Design equipment for heat treatment devices

Abstract

To provide a design device of a heating treatment device, capable of conducting an optimal shape of an outer shape of a coil in the heating treatment device that heats a workpiece in an induction heating.SOLUTION: A design device 1 is for designing a heating treatment device 30 for performing an induction heating of a front surface temperature of a heated part Wh of a workpiece W to Curie point or larger of the workpiece W by a coil 10. The design device 1 comprises: a depth position setting part 31 that sets a predetermined depth position Wa from a front surface of the heated part Wh; a target function setting part 33 that sets a plurality of optional points at the depth position Wa of the heated part Wh is to measurement points W1 to W3 ..., and a target function Q related to a temperature difference between measurement points at a time when a designation time Ts previously designated from a start of the induction heating elapses; and an optimal shape calculation part 35 that calculates an optimal shape of an outer shape of the coil 10 so that the target function Q becomes the minimum value in a state where the minimum value of an increase ratio of the front surface temperature of the heated part Wh in a period before an elapse of the designated time Ts from the start of the induction heating is regulated.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a design apparatus for a heat treatment apparatus. [Background Art]

[0002] Patent Document 1 discloses a configuration in which a workpiece is subjected to induction heating using a coil to perform heat treatment. In this configuration, an auxiliary base material is brought into contact with an end portion of the workpiece, and the auxiliary base material is also induction-heated together with the workpiece. Thereby, eddy current is generated in the auxiliary base material, excessive heating of the end portion of the workpiece due to the edge effect is suppressed, and uniform heat treatment in the workpiece is achieved. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2018-032511 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] However, when the surface temperature of the heated portion of the workpiece exceeds the Curie point due to induction heating, the surface of the heated portion loses ferromagnetism. As a result, the induced current that has been generated on the surface of the heated portion moves to the inside of the heated portion, increasing the current density inside the heated portion. On the other hand, the current density on the surface of the heated portion decreases. Thereby, although induction heating continues to be performed inside the heated portion, the temperature partially decreases on the surface of the heated portion, causing variation in surface temperature, and heat treatment may not be performed uniformly. Therefore, in a heat treatment apparatus that induction-heats a workpiece, it is required to find the optimal outer shape of a coil that suppresses the occurrence of variation in the surface temperature of the workpiece.

[0005] The present invention has been made in view of such a problem, and an object of the present invention is to provide a design apparatus for a heat treatment apparatus that can derive the optimal outer shape of a coil in a heat treatment apparatus that induction-heats a workpiece. [Means for solving the problem]

[0006] One aspect of the present invention is a design apparatus for designing a heat treatment apparatus that induces heating of a portion of a workpiece to a point above the Curie point of the workpiece by using a coil arranged opposite the portion of the workpiece to be heated, A depth position setting unit for setting a predetermined depth from the surface of the heated portion, An objective function setting unit sets an objective function that correlates with the temperature difference between arbitrary points at a predetermined depth in the heated section after a predetermined time has elapsed from the start of induction heating, The design apparatus includes an optimal shape calculation unit that derives an optimized shape for the coil's outer shape such that the objective function is minimized, while restricting the minimum value of the rate of increase in the surface temperature of the heated part during the period from the start of induction heating to the time specified above has elapsed. [Effects of the Invention]

[0007] In the design apparatus of the above embodiment, the external shape of the coil in the heat treatment apparatus that induces heating of the surface temperature of the heated portion of a workpiece to a temperature above the Curie point is optimized so that the objective function correlated with the temperature difference between any point at a predetermined depth from the surface of the heated portion at a predetermined time after induction heating has elapsed is minimized. This makes it possible to consider changes in the current density inside the heated portion when optimizing the external shape of the coil, and to derive an external shape of the coil that can suppress variations in the surface temperature of the heated portion of the workpiece.

[0008] Furthermore, in the design apparatus of the above embodiment, the objective function is to minimize the temperature difference at the time specified above has elapsed from the start of induction heating. Therefore, it is not necessary to consider the temperature difference at times other than the specified time elapsed. This significantly reduces the amount of computation required in the design apparatus and thus reduces the computational load.

[0009] Furthermore, the derivation of the optimal shape described above is performed while restricting the minimum rate of increase in the surface temperature of the heated part during the period before the specified time has elapsed from the start of induction heating. Therefore, by simply slowing down the temperature rise of the heated part due to induction heating, it is possible to exclude cases where the surface temperature has not reached the Curie point after the specified time has elapsed, thereby improving the accuracy of the optimal shape.

[0010] As described above, according to the above embodiment, it is possible to provide a design apparatus for a heat treatment apparatus that can derive the optimal shape of the coil in a heat treatment apparatus that inductively heats a workpiece. [Brief explanation of the drawing]

[0011] [Figure 1] Conceptual diagram of the design device in Embodiment 1. [Figure 2] Functional block diagram of the design device in Embodiment 1. [Figure 3] A cross-sectional view of the workpiece and the coil having its initial shape, taken along line III-III in Figure 1, according to Embodiment 1. [Figure 4] A diagram illustrating the overview of the heat treatment analysis and optimization process performed by the design device in Embodiment 1. [Figure 5] A flowchart of the optimization process by the design device in Embodiment 1. [Figure 6] A cross-sectional view of the workpiece and the coil having the optimal shape in Embodiment 1, located along line III-III in Figure 1. [Figure 7] The figure shows examples of (a) the temperature at the measurement point inside the coil in the test example and (b) the temperature at the measurement point on the surface of the coil in the test example during the verification test. [Figure 8] (a) A figure showing an example of the measured point temperature on the coil surface of Comparative Example 1 in the confirmation test, and (b) A figure showing an example of the measured point temperature on the coil surface of Comparative Example 2. [Modes for carrying out the invention]

[0012] (Embodiment 1) 1. Configuration of Design Device 1 The design apparatus 1 in Embodiment 1 will be described with reference to Figure 1. The design apparatus 1 consists of a memory device and a computing device, and includes a heat treatment analysis unit 2 and an optimization processing unit 3. The design apparatus 1 calculates the optimal shape of the outer shape of the coil 10, which will be described later.

[0013] 2. Configuration of Heat Treatment Analysis Unit 2 As shown in Figures 1 and 2, the heat treatment analysis unit 2 includes a heat treatment apparatus 30 comprising a coil 10 and a control unit 20, and a workpiece W, as an analysis model. The external shape of the coil 10 is the target of design of the design apparatus 1, which will be described later. As shown in Figure 1, the coil 10 is annular in shape and has a refrigerant flow path 10a through which a cooling refrigerant flows, as shown in Figure 3. The workpiece W, which will be described later, is located inside the coil 10. As shown in Figure 3, in the initial state before optimization, the cross-sectional external shape of the coil 10 is rectangular, and the inner surface 10b of the coil facing the workpiece W is initially flat. The control unit 20 applies a high-frequency alternating current to the coil 10 to induce heating of the workpiece W located inside the coil 10.

[0014] The type of heat treatment performed by the heat treatment apparatus 30 is not limited, but it is a treatment that heats the workpiece W to a temperature above the Curie point Cp described later, and can be, for example, quenching, annealing, or normalizing. In this embodiment 1, the heat treatment apparatus 30 is used to perform quenching on the workpiece W. The conditions for the quenching treatment are, for example, induction heating at approximately 900°C for 10 seconds. Furthermore, quenching using high-frequency induction current allows for partial hardening of only the necessary parts of the workpiece W and shortens the processing time.

[0015] As shown in Fig. 1, the workpiece W is induction-heated by the heat treatment apparatus 30 while being inserted through the inner side of the coil 10. The workpiece W may be made of any ferromagnetic material, for example, iron, carbon steel, stainless steel, or the like. The Curie point Cp (Curie temperature) of the workpiece W is determined based on the material forming the workpiece W. For example, the Curie point Cp is about 770°C for iron, 700 to 800°C for carbon steel, and about 750°C for stainless steel. In the first embodiment, the material of the workpiece W is S55C (carbon steel for machine structural use), and the Curie point thereof is about 735°C. The Curie point Cp is the temperature at which the phase transition between ferromagnetism and paramagnetism occurs in a magnetic material. When the temperature exceeds the Curie point, the ferromagnetism of the magnetic material disappears and the material becomes paramagnetic.

[0016] The shape of the workpiece W is not limited, but it shall be of a shape and size that can be inserted through the inner side of the coil 10. In the first embodiment, the workpiece W has a substantially columnar shape, and is provided with a recess W0 in the middle in the axial direction Z. The recess W0 is formed in a groove shape continuous in the circumferential direction of the workpiece W, and the cross-sectional shape thereof is a substantially semicircular arc-shaped concave curved surface as shown in Fig. 3.

[0017] 3. Configuration of optimization processing unit 3 The optimization processing unit 3 shown in Fig. 1 performs processing for optimizing the outer shape of the coil 10. As shown in Fig. 2, the optimization processing unit 3 includes a depth position setting unit 31, a measurement point temperature acquisition unit 32, an objective function setting unit 33, a fixed point setting unit 34, and an optimal shape calculation unit 35.

[0018] The depth position setting unit 31 sets the depth positions Wa of the measurement points W1 to W3 in the heated portion Wh of the workpiece W shown in Figure 3. The depth position Wa refers to a predetermined depth from the surface of the heated portion Wh. The depth a of the depth position Wa is not limited, but if the heat treatment device 30 performs a quenching treatment on the workpiece W, it can be set to be equivalent to the effective hardening depth in the quenching treatment that has been set in advance. For example, the depth a can be 1.0 to 10 mm, preferably 1.0 to 5.0 mm, and in this embodiment 1, the depth a is set to 3.0 mm. In this embodiment 1, the depth position Wa has an arc portion corresponding to the shape of the recess W0. The effective hardening depth refers to the distance from the surface of the hardened layer to the position of Vickers hardness 550 (550 HV) when the workpiece is in the as-quenched state or when tempering is performed at a temperature not exceeding 200°C.

[0019] The measurement point temperature acquisition unit 32 acquires the temperature of a measurement point at depth position Wa in the heated portion Wh of the workpiece W. The measurement point can be set to any point on depth position Wa. In this embodiment 1, the first to third measurement points W1 to W3 on depth position Wa are shown as examples. The first measurement point W1 is at the upper end of the arc portion of depth position Wa, the second measurement point W2 is at the center of the arc portion of depth position Wa, and the third measurement point W3 is at the lower end of the arc portion of depth position Wa. The temperature of the measurement point acquired by the measurement point temperature acquisition unit 32 can be a theoretical value calculated by the heat treatment analysis unit 2 or an estimated value based on simulation, but instead, it may be an actual measured value obtained by induction heating the actual workpiece W.

[0020] The objective function setting unit 33 sets an objective function for optimizing the external shape of the coil 10. The objective function is set as a function that correlates with the temperature difference between measurement points at a specified time Ts elapsed from the start of induction heating of the heated part Wh of the workpiece W. For example, the objective function can be defined based on the temperature difference between the average temperature of all measurement points and the temperature of any measurement point at a specified time Ts elapsed from the start of induction heating of the workpiece W. In this embodiment 1, the objective function Q is the average temperature of all measurement points T at a specified time Ts elapsed from the start of induction heating of the workpiece W. ave Given that the temperature T is at an arbitrary measurement point and the range Ω of the heated part Wh is defined as a function expressed by the following equation (1).

[0021]

number

[0022] The specified time Ts for obtaining the temperature difference in the objective function is not limited, but for example, if the heat treatment device 30 performs a quenching treatment on the workpiece W, the specified time Ts can be set to a time equivalent to the pre-set quenching treatment time. In this embodiment 1, the specified time Ts is set to 10 seconds, which is equivalent to the quenching treatment time. Note that the specified time Ts may be any time pre-set by the user, regardless of the type of heat treatment performed in the heat treatment device 30.

[0023] As shown in Figure 3, the fixed point setting unit 34 sets fixed points 17 that do not change during the optimization of the outer shape of the coil 10. The position of the fixed points 17 on the coil 10 is not limited, but in this embodiment 1, it is a point located on a virtual line Wb that extends in the normal direction (X direction in the cross-section shown in Figure 3) from the deepest part of the recess W0. That is, the intersection of the virtual line Wb and the workpiece W and the inner surface 10b of the coil in the initial state before optimization is set as the fixed point 17.

[0024] In the external shape of the coil 10, points other than the fixed point 17 become tolerance points where variation is permitted in the optimization of the external shape of the coil 10. The tolerance points can be any points other than the fixed point 17 of the external shape of the coil 10. In this embodiment 1, Figure 3 shows examples of tolerance points 11 to 16 on the inner surface 10b of the coil.

[0025] By setting the fixed point 17 using the fixed point setting unit 34, the coil 10 is prevented from moving excessively far from the workpiece W. This restricts the minimum value of the rate of increase in the surface temperature of the heated part Wh during the period before the specified time Ts has elapsed from the start of induction heating of the workpiece W. Alternatively, to restrict this minimum value, instead of setting the fixed point 17, the surface temperature of the heated part Wh may be obtained at two or more time points during the period before the specified time Ts has elapsed from the start of induction heating of the workpiece W, the rate of change may be calculated as the rate of increase, and the optimization described later may be performed so that the minimum value of this rate of increase is restricted.

[0026] The optimal shape calculation unit 35 derives an optimized shape for the coil 10 such that the objective function Q is minimized, while restricting the minimum value of the rate of increase of the surface temperature of the heated part Wh during the period from the start of induction heating of the workpiece W until the specified time Ts has elapsed. In this embodiment 1, as described above, a fixed point 17 is set as the state in which the rate of increase is restricted, and the optimized shape for the coil 10 is derived at the variable tolerance points 11 to 16 excluding the fixed point.

[0027] The optimization algorithm in the optimal shape calculation unit 35 is not limited, and known algorithms such as the least squares method, steepest descent method, pattern search method, Nelder-Mead method, genetic algorithm, particle swarm optimization, differential evolution method, cuckoo search, and firefly algorithm can be used. In this embodiment 1, the least squares method is adopted as the optimization algorithm.

[0028] 4. Optimization process for the coil's outer shape The flow of the optimization process for the external shape of the coil 10 in this embodiment 1 will be explained with reference to Figures 4 and 5. As shown in Figure 4, the optimization process involves repeatedly performing a heat treatment in the heat treatment analysis unit 2 and changing the external shape of the coil 10 in the optimization processing unit 3, and calculating the optimal shape of the external shape of the coil 10 based on the optimization algorithm.

[0029] The specific flow is shown in Figure 5. First, in step S1 of Figure 5, the workpiece W to be hardened is set as the analysis model in the heat treatment analysis unit 2. The workpiece W is cylindrical with a diameter D1 of 50 mm and a length of 149 mm, and as shown in Figure 1, a semicircular recess W0 with a depth a of 3 mm is provided in the heated part Wh set in the middle of the axial direction Z, as shown in Figure 3. The workpiece W is then inserted inside the coil 10 provided in the heat treatment device 30.

[0030] Next, in step S2 of Figure 5, the initial shape of the coil 10's outer form and the fixed point 17 are set. In this embodiment 1, as shown in Figure 1, the initial shape of the coil 10's outer form is annular, with an inner diameter of D2, an outer diameter of D3, a height of H1, and a rectangular cross-sectional shape. The workpiece W is positioned such that the inner surface 10b of the coil facing the workpiece W is parallel to the axial direction Z of the workpiece W. As described above, the fixed point 17 is the intersection of the imaginary line Wb and the inner surface 10b of the coil in the initial state.

[0031] Next, in step S3, the depth position setting unit 31 sets the depth position Wa of the workpiece W, and in step S4, the objective function setting unit sets the objective function Q shown in equation (1) above. Then, in step S5, the heat treatment analysis unit 2 starts induction heating of the workpiece W by passing a high-frequency current through the coil 10 and performs a heat treatment analysis of the workpiece W.

[0032] Then, in step S6, the measurement point temperature acquisition unit 32 acquires the temperature of an arbitrary measurement point on the depth position Wa after a preset specified time Ts of 10 seconds has elapsed, and the optimal shape calculation unit 35 calculates the value of the objective function Q. Subsequently, in step S7, it is determined whether the objective function Q is at its minimum value based on the least squares algorithm. If it is determined that the objective function Q is not at its minimum value, the process proceeds to step S7 No., and in step S8, the external shape of the next coil 10 is changed. The external shape of the coil 10 is changed by changing the positions of the allowable variation points 11 to 16 while maintaining the fixed point 17. Then, the process returns to step S5, induction heating of the workpiece W is started based on the new external shape of the coil 10, and the heat treatment analysis of the workpiece W is performed.

[0033] On the other hand, if in step S7 the objective function Q is determined to be at its minimum value based on the least squares algorithm, the process proceeds to Yes in step S7, and in step S9 the optimal shape of the coil 10's outer form is determined, ending the flow. In this embodiment 1, the outer form of the coil 10 shown in Figure 6 was calculated as the optimal shape. The flow then ends.

[0034] 5. Confirmation test of optimal shape Next, a verification test was performed on the coil 10 having the optimal shape calculated by the design apparatus 1 of Embodiment 1. The test conditions for the verification test were as follows: the material of the workpiece W was S55C (Curie point 735℃), the depth a of the depth position Wa was 3.0 mm, the frequency of the high-frequency current flowing through the coil 10 was 6.8 kHz, the current value was 5800 A, and the heating time was 20 sec. The workpiece W was inductively heated by the coil 10 in the heating apparatus 30.

[0035] As a test example, when a workpiece W was induction heated under the above conditions using a coil 10 having the optimal shape shown in Figure 6, calculated by design device 1, the temperature changes at measurement points W1 to W3 on the depth position Wa of the workpiece W and the temperature changes at measurement points W1' to W3' on the surface of the heated part Wh were obtained and shown in Figures 7(a) and 7(b), respectively. The first measurement point W1' is at the upper end of the arc portion of the recess W0, the second measurement point W2' is at the deepest part of the recess W0, and the third measurement point W3 is at the lower end of the arc portion at depth position Wa. In addition, as comparative example 1, when a workpiece W was induction heated under the above conditions using a coil 10 with its initial shape, the temperature changes at measurement points W1' to W3' on the surface of the heated part Wh were obtained and shown in Figure 8(a).

[0036] Furthermore, as Comparative Example 2, when the workpiece W was induction heated using a coil having a comparatively optimal shape calculated to minimize the temperature variation of the surface measurement points (including W1' to W3') on the heated portion Wh of the workpiece W 10 seconds after the start of induction heating, the temperature change of the measurement points W1' to W3' on the surface of the heated portion Wh was obtained and is shown in Figure 8ba).

[0037] As shown in Figure 7(a), in the coil 10 with the optimal shape, the objective function Q is at its minimum value 10 seconds after the start of induction heating, as calculated by the optimal shape calculation unit 35. At this time, as shown in Figure 7(b), the temperatures of the surface W1'~W3' of the workpiece W show little variation and exceed the Curie point Cp almost simultaneously, indicating early heating and a stable temperature approximately 9 seconds after the start of induction heating.

[0038] On the other hand, as shown in Figure 8(a), in the initial state of coil 10, a temperature drop occurred at the second measurement point W2', which is the deepest part of the recess W0 among the surface W1' to W3' of the workpiece W, approximately 7 to 11 seconds after the start of induction heating. Then, it took approximately 12 seconds for the temperature to stabilize at measurement points W1' to W3'.

[0039] Here, as shown in Figure 8(a), in the comparative example, the first measurement point W1' and the third measurement point W3' are located at the edge of the recess W0, so the magnetic flux is easily concentrated by induction heating, and the Curie point is reached earlier than at the second measurement point W2'. As a result, at the first measurement point W1' and the third measurement point W3', the ferromagnetism disappears and the induced current moves into the interior of the workpiece W and disperses. Then, at the first measurement point W1' and the third measurement point W3', although there is an inflow of heat from the interior where the current density has increased, the temperature does not drop. However, at the second measurement point W2', it is inferred that the temperature drops as a result of the dispersion of the induced current and the cessation of the inflow of heat from the first measurement point W1' and the third measurement point W3' where the ferromagnetism has disappeared.

[0040] Furthermore, as shown in Figure 8(b), in Comparative Example 2, the surface temperature was generally uniform 10 seconds after the start of induction heating. However, in this case, the rate of increase in surface temperature from the start of induction heating to 10 seconds was smaller than in the test example shown in Figure 7(a), and the temperature of the surface measurement point had not reached the Curie point Cp by 10 seconds from the start of induction heating. Then, when the temperature of the surface measurement point reached the Curie point Cp due to subsequent induction heating, a temperature decrease occurred at the second measurement point W2', similar to the case of the initial shape.

[0041] As described above, according to this verification test, with the coil 10 having the optimal shape according to the design device 1 of this embodiment, it was confirmed that the temperature at depth position Wa 10 seconds after the start of induction heating was made uniform, and it was confirmed that the surface temperature of the heated part Wh of the workpiece W can be heated to a stable temperature early on, exceeding the Curie point while maintaining a uniform surface temperature.

[0042] In this verification test, the surface temperature of the workpiece W was kept below 800°C, which is below the target temperature of approximately 900°C for normal quenching. However, since the surface temperature of the workpiece W exceeds the Curie point Cp, it is presumed that equivalent results to this verification test can be obtained even if the surface temperature of the workpiece W is heated to the target temperature for quenching.

[0043] 6. Effects The following describes the effects of the design apparatus 1 of this embodiment 1. In the design apparatus 1, the external shape of the coil 10 in the heat treatment apparatus 30 that induces heating of the surface temperature of the heated portion Wh of the workpiece W to a temperature above the Curie point Cp is optimized so that the objective function Q, which correlates with the temperature difference between any point Wa at a predetermined depth from the surface of the heated portion Wh after a predetermined time Ts has elapsed since induction heating, is minimized. As a result, in optimizing the external shape of the coil 10, it is possible to consider the change in current density inside the heated portion Wh, and to derive an external shape of the coil 10 that can suppress variations in the surface temperature of the heated portion Wh of the workpiece W.

[0044] Furthermore, in the design apparatus 1 of this embodiment, the objective function Q correlates with the temperature difference at a specified time Ts after the start of induction heating. Therefore, it is not necessary to consider the temperature difference at times other than the specified time Ts. This significantly reduces the amount of computation required in the design apparatus 1 and thus reduces the computational load.

[0045] Furthermore, the optimal shape of the coil 10 is derived while restricting the minimum rate of increase in the surface temperature of the heated part Wh during the period before the specified time Ts has elapsed from the start of induction heating. Therefore, by simply slowing down the temperature rise of the heated part Wh due to induction heating, it is possible to exclude cases where the surface temperature has not reached the Curie point after the specified time Ts has elapsed, thereby improving the accuracy of the optimal shape.

[0046] Furthermore, in this embodiment 1, a fixed point setting unit 34 is provided in which one point on the surface of the coil 10 is set as a fixed point 17 whose position is fixed, and the other arbitrary points on the surface of the coil 10 are set as variable-allowance points 11 to 16 whose position is allowed to change. This restricts the minimum value of the rate of increase of the surface temperature of the heated part Wh during the period before the specified time Ts has elapsed from the start of induction heating. The optimal shape calculation unit 35 then derives an optimized shape of the coil 10 excluding the fixed point 17 so that the objective function Q is minimized. This prevents the coil 10 from moving too far away from the workpiece W without performing calculations that place an excessive load on the system, and ensures that the temperature of the surface measurement point reaches the Curie point by the time Ts has elapsed from the start of induction heating, thereby reducing the computational load of optimizing the coil 10.

[0047] Furthermore, in this embodiment 1, the heated portion Wh has a recess W0, and the fixed point 17 is located on a virtual line Wb extending in the normal direction from the deepest part W2' of the recess W0. The deepest part W2' is the position in the heated portion Wh that is furthest from the coil 10 and is therefore difficult to heat. By setting this deepest part W2' as the fixed point 17, it is possible to prevent the difficult-to-heat area from becoming a variable tolerance point, further moving away from the workpiece W, and preventing the surface of the heated portion Wh of the workpiece W from exceeding the Curie point Cp by the specified time Ts from the start of induction heating.

[0048] Furthermore, in this embodiment 1, the heat treatment apparatus 30 is configured to perform a quenching treatment on the workpiece W by induction heating, and the depth position setting unit 31 sets the position of depth a based on the effective hardening depth in the quenching treatment of the workpiece W, which is set in advance. As a result, the temperature at the depth position Wa where the quenching treatment is performed is calculated, so the effect of the quenching treatment can be taken into consideration, and the accuracy of the optimization of the coil 10 can be improved.

[0049] Furthermore, in this embodiment 1, the objective function setting unit 33 sets the objective function Q based on the temperature difference between the average temperature of all measurement points W at depth position Wa and the temperature of any measurement point at depth position Wa when a specified time Ts has elapsed from the start of induction heating. This makes it possible to confirm that a hardened layer has been formed up to the effective hardening depth when performing quenching treatment on the workpiece W, thereby improving reliability.

[0050] In the design apparatus 1 of this embodiment, a rectangular cross-sectional shape was adopted as the initial shape of the coil 10 before optimization, as shown in Figure 3. However, the apparatus is not necessarily limited to this, and a different shape may be used as the initial shape.

[0051] As described above, according to the above embodiment, it is possible to provide a design apparatus 1 for a heat treatment apparatus 30 that can derive the optimal shape of the outer shape of the coil 10 in a heat treatment apparatus 30 that inductively heats a workpiece.

[0052] The present invention is not limited to the embodiments described above, and can be applied to various embodiments without departing from its spirit. [Explanation of Symbols]

[0053] 1 Design equipment 2. Heat Treatment Analysis Department 20 Heat treatment apparatus 10 coils 11-16 Permissible variation points 17 Fixed points 3. Optimization Processing Unit 31 Depth position setting section 32 Measurement point temperature acquisition section 33 Objective Function Setting Section 34 Fixed point setting section 35 Optimal Shape Calculation Unit Double job W1~W3 measurement points

Claims

1. A design apparatus for designing a heat treatment apparatus that induces heating of a workpiece to a surface temperature above the Curie point of the workpiece by using a coil positioned opposite the part of the workpiece to be heated, A depth position setting unit for setting a predetermined depth from the surface of the heated portion, A unit for setting an objective function that sets an objective function correlated with the temperature difference between multiple arbitrary points at a predetermined depth in the heated portion, and that occurs after a predetermined time has elapsed from the start of induction heating, A design apparatus for a heating apparatus, comprising: an optimal shape calculation unit that derives an optimized shape for the coil so that the objective function is minimized, while restricting the minimum value of the rate of increase of the surface temperature of the heated part during the period from the start of induction heating to the time specified above has elapsed.

2. The device includes a fixed point setting unit that restricts the rate of increase by setting one point on the surface of the coil as a fixed point with a fixed position, and setting other arbitrary points on the surface of the coil as variable points where positional variation is permitted. The design apparatus for a heat treatment apparatus according to claim 1, wherein the above-mentioned optimal shape calculation unit derives an optimized shape of the coil, excluding the fixed points, such that the above-mentioned objective function is minimized.

3. The design apparatus for a heat treatment apparatus according to claim 2, wherein the heated portion has a recess, and the fixing point is located on a virtual line extending in the normal direction from the deepest part of the recess.

4. The above-mentioned heating apparatus is configured to perform the quenching treatment of the workpiece by induction heating, The design apparatus for a heat treatment apparatus according to any one of claims 1 to 3, wherein the depth position setting unit sets the depth position based on the effective hardening depth of the workpiece in the heat treatment described above, which has been set in advance.

5. The design apparatus for a heating apparatus according to any one of claims 1 to 3, wherein the objective function setting unit sets the objective function based on the temperature difference between the average temperature of all measurement points and the temperature of any measurement point at a specified time elapsed from the start of induction heating.

Images