A method for measuring surface heat transfer coefficient of steel quenching considering latent heat of phase transition

Abstract

The present application relates to the technical field of thermal physical property measurement, and is a steel quenching surface heat transfer coefficient determination method considering phase change latent heat, comprising: discretizing the heat transfer coefficient in the measured temperature range, and giving the heat transfer coefficient initial value, and calculating the temperature field of pure heat conduction process; considering radial heat transfer, and establishing a temperature control equation under one-dimensional cylindrical coordinate system; linearly regressing the TTT curve, and establishing a structure field model; the structure field model is established respectively for diffusion type phase change and non-diffusion type phase change; the released latent heat is converted into temperature rise value, and the temperature field is corrected; the sum of squares of differences between temperature measurement value and temperature calculation value is calculated, and the heat transfer coefficient is corrected. The present application can accurately determine the heat transfer coefficient containing phase change, can accurately predict the temperature field, structure field and stress field changes of the material in the quenching process, and thus guides and optimizes the heat treatment process.

Description

Technical Field

[0001] This invention relates to the field of thermophysical property measurement technology, and in particular to a method for determining the heat transfer coefficient of quenched steel surfaces considering latent heat of phase transformation. Background Technology

[0002] The surface heat transfer coefficient is a comprehensive equivalent coefficient representing the various forms of heat exchange between the workpiece and the quenching medium during quenching. As a commonly used method for evaluating the cooling capacity of quenching media, it not only has the advantages of being objective and direct, but is also an important boundary condition for the temperature field in numerical simulations. It directly affects the calculation accuracy of the temperature field, and thus indirectly affects the simulation results of the microstructure and stress fields. Therefore, the accurate measurement of the heat transfer coefficient is of great significance. Traditional methods for determining the heat transfer coefficient are generally the reverse heat transfer method, and do not consider the correction of the latent heat of phase change to the temperature field; or the heat transfer coefficient is determined using finite element software.

[0003] The invention patent with publication number CN105046030B discloses a method for obtaining the quenching heat transfer coefficient of aluminum alloy components under three-dimensional heat transfer conditions based on the finite element method. The method establishes a temperature field model using finite element software and optimizes the heat transfer coefficient according to a genetic algorithm, ultimately obtaining the quenching heat transfer coefficient that meets the convergence condition.

[0004] The invention application with publication number CN102521439A discloses a method for calculating the heat transfer coefficient of a quenching medium by combining the finite element method and the inverse heat transfer method. The method involves establishing a heat probe model using finite element software, solving for the heat flux density using the inverse heat transfer method, and then obtaining the heat transfer coefficient according to Newton's law of heat transfer.

[0005] The invention application with publication number CN102507636A discloses a method for determining the interfacial heat transfer coefficient of steel during rapid cooling. The method calculates the temperature change at the measuring point using the heat transfer coefficient and then verifies and optimizes the heat transfer coefficient by comparing it with the actual temperature measurement.

[0006] The aforementioned methods for determining heat transfer coefficients partially employ finite element method (FEM) software for thermal probe modeling, and none of them specify whether the latent heat generated during phase transformation in the metal cooling process is considered. This fails to achieve real-time integration of the phase transformation kinetic model and the heat transfer control equations. Consequently, temperature predictions become inaccurate within the temperature range where severe phase transformations occur, thus reducing the reliability and accuracy of the heat transfer coefficient determination results. Therefore, developing a heat transfer coefficient determination method that considers phase transformation kinetics and the heat transfer process, accurately incorporates the latent heat effect of phase transformation, and eliminates the need for software modeling is of great significance for improving the predictive capabilities of quenching process simulations. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for determining the heat transfer coefficient of quenched steel surfaces considering latent heat of phase change. This invention is applicable to calculating the heat transfer coefficient of quenched surfaces under varying temperature conditions. It considers the influence of latent heat of phase change on the temperature field through a heat transfer-phase change-latent heat sequence. Without utilizing finite element method software, it iteratively considers the correction of the temperature field by latent heat of phase change using the Picard method, accurately determining the heat transfer coefficient including phase change.

[0008] The technical means employed in this invention are as follows:

[0009] A method for determining the heat transfer coefficient of a quenched steel surface considering latent heat of phase transformation includes: discretizing the heat transfer coefficient within the measured temperature range and assigning an initial value to the heat transfer coefficient; calculating the temperature field of a pure heat conduction process; considering radial heat transfer, establishing a temperature control equation in a one-dimensional cylindrical coordinate system; performing linear regression processing on the TTT curve to establish a microstructure field model; the microstructure field model is established for both diffusion-type and non-diffusion-type phase transformations; converting the released latent heat into a temperature rise value to correct the temperature field; and calculating the sum of the variances between the measured temperature value and the calculated temperature value to correct the heat transfer coefficient.

[0010] Furthermore, the establishment of the temperature control equation specifically includes: A thermocouple is inserted near the surface of the quenching probe and connected to the acquisition interface of the temperature acquisition system. After the quenching probe is heated to complete austenitization, it is transferred to a medium for quenching. The heat conduction equation is expressed as:

[0011] in, For specific heat capacity, ρ For density, t For time, λ Thermal conductivity, Radial coordinates; The initial conditions for the heat conduction model are:

[0012] The boundary conditions for the heat conduction model are:

[0013] in, The initial temperature. h The surface heat transfer coefficient, T The probe surface temperature. The temperature of the medium; The direction of the outward normal to the boundary; For the central location of the heat conduction model, the adiabatic condition is expressed as: .

[0014] Furthermore, the temperature control equation is expressed in an implicit difference scheme, and the equations for the center node, internal node and boundary node of the quenching probe are established respectively. The equation for the central node is expressed as:

[0015] in, F r It is the Fourier number; Let be the temperature of the central node 1 at time n. for n The temperature of central node 1 at time +1. for n The temperature of node 2 at time +1; The equations for the internal nodes are expressed as follows:

[0016] in, , for n +1 time node i -1 temperature; for n +1 time node i Temperature; for n +1 time node i +1 temperature; for n Time Node i Temperature; The equations for the boundary nodes are expressed as:

[0017]

[0018]

[0019]

[0020] in, N Number of nodes , , , for n +1 time node N -1 temperature, for n +1 time node N -1 temperature, for n +1 time nodeN -1 temperature, For a unit time step, The unit spatial step size.

[0021] Furthermore, for the aforementioned diffusion-type phase transition, the kinetics are described using the Johnson-Mehl-Avrami equation:

[0022] in, V For transformation variables, t Isothermal time, b and n It is a constant; The superposition principle can be used to determine whether a phase transition has begun. When the sum of the relative consumption during the incubation period of various tissues is greater than or equal to 1, tissue transformation begins.

[0023] in, The number of historical temperature ranges. For the first i The time elapsed in each temperature range For the first i The gestation period corresponding to each temperature range; Virtual time is used as the computation time step during iteration, and the formula for calculating virtual time is:

[0024] in, For virtual time, Indicates the first i Phase transition volume fraction at the end of the phase. For the first i The dynamic parameters of the +1 stage, Indicates the first i Avrami index at stage +1.

[0025] When the temperature of a certain node on the probe cools down to At temperature, the diffusion phase transition variable at this node is: .

[0026] Furthermore, for the aforementioned non-diffusional phase transition, the transformation variable is expressed as:

[0027] in, V For transformation variables, This marks the starting point of the martensitic transformation. k It is a constant. T This refers to the probe surface temperature.

[0028] Furthermore, the correction of the temperature field specifically includes: Calculate the equivalent temperature rise of the latent heat of phase change using the tissue transformation variable. :

[0029] in, ΔV For organizational transformation variables within a time step, Q This is converted into the average latent heat released per unit volume of tissue. ρ For material density, Specific heat capacity at constant pressure; During the temperature field correction process, Picard iteration is used to update the temperature field through energy conservation:

[0030] in, For nodes Temperature field after the (k+1)th Picard iteration For nodes i Temperature field after the kth Picard iteration For nodes The temperature rise calculated from the latent heat of phase change after the kth Picard iteration; The iteration converges when the absolute value of the maximum difference between the two values ​​after iteration satisfies the convergence condition.

[0031] in, For temperature convergence tolerance; Furthermore, the correction of the heat transfer coefficient specifically includes: Calculate the sum of squares of the differences between the measured temperature value and the calculated temperature value. S :

[0032] in, Indicates the current thermocouple position The experimental measurements Indicates the current thermocouple position Calculated temperature value; Determine if the variance and sum of squares S have reached their minimum. If convergence is achieved, output the optimal heat transfer coefficient; otherwise, correct the heat transfer coefficient.

[0033] Among them, heat transfer coefficient It is a function of surface temperature.

[0034] Compared with the prior art, the present invention has the following advantages: This invention provides a method for determining the heat transfer coefficient of quenched steel surfaces considering latent heat of phase change. The method involves using a thermal probe to measure the cooling curve near the surface during quenching experiments; discretizing the heat transfer coefficient according to the temperature range and assigning initial values; establishing a temperature field model; calculating the temperature field and the thermal history of the sample surface temperature using an implicit scheme based on the current heat transfer coefficient; establishing a microstructure field model; performing linear regression on the TTT curve of the material to calculate the volume fraction changes of each phase; processing the latent heat of phase change using a temperature rise method and correcting the temperature field; iterating the heat transfer coefficient according to the temperature field changes to ensure the stability of the solution process, with the outer layer using Gauss-Newton iteration and the inner layer using Picard iteration; outputting the optimal heat transfer coefficient after meeting the convergence condition; and efficiently determining the heat transfer coefficient by considering the latent heat of phase change in the order of heat transfer-phase change-latent heat.

[0035] The method of this invention considers the influence of latent heat of phase change on the temperature field through the heat transfer-phase change-latent heat sequence. Without using finite element software, it uses the Picard method to iteratively consider the correction of the temperature field by latent heat of phase change, accurately measure the heat transfer coefficient including phase change, and can accurately predict the changes in temperature field, microstructure field and stress field of material during quenching, thereby guiding and optimizing the heat treatment process. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart of the method for determining the heat transfer coefficient of quenched steel surface considering latent heat of phase transformation in this invention.

[0038] Figure 2 This is a schematic diagram of the structure of the quenching probe into which a thermocouple is inserted in this invention.

[0039] Figure 3 This is a curve showing the change of the surface heat transfer coefficient of the probe as a function of surface temperature during water quenching in Embodiment 1 of the present invention.

[0040] Figure 4 This is a curve showing the change of the surface heat transfer coefficient of the probe as a function of surface temperature during oil quenching in Embodiment 2 of the present invention.

[0041] Figure 5 This is a fitting graph of the calculated temperature and the experimentally measured temperature during the water cooling process of the fire probe in Embodiment 1 of the present invention.

[0042] Figure 6 This is a fitting graph of the calculated temperature and the experimentally measured temperature during the oil cooling process of the quenching probe in Embodiment 2 of the present invention. Detailed Implementation

[0043] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0046] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0047] like Figure 1As shown, this invention provides a method for determining the heat transfer coefficient of a quenched steel surface considering latent heat of phase transformation, comprising: discretizing the heat transfer coefficient within the measured temperature range, with 8-12 discretization points, assigning an initial value to the heat transfer coefficient, and calculating the temperature field of the pure heat conduction process; in the experiment, the length and diameter of the heat probe differ significantly, only radial heat transfer is considered, and half of the heat probe is used, establishing a temperature control equation in a one-dimensional cylindrical coordinate system; in a preferred embodiment of this invention, a thermocouple is inserted near the surface of the quenching probe, connected to the acquisition interface of the temperature acquisition system, and the quenching probe is heated to 800-1100℃ for complete austenitization, then transferred to a medium for quenching; the transfer time to the medium after quenching is within 60 seconds, and the medium is water, oil, or other quenching media. The heat conduction equation is expressed as:

[0048] in, For specific heat capacity, ρ For density, t For time, λ Thermal conductivity, Radial coordinates; The initial conditions for the heat conduction model are:

[0049] The boundary conditions for the heat conduction model are:

[0050] in, The initial temperature. h The surface heat transfer coefficient, T The probe surface temperature. The temperature of the medium; The direction of the outward normal to the boundary; For the central location of the heat conduction model, the adiabatic condition is expressed as: .

[0051] In a specific implementation, as a preferred embodiment of the present invention, the temperature control equation is expressed in an implicit difference format, and the equations for the center node, internal node and boundary node of the quenching probe are established respectively. The equation for the central node is expressed as:

[0052] in, F r It is the Fourier number; Let be the temperature of the central node 1 at time n. for n The temperature of central node 1 at time +1. for n The temperature of node 2 at time +1; The equations for the internal nodes are expressed as:

[0053] in, , for n +1 time node i -1 temperature; for n +1 time node i Temperature; for n +1 time node i +1 temperature; for n Time Node i Temperature; The equations for the boundary nodes are expressed as:

[0054]

[0055]

[0056]

[0057] in, N The number of nodes; , , , for n +1 time node N -1 temperature, for n +1 time node N -1 temperature, for n +1 time node N -1 temperature, For a unit time step, The unit spatial step size.

[0058] Linear regression was performed on the TTT curve to establish a tissue field model; the tissue field model was established for both diffusion-type and non-diffusion-type phase transitions; in a preferred embodiment of the invention, the Johnson-Mehl-Avrami equation was applied to describe the kinetics of the diffusion-type phase transition:

[0059] in, V For transformation variables,t Isothermal time, b and n It is a constant; The superposition principle can be used to determine whether a phase transition has begun. When the sum of the relative consumption during the incubation period of various tissues is greater than or equal to 1, tissue transformation begins.

[0060] in, The number of historical temperature ranges. For the first i The time elapsed in each temperature range For the first i The gestation period corresponding to each temperature range; Virtual time is used as the computation time step during iteration. The formula for calculating virtual time is:

[0061] in, For virtual time, Indicates the first i Phase transition volume fraction at the end of the phase. For the first i The dynamic parameters of the +1 stage, Indicates the first i Avrami index at stage +1.

[0062] When the temperature of a certain node on the probe cools down to At temperature, the diffusion phase transition variable at this node is: .

[0063] Because the microstructure transformation variables of diffusion-type phase transitions are simulated using the superposition rule and according to the TTT curve, linear regression processing of the TTT curve is required. First, the TTT curve is segmented, and within each temperature range, the relationship between lg(t) and T is replaced by a short straight line segment: .

[0064] In a specific implementation, as a preferred embodiment of the present invention, for non-diffusional phase transitions, the transformation variable is expressed as:

[0065] in, V For transformation variables, This marks the starting point of the martensitic transformation. k It is a constant. T This refers to the probe surface temperature.

[0066] The released latent heat is converted into a temperature rise value to correct the temperature field; in a preferred embodiment of the present invention, the temperature rise value equivalent to the latent heat of phase change is calculated using tissue transformation variables. :

[0067] in, ΔV For organizational transformation variables within a time step, Q This is converted into the average latent heat released per unit volume of tissue. ρ For material density, Specific heat capacity at constant pressure; During the temperature field correction process, Picard iteration is used to update the temperature field through energy conservation:

[0068] in, For nodes Temperature field after the (k+1)th Picard iteration For nodes i Temperature field after the kth Picard iteration For nodes The temperature rise calculated from the latent heat of phase change after the kth Picard iteration; The iteration converges when the absolute value of the maximum difference between the two values ​​after iteration satisfies the convergence condition.

[0069] in, For temperature convergence tolerance; The sum of the variances between the measured and calculated temperature values ​​is used to correct the heat transfer coefficient. Specifically, in a preferred embodiment of this invention, the sum of the variances between the measured and calculated temperature values ​​is calculated. S :

[0070] in, Indicates the current thermocouple position The experimental measurements Indicates the current thermocouple position Calculated temperature value; Determine if the variance and sum of squares S have reached their minimum. If convergence is achieved, output the optimal heat transfer coefficient; otherwise, correct the heat transfer coefficient.

[0071] Among them, heat transfer coefficient It is a function of surface temperature.

[0072] The heat transfer coefficient was verified using a two-dimensional model in Deform software. The difference between the simulated temperature field and the experimental temperature field was compared, and the error between the two did not exceed 10%. The method of this invention is applicable to various steel grades that undergo phase transformation (including diffusion-type and non-diffusion-type phase transformation) during quenching, and theoretically it is also applicable to other metallic materials that contain phase transformation.

[0073] Example 1 This embodiment uses a cylindrical steel heating probe with a diameter of 20mm and a length of 50mm. The material is a high-molybdenum mold steel. The method of this invention is also applicable to other steels that undergo phase transformation during quenching. The specific structure is as follows: Figure 2 As shown, a type K thermocouple was inserted 1 mm from the probe surface near the probe surface and connected to the temperature acquisition system. The probe was placed in a tube furnace and heated to 1050°C and held for 30 minutes to fully austenitize it. Then, within 5 seconds, the probe was transferred to a 20°C still aqueous solution for quenching, and the temperature change curve of the probe's near-surface over time was recorded throughout the process.

[0074] The heat transfer coefficient is determined using the method described in this invention: 1) Discretize the temperature measurement range (1050℃ to 20℃) into 8 temperature intervals and assign initial values ​​to the heat transfer coefficient; 2) Establish a one-dimensional radial heat transfer model and a tissue field model; 3) A program was written in Matlab to solve the temperature field coupled with the latent heat of phase change. The temperature field was corrected using Picard iteration. The temperature rise equivalent to the latent heat of phase change was calculated using the microstructure transformation variable, and then the temperature field was updated by energy conservation. 4) Calculate the sum of squares of the differences between the measured temperature value and the calculated temperature value. S Determine whether S has reached its minimum. If the convergence condition is met, output the optimal heat transfer coefficient; otherwise, correct the heat transfer coefficient.

[0075] The final curve showing the change of the surface heat transfer coefficient of the probe with surface temperature during water quenching at 20℃ is shown below. Figure 3 As shown, the obtained heat transfer coefficient was substituted into the Deform software for simulation, and the calculated temperature was compared with the experimental temperature. Figure 5 As shown, the two match well, with an average error of less than 5%.

[0076] Example 2 This embodiment uses the same probe size (20mm in diameter and 50mm in length) and temperature measurement method as in Embodiment 1, but the quenching medium is changed to 45℃ quenching oil. After the probe is heated to 900℃ for austenitization, it is transferred to 45℃ static oil for quenching, and the cooling curve is recorded.

[0077] The procedure for determining the heat transfer coefficient is the same as in Example 1, except that: 1) The medium temperature is 45℃; 2) The release of latent heat from phase change has a more significant impact on the temperature field.

[0078] The final heat transfer coefficient-temperature curve is as follows: Figure 4 As shown. The results were imported into Deform for verification, and the simulated and experimental temperatures were compared, for example... Figure 6 As shown, the maximum error does not exceed 8%, indicating that the method of the present invention can still accurately reflect the influence of latent heat of phase change on the heat transfer coefficient under oil quenching conditions.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the surface heat transfer coefficient of quenched steel considering latent heat of phase transformation, characterized in that, include: Discretize the heat transfer coefficient within the measured temperature range, assign initial values ​​to the heat transfer coefficient, and calculate the temperature field of the pure heat conduction process. Considering radial heat transfer, a temperature control equation is established in a one-dimensional cylindrical coordinate system. Linear regression was performed on the TTT curve to establish a tissue field model; the tissue field model was established for both diffusion-type and non-diffusion-type phase transitions. The released latent heat is converted into a temperature rise value to correct the temperature field; Calculate the sum of the variances between the measured and calculated temperature values ​​to correct the heat transfer coefficient.

2. The method for determining the heat transfer coefficient of quenched steel surface considering latent heat of phase transformation according to claim 1, characterized in that, The establishment of the temperature control equation specifically includes: A thermocouple is inserted near the surface of the quenching probe and connected to the acquisition interface of the temperature acquisition system. After the quenching probe is heated to complete austenitization, it is transferred to a medium for quenching. The heat conduction equation is expressed as: in, For specific heat capacity, ρ For density, t For time, λ Thermal conductivity, Radial coordinates; The initial conditions for the heat conduction model are: The boundary conditions for the heat conduction model are: in, The initial temperature. h The surface heat transfer coefficient, T The probe surface temperature. The temperature of the medium; The direction of the outward normal to the boundary; For the central location of the heat conduction model, the adiabatic condition is expressed as: 。 3. The method for determining the surface heat transfer coefficient of quenched steel considering latent heat of phase transformation according to claim 2, characterized in that, The temperature control equation is expressed in an implicit difference scheme, and the equations for the center node, internal node and boundary node of the quenching probe are established respectively. The equation for the central node is expressed as: in, F r It is the Fourier number; Let be the temperature of the central node 1 at time n. for n The temperature of central node 1 at time +1. for n The temperature of node 2 at time +1; The equations for the internal nodes are expressed as follows: in, , for n +1 time node i -1 temperature; for n +1 time node i Temperature; for n +1 time node i +1 temperature; for n Time Node i Temperature; The equations for the boundary nodes are expressed as: in, N The number of nodes; , , , for n +1 time node N -1 temperature, for n +1 time node N -1 temperature, for n +1 time node N -1 temperature, For a unit time step, The unit spatial step size.

4. The method for determining the surface heat transfer coefficient of quenched steel considering latent heat of phase transformation according to claim 1, characterized in that, For the aforementioned diffusion-type phase transition, the kinetics are described using the Johnson-Mehl-Avrami equation: in, V For transformation variables, t Isothermal time, b and n It is a constant; The superposition principle can be used to determine whether a phase transition has begun. When the sum of the relative consumption during the incubation period of various tissues is greater than or equal to 1, tissue transformation begins. in, The number of historical temperature ranges. For the first i The time elapsed in each temperature range For the first i The gestation period corresponding to each temperature range; Virtual time is used as the computation time step during iteration, and the formula for calculating virtual time is: in, For virtual time, Indicates the first i Phase transition volume fraction at the end of the phase. For the first i The dynamic parameters of the +1 stage, Indicates the first i Avrami index at stage +1; When the temperature of a certain node on the probe cools down to At temperature, the diffusion phase transition variable at this node is: 。 5. The method for determining the heat transfer coefficient of quenched steel surface considering latent heat of phase transformation according to claim 1, characterized in that, For the aforementioned non-diffusional phase transition, the transformation variable is expressed as: in, V For transformation variables, This marks the starting point of the martensitic transformation. k It is a constant. T This refers to the probe surface temperature.

6. The method for determining the heat transfer coefficient of quenched steel surface considering latent heat of phase transformation according to claim 1, characterized in that, The correction of the temperature field specifically includes: Calculate the equivalent temperature rise of the latent heat of phase change using the tissue transformation variable. : in, ΔV For organizational transformation variables within a time step, Q This is converted into the average latent heat released per unit volume of tissue. ρ For material density, Specific heat capacity at constant pressure; During the temperature field correction process, Picard iteration is used to update the temperature field through energy conservation: in, For nodes Temperature field after the (k+1)th Picard iteration For nodes i Temperature field after the kth Picard iteration For nodes The temperature rise calculated from the latent heat of phase change after the kth Picard iteration; The iteration converges when the absolute value of the maximum difference between the two values ​​after iteration satisfies the convergence condition. in, This refers to the temperature convergence tolerance.

7. The method for determining the surface heat transfer coefficient of quenched steel considering latent heat of phase transformation according to claim 1, characterized in that, The correction of the heat transfer coefficient specifically includes: Calculate the sum of squares of the differences between the measured temperature value and the calculated temperature value. S : in, Indicates the current thermocouple position The experimental measurements Indicates the current thermocouple position Calculated temperature value; Determine if the variance and sum of squares S have reached their minimum. If convergence is achieved, output the optimal heat transfer coefficient; otherwise, correct the heat transfer coefficient. Among them, heat transfer coefficient It is a function of surface temperature.

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