A Temperature Field Simulation Method for the Roller Continuous Quenching Process Based on FLUENT

Abstract

The present invention discloses a method for simulating the temperature field in the roll continuous quenching process based on FLUENT, which includes the following steps: clarify the process machine equipment parameters in the roll quenching process according to the roll speed of the quenching machine and the relevant parameters of each cooling section of the quenching machine; use FLUENT to perform finite element analysis on the jet impingement cooling process of the steel plate in each cooling section and the flow cooling process of the retained water on the upper surface of the steel plate, and analyze the internal surface heat transfer situation of the steel plate in this cooling section based on the basic principle of incompressible fluid flow and the fluid-thermal-solid coupling finite element method to obtain the heat transfer boundary conditions of the steel plate in this cooling section; conduct quenching experiments according to the quenching process parameters in each cooling section, verify the heat transfer boundary conditions obtained by FLUENT, and make corrections; write the surface heat transfer load of the steel plate according to the corrected surface heat transfer conditions to obtain the temperature field in the actual roll continuous quenching process. The present invention can effectively reduce the experimental cost on the premise of ensuring the simulation accuracy and can obtain more accurate temperature field data in the roll continuous quenching process.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel heat treatment, and particularly relates to a method for simulating the temperature field of a roller continuous quenching process based on FLUENT. Background Art

[0002] Quenching can significantly improve the strength and hardness of steel plates and is an important process for producing high-performance and high-value-added steel plates. In recent years, in the heat treatment production workshops of medium and heavy plate enterprises, roller quenching machines are usually used to complete the quenching process of steel plates. Compared with other quenching methods, medium and heavy plate roller quenching has obvious advantages. During the roller quenching process, the steel plate is quenched while moving, with a large cooling intensity and uniform quenching. The steel plate can be cooled to room temperature at an extremely high cooling rate, with high production efficiency and good product quality. It is the preferred equipment for modern medium and heavy plate heat treatment production lines. However, the roller quenching process is complex and the cooling process is difficult to control. The rationality of the quenching process mainly depends on the quenching cooling rate and the uniformity of the steel plate cooling. Therefore, the calculation of the steel plate quenching temperature field, especially for the temperature field of the roller continuous quenching process, is a very important issue in the steel field.

[0003] In the existing research on the temperature field of the roller continuous quenching process, the experimental method is mostly used. By measuring the temperature drop data of the steel plate and using the inverse heat transfer method to calculate the average convective heat transfer coefficient, the average convective heat transfer coefficient is used as the boundary condition to calculate the quenching temperature field. However, this method cannot truly and objectively reflect the internal temperature change of the steel plate. The simulation results can only provide qualitative analysis and have poor flexibility. When the quenching process parameters change, industrial experiments need to be carried out again, resulting in high experimental costs. Or the numerical simulation method is used to directly simulate the temperature change during the steel plate moving quenching process. This method ignores the influence of boiling heat transfer caused by the high surface temperature of the steel plate at the initial stage of quenching. Therefore, this research method has a large error. Summary of the Invention

[0004] The present invention aims to provide a method for simulating the temperature field of a roller continuous quenching process based on FLUENT, so as to solve the problems in the previous research on the temperature field of the roller continuous quenching process, such as high industrial experiment costs, poor flexibility, inability to objectively and truly reflect the temperature change of the steel plate, and large errors in the direct numerical simulation process due to the omission of boiling heat transfer. On the premise of saving experimental costs and ensuring simulation accuracy, the simulation results can truly and objectively reflect the temperature change of the steel plate and provide a judgment basis for the rationality of the quenching process.

[0005] In order to achieve the above invention purpose, the present invention is implemented by adopting the following technical solutions:

[0006] A method for simulating the temperature field of a roller continuous quenching process based on FLUENT, characterized by comprising the following steps:

[0007] Step 1: Collect and analyze the equipment parameters of the roller quenching machine to clarify the roller quenching process parameters;

[0008] Step 2: Establish a heat transfer model on the steel plate surface based on FLUENT, simulate the heat transfer situation on the steel plate surface under the quenching process, and obtain the convective heat transfer coefficient on the steel plate surface; introduce an influence coefficient, that is, the ratio of the convective heat transfer coefficient value on the steel plate surface at different surface temperatures to the convective heat transfer coefficient value on the steel plate surface when the surface temperature is the set value. Through the relationship between the steel plate surface temperature and the influence coefficient, obtain the relational expression between the convective heat transfer coefficient on the steel plate surface and the steel plate surface temperature, and use this as the heat transfer boundary condition on the steel plate surface;

[0009] Step 3: Conduct a steel plate quenching experiment according to the actual quenching process parameters to obtain experimental temperature data; simulate the temperature field of the experimental steel plate according to the heat transfer boundary condition on the steel plate surface obtained in Step 2 to obtain simulation temperature data; compare and analyze the experimental temperature data and the simulation temperature data, and correct the heat transfer boundary condition on the steel plate surface by adjusting the influence coefficient to narrow the gap between the experimental temperature data and the simulation temperature data;

[0010] Step 4: According to the corrected heat transfer boundary condition on the steel plate surface, write a dynamic heat transfer load on the steel plate surface through the user-defined function UDF to conduct a temperature field simulation of the roller continuous quenching process;

[0011] Step 5: Analyze the actual problems based on the temperature field simulation results.

[0012] Preferably, the quenching process parameters in Step 1 include: the type of nozzle, the layout form, the jet velocity of each nozzle, the jet height, the jet angle, the steel plate size specification, and the steel grade; the equipment parameters include: the roller speed, the type of nozzle in each cooling section, the spacing between different cooling sections, and the effective length of the quenching machine.

[0013] Preferably, the heat transfer model on the steel plate surface in Step 2 includes a heat transfer model under the jet impact of the nozzle in each cooling section and a heat transfer simulation model on the steel plate surface under the flow cooling effect of the stagnant water on the upper surface of the steel plate between each cooling section.

[0014] Furthermore, establishing the heat transfer model under the jet impact of the nozzle in each cooling section includes the following steps:

[0015] 1) Establish a heat transfer simulation model on the steel plate surface under the jet impact of the nozzle in each cooling section. Through the clear process and equipment parameters in each cooling section, establish finite element mesh models of the nozzle, the steel plate, and the surrounding air in each cooling section respectively;

[0016] 2) Define the boundary conditions of each part, including the boundary conditions at the nozzle outlet and the steel plate surface;

[0017] 3) Import the finite element mesh models of the nozzles, steel plates, and surrounding air in each cooling section into FLUENT, perform mesh inspection, set up the calculation model, select the VOF for the multiphase flow model, adopt the Standard k-ε for the turbulence model, and at the same time consider the variation of the physical properties of the quenching medium water and the cooling steel plate with temperature;

[0018] 4) According to the actual quenching process parameters, assign initial values to the boundary conditions, including the initial value of the nozzle outlet velocity and the initial temperature of the steel plate surface;

[0019] 5) Set the solution method to the PISO algorithm, adopt the body forced weighted method for pressure discretization, and use the first-order upwind scheme for the discretization formats of turbulent kinetic energy and dissipation rate;

[0020] 6) Set the solution time step and perform FLUENT simulation operations;

[0021] 7) After the operation is completed, check the heat transfer situation on the steel plate surface and export the convective heat transfer coefficient on the inner surface of the steel plate in this cooling section;

[0022] 8) Taking the convective heat transfer coefficient at the steel plate surface temperature of 373K as the benchmark, introduce the influence coefficient, that is, divide the convective heat transfer coefficient value on the steel plate surface at different surface temperatures by the convective heat transfer coefficient value at the steel plate surface temperature of 373K, so as to obtain the relationship between the steel plate surface temperature and the influence coefficient. When the steel plate surface temperature changes to a certain temperature, multiply the influence coefficient at this temperature by the convective heat transfer coefficient at 373K, that is, obtain the convective heat transfer coefficient on the steel plate surface at this temperature, and obtain the relational expression between the convective heat transfer coefficient on the steel plate surface and the steel plate surface temperature under the jet impingement action in this cooling section, and use this as the heat transfer boundary condition on the steel plate surface.

[0023] Furthermore, the established simulation model for the heat transfer on the steel plate surface under the action of the flowing cooling of the stagnant water on the upper surface of the steel plate between each cooling section includes the following steps:

[0024] 1) Establish a simulation model for the heat transfer on the steel plate surface under the action of the flowing cooling of the stagnant water layer, and establish a two-dimensional finite element mesh model in the length-thickness direction of the steel plate according to the collected steel plate size specifications under the quenching process;

[0025] 2) Define the boundary conditions for each part, including the boundary conditions for the upper surface of the steel plate and the water inlet;

[0026] 3) Import the two-dimensional finite element mesh model in the length-thickness direction of the steel plate into FLUENT, perform mesh inspection, set up the calculation model, select the VOF for the multiphase flow model, adopt the Standard k-ε for the turbulence model, and at the same time insert the thermal physical properties of steel and water into the model;

[0027] 4) Assign an initial value to the water inlet velocity according to the actual situation, and assign an initial value of 373 K to the temperature of the upper surface of the steel plate. Set the solution method to the PISO algorithm, use the body forced weighted method for pressure discretization, and use the first-order upwind scheme for the discretization formats of turbulent kinetic energy and dissipation rate.

[0028] 5) Set the solution time step and perform FLUENT simulation calculations.

[0029] 6) After the operation is completed, check the heat transfer situation on the surface of the steel plate and export the convective heat transfer coefficient on the surface of the steel plate under this flow velocity condition of the water flow.

[0030] 7) Repeat steps 4) - 7), continuously change the water flow velocity, and it can be known the convective heat transfer coefficient on the surface of the steel plate under different flow velocity conditions of the water flow. From this, the relationship curve between the flow velocity and the convective heat transfer coefficient on the surface of the steel plate under the water cooling effect can be obtained.

[0031] 8) According to the equipment and process parameters specified in step 1, the equipment parameters include the spacing between each cooling section and the nozzle type, and the process parameters include the jet velocity, jet angle, and jet height. Establish a finite element mesh model of the flow field between each cooling section of the quenching machine.

[0032] 9) Define the boundary conditions for each part, including the boundary conditions for each nozzle and the steel plate wall surface.

[0033] 10) Import the finite element mesh model of the flow field between each cooling section of the quenching machine into FLUENT, perform mesh inspection, set the calculation model, select the VOF for the multiphase flow model, and use the Standard k - ε for the turbulence model.

[0034] 11) Assign initial values to the boundary conditions according to the actual situation, including the initial value of the outlet velocity of each nozzle.

[0035] 12) Set the solution method to the PISO algorithm, use the body forced weighted method for pressure discretization, and use the first-order upwind scheme for the discretization formats of turbulent kinetic energy and dissipation rate.

[0036] 13) Set a sufficiently long solution time step and perform FLUENT simulation calculations.

[0037] 14) After the simulation calculation is completed, check the flow field distribution situation of each cooling section, judge whether the flow field is stable, and after stabilization, export the flow field velocity between the cooling sections to obtain the flow field velocity distribution curve between each cooling section.

[0038] 15) Multiply the obtained curve of the flow velocity and the convective heat transfer coefficient on the surface of the steel plate by the flow field velocity distribution curve between each cooling section to obtain the distribution situation of the convective heat transfer coefficient on the surface of the steel plate under the water cooling effect between each cooling section of the quenching machine.

[0039] Preferably, the correction of the heat transfer boundary condition on the steel plate surface in step 3 includes the following steps:

[0040] 1) Establish an experimental model based on the heat transfer model of the steel plate surface established in step 2;

[0041] 2) According to the actual quenching process parameters, conduct a steel plate quenching experiment, measure the cooling conditions at different positions of the steel plate, and obtain experimental temperature data;

[0042] 3) According to the heat transfer boundary condition of the steel plate surface obtained by simulation analysis in step 2, simulate the temperature field of the experimental steel plate to obtain simulation temperature data;

[0043] 4) Compare and analyze the experimental temperature data with the simulation temperature data, adjust the influence coefficient, correct the heat transfer boundary condition of the steel plate surface, and narrow the gap between the experimental temperature data and the simulation temperature data;

[0044] 5) When the gap between the experimental temperature data and the simulation temperature data reaches the expected range, the correction of the simulation heat transfer boundary condition is completed, and the heat transfer boundary condition of the steel plate surface adopted is directly applied to the heat transfer condition of the steel plate surface under the jet impingement of each nozzle in the actual working condition, and the relationship between the accurate convective heat transfer coefficient of the steel plate surface and the steel plate temperature is obtained.

[0045] Preferably, the writing of the dynamic heat transfer load on the steel plate surface by using the user-defined function UDF in step 4 includes the following steps:

[0046] 1) Based on the relevant parameters collected in step 1, since the heat transfer form at the same part of the steel plate surface is different at different times and the spatial coordinate positions are also different, use F_CENTROID(y,f,t) to obtain the grid coordinate position of the steel plate surface and RP_Get_Real("flow-time") to obtain the simulation initial time, and obtain the relationship between the position of the steel plate during the quenching process in time and space;

[0047] 2) Based on the corrected heat transfer boundary condition of the steel plate surface in step 3, use F_T(f,t) to obtain the real-time temperature of the grid surface, that is, the real-time temperature of the steel plate surface, so as to accurately describe the heat transfer situation on the steel plate surface during the roller quenching process;

[0048] 3) Write the dynamic heat transfer load on the steel plate surface based on the relationship between the position of the steel plate in space and time and the real-time temperature data of the steel plate surface. The movement of a certain part of the steel plate to a certain cooling section at a certain moment is described by the relationship between position and time, and the heat transfer situation is described by the relationship between the obtained real-time steel plate surface temperature and the convective heat transfer coefficient;

[0049] 4) Insert the written dynamic heat transfer load into the FLUENT model to complete the temperature field simulation of the roller continuous quenching process.

[0050] Preferably, the heat transfer boundary condition on the steel plate surface described in step 2 includes the heat transfer boundary condition under nozzle jet impingement and the heat transfer boundary condition of running water on the upper surface of the steel plate, and the convective heat transfer coefficient on the steel plate surface is obtained through simulation.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] The present invention discloses a method for simulating the temperature field in the roller continuous quenching process based on FLUENT. Aiming at the cooling characteristics of the roller continuous quenching process, this method uses simulation to obtain the heat transfer boundary conditions on the steel plate surface. The heat transfer boundaries include the heat transfer boundary condition under nozzle jet impingement and the heat transfer boundary condition of running water on the upper surface of the steel plate. Influence coefficients are introduced, and thus the distribution of the convective heat transfer coefficient at any temperature on the steel plate surface can be known; an experimental model is established through the simulation model, and experimental temperature data are obtained. Taking the convective heat transfer coefficient obtained by simulation as the boundary condition, simulation temperature data are obtained. By comparing the two and continuously correcting the influence coefficients, the purpose of correcting the heat transfer boundary conditions obtained by simulation is achieved. The relationship between the corrected influence coefficient and the steel plate surface temperature can be directly applied to the heat transfer conditions on the steel plate surface under the action of jet impingement of each nozzle in the actual working condition, and the relationship between the accurate convective heat transfer coefficient on the steel plate surface and the steel plate surface temperature can be obtained; based on the known relationship between the convective heat transfer coefficient on the steel plate surface and the steel plate surface temperature, a dynamic heat transfer load is compiled and inserted into the FLUENT model, and thus the temperature field in the roller continuous quenching process can be obtained.

[0053] Based on the simulation model, the present invention establishes an experimental model to verify and correct the simulation, obtains appropriate influence coefficients, and avoids industrial experiments on the premise of verifying the simulation results, reducing the experimental cost. The simulation of the roller continuous quenching process is carried out through computer software, improving the simulation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is the flow chart of the present invention;

[0055] Figure 2 is the finite element mesh model of heat transfer under the action of nozzle jet impingement;

[0056] Figure 3 is the simulation result of heat transfer under the action of jet impingement;

[0057] Figure 4 is the curve of the influence coefficient initially adopted;

[0058] Figure 5 is the finite element mesh model of heat transfer simulation on the steel plate surface under the action of the flowing cooling of the stagnant water on the upper surface of the steel plate;

[0059] Figure 6 is the distribution of the convective heat transfer coefficient on the steel plate surface under the condition of a 5 mm thick water layer and a flow velocity of 1 m / s;

[0060] Figure 7 It is the relationship curve between the flow velocity and the convective heat transfer coefficient on the steel plate surface under the action of flowing water cooling;

[0061] Figure 8 It is the flow field distribution between cooling sections;

[0062] Figure 9 It is the flow field velocity distribution curve between cooling sections;

[0063] Figure 10 It is the comparison of the experimental and simulation temperature data after correction;

[0064] Figure 11 It is the relationship curve between the corrected influence coefficient and the steel plate surface temperature;

[0065] Figure 12 It is the change curve of the temperatures of the upper and lower surfaces and the core of the steel plate with time during the roller continuous quenching process. Specific implementation mode

[0066] The technical solution of the present invention will be further described in detail below.

[0067] Example 1

[0068] Refer to Figure 1 , the present invention provides a temperature field simulation method for the roller continuous quenching process based on FLUENT, including the following steps:

[0069] Step 1: Collect and analyze the equipment parameters of the roller quenching machine, and clarify the roller quenching process parameters;

[0070] Step 2: Based on FLUENT, establish a heat transfer model on the steel plate surface, conduct a simulation analysis of the heat transfer situation on the steel plate surface under this quenching process, and obtain the heat transfer boundary conditions on the steel plate surface;

[0071] Step 3: According to the quenching process parameters of each cooling section in the quenching machine, conduct a quenching experiment, verify the heat transfer boundary conditions obtained by FLUENT analysis, and correct the heat transfer boundary conditions;

[0072] Step 4: According to the corrected heat transfer boundary conditions of the steel plate, write the dynamic heat transfer load on the steel plate surface through the user-defined function (UDF) to conduct a temperature field simulation of the roller continuous quenching process;

[0073] Step 5: Analyze the actual problems based on the temperature field simulation results.

[0074] The quenching process parameters in Step 1 include: the type of nozzle, the arrangement form, the jet velocity of each nozzle, the jet height, the jet angle, the size specification of the steel plate, and the steel grade; the equipment parameters include: the roll speed, the type of nozzle in each cooling section, the spacing between different cooling sections, and the effective length of the quenching machine.

[0075] The heat transfer model of the steel plate surface in Step 2 includes the heat transfer model under the jet impingement of the nozzles in each cooling section and the heat transfer simulation model of the steel plate surface under the flow cooling of the stagnant water on the upper surface of the steel plate between each cooling section.

[0076] The steps for establishing the heat transfer model under the jet impingement of the nozzles in each cooling section are as follows:

[0077] 1) Establish a heat transfer simulation model of the steel plate surface under the jet impingement of the nozzles in each cooling section. By specifying the process and equipment parameters in each cooling section, establish a finite element mesh model of the nozzles, the steel plate, and the surrounding air in each cooling section respectively.

[0078] 2) Define the boundary conditions of each part, such as the nozzle outlet, the steel plate surface, etc.

[0079] 3) Import the finite element mesh models of the nozzles, the steel plate, and the surrounding air in each cooling section into FLUENT, perform mesh inspection, set the calculation model, select the VOF for the multiphase flow model, adopt the Stand k-ε for the turbulence model, and at the same time consider the variation of the physical properties of the quenching medium water and the cooling steel plate with temperature.

[0080] 4) According to the actual quenching process parameters, assign the initial values to the boundary conditions, such as the nozzle outlet velocity and the initial temperature of the steel plate.

[0081] 5) Set the solution method as the improved PISO algorithm of the segregated solution SIMPLE, adopt the bodyforced weighted method for pressure discretization, and the discretization format of the turbulent kinetic energy and dissipation rate is the first-order upwind format.

[0082] 6) Set the solution time step and perform FLUENT simulation operation.

[0083] 7) After the operation is completed, check the heat transfer situation of the steel plate surface and export the convective heat transfer coefficient of the inner surface of the steel plate in this cooling section.

[0084] 8) Taking the convective heat transfer coefficient at the steel plate surface temperature of 373K as the benchmark, an influence coefficient is introduced. The convective heat transfer coefficient value of the steel plate at different surface temperatures is divided by the convective heat transfer coefficient value at the steel plate surface temperature of 373K, so as to obtain the relationship between the steel plate surface temperature and the influence coefficient. When the steel plate surface temperature changes to a certain temperature, the influence coefficient at this temperature is multiplied by the convective heat transfer coefficient at 373K, that is, the convective heat transfer coefficient of the steel plate at this temperature is obtained. The relational expression between the convective heat transfer coefficient on the steel plate surface under the action of jet impingement and the steel plate surface temperature in this cooling section is obtained and used as the heat transfer boundary condition of the steel plate.

[0085] The established simulation model of heat transfer on the steel plate surface under the flow cooling of the retained water on the upper surface of the steel plate between each cooling section includes the following steps:

[0086] 1) Establish a simulation model of heat transfer on the steel plate surface under the flow cooling of the retained water layer. According to the collected steel plate size specifications under this quenching process, a two-dimensional finite element mesh model in the length-thickness direction of the steel plate is established;

[0087] 2) Define the boundary conditions of each part, such as the upper surface of the steel plate, the water inlet and outlet, etc.;

[0088] 3) Import the two-dimensional finite element mesh model in the length-thickness direction of the steel plate into FLUENT, check the mesh, set the calculation model, select the VOF for the multiphase flow model, adopt the Stand k-ε for the turbulence model, and insert the thermal physical properties of steel and water into the model at the same time;

[0089] 4) Assign the initial value to the water inlet according to the actual situation, and assign the initial value of the steel plate temperature as 373K;

[0090] Set the solution method as the improved PISO algorithm of the segregated solution SIMPLE, adopt the bodyforcedweighted method for pressure discretization, and the discretization format of turbulent kinetic energy and dissipation rate is the first-order upwind format;

[0091] 5) Set the solution time step and perform the FLUENT simulation operation;

[0092] 6) After the operation is completed, check the heat transfer situation on the steel plate surface and export the convective heat transfer coefficient on the steel plate surface under this water flow velocity condition;

[0093] 7) Repeat steps 4) to 7), continuously change the water flow velocity, and it can be known the convective heat transfer coefficient on the steel plate surface under different water flow velocity conditions. Thus, the relationship curve between the water flow velocity and the convective heat transfer coefficient on the steel plate surface under the water flow cooling can be obtained;

[0094] 8) Based on the equipment and process parameters identified in step 1, where the equipment parameters include the spacing between each cooling section and the nozzle type, and the process parameters include the jet velocity, jet angle, jet height, etc., establish a finite element mesh model of the flow field between the cooling sections of the quenching machine;

[0095] 9) Define the boundary conditions for each part, such as each nozzle, the steel plate wall surface, etc.;

[0096] 10) Import the finite element mesh model of the flow field between the cooling sections of the quenching machine into FLUENT, perform mesh inspection, set the calculation model, select the VOF for the multiphase flow model, and adopt the Standard k-ε for the turbulence model;

[0097] 11) Assign initial values to the boundary conditions according to the actual situation, such as the outlet velocity of each nozzle;

[0098] 12) Set the solution method as the improved PISO algorithm of the segregated solution SIMPLE, adopt the body forced weighted method for pressure discretization, and the discretization format of turbulent kinetic energy and dissipation rate is the first-order upwind format;

[0099] 13) Set a sufficiently long solution time step and perform FLUENT simulation operations;

[0100] 14) After the simulation operations are completed, check the flow field distribution of each cooling section, judge whether the flow field is stable, and after stabilization, export the flow field velocity between the cooling sections to obtain the flow field velocity distribution curve between each cooling section;

[0101] 15) Multiply the obtained flow velocity by the convective heat transfer coefficient curve on the steel plate surface and the flow field velocity distribution curve between each cooling section to obtain the distribution of the convective heat transfer coefficient on the steel plate surface under the water cooling effect between the cooling sections of the quenching machine;

[0102] Step 3 for modifying the heat transfer boundary conditions specifically includes the following steps:

[0103] 1) According to the FLUENT simulation model in different cooling sections inside the roller quenching machine established in step 2, design an experimental model;

[0104] 2) Based on the actual quenching process parameters, conduct a steel plate quenching experiment, measure the cooling conditions at different positions of the steel plate, and obtain experimental temperature data;

[0105] 3) Take the heat transfer boundary conditions on the steel plate surface obtained by simulation in step 2) as the boundary conditions, simulate the temperature field of the experimental steel plate, and obtain simulation temperature data;

[0106] 4) Compare and analyze the experimental temperature data with the simulation temperature data, adjust the influence coefficient, modify the heat transfer boundary conditions on the steel plate surface, and narrow the gap between the experimental temperature data and the simulation temperature data;

[0107] 5) The gap between the experimental and simulation temperature data reaches the expected range. The correction of the simulation heat transfer boundary conditions is completed. The relationship between the convective heat transfer coefficient on the steel plate surface and the steel plate surface temperature can be directly applied to the heat transfer conditions on the steel plate surface under the jet impingement of each nozzle in the actual working conditions, and the relationship between the accurate convective heat transfer coefficient on the steel plate surface and the steel plate surface temperature can be obtained.

[0108] The steps for writing the dynamic heat transfer load on the steel plate surface in step 4 are as follows:

[0109] 1) Based on the relevant parameters collected in step 1, the heat transfer forms at different times at the same position on the steel plate surface are different, and the spatial coordinate positions are also different. Use F_CENTROID(y, f, t) to obtain the grid coordinate position on the steel plate surface and RP_Get_Real("flow-time") to obtain the simulation initial time, so as to obtain the relationship between the position of the steel plate during quenching in terms of time and space;

[0110] 2) Based on the relationship between the corrected convective heat transfer coefficient on the steel plate surface and the steel plate surface temperature obtained in step 3, use F_T(f, t) to obtain the real-time temperature on the grid surface, that is, the real-time temperature on the steel plate surface, so as to accurately describe the heat transfer situation on the steel plate surface during the roller quenching process;

[0111] 3) Write the dynamic heat transfer load on the steel plate surface based on the relationship between the steel plate in terms of spatial position and time and the real-time temperature data on the steel plate surface. The movement of a certain part of the steel plate to a certain cooling section at a certain moment is described by the relationship between position and time, and the heat transfer situation is described by the relationship between the obtained real-time temperature on the steel plate surface and the convective heat transfer coefficient;

[0112] 4) Insert the written dynamic heat transfer load into the FLUENT model to complete the temperature field simulation of the roller continuous quenching process.

[0113] Based on the obtained temperature field of the roller continuous quenching process of the present invention, it can truly and objectively reflect the temperature change situation of any part of the steel plate at any time, thus providing a judgment basis for formulating a reasonable quenching process.

[0114] Figure 12 It is the curve of the temperature change of the upper and lower surfaces and the core of the steel plate during the roller continuous quenching process with time.

[0115] Example Two

[0116] In this example, for the N800CF steel plate, a method for simulating the temperature field of the roller continuous quenching process based on FLUENT is provided, which specifically includes the following steps:

[0117] 1) Collect and analyze the equipment parameters of the roller quenching machine, and clarify the roller quenching process parameters. The equipment parameters to be clarified include: the nozzle types of the quenching machine include slot nozzles and circular nozzles, the spacing between each cooling section is 600 / 800 mm, the nozzle layout form within each cooling section, the effective quenching length of the quenching machine is 23000 mm, the roller speed is 0.045 m / s, etc.; the process parameters to be clarified include: the jet outlet velocity, jet height, and jet angle of each nozzle, the steel plate specifications: 8000×3000×58 mm, the steel grade is N800CF, etc.;

[0118] 2) Based on FLUENT, establish a heat transfer model on the steel plate surface, and conduct a simulation analysis of the heat transfer situation on the steel plate surface under this quenching process. Establish a heat transfer model under the jet impact of the nozzles within each cooling section and a simulation model of the heat transfer on the steel plate surface under the flow cooling effect of the stagnant water on the upper surface of the steel plate between each cooling section, so as to obtain the heat transfer boundary conditions on the steel plate surface;

[0119] 3) According to the quenching process parameters of each cooling section in the quenching machine, design and conduct quenching experiments to obtain experimental data. Use the heat transfer boundary obtained by FLUENT analysis as the model boundary conditions, simulate the temperature field, compare the differences between the model and the experiment, and correct the heat transfer boundary conditions;

[0120] 4) According to the corrected heat transfer boundary conditions of the steel plate, write the dynamic heat transfer load on the steel plate surface through the user-defined function (UDF) to conduct a temperature field simulation of the continuous roller quenching process;

[0121] 5) Analyze the actual problems based on the temperature field simulation results.

[0122] The heat transfer model established under the jet impact of the nozzles within each cooling section in step 2) is specifically as follows:

[0123] 201) Establish a heat transfer simulation model on the steel plate surface under the jet impact of the nozzles within each cooling section. Through the clear process and equipment parameters within the cooling section, establish a finite element mesh model of the nozzles, steel plate, and surrounding air within each cooling section. The jet height of the slot nozzle is 30 mm, and the jet angle is 25°. The established finite element mesh model is shown in Figure 2 ;

[0124] 202) Define the boundary conditions of each part. The nozzle outlet adopts the Velocity–inlet, the steel plate surface adopts the no-slip wall condition, and the remaining boundaries adopt the Pressure-outlet;

[0125] 203) Import the finite element mesh model of the nozzles, steel plate, and surrounding air within each cooling section into FLUENT, conduct mesh inspection, set the calculation model, select the VOF for the multiphase flow model, adopt the Stand k-ε for the turbulence model, and at the same time consider the variation of the physical properties of the quenching medium water and the cooling steel plate with temperature;

[0126] 204) According to the actual quenching process parameters, initial values of boundary conditions are assigned. The nozzle outlet velocity is 31.5 m / s, the water temperature is 300 K, the initial temperature of the steel plate is 373 K, and the pressure outlet pressure value is 0 Pa;

[0127] 205) Set the solution method as the improved PISO algorithm of the segregated solution SIMPLE. The pressure discretization adopts the body forced weighted method, and the discretization formats of turbulent kinetic energy and dissipation rate are the first-order upwind format;

[0128] 206) Set the solution time step and perform FLUENT simulation operations;

[0129] 207) After the operation is completed, check the heat transfer situation on the surface of the steel plate, and export the convective heat transfer coefficient on the inner surface of the steel plate in this cooling section as shown in Figure 3 ;

[0130] 208) Taking the convective heat transfer coefficient when the surface temperature of the steel plate is 373 K as the benchmark, introduce the influence coefficient, as shown in Figure 4 , divide the convective heat transfer coefficient value of the steel plate at different surface temperatures by the convective heat transfer coefficient value when the surface temperature of the steel plate is 373 K, and thus obtain the relationship between the surface temperature of the steel plate and the influence coefficient. When the surface temperature of the steel plate changes to a certain temperature, multiply the influence coefficient at this temperature by the convective heat transfer coefficient at 373 K, that is, obtain the convective heat transfer coefficient of the steel plate at this temperature, and obtain the relational expression between the convective heat transfer coefficient on the surface of the steel plate and the surface temperature of the steel plate under the action of jet impingement in this cooling section, and use this as the heat transfer boundary condition of the steel plate.

[0131] The specific heat transfer simulation model of the steel plate surface under the action of the stagnant water flow cooling established in step 2) is as follows:

[0132] 201) Establish a heat transfer simulation model of the steel plate surface under the action of the stagnant water layer flow cooling. According to the collected steel plate size specifications under this quenching process, establish a two-dimensional finite element mesh model in the length-thickness direction of the steel plate. The water layer thickness is taken as 5 mm, and the established finite element mesh model is shown in Figure 5 ;

[0133] 202) Define the boundary conditions of each part. The upper surface of the steel plate adopts the no-slip wall condition, the water flow inlet adopts Velocity–inlet, the outlet adopts Pressure-outlet, and the atmospheric boundary adopts Pressure-inlet;

[0134] 203) Import the finite element mesh model into FLUENT, perform mesh inspection, set the calculation model, select the VOF for the multiphase flow model, adopt the Stand k-ε for the turbulence model, and insert the thermal physical parameters of steel and water into the model at the same time;

[0135] 204) Assign an initial value to the water inlet according to the actual situation, take the water flow velocity as 1 m / s, assign the initial value of the steel plate temperature as 373 K, and the pressure values at the pressure inlet and outlet are 0 Pa;

[0136] 205) Set the solution method as the improved PISO algorithm of the segregated solution SIMPLE. The pressure discretization adopts the bodyforced weighted method, and the discretization formats of the turbulent kinetic energy and dissipation rate are the first-order upwind format;

[0137] 206) Set the solution time step and perform the FLUENT simulation operation;

[0138] 207) After the operation is completed, check the heat transfer situation on the steel plate surface, and export the convective heat transfer coefficient on the steel plate surface under this flow velocity condition, as shown in Figure 6 ;

[0139] 208) Repeat steps 204) - 207). According to the actual conditions of the working conditions, the water outlet velocity can meet the requirements when it is selected between 0.045 m / s and 30 m / s. From this, the convective heat transfer coefficient on the steel plate surface under different flow velocities can be known, and the relationship curve between the flow velocity and the convective heat transfer coefficient on the steel plate surface under the action of flowing water cooling can be obtained, as shown in Figure 7 ;

[0140] 209) Based on the determined equipment and process parameters, the equipment parameters include the spacing between each cooling section and the nozzle type, and the process parameters include the jet velocity, jet angle, jet height, etc. Establish a finite element mesh model of the flow field between each cooling section of the quenching machine. The nozzle spacing between the two cooling sections is 600 mm, and a finite element mesh model is established according to the nozzle layout form, jet height, etc. of each cooling section;

[0141] 209) Define the boundary conditions of each part. The nozzle outlet adopts the Velocity–inlet, the steel plate surface adopts the no-slip wall condition, and the remaining boundaries adopt the Pressure-outlet;

[0142] 210) Import the finite element mesh model into FLUENT, perform mesh inspection, set the calculation model, select the VOF for the multiphase flow model, and adopt the Stand k-ε for the turbulent model;

[0143] 211) Assign the initial values to the boundary conditions according to the actual situation, such as the outlet velocity of each nozzle;

[0144] 212) Set the solution method as the improved PISO algorithm of the segregated solution SIMPLE. The pressure discretization adopts the bodyforced weighted method, and the discretization formats of the turbulent kinetic energy and dissipation rate are the first-order upwind format;

[0145] 213) Set a sufficiently long solution time step for FLUENT simulation operation;

[0146] 214) After the simulation operation is completed, check the flow field distribution between each cooling section, as shown in Figure 8 , determine whether the flow field has stabilized. After stabilization, export the flow field velocity between the cooling sections to obtain the flow field velocity distribution curve between each cooling section, as shown in Figure 9 ;

[0147] 215) Multiply the obtained flow velocity and the convective heat transfer coefficient curve on the steel plate surface by the flow field velocity distribution curve between each cooling section to obtain the convective heat transfer coefficient distribution on the steel plate surface under the water cooling action between each cooling section of the quenching machine.

[0148] The specific steps for step 3) to correct the heat transfer boundary conditions are as follows:

[0149] 301) Design an experimental model based on the FLUENT simulation model in different cooling sections of the roller quenching machine established in step 2);

[0150] 302) According to the actual quenching process parameters, conduct a steel plate quenching experiment, measure the cooling conditions at different positions of the steel plate, and obtain experimental temperature data;

[0151] 303) Use the heat transfer boundary condition on the steel plate surface obtained by simulation in step 2) as the boundary condition to simulate the temperature field of the experimental steel plate and obtain simulation temperature data;

[0152] 304) Compare and analyze the experimental temperature data with the simulation temperature data, adjust the influence coefficient, correct the heat transfer boundary condition on the steel plate surface, and narrow the gap between the experimental temperature data and the simulation temperature data;

[0153] 305) When the gap between the experimental and simulation temperature data reaches the expected range, as shown in Figure 10 , the correction of the simulation heat transfer boundary condition is completed. The relationship between the convective heat transfer coefficient on the steel plate surface and the steel plate surface temperature can be directly applied to the heat transfer conditions on the steel plate surface under the jet impingement of each nozzle in the actual working condition to obtain an accurate relationship between the convective heat transfer coefficient on the steel plate surface and the steel plate temperature. The corrected influence coefficient is shown in Figure 11 ;

[0154] The specific dynamic heat transfer load on the steel plate surface in step 4) is as follows:

[0155] 401) Based on the relevant parameters collected in step 1), the heat transfer form at the same part of the steel plate surface is different at different times, and the spatial coordinate positions are also different. Use F_CENTROID(y, f, t) to obtain the grid coordinate position on the steel plate surface and RP_Get_Real("flow-time") to obtain the initial simulation time, and obtain the time and space relationship of the steel plate position during the quenching process;

[0156] 402) According to the relationship between the corrected convective heat transfer coefficient on the steel plate surface and the steel plate surface temperature obtained in step 3), use F_T(f,t) to obtain the real-time temperature of the grid surface, that is, the real-time temperature of the steel plate surface, so as to accurately describe the heat transfer situation on the steel plate surface during the roller quenching process;

[0157] 403) Compile the dynamic heat transfer load on the steel plate surface according to the relationship between the steel plate in terms of spatial position and time and the real-time temperature data of the steel plate surface. The movement of a certain part of the steel plate to a certain cooling section at a certain moment is described by the relationship between position and time, and the heat transfer situation is described by the relationship between the obtained real-time steel plate surface temperature and the convective heat transfer coefficient;

[0158] 404) Insert the compiled dynamic heat transfer load into the FLUENT model to complete the temperature field simulation of the roller continuous quenching process. The simulation results are shown in Figure 12 。

[0159] In addition to the above embodiments, the present invention may also have other embodiments. All technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. A temperature field simulation method for the roller continuous quenching process based on FLUENT, characterized in that It includes the following steps: Step 1: Collect and analyze the equipment parameters of the roller quenching machine, and clarify the roller quenching process parameters; Step 2: Based on FLUENT, establish a heat transfer model on the steel plate surface, simulate the heat transfer situation on the steel plate surface under the quenching process, and obtain the convective heat transfer coefficient on the steel plate surface; introduce an influence coefficient, that is, the ratio of the convective heat transfer coefficient value on the steel plate surface at different surface temperatures to the convective heat transfer coefficient value on the steel plate surface when the surface temperature is the set value. Through the relationship between the steel plate surface temperature and the influence coefficient, obtain the relational expression between the convective heat transfer coefficient on the steel plate surface and the steel plate surface temperature, and use this as the heat transfer boundary condition on the steel plate surface; The heat transfer model on the steel plate surface includes a heat transfer model under the jet impingement of nozzles in each cooling section and a heat transfer simulation model on the steel plate surface under the flow cooling of the stagnant water on the upper surface of the steel plate between each cooling section; Establishing the heat transfer model under the jet impingement of nozzles in each cooling section includes the following steps: 1) Establish a heat transfer simulation model on the steel plate surface under the jet impingement of nozzles in each cooling section. Through the clear process and equipment parameters in each cooling section, establish a finite element mesh model of the nozzles, steel plate and surrounding air in each cooling section respectively; 2) Define the boundary conditions of each part, including the boundary conditions at the nozzle outlet and the steel plate surface; 3) Import the finite element mesh models of the nozzles, steel plate and surrounding air in each cooling section into FLUENT, conduct mesh inspection, set the calculation model, select the VOF for the multiphase flow model and the Stand k-ε for the turbulence model, and at the same time consider the variation of the physical properties of the quenching medium water and the cooling steel plate with temperature; 4) According to the actual quenching process parameters, assign initial values to the boundary conditions, including the initial value of the nozzle outlet velocity and the initial temperature of the steel plate surface; 5) Set the solution method as the PISO algorithm, adopt the body forced weighted method for pressure discretization, and the discretization format of turbulent kinetic energy and dissipation rate as the first-order upwind format; 6) Set the solution time step and conduct FLUENT simulation operation; 7) After the operation is completed, check the heat transfer situation on the steel plate surface and export the convective heat transfer coefficient on the inner surface of the steel plate in this cooling section; 8) Based on the convective heat transfer coefficient when the steel plate surface temperature is 373K as the benchmark, introduce an influence coefficient, that is, divide the convective heat transfer coefficient value on the steel plate surface at different surface temperatures by the convective heat transfer coefficient value on the steel plate surface at 373K. Thus, obtain the relationship between the steel plate surface temperature and the influence coefficient. When the steel plate surface temperature changes to a certain temperature, multiply the influence coefficient at this temperature by the convective heat transfer coefficient at 373K, that is, obtain the convective heat transfer coefficient on the steel plate surface at this temperature, and obtain the relational expression between the convective heat transfer coefficient on the steel plate surface under the jet impingement in this cooling section and the steel plate surface temperature, and use this as the heat transfer boundary condition on the steel plate surface; Step 3: Conduct a quenching experiment on the steel plate according to the actual quenching process parameters to obtain experimental temperature data; simulate the temperature field of the experimental steel plate based on the heat transfer boundary conditions of the steel plate surface obtained in Step 2 to obtain simulation temperature data; compare and analyze the experimental temperature data with the simulation temperature data, and correct the heat transfer boundary conditions of the steel plate surface by adjusting the influence coefficient to narrow the gap between the experimental temperature data and the simulation temperature data. Step 4: Write a dynamic heat transfer load on the steel plate surface through a user-defined function (UDF) according to the corrected heat transfer boundary conditions of the steel plate surface, and conduct a temperature field simulation of the roller continuous quenching process. Step 5: Analyze the actual problems based on the temperature field simulation results.

2. The temperature field simulation method for the roller continuous quenching process based on FLUENT according to claim 1, wherein The quenching process parameters in Step 1 include: the type of nozzle, the layout form, the jet velocity of each nozzle, the jet height, the jet angle, the size specification of the steel plate, and the steel grade; the equipment parameters include: the roller speed, the type of nozzle in each cooling section, the spacing between different cooling sections, and the effective length of the quenching machine.

3. The temperature field simulation method for the roller continuous quenching process based on FLUENT according to claim 1, wherein The steps for establishing a heat transfer simulation model of the steel plate surface under the action of the flowing and cooling of the stagnant water on the upper surface of the steel plate between each cooling section are as follows: 1) Establish a heat transfer simulation model of the steel plate surface under the action of the flowing and cooling of the stagnant water layer, and establish a two-dimensional finite element mesh model in the length-thickness direction of the steel plate according to the size specification of the steel plate under the collected quenching process. 2) Define the boundary conditions of each part, including the boundary conditions of the upper surface of the steel plate and the water inlet boundary. 3) Import the two-dimensional finite element mesh model in the length-thickness direction of the steel plate into FLUENT, conduct mesh inspection, set the calculation model, select the VOF for the multiphase flow model, and adopt the Standard k-ε for the turbulence model. At the same time, insert the thermal physical properties of steel and water into the model. 4) Assign an initial value to the water inlet velocity according to the actual situation, and assign an initial value of 373K to the temperature of the upper surface of the steel plate; set the solution method as the PISO algorithm, adopt the body forced weighted method for pressure discretization, and the discretization format of turbulent kinetic energy and dissipation rate is the first-order upwind format. 5) Set the solution time step and conduct FLUENT simulation operations. 6) After the operation is completed, check the heat transfer situation on the steel plate surface and export the convective heat transfer coefficient of the steel plate surface under the water inlet velocity of the water flow. 7) Repeat Steps 4) - 6), continuously change the water inlet velocity, and it can be known the convective heat transfer coefficient of the steel plate surface under different flow velocities of the water flow, so as to obtain the relationship curve between the flow velocity and the convective heat transfer coefficient of the steel plate surface under the action of water cooling. 8) According to the equipment and process parameters specified in Step 1, the equipment parameters include the spacing between each cooling section and the type of nozzle, and the process parameters include the jet velocity, the jet angle, and the jet height. Establish a finite element mesh model of the flow field between each cooling section of the quenching machine. 9) Define the boundary conditions of each part, including the boundary conditions of each nozzle and the steel plate wall surface. 10) Import the finite element mesh model of the flow field between each cooling section of the quenching machine into FLUENT, conduct mesh inspection, set the calculation model, select the VOF for the multiphase flow model, and adopt the Standard k-ε for the turbulence model. 11) Assign initial values to the boundary conditions according to the actual situation, including the initial value of the outlet velocity of each nozzle. 12) Set the solution method to the PISO algorithm, use the body forced weighted method for pressure discretization, and use the first-order upwind scheme for the discretization formats of turbulent kinetic energy and dissipation rate; 13) Set a sufficiently long solution time step and perform FLUENT simulation operations; 14) After the simulation operations are completed, check the flow field distribution in each cooling section, determine whether the flow field has stabilized, and export the flow field velocity between the cooling sections after stabilization to obtain the flow field velocity distribution curve between each cooling section; 15) Multiply the obtained flow velocity and the convective heat transfer coefficient curve on the steel plate surface by the flow field velocity distribution curve between each cooling section to obtain the convective heat transfer coefficient distribution on the steel plate surface under the action of flowing water cooling between each cooling section of the quenching machine.

4. The method for simulating the temperature field of the roller continuous quenching process based on FLUENT according to claim 1, characterized in that The correction of the heat transfer boundary condition on the steel plate surface in step 3 includes the following steps: 1) Establish an experimental model based on the heat transfer model on the steel plate surface established in step 2; 2) Conduct a steel plate quenching experiment according to the actual quenching process parameters, measure the cooling conditions at different positions of the steel plate, and obtain experimental temperature data; 3) Simulate the temperature field of the experimental steel plate according to the heat transfer boundary condition on the steel plate surface obtained by the simulation analysis in step 2 to obtain simulation temperature data; 4) Compare and analyze the experimental temperature data with the simulation temperature data, adjust the influence coefficient, correct the heat transfer boundary condition on the steel plate surface, and narrow the gap between the experimental temperature data and the simulation temperature data; 5) When the gap between the experimental temperature data and the simulation temperature data reaches the expected requirement range, the correction of the simulation heat transfer boundary condition is completed, and the heat transfer boundary condition on the steel plate surface adopted is directly applied to the heat transfer condition on the steel plate surface under the jet impingement of each nozzle in the actual working condition to obtain the accurate relationship between the convective heat transfer coefficient on the steel plate surface and the steel plate temperature.

5. The temperature field simulation method for the roller continuous quenching process based on FLUENT according to claim 1, characterized in that The writing of the dynamic heat transfer load on the steel plate surface through the user-defined function UDF in step 4 includes the following steps: 1) According to the relevant parameters collected in step 1, the heat transfer forms at the same part of the steel plate surface are different at different times, and the spatial coordinate positions are also different. Use F_CENTROID(y, f, t) to obtain the grid coordinate position on the steel plate surface and RP_Get_Real("flow-time") to obtain the initial simulation time, and obtain the relationship between the position of the steel plate during the quenching process in time and space; 2) According to the corrected heat transfer boundary condition on the steel plate surface in step 3, use F_T(f, t) to obtain the real-time temperature on the grid surface, that is, the real-time temperature on the steel plate surface, so as to accurately describe the heat transfer situation on the steel plate surface during the roller quenching process; 3) Write the dynamic heat transfer load on the steel plate surface according to the relationship between the position of the steel plate in space and time and the real-time temperature data on the steel plate surface. The movement of a certain part of the steel plate to a certain cooling section at a certain moment is described by the position-time relationship, and the heat transfer situation is described by the relationship between the obtained real-time steel plate surface temperature and the convective heat transfer coefficient; 4) Insert the written dynamic heat transfer load into the FLUENT model to complete the temperature field simulation of the roller continuous quenching process.

6. The method for simulating the temperature field of the roller continuous quenching process based on FLUENT according to claim 1, wherein The heat transfer boundary condition on the steel plate surface described in step 2 includes the heat transfer boundary condition under the jet impingement of the nozzle and the heat transfer boundary condition of flowing water on the upper surface of the steel plate, and the convective heat transfer coefficient on the steel plate surface is obtained through simulation.

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