Finite element simulation vertical vacuum heat treatment furnace heating lag detection method

Abstract

A finite element simulation vertical vacuum heat treatment furnace heating lag detection method comprises the steps that firstly, a radiation heating model is established, and then a target heating temperature is set in the radiation heating model; respectively carrying out temperature field distribution simulation under an empty furnace state, temperature field distribution simulation under different workpiece numbers and temperature field distribution simulation under a shielding state of stacked workpieces, so as to obtain factors of the workpiece numbers in the vacuum furnace and a loading mode on generation of heating lag, and obtain optimized process parameters of the workpieces. According to the invention, the temperature field distribution in the heating process of the vertical vacuum furnace is accurately simulated, and theoretical guidance is provided for formulating a reasonable vacuum heat treatment process; meanwhile, according to simulation data, process parameters can be optimized, the furnace temperature uniformity is improved, the problems of heating lag, deformation and the like are reduced, and the product quality is improved; the experiment cost can be reduced, and particularly for high-cost workpieces, the requirement of repeated experiments is avoided; the production efficiency is improved, and the product development period is shortened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vacuum heat treatment, and particularly relates to a finite element simulation vertical vacuum heat treatment furnace heating hysteresis detection method. BACKGROUND

[0002] Vacuum heat treatment technology has the advantages of high production efficiency, less working time, no pollution, high automation, etc., and is widely used in the fields of vacuum carburizing, vacuum annealing, nitriding, vacuum tempering, etc. However, the current vacuum heat treatment process has problems such as heating hysteresis, heating deformation, grain growth, and high cost of heating materials. Because of the high experimental cost, these problems are difficult to improve through a large number of experiments, and for high-cost workpieces, relevant optimal processing parameters cannot be obtained through repeated experiments. SUMMARY

[0003] The technical problem solved by the present application is to provide a finite element simulation vertical vacuum heat treatment furnace heating hysteresis detection method to solve the problems in the background.

[0004] The technical problem solved by the present application is solved by the following technical solution: A finite element simulation vertical vacuum heat treatment furnace heating hysteresis detection method, the specific steps are as follows: 1) Establish a radiation heating model A, construct a geometric model Using AnsysWorkbench drawing software, according to the measured size data of the main components of the vertical vacuum furnace, a three-dimensional model of the vacuum furnace is drawn, including the workpiece workbench, heating element, reflective heat insulation plate, cooling wall, and then the three-dimensional model of the vacuum furnace is imported into Ansys finite element analysis software for meshing; B, select materials According to the actual use of the vertical vacuum furnace, the workpiece workbench and the cooling screen, select PH17-4 stainless steel material as the preparation material of the furnace body and the workpiece workbench, molybdenum as the material of the heating element, and graphite as the material of the reflective heat insulation plate; C, boundary condition setting Set the heating rate of radiation heating, make basic assumptions for the radiation heating process to simplify the model, ignore the influence of thin air, only consider radiation heating; the influence of austenite transformation is not considered; the material is isotropic and uniform, the specific heat, thermal conductivity coefficient, surface emissivity, etc. are independent of the spatial position, which is a function of temperature, thereby establishing a radiation heating model; 2) simulation and analysis I, simulate the radiation heating process of the empty furnace, and obtain the radiation law of single heat source in vacuum state is ideal state; Set the target heating temperature in the radiation heating model, simulate the radiation heating process in the empty furnace state, analyze the temperature field distribution at different time points, and find that the temperature near the heat source is the highest, and the closer the other parts are to the heat source, the faster the temperature rises; when the set holding time is reached, the temperature field distribution in the furnace is basically uniform except for the heat source, thereby verifying that the radiation law of a single heat source in the vacuum state is an ideal state; II、Simulate the workpiece radiation heating process In the radiation heating model, simulate the temperature field distribution under different workpiece quantities, and compare it with the temperature field in the empty furnace state. After placing the workpieces, the radiation to the heat source has an impact on the initial heating stage, and the temperature of the first group of workpieces rises faster, while the initial temperature rise slows down when the number of workpieces increases to multiple, which indicates that there is a heat transfer lag in the heating process, and the uneven heat transfer inside the workpiece also easily leads to overall heat transfer lag. In the later heating stage, the overall temperature field distribution of the furnace body tends to be stable, and the influence of the number of workpieces on the temperature difference basically disappears. III、Analysis of temperature field simulation and shielding degree under stacked workpiece state In the radiation heating model, a set of stacked control group is added to simulate the radiation heating process of multiple stacked workpieces in the vacuum state. The unshielded and shielded parts at the upper and lower ends of the workpieces are selected for comparison of the temperature probe simulation curves, and the influence of the shielding degree on the temperature rise of the workpieces is analyzed. It is found that the simulation temperature of the probe in the unshielded part is higher than that in the shielded part. The temperature difference caused by shielding is smaller at the edge of the workpiece, and larger in the middle part of the workpiece, which indicates that when placing the workpieces, shielding should be reduced or avoided as much as possible to reduce the unevenness of the workpiece organization and performance caused by temperature difference. IV、Heating temperature and heating lag simulation Simulate different temperature heating of the same part of the workpiece and extend the holding time, and get that the heating lag is inversely proportional to the heating temperature, that is, the lower the heating temperature, the longer the heating lag time. 3) Optimize process parameters According to the heat transfer characteristics of the vacuum heat treatment furnace, combined with the factors affecting the heating lag obtained, the optimized process parameters of the workpiece are obtained.

[0005] Beneficial effects: The present application accurately simulates the temperature field distribution in the heating process of the vertical vacuum furnace, provides theoretical guidance for formulating a reasonable vacuum heat treatment process; at the same time, the process parameters can be optimized according to the simulation data, the furnace temperature uniformity is improved, the problems of heating lag and deformation are reduced, and the product quality is improved; and the experimental cost is reduced, especially for high-cost workpieces, the need for repeated experiments is avoided; in improving the production efficiency, the product development cycle is shortened. BRIEF DESCRIPTION OF DRAWINGS

[0006] Figure 1 It is a three-dimensional model schematic diagram of the vacuum furnace in the preferred embodiment of the present application.

[0007] Figure 2 The temperature field in the vacuum furnace with 4 workpieces in the preferred embodiment of the present application.

[0008] Figure 3 The temperature field in the vacuum furnace with 4 workpieces in the preferred embodiment of the present application.

[0009] Figure 4 The temperature field in the vacuum furnace with 4 workpieces in the preferred embodiment of the present application.

[0010] Figure 5 The temperature field in the vacuum furnace with 12 workpieces in the preferred embodiment of the present application.

[0011] Figure 6 The temperature field in the vacuum furnace with 12 workpieces in the preferred embodiment of the present application.

[0012] Figure 7 The temperature field in the vacuum furnace with 4 workpieces in the preferred embodiment of the present application.

[0013] Figure 8 The temperature field in the vacuum furnace with 4 workpieces in the preferred embodiment of the present application.

[0014] Figure 9 The temperature field in the vacuum furnace with 4 workpieces in the preferred embodiment of the present application. DETAILED DESCRIPTION

[0015] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application is further described below in combination with specific drawings.

[0016] A finite element simulation method for detecting the heating lag of a vertical vacuum heat treatment furnace, and the specific steps are as follows: 1) Establish a radiation heating model A, construct a geometric model Using AnsysWorkbench drawing software, according to the measured size data of the main components of the vertical vacuum furnace, a three-dimensional model of the vacuum furnace is drawn, including a workpiece workbench a, a heating element b, a reflective heat insulation plate c, and a cooling wall d. Then the three-dimensional model of the vacuum furnace is imported into Ansys finite element analysis software for meshing; B, select materials According to the actual use of the vertical vacuum furnace, the workpiece workbench and the cooling wall, PH17-4 stainless steel material is selected as the preparation material of the furnace body and the workpiece workbench, molybdenum is selected as the material of the heating element, and graphite is selected as the material of the reflective heat insulation plate; C, boundary condition setting The heating rate of radiation heating is set to 10℃ / min, the basic assumptions are made for the radiation heating process to simplify the model, the effect of thin air is ignored, only the radiation heating is considered; the effect of austenitic transformation is not considered; the material is isotropic and uniform, the specific heat, thermal conductivity coefficient, surface emissivity, etc. are independent of spatial position, which are functions of temperature, so as to establish the radiation heating model; 2) Simulation and analysis I. Simulate the radiation heating process of empty furnace In the radiation heating model, the target heating temperature is set to 600℃, the radiation heating process in the empty furnace state is simulated, and the temperature field distribution at different time points is analyzed. It is found that the temperature near the heat source is the highest, and the closer the other parts are to the heat source, the faster the temperature rises. When the time reaches about 3600s, the temperature field distribution in the furnace is basically uniform except for the heat source, thereby verifying that the radiation law of single heat source in vacuum state is an ideal state; II. Simulate the radiation heating process of workpiece In the radiation heating model, the temperature field distribution under different workpiece quantities (4 and 12) is simulated, and compared with the temperature field in the empty furnace state. After the workpiece is placed, it has an impact on the radiation of the heat source in the initial heating stage. The temperature of the first group of workpieces rises faster, while the initial temperature rise slows down after the number of workpieces increases to 12, which indicates that there is a heat transfer lag in the heating process, and the uneven heat transfer inside the workpiece also easily leads to overall heat transfer lag. In the later heating stage, the overall temperature field distribution of the furnace body tends to be stable, and the influence of the number of workpieces on the temperature difference basically disappears; III. Analysis of temperature field simulation and shielding degree under stacked workpiece state In the radiation heating model, a group of stacked control group is added to simulate the radiation heating process of 8 stacked workpieces in vacuum state. The unshielded part (probe 1, 2, 3) and the shielded part (probe 4, 5, 6) of the upper end and lower end of the workpiece are selected, and the temperature probe simulation curves at 600℃ are compared to analyze the influence of shielding degree on the temperature rise of the workpiece. It is found that the simulation temperature of the probe in the unshielded part is higher than that in the shielded part. The temperature difference caused by shielding is smaller at the edge of the workpiece, and larger in the middle of the workpiece, which indicates that when placing the workpiece, shielding should be reduced or avoided as much as possible to reduce the unevenness of the workpiece organization and performance caused by temperature difference; IV. Heating temperature and heating lag simulation Taking the center part of the workpiece as an example, at 600 s, when the heating temperature is 600 ℃, the temperature of the center part of the workpiece is about 490 ℃, and when the heating temperature is 850 ℃, the temperature of the center part of the workpiece is about 520 ℃; at 1200 s, when the heating temperature is 600 ℃, the temperature of the center part of the workpiece is about 580 ℃, and when the heating temperature is 850 ℃, the temperature of the center part of the workpiece is about 800 ℃; at 3600 s, when the heating temperature is 600 ℃, the temperature of the center part of the workpiece is about 597 ℃, and when the heating temperature is 850 ℃, the temperature of the center part of the workpiece is about 850 ℃; at 3600 s, both reach the heating temperature, which are 600 ℃ and 850 ℃ respectively, so it can be seen that the heating lag of the heating temperature of 850 ℃ is less than that of the heating temperature of 600 ℃, as shown in Figure 9 ; 3) optimizing the process parameters such as the placement mode and the number of workpieces According to the heat transfer characteristics of the vacuum heat treatment furnace, the factors affecting the heating lag are obtained, as follows: ①, the closer to the heat source, the faster the temperature rises, in the empty furnace state, the maximum temperature difference in the initial stage of temperature rise is 26.81 ℃, with the extension of time, the temperature difference of each point gradually decreases, and at 3600 s, the maximum temperature difference is only about 2.28 ℃, the temperature uniformity of the empty furnace state is good; ②, compared with the empty furnace state, the temperature rises faster in the initial stage of heating after the workpiece is installed; and in the later heating stage, the temperature in the furnace in the empty furnace state and the state with workpiece is very close to the theoretical temperature, but the temperature field distribution of the overall empty furnace state is more uniform; ③, the number and placement position of the workpiece mainly affect the initial temperature field distribution in the furnace, and the placement position has a greater impact; ④, the heating lag is inversely proportional to the heating temperature, that is, the lower the heating temperature, the longer the heating lag time, and the heating lag time of the heating temperature of 600 ℃ is close to 3600 s; According to the above factors affecting the heating lag, the optimized process parameters of the workpiece are obtained, that is, the placement position of the workpiece is optimized, and the holding time of heating is appropriately prolonged, and the shielding between workpieces is reduced or avoided.

[0017] In this embodiment, the workpiece is placed in the furnace in the following manner: Figures 2~7 In the embodiment, h represents holding for 600 s; i represents holding for 1200 s; j represents holding for 3600 s; and k represents holding for 21600 s.

[0018] The specific embodiments described herein are merely illustrative of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or replace them with similar manners without departing from the spirit of the present application or exceeding the scope defined by the appended claims.

Claims

1. A finite element method for detecting heating hysteresis in a vertical vacuum heat treatment furnace, characterized in that, First, a radiant heating model is established. Then, the target heating temperature is set in the radiant heating model, and the temperature field distribution under empty furnace conditions, temperature field distribution under different workpiece numbers, and temperature field distribution under shielded conditions are simulated. In this way, the factors of the number of workpieces and loading method in the vacuum furnace that cause heating lag are obtained, and the optimized process parameters of the workpieces are obtained.

2. The method for detecting heating hysteresis in a vertical vacuum heat treatment furnace using finite element simulation according to claim 1, characterized in that, The specific steps are as follows: 1) Establish a radiative heating model A. Constructing the geometric model Using AnsysWorkbench drawing software, a three-dimensional model of the vacuum furnace was drawn based on the measured dimensional data of the main components of the vertical vacuum furnace. Then, the three-dimensional model of the vacuum furnace was imported into Ansys finite element analysis software for mesh generation. B. Selecting Materials Select the materials to use in the 3D model of the vacuum furnace; C. Boundary Condition Setting The heating rate of radiative heating is set, and basic assumptions are made about the radiative heating process to simplify the model; the material is isotropic and homogeneous, and its specific heat, thermal conductivity, and surface emissivity are independent of spatial position and are functions of temperature, thus establishing a radiative heating model. 2) Simulation and Analysis I. Set the target heating temperature in the radiation heating model to simulate the radiation heating process in an empty furnace state, and obtain the ideal radiation law of a single heat source in a vacuum state. II. Simulation of workpiece radiation heating process In the radiation heating model, the temperature field distribution under different numbers of workpieces was simulated. Compared with the temperature field under empty furnace conditions, the temperature rises faster in the initial heating stage after the workpieces are installed. However, in the later heating stage, the furnace temperature in the empty furnace state and the furnace state with workpieces are very close to the theoretical temperature, but the temperature field distribution in the overall empty furnace state is more uniform. III. Analysis of temperature field simulation and shielding degree under stacked workpiece conditions A stacked control group was added to the radiation heating model to simulate the radiation heating process of multiple stacked workpieces under vacuum. The results showed that the number and placement of the workpieces mainly affect the initial temperature field distribution inside the furnace, with the placement having a greater impact. IV. Simulation of Heating Temperature and Heating Hysteresis Simulations were performed on the same part of the workpiece, heating it at different temperatures and extending the holding time. The results showed that the heating lag was inversely proportional to the heating temperature, that is, the lower the heating temperature, the longer the heating lag time. 3) Optimize process parameters Based on the heat transfer characteristics of the vacuum heat treatment furnace and the factors affecting heating hysteresis, the optimized process parameters for the workpiece are obtained.

3. The method for detecting heating hysteresis in a vertical vacuum heat treatment furnace using finite element simulation according to claim 2, characterized in that, The three-dimensional model of the vacuum furnace includes the worktable, heating elements, reflective heat insulation plate, and cooling wall.

4. The method for detecting heating hysteresis in a vertical vacuum heat treatment furnace using finite element simulation according to claim 3, characterized in that, PH17-4 stainless steel was selected as the material for the furnace body and worktable.

5. The method for detecting heating hysteresis in a vertical vacuum heat treatment furnace using finite element simulation according to claim 3, characterized in that, Molybdenum is used as the material for the heating element, and graphite is used as the material for the reflective heat insulation plate.

6. The method for detecting heating hysteresis in a vertical vacuum heat treatment furnace using finite element simulation according to claim 2, characterized in that, In the radiation heating model, a target heating temperature was set to simulate the radiation heating process in an empty furnace. The temperature field distribution at different time points was analyzed, and it was found that the temperature was highest near the heat source. The closer other parts were to the heat source, the faster the temperature rose. When the set holding time was reached, the temperature field distribution in the furnace except for the heat source was basically uniform, thus verifying that the radiation law of a single heat source in a vacuum state is ideal.

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