JP2004124247A - Heat treatment method and heat treatment apparatus for annular member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method with which even an annular thin member having large diameter can be subjected to quenching at small deformation and a low cost. <P>SOLUTION: The size of a first gap C1 between the inner peripheral surface of the steel-made annular member 1 and the outer peripheral surface 21 of a cylindrical projecting part 11b in a holding tool 10, is made to be > 0% to ≤ 0.11% of the inner diameter D of the annular member 1 so as to insert the projecting part 11b through a center hole of the annular member 1. Further, the size of a second gap C2 between the annular member 1 and a holding surface 23, is made to be ≤ 6% of the width h of the annular member 1 so as to interpose the annular member 1 between the upper and the lower parts with two holding surfaces 22, 23 in the holding tool 10. A plurality of pins 32 are radially disposed in the inside of the annular member 1 and the positions in the diameter direction of the outer end parts of the pins 32, are adjusted by adjusting the length of a connecting member 40. Then, the quenching is applied while pushing the inner peripheral surface of the annular member 1 with the outer end parts of the pins 32. <P>COPYRIGHT: (C)2004,JPO

Description

【００１６】
さらに、本発明に係る請求項６の環状部材の熱処理方法は、請求項１〜５のいずれかに記載の熱処理方法において、相互に対向する２つの保持面を備える第二保持治具で、径方向に垂直な方向の両側から前記環状部材を前記両保持面の間に挟み、前記環状部材と前記保持面との間の第二隙間の大きさを、熱処理前においては前記環状部材の径方向に垂直な方向の幅の６％以下として、前記環状部材の加熱及び冷却を行うことを特徴とする。
【００１７】
このような構成であれば、大径で薄肉の環状部材であっても、十分な硬さが確保され変形を抑制しながら低コストで焼入れ又は焼戻しを施すことができる。
前記第一隙間の大きさは、熱処理前においては前記環状部材の内径の０％超過且つ０．１１％以下とし、前記第二隙間の大きさは、熱処理前においては前記環状部材の径方向に垂直な方向の幅の６％以下とすることが好ましい。前記第一隙間の大きさ及び前記第二隙間の大きさの少なくとも一方が前記各範囲を外れると、焼入れ又は焼戻しの際の前記環状部材の変形を十分に抑制することが困難となる場合がある。
【００１８】
また、本発明に係る請求項７の環状部材の熱処理装置は、鋼製の環状部材に変形を抑制しながら焼入れ又は焼戻しを施す熱処理装置であって、前記環状部材の中心穴に挿通される円柱状の第一保持治具と、放射状に配置され、前記環状部材の内周面をその外端部で押圧する複数のピンと、前記環状部材の内径に応じて前記ピンの外端部の径方向位置を前記各ピン毎に調整するピン位置調整手段と、を備えるとともに、前記環状部材の内周面と前記第一保持治具の外周面との間の第一隙間の大きさは、熱処理前においては、０より大きい値で且つ前記環状部材の収縮時の前記第一隙間の最小部分がマイナスの値となるような大きさであることを特徴とする。
【００１９】
さらに、本発明に係る請求項８の環状部材の熱処理装置は、請求項７に記載の熱処理装置において、前記環状部材が転がり軸受の外輪であり、該外輪の軌道溝を前記ピンの外端部で押圧することを特徴とする。
さらに、本発明に係る請求項９の環状部材の熱処理装置は、請求項７又は請求項８に記載の熱処理装置において、前記環状部材と接触する部分をセラミック材で構成したことを特徴とする。
【００２０】
本発明の環状部材の熱処理方法及び熱処理装置においては、真円度を良好なものとするため、環状部材の膨張・収縮に適正に追従する機構を設けてある。また、環状部材が転がり軸受の外輪である場合には、反りを抑制するため、外輪の軌道溝に接触するピンの外端の形状を適正化してある。さらに、真円度を良好なものとし、且つ倒れを抑制するため、環状部材の内周面と第一保持治具の外周面との間の第一隙間の大きさが適正となるような寸法の第一保持治具を使用している。
【００２１】
また、環状部材の内径に応じてピンの外端部の径方向位置が調整できるので、ピン等の熱処理装置を構成する部材の精度はそれほど高精度である必要がない。よって、前記部材の製造コストを低く抑えることができる。また、ピン等に摩耗が生じたとしても、交換することなく外端部の径方向位置を調整することによって対応可能である。
【００２２】
さらに、熱源として高周波加熱装置を用い、冷却は水系の冷却剤を使用して行い、加熱時と同じ状態（環状部材を保持治具に装着した状態）でそのまま冷却を行うようにすれば、熱処理装置を小型化することができる。
さらに、本発明の環状部材の熱処理装置は、熱処理前に環状部材が装着されるので、加熱した環状部材を金型に装着する装置や加熱した環状部材を加熱炉から前記装着装置へ搬送する設備等が不要である。よって、熱処理装置は全体的に簡易で小型である。また、加熱後直ちに焼入れを行うため、搬送中の温度低下もなく、よって、十分な硬さが確保され変形を抑制することができる。したがって、熱処理後の取代も少なくすることができるので、研削コストを抑えることができる。
【００２３】
【発明の実施の形態】
本発明に係る環状部材の熱処理方法及び熱処理装置の実施の形態を、図面を参照しながら詳細に説明する。
〔第一実施形態〕
図１は、環状部材１を保持治具１０に装着して焼入れを施す方法を説明する部分断面図であり、図２はその部分平面図である。なお、以下の説明における「上」，「下」等の方向を示す用語は、特に断りがない限り、説明の便宜上、図１におけるそれぞれの方向を意味するものである。
【００２４】
まず、焼入れが施される環状部材１について説明する。この環状部材１はＳＵＪ２製であり、転がり軸受の軌道輪（外輪）として使用されるものである。よって、その円周方向に対して垂直な断面は略矩形をなしており、また、その内周面には軌道溝が全周にわたって連続して設けられている。そして、環状部材１の外径は９４０ｍｍ、内径は９２０ｍｍ、幅（径方向に対して垂直な方向の幅）は２６ｍｍである。なお、以下に環状部材１が外輪である場合を例に焼入れ方法を説明するが、環状部材１が内輪である場合であっても、ほぼ同様に焼入れを行うことができる。
【００２５】
環状部材１への焼入れは、保持治具１０に装着した状態で施される。この保持治具１０は、略円柱状の円柱状部材１１と円板状部材１２とで構成されており、円柱状部材１１は、大径な円柱状の基台部１１ａと、該基台部１１ａの一端に設けられた小径な円環状の凸部１１ｂと、同じく基台部１１ａの一端に設けられた棒状部１１ｃと、を備えている。これら基台部１１ａ，凸部１１ｂ，及び棒状部１１ｃは全て、保持治具１０の軸線と同心に配されている。
【００２６】
また、凸部１１ｂの上下方向ほぼ中間位置には、複数の穴が環状部材１の軌道溝に対向するように放射状に設けられていて、該穴には断面円形のピン３２が径方向に進退可能に挿通されている。このピン３２は、後述する誘導加熱コイル３３によって高周波誘導を受けにくいような材質で構成されており、例えば、オーステナイト系ステンレス鋼が好ましく、セラミック材がさらに好ましい。
【００２７】
なお、径方向外方を向いたピン３２の端部（以降は外端と記す）は、環状部材１の軌道溝と接触することとなるので、加熱時や冷却時の加熱ムラ，冷却ムラを抑制し、可能な限り接触面積を小さくするために、前記軌道溝を構成する曲面よりも小径の球面とされている。ただし、環状部材１が内輪の場合は、内輪の内周面には軌道溝はないので、前記球面の大きさは特に限定されない。
【００２８】
なお、この保持治具１０が、本発明の構成要件たる第一保持治具と第二保持治具とに相当する。本実施形態においては、保持治具１０が第一保持治具と第二保持治具との両方の機能を備えている（すなわち、第一保持治具と第二保持治具とが一体とされた保持治具である）が、それぞれの機能を備える２つの保持治具を用いてもよい。また、保持治具１０の材質は非磁性材料が望ましいが、軟鋼等でも差し支えない。
【００２９】
一方、径方向内方を向いたピン３２の端部（以降は内端と記す）には、連結部材４０の一端が連結されていて、連結部材４０は該連結部分を中心に上下方向に回転可能とされている。また、連結部材４０の他端は、棒状部１１ｃが挿通されたウェイト５０に連結されていて、連結部材４０は該連結部分を中心に上下方向に回転可能とされている。
【００３０】
なお、連結部材４０は、ピン３２の内端に連結された第一ロッド４１と、ウェイト５０に連結された第二ロッド４２と、第一ロッド４１及び第二ロッド４２の間に介在された連結ループ４３と、で構成されている。第一ロッド４１及び第二ロッド４２と連結ループ４３とはねじ構造によって取り付けられていて、第一ロッド４１及び第二ロッド４２は前記ねじ構造によって連結部材４０の長手方向に進退するようになっているので、連結部材４０は該進退によって所望の長さに調節可能となっている。そして、各連結部材４０の長さは環状部材１の内径に応じて調整され、さらに、全てのピン３２の外端が保持治具１０の軸線と同心となるように調整されている。なお、この連結部材４０が、本発明の構成要件たるピン位置調整手段に相当する。
【００３１】
このようなリンク機構を備えており、さらに、棒状部１１ｃが挿通されたウェイト５０は、棒状部１１ｃに沿って上下方向に移動可能となっているので、ウェイト５０が下方に移動すると径方向外方へ向いた力がピン３２に作用し、ウェイト５０が上方に移動すると径方向内方へ向いた力がピン３２に作用することとなる。
【００３２】
なお、ウェイト５０の移動に対する摩擦抵抗を減少させるため、ウェイト５０と棒状部１１ｃとの間にすべり軸受や転がり軸受を介在させてもよい。さらに、本実施形態においては、ウェイト５０の下方への移動は、ウェイト５０自身に作用する重力によって生じるようになっているが、エアシリンダ等のアクチュエータによって移動させるようにしてもよい。本実施形態においては、９８〜２９４０Ｎのウェイト５０を用いた。
【００３３】
ウェイト５０を下方に移動させると、ピン３２が凸部１１ｂに設けられた前記穴にすべり案内されて径方向外方に移動して、ピン３２の外端の球面が環状部材１の軌道面に嵌め合わされる。このように、第一実施形態においては、連結部材４０によるリンク機構を用いて、環状部材１の軌道溝にピン３２を接触させている。そして、環状部材１は前記リンク機構によって径方向外方に凸部１１ｂの軸線と同心状に押圧されているので、加熱による膨張及び冷却による収縮等の際に、環状部材１と後述する誘導加熱コイル３３との偏心が防止される。
【００３４】
このとき、ピン３２の適正な数は環状部材１の外径によって異なるが、放射状に配されたピン３２において、隣接するピン３２の外端の間の距離Ｃが２５０ｍｍ以下となるような数とすることが好ましい。前記距離Ｃが２５０ｍｍを超えると、環状部材１の変形を抑制する効果が低下するおそれがある。このような問題がより生じにくくするためには、距離Ｃが１５０ｍｍ以下となるようなピン数とすることがより好ましい。本実施形態においては１２個のピン３２を使用したが、環状部材１の変形を抑制する効果と保持治具１０の製造しやすさとを考え合わせると、６〜８個でも差し支えない。
【００３５】
また、連結部材４０の長さを調整することにより、環状部材１の内径に応じてピン３２の外端部の径方向位置を調整できるので、前記リンク機構を構成する部材やピン３２の精度はそれほど高精度である必要がない。よって、熱処理装置の製造コストを低く抑えることができる。また、前記リンク機構を構成する部材の特定の部分やピン３２の先端などは摩耗が生じやすいが、仮に摩耗が生じたとしても、それらを交換することなくピン３２の外端部の径方向位置を調整することによって対応可能である。
【００３６】
次に、環状部材１を保持治具１０に装着する方法について説明する。
初期においては、ウェイト５０は図示しないストッパーによって棒状部１１ｃの上部に固定されており、このときピン３２の外端は、凸部１１ｂの外周面２１よりも径方向外方に突出していない状態となっている。
このような保持治具１０の凸部１１ｂを環状部材１の中心穴に挿通した上、中心に穴を有する（すなわち環状の）円板状部材１２を凸部１１ｂの上端に取り付ける。そうすると、環状部材１は、凸部１１ｂの外周面２１によって径方向の動きが規制される。また、凸部１１ｂの径方向外方に位置する基台部１１ａの上端面２２と、円板状部材１２の下面２３と、によって環状部材１が上下から挟まれるため、上下方向の動きが規制される。なお、凸部１１ｂの径方向外方に位置する基台部１１ａの上端面２２と円板状部材１２の下面２３とが、本発明の構成要件たる保持面に相当するので、以降は前記各面２２，２３を保持面と記す場合もある。
【００３７】
このとき、環状部材１の内周面（軌道溝の部分は除く）と凸部１１ｂの外周面２１（円柱面）との間の径方向隙間（第一隙間Ｃ１）は、環状部材１の内径Ｄの０％超過且つ０．１１％以下とされている。また、環状部材１の上下の両平面と２つの保持面２２，２３との間の上下方向の隙間（第二隙間Ｃ２）は、環状部材１の幅ｈの６％以下とされている。ただし、本実施形態においては、環状部材１の上側の平面と保持面２３との間に、第二隙間Ｃ２が形成されている。
【００３８】
次に、環状部材１に焼入れを施す手順を説明する。
上記のように保持治具１０に装着された環状部材１の径方向外方には、適当な隙間をおいて円周状にヒータの誘導加熱コイル３３が配置されていて、図示しない放射温度計により環状部材１の温度を監視しながら、このヒータにより加熱を行うことができるようになっている。
【００３９】
また、誘導加熱コイル３３の下側には冷却ジャケット３４が円周状に配置されている。冷却ジャケット３４の内径面には複数の噴射口（図示せず）が設けられていて、該噴射口から水等の冷媒が環状部材１に向けて噴射され、環状部材１の冷却が行われるようになっている。さらに、保持治具１０は図示しない回転テーブルに固定されていて、環状部材１を回転させながら加熱することができる。静止した状態で加熱した場合は、環状部材１と誘導加熱コイル３３との軸心が一致していないと加熱ムラが生じて、硬さムラや変形が生じやすくなるが、環状部材１を回転させながら加熱するので、環状部材１と誘導加熱コイル３３との軸心が多少一致していなかったとしても、環状部材１は均一に加熱される。
【００４０】
なお、保持治具１０と誘導加熱コイル３３との間の距離は、環状部材１と誘導加熱コイル３３との間の距離よりも大きくなるようにすることが好ましい。これは、保持治具１０と誘導加熱コイル３３との間の距離が近すぎると、保持治具１０が加熱されて環状部材１の加熱効率が低下するからである。
保持治具１０に装着した環状部材１を回転させながら、誘導加熱コイル３３によって所望の温度（９００〜１１００℃）に誘導加熱する。その際には、設定温度に到達した時点で加熱を止め、その後は熱拡散によって均熱する。
【００４１】
環状部材１を加熱すると、膨張した環状部材１が基台部１１ａの上端面２２上を滑ることとなるが、環状部材１と保持治具１０とは同じ鉄系材料であり、さらに環状部材１は８００℃を超える高温となることから、両者の摩擦抵抗が大きくなる。さらに、環状部材１の径が大きくなると上端面２２上を滑る距離が大きくなるので、摩擦抵抗が環状部材１の真円度に悪影響を及ぼすおそれがある。このため、基台部１１ａの保持面２２が位置する部分を、摩擦抵抗を低減し且つ耐熱性を有するセラミック材で構成したり、セラミック材や黒鉛で被覆することが好ましい。また、保持面２２に凹凸を設けて、接触面積を小さくすることも有効である。
【００４２】
環状部材１の全体が均一に加熱されたところで、環状部材１の径方向外方に冷却ジャケット３４が位置するまで、保持治具１０を下方に移動させる。そして、冷却ジャケット３４から冷却水を噴射（５０〜１００Ｌ／ｍｉｎ）して環状部材１を急冷し、焼入れを施す。
軸受鋼などのような高炭素鋼で構成された環状部材１は、全体を均一に冷却すると過冷却により割れを生じやすいため、焼き割れ対策として、環状部材１の径方向外方側のみから冷却を行うことが重要である。環状部材１の径方向外方側のみから冷却され、さらに、周方向において均一に冷却されるように、円板状部材１２を設けて環状部材１の上方をカバーして、径方向内方側に冷却水が至らないようにすることが好ましい。このとき、円板状部材１２の下面２３と環状部材１との間には、環状部材１の膨張を妨げないように、隙間を設ける必要がある。
【００４３】
冷却が終了したら、図示しないシリンダによりウェイト５０を上方に移動させてピン３２を径方向内方に移動させ、環状部材１に作用している径方向外方に向いた力を取り除く。
焼入れ後は、以下のようにして焼戻しを施した。まず、保持治具１０を上方に移動させ、再び環状部材１の径方向外方にヒータが位置するようにした。そして、ヒータに通電して２５０〜３００℃に加熱した。その際には、設定温度に到達した時点でヒータの電源を切り、その後は熱拡散によって均熱し徐冷（空冷）した。なお、焼戻しは大気炉内で行っても差し支えない。また、その際に反りや真円度の矯正を行うことも有効である。
【００４４】
ここで、焼入れ時の変形が抑制される機構について説明する。
環状部材１は加熱によって膨張するので、第一隙間Ｃ１は拡大する。このとき、第一隙間Ｃ１の拡大に応じてウェイト５０が下方に移動し、ピン３２が径方向外方に移動する。環状部材１が径方向に均一に膨張しないと（真円を保たないと）、環状部材１の円周上の位置によって誘導加熱コイル３３との相対位置にバラツキが生じて加熱ムラが起き、その結果、環状部材１に変形，割れ，硬さムラ等の不具合が生じるおそれがある。しかしながら、全てのピン３２が径方向外方に均一に移動して環状部材１を押圧するので、環状部材１が均一に膨張して、上記のような不具合が生じることを防止している。
【００４５】
また、冷却時には環状部材１は収縮し、環状部材１の内周面のほぼ全面において保持治具１０（凸部１１ｂの外周面２１）に接触するので、環状部材１は保持治具１０の形状に沿って真円度が矯正される。そして、環状部材１の温度がＭｓ点以下となると環状部材１は膨張するので、環状部材１の内周面は凸部１１ｂの外周面２１から離れるが、ピン３２により径方向外方に押圧されているので、このときの変形も防止される。
【００４６】
なお、本実施形態のような保持治具１０を用いる方法は、前述のリンク機構により、環状部材１の変形を抑制することと環状部材１を保持治具１０と同心に配置することとを同時に行うことができるので、環状部材１の焼入れを高い生産性で行うことができる。また、本実施形態における環状部材１の変形抑制は、位置によるものではなくウェイト５０の定圧によるものであることも、焼入れの生産性を向上させる理由となっている。
【００４７】
さらに、環状部材１をあらかじめ保持治具１０に装着して焼入れを施すので、従来のように、加熱した環状部材を金型に装着する装置や、加熱した環状部材を加熱炉から前記装置へ搬送する設備は不要である。したがって、焼入れを行う設備がそれほど巨大なものとはならず、簡易なものとすることができる。
さらに、加熱後は搬送することなく直ちに焼入れを行うことができるので、搬送による温度低下もなく焼入れにより十分な硬さが確保され、変形を少なく抑制することができる。よって、焼入れ後の研削取代を少なくすることができるので、加工コストを低く抑えることができ、環状部材を低コストで製造することができる。
【００４８】
次に、内径Ｄを種々変更した環状部材１に上記のように焼入れを施して、第一隙間Ｃ１の大きさと環状部材１の変形の抑制効果との関係を評価した。
図３のグラフは、環状部材１の内径Ｄに対する第一隙間Ｃ１の大きさの比率と、焼入れ後の環状部材１の真円度と、の相関を示すものである。このグラフの横軸は、環状部材１の内径Ｄに対する第一隙間Ｃ１の大きさの比率を示しており、常温における環状部材１の内径をＤ、常温における保持治具１０の凸部１１ｂの外径をｄとしたときに、（Ｄ−ｄ）／Ｄ×１００（％）で算出される値である。なお、第二隙間Ｃ２の大きさは、環状部材１の幅ｈの１％に統一した。
【００４９】
図３のグラフから、第一隙間Ｃ１の大きさが環状部材１の内径Ｄの０％超過且つ０．１１％以下であると、焼入れ後の環状部材１の真円度が優れていて、変形の抑制効果が高いことが分かる。そして、０．０７％以下であると変形の抑制効果がより高く、０．０３％以下であると変形の抑制効果が極めて高いことが分かる。なお、第一隙間Ｃ１を０％超過とする理由は、０％以下であると加熱前に環状部材１に凸部１１ｂを挿通することが困難となるためである。
【００５０】
次に、環状部材１の外径，ウェイト５０の荷重，及びピン３２の数を種々変更しつつ上記のように焼入れを施して、焼入れ後の環状部材１の真円度を測定した結果を説明する。
環状部材１は外径が４５０，６００，９６０ｍｍの３種類、ピン３２の数は６，８，１２個のいずれかとして、ウェイト５０を９８〜２９４０Ｎの間で種々変更して焼入れを施した。なお、第一隙間Ｃ１の大きさは環状部材１の内径Ｄの０．０５％に、第二隙間Ｃ２の大きさは環状部材１の幅ｈの１％に統一した。
【００５１】
その結果を図４のグラフに示す。このグラフの横軸は、矯正指数Ｋと称する本発明独自のパラメータである。この矯正指数Ｋは外径４００ｍｍの薄肉の環状部材を基準としており、前述の式から算出される。
図４のグラフから分かるように、矯正指数Ｋが２３．５〜１３８．２の場合は、真円度が１ｍｍ以下と優れた値で安定しているが、矯正指数Ｋが２３．５未満の場合及び１３８．２超過の場合は、真円度が１ｍｍを超える値となっている。そして、矯正指数Ｋが４９〜１２７．４の場合は、真円度が特に優れた値となっている。
【００５２】
矯正指数Ｋが２３．５未満の場合に真円度が大きくなるのは、ピンが環状部材に与える負荷が小さいために、前加工により付与されていた残留応力がオーステナイト変態時に開放することによる変形を抑えることができないことと、マルテンサイト変態時に生じる変態を抑えることができないことが理由として考えられる。
【００５３】
また、矯正指数Ｋが１３８．２超過の場合に真円度が大きくなるのは、ピンが環状部材に与える負荷が環状部材の剛性に対して大き過ぎるために、オーステナイト変態時に塑性変形を起こすことと、焼入れの途中過程で均一に収縮できなかったため多角形状に変形することが理由として考えられる。
なお、図５に示す変形例のように、ピン３２の外端部を平面状とすれば、環状部材１の軌道溝の幅方向の離れた上下２カ所に各ピン３２の外端が接触することとなる。そうすると、環状部材１の軌道溝とピン３２とが１カ所で接触する場合と比較して、環状部材１の反りをより効果的に抑制することができる。
【００５４】
〔第二実施形態〕
以下に、第一実施形態とは別の焼入れ方法を説明する。ただし、第二実施形態の方法は、ウェイトによる荷重を環状部材に伝える機構等が異なる点を除いては第一実施形態とほぼ同様であるので、異なる部分のみ説明し、同様の部分の説明は省略する。
【００５５】
図６は、環状部材を保持治具に装着して焼入れを施す方法を説明する正面図であり、一部を破断して示してある。なお、以下の説明における「上」，「下」等の方向を示す用語は、特に断りがない限り、説明の便宜上、図６におけるそれぞれの方向を意味するものである。また、図６においては、図１と同一又は相当する部分には、図１と同一の符号を付してある。
【００５６】
環状部材１の構成は前述の第一実施形態と同様であり、また、環状部材１への焼入れは、第一実施形態と同様に保持治具１０に装着した状態で施される。
この保持治具１０の構成は第一実施形態と同様であり、また、第一実施形態と同様に、凸部１１ｂに設けられた穴に断面円形のピン３２が径方向に進退可能に挿通されている。なお、図６においては環状部材１の軌道溝と接触するピン３２の外端は平面状であるが、第一実施形態と同様に、環状部材１の軌道溝を構成する曲面よりも小径の球面としてもよい。
【００５７】
このピン３２の内端は、略円錐状のスライドリング５１が有する円錐面５１ａに接触している。そして、スライドリング５１はウェイト５０が載置されたうえ、円錐の頂点を下方に向けて、上下方向に移動可能に棒状部１１ｃに取り付けられている。よって、スライドリング５１を下方に移動させると、円錐面５１ａによりピン３２の内端が押され、凸部１１ｂに設けられた前記穴にすべり案内されてピン３２が径方向外方へ移動することとなる。一方、スライドリング５１を上方に移動させると、円錐面５１ａとピン３２の内端とが離れるから、ピン３２に取り付けられたバネ５２の付勢力によりピン３２が径方向内方へ移動することとなる。
【００５８】
なお、ピン３２には、第一実施形態において前述した連結部材４０とほぼ同様の構造を有するピン長さ調整部６０が備えられている。そして、ピン長さ調整部６０でピン３２の長さを調整することにより、環状部材１の内径に応じてピン３２の外端部の径方向位置を調整できるようになっている。このピン長さ調整部６０が、本発明の構成要件たるピン位置調整手段に相当する。
【００５９】
このように、第二実施形態においては、第一実施形態の連結部材４０によるリンク機構の代わりにスライドリング５１による垂直方向変位を水平方向変位に変換する機構を用いて、環状部材１の軌道溝にピン３２を接触させている。そして、環状部材１は前記変換機構によって径方向外方に凸部１１ｂの軸線と同心状に押圧されているので、加熱による膨張及び冷却による収縮等の際に、環状部材１と後述する高周波誘導加熱コイル３３との偏心が防止される。
【００６０】
環状部材１を保持治具１０に装着する方法及び環状部材１に焼入れを施す手順については、第一実施形態と同様であるので詳細な説明は省略するが、環状部材１の径方向外方にヒータの高周波誘導加熱コイル３３が配置されており、このヒータによって加熱が行われる。このとき、保持治具１０はモータ５４により回転駆動することが可能とされており、環状部材１を回転させながら加熱することができるようになっている。また、高周波誘導加熱コイル３３の下側には冷却ジャケット３４が配置されており、環状部材１の冷却が行われる。これらのことから、環状部材１にずぶ焼入れ等の焼入れ処理や焼戻し処理が施される。
【００６１】
上記のように熱処理を施した際に変形が抑制される機構及び上記のように熱処理を施した場合の効果は第一実施形態と同様であるが、環状部材１の変形を抑制して真円状に近い形状を保つためには、放射状に配置されたピン３２の外端がほぼ真円状に配されている必要がある。そのためには、保持面２２の水平性，棒状部１１ｃの垂直性，円錐面５１ａの精度等が高精度である必要があるが、これらの部材は機械加工により製造されているので必要な精度で製造することが可能である。
【００６２】
例えば、第一実施形態のようなリンク機構の場合は、ピン３２と連結部材４０との連結部分やウェイト５０と連結部材４０との連結部分に、隙間や摩擦などの誤差要因が存在するため、これらを考慮して熱処理装置の設計を行う必要があるが、本実施形態のような垂直方向変位を水平方向変位に変換する機構の場合は、前記各部材を高精度に加工すればよいので、熱処理装置の精度の確保や維持管理等に大変有利である。
【００６３】
なお、ピン３２の外端と環状部材１との接触部分の面積は、できるだけ小さい方が好ましい（点接触や線接触が好ましい）。高周波誘導加熱コイル３３による加熱は環状部材１の外側から行われるので、前記接触部分の面積が大きいと熱が前記接触部分からピン３２に伝導しやすくなり、環状部材１を均熱化しにくくなる。そうすると、環状部材１の内周面に硬さの低い部分が生じ、それにより環状部材１に変形が生じるおそれがある。また、冷却時にも同様な冷却ムラが発生しやすくなる。
【００６４】
また、熱処理時に環状部材１が膨張又は収縮した際の環状部材１と保持面２２との摩擦抵抗を減少させるために、下記のような手段を講じることが好ましい。すなわち、環状部材１の下部の保持面２２と接触する部分を少なくする、セラミック，炭素材等の高融点材料で保持面２２を構成する、又は、セラミック，炭素材等で構成された潤滑剤を保持面２２に塗布する等の手段である。
【００６５】
本実施形態においてはセラミックで保持面２２を構成する手段が採用されており、図６のように基台部１１ａの保持面２２が位置する部分に、セラミックで構成された部材５５が埋設されている。
さらに、軸受鋼等のような高炭素鋼に焼入れを施す場合には、焼き割れ対策として環状部材１の外径側からのみ冷却を行うことが重要である。均一に冷却することを考慮すると、水等の冷媒が環状部材１の内周面に接触しないように環状部材１の上方に蓋等を設けることが好ましい。
【００６６】
さらに、図６のようにピン３２にバネ５２を取り付けると、環状部材１の保持治具１０からの取り外しが容易となる。
さらに、ピン３２の外端が環状部材１の軌道溝の中心に位置するように、上下方向の位置を調整してピン３２を設けておけば、環状部材１の反りが防止されやすい。
【００６７】
さらに、軸受鋼はＭｆ点が常温以下であるので、冷却は十分に行う必要がある。Ｍｆ点より高い温度で冷却を終了してしまうと、その後もマルテンサイト変態が進行して変形が生じるおそれがある。
なお、前述の第一及び第二実施形態は本発明の一例を示したものであって、本発明は各実施形態に限定されるものではない。
【００６８】
例えば、前記各実施形態においては環状部材１はＳＵＪ２で構成されていたが、焼入れにより硬化するものであるならば、他の材料で構成されていても差し支えない。
また、前記各実施形態においては、転がり軸受の軌道輪として使用される環状部材を例示して焼入れ方法を説明したが、本発明の熱処理方法はこれに限らず種々の環状部材に適用可能であることはもちろんである。
【００６９】
【発明の効果】
以上のように、本発明の環状部材の熱処理方法及び熱処理装置によって熱処理を行えば、大径で薄肉の環状部材であっても焼入れ時の変形が少なく、また低コストである。
【図面の簡単な説明】
【図１】本発明に係る環状部材の熱処理方法の第一実施形態を説明する部分断面図である。
【図２】本発明に係る環状部材の熱処理方法の第一実施形態を説明する部分平面図である。
【図３】環状部材の内径に対する第一隙間の大きさの比率と環状部材の真円度との相関を示すグラフである。
【図４】矯正指数Ｋと環状部材の真円度との相関を示すグラフである。
【図５】本発明に係る環状部材の熱処理方法の第一実施形態の変形例を説明する部分断面図である。
【図６】本発明に係る環状部材の熱処理方法の第二実施形態を説明する一部を破断して示した正面図である。
【符号の説明】
１　　　　環状部材
１０　　　　保持治具
１１　　　　円柱状部材
１１ａ　　　基台部
１１ｂ　　　凸部
１１ｃ　　　棒状部
１２　　　　円板状部材
２１　　　　凸部の外周面
２２，２３　保持面
４０　　　　連結部材
６０　　　　ピン長さ調整部
Ｃ１　　　　第一隙間
Ｃ２　　　　第二隙間
Ｄ　　　　　環状部材の内径
ｄ　　　　　凸部の外径
ｈ　　　　　環状部材の幅
ｔ　　　　　保持面間の距離[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heat treatment method and a heat treatment apparatus for an annular member, and more particularly, to a method and an apparatus for quenching or tempering a steel annular member used for a bearing ring of a rolling bearing while suppressing deformation.
[0002]
[Prior art]
Conventionally, quenching of an annular member has been performed by, for example, maintaining the austenitizing temperature of 800 to 850 ° C. in an electric furnace and then immersing the member in oil or the like to rapidly cool the member. However, since the annular member has insufficient rigidity, distortion occurs at the time of quenching, and the roundness and flatness are likely to be reduced.
[0003]
Therefore, when performing the quenching as described above, by mounting the annular member heated to the austenitizing temperature in a mold, by cooling the inner peripheral surface or the outer peripheral surface of the annular member in a state held by the mold, Deformation during quenching was suppressed. This utilizes a shrinkage phenomenon during cooling during quenching and an expansion phenomenon due to martensitic transformation.
[0004]
Japanese Patent Application Laid-Open No. 2000-96131 discloses a method of performing induction hardening while suppressing distortion of a work by using a work support having the following configuration.
That is, the work support includes a plurality of radially movable movable heads radially arranged on the base member, and a spring provided at the center of the base member to bias the movable head radially outward. , A slide ring and a link for transmitting the urging force of the spring to the movable head. Then, the workpiece is suppressed by distortion by performing high frequency quenching while pressing the inner surface of the work outward at a plurality of locations in the circumferential direction with the movable head.
[0005]
[Patent Document 1]
JP-A-2000-96131
[0006]
[Problems to be solved by the invention]
However, the method using the conventional mold as described above can be applied to a relatively small annular member, but can be applied to a large annular member having an outer diameter exceeding 400 mm, for example. was difficult.
In other words, in the conventional method as described above, an apparatus for mounting the heated annular member on the mold, and a facility for transporting the heated annular member from the heating furnace to the apparatus require a huge one. There was a problem that the equipment was enormously expensive.
[0007]
Further, the conventional method as described above can be applied to a relatively thick annular member, but for example, when the thickness ratio ((outer diameter−inner diameter) / outer diameter × 100) is less than 10%. In the case of a thin annular member, it has been difficult to apply.
In other words, if the annular member is thin and has a small heat capacity, the temperature of the annular member decreases while the heated annular member is conveyed to the mold, and there is a problem that sufficient hardness cannot be obtained by quenching. Was.
[0008]
For this reason, a large and thin annular member was subjected to a large amount of grinding allowance and a normal quenching (quenching without using the mold) in order to reduce the degree of deformation due to heat treatment and secure heat capacity. After that, it was formed by turning and grinding. That is, an annular member having a size larger than that of the final product is quenched, and turned into a size of the final product by turning and grinding. Therefore, there is a problem that the processing cost is high.
[0009]
On the other hand, when the method described in Japanese Patent Application Laid-Open No. 2000-96131 is applied to quenching of a bearing race, the method focuses only on improving the roundness of the method, and warping and Since no consideration has been given to suppression of falling down, it is difficult to improve the roundness as a result.
Further, there is a possibility that the temperature of the contact portion between the bearing ring and the movable head does not rise sufficiently and the hardness becomes insufficient. Therefore, there is a possibility that the rolling life is adversely affected. Therefore, the method is not suitable for a component in which hardness is emphasized, such as a bearing race.
[0010]
Further, the coolant may not be sufficiently distributed to the contact portion, and the cooling may be delayed more than other portions, and the deformation may be increased. This is a problem specific to bearing steel, that is, the method was not suitable for bearing races.
Furthermore, although the bearing ring has been partially quenched by induction hardening, so-called hardening has never been performed due to its difficulty.
[0011]
Therefore, the present invention solves the problems of the prior art described above, and performs quenching or tempering at a low cost with sufficient hardness being ensured even with a large-diameter thin-walled annular member. It is an object of the present invention to provide a heat treatment method and a heat treatment apparatus which can perform heat treatment.
[0012]
[Means for Solving the Problems]
In order to solve the above problem, the present invention has the following configuration. That is, the heat treatment method for an annular member according to claim 1 of the present invention is a heat treatment method for performing quenching or tempering while suppressing deformation of a steel annular member. Inserting one holding jig, the size of the first gap between the inner peripheral surface of the annular member and the outer peripheral surface of the first holding jig, before heat treatment, a value greater than 0 and the With the size such that the minimum portion of the first gap when the annular member contracts is a negative value, a plurality of pins are radially arranged inside the annular member, and according to the inner diameter of the annular member. After adjusting the radial position of the outer end of the pin, heating and cooling of the annular member are performed while pressing the inner peripheral surface of the annular member with the outer end of the pin.
[0013]
The heat treatment method for an annular member according to claim 2 of the present invention is the heat treatment method according to claim 1, wherein the first gap before heat treatment exceeds 0% of the inner diameter of the annular member and is 0.11% or less. It is characterized by the following.
Further, the heat treatment method for an annular member according to claim 3 according to the present invention is the heat treatment method according to claim 1 or 2, wherein the annular member is an outer ring of a rolling bearing, and the raceway groove of the outer ring is connected to the pin by the pin. Characterized by being pressed at the outer end.
[0014]
Furthermore, in the heat treatment method for an annular member according to a fourth aspect of the present invention, in the heat treatment method according to the third aspect, two spaced apart portions in the width direction of the raceway groove are pressed by outer ends of the pins. It is characterized by.
Furthermore, in the heat treatment method for an annular member according to claim 5 according to the present invention, in the heat treatment method according to any one of claims 1 to 4, the inner ends of the plurality of pins are pressed by a weight load, and The inner peripheral surface of the annular member is pressed against the outer end of the pin, and the heating and cooling of the annular member are performed by setting the correction index K defined by the following equation to 23.5 to 138.2. I do.
[0015]
(Equation 2)

[0016]
Further, the heat treatment method for an annular member according to claim 6 according to the present invention is the heat treatment method according to any one of claims 1 to 5, wherein the second holding jig provided with the two holding surfaces facing each other has a diameter. The annular member is sandwiched between the two holding surfaces from both sides in a direction perpendicular to the direction, and the size of the second gap between the annular member and the holding surface is adjusted in a radial direction of the annular member before heat treatment. The heating and cooling of the annular member is performed by setting the width to 6% or less of the width in the direction perpendicular to.
[0017]
With such a configuration, even with a large-diameter and thin annular member, quenching or tempering can be performed at low cost while securing sufficient hardness and suppressing deformation.
The size of the first gap is more than 0% and 0.11% or less of the inner diameter of the annular member before heat treatment, and the size of the second gap is in the radial direction of the annular member before heat treatment. Preferably, the width is 6% or less of the width in the vertical direction. When at least one of the size of the first gap and the size of the second gap is out of the respective ranges, it may be difficult to sufficiently suppress deformation of the annular member during quenching or tempering. .
[0018]
A heat treatment apparatus for an annular member according to claim 7 of the present invention is a heat treatment apparatus for performing quenching or tempering while suppressing deformation of a steel annular member, wherein the circular member is inserted into a center hole of the annular member. A first holding jig having a columnar shape, a plurality of pins arranged radially and pressing an inner peripheral surface of the annular member at an outer end thereof, and a radial direction of an outer end of the pin according to an inner diameter of the annular member. A pin position adjusting means for adjusting the position for each of the pins, and the size of the first gap between the inner peripheral surface of the annular member and the outer peripheral surface of the first holding jig is set before the heat treatment. Is characterized by a value larger than 0 and a size such that a minimum portion of the first gap at the time of contraction of the annular member becomes a negative value.
[0019]
Furthermore, the heat treatment apparatus for an annular member according to claim 8 according to the present invention is the heat treatment apparatus according to claim 7, wherein the annular member is an outer ring of a rolling bearing, and a raceway groove of the outer ring is connected to an outer end of the pin. Pressing with.
According to a ninth aspect of the present invention, there is provided the heat treatment apparatus for an annular member according to the seventh or eighth aspect, wherein a portion in contact with the annular member is formed of a ceramic material.
[0020]
In the heat treatment method and heat treatment apparatus for an annular member according to the present invention, a mechanism for appropriately following expansion and contraction of the annular member is provided in order to improve the roundness. When the annular member is the outer ring of a rolling bearing, the shape of the outer end of the pin that contacts the raceway groove of the outer ring is optimized in order to suppress warpage. Furthermore, in order to improve the roundness and suppress the fall, the size of the first gap between the inner peripheral surface of the annular member and the outer peripheral surface of the first holding jig is appropriate. The first holding jig is used.
[0021]
Further, since the radial position of the outer end portion of the pin can be adjusted according to the inner diameter of the annular member, the accuracy of the members constituting the heat treatment apparatus such as the pin does not need to be very high. Therefore, the manufacturing cost of the member can be reduced. Also, even if the pin or the like is worn, it can be dealt with by adjusting the radial position of the outer end without replacing the pin.
[0022]
Further, if a high-frequency heating device is used as a heat source and cooling is performed using a water-based coolant, and cooling is performed as it is in the same state as when heating (the state in which the annular member is attached to the holding jig), heat treatment can be performed. The device can be miniaturized.
Further, since the annular member is heat-treated before the heat treatment, the apparatus for mounting the heated annular member to the mold and the equipment for transporting the heated annular member from the heating furnace to the mounting apparatus are provided. Is unnecessary. Therefore, the heat treatment apparatus is simple and small as a whole. In addition, since quenching is performed immediately after heating, there is no decrease in temperature during transportation, so that sufficient hardness is ensured and deformation can be suppressed. Therefore, the stock removal after the heat treatment can be reduced, so that the grinding cost can be suppressed.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of a heat treatment method and a heat treatment apparatus for an annular member according to the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a partial cross-sectional view for explaining a method of mounting the annular member 1 on a holding jig 10 and performing quenching, and FIG. 2 is a partial plan view thereof. Note that terms indicating directions such as “up” and “down” in the following description mean respective directions in FIG. 1 for convenience of description, unless otherwise specified.
[0024]
First, the annular member 1 to be hardened will be described. This annular member 1 is made of SUJ2 and is used as a raceway (outer ring) of a rolling bearing. Therefore, the cross section perpendicular to the circumferential direction is substantially rectangular, and the raceway groove is continuously provided on the inner peripheral surface over the entire circumference. The outer diameter of the annular member 1 is 940 mm, the inner diameter is 920 mm, and the width (width in a direction perpendicular to the radial direction) is 26 mm. The quenching method will be described below taking the case where the annular member 1 is an outer ring as an example. However, even when the annular member 1 is an inner ring, quenching can be performed in substantially the same manner.
[0025]
Quenching of the annular member 1 is performed in a state where the annular member 1 is mounted on the holding jig 10. The holding jig 10 includes a substantially cylindrical columnar member 11 and a disk-shaped member 12. The cylindrical member 11 includes a large-diameter cylindrical base 11 a and a base A small-diameter annular convex portion 11b provided at one end of the base 11a and a rod-shaped portion 11c also provided at one end of the base 11a are provided. The base 11a, the protrusion 11b, and the rod 11c are all disposed concentrically with the axis of the holding jig 10.
[0026]
Also, a plurality of holes are provided radially at approximately middle positions in the vertical direction of the convex portion 11b so as to face the raceway grooves of the annular member 1, and pins 32 having a circular cross section advance and retreat in the radial direction. It is inserted as possible. The pin 32 is made of a material that is unlikely to receive high-frequency induction by an induction heating coil 33 described later. For example, an austenitic stainless steel is preferable, and a ceramic material is more preferable.
[0027]
Since the end of the pin 32 facing outward in the radial direction (hereinafter referred to as the outer end) comes into contact with the raceway groove of the annular member 1, unevenness in heating and cooling during heating and cooling is reduced. In order to suppress and minimize the contact area as much as possible, the spherical surface has a smaller diameter than the curved surface constituting the track groove. However, when the annular member 1 is an inner race, there is no raceway groove on the inner peripheral surface of the inner race, so the size of the spherical surface is not particularly limited.
[0028]
The holding jig 10 corresponds to a first holding jig and a second holding jig which are constituent elements of the present invention. In the present embodiment, the holding jig 10 has both functions of the first holding jig and the second holding jig (that is, the first holding jig and the second holding jig are integrated). However, two holding jigs having respective functions may be used. The holding jig 10 is preferably made of a non-magnetic material, but may be made of mild steel or the like.
[0029]
On the other hand, one end of a connecting member 40 is connected to an end of the pin 32 facing inward in the radial direction (hereinafter referred to as an inner end), and the connecting member 40 rotates vertically around the connecting portion. It is possible. The other end of the connecting member 40 is connected to a weight 50 into which the rod-shaped portion 11c is inserted, and the connecting member 40 is rotatable up and down around the connecting portion.
[0030]
The connecting member 40 includes a first rod 41 connected to the inner end of the pin 32, a second rod 42 connected to the weight 50, and a connection interposed between the first rod 41 and the second rod 42. And a loop 43. The first rod 41 and the second rod 42 and the connection loop 43 are attached by a screw structure, and the first rod 41 and the second rod 42 advance and retreat in the longitudinal direction of the connection member 40 by the screw structure. Therefore, the connecting member 40 can be adjusted to a desired length by the advance and retreat. The length of each connecting member 40 is adjusted according to the inner diameter of the annular member 1, and further, the outer ends of all the pins 32 are adjusted so as to be concentric with the axis of the holding jig 10. The connecting member 40 corresponds to a pin position adjusting unit which is a constituent element of the present invention.
[0031]
Since such a link mechanism is provided, and the weight 50 into which the bar-shaped portion 11c is inserted is movable in the vertical direction along the bar-shaped portion 11c, when the weight 50 moves downward, the weight 50 moves outward. The force directed in the direction acts on the pin 32, and when the weight 50 moves upward, the force directed inward in the radial direction acts on the pin 32.
[0032]
Note that a sliding bearing or a rolling bearing may be interposed between the weight 50 and the rod-shaped portion 11c in order to reduce frictional resistance to the movement of the weight 50. Further, in the present embodiment, the downward movement of the weight 50 is caused by gravity acting on the weight 50 itself, but it may be moved by an actuator such as an air cylinder. In this embodiment, a weight 50 of 98 to 2940N is used.
[0033]
When the weight 50 is moved downward, the pin 32 is slid and guided by the hole provided in the convex portion 11b and moves radially outward, so that the spherical surface at the outer end of the pin 32 is on the raceway surface of the annular member 1. Be fitted. As described above, in the first embodiment, the pin 32 is brought into contact with the raceway groove of the annular member 1 using the link mechanism of the connecting member 40. Since the annular member 1 is pressed radially outward by the link mechanism concentrically with the axis of the convex portion 11b, the annular member 1 and the induction heating described later are used when expanding by heating and contracting by cooling. Eccentricity with the coil 33 is prevented.
[0034]
At this time, the appropriate number of the pins 32 varies depending on the outer diameter of the annular member 1, but the number of the pins 32 arranged radially is such that the distance C between the outer ends of the adjacent pins 32 is 250 mm or less. Is preferred. If the distance C exceeds 250 mm, the effect of suppressing the deformation of the annular member 1 may be reduced. In order to make such a problem less likely to occur, it is more preferable to set the number of pins such that the distance C is 150 mm or less. In the present embodiment, twelve pins 32 are used. However, considering the effect of suppressing the deformation of the annular member 1 and the ease of manufacturing the holding jig 10, six to eight pins may be used.
[0035]
Further, by adjusting the length of the connecting member 40, the radial position of the outer end of the pin 32 can be adjusted according to the inner diameter of the annular member 1, so that the accuracy of the members constituting the link mechanism and the accuracy of the pin 32 are improved. It does not need to be so precise. Therefore, the manufacturing cost of the heat treatment apparatus can be reduced. Also, a specific portion of the member constituting the link mechanism and the tip of the pin 32 are liable to be worn, but even if the abrasion occurs, the radial position of the outer end portion of the pin 32 is not replaced. It can be dealt with by adjusting.
[0036]
Next, a method of attaching the annular member 1 to the holding jig 10 will be described.
Initially, the weight 50 is fixed to the upper part of the rod-shaped portion 11c by a stopper (not shown). At this time, the outer end of the pin 32 does not protrude radially outward from the outer peripheral surface 21 of the convex portion 11b. Has become.
The protrusion 11b of the holding jig 10 is inserted into the center hole of the annular member 1, and a disk-shaped member 12 having a hole at the center (that is, an annular shape) is attached to the upper end of the protrusion 11b. Then, the movement of the annular member 1 in the radial direction is restricted by the outer peripheral surface 21 of the projection 11b. In addition, since the annular member 1 is sandwiched from above and below by the upper end surface 22 of the base portion 11a located radially outward of the convex portion 11b and the lower surface 23 of the disk-shaped member 12, movement in the vertical direction is restricted. Is done. Note that the upper end surface 22 of the base 11a and the lower surface 23 of the disc-shaped member 12 located radially outward of the protrusion 11b correspond to a holding surface, which is a constituent element of the present invention. The surfaces 22, 23 may be referred to as holding surfaces.
[0037]
At this time, the radial gap (first gap C1) between the inner peripheral surface (excluding the raceway groove) of the annular member 1 and the outer peripheral surface 21 (cylindrical surface) of the projection 11b is the inner diameter of the annular member 1. D is more than 0% and 0.11% or less. The vertical gap (second gap C2) between the upper and lower planes of the annular member 1 and the two holding surfaces 22 and 23 is 6% or less of the width h of the annular member 1. However, in the present embodiment, a second gap C2 is formed between the upper surface of the annular member 1 and the holding surface 23.
[0038]
Next, a procedure for quenching the annular member 1 will be described.
The induction heating coil 33 of the heater is disposed radially outward of the annular member 1 mounted on the holding jig 10 as described above, with an appropriate gap therebetween, and a radiation thermometer (not shown) While the temperature of the annular member 1 is monitored, the heater can be used to perform heating.
[0039]
Further, a cooling jacket 34 is circumferentially arranged below the induction heating coil 33. A plurality of injection ports (not shown) are provided on the inner diameter surface of the cooling jacket 34, and a coolant such as water is injected from the injection ports toward the annular member 1 so that the annular member 1 is cooled. It has become. Further, the holding jig 10 is fixed to a rotary table (not shown), and can heat the annular member 1 while rotating it. When the heating is performed in a stationary state, if the axes of the annular member 1 and the induction heating coil 33 do not coincide with each other, uneven heating may occur, and uneven hardness and deformation may easily occur. Since the heating is performed while heating, the annular member 1 is uniformly heated even if the axes of the annular member 1 and the induction heating coil 33 do not slightly coincide with each other.
[0040]
It is preferable that the distance between the holding jig 10 and the induction heating coil 33 is larger than the distance between the annular member 1 and the induction heating coil 33. This is because if the distance between the holding jig 10 and the induction heating coil 33 is too short, the holding jig 10 is heated and the heating efficiency of the annular member 1 is reduced.
While rotating the annular member 1 mounted on the holding jig 10, induction heating is performed to a desired temperature (900 to 1100 ° C.) by the induction heating coil 33. At that time, the heating is stopped when the set temperature is reached, and thereafter, the temperature is uniformed by thermal diffusion.
[0041]
When the annular member 1 is heated, the expanded annular member 1 slides on the upper end surface 22 of the base 11a. However, the annular member 1 and the holding jig 10 are made of the same iron-based material. Is higher than 800 ° C., so that the frictional resistance between the two increases. Further, as the diameter of the annular member 1 increases, the distance to slide on the upper end surface 22 increases, so that the frictional resistance may adversely affect the roundness of the annular member 1. For this reason, it is preferable that the portion where the holding surface 22 of the base portion 11a is located is made of a ceramic material having reduced frictional resistance and heat resistance, or coated with a ceramic material or graphite. It is also effective to provide unevenness on the holding surface 22 to reduce the contact area.
[0042]
When the entire annular member 1 is uniformly heated, the holding jig 10 is moved downward until the cooling jacket 34 is positioned radially outward of the annular member 1. Then, cooling water is injected from the cooling jacket 34 (50 to 100 L / min) to rapidly cool the annular member 1 and to perform quenching.
Since the annular member 1 made of high carbon steel such as bearing steel is likely to be cracked by supercooling when the whole is uniformly cooled, the annular member 1 is cooled only from the radially outer side of the annular member 1 as a countermeasure against burning cracks. It is important to do. The disk-shaped member 12 is provided to cover the upper part of the annular member 1 so as to be cooled only from the radially outer side of the annular member 1 and to be uniformly cooled in the circumferential direction. It is preferable that the cooling water does not come to a predetermined temperature. At this time, a gap needs to be provided between the lower surface 23 of the disk-shaped member 12 and the annular member 1 so as not to hinder the expansion of the annular member 1.
[0043]
When the cooling is completed, the weight 50 is moved upward by a cylinder (not shown) to move the pin 32 radially inward, and the radially outward force acting on the annular member 1 is removed.
After quenching, tempering was performed as follows. First, the holding jig 10 was moved upward so that the heater was positioned outside the annular member 1 in the radial direction again. Then, the heater was energized and heated to 250 to 300 ° C. At that time, the power supply of the heater was turned off when the temperature reached the set temperature, and thereafter, the temperature was uniformed by thermal diffusion and gradually cooled (air cooled). In addition, tempering may be performed in an atmospheric furnace. At that time, it is also effective to correct the warpage and the roundness.
[0044]
Here, a mechanism for suppressing deformation during quenching will be described.
Since the annular member 1 expands by heating, the first gap C1 expands. At this time, the weight 50 moves downward according to the enlargement of the first gap C1, and the pin 32 moves radially outward. If the annular member 1 does not expand uniformly in the radial direction (unless a perfect circle is maintained), the relative position with respect to the induction heating coil 33 varies depending on the position on the circumference of the annular member 1 and uneven heating occurs. As a result, problems such as deformation, cracking, and uneven hardness may occur in the annular member 1. However, since all the pins 32 uniformly move radially outward to press the annular member 1, the annular member 1 is uniformly expanded, thereby preventing the above-described problem.
[0045]
Further, at the time of cooling, the annular member 1 contracts, and almost the entire inner peripheral surface of the annular member 1 comes into contact with the holding jig 10 (the outer peripheral surface 21 of the convex portion 11b). The roundness is corrected along. When the temperature of the annular member 1 becomes equal to or lower than the Ms point, the annular member 1 expands. Therefore, the inner peripheral surface of the annular member 1 separates from the outer peripheral surface 21 of the convex portion 11b, but is pressed radially outward by the pin 32. Therefore, deformation at this time is also prevented.
[0046]
Note that the method using the holding jig 10 as in the present embodiment simultaneously suppresses deformation of the annular member 1 and arranges the annular member 1 concentrically with the holding jig 10 by the above-described link mechanism. Since it can be performed, quenching of the annular member 1 can be performed with high productivity. In addition, the suppression of deformation of the annular member 1 in the present embodiment is based not on the position but on the constant pressure of the weight 50, which is a reason for improving the productivity of quenching.
[0047]
Furthermore, since the annular member 1 is previously mounted on the holding jig 10 and quenched, a conventional device for mounting the heated annular member on a mold or a device for transporting the heated annular member from a heating furnace to the above-described device. No equipment is required. Therefore, the equipment for quenching is not so large and can be simplified.
Furthermore, since quenching can be performed immediately after heating without transporting, sufficient hardness is ensured by quenching without temperature drop due to transport, and deformation can be suppressed to a small extent. Therefore, the grinding allowance after quenching can be reduced, so that the processing cost can be suppressed and the annular member can be manufactured at low cost.
[0048]
Next, the annular member 1 having variously changed inner diameters D was quenched as described above, and the relationship between the size of the first gap C1 and the effect of suppressing the deformation of the annular member 1 was evaluated.
The graph of FIG. 3 shows the correlation between the ratio of the size of the first gap C1 to the inner diameter D of the annular member 1 and the roundness of the annular member 1 after quenching. The horizontal axis of this graph shows the ratio of the size of the first gap C1 to the inner diameter D of the annular member 1, where D is the inner diameter of the annular member 1 at room temperature, and the outside diameter of the projection 11b of the holding jig 10 at room temperature. This is a value calculated by (D−d) / D × 100 (%), where d is the diameter. In addition, the size of the second gap C2 was unified to 1% of the width h of the annular member 1.
[0049]
According to the graph of FIG. 3, when the size of the first gap C1 is more than 0% and 0.11% or less of the inner diameter D of the annular member 1, the circularity of the annular member 1 after quenching is excellent, and It can be seen that the effect of suppressing the occurrence of is high. It can be seen that when the content is 0.07% or less, the effect of suppressing deformation is higher, and when the content is 0.03% or less, the effect of suppressing deformation is extremely high. The reason why the first gap C1 is set to exceed 0% is that if it is 0% or less, it becomes difficult to insert the convex portion 11b into the annular member 1 before heating.
[0050]
Next, the results of measuring the roundness of the annular member 1 after quenching by quenching as described above while variously changing the outer diameter of the annular member 1, the load of the weight 50, and the number of pins 32 will be described. I do.
The annular member 1 was quenched with three kinds of outer diameters of 450, 600 and 960 mm and the number of the pins 32 being any of 6, 8, and 12, and the weight 50 was variously changed between 98 and 2940N. The size of the first gap C1 was unified to 0.05% of the inner diameter D of the annular member 1, and the size of the second gap C2 was unified to 1% of the width h of the annular member 1.
[0051]
The results are shown in the graph of FIG. The horizontal axis of this graph is a parameter unique to the present invention called a correction index K. The correction index K is based on a thin annular member having an outer diameter of 400 mm, and is calculated from the above-described equation.
As can be seen from the graph of FIG. 4, when the correction index K is 23.5 to 138.2, the roundness is stable at an excellent value of 1 mm or less, but the correction index K is less than 23.5. In the case and the case of exceeding 138.2, the roundness is a value exceeding 1 mm. When the correction index K is 49 to 127.4, the roundness is a particularly excellent value.
[0052]
When the correction index K is less than 23.5, the roundness is increased because the load applied to the annular member by the pin is small, and the deformation caused by the release of the residual stress applied by the pre-processing during the austenite transformation. It is considered that the reason is that the transformation cannot be suppressed and the transformation that occurs during martensitic transformation cannot be suppressed.
[0053]
Also, when the correction index K is more than 138.2, the roundness is increased because the load applied by the pin to the annular member is too large for the rigidity of the annular member, so that plastic deformation occurs during austenite transformation. It is considered that the reason for this is that the material cannot be uniformly shrunk in the middle of quenching and is deformed into a polygonal shape.
If the outer end of the pin 32 is made flat as in the modification shown in FIG. 5, the outer end of each pin 32 comes into contact with two upper and lower portions of the raceway groove of the annular member 1 which are separated in the width direction. It will be. Then, the warpage of the annular member 1 can be more effectively suppressed as compared with the case where the raceway groove of the annular member 1 and the pin 32 contact at one place.
[0054]
(Second embodiment)
Hereinafter, a quenching method different from the first embodiment will be described. However, the method of the second embodiment is almost the same as the first embodiment except that the mechanism for transmitting the load by the weight to the annular member is different, so only the different parts will be described, and the description of the same parts will be omitted. Omitted.
[0055]
FIG. 6 is a front view for explaining a method of performing quenching by attaching the annular member to the holding jig, and is partially cut away. Note that terms indicating directions such as “up” and “down” in the following description mean respective directions in FIG. 6 for convenience of description, unless otherwise specified. In FIG. 6, the same or corresponding parts as those in FIG. 1 are denoted by the same reference numerals as those in FIG.
[0056]
The configuration of the annular member 1 is the same as that of the above-described first embodiment, and quenching to the annular member 1 is performed in a state of being mounted on the holding jig 10 as in the first embodiment.
The configuration of the holding jig 10 is the same as that of the first embodiment, and similarly to the first embodiment, a pin 32 having a circular cross section is inserted into a hole provided in the projection 11b so as to be able to advance and retreat in the radial direction. ing. In FIG. 6, the outer end of the pin 32 that comes into contact with the raceway groove of the annular member 1 is flat, but similarly to the first embodiment, the spherical surface has a smaller diameter than the curved surface forming the raceway groove of the annular member 1. It may be.
[0057]
The inner end of the pin 32 is in contact with the conical surface 51a of the substantially conical slide ring 51. The slide ring 51 has the weight 50 placed thereon, and is attached to the rod-shaped portion 11c so as to be movable up and down with the apex of the cone facing downward. Therefore, when the slide ring 51 is moved downward, the inner end of the pin 32 is pushed by the conical surface 51a, and the pin 32 is slid and guided by the hole provided in the convex portion 11b, so that the pin 32 moves radially outward. It becomes. On the other hand, when the slide ring 51 is moved upward, the conical surface 51a and the inner end of the pin 32 are separated, so that the pin 32 moves radially inward by the urging force of the spring 52 attached to the pin 32. Become.
[0058]
Note that the pin 32 is provided with a pin length adjusting section 60 having substantially the same structure as the connecting member 40 described in the first embodiment. Then, by adjusting the length of the pin 32 by the pin length adjusting section 60, the radial position of the outer end of the pin 32 can be adjusted according to the inner diameter of the annular member 1. The pin length adjusting unit 60 corresponds to a pin position adjusting unit which is a constituent element of the present invention.
[0059]
As described above, in the second embodiment, instead of the link mechanism using the connecting member 40 of the first embodiment, a mechanism that converts vertical displacement by the slide ring 51 into horizontal displacement is used, and the raceway groove of the annular member 1 is used. Is brought into contact with the pin 32. The annular member 1 is pressed radially outward by the conversion mechanism concentrically with the axis of the convex portion 11b. Therefore, when the annular member 1 is expanded by heating and contracted by cooling, it is connected to the annular member 1 and a high-frequency induction (described later). Eccentricity with the heating coil 33 is prevented.
[0060]
The method of attaching the annular member 1 to the holding jig 10 and the procedure of quenching the annular member 1 are the same as those in the first embodiment, and thus detailed description is omitted. A high-frequency induction heating coil 33 of a heater is provided, and heating is performed by the heater. At this time, the holding jig 10 can be driven to rotate by the motor 54, and can be heated while rotating the annular member 1. A cooling jacket 34 is arranged below the high-frequency induction heating coil 33 to cool the annular member 1. For these reasons, the annular member 1 is subjected to a quenching process such as soot quenching or a tempering process.
[0061]
The mechanism in which the deformation is suppressed when the heat treatment is performed as described above and the effect in the case where the heat treatment is performed as described above are the same as those in the first embodiment, but the deformation of the annular member 1 is suppressed and the roundness is suppressed. In order to maintain the shape close to the shape, the outer ends of the radially arranged pins 32 need to be arranged in a substantially perfect circle. For this purpose, the horizontality of the holding surface 22, the verticality of the rod-shaped portion 11c, the accuracy of the conical surface 51a, and the like need to be high. However, since these members are manufactured by machining, they are required to have the required accuracy. It is possible to manufacture.
[0062]
For example, in the case of the link mechanism as in the first embodiment, there are error factors such as gaps and friction in the connecting portion between the pin 32 and the connecting member 40 and the connecting portion between the weight 50 and the connecting member 40. Although it is necessary to design the heat treatment apparatus in consideration of these, in the case of a mechanism for converting the vertical displacement into the horizontal displacement as in the present embodiment, since each of the members may be processed with high precision, This is very advantageous for securing the accuracy of the heat treatment equipment and for maintaining the heat treatment equipment.
[0063]
It is preferable that the area of the contact portion between the outer end of the pin 32 and the annular member 1 be as small as possible (preferably point contact or line contact). Since the heating by the high-frequency induction heating coil 33 is performed from the outside of the annular member 1, if the area of the contact portion is large, heat is easily conducted from the contact portion to the pin 32, and the annular member 1 is hard to be evenly heated. Then, a portion having low hardness is formed on the inner peripheral surface of the annular member 1, which may cause deformation of the annular member 1. Further, similar cooling unevenness is likely to occur during cooling.
[0064]
In order to reduce the frictional resistance between the annular member 1 and the holding surface 22 when the annular member 1 expands or contracts during the heat treatment, it is preferable to take the following measures. That is, the holding surface 22 is made of a high melting point material such as a ceramic or carbon material, or a lubricant made of a ceramic, a carbon material, or the like is used to reduce the portion of the annular member 1 that contacts the holding surface 22. For example, it is a method of applying to the holding surface 22.
[0065]
In the present embodiment, means for forming the holding surface 22 with ceramic is employed. As shown in FIG. 6, a member 55 made of ceramic is embedded in a portion of the base 11a where the holding surface 22 is located. I have.
Further, when quenching high carbon steel such as bearing steel, it is important to cool only the outer diameter side of the annular member 1 as a measure against quenching cracks. In consideration of uniform cooling, it is preferable to provide a lid or the like above the annular member 1 so that a coolant such as water does not contact the inner peripheral surface of the annular member 1.
[0066]
Further, when the spring 52 is attached to the pin 32 as shown in FIG. 6, the removal of the annular member 1 from the holding jig 10 becomes easy.
Furthermore, if the pin 32 is provided by adjusting the vertical position so that the outer end of the pin 32 is located at the center of the raceway groove of the annular member 1, the annular member 1 is easily prevented from warping.
[0067]
Furthermore, since the bearing steel has an Mf point of room temperature or lower, it is necessary to sufficiently cool the bearing steel. If the cooling is terminated at a temperature higher than the Mf point, the martensitic transformation may proceed and deformation may occur thereafter.
The first and second embodiments described above are examples of the present invention, and the present invention is not limited to each embodiment.
[0068]
For example, in each of the above embodiments, the annular member 1 is made of SUJ2, but may be made of another material as long as it is hardened by quenching.
Further, in each of the above embodiments, the quenching method has been described by exemplifying the annular member used as the bearing ring of the rolling bearing. However, the heat treatment method of the present invention is not limited to this and can be applied to various annular members. Of course.
[0069]
【The invention's effect】
As described above, if the heat treatment is performed by the heat treatment method and heat treatment apparatus for an annular member of the present invention, even a large-diameter and thin-walled annular member has little deformation during quenching and is low in cost.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view illustrating a first embodiment of a heat treatment method for an annular member according to the present invention.
FIG. 2 is a partial plan view illustrating a first embodiment of a heat treatment method for an annular member according to the present invention.
FIG. 3 is a graph showing a correlation between a ratio of a size of a first gap to an inner diameter of an annular member and roundness of the annular member.
FIG. 4 is a graph showing a correlation between a correction index K and a circularity of an annular member.
FIG. 5 is a partial sectional view illustrating a modification of the first embodiment of the heat treatment method for an annular member according to the present invention.
FIG. 6 is a partially cutaway front view illustrating a heat treatment method for an annular member according to a second embodiment of the present invention.
[Explanation of symbols]
1 annular member
10 Holding jig
11 cylindrical member
11a Base
11b convex part
11c rod
12 Disc-shaped member
21 Outer peripheral surface of convex part
22, 23 Holding surface
40 connecting members
60 pin length adjustment part
C1 First gap
C2 Second gap
D Inner diameter of annular member
d Outer diameter of convex part
h Width of annular member
t Distance between holding surfaces

Claims (9)

A heat treatment method of performing quenching or tempering while suppressing deformation of a steel annular member,
A cylindrical first holding jig is inserted into the center hole of the annular member, and the size of the first gap between the inner peripheral surface of the annular member and the outer peripheral surface of the first holding jig is reduced by heat treatment. Before, with a value larger than 0 and a size such that the minimum portion of the first gap when the annular member contracts is a negative value,
A plurality of pins are radially arranged inside the annular member, and the radial position of the outer end of the pin is adjusted according to the inner diameter of the annular member.
A heat treatment method for an annular member, comprising heating and cooling the annular member while pressing an inner peripheral surface of the annular member with an outer end of the pin. The heat treatment method for an annular member according to claim 1, wherein the first gap before the heat treatment is set to be more than 0% and 0.11% or less of the inner diameter of the annular member. The heat treatment method for an annular member according to claim 1 or 2, wherein the annular member is an outer ring of a rolling bearing, and a raceway groove of the outer ring is pressed by an outer end portion of the pin. 4. The heat treatment method for an annular member according to claim 3, wherein two locations separated in the width direction of the raceway groove are pressed by outer ends of the pins. 5. The load of the weight presses the inner ends of the plurality of pins to cause the outer ends of the pins to press the inner peripheral surface of the annular member, and the correction index K defined by the following equation to be 23.5 to 23.5. 13. The heat treatment method for an annular member according to claim 1, wherein heating and cooling the annular member are performed.

A second holding jig having two holding surfaces opposed to each other, sandwiching the annular member between the two holding surfaces from both sides in a direction perpendicular to the radial direction, and providing a gap between the annular member and the holding surface; The heating and cooling of the annular member is performed by setting the size of the second gap to 6% or less of a width of the annular member in a direction perpendicular to a radial direction before the heat treatment before the heat treatment. The heat treatment method for an annular member according to any one of the above. A heat treatment apparatus for performing quenching or tempering while suppressing deformation of the steel annular member,
A cylindrical first holding jig inserted into the center hole of the annular member, a plurality of pins radially arranged, and pressing the inner peripheral surface of the annular member at its outer end, and an inner diameter of the annular member. And pin position adjusting means for adjusting the radial position of the outer end of the pin for each of the pins accordingly.
Before the heat treatment, the size of the first gap between the inner peripheral surface of the annular member and the outer peripheral surface of the first holding jig has a value larger than 0 and the first gap when the annular member contracts. A heat treatment apparatus for an annular member, characterized in that the minimum portion of the gap has a negative value. The heat treatment apparatus for an annular member according to claim 7, wherein the annular member is an outer ring of a rolling bearing, and a raceway groove of the outer ring is pressed by an outer end of the pin. The heat treatment apparatus for an annular member according to claim 7 or 8, wherein a portion that contacts the annular member is formed of a ceramic material.

Images