JP2002256336A - Induction hardening method, and steel parts - Google Patents
Induction hardening method, and steel partsInfo
- Publication number
- JP2002256336A JP2002256336A JP2001056301A JP2001056301A JP2002256336A JP 2002256336 A JP2002256336 A JP 2002256336A JP 2001056301 A JP2001056301 A JP 2001056301A JP 2001056301 A JP2001056301 A JP 2001056301A JP 2002256336 A JP2002256336 A JP 2002256336A
- Authority
- JP
- Japan
- Prior art keywords
- quenching
- induction hardening
- steel part
- transformation point
- cooling
- Prior art date
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Classifications
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
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- Heat Treatment Of Articles (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、ミクロ組織を微細
化し、表層硬度を高くして、長寿命化をはかった高周波
焼入れ方法、およびその高周波焼入れ方法を適用した鋼
部品に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction hardening method for making a microstructure finer, increasing the surface hardness and extending the life, and a steel part to which the induction hardening method is applied.
【０００２】[0002]
【従来の技術】高周波焼入れ技術は、必要な部分だけを
硬化することができ、エネルギーロスが少ないので、現
在も盛んに用いられているが、エコロジー重視の傾向か
ら、今後さらに多用されてゆく技術である。転がり軸受
部品に対して高周波焼入れ法が適用される場合がある
が、高周波焼入れが用いられる鋼は、元来、ＪＩＳのＳ
５３Ｃのような中炭素鋼である。このような中炭素鋼
は、化学成分上の制約から、通常の軸受用鋼であるＣｒ
を含むＳＵＪ２等に比べて短寿命になりやすい。高周波
焼入れ品を長寿命化するためには、従来から、化学成分
を高合金化する方策がとられてきた。2. Description of the Related Art Induction quenching technology can be used for hardening only necessary parts and has low energy loss, so it is still used frequently. However, due to the emphasis on ecology, it will be used more frequently in the future. It is. Induction hardening may be applied to rolling bearing parts, but steels using induction hardening are originally JIS S
Medium carbon steel such as 53C. Such a medium carbon steel is made of Cr, which is a normal bearing steel, due to restrictions on chemical components.
, It is more likely to have a shorter life than SUJ2 etc. In order to prolong the life of induction hardened products, measures for increasing the chemical composition of the alloy have been conventionally taken.
【０００３】[0003]
【発明が解決しようとする課題】しかしながら、合金化
すると、コストの上昇や加工性の劣化を招く欠点があっ
た。また、高合金鋼では焼入性が高いため、わずかな加
熱条件の違いで焼入温度が異なり、残留オーステナイト
が過剰になり、所定の表層硬度が得られなかったり、焼
き割れが発生するなどの問題を生じる。However, alloying has the disadvantage of increasing costs and deteriorating workability. In addition, since the hardenability of high alloy steel is high, the quenching temperature differs due to slight differences in heating conditions, the residual austenite becomes excessive, the desired surface hardness cannot be obtained, and quenching cracks occur. Cause problems.
【０００４】高周波焼入れ法では、短時間の加熱とそれ
に引き続く焼入れ処理のため、通常の炭素鋼の場合、炭
化物が充分に素地に炭素として溶け込まない。溶け込み
を促進するために、投入電力を高めたり、長時間加熱す
ると、高周波パターンが崩れたり、結晶粒が粗くなって
しまい、転動寿命や割れ強度が向上しにくかった。ま
た、最悪の場合には、オーバーヒート状態となって、焼
き割れが発生する可能性もある。In the induction quenching method, carbide is not sufficiently dissolved in the base material as carbon in the case of ordinary carbon steel due to short-time heating and subsequent quenching. If the input power is increased or heating is performed for a long time in order to promote the penetration, the high-frequency pattern is broken or the crystal grains are coarsened, and the rolling life and the cracking strength are hardly improved. In the worst case, there is a possibility that an overheating state will occur and burning cracks will occur.
【０００５】本発明は、高周波焼入れ方法を見直し、ミ
クロ組織を微細化し、高い表層硬度を得て、長寿命等を
得ることができる高周波焼入れ方法およびその方法を適
用した鋼部品を提供することを目的とする。It is an object of the present invention to provide an induction quenching method capable of reexamining the induction quenching method, refining the microstructure, obtaining a high surface hardness, and obtaining a long life, and a steel part to which the method is applied. Aim.
【０００６】[0006]
【課題を解決するための手段】本発明の高周波焼入れ方
法は、ワークに対して高周波焼入れ処理を施す方法にお
いて、高周波加熱して焼入れる工程と、焼入工程の前
に、少なくとも１回、Ａ 3変態点を超えて高周波加熱し
てＡ1変態点以下に冷却する工程とを備える（請求項
１）。以後の説明で、Ａ3変態点およびＡ1変態点を、そ
れぞれ、Ａ3点およびＡ1点と記す。SUMMARY OF THE INVENTION Induction hardening method of the present invention
The method is to perform induction hardening on the workpiece.
And before the quenching process
A at least once ThreeHigh-frequency heating beyond the transformation point
A1Cooling below the transformation point.
1). In the following description, AThreeTransformation point and A1The transformation point
AThreeDot and A1It is written as a point.
【０００７】上記の構成の予備加熱において、あらかじ
めワークである鋼のＡ3点を超えて加熱し、オーステナ
イト単相にすることにより、炭化物を固溶させて炭素を
素地に溶け込ませることができる。[0007] In the preheating of the above configuration, previously heated beyond the three points A in steel which is work, by the austenite single phase, carbon by solid solution carbides can be dissolve the matrix.
【０００８】冷却工程において、Ａ1点を切る温度まで
冷却し、再び焼入れ加熱することにより、結晶粒を微細
化し、安定して高硬度を得ることができる。この冷却工
程で、たとえば、炭素が素地に溶け込む温度域を時間を
かけて冷却する場合には、ワークがこの温度域を冷却さ
れてゆく間にも炭素は素地に溶け込むことが可能とな
る。また、この冷却工程では、たとえば、水冷などを適
用することにより、スピードアップをはかり製造能率を
向上させることができる。この結果、転動寿命と割れ強
度とに優れた高周波焼入れ部品を高能率で製造すること
が可能となる。なお、上記の高周波焼入れでは、表層部
への焼入れを前提にしているので、上記の処理は、表層
部を対象にしている。また、Ａ3点は、高周波加熱にお
いて略オーステナイト単相になる温度であり、Ａ1点
は、残留オーステナイト等を除いて、冷却時にオーステ
ナイトからのパーライト変態がおよそ終了する温度であ
る。[0008] In the cooling step, by cooling to a temperature off a point A, again quenching heating, fine crystal grains can be stably obtain a high hardness. In this cooling step, for example, if the temperature range in which carbon melts into the base is cooled over time, the carbon can be melted into the base while the work is cooled down in this temperature range. In this cooling step, for example, by applying water cooling or the like, the speed can be increased and the production efficiency can be improved. As a result, it is possible to manufacture an induction hardened part having excellent rolling life and crack strength with high efficiency. In addition, in the above-mentioned induction hardening, since quenching to a surface layer part is premised, the above-mentioned processing is aimed at a surface layer part. Point A 3 is a temperature at which a single phase of austenite is formed by high-frequency heating, and point A 1 is a temperature at which pearlite transformation from austenite is almost completed during cooling, except for residual austenite and the like.
【０００９】上記本発明の高周波焼入れ方法では、たと
えば、焼入工程の前に、Ａ3点を超えて高周波加熱し、
Ａ3点を超える温度域に所定時間以上保持し、次いで、
そのままＡ1点以下に冷却する工程を備えることができ
る（請求項２）。[0009] In induction hardening method of the present invention, for example, prior to the quenching step, and high frequency heating beyond the three points A,
A Keep in a temperature range exceeding 3 points for a predetermined time or longer,
It may comprise a step of cooling below point A (Claim 2).
【００１０】Ａ3点を超える温度域に、所定時間以上、
保持されるので、さらに確実に炭化物を固溶させること
ができ、焼入性や焼入れ硬度を確保しやすくなる。すな
わち、この炭素の素地への十分な固溶により、成分偏析
に起因する硬度むらを薄め、高周波焼入れ部位全体の硬
度上昇を得ることができる。A For a predetermined time or more in a temperature range exceeding 3 points,
Since the carbide is held, the carbide can be more reliably dissolved in the solid solution, and the hardenability and the quench hardness can be easily secured. That is, due to the sufficient solid solution of carbon in the base material, unevenness of hardness caused by component segregation can be reduced, and the hardness of the entire induction hardened portion can be increased.
【００１１】上記本発明の高周波焼入れ方法では、たと
えば、Ａ3点を超える温度域に所定時間以上保持する工
程では、そのまま焼入温度に保持する処理、および高周
波電源を切って放置する処理の少なくとも一方を行なう
ことができる（請求項３）。[0011] In induction hardening method of the present invention, for example, in the step of holding a predetermined time or more in a temperature range over three points A, as a process of holding the quenching temperature, and at least the process of leaving off the high frequency power source One of them can be performed (claim 3).
【００１２】保持と放置との少なくとも一方を行なう工
程においては、Ａ3点を超える温度域に保持される時間
が長いので、さらに確実に炭化物を固溶させることがで
き、焼入性や焼入れ硬度を確保しやすくなる。なお、保
持と放置とを組み合わせてもよい。上記の放置処理に
は、高周波コイルに囲まれた状態で空冷される場合、高
周波コイルまたはワークを移動させて、ワークの周りか
ら高周波コイルをなくした状態で空冷される場合等が含
まれる。[0012] In the step of performing at least one of the standing and holding, the time held in a temperature range of more than three points A is long, it is possible to more reliably solid solution carbides, hardenability and Hardness Is easy to secure. Note that holding and leaving may be combined. The above-described leaving processing includes a case where air cooling is performed in a state surrounded by the high-frequency coil, a case where the high-frequency coil or the work is moved, and the work is air-cooled without the high-frequency coil around the work.
【００１３】上記本発明の高周波焼入れ方法では、たと
えば、Ａ1点以下に冷却する工程では、高周波電源を切
って放置する処理、および強制的に冷却する強制冷却処
理のうちの少なくとも１つの処理により、ワークを冷却
することができる（請求項４）。[0013] In induction hardening method of the present invention, for example, in the step of cooling below point A, the process of leaving off the high frequency power source, and by at least one treatment of the forced cooling process of forcibly cooling The work can be cooled (claim 4).
【００１４】炭素を素地に溶け込ませた後にＡ1点以下
に冷却することにより、その後で、焼入れ温度に加熱し
た際に生じるオーステナイト粒度をはじめミクロ組織を
微細にすることができる。上記したように、放置処理に
は、高周波コイルに囲まれた状態で空冷される場合、高
周波コイルまたはワークを移動させて、ワークの周りか
ら高周波コイルをなくした状態で空冷される場合等が含
まれる。このため、保持および放置の少なくとも一方を
所定時間行なう工程と、その後の引き続いた冷却工程と
で、空冷処理が連続して行なわれる場合がある。By cooling the carbon to the point A 1 or less after dissolving the carbon in the base material, the microstructure including the austenite grain size generated when heated to the quenching temperature can be refined thereafter. As described above, the leaving process includes a case where air cooling is performed in a state surrounded by the high-frequency coil, a case where the high-frequency coil or the work is moved, and air cooling is performed with the high-frequency coil removed from around the work. It is. Therefore, the air cooling process may be continuously performed in the step of performing at least one of the holding and the leaving for a predetermined time and the subsequent cooling step.
【００１５】本発明の高周波焼入れ方法では、たとえ
ば、焼入工程の前に、焼入れ温度に高周波加熱して焼き
入れる処理を１回以上行なうことができる（請求項
５）。In the induction hardening method according to the present invention, for example, before the quenching step, a hardening process can be performed one or more times by induction heating to a quenching temperature.
【００１６】焼入れを繰り返すことにより、素地への炭
素の溶け込みを十分行なうとともに、Ａ1点を繰り返し
上下する熱処理パターンによって最終的な焼入温度を下
げても充分に炭素が固溶しているためオーステナイト結
晶粒度、ミクロ組織を細かくして、硬度、転動寿命、割
れ強度に優れる高周波鋼部品を得ることができる。ま
た、焼入れ回数を所定回数以内にすることにより、第１
の局面の高周波焼入れ方法よりも、スピードアップをは
かることができる場合がある。[0016] By repeating the quenching, carries out the penetration of carbon into the matrix sufficient, since sufficient carbon be lowered final quenching temperature by the heat treatment pattern for the vertical repeatedly point A is dissolved A high-frequency steel part having excellent hardness, rolling life, and crack strength can be obtained by reducing the austenite grain size and microstructure. In addition, by setting the number of times of quenching within a predetermined number,
In some cases, the speed can be increased as compared with the induction hardening method of the aspect.
【００１７】上記本発明の高周波焼入れ方法では、高周
波焼入れが行なわれたワークに対してさらに焼戻しを行
なうことが望ましい。焼戻しにより、固溶した炭素を析
出させて、安定化させることにより、寸法等の経年変化
を無くしたり、靭性を向上させたり、残留応力等を除去
することができる。焼戻しを低温域で行なうことによ
り、硬度の低下は最小限に抑えることができる。In the above-described induction hardening method of the present invention, it is desirable that the work subjected to the induction hardening is further tempered. By tempering and precipitating and stabilizing solid solution carbon, it is possible to eliminate the secular change of dimensions and the like, improve toughness, and remove residual stress and the like. By performing the tempering in a low temperature range, a decrease in hardness can be minimized.
【００１８】本発明の鋼部品は、上記のいずれかの高周
波焼入れ方法を適用して得られた鋼部品であって、鋼部
品の表層部のオーステナイト結晶粒度番号が平均９番以
上である（請求項６）。The steel part of the present invention is a steel part obtained by applying any one of the above-mentioned induction hardening methods, and has an average austenite grain size number of 9 or more in the surface layer of the steel part. Item 6).
【００１９】オーステナイト結晶粒を細かくすることに
より、硬度を上昇させ、また、細かいオーステナイト結
晶粒独自の効果により、転動疲労や割れ強度を改善する
ことができる。By making the austenite crystal grains fine, hardness can be increased, and rolling fatigue and crack strength can be improved by the unique effect of fine austenite grains.
【００２０】上記本発明の鋼部品では、炭素を０．５重
量％以上含み、さらに表層硬度ＨＶ７００以上を備える
ことができる（請求項７）。[0020] The steel part of the present invention can contain carbon in an amount of 0.5% by weight or more and further have a surface hardness HV of 700 or more.
【００２１】炭素を０．５重量％以上含むことにより、
繰り返し変態によるミクロ組織の微細化を促進し、かつ
硬度を高くすることができる。また、このような高硬度
を得ることにより、耐摩耗性、転動疲労、割れ強度等を
改善することができる。By containing 0.5% by weight or more of carbon,
It can promote microstructural refinement by repeated transformation and increase hardness. Further, by obtaining such high hardness, wear resistance, rolling fatigue, crack strength, and the like can be improved.
【００２２】上記本発明の鋼部品は、たとえば、軸受部
品に用いることができる（請求項８）。The steel part of the present invention can be used, for example, as a bearing part.
【００２３】本発明の高周波焼入れ方法を軸受部品に用
いることにより、耐摩耗性、転動疲労、割れ強度に優れ
た軸受部品を得ることができる。By using the induction hardening method of the present invention for a bearing component, a bearing component excellent in wear resistance, rolling fatigue and cracking strength can be obtained.
【００２４】[0024]
【実施例】次に、本発明の実施例について説明する。図
１（ａ）と図１（ｂ）とに、本実施例で用いた２種類の
高周波焼入れ方法のヒートパターンを示す。これらの高
周波焼入れ方法を適用した鋼を表１に示す。Next, an embodiment of the present invention will be described. FIGS. 1A and 1B show heat patterns of two types of induction hardening methods used in the present embodiment. Table 1 shows steels to which these induction hardening methods were applied.
【００２５】[0025]
【表１】 [Table 1]
【００２６】また、図１（ｃ）に比較のための高周波焼
入れのヒートパターンを示す。本実施例の２種類の高周
波焼入れのヒートパターンは、次のものである。 （Ａ）いったん、所定温度まで高周波加熱（予備加熱工
程）後、空冷または空冷後水冷して、Ａ1点以下まで降
温し、その後、再度、焼入れ温度まで高周波加熱し、焼
入れを行なう。（Ａパターン） （Ｂ）焼入温度まで高周波加熱した後水冷する操作を１
サイクルとして、複数サイクル繰り返す。（Ｂパター
ン） 一方、比較のための熱処理ヒートパターンは、図１
（ｃ）に示すように、通常の高周波焼入れ法であるが、
炭化物の溶け込みが十分生じるように保持時間を変化さ
せた。（Ｃ、Ｄ、Ｅパターン） 表２〜表４に高周波焼入れの詳細な条件を示す。FIG. 1C shows a heat pattern of induction hardening for comparison. The two types of induction hardening heat patterns of the present embodiment are as follows. (A) once, after up to a predetermined temperature high-frequency heating (pre-heating step), air or water cooling after air cooling, the temperature was lowered to below 1 point A, then, again, high-frequency heating to the quenching temperature, performing quenching. (Pattern A) (B) The operation of high-frequency heating to the quenching temperature and then water cooling
A plurality of cycles are repeated. (B pattern) On the other hand, the heat treatment heat pattern for comparison is shown in FIG.
As shown in (c), a normal induction hardening method is used.
The holding time was changed so that the carbide could sufficiently dissolve. (C, D, and E patterns) Tables 2 to 4 show detailed conditions of induction hardening.
【００２７】[0027]
【表２】 [Table 2]
【００２８】[0028]
【表３】 [Table 3]
【００２９】[0029]
【表４】 [Table 4]
【００３０】高周波焼入れを適用する鋼としては、表１
に示すＪＩＳの炭素鋼Ｓ５３ＣおよびＳ５３Ｃに対して
若干の合金元素を含有させた鋼を用いた。表１に示す鋼
について、直径１２ｍｍの円筒転動試験片、リング回転
割れ試験片、ミクロ組織試験片を採取して、それぞれに
上記Ａ〜Ｅパターンの高周波焼入れ処理を施し、それぞ
れ、転動試験、回転割れ試験、ミクロ組織検査の試験を
行なった。なお、パターンＡの高周波焼入れ条件を示す
表２の欄の「空冷時間」は、高周波コイルの電源を切っ
て、高周波コイルが試験片を取り囲んだ状態で冷却した
時間を表わす。高周波加熱の場合、表層のみに電力が投
入されるので、高周波電源を切って放置することによ
り、熱が内部に伝導し、また外部に放散されるので、比
較的大きな冷却速度を得ることができる。また、実施例
および比較例ともに、高周波焼入れ装置における加熱コ
イル、焼入れ装置は同じであり、上記のようにヒートパ
ターンを変化させた。焼戻しはいずれも１５０℃で行な
った。それぞれの試験の条件は次のとおりである。 （１）転動疲労試験 転動疲労試験は、所定の高周波焼入れ深さを得た試験片
を高面圧、高負荷速度の条件下で、加速的にサンプルを
疲労させて評価する試験である。この試験では、サンプ
ル数Ｎを１０とし、疲労強度をＬ10寿命（サンプルの９
０％が破損しない負荷回数）により評価した。詳細な条
件は次のとおりである。 ・試験片寸法 ：外径１２ｍｍ、長さ２２ｍｍ ・相手鋼球寸法 ：直径１９．０５ｍｍ ・接触応力Ｐmax ：５．８８ＧＰａ ・負荷速度 ：４６２４０回／分 ・硬化深さ ：２ｍｍ〜２．５ｍｍ（外径部を表
面から高周波焼入れ後、研磨して確認） （２）割れ強度試験 割れ強度試験は、静的および動的な割れ強度を確認する
ための試験である。詳細な条件は次のとおりである。 ・試験片寸法 ：φ６０×φ４５×Ｌ１５リング ・硬化深さ ：２．１±０．１ｍｍ（内径、外径
から高周波焼入れ後に研磨して確認） ・静的割れ試験：アムスラ試験機で静的に圧壊。試験数
３個 ・動的疲労割れ試験 （ａ）試験機 ：リング回転割れ疲労試験機 （ｂ）荷重 ：９．８ｋＮ （ｃ）負荷速度 ：８０００回／分（回転速度４０００
ｒｐｍ） （ｄ）応力振幅 ：-４１０ＭＰａ〜+６２７ＭＰａ （ｅ）潤滑 ：タービンＶＧ６８ （ｆ）試験個数 ：４個 上記の転動試験および割れ強度試験の結果を、併せて表
５に示す。Table 1 shows the steels to which induction hardening is applied.
JIS carbon steels S53C and S53C containing a small amount of alloying elements were used. For the steels shown in Table 1, cylindrical rolling test pieces, ring rolling crack test pieces, and microstructure test pieces having a diameter of 12 mm were sampled, subjected to the induction hardening treatment of the above-described A to E patterns, and subjected to the rolling test, respectively. , Rotational cracking test and microstructure inspection test. The "air cooling time" in the column of Table 2 showing the induction hardening conditions of the pattern A indicates the time during which the power of the high frequency coil was turned off and the high frequency coil cooled while surrounding the test piece. In the case of high-frequency heating, power is supplied only to the surface layer, so by leaving the high-frequency power off and leaving it, heat is conducted inside and dissipated outside, so a relatively large cooling rate can be obtained. . In both the examples and the comparative examples, the heating coil and the quenching device in the induction hardening device were the same, and the heat patterns were changed as described above. All tempering was performed at 150 ° C. The conditions for each test are as follows. (1) Rolling Contact Fatigue Test The rolling contact fatigue test is a test for estimating a test piece having a predetermined induction hardened depth under accelerated fatigue under high surface pressure and high load speed conditions. . In this test, the number of samples N was set to 10, and the fatigue strength was set to L10 life (9
(The number of times that 0% is not damaged). Detailed conditions are as follows.・ Specimen dimensions: Outer diameter 12 mm, length 22 mm ・ Material steel ball dimensions: Diameter 19.05 mm ・ Contact stress Pmax: 5.88 GPa ・ Load speed: 46240 times / min ・ Hardening depth: 2 mm to 2.5 mm (Outer (2) Crack strength test The crack strength test is a test for checking static and dynamic crack strength. Detailed conditions are as follows.・ Specimen dimensions: φ60 × φ45 × L15 ring ・ Curing depth: 2.1 ± 0.1mm (confirmed by polishing after induction hardening from inner and outer diameters) ・ Static cracking test: Static with Amsula testing machine Crush. Number of tests: 3 Dynamic fatigue cracking test (a) Testing machine: Ring rotating cracking fatigue testing machine (b) Load: 9.8 kN (c) Loading speed: 8000 times / minute (rotating speed 4000)
rpm) (d) Stress amplitude: -410 MPa to +627 MPa (e) Lubrication: Turbine VG68 (f) Number of tests: 4 The results of the above rolling test and crack strength test are also shown in Table 5.
【００３１】[0031]
【表５】 [Table 5]
【００３２】（転動疲労試験結果）： 比較例は通常の
高周波焼入れを１回行なったものであるが、標準条件の
パターンＣでは短寿命である。加熱時間を長くすると、
パターンＤのように長寿命になる傾向があるが、時間が
長すぎると表層硬度を得にくく、パターンＥのように転
動寿命も低下する傾向にある。これに対して、実施例の
うち、パターンＡにおいて、いったんＡ3点以上の所定
温度まで加熱後、１６秒間空冷し、その後、再び焼入れ
温度まで加熱して焼き入れたものは、安定して長寿命で
ある。このパターンＡでは、熱処理時間はやや長くなる
が、炭化物が十分溶け込む時間があるので、表層硬度が
安定してくるため長寿命が確保される。また、パターン
Ｂの複数回高周波焼入れを行なったものは、表層硬度は
さほど向上しないが、転動寿命はやや長寿命になる傾向
がある。この長寿命の傾向は、繰り返し回数が多くなる
ほど促進される。(Results of Rolling Contact Fatigue Test): In the comparative example, the normal induction hardening was performed once, but the pattern C under the standard condition has a short life. If you increase the heating time,
Although the life tends to be long as in pattern D, if the time is too long, it is difficult to obtain the surface layer hardness, and the rolling life tends to decrease as in pattern E. In contrast, among the embodiments, the pattern A, once after heating to a predetermined temperature of the three or more points A, and 16 seconds cooling, then, is that quenching by heating again to a quenching temperature, long stable Life is long. In this pattern A, the heat treatment time is slightly longer, but since the carbide has sufficient time to dissolve, the surface layer hardness is stabilized and a long life is ensured. When the pattern B is subjected to the induction hardening a plurality of times, the surface hardness is not so much improved, but the rolling life tends to be slightly longer. This tendency of long life is promoted as the number of repetitions increases.
【００３３】表６に示すミクロ組織や表層硬度の結果か
ら、パターンＡとパターンＢとは、どちらも硬度むらが
でき難く、オーステナイト結晶粒度番号は９以上で、か
つ表層硬度ＨＶ７００以上が得られている。このため、
結晶粒度、ミクロ組織が微細であることが転動疲労寿命
や割れ強度に好影響を与えている。From the results of the microstructure and the surface hardness shown in Table 6, both Pattern A and Pattern B are hard to have uneven hardness, and have an austenite grain size number of 9 or more and a surface hardness of HV 700 or more. I have. For this reason,
The fine grain size and microstructure have a favorable effect on rolling fatigue life and crack strength.
【００３４】[0034]
【表６】 [Table 6]
【００３５】（割れ強度試験結果）： 比較例である標
準的な高周波焼入れ品（パターンＣ）に比べ、実施例の
パターンＡやパターンＢは、静的強度で１．２倍以上、
疲労寿命で２倍以上となっている。表６のミクロ組織や
表層硬度の結果によれば、パターンＡ、パターンＢのい
ずれも、硬度むらが生じにくく、オーステナイト結晶粒
度番号９番以上、かつ表層硬度ＨＶ７００以上が得られ
ている。このように、結晶粒度、ミクロ組織が細かく表
層硬度が高いことが、割れ強度試験に好影響を及ぼして
いると判断できる。(Results of Crack Strength Test): Compared with a standard induction hardened product (pattern C) as a comparative example, the static strength of the pattern A and the pattern B of the embodiment is 1.2 times or more.
The fatigue life is twice or more. According to the results of the microstructure and the surface hardness shown in Table 6, in each of Pattern A and Pattern B, hardness unevenness hardly occurs, and an austenite crystal grain size No. 9 or more and a surface hardness HV 700 or more are obtained. Thus, it can be determined that the fine grain size and microstructure and high surface layer hardness have a favorable effect on the crack strength test.
【００３６】本実施例では、パターンＡとして、高周波
加熱後に空冷する例を示したが、十分な炭素や合金元素
の溶け込みが得られれば、変態点を切る速度は本発明の
効果に影響はなく、水冷やガス冷却等を採用することが
できる。また、パターンＢでは、３サイクルの焼入れ処
理の例を示したが、結晶粒度が細かくなる複数回の焼入
れ処理であるかぎり、回数によらず採用することができ
る。また、鋼の代表例としてＳ５３Ｃ鋼をベースとして
実験を組み立てたが、炭素含有率０．５ｗｔ％以上の鋼
ならば、本実施例の熱処理パターンを用いることによ
り、表層硬度ＨＶ７００以上、オーステナイト結晶粒度
番号９番以上を得ることができる。このため、炭素含有
率０．５％以上であるかぎり、化学成分上の制約はほと
んどないといえる。In this embodiment, the pattern A is air-cooled after high-frequency heating. However, if sufficient penetration of carbon and alloy elements is obtained, the speed at which the transformation point is cut does not affect the effect of the present invention. , Water cooling or gas cooling can be adopted. Further, in the pattern B, an example of the quenching process of three cycles is shown. However, as long as the quenching process is performed a plurality of times to reduce the crystal grain size, the quenching process can be adopted regardless of the number of times. In addition, an experiment was set up based on S53C steel as a typical example of steel. However, if the steel has a carbon content of 0.5 wt% or more, the heat treatment pattern of this embodiment can be used to obtain a surface hardness of HV700 or more and an austenite grain size. Number 9 or higher can be obtained. For this reason, as long as the carbon content is 0.5% or more, it can be said that there is almost no restriction on the chemical components.
【００３７】上記において、本発明の実施の形態につい
て説明を行なったが、上記に開示された本発明の実施の
形態は、あくまで例示であって、本発明の範囲はこれら
発明の実施の形態に限定されない。本発明の範囲は、特
許請求の範囲の記載によって示され、さらに特許請求の
範囲の記載と均等の意味および範囲内でのすべての変更
を含むものである。Although the embodiments of the present invention have been described above, the embodiments of the present invention disclosed above are merely examples, and the scope of the present invention is not limited to these embodiments. Not limited. The scope of the present invention is shown by the description of the claims, and further includes all modifications within the meaning and scope equivalent to the description of the claims.
【図１】 本発明の実施例における高周波焼入れパター
ンを示す図である。（ａ)は本発明の実施例のパターン
Ａであり、（ｂ）は本発明の他の実施例のパターンＢで
あり、（ｃ）は比較のためのパターンＣ，Ｄ，Ｅであ
る。FIG. 1 is a diagram showing an induction hardening pattern according to an embodiment of the present invention. (A) is a pattern A of an embodiment of the present invention, (b) is a pattern B of another embodiment of the present invention, and (c) is patterns C, D, and E for comparison.
【図２】 オーステナイト結晶粒度を示す図である。
（ａ）は、本発明の実施例のオーステナイト結晶粒を示
す図であり、（ｂ）は比較材のオーステナイト結晶粒を
示す図である。FIG. 2 is a diagram showing austenite grain size.
(A) is a figure which shows the austenite crystal grain of the Example of this invention, (b) is a figure which shows the austenite crystal grain of a comparative material.
Claims (8)
方法において、 高周波加熱して焼入れる工程と、 前記焼入工程の前に、少なくとも１回、Ａ3変態点を超
えて高周波加熱してＡ1変態点以下に冷却する工程とを
備える、高周波焼入れ方法。1. A method of performing an induction hardening treatment on a work, comprising: a step of performing high-frequency heating and quenching; and a step of performing high-frequency heating beyond the A 3 transformation point at least once before the quenching step. A step of cooling to below one transformation point.
て高周波加熱し、前記Ａ3変態点を超える温度域に所定
時間以上保持し、次いで、そのままＡ1変態点以下に冷
却する工程を備える、請求項１に記載の高周波焼入れ方
法。To wherein prior to said quenching step, and high frequency heating beyond the A 3 transformation point, and held for a predetermined time or more in a temperature range exceeding the A 3 transformation point, then, as it is cooled below the A 1 transformation point The induction hardening method according to claim 1, further comprising a step of performing quenching.
間以上保持する工程では、そのまま焼入温度に保持する
処理、および高周波電源を切って放置する処理の少なく
とも一方を行なう、請求項１または２に記載の高周波焼
入れ方法。3. The process of maintaining the quenching temperature in the temperature range exceeding the A 3 transformation point for a predetermined time or more includes performing at least one of a process of maintaining the quenching temperature as it is and a process of turning off the high-frequency power supply and leaving the process. Or the induction hardening method according to 2.
は、高周波電源を切って放置する処理、および強制的に
冷却する強制冷却処理のうちの少なくとも１つの処理に
より、前記ワークを冷却する、請求項１〜３のいずれか
に記載の高周波焼入れ方法。4. The step of cooling the work to a temperature lower than the A 1 transformation point, wherein the work is cooled by at least one of a process of leaving the high-frequency power supply off and a forced cooling process of forcibly cooling. The induction hardening method according to claim 1.
波加熱して焼き入れる処理を１回以上行なう、請求項１
に記載の高周波焼入れ方法。5. The method according to claim 1, wherein, before the quenching step, a quenching process is performed at least once by high frequency heating to a quenching temperature.
Induction hardening method described in 1.
周波焼入れ方法を適用して得られた鋼部品であって、 前記鋼部品の表層部のオーステナイト結晶粒度番号が平
均９番以上である、鋼部品。6. A steel part obtained by applying the induction hardening method according to any one of claims 1 to 5, wherein an austenite grain size number of a surface layer portion of the steel part is 9 or more on average. There are steel parts.
み、さらに表層硬度ＨＶ７００以上を備える、請求項６
に記載の鋼部品。7. The steel part according to claim 6, wherein the steel part contains 0.5% by weight or more of carbon and further has a surface hardness HV of 700 or more.
A steel part according to.
または７に記載の鋼部品。8. The steel part according to claim 6, wherein the steel part is a bearing part.
Or a steel part according to 7.
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