JP2005330545A - High frequency induction hardening method and its apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency induction hardening method and its apparatus, with which even in the case of being a work of comparatively small size, a limited hardening of only the hardening desired surface is performed so as not to harden onto the hardening non-desired surface, and which are applied to the hardening of a raceway ring of a rolling bearing, or the like. <P>SOLUTION: This method is the high frequency induction hardening method for work W having the hardening desired surface S1 and the non-hardening desired surface S2. While the non-hardening desired surface S2 is covered with an electric-conductive protecting tool 5, the hardening desired surface S1 is heated with the high frequency induction current with a heating coil 1 faced to the hardening desired surface S1. The protecting tool 5 is preferably a material having high electric conductive ratio, such as copper, aluminum, and for the protecting tool 5, a flow passage 6 for cooling medium can be arranged in this inner part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  This invention relates to a mechanical part having a desired hardened surface and a non-hardened desired surface, such as a rolling bearing raceway in which the raceway surface is hardened, by high frequency induction heating. The present invention relates to an induction hardening method and an apparatus therefor.

As a heating method for quenching a machine part, for example, a ring-shaped workpiece, there is a method in which a single-turn heating coil is used, a workpiece is arranged concentrically on the inner periphery, and high-frequency induction heating is performed (for example, non-patent literature). 1).
However, it is common to quench a machine part such as a bearing race that is mass-produced in an atmosphere furnace. Induction hardening in a bearing is employed when locally hardening, such as quenching only a raceway surface in a wheel bearing. This local quenching is performed by moving quenching or the like.
Edited by Japan Heat Treatment Technology Association / Edited by Japan Metal Heat Treatment Industry Association, “Introduction to Heat Treatment Technology”, Okawa Publishing, April 25, 2001, page 285

Heating when quenching machine parts such as bearing rings is generally performed in a furnace as described above. However, in the case of high-mix, low-volume production, the number of furnaces that can be processed in the furnace heat treatment is high. However, the efficiency may be poor. In addition, when a required number of hardened products are supplied to the line or delivered to the outside as needed, it is necessary to hold a large amount of inventory in the quenching by the furnace. The heating temperature in the furnace may vary depending on the position of the machine parts placed in the furnace.
For this reason, an attempt was made to quench the bearing races one by one by induction quenching. According to induction hardening, only the required number can be processed, and uniform heat treatment with little variation between processed products can be achieved.
Moreover, induction hardening has the advantage that only a necessary part can be hardened, and it is excellent as a method for hardening a machine part having a hardening desired surface and a non-quenching desired surface.

  However, in induction hardening, partial hardening is relatively easy in moving hardening in which a heating coil is moved while moving a relatively large work, but one-time hardening is performed like a small work. However, the influence of the magnetic flux of the heating coil also reaches the non-quenching desired surface. For this reason, it is difficult to quench only the desired quenching surface, and the peripheral portion is quenched. In some cases, it is not preferable that the peripheral portion is hardened from the viewpoint of ensuring the toughness of the workpiece and various other demands. For example, in a bearing ring of a rolling bearing, it is necessary to harden the raceway surface to increase hardness, but it is preferable that the inner diameter surface portion or the outer diameter surface portion adjacent to the raceway surface is hardened by quenching. Absent.

  An object of the present invention is to provide an induction hardening method and apparatus capable of performing limited hardening only on a desired hardening surface so that a non-hardening desired surface is not hardened even for a relatively small work. Is to provide.

The induction hardening method of the present invention is an induction hardening method for a work in which a desired hardening surface and a non-hardening desired surface are arranged, and the non-hardening desired surface is covered with a conductive protective jig. The high-frequency induction heating is performed on the desired hardening surface by a heating coil facing the desired hardening surface.
According to this method, the non-hardening desired surface of the workpiece is covered with the conductive protection jig, so that the magnetic flux of the alternating magnetic field generated by the heating coil passes through the inside of the conductive protection jig and the desired hardening surface. The inside of the non-quenching desired surface does not pass. Therefore, a heat generation phenomenon caused by eddy current loss, hysteresis loss, or the like due to a change in magnetic flux passing through the workpiece occurs only in the desired hardening surface and in the protective jig, and does not occur in the non-hardening desired surface. The inside of the non-quenching desired surface is heated only by heat conduction from the periphery, and is not easily heated. Therefore, even a relatively small work can be subjected to limited quenching only on the desired quenching surface so that the non-quenched desired surface is not quenched.

The induction hardening apparatus of the present invention is an induction hardening apparatus for a workpiece in which a desired hardening surface and a non-hardening desired surface are arranged, and a conductive protective jig that covers the non-hardening desired surface of the work, And a heating coil facing the quenching desired surface.
According to the induction hardening apparatus of this configuration, due to the above-described action in the method of the present invention, only a desired quenching surface is limited so that a non-hardening desired surface is not hardened even with a relatively small workpiece. Quenching can be performed.

The heating coil may include a quenching coolant flow path and a discharge port for discharging the quenching coolant in the flow path toward the workpiece.
If the heating coil has a quenching coolant discharge port, it is possible to perform a single quenching in which the heated workpiece is rapidly cooled at the heating position. Unlike moving quenching, an induction quenching apparatus that performs one-time quenching heats by fixing the positional relationship between the heating coil and the workpiece, and therefore it is usually difficult to perform partial quenching. Therefore, the effect of limiting the quenching range by using the protective jig is great.

The protective jig may have a cooling medium flow path therein. In that case, jig cooling medium supply means for supplying the cooling medium to this flow path is provided.
Since the protective jig passes through the magnetic flux of the heating coil and induction heating occurs, cooling by flowing a cooling medium can alleviate the temperature rise due to heat conduction on the desired non-hardened surface of the workpiece, and durability of the protective jig It is preferable in terms of improving the property.

In the induction hardening apparatus of the present invention, the heating coil is a single winding, and the workpiece is a ring-shaped product disposed on the inner periphery or outer periphery of the heating coil, and the quenching is performed on the surface facing the heating coil. There may be provided a workpiece support means that has a desired hardening surface and a non-quenched desired surface, and supports the workpiece and the protective jig with respect to the heating coil and rotates them around the center of the heating coil.
When the workpiece is a ring-shaped product, uniform heating can be performed on the entire circumference by heating while rotating as described above. In this case, the protective member may be fixed together with the heating coil. However, when the protective member is rotated together with the workpiece as described above, the protective member is not hardened on the workpiece without obstructing the rotation of the workpiece. The magnetic flux which is a function of the protective member can be effectively obtained by preventing the magnetic flux from passing through the non-quenched desired surface.

In the induction hardening apparatus having this configuration, the ring-shaped workpiece may be a bearing ring of a rolling bearing, and the desired hardening surface may be a raceway surface.
In rolling bearings, the raceway surface, on which rolling elements roll, is required to have high surface hardness from the viewpoint of wear prevention and rolling life. In order to improve the toughness of the ring, it is preferable to prevent burning. For this reason, the advantage that limited quenching of only the desired quenching surface can be effectively performed so that the non-quenching desired surface does not quench in the apparatus of the present invention.

The induction hardening method of the present invention is a method of quenching a workpiece in which a desired quenching surface and a desired non-quenching surface are aligned, and the desired non-quenching surface is covered with a conductive protective jig. In this method, the surface to be hardened is induction-heated by a heating coil facing the surface to be hardened, so that even a relatively small work piece is hardened so that the non-hardened desired surface is not hardened. Limited quenching can be performed only on the desired surface.
The induction hardening apparatus of the present invention is an induction hardening apparatus for a workpiece in which a desired hardening surface and a non-hardening desired surface are arranged, and a conductive protective jig that covers the non-hardening desired surface of the work, Since it has a heating coil facing the desired quenching surface, limited quenching of only the desired quenching surface is possible so that even non-hardening desired surfaces will not be quenched even with relatively small workpieces. Yes.

  A first embodiment of the present invention will be described with reference to FIGS. This induction hardening apparatus is an apparatus for induction hardening of a workpiece W that is a heat-treated product, in which a hardened desired surface S1 and a non-hardened desired surface S2 are aligned. The heating coil 1 and the heating coil 1, a high-frequency power source 2 that supplies a high-frequency current to 1, a conductive protection jig 5 that covers a non-quenching desired surface S <b> 2 of the workpiece W, a workpiece support means 3 that supports the workpiece W and the protection jig 5, and quenching And a coolant supply device 4. The heating coil 1 is provided so as to face the desired hardening surface S1 of the workpiece W supported by the workpiece support means 3.

  The workpiece W is a ring-shaped product, specifically a rolling bearing race. In the illustrated example, the workpiece W is an inner ring of a ball bearing and has a raceway groove Wa on the outer periphery. The inner surface of the raceway groove Wa serves as a desired quenching surface S1, and portions on both sides of the raceway groove Wa on the outer diameter surface of the workpiece W serve as non-hardening desired surfaces S2.

  Two protective jigs 5 are provided so as to cover the non-quenching desired surfaces S2 on both sides of the workpiece W, respectively, and each has a ring shape. The protective jig 5 is preferably made of a material having high conductivity, and is made of, for example, copper, aluminum, or iron. The protective jig 5 has a cooling medium flow path 6 therein, and an outlet and an inlet (not shown) of the flow path 6 are provided in a part of the circumferential direction. The protective jig 5 has an engagement piece (not shown) that engages with the width surface or inner peripheral surface of the workpiece W, and is engaged with the engagement piece while being fitted to the workpiece W. The workpiece W is held.

  A jig cooling medium supply means 15 for circulating a cooling medium such as a cooling liquid is provided for the flow path 6 of the protective jig 5.

  The heating coil 1 has a cylindrical single winding, and has a quenching coolant flow path 7 therein, and a discharge hole 8 for discharging the quenching coolant toward the inner diameter side on the inner wall surface. Is provided. The cross-sectional shape of the heating coil 1 is rectangular or square as shown in FIG. Pipe-shaped connection ports 9 serving as quenching coolant inlets are provided at a plurality of locations in the circumferential direction on the outer peripheral surface of the heating coil 1. A quenching coolant for cooling the heating coil 1 and cooling the workpiece W is supplied from the quenching coolant supply device 4 to the connection port 9 at a predetermined timing.

  As shown in the perspective view of FIG. 2, the heating coil 1 has a pair of terminal plates 10 at both ends in the circumferential direction as divided portions, and sandwiches an insulating plate 11 between the two terminal plates 10. It is said that. Between these terminal boards 10, the high frequency power supply 2 is connected via the said current transformer.

  In FIG. 1, a high frequency power source 2 is means for converting a current obtained from an AC commercial power source or the like through a power receiving board into a high frequency of a predetermined frequency and supplying it to the heating coil 1, such as a thyristor inverter type or a transistor inverter type. Is used. A current transformer (not shown) is interposed between the high frequency power source 2 and the heating coil 1.

  The work support means 3 includes a lower support member 13 on which the work W is placed and an upper support member 12 that presses the upper surface of the work W, and the upper and lower support members 12 and 13 are rotated by a drive source 14 such as a motor. By doing so, the work W is rotated. The lower support member 13 and the upper support member 12 are rotatably supported by a bearing (not shown) or the like at a concentric position with the heating coil 1. The upper and lower support members 12 and 13 support the workpiece W via protrusions 12a and 13a equally distributed at a plurality of locations (for example, three locations) in the circumferential direction so that the contact area with the workpiece W can be reduced as much as possible. There is something to do. The material of the work support means 12, 13 is ceramics or the like.

Either one or both of the upper and lower support members 12 and 13 can be moved up and down, and the workpiece W can be taken in and out by moving up and down.
Note that a loading device (not shown) for automatically loading and unloading the workpiece W with respect to the workpiece support means 3 may be provided.

  The heat treatment process by the induction hardening apparatus having the above configuration will be described. A workpiece W with the non-quenching desired surface S2 covered with the protective jig 5 is placed between the upper and lower support members 12, 13 of the workpiece support means 3, and the workpiece W and the protection are protected by the drive source 14 together with the support members 12, 13. High-frequency power is supplied from the high-frequency power source 2 to the heating coil 1 while rotating the jig 5. When a high-frequency current flows through the heating coil 1, an alternating magnetic flux is generated, and the workpiece W is induction-heated. That is, a heat generation phenomenon occurs due to eddy current loss, hysteresis loss, and the like due to a change in magnetic flux passing through the workpiece W. When the temperature of the workpiece W rises to the maximum heating temperature before quenching, that is, the austenitizing temperature, the temperature is maintained for a certain time, and then a quenching coolant is supplied into the heating coil 1 and discharged from the discharge holes 8. The workpiece W is rapidly cooled. Thereby, the workpiece W is hardened.

  At the time of induction heating by the heating coil 1, the non-hardening desired surface S2 of the workpiece W is covered with the conductive protection jig 5, so that the magnetic flux of the alternating magnetic field generated by the heating coil 1 is as shown in FIG. ) Passes through the inside of the conductive protection jig 5 and the desired quenching surface S1 and does not pass through the non-quenching desired surface S2. Therefore, a heat generation phenomenon caused by an eddy current loss, a hysteresis loss, or the like due to a change in magnetic flux passing through the workpiece W occurs only inside the desired hardening surface S1 and the protective jig 5, and occurs inside the non-hardening desired surface S2. Absent. The inside of the non-quenching desired surface S2 is heated only by heat conduction from the periphery, and is not easily heated. Therefore, even a relatively small work W can be subjected to limited quenching of only the desired quenching surface S1 so that the non-quenching desired surface S2 is not quenched.

  In this embodiment, the workpiece W is a bearing ring of a rolling bearing, and only the inner surface of the raceway groove Wa serving as the quenching desired surface S1 is induction-heated to a high temperature and quenched. Therefore, the non-quenching desired surface S2 is not hardened, and excellent toughness can be maintained.

  The protective jig 5 passes through the magnetic flux of the heating coil 1 and induction heating occurs. The protective jig 5 has a cooling medium flow path 6 inside, and a cooling medium such as cooling water is circulated from the jig cooling medium supply means 15. Therefore, the temperature rise is mitigated, which is preferable in terms of mitigating the temperature rise due to heat conduction of the non-quenching desired surface S2 of the workpiece W and improving the durability of the protective jig 5.

  The heating coil 1 has a quenching coolant discharge port 8 and can perform one-time quenching in which the workpiece W heated as described above is rapidly cooled at the heating position. For this reason, there is no need to move the heated workpiece W to a high temperature, and deformation hardly occurs. Unlike the moving quenching, the induction quenching apparatus that performs the single quenching performs heating while fixing the positional relationship between the heating coil 1 and the workpiece W, so that it is usually difficult to perform partial quenching. However, the quenching range can be effectively limited by using the protective jig 5 described above.

  In this embodiment, since the single heating coil 1 is used and the work W is rotated by the support means 3 on the inner periphery thereof and induction heating and liquid cooling are performed, the ring-shaped work W is evenly distributed over the entire periphery. Can be heated and rapidly cooled, so that the quenching quality is uniform over the entire circumference. Therefore, when the workpiece W is a bearing race that requires strict accuracy and quality in terms of shape, dimensions, material, etc., the advantages in accuracy and quality in the induction hardening apparatus of this embodiment are effectively exhibited. .

In addition, although the said embodiment demonstrated the case where the workpiece | work W was heated from the outer periphery, the induction hardening apparatus of this invention is good also as an apparatus which heats the workpiece | work WA from an inner periphery, as shown, for example in FIG. The workpiece WA in this case is, for example, an outer ring of a rolling bearing. Also in this case, the inner surface of the raceway groove WAa becomes the quenching desired surface S1, and the non-quenching desired surfaces S2 on both sides thereof are covered with the protective jig 5 for quenching. As the heating coil 1A, a single winding coil having a terminal portion 10A provided inside is used as shown in FIG.
Moreover, although each said embodiment demonstrated the case where the workpiece | work W was a ring-shaped article, this invention is applied to induction hardening of the workpiece | work W with which the desired hardening surface S1 and the non-hardening desired surface S2 are located in a line adjacently. can do.

(A) is a fracture | rupture front view of the induction hardening apparatus concerning 1st Embodiment of this invention, (B) is an effect explanatory view shown in the expanded section of the B section of the same figure (A). It is a perspective view of the heating coil. It is sectional drawing which shows the relationship between the heating coil and workpiece | work in other embodiment of this invention. It is a perspective view of the heating coil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A ... Heating coil 2 ... High frequency power supply 3 ... Work support means 4 ... Quenching coolant supply device 5 ... Protection jig 6 ... Channel 7 ... Channel 8 ... Discharge port S1 ... Hardening desired surface S2 ... Non-hardening Desired surface W, WA ... Workpiece

Claims (6)

  An induction hardening method for a workpiece in which a hardened desired surface and a non-hardened desired surface are arranged, facing the desired hardened surface with the non-hardened desired surface covered with a conductive protective jig. An induction hardening method, wherein a desired hardening surface is induction-heated by a heating coil.   An induction hardening apparatus for a workpiece in which a desired quenching surface and a non-quenching desired surface are arranged, and a conductive protection jig covering the non-quenching desired surface of the workpiece, and heating facing the desired quenching surface Induction hardening device with a coil.   3. The induction hardening apparatus according to claim 2, wherein the heating coil has a quenching coolant flow path and a discharge port for discharging the quenching coolant in the flow path toward the workpiece.   4. The induction hardening apparatus according to claim 2, wherein the protective jig has a cooling medium flow path inside, and jig cooling medium supply means for supplying the cooling medium to the flow path is provided.   The heating coil according to any one of claims 2 to 4, wherein the heating coil is a single winding, and the workpiece is a ring-shaped product disposed on the inner periphery or outer periphery of the heating coil, The opposite surface has the desired quenching surface and the non-quenched desired surface, and provided with a workpiece support means for supporting the workpiece and the protective jig with respect to the heating coil and rotating around the center of the heating coil. Induction hardening equipment. 6. The induction hardening apparatus according to claim 5, wherein the workpiece is a bearing ring of a rolling bearing, and the hardened desired surface is a raceway surface.

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