JP2018131642A - Quenching method for annular work - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a quenched annular work having good roundness at low cost.SOLUTION: Provided is a method including a heating step, an analyzing step, and a cooling step for quenching an annular work made of metal. In the heating step, the annular work is heated and raised to a hardening temperature, and held at a quenching temperature. In the analyzing step, a radial dimension of the annular work is acquired after starting heating in the heating step and a reference dimension is obtained based on the acquired radial dimension. In the analyzing step, the annular work is partitioned into a part having a radius larger than the reference dimension and a part having a radius smaller than the reference dimension, and a dimensional difference between the parts is calculated. In the cooling step, cooling liquid is injected into the annular work at least partitioned into the large-diameter part and the small-diameter part in the analysis step after the heating step. In the cooling step, the start of the injection of the cooling liquid to the large-diameter part and the small-diameter part is adjusted on the basis of the dimensional difference between the maximum value of the radius of the large-diameter part and the minimum value of the radius of the small-diameter part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for quenching an annular workpiece made of a metal material.

  A ring of a rolling bearing which is an example of an annular member needs to have a desired mechanical strength. Therefore, when manufacturing the annular member, a heat treatment such as quenching of the annular workpiece is performed. However, quenching into an annular workpiece may lead to deterioration in the roundness of the resulting annular member and variations in the outer diameter or inner diameter.

  As a technique for suppressing variations in the outer diameter or inner diameter of the annular member, for example, Patent Document 1 discloses that excessive deformation of the annular workpiece radially outward during contact with the outer peripheral surface of the annular workpiece is performed. Quenching using a quenching apparatus provided with an outer peripheral restraining device that regulates and an inner circumferential restraining device that abuts against the inner peripheral surface of the annular workpiece and restricts excessive deformation of the annular member radially inward during heating. A method for performing processing has been proposed.

JP 2014-62308 A

  However, the technique described in Patent Document 1 has a drawback in that cost is increased because it is necessary to prepare a restraining tool separately.

  The present invention has been made in view of such circumstances, and it is an annular work that can provide an annular member as a quenched product having good roundness and less dimensional variation at low cost. An object is to provide a quenching method.

In one aspect, the present invention is a method for quenching an annular workpiece made of a metal material,
Heating the annular workpiece, heating the annular workpiece to a quenching temperature, and then holding the annular workpiece at the quenching temperature,
After starting heating in the heating step, a radial dimension of the annular workpiece is acquired, a reference dimension is acquired based on the acquired radial dimension, and the annular workpiece is smaller than the reference dimension with a large-diameter portion larger than the reference dimension. An analysis step for calculating a dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion, and an analysis step for calculating the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion. A cooling step of injecting a cooling liquid to the annular workpiece divided into at least
Including
In the cooling step, based on a dimensional difference between the maximum value of the radius of the large diameter portion and the minimum value of the radius of the small diameter portion, the injection timing of the coolant to the large diameter portion and the small diameter portion The present invention relates to a quenching method for an annular workpiece, characterized by adjusting a start timing of injection of a coolant.

  When the annular workpiece is heated to the quenching temperature, distortion occurs. Therefore, the roundness of the annular member as the quenched product may be significantly deteriorated as compared with the roundness of the unheated annular workpiece. Further, in the quenching process, in the cooling step of cooling the annular workpiece heated to the quenching temperature, the diameter dimension of the annular workpiece changes as the temperature decreases. At this time, the method of changing the diameter of the annular workpiece varies depending on the cooling conditions. Therefore, the dimension of the obtained annular member is likely to vary.

  On the other hand, in the quenching method for an annular workpiece according to the present invention, the radial dimension of the annular workpiece is acquired after the start of heating in the heating step, and the annular workpiece is classified based on the reference dimension obtained from the acquired radial dimension. A dimensional difference between the radius of the diameter portion and the radius of the small diameter portion is calculated, and based on the dimensional difference, the cooling liquid injection start timing to the large diameter portion and the cooling liquid injection start timing to the small diameter portion are calculated. A series of operations to adjust the is adopted. Since such an operation is adopted, according to the quenching method of the present invention, in the cooling step, the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion is eliminated, and the annular workpiece is quenched with a quenching temperature. The annular workpiece can be deformed so as to eliminate the distortion generated when heated. Moreover, in the hardening method of this invention, since the said operation is employ | adopted, generation | occurrence | production of the variation in a dimension can be suppressed without using a restraint tool in a cooling process. As a result, it is possible to obtain an annular member as a quench-treated product having good roundness and less dimensional variation at low cost.

  In the cooling step, the coolant is applied to the annular work so that the injection amount of the coolant per unit time to the large diameter portion is the same as the injection amount of the coolant per unit time to the small diameter portion. Is preferably injected. In this case, it is not necessary to adjust the injection amount of the cooling water per unit time to each of the large diameter portion and the small diameter portion, so that it is easy to manage and control the cooling conditions in the cooling process.

  The wall thickness of the annular workpiece is preferably 1 to 10 mm. In this case, a quenched product (quenched annular member) with good roundness can be obtained.

  In an annular workpiece having a wall thickness of 1 to 10 mm, when the dimensional difference is less than 0.15 mm, the passage to the large diameter portion is started until 0.1 second from the start of the injection of the coolant to the small diameter portion. It is preferable to start injection of the coolant. The structure of the small-diameter portion is a soft austenite structure until 0.1 second has elapsed from the start of cooling to the small-diameter portion of the annular workpiece heated to the quenching temperature. When the elapsed time from the start of cooling to the small-diameter portion is a short time, the effect of deformation due to thermal contraction is relatively large because the effect of martensitic transformation is small. Therefore, the deformation amount of the elliptical deformation is reduced as a whole. Therefore, a quenched product with good roundness can be obtained.

  In an annular workpiece having a wall thickness of 1 to 10 mm, when the dimensional difference is 0.15 mm or more, when 0.1 to 5 seconds elapses from the start of injection of the coolant to the small diameter portion, It is preferable to start injection of the coolant. When 0.1 to 5 seconds elapses from the start of cooling to the small-diameter portion of the annular workpiece heated to the quenching temperature, the influence of the deformation amount due to the martensitic transformation increases in addition to the influence of the deformation amount due to the heat shrinkage. Since the deformation due to martensite transformation occurs as the elapsed time from the start of cooling to the small diameter portion increases, the deformation amount of the elliptical deformation is compared with the deformation amount of the elliptical deformation when the dimensional difference is less than 0.15 mm. Become bigger. In particular, when the elapsed time from the start of cooling to the small-diameter portion is 1 to 5 seconds, 80% or more of the structure of the small-diameter portion is a hard martensite structure and is not easily deformed. That is, when 1 to 5 seconds have elapsed from the start of injection of the coolant to the small diameter portion of the annular workpiece heated to the quenching temperature, the structure of the small diameter portion is a martensitic structure having high hardness and high rigidity after the martensitic transformation. is there. When the small diameter portion is cooled prior to the large diameter portion, the martensite transforms and expands before the large diameter portion. Thereafter, the small diameter portion contracts as the temperature further decreases. On the other hand, when cooling of the large diameter portion is started after 1 to 5 seconds from the start of the injection of the coolant to the small diameter portion, the large diameter portion is also martensitic transformed behind the small diameter portion and starts to expand. At this time, the small diameter portion has already transformed into a martensite structure having no incompletely quenched structure. The martensite structure without an incompletely quenched structure has a higher yield point than the austenite structure and is not easily deformed. Therefore, the expansion of the large-diameter portion cooled with a delay is suppressed by the small-diameter portion. Therefore, the amount of deformation accompanying expansion during the martensitic transformation of the large-diameter portion is smaller than the amount of deformation of the small-diameter portion expanded in advance by martensitic transformation. As a result, the dimensional difference due to strain generated when the annular workpiece is heated to the quenching temperature is alleviated when the annular workpiece is cooled. In this case, the deformation amount of the elliptical deformation is 0.15 to 0.175 mm, and the deformation amount shows a substantially constant value with respect to the difference in cooling start timing (1 to 5 seconds). Therefore, when the metal material is a bearing steel and the thickness difference is 0.15 to 0.175 mm in an annular workpiece having a wall thickness of 1 to 10 mm, from the start of injection of the coolant to the small diameter portion. It is effective to start the injection of the coolant to the large diameter portion when 1 to 5 seconds have elapsed. Thereby, the quenching processed goods of favorable roundness can be obtained. On the other hand, when the elapsed time from the start of cooling to the small diameter portion is 0.1 second or more and less than 1 second, 20% or more and less than 80% of the structure of the small diameter portion is a hard martensite structure, and the remainder is It is a soft austenite structure. In this case, since the austenite structure remains to some extent, the deformation form is different from the case of 1 to 5 seconds. In this case, the deformation amount of the elliptical deformation exceeds 0.175 mm and becomes relatively large. Therefore, when the dimensional difference exceeds 0.175 mm in an annular work whose metal material is bearing steel and has a wall thickness of 1 to 10 mm, 0.1 second from the start of injection of the coolant to the small diameter portion. It is effective to start the injection of the coolant to the large diameter portion when less than 1 second has passed. Thereby, the quenching processed goods of favorable roundness can be obtained.

  According to the present invention, it is possible to provide a hardened annular member having good roundness and less dimensional variation at a low cost.

(A) is process drawing which shows the procedure of the hardening method of the cyclic | annular workpiece | work concerning 1st Embodiment, (B) is a schematic diagram which shows an example of the hardening apparatus used with the hardening method shown by (A). It is a top view which shows typically a part of cooling device used at the cooling process of the hardening method which concerns on 1st Embodiment. (A) is process drawing which shows the procedure of the hardening method of the cyclic | annular workpiece | work concerning 2nd Embodiment, (B) is a schematic diagram which shows an example of the hardening apparatus used with the hardening method shown by (A). It is a top view which shows typically a part of cooling device used at the cooling process of the hardening method which concerns on 2nd Embodiment. In reference example 1, the graph which shows the result of having investigated the relation between the difference (difference of cooling start time) between the injection start timing of the cooling water to the small diameter portion and the injection start timing of the cooling water to the large diameter portion and the deformation amount It is.

The method for quenching an annular workpiece according to the present invention is a method for quenching an annular workpiece made of a metal material. The method for quenching an annular workpiece according to the present invention is a heating step of heating the annular workpiece, raising the temperature of the annular workpiece to a quenching temperature, and then holding the annular workpiece at the quenching temperature,
After starting heating in the heating step, a radial dimension of the annular workpiece is acquired, a reference dimension is acquired based on the acquired radial dimension, and the annular workpiece is smaller than the reference dimension with a large-diameter portion larger than the reference dimension. An analysis step for calculating a dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion, and an analysis step for calculating the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion. A cooling step of injecting a cooling liquid to the annular workpiece divided into at least
including. In the method according to the present embodiment, in the cooling step, on the basis of a dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion, the cooling liquid injection start timing to the large diameter portion and the small diameter portion Adjust the start timing of coolant injection to the tank.

  The method of the present invention includes two embodiments having different timings for performing the analysis step. In the method according to the first embodiment, the analysis step is performed after the heating step. On the other hand, in the method according to the second embodiment, the analysis step is performed after the first heating step of heating the annular workpiece until the surface temperature of the annular workpiece reaches a predetermined temperature at which the deformation of the annular workpiece does not proceed during heating. It is. In the method according to the second embodiment, after the analyzing step, the annular workpiece is heated until the surface temperature of the annular workpiece reaches the quenching temperature, and then the second heating step of holding the annular workpiece at the quenching temperature. Is done.

[First Embodiment]
Hereinafter, a method for quenching an annular workpiece according to the first embodiment will be described with reference to the accompanying drawings. FIG. 1A is a process diagram showing a quenching method for an annular workpiece according to the first embodiment, and FIG. 1B is a schematic diagram showing an example of a quenching apparatus used in the quenching method shown in FIG. is there. FIG. 2 is a plan view schematically showing a part of the cooling device used in the cooling step of the quenching method according to the first embodiment. Hereinafter, the annular workpiece is also simply referred to as “work”.

  The method according to the present embodiment can be performed using, for example, a quenching apparatus 100 shown in FIG. The quenching apparatus 100 includes an induction heating zone 10, an outer periphery analysis zone 20, and a cooling zone 30.

  In the method according to the present embodiment, the heating process, the analysis process, and the cooling process shown in FIG. 1A are quenching processes for quenching the workpiece W1.

  The workpiece W1 to be quenched is made of a metal material. Examples of the metal material include, but are not limited to, steel for bearings. The metal material may be a non-ferrous metal such as aluminum. Examples of the bearing steel include, but are not particularly limited to, high carbon chromium bearing steel such as JIS SUJ2 and JIS SUJ3; carburized steel (skin-hardened steel) such as SAE5120 and SCr420.

  The workpiece W1 can be manufactured, for example, by manufacturing an annular material from a metal material by forging, and processing the obtained annular material into a predetermined shape by cutting or the like (turning process).

  The outer diameter of the workpiece W1 is not particularly limited. In the present embodiment, a workpiece having an arbitrary outer diameter can be used as a quenching target. The thickness of the workpiece W1 in the radial direction may be any thickness that allows the entire workpiece W1 to be induction-heated by the heating coil. Further, the lower limit of the thickness of the workpiece W1 depends on the thickness required for the target annular member. In the method according to the present embodiment, for example, an annular workpiece having a thickness of 1 to 10 mm can be used as the workpiece W1. In the present specification, “the thickness in the radial direction of the workpiece W1” means a value that is half the difference between the outer diameter and the inner diameter when the thickness of the workpiece W1 is uniform in the axial direction. When the thickness of the workpiece W1 is not uniform in the axial direction, it means a value that is ½ of the difference between the outer diameter and the inner diameter at the axial position where the difference between the inner diameter and the outer diameter becomes the largest.

  In the method according to this embodiment, first, a heating step is performed. In the heating step, the workpiece W1 manufactured through the turning step is heated, and the temperature of the workpiece W1 is raised to the quenching temperature. Thereafter, the workpiece W1 is held at the quenching temperature. In the heating step, first, the workpiece W1 manufactured through the turning step is set in the quenching apparatus 100. As shown in FIG. 1B, the workpiece W1 is conveyed to the induction heating zone 10 including the turntable 1 and the heating coil 11 (see arrow (1) in FIG. 1). The conveyed workpiece W1 is placed on the turntable 1 and set on the inner peripheral side of the heating coil 11. Then, the work W1 is induction-heated to a predetermined quenching temperature by passing a current through the heating coil 11 while rotating the work W1 on the turntable 1. Thereby, the workpiece | work W1 can be heated uniformly and the austenitization of the workpiece | work W1 can be performed uniformly.

  The quenching temperature can be appropriately determined according to the type of metal material constituting the workpiece W1, the heating method, and the like. For example, when the workpiece W1 is a workpiece made of JIS SUJ2, the quenching temperature is usually 900 to 1000 ° C.

  In induction heating, conditions such as output, frequency, and heating time may be adjusted as appropriate so that the entire part from the surface to the inside of the workpiece W1 can be heated uniformly. The frequency for induction heating is preferably 0.1 to 5 kHz. According to the induction heating, the workpiece W1 itself is rapidly heated, so that the time required for heating can be shortened. Therefore, the induction heating is suitable for making the heating process inline. The workpiece W1 may be heated, for example, in an inert gas atmosphere.

  Note that the thicker the workpiece W1, the more difficult it is to heat it uniformly with only the heating coil. Therefore, when the thickness of the workpiece W1 is 10 mm or more, induction heating may be performed by disposing a center core in a non-contact manner on the inner side in the radial direction of the workpiece W1. The center core is formed of, for example, a silicon steel plate. The shape of the center core is, for example, a cylindrical shape.

  Next, an analysis process is performed. In the analysis step, first, the heated workpiece W1 on the turntable 1 is moved to the outer periphery analysis zone 20 having a laser displacement sensor (gap sensor) (see arrow (2) in FIG. 1). In the outer periphery analysis zone 20, the radial dimension at each circumferential position on the outer periphery of the workpiece W1 is measured. A reference dimension is acquired from the measurement result of the obtained radial dimension. Next, the workpiece W1 is divided into a large diameter part larger than the reference dimension and a small diameter part smaller than the reference dimension. Next, a dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion is calculated. Here, in the present specification, “each position in the circumferential direction of the outer periphery” indicates the position of each point that can be measured due to restrictions such as the resolution of the sensor among the points constituting the entire outer periphery.

  A sensor element 21 of a laser displacement sensor is attached to the outer periphery analysis zone 20 so as to be positioned on the outer side of the workpiece W1. By rotating the turntable 1 in the outer periphery analysis zone 20, the work W <b> 1 is rotated inside the sensor element 21. Thereby, the distance between each circumferential position on the outer periphery of the workpiece W1 and the sensor element 21 can be measured. A radial dimension can be determined using the distance.

  A known laser displacement sensor can be used as the laser displacement sensor. A commercially available laser displacement sensor can also be used as the laser displacement sensor. Although the color of the laser beam in a laser displacement sensor is not specifically limited, Blue or green is preferable. This is because the heated workpiece W1 has a red color, and therefore, when a blue or green laser beam is used, the distance from the workpiece W1 can be measured more accurately. A technique for acquiring the radial dimension of the workpiece W1 based on the measurement result using the laser displacement sensor is suitable for in-line analysis.

  The time required for the analysis step is preferably as short as possible from the viewpoint of securing a martensite structure and suppressing the occurrence of an incompletely quenched structure in the cooling step described later. Therefore, the measurement time of the workpiece W1 is preferably less than about 3 seconds. Such measurement in a short time can be achieved by using a laser displacement sensor. By setting the measurement time to less than 3 seconds, the decrease in the surface temperature of the workpiece W1 during measurement can be suppressed to 30 ° C. or less.

  In the analysis step, the method for obtaining the radius of the workpiece W1 at each circumferential position on the outer periphery of the workpiece W1 is not limited to the method using the laser displacement sensor, and may be another method. .

  In the analysis step, the division of the large diameter portion and the small diameter portion in the workpiece W1 and the calculation of the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion are performed by the calculation unit 22 of the outer periphery analysis zone 20. Further, information related to the classification result and information related to the dimensional difference are stored in the storage unit 23 of the outer periphery analysis zone 20.

The division of the large diameter portion and the small diameter portion in the workpiece W1 can be performed, for example, through the following steps (A) and (B).
(A) A step of measuring each circumferential position of the outer periphery of the heated workpiece W1 and acquiring a radial dimension (B) A reference dimension is acquired based on the obtained radial dimension, and the workpiece W1 is larger than the reference dimension. The step of dividing into a large diameter portion and a small diameter portion smaller than the reference dimension.

In the step (A), specifically, the radial dimension of the workpiece W1 is grasped by performing the following processes (A-1) to (A-4).
(A-1) First, to determine the virtual center _{C 0} of the heated workpiece W1. Method for determining the virtual center C ₀ is not particularly limited. Virtual center C ₀ can be determined by any method. For example, the center of the master work placed on the turntable 1 may be set as the virtual center C ₀ in advance.
(A-2) Next, each circumferential position on the outer periphery of the heated workpiece W1 is measured using a laser displacement sensor. Thus, to obtain the distance between the circumferential direction each position on the outer circumference of the virtual center C ₀ and the workpiece W1.
(A-3) The distance acquired in the processing of (A-2) is converted into XY coordinates with the virtual center _C0 as the origin.
(A-4) By approximating the coordinate data acquired in the processing of (A-3) by the least square method, a circle (approximate circle) approximating the outer peripheral shape of the workpiece W1 is calculated. Further, the distance from the calculated center coordinate C of the approximate circle to each circumferential position on the outer periphery of the workpiece W1 is calculated. The calculated distance is defined as a radial dimension at each circumferential position on the outer periphery of the workpiece W1. The information acquired in the step (A) is stored in the storage unit 23. Information acquired in the step (A) includes information on approximate circles (information on center coordinates C and radius r) and information on radii at respective positions in the circumferential direction on the outer periphery of the work W1.

Next, a process (B) is performed. In the step (B), specifically, the work W1 is divided into a large diameter portion and a small diameter portion by performing the following processes (B-1) to (B-4).
(B-1) First, a first virtual circle and a second virtual circle centered on the center coordinate C are obtained based on the information acquired in the step (A). The first virtual circle is a circle centered on the central coordinate C and having the maximum value of the radii at the circumferential positions of the outer periphery of the work W1 acquired in step (A) as the radius of the first virtual circle. It is. The second virtual circle is centered on the center coordinate C, and the minimum value of the radii at the circumferential positions of the outer periphery of the work W1 obtained in the step (A) is set as the radius of the second virtual circle. Circle.

(B-2) Next, using the radius a of the first imaginary circle and the radius b of the second imaginary circle, a reference dimension for dividing the large diameter portion and the small diameter portion according to the formula (I) The reference radius c is calculated.
Reference radius c (mm) = (a + b) / 2 (I)

(B-3) Separately from (B-1) and (B-2), the work W1 viewed in plan has a central angle in the circumferential direction of the first virtual circle (or the second virtual circle). It is divided into 16 equal parts so as to be uniform and virtually divided into 16 circular work pieces W1a to W1p (see FIG. 2). Next, the average value of the radii at the respective circumferential circumferential positions included in each of the annular workpiece pieces W1a to W1p is calculated for each of the annular workpiece pieces W1a to W1p.

(B-4) Then, the average value of the radii at the respective circumferential positions of the respective circular workpiece pieces W1a to W1p is compared with the reference radius c. An annular work piece having an average value larger than the reference radius c is a large diameter part, and an annular work piece having an average value equal to or less than the reference radius c is a small diameter part.

  In the present specification, the dimensional difference between the radius of the large-diameter portion and the radius of the small-diameter portion is a difference between the radius a of the first virtual circle and the radius b of the second virtual circle. In the present specification, the dimensional difference is also referred to as roundness. The dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion is calculated by subtracting the radius b of the second virtual circle from the radius a of the first virtual circle.

  Next, a cooling process is performed. In the cooling step, first, the workpiece W1 is moved to the cooling zone 30 (see arrow (3) in FIG. 1). Thereafter, the coolant is sprayed onto the workpiece W1 which is divided into at least a large diameter portion and a small diameter portion in the analysis step. At this time, based on a dimensional difference between the radius of the large-diameter portion and the radius of the small-diameter portion, the timing for injecting the coolant to the large-diameter portion and the timing to start the injection of the coolant to the small-diameter portion are adjusted. To do.

  As shown in FIG. 2, the cooling device configuring the cooling zone 30 includes a plurality (16 in the example of FIG. 2) of injection nozzles 32 (32 a to 32 p). These injection nozzles 32a to 32p are arranged so as to be positioned at equal intervals around the outer periphery of the work W1 when the work W1 is arranged. In the cooling step, the workpiece W1 is cooled by spraying a coolant from the outside of the workpiece W1 using the plurality of jet nozzles 32. The cooling zone 30 may include a flow rate adjustment valve (not shown) for adjusting the injection amount of the coolant.

  In this cooling step, based on the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion calculated in the analysis step, the cooling water injection start timing for the small diameter portion of the workpiece W1 and the cooling water for the large diameter portion Adjust the injection start time.

  The workpiece W1 heated in the heating process may be deformed in the heating process and deteriorate in roundness even if the workpiece W1 before heating has a good roundness shape. . The planar view shape of the workpiece W1 after the heating step can be an approximately elliptic shape and various shapes having a plurality of convex portions (for example, three locations). The method of deformation of the workpiece W1 in the heating process may not be uniform even if the heating conditions are the same. Moreover, if the workpiece | work W1 deform | transformed at the said heating process is cooled uniformly, it will cool, maintaining the deformation | transformation state at the time of a heating. Therefore, the obtained quenched product is inferior in roundness.

  On the other hand, in the method according to the present embodiment, the cooling water injection start timing for the small diameter portion of the workpiece W1 is based on the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion calculated in the analysis step. And the operation | movement of adjusting the injection start time of the cooling water with respect to a large diameter part is employ | adopted. Since such an operation is employed, according to the method according to the present embodiment, in the cooling step, distortion generated when the annular workpiece is heated to the quenching temperature is eliminated, and the radius of the large diameter portion and the small diameter portion The annular workpiece can be deformed so as to eliminate the dimensional difference with the radius. Further, in the method according to the present embodiment, since the above operation is adopted, the dimensional variation can be suppressed without using a restraint tool in the cooling process. As a result, it is possible to obtain a quenched product (quenched annular member) having good roundness and little variation in dimensions at a low cost. The method according to the present embodiment is also suitable for inlining.

  The adjustment of the cooling water injection start time is set as follows based on the dimensional difference when, for example, an annular workpiece having a metal material of bearing steel and a wall thickness of 1 to 10 mm is used as the workpiece W1. It is preferable.

  When the metal material is a bearing steel and the annular workpiece has a wall thickness of 1 to 10 mm, when the dimensional difference is less than 0.15 mm, 0.1 second has elapsed since the start of injection of the coolant to the small diameter portion. It is preferable that the injection of the coolant to the large diameter portion is started by the time. The structure of the small-diameter portion is a soft austenite structure when 0.04 seconds or more and less than 0.1 seconds have elapsed since the start of cooling to the small-diameter portion of the annular workpiece heated to the quenching temperature. When the elapsed time from the start of cooling to the small-diameter portion is a short time, the effect of deformation due to thermal contraction is relatively large because the effect of martensitic transformation is small. Therefore, the deformation amount of the elliptical deformation is reduced as a whole. Therefore, a quenched product with good roundness can be obtained.

  In an annular workpiece in which the metal material is bearing steel and the wall thickness is 1 to 10 mm, when the dimensional difference is 0.15 mm or more, 0.1 to 5 from the start of cooling liquid injection to the small diameter portion. It is preferable that the injection of the coolant to the large diameter portion is started when the second has elapsed. When 0.1 to 5 seconds elapses from the start of cooling to the small-diameter portion of the annular workpiece heated to the quenching temperature, the influence of the deformation amount due to the martensitic transformation increases in addition to the influence of the deformation amount due to the heat shrinkage. Since the deformation due to martensite transformation occurs as the elapsed time from the start of cooling to the small diameter portion increases, the deformation amount of the elliptical deformation is compared with the deformation amount of the elliptical deformation when the dimensional difference is less than 0.15 mm. Become bigger. When the elapsed time from the start of cooling to the small-diameter portion is 1 to 5 seconds, 80% or more of the structure of the small-diameter portion is a hard martensite structure and is not easily deformed. In this case, the deformation amount of the elliptical deformation is 0.15 to 0.175 mm. Therefore, when the metal material is a bearing steel and the thickness difference is 0.15 to 0.175 mm in an annular workpiece having a wall thickness of 1 to 10 mm, from the start of injection of the coolant to the small diameter portion. It is preferable to start the injection of the coolant to the large diameter portion when 1 to 5 seconds have elapsed. Thereby, the quenching processed goods of favorable roundness can be obtained. On the other hand, when the elapsed time from the start of cooling to the small diameter part is 0.1 second or more and less than 1 second, 20% or more to less than 80% of the structure of the small diameter part is a hard martensite structure, and the remainder is It is a soft austenite structure. In this case, the deformation amount of the elliptical deformation exceeds 0.175 mm. Therefore, when the dimensional difference exceeds 0.175 mm in an annular work whose metal material is bearing steel and has a wall thickness of 1 to 10 mm, 0.1 second from the start of injection of the coolant to the small diameter portion. It is preferable to start the injection of the coolant to the large diameter portion when less than 1 second has elapsed. Thereby, the quenching processed goods of favorable roundness can be obtained. In this case, the thickness of the workpiece W1 is normally 1 to 10 mm from the viewpoint of sufficiently securing the effect of the present method.

  In the cooling process, the cooling liquid is sprayed onto the workpiece W1 using 16 spray nozzles to cool the work W1, but in this embodiment, the number of spray nozzles used in the cooling process is particularly limited. Not. The number of the injection nozzles is preferably 4 or more.

  The cooling liquid may be any liquid that can cool the workpiece W1. Examples of the cooling liquid include water, oil, and a water-soluble polymer, but are not particularly limited. Examples of the oil include quenching oil, but are not particularly limited. Examples of the water-soluble polymer include, but are not limited to, polyalkylene glycol. The water-soluble polymer can be used as an aqueous solution dissolved in water. In this case, the blending amount of the water-soluble polymer in water can be appropriately set according to the type of the water-soluble polymer. These cooling liquids may be used independently and may use 2 or more types together.

  The cooling process is preferably started as soon as possible after the heating process. After the heating step, if it takes time to start cooling by spraying the coolant onto the workpiece W1, it may be difficult to transform the workpiece W1 into martensite by the cooling step. For this reason, the shorter the time from the start of the heating step to the start of injection of the coolant onto the workpiece W1, the better. Therefore, it is preferable to perform the cooling step immediately after the analysis step. The time from the end of the heating process to the start of jetting of the coolant to the workpiece W1 is preferably 5 seconds or less, more preferably 3.5 seconds or less, and even more preferably 3.2 seconds or less.

  Further, it is preferable that the change in the surface temperature of the workpiece W1 from the end of the heating step to the start of the cooling step (until the injection of the coolant to the workpiece W1 is started) is smaller.

  The jetting time of the coolant is not particularly limited. The cooling liquid injection time may be appropriately set in consideration of the temperature of the workpiece W1, the cooling liquid injection amount (flow rate) per unit time, and the like. In the cooling step, it is preferable that an injection time of the coolant to the small diameter portion and an injection time of the coolant to the large diameter portion are the same. Because it is not necessary to separately adjust the cooling water injection time to the small diameter portion and the cooling water injection time to the large diameter portion, it is easy to manage and control the cooling conditions in the cooling step. is there.

  The injection amount (flow rate) of the coolant per unit time is not particularly limited. The injection amount (flow rate) of the coolant per unit time may be appropriately selected according to the size of the workpiece W1, the number of injection nozzles, and the like. In the cooling step, it is preferable that the cooling water injection amount per unit time to the small diameter portion and the cooling water injection amount per unit time to the large diameter portion are the same. Since it is unnecessary to separately adjust the cooling water injection amount per unit time to the small diameter portion and the cooling water injection amount per unit time to the large diameter portion, management of the cooling conditions in the cooling step This is because control is easy.

  The workpiece W1 after the quenching process is usually subjected to a tempering process (see arrow (4) in FIG. 1).

  According to the method according to the present embodiment, the workpiece W1 is subjected to a quenching treatment through such steps, thereby forming a martensite structure without an incompletely quenched structure, having a good roundness, and dimensions. An annular member as a quench-treated product with little variation can be obtained at low cost. Therefore, the annular member as the quenched product obtained by the quenching method according to the present embodiment can be suitably used for a bearing race and the like.

[Second Embodiment]
Next, a method for quenching an annular workpiece according to the second embodiment will be described with reference to the accompanying drawings. FIG. 3A is a process diagram showing a method of quenching an annular workpiece according to the second embodiment, and FIG. 3B is a schematic diagram showing an example of a quenching apparatus used in the quenching method shown in FIG. is there. FIG. 4 is a plan view schematically showing a part of the cooling device used in the cooling step of the quenching method according to the second embodiment.

  The method according to the present embodiment can be performed using, for example, a quenching apparatus 300 shown in FIG. The quenching apparatus 300 includes an induction heating zone 210, an outer periphery analysis zone 220, and a cooling zone 230.

  The metal material constituting the workpiece W2 to be quenched by the method according to the present embodiment, the manufacturing method of the workpiece W2, the outer diameter of the workpiece W2, and the thickness of the workpiece W2 are used as the quenching target by the method according to the first embodiment. This is the same as the metal material constituting the workpiece W1, the manufacturing method of the workpiece W1, the outer diameter of the workpiece W1, and the thickness of the workpiece W1.

  In the method according to the present embodiment, the first heating process, the analysis process, the second heating process, and the cooling process shown in FIG. 3A are quenching processes for quenching the workpiece W2.

  In the method according to this embodiment, first, the first heating step is performed. In the first heating step, the workpiece W2 manufactured through the turning step is heated, and the temperature of the workpiece W2 is raised to a predetermined temperature at which the deformation of the workpiece W2 does not proceed during heating. In the first heating step, first, the workpiece W2 produced through the turning process is transferred to the induction heating zone 210 including the turntable 201 and the heating coil 211 as shown in FIG. 3 (see arrow (1)). The conveyed workpiece W2 is placed on the turntable 201 and set on the inner peripheral side of the heating coil 211. Thereafter, while rotating the work W2 on the turntable 201, a current is passed through the heating coil 211 to inductively heat the work W2 to the predetermined temperature.

  In induction heating, conditions such as output, frequency, and heating time may be adjusted as appropriate so that the whole can be uniformly heated from the surface to the inside of the workpiece W2. The frequency for induction heating is preferably 0.1 to 5 kHz. The workpiece W2 may be heated, for example, in an inert gas atmosphere.

  Note that the thicker the workpiece W2, the more difficult it is to heat it uniformly with only the heating coil. Therefore, similarly to the method according to the first embodiment, when the thickness of the workpiece W2 is 10 mm or more, the center core is arranged in a non-contact manner on the inner side in the radial direction of the workpiece W2 and induction heating is performed. Good.

  The predetermined temperature in the first heating step is a temperature lower than the quenching temperature. The predetermined temperature in the first heating step is preferably 500 to 700 ° C, more preferably 500 to 650 ° C, and still more preferably 600 to 650 ° C. The workpiece W2 heated to a temperature in this range is in a state where the influence of residual stress or the like is released and random deformation has been completed.

  Next, an analysis process is performed. In the analysis step, first, the workpiece W2 heated to the predetermined temperature is moved to the outer periphery analysis zone 220 provided with a laser displacement sensor (gap sensor) (see arrow (2) in FIG. 3). Next, in the outer periphery analysis zone 220, the radial dimension at each circumferential position on the outer periphery of the workpiece W2 is measured. Based on the measurement result of the obtained radial dimension, the workpiece W2 is divided into a large diameter part having a large radial size and a small diameter part having a small radial size. Next, a dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion is calculated. In the analysis step, the division of the large diameter portion and the small diameter portion in the work W2 and the calculation of the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion are performed by the calculation unit 222 of the outer periphery analysis zone 220. Further, information related to the classification result and information related to the dimensional difference are stored in the storage unit 223 of the outer periphery analysis zone 220.

  A 2nd heating process is performed after an analysis process. In the second heating step, first, the workpiece W2 after the analysis step is transported to the induction heating zone 210 (see arrow (3) in FIG. 3). Next, in the induction heating zone 210, the workpiece W2 is induction heated to a predetermined quenching temperature. In the second heating step, as in the first heating step, a current is passed through the heating coil 211 while rotating the workpiece W2 placed on the turntable 201 and set on the inner peripheral side of the heating coil 211. The work W2 is induction-heated. At this time, the frequency during induction heating is preferably 0.1 to 5 kHz.

  In the second heating step, since the workpiece W2 can be heated uniformly, the austenite of the workpiece W2 can be uniformly formed.

  The quenching temperature may be appropriately selected in consideration of the type of metal material constituting the workpiece W2, the heating method, and the like. Moreover, you may perform the heating of the workpiece | work W2 in inert gas atmosphere, for example.

  Then, a cooling process is performed. In the cooling step, first, the workpiece W2 heated to the quenching temperature is moved to the cooling zone 230 (see arrow (4) in FIG. 3). Thereafter, the coolant is sprayed onto the workpiece W2 divided into the large diameter portion and the small diameter portion in the analysis step. At this time, similarly to the cooling step of the method according to the first embodiment, the injection start timing of the coolant to the large diameter portion based on the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion. And adjusting the start timing of injecting the coolant into the small diameter portion.

  The cooling zone 230 is configured to inject a cooling liquid onto the workpiece W2 from each of the outer side and the inner side of the workpiece W2. As shown in FIG. 4, the cooling device constituting the cooling zone 230 includes a plurality (16 in the example of FIG. 4) of the injection nozzles 232 (232a to 232p) and a plurality (16 in the example of FIG. 4). ) Injection nozzles 234 (234a to 232p). The injection nozzles 232a to 232p are arranged so as to be positioned at equal intervals around the outer periphery of the work W2 when the work W2 is arranged. Moreover, when the workpiece | work W2 is arrange | positioned, the injection nozzles 234a-232p are arrange | positioned so that it may be located in the inner periphery of the workpiece | work W2 at equal intervals. In the cooling zone 230, the coolant 233 is sprayed onto the workpiece W2 via the spray nozzles 232a to 232p and 234a to 234p. The cooling zone 230 may include a flow rate adjustment valve (not shown) for adjusting the injection amount of the coolant.

  In the method according to the present embodiment, the adjustment of the injection start timing of the cooling water 233 to the small diameter portion of the workpiece W2 and the injection start timing of the cooling water 233 to the large diameter portion are adjusted to the small diameter portion in the method according to the first embodiment. The cooling water injection start timing and the adjustment of the cooling water injection start timing to the large diameter portion can be performed by the same method and conditions.

  In such a method according to the present embodiment, similarly to the method according to the first embodiment, in the cooling step, distortion generated when the annular workpiece is heated to the quenching temperature is eliminated, and the radius of the large diameter portion is reduced. And the annular workpiece can be deformed so that the difference between the radius and the radius of the small diameter portion is eliminated. Also in the method according to the present embodiment, the dimensional variation can be suppressed without using a restraining tool in the cooling step. As a result, it is possible to obtain a quenched product (quenched annular member) having good roundness and little variation in dimensions at a low cost. Further, the quenching method according to the present embodiment is also suitable for in-line.

  In the method according to the present embodiment, between the first heating step of heating the workpiece W2 to a predetermined temperature at which the deformation of the annular workpiece does not proceed during heating and the second heating step of heating the workpiece W2 to the quenching temperature. The analysis step is performed. In the method according to this embodiment, the cooling step is performed after the second heating step. Therefore, unlike the method according to the first embodiment, after the workpiece W2 is heated to the quenching temperature, the cooling process can be immediately performed. Further, in the cooling step, the workpiece W2 is cooled not only from the outer side of the heated workpiece W2 but also from the inner side, thereby cooling the workpiece W2. Therefore, in this embodiment, the work W2 can be cooled to the inside in a shorter time after the heating process is completed. Therefore, in this embodiment, even if the workpiece to be quenched is a thick workpiece (thickness exceeding 10 mm and 15 mm or less), the workpiece is sufficiently quenched to the inside and has a good roundness. Can be obtained. Of course, the method according to the present embodiment is also suitable for a quenching process for thin workpieces.

  In the cooling step, the workpiece W2 is cooled by injecting a coolant onto the workpiece W2 using the 16 injection nozzles on the outer peripheral side of the workpiece W2 and the 16 injection nozzles on the inner peripheral side of the workpiece W2. However, in this embodiment, the number of spray nozzles used in the cooling step is not particularly limited. The number of jet nozzles on the outer peripheral side of the work W2 and the number of jet nozzles on the inner peripheral side of the work W2 are both preferably 4 or more.

  Further, the coolant used in the method according to the present embodiment is the same as the coolant used in the method according to the first embodiment. In the method according to this embodiment, the coolant injection time and the coolant injection amount (flow rate) per unit time are the coolant injection time and the coolant injection per unit time in the method according to the first embodiment. It is the same as the amount (flow rate).

  The cooling step in the method according to this embodiment is preferably started as soon as possible after the second heating step. After the second heating step, if it takes time to start cooling by spraying the coolant onto the workpiece W2, it may be difficult to transform the workpiece into the martensite by the cooling step. Therefore, it is preferable that the time from the start of the injection of the coolant to the workpiece W1 after the second heating step is as short as possible. Therefore, it is preferable to perform the cooling step immediately after the analysis step. The time from the end of the heating process to the start of jetting of the coolant to the workpiece W1 is preferably 5 seconds or less, more preferably 3.5 seconds or less, and even more preferably 3.2 seconds or less.

  The workpiece W2 after the quenching process is usually subjected to a tempering process (see arrow (5) in FIG. 3).

  By performing a quenching process on the workpiece W2 through each of these steps, an annular member having a martensite structure without an incompletely quenched structure, having a good roundness, and having a small dimensional variation. Can be obtained at low cost. The annular member quenched by the quenching method according to the present embodiment can be suitably used for a bearing race or the like.

[Modification]
In the method according to the first embodiment and the second embodiment, the method of dividing into the large diameter portion and the small diameter portion is not particularly limited. For example, the radius r of the approximate circle is used as a reference, the radius r is compared with the average value of the radii at each circumferential position on the outer periphery of each annular work piece, and the workpiece is divided into a large diameter portion and a small diameter portion. Also good.

  In the method according to the first embodiment and the second embodiment, the work is divided into three or more types of parts (for example, three kinds of parts such as a large diameter part, a medium diameter part, and a small diameter part) based on the radial dimension. Then, the timing of injecting the coolant to each part may be adjusted based on the dimensional difference between the radii of the divided parts. In this case, based on the dimensional difference, for example, a portion having a smaller radius may have a larger amount of deformation.

  In the method according to the first embodiment and the second embodiment, in the analysis step, each position in the circumferential direction of the inner periphery of the work is measured, and the inner peripheral shape of the work is grasped based on the measurement result. The workpiece may be divided into a large diameter portion and a small diameter portion based on the inner peripheral shape. In this case, the large-diameter portion and the small-diameter portion of the work may be distinguished by a technique that is substantially the same as the technique that is performed based on the outer peripheral shape of the work described above. Moreover, you may acquire the radial dimension of a workpiece | work other than a laser displacement sensor, for example using thermography etc.

  In the method according to the first embodiment and the second embodiment, the method for heating the workpiece may be a method other than induction heating, for example, a known heating method such as furnace heating.

Example 1
(1) Manufacture of annular workpiece Annular material was obtained from a steel material made of high carbon chromium bearing steel (JIS SUJ2). The obtained annular material was cut into a predetermined shape to obtain an annular workpiece (outer diameter: 125 mm, wall thickness: 4 mm).

(2) Calculation of roundness of annular workpiece before quenching treatment The roundness of the annular workpiece (annular workpiece before quenching treatment) obtained in Example 1 (1) was calculated by performing the following operation. . The center of the mounted master workpiece turntable and a virtual center C _0. Next, each position in the circumferential direction of the outer periphery of the annular workpiece was measured using a laser displacement sensor (manufactured by Keyence Corporation). Thereby, the distance between the virtual center _C0 and each circumferential position on the outer periphery of the annular workpiece was obtained. Next, the acquired distance was converted into coordinate data of XY coordinates with the virtual center _C0 as the origin. Using the obtained coordinate data, a circle (approximate circle) approximated to the outer peripheral shape of the annular workpiece was calculated by the least square method. Then, the distance from the coordinate of the center C of the approximate circle to each circumferential position on the outer periphery of the annular workpiece was calculated. The obtained distance was defined as the radius at each circumferential position on the outer periphery of the annular workpiece.

  Based on the coordinates of the center C of the approximate circle, the radius of the approximate circle, and the radius at each circumferential position on the outer periphery of the annular workpiece, the first virtual circle and the second virtual circle centered on the center C of the approximate circle were obtained. The first virtual circle is a circle centered on the center C of the approximate circle and having the maximum value of the radii at the circumferential positions of the outer periphery of the annular workpiece as the radius (radius a) of the first virtual circle. . The second virtual circle is a circle centered on the center C of the approximate circle and having the minimum value of the radii at the circumferential positions of the outer periphery of the annular workpiece as the radius (radius b) of the second virtual circle. . The radius a of the first virtual circle corresponds to the radius of the large diameter portion, and the radius b of the second virtual circle corresponds to the radius of the small diameter portion.

Using the radius a of the first virtual circle and the radius b of the second virtual circle, the formula (II):
Roundness (mm) = ab (II)
The roundness (dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) was calculated according to

  As a result, the roundness (the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) of the annular workpiece before quenching treatment obtained in Example 1 (2) was 0.145 mm.

(3) Quenching As shown below, the annular workpiece obtained in Example 1 (1) was quenched by performing the cooling process from the heating process.

(3-1) Induction heating (heating process)
For induction heating, a quenching apparatus 100 shown in FIG. 1B was used. The quenching apparatus 100 includes an induction heating zone 10, an outer periphery analysis zone 20, and a cooling zone 30. The annular workpiece obtained in Example 1 (1) was introduced into the induction heating zone 10 of the quenching apparatus 100. Next, the entire annular workpiece was induction-heated at 900 ° C. for 20 seconds at a frequency of 1 kHz. In addition, the temperature at the time of induction heating was made into the surface temperature of the cyclic | annular workpiece | work measured with the thermocouple. Under the naked eye observation, the planar view shape of the annular workpiece after the heating step was examined. As a result, the planar view shape of the annular workpiece after the heating step was an elliptical shape.

  By performing the same operation as in Example 1 (2), the roundness of the annular workpiece after the heating step (the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) was calculated. As a result, the roundness (the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) of the annular workpiece after the heating step was 0.130 mm.

(3-2) Analysis Step The annular workpiece after the heating step of Example 1 (3-1) was moved to the outer periphery analysis zone 20. Next, the annular workpiece after the heating step was divided into a large diameter portion and a small diameter portion.

First, each circumferential position of the outer periphery of the annular workpiece disposed in the outer periphery analysis zone 20 was measured. Thereby, the distance between the virtual center _C0 and each circumferential position on the outer periphery of the annular workpiece was obtained. Using the acquired distance, the same operation as in Example 1 (2) was performed to obtain the radius a of the first virtual circle and the radius b of the second virtual circle. Thereafter, based on the radius a of the first virtual circle and the radius b of the second virtual circle, the reference radius c for dividing the large-diameter portion and the small-diameter portion was calculated according to the above formula (I).

  Further, the annular work after the heating step was divided into 16 equal parts so that the central angle became uniform in the circumferential direction of the first virtual circle, and virtually divided into 16 annular work pieces W1a to W1p. Next, the average value of the radii at the respective circumferential positions on the outer periphery was calculated for each of the annular workpiece pieces W1a to W1p.

  Thereafter, the obtained average value is compared with the reference radius c, and the annular work piece whose average value is larger than the reference radius c is a large diameter portion, and the annular work whose average value is the reference radius c or less. The fragment was a small diameter part. Thus, each of the 16 annular workpiece pieces was divided into either a large diameter portion or a small diameter portion. The time required for the analysis process was 3 seconds.

(3-3) Cooling Step The cooling step was performed in the cooling zone 30 of the quenching apparatus 100. As shown in FIG. 2, the cooling zone 30 includes a cooling device including injection nozzles 32 (32 a to 32 p) for injecting a coolant. As shown in FIG. 2, the injection nozzles 32a to 32p are arranged at equal intervals on the same circumference.

The analyzed annular workpiece was moved to the cooling zone 30, and the annular workpiece was arranged inside the injection nozzle 32. Next, a cooling liquid was sprayed on the outer peripheral side of the annular workpiece to cool the annular workpiece. Thereby, a quenched workpiece was obtained. The following conditions were adopted as the coolant injection conditions.
[Cooling liquid injection conditions]
(A) Small-diameter portion Coolant injection was started after 4.00 seconds from the end of the heating process (after 1.00 seconds from the end of the analysis process). The coolant was sprayed for 30 seconds at a spray amount (flow rate) of 2.0 L / min per spray nozzle. The jet angle of the coolant was 0 °. In the present specification, the coolant injection angle is an angle formed by the central axis of the nozzle hole of the injection nozzle 32 and the normal line of the outer peripheral surface of the annular workpiece with respect to the outer peripheral surface of the annular workpiece.
(B) Large-diameter portion Coolant injection was started after 4.06 seconds had elapsed from the end of the heating process (after 1.06 seconds had elapsed since the end of the analysis process). The coolant was sprayed for 30 seconds at a spray amount (flow rate) of 2.0 L / min per spray nozzle. The jet angle of the coolant was 0 °.
(C) Timing of cooling start The difference between the cooling water injection start timing to the small diameter portion and the cooling water injection start timing to the large diameter portion was set to 0.06 seconds.

  By performing the same operation as in Example 1 (2), the roundness of the quenched annular workpiece (dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) was calculated. As a result, the roundness (dimensional difference between the radius of the large-diameter portion and the radius of the small-diameter portion) of the quenched annular workpiece was 0.040 mm. Moreover, the planar view shape of the cyclic | annular workpiece | work after a heating process is an ellipse shape.

  In addition, the internal structure of the quenched annular workpiece was examined with an electron microscope. As a result, the internal structure of the quenched annular workpiece was a complete martensitic structure without an incompletely quenched structure.

(Example 2)
Except that the coolant injection conditions were changed as follows, the same operation as in Example 1 was performed, and the annular workpiece was quenched.
[Cooling liquid injection conditions]
(A) Small-diameter portion Coolant injection was started after 4.00 seconds from the end of the heating process (after 1.00 seconds from the end of the analysis process). The coolant was sprayed for 30 seconds at a spray amount (flow rate) of 2.0 L / min per spray nozzle. The jet angle of the coolant was 0 °.
(B) Large-diameter portion Coolant injection was started after 9.00 seconds had elapsed from the end of the heating process (after 6.00 seconds had elapsed since the end of the analysis process). The coolant was sprayed for 30 seconds at a spray amount (flow rate) of 2.0 L / min per spray nozzle. The jet angle of the coolant was 0 °.
(C) Timing of cooling start The difference between the cooling water injection start timing to the small diameter portion and the cooling water injection start timing to the large diameter portion was set to 5.00 seconds.

  In the quenching process, the roundness of each of the annular work before the quenching process, the annular work after the heating process, and the quenched annular work is performed by performing the same operation as in Example 1 (2). The dimensional difference between the radius and the radius of the small diameter part) was calculated. Further, by performing the same operation as in Example 1 (3), the planar view shape of the annular workpiece after the heating step and the internal structure of the quenched annular workpiece were examined.

  As a result, the roundness (annular difference between the radius of the large diameter portion and the small diameter portion) of the annular workpiece before quenching is 0.175 mm, and the roundness of the annular workpiece after the heating step (large diameter portion). The dimensional difference between the radius of the small diameter portion and the radius of the small diameter portion is 0.160 mm, and the roundness of the quenched annular workpiece (the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) is 0.030 mm. Met. Moreover, the planar view shape of the cyclic | annular workpiece | work after a heating process was elliptical shape, and the internal structure | tissue of the quenched cyclic | annular workpiece | work was a complete martensitic structure without incomplete hardening structure | tissue.

(Example 3)
Except that the coolant injection conditions were changed as follows, the same operation as in Example 1 was performed, and the annular workpiece was quenched.
[Cooling liquid injection conditions]
(A) Small-diameter portion Coolant injection was started after 4.00 seconds from the end of the heating process (after 1.00 seconds from the end of the analysis process). The coolant was sprayed for 30 seconds at a spray amount (flow rate) of 2.0 L / min per spray nozzle. The jet angle of the coolant was 0 °.
(B) Large-diameter portion Coolant injection was started after 4.20 seconds from the end of the heating step (after 1.20 seconds from the end of the analysis step). The coolant was sprayed for 30 seconds at a spray amount (flow rate) of 2.0 L / min per spray nozzle. The jet angle of the coolant was 0 °.
(C) Timing of cooling start The difference between the cooling water injection start timing to the small diameter portion and the cooling water injection start timing to the large diameter portion was 0.20 seconds.

  In the quenching process, the roundness of each of the annular work before the quenching process, the annular work after the heating process, and the quenched annular work is performed by performing the same operation as in Example 1 (2). The dimensional difference between the radius and the radius of the small diameter part) was calculated. Further, by performing the same operation as in Example 1 (3), the planar view shape of the annular workpiece after the heating step and the internal structure of the quenched annular workpiece were examined.

  As a result, the roundness (annular difference between the radius of the large diameter portion and the small diameter portion) of the annular workpiece before quenching is 0.300 mm, and the roundness of the annular workpiece after the heating step (large diameter portion). Dimensional difference between the radius of the small diameter portion and the radius of the small diameter portion) is 0.275 mm, and the roundness of the quenched annular workpiece (the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) is 0.060 mm. Met. Moreover, the planar view shape of the cyclic | annular workpiece | work after a heating process was elliptical shape, and the internal structure | tissue of the quenched cyclic | annular workpiece | work was a complete martensitic structure without incomplete hardening structure | tissue.

(Comparative Example 1)
Except that the coolant injection conditions were changed as follows, the same operation as in Example 1 was performed, and the annular workpiece was quenched.
[Cooling liquid injection conditions]
(A) Small-diameter portion Coolant injection was started after 4.00 seconds from the end of the heating process (after 1.00 seconds from the end of the analysis process). The coolant was sprayed for 30 seconds at a spray amount (flow rate) of 2.0 L / min per spray nozzle. The jet angle of the coolant was 0 °.
(B) Large-diameter portion Coolant injection was started after 4.00 seconds had elapsed from the end of the heating step (after 1.00 seconds had elapsed since the end of the analysis step). The coolant was sprayed for 30 seconds at a spray amount (flow rate) of 2.0 L / min per spray nozzle. The jet angle of the coolant was 0 °.
(C) Timing of starting cooling Cooling water injection start timing to the small diameter portion and cooling water injection start timing to the large diameter portion are the same time.

  In addition, by performing the same operation as in Example 1 (2), the roundness of each of the annular workpiece before quenching and the quenched annular workpiece (the dimension between the radius of the large diameter portion and the radius of the small diameter portion). Difference) was calculated. Further, by performing the same operation as in Example 1 (3), the planar view shape of the annular workpiece after the heating step and the internal structure of the quenched annular workpiece were examined.

  As a result, the circularity of the annular workpiece before quenching (the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) is 0.340 mm, and the circularity of the quenched annular workpiece (of the large diameter portion) The dimensional difference between the radius and the radius of the small diameter part) was 0.425 mm. Moreover, the planar view shape of the cyclic | annular workpiece | work after a heating process was elliptical shape, and the internal structure | tissue of the quenched cyclic | annular workpiece | work was a complete martensitic structure without incomplete hardening structure | tissue.

(Comparative Example 2)
Except that the coolant injection conditions were changed as follows, the same operation as in Example 1 was performed, and the annular workpiece was quenched.
[Cooling liquid injection conditions]
(A) Small-diameter portion Coolant injection was started after 4.00 seconds from the end of the heating process (after 1.00 seconds from the end of the analysis process). The cooling liquid was injected for 30 seconds at an injection amount (flow rate) of 1.8 L / min per injection nozzle. The jet angle of the coolant was 0 °.
(B) Large-diameter portion Coolant injection was started after 4.00 seconds had elapsed from the end of the heating step (after 1.00 seconds had elapsed since the end of the analysis step). The coolant was sprayed for 30 seconds at a spray amount (flow rate) of 2.0 L / min per spray nozzle. The jet angle of the coolant was 0 °.
(C) Timing of starting cooling Cooling water injection start timing to the small diameter portion and cooling water injection start timing to the large diameter portion are the same time.

  In addition, by performing the same operation as in Example 1 (2), the roundness of each of the annular workpiece before quenching and the quenched annular workpiece (the dimension between the radius of the large diameter portion and the radius of the small diameter portion). Difference) was calculated. Further, by performing the same operation as in Example 1 (3), the planar view shape of the annular workpiece after the heating step and the internal structure of the quenched annular workpiece were examined.

  As a result, the roundness of the annular workpiece before quenching (the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) is 0.310 mm, and the roundness of the quenched annular workpiece (of the large diameter portion) The dimensional difference between the radius and the radius of the small diameter portion was 0.040 mm. Moreover, the planar view shape of the cyclic | annular workpiece | work after a heating process was elliptical shape, and the internal structure | tissue of the quenched cyclic | annular workpiece | work was a complete martensitic structure without incomplete hardening structure | tissue. However, since the method of Comparative Example 2 needs to control the injection amount (flow rate), it is difficult to set the cooling rate condition as compared with the methods of Examples 1 and 2.

(Comparative Example 3)
(1) Production of annular workpiece The same operation as in Example 1 (1) was performed to obtain an annular workpiece (annular workpiece before quenching). By performing the same operation as in Example 1 (2), the roundness of the annular work before quenching (the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) was calculated. As a result, the roundness (dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) of the annular work before quenching was 0.315 mm.

(2) Quenching step As shown below, the annular workpiece obtained in Example 1 (1) was quenched by performing the cooling step from the heating step.

(2-1) Heating step The annular workpiece obtained in Example 1 (1) was introduced into a heating furnace. Next, the annular workpiece in the heating furnace was heated at 830 ° C. for 0.5 hour.

(2-2) Cooling Step Oil cooling was performed by putting the annular work after the heating step into 80 ° C. cooling oil. Thereby, a quenched workpiece was obtained.

  By performing the same operation as in Example 1 (2), the roundness of the quenched annular workpiece (dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) was calculated. As a result, the roundness (dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) of the quenched annular workpiece was 0.400 mm.

  In addition, the internal structure of the quenched annular workpiece was examined with an electron microscope. As a result, the internal structure of the quenched annular workpiece was a complete martensitic structure without an incompletely quenched structure.

(result)
A summary of the methods of Examples 1-3 and Comparative Examples 1-3 is shown in Table 1, and the results of Examples 1-2 and Comparative Examples 1-3 are shown in Table 2.

  As shown in Table 2, in Example 1, the roundness (the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) of the annular work after the heating step was 0.130 mm. In Example 1, the injection of the cooling liquid to the large diameter portion is started when one second has elapsed from the start of the injection of the cooling liquid to the small diameter portion with respect to the annular work after the heating process having the dimensional difference. Thus, a quenched product (quenched annular workpiece) having a good roundness (0.040 mm) was obtained. Further, as shown in Table 2, in Example 2, the roundness (the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) of the annular workpiece after the heating process was 0.160 mm. It was. In Example 2, for the annular workpiece after the heating step having this dimensional difference, the injection of the coolant to the large diameter portion is started when 3 seconds have elapsed from the start of the injection of the coolant to the small diameter portion. Thus, a quenched product (quenched annular workpiece) having good roundness (0.030 mm) was obtained. Further, as shown in Table 2, in Example 3, the roundness (the dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) in the annular workpiece after the heating process was 0.275 mm. It was. In Example 3, for the annular workpiece after the heating step having this dimensional difference, the injection of the coolant to the large diameter portion is started after 3 seconds from the start of the injection of the coolant to the small diameter portion. Thus, a quenched product (quenched annular workpiece) having a good roundness (0.060 mm) was obtained.

  On the other hand, in Comparative Example 1, the coolant is sprayed simultaneously on the large diameter portion and the small diameter portion. However, the quench-treated product obtained in Comparative Example 1 did not have sufficient roundness. Moreover, since the method of the comparative example 2 needs to control the injection amount (flow rate) of the coolant, it is difficult to control the cooling rate as compared with the methods of the first and second embodiments. Furthermore, in the comparative example 3, in the cooling process, oil cooling of the annular workpiece after the heating process is performed. However, the quenched product obtained in Comparative Example 3 did not have sufficient roundness.

  From these results, as in Examples 1 to 3, in the quenching process, based on the dimensional difference between the radius of the large-diameter portion and the radius of the small-diameter portion, the injection start timing of the coolant to the large-diameter portion and the small-diameter It can be seen that a quench-treated product (quenched annular workpiece) having a good roundness can be obtained by performing a simple operation of adjusting the timing of injecting the coolant into the section.

(Reference Example 1)
In Example 1, the difference between the cooling water injection start timing for the small diameter portion and the cooling water injection start timing for the large diameter portion is set to 0.04 seconds, 0.06 seconds, 0.10 seconds, and 0.20 seconds. , 0.50 seconds, 1.00 seconds, 1.50 seconds, 3.00 seconds, or 5.00 seconds, except that the operation is the same as in Example 1, and a circular workpiece (wall thickness: 4 mm) The material was subjected to quenching treatment.

In the quenching process, the radius a of the first virtual circle and the radius b of the second virtual circle of the annular workpiece after the heating step were obtained by performing the same operation as in Example 1 (2). Using the radius a of the first virtual circle and the radius b of the second virtual circle, the formula (IIa):
Deformation amount (mm) = ab (IIa)
Accordingly, a deformation amount (that is, “a dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion”) was obtained. In Reference Example 1, the difference between the cooling water injection start timing to the small diameter portion and the cooling water injection start timing to the large diameter portion (difference in cooling start timing) and the deformation amount (the radius of the large diameter portion and the small diameter portion FIG. 5 shows the result of examining the relationship with the dimensional difference between the radius and the radius.

  From the results shown in FIG. 5, when the difference in the cooling start time is less than 0.1 seconds, the deformation amount (dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) is less than 0.15 mm. I know that there is. From this result, among the annular workpieces, the deformation amount (dimensional difference between the radius of the large-diameter portion and the radius of the small-diameter portion) is preferably 0.1 in the quenching treatment of the annular workpiece having a thickness of 1 to 10 mm. When it is less than 15 mm, a good roundness quenching treatment is started by starting the injection of the coolant to the large diameter portion until 0.1 second has elapsed from the start of the injection of the coolant to the small diameter portion. It can be seen that the product is obtained.

  From the results shown in FIG. 5, when the difference in the cooling start time is 0.1 to 5 seconds, the deformation amount (dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) is 0. It turns out that it is 15 mm or more. More specifically, when the difference in the cooling start timing is 1 to 5 seconds, the deformation amount (dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) is 0.15 to 0.175 mm. I understand that. It can also be seen that when the difference in the cooling start timing is 0.1 second or more and less than 1 second, the deformation amount (dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) exceeds 0.175 mm. Therefore, from these results, the amount of deformation (dimensional difference between the radius of the large-diameter portion and the radius of the small-diameter portion) in the quenching treatment of the annular workpiece preferably having a thickness of 1 to 10 mm among the annular workpieces. Is 0.15 to 0.175 mm, a good perfect circle is obtained by starting the injection of the coolant to the large diameter portion after 1 to 5 seconds from the start of the injection of the coolant to the small diameter portion. It can be seen that a quenched product can be obtained. Further, among the annular workpieces, preferably, in the quenching treatment of the annular workpiece having a thickness of 1 to 10 mm, the deformation amount (dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion) is 0.175 mm. When exceeding, a quenching product with good roundness is obtained by starting the injection of the coolant to the large diameter portion when 0.1 second or more and less than 1 second has elapsed since the start of the injection of the coolant to the small diameter portion Can be obtained.

  W1, W2: Workpiece; 1, 201: Turntable; 10, 210: Induction heating zone; 11, 211: Heating coil; 20, 220: Peripheral analysis zone; 21, 221: Sensor element; 23, 223: Storage unit; 30, 230: Cooling zone; 32, 232, 234: Injection nozzle; 33, 233: Coolant; 100, 300: Quenching device

Claims (5)

A method of quenching an annular workpiece made of a metal material,
Heating the annular workpiece, heating the annular workpiece to a quenching temperature, and then holding the annular workpiece at the quenching temperature,
After starting heating in the heating step, a radial dimension of the annular workpiece is acquired, a reference dimension is acquired based on the acquired radial dimension, and the annular workpiece is at least larger than the reference dimension and smaller than the reference dimension. An analysis step of calculating a dimensional difference between the radius of the large diameter portion and the radius of the small diameter portion, and after the heating step, the large diameter portion and the small diameter portion in the analysis step. A cooling step of injecting a coolant onto at least the divided annular workpiece;
Including
In the cooling step, based on a dimensional difference between the maximum value of the radius of the large diameter portion and the minimum value of the radius of the small diameter portion, the injection timing of the coolant to the large diameter portion and the small diameter portion A method for quenching an annular workpiece, characterized by adjusting a start time of injection of a coolant.   In the cooling step, the coolant is applied to the annular work so that the injection amount of the coolant per unit time to the large diameter portion is the same as the injection amount of the coolant per unit time to the small diameter portion. The method according to claim 1.   The method according to claim 2, wherein a thickness of the annular workpiece in a radial direction is 1 to 10 mm.   4. The injection of the coolant to the large-diameter portion is started when 0 or 1 second elapses from the start of the injection of the coolant to the small-diameter portion when the dimensional difference is less than 0.15 mm. the method of.   The said dimensional difference is 0.15 mm or more, The injection of the cooling liquid to the said large diameter part is started when 0.1 to 5 second passes since the injection start of the cooling liquid to the said small diameter part. the method of.