JP2008075116A - Method for restraint-hardening annular member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for restraint-hardening an annular member by which the effect of the sufficient restraint is easily secured, the efficiency of a hardening treatment is enhanced and the manufacturing cost of the annular member can be reduced. <P>SOLUTION: The method for restraint-hardening a bearing ring 10 being the annular member is provided with: a heating process: a first cooling process; a restraining process; and a second cooling process. In the heating process, the bearing ring 10 is heated to the temperature of the A<SB>1</SB>point or higher. In the first cooling process, the ring is cooled to a first cooling temperature of the M<SB>S</SB>point or lower, and in the restraining process, the ring is restrained with a restraining member 30 and in the second cooling process, the ring is cooled while restraining, to a second cooling temperature of lower than the restraining starting temperature. Then, in the restraining process and the second cooling process, the bearing ring 10 is restrained in a ridge line part 14 so that the bearing ring 10 is not in contact with the restraining member 30 on the outer peripheral surface 11 of the bearing ring 10 and the end face 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for restraining and quenching an annular member, and more particularly to a method for restraining and quenching an annular member that restrains deformation by restraining the annular member.

  In quench hardening for annular members such as bearing rings, quenching cooling is performed in a state in which the annular member is constrained in order to suppress deformation (heat treatment deformation) and roundness reduction that occur during heat treatment. In some cases, restraint quenching is performed. This restraint quenching utilizes the fact that the steel constituting the annular member expands due to martensitic transformation during quenching. That is, by quenching quenching while the annular member is surrounded by the restraining member, the annular member expands along the wall surface of the restraining member, and an annular member having a desired shape can be obtained. However, according to this method, since the inner wall of the restraint member and the annular member come into close contact with each other when the quenching of the restraint quenching is completed, it becomes difficult to separate the annular member from the restraint member. Efficiency may be reduced.

In contrast, a constraining member having a cylindrical inner wall with circular openings formed in the upper and lower portions was adopted, and the annular member was sequentially pushed from the upper opening to cool the annular member, and the cooling was completed. There has been proposed a constrained quenching method in which the annular member is pushed out from the lower opening. Thereby, separation of the annular member from the restraining member is sequentially performed, and a decrease in the efficiency of the quench hardening process can be suppressed (for example, see Patent Document 1).
JP-A-9-176740

  However, in the conventional constraining quenching method in which the annular member is restrained by bringing the wall surface of the constraining member into close contact with the outer peripheral surface or the inner peripheral surface of the annular member, including the constraining quenching method described in Patent Document 1. There is a problem that the dimensions at the time of starting restraint must be accurately predicted in advance. That is, when the dimension of the annular member at the start of restraint is larger than the space surrounded by the wall surface of the restraint member, restraint itself becomes impossible. On the other hand, if the dimension of the annular member at the start of restraint is too small than the space surrounded by the wall surface of the restraint member, the annular member is not sufficiently restrained by the restraint member even if the annular member expands due to quenching.

  Further, in the above-described conventional constraining and quenching method, even when the dimension of the annular member at the time of restraint start can be accurately predicted, the constraining member having a dimension corresponding to each dimension of the annular member to be quenched. Need to prepare. Furthermore, in an actual production line, it is necessary to replace the restraining member to be used every time the dimensions of the annular member to be quenched are changed, and the quenching processing efficiency is lowered.

  As described above, the conventional restraint quenching method requires accurate prediction of the dimensions of the annular member and preparation of a large number of restraint members in order to ensure sufficient restraint effect. ) Is troublesome. And the said problem makes it difficult to ensure the effect of sufficient restraint, lowers the processing efficiency of a quench hardening process, and causes the raise of the production cost of an annular member.

  Accordingly, an object of the present invention is to easily restrain the annular member that can secure the sufficient restraining effect, increase the processing efficiency of the quench hardening process, and suppress the production cost of the annular member. Is to provide a method.

The annular member restraining and quenching method according to the present invention includes a heating step, a first cooling step, a restraining step, and a second cooling step. In the heating step, an annular member made of steel is heated to a temperature of A ₁ point or higher. In the first cooling step, the annular member heated in the heating step is cooled from a temperature of A ₁ point or higher to a first cooling temperature that is a temperature of _MS point or lower. In the restraining step, the annular member cooled to the first cooling temperature is restrained by the restraining member. In the second cooling step, the annular member restrained by the restraining member is a temperature at which restraint by the restraining member is started, and reaches a second cooling temperature that is a temperature lower than the restraint start temperature that is a temperature equal to or lower than the M _S point. The cooling is performed while being restrained by the restraining member. In the restraining step and the second cooling step, the outer circumferential surface of the annular member intersects with the at least one end surface without contacting the annular member and the restraining member on the outer circumferential surface and at least one end surface of the annular member. The annular member is restrained so that the restraining member and the annular member come into contact with each other at the ridge line portion that is the portion to be operated.

  In general, in cooling by restraint quenching of the annular member, the annular member is restrained so that the outer peripheral surface and the end surface of the annular member are in contact with the restraint member throughout. On the other hand, the present inventor has made a detailed study on the relationship between the constrained part in the constraining quenching of the annular member and the dimensional accuracy and roundness of the annular member after quenching. As a result, the following findings were obtained.

  That is, in restraint quenching cooling of the annular member, a ridge line that is a portion where the outer circumferential surface and the end surface of the annular member intersect even if the annular member and the restraining member do not contact each other on the outer circumferential surface and the end surface of the annular member. In the portion, the annular member is restrained so that the restraining member and the annular member are in contact with each other, so that sufficient dimensional accuracy and roundness can be obtained, and the restraint in the ridge line portion is not necessarily adjacent to the end surfaces on both sides. The present inventor has found that sufficient dimensional accuracy and roundness can be obtained even if it is performed only on one side, without being performed at the ridge line portion.

The constrained quenching method of the annular member of the present invention, an annular member made in the heating step was heated to a temperature of more than A ₁ point austenitized steel, the first cooling temperature below M _S point in the first cooling step The martensite transformation is started by being cooled. Here, the martensitic transformation of steel does not proceed unless the temperature is lowered. Moreover, steel, if it is cooled to a temperature below M _S point, no progress pearlite and bainite transformation. In the restraining step, the annular member is restrained at the ridgeline portion, and further cooled to the second cooling temperature in the second cooling step, whereby the martensitic transformation proceeds, and the decrease in roundness and the heat treatment deformation are suppressed. The annular member is cured.

  Here, for example, a constraining surface that is a wall surface for contacting an annular member is a constraining member having a circular cross section in a plane perpendicular to one axis, or a portion in which the constraining surface is inclined with respect to one axis. A constraining member having a constraining surface such as a conical surface shape or a spherical surface shape is employed. Then, by bringing the restraining surface of the restraining member and the ridge line portion of the annular member into contact with each other so that the one axis of the restraining member and the axis of the annular member coincide with each other, the dimensions of the annular member at the start of restraining are accurately determined in advance. Without predicting, the annular member can be restrained at the ridge line portion. On the other hand, as described above, sufficient dimensional accuracy and roundness can be obtained by restraining the annular member so that the restraining member and the annular member come into contact with each other at the ridge line portion. Therefore, a sufficient restraining effect can be easily ensured.

  Further, when the annular member is constrained at the ridge portion as described above, for example, when the above-described constraining member is adopted, the shape of the constraining surface corresponding to each dimension of the annular member (the one axis described above) It is not necessary to prepare a constraining member having a cross-sectional diameter perpendicular to the same, and one constraining member can be used for constraining annular members of various sizes. Further, even in an actual production line, it is not necessary to replace the restraining member to be used every time the dimensions of the annular member to be quenched are changed, and the quenching processing efficiency is improved. Therefore, it is possible to increase the processing efficiency of the quench hardening process and suppress the production cost of the annular member.

  As described above, according to the constraining and quenching method for an annular member of the present invention, it is possible to easily secure a sufficient restraining effect, increase the processing efficiency of the quench hardening process, and suppress the production cost of the annular member. be able to.

  In addition, the constraining surface of the constraining member to be adopted has a circular cross section perpendicular to the axial direction, such as a conical surface shape or a spherical shape, and a wall surface in which the diameter of the cross section continuously decreases (or increases) in the axial direction. Any restraining member may be used. In addition, the angle (constraint member taper angle) formed by the surface perpendicular to the axis and the restraint surface at the contact portion between the restraint member and the annular member in the cross section including the shaft of the restraint member is the radial restraint force and the axial direction. It is ideal to set the angle to 45 degrees in consideration of the balance with the restraining force. However, in consideration of the processing accuracy of the restraining member, it is necessary to allow for a variation of about ± 0.5 degrees. It can be set to 45.5 degrees or less. Furthermore, in the restraining step and the second cooling step, the inner peripheral surface of the annular member may be restrained, but basically, the restraint effect can be ensured by restraining the ridgeline portion, so It does not have to be done.

Further, the _1-point A when heated steel refers to a point that the structure of the steel corresponds to the temperature to start the transformation from ferrite to austenite. Further, the M _S point when the steel was austenitized is cooled, it refers to a point corresponding to a temperature to initiate the martensite.

  Preferably, in the restraint quenching method for the annular member, the restraint start temperature is 150 ° C. or higher. As described above, in the constrained quenching method for an annular member of the present invention, the annular member is cooled while being constrained, and the martensitic transformation of the steel constituting the annular member proceeds, whereby the roundness of the annular member is increased. Reduction and heat treatment deformation are suppressed. However, if the restraint start temperature is less than 150 ° C., martensitic transformation has already progressed to a considerable extent before restraint starts, and the proportion of austenite that transforms to martensite after restraint starts is reduced. Therefore, the effect of suppressing the heat treatment deformation due to restraint and the decrease in roundness becomes insufficient. By setting the restraint start temperature to 150 ° C. or higher, a sufficient ratio of austenite that transforms into martensite after restraint starts is sufficiently secured, and the heat treatment deformation and the roundness reduction of the annular member are further suppressed.

In the constrained quenching method for the annular member, the second cooling temperature is preferably 100 ° C. or lower. When the restraint of the annular member is finished at a temperature higher than 100 ° C., since there is a large proportion of austenite that newly undergoes martensitic transformation in the subsequent cooling, there is a possibility that heat treatment deformation and a decrease in roundness may occur in the subsequent cooling. is there. By setting the second cooling temperature to 100 ° C. or less, it is possible to sufficiently suppress the ratio of austenite that subsequently undergoes martensitic transformation, and to further suppress the heat treatment deformation of the annular member and the decrease in roundness. If the restraint of the annular member is continued up to the _Mf point of the steel constituting the annular member, the remaining austenite disappears, and the reduction in roundness and heat treatment deformation due to subsequent cooling can be avoided almost completely. it can. Therefore, even if the annular member is cooled to a temperature range lower than the _Mf point, no further effect can be expected and the efficiency of the quench hardening process is reduced. Therefore, the second cooling temperature should be equal to or higher than the _Mf point. Can do. Here, the _Mf point refers to a point corresponding to a temperature at which martensite formation is completed when the austenitized steel is cooled.

  In the constrained quenching method for the annular member, the cooling rate in the second cooling step is preferably 6 ° C./second or less. By setting the cooling rate in the second cooling step to 6 ° C./second or less, it is possible to further suppress a decrease in roundness and heat treatment deformation. If the cooling rate is less than 1 ° C./second, the effect of suppressing the heat treatment deformation and the decrease in roundness is saturated, while the time required for the second cooling step becomes long, and the processing efficiency of the quench hardening process decreases. Therefore, the cooling rate in the second cooling step is preferably 1 ° C./second or more. Here, the cooling rate refers to the temperature decrease per unit time.

  Preferably, in the restraining quenching method for the annular member, in the restraining step and the second cooling step, the annular member is expressed by the following formula using a restraining member having a restraining member taper angle of 44.5 degrees or more and 45.5 degrees or less. A load equal to or greater than the load L satisfying the relationship (1) is applied and restrained.

L = 3.175 × (C ₂ / C ₁ ) ^−1.754 × S (1)
Here, L is a load (N), S is a cross-sectional area (mm ² ) of one of the two separated cross sections in the cross section of the annular member including the shaft, and C ₁ is an annular member before restraint. Roundness (μm), C ₂ is the roundness (μm) of the annular member required after quenching.

As a result of the study by the present inventor, the circularity of the annular member before restraint is C ₁ and has a restraint member taper angle of 45 ° ± 0.5 ° (44.5 ° to 45.5 °). When the annular member is constrained by the constraining member, it becomes clear that a load equal to or greater than the load L represented by the above formula (1) is necessary to improve the roundness to C ₂ after quenching. It was. Therefore, by the annular member is restrained load is applied over the load L, thereby making it possible to improve the roundness to the desired roundness C _2.

In addition, the roundness (C ₁ ) of the annular member before restraint is almost the same value as the roundness before the start of quench hardening (before heating). Therefore, in Formula (1), instead of the roundness (C ₁ ) of the annular member before restraint, the roundness before the start of quench hardening (before heating) may be employed. The roundness is roundness according to the least square center method (LSC) defined in JIS B7451.

  As is clear from the above description, according to the constraining and quenching method of the annular member of the present invention, it is easy to secure a sufficient restraining effect and increase the processing efficiency of the quench hardening process. It is possible to provide a constrained quenching method for an annular member capable of suppressing production costs.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of a bearing race 10 as an annular member according to Embodiment 1, which is an embodiment of the method for restraining and quenching an annular member according to the present invention. FIG. 2 is a flowchart showing an outline of the constraining quenching method for the annular member in the first embodiment. FIG. 3 is a schematic cross-sectional view for explaining a restraining step and a second cooling step of the restraining quenching method for the annular member in the first embodiment. With reference to FIGS. 1-3, the constrained quenching method of the annular member in Embodiment 1 is demonstrated.

  Referring to FIG. 1, the bearing race 10 has a cylindrical shape, and includes an outer peripheral surface 11 and an inner peripheral surface 13 parallel to the outer peripheral surface 11 in a cross section including the axis α of the bearing race 10. , Two end surfaces 12 and 12 intersecting (orthogonal) the outer peripheral surface 11 and the inner peripheral surface 13 are provided. Further, ridge line portions 14 and 14 are formed at portions where each of the two end surfaces 12 and 12 intersects with the outer peripheral surface 11. The ridge line portion 14 is a chamfered portion that is a chamfered region, for example. Hereinafter, a method for restraining and quenching the annular member according to the first embodiment performed on the bearing race 10 will be described.

Referring to FIG. 2, the constrained quenching method for the annular member in the first embodiment includes a heating step, a first cooling step, a constraining step, and a second cooling step. In the heating process, the bearing race 10 as an annular member made of steel such as bearing steel (for example, JIS standard SUJ2) is heated to a temperature of 800 ° C. or higher and 1000 ° C. or lower, which is a temperature of A ₁ point or higher, for example, 850 ° C. . In the first cooling process, the bearing race 10 heated in the heating process is a temperature of 150 ° C. or higher and 250 ° C. or lower, which is a temperature of A ₁ point or higher and M _S point or lower, for example, a first cooling temperature of 230 ° C. Until cooled.

Further, referring to FIG. 2 and FIG. 3, in the restraining step, bearing ring 10 cooled to the first cooling temperature is restrained by restraining member 30. In the second cooling step, the bearing race 10 restrained by the restraining member 30 is a temperature at which restraint by the restraining member 30 is started, and is a temperature lower than a restraint start temperature that is a temperature below the _MS point 30. Cooling while being restrained by the restraining member 30 to a temperature of not lower than 100 ° C. and not higher than 100 ° C., for example, a second cooling temperature of 80 ° C.

  Here, as the quench hardening process performed by the above heating and cooling, a normal quench hardening process that is heated in the air and then cooled may be employed, or control such as bright heat treatment, carbonitriding process, etc. A quench hardening process that is heated in a heated atmosphere and then cooled may be employed.

  And in a restraint process and a 2nd cooling process, with reference to FIG. 3, the bearing race 10 and the restraint member 30 do not contact in the outer peripheral surface 11 and the two end surfaces 12 and 12 of the bearing race 10. The bearing race 10 is restrained so that the restraining member 30 and the bearing race 10 come into contact with each other at the ridge portion 14 where the outer peripheral surface 11 of the bearing race 10 and the two end faces 12, 12 intersect. .

  More specifically, in the restraint process, the bearing race ring 10 cooled to the first cooling temperature is restrained by using the restraint cooling device 20, and in the second cooling process, the bearing race ring restrained in the restraint process. 10 is cooled to the second cooling temperature while maintaining the restrained state. Here, the restraint cooling device 20 in the first embodiment includes a support base 33, a lower restraint member 32 disposed on the support base 33, an upper restraint member 31 disposed on the lower restraint member 32, and an upper restraint. And a load transmission member 34 disposed on the member 31. The lower restraining member 32 and the upper restraining member 31 constitute a restraining member 30.

  The support base 33 is formed with a support surface 33A which is a flat surface. The lower restraining member 32 is formed with a restraining surface 32A having a conical surface shape. The constraining surface 32A has a shape constituting a part of the side surface of the right cone. And the lower restraint member 32 is arrange | positioned so that the support surface 33A of the support stand 33 may be contacted in the bottom face 32B which is a flat surface. Further, the lower restraining member 32 has a support surface formed by a circle formed by intersecting the restraint surface 32A with a surface perpendicular to the axis β, which is an axis connecting the apex of the right cone including the restraint surface 32A and the center of the bottom surface. It is arranged so as to be parallel to 33A. Further, the lower restraining member 32 is disposed on the support base 33 so that the apex of the right cone including the restraint face 32A is on the support base 33 side when viewed from the restraint face 32A. That is, the lower restraining member 32 is arranged on the support base 33 so that the diameter of a circle formed by intersecting the face perpendicular to the axis β and the restraint face 32A becomes smaller as the support base 33 is approached. ing.

  On the other hand, like the lower restraining member 32, the upper restraining member 31 has a conical surface 31 A having a conical shape and basically has the same configuration as the lower restraining member 32. The upper restraint member 31 is arranged so that the restraint surface 31A of the upper restraint member 31 and the restraint surface 32A of the lower restraint member 32 face each other. The upper restraining member 31 has a support surface formed by a circle formed by intersecting the restraining surface 31A with a surface perpendicular to the axis γ that is an axis connecting the apex of the right cone including the restraining surface 31A and the center of the bottom surface. It is arranged so as to be parallel to 33A. Further, the upper restraining member 31 is arranged so that the apex of the right cone including the restraining surface 31 </ b> A is on the side opposite to the support base 33 as viewed from the restraining surface 31 </ b> A. In other words, the upper restraining member 31 is disposed on the lower restraining member 32 so that the diameter of a circle formed by intersecting the face perpendicular to the axis γ and the restraining face 31A becomes larger as the support base 33 is approached. Has been. Further, the upper restraining member 31 and the lower restraining member 32 are arranged so that the axes β and γ of the upper restraining member 31 and the lower restraining member 32 coincide with each other.

  Furthermore, the load transmission member 34 is disposed such that a flat surface 34A, which is a flat surface, is parallel to the support surface 33A and is in contact with a bottom surface 31B, which is a flat surface of the upper restraining member 31. .

  Next, a procedure for restraining the bearing ring 10 using the restraining cooling device 20 in the restraining process will be described. First, the bearing race 10 is adjusted so that the axis α of the bearing race 10 cooled to the first cooling temperature coincides with the axis β of the lower restraint member 32 disposed on the support base 33. It is set so as to come into contact with the restraining surface 32A. Here, as described above, since the restraint surface 32A is a part of the side surface of the right cone, the bearing race 10 contacts the restraint surface 32A of the lower restraint member 32 at the ridge line portion 14, and the outer peripheral surface 11, The peripheral surface 13 and the end surface 12 do not contact the lower restraining member 32.

  Thereafter, the upper restraint member 31 reduces the distance from the lower restraint member 32 while maintaining the state where the axis γ of the upper restraint member 31 coincides with the axis α of the bearing race 10 and the axis β of the lower restraint member 32. And contact with the bearing race 10. Here, as described above, since the constraining surface 31A is also a part of the side surface of the right cone, the bearing race 10 contacts the constraining surface 31A of the upper constraining member 31 at the ridge line portion 14, and the outer peripheral surface 11, The peripheral surface 13 and the end surface 12 do not contact the upper restraining member 31. A load transmitting member 34 is disposed on the upper restraining member 31 so as to be in contact with the bottom surface 31B, and a desired load L is applied to the load transmitting member 34 by a load loading device such as a press weight or a hydraulic cylinder (not shown). Is done. Thereby, the bearing race 10 is restrained at the ridge line portion 14.

  In the second cooling step, the bearing ring 10 restrained in the restraining step as described above is cooled to the second cooling temperature while maintaining the restrained state. Here, the bearing race 10 may be cooled by being left in the atmosphere in a restrained state as described above (cooling), or a blower or other blower may be used to generate a gas such as air. It may be blown and cooled (blast cooling). Further, in order to increase the efficiency of quench hardening treatment, the bearing race 10 may be immersed in oil, or may be cooled by spraying oil (oil cooling), immersed in water, or water. May be sprayed and cooled (water cooling).

  As described above, in the restraint process and the second cooling process of the first embodiment, the bearing race 10 is restrained so that the restraint member 30 and the bearing race 10 as an annular member come into contact with each other at the ridge line portion 14. Thus, sufficient dimensional accuracy and roundness can be obtained. Here, according to the restraining step of the first embodiment, the dimensions at the start of restraint of the bearing race 10 are accurately predicted in advance by restraining the shaft α, the shaft β, and the shaft γ to coincide with each other. The bearing race 10 can be restrained at the ridge line portion 14. Therefore, a sufficient restraining effect can be easily ensured.

  Moreover, it is necessary to prepare the restraint member 30 which has the shape of restraint surface 31A, 32A according to the dimension of the bearing race ring 10 for every dimension of the bearing race ring 10 by restraining the bearing race ring 10 in the ridgeline part 14 as mentioned above. Instead, the single restraining member 30 can be used to restrain the bearing race 10 having various dimensions. Further, even in an actual production line, it is not necessary to replace the restraining member 30 to be used every time the dimensions of the bearing race 10 to be quenched are changed, and the quenching processing efficiency is improved. Therefore, the processing efficiency of the quench hardening process can be increased, and the production cost of the bearing race 10 can be suppressed.

  As described above, according to the constraining and quenching method of the annular member in the first embodiment, the bearing race as the annular member can be easily secured while ensuring the sufficient restraining effect and increasing the processing efficiency of the quench hardening process. The production cost of the wheel 10 can be suppressed.

  Furthermore, in the restraining quenching method for the annular member in the first embodiment, the restraining start temperature is preferably 150 ° C. or higher. As a result, a sufficient proportion of austenite that transforms into martensite after the start of restraint is ensured, and the heat treatment deformation and the decrease in roundness of the bearing race 10 are further suppressed.

  Furthermore, in the restraining quenching method for the annular member in the first embodiment, the second cooling temperature is preferably 100 ° C. or lower. Thereby, the ratio of the austenite which carries out a martensitic transformation after a 2nd cooling process can fully be suppressed, and the heat treatment deformation | transformation of the bearing ring 10 and a roundness fall can be suppressed further.

  Furthermore, in the restraining quenching method for the annular member in the first embodiment, the cooling rate in the second cooling step is preferably 6 ° C./second or less. Thereby, the heat treatment deformation | transformation of the bearing race 10 and the fall of roundness can be suppressed further.

Furthermore, in the restraint quenching method for the bearing race 10 according to the first embodiment, the restraint member taper angle of the bearing race 10 is 44.5 degrees or more and 45.5 degrees or less in the restraining step and the second cooling step (see FIG. The restraint member 30 having the lower restraint member taper angle θ ₁ and the upper restraint member taper angle θ ₂ ) is preferably restrained by being loaded with a load equal to or greater than the load L satisfying the relationship of the following expression (1).

L = 3.175 × (C ₂ / C ₁ ) ^−1.754 × S (1)
Thus, it is possible to improve the roundness of the desired bearing ring 10 to the roundness C _2.

  Furthermore, the manufacturing method of an annular member can be provided by adopting the constrained quenching method of the annular member in the first embodiment of the present invention. FIG. 4 is a flowchart showing an outline of the manufacturing method of the annular member in the first embodiment. With reference to FIG. 4, the manufacturing method of the annular member in Embodiment 1 is demonstrated.

With reference to FIG. 4, the manufacturing method of the annular member in Embodiment 1 includes a molded member preparation step, a quench hardening step, a tempering step, and a finishing step. In the molded member preparation step, a molded member that is a member made of steel and molded into the approximate shape of the bearing race 10 as an annular member is prepared. Specifically, for example, a steel material made of JIS standard SUJ2 is processed by forging, cutting, or the like to produce a molded member. In the quench hardening process, the molded member prepared in the molded member preparation process is hardened and cured. In the tempering step, the molded member quenched and hardened in the quench-hardening step is heated to a temperature of 150 ° C. or higher and 300 ° C. or lower, which is a temperature less than _one point A, for example, 180 ° C. It is held for a time, for example 120 minutes, and then allowed to cool in air at room temperature (air cooling). In the finishing process, the molded member that has been tempered in the tempering process is finished. Specifically, finishing processing such as grinding and super finishing is performed on the molded member, and the bearing race 10 as an annular member is completed.

  And the quenching process in the said quench hardening process is implemented using the restraint quenching method of the annular member in Embodiment 1 of this invention. As described above, the constraining quenching method for the annular member in the first embodiment that can easily ensure sufficient restraint effect and increase the processing efficiency of the quench hardening process is the quench hardening process. By being adopted, according to the manufacturing method of the annular member in the first embodiment of the present invention, the heat treatment deformation and the decrease in roundness are stably suppressed, and the production cost is suppressed.

(Embodiment 2)
FIG. 5 is a schematic cross-sectional view of a bearing race 10 as an annular member of the second embodiment, which is an embodiment of the method for restraining and quenching an annular member of the present invention. FIG. 6 is a schematic cross-sectional view for explaining the restraining step and the second cooling step of the annular member restraining and quenching method according to the second embodiment. With reference to FIG. 5 and FIG. 6, the constrained quenching method for the annular member in the second embodiment will be described.

  Referring to FIG. 5, the bearing race 10 as an annular member in the second embodiment basically has the same configuration as the bearing race 10 in the first embodiment. However, the bearing race 10 according to the second embodiment has a tapered shape in which the outer peripheral surface 11 and the inner peripheral surface 13 are not parallel in the cross section including the axis α, and form a raceway taper angle A as a taper angle of the annular member. Is different from the bearing race 10 of the first embodiment. The bearing race 10 has a thick-side end face 12A having a large radial thickness and a thin-side end face 12B having a smaller radial thickness than the thick-side end face 12A. Hereinafter, a method for restraining and quenching the annular member according to the second embodiment that is performed on the bearing race 10 will be described. The taper angle of the annular member is an angle formed by a straight line extending from the inner peripheral surface and the axis in a cross section passing through the axis of the annular member.

  Referring to FIG. 6, the constraining quenching method for the annular member in the second embodiment is basically performed in the same manner as the constraining quenching method for the annular member in the first embodiment. However, due to the difference in the shape of the bearing race 10 as an annular member and the configuration of the restraining member 30, there is a difference from the restraining quenching method for the annular member in the first embodiment. .

  That is, referring to FIG. 6, restraint cooling device 20 in the second embodiment does not include lower restraint member 32 in the first embodiment, and support base 33 serves as the role of lower restraint member 32 in the first embodiment. Plays. That is, in the restraint cooling device 20 according to the second embodiment, the upper restraint member 31 and the support base 33 constitute the restraint member 30.

  Next, a procedure for restraining the bearing race 10 using the restraint cooling device 20 according to the second embodiment will be described. First, the bearing ring 10 cooled to the first cooling temperature is set on the support base 33 so as to contact the support surface 33A of the support base 33 at the thin end surface 12B. That is, the bearing race 10 contacts the restraining member 30 on the thin end surface 12B that is one end surface.

  Thereafter, the upper restraint member 31 moves so as to reduce the distance from the support base 33 while maintaining the state where the axis γ of the upper restraint member 31 coincides with the axis α of the bearing raceway ring 10. Contact with. Here, as in the case of the first embodiment, the constraining surface 31A is a part of the side surface of a right cone, so that the bearing race 10 is located at the upper portion of the thick side ridge line portion 14A adjacent to the thick side end surface 12A. It contacts the restraining surface 31A of the restraining member 31, and does not contact the upper restraining member 31 on the outer peripheral surface 11, the inner peripheral surface 13 and the thick wall side end surface 12A. A load transmitting member 34 is disposed on the upper restraining member 31 so as to be in contact with the bottom surface 31B, and a desired load L is applied to the load transmitting member 34 by a load loading device such as a press weight or a hydraulic cylinder (not shown). Is done. As a result, the bearing race 10 is restrained at the thick side ridge line portion 14A adjacent to the thick side end surface 12A and the thin side end surface 12B.

  In the second cooling step, the bearing race 10 restrained in the restraining step is cooled to the second cooling temperature while maintaining the restrained state as in the case of the first embodiment.

  As described above, in the constraining and quenching method for the annular member according to the second embodiment, the bearing race 10 serving as the annular member is constrained at the thick-side ridge line portion 14A that is one ridge line portion. Here, the restraint of the annular member in the ridge line portion does not necessarily have to be performed in the ridge line portion adjacent to the end faces on both sides, and sufficient dimensional accuracy and roundness can be obtained even if performed on only one side. . Further, when the ridge line portion is constrained only on one side, and the constrained annular member has a tapered shape, the ridge line adjacent to the end surface on the side where the radial thickness is large in the annular member The portion (the ridge line portion adjacent to the end surface on the side close to the portion having a large radial thickness in the annular member) is restrained, so that the ridge line portion adjacent to the end surface on the side having a small radial thickness is restrained. Also, higher dimensional accuracy and roundness can be obtained.

  Therefore, in the constrained quenching method of the annular member in the second embodiment, the bearing race 10 is constrained in the thick ridge line part 14A that is one of the ridge line parts, thereby being constrained in both the ridge line parts 14A and 14B. Dimensional accuracy and roundness comparable to those obtained can be obtained. Further, by restraining the shaft α and the shaft γ to coincide with each other, the bearing race 10 is restrained at the thick-side ridge line portion 14A without accurately predicting in advance the size of the bearing race 10 at the start of restraint. can do. Therefore, a sufficient restraining effect can be easily ensured.

  Further, the thick side ridge line portion 14A is restrained by the restraining surface 31A of the upper restraining member 31 and the thin side end surface 12B is restrained by the support surface 33A of the support base 33, so that for each dimension of the bearing race ring 10, There is no need to prepare a restraining member 30 having a shape corresponding to that, and one restraining member 30 can be used for restraining the bearing race 10 having various dimensions. Further, even in an actual production line, it is not necessary to replace the restraining member 30 to be used every time the dimensions of the bearing race 10 to be quenched are changed, and the quenching processing efficiency is improved. Therefore, the processing efficiency of the quench hardening process can be increased, and the production cost of the bearing race 10 can be suppressed.

  Moreover, according to the restraint quenching method of the annular member of the second embodiment, the constituent elements (lower restraint member 32) of the restraint cooling device 20 can be reduced as compared with the case of the first embodiment. Therefore, not only can the constraint cooling device 20 be simplified, but also when the length of the bearing race 10 in the direction of the axis α (height of the bearing race 10) is small, the restraint members 30 are less likely to interfere with each other. The bearing ring 10 having a wide size range can be restrained.

  In addition, even if the quenching process in the quenching hardening process of the manufacturing method of the annular member in Embodiment 1 demonstrated based on FIG. 4 is implemented using the constraining quenching method of the annular member in the said Embodiment 2. FIG. Good.

  Embodiment 1 of the present invention will be described below. (1) Presence / absence of restraint, (2) Restraint start temperature, (3) Restraint end temperature (second cooling temperature), (4) Cooling rate in second cooling step, (5) Tests were conducted to investigate the effects of the shape of the annular member, (6) taper angle of the lower restraining member, and (7) restraining load.

  First, the test method will be described. First, a steel material of JIS standard SUJ2, which is a high carbon chromium bearing steel, is formed by turning or the like, and a cylindrical (non-tapered) annular member (FIG. 1) having an outer diameter of φ85.0 mm and an inner diameter of φ70.0 mm and an outer diameter of φ80. Two kinds of annular members (FIG. 5) having a tapered shape of 4 mm, a thick-side inner diameter φ68.5 mm, and a thin-side inner diameter φ75.6 mm were produced. And the said annular member was inserted in the heating furnace adjusted to the reducing atmosphere in order to prevent decarburization, and it hold | maintained at 810 degreeC for 40 minutes.

Then removed annular member from the heating furnace, soaked immediately (within one second in) quenching oil (cold type, Nippon Grease Co. High Speed quench oil Nanba1070S) adjusted to 80 ° C. during, M _S It cooled to the 1st cooling temperature which is the temperature below a point. And the cyclic | annular member was taken out out of quenching oil, and was restrained using the restraint cooling device 20 in Embodiment 1 demonstrated based on FIG. At this time, with respect to the annular member having a tapered shape, the ridge line portion adjacent to the end face on the thin side was restrained so as to contact the lower restraining member 32. Further, the temperature of the annular member (restraint start temperature) at the time when restraint was started was measured. Restraint start temperature is a M _S point temperature below, and has been a lower temperature than the first cooling temperature.

  Furthermore, the restrained annular member was cooled to a second cooling temperature lower than the restraint start temperature, and then taken out from the restraint cooling device. In the procedure described above, an annular member in which the restraint start temperature, the restraint end temperature (second cooling temperature), the cooling rate in the second cooling step, the shape of the annular member, and the taper angle of the lower restraint member are changed, and a sample is prepared. It was.

  And the roundness by the least square center method (LSC) prescribed | regulated to JISB7451 was measured about the sample produced as mentioned above using the roundness measuring apparatus. The roundness indicates that the smaller the numerical value, the closer to the roundness, the better the roundness.

  Moreover, in order to confirm the effect of restraint, the sample which abbreviate | omitted restraint by a restraint cooling device was produced among the above-mentioned procedures, and the roundness was measured.

  Next, the results of the test will be described. Table 1 shows the test conditions and the roundness measurement results. Here, in consideration of an actual mass production process, it is also important that the roundness has a small variation. Therefore, the standard deviation is calculated together with the average value of the measured roundness and is displayed in Table 1.

(1) Presence / absence of restraint First, the influence of the presence / absence of restraint in the ridge line portion will be described. Referring to Table 1, comparing sample numbers 1 and 2 that are not restrained with sample numbers 3 to 18 that are restrained at the ridgeline as described above, sample numbers that are restrained at the ridgeline 3 to 18 are smaller in roundness average value and standard deviation than sample numbers 1 and 2. From this, it was confirmed that the roundness can be improved by restraining the annular member at the ridge line portion.

(2) Restraint start temperature Next, the influence of the restraint start temperature will be described. FIG. 7 is a diagram showing the relationship between the constraint start temperature and the roundness based on the data of sample numbers 10, 11, and 4 in Table 1. In FIG. 7, the horizontal axis indicates the restraint start temperature, the vertical axis indicates the roundness, the circle indicates the average value of roundness, and the cross indicates the standard deviation of roundness.

  Referring to FIG. 7, the average value of roundness is constant when the restraint start temperature is 150 ° C. or higher, whereas the roundness deteriorates more than twice when the restraint start temperature is less than 150 ° C. is doing. This is because, when the restraint start temperature is less than 150 ° C., the ratio of austenite that transforms to martensite after restraint starts is small, so that the effect of suppressing heat treatment deformation and roundness reduction due to restraint becomes insufficient. It is believed that there is. In addition, referring to FIG. 7, when the restraint start temperature is 250 ° C., there is no difference in the average value of roundness, but the standard deviation is greatly suppressed, and the variation in roundness is reduced. I understand that.

  From the above, in order to improve the roundness, it was confirmed that the constraint start temperature is preferably 150 ° C. or higher, and more preferably 250 ° C. or higher.

(3) Restraint end temperature (second cooling temperature)
Next, the influence of the constraint end temperature (second cooling temperature) will be described. FIG. 8 is a diagram showing the relationship between the constraint end temperature (second cooling temperature) and the roundness based on the data of sample numbers 12 to 14 and 4 in Table 1. In FIG. 8, the abscissa indicates the constraint end temperature (second cooling temperature), the ordinate indicates the roundness, the circle indicates the average value of roundness, and the cross indicates the standard deviation of roundness. Yes.

  Referring to FIG. 8, when the constraint end temperature is 100 ° C. or lower, the average value of roundness is constant, whereas when the constraint end temperature exceeds 100 ° C., the roundness is greatly increased. It is getting worse. This is because, when the restraint of the annular member is finished at a temperature higher than 100 ° C., since the ratio of austenite that newly undergoes martensitic transformation in the subsequent cooling is large, heat treatment deformation and a decrease in roundness occur in the subsequent cooling. This is probably because In addition, referring to FIG. 8, when the constraint end temperature is 80 ° C. or less, the average value of roundness is not different, but the standard deviation is greatly suppressed, and the variation in roundness is reduced. I understand that

  From the above, in order to improve the roundness, it was confirmed that the constraint end temperature is preferably 100 ° C. or less, and more preferably 80 ° C. or less.

(4) Cooling rate in the second cooling step Next, the influence of the cooling rate in the second cooling step will be described. FIG. 9 is a diagram showing the relationship between the cooling rate and the roundness in the second cooling step based on the data of sample numbers 15 to 17 and 4 in Table 1. In FIG. 9, the horizontal axis indicates the cooling rate in the second cooling step, the vertical axis indicates the roundness, the circle indicates the average value of roundness, and the cross indicates the standard deviation of roundness. .

  Referring to FIG. 9, when the cooling rate is 6 ° C./second or less, the average value of roundness is substantially constant, whereas when the cooling rate exceeds 6 ° C./second, the roundness is Has deteriorated significantly. This is considered to be because when the annular member is cooled at a cooling rate exceeding 6 ° C./second, the dependency on the cooling rate of the relationship between stress and strain in the transformation superplasticity at the time of transformation increases. In addition, referring to FIG. 9, when the cooling rate is 3 ° C./second or less, although there is no difference in the average value of roundness, the standard deviation is greatly suppressed and the variation in roundness is small. You can see that

  From the above, in order to improve the roundness, it was confirmed that the cooling rate in the second cooling step is preferably 6 ° C./second or less, more preferably 3 ° C./second or less. .

(5) Shape of annular member Next, the influence of the shape of the annular member will be described. FIG. 10 is a diagram showing the relationship between the shape of the annular member and the roundness based on the data of sample numbers 18 and 5 in Table 1. In FIG. 10, the horizontal axis indicates whether or not the annular member has a taper shape (A: taper shape in FIG. 5, B: non-taper shape in FIG. 1), and the vertical axis indicates roundness. The mark indicates the average value of roundness, and the cross indicates the standard deviation of roundness.

  Referring to FIG. 10, almost the same roundness is obtained with any annular member shape, and whether or not the annular member has a tapered shape has little effect on the roundness. I understood.

(6) Taper angle of lower restraint member Next, the influence of the taper angle of the lower restraint member will be described. FIG. 11 is a diagram showing the relationship between the taper angle and the roundness of the lower restraining member based on the data of sample numbers 6 to 9 and 5 in Table 1. In FIG. 11, the horizontal axis indicates the taper angle of the lower restraining member, the vertical axis indicates the roundness, the circle indicates an average value of roundness, and the cross indicates a standard deviation of roundness.

  Referring to FIG. 11, it is considered that when the taper angle of the lower restraint member is increased, the average value of the roundness tends to be slightly increased. However, considering that the standard deviation is substantially constant, the lower restraint member It can be said that the influence of the taper angle on the roundness is small. Further, even when the taper angle of the lower restraining member is 0 degree, that is, when the lower restraining member has a flat plate shape and does not restrain the annular member in the radial direction, the roundness is not lowered.

  From the above, the restraint at the ridge line portion of the annular member does not necessarily have to be performed at the ridge line portion adjacent to the end surfaces on both sides, and even when performed only on one side, the roundness equivalent to that performed on both sides is the same. It was confirmed that it was obtained.

(7) Restraint load Next, the influence of the restraint load will be described. FIG. 12 is a diagram showing the relationship between the restraint load and the roundness based on the data of sample numbers 3 to 5 in Table 1. In FIG. 12, the horizontal axis indicates the restraint load (the load L applied to the load transmitting member 34 in FIG. 3), the vertical axis indicates the roundness, the circle indicates the average value of roundness, and the cross indicates true. The standard deviation of circularity is shown.

  Referring to FIG. 12, the roundness is substantially constant when the restraint load is 20 kgf or more, whereas the roundness is greatly deteriorated when the restraint load is less than 20 kgf. Therefore, it can be said that the restraining load is preferably 20 kgf or more in the range of the shape of the annular member.

  Here, under the quenching conditions in which the cooling rate in the first cooling step is sufficient and quenching and hardening is uniform from the surface to the inside, the annular member is uniformly cooled from the surface to the inside. Therefore, it is considered that the relationship described in the above (1) to (7) is established regardless of the size and shape of the annular member. However, the relationship between the restraint load and roundness described in (8) may depend on the size and shape of the annular member. Therefore, the relationship between the restraining load and the roundness was separately examined in detail in Example 2 below.

  Embodiment 2 of the present invention will be described below. An analysis was conducted to investigate the restraint load necessary to obtain the desired roundness. Hereinafter, the analysis method will be described.

First, a three-dimensional FEM (Finite Element Method) analysis model was created for the annular member described based on FIGS. 1 and 5. FIG. 13 is a diagram showing a three-dimensional FEM analysis model of the annular member of FIG. Referring to FIG. 13, the three-dimensional FEM analysis model of the annular member in FIG. 5 is a model in which the annular member in FIG. 5 is restrained by a load L by the restraint cooling device 20 described based on FIG. Further, for the annular member of FIG. 1, similarly to FIG. 13, a model restrained by the load L was created by the restraint cooling device 20 described based on FIG. 3. The lower restraining member taper angle θ ₁ and the upper restraining member taper angle θ ₂ were both 45 degrees. In addition, an elliptical deformation with a roundness of 150 μm was previously applied to the annular member of the analysis model.

  Next, the relationship between the stress σ and the strain ε in the transformation superplasticity during the martensitic transformation by FEM analysis so as to match the relationship between the constraint load and the average value of the roundness in the test result in Example 1 described above. (Σ-ε diagram) was derived. As a result, the relationship between stress σ and strain ε shown in the following formula (2) was obtained. However, the Young's modulus of the annular member was 210 GPa.

σ = 1.4 × 10 ⁷ + 2 × 10 ¹⁰ ε ^P (2)
Here, σ is stress (Pa), and ε ^P is equivalent plastic strain.

  Using this σ-ε relationship, the roundness when an annular member having various shapes and sizes was constrained by various constraining loads was calculated. Table 2 shows the analysis conditions and the roundness after the end of the restriction (after the quenching process) obtained as a result of the analysis.

And when the result of Table 2 was regression-analyzed, the following formula | equation (3) was obtained.
L / S = 3.175 × (C ₂ / C ₁ ) ^−1.754 (3)
Here, L is a load (N), S is a cross-sectional area (mm ² ) of one of the two separated cross sections in the cross section of the annular member including the shaft, and C ₁ is an annular member before restraint. Roundness (μm), C ₂ is the roundness (μm) of the annular member required after quenching.

From this equation (3), the following equation (1) is obtained. If C ₂ is the roundness (μm) of the annular member required after quenching, that is, the desired roundness, a load equal to or greater than the load L calculated by the equation (1) is applied. Thus, the desired roundness can be obtained.

L = 3.175 × (C ₂ / C ₁ ) ^−1.754 × S (1)
The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The method for constraining and quenching an annular member of the present invention can be particularly advantageously applied to a method for constraining and quenching an annular member that restrains deformation by restraining an annular member made of steel.

2 is a schematic cross-sectional view of a bearing race as an annular member according to Embodiment 1. FIG. 3 is a flowchart showing an outline of a constrained quenching method for an annular member in the first embodiment. It is a schematic sectional drawing for demonstrating the restraint process and 2nd cooling process of the restraint hardening method of the annular member in Embodiment 1. FIG. 3 is a flowchart showing an outline of a method for manufacturing the annular member in the first embodiment. FIG. 5 is a schematic cross-sectional view of a bearing race 10 as an annular member according to the second embodiment. It is a schematic sectional drawing for demonstrating the restraint process and 2nd cooling process of the restraint hardening method of the annular member in Embodiment 2. FIG. It is the figure which showed the relationship between restraint start temperature and roundness. It is the figure which showed the relationship between restraint completion temperature (2nd cooling temperature) and roundness. It is the figure which showed the relationship between the cooling rate in a 2nd cooling process, and roundness. It is the figure which showed the relationship between the shape of an annular member, and roundness. It is the figure which showed the relationship between the taper angle of a lower restraint member, and roundness. It is the figure which showed the relationship between a restraint load and roundness. It is a figure which shows the three-dimensional FEM analysis model of the annular member of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Bearing ring, 11 Outer peripheral surface, 12 End surface, 12A Thick side end surface, 12B Thin side end surface, 13 Inner peripheral surface, 14 Ridge part, 20 Restraint cooling device, 30 Restraint member, 31 Upper restraint member, 31A Restraint surface, 31B bottom surface, 32 lower restraint member, 32A restraint surface, 32B bottom surface, 33 support base, 33A support surface, 34 load transmission member, 34A flat surface.

Claims (5)

A heating step in which an annular member made of steel is heated to a temperature of A ₁ point or higher;
A _first cooling step in which the annular member heated in the heating step is cooled from a temperature of A ₁ point or higher to a first cooling temperature that is a temperature of M _S point or lower;
A restraining step in which the annular member cooled to the first cooling temperature is restrained by a restraining member;
The annular member constrained by the constraining member is at a temperature lower than a constraining start temperature that is a temperature at which constraining by the constraining member is started, and reaches the second cooling temperature that is a temperature equal to or lower than the _MS point. A second cooling step that is cooled while being restrained by the member,
In the restraining step and the second cooling step, the annular member and the restraining member do not come into contact with each other on the outer circumferential surface and at least one end surface of the annular member, and the at least one of the outer circumferential surface of the annular member and the at least one of them. A constraining quenching method for an annular member, wherein the annular member is constrained so that the constraining member and the annular member are in contact with each other at a ridge line portion where the end surface intersects.   The method for constraining and quenching an annular member according to claim 1, wherein the constraining start temperature is 150 ° C. or higher.   3. The constrained quenching method for an annular member according to claim 1, wherein the second cooling temperature is 100 ° C. or less.   The method for restraining and quenching an annular member according to claim 1, wherein a cooling rate in the second cooling step is 6 ° C./second or less. In the restraint step and the second cooling step, the annular member is a load satisfying the relationship of the following expression (1) by the restraint member having a restraint member taper angle of 44.5 degrees or more and 50.5 degrees or less. The method for restraining and quenching an annular member according to any one of claims 1 to 4, wherein a load of L or more is applied and restrained.
L = 3.175 × (C ₂ / C ₁ ) ^−1.754 × S (1)
Here, L is a load (N), S is a cross-sectional area (mm ² ) of one of the two separated cross sections in the cross section of the annular member including the shaft, and C ₁ is an annular member before restraint. Roundness (μm), C ₂ is the roundness (μm) of the annular member required after quenching.

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