JP5742214B2 - Method of quenching annular body using continuous quenching furnace - Google Patents

Description

  The present invention relates to an annular body quenching method using a continuous quenching furnace.

A hardening process by quenching is performed on the inner ring and the outer ring of the rolling bearing. Quenching consists of a heating process and a cooling process. In the quenching furnace used in the heating process, a continuous quenching furnace that continuously heats the work while conveying the work by driving a belt, etc., and heating the work one by one There are batch-type quenching furnaces to process. In general, it has been found that quenching deformation is greater in a continuous quenching furnace than in a batch quenching furnace. In addition, the continuous quenching furnace is suitable for a case where a large amount of workpieces are quenched with an emphasis on productivity, and the batch-type quenching furnace is easy to deal with various types and different conditions.
FIG. 1 shows a general continuous heat treatment facility for an inner ring and an outer ring of a rolling bearing. This equipment includes a continuous heating furnace 1, a heat-resistant link belt 3 disposed therein, a feeder 2 for introducing a work 5 upstream of the belt 3, and a work (heating) that reaches the downstream of the belt 3. A shooter 4 for dropping the later workpiece 6) into a container 7 containing quenching oil 8 is provided.

In the container 7, a transport mesh belt 9 is arranged that raises the work 6 while being immersed in the quenching oil 8 and guides the work 6 to the outside of the container 7. Then, the workpiece 10 after quenching is dropped from the transport mesh belt 9 to the upstream side of the transport belt 16 disposed in the cleaning tank 11 and across the front and rear thereof. The work (work after quenching) 10 placed on the transport belt 16 proceeds while being cleaned in the cleaning tank 11, and the cleaned work 14 is placed on the transport belt 17 for the tempering furnace 12 to be tempered and tempered. The workpiece 15 after completion is collected for the next process.
The cooling state of the workpiece 6 changes depending on the posture of the workpiece 6 and the timing of the dropping when the workpiece 6 is naturally dropped into the container 7 containing the quenching oil 8 and falls relatively straightly as shown in FIG. As shown in FIG. 2B, when the fall is delayed due to interference with the rear workpiece 6, the latter is more likely to cause uneven cooling, and thus quenching deformation becomes larger.

[Background to the present invention]
In the continuous heat treatment facility shown in FIG. 1, the outer ring of a deep groove ball bearing having a nominal number of 6009 was heat-treated, and a test for examining the deformation amount of the outer ring caused by performing each step was performed.
The outer ring is an annular body having an outer diameter of 75 mm, an effective thickness of 3.734 mm, and a width of 16 mm. The outer ring is made of high-carbon chromium bearing steel type 2 (SUJ2).
As the continuous heating furnace 1, the one that is conveyed by the link belt 3 is used, and as the feeder 2, a vibration feeder that applies vibration to the work 5 toward the link belt 3 is used. As the quenching agent, “Daffney Bride Quenched Oil” manufactured by Idemitsu Kosan Co., Ltd. was used, and “Krin Super 285N” manufactured by Kanei Sangyo Co., Ltd. was used as the cleaning liquid to be put into the cleaning tank.

  First, the feeder 2 is operated at 25 to 50 Hz, and the work 5 is placed on the link belt 3 in the continuous heating furnace 1. The driving speed of the link belt 3 is 15 to 43 minutes per length of the heating section of the furnace. When the workpiece 5 is moved under this condition, the workpiece 5 is placed on the link belt 3 from the feeder 2 as shown in FIG. 3 (a), and inside the feeder 2 as shown in FIG. 3 (b). Although the work 5 may be clogged and a space may be formed, the clogging is eliminated by being pushed by the work put in from the feeder 2 after that, and as shown in FIG. It is heated while being conveyed by the link belt 3. The heating temperature was 830 to 850 ° C., and the heating time was 15 to 43 minutes.

  The work 6 that has advanced to the downstream end on the feeder 2 falls from the shooter 4 into the container 7 containing the quenching oil 8 and is placed on the transport mesh belt 9. The workpiece 10 placed on the transport mesh belt 9 is quenched by being gradually lifted from the bottom side of the container 7 and transported to above the quenching oil 8 by driving the mesh belt 9. The workpiece 10 after quenching is dropped from the transport mesh belt 9 to the upstream side of the transport belt 16 disposed in the cleaning tank 11 and across the front and rear thereof. The work (work after quenching) 10 placed on the transport belt 16 proceeds while being cleaned in the cleaning tank 11, and the cleaned work 14 is placed on the transport belt 17 for the tempering furnace 12 to be tempered and tempered. The completed work 15 is obtained.

The deformation amount of the work after each process was compared by measuring the roundness and warpage and the rate of change. Regarding the deformation in the radial direction of the annular body (elliptical deformation), the maximum and minimum values of the outer diameter of the outer ring as the workpiece are measured, and the difference is defined as the roundness. The value divided by the minimum value was defined as the elliptic deformation rate (%). Regarding the deformation of the annular body in the axial direction (warp deformation), the maximum value and minimum value of the axial dimension of the outer ring, which is the workpiece, are measured, and the difference is taken as the warp. The divided value was defined as the warpage deformation rate (%). The elliptic deformation rate and the warp deformation rate were measured 60 after each step. Moreover, the average value of each deformation rate was calculated from these measured values.
The results are shown in Table 1 below and FIG.

From these results, transformation stress and thermal stress act in the heating process and cooling process during quenching, so that elliptical deformation and warping deformation after quenching increase, but in subsequent processes, dropping during transportation and collision between workpieces It is thought that it changed gradually.
Next, in order to investigate the deformation amount of the work only in the heating process at the time of quenching, the work that has reached the most downstream position of the link belt 3 is changed to the position of the link belt 3 by alternately changing the direction of rotation. The steel was slowly cooled in a furnace while remaining in the furnace, taken out without quenching and examined for deformation rate. Moreover, the deformation rate of the workpiece | work after performing washing | cleaning and a tempering process after slow cooling was also investigated. The results are shown in Table 2 below and FIG.

From this result, it can be seen that the elliptical deformation and warping deformation are greatly caused only by the heating process at the time of quenching.
Next, as a part of deformation caused by heat quenching, there is deformation that occurs due to the release of residual stress applied by machining such as turning performed as a previous process. Only examined. That is, after heating a workpiece | work using a batch-type heat processing furnace, the deformation | transformation amount at the time of cooling slowly over time with the heat processing pattern of spherical annealing was measured. The results are shown in Table 3 and FIG.

From this result, it can be seen that the deformation amount caused only by the deformation due to the release of the residual stress is smaller than the deformation amount (see Table 2) when the elliptical deformation is allowed to cool after heating in the heating furnace. The warpage deformation was equivalent to the deformation amount (see Table 2) when it was allowed to cool after heating in a heating furnace.
From the above, it can be seen that the workpiece processed by the continuous heat treatment equipment shown in FIG. 1 is largely elliptically deformed in the heating process in the heating furnace 1, but the main cause is not the release of the residual stress.

  In a standard continuous quenching facility, as shown in FIG. 7A which is a plan view and FIG. 7B which is a side view, the workpiece 5 on the feeder 2 and the workpiece 6 in the heating furnace 1 are in contact with each other. Then, since they are densely in contact with each other, when the temperature rises and the workpiece is thermally expanded, the state shown in FIG. 8 (a) is changed to the state shown in FIG. 8 (b). Since the workpiece is an outer ring having the above dimensions made of SUJ2, the workpiece expands by about 1 mm at 730 ° C. (d2−d1≈1 mm). Since the outer ring is pressed and transformed into an austenite structure, the transformation superplasticity acts to make it easy to deform. Transformation superplasticity is a phenomenon in which plasticity occurs with a low acting stress when transformation occurs and progresses. As shown in FIG. 8 (b), the transformation superplasticity acts in a state where they are pressed against each other, and the workpiece is deformed.

On the other hand, with regard to warpage deformation, it is considered that the amount of warpage deformation was the same in a batch-type heating furnace as there is no constraint to suppress warpage deformation as in the case of continuous quenching equipment.
Thus, it is difficult to suppress the elliptical deformation of the workpiece by the conventional continuous quenching method, and it is difficult to suppress the warp deformation of the workpiece even by the conventional batch quenching.
In Patent Document 1, in order to reduce quenching deformation, the surface pressure of the quenching oil when the treatment material is introduced is reduced, and the surface of the treatment material is in an inert gas or air state in a vapor film stage or a boiling stage. Describes a method of reducing distortion generated due to uneven cooling by introducing quenching to increase the quenching oil surface pressure. However, this method is not a continuous quenching furnace but a method applied to a batch-type quenching furnace.

  In Patent Document 2, in the cooling process in the quenching of the annular body of the rolling bearing, while the structure of the annular body is in the austenite state, the annular body is press-fitted into a mold and the deformation is corrected by plastic working. It is described to make it smaller. However, this method is a method of processing workpieces one by one in the cooling step after heating in a continuous quenching furnace, so that the productivity is low and it is not suitable for mass production.

  Patent Document 3 describes a method shown in FIG. 9 as a method for quenching an annular body using a continuous quenching furnace. The equipment used in this method is a continuous heating furnace 1 that continuously heats the work (annular body) 5 while being conveyed by the belt 3, and the work 5 is placed on the belt 3 along the horizontal direction in the radial direction. A feeder 2 that guides, a container 7 containing quenching oil (quenching agent) 8, a shooter 4 that drops the heated workpiece 6 from the conveyor belt 3 onto a conveyor mesh belt 9 disposed in the container 7, Consists of.

In the method of Patent Document 3, the workpiece 2 is moved on the feeder 2, on the conveyor belt 3 of the heating furnace 1, and on the conveyor mesh belt 9 while keeping all the workpieces 5, 6, 10 out of contact with each other. Elliptical deformation of the body (the deformation described in FIG. 8) can be suppressed.
However, the method of Patent Document 3 cannot suppress deformation (warp deformation) in the axial direction of the annular body. In addition, since this method moves on the conveyor belt of the heating furnace while keeping all the annular bodies in contact with each other, since the number of workpieces that can be processed in the heating furnace is small, it is improved in terms of productivity. There is room.

JP 2001-316722 A Japanese Patent No. 3817764 JP 2009-84635 A

  The subject of the present invention is a method of quenching deformation, not only elliptical deformation but also warping deformation, as a method of quenching an annular body using a continuous quenching furnace, and a method with higher productivity than the method of Patent Document 3. Is to provide.

  In order to solve the above-described problems, the present invention provides a heating furnace that continuously heats a workpiece made of an annular body while conveying the workpiece with a belt, and an annular body on the conveying belt of the heating furnace so that the radial direction is horizontal. A feeder that guides it to be placed along, a container containing a quenching agent, and a shooter that drops the heated workpiece from the conveyor belt onto the conveyor mesh belt disposed in the container, In the method of quenching an annular body using a continuous quenching furnace, which guides the workpiece to the outside of the container while immersing the workpiece in the quenching agent, all the annular bodies are arranged on the outer peripheral surface on the feeder and on the conveyor belt of the heating furnace. Are not in contact with each other, and are moved while being held in a state where two or more are stacked in the vertical direction, so that all the annular bodies are not in contact with each other on the transport mesh belt. It provides a method of hardening the annular body using a continuous hardening furnace, characterized in that to move while.

In the method of the present invention, on the feeder and the conveyor belt of the heating furnace, all the annular bodies are moved while being held in a state where two outer peripheral surfaces are not in contact with each other and are stacked in the vertical direction. , Where the thickness of the annular body is t, the outer diameter is D, and the axial dimension is B, the thickness ratio represented by “D / t” is 11.2 to 27.2, D / B " is 3 . A particularly high effect is obtained when an annular body of 5 or more and 8.2 or less is a target.

  According to the method for quenching an annular body using the continuous quenching furnace of the present invention, elliptical deformation and warping deformation of the annular body during quenching can be suppressed, and productivity can be made higher than the method of Patent Document 3. it can.

It is a schematic block diagram which shows the general continuous heat processing equipment with respect to the inner ring | wheel and outer ring | wheel of a rolling bearing. It is a figure explaining the posture of the work and the timing of the fall when it naturally falls into the container filled with quenching oil from the downstream end of the heating furnace. (B) is shown when the fall is delayed. Side view (a) showing a state where the work is placed on the link belt from the feeder, Plan view (b) showing a case where the work is clogged and a space is formed in the feeder, and pushed by the work put from the feeder It is a top view (c) which shows the state from which clogging was eliminated. It is a graph which shows the average deformation rate of the workpiece | work after each process by the conventional method. It is a graph which shows the deformation rate which it took out and investigated in the state which is not quenched after heating (after slow cooling) by the conventional method, and the deformation rate of the work investigated after performing a washing and tempering process after slow cooling. It is a figure which shows the result of having measured the deformation | transformation amount when heating a workpiece | work using a batch type heat processing furnace, and cooling slowly over time with the heat processing pattern of spherical annealing. It is the top view (a) and side view (b) which show a standard continuous hardening equipment. It is a figure which shows the change when temperature rises with the continuous hardening equipment of FIG. 7, and a workpiece | work thermally expands, and shows the state (a) before a heating, and the state (b) after a heating. It is the top view (a) and side view (b) which show the method of patent document 3. FIG. It is the top view (a) and side view (b) which show the method of embodiment of this invention. It is the graph which shows the deformation rate which it took out in the state of not quenching after heating (after slow cooling) by the method of an example, and investigated, and the deformation rate of the work investigated after performing a washing and tempering process after slow cooling. , (A) shows the elliptic deformation rate and (b) shows the warp deformation rate. It is a graph which shows the result (elliptical deformation rate) which produced the rectangular ring using the stainless steel which does not transform at the time of quenching, and performed a series of processes of continuous quenching, washing, and tempering, using (a) The result by the conventional method is shown, and (b) shows the result by the method of the example. It is a graph which shows the result (warp deformation rate) which produced the rectangular ring using the stainless steel which does not transform at the time of quenching, and performed a series of processes of continuous quenching, washing, and tempering, using (a) The result by the conventional method is shown, and (b) shows the result by the method of the example. It is a figure explaining the attitude | position of a workpiece | work when it is made to fall naturally to the container which put quenching oil from the downstream end of the heating furnace with the method of an Example, and the timing of dropping. For each of the 1000 inner rings and outer rings shown in Table 7, continuous quenching, cleaning, and tempering were performed by the conventional method, the method of the present invention, and the method of Comparative Example (Patent Document 3), and the defect rate was measured. (A) shows the relationship between the oval deformation defect rate and the wall thickness ratio (D / t), the conventional method is indicated by “◯”, and the method of the present invention is indicated by “●”. (B) shows the relationship between the warp deformation rate defect rate and D / B, the conventional method is indicated by “◯”, the method of the present invention is indicated by “●”, and the method of the comparative example is indicated by “Δ”. For 1000 pieces of inner ring and outer ring of each dimension shown in Table 7, continuous quenching, washing and tempering are performed by the conventional method, the method of the present invention and the method of Patent Document 3 (comparative example), and the defect rate is measured. (A) shows the relationship between the "difference in elliptic deformation defect rate between the conventional example and the present invention example" and the wall thickness ratio (D / t), (b) Relationship between “difference in warp deformation defect rate between conventional example and present invention example” and D / B (◯), “difference in warp deformation defect rate between comparative example and present invention example” and D / B (Δ) is shown.

Hereinafter, embodiments of the present invention will be described.
FIG. 10 is a plan view (a) and a side view (b) showing the method of this embodiment. The equipment used in this method includes a continuous heating furnace 1 that continuously heats the workpieces (annular bodies) 5a and 5b while being conveyed by the belt 3, and the workpieces 5a and 5b on the belt 3 with the radial direction in the horizontal direction. Feeder 2 that is guided so as to be placed along, container 7 containing quenching oil (quenching agent) 8, and heated workpieces 6 a and 6 b are placed on conveyor mesh belt 9 disposed in container 7 from conveyor belt 3. A shooter 4 to be dropped.

  Then, on the feeder 2 and on the conveyor belt 3 of the heating furnace 1, all the workpieces 5a, 5b, 6a, 6b are moved while keeping the outer peripheral surfaces thereof in contact with each other and being stacked in the vertical direction. Let On the feeder 2, the upper work 5a is arranged by aligning the center of the gap formed by the lower three adjacent works 5b with the center of each work 5a, and this state is maintained and the works 6a and 6b are maintained. Moves on the conveyor belt 3. This movement is calculated so that the gap between the workpieces before heating is calculated from the workpiece maximum diameter at the time of heating, etc., and the workpiece outer peripheral surfaces do not contact each other even when the workpiece is heated, and the arrangement of the workpieces on the feeder 2 is maintained. This is realized by adjusting the frequency of the feeder 2.

Further, on the transport mesh belt 9, all the workpieces 10 are moved while being held in a state where only one piece exists in the vertical direction without being in contact with each other. This movement is realized by calculating the gap between the workpieces before heating from the workpiece maximum diameter during heating and adjusting the frequency of the feeder 2 so that the outer peripheral surfaces of the workpieces do not contact each other even during heating of the workpiece.
In this embodiment, two workpieces are stacked in the vertical direction, but the number of workpieces stacked in the vertical direction may be three or more, and the uppermost workpiece is a dummy that is not used as a product. May be.

  In order to investigate the deformation amount of the work 6 only by the heating process at the time of quenching using the equipment described in the embodiment, the work that has reached the most downstream position of the link belt 3 is alternately switched in the direction of rotation of the link belt 3. By changing to, it was gradually cooled in the furnace while staying at that position, taken out without quenching and examined for deformation rate. Moreover, the deformation rate of the workpiece | work after performing washing | cleaning and a tempering process after slow cooling was also investigated. The results are shown in Table 4 below and FIG. FIG. 11A is a graph showing the elliptic deformation rate, and FIG. 11B is a graph showing the warp deformation rate.

  When this result is compared with the result of the above-described conventional method (Table 2 and FIG. 5), the deformation amount of the workpiece is reduced only in the heating process at the time of quenching (average deformation amount: elliptic deformation 0.18 → 0. 11, warping deformation 1.5 → 1.0). However, the deformation amount after tempering was reduced in the conventional method (in Table 2, the elliptical deformation 0.18 → 0.14, the warp deformation 1.5 → 1.2), but the method of this example. However, it slightly increased (in Table 4, elliptic deformation 0.11 → 0.16, warpage deformation 1.0 → 1.3). In addition, the maximum deformation rate was elliptic deformation 0.94 and warpage deformation 4.7 in the conventional method, whereas in the method of this embodiment, the elliptic deformation 0.38 and warpage deformation 2.3 were significantly reduced. It was.

  The reason why the deformation rate after tempering increases is that the gap between the workpieces is not properly maintained in the quenching cooling process. Therefore, a rectangular ring was produced using stainless steel that does not transform during quenching, and a series of steps of continuous quenching, cleaning, and tempering were performed using the conventional method and the method of this example. The results are shown in Table 5 for the conventional methods and Table 6 for the methods of the examples.

FIG. 12 shows a graph of the elliptical deformation rate (a) according to the conventional method and the elliptical deformation rate (b) according to the method of the example. FIG. 13 shows a graph of the warp deformation rate (a) according to the conventional method and the warp deformation rate (b) according to the method of the example.
From these results, the example (Table 6, FIG. 12 (b) and FIG. 13 (b)) is more heated and allowed to cool than the conventional example (Table 5 and FIG. 12 (a) and FIG. 13 (a)). It can be seen that the deformation rate decreases even after tempering. However, the increase amount of the deformation rate after heating and cooling and after tempering is the same in the conventional example and the example. From this, it is presumed that the method of the example has an effect of controlling the transformation stress in the quenching cooling step.
Further, in the method of the embodiment, as shown in FIG. 14, when the work 6 is naturally dropped from the belt 3 to the container 7 containing the quenching oil 8, it is stably dropped at a constant timing. As shown in FIG. 2 (a) and FIG. 2 (b), the timing of dropping the workpiece 6 varies, and the dropping posture and the amount of rotation at the time of dropping are not stable.

Next, continuous quenching, cleaning, and tempering were performed on each of 1000 inner rings and outer rings shown in Table 7 below by the conventional method, the method of the present invention, and the method of Patent Document 3 (comparative example). It was. And about what was obtained by the conventional method and the method of this invention, the defective rate of elliptical deformation was measured by making the thing whose maximum roundness exceeded 0.15 mm into a defective article. Moreover, about the thing obtained by the method of the conventional method, the method of this invention, and the method of patent document 3 (comparative example), the thing with the largest curvature exceeding 0.15 mm was made into a defective article, and the defect rate of curvature deformation was measured. .
As the method of Patent Document 3, the same method as that of the embodiment (that is, the method shown in FIG. 9) is used except that only the lower work 5b is placed in the same arrangement without placing the upper work 5a in FIG. Carried out.

Note that the same sample is measured twice at different timings with different lots in the previous process in consideration of the variation in residual stress generated in the turning process and cold working before the heat treatment. The results are shown together in Table 7 below, and are shown graphically in FIG.
FIG. 15A is a graph showing the relationship between the thickness ratio and the elliptic deformation defect rate, and FIG. 15B is a graph showing the relationship between “D / B” and the warp deformation defect rate. In these graphs, “●” indicates the result by the method of the example, and “◯” indicates the result by the method of the conventional example. In FIG. 15B, “Δ” indicates the result obtained by the method of Patent Document 3 (Comparative Example).
Of the two types of elliptic deformation defect rates of the conventional example having the same thickness ratio and the two types of elliptic deformation defect rates of the example of the present invention, the elliptic deformation defect of the example of the present invention is determined from the minimum value of the elliptic deformation defect rate of the conventional example. A value obtained by subtracting the maximum value of the rate was calculated as a difference in the oval deformation rate. The results are shown together in Table 7 below, and the relationship between the wall thickness ratio and the “difference in elliptic deformation rate” is shown in a graph in FIG.

Of the two types of warp deformation failure rate of the conventional example of the same “D / B” and the two types of warp deformation failure rate of the example of the present invention, the warp of the example of the present invention is determined from the minimum value of the warp deformation defect rate of the conventional example. A value obtained by subtracting the maximum value of the deformation defect rate was calculated as a difference in the warp deformation defect rate (vs. conventional example). Further, of the two types of warp deformation failure rate of the same “D / B” comparative example (obtained by the method of Patent Document 3) and the two types of warp deformation failure rate of the present invention example, the warp of the comparative example A value obtained by subtracting the maximum value of the warp deformation defect rate of the example of the present invention from the minimum value of the deformation defect rate was calculated as a difference of the warp deformation defect rate (vs. comparative example).
These results are also shown in Table 7 below, and the relationship between “D / B” and “difference in warp deformation failure rate” is shown in a graph in FIG. In FIG. 16B, “◯” indicates the difference from the conventional example, and “Δ” indicates the difference from the comparative example (obtained by the method of Patent Document 3).

  From this result, regarding the elliptical deformation, when the wall thickness ratio is 8.7, the defect rate is 0 even in the conventional method, and when the wall thickness ratio is 31.7, the defect ratio is higher in the example of the present invention. It can be seen that when the rate is 11.2 or more and 27.2 or less, the effect of the method of the present invention is obtained, and when the thickness ratio is 13.7 or more and 24.0 or less, a further higher effect is obtained. Regarding warpage deformation, when “D / B” is 9.5, the defect rate is 0 even in the conventional method, and in the case of 2.8 and 3.1, the defect rate is higher in the example of the present invention. The effect of the method of the present invention can be obtained when “D / B” is 3.5 or more and 8.2 or less, and a higher effect can be obtained when “D / B” is 3.9 or more and 8.2 or less. I understand.

DESCRIPTION OF SYMBOLS 1 Continuous heating furnace 2 Feeder 3 Heat resistant link belt 4 Shooter 5 Work 5a Upper work 5b Lower work 6 Heated work 6a Heated upper work 6b Heated lower work 7 Container 8 Quenching oil 9 Conveyance Mesh belt 10 Work after quenching 11 Cleaning tank 12 Tempering furnace 14 Work after washing 15 Work after tempering completion 16 Conveying belt 17 Conveying belt

Claims (2)

A heating furnace that continuously heats a workpiece made of an annular body while being conveyed by a belt, a feeder that guides the annular body on the conveying belt of the heating furnace so that the radial direction is placed along the horizontal direction, and a quenching agent And a shooter for dropping the heated work from the transport belt onto the transport mesh belt disposed in the container, the transport mesh belt guiding the work outside the container while immersing the work in the quenching agent. In the method of quenching an annular body using a continuous quenching furnace,
When the thickness of the annular body is t, the outer diameter is D, and the axial dimension is B, the thickness ratio represented by “D / t” is 11.2 to 27.2, / B "is intended for an annular body having a value of 3.5 or more and 8.2 or less,
On the conveyor mesh belt, all the annular bodies are moved on the feeder and the conveyor belt of the heating furnace while maintaining the state in which two or more annular bodies are stacked in the vertical direction without contacting each other. The method of quenching an annular body using a continuous quenching furnace, wherein all the annular bodies are moved while being held in a state of not contacting each other. A heating furnace that continuously heats a workpiece made of an annular body while being conveyed by a belt, a feeder that guides the annular body on the conveying belt of the heating furnace so that the radial direction is placed along the horizontal direction, and a quenching agent And a shooter for dropping the heated work from the transport belt onto the transport mesh belt disposed in the container, the transport mesh belt guiding the work outside the container while immersing the work in the quenching agent. In the method of quenching an annular body using a continuous quenching furnace,
When the thickness of the annular body is t, the outer diameter is D, and the axial dimension is B, the thickness ratio represented by “D / t” is 11.2 to 27.2, / B " is 3 . For cyclic bodies that are 5 or more and 8.2 or less,
On the feeder and on the conveyor belt of the heating furnace, all the annular bodies are moved while being held in a state where two outer peripheral surfaces are not in contact with each other and stacked in the vertical direction, on the conveyor mesh belt, A method for quenching an annular body using a continuous quenching furnace, wherein all the annular bodies are moved while being kept out of contact with each other.

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