Heat treatment method and heat treatment apparatus

Abstract

The present invention provides a heat treatment method and a heat treatment apparatus that can heat the peripheral edge of a workpiece having an annular or disc shape to a temperature that changes its properties, such as hardening. [Solution] The heat treatment method of this invention is a method for applying heat treatment to the peripheral edge 52 of a workpiece 51 having an annular or disc shape, and comprises a multi-stage process including: heating the peripheral edge 52 while the workpiece 51 is rotated around a central axis CL, and raising the temperature of the peripheral edge 52 by energizing an induction heating coil 21 located at a distance D1 from the peripheral edge 52; and a subsequent heating process that, after the preliminary heating process, further raises the temperature of the peripheral edge 52 by narrowing the distance D1.

Description

Technical Field

[0001] The present invention relates to a heat treatment method for performing heat treatment such as quenching on the peripheral portion of a workpiece having an annular or disc shape, and a heat treatment apparatus used for such heat treatment.

Background Art

[0002] For example, quenching of a steel material typically involves heating the workpiece of the steel material to a high temperature and then rapidly cooling it, and is performed for the purpose of improving hardness, strength, wear resistance, etc. due to the transformation of the structure during heating and rapid cooling.

[0003] Such a heat treatment method needs to be carried out in an appropriate manner considering various conditions including the shape of the workpiece.

[0004] For example, Patent Document 1 relates to "a method and apparatus for quenching a ring member such as a bush by induction heating", and under the purpose of "heating the ring member uniformly in a short time to improve productivity and reduce costs", "a pair of circular or semi-circular heating coils arranged on both side surfaces of the ring member to be quenched and flowing current in the same direction heat the ring member while rotating it, and the inner and outer circumferential surfaces and both side surfaces of the ring member are quenched. A method for induction heating and quenching of a ring member characterized by this" is proposed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, for an annular or disc-shaped part or member, in order to change the properties such as hardening at its peripheral portion, it may be used as a workpiece and the peripheral portion may be subjected to heat treatment over its entire circumference.

[0007] In this case, it is necessary to rotate the annular or disc-shaped workpiece around its central axis while energizing an induction heating coil placed close to the peripheral edge of the workpiece, thereby heating the peripheral edge to a temperature that changes its properties, such as hardening.

[0008] This invention aims to address the issues described above, and its objective is to provide a heat treatment method and a heat treatment apparatus that can heat the peripheral edge of a workpiece having an annular or disc shape to a temperature that changes its properties, such as hardening. [Means for solving the problem]

[0009] The heat treatment method of this invention is a method for applying heat treatment to the peripheral edge of a workpiece having an annular or disc shape, and comprises a multi-stage process including a preliminary heating process in which the peripheral edge is heated while the workpiece is rotated around a central axis, and the heating of the peripheral edge is increased by energizing an induction heating coil located at a distance from the peripheral edge, and a subsequent heating process in which, after the preliminary heating process, the distance is narrowed and the temperature of the peripheral edge is further increased.

[0010] In the heat treatment method described above, the induction heating coil has a one-side coil portion located on one side and a other-side coil portion located on the other side, separated by the peripheral edge in a direction parallel to the central axis of the workpiece, and when heating the peripheral edge, it is preferable to position the peripheral edge between the one-side coil portion and the other-side coil portion in the preceding heating process, and then narrow the gap between the peripheral edge and either the one-side coil portion or the other-side coil portion in the subsequent heating process.

[0011] In the above heat treatment method, when heating the peripheral portion, it is preferable to generate eddy currents in opposite directions around the central axis on the surface of the peripheral portion on one side and the surface of the peripheral portion on the other side, respectively, using the one-side coil portion and the other-side coil portion.

[0012] In the heat treatment method described above, it is preferable to narrow the gap between the induction heating coil and the workpiece by moving the workpiece during the subsequent heating process.

[0013] In the heat treatment method described above, it is preferable to raise the temperature of the peripheral portion to a temperature higher than the Curie point of the workpiece in the subsequent heating process.

[0014] In the heat treatment method described above, it is preferable to cool the peripheral portion after the subsequent heating process.

[0015] The heat treatment apparatus of this invention is used for heat treatment of the peripheral edge of a workpiece having an annular or disc shape, and comprises a rotation drive unit that rotates the workpiece around a central axis, an induction heating coil that is spaced apart from the peripheral edge and is energized to heat the peripheral edge, and a spacing adjustment unit that changes the spacing while the workpiece is rotated by the rotation drive unit.

[0016] In the heat treatment apparatus described above, it is preferable that the induction heating coil has a one-side coil portion located on one side separated by the peripheral edge in a direction parallel to the central axis of the workpiece, and a other-side coil portion located on the other side.

[0017] In the heat treatment apparatus described above, it is preferable that the induction heating coil is configured such that the one coil portion and the other coil portion each generate eddy currents in opposite directions around the central axis on the one surface and the other surface of the peripheral portion.

[0018] In the heat treatment apparatus described above, it is preferable that the spacing adjustment unit narrows the spacing by moving the workpiece.

[0019] In the heat treatment apparatus described above, it is preferable to further include a cooling unit for cooling the peripheral portion.

[0020] The above heat treatment apparatus further includes a transport unit that transports the rotation drive unit along the transport path, the induction heating coil is disposed on a side portion of the transport path along at least a part of the transport path, and the interval adjustment unit is configured to change the interval during the transport of the rotation drive unit by the transport unit due to a change in the shape of the induction heating coil and / or the movement of the workpiece during the extension along at least a part of the transport path. It is preferable that the interval can be changed.

[0021] In such a heat treatment apparatus, it further includes a cooling unit that cools the peripheral portion, the transport path is in a loop shape, the rotation drive unit circulates along the loop-shaped transport path by the transport unit, and after the rotation drive unit passes through the induction heating coil and then passes through the cooling unit, it is preferable that the induction heating coil and the cooling unit are arranged in this order along a part of the transport path in the transport direction of the rotation drive unit. [Effect of the Invention]

[0022] According to the heat treatment method and heat treatment apparatus of this invention, the peripheral portion of a workpiece having an annular or disc shape can be heated to a temperature that changes properties such as hardening. [Brief Description of the Drawings]

[0023] [Figure 1] It is a perspective view showing a heat treatment method (heat treatment apparatus) of an embodiment of this invention. [Figure 2] It is a perspective view showing a state where the induction heating coil is brought close to the peripheral portion of the workpiece in FIG. 1. [Figure 3] It is a cross-sectional view along the central axis CL of the workpiece in FIG. 2. [Figure 4] It is a cross-sectional view showing an enlarged main part of FIG. 3. [Figure 5] It is a cross-sectional view showing a state where the interval between the peripheral portion of the workpiece and the induction heating coil is narrowed from the state of FIG. 4. [Figure 6] It is a top view concept diagram showing a heat treatment apparatus of another embodiment of this invention. [Figure 7] Figure 6 is a side view showing the configuration of the heating element. [Modes for carrying out the invention]

[0024] Embodiments of this invention will be described in detail below with reference to the drawings. One embodiment of this invention involves a heat treatment method applied to an annular or disc-shaped workpiece 51, as illustrated in Figures 1 and 2, and to the peripheral edge 52 located on the outside of the workpiece 51 in the radial direction R, such as quenching.

[0025] The workpiece 51 can be subjected to the heat treatment method of this embodiment as long as it has an annular or disc-like shape. In the illustrated example, as can be seen from the cross-sectional view in the direction of the central axis CL shown in Figure 3, the workpiece 51 has a substantially circular hole 53C that penetrates in the direction of the central axis CL or the thickness direction of the workpiece 51 at the center of the central axis CL, and a hole 53 that penetrates in the direction of the central axis CL or the thickness direction of the workpiece 51 in a part of the circumferential direction (circumferential direction C) at the center (1 / 2R) toward the peripheral edge 52 (radius R direction) from the central axis CL (see also the enlarged views of Figures 4 and 5), and the outer contour shape in plan view is substantially circular, making it an annular or ring-shaped workpiece. Note that the substantially circular shape here includes not only a perfect circle but also an ellipse, and also includes cases where the shape of the circumferential direction C of the outer contour is a perfect circle or an ellipse and an uneven portion is formed along the circumferential direction C of the outer contour.

[0026] Furthermore, as shown in Figures 1 and 2, the peripheral edge 52 of the workpiece 51 is formed with a group of holes 52a, which consists of multiple elliptical holes that curve along the circumferential direction C in a plan view (the major axis is the circumferential direction C and the minor axis is the radial direction R), and substantially circular (perfectly circular or elliptical) holes, which penetrate in the direction of the central axis CL or the thickness direction, and are arranged in the circumferential direction C. In this embodiment, the peripheral edge 52 of the workpiece 51 is hardened by quenching. However, as long as the workpiece 51 is annular or disc-shaped, the shape of the details, such as the presence or absence of such holes 53 or the group of holes 52a, is not particularly important.

[0027] The material of workpiece 51 may be, for example, carbon steel or alloy steel.

[0028] A heat treatment apparatus 1 according to one embodiment of this invention, used for hardening the peripheral edge 52 of a workpiece 51, comprises a rotation drive unit 11 that rotates the workpiece 51 around a central axis CL, and an induction heating coil 21 that is positioned at a distance from the peripheral edge 52 of the workpiece 51 and heats the peripheral edge 52 by energizing it.

[0029] In the illustrated embodiment, the rotary drive unit 11 is configured, for example, to include rotary shaft portions 12a and 12b that rotate around the central axis CL of the workpiece 51 by the application of rotational driving force from a drive source (not shown), and workpiece holding portions 13a and 13b that are attached to the rotary shaft portions 12a and 12b and rotate together with the rotary shaft portions 12a and 12b, and hold the workpiece 51 by clamping it from the direction of the central axis CL.

[0030] More specifically, the rotary drive unit 11 is provided, for example, in one direction in the direction of the central axis CL of the workpiece 51, with its end attached to the hole 53C of the central axis CL of the workpiece 51, and rotates around the central axis CL of the workpiece 51 by the application of rotational driving force from a drive source (not shown), and a workpiece holding unit 13a attached to the rotary shaft unit 12a and rotating together with the rotary shaft unit 12a, pressing the workpiece 51 from one direction in the direction of the central axis CL, and in the other direction in the direction of the central axis CL of the workpiece 51 The device includes a rotating shaft portion 12b, which is provided on the device and is rotatable by the application of rotational driving force from a drive source (not shown) or in conjunction with the application of rotational driving force to the rotating shaft portion 12a, and which rotates around the central axis CL of the workpiece 51, and a workpiece holding portion 13b, which is attached to the rotating shaft portion 12b and rotates together with the rotating shaft portion 12b, and which presses the workpiece 51 from the other direction in the direction of the central axis CL, and the workpiece holding portions 13a and 13b are configured to hold the workpiece 51 by clamping it from the direction of the central axis CL.

[0031] Furthermore, the induction heating coil 21 can be positioned close to the peripheral edge 52 of the workpiece 51. By applying a high-frequency alternating current, an alternating magnetic flux is applied, which generates high-frequency eddy currents in the peripheral edge 52, and the peripheral edge 52 is heated by Joule heat. The induction heating coil 21 is connected to a power supply, although this is not shown in the figure, in order to enable current flow. Various forms of induction heating coils 21 can be used as long as such induction heating is possible.

[0032] The induction heating coil 21 of this embodiment has a one-side coil portion 22 located on one side (upper side in Figure 3) separated by a peripheral edge 52 in a direction parallel to the central axis CL direction of the workpiece 51, and a other-side coil portion 23 located on the other side (lower side in Figure 3). Furthermore, this induction heating coil 21 is provided on a part of the peripheral edge 52 in the circumferential direction. When the peripheral edge 52 is heated by the induction heating coil 21, as shown in Figures 2 to 5, it is sandwiched between the one-side coil portion 22 and the other-side coil portion 23 in a direction parallel to the central axis CL direction, and is positioned with intervals D1 and D2 from the one-side coil portion 22 and the other-side coil portion 23, respectively.

[0033] Preferably, when heating the peripheral portion 52, the one-sided coil portion 22 and the other-sided coil portion 23 are configured to pass currents in opposite directions to each other, thereby generating eddy currents in opposite directions around the central axis CL on the one-sided and other-sided surfaces of the peripheral portion 52. In other words, it is preferable that the induction heating coil 21 can perform induction heating of the peripheral portion 52 such that the direction of the eddy currents generated on one-sided surface of the peripheral portion 52 by the one-sided coil portion 22 and the direction of the eddy currents generated on the other-sided surface of the peripheral portion 52 by the other-sided coil portion 23 are opposite around the central axis CL. As a result, the one-sided surface of the peripheral portion 52 and the other-sided surface on its reverse side are heated at roughly the same rate, and the entire peripheral portion 52 can be heated uniformly.

[0034] However, in this case, especially with thin-walled workpieces 51 with a thickness of about 1.0 mm to 5.0 mm, when raising the temperature of the peripheral portion 52 to a high temperature exceeding the Curie point, the eddy currents generated on one surface of the peripheral portion 52 in the one-side coil portion 22 and the eddy currents generated on the other surface of the peripheral portion 52 in the other-side coil portion 23 cancel each other out, which may prevent the temperature of the peripheral portion 52 from rising to a sufficiently high temperature. To address this, as will be described in detail later, it is effective to narrow the distance D1 between the peripheral portion 52 and the induction heating coil 21 (in this case, the one-side coil portion 22) in the subsequent heating process, thereby enabling the peripheral portion 52 to be heated to a higher temperature.

[0035] In order to change the spacing D1 and D2 between the peripheral edge 52 and the induction heating coil 21 (one coil portion 22, the other coil portion 23), the heat treatment apparatus 1 of this embodiment is further equipped with a spacing adjustment unit 31. The spacing adjustment unit 31 changes the spacing D1 and D2 between the peripheral edge 52 and the induction heating coil 21 (one coil portion 22, the other coil portion 23) by moving at least one of the workpiece 51 and the induction heating coil 21 while the workpiece 51 is being rotated by the rotary drive unit 11.

[0036] In the illustrated embodiment, the rotating shaft portion 12a is provided with a driving force from a drive source (not shown), allowing it to move together with the rotating shaft portion 12b and the workpiece holding portions 13a, 13b in a direction parallel to the central axis CL direction, and this is designated as the spacing adjustment portion 31. When the rotating shaft portions 12a, 12b move together with the workpiece holding portions 13a, 13b in the aforementioned direction, the workpiece 51 held by the workpiece holding portions 13a, 13b is also moved in the aforementioned direction, and the spacing D1, D2 between the peripheral edge portion 52 of the workpiece 51 and the coil portion 22 on one side and the coil portion 23 on the other side is changed (see Figures 4 and 5). In other words, this spacing adjustment portion 31 moves the workpiece 51. However, in addition to or instead of this, the spacing adjustment portion 31 may move the induction heating coil 21.

[0037] Incidentally, when the heat treatment apparatus 1 is used for quenching, for example, among other heat treatments, it may be further equipped with a cooling unit 41 for cooling the peripheral portion 52. The illustrated cooling unit 41 is, as an example, located on the side of the peripheral portion 52, at a different position from the induction heating coil 21 in the circumferential direction C, and has a number of coolant injection ports on the peripheral portion 52 side, and when cooling the peripheral portion 52, it sprays liquid such as water or other coolant from the coolant injection ports toward the peripheral portion 52.

[0038] To perform heat treatment on the peripheral portion 52 of the workpiece 51 using the heat treatment apparatus 1 described above, for example, first, the end of the rotating shaft portion 12a is attached to the hole 53C of the central axis CL of the workpiece 51, and the workpiece 51 is held by being sandwiched between the workpiece holding portions 13a and 13b, and the workpiece 51 is rotated around the central axis CL by rotating the rotating shaft portions 12a and 12b as shown in Figures 1 and 2.

[0039] Next, in that state, as shown by the white arrows in Figure 2, the induction heating coil 21 is brought closer to the workpiece 51, so that a portion of the circumferential edge 52 of the workpiece 51 is positioned between the one coil portion 22 and the other coil portion 23. As a result, the workpiece 51, which is rotating around the central axis CL, has each circumferential portion of its circumferential edge 52 continuously pass between the one coil portion 22 and the other coil portion 23.

[0040] Here, when current is passed from the power supply to the induction heating coil 21, each circumferential portion of the peripheral edge 52 is subjected to induction heating each time it passes between the one coil portion 22 and the other coil portion 23, and the entire circumferential portion of the peripheral edge 52 is heated. When heating the peripheral edge 52 in this manner, in this embodiment, a preliminary heating process is performed to raise the temperature of the peripheral edge 52, followed by a subsequent heating process to further raise the temperature of the peripheral edge 52.

[0041] In the preliminary heating process, the peripheral portion 52 can be positioned at any axial location between the one coil portion 22 and the other coil portion 23, but it is preferable to position it in the center of the space between the one coil portion 22 and the other coil portion 23, as shown in Figure 4, for example. When the peripheral portion 52 is in this position, the distance D1 between the peripheral portion 52 and the one coil portion 22 and the distance D2 between the peripheral portion 52 and the other coil portion 23 become substantially equal. In one example, the distances D1 and D2 in the preliminary heating process may both be 5 mm.

[0042] In this case, as mentioned above, in the preceding heating process, it is preferable to generate eddy currents in opposite directions around the central axis CL on the surface of one side of the peripheral portion 52 and the surface of the other side of the peripheral portion 52 using the one-side coil portion 22 and the other-side coil portion 23. This allows the entire peripheral portion 52 to be heated uniformly to a certain temperature.

[0043] On the other hand, in this case, as also mentioned earlier, with a thin-walled workpiece 51, the effect of eddy currents generated on one surface of the peripheral portion 52 in one coil portion 22 and eddy currents generated on the other surface of the peripheral portion 52 in the other coil portion 23 canceling each other out becomes significant. Therefore, in the predetermined intervals D1 and D2 in the preceding heating process, when it is necessary to raise the temperature of the peripheral portion 52 to a temperature that exceeds the Curie point, it may not be possible to raise the temperature to that high.

[0044] To address this, a subsequent heating process is performed in this embodiment. In the subsequent heating process, the gap D1 between the peripheral edge 52 and the coil portion 22 is narrowed by moving the workpiece 51 in the gap adjustment unit 31, as shown by the white arrow in Figure 5. For example, the gap D1 may be set to 2 mm in the subsequent heating process. Consequently, the gap D2 between the peripheral edge 52 and the coil portion 23 widens. Here, it is sufficient that the gap D1 between at least a part of the induction heating coil 21 (such as the coil portion 22 on one side) and the peripheral edge 52 is narrowed.

[0045] According to this, in the subsequent heating process, as the peripheral portion 52 approaches the one-side coil portion 22, the heating efficiency of the peripheral portion 52 by the one-side coil portion 22 increases, and the temperature of the peripheral portion 52 can rise further. Therefore, according to this embodiment, it is possible to heat the peripheral portion 52 uniformly in the preceding heating process, and then heat the peripheral portion 52 to a desired temperature, for example, higher than the Curie temperature, in the subsequent heating process. The Curie point is a unique temperature determined according to the material of the workpiece 51.

[0046] Further processes such as constant temperature, heating, or cooling may be performed before the initial heating process, between the initial and subsequent heating processes, and / or after the subsequent heating process. At least the initial heating process and the subsequent heating process, performed at a later time, are included in the heat treatment method of this invention if the temperature of the peripheral portion 52 is increased by energizing the induction heating coil 21 in both the initial and subsequent heating processes, and the initial heating process is in a relatively low temperature range and the subsequent heating process is in a relatively high temperature range.

[0047] After heating the peripheral portion 52, the peripheral portion 52 can be cooled by continuing to rotate it as needed and spraying refrigerant from the cooling unit 41 toward the peripheral portion 52. It is preferable to cool the peripheral portion 52 after the subsequent heating process. This allows for effective hardening of the peripheral portion 52.

[0048] As can be seen from the above, according to the heat treatment method described here, in the subsequent heating process, the distance D1 between the peripheral portion 52 and the induction heating coil 21 is narrowed compared to the distance in the preceding heating process, thereby allowing the peripheral portion 52 of the workpiece 51 to be heated to a relatively high temperature.

[0049] Another embodiment of the present invention, the heat treatment apparatus 1A used for hardening the peripheral edge 52 of the workpiece 51, is provided with a transport unit 10, a heating unit 20, a cooling unit 40, a rotary drive unit 30, and a spacing adjustment unit 31A, as shown in Figure 6. The same rotary drive unit 30 as the rotary drive unit 11 shown in Figure 1 above can be used. Similarly, the same cooling unit 40 as the cooling unit 41 shown in Figure 1 above can be used.

[0050] The transport unit 10 transports the rotary drive unit 30, to which the workpiece 51 (see Figure 7) is attached, along the transport direction C1. The path along which the rotary drive unit 30 is transported along the transport direction C1 is called the transport path. The transport unit 10 includes, for example, a conveyor 10A with multiple rotary drive units 30 mounted on it at intervals from each other in the transport direction C1, as shown in Figure 6. The operation of the conveyor 10A causes the rotary drive units 30 to move along the transport direction C1 on the conveyor 10A and be transported. The transport unit 10 can employ any configuration as long as it can move the rotary drive units 30 in the transport direction C1.

[0051] As shown in Figure 6, the heating unit 20 is located on at least one side (both sides in Figure 6) of the side of the transport path (the portion adjacent to the lateral direction L1 perpendicular to the transport direction C1 of the transport path), and includes a heating element 20A that induces heating of the peripheral edge 52 of the workpiece 51 supported by the rotary drive unit 30 passing through there. The heating element 20A includes an induction heating coil (for example, the induction heating coil 21 shown in Figure 1). The heating unit 20 can adopt any configuration as long as it includes an induction heating coil capable of heating the workpiece 51 transported by the transport unit 10.

[0052] It is preferable that the heating unit 20 is positioned on both sides of the transport path, as shown in Figure 6. By positioning it on both sides of the transport path, the heating of the peripheral edge 52 of the workpiece 51 in the circumferential direction C can be made uniform. Furthermore, it is preferable that the cooling unit 40 is also positioned on both sides of the transport path, as shown in Figure 6. By positioning it on both sides of the transport path, the cooling of the peripheral edge 52 of the workpiece 51 in the circumferential direction C can be made uniform.

[0053] In this example, the spacing adjustment section 31A is comprised of a portion where the shape of the heating element 20A of the induction heating coil changes as it extends along the transport path, as shown in Figure 7. Figure 7 is a side view mainly showing the configuration of the heating element 20A in Figure 6. In addition to the heating element 20A (induction heating coil), Figure 7 also shows the change in the distance between the peripheral edge 52 of the workpiece 51 and the heating element 20A as the workpiece 51, held by the rotary drive unit 30, rotates and is transported in the transport direction C1 together with the rotary drive unit 30. Here, as the workpiece 51 moves along the transport direction C1, the distance between the peripheral edge 52 and the heating element 20A changes from T1 to T2.

[0054] More specifically, the heating element 20A includes a one-sided coil portion located on the upper side in Figure 7, and a other-sided coil portion located below the one-sided coil portion, separated by the workpiece 52. As shown in Figure 7, the one-sided coil portion and the other-sided coil portion each consist of a first region 20A1 located upstream in the transport direction C1, a second region 20A2 located downstream in the transport direction C1 and shifted downward from the first region 20A1, and a third region 20A3 extending diagonally, connecting the first region 20A1 and the second region 20A2. In this heating element 20A, as the workpiece 51 moves in the transport direction C1 together with the rotary drive unit 30, the first region 20A1 of the one-sided coil portion has a gap T1 between it and the peripheral edge 52 of the workpiece 51, but after passing through the second region 20A3, the gap between the second region 20A2 of the one-sided coil portion and the peripheral edge 52 of the workpiece 51 changes to T2. The spacing adjustment section 31A can also be formed by changing the shape of the heating element 20A (induction heating coil) along the transport path.

[0055] By using the shape of the heating element 20A as described above (by using the spacing adjustment unit 31A), it is possible to heat both sides of the peripheral edge 52 of the workpiece 51 to a relatively uniform temperature over its entire circumference while raising the temperature to a reasonably high level. Furthermore, in this case, since the rotary drive unit 30 does not require a mechanism to move the workpiece 51, such as the spacing adjustment unit 31 shown in Figure 5, or a mechanism to move the induction heating coil, the manufacturing cost of the heat treatment apparatus 1A in the embodiment shown in Figures 6 and 7 can be reduced.

[0056] In addition to providing a spacing adjustment unit 31A that adjusts the spacing by changing the shape of the heating element 20A, the heat treatment apparatus 1A may also be provided with a spacing adjustment unit that moves the workpiece 51 and / or the heating element 20A.

[0057] In other words, the heat treatment apparatus 1A of the embodiment shown in Figures 6 and 7 is used for heat treatment of the peripheral edge 52 of a workpiece 51 having an annular or disc shape, and comprises a rotary drive unit 30 that rotates the workpiece 51 around a central axis, a transport unit 10 that transports the rotary drive unit 30 along a transport path, and a heating unit 20 (induction heating coil) which is positioned on the side of the transport path along at least a part of the transport path of the transport unit 10 and is energized to heat the peripheral edge 52, and the heating unit 20 constitutes a heating body 20A, and the heating body 20A comprises a spacing adjustment unit 31A which can change the spacing during transport by the rotary drive unit 30 by the transport unit 10 due to a change in shape along the transport path.

[0058] Specifically, as shown in Figure 6, the conveying unit 10 of the heat treatment apparatus 1A has multiple rotary drive units 30 mounted so as to be rotatable in the conveying direction C1 with a distance between them, and the rotary drive units 30 move in the conveying direction C1 as the conveying unit 10 operates. In addition, in the heat treatment apparatus 1A, the conveying path of the conveying unit 10 is loop-shaped or endlessly ring-shaped, and the conveying unit 10 is configured to cause the rotary drive units 30 to circumvent the loop-shaped conveying path.

[0059] Furthermore, the heat treatment apparatus 1A has, in a loop-shaped transport path, a workpiece installation area 100, an induction heating area 200 (heating unit 20 (heating body 20A)), a cooling area 300 (cooling unit 40), a workpiece removal area 400, and a rotary drive unit return area 500, in order in the circumferential direction of the rotary drive unit 30 (i.e., the transport direction C1). For this reason, the heating body 20A (induction heating coil) and the cooling unit are each arranged along a part of the transport path, and the rotary drive unit 30, which is transported along the transport direction C1, passes through the heating body 20A and then through the cooling unit 40.

[0060] In the workpiece installation area 100, the workpiece 51 is attached to the rotary drive unit 30. The workpiece 51 is set in the rotary drive unit 30 when the rotary drive unit 30 returns to the workpiece installation area 100 via the workpiece support return area 500. Next, the rotary drive unit 30 with the workpiece 51 set enters the induction heating area 200 (induction heating coil), where the peripheral edge 52 of the workpiece 51 enters the space between one coil portion and the other coil portion, and is induction heated by the heating element 20A (induction heating coil) as it passes through the space in the first area 20A1, the third area 20A3, and the second area 20A2. Next, the induction heated workpiece 51 enters the cooling area (cooling unit 40) 300, where it is cooled from the peripheral edge 52 by the cooling element (cooling jacket 40A). Next, the cooled workpiece 51 enters the workpiece removal area 400 and is removed from the rotary drive unit 30. The rotary drive unit 30, from which the workpiece 51 has been removed, passes through the workpiece support return area 500 and then circulates back to the workpiece installation area 100.

[0061] As shown in Figure 6, the heat treatment apparatus 1A further includes a cooling unit 40 for cooling at least the peripheral portion 51 of the workpiece 51. The transport path of the transport unit 10 is loop-shaped, and the rotary drive unit 30 is driven by the transport unit 10 to circulate along the loop-shaped transport path. The heating unit 20 and the cooling unit 40 are arranged along a part (transport section) of the transport path in the transport direction C1 of the rotary drive unit 30, such that the rotary drive unit 30 passes the induction heating coil 20 and then the cooling unit 40. Therefore, the heat treatment apparatus 1A can also be applied to tempering treatment in induction heating by adjusting the heating temperature of the heating unit 20A. [Explanation of Symbols]

[0062] 1 Heat treatment apparatus 1A Heat treatment apparatus 10 Conveying section 11 Rotary drive unit 12 Rotating shaft section 13a Workpiece holding section 13b Workpiece holding section 20 Heating Units 21 Induction heating coil 22 One-sided coil section 23 Other side coil section 31 Spacing adjustment section 41 Cooling section 51 Work 52 Peripheral area 52a Hole group 53 Hole CL center axis

Claims

1. A method for applying heat treatment to the peripheral edge of a workpiece having an annular or disc shape, While the workpiece is rotated around its central axis, the peripheral portion is heated. A heat treatment method having multiple stages, the heating of the peripheral portion being performed by energizing an induction heating coil located at a distance from the peripheral portion to raise the temperature of the peripheral portion, and the subsequent heating process being performed after the preliminary heating process by narrowing the distance to further raise the temperature of the peripheral portion.

2. The induction heating coil has a one-side coil portion located on one side separated by the peripheral edge in a direction parallel to the central axis of the workpiece, and a other-side coil portion located on the other side. The heat treatment method according to claim 1, wherein, when heating the peripheral portion, in the preceding heating process, the peripheral portion is positioned between the one coil portion and the other coil portion, and in the subsequent heating process, the distance between the peripheral portion and either the one coil portion or the other coil portion is narrowed.

3. The heat treatment method according to claim 2, wherein, when heating the peripheral portion, the one coil portion and the other coil portion each generate eddy currents in opposite directions around the central axis on the one surface and the other surface of the peripheral portion.

4. The heat treatment method according to claim 1 or 2, wherein in the subsequent heating process, the distance between the induction heating coil and the workpiece is narrowed by moving the workpiece.

5. The heat treatment method according to claim 1 or 2, wherein in the subsequent heating process, the temperature of the peripheral portion is raised to a temperature higher than the Curie point of the workpiece.

6. The heat treatment method according to claim 1 or 2, wherein the peripheral portion is cooled after the subsequent heating process.

7. A heat treatment apparatus used for heat treatment of the peripheral edge of a workpiece having an annular or disc shape, A rotational drive unit that rotates the workpiece around a central axis, An induction heating coil is positioned at a distance from the aforementioned peripheral portion and is energized to heat the peripheral portion, With the workpiece being rotated by the aforementioned rotation drive unit, the interval adjustment unit changes the interval. A heat treatment apparatus equipped with the following features.

8. The heat treatment apparatus according to claim 7, wherein the induction heating coil has a one-side coil portion located on one side separated by the peripheral edge in a direction parallel to the central axis of the workpiece, and a other-side coil portion located on the other side.

9. The heat treatment apparatus according to claim 8, wherein the induction heating coil is configured such that the one coil portion and the other coil portion each generate eddy currents in opposite directions around the central axis on the one surface and the other surface of the peripheral portion.

10. The heat treatment apparatus according to claim 7 or 8, wherein the interval adjustment unit narrows the interval by moving the workpiece.

11. The heat treatment apparatus according to claim 7 or 8, further comprising a cooling unit for cooling the peripheral portion.

12. The system further comprises a transport unit that transports the aforementioned rotary drive unit along a transport path, The induction heating coil is positioned on the side of the transport path, along at least a portion of the transport path. The heat treatment apparatus according to claim 7 or 8, wherein the spacing adjustment unit can change the spacing during transport of the rotary drive unit by the transport unit due to a change in the shape of the induction heating coil and / or the movement of the workpiece as it extends along at least a portion of the transport path.

13. The system further comprises a cooling unit for cooling the aforementioned peripheral portion. The transport path is loop-shaped, and the transport unit causes the rotary drive unit to rotate along the loop-shaped transport path. The heat treatment apparatus according to claim 12, wherein the induction heating coil and the cooling unit are arranged in this order along a part of the transport path in the transport direction of the rotary drive unit, such that the rotary drive unit passes through the induction heating coil and then the cooling unit.

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