JP2019061833A - Induction heating method and induction heating apparatus - Google Patents

Abstract

To easily increase the heating accuracy of an annular work when an annular work is inductively heated to a target temperature by a continuous heating method.SOLUTION: When each of a plurality of annular works W is sequentially inductively heated to a target temperature by intermittently feeding the plurality of annular work pieces W coaxially arranged from one side in the axial direction toward the other side in the axial direction to pass through the opposing region of the heating coil 3 in the energized state, the end 3a of the heating coil 3 on the other side in the axial direction is located on the other side in the axial direction as compared with the end Wa of the annular work W on the other side in the axial direction located at the position P2 immediately before the heating is completed from among the plurality of annular works W located in the opposing region of the heating coil 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an induction heating method and an induction heating apparatus.

  For example, in the manufacturing process of mechanical parts made of steel such as SUJ2 like bearing rings of rolling bearings, heat treatment (quench hardening) is performed to give the mechanical parts etc. required for the mechanical parts. Be done. The hardening and hardening process includes a heating step of heating the necessary region of machine parts (workpieces) to a target temperature, and a cooling step of cooling and quenching the required region.

By the way, hardening of a work is roughly classified into whole hardening which hardens the whole work and hardening which hardens only the surface of the work and forms a hardened layer on the surface layer of the work. As the heating method when carrying out the entire hardening, adopt the atmosphere heating which easily heats the whole work uniformly, and as the heating method when carrying out the surface hardening, use the induction heating which easily makes the work partial heating However, in recent years, it has been considered to adopt induction heating also when carrying out the entire hardening. The reason is that induction heating (induction heating apparatus) has various advantages as follows.
・ Because only the work can be heated directly, high energy efficiency can be achieved.
-A much more compact heating device can be realized compared to an atmosphere heating furnace.
-Productivity can be improved because start-up and shut-down of the heating device can be completed in an instant.
-Since the atmosphere control is unnecessary, the heating device (heating step) can be simplified.

  However, particularly in the case of generally quenching a large-lot workpiece such as the above-mentioned raceway ring, when inductively heating the workpiece, how to efficiently heat a plurality of workpieces becomes an issue. As technical means for solving such a problem, a plurality of coaxially arranged workpieces and a heating coil in an energized state are relatively moved in the axial direction, and the plurality of workpieces are sequentially passed through the opposing regions of the heating coil. A so-called continuous heating method is known in which each of a plurality of workpieces is induction-heated sequentially to a target temperature (for example, Patent Document 1).

JP, 2015-67880, A

  In adopting the continuous heating method, it is necessary to design and use a heating coil capable of inductively heating a workpiece with a heat pattern (temperature history) such that the workpiece after quenching can obtain desired mechanical properties. The heat pattern differs depending on the shape, material and the like of the work, but in any case, it is required to minimize the variation in temperature in the work (heated work) at the completion of heating. If the variation in temperature becomes large, the work is likely to be deformed along with the hardening of the work due to the difference in the timing of reaching the martensitic transformation start temperature (Ms point) at the time of hardening.

  In order to prevent as much as possible deformation of the workpiece accompanying hardening, it is preferable to make the temperature variation within the heated workpiece within 5 ° C. However, the shape (coil pitch) of the heating coil that can realize this can not be set uniquely, and trial and error are repeatedly set according to the shape, size (mass), material, etc. of the work. The fact is that

  In view of the above situation, the present invention makes it possible to easily enhance the heating accuracy of the work when induction heating the work (annular work) to the target temperature by the continuous heating method, thereby having the desired mechanical characteristics. The purpose is to make it possible to mass-produce the machine parts at low cost and stably.

  In order to achieve the above object, in the present invention, a plurality of coaxially arranged annular workpieces are intermittently fed from one side to the other side in the axial direction to pass through the opposing region of the heating coil in the energized state. Thus, when induction heating each of the plurality of annular workpieces sequentially to the target temperature, the other axial end of the heating coil is located at a position immediately before the heating is completed among the plurality of annular workpieces located in the opposing region of the heating coil. There is provided an induction heating method characterized in that it is positioned on the other side in the axial direction than the end on the other side in the axial direction of the annular work to be positioned. In addition, "a position just before the completion of heating" here is synonymous with the position discharged | emitted out of the opposing area | region of a heating coil, when several cyclic | annular workpieces are intermittently fed next.

  According to such an induction heating method, temperature variation in the annular work (heated work) after completion of heating can be suppressed to within 5 ° C. Furthermore, such effects can be realized by a plurality of coaxially arranged It can be enjoyed only by appropriately setting the axial relative position of the annular work and the heating coil. Therefore, even when the plurality of annular works are sequentially inductively heated to the target temperature by the continuous heating method, the heating accuracy of the annular works can be easily and inexpensively improved.

  In the above configuration, the annular work (following work to be heated) at a normal temperature is between the support member for supporting the plurality of annular works coaxially arranged in a stacked state from the lower side and the annular work adjacent to the support member. It is preferable to intermittently feed a plurality of annular works as they are supplied. In this way, the heat treatment can be efficiently performed on a large number of annular works while simplifying the apparatus configuration of the induction heating apparatus used to perform the continuous heating.

  Further, in order to achieve the above object, according to the present invention, a feeding means for intermittently feeding a plurality of coaxially arranged annular works from one side in the axial direction toward the other side in the axial direction, and a plurality of annular works coaxially It is an induction heating apparatus provided with a heating coil which arranges and inductively heats each of a plurality of annular works intermittently fed to a target temperature sequentially, the other end of the heating coil in the axial direction being opposed to the heating coil An induction heating device is provided, which is positioned on the other axial direction side of an end portion on the other axial direction side of an annular work located on a position immediately before completion of heating among a plurality of annular works located on a region.

  Even in the induction heating apparatus having the above configuration, the same effects as those of the above-described induction heating method according to the present invention can be obtained.

  The feed means comprises a support member for supporting from a lower side a plurality of annular works coaxially arranged in a stacked state, and a work supply means for supplying an annular work at a normal temperature between the annular works adjacent to the support member. be able to.

  The induction heating method and the induction heating apparatus according to the present invention should preferably be applied, for example, to induction heating an annular work which is generally a large lot such as a race (ring or outer ring) of a rolling bearing. Can.

  From the above, according to the induction heating method and the induction heating apparatus according to the present invention, it is possible to easily increase the heating accuracy of the work even when the plurality of annular works are sequentially induction heated to the target temperature by the continuous heating method. it can. This makes it possible to mass-produce high-quality machine parts having desired mechanical properties at low cost and stably.

It is a schematic diagram of an induction heating device concerning an embodiment of the present invention. It is a figure for demonstrating the operation | movement aspect of a supporting member, Comprising: (a) A schematic plan view in case a supporting member is in the 1st state which can support annular work, (b) A supporting member It is a schematic plan view when in the second state. (A) Figure-(f) Each figure is a schematic diagram which shows the induction heating apparatus in working. It is a figure which shows the test result of a confirmation test (evaluation test).

  Hereinafter, embodiments of the present invention will be described based on the drawings.

  FIG. 1 shows a schematic view of an induction heating apparatus according to an embodiment of the present invention. The induction heating apparatus 1 shown in the figure constitutes a heating portion of a heat treatment apparatus used to totally quench an annular work W (for example, the inner ring of a rolling bearing) made of steel such as SUJ 2 A coil 3, a support member 2 capable of supporting an annular work W to be heated disposed in an opposing area (inner circumference) of the heating coil 3, and an annular work W disposed on the lower side of the support member 2 , And a high frequency power supply (not shown) electrically connected to the heating coil 3.

The heating coil 3 is formed of, for example, a so-called multi-turn coil (multi-turn coil) formed by spirally winding a copper tube, and is held in a vertical posture in which the central axis is aligned in the vertical direction. The heating coil 3 can be inductively heated to a target temperature (for example, a temperature range higher than the A ₁ transformation point) sequentially while intermittently feeding a plurality of annular works W coaxially arranged on the inner periphery thereof in the axial direction In addition, when an axial dimension of the annular work W is L, a workpiece having an axial dimension of L × n (where n22) is used. The output of the heating coil 3 is such that an annular work W intermittently fed from one axial side (lower side in the present embodiment) to the other axial side (upper side) passes the inner periphery of the heating coil 3 in the energized state. When it is discharged to the upper side of the heating coil 3 (when it reaches the heating completion position P3), the entire annular work W is set so as to be inductively heated to the target temperature. The output of the heating coil 3 is adjusted by the shape (coil pitch) of the heating coil 3 and the amount of high frequency current supplied from the high frequency power source to the heating coil 3.

  As shown in FIGS. 2 (a) and 2 (b), the support member 2 is disposed at a plurality of locations (three locations in the illustrated example) spaced apart in the circumferential direction of the annular workpiece W to be heated. A plurality of annular works W) coaxially arranged in a stacked state are supported from the lower side. As shown in FIG. 1 and FIG. 2A, each support member 2 is formed by connecting the radial inner end portions of the three support members 2 and the diameter R1 of the circular track T is the diameter R2 of the annular work W The diameter R1 of the circular orbit T is larger than the diameter R2 of the annular work W, as shown in FIG. 2B, which is smaller than the first position where the annular work W can be supported from the lower side. Of the annular work W so as to mutually transfer between the second position where the annular work W (annular work W 'at normal temperature) supplied from the work supply means 4 disposed on the lower side of It is provided to be movable back and forth along the direction.

  The work supply means 4 is constituted by a power cylinder (hydraulic cylinder, air cylinder, or electric cylinder) having a telescopic cylinder rod 4a coaxially arranged with the annular work W to be heated. At the tip of the cylinder rod 4a, a flange portion 4b is provided on which an annular work W 'at normal temperature supplied from a parts feeder or the like not shown can be placed.

  The basic configuration of the induction heating device 1 of the present embodiment is as described above, and the annular work W is induction-heated to a target temperature as follows.

  First, as shown in FIG. 3 (a), when the annular work W 'at normal temperature supplied from a parts feeder etc. not shown is placed on the flange 4b of the work supply means 4, as shown in FIG. 3 (b) As shown, the cylinder rod 4a of the work supply means 4 is extended and moved, and the normal temperature annular work W 'placed on the flange portion 4b is moved up. Along with this, each support member 2 moves radially outward so as to shift from the above first position to the above second position, and the annular work W 'at normal temperature is in the lower end inner periphery of the heating coil 3 in the energized state. (The heating start position P1. See FIG. 1).

  Although illustration is abbreviate | omitted, after cyclic | annular workpiece | work W 'of normal temperature is introduce | transduced to the heating start position P1, the cylinder rod 4a carries out shortening movement, and the workpiece | work supply means 4 returns to origin. At this time, when the cylinder rod 4a is shortened to such an extent that the upper end surface of the flange portion 4b is positioned lower than the upper end surface of the support member 2, each support member 2 is moved from the second position to the first position. It moves radially inward so as to shift to the position, and supports the annular work W 'at normal temperature introduced to the heating start position P1 from the lower side. As described above, the annular work W 'introduced at the heating start position P1 and supported from the lower side by the support member 2 starts self-heating.

  Thereafter, the above operation is repeated, and the annular work W 'at normal temperature is introduced to the heating start position P1 (an annular work at normal temperature between the support member 2 and the annular work W in heating adjacent to the support member 2) At the same time when the annular work W is stacked on the inner circumference of the heating coil 3 by W 'being supplied, the annular work W being heated disposed on the inner circumference of the heating coil 3 is from the lower side It is intermittently fed upward.

  Then, as shown in FIG. 3C, after the inner circumference of the heating coil 3 is filled with a predetermined number (eight in the illustrated example) of annular work pieces W (a plurality of heating elements coaxially arranged in a stacked state) Among the annular works W, after the uppermost stage annular work W is disposed at the position P2 immediately before the heating completion shown in FIG. 1), as shown in FIGS. 3 (d) and 3 (e), the heating start position P1. When the annular work W 'at normal temperature is introduced, the uppermost annular work W (heated work W "induction-heated to the target temperature) is on the upper side (heating complete position P3 of the heating coil 3; see FIG. 1). Exhausted.

  The annular work W (heated work W ′ ′) discharged to the heating completion position P3 is radially outside (induction of the heating coil 3) by the discharge means 5 such as a power cylinder as shown in FIGS. 1 and 3 (f). The heated work W ′ ′ discharged to the outside of the induction heating device 1 is transferred to a cooling unit (not shown) and cooled and hardened. In addition, in order to prevent the heated work W ′ ′ from interfering with the heating coil 3 with the delivery of the heated work W ′ ′, (the cylinder rod 4a of the work supply means 4 is substantially the same as the heated work W ′ ′). The shortening movement is started after the whole is discharged to the outside in the radial direction of the heating coil 3. In other words, the work supply means 4 takes a predetermined time when the flange portion 4b reaches the rising limit. It is configured to be stationary.

  Thereafter, by repeating the operations shown in FIG. 3C to FIG. 3F, the plurality of annular works W coaxially arranged in a stacked state on the inner periphery of the heating coil 3 in the energized state are viewed from the lower side. While being intermittently fed upward, induction heating is sequentially performed to the target temperature, and then it is cooled and quenched.

The characteristic configuration of the induction heating device 1 described above is the end (upper end) 3 a on the other side in the axial direction of the heating coil 3 and a plurality of annular works W coaxially arranged on the inner periphery of the heating coil 3. Of these points, particular attention is paid to the positional relationship in the axial direction with the upper end portion Wa of the annular work W located at the position P2 immediately before the heating completion (uppermost stage). Specifically, as shown in FIG. 1, the upper end 3a of the heating coil 3 is positioned above the upper end Wa of the annular work W located at the position P2 immediately before the heating completion. In other words, when the coordinates of the upper end portion 3a of the heating coil 3 are Z _C and the coordinates of the upper end portion Wa of the annular work W located at the position P2 immediately before the heating completion is Z _W , the relational expression Z _C -Z _W > 0 Is to be established.

  By adopting such a configuration, temperature variation within the annular work W after heating completion (within the heated work W ′ ′ discharged to the heating completion position P3) can be suppressed to within 5 ° C. Therefore, the heating completion is completed. When cooling and hardening the subsequent annular work W (heated work W ′ ′), the possibility of occurrence of hardening deformation due to temperature variation in the work is effectively reduced, and desired mechanical characteristics are obtained. It is possible to obtain a high quality annular machine part (in the present embodiment, an inner ring of a rolling bearing). Moreover, such an effect can be enjoyed only by appropriately setting the axial relative position of the heating coil 3 and the plurality of annular works W coaxially arranged on the inner periphery of the heating coil 3. As described above, according to the present invention, even in the case of induction heating a plurality of annular works W sequentially to a target temperature by continuous heating, it is possible to easily increase the heating accuracy of the annular works W at low cost. Thus, annular machine parts having desired mechanical properties can be mass-produced at low cost and stably.

  The above-described effects exerted by the present invention will become apparent from the examples described later.

  As mentioned above, although the induction heating apparatus 1 which concerns on one Embodiment of this invention and the induction heating method using the same were demonstrated, embodiment of this invention is not limited to this.

  For example, in the embodiment described above, the heating coil 3 is disposed radially outward of the annular work W fed in the axial direction, because the illustrated annular work W is the inner ring of the rolling bearing. That is, the inner ring of the rolling bearing has an inner raceway surface on which the rolling elements roll on the outer diameter surface thereof, and the inner raceway surface is a plane that is required to have particularly high mechanical characteristics among the inner rings. Therefore, depending on the type of annular work W to be heated, the heating coil 3 may be disposed radially inward of the annular work W, or both radially outward and radially inward. In such a case The present invention is preferably applicable even if it is present.

  Further, although the feed direction of the plurality of annular work W coaxially arranged is the vertical direction in the above, the present invention is preferably applied to the case where the feed direction of the plurality annular work W coaxially arranged is the horizontal direction. be able to.

  In the above, the inner ring of the rolling bearing is exemplified as the annular work W, but the present invention is not limited to other annular works made of hardenable steel, such as outer ring of rolling bearing, slide bearing, inner joint of constant velocity universal joint It can be preferably used also for induction heating of a member, a rolling bearing, a cage incorporated in a constant velocity universal joint, and the like.

  The present invention is not limited to the embodiment described above, and may be embodied in various forms without departing from the scope of the present invention. That is, the scope of the present invention is indicated by the claims, and further includes the equivalent meaning described in the claims and all the modifications within the scope.

  In order to demonstrate the usefulness of the present invention, an analysis test as a confirmation test was conducted under the premise that the annular work W is inductively heated to a target temperature using the induction heating device 1 shown in FIG. The confirmation test is an axial relative between the other end (upper end in FIG. 1) 3a of the heating coil 3 in the axial direction and the other end Wa of the annular work W located at the position P2 immediately before the heating is completed. The position is to confirm (evaluate) what kind of influence it has on the temperature variation of the annular work W (the heated area of the annular work W, and in the test, the outer diameter surface of the annular work W in this test) . Details of the test body (the annular work W to be heated), the heating conditions and the evaluation method are shown below.

[Circle work W]
The inner ring (inner diameter: 40 mm, outer diameter: 53 mm, axial dimension: 23 mm) of NTN's tapered roller bearing 22208 formed of SUJ2.

[Heating condition]
Adjust the shape of the heating coil 3 (coil pitch; in other words, the distance between two adjacent turns) and the amount of high frequency current to be supplied to the heating coil 3 and complete heating of the annular work W at the position P2 just before the heating is completed ( The area ratio of residual carbides on the outer diameter surface of the annular work W immediately before being discharged to the upper side of the heating coil 3 is set to 8 to 10%. Here, the area ratio of the residual carbides is a parameter that has a correlation with the mechanical properties of the quenched SUJ2 material, that is, the heating temperature of the workpiece made of SUJ2, and is calculated from the heat pattern. Other conditions are as follows.
・ Applying interval of feed force to annular work W (supply interval of annular work W at normal temperature): 17 seconds ・ Number of work pieces that can be arranged on the inner circumference of heating coil 3: 8 ・ Number of turns of heating coil 3: 6
· Radial gap width (radial value) between heating coil 3 and annular work W: 30 mm
· Frequency of high frequency current supplied to heating coil 3 from high frequency power supply: 3 kHz
Others: Supply of annular work W ′ ′ at normal temperature shown in FIGS. 3D to 3F to removal of heated work W ′ ′, that is, one cycle operation of work supply means 4 (upward movement of cylinder rod 4a It is assumed that the start-origin return) is completed in an instant.

[Evaluation method]
The axial relative position of the upper end 3a of the heating coil 3 and the upper end Wa of the annular work W located at the position P2 immediately before the completion of heating is changed stepwise, and the temperature variation of the heating required area of the annular work W at each stage evaluated. The temperature variation was evaluated by the standard deviation of the temperatures at seven points on the outer diameter surface of the annular work W immediately before being discharged to the upper side of the heating coil 3.

The test results of the verification (evaluation) test are shown in FIG. 4 in which the parameter of the vertical axis is the above-mentioned temperature variation [unit: ° C.] and the parameter of the horizontal axis is Z _C -Z _W [unit: mm]. Incidentally, Z _C is the coordinate of the upper end portion 3a of the heating coil 3, Z _W is the coordinate of the upper end portion Wa of the annular workpiece W is located in the heating immediately before completion position P2. Therefore, in the case of Z _C -Z _W = 0, meaning that the upper end portion 3a of the heating coil 3, an upper end Wa of the annular workpiece W is located in the heating immediately before completion position P2 is positioned on the same plane and, in the case of Z _C -Z _W> 0, it means that the upper end portion 3a of the heating coil 3 is positioned above the upper end portion Wa of the annular workpiece W is located in the heating immediately before completion position P2.

As apparent from FIG. 4, in the case of Z _C −Z _W = 0, the temperature variation (standard deviation of temperature) is about 5 ° C., and as the value of Z _C −Z _W increases, the temperature variation becomes larger. It is getting smaller. Therefore, as in the present invention, the end 3a of the other axial direction side (the forward direction of the annular work W) of the heating coil 3 is heated among the plurality of annular works W located in the opposing area of the heating coil 3 Annular work at the time of induction heating the annular work W to a target temperature by so-called continuous heating method by positioning the annular work W on the other side in the axial direction with respect to the end Wa on the other side in the axial direction of the annular work W located immediately before completion. It turns out that it is effective in suppressing the temperature variation of the heating required area of W.

1 induction heating device 2 support member 3 heating coil 3a upper end (end on the other side in the axial direction)
4 Work supply means (work feed means)
P2 Immediately before heating completion position W annular work Wa upper end (end on the other side in the axial direction)
Annular work W "at normal temperature

Claims (4)

The plurality of annular works coaxially arranged are intermittently fed from one side to the other side in the axial direction to pass through the opposing region of the heating coil in the energized state, thereby sequentially aiming each of the plurality of annular works In induction heating to temperature,
The other axial end of the heating coil is the axial direction other than the axial other end of the annular work positioned at a position immediately before completion of heating among the plurality of annular works located in the opposing region of the heating coil An induction heating method characterized in that it is located on the side.   The annular work is supplied at a room temperature between a support member for supporting a plurality of annular works coaxially arranged in a stacked state from the lower side and the annular work adjacent to the support member. The induction heating method according to claim 1, wherein the work is intermittently fed. Workpiece feeding means for intermittently feeding a plurality of annular workpieces coaxially arranged from one side in the axial direction toward the other side in the axial direction, and the plurality of annular workpieces coaxially arranged with the plurality of annular workpieces and intermittently fed An induction heating device including a heating coil for induction heating each to a target temperature sequentially,
The other axial end of the heating coil is the axial direction other than the axial other end of the annular work positioned at a position immediately before completion of heating among the plurality of annular works located in the opposing region of the heating coil An induction heating device characterized in that it is located on the side.   The work feed means is a work supply means for supplying an annular work at a normal temperature between a support member for supporting the plurality of annular works coaxially arranged in a stacked state from the lower side and the annular work adjacent to the support member. The induction heating device according to claim 3, which is configured.

Images