JP2014081208A - Simulation program of heat treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simulation program of heat treatment, which has a reduced analysis time.SOLUTION: Simulation of heat treatment in which a workpiece is subjected to induction heating while the workpiece is moved around an axis or along a shape of the workpiece relative to a heating coil or the heating coil is moved around the axis or along the shape of the workpiece relative to the workpiece includes: a magnetic field analysis step (STEP2) of obtaining a distribution of heat generation densities occurring in the workpiece due to induction heating in a state where the workpiece is fixed relative to the heating coil; and a heat treatment analysis step (STEP3) of computing a heat generation density distribution at the time of a trace of movement of the workpiece around the axis or along the shape of the workpiece relative to the heating coil, by rotating the heat generation density distribution obtained in the magnetic field analysis step around the axis or moving it along the shape of the workpiece, and obtaining a temperature distribution of the workpiece each time when computing the heat generation density distribution.

Description

  The present invention applies a high-frequency current to the heating coil and moves the workpiece around the axis or along the shape of the workpiece relative to the heating coil, or moves the heating coil around the axis or along the shape of the workpiece relative to the workpiece. However, the present invention relates to a heat treatment simulation program for induction heating of a workpiece.

  When manufacturing automobile parts, construction machine parts, etc., heat treatment is performed for the purpose of improving fatigue strength and wear resistance. Induction hardening is one of the heat treatments that has features such as short-time heating and in-line treatment, and excellent quenching quality reproducibility.

  In the induction hardening, the inventors have many factors that affect the quality of heat treatment such as quenching range, hardness distribution, deformation amount, etc. Research and development of computer simulation technology that can predict the setting with high accuracy is performed (for example, Patent Document 1).

  In the induction hardening simulation, the quality of heat treatment can be predicted by alternately performing magnetic field analysis and heat treatment analysis. In order to improve the prediction accuracy, Patent Document 1 discloses an FEM model for magnetic field analysis suitable for obtaining an eddy current / heat generation density distribution of a metal part by induction heating, a temperature distribution of a metal part, a metal structure distribution, a stress / An FEM model for heat treatment analysis suitable for analyzing the strain distribution in correlation with each other is used. In order to use the plurality of FEM models, a coupled analysis program that exchanges analysis results with each other is used (for example, Patent Document 2).

JP 2010-230331 A JP 11-328157 A

  When the heating region of the workpiece is axisymmetric and the heating coil has a complicated shape, induction heating is performed while rotating the workpiece around the axis. In order to simulate the temperature rise by induction heating, the relative rotation angle θ is increased by Δθ from 0 to 2π on the same axis with respect to the heating coil, and magnetic field analysis and heat treatment analysis are alternately performed each time Δθ is increased. Will be executed. Magnetic field analysis is to obtain the distribution of heat generation density generated in the work using a heating coil by magnetic field analysis, and heat treatment analysis is to calculate the temperature distribution, metal structure distribution and stress of work by heat conduction analysis from the result of magnetic field analysis.・ To obtain strain distribution.

  Then, the magnetic field analysis and the heat treatment analysis are frequently performed alternately for each Δθ, and the time required to obtain the simulation result becomes long, which hinders the rapid heating coil design.

  Accordingly, an object of the present invention is to provide a heat treatment simulation program that greatly shortens the analysis time.

  In order to achieve the above object, the present invention moves the heating coil around the axis or along the shape of the workpiece relative to the heating coil or moves the heating coil around the axis or along the shape of the workpiece relative to the workpiece. In the heat treatment simulation program for induction heating of the workpiece, the magnetic field analysis step for obtaining the distribution of the heat generation density amount generated in the workpiece by induction heating with the workpiece fixed to the heating coil, and either the heating coil or the workpiece About the calorific density distribution when moving a small amount around the axis or along the shape of the workpiece, the calorific density distribution calculated in the magnetic field analysis step is calculated by moving around the axis or along the shape of the workpiece, And a heat treatment analysis step for obtaining a temperature distribution of the workpiece for each calculation.

  Preferably, in the magnetic field analysis step, the amount of heat generation density is obtained in units of mesh, and in the heat treatment analysis step, the amount of heat generation density in units of mesh obtained in the magnetic field analysis step is moved to reduce the number of times of magnetic field analysis. And

  Preferably, in the heat treatment analysis step, it is determined whether or not the magnetic field distribution due to the heating coil changes so as to greatly affect the analysis result due to the temperature rise of the workpiece, and the magnetic field analysis step is executed when it is determined that the change has occurred. .

  Preferably, in the heat treatment analysis step, the heat conduction analysis is executed using the result of the heat generation density amount distribution, and the temperature distribution of the workpiece is obtained.

  Preferably, in the heat treatment analysis step, when performing the heat conduction analysis, a coupled analysis of the phase transformation of the metal structure of the workpiece and the stress and strain is performed to obtain the temperature distribution of the workpiece.

  According to the present invention, when the heating coil and the workpiece are in a certain positional relationship, the magnetic field analysis is performed, and then, when the temperature distribution of the workpiece is obtained by the heat treatment analysis, the result of the magnetic field analysis is obtained around the axis or the shape of the workpiece The heat generation density distribution is obtained by moving a small amount along the line. Thereby, it is not necessary to perform a magnetic field analysis every time the work is moved minutely with respect to the heating coil. Conventionally, when magnetic field analysis and heat treatment analysis are performed alternately, most of the total analysis time is used for magnetic field analysis. According to the present invention, since the number of times of magnetic field analysis is greatly reduced, the time required for the heat treatment simulation can be greatly shortened.

It is a block block diagram of the heat processing simulation apparatus implement | achieved by installing the heat processing simulation program which concerns on embodiment of this invention. It is sectional drawing which shows typically an example of the workpiece | work and heating coil used as the object of the simulation of the heat processing which concerns on embodiment of this invention. It is a figure which shows typically distribution of the heat-generation density amount of the workpiece | work surface produced by a heating coil in arrangement | positioning shown in FIG. It is the schematic for demonstrating the coupled analysis performed in the heat processing analysis part shown in FIG. It is a figure which shows the processing flow by the simulation program of the heat processing which concerns on embodiment of this invention. It is a figure which shows the time chart by the simulation program of the heat processing which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Heat treatment simulation equipment]
FIG. 1 is a block configuration diagram of a heat treatment simulation apparatus realized by installing a heat treatment simulation program according to an embodiment of the present invention. A heat treatment simulation apparatus 1 according to an embodiment of the present invention includes an input unit 2, an output unit 3, and an analysis unit 4.
The input unit 2 includes a keyboard, a mouse, and the like, and the input unit 2 outputs signals about various commands and information input from the user to the analysis unit 4. The output means 3 is composed of a display device or the like, and the output means 3 displays based on the output signal from the analysis means 4. The analysis unit 4 receives a signal input from the input unit 2 and outputs an output signal to the output unit 3 to perform a simulation analysis.

  The analysis unit 4 includes a CPU or MPU and a recording medium that stores the heat treatment simulation program according to the embodiment of the present invention. The analysis means 4 functions by executing a heat treatment simulation program by the CPU or MPU. The analysis means 4 includes a magnetic field analysis unit 4A, a heat treatment analysis unit 4B, an analysis control unit 4C, and an analysis database 4D.

  As a premise for explaining each part of the analysis means 4 in detail, the object of the heat treatment simulation according to the embodiment of the present invention will be explained. FIG. 2 is a cross-sectional view schematically showing an example of a workpiece and a heating coil that are targets of a heat treatment simulation according to the embodiment of the present invention.

  In many cases, a metal part to be subjected to a heat treatment simulation has a heating region set around an axis or along a part shape. Here, “the heating region is about the axis” includes, for example, not only the case where the heating region is symmetric about the axis, but also the case where the heating region can be approximated about the axis. The phrase “the heating region is along the part shape” includes, for example, a case where the predetermined cross-sectional shape extends along a certain direction. FIG. 2 is only schematically shown to facilitate understanding of the simulation. Coordinate axes are set for the workpiece when performing magnetic field analysis and heat treatment analysis, but the present invention is applied as long as the heating region can be expressed by rotating and translating the coordinate axes.

  The workpiece w and the heating coil 10 shown in FIG. 2 will be described. As shown in FIG. 2, the workpiece w has a symmetrical shape around the axis and has a truncated cone shape. The heating coil 10 is designed according to the shape of the workpiece w. As shown in FIG. 2, for example, the heating coil 10 is designed so as to be arranged coaxially with the workpiece w and to face the outer peripheral side surface of the workpiece w. A predetermined thickness portion from the outer peripheral surface is selected as the heating region. As shown in FIG. 2, the heating coil 10 is composed of a left heating coil 10 </ b> L and a right heating coil 10 </ b> R so as to face the outer peripheral side surface of the workpiece w and to form a pair on the left and right sides of the workpiece w.

  Next, each part of the analysis means 4 will be described in detail.

  The magnetic field analysis unit 4A performs analysis by the finite element method based on Maxwell's electromagnetic equations. As the analysis method, the A method or the A-φ method is used. The magnetic field analysis unit 4A divides the work, the heating coil, and the surrounding space into a plurality of elements, and calculates the eddy current generated in the vicinity of the work surface in accordance with the temporal change of the magnetic flux distribution generated in the heating coil and its surroundings. The amount of heat generation is determined for each element or node. In the embodiment of the present invention, the heat treatment situation in which the workpiece is moved around the axis or along the shape of the workpiece with respect to the heating coil is simulated. In the magnetic field analysis unit 4A, there is a workpiece with respect to the heating coil. The magnetic field analysis is performed in a fixed state at a certain position, and the magnetic field analysis is not performed in a state where the magnetic field is moved slightly from a certain position in order.

  FIG. 3 is a diagram schematically showing the distribution of the heat generation density amount on the workpiece surface generated by the heating coil in the arrangement shown in FIG. As shown in FIG. 3, the horizontal axis represents the angle θ around the axis of the heating region, and the vertical axis represents the heat generation density. It is assumed that the coordinate axis of the angle θ around the axis of the heating region is set to a non-rotating system.

By the magnetic field analysis, the heat generation density distribution at time t is obtained as f (θ, t) as shown by a solid line in FIG. In FIG. 3, since the workpiece w and the heating coil 10 are substantially symmetrical about the axis, the heat generation density distribution f (θ, t) is also symmetric.
The heat generation density amount distribution f (θ, t + Δt) at time t + Δt is approximated to be equal to the heat generation density amount distribution f (θ + Δθ, t) when the heating coil 10 is rotated by Δθ with respect to the workpiece w at time t. be able to. That is, f (θ, t + Δt) ≈f (θ + Δθ, t) holds.
At time t + Δt, if any of the positional relationship between the heating coil 10 and the workpiece w is rotated by Δθ, the relationship between Δθ and Δt is expressed as Δθ = Δt × (around the axis of the workpiece w or the heating coil 10). Angular velocity) is established.

Therefore, the heat generation density distribution f (θ + nΔθ, t) when the heating coil 10 is rotated by nΔθ from the state where the magnetic field analysis has been performed is evaluated as f (θ, t + nΔt) where the temperature rise amount of the work w is small. And the coordinates of the angle θ may be converted. However, n is a natural number.
Therefore, even if the heating coil 10 slightly moves with respect to the workpiece w, it is not necessary to perform the magnetic field analysis step by step.

  An outline of a method for analyzing an electromagnetic equation by a finite element method and a numerical analysis method are as follows. The shape and dimensions of the workpiece, the heating coil, etc., and the surrounding space are divided into a plurality of elements at each node by the FEM model. As the FEM model, a combination of node information indicated by coordinates and node information constituting each element (hereinafter simply referred to as “element information”) is set in the analysis database 4D. As material property information regarding each material of the workpiece and the heating coil, temperature-dependent data is stored in, for example, the analysis database 4D for the electrical conductivity and relative permeability data for each tissue. In the FEM model, the initial value of the temperature data at each node is set, and the frequency and the coil current or the coil voltage are input as analysis conditions, so that the magnetic field analysis unit 4A performs an analysis on the magnetic field for each node or each element. The amount of heat generation density is required.

  The heat treatment analysis unit 4B solves the heat conduction equation when the work is moved by a minute amount around the axis or along the shape of the work using the result obtained by the magnetic field analysis unit 4A, that is, the distribution of the heat generation density. When the heat treatment analysis unit 4B solves the heat conduction equation and performs a coupled analysis, the heat treatment can be analyzed.

  FIG. 4 is a schematic diagram for explaining the coupled analysis performed in the heat treatment analysis unit 4B. As shown in FIG. 4, the temperature, structure, stress, and strain of an arbitrary region in the workpiece, that is, the metal part are correlated with each other. “Coupled analysis” means that analysis is performed in consideration of complex mutual influences of a plurality of physical phenomena. By this coupled analysis, the temperature and strain of each node set in the FEM model, stress for each element, metal structure, and the like can be predicted.

  The complex interaction of multiple physical phenomena will be described in detail. While a phase transformation due to a time-series temperature change occurs in an arbitrary region of the workpiece, conversely, if a phase transformation occurs in an arbitrary region, generation / absorption of latent heat occurs. If the phase transformation is not uniform in any region of the workpiece, stress is generated due to the local volume change. Conversely, if the stress is generated, the start time of the phase transformation is affected. Further, when the workpiece is deformed, the deformed portion generates heat. On the contrary, when a temperature difference is generated in an arbitrary region, stress is generated.

  For this reason, heat transfer analysis, composition analysis, and stress / strain analysis are correlated with each other, and when the structure changes due to temperature change or stress or strain occurs, phase transformation or stress / strain occurs. The temperature in that region changes.

  The processing of the heat treatment analysis unit 4B will be described by taking the work w and the heating coil 10 shown in FIG. 2 as an example.

  In the state where the positional relationship between the workpiece w and the heating coil 10 is fixed, the magnetic field analysis unit 4A determines the heat generation density distribution f (θ, t) as shown in FIG. Wanted. Therefore, coupled analysis is performed, heat treatment analysis is performed for each node or element, and the composition for each element, temperature for each node or element is obtained.

  Next, when the workpiece w rotates about the axis of the heating coil 10 by Δθ, a heat generation density amount distribution is obtained. Since the heating region is symmetric about the axis, the heat generation density distribution f (θ, t + Δt) can be approximated as f (θ + Δθ, t). As a result, the calorific value is obtained for each element, so heat treatment analysis is performed by coupled analysis, and the temperature for each composition, node or element is obtained.

  In this way, while the work w is slightly rotated, the heat generation density distribution f (θ, t) obtained by the magnetic field analysis unit 4A is calculated from the heat generation density distribution generated in the heating region of the work w every Δt. Is obtained as f (θ + nΔθ, t).

  Therefore, the heat treatment analysis may be performed based on the result obtained by rotating the heat generation density amount distribution.

  In this way, the heat treatment analysis unit 4B repeatedly obtains the distribution of the heat generation density by coordinate conversion and repeats the heat treatment analysis based on the obtained distribution, so that the magnetic field analysis and the heat treatment analysis are alternately performed one by one. As in the case where the work is performed, the temperature distribution can be obtained for each node or element when the work is rotated around the axis.

  The analysis control unit 4C determines whether or not the magnetic field distribution due to the heating coil changes due to the temperature rise of the workpiece so as to greatly affect the analysis result. Control related to

  Specifically, the analysis control unit 4C determines whether or not the magnetic field distribution due to the heating coil is affected by the temperature increase of the workpiece from the workpiece temperature distribution obtained by the heat treatment analysis unit 4B, and determines that the influence is exerted. In such a case, the processing of the magnetic field analysis unit 4A and the heat treatment analysis unit 4B is controlled so that the magnetic field analysis unit 4A performs the magnetic field analysis again. This determination may be made by setting the temperature rising range of the workpiece or by the number of times the workpiece is moved by a minute amount around the axis or along the shape of the workpiece.

  The reason why the analysis control unit 4C performs such control is that the distribution of the heat generation density obtained by fixing the positional relationship between the workpiece w and the heating coil changes the permeability due to the temperature rise of the workpiece w. This is because the depth and magnitude at which the eddy current is generated changes.

  The determination by the analysis control unit 4C may be performed not only when the temperature of the workpiece exceeds a certain range but also as follows. For example, as shown in FIG. 2, when the left and right heating coils 10 </ b> L and 10 </ b> R are arranged to face each other so as to make a pair with the outer peripheral side surface of the work w, the work w is rotated by π. It may be assumed that the workpiece is heated up uniformly by performing the heat treatment analysis. That is, there is a case where an error occurs if the result of the previous magnetic field analysis is used as it is.

  In the analysis database 4D, various data required in the magnetic field analysis unit 4A, the heat treatment analysis unit 4B, and the analysis control unit 4C are stored. The various data includes data modeled using a three-dimensional CAD such as the shape of the workpiece w and the heating coil 10 in addition to the material property data.

  Here, the heat treatment simulation apparatus, method, and program according to the embodiment of the present invention are not limited to the case where the work and the heating coil corresponding to the work as shown in FIG. Depending on the case, the heating coil may rotate. The present invention is also applied to the case where the workpieces are aligned in one direction, and particularly a surface portion such as a rail is heat-treated. The heating area may be set linearly or curved along the longitudinal direction of the workpiece. In the following, a simulation method and a program will be described on the assumption of both.

[Simulation method, simulation program]
A heat treatment simulation method performed by executing a heat treatment simulation program according to an embodiment of the present invention will be described in detail. FIG. 5 is a diagram showing a processing flow by a heat treatment simulation program according to the embodiment of the present invention.

  As STEP 1, various data are input from the input means 2. The input data includes workpiece and heating coil shape data. The shape data includes various types of information such as shape, size, and material. These shape data are obtained as FEM models used in the magnetic field analysis unit 4A and the heat treatment analysis unit 4B, by defining the nodes as coordinates along the shapes of the workpiece and the heating coil, and by combining the nodes, that is, based on the element information And the area | region which refined the heating coil, ie, each element, is defined.

  When the heating area of the workpiece is symmetrical around the axis, the workpiece is divided into a plurality of parts around the axis, and each element is determined for each divided area. When the heating area of the workpiece extends in one direction, it is divided into a plurality along the one direction, and each element is determined for each divided area. Data related to the FEM model is stored in the analysis database unit 4D.

  In STEP 2, it is assumed that the workpiece is fixed to the heating coil by the magnetic field analysis unit 4A using the finite element method based on the FEM model, and the workpiece, the heating coil, and the entire periphery thereof are converted into a plurality of elements. The distribution of magnetic flux generated in each element is obtained by division, the eddy current distribution is obtained from the magnetic flux density distribution in each element, and the heat generation density amount of each element is obtained. At this time, to what depth the eddy current is generated from the workpiece surface by the magnetic flux from the heating coil is determined from the electrical conductivity and the relative permeability that are referred to from the temperature of the workpiece at the time of analysis.

  As STEP3, STEP3-1 and STEP3-2 are performed in order to analyze the heat distribution of each element of the workpiece by the heat treatment analysis unit 4B.

  As STEP 3-1, the heat treatment analysis unit 4B performs coordinate conversion of the distribution of the heat generation density obtained by the magnetic field analysis unit 4A at STEP2. That is, the heat generation density distribution in a state where the workpiece or the heating coil is moved by a minute amount around the axis or along the shape of the workpiece from the positional relationship between the heating coil and the workpiece when the magnetic field analysis is performed by the magnetic field analysis unit 4A. Is obtained by coordinate transformation or the like. If the magnetic field analysis obtained in STEP 2 can be used as it is, coordinate conversion is not necessary.

  In STEP 3-2, the heat treatment analysis unit 4B obtains the temperature of each element by performing coupled analysis by structure analysis and stress / strain analysis based on the heat generation density distribution obtained by coordinate transformation in STEP 3-1.

  In STEP 4, the analysis control unit 4 </ b> C determines whether or not the magnetic field distribution by the heating coil is greatly changed by raising the temperature of the workpiece. If it is determined that the analysis has changed significantly, the process returns to the magnetic field analysis step (STEP 2) unless the analysis end condition is satisfied (NO in STEP 6). When the magnetic field distribution due to the heating coil changes greatly, for example, when the temperature rise range from the workpiece temperature when the magnetic field analysis exceeds the threshold, or when the Joule heat loss distribution is rotated around the axis There is a case where the temperature of each part of the heating part faces each part of the heating coil.

  If it is determined in STEP4 that the magnetic field distribution by the heating coil does not change significantly, the process returns to STEP3.

  Therefore, it is possible to repeat the heat treatment analysis by converting the calorific density distribution into coordinates. Thereby, when the number of minute movements reaches a predetermined number, that is, the number of minute sections, or when the number of movements reaches a predetermined number determined in consideration of the symmetry of the heating coil 10, the temperature of each element of the workpiece has changed. Simulate that the magnetic field distribution in the heating coil has changed, and return to STEP2.

  A simulation can be performed by moving a predetermined amount around the workpiece axis or along the workpiece shape along the above procedure.

  FIG. 6 is a diagram showing a time chart by the heat treatment simulation program according to the embodiment of the present invention. The upper stage is the process of the magnetic field analysis unit 4A, and the lower stage is the process of the heat treatment analysis unit 4B. For example, when the workpiece w having a shape as shown in FIG. 2 is induction-heated by the heating coil 10, only one positional relationship between the workpiece w and the heating coil 10 is calculated by the magnetic field analysis unit 4A, and the calculation by the heat treatment analysis unit 4B. Is performed while rotating the workpiece w by Δθ (for example, 3 °). That is, in the magnetic field analysis step, the heat generation density amount is obtained in mesh units, and in the heat treatment analysis step, the heat generation density amount in mesh units obtained in the magnetic field analysis step is rotated or moved. Therefore, the number of magnetic field analyzes can be greatly reduced, and the analysis time can be greatly shortened.

  The present invention is not limited to the above-described embodiment, and may be appropriately changed within the scope of the present invention. In the above description, the heat treatment analysis unit performs the coupled analysis, but only the heat transfer analysis may be performed. Further, the FEM model is obtained by dividing each region (called “element” in the above description) into a mesh for easy analysis, and a combination of a plurality of nodes constituting the mesh (described above). Is called “element information” in Japanese Patent Application Laid-Open No. 2004-26883. Note that coordinate conversion may be performed in accordance with Patent Documents 1 and 2 so that the FEM model is separately used by the magnetic field analysis unit 4A and the heat treatment analysis unit 4B, and the results are mutually used.

1: heat treatment simulation device 2: input means 3: output means 4: analysis means 4A: magnetic field analysis unit 4B: heat treatment analysis unit 4C: analysis control unit 4D: analysis database 10: heating coil 10L: left heating coil 10R: right side Heating coil W: Metal member (work)

Claims (5)

In a simulation program of heat treatment for inductively heating a workpiece while moving the workpiece around the axis or along the shape of the workpiece relative to the heating coil or moving the heating coil around the axis or along the shape of the workpiece relative to the workpiece,
A magnetic field analysis step for obtaining a distribution of a heat generation density amount generated in the workpiece by induction heating in a state where the workpiece is fixed to the heating coil;
Regarding the heat generation density amount distribution when the heating coil or the workpiece is moved by a minute amount around the axis or along the shape of the workpiece, the heat generation density amount distribution obtained in the magnetic field analysis step is about the axis or along the shape of the workpiece. A heat treatment analysis step to calculate the temperature distribution of the workpiece for each calculation,
A heat treatment simulation program characterized by comprising: In the magnetic field analysis step, the amount of heat generation density is determined in mesh units,
2. The heat treatment simulation program according to claim 1, wherein in the heat treatment analysis step, the heat generation density amount in mesh units obtained in the magnetic field analysis step is moved to reduce the number of times of magnetic field analysis.   In the heat treatment analysis step, it is determined whether or not the magnetic field distribution due to the heating coil changes so as to greatly affect the analysis result due to the temperature rise of the workpiece, and the magnetic field analysis step is executed when it is determined that the change has occurred. 2. A heat treatment simulation program according to 1.   The heat treatment simulation program according to claim 1, wherein in the heat treatment analysis step, a heat conduction analysis is executed using a result of the heat generation density amount distribution to obtain a temperature distribution of the workpiece.   5. The heat treatment simulation according to claim 4, wherein in the heat treatment analysis step, when the heat conduction analysis is performed, the temperature distribution of the workpiece is obtained by performing a coupled analysis of the phase transformation of the metal structure of the workpiece and the stress and strain. program.

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