JP2019157232A - Method of tempering annular work - Google Patents

Abstract

To suppress the occurrence of downtime due to the change of an annular work to be heated (tempered) as much as possible.SOLUTION: An induction heating device 20 has a plurality of coil parts 25 (25A to 25C) which are mutually different in diameter, separated from each other and arranged coaxially with each other in the axial direction of the annular work W. When executing an induction heating step S211 for induction-heating a hardened annular work W to a target temperature r1, The induction heating device 20 is energized in a state where the annular work W is coaxially arranged on an inner periphery of a coil part 25 having a minimum distance from the annular work W in the radial direction of the annular work W.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a method for tempering an annular workpiece.

  For example, in the manufacturing process of a machine part made of steel such as SUJ2, such as a bearing ring of a rolling bearing, an annular work (hereinafter simply referred to as “work”) as a base material of a machine part is usually used as a machine part. A quench hardening treatment is applied for imparting sufficient strength and hardness, and then a tempering treatment is performed for the purpose of relaxing residual stress and reducing residual austenite (improving toughness). The tempering process includes a heating process for heating a quenched workpiece to a target temperature and a cooling process for cooling the heated workpiece. In the heating process, the workpiece is heated using an atmospheric heating furnace or an induction heating device. The The “target temperature” is set mainly according to the operating temperature of the machine part.

  Atmospheric heating furnace has the advantage that temperature control is easy and multiple workpieces can be heated at the same time, but energy efficiency is low and it takes time to heat the workpiece to the target temperature. There are disadvantages such as. For this reason, the case where the workpiece | work is heated by induction heating in the said heating process is increasing (for example, patent document 1).

JP 2013-221199 A

  By the way, the heating efficiency of the work in the case of induction heating of the work depends on the distance in the radial direction between the coil for induction heating of the work and the work arranged coaxially in the opposing region (inner circumference and / or outer circumference). When the amount of current flowing through the coil is constant, the work can be efficiently heated as the distance between the coil and the work in the radial direction is smaller. For this reason, when a work is induction-heated by energizing a coil arranged coaxially with the work (see, for example, FIG. 5 of Patent Document 1), a coil having an appropriate diameter according to the diameter of the work is used. It can be said that it is preferable to do. However, if the workpiece is changed every time the workpiece to be heated is changed to one having a different diameter, the downtime increases and the productivity decreases, so that it is enjoyed by adopting induction heating. Cost merit is impaired.

  In view of the above circumstances, the present invention makes it possible to suppress as much as possible the occurrence of downtime associated with the change of the annular workpiece to be heated (tempered), thereby improving the processing efficiency of the tempering process and thus the productivity of machine parts. The purpose is to contribute to improvement.

  In order to achieve the above object, according to the present invention, in the method of tempering an annular workpiece provided with an induction heating step of induction heating the quenched annular workpiece to a target temperature, the diameter dimension is mutually reduced when the induction heating step is executed. And an induction heating device having a plurality of coil portions arranged coaxially and spaced apart from each other in the axial direction of the annular workpiece, the coil portion having the smallest separation distance from the annular workpiece in the radial direction of the annular workpiece An annular work is tempered by arranging an annular work on the opposite area of the coil and energizing the induction heating device in that state.

  According to said method, the induction heating apparatus which has two coil parts (1st and 2nd coil part) suitable for induction heating of the cyclic | annular workpiece | work of the model numbers A and B from which diameter dimensions differ mutually, for example is used If the annular workpiece to be heated is changed from the model number A to the model number B, when the annular workpiece of the model number B is induction-heated, the annular workpiece is guided coaxially in the opposing region of the second coil portion. What is necessary is just to energize a heating apparatus (2nd coil part), and it is not necessary to replace | exchange an induction heating apparatus. Therefore, it becomes possible to suppress or prevent the occurrence of downtime due to the change of the annular workpiece to be heated, and the tempering process can be efficiently performed.

  At the time of performing the induction heating process, it is preferable that the annular work is relatively rotated around the central axis with respect to the induction heating device while being held by a work holding member provided so as to be movable back and forth along the central axis. In this way, since each part in the circumferential direction of the annular workpiece can be heated uniformly, it becomes easy to obtain a high-quality annular workpiece having no variation in hardness or the like in the workpiece after the tempering process is completed.

  As the work holding member, for example, a work holding member which is provided so as to be movable back and forth in the radial direction of the annular work and has a work holding part for holding the annular work by engaging with the annular work in the radial direction, or the axial direction of the annular work And having a plurality of workpiece holding portions having different diameter dimensions of circular tracks passing through a portion that substantially holds the annular workpiece can be used.

In the tempering method according to the present invention, after the induction heating step is performed as described above, a heat retaining step is performed in which the annular workpiece is kept warm for a predetermined time within a predetermined temperature range including the target temperature by atmospheric heating. Also good. If it does in this way, while reducing the amount of retained austenite contained in the annular work after tempering processing to below a predetermined level, it will keep work hardness in a predetermined range (a work hardness is prevented from falling excessively). ) Is possible. Especially if the atmosphere is heated
-Since the entire workpiece can be kept at a uniform temperature, the variation in temperature within the workpiece is suppressed, and the annular workpiece after tempering is of high quality.
・ Temperature control at the time of executing the heat retention process can be performed easily and accurately.
・ Heat insulation can be applied to multiple workpieces simultaneously.
There are various advantages such as.

  As described above, when the heating method of the annular workpiece is different between the induction heating step and the heat retaining step, after the annular workpiece is heated to the target temperature (after the induction heating step is performed), the annular workpiece is heated. Need to be transferred to (heating device for performing). At this time, the temperature of the annular workpiece is reduced by a small amount. However, if the target temperature is set high in anticipation of this temperature decrease, there is a possibility that desired hardness or the like cannot be secured for the annular workpiece after tempering.

  Such a problem can be solved as much as possible by providing a rewarming step for recovering the temperature of the annular workpiece to the target temperature by atmospheric heating between the induction heating step and the heat retaining step. That is, if the temperature of the annular workpiece is restored to the target temperature before the heat retention step, the desired hardness or the like can be secured on the annular workpiece after the tempering process while efficiently performing the heat retention step. it can. In particular, if the temperature of the annular workpiece is recovered by atmospheric heating, the reheating process and the heat retaining process can be performed continuously using one atmosphere heating furnace, so the process shifts from the rewarming process to the heat retaining process. Both steps can be performed efficiently while suppressing a decrease in the temperature of the workpiece during the process.

  In this case, it is preferable to set the ambient temperature during the reheating process to be higher than the target temperature. In this way, since the time required for reheating can be shortened, the processing efficiency of the tempering process can be increased.

  The tempering method according to the present invention can be preferably applied to tempering an annular workpiece having a number of model numbers having different diameters, such as a bearing ring of a rolling bearing.

  As described above, according to the present invention, it is possible to suppress as much as possible the occurrence of downtime associated with the change of the annular workpiece to be heated (tempered). Thereby, the processing efficiency of a tempering process and by extension, productivity of a machine part can be improved.

It is a whole flowchart of the heat treatment process concerning the embodiment of the present invention. FIG. 4A is a flowchart of a tempering process, and FIG. 4B is a flowchart of a heating process included in the tempering process. It is the schematic of the tempering apparatus used at a tempering process. It is a schematic sectional drawing of the part in which a heating process is performed among tempering apparatuses. (A) A figure is a partial top view when the induction heating apparatus which concerns on one Embodiment is seen from upper side, (b) A figure is a schematic sectional drawing of the coil part which comprises the induction heating apparatus. FIG. 6 is a partially exploded perspective view of the induction heating device shown in FIG. It is a rear view of the induction heating apparatus shown to Fig.5 (a). It is a schematic sectional drawing of the workpiece | work holding member provided in an induction heating part, (a) A figure shows the state just before a workpiece | work holding member hold | maintains a workpiece | work, (b) The figure showed the workpiece | work holding member held the workpiece | work. It is a figure which shows a state. (A)-(c) figure is all sectional drawing which shows notionally the implementation state of an induction heating process. It is a figure which shows the temperature history of the workpiece | work at the time of execution of a tempering process. It is a schematic sectional drawing which shows the mode at the time of execution of the induction heating process which concerns on other embodiment. It is a top view when the workpiece holding member shown in FIG. 11 is seen from the upper side.

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

  FIG. 1 is a flowchart of a heat treatment process including a tempering process to which a tempering method according to an embodiment of the present invention is applied. The heat treatment step is, for example, a quenching step in which a hardening work is performed on an annular workpiece W made of a steel material such as a base material of an outer ring of a rolling bearing (see FIGS. 4 and 8; hereinafter, also simply referred to as “work W”). S1 and a tempering step S2 for tempering the hardened workpiece W. Examples of the steel material include SUJ2 and SUJ3 classified as high carbon chrome bearing steel defined in JIS G4805.

  In FIG. 1, between the quenching step S1 and the tempering step S2, a cleaning step S3 for cleaning the quenched workpiece W, and whether the cleaned and quenched workpiece W is a non-defective product that satisfies the quality standards. And an inspection step S4 for inspecting, and after the tempering step S2, a cleaning step S5 for cleaning the tempered workpiece W, and an inspection whether the cleaned tempered workpiece W satisfies a quality standard. An inspection step S6 is provided. However, all of the above steps S3 to S6 are not necessarily executed, and some or all of them may be omitted. Although illustration is omitted, after the quenching step S1 and / or tempering step S2, a finishing step for performing a finishing process such as polishing on the workpiece W may be additionally executed. Hereinafter, tempering process S2 which is the summary of this invention is demonstrated in detail.

  As shown in FIGS. 2 (a) and 2 (b), the tempering step S2 includes a heating step S21 for heating the quenched workpiece W and a cooling step S22 for cooling the workpiece W heated in the heating step S21. The heating step S21 aims at the temperatures of the induction heating step S211 for induction heating the workpiece W to the target temperature r1 (see FIG. 10) and the temperature of the workpiece W (the workpiece W whose temperature has dropped after being heated to the target temperature r1). It has a reheating step S212 for recovering to the temperature r1, and a heat retaining step S213 for keeping the work W recovered to the target temperature r1. Although details will be described later, in the reheating step S212 and the heat retaining step S213, the workpiece W is heated and kept warm by atmospheric heating.

  In FIG. 3, the schematic of the tempering apparatus 10 used in order to perform tempering process S2 is shown. The tempering apparatus 10 includes a transport path 11 in which the workpiece W is transported in a horizontal posture (a posture in which the central axis of the workpiece W is aligned in the vertical direction), a heating unit 12 that performs the heating step S21, and a heating unit 12. Is also provided on the downstream side of the transport path 11 and includes a cooling unit 13 that performs the cooling step S22. The heating unit 12 includes an induction heating unit 14 that performs the induction heating step S211, a rewarming unit 15 that performs the reheating step S212, and a heat retaining unit 16 that performs the heat retaining step S213, which are provided from the upstream side of the conveyance path 11. It arranges in order toward the downstream side.

  Although not shown in the drawings, examples of the transfer device for transferring the workpiece W along the transfer path 11 include a transfer conveyor, a power cylinder (such as a hydraulic cylinder, an air cylinder, and an electric cylinder), or an outside of the workpiece W. One that is horizontally moved along the conveyance path 11 in a state where the radial surface is chucked (a state in which the workpiece W is constrained in the reduced diameter direction) can be used alone or in combination of two or more.

  As shown in FIG. 4, the induction heating unit 14 accommodates the induction heating device 20 disposed above the conveyance path 11, the workpiece holding member 30 that holds the workpiece W to be heated, the induction heating device 20, and the like. The induction heating chamber 40 is provided.

  The induction heating chamber 40 has an inlet-side opening 40a and an outlet-side opening 40b, and both the openings 40a and 40b are opened or closed by opening / closing means 41 and 42, respectively. The induction heating chamber 40 is not necessarily provided, but if the induction heating chamber 40 is provided and the induction heating step S211 is performed in the internal space, it is easy to adjust the ambient temperature during the execution of the induction heating step S211. This is advantageous in accurately heating the workpiece W by induction and suppressing the temperature drop of the workpiece W after induction heating.

  As shown in FIGS. 5 (a) and 5 (b), the induction heating device 20 includes a plurality of coil members 21 (21A-21F) that are spaced apart from each other in the axial direction (vertical direction) of the workpiece W. Each coil member 21 is detachably fixed to a frame body (not shown) formed of an insulating material.

  As shown in FIG. 5 (a), each coil member 21 is formed of a tubular body made of a conductive metal such as a copper tube, and has an annular portion 22 having a ring shape with an end in the circumferential direction. It has the 1st and 2nd extension parts 23 and 24 extended from the circumferential direction one end part and the other end part. Of the coil member 21, at least the annular portion 22 is positioned on the same plane (here, on the horizontal plane) in the circumferential direction. Each coil member 21 is fixed to a frame body (not shown) in a state where the central axis of the annular portion 22 coincides with the central axis of the annular portion 22 of the other coil member 21.

  As shown in FIGS. 5 (a) and 5 (b), the induction heating device 20 includes a plurality of coils having different diameter dimensions (inner diameter dimensions) and coaxially spaced apart from each other in the axial direction of the workpiece W. Part 25. The induction heating device 20 of the present embodiment has three coil portions 25 (25A-25C), and is arranged on the inner diameter dimension D1 of the first coil portion 25A arranged on the lowermost side and on the upper side of the first coil portion 25A. The relational expression of D1> D2> D3 is established between the inner diameter dimension D2 of the second coil portion 25B and the inner diameter dimension D3 of the third coil portion 25C disposed on the upper side of the second coil portion 25B. .

  In the present embodiment, the first coil portion 25A is formed by the annular portion 22 of the coil members 21A and 21B arranged second from the bottom and the bottom, and the second coil portion 25B is the third and fourth from the bottom. The third coil portion 25C is formed by the annular portions 22 of the coil members 21E and 21F disposed at the fifth and sixth (topmost) positions from the bottom. Is done. In addition, each coil part 25 (25A-25C) can also be formed by the annular part 22 of the coil member 21 of 1 or 3 or more, and the axial direction dimension of each coil part 25 is the axial direction of the workpiece | work W which should be heated. It can be changed according to the dimensions.

  As shown in FIGS. 6 and 7, the induction heating device 20 includes connection means 26 that connects two coil members 21, 21 adjacent in the vertical direction so as to be conductive. The connecting means 26 in the illustrated example includes a receiving member 27 made of a conductive metal fixed to the coil member 21 and a conductive metal, and one end 28 a and the other end 28 b are each of two adjacent coil members 21. And a connecting member 28 fixed by bolt members 29 to the upper and lower coil members 21 (receiving members 27). The receiving member 27 is fixed to the coil member 21 by, for example, welding or adhesion using a conductive adhesive. In this case, the two adjacent coil members 21 and 21 can be conducted through the receiving member 27, the bolt member 29, and the connecting member 28. Therefore, in the induction heating device 20 of the present embodiment, among the plurality of coil members 21, the lowermost coil member 21A and the uppermost coil member 21F are electrically connected to the power source 17 shown in FIG.

  The connecting means 26 described above is merely an example, and other configurations can be employed. However, in the case of the connecting means 26 having the above configuration, the distance between the two coil members 21 and 21 adjacent in the axial direction (the axial dimension of each coil portion 25) is set to a predetermined value by the connecting member 28 made of a rigid body. There is an advantage that it is easy to keep.

  Further, when the induction heating device 20 having the above-described configuration is energized, a current flows uniformly to all the coil members 21 (coil portions 25A-25C), but the workpiece W to be heated is the first coil portion 25A, the first coil It arrange | positions in the opposing area | region of any one coil part among 2 coil part 25B and 3rd coil part 25C (it mentions later for details). For this reason, the induction heating apparatus 20 may be configured to allow a current to flow only through the coil portion 25 (any one of 25A-25C) for induction heating the workpiece W. Such a configuration can be achieved, for example, by (1) individually connecting the power supply 17 to each of the first coil unit 25A, the second coil unit 25B, and the third coil unit 25C, or (2) the first coil unit. This can be realized by providing the control device 18 with a switching device that selectively supplies current to any one of the coil portions 25A, the second coil portion 25B, and the third coil portion 25C. In this case, power saving in the induction heating step S211 can be achieved.

  The induction heating device 20 can be provided with a cooling circuit for cooling each coil member 21. If such a cooling circuit is provided, the temperature of the coil member 21 (particularly the annular portion 22 constituting the coil portion 25) can be controlled appropriately and efficiently, and the durability of the coil member 21 can be improved. Can do. For example, as shown in FIG. 7, the cooling circuit communicates the internal spaces of two coil members 21, 21 adjacent in the vertical direction via a tubular communication member 29 </ b> A and the first coil member 21 </ b> A (the first coil member 21 </ b> A). It can be formed by connecting a water supply pipe 29B and a drain pipe 29C to the free end of the extension 23) and the uppermost coil member 21F (the free end of the first extension 23), respectively.

  In this case, each coil member 21 is cooled by circulating the cooling water supplied from a water storage tank (not shown) as follows. First, the cooling water supplied from the water storage tank flows into the inner space of the lowermost coil member 21A via the water supply pipe 29B as shown by the white arrow in FIG. 7, and then the inside of the communication member 29A. The space and the internal space of the coil member 21 are alternately circulated and directed upward. And the cooling water which distribute | circulated the inner space of the uppermost coil member 21F is discharged | emitted outside via the drain pipe 29C connected to the uppermost coil member 21F. Note that, as described above, when a current is individually (selectively) passed through the first coil portion 25A, the second coil portion 25B, and the third coil portion 25C, the coil member 21 that forms each coil portion 25 ( A cooling circuit may be provided in each of the coil member 21 sets) to cool only the coil portion 25 (coil member 21) through which a current flows.

  As shown in FIGS. 8A and 8B, the work holding member 30 of the present embodiment is arranged coaxially with the coil portion 25 (25A-25C) of the induction heating device 20 shown in FIGS. 5A and 5B. A plurality of chucks that are arranged at predetermined intervals in the circumferential direction of the workpiece W and move forward and backward in the radial direction of the flange portion 32 (workpiece W). A claw 33 and a lifting mechanism (not shown) for moving the shaft portion 31 back and forth (moving up and down) in the axial direction of the workpiece W are provided. The workpiece holding member 30 having such a configuration acquires and holds the workpiece W transported along the transport path 11 as follows, for example.

  The work holding member 30 is conveyed at its upper end until the work W reaches a position directly below the coil part 25 of the induction heating device 20 (a position where the central axis of the work W and the central axis of the coil part 25 coincide). It is located below the path 11. When the workpiece W reaches a position directly below the coil portion 25, the shaft portion 31 moves upward as shown in FIG. 8A, and the chuck claw 33 is inserted into the inner periphery of the workpiece W. After the chuck claw 33 is inserted into the inner periphery of the workpiece W (after the lower end surface of the workpiece W comes into contact with the upper end surface of the flange portion 32), as shown in FIG. The chuck claw 33 and the workpiece W are engaged in the radial direction of the workpiece W. Thereby, the workpiece W is held by the workpiece holding member 30 in a state in which the center axis thereof coincides with the center axis of the shaft portion 31 (center axis of the coil portion 25). In addition, since the workpiece | work W is hold | maintained in the said aspect, the chuck | zipper claw 33 comprises a "work holding | maintenance part" in the workpiece holding member 30 of this embodiment.

  As schematically shown in FIG. 4, the work holding member 30 includes a rotation drive unit M coupled to a shaft unit 31. The rotation driving unit M allows the workpiece W held by the workpiece holding member 30 to rotate around its central axis. The rotational drive unit M is configured by an electric motor or the like.

  As shown in FIGS. 3 and 4, the reheating unit 15 is disposed in the first furnace chamber 51, which is connected to the induction heating chamber 40 via the first passage chamber 55, and in the first furnace chamber 51. 17 and a heater 52 electrically connected. The heater 52 is, for example, an electric heater, and heats the atmosphere (gas) in the first furnace chamber 51 to heat and recover the work W transported in the first furnace chamber 51.

  As shown in FIGS. 3 and 4, the heat retaining unit 16 includes a second furnace chamber 53 and a heater 54 that is disposed in the second furnace chamber 53 and is electrically connected to the power source 17. The heater 54 is, for example, an electric heater, and heats the atmosphere in the second furnace chamber 53 to keep the work W conveyed in the second furnace chamber 53 warm.

  The inlet side opening 51a of the first furnace chamber 51 is provided with opening / closing means 56 for opening and closing the opening 51a, and the outlet side opening of the first furnace chamber 51 (the inlet side of the second furnace chamber 53). The opening 51b is provided with opening / closing means 57 for opening / closing the opening 51b. Although not shown, the second furnace chamber 53 has an outlet side opening, and opening / closing means is also provided in this opening. With the above configuration, the sealing performance of the first furnace chamber 51 and the second furnace chamber 53 is ensured.

  As shown in FIG. 3, the heat retaining section 16 (the second furnace chamber 53 that constitutes the thermal insulation section 16) is connected to the cooling section 13 (the cooling chamber 59 that constitutes the thermal chamber 13) via the second passage chamber 58. As a result, the workpiece W heated by the heating unit 12 is carried into the cooling chamber 59 through the internal space of the second passage chamber 58 and then cooled (tempered). The cooling method of the workpiece W in the cooling unit 13 may be air cooling or water cooling.

  Next, the temperature condition (temperature history) of the tempering process in the tempering step S2 will be described based on FIG. 4 and FIG.

  As shown in FIG. 10, in the tempering step S2, first, in the induction heating step S211, the workpiece W is induction heated until the temperature of the workpiece W reaches the target temperature r1 from the heating start temperature r0. At this time, the rate of temperature increase is, for example, constant, and the induction heating device 20 is energized so that the temperature of the workpiece W increases continuously as time elapses. Such temperature history is, for example, maintaining the output of the induction heating device 20 at a constant value until the temperature of the workpiece W reaches the target temperature r1 (from the heating start time t0 to the heating end time t1). Can be realized.

  Next, the temperature of the workpiece W is recovered from the temperature r2 at the start of the recovery to the target temperature r1 by heating the workpiece W in the atmosphere in the recovery temperature step S212. As described above, since the heating method of the workpiece W is different between the induction heating unit 14 in which the induction heating step S211 is performed and the heat retaining unit 16 in which the heat retention step S213 is performed, the heat insulation is performed after the induction heating step S211 is performed. Until the process S213 is executed (started), the temperature of the workpiece W decreases from the target temperature r1. Therefore, as shown in FIG. 4, the work W carried out from the induction heating chamber 40 is carried into the first furnace chamber 51 and heated in the atmosphere, whereby the temperature of the work W is recovered to the target temperature r1 as quickly as possible. Let Such a temperature history is, for example, in the first furnace chamber 51 until the workpiece W reaches the target temperature r1 from the reheating start temperature r2 (between the reheating start time t2 and the rewarming end time t3). Can be realized by adjusting the output of the heater 52 of the reheating section 15 so that the ambient temperature becomes a temperature slightly higher than the target temperature r1 (for example, the target temperature r1 + 20 to 30 ° C.).

  After the temperature of the workpiece W is recovered to the target temperature r1, the workpiece W after rewarming is heated in the atmosphere in the heat retaining step S213, so that a temperature range of a predetermined width including the target temperature r1 (for example, the workpiece W) The temperature is kept for a predetermined time in the allowable temperature range R set according to the required amount of retained austenite and hardness. In the present embodiment, during the period from the heat retention start time t3 to the heat retention end time t4 (while the work W is transported in the second furnace chamber 53), the work W is maintained at a temperature substantially equal to the target temperature r1 (first operation). 2) The output of the heater 54 of the heat retaining section 16 is adjusted so that the atmospheric temperature in the furnace chamber 53 is maintained substantially equal to the target temperature r1. When the workpiece W is an outer ring of a rolling bearing made of high carbon chromium bearing steel as in this embodiment, the allowable temperature range R is, for example, 290 ° C. or higher and 340 ° C. or lower, preferably 303 ° C. or higher and 315 ° C. or lower. Can be set.

  Finally, the workpiece W is cooled in the cooling step S22, and the temperature of the workpiece W is lowered from the target temperature r1 to a predetermined temperature r3 (here, a temperature lower than the heating start temperature r0). Thereby, the tempering process for the workpiece W is completed.

  In the present embodiment, the output patterns of the induction heating device 20 and the heaters 52 and 54 are respectively controlled by the control unit so that the workpiece W put into the heating step S21 of the tempering step S2 follows the temperature history described above. 18 (see FIG. 4), and when the heating step S21 is performed, the control unit 18 sends a control signal to the power source 17 based on the stored output pattern. Thereby, electric power of a predetermined pattern is supplied to the induction heating device 20 and the heaters 52 and 54 connected to the power source 17, and the workpiece W is heated so as to follow the temperature history shown in FIG.

  Hereinafter, an example of a specific embodiment of the tempering step S2 executed using the tempering apparatus 10 having the above configuration will be described mainly with reference to FIGS.

  First, the inlet side opening 40 a of the induction heating chamber 40 is opened, and the workpiece W transferred on the transfer path 11 in a horizontal posture is carried into the internal space of the induction heating chamber 40. When the workpiece W reaches a position immediately below the induction heating device 20 (a position where the central axis of the workpiece W coincides with the central axis of the coil portion 25 provided in the induction heating device 20), FIG. The workpiece W is held by the workpiece holding member 30 as described with reference to FIG. The workpiece holding member 30 holding the workpiece W moves upward and introduces the workpiece W into the opposing region (inner circumference) of the coil portion 25.

  At this time, in this embodiment, the upward movement amount of the work holding member 30 is adjusted according to the diameter dimension (outer diameter dimension) of the work W. Specifically, as shown in FIG. 9A, the outer diameter D of the work W is the inner diameter D3 of the third coil portion 25C having the smallest diameter (inner diameter) among the coil portions 25A-25C. If smaller than [see FIG. 5B], the workpiece W is introduced into the inner periphery of the first coil portion 25C. As shown in FIG. 9B, the outer diameter D of the workpiece W is larger than the inner diameter D3 of the third coil portion 25C, and the inner diameter D2 of the second coil portion 25B [see FIG. 5B. ], The workpiece W is introduced into the inner periphery of the second coil portion 25B. Further, as shown in FIG. 9C, the outer diameter D of the workpiece W is larger than the inner diameter D2 of the second coil portion 25B, and the inner diameter D1 of the first coil portion 25A [see FIG. 5B. ], The workpiece W is introduced into the inner periphery of the first coil portion 25A. That is, the workpiece W has a plurality of coil portions 25 (25A-25C) that have different inner diameters and are coaxially arranged apart from each other in the axial direction of the workpiece W. It is coaxially arranged on the inner periphery of the coil portion 25 that minimizes the radial separation distance from the outer diameter surface of W.

  As described above, after the workpiece W is introduced into the inner periphery of the coil portion 25 (any one of 25A-25C), the induction heating device 20 is energized. Specifically, a predetermined pattern of electric power is supplied from the power source 17 toward the coil member 21 of the induction heating device 20 based on a control signal output from the control unit 18. Thereby, the workpiece | work W is induction-heated to target temperature r1 (refer FIG. 10). The power supplied from the power source 17 is preferably a low frequency band power of several kHz or less. Thereby, not only the surface layer portion of the workpiece W but also the entire workpiece W including the core portion of the workpiece W can be heated to the target temperature r1. Further, while the induction heating device 20 is energized and the work W is induction heated, the rotation driving unit M shown in FIG. 4 is driven to rotate the work W around its central axis. Thereby, the whole workpiece | work W can be heated equally.

  After the workpiece W is heated to the target temperature r1, as shown in FIG. 4, the workpiece holding member 30 is moved downward to return the workpiece W onto the conveyance path 11. After the workpiece W returned to the conveyance path 11 is carried out to the outside of the induction heating chamber 40 through the outlet side opening 40b of the induction heating chamber 40 in the open state, the internal space of the first passage chamber 55, and It is carried into the internal space of the first furnace chamber 51 through the inlet side opening 51 a of the first furnace chamber 51 opened by the opening / closing means 56. After the workpiece W is carried into the internal space of the first furnace chamber 51, the inlet side opening 51 a of the first furnace chamber 51 is closed by the opening / closing means 56.

  The workpiece W carried into the internal space of the first furnace chamber 51 is heated in the atmosphere while being conveyed in the first furnace chamber 51. As a result, as shown in FIG. 10, from the heating end time t <b> 1 to the reheating start time t <b> 2 (after the heating of the work W by the induction heating device 20 is finished, the work W is carried into the first furnace chamber 51. Until the temperature r2 is reduced to the target temperature r1.

  As shown in FIG. 4, the workpiece W whose temperature has recovered to the target temperature r <b> 1 passes through the outlet side opening 51 b of the first furnace chamber 51 (the inlet side opening of the second furnace chamber 53). It is carried into the interior space. The workpiece W carried into the internal space of the second furnace chamber 53 is kept warm within the allowable temperature range R (see FIG. 10) including the target temperature r1 while being transferred through the second furnace chamber 53. The heat retention time of the workpiece W (the conveyance time of the workpiece W in the second furnace chamber 53) is set to, for example, 3 minutes or more and 7 minutes or less, preferably 4 minutes or more and 6 minutes or less.

  As shown in FIG. 3, the work W that has passed through the internal space of the second furnace chamber 53 and is carried out of the second furnace chamber 53 passes through the second passage chamber 58 and enters the cooling chamber 59 of the cooling unit 13. Then, it is cooled to a predetermined temperature r3 (see FIG. 10) at a predetermined cooling rate. Thereby, the tempering process for the workpiece W is completed. A tempering process is performed on the subsequent workpiece W by following the same route.

  As described with reference to FIGS. 9A to 9C, in the present embodiment, when performing the induction heating step S211 included in the tempering step S2, the diameter size (inner diameter size) is different from each other, and Among induction heating devices 20 including a plurality of coil portions 25 (25A-25C) that are coaxially spaced apart from each other in the axial direction of the workpiece W, the separation distance from the workpiece W in the radial direction of the workpiece W is the smallest. The work W is coaxially arranged on the inner periphery of the coil portion 25 to be energized, and the induction heating device 20 is energized in that state.

  In this way, even when the induction heating is performed to the temperature r1 aiming at the workpieces W having different diameter dimensions (outer diameter dimensions), it is only necessary to adjust the relative position in the axial direction of the workpiece W with respect to the induction heating device 20. There is no need to replace the heating device 20. Therefore, it is possible to suppress or prevent the occurrence of downtime due to the change of the workpiece W to be heated, and the tempering process can be performed efficiently. Further, if the workpiece W is heated to the target temperature r1 by induction heating, the heating time of the workpiece W (required for executing the heating step S21 is greater than the case where the workpiece W is heated to the target temperature r1 by atmospheric heating. Time) can be greatly reduced. Therefore, it is possible to improve the processing efficiency of the tempering process, and consequently the productivity of the machine parts.

  On the other hand, in the present embodiment, an allowable temperature range R including the target temperature r1 is set according to the amount of retained austenite and hardness required for the workpiece W, and the target temperature r1 is heated within the allowable temperature range R. Since the workpiece W is kept warm, it is possible to keep the hardness of the workpiece W within a predetermined range while reducing the amount of retained austenite contained in the workpiece W after the tempering process to a required level or less. Moreover, since the workpiece | work W was kept warm by atmospheric heating, the whole workpiece | work W can be kept warm uniformly. Therefore, it is possible to stably obtain a mechanical component (here, the outer ring of a rolling bearing) suitable for use in a high temperature environment.

  In the present embodiment, a reheating step S212 for recovering the temperature of the workpiece W to the target temperature r1 between the induction heating step S211 and the heat holding step S213 where the workpiece W is heated (heated) by different heating methods is performed. Since it is provided, after the induction heating step S211 is completed, the heat retaining step S213 can be executed in a state in which the temperature of the workpiece W that has undergone a temperature drop before the heat retaining step S213 is started is recovered to the target temperature r1. it can. Therefore, the heat retention time of the workpiece W can be shortened. Further, in the rewarming step S212 and the heat retaining step S213, since the workpiece W is heated and kept warm by atmospheric heating, the rewarming step S212 and the heat retaining step S213 are continuously performed using one atmosphere heating furnace. Can do. Therefore, both processes S212 and 213 can be efficiently performed while suppressing a decrease in the temperature of the workpiece W when shifting from the rewarming process S212 to the heat retaining process S213.

  As mentioned above, although the tempering method which concerns on one Embodiment of this invention, and the tempering apparatus 10 used in order to perform this were demonstrated, embodiment of this invention is not restricted to this.

  For example, a work holding member 30 as shown in FIGS. 11 and 12 can be used for the induction heating unit 14. The workpiece holding member 30 shown in the figure includes a shaft portion 31 that moves up and down along the central axis of the coil portion 25, and workpiece holding portions 34A and 34B provided at a plurality of locations (three locations) spaced apart from each other in the vertical direction. , 34C. The workpiece holding portions 34A to 34C are provided at a plurality of locations (three locations in the illustrated example) spaced apart in the circumferential direction and extend radially outward, and near the outer diameter end of the radial portion 35. And a protrusion 36 that restrains (holds) the workpiece W in cooperation with another protrusion 36. The workpiece holding portions 34A to 34C have mutually different diameter dimensions of circular orbits passing through a portion that substantially holds the workpiece W (here, the outer diameter end portion of the protrusion 36), and each of the workpiece holding portions 34A to 34C is Between the diameter dimensions of the circular orbits T <b> 1 to T <b> 3, a relational expression of T <b> 1 diameter dimension> T <b> 2 diameter dimension> T <b> 3 diameter dimension is established.

  When such a workpiece holding member 30 is used and the outer diameter D of the workpiece W is smaller than the inner diameter D3 of the third coil portion 25C, the workpiece W is held by the workpiece holding portion 34C and the third coil. When the outer diameter D of the workpiece W is larger than the inner diameter D3 of the third coil portion 25C and smaller than the inner diameter D2 of the second coil portion 25B, introduced into the inner periphery of the portion 25C [see FIG. 9A]. The workpiece W is introduced into the inner periphery of the second coil portion 25B while being held by the workpiece holding portion 34B [see FIG. 9B and FIG. 11], and the outer diameter D of the workpiece W is the second coil portion 25B. 9 is smaller than the inner diameter D1 of the first coil portion 25A, the workpiece W is introduced into the inner periphery of the first coil portion 25A while being held by the workpiece holding portion 34A [FIG. c)]. Therefore, even if it is a case where such a workpiece holding member 30 is used, the effect as demonstrated above can be enjoyed similarly. However, unlike the workpiece holding member 30 described with reference to FIGS. 8A and 8B, the workpiece holding member 30 is moved up and down by a predetermined amount when the induction heating step S211 is performed (the two positions of the raised position and the lowered position). Move up and down between positions).

  The induction heating device 20 described above is provided with three coil portions 25 having different diameter dimensions (inner diameter dimensions), but the induction heating apparatus 20 has different diameter dimensions (inner diameter dimensions). Also, two or four or more coil portions 25 that are spaced apart from each other in the axial direction can be provided.

  Further, in the above, the present invention is applied to the case where the work W is heated to the target temperature r1 (see FIG. 10) by energizing the induction heating device 20 in a state where the work W is coaxially arranged on the inner periphery of the coil portion 25. However, the present invention can also be applied to the case where the work W is heated to the target temperature r <b> 1 by energizing the induction heating device 20 in a state where the work W is coaxially arranged on the outer periphery of the coil portion 25.

  Further, in the above, the tempering method according to the present invention is applied to tempering the outer ring (base material) of the rolling bearing. However, the present invention is applicable to other annular workpieces W, for example, the inner ring of a rolling bearing, a sliding bearing The present invention can also be preferably applied to a case where a tempering process is performed on a cage incorporated in an outer joint member, an inner joint member, a rolling bearing, or a constant velocity universal joint constituting the constant velocity universal joint.

  The present invention is not limited to the embodiment described above, and can be implemented in various forms without departing from the gist of the present invention. That is, the scope of the present invention is defined by the terms of the claims, and includes the equivalent meanings recited in the claims and all modifications within the scope.

DESCRIPTION OF SYMBOLS 10 Tempering apparatus 11 Conveying path 14 Induction heating part 15 Reheating part 16 Insulation part 20 Induction heating apparatus 25 Coil part 30 Work holding member D Diameter (outer diameter) dimensions D1, D2, D3 S21 Heating process S211 Induction heating process S212 Reheating process S213 Thermal insulation process W Work M Rotation drive part

Claims (7)

In the tempering method of the annular workpiece provided with the induction heating step of induction heating to the target temperature of the quenched annular workpiece, when performing the induction heating step,
Of the induction heating apparatus having a plurality of coil portions that are different in diameter from each other and are coaxially spaced apart from each other in the axial direction of the annular workpiece, the diameter of the annular workpiece in the radial direction of the annular workpiece is A method for tempering an annular workpiece, wherein the annular workpiece is coaxially arranged in an opposing region of a coil portion where a separation distance is minimized, and the induction heating device is energized in that state.   When the induction heating step is performed, the annular workpiece is relatively rotated about the central axis with respect to the induction heating device while being held by a workpiece holding member provided so as to be movable back and forth along the central axis. Item 2. A method for tempering an annular workpiece according to Item 1.   The work holding member is provided so as to be capable of moving forward and backward in the radial direction of the annular workpiece, and has a workpiece holding portion that holds the annular workpiece by engaging the annular workpiece in the radial direction of the annular workpiece. A method for tempering an annular workpiece according to claim 1.   The workpiece holding member includes a plurality of workpiece holding portions which are provided apart from each other in the axial direction of the annular workpiece and have different diameter dimensions of circular orbits passing through a portion which substantially holds the annular workpiece. Item 3. A method for tempering an annular workpiece according to Item 2.   5. The heat retaining step of retaining the annular work for a predetermined time within a predetermined temperature range including the target temperature is performed by atmospheric heating after the induction heating step is performed. Tempering method for annular workpieces.   The method for tempering an annular workpiece according to claim 5, further comprising a reheating step for recovering the temperature of the annular workpiece to the target temperature by atmospheric heating between the induction heating step and the heat retaining step.   The method for tempering an annular workpiece according to any one of claims 1 to 6, wherein the annular workpiece is a bearing ring of a rolling bearing.

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