that is, the temperature of the tissue transformation. Because when the vacuum degree decreases, the atomic diffusion rate may accelerate, causing the tissue transformation to occur earlier or the transformation rate to accelerate, which in turn leads to incomplete pearlite transformation and spheroidization, reducing the performance of the workpiece. Therefore, the tissue transformation influence factor can be calculated based on the influence of the phase change temperature offset on the diffusion coefficient to characterize the influence of heat transfer on the tissue transformation, and the phase change temperature offset can be reflected by the heat transfer influence factor, thereby regulating the temperature and time during the annealing process. Specifically:

[0074] Influencing factors of tissue transformation at the jth acquisition moment in stage i The expression is: ; In the formula, It represents the difference of heat transfer influence factor between the jth acquisition moment and the previous acquisition moment in stage i; , They represent the preset basic diffusion coefficient and the preset third value respectively; norm[ ] represents the normalization function; exp( ) represents the exponential function with the natural constant as the base.

[0075] It should be noted that the preset basic diffusion coefficient and preset third value The values ​​of are all set manually. In this embodiment, the basic diffusion coefficient is preset The value of , preset the third value The value is 30 The implementer can also set it according to the specific situation, and this embodiment does not impose any special restrictions.

[0076] Among them, the third value is preset It represents the diffusion coefficient of carbon in austenite, which is a well-known technology and the specific concept will not be repeated here.

[0077] According to the organizational transformation influencing factors at each acquisition moment in each stage, it can be understood that during the annealing process, the diffusion of carbon in the organization is affected by the change in vacuum and heat transfer. When the vacuum and heat transfer efficiency are reduced, the diffusion of carbon will be inhibited, resulting in the influence of organizational transformation, which in turn affects the performance of metal materials, so the temperature and time must be adjusted. The larger the organizational transformation influencing factor, the greater the influence of organizational transformation on vacuum and heat transfer changes during the annealing process, that is, the larger the adjustment range of annealing temperature and time; on the contrary, the smaller the organizational transformation influencing factor, the smaller the change in vacuum, that is, the smaller the adjustment range of annealing temperature and time, the less influence on organizational transformation, and the stable annealing process of metal materials.

[0078] Step S5: Based on the heat transfer influencing factor and the structure transformation influencing factor, the annealing temperature adjustment value and the holding time adjustment value at each sampling moment in each stage are determined to control the annealing of the vacuum heat treatment of the cold working die steel.

[0079] The temperature and time during annealing are adjusted according to the heat transfer influencing factors and the organizational transformation influencing factors, specifically:

[0080] The expression of the annealing temperature adjustment value at the jth acquisition time in stage i is: ; In the formula, represents the preset initial annealing temperature of stage i; represents the heat transfer impact factor at the jth acquisition moment under stage i; represents the organizational transformation influencing factor at the jth acquisition moment under stage i; , Respectively represent the preset first and second adjustment factors;

[0081] The expression of the holding time adjustment value at the jth collection moment in stage i is: ; In the formula, Indicates the preset initial holding time of stage i; , Respectively represent the preset third and fourth adjustment factors.

[0082] It should be noted that the first, second, third and fourth adjustment factors are preset , , , The values ​​of are all artificially set. In this embodiment, the ratios of the values ​​of the first, second, third, and fourth adjustment factors of the color number are 0.6, 0.8, 0.5, and 0.4 respectively. The implementer can also set them according to the specific situation. This embodiment does not impose any special restrictions.

[0083] In addition, in this embodiment, since the annealing process is divided into three stages, namely, the austenitization stage, the structure transformation stage (austenite to pearlite transformation), and the structure spheroidization stage. The preset initial annealing temperature and the preset initial holding time of each stage are artificially set. In this embodiment, since the temperature of the austenite transformation starting point is 827°C and the transformation end point is 870°C, the preset initial annealing temperature is set to 860°C and the preset initial holding time is 8h in the austenitization stage; the preset initial annealing temperature is set to 700°C and the preset initial holding time is 8h in the structure transformation stage; the preset initial annealing temperature is set to 820°C and the preset initial holding time is 16h in the structure spheroidization stage; the implementer can also set it by himself according to the specific situation, and this embodiment does not impose any special restrictions.

[0084] Preferably, the schematic diagram of the annealing temperature and holding time adjustment process provided in this embodiment is as follows: Figure 3 shown.

[0085] Further, the insulation time of the cold-working mold steel at each acquisition moment in each stage is obtained, and the error between the temperature measurement value and the annealing temperature adjustment value at each acquisition moment in each stage, as well as the error between the insulation time and the insulation time adjustment value at each acquisition moment are respectively used as the input of the PID controller, and the temperature control signal and the time control signal are output to respectively regulate the temperature and insulation time at the corresponding acquisition moment. In this embodiment, the proportional coefficients of the two controllers are both 3, the integral coefficients are both 0.1, and the differential coefficients are both 0.2. The implementer can also set them according to the specific situation, and this embodiment does not impose any special restrictions.

[0086] The working principle of the PID controller is a well-known technology, and its specific control process will not be described in detail.

[0087] Based on the same inventive concept as the above-mentioned method, an embodiment of the present application also provides an annealing collaborative control system for vacuum heat treatment of cold-working die steel, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, the steps of any one of the above-mentioned annealing collaborative control methods for vacuum heat treatment of cold-working die steel are implemented.

[0088] It should be noted that the above sequence of the embodiments of the present application is for description only and does not represent the advantages and disadvantages of the embodiments. The above is a description of a specific embodiment of this specification. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0089] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0090] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present application should be included in the protection scope of the present application.

Claims

1. A coordinated annealing control method for vacuum heat treatment of cold working die steel, characterized in that: The method comprises the following steps: After the vacuuming is completed in the vacuum heat treatment annealing process of cold-working die steel, the vacuum degree and temperature measurement values ​​in the vacuum furnace and the surface temperature of the workpiece are obtained at each stage and each acquisition time; Based on the extreme changes in the vacuum degree measurement values ​​at all collection moments between the end of vacuuming and each collection moment in each stage, the vacuum degree change amplitude at each collection moment in each stage is determined; the number of times the vacuum degree measurement value between the end of vacuuming and each collection moment in each stage exceeds the preset value is recorded as the vacuum degree change frequency at each collection moment in each stage; the average change rate of the vacuum degree measurement value between the end of vacuuming and each collection moment in each stage, the vacuum degree change amplitude, and the vacuum degree change frequency are normalized as the absolute value of the multiplication result of the three, as the vacuum degree change factor at each collection moment in each stage; Based on the difference in the vacuum degree measurement value between each acquisition moment and the previous acquisition moment, and the preset ideal thermal conductivity coefficient, the thermal conductivity correction coefficient at each acquisition moment in each stage is determined, and the thermal conductivity index at each acquisition moment in each stage is determined in combination with the difference between the temperature measurement value at each acquisition moment and the temperature of the workpiece surface; the normalized value of the multiplication result of the thermal conductivity index and the vacuum degree change factor is used as the heat transfer influence factor at each acquisition moment in each stage; Based on the difference in the vacuum degree measurement value and the difference in the heat transfer influencing factor between each acquisition moment and the previous acquisition moment, the tissue transformation influencing factor at each acquisition moment in each stage is determined; Based on the heat transfer influencing factor and the organizational transformation influencing factor, the annealing temperature adjustment value and the holding time adjustment value at each sampling moment in each stage are determined to control the annealing of the vacuum heat treatment of the cold working die steel; The expression of the heat conduction correction coefficient at each acquisition time in each stage is: ; In the formula, represents the heat conduction correction coefficient at the jth acquisition moment in stage i; Indicates the preset ideal heat transfer coefficient; represents the difference in vacuum degree measurement between the jth acquisition moment and the previous acquisition moment in stage i; , Respectively represent the preset first value and the preset second value; wherein ; The expression of the heat transfer index at each acquisition time in each stage is: ; In the formula, represents the heat transfer index at the jth acquisition moment in stage i; , They represent the temperature measurement value and the temperature of the workpiece surface at the jth acquisition moment in stage i, respectively; , denote the preset firing rate and the preset Stefan-Boltzmann constant, respectively; The expression of the tissue transformation influencing factor at each acquisition moment in each stage is: ; In the formula, represents the organizational transformation influencing factor at the jth acquisition moment under stage i; It represents the difference of heat transfer influence factor between the jth acquisition moment and the previous acquisition moment in stage i; , Respectively represent the preset basic diffusion coefficient and the preset third value; norm[ ] represents the normalization function; exp( ) represents the exponential function with the natural constant as the base; The method for determining the annealing temperature adjustment value and the holding time adjustment value at each acquisition moment in each stage is as follows: The expression of the annealing temperature adjustment value at the jth acquisition time in stage i is: ; In the formula, represents the preset initial annealing temperature of stage i; represents the heat transfer impact factor at the jth acquisition moment under stage i; , Respectively represent the preset first and second adjustment factors; The expression of the holding time adjustment value at the jth collection moment in stage i is: ; In the formula, Indicates the preset initial holding time of stage i; , Respectively represent the preset third and fourth adjustment factors.

2. The annealing coordinated control method for vacuum heat treatment of cold working die steel according to claim 1, characterized in that: The variation range of the vacuum degree at each sampling moment in each stage is the range of the vacuum degree measurement values ​​at all sampling moments between the vacuuming end moment and each sampling moment in each stage.

3. The annealing coordinated control method for vacuum heat treatment of cold working die steel according to claim 1, characterized in that: The process of controlling the annealing of the vacuum heat treatment of cold working die steel is as follows: The insulation time of the cold-working mold steel at each sampling moment in each stage is obtained, and the error between the temperature measurement value and the annealing temperature adjustment value at each sampling moment in each stage, as well as the error between the insulation time and the insulation time adjustment value at each sampling moment are used as the input of the PID controller, and the temperature control signal and time control signal are output to regulate the temperature and insulation time at the corresponding sampling moment respectively.

4. An annealing coordination control system for vacuum heat treatment of cold working die steel, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the annealing coordinated control method for vacuum heat treatment of cold working die steel as described in any one of claims 1 to 3 are implemented.

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