JP7266426B2 - Workpiece tempering method and machine parts obtained by this method - Google Patents

Workpiece tempering method and machine parts obtained by this method Download PDF

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JP7266426B2
JP7266426B2 JP2019040276A JP2019040276A JP7266426B2 JP 7266426 B2 JP7266426 B2 JP 7266426B2 JP 2019040276 A JP2019040276 A JP 2019040276A JP 2019040276 A JP2019040276 A JP 2019040276A JP 7266426 B2 JP7266426 B2 JP 7266426B2
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JP2019157272A (en
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慎太郎 鈴木
智哉 村川
大 齊藤
誠 堀
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description

本発明は、ワークの焼き戻し方法、及びこの方法で得られた機械部品に関し、特に高温環境下で使用される機械部品に適した焼き戻し技術に関する。 TECHNICAL FIELD The present invention relates to a work tempering method and a machine part obtained by this method, and more particularly to a tempering technique suitable for machine parts used in a high temperature environment.

例えば、転がり軸受の軌道輪のように、ＳＵＪ２等の鋼材からなる機械部品の製造過程においては、機械部品に必要とされる機械的強度等を付与するための熱処理（焼入硬化処理）を実施した後、例えば残留応力の緩和や残留オーステナイトの低減化を目的として、焼き戻し処理を実施するのが一般的である。 For example, in the manufacturing process of machine parts made of steel such as SUJ2, such as bearing rings of rolling bearings, heat treatment (quench hardening treatment) is performed to give the machine parts the mechanical strength required. After that, it is common to carry out a tempering treatment, for example, for the purpose of relaxing residual stress and reducing retained austenite.

ここで、焼き戻し処理には、例えば電気炉等による雰囲気加熱で、炉内に配置されたワークを加熱する方法の他、短時間での加熱を目的として、誘導加熱によりワークを加熱する方法（例えば、特許文献１を参照）などが知られている。 Here, the tempering treatment includes, for example, a method of heating the work placed in the furnace by atmospheric heating using an electric furnace, etc., and a method of heating the work by induction heating for the purpose of heating in a short time ( For example, see Patent Document 1) and the like are known.

特開２０１１－１４４４４８号公報JP 2011-144448 A

ところで、高温環境下で使用される軸受においては、使用時、高温に晒されることで、軸受に含まれる残留オーステナイトが変態して、過大な寸法変化が生じる傾向にある。そのため、この種の用途に用いられる製品（軸受）については、残留オーステナイト量を通常の製品よりも更に低減化する必要が生じる。具体的には、焼き戻し処理時の温度（例えば最高温度）を、通常の焼き戻し処理の場合よりも高温域に設定する必要が生じる。 By the way, in a bearing used in a high-temperature environment, the residual austenite contained in the bearing tends to undergo transformation due to exposure to high temperature during use, resulting in excessive dimensional change. Therefore, products (bearings) used for this type of application need to have a smaller amount of retained austenite than normal products. Specifically, it is necessary to set the temperature (for example, the maximum temperature) during tempering to a higher temperature range than in normal tempering.

電気炉などの雰囲気加熱装置は、温度制御が比較的容易である一方で、昇温速度に限界があるため、どうしても昇温に多大な時間を要する。そのため、上述の理由で、高温域に焼き戻し条件（加熱条件）を設定すると、処理時間が今まで以上に長くなり、生産性の悪化が避けられない。 An atmosphere heating apparatus such as an electric furnace is relatively easy to control the temperature, but it has a limit to the rate of temperature increase, so it inevitably takes a long time to raise the temperature. Therefore, if the tempering condition (heating condition) is set in the high temperature range for the reasons described above, the treatment time becomes longer than before, and the deterioration of productivity is inevitable.

誘導加熱は、金属部品の温度を上げる際のエネルギー効率が高いため、雰囲気加熱と比べて短時間で高温域までワークを加熱することができる。しかしながら、従来よりも高温域（例えば２５０℃以上）にまでワークを加熱した場合、残留オーステナイト量が低減化するだけでなく、ワークの硬さも大きく低下するおそれが生じる。そのため、単に、誘導加熱でワークを高温域まで加熱し、冷却しただけでは、高温環境下での使用に適した機械部品を得ることは難しい。 Induction heating has high energy efficiency when raising the temperature of metal parts, so it is possible to heat the work to a high temperature range in a short time compared to atmospheric heating. However, if the work is heated to a higher temperature range (for example, 250° C. or higher) than conventionally, not only the amount of retained austenite is reduced, but also the hardness of the work may be greatly reduced. Therefore, it is difficult to obtain mechanical parts suitable for use in high-temperature environments simply by heating the workpiece to a high temperature range by induction heating and then cooling the workpiece.

また、等速自在継手の外側継手部材のように、軸方向の厚み寸法分布が偏った機械部品に対して誘導加熱を適用する場合、磁束が相対的に密となって加熱され易い部分と、磁束が相対的に疎となって加熱され難い部分とが生じる。そのため、一つのワーク内での温度差が大きくなり、均熱加熱が難しい。誘導加熱のみで焼き戻しに必要な均熱加熱を達成するためには、ワークのサイズや形状に適した形態の誘導加熱装置（例えば誘導加熱用コイル）を準備する必要があるが、これだと型番（処理すべきワークの種類）の増加に伴い準備すべき上記コイルの種類が増えるため、生産性の低下は免れ得ない。 In addition, when induction heating is applied to a mechanical part with a biased thickness distribution in the axial direction, such as the outer joint member of a constant velocity universal joint, a portion where the magnetic flux is relatively dense and is likely to be heated, The magnetic flux is relatively sparse, and there is a portion that is difficult to heat. As a result, the temperature difference within one work increases, making uniform heating difficult. In order to achieve the uniform heating required for tempering only with induction heating, it is necessary to prepare an induction heating device (for example, an induction heating coil) suitable for the size and shape of the workpiece. As the number of models (types of workpieces to be processed) increases, the number of types of coils to be prepared increases, which inevitably lowers productivity.

以上の実情に鑑み、本明細書では、高温環境下での使用に適した機械部品を得ることができ、かつ生産性に優れた焼き戻し方法を提供することを、解決すべき技術課題とする。 In view of the above circumstances, the technical problem to be solved in this specification is to provide a tempering method that can obtain a mechanical part suitable for use in a high-temperature environment and has excellent productivity. .

前記課題の解決は、本発明に係るワークの焼き戻し方法によって達成される。すなわち、この方法は、ワークを加熱する加熱工程と、加熱工程で加熱されたワークを冷却する冷却工程とを備え、加熱工程及び冷却工程における温度履歴を制御することで、ワークに焼き戻し処理を施す、ワークの焼き戻し方法において、加熱工程は、誘導加熱によりワークを狙い温度まで加熱する昇温工程と、所定幅の温度域の範囲内で昇温後のワークが所定時間の間保温されるように、雰囲気加熱によるワークの加熱を制御する保温工程とを有する点をもって特徴付けられる。 The above problems are solved by the work tempering method according to the present invention. That is, this method includes a heating step of heating the workpiece and a cooling step of cooling the workpiece heated in the heating step, and tempering the workpiece by controlling the temperature history in the heating step and the cooling step. In the work tempering method, the heating process includes a temperature raising process in which the work is heated to a target temperature by induction heating, and the work after the temperature rise within a temperature range of a predetermined width is kept warm for a predetermined time. As described above, the method is characterized by having a heat insulating step for controlling the heating of the workpiece by atmospheric heating.

本発明者らは、所定幅の温度域内で昇温後のワークを所定時間の間保温することにより、焼き戻し処理後のワークに含まれる残留オーステナイト量を所要レベル以下にまで低減化し、かつワークの硬さを所定範囲内に収めることが可能となる場合があることを見出した。本発明はこの知見に基づきなされたもので、誘導加熱によりワークを狙い温度まで加熱することにより（昇温工程）、従来よりも短時間でワークを所定の高温域にまで加熱することができる。また、昇温後のワークを上述のように所定幅の温度域の範囲内で所定時間の間保温することにより、焼き戻し処理後の残留オーステナイト量と硬さを共に許容範囲内に収めることができる。また、ワークを上記温度域内で保温するための加熱制御を、雰囲気加熱により実施するようにしたので、ワークを均等に加熱しながらワークを保温することができる。よって、ワーク内部の温度のばらつきを抑えて、均質な焼き戻し処理を施すことができる。また、等速自在継手の外側継手部材のように軸方向で厚み寸法分布に偏りがある機械部品であっても、誘導加熱時に生じたワーク内での温度のばらつきを雰囲気加熱で均すことができる。よって、複数のコイル等を準備せずとも、均質な焼き戻し処理を施すことができる。また、雰囲気加熱であれば、誘導加熱等と比べてワークの温度が下がりにくい。そのため、保温工程時の加熱制御も比較的容易に行うことができる。もちろん、雰囲気加熱であれば、一度に大量のワークを処理することができる。以上より、本発明によれば、ワークに含まれる残留オーステナイト量を所要レベル以下にまで低減化できると共に、ワークの硬さを所定範囲内に収めることができるので、高温環境下での使用にも適した機械部品を得ることができる。また、昇温に要する時間が短くて済み、比較的短時間で多くのワークに均質な処理を施すことができるので、生産性にも優れている。 The inventors of the present invention have found that the amount of retained austenite contained in the work after tempering treatment is reduced to a required level or less by keeping the work warmed within a temperature range of a predetermined width for a predetermined time. It has been found that it may be possible to keep the hardness of the rubber within a predetermined range. The present invention was made based on this knowledge, and by heating the work to a target temperature by induction heating (heating step), it is possible to heat the work to a predetermined high temperature range in a shorter time than before. In addition, by keeping the temperature of the workpiece after the temperature rise for a predetermined period of time within the temperature range of a predetermined width as described above, both the amount of retained austenite and the hardness after the tempering treatment can be kept within the allowable range. can. Moreover, since the heating control for keeping the workpiece within the above temperature range is performed by atmospheric heating, the workpiece can be kept warm while being uniformly heated. Therefore, uniform tempering can be performed while suppressing variations in temperature inside the work. In addition, even for a machine part with uneven thickness dimension distribution in the axial direction, such as the outer joint member of a constant velocity universal joint, it is possible to even out the temperature variation in the work that occurs during induction heating by atmospheric heating. can. Therefore, uniform tempering can be performed without preparing a plurality of coils or the like. Also, if the atmosphere heating is used, the temperature of the workpiece is less likely to decrease than the induction heating or the like. Therefore, it is possible to relatively easily perform heating control during the heat-retaining process. Of course, atmospheric heating can process a large number of workpieces at once. As described above, according to the present invention, the amount of retained austenite contained in the work can be reduced to a required level or less, and the hardness of the work can be kept within a predetermined range. You can get suitable mechanical parts. Moreover, the time required for temperature rise is short, and many workpieces can be uniformly treated in a relatively short period of time, resulting in excellent productivity.

また、本発明に係るワークの焼き戻し方法においては、昇温工程の後でかつ保温工程の前に、昇温後のワークを雰囲気加熱して、昇温時の狙い温度までワークの温度を回復させる復温工程をさらに設けてもよい。 Further, in the work tempering method according to the present invention, after the temperature raising process and before the heat retention process, the work after the temperature rise is atmospherically heated to recover the temperature of the work to the target temperature at the time of temperature rise. A rewarming step may be further provided.

誘導加熱によりワークを昇温すると、当該誘導加熱を図るための装置から取り出された直後から、ワークの温度は少なからず低下する。この温度低下を見越して予め狙い温度を高めに設定すると、上述のようにワークの硬さが必要以上に低下してしまう。そこで、昇温工程の後に昇温時の狙い温度までワークの温度を回復させる復温工程を設けることで、ワークの温度を狙い温度にまで戻した状態で保温工程に移行させることができる。また、復温工程と保温工程ともに雰囲気加熱でワークを加熱することで、復温工程から保温工程に移行する際の温度低下を抑制できる。以上より、復温工程を設けることで、ワークを効率よく保温工程に移行することができる。 When the temperature of the workpiece is raised by induction heating, the temperature of the workpiece drops not a little immediately after it is removed from the device for the induction heating. If the target temperature is set high in advance in anticipation of this temperature drop, the hardness of the work will be lowered more than necessary as described above. Therefore, by providing a reheating process for recovering the temperature of the workpiece to the target temperature at the time of heating after the heating process, it is possible to shift to the heat retention process in a state where the temperature of the workpiece has been returned to the target temperature. In addition, by heating the work by atmospheric heating in both the rewarming process and the heat retaining process, it is possible to suppress the temperature drop when shifting from the rewarming process to the heat retaining process. As described above, by providing the rewarming process, the work can be efficiently transferred to the heat retaining process.

また、この場合、本発明に係るワークの焼き戻し方法においては、復温工程で、雰囲気加熱の設定温度は、昇温時の狙い温度よりも高く設定されてもよい。 Further, in this case, in the work tempering method according to the present invention, in the reheating step, the set temperature for atmospheric heating may be set higher than the target temperature during the heating.

保温工程の前に復温工程を設けるのであれば、復温工程に使用する装置（雰囲気加熱炉）内の雰囲気温度を保温工程に使用する装置（雰囲気加熱炉）内の雰囲気温度よりも容易に高くすることができる。これにより、復温に要する時間を短くできるので、さらに効率よく狙い温度のワークを保温工程に導入することが可能となる。 If the rewarming process is provided before the heat retention process, the atmosphere temperature in the device (atmosphere heating furnace) used in the rewarming process can be more easily adjusted than the atmosphere temperature in the device (atmosphere heating furnace) used in the heat retention process. can be higher. As a result, the time required for reheating can be shortened, so that it is possible to more efficiently introduce the workpiece at the target temperature into the heat retention process.

また、本発明に係るワークの焼き戻し方法においては、保温工程で、雰囲気加熱の設定温度は、昇温時の狙い温度と同じ温度に設定されてもよい。 Further, in the work tempering method according to the present invention, in the heat insulating step, the set temperature for atmospheric heating may be set to the same temperature as the target temperature when raising the temperature.

雰囲気加熱であれば、誘導加熱装置よりも温度を一定に保ちやすい。よって、保温工程における雰囲気加熱の設定温度を昇温時の狙い温度と同じ温度にすることで、より狙い通りの焼き戻し品質（残留オーステナイト量、硬さ）を得ることが可能となる。 If it is atmospheric heating, it is easier to keep the temperature constant than with an induction heating device. Therefore, by setting the set temperature of atmosphere heating in the heat retaining step to the same temperature as the target temperature during temperature rise, it is possible to obtain more targeted tempering quality (amount of retained austenite, hardness).

また、本発明に係るワークの焼き戻し方法においては、ワークに要求される残留オーステナイト量及び硬さに応じて所定幅の温度域としての許容温度域を設定し、この許容温度域の範囲内でワークが所定時間の間保温されるように、誘導加熱によるワークの加熱を制御してもよい。 Further, in the work tempering method according to the present invention, an allowable temperature range is set as a temperature range of a predetermined width according to the amount of retained austenite and hardness required for the work, and within this allowable temperature range Heating of the work by induction heating may be controlled so that the work is kept warm for a predetermined time.

このように、ワークに要求される残留オーステナイト量及び硬さに応じて許容温度域を設定することにより、より短い保温時間でもって、残留オーステナイト量と硬さを共に許容範囲内に収めることが可能となる。従って、更なる生産性の向上が可能となる。 In this way, by setting the allowable temperature range according to the amount of retained austenite and hardness required for the workpiece, it is possible to keep both the amount of retained austenite and hardness within the allowable range with a shorter heat retention time. becomes. Therefore, it becomes possible to further improve productivity.

また、この場合、本発明に係るワークの焼き戻し方法においては、ワークの昇温時の狙い温度と残留オーステナイト量との関係に基づき、残留オーステナイト量が許容範囲内に収まる第一温度下限値を設定すると共に、ワークの昇温時の狙い温度と硬さとの関係に基づき、硬さが許容範囲内に収まる第二温度上限値及び第二温度下限値を設定し、これら第一温度下限値よりも大きな領域と、第二温度上限値と第二温度下限値との間の領域とが重複する範囲内で、許容温度域を設定してもよい。 Further, in this case, in the work tempering method according to the present invention, the first temperature lower limit is set so that the amount of retained austenite falls within the allowable range based on the relationship between the target temperature when the temperature of the work is raised and the amount of retained austenite. In addition to setting, based on the relationship between the target temperature and hardness at the time of temperature rise of the workpiece, set the second upper temperature limit and the second lower temperature limit that the hardness falls within the allowable range, and from these first temperature lower limit The allowable temperature range may be set within a range in which the area with the largest temperature overlaps with the area between the second upper temperature limit and the second lower temperature limit.

残留オーステナイト量は、加熱温度（正確には昇温工程時の狙い温度）が上昇するにつれて低下し、硬さもまた加熱温度が上昇するにつれて低下する。そのため、これらの傾向に基づき、ワークに要求される残留オーステナイト量及び硬さに応じて、上述のように、第一温度下限値を設定し、かつ第二温度上限値及び第二温度下限値を設定する。そして、これら第一温度下限値よりも大きな領域と、第二温度上限値と第二温度下限値との間の領域とが重複する範囲内で、許容温度域を設定することにより、ワークの種類（特に材質）ごとに最適な許容温度域を的確に設定することが可能となる。 The amount of retained austenite decreases as the heating temperature (more precisely, the target temperature in the heating process) increases, and the hardness also decreases as the heating temperature increases. Therefore, based on these tendencies, the first temperature lower limit is set as described above, and the second upper temperature limit and second lower temperature limit are set according to the amount of retained austenite and hardness required for the work. set. Then, by setting the allowable temperature range within the range where the range larger than the first temperature lower limit value and the range between the second temperature upper limit value and the second temperature lower limit value overlap, the type of workpiece It is possible to accurately set the optimum allowable temperature range for each (especially material).

また、本発明に係るワークの焼き戻し方法においては、ワークの材質が高炭素クロム軸受鋼である場合、許容温度域が２９０℃以上でかつ３４０℃以下の範囲内で設定されてもよい。 Further, in the work tempering method according to the present invention, when the material of the work is high carbon chromium bearing steel, the allowable temperature range may be set within the range of 290° C. or higher and 340° C. or lower.

また、ワークの材質が高炭素クロム軸受鋼である場合、ワークの保温時間が３分以上でかつ７分以下に設定されてもよい。 Further, when the material of the work is high carbon chromium bearing steel, the heat retention time of the work may be set to 3 minutes or more and 7 minutes or less.

このように、ワークの材質が高炭素クロム軸受鋼である場合には、例えば上述した設定手法を用いることで、適切な許容温度域が具体的に導出される。よって、適正な許容温度域内でワークを保温することができ、これにより焼き戻し処理後のワークに適切な残留オーステナイト量と硬さとを安定的に付与することが可能となる。 Thus, when the material of the workpiece is high-carbon chromium bearing steel, for example, by using the setting method described above, an appropriate allowable temperature range can be specifically derived. Therefore, the workpiece can be kept warm within an appropriate allowable temperature range, thereby stably imparting an appropriate amount of retained austenite and hardness to the workpiece after the tempering treatment.

あるいは、本発明に係るワークの焼き戻し方法においては、ワークの材質が機械構造用炭素鋼である場合、許容温度域が１３０℃以上でかつ２２０℃以下の範囲内で設定されてもよい。 Alternatively, in the work tempering method according to the present invention, when the material of the work is carbon steel for machine structural use, the allowable temperature range may be set within the range of 130° C. or higher and 220° C. or lower.

また、ワークの材質が機械構造用炭素鋼である場合、ワークの保温時間が１０秒以上でかつ７０分以下に設定されてもよい。 Further, when the material of the work is carbon steel for machine structural use, the heat retention time of the work may be set to 10 seconds or more and 70 minutes or less.

このように、ワークの材質が機械構造用炭素鋼である場合においても、上述した設定手法を用いることで、適切な許容温度域が具体的に導出される。よって、適正な許容温度域内でワークを保温することができ、これにより焼き戻し処理後のワークに適切な残留オーステナイト量と硬さとを安定的に付与することが可能となる。 Thus, even when the material of the work is carbon steel for machine structural use, an appropriate allowable temperature range can be specifically derived by using the setting method described above. Therefore, the workpiece can be kept warm within an appropriate allowable temperature range, thereby stably imparting an appropriate amount of retained austenite and hardness to the workpiece after the tempering treatment.

また、本発明に係るワークの焼き戻し方法においては、電気ヒーターを有する雰囲気加熱炉を用いて、保温工程におけるワークの加熱を行ってもよい。 Further, in the work tempering method according to the present invention, an atmosphere heating furnace having an electric heater may be used to heat the work in the heat retaining step.

例えば赤外線ヒーターだと、金属製のワーク表面の色（光沢）によって温度の上昇度合いが変化する可能性があるが、電気ヒーターによる雰囲気加熱であれば、ワークではなくその周囲の雰囲気（気体）を加熱するため、上述のような問題は生じない。よって、ワークの個体差の影響を受けることなく安定した加熱が可能となる。 For example, with an infrared heater, the degree of temperature rise may change depending on the color (gloss) of the surface of the metal work. Since it is heated, the above problems do not occur. Therefore, stable heating is possible without being affected by individual differences in workpieces.

また、以上述べたように、本発明に係るワークの焼き戻し方法は、高温環境下での使用に適した機械部品を得ることができ、かつ生産性に優れているため、例えば転がり軸受の軌道輪（外輪、内輪）や、等速自在継手の外側継手部材のような機械部品の量産品に熱処理を施すための方法として好適である。 Further, as described above, the work tempering method according to the present invention can obtain mechanical parts suitable for use in a high-temperature environment, and is excellent in productivity. It is suitable as a method for applying heat treatment to mass-produced machine parts such as rings (outer rings, inner rings) and outer joint members of constant velocity universal joints.

以上述べたように、本発明によれば、高温環境下での使用に適した機械部品を得ることができ、かつ生産性に優れた焼き戻し方法を提供することが可能となる。 INDUSTRIAL APPLICABILITY As described above, according to the present invention, it is possible to obtain a mechanical component suitable for use in a high-temperature environment and to provide a tempering method with excellent productivity.

本発明の第一実施形態に係る熱処理工程の全体の流れを示すフローチャートである。It is a flow chart which shows the flow of the whole heat treatment process concerning a first embodiment of the present invention. （ａ）（ｂ）ともに、図１に示す焼き戻し工程の流れを示すフローチャートである。2(a) and 2(b) are both flow charts showing the flow of the tempering process shown in FIG. 1. FIG. 本発明の第一実施形態に係る焼き戻し装置の全体概要を示す断面図である。BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows the whole outline|summary of the tempering apparatus which concerns on 1st embodiment of this invention. 加熱装置の断面図である。It is a sectional view of a heating device. 誘導加熱装置の断面図である。It is a sectional view of an induction heating device. 図２に示す焼き戻し工程の間の温度履歴を示すグラフである。Figure 3 is a graph showing the temperature history during the tempering process shown in Figure 2; 焼き戻し処理時における（ａ）加熱温度と残留オーステナイト量との関係を概念的に示すグラフと、（ｂ）加熱温度と硬さとの関係を概念的に示すグラフ、及び（ｃ）許容温度域の範囲を概念的に示すグラフである。(a) A graph conceptually showing the relationship between the heating temperature and the amount of retained austenite, (b) a graph conceptually showing the relationship between the heating temperature and the hardness, and (c) the allowable temperature range during the tempering process. It is a graph which shows a range conceptually. ワークが転がり軸受の軌道輪である場合、ワークの表面に設けた複数の温度測定点の位置を示す断面図の一例である。FIG. 10 is an example of a cross-sectional view showing the positions of a plurality of temperature measurement points provided on the surface of the work when the work is a bearing ring of a rolling bearing. 本発明の第二実施形態に係る昇温装置の断面図である。It is a sectional view of a temperature raising device concerning a second embodiment of the present invention. ワークが等速自在継手の外側継手部材である場合、ワークの表面に設けた複数の硬度測定点の位置を示す断面図の一例である。When the work is an outer joint member of a constant velocity universal joint, it is an example of a cross-sectional view showing the positions of a plurality of hardness measurement points provided on the surface of the work.

以下、本発明の第一実施形態を図面に基づいて説明する。 A first embodiment of the present invention will be described below with reference to the drawings.

図１は、本発明の第一実施形態に係る熱処理工程の全体の流れを示すフローチャートである。図１に示すように、本実施形態に係る熱処理工程は、対象となるワークＷ（図３を参照）に焼入れ処理を施す焼入れ工程Ｓ１と、焼入れ後のワークＷに焼き戻し処理を施す焼き戻し工程Ｓ２とを備える。また、焼入れ工程Ｓ１と焼き戻し工程Ｓ２の後にはそれぞれ、洗浄工程Ｓ３，Ｓ５と、検査工程Ｓ４，Ｓ６とを備える。なお、これら洗浄工程Ｓ３，Ｓ５や検査工程Ｓ４，Ｓ６は、必要に応じてその一部又は全部を省略可能である。もしくは図示は省略するが、必要に応じて、焼入れ工程Ｓ１又は焼き戻し工程Ｓ２の後に、研磨工程などを追加してもよい。 FIG. 1 is a flow chart showing the overall flow of the heat treatment process according to the first embodiment of the present invention. As shown in FIG. 1, the heat treatment process according to the present embodiment includes a quenching process S1 in which a target work W (see FIG. 3) is quenched, and a tempering process in which a tempering process is performed on the work W after quenching. and step S2. Cleaning steps S3 and S5 and inspection steps S4 and S6 are provided after the hardening step S1 and the tempering step S2, respectively. Part or all of these cleaning steps S3 and S5 and inspection steps S4 and S6 can be omitted as necessary. Alternatively, although not shown, a polishing step or the like may be added after the hardening step S1 or the tempering step S2, if necessary.

ここで、焼き戻し工程Ｓ２は、図２（ａ）に示すように、焼入れ後のワークＷを加熱する加熱工程Ｓ２１と、加熱したワークＷを冷却する冷却工程Ｓ２２とを備える。また、加熱工程Ｓ２１は、図２（ｂ）に示すように、ワークＷを誘導加熱により狙い温度ｒ１にまで加熱する昇温工程Ｓ２１１と、昇温後のワークＷを雰囲気加熱して、ワークＷの温度を狙い温度ｒ１にまで回復させる復温工程Ｓ２１２と、狙い温度ｒ１にまで回復させたワークＷを同じく雰囲気加熱により保温する保温工程Ｓ２１３とを有する。 Here, as shown in FIG. 2A, the tempering step S2 includes a heating step S21 for heating the workpiece W after quenching, and a cooling step S22 for cooling the heated workpiece W. Further, as shown in FIG. 2B, the heating step S21 includes a temperature raising step S211 in which the work W is heated to the target temperature r1 by induction heating, and an atmosphere heating of the work W after the temperature rise to A reheating step S212 for recovering the temperature of the workpiece W to the target temperature r1, and a heat retaining step S213 for keeping the work W recovered to the target temperature r1 warm by atmospheric heating.

図３は、図２に示す焼き戻し工程Ｓ２に使用する熱処理装置（焼き戻し装置１０）の正面図である。この焼き戻し装置１０は、搬送路１１上を所定の方向に搬送される複数のワークＷに対して連続的に焼き戻し処理を施すように構成されたもので、搬送路１１の上流側に配設される加熱装置１２と、加熱装置１２よりも搬送路１１の下流側に配設される冷却装置１３とを備える。以下、まず焼き戻し装置１０の構成について加熱装置１２を中心に説明し、次いで、この焼き戻し装置１０を用いた焼き戻し方法（焼き戻し工程Ｓ２）の一例を説明する。 FIG. 3 is a front view of a heat treatment apparatus (tempering apparatus 10) used in the tempering step S2 shown in FIG. The tempering device 10 is configured to continuously temper a plurality of works W conveyed in a predetermined direction on the conveying path 11 , and is arranged upstream of the conveying path 11 . and a cooling device 13 arranged downstream of the conveying path 11 from the heating device 12 . Hereinafter, the configuration of the tempering apparatus 10 will be described with a focus on the heating apparatus 12, and then an example of the tempering method (tempering step S2) using this tempering apparatus 10 will be described.

ここで、対象となるワークＷの形状は原則として任意であり、例えば環状をなすものであってもよい。また、ワークＷの材質についても原則任意であり、例えばＳＵＪ２等の高炭素クロム軸受鋼を挙げることができる。また、用途の面から見たワークＷの種類についても任意であり、例えば転がり軸受の外輪、内輪をはじめとして、滑り軸受、等速自在継手を構成する外側継手部材や内側継手部材、転がり軸受や等速自在継手に組み込まれる保持器（の基材）などが対象となり得る。本実施形態では、例えば転がり軸受の軌道輪（外輪又は内輪）が焼き戻し工程Ｓ２の対象となる。 Here, the shape of the target work W is in principle arbitrary, and may be, for example, an annular shape. Also, the material of the work W may be any material in principle, and examples thereof include high carbon chromium bearing steel such as SUJ2. In addition, the type of work W from the viewpoint of use is also arbitrary. (Base material of) a retainer incorporated in a constant velocity universal joint can be the target. In this embodiment, for example, the bearing ring (outer ring or inner ring) of the rolling bearing is subjected to the tempering step S2.

加熱装置１２は、搬送路１１の上流側から順に、昇温装置１４、復温装置１５、及び保温装置１６を有する。ここで、昇温装置１４は、例えばワークＷを一個ずつ加熱するためのもので、本実施形態では、図４に示すように、昇温装置１４は、搬送路１１上を所定の方向に搬送される複数のワークＷを一個ずつ支持可能な支持部１７と、支持部１７を昇降駆動する昇降部１８と、支持部１７の上方に位置する誘導加熱装置１９とを主に備える。誘導加熱装置１９は、例えば銅管等の導電性金属で環状に形成された加熱コイル２０（図５では二巻状の加熱コイル２０，２０を例示している）と、加熱コイル２０に電力を供給する電源２１とを有しており、昇降部１８により支持部１７を上昇させることで、支持部１７上に載置された状態のワークＷを加熱コイル２０の内周に導入可能としている。この場合、昇降部１８の中心線と、加熱コイル２０の中心線とが一致していることが望ましい。また、図示は省略するが、支持部１７と、支持部１７と連結される昇降部１８の一部が上記中心線まわりに回転できるように構成してもよい。また、同様に図示は省略するが、搬送路１１上を搬送されるワークＷを支持部１７上の所定位置で停止可能なように、搬送路１１又はその周囲の上面に対して出没可能なピンなどの位置決め部を設けてもよい。 The heating device 12 has a temperature increasing device 14 , a reheating device 15 and a heat retaining device 16 in order from the upstream side of the conveying path 11 . Here, the temperature raising device 14 is for heating the workpieces W one by one, for example. In this embodiment, as shown in FIG. It mainly includes a support portion 17 capable of supporting a plurality of workpieces W one by one, an elevating portion 18 that drives the support portion 17 up and down, and an induction heating device 19 positioned above the support portion 17 . The induction heating device 19 supplies electric power to the heating coil 20 (two heating coils 20, 20 are illustrated in FIG. The work W placed on the support portion 17 can be introduced into the inner circumference of the heating coil 20 by lifting the support portion 17 by the lifting portion 18 . In this case, it is desirable that the center line of the lifting section 18 and the center line of the heating coil 20 match. Although not shown, the supporting portion 17 and a part of the lifting portion 18 connected to the supporting portion 17 may be configured to be rotatable around the center line. Also, although not shown in the drawings, a pin that can protrude from the upper surface of the conveying path 11 or its surroundings so that the work W conveyed on the conveying path 11 can be stopped at a predetermined position on the support portion 17 You may provide positioning parts, such as.

上記構成の昇温装置１４は、例えば図４に示すように、誘導加熱装置１９等の周囲を囲む壁部２２をさらに有するものであってもよい。この場合、昇温装置１４内部の雰囲気温度を、図示しない所定の温度調整装置により調整することも可能となる。図４中、符号２３で示す部材は、搬送路１１の上流側で昇温装置１４の入口側開口部１４ａを開閉する第一開閉手段、符号２４で示す部材は、搬送路１１の下流側で昇温装置１４の出口側開口部１４ｂを開閉する第二開閉手段である。もちろん、特段の雰囲気温度制御が必要ない場合（例えば本実施形態のように、昇温工程Ｓ２１１の後に復温工程Ｓ２１２が設けられており、スムーズに保温工程Ｓ２１３に移行できる場合）には、壁部２２は不要である。 For example, as shown in FIG. 4, the temperature raising device 14 configured as described above may further include a wall portion 22 surrounding the induction heating device 19 and the like. In this case, it is also possible to adjust the ambient temperature inside the temperature raising device 14 by a predetermined temperature adjusting device (not shown). In FIG. 4, the member indicated by reference numeral 23 is the first opening/closing means for opening and closing the inlet side opening 14a of the temperature raising device 14 on the upstream side of the conveying path 11, and the member indicated by reference numeral 24 is on the downstream side of the conveying path 11. It is a second opening/closing means for opening/closing the exit side opening 14b of the temperature raising device 14 . Of course, when special atmospheric temperature control is not required (for example, as in the present embodiment, the warming step S212 is provided after the heating step S211, and the heat insulating step S213 can be smoothly performed), the wall Part 22 is unnecessary.

上記構成の昇温装置１４は、搬送路１１上で、復温装置１５と第一通路室２５を介してつながっている（図３を参照）。これにより、昇温装置１４内で昇温処理が施されたワークＷが第一通路室２５内を通って復温装置１５内に搬入されるようになっている。 The temperature raising device 14 configured as described above is connected to the reheating device 15 via the first passage chamber 25 on the conveying path 11 (see FIG. 3). As a result, the work W heated in the temperature raising device 14 is carried into the reheating device 15 through the first passage chamber 25 .

復温装置１５は、昇温後のワークＷを雰囲気加熱するためのもので、第一炉室２６と、第一炉室２６内に配設される第一ヒーター２７とを有する。第一ヒーター２７は、例えば電気ヒーターであり、第一炉室２６内の雰囲気（気体）を加熱する。これにより第一炉室２６内のワークＷに対する雰囲気加熱を可能としている。 The reheating device 15 is for atmospherically heating the workpiece W after the temperature has been raised, and has a first furnace chamber 26 and a first heater 27 arranged in the first furnace chamber 26 . The first heater 27 is, for example, an electric heater, and heats the atmosphere (gas) inside the first furnace chamber 26 . This enables atmospheric heating of the workpiece W in the first furnace chamber 26 .

保温装置１６は、復温装置１５により加熱されたワークＷを雰囲気加熱するためのもので、第二炉室２８と、第二炉室２８内に配設される第二ヒーター２９とを有する。第二ヒーター２９は、例えば電気ヒーターであり、第二炉室２８内の雰囲気（気体）を加熱する。これにより第二炉室２８内のワークＷに対する雰囲気加熱を可能としている。 The heat retaining device 16 is for atmospheric heating of the work W heated by the reheating device 15 , and has a second furnace chamber 28 and a second heater 29 arranged in the second furnace chamber 28 . The second heater 29 is, for example, an electric heater, and heats the atmosphere (gas) inside the second furnace chamber 28 . This enables atmosphere heating of the workpiece W in the second furnace chamber 28 .

また、復温装置１５の入口側開口部１５ａには、入口側開口部１５ａを開閉するための手段（第三開閉手段３０）が設けられると共に、復温装置１５の出口側開口部１５ｂには、出口側開口部１５ｂを開閉するための手段（第四開閉手段３１）が設けられている。これにより復温装置１５内の密閉性が担保される。もちろん、図示は省略するが、保温装置１６の入口側開口部（すなわち復温装置１５の出口側開口部１５ｂ）と出口側開口部にも開閉手段が設けられている。また、保温装置１６の入口側開口部は復温装置１５の出口側開口部１５ｂとなっているので（図４を参照）、保温装置１６内の密閉性が担保される。 Means (third opening/closing means 30) for opening and closing the inlet side opening 15a of the rewarming device 15 is provided at the inlet side opening 15a of the rewarming device 15, and the outlet side opening 15b of the rewarming device 15 is provided with , a means (fourth opening/closing means 31) for opening and closing the exit side opening 15b is provided. As a result, the airtightness inside the rewarming device 15 is ensured. Of course, although illustration is omitted, opening/closing means are also provided at the inlet-side opening of the heat retaining device 16 (that is, the outlet-side opening 15b of the rewarming device 15) and the outlet-side opening. Further, since the inlet side opening of the heat retaining device 16 is the outlet side opening 15b of the rewarming device 15 (see FIG. 4), the inside of the heat retaining device 16 is sealed.

以上の構成を有する加熱装置１２は、搬送路１１上で、冷却装置１３と第二通路室３２を介してつながっている（図３を参照）。これにより、加熱装置１２内で所定の加熱処理が施されたワークＷが第二通路室３２を通って冷却装置１３内に搬入されるようになっている。 The heating device 12 having the above configuration is connected to the cooling device 13 via the second passage chamber 32 on the transport path 11 (see FIG. 3). As a result, the workpiece W that has undergone a predetermined heat treatment in the heating device 12 is carried into the cooling device 13 through the second passage chamber 32 .

また、ワークＷを搬送路１１に沿って搬送するための手段としては任意であり、例えば図示は省略するが、加熱装置１２及び冷却装置１３の底部に跨るようにして配設された搬送コンベア、あるいは動力シリンダ（油圧シリンダ、エアシリンダ、電動シリンダ）などを採用することができる。 Any means for transporting the workpiece W along the transport path 11 may be used. Alternatively, a power cylinder (hydraulic cylinder, air cylinder, electric cylinder) or the like can be employed.

冷却装置１３は、加熱装置１２により所定の温度履歴を伴って加熱されたワークＷを冷却する冷却工程を実施するための装置であり、冷却の方式に応じた装置構成をとる。例えば空冷であれば冷却装置１３の内部空間は図示しない温度調整装置により所定の雰囲気温度に管理されており、冷却装置１３内に搬入されたワークＷが所定の冷却速度で所定の温度まで冷却される。あるいは、水冷であれば冷却装置１３は図示しない冷却液の液槽を有しており、冷却装置１３内に搬入されたワークＷを冷却液中に浸漬することで所定の冷却速度で所定の温度まで冷却される。 The cooling device 13 is a device for performing a cooling step of cooling the work W heated with a predetermined temperature history by the heating device 12, and has a device configuration corresponding to the cooling method. For example, in the case of air cooling, the internal space of the cooling device 13 is controlled at a predetermined ambient temperature by a temperature control device (not shown), and the work W carried into the cooling device 13 is cooled to a predetermined temperature at a predetermined cooling rate. be. Alternatively, in the case of water cooling, the cooling device 13 has a liquid tank of cooling liquid (not shown). cooled to

次に、焼き戻し処理の温度条件（温度履歴）について、図４を参照しながら図６にて説明する。 Next, the temperature conditions (temperature history) of the tempering process will be described with reference to FIG. 6 while referring to FIG.

本発明に係る焼き戻し方法（焼き戻し工程Ｓ２）では、図６に示すように、昇温開始時温度ｒ０から狙い温度ｒ１まで誘導加熱によりワークＷを昇温する（昇温工程Ｓ２１１）。この際、昇温速度は例えば一定とし、加熱開始時から時間が経過するにつれて温度が上昇するようにワークＷを連続的に加熱する。このような温度履歴は、例えばワークＷが狙い温度ｒ１に到達するまでの間（昇温開始時ｔ０から昇温終了時ｔ１までの間）、誘導加熱装置１９の昇温工程Ｓ２１１時の出力（昇温時出力）を一定の値に維持することで実現できる。 In the tempering method (tempering step S2) according to the present invention, as shown in FIG. 6, the workpiece W is heated by induction heating from a temperature r0 at the start of heating to a target temperature r1 (heating step S211). At this time, the temperature rise rate is, for example, constant, and the workpiece W is continuously heated so that the temperature increases as time elapses from the start of heating. Such a temperature history includes, for example, the output ( This can be achieved by maintaining the temperature rising output) at a constant value.

次に、狙い温度ｒ１まで加熱（昇温）した後のワークＷに対して雰囲気加熱を施し、当該ワークＷの温度を復温開始時温度ｒ２から狙い温度ｒ１にまで回復させる（復温工程Ｓ２１２）。昇温工程Ｓ２１１と保温工程Ｓ２１３とは互いに異なる加熱方式の装置（誘導加熱装置１９と雰囲気加熱装置としての第二炉室２８及び第二ヒーター２９）により行われるため、昇温工程Ｓ２１１から保温工程Ｓ２１３に移行するまでの間に、ワークＷの温度が狙い温度ｒ１から時間の経過と共に低下する。そこで、昇温工程Ｓ２１１を終えたワークＷを復温装置１５内（図４を参照）に搬入し、雰囲気加熱によりワークＷの温度を狙い温度ｒ１にまで回復させる。このような温度履歴は、例えばワークＷが復温開始時温度ｒ２から狙い温度ｒ１に到達するまでの間（復温開始時ｔ２から復温終了時ｔ３までの間）、復温装置１５の第一ヒーター２７（図４を参照）で第一炉室２６内の雰囲気温度が狙い温度ｒ１よりも少し高い温度（例えば狙い温度ｒ１＋２０～狙い温度ｒ１＋３０℃）となるよう雰囲気加熱することによって実現できる。 Next, the workpiece W heated (heated) to the target temperature r1 is subjected to atmospheric heating to restore the temperature of the workpiece W from the temperature r2 at the start of reheating to the target temperature r1 (reheating step S212). ). Since the temperature raising step S211 and the heat retaining step S213 are performed by different heating methods (the induction heating device 19 and the second furnace chamber 28 and the second heater 29 as the atmosphere heating device), the temperature increasing step S211 to the heat retaining step are performed. The temperature of the workpiece W decreases from the target temperature r1 with the lapse of time until the process proceeds to S213. Therefore, the work W that has undergone the temperature raising step S211 is carried into the reheating device 15 (see FIG. 4), and the temperature of the work W is restored to the target temperature r1 by atmospheric heating. For example, the temperature history of the work W reaches the target temperature r1 from the reheating start temperature r2 (from the reheating start time t2 to the reheating end time t3). It can be realized by heating the atmosphere in the first furnace chamber 26 with one heater 27 (see FIG. 4) so that the atmosphere temperature in the first furnace chamber 26 is slightly higher than the target temperature r1 (for example, the target temperature r1+20 to the target temperature r1+30° C.).

このようにしてワークＷの温度を狙い温度ｒ１にまで回復させた後、当該ワークＷに雰囲気加熱を施し、狙い温度ｒ１を含む所定幅の温度域、具体的にはワークＷに要求される残留オーステナイト量及び硬さに応じて設定される許容温度域Ｒの範囲内で復温後のワークＷを所定時間の間保温する（保温工程Ｓ２１３）。本実施形態では、保温開始時ｔ３から保温終了時ｔ４までの間、ワークＷがほぼ狙い温度ｒ１に等しい温度を保つよう、ワークＷの雰囲気加熱を制御する。このような温度履歴は、例えば保温開始時ｔ３から保温終了時ｔ４までの間、保温装置１６の第二ヒーター２９（図４を参照）で第二炉室２８内の雰囲気温度が狙い温度ｒ１にほぼ等しい状態を維持できるよう雰囲気加熱することによって実現できる。 After the temperature of the work W is recovered to the target temperature r1 in this way, the work W is subjected to atmosphere heating, and the temperature range of a predetermined width including the target temperature r1, specifically, the residual required for the work W. The work W after rewarming is kept warm for a predetermined time within the allowable temperature range R set according to the amount of austenite and hardness (heat keeping step S213). In this embodiment, the atmospheric heating of the workpiece W is controlled so that the temperature of the workpiece W is maintained substantially equal to the target temperature r1 from the start of heat retention t3 to the end of heat retention t4. In such a temperature history, for example, from the start of heat retention t3 to the end of heat retention t4, the second heater 29 (see FIG. 4) of the heat retention device 16 raises the ambient temperature in the second furnace chamber 28 to the target temperature r1. It can be realized by heating the atmosphere so as to maintain a substantially equal state.

ここで、許容温度域Ｒは、例えば以下のようにして設定される。まず、ワークＷの昇温時の狙い温度ｒ１を変化させたときのワークＷの熱処理後（焼き戻し後）の残留オーステナイト量を測定する。そして、測定した残留オーステナイト量と狙い温度ｒ１との関係に基づき、残留オーステナイト量が許容範囲内に収まる第一温度下限値を設定する。本実施形態では、図７（ａ）に示すように、測定した複数の残留オーステナイト量の値に基づいて、狙い温度ｒ１と残留オーステナイト量との関係を示す近似曲線Ｃ１，Ｃ２を導出する。図７（ａ）において、Ｃ１は、残留オーステナイト量の測定値のばらつきを考慮した場合のばらつきの上限側の近似曲線を示しており、Ｃ２は、残留オーステナイト量の測定値のばらつきの下限側の近似曲線を示している。ここで、例えば残留オーステナイト量の許容上限値をＱ１とした場合、上限側近似曲線Ｃ１に基づき、許容上限値Ｑ１に対応する狙い温度ｒａ１を算出する。この狙い温度ｒａ１よりも高い温度域Ｒ１が、残留オーステナイト量が許容範囲内に収まる温度域（第一許容温度域）であり、その際の狙い温度ｒａ１が本発明でいう第一温度下限値となる。 Here, the allowable temperature range R is set, for example, as follows. First, the retained austenite amount of the work W after heat treatment (after tempering) is measured while changing the target temperature r1 when the work W is heated. Then, based on the relationship between the measured amount of retained austenite and the target temperature r1, the first temperature lower limit is set so that the amount of retained austenite falls within the allowable range. In this embodiment, as shown in FIG. 7A, approximate curves C1 and C2 representing the relationship between the target temperature r1 and the amount of retained austenite are derived based on the measured values of the amount of retained austenite. In FIG. 7(a), C1 shows an approximate curve on the upper limit side of the variation when considering the variation in the measured value of the retained austenite amount, and C2 shows the lower limit side of the variation in the measured value of the retained austenite amount. An approximation curve is shown. Here, for example, when the allowable upper limit value of the amount of retained austenite is set to Q1, the target temperature ra1 corresponding to the allowable upper limit value Q1 is calculated based on the upper approximated curve C1. The temperature range R1 higher than the target temperature ra1 is the temperature range (first allowable temperature range) in which the amount of retained austenite falls within the allowable range, and the target temperature ra1 at that time is the first temperature lower limit value in the present invention. Become.

次に、ワークＷの昇温時の狙い温度ｒ１を変化させたときのワークＷの熱処理後（焼き戻し後）の硬さを測定する。硬さの種類は特に問わないが、例えばロックウェル硬さを測定する。そして、測定した硬さと狙い温度ｒ１との関係に基づき、硬さが許容範囲内に収まる第二温度上限値及び第二温度下限値を設定する。本実施形態では、図７（ｂ）に示すように、測定した複数の硬さの値に基づいて、狙い温度ｒ１と硬さとの関係を示す近似曲線Ｃ３，Ｃ４を導出する。図７（ｂ）において、Ｃ３は、硬さの測定値のばらつきを考慮した場合のばらつきの上限側の近似曲線を示しており、Ｃ４は、硬さの測定値のばらつきの下限側の近似曲線を示している。ここで、例えば硬さの許容上限値をＨ１、許容下限値をＨ２とした場合、上限側近似曲線Ｃ３に基づき、許容上限値Ｈ１に対応する狙い温度ｒｂ１を算出する。また、下限側近似曲線Ｃ４に基づき、許容下限値Ｈ２に対応する狙い温度ｒｂ２を算出する。これら狙い温度ｒｂ１，ｒｂ２の間の温度域Ｒ２が、硬さが許容範囲内に収まる温度域（第二許容温度域）であり、またその際の狙い温度ｒｂ１，ｒｂ２がそれぞれ本発明でいう第二温度上限値と第二温度下限値となる。 Next, the hardness of the work W after heat treatment (after tempering) is measured while changing the target temperature r1 when the temperature of the work W is raised. Although the type of hardness is not particularly limited, for example, Rockwell hardness is measured. Then, based on the relationship between the measured hardness and the target temperature r1, a second temperature upper limit and a second temperature lower limit are set so that the hardness falls within the allowable range. In this embodiment, as shown in FIG. 7B, approximate curves C3 and C4 representing the relationship between target temperature r1 and hardness are derived based on a plurality of measured hardness values. In FIG. 7(b), C3 shows an approximate curve on the upper limit side of the variation when considering the variation in the measured hardness values, and C4 shows an approximate curve on the lower limit side of the variation in the measured hardness values. is shown. Here, for example, if the allowable upper limit value of hardness is H1 and the allowable lower limit value is H2, the target temperature rb1 corresponding to the allowable upper limit value H1 is calculated based on the upper approximated curve C3. Also, the target temperature rb2 corresponding to the allowable lower limit value H2 is calculated based on the lower approximated curve C4. A temperature range R2 between these target temperatures rb1 and rb2 is a temperature range (second allowable temperature range) in which the hardness falls within the allowable range, and the target temperatures rb1 and rb2 at that time are the second temperature range referred to in the present invention, respectively. There are two temperature upper limits and second temperature lower limits.

このように、残留オーステナイト量が許容範囲内に収まる第一許容温度域Ｒ１と、硬さが許容範囲内に収まる第二許容温度域Ｒ２とを求めた後、第一許容温度域Ｒ１と第二許容温度域Ｒ２とが重複する範囲内で、許容温度域Ｒ（図６を参照）を設定する。本実施形態の場合、図７（ｃ）に示すように、第一許容温度域Ｒ１と第二許容温度域Ｒ２とが重複する範囲全体を許容温度域Ｒとしている。このようにして、保温時の許容温度域Ｒが設定され得る。この場合、狙い温度ｒ１は、許容温度域Ｒの範囲内で設定される。 Thus, after obtaining the first allowable temperature range R1 in which the amount of retained austenite falls within the allowable range and the second allowable temperature range R2 in which the hardness falls within the allowable range, the first allowable temperature range R1 and the second A permissible temperature range R (see FIG. 6) is set within a range overlapping with the permissible temperature range R2. In this embodiment, as shown in FIG. 7(c), the allowable temperature range R is the entire range where the first allowable temperature range R1 and the second allowable temperature range R2 overlap. In this manner, the allowable temperature range R during heat retention can be set. In this case, the target temperature r1 is set within the allowable temperature range R.

そして、最後に、許容温度域Ｒの範囲内で所定時間の間保温されたワークＷを冷却する。本実施形態では、雰囲気加熱装置（保温装置１６）の第二炉室２８からワークＷを搬出し、第二通路室３２を通って冷却装置１３に搬送する（図３を参照）。これにより、ワークＷを所定の冷却速度で所定の温度ｒ５まで冷却し、ワークＷに焼き戻し処理を施す（冷却工程Ｓ２２）。 Finally, the workpiece W kept warm within the allowable temperature range R for a predetermined time is cooled. In this embodiment, the work W is unloaded from the second furnace chamber 28 of the atmosphere heating device (thermal insulation device 16) and transferred to the cooling device 13 through the second passage chamber 32 (see FIG. 3). As a result, the work W is cooled to a predetermined temperature r5 at a predetermined cooling rate, and the work W is tempered (cooling step S22).

本実施形態では、例えば上述した温度履歴を辿るように、誘導加熱装置１９の出力パターンと第一及び第二ヒーター２７，２９の出力パターンをそれぞれ制御部３３（図４を参照）に記憶させておき、加熱工程Ｓ２１（昇温工程Ｓ２１１、復温工程Ｓ２１２、保温工程Ｓ２１３）及び冷却工程Ｓ２２において、上記記憶させておいた出力パターンに基づいて制御部３３が電源２１に指令を送る。これにより、電源２１に接続された誘導加熱装置１９の加熱コイル２０（図４及び図５を参照）と、同じく電源２１に接続された第一及び第二ヒーター２７，２９に所定パターンの電力が供給され、図６に示す温度履歴をワークＷに付与し得る。 In this embodiment, for example, the output pattern of the induction heating device 19 and the output patterns of the first and second heaters 27 and 29 are stored in the control unit 33 (see FIG. 4) so as to follow the temperature history described above. Then, in the heating step S21 (heating step S211, warming step S212, heat retaining step S213) and cooling step S22, the controller 33 sends a command to the power source 21 based on the stored output pattern. As a result, the heating coil 20 (see FIGS. 4 and 5) of the induction heating device 19 connected to the power supply 21 and the first and second heaters 27 and 29 similarly connected to the power supply 21 are supplied with a predetermined pattern of electric power. The temperature history shown in FIG. 6 can be applied to the workpiece W.

次に、上記構成の焼き戻し装置１０を用いたワークＷの焼き戻し工程Ｓ２の一例を説明する。 Next, an example of the tempering process S2 of the workpiece W using the tempering apparatus 10 having the above configuration will be described.

（Ｓ２１）加熱工程
（Ｓ２１１）昇温工程
この工程では、まず図４に示す第一開閉手段２３により昇温装置１４の入口側開口部１４ａを開口した状態で、搬送路１１上を所定の方向に搬送されるワークＷを昇温装置１４の内部に搬入する。この時点では、支持部１７の上面は、搬送路１１と同一平面レベルにある。また、誘導加熱装置１９の出力は零もしくは零に近いレベルにある。そして、ワークＷが支持部１７上に到達すると、必要に応じてワークＷの支持部１７に対する水平方向の位置決めを伴って、昇降部１８により支持部１７を上昇させる。これにより、支持部１７上に載置された状態のワークＷが誘導加熱装置１９の所定位置、本実施形態では誘導加熱装置１９の加熱コイル２０の内周所定位置に導入され、保持される（図４を参照）。この状態で、制御部３３は電源２１に指令を送り、加熱コイル２０に所定パターンの電力を供給することにより、ワークＷの加熱を開始し、ワークＷを狙い温度ｒ１にまで一定の勾配で加熱する（図６を参照）。上述した誘導加熱は、いわゆる低周波域（～数ｋＨｚ）で実施するのがよい。これによりワークＷの表層部だけでなく芯部まで高温に加熱することができる。なお、この間（昇温開始時ｔ０から昇温終了時ｔ１までの間）、ワークＷの温度が許容温度域Ｒの上限（許容温度上限値ｒ３）を超えないように、制御部３３によりワークＷの加熱を制御するのがよい。この場合、狙い温度ｒ１は、許容温度域Ｒの範囲内（許容温度下限値ｒ４以上でかつ許容温度上限値ｒ３以下）に設定される。また、加熱している間、支持部１７を制御部３３により軸回転させて昇温させてもよい。支持部１７を軸回転させることによって支持部１７上のワークＷ全体が均等に昇温される。 (S21) Heating step (S211) Temperature raising step In this step, first, the first opening/closing means 23 shown in FIG. is carried into the temperature raising device 14 . At this point, the upper surface of the support portion 17 is on the same plane level as the transport path 11 . Also, the output of the induction heating device 19 is at a level of zero or close to zero. When the work W reaches the support portion 17 , the support portion 17 is lifted by the elevating portion 18 while horizontally positioning the work W with respect to the support portion 17 as necessary. As a result, the workpiece W placed on the support portion 17 is introduced to a predetermined position of the induction heating device 19, in this embodiment, to a predetermined position on the inner circumference of the heating coil 20 of the induction heating device 19, and is held ( See Figure 4). In this state, the control unit 33 sends a command to the power supply 21 to supply a predetermined pattern of electric power to the heating coil 20, thereby starting to heat the work W and heating the work W to the target temperature r1 at a constant gradient. (see Figure 6). The induction heating described above is preferably performed in a so-called low frequency range (up to several kHz). As a result, not only the surface layer of the work W but also the core can be heated to a high temperature. During this period (from the temperature rise start time t0 to the temperature rise end time t1), the temperature of the work W is controlled by the control unit 33 so that the temperature of the work W does not exceed the upper limit of the allowable temperature range R (allowable temperature upper limit value r3). heating should be controlled. In this case, the target temperature r1 is set within the allowable temperature range R (above the allowable temperature lower limit value r4 and below the allowable temperature upper limit value r3). Further, during the heating, the support portion 17 may be axially rotated by the control portion 33 to raise the temperature. By axially rotating the support portion 17, the temperature of the entire workpiece W on the support portion 17 is uniformly raised.

（Ｓ２１２）復温工程
このようにしてワークＷを狙い温度ｒ１まで昇温した後、ワークＷを誘導加熱装置１９の加熱処理位置（加熱コイル２０の内周所定位置）から離脱させ、開口状態にある出口側開口部１４ｂを通って昇温装置１４外に搬出する。具体的には、制御部３３が電源２１に指令を送り、誘導加熱装置１９によるワークＷの加熱を停止すると共に、昇降部１８により支持部１７を降下させて、支持部１７上のワークＷを搬送路１１上に復帰させる。そして、第二開閉手段２４により昇温装置１４の出口側開口部１４ｂを開口した状態で、図示しない適当な手段で搬送路１１上を所定の方向に搬送し、昇温装置１４内からワークＷを搬出する。そして、搬出したワークＷを、第一通路室２５を介して、復温装置１５の第一炉室２６内へ搬入し、ワークＷに対して所定の雰囲気加熱を施す。これにより、昇温後、昇温終了時ｔ１から復温開始時ｔ２までの間に温度ｒ２まで温度低下を生じていたワークＷ（図６を参照）の温度を狙い温度ｒ１にまで回復させる。この際、復温装置１５の入口側開口部１５ａは一旦開き、ワークＷが復温装置１５内に搬入された後、閉じる。なお、この間（復温開始時ｔ２から復温終了時ｔ３までの間）も、ワークＷの温度が許容温度域Ｒの上限（許容温度上限値ｒ３）を超えないように、制御部３３によりワークＷの加熱を制御するのがよい。 (S212) Reheating step After heating the work W to the target temperature r1 in this manner, the work W is removed from the heat treatment position of the induction heating device 19 (predetermined position on the inner circumference of the heating coil 20), and is opened. It is transported out of the temperature raising device 14 through a certain outlet side opening 14b. Specifically, the control unit 33 sends a command to the power source 21 to stop the heating of the workpiece W by the induction heating device 19, and the lifting unit 18 lowers the support unit 17 to lift the workpiece W on the support unit 17. It is returned to the conveying path 11 . Then, with the outlet side opening 14b of the temperature raising device 14 opened by the second opening/closing means 24, the work W is conveyed in a predetermined direction on the conveying path 11 by an appropriate means (not shown), and the work W is removed from the temperature raising device 14. to carry out. Then, the work W carried out is carried into the first furnace chamber 26 of the reheating device 15 via the first passage chamber 25, and the work W is heated in a predetermined atmosphere. As a result, the temperature of the workpiece W (see FIG. 6), which had dropped to temperature r2 between the end of temperature rise t1 and the start of reheating t2 after the temperature rise, is restored to target temperature r1. At this time, the entrance side opening 15a of the rewarming device 15 is once opened, and after the workpiece W is carried into the rewarming device 15, it is closed. During this period (from t2 when reheating starts to t3 when reheating ends), the control unit 33 controls the work W so that the temperature of the work W does not exceed the upper limit of the allowable temperature range R (allowable temperature upper limit value r3). The heating of W should be controlled.

（Ｓ２１３）保温工程
このようにしてワークＷを再び狙い温度ｒ１にまで加熱した後、出口側開口部１５ｂを開けてワークＷを復温装置１５外に搬出し、隣接する保温装置１６内に搬入する。この際、保温装置１６の入口側開口部（すなわち復温装置１５の出口側開口部１５ｂ）は一旦開き、ワークＷが保温装置１６内に搬入された後、閉じる。そして、ワークＷに雰囲気加熱を施して、許容温度域Ｒの範囲内で当該ワークＷを所定時間の間、保温する。なお、この間（保温開始時ｔ３から保温終了時ｔ４までの間）、ワークＷの温度が許容温度域Ｒの範囲内に維持されるように（許容温度上限値ｒ３以下でかつ許容温度下限値ｒ４以上であるように）、制御部３３によりワークＷの加熱を制御するのがよいが、この間の加熱は電気ヒーター（第二ヒーター２９）による雰囲気加熱で行われるため、上述の温度制御は比較的容易である。なお、一例として、ワークＷの材質が高炭素クロム軸受鋼である場合、許容温度域Ｒは２９０℃以上でかつ３４０℃以下の範囲内で設定され、好ましくは３０３℃以上でかつ３１５℃以下の範囲内で設定される。また、ワークＷの保温時間（保温開始時ｔ３から保温終了時ｔ４までの間）は３分以上でかつ７分以下の範囲内で設定され、好ましくは４分以上でかつ６分以下の範囲内で設定される。 (S213) Heat Retention Process After heating the work W to the target temperature r1 again in this manner, the exit side opening 15b is opened to carry the work W out of the reheating device 15 and into the adjacent heat retention device 16. do. At this time, the entrance side opening of the heat retaining device 16 (that is, the exit side opening 15b of the rewarming device 15) is once opened, and after the workpiece W is carried into the heat retaining device 16, it is closed. Then, the work W is heated in the atmosphere, and the work W is kept warm within the allowable temperature range R for a predetermined time. During this period (from the start of heat retention t3 to the end of heat retention t4), the temperature of the workpiece W is maintained within the allowable temperature range R (below the allowable temperature upper limit r3 and the allowable temperature lower limit r4 As described above), it is preferable to control the heating of the work W by the control unit 33, but since the heating during this time is performed by atmospheric heating by the electric heater (second heater 29), the above-mentioned temperature control is relatively Easy. As an example, when the material of the workpiece W is high carbon chromium bearing steel, the allowable temperature range R is set within the range of 290° C. or higher and 340° C. or lower, preferably 303° C. or higher and 315° C. or lower. Set within the range. In addition, the heat retention time of the workpiece W (from the heat retention start time t3 to the heat retention end time t4) is set within the range of 3 minutes or more and 7 minutes or less, preferably 4 minutes or more and 6 minutes or less. is set by

（Ｓ２２）冷却工程
このようにして所定時間の間ワークＷの保温を行った後、図示しない出口側開口部を開けてワークＷを保温装置１６外に搬出する。搬出されたワークＷは、第二通路室３２を通って冷却装置１３内に搬入され（図３を参照）、所定の冷却速度で所定の温度ｒ５、例えば昇温開始時温度ｒ０よりも低い温度にまで冷却される（冷却終了時ｔ５）。これにより、ワークＷに対する焼き戻し処理が完了する。後続のワークＷについても同様の経路を辿って、焼き戻し処理が施され、焼き戻し装置１０の外側に排出される。排出されたワークＷは例えば洗浄工程Ｓ５あるいは研磨工程（図示は省略）など次の工程へ搬送される。以上のようにして、複数のワークＷに対して連続的にかつ自動的に焼き戻し処理が施される。 (S22) Cooling Step After the work W is kept warm for a predetermined period of time in this manner, the work W is carried out of the heat retaining device 16 by opening an exit-side opening (not shown). The unloaded workpiece W is carried into the cooling device 13 through the second passage chamber 32 (see FIG. 3), and cooled at a predetermined cooling rate to a predetermined temperature r5, for example, a temperature lower than the temperature r0 at the start of heating. (cooling end time t5). Thereby, the tempering process for the workpiece W is completed. The subsequent work W is subjected to the tempering process along the same route and discharged outside the tempering device 10 . The discharged work W is conveyed to the next process such as a cleaning process S5 or a polishing process (not shown). As described above, a plurality of works W are continuously and automatically tempered.

以上述べたように、本発明に係る焼き戻し方法によれば、誘導加熱でワークＷを狙い温度ｒ１にまで加熱するようにしたので（昇温工程Ｓ２１１）、従来よりも短時間でワークＷを必要な温度域（例えば２５０℃以上）にまで加熱することができる。また、本発明では、ワークＷに要求される残留オーステナイト量及び硬さに応じて許容温度域Ｒを設定し、この許容温度域Ｒ内で昇温後のワークＷを保温するようにしたので、短時間で昇温しつつも、焼き戻し処理後のワークＷに含まれる残留オーステナイト量を所要レベル以下にまで低減化し、かつワークＷの硬さを所定範囲内に収めることが可能となる。また、ワークＷを上記温度域Ｒ内で保温するための加熱制御を、雰囲気加熱により実施するようにしたので、ワークＷを均等に加熱しながらワークＷを保温することができる。よって、ワークＷ内部の温度のばらつきを抑えて、均質な焼き戻し処理を施すことができる。また、雰囲気加熱であれば、誘導加熱等と比べてワークＷの温度が下がりにくい。そのため、保温工程Ｓ２１３時の加熱制御も比較的容易に行うことができる。もちろん、雰囲気加熱であれば、一度に大量のワークＷを処理することができる。以上より、本発明によれば、ワークＷに含まれる残留オーステナイト量を所要レベル以下にまで低減化できると共に、ワークＷの硬さを所定範囲内に収めることができるので、高温環境下での使用にも適した機械部品を得ることができる。また、昇温に要する時間が短くて済み、比較的短時間で多くのワークＷに均質な処理を施すことができるので、生産性にも優れている。もちろん、昇温工程Ｓ２１１から保温工程Ｓ２１３までの熱処理を全て雰囲気加熱炉で行う場合と比べて、設備も小型化できる。 As described above, according to the tempering method according to the present invention, the workpiece W is heated to the target temperature r1 by induction heating (heating step S211), so that the workpiece W can be heated in a shorter time than conventionally. It can be heated to a required temperature range (for example, 250° C. or higher). In addition, in the present invention, the allowable temperature range R is set according to the amount of retained austenite and hardness required for the work W, and the work W after the temperature rise is kept warm within this allowable temperature range R. While raising the temperature in a short time, it is possible to reduce the amount of retained austenite contained in the work W after tempering to a required level or less, and keep the hardness of the work W within a predetermined range. Further, since the heating control for keeping the work W within the above temperature range R is performed by atmospheric heating, the work W can be kept warm while being uniformly heated. Therefore, uniform tempering treatment can be performed while suppressing variations in temperature inside the work W. Further, if the atmosphere heating is used, the temperature of the workpiece W is less likely to drop than if the induction heating is used. Therefore, it is possible to relatively easily perform heating control during the heat retention step S213. Of course, if atmospheric heating is used, a large number of workpieces W can be processed at once. As described above, according to the present invention, the amount of retained austenite contained in the work W can be reduced to a required level or less, and the hardness of the work W can be kept within a predetermined range, so that it can be used in a high-temperature environment. It is possible to obtain mechanical parts suitable for In addition, the time required for temperature rise is short, and many workpieces W can be uniformly treated in a relatively short period of time, resulting in excellent productivity. Of course, compared with the case where all the heat treatments from the temperature raising step S211 to the heat retaining step S213 are performed in the atmosphere heating furnace, the equipment can be made smaller.

また、本実施形態では、昇温工程Ｓ２１１の後でかつ保温工程Ｓ２１３の前に、昇温後のワークＷを雰囲気加熱して、昇温時の狙い温度ｒ１までワークＷの温度を回復させる復温工程Ｓ２１２をさらに設けるようにしたので、ワークＷの温度を復温装置１５搬入時の温度ｒ２から狙い温度ｒ１にまで戻した状態で保温工程Ｓ２１３に移行させることができる（図６を参照）。また、復温工程Ｓ２１２と保温工程Ｓ２１３ともに雰囲気加熱でワークＷを加熱することで、復温工程Ｓ２１２から保温工程Ｓ２１３に移行する際の温度低下を抑制できる。そのため、復温工程Ｓ２１２を設けることで、ワークＷを効率よく保温工程Ｓ２１３に移行することができる。 Further, in the present embodiment, after the temperature raising step S211 and before the heat retaining step S213, the work W after the temperature rise is atmospherically heated to recover the temperature of the work W to the target temperature r1 at the time of temperature rise. Since the warming step S212 is further provided, the temperature of the work W can be returned to the target temperature r1 from the temperature r2 when the rewarming device 15 was brought in, and then the heat insulating step S213 can be performed (see FIG. 6). . Further, by heating the work W by atmospheric heating in both the rewarming step S212 and the heat retaining step S213, it is possible to suppress the temperature drop when shifting from the rewarming step S212 to the heat retaining step S213. Therefore, by providing the rewarming step S212, the work W can be efficiently transferred to the heat retaining step S213.

また、この場合、復温工程Ｓ２１２で、雰囲気加熱の設定温度を、昇温時の狙い温度ｒ１よりも少し高く設定しておくことで（例えば狙い温度＋２０～狙い温度＋３０℃）、復温に要する時間を短くできる。また、復温装置１５と保温装置１６とは内部空間が別個に密閉された状態にあるため、個々の雰囲気温度を異ならせることも容易である。 Also, in this case, in the reheating step S212, by setting the set temperature of the atmosphere heating slightly higher than the target temperature r1 at the time of heating (for example, target temperature +20 to target temperature +30 ° C.), The time required can be shortened. In addition, since the internal spaces of the rewarming device 15 and the heat retaining device 16 are separately sealed, it is easy to vary the ambient temperature of each.

以上、本発明の第一実施形態に係る焼き戻し方法及び焼き戻し装置１０について説明したが、焼き戻し装置１０には、本発明の要旨を逸脱しない範囲で適宜の変更を施すことが可能である。 Although the tempering method and the tempering apparatus 10 according to the first embodiment of the present invention have been described above, the tempering apparatus 10 can be appropriately modified without departing from the gist of the present invention. .

例えば、図８に示すように、ワークＷの表面に複数の温度測定点ｗ１～ｗ６を設けて、誘導加熱によりこれら複数の温度測定点ｗ１～ｗ６のうち最も昇温し易い易昇温点を予め求めておき、特に昇温工程Ｓ２１１で、易昇温点の温度が許容温度域Ｒの上限（許容温度上限値ｒ３）を超えないように、ワークＷの加熱を制御してもよい。これにより、ワークＷが部分的に過剰に加熱される事態を回避することができるので、ワークＷの熱処理後の硬さをその全域にわたって均質化しつつ許容範囲内に収めて、より高精度な焼き戻し処理を行うことが可能となる。 For example, as shown in FIG. 8, a plurality of temperature measurement points w1 to w6 are provided on the surface of the workpiece W, and the easiest temperature rise point is selected from among the plurality of temperature measurement points w1 to w6 by induction heating. The heating of the workpiece W may be controlled in advance so that the temperature at the easy heating point does not exceed the upper limit of the allowable temperature range R (allowable temperature upper limit value r3), particularly in the temperature raising step S211. As a result, it is possible to avoid a situation in which the work W is partially excessively heated, so that the hardness of the work W after the heat treatment is homogenized over the entire area and is kept within an allowable range, thereby achieving a more accurate firing. It is possible to perform return processing.

また、上記実施形態では、昇温工程Ｓ２１１でワークＷが許容温度域Ｒの上限を超えることなく当該ワークＷを狙い温度ｒ１にまで加熱し得る誘導加熱の出力パターンを予め制御部３３に記憶させておき、昇温工程Ｓ２１１で、記憶させておいた上記出力パターンに基づいてワークＷの加熱を制御する場合を例示したが、これとは異なる制御方式をとることも可能である。例えば図示は省略するが、加熱装置１２内に設けた温度測定装置（熱電対など）でワークＷの表面温度を測定しながらワークＷを昇温し、かつ測定した温度に基づいてその都度制御部３３が適切な出力の指令を電源２１に送ることで、ワークＷの昇温を制御してもよい。これによれば、ワークＷごとのばらつきを反映したより精密な加熱制御が可能となる。この際、上述したワークＷの易昇温点の温度を測定しながらワークＷの昇温を制御してもよい。 Further, in the above-described embodiment, in the temperature raising step S211, the output pattern of the induction heating that can heat the work W to the target temperature r1 without exceeding the upper limit of the allowable temperature range R is stored in the control unit 33 in advance. In the heating step S211, the heating of the workpiece W is controlled based on the stored output pattern, but a different control method can be used. For example, although illustration is omitted, the temperature of the work W is increased while measuring the surface temperature of the work W with a temperature measuring device (such as a thermocouple) provided in the heating device 12, and based on the measured temperature, the control unit 33 may control the temperature rise of the workpiece W by sending an appropriate output command to the power supply 21 . According to this, more precise heating control that reflects variations for each work W can be performed. At this time, the temperature rise of the work W may be controlled while measuring the temperature of the work W at the easy temperature rise point described above.

もちろん、上述の制御方式は復温工程Ｓ２１２及び保温工程Ｓ２１３にも適用し得る。すなわち、同様に図示は省略するが、加熱装置１２内に設けた温度測定装置でワークＷの表面温度を測定しながらワークＷを加熱保温し、かつ測定した温度に基づいてその都度制御部３３が適切な出力の指令を電源２１に送ることで、ワークＷの加熱保温を制御してもよい。 Of course, the control method described above can also be applied to the rewarming step S212 and the heat retaining step S213. That is, although not shown in the drawings, the work W is heated and kept warm while measuring the surface temperature of the work W with a temperature measuring device provided in the heating device 12, and based on the measured temperature, the control unit 33 is operated each time. By sending an appropriate output command to the power supply 21, heating and keeping of the workpiece W may be controlled.

また、上記実施形態では、誘導加熱装置１９によりワークＷを一個ずつ加熱（昇温及び保温）する場合を例示したが、これ以外の方式を採ることも可能である。例えば図示は省略するが、縦積みした状態の二個以上のワークＷを一度に上昇させて、例えば三巻以上の加熱コイルを有する誘導加熱装置の所定位置（三巻以上の加熱コイルの内周）に二個以上のワークをまとめて導入する。そして、上記構成の誘導加熱装置を起動することにより、二個以上のワークＷに対して一度に昇温工程Ｓ２１１を実施する。このように加熱処理を施すことで、更なる生産性の向上を図ることが可能となる。なお、ワークＷの縦積み方向位置によって異なる出力パターンが必要となる場合には、複数ある加熱コイルのうち一部の加熱コイルを残りの加熱コイルと別個独立して加熱制御してもよい。 Further, in the above embodiment, the induction heating device 19 heats (heats and keeps) the workpieces W one by one, but other methods can be adopted. For example, although illustration is omitted, two or more vertically stacked workpieces W are raised at a time to a predetermined position of an induction heating device having, for example, three or more heating coils (the inner circumference of the three or more heating coils ) to introduce two or more workpieces together. Then, by activating the induction heating device having the above configuration, two or more workpieces W are subjected to the temperature raising step S211 at once. By performing the heat treatment in this manner, productivity can be further improved. If different output patterns are required depending on the positions of the workpieces W in the vertical stacking direction, some of the plurality of heating coils may be heated and controlled separately from the rest of the heating coils.

また、上記実施形態では、本発明に係る焼き戻し方法の対象として、ワークＷが転がり軸受の軌道輪（外輪又は内輪）である場合を例示したが、もちろん本発明は他の機械部品となるワークに対しても適用可能である。図９は、その一例（本発明の第二実施形態）に係る焼き戻し装置を構成する昇温装置１０１の縦断面図を示している。この昇温装置１０１は、図９に示すように、ワークＷａとしての等速自在継手の外側継手部材に対して誘導加熱により所定の加熱処理を施すためのもので、搬送路１１上を所定の方向に搬送される複数のワークＷａを一個ずつ支持可能な支持部１０２と、支持部１０２を昇降駆動する昇降部１０３と、支持部１０２の上方に位置する誘導加熱装置１０４とを主に備える。誘導加熱装置１０４は、例えば銅管等の導電性金属で環状に形成された加熱コイル１０５と、加熱コイル１０５に電力を供給する電源２１とを有する。本実施形態では、加熱コイル１０５は例えばソレノイドコイルなどの汎用の多巻状加熱コイルであって、かつ昇降部１０３により支持部１０２を上昇させて、支持部１０２上に載置された状態のワークＷを加熱コイル１０５の内周に導入した際、図９に示すように、ワークＷａの軸方向全域が加熱コイル１０５で覆われるよう、加熱コイル１０５の巻き数（軸方向寸法）が設定される。 Further, in the above-described embodiment, the case where the workpiece W is a raceway ring (outer ring or inner ring) of a rolling bearing is illustrated as an object of the tempering method according to the present invention. It is also applicable to FIG. 9 shows a longitudinal sectional view of a temperature raising device 101 that constitutes a tempering device according to one example (second embodiment of the present invention). As shown in FIG. 9, the temperature raising device 101 is for applying a predetermined heat treatment by induction heating to the outer joint member of a constant velocity universal joint as a work Wa. It mainly includes a support portion 102 capable of supporting a plurality of works Wa conveyed in a direction one by one, an elevating portion 103 that drives the support portion 102 up and down, and an induction heating device 104 positioned above the support portion 102 . The induction heating device 104 has a heating coil 105 formed in an annular shape with a conductive metal such as a copper tube, and a power source 21 for supplying power to the heating coil 105 . In this embodiment, the heating coil 105 is a general-purpose multi-turn heating coil such as a solenoid coil. The number of turns (axial dimension) of the heating coil 105 is set so that the entire axial region of the workpiece Wa is covered with the heating coil 105 when W is introduced into the inner circumference of the heating coil 105, as shown in FIG. .

また、ワークＷａが外側継手部材である場合、外側継手部材のカップ部Ｗｂを下向きに、外側継手部材のステム部Ｗｃを上向きにして支持部１０２の上に載置することが望ましく、かつワークＷａ（外側継手部材）の中心線を加熱コイル１０５の中心線に一致させることが望ましい。よって、この場合、上述の関係を満たす位置にワークＷａが支持部１０２上に位置決め固定されるよう、搬送路１１又はその周囲に位置決め装置を設けることが望ましい。また、図示は省略するが、第一実施形態と同様、支持部１０２と、支持部１０２と連結される昇降部１０３の一部が上記中心線まわりに回転できるように構成することが望ましい。 Further, when the work Wa is the outer joint member, it is desirable to place the cup portion Wb of the outer joint member downward and the stem portion Wc of the outer joint member upward, and place the work Wa on the support portion 102 . It is desirable to align the center line of (the outer joint member) with the center line of the heating coil 105 . Therefore, in this case, it is desirable to provide a positioning device on or around the transport path 11 so that the work Wa is positioned and fixed on the support portion 102 at a position that satisfies the above relationship. Also, although illustration is omitted, it is desirable that the supporting portion 102 and a part of the lifting portion 103 connected to the supporting portion 102 be configured to be rotatable around the center line, as in the first embodiment.

なお、焼き戻し装置のうち上述した昇温装置１０１以外の構成については、第一実施形態と同様に構成してもかまわない。すなわち、昇温装置１０１と共に加熱装置１２を構成する復温装置、保温装置、及び冷却装置については、図３及び図４に示す復温装置１５、保温装置１６、及び冷却装置１３を用いることが可能である。 In addition, the configuration of the tempering device other than the temperature raising device 101 described above may be configured in the same manner as in the first embodiment. That is, as for the rewarming device, the heat retaining device, and the cooling device that constitute the heating device 12 together with the temperature raising device 101, the rewarming device 15, the heat retaining device 16, and the cooling device 13 shown in FIGS. 3 and 4 can be used. It is possible.

また、焼き戻し処理の温度条件（温度履歴）について、第一実施形態と同様の考えに基づいて設定することが可能である。すなわち、焼き戻し工程Ｓ２の昇温工程Ｓ２１１では、図６に示すように、昇温速度一定で狙い温度ｒ１までワークＷａを加熱する。ここで図９に示す形態の加熱コイル１０５を用いた場合、外側継手部材のカップ部Ｗｂとステム部Ｗｃとでは昇温のし易さが異なるため、例えば相対的に昇温し易いカップ部Ｗｂが狙い温度ｒ１を超えないように制御することが望ましい。復温工程Ｓ２１２、保温工程Ｓ２１３における温度履歴については、第一実施形態と同様、図６に示すように制御してもかまわない。また、保温工程Ｓ２１３時における許容温度域Ｒについても、第一実施形態と同様に設定してもよい。この場合、狙い温度ｒ１は、許容温度域Ｒの範囲内で設定される。 Also, the temperature condition (temperature history) of the tempering process can be set based on the same idea as in the first embodiment. That is, in the temperature raising step S211 of the tempering step S2, as shown in FIG. 6, the workpiece Wa is heated to the target temperature r1 at a constant temperature raising rate. Here, when the heating coil 105 having the configuration shown in FIG. 9 is used, the cup portion Wb and the stem portion Wc of the outer joint member are different in ease of temperature rise. should be controlled so as not to exceed the target temperature r1. The temperature history in the rewarming step S212 and the heat retaining step S213 may be controlled as shown in FIG. 6, as in the first embodiment. Also, the permissible temperature range R during the heat retention step S213 may be set in the same manner as in the first embodiment. In this case, the target temperature r1 is set within the allowable temperature range R.

本実施形態では、例えば上述した温度履歴を辿るように、誘導加熱装置１０４の出力パターンと第一及び第二ヒーター２７，２９の出力パターンをそれぞれ制御部３３（図４を参照）に記憶させておき、加熱工程Ｓ２１（昇温工程Ｓ２１１、復温工程Ｓ２１２、保温工程Ｓ２１３）及び冷却工程Ｓ２２において、上記記憶させておいた出力パターンに基づいて制御部３３が電源２１に指令を送る。これにより、電源２１に接続された誘導加熱装置１０４の加熱コイル１０５（図９を参照）と、同じく電源２１に接続された第一及び第二ヒーター２７，２９に所定パターンの電力が供給され、図６に示す温度履歴をワークＷａに付与し得る。 In this embodiment, for example, the output pattern of the induction heating device 104 and the output patterns of the first and second heaters 27 and 29 are stored in the control unit 33 (see FIG. 4) so as to trace the temperature history described above. Then, in the heating step S21 (heating step S211, warming step S212, heat retaining step S213) and cooling step S22, the controller 33 sends a command to the power source 21 based on the stored output pattern. As a result, the heating coil 105 (see FIG. 9) of the induction heating device 104 connected to the power supply 21 and the first and second heaters 27 and 29 similarly connected to the power supply 21 are supplied with power in a predetermined pattern, The temperature history shown in FIG. 6 can be given to the work Wa.

次に、上記構成の焼き戻し装置を用いたワークＷａの焼き戻し工程Ｓ２の一例を説明する。 Next, an example of the tempering process S2 of the workpiece Wa using the tempering apparatus having the above configuration will be described.

（Ｓ２１）加熱工程
（Ｓ２１１）昇温工程
この工程では、まず図４に示す第一開閉手段２３により昇温装置１０１（図９）の入口側開口部１４ａを開口した状態で、搬送路１１上を所定の方向に搬送されるワークＷａを昇温装置１４の内部に搬入する。そして、ワークＷが支持部１０２（図９）上に到達すると、必要に応じてワークＷａの支持部１０２に対する水平方向の位置決めを伴って、昇降部１０３により支持部１０４を上昇させる。これにより、支持部１０２上に載置された状態のワークＷａの軸方向全域が誘導加熱装置１０４の所定位置、本実施形態では誘導加熱装置１０４の加熱コイル１０５の内周所定位置に導入され、保持される（図９を参照）。この状態で、制御部３３は電源２１に指令を送り、加熱コイル１０５に所定パターンの電力を供給することにより、ワークＷａの加熱を開始し、ワークＷａを狙い温度ｒ１にまで一定の勾配で加熱する（図６を参照）。上述した誘導加熱は、ワークＷａの材質、形状、サイズ等に合わせて適切な周波数域で実施するのがよく、例えば本実施形態では低周波域（～数ｋＨｚ）で実施するのがよい。これによりワークＷａの表層部だけでなく芯部まで高温に加熱することができる。なお、この間（昇温開始時ｔ０から昇温終了時ｔ１までの間）、ワークＷａのうち相対的に昇温し易いカップ部Ｗｂの温度が許容温度域Ｒの上限（許容温度上限値ｒ３）を超えないように、制御部３３によりワークＷａの加熱を制御するのがよい。この場合、狙い温度ｒ１は、許容温度域Ｒの範囲内（許容温度下限値ｒ４以上でかつ許容温度上限値ｒ３以下）に設定される。また、加熱している間、支持部１０２を制御部３３により軸回転させながら昇温させることで、支持部１０２上のワークＷａ全体が均等に昇温される。 (S21) Heating step (S211) Temperature rising step In this step, first, the first opening/closing means 23 shown in FIG. is carried into the temperature raising device 14, the work Wa being transported in a predetermined direction. When the work W reaches the support portion 102 (FIG. 9), the support portion 104 is lifted by the elevating portion 103 while horizontally positioning the work Wa with respect to the support portion 102 as necessary. As a result, the entire axial direction of the workpiece Wa placed on the support portion 102 is introduced into a predetermined position of the induction heating device 104, in this embodiment, a predetermined position of the inner periphery of the heating coil 105 of the induction heating device 104, retained (see FIG. 9). In this state, the control unit 33 sends a command to the power source 21 to supply power in a predetermined pattern to the heating coil 105, thereby starting to heat the workpiece Wa, and heating the workpiece Wa to the target temperature r1 at a constant gradient. (see Figure 6). The induction heating described above is preferably performed in an appropriate frequency range according to the material, shape, size, etc. of the workpiece Wa. For example, in this embodiment, it is preferably performed in a low frequency range (up to several kHz). Thereby, not only the surface layer portion of the work Wa but also the core portion can be heated to a high temperature. During this period (from the temperature rise start time t0 to the temperature rise end time t1), the temperature of the cup portion Wb of the workpiece Wa, which is relatively easy to rise, is the upper limit of the allowable temperature range R (allowable temperature upper limit value r3). is preferably controlled by the control unit 33 so as not to exceed the heating of the workpiece Wa. In this case, the target temperature r1 is set within the allowable temperature range R (above the allowable temperature lower limit value r4 and below the allowable temperature upper limit value r3). Further, during heating, the temperature of the entire workpiece Wa on the support portion 102 is uniformly increased by raising the temperature while rotating the support portion 102 by the control portion 33 .

（Ｓ２１２）復温工程
このようにしてワークＷａを狙い温度ｒ１まで昇温した後、ワークＷａを誘導加熱装置１０４の加熱処理位置（加熱コイル１０５の内周所定位置）から離脱させ、開口状態にある出口側開口部１４ｂを通って昇温装置１０１外に搬出する。具体的には、制御部３３が電源２１に指令を送り、誘導加熱装置１０４によるワークＷａの加熱を停止すると共に、昇降部１０３により支持部１０２を降下させて、支持部１０２上のワークＷａを搬送路１１上に復帰させる。そして、第二開閉手段２４により昇温装置１０１の出口側開口部１４ｂを開口した状態で、図示しない適当な手段で搬送路１１上を所定の方向に搬送し、昇温装置１０１内からワークＷａを搬出する。そして、搬出したワークＷａを、第一通路室２５を介して、復温装置１５の第一炉室２６内へ搬入し、ワークＷａに対して所定の雰囲気加熱を施す。これにより、昇温後、昇温終了時ｔ１から復温開始時ｔ２までの間に温度ｒ２まで温度低下を生じていたワークＷａ（図６を参照）の温度を狙い温度ｒ１にまで回復させる。なお、この間（復温開始時ｔ２から復温終了時ｔ３までの間）も、ワークＷａのカップ部Ｗｂの温度が許容温度域Ｒの上限（許容温度上限値ｒ３）を超えないように、制御部３３によりワークＷａの加熱を制御するのがよい。 (S212) Reheating step After heating the work Wa to the target temperature r1 in this manner, the work Wa is removed from the heat treatment position of the induction heating device 104 (predetermined position on the inner periphery of the heating coil 105), and is opened. It is transported out of the temperature raising device 101 through a certain outlet side opening 14b. Specifically, the control unit 33 sends a command to the power supply 21 to stop the heating of the workpiece Wa by the induction heating device 104, and the lifting unit 103 lowers the support unit 102 to lift the workpiece Wa on the support unit 102. It is returned to the conveying path 11 . Then, in a state in which the outlet side opening 14b of the temperature raising device 101 is opened by the second opening/closing means 24, the workpiece Wa is conveyed in a predetermined direction on the conveying path 11 by an appropriate means (not shown), and the work Wa is removed from the temperature raising device 101. to carry out. Then, the carried-out workpiece Wa is carried into the first furnace chamber 26 of the reheating device 15 via the first passage chamber 25, and the workpiece Wa is heated in a predetermined atmosphere. As a result, the temperature of the work Wa (see FIG. 6), which had dropped to temperature r2 between the end of temperature rise t1 and the start of reheating t2 after the temperature rise, is restored to target temperature r1. During this period (from t2 to the end of reheating t3), the temperature of the cup portion Wb of the workpiece Wa is controlled so as not to exceed the upper limit of the allowable temperature range R (allowable temperature upper limit value r3). It is preferable that the heating of the workpiece Wa is controlled by the unit 33 .

（Ｓ２１３）保温工程
このようにしてワークＷａを再び狙い温度ｒ１にまで加熱した後、出口側開口部１５ｂを開けてワークＷａを復温装置１５外に搬出し、隣接する保温装置１６内に搬入する。そして、ワークＷａに雰囲気加熱を施して、許容温度域Ｒの範囲内で当該ワークＷａを所定時間の間、保温する。なお、この間（保温開始時ｔ３から保温終了時ｔ４までの間）、ワークＷａのカップ部Ｗｂの温度が許容温度域Ｒの範囲内に維持されるように（許容温度上限値ｒ３以下でかつ許容温度下限値ｒ４以上であるように）、制御部３３によりワークＷａの加熱を制御するのがよい。なお、一例として、ワークＷａの材質が機械構造用炭素鋼である場合、許容温度域Ｒは１３０℃以上でかつ２２０℃以下の範囲内で設定され、好ましくは１５０℃以上でかつ２００℃以下の範囲内で設定される。また、ワークＷａの保温時間（保温開始時ｔ３から保温終了時ｔ４までの間）は１０秒以上でかつ７０分以下の範囲内で設定され、好ましくは３０秒以上でかつ６０分以下の範囲内で設定される。 (S213) Heat Retention Step After the work Wa is heated again to the target temperature r1 in this manner, the exit side opening 15b is opened to carry the work Wa out of the reheating device 15 and into the adjacent heat retention device 16. do. Then, the work Wa is heated in the atmosphere, and the work Wa is kept warm within the allowable temperature range R for a predetermined time. During this period (from the start of heat retention t3 to the end of heat retention t4), the temperature of the cup portion Wb of the work Wa is maintained within the allowable temperature range R (below the allowable temperature upper limit value r3 and the allowable It is preferable that the heating of the workpiece Wa is controlled by the controller 33 so that the temperature is equal to or higher than the lower temperature limit r4. As an example, when the material of the workpiece Wa is carbon steel for machine structural use, the allowable temperature range R is set within a range of 130° C. or higher and 220° C. or lower, preferably 150° C. or higher and 200° C. or lower. Set within the range. In addition, the heat retention time of the work Wa (from the heat retention start time t3 to the heat retention end time t4) is set within a range of 10 seconds or more and 70 minutes or less, preferably 30 seconds or more and 60 minutes or less. is set by

（Ｓ２２）冷却工程
このようにして所定時間の間ワークＷａの保温を行った後、図示しない出口側開口部を開けてワークＷａを保温装置１６外に搬出する。搬出されたワークＷａは、第二通路室３２を通って冷却装置１３内に搬入され（図３を参照）、所定の冷却速度で所定の温度ｒ５、例えば昇温開始時温度ｒ０よりも低い温度にまで冷却される（冷却終了時ｔ５）。これにより、ワークＷａに対する焼き戻し処理が完了する。後続のワークＷａについても同様の経路を辿って、焼き戻し処理が施され、焼き戻し装置の外側に排出される。排出されたワークＷａは例えば洗浄工程Ｓ５あるいは研磨工程（図示は省略）など次の工程へ搬送される。以上のようにして、複数のワークＷａに対して連続的にかつ自動的に焼き戻し処理が施される。 (S22) Cooling Step After the work Wa is kept warm for a predetermined period of time in this manner, the work Wa is carried out of the heat retaining device 16 by opening an exit-side opening (not shown). The unloaded workpiece Wa is carried into the cooling device 13 through the second passage chamber 32 (see FIG. 3), and cooled at a predetermined cooling rate to a predetermined temperature r5, for example, a temperature lower than the temperature r0 at the start of heating. (cooling end time t5). This completes the tempering process for the workpiece Wa. The succeeding work Wa follows the same path, is subjected to tempering treatment, and is discharged outside the tempering device. The discharged work Wa is conveyed to the next process such as a cleaning process S5 or a polishing process (not shown). As described above, the plurality of works Wa are continuously and automatically tempered.

以上述べたように、本実施形態に係る焼き戻し方法によれば、誘導加熱でワークＷａを狙い温度ｒ１にまで加熱するようにしたので（昇温工程Ｓ２１１）、従来よりも短時間でワークＷａを必要な温度域にまで加熱することができる。また、本実施形態では、ワークＷａに要求される残留オーステナイト量及び硬さに応じて許容温度域Ｒを設定し、この許容温度域Ｒ内で昇温後のワークＷａを保温するようにしたので、短時間で昇温しつつも、焼き戻し処理後のワークＷａに含まれる残留オーステナイト量を所要レベル以下にまで低減化し、かつワークＷａの硬さを所定範囲内に収めることが可能となる。また、ワークＷａを上記温度域Ｒ内で保温するための加熱制御を、雰囲気加熱により実施するようにしたので、ワークＷａを均等に加熱しながらワークＷａを保温することができる。よって、ワークＷａ内部の温度のばらつきを抑えて、均質な焼き戻し処理を施すことができる。特に、本実施形態のようにワークＷａが等速自在継手の外側継手部材のように軸方向で厚み寸法分布に偏りがある機械部品であっても、誘導加熱時に生じたワークＷａ内での温度のばらつきを雰囲気加熱で均すことができる。よって、ワークＷａの種類に応じて複数の加熱コイル等を準備せずとも、あるいはワークＷａに応じた専用形態の加熱コイルを準備せずとも、均質な焼き戻し処理を施すことができる。これにより、加熱コイルの交換コストや交換作業に伴う段取り時間の増加を回避して、低コスト、短時間で均質な焼き戻し処理を施すことが可能となる。 As described above, according to the tempering method according to the present embodiment, the work Wa is heated to the target temperature r1 by induction heating (heating step S211), so that the work Wa can be heated in a shorter time than conventionally. can be heated to the required temperature range. Further, in the present embodiment, the allowable temperature range R is set according to the amount of retained austenite and hardness required for the work Wa, and the work Wa after the temperature rise is kept warm within this allowable temperature range R. , the amount of retained austenite contained in the work Wa after tempering can be reduced to a required level or less while the temperature is raised in a short time, and the hardness of the work Wa can be kept within a predetermined range. Further, since the heating control for keeping the work Wa within the above temperature range R is performed by atmospheric heating, the work Wa can be kept warm while being evenly heated. Therefore, uniform tempering can be performed while suppressing variations in temperature inside the work Wa. In particular, even if the workpiece Wa is a mechanical component with a biased thickness distribution in the axial direction, such as the outer joint member of a constant velocity universal joint, as in the present embodiment, the temperature inside the workpiece Wa generated during induction heating can be smoothed out by atmospheric heating. Therefore, uniform tempering can be performed without preparing a plurality of heating coils or the like according to the type of the work Wa, or without preparing a special heating coil according to the work Wa. As a result, it is possible to avoid the cost of exchanging the heating coil and the increase in setup time associated with the exchanging work, and to perform uniform tempering treatment at low cost in a short time.

もちろん、ワークＷａの保温を雰囲気加熱により行うことで、誘導加熱等と比べてワークＷａの温度を下げにくくすることができる。そのため、保温工程Ｓ２１３時の加熱制御も比較的容易に行うことができる。もちろん、雰囲気加熱であれば、一度に大量のワークＷａを処理することができる。以上より、本実施形態に係る焼き戻し方法によれば、ワークＷａに含まれる残留オーステナイト量を所要レベル以下にまで低減化できると共に、ワークＷａの硬さを所定範囲内に収めることができるので、高温環境下での使用にも適した機械部品を得ることができる。また、昇温に要する時間が短くて済み、比較的短時間で多くのワークＷａに均質な処理を施すことができるので、生産性にも優れている。具体的には、加工リードタイムが短くなるため、生産性の向上と仕掛在庫の削減につながる。もちろん、昇温工程Ｓ２１１から保温工程Ｓ２１３までの熱処理を全て雰囲気加熱炉で行う場合と比べて、設備も小型化できる。 Of course, it is possible to make it difficult to lower the temperature of the work Wa by heating the work Wa by atmospheric heating, as compared with induction heating or the like. Therefore, it is possible to relatively easily perform heating control during the heat retention step S213. Of course, if atmospheric heating is used, a large number of workpieces Wa can be processed at once. As described above, according to the tempering method according to the present embodiment, the amount of retained austenite contained in the work Wa can be reduced to a required level or less, and the hardness of the work Wa can be kept within a predetermined range. It is possible to obtain mechanical parts that are also suitable for use in high temperature environments. Moreover, the time required for temperature rise is short, and many workpieces Wa can be uniformly treated in a relatively short time, so the productivity is also excellent. Specifically, processing lead time is shortened, leading to improved productivity and reduced in-process inventory. Of course, compared with the case where all the heat treatments from the temperature raising step S211 to the heat retaining step S213 are performed in the atmosphere heating furnace, the equipment can be made smaller.

本発明は前述した実施形態に何ら限定されるものではなく、本発明の要旨を逸脱しない範囲内において、さらに種々なる形態で実施し得る。すなわち、本発明の範囲は、特許請求の範囲によって示され、さらに特許請求の範囲に記載の均等の意味、および範囲内のすべての変更を含む。 The present invention is by no means limited to the above-described embodiments, and can be embodied in various forms without departing from the gist of the present invention. That is, the scope of the present invention is indicated by the claims, and includes equivalent meanings and all changes within the scope of the claims.

以下、本発明に係る焼き戻し方法の有用性を実証する実験の詳細について説明する。 Details of an experiment for demonstrating the usefulness of the tempering method according to the present invention will be described below.

本実験では、等速自在継手の外側継手部材をワークとして所定の焼き戻し処理を施した。ここで外側継手部材には、機械構造用炭素鋼であるＳ５３Ｃで、カップ部Ｗｂ（図１０を参照）の外径寸法が６０．８５ｍｍ、ステム部Ｗｃの大径側領域の外径寸法が３０ｍｍ、小径側領域の外径寸法が２４ｍｍとなるように形成され、高周波加熱による焼入れ処理が施されたものを使用した。 In this experiment, the outer joint member of the constant velocity universal joint was used as a work and subjected to a predetermined tempering treatment. Here, the outer joint member is made of S53C carbon steel for machine structural use, the outer diameter of the cup portion Wb (see FIG. 10) is 60.85 mm, and the outer diameter of the large diameter region of the stem Wc is 30 mm. , formed so that the outer diameter dimension of the small-diameter side region was 24 mm, and was subjected to quenching treatment by high-frequency heating.

また、焼き戻し処理は、例えば図３、図４、及び図９に示す焼き戻し装置を用いると共に、表１に示す条件下で行った。

Figure 0007266426000001
The tempering treatment was performed under the conditions shown in Table 1 using the tempering apparatus shown in FIGS. 3, 4 and 9, for example.
Figure 0007266426000001

そして、焼き戻し処理後のワークに対して、図１０に示すように、複数の硬度測定点Ｗ７～Ｗ１１を設けて、各測定点Ｗ７～Ｗ１１におけるワークの硬度［ＨＶ］を測定した。正確には、ワークＷａの表面に設定した各測定点Ｗ７～Ｗ１１から０．２５ｍｍ深部の位置における硬度［ＨＶ］を測定した。測定結果を表２に示す。表２より、従来の雰囲気加熱のみによる焼き戻し処理と同レベルの硬度を得られることがわかった。また、硬度のばらつき（例えばカップ部Ｗｂとステム部Ｗｃ間の硬度のばらつき）も小さく抑えられることがわかった。

Figure 0007266426000002
Then, as shown in FIG. 10, a plurality of hardness measurement points W7 to W11 were provided for the tempered work, and the hardness [HV] of the work was measured at each of the measurement points W7 to W11. More precisely, the hardness [HV] was measured at positions 0.25 mm deep from each measurement point W7 to W11 set on the surface of the work Wa. Table 2 shows the measurement results. From Table 2, it was found that the same level of hardness as that obtained by the conventional tempering treatment only by atmospheric heating can be obtained. Further, it was found that variations in hardness (for example, variations in hardness between the cup portion Wb and the stem portion Wc) can be kept small.
Figure 0007266426000002

１０ 焼き戻し装置
１１ 搬送路
１２ 加熱装置
１３ 冷却装置
１４，１０１ 昇温装置
１５ 復温装置
１６ 保温装置
１７，１０２ 支持部
１８，１０３ 昇降部
１９，１０４ 誘導加熱装置
２０，１０５ 加熱コイル
２１ 電源
２２ 壁部
２３，２４，３０，３１ 開閉手段
２５，３２ 通路室
２６，２８ 炉室
２７，２９ ヒーター
３３ 制御部
Ｈ１ 許容上限値（硬さ）
Ｈ２ 許容下限値（硬さ）
Ｑ１ 許容上限値（残留オーステナイト量）
Ｒ 許容温度域
Ｒ１ 第一許容温度域（残留オーステナイト量）
Ｒ２ 第二許容温度域（硬さ）
ｒ０ 昇温開始時温度
ｒ１ 狙い温度
ｒ２ 復温開始時温度
ｒ３ 許容温度上限値
ｒ４ 許容温度下限値
ｒ５ 冷却終了時温度
Ｓ２１ 加熱工程
Ｓ２１１ 昇温工程
Ｓ２１２ 復温工程
Ｓ２１３ 保温工程
Ｓ２２ 冷却工程
ｔ０ 昇温開始時
ｔ１ 昇温終了時
ｔ２ 復温開始時
ｔ３ 復温終了時（保温開始時）
ｔ４ 保温終了時
ｔ５ 冷却終了時
Ｗ，Ｗａ ワーク 10 Tempering device 11 Conveying path 12 Heating device 13 Cooling device 14, 101 Heating device 15 Reheating device 16 Thermal insulation device 17, 102 Supporting units 18, 103 Lifting unit 19, 104 Induction heating device 20, 105 Heating coil 21 Power source 22 Walls 23, 24, 30, 31 Opening/closing means 25, 32 Passage chambers 26, 28 Furnace chambers 27, 29 Heater 33 Controller H1 Permissible upper limit (hardness)
H2 Allowable lower limit (hardness)
Q1 Allowable upper limit (amount of retained austenite)
R Allowable temperature range R1 First allowable temperature range (amount of retained austenite)
R2 Second allowable temperature range (hardness)
r0 temperature at the start of heating r1 target temperature r2 temperature at the start of reheating r3 upper limit of allowable temperature r4 lower limit of allowable temperature r5 temperature at the end of cooling S21 heating step S211 heating step S212 rewarming step S213 heat retention step S22 cooling step t0 temperature rise Start time t1 End of heating t2 Start of rewarming t3 End of rewarming (start of heat retention)
t4 End of heat retention t5 End of cooling W, Wa Workpiece

Claims (9)

ワークを加熱する加熱工程と、前記加熱工程で加熱された前記ワークを冷却する冷却工程とを備え、前記加熱工程及び前記冷却工程での前記ワークの温度履歴を制御することで、前記ワークに焼き戻し処理を施す、ワークの焼き戻し方法において、
前記加熱工程は、誘導加熱により前記ワークを狙い温度まで加熱する昇温工程と、
所定幅の温度域の範囲内で前記昇温後のワークが所定時間の間保温されるように、雰囲気加熱による前記ワークの加熱を制御する保温工程とを有し、
前記保温工程で、前記ワークに要求される残留オーステナイト量及び硬さに応じて前記所定幅の温度域としての許容温度域を設定し、この許容温度域の範囲内で前記昇温後のワークが所定時間の間保温されるように、雰囲気加熱による前記ワークの加熱を制御し、かつ
前記ワークの昇温時の狙い温度と残留オーステナイト量との関係に基づき、前記残留オーステナイト量が許容範囲内に収まる第一温度下限値を設定すると共に、前記ワークの昇温時の狙い温度と硬さとの関係に基づき、前記硬さが許容範囲内に収まる第二温度上限値及び第二温度下限値を設定し、
これら前記第一温度下限値よりも大きな領域と、前記第二温度上限値と前記第二温度下限値との間の領域とが重複する範囲内で、前記許容温度域を設定することを特徴とするワークの焼き戻し方法。 A heating step of heating a workpiece and a cooling step of cooling the workpiece heated in the heating step are provided. In the method of tempering a work, which is subjected to a return treatment,
The heating step includes a temperature raising step of heating the workpiece to a target temperature by induction heating;
a heat retaining step of controlling heating of the work by atmospheric heating so that the work after the temperature rise is kept warm for a predetermined time within a temperature range of a predetermined width ;
In the heat insulating step, an allowable temperature range is set as the temperature range of the predetermined width according to the amount of retained austenite and hardness required for the work, and the work after the temperature rise is within the allowable temperature range. controlling the heating of the workpiece by atmospheric heating so that the temperature is maintained for a predetermined time; and
Based on the relationship between the target temperature and the amount of retained austenite when the temperature of the work is raised, the first temperature lower limit value is set so that the amount of retained austenite falls within an allowable range, and the target temperature and hardness when the temperature of the work is raised. Based on the relationship between, set a second upper temperature limit and a second lower temperature limit at which the hardness falls within the allowable range,
The allowable temperature range is set within a range in which a range greater than the first temperature lower limit and a range between the second temperature upper limit and the second temperature lower limit overlap. Workpiece tempering method. 前記昇温工程の後でかつ前記保温工程の前に設けられ、前記昇温後のワークを雰囲気加熱して、前記昇温時の狙い温度まで前記ワークの温度を回復させる復温工程をさらに有する請求項１に記載のワークの焼き戻し方法。 The method further includes a reheating step provided after the temperature raising step and before the heat insulating step, in which the workpiece after the temperature raising is atmospherically heated to recover the temperature of the workpiece to the target temperature at the time of the temperature raising. The work tempering method according to claim 1 . 前記復温工程で、前記雰囲気加熱の設定温度は、前記昇温時の狙い温度よりも高く設定される請求項２に記載のワークの焼き戻し方法。 3. The work tempering method according to claim 2, wherein in said reheating step, the set temperature of said atmospheric heating is set higher than the target temperature during said temperature increase. 前記保温工程で、前記雰囲気加熱の設定温度は、前記昇温時の狙い温度と同じ温度に設定される請求項１～３の何れか一項に記載のワークの焼き戻し方法。 4. The work tempering method according to any one of claims 1 to 3, wherein in said heat retaining step, the set temperature of said atmosphere heating is set to the same temperature as the target temperature during said temperature increase. 前記ワークの材質が高炭素クロム軸受鋼である場合、前記許容温度域が２９０℃以上でかつ３４０℃以下の範囲内で設定される請求項１に記載のワークの焼き戻し方法。 The work tempering method according to claim 1 , wherein the allowable temperature range is set within a range of 290°C or more and 340°C or less when the material of the work is high carbon chromium bearing steel. 前記ワークの材質が高炭素クロム軸受鋼である場合、前記保温工程における前記ワークの保温時間が３分以上でかつ７分以下に設定される請求項１又は５に記載のワークの焼き戻し方法。 6. The work tempering method according to claim 1 or 5 , wherein when the material of the work is high carbon chromium bearing steel, the heat retention time of the work in the heat retention step is set to 3 minutes or more and 7 minutes or less. 前記ワークの材質が機械構造用炭素鋼である場合、前記許容温度域が１３０℃以上でかつ２２０℃以下の範囲内で設定される請求項１に記載のワークの焼き戻し方法。 The work tempering method according to claim 1 , wherein the allowable temperature range is set within a range of 130°C or more and 220°C or less when the material of the work is carbon steel for machine structural use. 前記ワークの材質が機械構造用炭素鋼である場合、前記保温工程における前記ワークの保温時間が１０秒以上でかつ７０分以下に設定される請求項１又は７に記載のワークの焼き戻し方法。 8. The work tempering method according to claim 1 or 7 , wherein when the material of the work is carbon steel for machine structural use, the heat retention time of the work in the heat retention step is set to 10 seconds or more and 70 minutes or less. 電気ヒーターを有する雰囲気加熱炉を用いて、前記保温工程における前記ワークの加熱を行う請求項１～８の何れか一項に記載のワークの焼き戻し方法。 The work tempering method according to any one of claims 1 to 8 , wherein the work is heated in the heat insulating step using an atmosphere heating furnace having an electric heater.
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