JP3669547B2 - Induction hardening method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction hardening method for curing an uneven portion formed on an object to be processed.
[0002]
[Prior art]
Conventionally, rolling bearings have been widely used in automobiles and the like. In this rolling bearing, a plurality of balls and rollers roll between an inner ring (inner race) and an outer ring (outer race), and these balls and rollers are fitted on the inner wall surface of the outer ring. A groove for rolling is formed. Since balls and rollers roll in this groove, the wall surface of the groove is easily worn. For this reason, normally, a hardened layer is formed on the wall surface of the groove by induction hardening or the like, and is difficult to wear.
[0003]
When hardening the wall surface of the groove by induction hardening, an induction heating coil is placed inside the outer ring, the inner wall surface is induction-heated to the quenching temperature, and then a cooling liquid is jetted onto the inner wall surface to quench it. To do. According to this method, not only the wall surface of the groove but the entire inner wall surface of the outer ring is cured. Since the inner ring contacts the surface (inner spherical surface) other than the wall surface of the groove in the entire inner wall surface, it is preferable that the inner spherical surface is also hardened and hardly worn.
[0004]
However, the inner wall surface of the groove is in a position retracted from the inner spherical surface. For this reason, the distance between the induction heating coil placed inside the outer ring and the inner wall surface of the groove is wider than the distance between the induction heating coil and the inner spherical surface. That is, the inner spherical surface is closer to the induction heating coil than the inner wall surface of the groove, and the inner spherical surface is heated deeper than the inner wall surface of the groove. Therefore, when the inner wall surface is heated to the quenching temperature to a predetermined depth in order to make the inner wall surface of the groove have a predetermined hardened layer depth, the inner spherical surface is heated to the quenching temperature to a position deeper than the inner wall surface. As a result, the hardened layer depth on the inner spherical surface becomes deeper than the hardened layer depth on the inner wall surface of the groove.
[0005]
[Problems to be solved by the invention]
Thus, if the hardened layer depth is different between the inner spherical surface and the inner wall surface of the groove, the difference may cause distortion or cracking in the outer ring after quenching.
[0006]
In view of the above circumstances, an object of the present invention is to provide an induction hardening method capable of making the depth of a hardened layer uniform even when a portion having a different thickness is formed on a workpiece.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the induction hardening method of the present invention has an uneven portion formed on either the inner wall surface or the outer wall surface, and has no unevenness on the portion corresponding to the back side of the uneven portion of the wall surface. In the induction hardening method of induction hardening the concavo-convex part of the cylindrical object to be processed,
(1) In the induction heating of the uneven portion, the non-recessed portion is also heated.
[0008]
here,
(2) When the uneven portion is heated, the uneven portion may be heated so that the uneven portion has a temperature lower than the transformation point.
[0009]
Also,
(3) You may heat this uneven | corrugated part so that the said uneven | corrugated part may become the temperature in the range of 500 to 600 degreeC.
[0010]
further,
(4) The uneven portion and the non-protruded portion may be induction heated at the same time.
[0011]
Furthermore,
(5) You may shift the timing which carries out induction heating of the said uneven part and the said uneven part.
Furthermore,
(6) In quenching the workpiece after induction heating the concavo-convex portion and the non-concavo-convex portion, even if the cooling liquid is jetted to both the concavo-convex portion and the non-concavo-convex portion and these are simultaneously quenched Good.
[0012]
Furthermore,
(7) When the unevenness portion and the non-protrusion portion are induction-heated and the workpiece is rapidly cooled, the unevenness portion may be rapidly cooled by jetting a cooling liquid only to the unevenness portion.
[0013]
Here, it is assumed that the unevenness does not include minute unevenness caused by machining accuracy.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0015]
FIG. 1 is a cross-sectional view schematically showing an outer ring and an induction heating coil of a rolling bearing, and FIG. 2 is a front view schematically showing the outer ring and the induction heating coil of FIG.
[0016]
A hollow portion 12 into which an inner ring (not shown) enters is formed in a steel outer ring 10 (which is an example of an object to be treated according to the present invention), and this hollow portion 12 is surrounded by a wall 14. . The wall 14 has an inner wall surface 20 and an outer wall surface 30 opposite to the inner wall surface 20.
[0017]
Grooves 22 extending in the length direction (arrow A direction) of the outer ring 10 are formed in the inner wall surface 20 at equal intervals in the circumferential direction (arrow B direction). Since balls or rollers (not shown) fit into the groove 22 and roll, the wall surface 22a of the groove 22 is easily worn. Further, an inner spherical surface 24 is formed between adjacent grooves 22 in the inner wall surface 20, and an inner ring (not shown) is in contact with the inner spherical surface 24. As a result of the grooves 22 being formed in the inner wall surface 20, the inner wall surface 20 is provided with the uneven portions referred to in the present invention.
[0018]
On the other hand, the outer wall surface 30 is not formed with an uneven portion, and has a fine unevenness due to machining, but is an uneven portion without the groove 22 or the like. Therefore, a portion corresponding to the back side of the uneven portion of the inner wall surface 20 is a non-recessed portion.
[0019]
Next, a method of induction hardening the inner wall surface 20 of the outer ring 10 and hardening the inner spherical surface 24 and the wall surface 22a of the groove 22 will be described.
[0020]
When induction hardening the inner wall surface 20 of the outer ring 10, first, the induction heating coil 40 is inserted into the hollow portion 12 to inductively heat the inner wall surface 20 (uneven portion). As a result, the inner wall surface 20 is induction-heated. However, since the inner spherical surface 24 is closer to the induction heating coil 40 than the wall surface 22a of the groove 22, the inner spherical surface 24 is heated to a quenching temperature to a position deeper than the wall surface 22a. Is done. Thus, when the cooling liquid is jetted onto the inner wall surface 20 and rapidly cooled while the difference in the heating layer depth remains between the wall surface 22a and the inner spherical surface 24, a difference also occurs in the hardened layer depth. Due to the difference in the depth of the hardened layer, there is a possibility that a large strain (deformation) occurs in the outer ring 10 or the outer ring 10 is cracked.
[0021]
Therefore, here, the induction heating coil 50 is disposed in the vicinity of the outer wall surface 30 and is heated from the outer wall surface 30 side as well (the uneven portion). When viewed from the side of the outer wall surface 30, the wall surface 22 a of the groove 22 is closer to the induction heating coil 50 than the inner spherical surface 24, and therefore the wall surface 22 a of the groove 22 is heated more than the inner spherical surface 24 when heated by the induction heating coil 50. It is easy to be done.
[0022]
In this way, not only the inner wall surface 20 is induction-heated by the induction heating coil 40 from the inner wall surface 20 side, but also the outer wall surface 30 is heated by the induction heating coil 50 from the outer wall surface 30 side. The heating layer depth and temperature distribution in the wall surface 22a and the inner spherical surface 24 are made uniform. That is, the frequency and output of the induction heating coils 40 and 50, the heating time, and the like are appropriately adjusted so that the wall surface 22a of the groove 22 and the inner spherical surface 24 are heated to the quenching temperature to the same depth.
[0023]
The timing for heating the inner wall surface 20 with the induction heating coil 40 and the timing for heating the outer wall surface 30 with the induction heating coil 50 may be the same or may be shifted. For example, as shown in FIG. 3, heating of the inner wall surface 20 may be started while the outer wall surface 30 is being heated. Further, as shown in FIG. 4, heating of the inner wall surface 20 may be started after the heating of the outer wall surface 30 is completed. In addition, the timing which heats these outer wall surfaces 30 and inner wall surfaces 20 changes according to the material, shape, etc. of a to-be-processed object.
[0024]
Further, the strain can be further reduced by heating the outer wall surface 30 to a temperature lower than the transformation point. However, if the temperature for heating the outer wall surface 30 is too low, the time for heating the wall surface 22a of the groove 22 and the inner spherical surface 24 to the quenching temperature becomes long. A temperature in the range of 600 ° C. or higher is preferable. However, this temperature is appropriately changed according to the thickness of the workpiece.
[0025]
Regardless of which method is used, the wall surface 22a of the groove 22 and the inner spherical surface 24 are heated to the quenching temperature to the same depth, and a cooling liquid is ejected to quench the inner wall surface 20 rapidly. As a result, the depth of the hardened layer on the inner wall surface 20 is the same for both the wall surface 22 a of the groove 22 and the inner spherical surface 24. For this reason, the distortion of the outer ring 10 is extremely reduced, the polishing step for removing the distortion can be eliminated, and the production cost of the outer ring 10 can be reduced.
[0026]
In order to rapidly cool the inner wall surface 20 by ejecting the coolant, the coolant may be ejected simultaneously to the inner wall surface 20 and the outer wall surface 30, or the coolant may be ejected only to the inner wall surface 20. When the coolant is jetted onto the inner wall surface 20 and the outer wall surface 30 simultaneously, the distortion of the outer ring 10 is further reduced. On the other hand, in the case where the coolant is jetted only to the inner wall surface 20, it is preferable from the viewpoint of “cracking”.
[0027]
Next, experimental examples will be described with reference to FIGS.
[0028]
FIG. 5 is a schematic diagram showing the depth of the hardened layer of the outer ring used in the experiment, and FIG. 6 is a graph showing the depth of the hardened layer. 6, a, b, c, and d represent the hardness measured from the directions of arrows a, b, c, and d shown in FIG. In these drawings, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals.
[0029]
The material of the outer ring 10 used in this experiment is S53C (JIS standard), the outer diameter D is 86 mm, and the inner diameter H is 67 mm. The depth h of the groove 22 is 4.5 mm.
[0030]
In heating the inner wall surface 20, the induction heating 40 (see FIG. 1) was used for heating for 2 seconds at 120 kW and 10 kHz. Moreover, when heating the outer wall surface 30, it was heated for about 3 seconds at 50 kW and 6 kHz using the induction heating coil 50 (refer FIG. 1). After heating in this way, the coolant was jetted onto the inner wall surface 20 for 10 seconds to quench. As a result, the depth of the hardened layer 60 on the inner wall surface 20 is the same for both the wall surface 22a of the groove 22 and the inner spherical surface 24, as shown in FIG. The depth of the effective hardened layer (Hv513 or higher) was about 1.5 mm for both the wall surface 22a and the inner spherical surface 24.
[0031]
In the above-described embodiment, the outer ring of the rolling bearing is cited as the object to be processed. However, the outer ring is not limited to a cylindrical object having an uneven part formed on the inner wall surface like the outer ring. For example, the uneven part is formed on the outer wall surface. In addition, the present invention can be applied to a cylindrical workpiece in which an uneven portion is formed on the inner wall surface corresponding to the back side of the uneven portion, and the uneven portion is cured to a uniform depth. Be made. In addition, the present invention can be applied to a plate-shaped object in which a concavo-convex portion is formed on one surface of a plate-like member such as a flat plate, and a portion corresponding to the back side of the concavo-convex portion is a non-concave portion, The uneven portion can be cured to a uniform depth.
[0032]
【The invention's effect】
As described above, according to the induction hardening method of the present invention, when the uneven portion of the workpiece is induction-heated, the uneven portion on the back side of the uneven portion is also heated. It becomes uniform (substantially the same), and the depth of the hardened layer of the uneven portion can be made uniform. As a result, it is possible to reduce deformation and distortion of the object to be processed due to variations in the hardened layer depth of the uneven portion. Thus, since deformation and distortion of the workpiece can be reduced, the polishing step after induction hardening can be omitted.
[0033]
Here, when the uneven portion is heated so that the uneven portion is heated to a temperature lower than the transformation point when the uneven portion is heated, the deformation and distortion of the workpiece can be further reduced.
[0034]
In addition, when the concavo-convex portion and the non-concavo-convex portion are simultaneously induction-heated, the high-frequency power source becomes large, but the heating depth in the concavo-convex portion can be made uniform in a relatively short time.
[0035]
Furthermore, when shifting the timing of induction heating of the uneven portion and the non-recessed portion, the high-frequency power source can be small.
[0036]
Furthermore, when rapidly cooling the object to be processed after induction heating of the uneven part and the uneven part, when cooling liquid is jetted to both the uneven part and the uneven part to quench them simultaneously, Distortion and deformation are further reduced.
[0037]
Furthermore, when rapidly cooling the object to be processed after induction heating of the uneven part and the uneven part, when the cooling liquid is jetted only to the uneven part to rapidly cool the uneven part, `` cracking of the object to be processed '' From the point of view, it is preferable.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing an outer ring of a rolling bearing.
FIG. 2 is a front view showing the outer ring of FIG. 1;
FIG. 3 is a graph showing an example of timing for heating an outer wall surface and an inner wall surface.
FIG. 4 is a graph showing another example of timing for heating the outer wall surface and the inner wall surface.
FIG. 5 is a schematic diagram showing the depth of the hardened layer of the outer ring used in the experiment.
6 is a graph showing the depth of the hardened layer of the outer ring in FIG. 5. FIG.
[Explanation of symbols]
10 outer ring 20 inner wall surface 22 groove 22a groove wall surface 24 inner spherical surface 30 outer wall surface

Claims (1)

The concave-convex portion of the cylindrical object to be processed in which the concave-convex portion is formed on either the inner wall surface or the outer wall surface, and the concave-convex portion is formed on the portion corresponding to the back side of the concave-convex portion of the wall surface. In the induction hardening method of induction hardening,
In induction heating the uneven portion from the uneven portion side ,
The uneven surface portion is also heated from the surface of the uneven portion by induction heating so that the temperature of the surface portion of the uneven portion is lower than the transformation point. By heating to a temperature higher than the temperature at the surface layer portion of the convex portion, the depth of the heating layer heated to the quenching temperature at the concave portion, and the depth of the heating layer heated to the quenching temperature at the convex portion Induction hardening method characterized by uniformizing .

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