JP5998438B2 - Restraint quenching method and restraint quenching apparatus - Google Patents

Description

  The present invention relates to a method of cooling and quenching while restraining and correcting a steel and annular workpiece used in a rolling bearing or the like, and an apparatus therefor.

In recent years, it has been required to manufacture parts at low cost, for example, by correcting the workpiece and reducing the number of steps in the grinding process. Therefore, many methods and apparatus for cooling and quenching the workpiece while correcting the workpiece have been proposed.
As an example of such a technique, for example, a technique described in Patent Document 1 has been proposed. In this document, after heating and holding a steel and annular workpiece with martensite transformation at a predetermined temperature during quenching, first, in the primary cooling step, it is cooled to a temperature higher than the martensite transformation start temperature, Next, in the secondary cooling step, the heat treatment straightening apparatus starts correction at a temperature lower than the martensite transformation start temperature and cools it to a temperature higher than the martensite transformation completion temperature (Mf point). Is disclosed. Further, the deformation correction method in the same document is a method in which a work piece is pressed while pressing the outer peripheral surface of a workpiece from the opposite side of the pair of receiving rolls with a pressure roll in a state where the outer peripheral surface of the annular workpiece is in contact with the pair of receiving rolls. The roundness is improved by rotating and correcting. The merit of the technique described in this document is that the quenching cooling time can be shortened by providing the secondary cooling step, and the deformation correction method has versatility.

JP 2009-84609 A

However, in the technique described in Patent Document 1, since the quenching temperature in the secondary cooling process is higher than the martensite transformation completion temperature (Mf point), the dimensional accuracy (dimension, roundness) deteriorates after the secondary cooling process. In order to further improve the accuracy of the workpiece after quenching, there is still room for improvement.
In other words, steel and annular workpieces used for rolling bearings and the like are made of carbon steel such as SUJ2 and 3 materials, but this type of steel material has a martensite transformation completion temperature (Mf point) of room temperature or lower. For this reason, when the temperature of the workpiece is lowered to room temperature or lower in the next process (for example, a cleaning process) after completion of quenching, the martensitic transformation further proceeds and the dimensional accuracy (dimension, roundness) deteriorates.

  In addition, in the technique described in Patent Document 1, the deformation correction method in the secondary cooling step is to improve the roundness by pressing the workpiece while rotating the roller. However, the workpiece after correction is corrected by the pressing force. There is a problem that the accuracy of the is different. That is, if the pressing force is weak, the accuracy of the workpiece after correction may not be improved, and if the pressing force is too strong, the workpiece may buckle or crack in the worst case. Therefore, sufficient experience is required to set the pressing force.

  Therefore, the present invention has been made paying attention to such problems, and can further reduce the manufacturing cost while further improving the accuracy of the workpiece after quenching (the cycle time can be shortened). ) It is an object to provide a method and apparatus for restraining and quenching a workpiece.

In order to solve the above-mentioned problem, a constrained quenching apparatus according to one aspect of the present invention is used in a rolling bearing in a stepwise manner while sequentially transporting steel and cylindrical workpieces with martensitic transformation during quenching. A constrained quenching apparatus comprising a plurality of cooling units for cooling and quenching, and a correction unit for constraining a workpiece being quenched in the plurality of cooling units as necessary and correcting the workpiece to a desired dimension, A first cooling section for cooling the workpiece from a state heated to a predetermined temperature to a correction start temperature higher than the martensite transformation start temperature (Ms point), and at least an outer diameter of the workpiece cooled to the correction start temperature. It has a first correction part that is constrained in the radial direction and corrects the first correction part, and it is lower than the martensite transformation start temperature (Ms point) and the martensite transformation completion temperature (Mf). 2) a second cooling part that cools to a predetermined quenching temperature higher than), and a second correction part that straightens the workpiece cooled to the predetermined quenching temperature by constraining at least its outer diameter in the radial direction. And a third cooling unit that cools the martensite transformation to a state where it can be considered that the martensite transformation has stopped at a temperature lower than the predetermined quenching temperature while correcting at the second correction unit, and proceeds with the martensite transformation, In the first straightening portion, the inner diameter dimension is set to a dimension at which the outer diameter dimension of the workpiece accompanying cooling when the workpiece is not restrained is changed from contraction to expansion by the start of martensitic transformation. And

Here, in the constrained quenching apparatus according to one aspect of the present invention, it is preferable that the first straightening portion further includes a side straightening portion that restrains the side surface of the workpiece in the axial direction in addition to restraining the outer diameter of the workpiece. .
Further, in the constrained quenching apparatus according to one aspect of the present invention, the second straightening part includes a general-purpose straightening part that restrains and corrects any other part of the work in addition to restraining the outer diameter of the work. It is preferable.

In the constrained quenching apparatus according to an aspect of the present invention, it is preferable that the first cooling unit further includes a third correction unit that constrains and corrects any part of the workpiece.
Furthermore, in order to solve the above-described problems, a method for restraining and quenching a workpiece according to an aspect of the present invention is to sequentially convey steel and cylindrical workpieces that are used in rolling bearings and have martensitic transformation during quenching. While constraining and quenching in stages, the work being quenched is constrained as necessary, and the work is constrained and quenched to correct a desired dimension, and the work is heated to a predetermined temperature. A first cooling step for cooling from the state to a correction start temperature higher than the martensite transformation start temperature (Ms point), and correction by constraining at least the outer diameter of the work cooled to the correction start temperature in the radial direction However, the second cooling is performed to a predetermined quenching temperature that is lower than the martensite transformation start temperature (Ms point) and higher than the martensite transformation completion temperature (Mf point). A cooling step, to a state which can be regarded as the predetermined martensitic transformation in the cooled at least further while restraining the outer diameter in the radial direction the predetermined temperature lower than the hardening temperature the workpiece until the quenching temperature is stopped A third cooling step that cools and advances martensite transformation, and the constraint of the outer diameter of the workpiece in the second cooling step is that the outer diameter dimension of the workpiece accompanying cooling when the workpiece is not restrained is It is characterized in that it is constrained by the dimensions when it turns from shrinkage to expansion by the start of martensitic transformation.

Here, in the constrained quenching method for a workpiece according to one aspect of the present invention, it is preferable that the second cooling step further constrains the side surface of the workpiece in the axial direction in addition to the constraint of the outer diameter of the workpiece.
Further, in the constrained quenching method for a workpiece according to one aspect of the present invention, the third cooling step is to restrain and correct any other part of the workpiece in addition to the constraint of the outer diameter of the workpiece. preferable.

  In the constrained quenching method for workpieces according to one aspect of the present invention, it is preferable that the first cooling step further corrects by restraining any part of the workpiece.

According to the present invention, the quenching time required for the heat treatment quality (heat treatment characteristics and mechanical accuracy such as roundness) is subdivided into three stages, and correction is made as necessary. In the constrained quenching apparatus according to an aspect of the invention, the third cooling unit corresponding to the third stage constrains at least the outer diameter of the steel and annular workpiece cooled to the quenching temperature in the radial direction. The martensite is cooled to a state in which it has a second straightening portion to be straightened and is straightened by the second straightening portion, and further considered to have stopped martensitic transformation at a temperature lower than a predetermined quenching temperature in the second cooling portion. Since the site transformation is advanced, the martensitic transformation can be advanced in the correction die (second correction portion). Therefore, the accuracy (dimension, roundness) after the heat treatment and the dimensional change after the heat treatment can be managed to further improve the accuracy.

Further, in the constrained quenching method for workpieces according to one aspect of the present invention, a steel and cylindrical workpiece in which the third cooling step corresponding to the third stage is cooled to the quenching temperature in the second cooling step. In contrast, the martensite transformation is progressed by cooling to a state where the martensitic transformation is stopped at a temperature lower than a predetermined quenching temperature while restraining at least the outer diameter in the radial direction. By constraining the outer diameter in the radial direction, the martensitic transformation can be advanced while correcting the workpiece as in the case of the above-described apparatus. Therefore, the accuracy (dimension, roundness) after the heat treatment and the dimensional change after the heat treatment can be managed to further improve the accuracy.

Furthermore, according to the present invention, in the first or second correction part or the second or third cooling step, at least the outer diameter of the work is constrained in the radial direction. Compared with the method of rotating and correcting the workpiece while pressing the workpiece with the pressure roll, it is not necessary to set the pressing force, and stable correction can be performed.
Therefore, according to the present invention, the manufacturing cost can be suppressed (the cycle time can be shortened) while further improving the accuracy of the workpiece after quenching.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram explaining 1st embodiment of the constrained hardening apparatus which concerns on 1 aspect of this invention, The figure (a) is the front view (A part is fractured | ruptured in the surface containing the axis line along a conveyance direction. (B) and (b) are plan views of a transport section included in each cooling section. It is a schematic block diagram explaining the workpiece mounting base (cooling mechanism part) with which each cooling part of FIG. 1 is provided. It is sectional drawing explaining the centering jig | tool. It is sectional drawing explaining an outer diameter correction jig. It is a principal part enlarged view explaining the state which is correcting the workpiece | work. It is a perspective view explaining the general purpose correction jig (viewed from below (work placement table side)). It is a process flow figure explaining the restraint hardening method of the work concerning one mode of the present invention. It is a graph which shows the relationship of the dimensional change of the workpiece | work with respect to cooling time, In the same figure, the period of three cooling processes employ | adopted with the restraint hardening method of the workpiece | work which concerns on 1 aspect of this invention is shown collectively. It is a figure which compares and shows the example of this invention and the comparative example (conventional) with respect to the precision of an outer diameter dimension. It is a figure which compares and shows the example of this invention and a comparative example (conventional) with respect to the variation of the turning dimension of a front process. It is a process flow figure explaining other examples (second embodiment) of the constraining hardening device concerning one mode of the present invention. It is a process flow figure explaining other examples (3rd embodiment) of the constrained hardening apparatus concerning one mode of the present invention. It is sectional drawing explaining the centering jig (with a collar) employ | adopted by 3rd embodiment. It is a principal part enlarged view explaining the state which is correcting the workpiece | work in 3rd embodiment. It is a process flow figure explaining other examples (fourth embodiment) of the constraining hardening device concerning one mode of the present invention.

Hereinafter, an embodiment of a constrained quenching apparatus according to an aspect of the present invention and a constrained quenching method for a workpiece using the same will be described with reference to the drawings as appropriate.
First, a first embodiment of a constrained quenching apparatus according to one aspect of the present invention will be described.
As shown in FIG. 1, the constrained quenching device 5 has a plurality of conveyance paths 60 that are separated in the conveyance direction, and three cooling units 1, 2, 3 are respectively provided between adjacent conveyance paths 60. Has been placed. In this example, the first cooling unit 1, the second cooling unit 2, and the third cooling unit 3 are sequentially arranged from the upstream side in the transport direction.

  Each of the cooling units 1, 2, and 3 includes a transport unit 40 for transporting the workpiece W and a mounting table 50 disposed below the upper surface of the transport path 60 for the workpiece W. Here, the workpiece W of the present embodiment is made of steel and annular with martensitic transformation at the time of quenching. In particular, in the first embodiment, the workpiece has a simple cylindrical outer shape. This is an example assuming that

  The transport unit 40 includes a transport arm 40a having a substantially V-shaped recess 40v with which the work W is brought into contact (see FIG. 5B). The transport arm 40a is moved by a slide movement mechanism (not shown). Is moved to the center of the mounting table 50 by sliding movement along the transport direction. The transport unit 40 further includes a rotation mechanism (not shown), and the transport arm is rotated by 90 degrees by the rotation mechanism, so that the transport arm is transported horizontally to the upper surface of the transport path 60. And a retracted posture V perpendicular to the upper surface of the transport path 60.

As shown in FIG. 2, the mounting table 50 has a seat surface 51 that is circular in plan view, and the workpiece W transported by the transport unit 40 is placed on the seat surface 51. A nozzle 52 is disposed in the center of the seat surface 51. The entire circumference of the seating surface 51 is surrounded by an annular side wall 53, and a gap formed between the seating surface 51 and the side wall 53 serves as a cooling medium discharge hole 54.
The side wall 53 has a slide part 53 s at the top thereof. The slide portion 53s is slidable in the vertical direction (the direction of the arrow shown in the figure). When the slide portion 53s is moved downward, the upper end portion 53t is the surface of the seat surface 51 and the surface and surface of the conveyance path 60. Move down to the position where it becomes unity. Further, when the slide portion moves upward, a quenching tub (cooling means) surrounding the periphery of the seat surface 51 is formed by the seat surface 51s (surface on which the workpiece W is placed) and the inner surface 53n of the side wall 53. At this time, the height of the upper end portion 53t of the slide portion 53s when the slide portion 53s of the side wall 53 slides upward is set to be higher than at least the upper portion of the work W placed on the seat surface 51. Grooves 55 are formed radially on the surface 51s of the seating surface 51 from a position substantially coaxial with the center axis CL of the workpiece W placed. The groove 55 is provided to bring the cooling medium filled in the quenching tank into contact with the lower surface of the workpiece W.

  The nozzle 52 is connected to a storage tank (not shown) in which a cooling medium is stored, and a quenching tank formed by sliding the side wall 53 upward with respect to the seating surface 51 from the nozzle 52. Is filled with a cooling medium. And the cooling medium discharged | emitted through the discharge hole 54 from the quenching tank is the structure circulated by the above-mentioned storage tank by a pump. Examples of the cooling medium include quenching oil and water-soluble coolant.

  Further, in the example of the first embodiment, as shown in FIG. 1, the first cooling unit 1 is disposed above the mounting table 50 so as to be slidable in the vertical direction, and the workpiece W is centered and knocked out. The centering jig 6 is also provided for performing the above-mentioned process (in addition, it is possible to perform further flattening). The second cooling unit 2 includes a centering jig 6 that is slidably movable in the vertical direction above the mounting table 50, and a first correction unit 10 that is provided coaxially with the centering jig 6. Have Furthermore, the 3rd cooling part 3 has the 2nd correction | amendment part 20 arrange | positioned above its mounting base 50 so that a slide movement is possible to an up-down direction.

Specifically, as shown in FIG. 3, the centering jig 6 includes a truncated cone part 6 d having a downwardly convex tapered surface 6 t provided coaxially with the central axis CL on the mounting table 50 at the tip part. Yes. The truncated cone portion 6d is formed with a plurality of slits 6s radially from the central axis CL, and the cooling medium can be passed through the plurality of slits 6s.
When the workpiece W is, for example, an outer ring of a tapered roller bearing (see the third embodiment to be described later), the centering jig 6 sets the taper angle of the convex tapered surface 6t to the outer ring of the tapered roller bearing. The taper angle of the inner peripheral surface is preferably the same angle. As described above, the centering jig 6 can appropriately change the shape of the centering jig 6 according to the shape of the workpiece W. However, even when the shape of the centering jig 6 is appropriately changed, in order to smoothly center the workpiece W, a truncated cone part 6d having a tapered surface 6t convex downward is provided. It is necessary to have a configuration. The tapered surface 6t is not limited to a linear shape, but may be a curved shape such as an arc shape.

Next, as shown in FIG. 4, the first correction portion 10 is a cylindrical member provided coaxially with the central axis CL on the mounting table 50, and the inner peripheral surface of the tip portion is the outer peripheral surface of the workpiece W. The correction part 10n. A taper surface 10t whose diameter increases downward is formed on the inner end on the front end side of the straightening portion 10n, and when the first straightening portion 10 is lowered from above and fitted with the outer peripheral surface of the workpiece W. The first correction part 10 can be smoothly inserted into the outer peripheral surface of the workpiece W.
FIG. 5 is a main part enlarged view showing the state of the workpiece W, the first correction portion 10 and the centering jig 6 in a state where the cylindrical workpiece W is restrained by the first correction portion 10.

  Next, as shown in the perspective view of FIG. 6, the second straightening portion 20 has an upper disk-shaped portion 20e and a plurality of straightening plates 20k provided on the lower surface of the disk-shaped portion 20e. doing. A plurality of (in this example, twelve) correction plates 20k are equally distributed radially about the central axis CL on the mounting table 50, similarly to the centering jig 6 and the first correction unit 10. Each of the correction plates 20k has the same shape, and has a slope 20s whose diameter is expanded downward on the inner peripheral surface of each of the correction plates 20k. It is formed on the circumferential side. In addition to general-purpose straightening, in addition to restraining the outer diameter of the workpiece, it can be straightened by restraining any other part of the workpiece. In particular, the outer diameter and end face (plane) of the workpiece W are simultaneously adjusted. This means that correction is possible. Thereby, it becomes possible to cope with various work sizes, and the change of the set of the correction part is facilitated accordingly. In particular, in the constrained quenching method for workpieces, which will be described later, since there is little change in dimensions when the workpiece W is not corrected in the third cooling step, general correction may be sufficient. If more strict correction is required in the third cooling step, the second correction section 20 having a dedicated outer diameter correction type may be used.

  Here, when determining the dimension of the correction part of the said centering jig | tool 6, the 1st correction part 10, and the 2nd correction part 20, it determines based on the information of the dimensional change of the workpiece | work W with time. That is, since the information on the dimensional change of the workpiece W over time varies depending on the material, diameter, thickness, width, shape, etc. of the workpiece W, the workpiece W accompanying cooling when the workpiece W is not restrained as shown in FIG. This is measured for each specific workpiece as in the graph showing the state of dimensional change. Then, time change timing and timing for inserting / removing the correction molds such as the first correction section 10 and the second correction section 20 with respect to the workpiece W, and the dimension change information obtained by sampling the correction mold with respect to the workpiece W in advance. Determine based on.

  More specifically, in the present embodiment, from the information on the dimensional change shown in FIG. 8, the dimension when the workpiece dimension indicates the minimum point la in FIG. Each part dimension, such as the correction | amendment part 20, is set. The time ta at the local minimum point la is defined as “optimum mold insertion timing”, and the time tb when the workpiece dimension is stabilized for a predetermined time is defined as “optimum cooling time”. Here, “the workpiece dimensions are stable for a predetermined time” refers to a state in which the martensitic transformation can be regarded as stopped. For example, it refers to a state in which the average sampling change rate in a sampling period of 10 seconds is 0.01% or less of the dimension master. This is because when the temperature control accuracy of the quenching oil is ± 5 ° C and the temperature difference between the workpiece and the quenching oil is 10 ° C, the dimensional change of the workpiece is about 0.01% of the workpiece diameter. This is because it can be considered that the martensitic transformation has stopped at 0.01% of the diameter of the workpiece that is below the measurement limit of the dimensional change due to the martensitic transformation.

  Next, a method for restraining and quenching a workpiece using the restraining and quenching apparatus 5 will be described with reference to FIGS. 7 and 8 as appropriate. This work constrained quenching method involves quenching the workpiece W, which is made of steel with martensite transformation during quenching and formed into an annular shape, in stages, and constraining as necessary during the quenching. Thus, the desired dimension is corrected.

Specifically, first, as shown in FIG. 7 (a), the workpiece W is heated to a predetermined temperature in a heating furnace in the upstream process, and then, in the first cooling section 1, as shown in FIG. 7 (b). A first cooling step is performed.
In the first cooling step, the workpiece W is transported along the transport path 60 by the transport unit 40 for the first cooling unit 1 (see FIG. 1) and placed on the mounting table 50 of the first cooling unit 1. . Next, the slide portion 53s of the side wall 53 moves upward from below to define a quenching tank, and the centering jig 6 is lowered from above to center the workpiece W. Next, when the cooling medium is supplied from the nozzle 52, the quenching tank is filled with the cooling medium. As the cooling medium in this case, for example, quenching oil is preferable, and the temperature of the quenching oil is preferably 60 ° C.

Here, in the 1st cooling process in this 1st cooling part 1, a workpiece | work is cooled to the correction start temperature higher than a martensitic transformation start temperature (Ms point) (refer code | symbol A of FIG. 8). When the workpiece W is cooled to the correction start temperature higher than the martensite transformation start temperature (Ms point), the supply of the cooling medium from the nozzle 52 is stopped, and the centering jig 6 is separated upward. The slide part of the side wall 53 moves downward from above. In the first cooling step in the first cooling unit 1, the centering jig 6 may be used also as a correction unit, and any part of the workpiece W may be restricted and corrected. .
After that, a second cooling step is performed in the second cooling unit 2 on the downstream side in the transport direction. In the second cooling step, the workpiece W is transported along the transport path 60 by the transport section 40 (see FIG. 1) for the second cooling section 2, and as shown in FIG. Is mounted on the mounting table 50.

  Next, the slide portion 53s of the side wall 53 moves upward from below to define a quenching tank, and the centering jig 6 and the first straightening portion 10 coaxial therewith are lowered from above in this order, and the workpiece W Centering and the outer diameter of the workpiece W are constrained. Next, when the cooling medium is supplied from the nozzle 52, the quenching tank is filled with the cooling medium. As the cooling medium in this case, for example, quenching oil is preferable, and the temperature of the quenching oil is preferably 60 ° C.

Here, in the second cooling step in the second cooling unit 2, the workpiece W cooled to the correction start temperature is cooled to the quenching temperature while correcting the outer diameter in the radial direction (see FIG. 8 reference B). When the workpiece W is held for a predetermined time at the quenching temperature, the supply of the cooling medium from the nozzle 52 is stopped, the centering jig 6 and the first correction unit 10 are separated upward, and the side wall 53 slide parts move downward from above.
Thereafter, a third cooling step is performed in the third cooling unit 3 on the downstream side in the transport direction. In this third cooling step, the workpiece W is transported through the transport path 60 by the transport section 40 (see FIG. 1) for the third cooling section 3, and as shown in FIG. 7 (d), the third cooling section 3 Is mounted on the mounting table 50.

  Next, the sliding portion of the side wall 53 moves upward from below to define the quenching tank, and the second straightening portion 20 is lowered from above to center the workpiece W and restrain the outer diameter and end of the workpiece. Are made at the same time. Next, when the cooling medium is supplied from the nozzle 52, the quenching tank is filled with the cooling medium. As the cooling medium in this case, for example, a water-soluble coolant is preferable, and the temperature of the water-soluble coolant is preferably 30 ° C.

Here, in the third cooling step in the third cooling section 3, the workpiece W cooled to the quenching temperature in the second cooling step further restrains at least the outer diameter in the radial direction and further The martensite transformation is advanced by cooling to a temperature lower than the quenching temperature (see symbol C in FIG. 8).
Then, the workpiece W is cooled to a temperature lower than the quenching temperature and is held for a predetermined time (a time until reaching the symbol Tb in FIG. 8) necessary for the martensitic transformation to sufficiently proceed. Then, the supply of the cooling medium from the nozzle 52 is stopped, the second correction portion 20 is separated upward, and the slide portion 53s of the side wall 53 moves downward from above. Then, as shown in FIG. 7E, the workpiece W is transferred to the next process (for example, a cleaning process) by a transfer device (not shown).

Next, the effect of the restraint quenching apparatus 5 described above and the restraint quenching method using the restraint quenching apparatus 5 will be described.
According to the constrained quenching apparatus 5 and the constrained quenching method using the same, the quenching time required for the heat treatment quality (heat treatment characteristics and mechanical accuracy such as roundness) is subdivided into three stages and necessary. In particular, the constraining quenching device 5 has a configuration in which the third cooling unit 3 corresponding to the third stage constrains the outer diameter of the workpiece W cooled to the quenching temperature in the radial direction. The second straightening part 20 is corrected, and the workpiece W is cooled to a temperature lower than the quenching temperature in the second cooling part 2 while being straightened by the second straightening part 20, and the martensitic transformation proceeds. Therefore, the martensitic transformation can be further advanced in the straightening mold (second straightening portion 20). Therefore, the accuracy (dimension, roundness) after the heat treatment and the dimensional change after the heat treatment can be managed to further improve the accuracy.

  Further, in the constrained quenching method using the constrained quenching device 5, the third cooling step (see symbol C in FIG. 8) corresponding to the third stage is the second cooling step (see symbol B in FIG. 8). Since the workpiece W cooled to the quenching temperature is cooled to a temperature lower than the quenching temperature while constraining at least the outer diameter thereof in the radial direction, the martensite transformation proceeds, so at least the workpiece W is cooled to the quenching temperature. By constraining the outer diameter in the radial direction, the martensitic transformation can be advanced while correcting the workpiece W. Therefore, the accuracy (dimension, roundness) after the heat treatment and the dimensional change after the heat treatment can be managed to further improve the accuracy.

  Furthermore, according to the restraint quenching apparatus 5 and the restraint quenching method using the same, in the first straightening part 10 or the second straightening part 20 (or the second or third cooling step), Since at least the outer diameter is constrained in the radial direction, setting of the pressing force is unnecessary as compared with the method of rotating the workpiece while pressing the workpiece with the pressure roll as described in the above-mentioned Patent Document 1. Therefore, stable correction can be performed.

  For the accuracy of roundness, the workpiece adopting the above-described restrained quenching method (example of the present invention) using the restraint quenching device 5 is compared with the case where the deformation correction in the third cooling unit 3 is omitted for comparison. The results of comparison with a workpiece employing a quenching method (comparative example) by a two-step cooling process are shown in Table 1 and FIGS. 9 and 10.

  As shown in Table 1, in the example of the present invention, the roundness (φ55.30 μm) after the roundness (φ54.21 μm) when the correction in the third cooling unit 3 is completed is φ1 .09 μm, there was little collapse of roundness. On the other hand, in the comparative example, the subsequent roundness (φ77.14 μm) is larger than the roundness (φ53.33 μm) when the correction in the second cooling step is completed, and the difference is φ23. The roundness greatly collapsed to .81 μm. As described above, in the example of the present invention and the comparative example, the accuracy of the roundness of the workpiece outer diameter at the time of completion of correction is equivalent, but at the time of completion of the subsequent cooling, the comparative example is greatly collapsed. In the example of the present invention, it can be seen that there is almost no collapse. Also, the cycle time can be greatly reduced to 39.4% in comparison with the comparative example by dividing the cooling process into three stages in the example of the present invention.

  Furthermore, as shown in FIG. 9, it can be seen that the dimensional variation between the example of the present invention and the comparative example is 33.3% less than the comparative example (about φ45 μm) as compared with the example of the present invention (about φ15 μm). . Further, as shown in FIG. 10, the correction method in the comparative example is strongly influenced by the variation in the turning dimension of the previous process (see FIG. 10A), whereas in the example of the present invention, the previous process It turns out that it is hard to be influenced by the dispersion | variation in the turning dimension of (refer the figure (b)).

  As described above, according to the restraint quenching apparatus 5 and the restraint quenching method using the restraint quenching apparatus 5 described above, it is possible to reduce the manufacturing cost while further improving the accuracy of the workpiece W after quenching (reducing the cycle time). can do). The restraint quenching method and the restraint quenching apparatus for workpieces according to the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. is there.

  For example, in the first embodiment, the correction in the third cooling unit 3 is a second general-purpose correction that is formed by forming a general-purpose correction part 20h including a concave tapered part on the inner peripheral side as a whole of the plurality of correction plates. Although the example using the straightening unit 20 has been described, the present invention is not limited to this. The straightening by the second straightening unit 20 may be performed by correcting at least the outer diameter of the workpiece W in the radial direction. . For example, as in the second embodiment shown in FIG. 11, instead of the second straightening portion 20, a straightening type only for the outer diameter having the same configuration as that of the first straightening portion 10 in the first embodiment may be adopted. Good. In the second embodiment, a quenching oil is used as the cooling medium in the third cooling unit 3 instead of the water-soluble coolant, and the temperature of the quenching oil is 40 ° C. (below). Supplied. As described above, the cooling medium used in each cooling process can be appropriately changed, and the temperature can be set to an appropriate temperature as long as the desired quenching characteristics are not adversely affected. can do.

  Further, for example, in the first embodiment described above, an example in which the correction die that exclusively restrains the outer diameter of the workpiece W is used in the first correction portion 10 is described. However, the present invention is not limited to this, and the third embodiment shown in FIG. Further, as in the embodiment, the configuration may further include an end surface correcting portion (in the centering jig 6 in this example) that constrains the end surface of the workpiece W in the axial direction. Specifically, as shown in FIG. 13, with respect to the centering jig 6 that cooperates with the first correction unit 10, a circle that protrudes in the horizontal direction at the base end portion of the convex tapered surface 6 t serving as the centering unit. An annular flange 6m may be formed. At this time, it is preferable that the outer diameter of the convex tapered surface 6t is slightly smaller than the inner diameter of the workpiece W so that the flange portion 6m abuts against the end surface of the workpiece W reliably. According to such a configuration, as shown in an enlarged view of the main part in FIG. 14, the function of restraining the upper end surface of the workpiece W from the axial direction can be further provided by the horizontal surface of the flange 6m. That is, in the first embodiment, the example in which the workpiece W has a simple cylindrical outer shape has been described. However, the configuration of the workpiece W applicable to the present invention is not limited to this, and the first embodiment Like 3 embodiment, it can apply to the cyclic | annular workpiece | work W which has another various cross-sectional shape. In particular, the configuration of the third embodiment is effective when the workpiece W is thin or easily warped, such as an outer ring for a tapered roller bearing.

In the third embodiment, the first cooling unit 1 also uses the centering jig 6 having the end surface correction function provided with the flange 6m similar to the second cooling unit 2. Thereby, generation | occurrence | production of curvature can be suppressed more effectively also with the outer ring | wheel for tapered roller bearings, a thin cylindrical workpiece | work, etc.
Here, Table 2 shows an example of a result obtained by comparing the example of the present invention adopting the configuration of the third embodiment with a comparative example similar to the above.

  Similar to the example described in Table 1 above, the difference between the example of the present invention and the comparative example is the same as the accuracy of the roundness of the workpiece outer diameter when the correction is completed in the example of the present invention and the comparative example. However, when the subsequent cooling is completed, it is greatly collapsed in the comparative example. On the other hand, in the example of this invention, it turns out that it has hardly collapsed. Further, the “sledge amount” which is a new comparison item in the example of the third embodiment is φ60.21 μm in the comparative example, whereas it is φ20.67 μm in the example of the present invention. It can be seen that the inventive example is superior. This difference is that the shape of the centering jig 6 that becomes the correction part cooperating with the first correction part 10 adopted in the configuration of the third embodiment is changed to the end face of the base end part of the convex taper surface 6t. It is thought that the point which formed the annular collar part 6m which protrudes in a horizontal direction as a correction | amendment part has contributed greatly.

  As still another configuration example, for example, a configuration in which the configuration of the third embodiment is further incorporated in the configuration of the second embodiment as in the fourth embodiment shown in FIG. . In other words, in this example, the workpiece W is likely to be warped like an outer ring for a tapered roller bearing, and the centering jig 6 is formed with an annular flange 6m protruding in the horizontal direction. Further, instead of the general-purpose correction of the third cooling unit 3, the outer diameter correction jig of the first correction unit 10 is employed.

DESCRIPTION OF SYMBOLS 1 1st cooling part 2 2nd cooling part 3 3rd cooling part 5 Restraint quenching device 6 Centering jig 10 1st correction part 20 2nd correction part 40 Conveyance part 50 Mounting stand 60 Conveyance path W Workpiece | work

Claims (8)

A plurality of cooling units that are used in rolling bearings and that are gradually cooled and quenched while sequentially conveying steel and cylindrical workpieces with martensitic transformation during quenching, and quenching in the plurality of cooling units A constraining quenching device comprising a correction unit that constrains the workpiece inside as necessary and corrects it to a desired dimension,
A first cooling unit that cools the workpiece from a state heated to a predetermined temperature to a correction start temperature higher than a martensite transformation start temperature (Ms point);
The workpiece that has been cooled to the straightening start temperature has a first straightening portion that straightens the workpiece by constraining at least its outer diameter in the radial direction, and the martensite transformation start temperature (Ms point) while straightening at the first straightening portion. ) And a second cooling section that cools to a predetermined quenching temperature that is lower than the martensitic transformation completion temperature (Mf point),
The workpiece has been cooled to the predetermined quenching temperature, and has a second straightening portion that corrects the workpiece by constraining at least the outer diameter thereof in the radial direction, and the second quenching portion is further corrected while being corrected by the second straightening portion. A third cooling section that cools the martensite transformation to a state where it can be regarded as stopped at a lower temperature and advances the martensitic transformation,
In the first straightening portion, the inner diameter dimension is set to a dimension at which the outer diameter dimension of the workpiece accompanying cooling when the workpiece is not restrained is changed from contraction to expansion by the start of martensitic transformation. Restraint quenching equipment.   2. The constraining and quenching apparatus according to claim 1, wherein the first straightening part further includes an end face straightening part that restrains an end face of the work in an axial direction in addition to restraining the outer diameter of the work.   3. The restraint according to claim 1, wherein the second straightening part further includes a general-purpose straightening part that restrains and corrects any other part of the work in addition to restraining the outer diameter of the work. Quenching equipment.   The said 1st cooling part further has the 3rd correction part which restrains and correct | amends any part of a workpiece | work, The constrained hardening apparatus as described in any one of Claims 1-3 characterized by the above-mentioned. Used for rolling bearings, steel and cylindrical workpieces with martensitic transformation at the time of quenching are sequentially cooled while being quenched, and the workpiece being quenched is constrained as necessary. A method for restraining and quenching a workpiece to correct to a desired dimension,
A first cooling step for cooling the workpiece from a state heated to a predetermined temperature to a correction start temperature higher than a martensite transformation start temperature (Ms point);
While the workpiece cooled to the straightening start temperature is straightened by constraining at least its outer diameter in the radial direction, it is lower than the martensite transformation start temperature (Ms point) and lower than the martensite transformation complete temperature (Mf point). A second cooling step for cooling to a high predetermined quenching temperature;
The workpiece cooled to the predetermined quenching temperature is cooled to a state where the martensitic transformation is stopped at a temperature lower than the predetermined quenching temperature while restraining at least the outer diameter in the radial direction. A third cooling step to advance site transformation,
The restriction of the outer diameter of the workpiece in the second cooling step is restricted by the dimension when the outer diameter dimension of the workpiece accompanying the cooling when the workpiece is not restrained is changed from contraction to expansion by the start of martensitic transformation. A method for constraining quenching of workpieces.   6. The method of constraining and quenching a workpiece according to claim 5, wherein the second cooling step further constrains the side surface of the workpiece in the axial direction in addition to the constraint of the outer diameter of the workpiece.   The method of constraining and quenching a workpiece according to claim 5 or 6, wherein the third cooling step further corrects by constraining any other part of the workpiece in addition to restraining the outer diameter of the workpiece. .   The said 1st cooling process further restrains any part of a workpiece | work and correct | amends, The restraint hardening method of the workpiece | work as described in any one of Claims 5-7 characterized by the above-mentioned.

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