A vacuum furnace temperature prediction method based on a multi-type heating element fixing device

Abstract

The present invention provides a method for predicting the temperature of a vacuum furnace based on a multi-type heating body fixing device, which relates to the technical field of vacuum furnaces. The present invention provides a method for predicting the temperature of a vacuum furnace based on a multi-type heating body fixing device, comprising a plurality of combined heating bodies, a plurality of graphite connecting blocks, a plurality of hexagonal bolts and a plurality of electrode plates. Toothed ports are designed at both ends of each combined heating body, and these toothed ports are respectively embedded in the upper graphite block and the lower graphite block. The mutual engagement of the toothed ports realizes the fixed connection of the heating body, thereby providing higher stability. This fixing device effectively solves the problem of loosening that may occur in threaded connection fixation under high temperature environment, and ensures the connection reliability of the heating body. The present invention provides a method for predicting the temperature of a vacuum furnace based on a multi-type heating body fixing device, which uses a random forest algorithm to obtain an optimal temperature prediction model, providing faster and more accurate prediction results, thereby optimizing the temperature control in the furnace and improving production efficiency and product quality.

Description

Technical Field

[0001] The invention relates to the technical field of vacuum furnaces, in particular to a vacuum furnace temperature prediction method based on a multi-type heating body fixing device. Background Art

[0002] Vacuum furnaces are essential equipment in industrial production. The heater, a core component, has a crucial influence on the temperature distribution within the furnace. Currently, vacuum furnace heaters primarily utilize a single, regular cross-sectional shape. Examples include the tubular and rod-shaped heaters commonly used in vertical and horizontal furnaces, as well as the emerging graphite ribbon and cloth heaters. These heaters offer simple structures, ease of assembly and disassembly, and a large radiating area. However, in practical applications, these single-section heaters present two major challenges: First, the center of the heater receives more heat than the edges, leading to uneven temperature distribution within the heater, impacting the vacuum furnace's heating efficiency and performance. Second, heaters with a single cross-sectional shape have limited adaptability and flexibility, making them suitable only for specific heating applications and unable to meet the complex demands of modern production. Furthermore, threaded connections, while commonly used for securing heaters, present significant limitations in terms of electrical and mechanical stability, particularly in high-temperature environments. These limitations include poor contact, resistance variations, and differences in thermal expansion coefficients, all of which can lead to loose connections and reduced stability.

[0003] In terms of temperature distribution prediction in vacuum furnaces, traditional heat distribution prediction methods mainly rely on empirical formulas or finite element simulations, which are often time-consuming, have limited accuracy, and lack real-time response capabilities.

[0004] The technical solution described in the Chinese patent "CN214901340U A New Structure of a Heating Body" is to utilize the pipe heating structure inside the heating body, combined with extended input and output pipes, a reasonable layout of control components and some innovative structural combination applications, so that the entire product can achieve small size, high power and high safety. However, the patent does not innovate on the shape of the heating body.

[0005] A utility model patent authorized on January 4, 2012, is a connection structure for a graphite rod heater. The technical solution is that the upper and lower ends of the graphite heating rod are respectively arranged in the conical holes of the upper connecting ring and the lower connecting ring and are fixedly connected by a graphite conical sleeve, and the electrode lead-out rod is fixed in the through hole arranged in the lower connecting ring at the lower end; the connecting ring is connected to a vertically arranged electrode lead-out rod. This patented connection method only introduces the applicability of a rod-shaped heater, which has limitations and is not suitable for heaters of other shapes and complex structures.

[0006] In the existing technology, there is no vacuum furnace temperature prediction scheme for different heating body shapes combined with random forest algorithm. For example, the Chinese patent authorized on July 12, 2024, a method and system for predicting the rough rolling outlet temperature of steel slabs from a heating furnace, with announcement number CN114798763B, uses a random forest algorithm to screen out the most accurate temperature prediction model, effectively improving the temperature prediction accuracy, but it cannot be directly used to predict the temperature distribution in vacuum furnaces with different heating body shapes and sizes. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the present invention aims to propose a vacuum furnace temperature prediction method based on a multi-type heating body fixing device, comprising:

[0008] Step 1: Simulate the heating process of the multi-type heating element fixture in the vacuum furnace to obtain the temperature of each combined heating element in the multi-type heating element fixture during the heating process, as well as the area of ​​the uniform temperature region in the vacuum furnace;

[0009] Step 2: For each combined heating element cross-sectional shape in the multi-type heating element fixture, construct a formula to characterize the cross-sectional shape: F = F(ρ, θ), where ρ and θ are polar coordinate parameters.

[0010] Step 3: The temperature during the heating process of each combined heating body and the formula F = F(ρ, θ) representing the cross-sectional shape are combined into a sample, thereby obtaining multiple samples to obtain a sample data set, and preprocessing the sample data set to obtain a preprocessed sample data set;

[0011] Step 4: Processing the preprocessed sample data set according to the random forest algorithm to obtain multiple prediction models, which are used to predict the area of ​​the uniform temperature region in the vacuum furnace;

[0012] Step 5: Calculate the predicted value of the uniform temperature area in the vacuum furnace using each prediction model to obtain the predicted value corresponding to each prediction model. Among all the predicted values, obtain the predicted value that is greater than or equal to the preset area threshold, and then determine the prediction model corresponding to the predicted value that is greater than or equal to the preset area threshold, and use it as the optimal prediction model.

[0013] Step 6: Randomly select a sample data from the preprocessed sample data set, bring it into the optimal prediction model, obtain the predicted value of the uniform temperature area in the vacuum furnace, and calculate the error with the uniform temperature area in the vacuum furnace obtained by simulation in step 1 to determine whether the error is less than or equal to the preset threshold. If the error is less than or equal to the preset threshold, the optimal prediction model is used as the final prediction model. If the error is greater than the preset threshold, return to step 4 and execute until the error is less than or equal to the preset threshold.

[0014] Optionally, step 4 specifically includes:

[0015] The preprocessed sample data set is randomly sampled by Bootstrap sampling to obtain multiple sub-sample training sets, where the number of samples in the sub-sample training set is the same as the number of samples in the preprocessed sample data set. A decision tree is established for each sub-sample training set, and each node in the decision tree contains multiple samples. For each decision tree, a preset number of samples are selected from the multiple samples contained in each node and used as specific variables. A prediction model is constructed based on the specific variables to obtain a prediction model corresponding to each sub-training set.

[0016] Optionally, a prediction model is constructed based on specific variables to obtain a prediction model corresponding to each sub-training set, including:

[0017] Substitute specific variables into the preset formula to obtain the prediction model. The preset formula is expressed as:

[0018] Y(i)=((T j (i) 4 )·ρ·(5.67e-8)·sinθ·(0.57-ρ·cosθ)) / (pi·(ρ 2 -2·cosθ·ρ·0.57+0.57 2 ) 2 );

[0019] Where i represents the time during the heating process, T j (i) represents the temperature of the heating body at time i during the heating process, and Y(i) represents the area of ​​the uniform temperature region in the vacuum furnace at time i.

[0020] Optionally, the multi-type heating body fixing device includes a plurality of combined heating bodies, a plurality of graphite connecting blocks, a plurality of hexagonal bolts and a plurality of electrode plates;

[0021] The multi-type heating body fixing device is a cube, consisting of a plurality of graphite connecting blocks connected to a plurality of different combined heating bodies. The first end of a combined heating body is connected to a graphite connecting block via a hexagonal bolt, and the second end of the combined heating body is connected to another graphite connecting block via a hexagonal bolt. The combined heating bodies are parallel to each other, and one graphite connecting block is connected to a plurality of different combined heating bodies. The graphite connecting blocks include right-angled graphite connecting blocks and linear graphite connecting blocks. The graphite connecting blocks are connected to the electrode plates.

[0022] The combined heating body is composed of at least two heating bodies, and the combined heating body includes a basic heating body, or a special-shaped heating body, or a basic heating body and a special-shaped heating body. The cross-sectional shape of the basic heating body is a single cross-sectional shape, and the single cross-sectional shape includes at least a circular ring, a circle, a square, and a diamond. The cross-sectional shape of the special-shaped heating body is a shape obtained by combining single cross-sectional shapes.

[0023] Optionally, both ends of the combined heating body are provided with toothed ports, the center of the toothed ports has an internal thread, the graphite connecting block is designed with a toothed hole corresponding to the toothed port, the toothed hole of the graphite connecting block is coupled with the toothed port, and the internal thread in the center of the toothed port engages with the hexagonal bolt.

[0024] Optionally, the combined heating body includes two heating bodies, and the combined heating body consists of a first heating body and a second heating body, the first heating body includes a tubular heating body or a rod-shaped heating body, the cross-sectional shape of the tubular heating body is a circular ring, and the cross-sectional shape of the rod-shaped heating body is a circle; the second heating body includes a basic heating body or a special-shaped heating body, one end face of the first heating body is designed with an internal thread, and the second heating body is provided with an extended stud, and the extended studs of the second heating body are all engaged with the internal thread of the first heating body.

[0025] Optionally, the combined heating body includes three heating bodies, and the combined heating body consists of a first heating body, a third heating body and a fourth heating body, the first heating body includes a tubular heating body or a rod-shaped heating body, the cross-sectional shape of the tubular heating body is a circular ring, the cross-sectional shape of the rod-shaped heating body is a circle, the third heating body includes a basic heating body or a special-shaped heating body, and the fourth heating body includes a basic heating body or a special-shaped heating body; both end faces of the first heating body are designed with internal threads, and the third heating body and the fourth heating body are both equipped with extended studs, the internal thread of the first end of the first heating body engages with the extended stud of the third heating body, and the internal thread of the second end of the first heating body engages with the extended stud of the fourth heating body.

[0026] Optionally, the combined heating body includes two heating bodies, and the combined heating body consists of a fifth heating body and a sixth heating body, the fifth heating body includes a basic heating body or a special-shaped heating body, the sixth heating body includes a basic heating body or a special-shaped heating body, one end face of the fifth heating body is designed with an internal thread, one end face of the sixth heating body is designed with an internal thread, the first end of the external stud is engaged with the internal thread of the fifth heating body, and the second end of the external stud is engaged with the internal thread of the sixth heating body.

[0027] The beneficial effects of adopting the above technical solution are:

[0028] The present invention provides a multi-type heating body fixing device, including multiple combined heating bodies, multiple graphite connecting blocks, multiple hexagonal bolts and multiple electrode plates. Both ends of each combined heating body are designed with toothed ports of uniform specifications. These toothed ports are respectively embedded in the upper graphite block and the lower graphite block. The mutual engagement of the toothed ports realizes the fixed connection of the heating body, thereby providing higher stability. This fixing device effectively solves the problem of loosening that may occur in threaded connection fixation under high temperature environment, and ensures the connection reliability of the heating body. The present invention provides a vacuum furnace temperature prediction method based on a multi-type heating body fixing device, which uses a random forest algorithm to obtain the optimal temperature prediction model, providing faster and more accurate prediction results, thereby optimizing the temperature control in the furnace and improving production efficiency and product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of a flow chart of a vacuum furnace temperature prediction method based on a multi-type heating body fixing device in an embodiment of the present invention;

[0030] Figure 2 Schematic diagram of the structure of a multi-type heating body fixing device in an embodiment of the present invention, wherein Figure (a) is a three-dimensional view of the multi-type heating body fixing device, and Figure (b) is a cross-sectional view of the multi-type heating body fixing device;

[0031] Figure 3 Schematic diagrams of single cross-sectional shapes in embodiments of the present invention, wherein (a) is a ring, (b) is a circle, (c) is a square, and (d) is a diamond;

[0032] Figure 4 Schematic diagram of the cross-sectional shape of the special-shaped heating body in the embodiment of the present invention, wherein Figure (e) is the combined cross-section 1, Figure (f) is the combined cross-section 2, Figure (g) is the combined cross-section 3, and Figure (h) is the combined cross-section 4;

[0033] Figure 5 Schematic diagram of the structure of a combined heating body composed of two heating bodies in an embodiment of the present invention, wherein Figure (a) is a schematic diagram of the two heating bodies A+B that constitute the combined heating body, and Figure (b) is a schematic diagram of the connection method of the two heating bodies A+B that constitute the combined heating body;

[0034] Figure 6 Schematic diagrams of the structure of a combined heating body composed of three heating bodies in an embodiment of the present invention, FIG (a) is a schematic diagram of the three heating bodies A+B+A that constitute the combined heating body, and FIG (b) is a schematic diagram of the three heating bodies A+B+C that constitute the combined heating body;

[0035] Figure 7Schematic diagrams of the structure of another combined heating body composed of two heating bodies in an embodiment of the present invention, wherein Figure (a) is a schematic diagram of the two heating bodies A+F that constitute the combined heating body, and Figure (b) is a schematic diagram of the connection method of the two heating bodies A+F that constitute the combined heating body;

[0036] Figure 8 This is a schematic structural diagram of the toothed ports at both ends of the combined heating body in an embodiment of the present invention;

[0037] Figure 9 Schematic diagram of the structure of the tooth-shaped hole of the graphite connecting block in an embodiment of the present invention;

[0038] Figure 10 A detailed diagram of the engagement between the internal thread at the center of the toothed port and the hexagonal bolt in an embodiment of the present invention;

[0039] Figure 11 A central cross-sectional view of a vacuum furnace and a schematic diagram of the overall layout of the heating body in an embodiment of the present invention;

[0040] Figure 12 The temperature cloud diagram and isotherms of the heating body of the combined cross-section 1 in the embodiment of the present invention;

[0041] Figure 13 Schematic diagram of the uniform temperature area in the combined cross section of the vacuum furnace heating body in an embodiment of the present invention;

[0042] Figure 14 The temperature cloud diagram and isotherms of the circular cross-section heating body in the furnace of the embodiment of the present invention;

[0043] Figure 15 Schematic diagram of the uniform temperature area of ​​a single furnace in a vacuum furnace heating element in an embodiment of the present invention;

[0044] Figure 16 Comparison of the uniform temperature area of ​​the vacuum furnace heating body with single and combined cross-sectional shapes in the embodiment of the present invention

[0045] Figure 17 Schematic diagram of the geometric relationship of the cross-sectional shape of the vacuum furnace heating body under the coordinate axes in an embodiment of the present invention;

[0046] Figure 18 Schematic diagram of radiation heat transfer between microelement surfaces of the cross-sectional shape of the vacuum furnace heating body in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0048] With the rapid development of big data and machine learning technology, the random forest algorithm provides a new solution for improving the accuracy and efficiency of temperature distribution prediction in vacuum furnaces. By constructing multiple decision tree models and integrating their prediction results, the random forest algorithm can effectively handle multiple factors that affect temperature distribution and provide better prediction performance. Specifically, the present invention proposes an innovative composite cross-section heating body design, which breaks through the limitations of traditional heating bodies by combining multiple single cross-sectional shapes, achieves a more uniform temperature distribution inside the vacuum furnace, and increases the uniform temperature area. This design not only improves the flexibility and adaptability of the heating body, enabling it to be customized and adjusted according to different sintering requirements and adapt to different materials and processes, but also allows for local replacement of the heating body in a specific area, and flexibly adjusts the shape of the heating body according to the furnace size and temperature requirements. In addition, the present invention also provides a fixing device with strong adaptability and stable performance, which is suitable for a variety of heating body shapes including rectangles, diamonds and special shapes.

[0049] In view of the problems existing in the prior art, the present invention provides a vacuum furnace temperature prediction method based on a multi-type heating body fixing device, combined with Figure 1 , which may include the following steps:

[0050] Step 1: Simulate the heating process of the multi-type heating element fixture in the vacuum furnace to obtain the temperature of each combined heating element in the multi-type heating element fixture during the heating process, as well as the area of ​​the uniform temperature region in the vacuum furnace;

[0051] Combine Figure 2 In Figures (a) and (b), the multi-type heating body fixing device includes multiple combined heating bodies 1, multiple graphite connecting blocks 2, multiple hexagonal bolts 3 and multiple electrode plates 4;

[0052] The multi-type heating body fixing device is a cube, which is composed of a plurality of graphite connecting blocks 2 and a plurality of combined heating bodies 1 connected to each other. The first end of a combined heating body 1 is connected to a graphite connecting block 2 by a hexagonal bolt 3, and the second end of the combined heating body 1 is connected to another graphite connecting block 2 by a hexagonal bolt 3. The combined heating bodies 1 are parallel to each other, and one graphite connecting block 2 is connected to a plurality of combined heating bodies 1. The graphite connecting blocks 2 include right-angled graphite connecting blocks and straight-line graphite connecting blocks. The graphite connecting blocks 2 are connected to the electrode plates 4; Figure 2 , Figure 2 This is a structural schematic diagram of a multi-type heating body fixing device, which includes.

[0053] It should be noted that the combined heating elements in the multi-type heating element may be of the same type or of multiple different types.

[0054] The combined heating body 1 is composed of at least two heating bodies, the combined heating body 1 includes a basic heating body, or a special-shaped heating body, or a basic heating body and a special-shaped heating body, the cross-sectional shape of the basic heating body is a single cross-sectional shape, and the single cross-sectional shape includes at least an annular shape, a circle, a square, a diamond shape, such as Figure 3 (a)-(d) are all single cross-sectional shapes. The cross-sectional shape of the special-shaped heating body is a shape obtained by combining single cross-sectional shapes. Figure 4 The cross-sectional shape of the special-shaped heating body includes a square and a circular cross-sectional shape compounded into a combined cross-sectional shape 1, namely Figure 4 Figure (e) in the figure; the rhombus and circular sections are combined into a combined section 2, that is, Figure 4 Figure (f) in the figure; the square and circular sections are combined into a combined section 3, that is, Figure 4 Figure (g); the rhombus and circular sections are combined into a combined section 4, that is, Figure 4 Figure (h) in .

[0055] The combined heating body 1 may include two heating bodies, and the combined heating body 1 is composed of a first heating body and a second heating body, the first heating body includes a tubular heating body or a rod-shaped heating body, the cross-sectional shape of the tubular heating body is annular, and the cross-sectional shape of the rod-shaped heating body is circular; the second heating body includes a basic heating body or a special-shaped heating body, Figure 5 Taking Figure (a) in FIG. 1 as an example, the combined heating body 1 may include a rod-shaped heating body B and a square heating body A. An end face of the first heating body is designed with an internal thread, and the second heating body is provided with an extended stud. The extended studs of the second heating body are all engaged with the internal thread of the first heating body, as shown in FIG. Figure 5 In Figure (b), E is the extended stud of the square heating body, and the end face of the rod-shaped heating body is designed with an internal thread.

[0056] The combined heating body 1 may further include three heating bodies, and the combined heating body 1 is composed of a first heating body, a third heating body and a fourth heating body, wherein the first heating body includes a tubular heating body or a rod-shaped heating body, the cross-sectional shape of the tubular heating body is annular, the cross-sectional shape of the rod-shaped heating body is circular, the third heating body includes a basic heating body or a special-shaped heating body, the fourth heating body includes a basic heating body or a special-shaped heating body, and the fourth heating body includes a basic heating body or a special-shaped heating body. Figure 6 Taking the middle figure (a) as an example, the combined heating body 1 may include a rod-shaped heating body B and two square heating bodies A. Figure 6Taking the middle figure (b) as an example, the combined heating body 1 can also include a rod-shaped heating body B, a square heating body A and a special-shaped heating body C; the two end faces of the first heating body are designed with internal threads, and the third heating body and the fourth heating body are both equipped with extended studs, the internal thread of the first end of the first heating body is engaged with the extended stud of the third heating body, and the internal thread of the second end of the first heating body is engaged with the extended stud of the fourth heating body.

[0057] The combined heating body 1 may further comprise two heating bodies, and the combined heating body 1 is composed of a fifth heating body and a sixth heating body, wherein the fifth heating body comprises a basic heating body or a special-shaped heating body, and the sixth heating body comprises a basic heating body or a special-shaped heating body. Figure 7 Taking the middle figure (a) as an example, the combined heating body 1 may include a diamond-shaped heating body F and a square heating body A. An end surface of the fifth heating body is designed with an internal thread, and an end surface of the sixth heating body is designed with an internal thread. The first end of the external stud is engaged with the internal thread of the fifth heating body, and the second end of the external stud is engaged with the internal thread of the sixth heating body. Figure 7 In Figure (b), D is a stud.

[0058] This combined heating body can realize the replacement of a certain section of the heating body in a specific area by connecting threaded studs of different heating body shapes. It also allows the shape of the heating body to be flexibly selected and adjusted according to the size and shape of the furnace and the temperature requirements of different areas in the furnace.

[0059] The two ends of the combined heating body 1 are provided with toothed ports 5, and the center of the toothed ports 5 has an internal thread, such as Figure 8 The graphite connection block 2 is designed with a toothed hole 6 corresponding to the toothed port, the toothed hole 6 of the graphite connection block is coupled with the toothed port 5, as Figure 9 , the internal thread at the center of the toothed port engages with the hexagonal bolt, such as Figure 10 Such a connection structure helps to reduce the relaxation coefficient of the connection and reduce the looseness of the connection.

[0060] The core advantage of this fixture lies in its toothed meshing mechanism, which provides a mechanical lock for the connected components, enhancing joint stability and effectively reducing displacement caused by vibration or thermal expansion, thereby avoiding the loosening and poor contact problems that can occur in threaded connections. The toothed meshing also increases the contact area between the connected components, improving heat transfer efficiency. Furthermore, the toothed meshing design can adapt to a variety of loads and operating environments, including high temperature, high pressure, and corrosive environments.

[0061] Based on the structure of the above multi-type heating body fixing device, it is placed in a vacuum furnace for simulation. Figure 11, including multiple combined heating bodies 1, a water cooling system 7, a steel plate 8, a carpet layer 9 and a graphite plate 10. The simulation includes the following steps:

[0062] Step 1.1: Due to the axisymmetric distribution of the furnace heating system, we selected 1 / 2 of the furnace cross section to construct the temperature field model. Automatic meshing was used, with a total of 32,979 meshes and 33,271 nodes. During the sintering process, only heat radiation was considered, ignoring heat conduction and convection. The DO radiation model was used, and the radiation heat transfer model was: Where: I is the radiation intensity, r is the radiation azimuth normal vector; s is the radiation length vector, s′ is the scattering direction; α is the material absorption coefficient; σ s is the heat dissipation coefficient; I(r,s) is the radiation intensity; n is the refractive index; σ is the blackbody radiation constant; Φ(s,s') is the energy source term; Ω' is the radiation solid angle.

[0063] The physical properties of the furnace material are set as shown in Table 1. The graphite heating tube is set as the body heat source. The rated power is 2,000,000 W / m3, and the heating time is 3 h. The step size is set to 360 steps, and each step is 30 s. The water cooling system is simplified to a wall surface and set as a constant temperature boundary. The initial temperature of the calculation domain is set to 25°C.

[0064] Table 1 Physical properties of furnace materials

[0065]

[0066] Step 1.2: Based on the above-mentioned furnace material properties and radiation heat transfer model, a simulation was performed. The energy equation and discrete ordinate DO radiation model were enabled. A temperature monitoring point was set at the center of the vacuum furnace cross section to obtain the temperature field distribution law of the vacuum furnace under no-load state.

[0067] Step 1.3: Perform heating simulation at constant power under no-load state to obtain the uniform temperature area in the vacuum furnace. Specifically, for different cross-sectional shapes of special-shaped heating bodies, the corresponding uniform temperature area in the vacuum furnace can be obtained. Taking the heating body of combined section 1 as an example, after simulation, the temperature cloud diagram of the heating body of combined section 1 in the furnace can be obtained at the end of heating, as shown in the figure below. Figure 12 Taking the furnace center temperature of 1356.45K as the benchmark, the isotherm of 1361.75K is drawn within the range of ±5K, and the area of ​​the uniform temperature zone is calculated to be 4997.58cm 2 The calculation of the uniform temperature area of ​​the simulation of the special-shaped heating body with other different combined cross sections is the same as above, and then the uniform temperature area of ​​the combined cross sections 1-4 can be obtained, such as Figure 13 .

[0068] Based on the above simulation process, the present invention simulates a heating body with a single cross section. Taking a circular heating body as an example, after the simulation, a temperature cloud diagram of the circular heating body in the furnace can be obtained at the end of heating, as shown in FIG. Figure 14 The cloud map intuitively shows the temperature distribution in the furnace. Taking the center temperature of the furnace body as 1350.75K as the benchmark, the isotherm of 1355.75K is drawn within the range of ±5K according to the relevant standard furnace temperature uniformity requirement. The origin software is further used to calculate the area of ​​the uniform temperature zone in the furnace under this cross-sectional shape to be 4863.75cm 2 , and then we can get the simulated uniform temperature area of ​​other single cross-section heating bodies, such as Figure 15 .

[0069] Based on this, we can also find that, under the condition of keeping the heating power unchanged, the cross-sectional shape of the heating body is changed, and it is found that the area of ​​the uniform temperature zone in the furnace changes significantly. Among them, the heating body with a single cross-sectional shape: (a) The circular cross-sectional heating body has the largest uniform temperature zone area of ​​4863.75cm 2 (d) The minimum uniform temperature zone in the rectangular cross-section heating element is 4189.02 cm 2 Combined cross-sectional shape of the heating element: (e) Combined cross-sectional shape of the heating element: The maximum uniform temperature zone in the furnace is 4997.58 cm 2 (g) The minimum uniform temperature zone area in the combined section 4 furnace is 4842.035 cm 2 See also Figure 16 , the heating simulation is carried out at constant power under no-load condition, and the maximum area of ​​uniform temperature zone of the combined cross section is 4997.58cm 2 The minimum uniform temperature zone area of ​​the rectangular cross section is 4189.02 cm 2 The innovative cross-sectional shape of the heating element reduces the temperature gradient in the furnace, expands the area of ​​the uniform temperature zone, and significantly improves the temperature uniformity of the furnace.

[0070] Step 2: For each combined heating element cross-sectional shape in the multi-type heating element fixture, construct a formula to characterize the cross-sectional shape: F = F(ρ, θ), where ρ and θ are polar coordinate parameters.

[0071] The interior of the vacuum furnace is a sealed vacuum chamber, and energy transfer is mainly achieved through radiation heat transfer. Therefore, the radiation heat transfer process inside the vacuum furnace is analyzed, mainly including the determination of key parameters such as radiation force, system emissivity, and angular coefficient. Among them, the focus is on the calculation of the angular coefficient between the two surfaces in the radiation heat transfer process, which is achieved by drawing a geometric relationship diagram based on the relative position of the vacuum furnace heating body and the heating chamber, combined with Figure 17, simplify the geometric cross-sectional shape of the heating body, take the moving axis ρ, the angle θ between ρ and OX as variables, and use the motion trajectory of the end point of the moving axis ρ to represent the geometric cross-sectional shape of the heating body. Then, the geometric cross-sectional shape of any heating body can be expressed as F=F(ρ,θ).

[0072] See also Figure 18 , according to the geometric relationship expression between the infinitesimal cross section of the heating body and a relative position of the heating chamber: L = x 2 +y 2 ;Radiative heat transfer expression: Where: dΦ 1,2 is the energy radiated from the micro-element surface dA1 to another micro-element surface dA2; T is the initial temperature of the micro-element surface dA1; β1 is the angle between the normal line of the dA1 surface and the line of sight from dA1 to dA2; L is the distance from dA1 to dA2; β2 is the angle between the normal line of the dA1 surface and the line of sight from dA1 to dA2; d is the distance from a certain position in the heating chamber to the central section of the sintering furnace, which is set to a constant value.

[0073] Step 3: The temperature during the heating process of each combined heating body and the formula F = F(ρ, θ) representing the cross-sectional shape are combined into a sample, thereby obtaining multiple samples to obtain a sample data set, and preprocessing the sample data set to obtain a preprocessed sample data set;

[0074] Among them, the preprocessing of the sample data set includes data deletion and abnormal data processing to eliminate abnormal and erroneous data.

[0075] Step 4: Processing the preprocessed sample data set according to the random forest algorithm to obtain multiple prediction models, which are used to predict the area of ​​the uniform temperature region in the vacuum furnace;

[0076] Among them, the random forest algorithm can be implemented through Matlab programming.

[0077] Among them, step 4 specifically includes:

[0078] The preprocessed sample data set is randomly sampled by Bootstrap sampling to obtain multiple sub-sample training sets, where the number of samples in the sub-sample training set is the same as the number of samples in the preprocessed sample data set. A decision tree is established for each sub-sample training set, and each node in the decision tree contains multiple samples. For each decision tree, a preset number of samples are selected from the multiple samples contained in each node and used as specific variables. A prediction model is constructed based on the specific variables to obtain a prediction model corresponding to each sub-training set.

[0079] Construct a prediction model based on specific variables to obtain the prediction model corresponding to each sub-training set, including:

[0080] Substitute specific variables into the preset formula to obtain the prediction model. The preset formula is expressed as:

[0081] Y(i)=((T j (i) 4 )·ρ·(5.67e-8)·sinθ·(0.57-ρ·cosθ)) / (pi·(ρ 2 -2·cosθ·ρ·0.57+0.57 2 ) 2 );

[0082] Where i represents the time during the heating process, T j (i) represents the temperature of the heating body at time i during the heating process, and Y(i) represents the area of ​​the uniform temperature region in the vacuum furnace at time i.

[0083] Step 5: Calculate the predicted value of the uniform temperature area in the vacuum furnace using each prediction model to obtain the predicted value corresponding to each prediction model. Among all the predicted values, obtain the predicted value that is greater than or equal to the preset area threshold, and then determine the prediction model corresponding to the predicted value that is greater than or equal to the preset area threshold, and use it as the optimal prediction model.

[0084] Among them, the preset area threshold is 4800cm 2 The optimal prediction model can be one or more. If no prediction model in this step has a prediction value greater than or equal to the preset area threshold, return to step 4.

[0085] Step 6: Randomly select a sample data from the preprocessed sample data set, bring it into the optimal prediction model, obtain the predicted value of the uniform temperature area in the vacuum furnace, and calculate the error with the uniform temperature area in the vacuum furnace obtained by simulation in step 1 to determine whether the error is less than or equal to the preset threshold. If the error is less than or equal to the preset threshold, the optimal prediction model is used as the final prediction model. If the error is greater than the preset threshold, return to step 4 and execute until the error is less than or equal to the preset threshold.

[0086] The preset threshold is 10% or 15%, and the final prediction model can be one or more.

[0087] The innovative composite heating body cross-section of the present invention achieves a more uniform temperature distribution in the vacuum furnace, and the area of ​​the uniform temperature zone is increased by 16%. The special-shaped heating body parts can realize the local replacement of the heating body in different specific areas. In addition, the present invention uses a random forest algorithm to predict the temperature in the furnace of different heating bodies.

[0088] The above description is merely a preferred embodiment of the present disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also encompass other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the above-mentioned inventive concept. For example, a technical solution formed by mutually replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in the embodiments of the present disclosure.

Claims

1. A vacuum furnace temperature prediction method based on a multi-type heating body fixing device, characterized in that: include: Step 1: Simulate the heating process of the multi-type heating element fixture in the vacuum furnace to obtain the temperature of each combined heating element in the multi-type heating element fixture during the heating process, as well as the area of ​​the uniform temperature region in the vacuum furnace; Step 2: For each combined heating element cross-sectional shape in the multi-type heating element fixture, construct a formula to characterize the cross-sectional shape: F = F(ρ, θ), where ρ and θ are polar coordinate parameters. Step 3: The temperature during the heating process of each combined heating body and the formula F = F(ρ, θ) representing the cross-sectional shape are combined into a sample, thereby obtaining multiple samples to obtain a sample data set, and preprocessing the sample data set to obtain a preprocessed sample data set; Step 4: Processing the preprocessed sample data set according to the random forest algorithm to obtain multiple prediction models, which are used to predict the area of ​​the uniform temperature region in the vacuum furnace; Step 5: Calculate the predicted value of the uniform temperature area in the vacuum furnace using each prediction model to obtain the predicted value corresponding to each prediction model. Among all the predicted values, obtain the predicted value that is greater than or equal to the preset area threshold, and then determine the prediction model corresponding to the predicted value that is greater than or equal to the preset area threshold, and use it as the optimal prediction model. Step 6: Randomly select a sample data from the preprocessed sample data set, bring it into the optimal prediction model, obtain the predicted value of the uniform temperature area in the vacuum furnace, and calculate the error with the uniform temperature area in the vacuum furnace obtained by simulation in step 1 to determine whether the error is less than or equal to the preset threshold. If the error is less than or equal to the preset threshold, the optimal prediction model is used as the final prediction model. If the error is greater than the preset threshold, return to step 4 and execute until the error is less than or equal to the preset threshold.

2. The vacuum furnace temperature prediction method based on a multi-type heating body fixing device according to claim 1 is characterized in that: Step 4 specifically includes: The preprocessed sample data set is randomly sampled by Bootstrap sampling to obtain multiple sub-sample training sets, where the number of samples in the sub-sample training set is the same as the number of samples in the preprocessed sample data set. A decision tree is established for each sub-sample training set, and each node in the decision tree contains multiple samples. For each decision tree, a preset number of samples are selected from the multiple samples contained in each node and used as specific variables. A prediction model is constructed based on the specific variables to obtain a prediction model corresponding to each sub-training set.

3. The vacuum furnace temperature prediction method based on a multi-type heating body fixing device according to claim 2 is characterized in that: Construct a prediction model based on specific variables to obtain the prediction model corresponding to each sub-training set, including: Substitute specific variables into the preset formula to obtain the prediction model. The preset formula is expressed as: Y(i)=((T j (i) 4 )·ρ·(5.67e-8)·sinθ·(0.57-ρ·cosθ)) / (pi·(ρ 2 -2·cosθ·ρ·0.57+0.57 2 ) 2 ); Where i represents the time during the heating process, T j (i) represents the temperature of the heating body at time i during the heating process, and Y(i) represents the area of ​​the uniform temperature region in the vacuum furnace at time i.

4. The vacuum furnace temperature prediction method based on a multi-type heating body fixing device according to claim 1 is characterized in that: The multi-type heating body fixing device includes a plurality of combined heating bodies, a plurality of graphite connecting blocks, a plurality of hexagonal bolts and a plurality of electrode plates; The multi-type heating body fixing device is a cube, consisting of a plurality of graphite connecting blocks connected to a plurality of different combined heating bodies. The first end of a combined heating body is connected to a graphite connecting block via a hexagonal bolt, and the second end of the combined heating body is connected to another graphite connecting block via a hexagonal bolt. The combined heating bodies are parallel to each other, and one graphite connecting block is connected to a plurality of different combined heating bodies. The graphite connecting blocks include right-angled graphite connecting blocks and linear graphite connecting blocks. The graphite connecting blocks are connected to the electrode plates. The combined heating body is composed of at least two heating bodies, and the combined heating body includes a basic heating body, or a special-shaped heating body, or a basic heating body and a special-shaped heating body. The cross-sectional shape of the basic heating body is a single cross-sectional shape, and the single cross-sectional shape includes at least a circular ring, a circle, a square, and a diamond. The cross-sectional shape of the special-shaped heating body is a shape obtained by combining single cross-sectional shapes.

5. The vacuum furnace temperature prediction method based on a multi-type heating body fixing device according to claim 4 is characterized in that: The two ends of the combined heating body are provided with toothed ports, the center of the toothed ports has an internal thread, the graphite connecting block is designed with a toothed hole corresponding to the toothed port, the toothed hole of the graphite connecting block is coupled with the toothed port, and the internal thread in the center of the toothed port engages with the hexagonal bolt.

6. The vacuum furnace temperature prediction method based on a multi-type heating body fixing device according to claim 4 is characterized in that: The combined heating body includes two heating bodies, and the combined heating body consists of a first heating body and a second heating body, the first heating body includes a tubular heating body or a rod-shaped heating body, the cross-sectional shape of the tubular heating body is a circular ring, and the cross-sectional shape of the rod-shaped heating body is a circle; the second heating body includes a basic heating body or a special-shaped heating body, one end face of the first heating body is designed with an internal thread, and the second heating body is equipped with an extended stud, and the extended studs of the second heating body are all engaged with the internal thread of the first heating body.

7. The vacuum furnace temperature prediction method based on a multi-type heating body fixing device according to claim 4 is characterized in that: The combined heating body includes three heating bodies, and the combined heating body consists of a first heating body, a third heating body and a fourth heating body. The first heating body includes a tubular heating body or a rod-shaped heating body. The cross-sectional shape of the tubular heating body is a circular ring. The cross-sectional shape of the rod-shaped heating body is a circle. The third heating body includes a basic heating body or a special-shaped heating body. The fourth heating body includes a basic heating body or a special-shaped heating body. Both end faces of the first heating body are designed with internal threads. The third heating body and the fourth heating body are both equipped with extended studs. The internal thread of the first end of the first heating body engages with the extended stud of the third heating body, and the internal thread of the second end of the first heating body engages with the extended stud of the fourth heating body.

8. The vacuum furnace temperature prediction method based on a multi-type heating body fixing device according to claim 4 is characterized in that: The combined heating body includes two heating bodies, and the combined heating body consists of a fifth heating body and a sixth heating body, the fifth heating body includes a basic heating body or a special-shaped heating body, the sixth heating body includes a basic heating body or a special-shaped heating body, one end face of the fifth heating body is designed with an internal thread, one end face of the sixth heating body is designed with an internal thread, the first end of the external stud is engaged with the internal thread of the fifth heating body, and the second end of the external stud is engaged with the internal thread of the sixth heating body.

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