JP2013120432A - Method for designing induction heating equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for designing induction heating equipment for improving the efficiency of equipment design.SOLUTION: The method for designing induction heating equipment includes: steps (S10 to S40) of inputting to an analysis device the physical property values and shape of a member to be heated and the shape and current data of a coil with which induction heating is carried out for the member to be heated; a step (S50) of analyzing the temperature of each site of the heated member using a finite element method, on the basis of the input physical property values, the shapes of the heated member and the coil, and the current data, by the analysis device, and of outputting the results thereof; and a step (S60) of constructing the induction heating equipment on the basis of the output temperature of each site. In this method for designing induction heating equipment, the physical property values of the heated member including the magnetic permeability and saturation magnetic flux density which does not depend on a magnetic field are input. When the temperature is output, the temperature of each site is output on the basis of the value of the magnetic flux density calculated from the magnetic field and the magnetic permeability until the magnetic flux density of each site reaches the saturation magnetic flux density, and after the magnetic flux density of each site reaches the saturation magnetic flux density, the temperature of each site is output on the basis of the value calculated by adding the saturation magnetic flux density to the magnetic flux density calculated from the magnetic field and vacuum magnetic permeability of each site.

Description

  The present invention relates to a method for designing an induction heating facility, and more specifically, to a method for designing an induction heating facility that can improve the efficiency of facility design.

  A heat treatment method by induction heating may be employed as a heat treatment method for mechanical parts. In the heat treatment by induction heating, a high-frequency current is passed through a coil disposed so as to face the heated member to be heated, and thereby the heated member is induction heated. In order to heat a desired range of a member to be heated to a desired temperature, it is necessary to arrange a coil having an appropriate shape according to the temperature and to pass an appropriate value of current for an appropriate time. And the design of the induction heating equipment for achieving such appropriate heating has been conventionally carried out by trial and error with reference to past results, operator experience, and the like.

  On the other hand, it has been proposed to use an electromagnetic field heat conduction analysis based on a finite element method (FEM) for designing an induction heat treatment facility and examining heating conditions (for example, Patent Document 1 and Non-Patent Document 1). reference). Specifically, the Joule loss due to the induced current in the heated member induced from the high-frequency current in the coil is first calculated using FEM by electromagnetic field analysis, and then the temperature distribution in the heated member is calculated by heat conduction analysis. Repeat the calculation routine several times. The analysis is performed a plurality of times by changing the coil shape, current frequency, applied active power, etc. so that the temperature distribution in the heated member thus obtained matches the desired temperature distribution, This can be useful for the design of induction heating devices.

JP 2001-49333 A

Takahashi et al., “Coupling analysis of electromagnetic and temperature fields of induction heating device for heating before forging”, Mitsui Engineering & Shipbuilding Technical Report, February 2009, No. 196, p31-37

  However, the above-described conventional method for designing an induction heating facility using FEM has a problem that the analysis result by FEM and the actual measurement value when the induction heating facility is actually constructed and heat treatment is not sufficiently matched. It was. As a result, in the conventional method for designing an induction heating facility using FEM, it is necessary to perform considerable trial and error after constructing an actual facility with reference to the analysis result by FEM.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for designing an induction heating facility that can improve the efficiency of facility design.

  The design method of induction heating equipment according to the present invention is a design method of induction heating equipment using a finite element method. In this design method, the physical property value of the heated member is input to the analyzing device, the shape of the heated member is input to the analyzing device, the facing member is disposed, A step in which the shape of the coil to be induction-heated is input to the analysis device, a step in which current data including the current value and frequency of the current passed through the coil is input to the analysis device, the input physical property value, and the heated member Based on the shape, coil shape and current data, the analysis device analyzes and outputs the temperature at each part of the heated member by the finite element method, and induction heating based on the outputted temperature of each part Building equipment.

  In the step of inputting the physical property values, the physical property values including the saturation magnetic flux density, the electrical conductivity, the specific heat, the thermal conductivity, and the magnetic permeability not depending on the change of the magnetic field of the heated member are input to the analysis device. In the step of outputting the temperature at each part of the heated member, the magnetic flux at each part calculated from the magnetic field at each part and the magnetic permeability until the magnetic flux density at each part reaches the saturation magnetic flux density. After the magnetic flux density of each part reaches the saturation magnetic flux density, the value in each part is determined based on the value obtained by adding the saturation magnetic flux density to the magnetic flux density calculated from the magnetic field of each part and the vacuum permeability. The temperature is output.

  The present inventor examined the cause of the fact that the analysis result by FEM and the actual measurement value when the induction heating equipment was actually constructed and heat treatment was not sufficiently matched (disagreement between the analysis result and the actual measurement value). Was done. As a result, when calculating the temperature of each part based on the input parameters, many approximations are adopted and the calculation is performed. Among them, the approximation that the permeability is constant with respect to the magnetic field It was found that the discrepancy between the analysis result and the actual measurement value was increased due to the influence of the error caused by. More specifically, in order to calculate the temperature at each part of the member to be heated, it is necessary to calculate the magnetic flux density formed in the member to be heated by the current flowing through the coil. This magnetic flux density can be calculated from the magnetic field formed by the current flowing through the coil and the magnetic permeability. Here, since the magnetic permeability changes with respect to the magnetic field, the magnetic permeability according to the magnetic field is calculated first, and the magnetic flux density is calculated from the calculated magnetic permeability and magnetic field value, thereby obtaining a more accurate magnetic flux density. Can be calculated. However, from the viewpoint of avoiding the complexity of this calculation and reducing the analysis speed, it is generally approximated that the magnetic permeability is constant with respect to the magnetic field and the magnetic flux density continues to increase as the magnetic field increases. Adopted. As a result, the discrepancy between the analysis result and the actual measurement value increases.

  On the other hand, in the design method of the induction heating equipment of the present invention, after the magnetic permeability of the member to be heated and the saturation magnetic flux density that are not dependent on the change of the magnetic field are input in the step of inputting the physical property value, In the temperature output step, until the magnetic flux density reaches the saturation magnetic flux density, the value of the magnetic flux density calculated from the magnetic field of each part and the above magnetic permeability, and after reaching the saturation magnetic flux density, the magnetic field of each part. And the temperature at each part are output based on the value obtained by adding the saturation magnetic flux density to the magnetic flux density calculated from the magnetic permeability of the vacuum. That is, in the design method of the induction heating equipment of the present invention, it is avoided that the analysis speed is reduced by calculating the magnetic flux density based on the magnetic permeability and the magnetic field that do not change with respect to the magnetic field until the saturation magnetic flux density is reached. On the other hand, after reaching the saturation magnetic flux density, the value obtained by adding the increase in the magnetic flux density calculated from the magnetic field and the magnetic permeability of the vacuum to the saturation magnetic flux density is adopted as the magnetic flux density. Inconsistency with the value can be suppressed. As a result, it is possible to improve analysis accuracy while suppressing a decrease in analysis speed. Thus, according to the design method for induction heating equipment of the present invention, it is possible to provide a design method for induction heating equipment that can improve the efficiency of equipment design.

  In the design method of the induction heating facility, in the step of inputting the physical property value, the physical property value including the magnetic permeability and the saturation magnetic flux density considering temperature dependence may be input to the analysis apparatus. Thereby, more accurate FEM analysis can be performed.

  In the design method of the induction heating facility, in the step of inputting the physical property value, a saturation magnetic flux density calculated in advance by an experiment using a test piece made of the same kind of material as the member to be heated may be input. Thereby, more accurate FEM analysis can be performed.

  In the design method of the induction heating facility, the member to be heated may be made of steel. The induction heating equipment design method is suitable for designing a heating equipment for heating a member made of steel.

  In the design method of the induction heating equipment, in the step of inputting the physical property value, the saturation magnetic flux density calculated based on the experimental results at a plurality of temperatures in the temperature range below the Curie point of the steel constituting the member to be heated. May be input. Thereby, a more accurate FEM analysis can be performed.

  In the design method of the induction heating equipment, in the step of inputting the physical property value, even if the saturation magnetic flux density calculated based on the experimental result at a temperature of 5 or higher in the temperature range below the Curie point of the steel is input. Good. Thereby, a more accurate FEM analysis can be performed.

  In the design method of the induction heating facility, the saturation magnetic flux density calculated based on the experimental results at a plurality of temperatures including normal temperature may be input in the step of inputting the physical property value. Thereby, a more accurate FEM analysis can be performed.

  In the above induction heating equipment design method, in the step of outputting the temperature at each part of the heated member, the temperature at each part may be output in consideration of the current value distribution in the coil. Thereby, a more accurate FEM analysis can be performed.

  As is apparent from the above description, the induction heating equipment design method of the present invention can provide an induction heating equipment design method capable of improving the efficiency of equipment design.

It is a flowchart which shows the outline of the design method of induction heating equipment. It is the schematic which shows the structure of induction heating equipment. It is the schematic which shows the state of the mesh at the time of performing FEM analysis. It is the schematic which shows the relationship between temperature and a saturation magnetic flux density. It is a figure which compares and shows the relationship between heating time and temperature in an analysis result and an experimental result. It is a figure which shows the relationship between the electric power value, the time required for heating, and the surface temperature. It is a figure which shows the relationship between the frequency of an electric current, the time required for a heating, and surface temperature.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  In the method of designing an induction heating facility according to an embodiment of the present invention, referring to FIG. 1, first, physical property values are input in step (S10). Specifically, physical properties of the member to be heated and the coil are input to the analyzer. Referring to FIG. 2, in the present embodiment, physical property values including magnetic permeability, saturation magnetic flux density, electrical conductivity, specific heat, and thermal conductivity of the inner ring 2 of a rolling bearing that is a bearing component made of steel are stored in the analysis device. Entered. In addition, physical property values including the electrical conductivity, specific heat, and thermal conductivity of the coil 1 are input to the analyzer. The coil 1 is made of copper, for example.

  Next, in step (S20), the shape of the object to be heated is input to the analyzer. In the present embodiment, referring to FIG. 2, the shape of inner ring 2 is input to the analysis device.

  Next, in step (S30), the shape of the coil is input to the analyzer. In the present embodiment, referring to FIG. 2, the shape of coil 1 arranged to face the outer peripheral surface (track surface) of inner ring 2 and induction-heating inner ring 2 is input to the analyzer. The coil 1 includes an annular portion 11 that is arranged facing the object to be heated and has an annular shape, and a base portion 12 that is connected to the annular portion 11. The base unit 12 is connected to a high frequency power source (not shown). In step (S30), specifically, the shape of the annular portion 11 is input to the analyzer.

  Next, the data of the current passed through the coil in step (S40) is input to the analyzer. In the present embodiment, referring to FIG. 2, current data including the current value and frequency of the current flowing through coil 1 is input to the analysis device. Here, the steps (S10) to (S40) are not limited to the above order, and are performed in an arbitrary order. That is, the parameters to be input in the above steps (S10) to (S40) can be input to the analyzer in any order.

  Next, in step (S50), the temperature at each part of the inner ring 2 as the member to be heated is analyzed and output by the finite element method. Specifically, referring to FIG. 3, based on the shapes of annular portion 11 and inner ring 2 of coil 1 input in steps (S20) and (S30), these cross sections are divided into virtual minute regions. The Although not shown in FIG. 3, the space between the annular portion 11 and the inner ring 2 is similarly divided into virtual minute regions. Then, based on the physical property values of the coil 1 and the inner ring 2, the shape of the inner ring 2, the shape of the coil 1, and the current data input in the steps (S10) to (S40), the analysis device performs each of the above parts (each The temperature in the micro area is analyzed and output by the finite element method.

  Next, in step (S60), induction heating equipment is constructed based on the temperature of each minute region output in step (S50). Specifically, the steps (S10) to (S50) are repeated as necessary, and when an appropriate temperature distribution is obtained in step (S50), the shape of the coil 1 is determined based on this. And a high-frequency power source capable of achieving the current value, frequency, etc. included in the current data. And an appropriate heat treatment installation is constructed | assembled by combining these. Thereafter, the heat treatment equipment is actually operated, and fine adjustment is performed as necessary, whereby the induction heating equipment capable of performing a desired heat treatment on the inner ring 2 is completed.

  And in the design method of the induction heating installation in this Embodiment, in step (S10), the magnetic permeability of the inner ring | wheel 2 which does not depend on the change of a magnetic field (it takes a constant value with respect to a magnetic field until it reaches a saturation magnetic flux density). The assumed physical permeability), saturation magnetic flux density, electrical conductivity, specific heat and thermal conductivity are input to the analyzer. Furthermore, in step (S50), until the magnetic flux density of each micro area reaches the saturation magnetic flux density, the value of the magnetic flux density of each micro area calculated from the magnetic field of each micro area and the magnetic permeability, and each micro area After reaching the saturation magnetic flux density, the temperature in each micro region is output based on the value obtained by adding the saturation magnetic flux density to the magnetic flux density calculated from the magnetic field of each micro region and the vacuum permeability. .

  Thus, in the design method of the induction heating equipment in the present embodiment, the analysis speed is reduced by calculating the magnetic flux density based on the magnetic permeability and the magnetic field that do not change with respect to the magnetic field until the saturation magnetic flux density is reached. After reaching the saturation magnetic flux density, the value obtained by adding the increase in the magnetic flux density calculated from the magnetic field and the magnetic permeability of the vacuum to the saturation magnetic flux density is used as the magnetic flux density. A mismatch between the result and the actual measurement value can be suppressed. Thus, according to the induction heating equipment design method in the present embodiment, the efficiency of equipment design can be improved.

  In step (S10), it is preferable that the physical property values including the magnetic permeability and the saturation magnetic flux density in consideration of temperature dependence are input to the analyzer. Thereby, more accurate FEM analysis can be performed.

  Furthermore, in step (S10), it is preferable that a saturation magnetic flux density calculated in advance by an experiment using a test piece made of the same material as the inner ring 2 is input. In particular, since data on saturation magnetic flux density considering temperature dependence is hardly disclosed, it is preferable to experimentally derive for each material in advance. In addition, the saturation magnetic flux density of steel varies greatly in the temperature range from room temperature to the Curie point. For this reason, it is preferable that experiments at a plurality of temperatures in a temperature range lower than the Curie point of steel constituting the member to be heated are performed in advance, and the saturation magnetic flux density calculated based on the experimental results is input. More specifically, experimental results at five levels (temperatures of five or more levels) of five levels, for example, room temperature, 300 ° C., 500 ° C., 700 ° C., a temperature just below the Curie point (eg, 750 ° C.). It is preferable that the saturation magnetic flux density calculated based on the above is input. Thereby, more accurate FEM analysis can be performed.

  In step (S50), the current value distribution in the annular portion 11 of the coil 1 (the current value for each minute region of the annular portion 11; see FIG. 3) is taken into consideration, and the temperature in each minute region of the inner ring 2 is output. It is preferred that Thereby, a more accurate FEM analysis can be performed.

  An experiment was conducted to confirm the analysis accuracy of the design method for induction heating equipment according to the present invention. Referring to FIG. 2, an inner ring 2 of a deep groove ball bearing 6206 model number manufactured by JIS standard S45C was adopted as a member to be heated. On the other hand, as the coil 1, a copper one-turn coil having an inner diameter φ46 mm, an outer diameter φ95 mm, and a width 17 mm of the annular portion 11 was adopted. The current frequency was 80 kHz, the active power was 15 kW, and heating was performed for 5 seconds. At this time, a thermocouple was welded to the outer surface and the raceway surface of the test piece, and the surface temperature of the test piece during high frequency induction heating was measured.

  On the other hand, parameters related to the coil 1 and the inner ring 2 were input to the analysis device in the same manner as in the above embodiment. The number of nodes in the FEM analysis was 17046, and the number of elements was 12661.

  Prior to the analysis, the saturation magnetic flux density of S45C was derived from experiments conducted at a plurality of temperatures below the Curie point. FIG. 4 shows the relationship between the derived temperature and the saturation magnetic flux density. Moreover, the relationship with temperature was also calculated about the magnetic permeability assumed that it did not change with respect to a magnetic field until it reached saturation magnetic flux density by the same experiment.

  Furthermore, as the other physical property values of S45C, the thermal conductivity, specific heat, and electrical conductivity, the values described in Non-Patent Document 1 were used in consideration of temperature dependence.

  As described above, assuming that the current is passed through the coil 1 so that the frequency of the current is 80 kHz and the active power is 15 kW, the electromagnetic field analysis is performed in the same manner as in the above embodiment, and the inner ring 2 The joule loss, that is, the heat generation density distribution was calculated. Further, the heat generation density distribution was given as a boundary condition for heat conduction analysis, and the temperature distribution in the inner ring 2 after a certain time was calculated. Further, the electromagnetic field analysis was advanced while changing the physical property values used in the calculation according to the temperature distribution in the inner ring 2. This calculation procedure was repeated until the actual heating time was reached, and the temperature in each minute region was calculated. In this analysis, this repetitive calculation was performed with a time interval of 0.05 s. Since the electromagnetic field analysis has a high calculation cost, the calculation cost can be reduced by performing the electromagnetic field analysis only when the temperature at which the physical property value greatly changes is detected.

  Next, the temperature rise curves (relationship between heating time and temperature) obtained by each of the above experiments and analyzes are shown in FIG. 5 and compared. With reference to FIG. 5, the temperatures of the two are in good agreement at all times studied. From this, according to the design method of the induction heating equipment of the present invention, it is possible to accurately simulate the heating state of the member to be heated by the induction heating equipment, so that the efficiency of the design of the induction heating equipment can be improved. Was confirmed.

  Next, an example of a specific heating equipment design method according to the induction heating equipment design method of the present invention will be described by taking, as an example, a quenching and heating equipment for products manufactured by induction hardening.

(1) Assumption of temperature distribution required for product Here, it is assumed that in a cylindrical product made of JIS standard S45C having a diameter of 45 mm and a width of 40 mm, the outer diameter side is cooled with water after high-frequency induction heating and quenched and hardened. This product requires a hardened layer from the outer diameter to a depth of 1.5 mm, and the outer diameter side surface crystal grains are not coarsened, and the heating time should be as short as possible. Assume that

  In quench hardening using high frequency induction heating, the temperature at which crystal grains coarsen and the heating temperature necessary for quench hardening differ depending on the steel type. Here, it is assumed that the crystal grain coarsening temperature of S45C is 900 ° C. and the heating temperature necessary for quench hardening is 800 ° C. In this case, in order to satisfy the above-described requirements, it is possible to make the ultimate temperature of the outer diameter surface less than 900 ° C. and the ultimate temperature of the 1.5 mm depth position to 800 ° C. or more in the shortest possible heating time What is necessary is just to design a heating apparatus. Although it is possible to design the coil shape, it is assumed here that a coil having the same shape as in the first embodiment is employed for the sake of simplicity.

(2) Estimating required active power and power supply capacity In order to estimate the required power, the effective power required to satisfy the above requirements is calculated. Specifically, the analysis was performed by changing the input current to the coil 1 so that the active power would be 10, 20 and 50 kW, and the product outer diameter and the 1.5 mm depth position from the outer diameter for each condition. The temperature at was determined. The frequency of the current was constant at 100 kHz. In FIG. 6, the square marks indicate the time required for the 1.5 mm depth position to reach 800 ° C., and the triangle marks indicate the temperature of the outer diameter surface when the 1.5 mm depth position reaches 800 ° C. Yes.

  Referring to FIG. 6, when the frequency of the current is 100 kHz, the reached temperature of the outer diameter surface is less than 900 ° C. and the depth position is 1.5 mm regardless of the active power of 10, 20 and 50 kW. It was found that the required temperature of 800 ° C. or higher can be satisfied. And according to the request | requirement of shortening heating time as much as possible, it is desirable for active power to be 50 kW, and it can be said that the power supply capacity which enables this is required. As shown in FIG. 6, when the active power is 50 kW, the temperature of the outer diameter surface rises to just below 900 ° C. when the temperature at the 1.5 mm depth position reaches 800 ° C. From this, it is considered that the above requirement cannot be satisfied if the active power exceeds 50 kW.

(3) Calculation of current frequency In order to calculate an appropriate current frequency, analysis was performed for frequencies of 50, 70, 100, and 220 kHz, and the product outer diameter and 1.5 mm from the outer diameter for each condition. The temperature at the depth position was determined. The effective power was 50 kW as determined in (2) above. In FIG. 7, the square mark indicates the time required for the 1.5 mm depth position to reach 800 ° C., and the triangle mark indicates the temperature of the outer diameter surface when the 1.5 mm depth position reaches 800 ° C. Yes.

  Referring to FIG. 7, under the conditions of 50, 70 and 100 kHz, there is a large difference in the time required for the 1.5 mm depth position to reach 800 ° C. and the temperature of the outer diameter surface at that time. There wasn't. On the other hand, in the case of the condition of frequency 220 kHz, the time required for heating is satisfied although the condition that the temperature of the outer diameter surface is less than 900 ° C. is satisfied when the temperature at the 1.5 mm depth position is 800 ° C. or higher. Became about 1.5 times. From the above results, it can be said that the appropriate frequency is about 50 to 100 kHz.

  In addition, in the said Example, although the design of the equipment in the state where the shape of the coil was decided was demonstrated, the design method of the induction heating equipment of this invention including the said FEM analysis is implemented about the case where the shape of a coil differs. Thus, the coil shape can be designed.

  Moreover, in the said embodiment and Example, although the case where the inner ring | wheel which is a bearing ring of a rolling bearing was made into a to-be-heated member was demonstrated as an example of a machine part, this invention is not limited to this, Other machine parts etc. It can be applied to the design of induction heating equipment for heating various members.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The induction heating equipment design method of the present invention can be particularly advantageously applied to an induction heating equipment design method that requires improvement in efficiency of equipment design.

  1 coil, 2 inner ring, 11 annular part, 12 base part.

Claims (8)

A method for designing an induction heating facility using a finite element method,
The step of inputting the physical property value of the member to be heated to the analyzer;
A step of inputting the shape of the heated member into the analysis device;
A step of inputting the shape of a coil that faces the member to be heated and induction-heats the member to be heated to the analysis device;
A step of inputting current data including a current value and a frequency of a current flowing through the coil to the analysis device;
Based on the input physical property value, the shape of the heated member, the shape of the coil, and the current data, the temperature at each part of the heated member is analyzed by the finite element method and output by the analysis device. And steps
Building the induction heating equipment based on the temperature of each part,
In the step of inputting the physical property value, the physical property value including a saturation magnetic flux density, an electric conductivity, a specific heat, a thermal conductivity, and a magnetic permeability that does not depend on a change in the magnetic field of the heated member is input to the analysis device. ,
In the step of outputting the temperature at each part of the heated member, until the magnetic flux density of each part reaches the saturation magnetic flux density, the temperature of each part calculated from the magnetic field and the magnetic permeability of each part is reached. After the magnetic flux density value reaches the saturation magnetic flux density, the magnetic flux density calculated based on the magnetic field density of each part and the vacuum permeability is added to the saturation magnetic flux density. A method for designing induction heating equipment, in which the temperature at each part is output.   The design method of the induction heating equipment according to claim 1, wherein in the step of inputting the physical property value, the physical property value including the magnetic permeability and the saturation magnetic flux density considering temperature dependency is input to the analysis device. .   The induction heating equipment according to claim 2, wherein in the step of inputting the physical property value, the saturation magnetic flux density calculated in advance by an experiment using a test piece made of the same kind of material as the member to be heated is input. Design method.   The induction heating equipment design method according to claim 3, wherein the member to be heated is made of steel.   5. The induction heating according to claim 4, wherein in the step of inputting the physical property value, the saturation magnetic flux density calculated based on experimental results at a plurality of temperatures in a temperature range below the Curie point of the steel is input. How to design the equipment.   6. The induction according to claim 5, wherein in the step of inputting the physical property value, the saturation magnetic flux density calculated based on an experimental result at a temperature of 5 or more in a temperature range below the Curie point of the steel is input. Heating equipment design method.   The induction heating equipment design method according to claim 5 or 6, wherein in the step of inputting the physical property value, the saturation magnetic flux density calculated based on experimental results at a plurality of temperatures including normal temperature is input.   8. The temperature output at each part according to claim 1, wherein the temperature at each part of the heated member is output in consideration of the current value distribution in the coil. Induction heating equipment design method.

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