JP4176501B2

JP4176501B2 - Method for heat treatment of annular member

Info

Publication number: JP4176501B2
Application number: JP2003032457A
Authority: JP
Inventors: 惠造堀; 秀樹國分; 隆司村井; 正則荒川; 克己大宮; 裕清澤
Original assignee: Neturen Co Ltd; NSK Ltd
Current assignee: Neturen Co Ltd; NSK Ltd
Priority date: 2002-02-08
Filing date: 2003-02-10
Publication date: 2008-11-05
Anticipated expiration: 2023-02-10
Also published as: JP2004124247A

Description

【０００１】
【発明の属する技術分野】
本発明は、環状部材の熱処理方法に係り、特に、転がり軸受の軌道輪等に使用される鋼製の環状部材に、変形を抑制しながら焼入れ又は焼戻しを施す方法に関する。
【０００２】
【従来の技術】
従来、環状部材の焼入れは、例えば、電気炉内で８００〜８５０℃のオーステナイト化温度に保持した後に、油等に浸漬して急冷することによって行われていた。ところが、環状部材は剛性が不十分であることから、焼入れ時に歪が生じて真円度や平面度が低下しやすい。
【０００３】
そこで、上記のような焼入れを行う際において、オーステナイト化温度に加熱した環状部材を金型に装着し、環状部材の内周面又は外周面を前記金型で保持した状態で冷却することによって、焼入れ時の変形を抑制していた。これは、焼入れの冷却時の収縮現象及びマルテンサイト変態による膨張現象を利用したものである。
【０００４】
また、特開２０００−９６１３１号公報には、下記のような構成のワーク支持具を用いることにより、ワークの歪を抑えつつ高周波焼入する方法が開示されている。
すなわち、このワーク支持具は、ベース部材上に放射状に配置された径方向に移動可能な複数の可動ヘッドと、ベース部材の中心部に設けられ可動ヘッドを径方向外方に付勢するスプリングと、スプリングの付勢力を可動ヘッドに伝達するスライドリング及びリンクと、で構成されている。そして、可動ヘッドでワークの内面を周方向複数箇所で外方へ押圧しながら高周波焼入することにより、ワークの歪みが抑制されるようになっている。
【０００５】
【特許文献１】
特開２０００−９６１３１号公報
【０００６】
【発明が解決しようとする課題】
しかしながら、上記のような従来の金型を用いる方法は、比較的小さな環状部材については適用可能であるが、例えば外径が４００ｍｍを超えるような大型の環状部材の場合には、適用することが難しかった。
つまり、上記のような従来の方法においては、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等も巨大なものが必要となるので、その設備に莫大な費用がかかってしまうという問題があった。
【０００７】
さらに、上記のような従来の方法は、比較的肉厚な環状部材については適用可能であるが、例えば肉厚比（（外径−内径）／外径×１００）が１０％を下回るような薄肉の環状部材の場合には、適用することが難しかった。
つまり、環状部材が薄肉で熱容量が少ないと、加熱された環状部材を金型に搬送する間に環状部材の温度が低下してしまい、焼入れにより十分な硬さが得られないという問題点があった。
【０００８】
このようなことから、大型で薄肉の環状部材については、熱処理による変形度合いの低減及び熱容量の確保のために、研削取代を多く取り、通常の焼入れ（前記金型を用いない焼入れ）を施した後、旋削及び研削により成形していた。つまり、最終的な製品よりも大きな寸法の環状部材に焼入れを施して、旋削及び研削により最終的な製品の寸法に加工していた。したがって、加工コストが高いという問題点があった。
【０００９】
一方、特開２０００−９６１３１号公報に記載の方法は、軸受の軌道輪の焼入れに適用した場合には、該方法が真円度を良好なものとすることのみに着目しており、反りや倒れなどの抑制に対する考慮がなされていないため、結果的に真円度を良好なものとすることは困難である。
また、軌道輪と可動ヘッドとの接触部分は、温度が十分に上昇せず硬さが不十分となってしまうおそれがある。よって、転がり寿命に悪影響を及ぼすおそれがあるため、軸受の軌道輪のように硬さを重視する部品に対しては、該方法は好適ではなかった。
【００１０】
さらに、前記接触部分には冷却剤が十分に行き渡らず、他の部分よりも冷却が遅れるおそれがあり、そうすると変形が大きくなってしまう。これは、軸受鋼に特有の問題であって、すなわち、該方法は軸受の軌道輪に対しては好適ではなかった。
さらにまた、高周波焼入れによって軸受の軌道輪に部分的に焼入れを施すことはあったが、ずぶ焼入れを施すことは、その困難性から従来行われたことはなかった。
【００１１】
そこで、本発明は、このような従来技術が有する問題点を解決し、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が少なく低コストで焼入れ又は焼戻しを施すことができる熱処理方法を提供することを課題とする。
【００１２】
【課題を解決するための手段】
前記課題を解決するため、本発明は次のような構成からなる。すなわち、本発明に係る環状部材の熱処理方法は、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方法であって、前記環状部材の中心穴に円柱状の第一保持治具を挿通して、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を、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が収縮した際に前記環状部材の内周面の全面が前記第一保持治具の外周面に接触するような大きさとするとともに、前記環状部材の内側に複数のピンを放射状に配置し、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調整した上、前記ピンの外端部で前記環状部材の内周面を押圧しながら前記環状部材の加熱及び冷却を行うことを特徴とする。
【００１３】
このような本発明に係る環状部材の熱処理方法においては、熱処理前の前記第一隙間を前記環状部材の内径の０％超過且つ０．１１％以下とすることが好ましい。また、本発明に係る環状部材の熱処理方法においては、前記環状部材を転がり軸受の外輪とし、該外輪の軌道溝を前記ピンの外端部で押圧するようにしてもよい。
【００１４】
さらに、本発明に係る環状部材の熱処理方法においては、前記軌道溝の幅方向の離れた２カ所を前記各ピンの外端部で押圧することが好ましい。
さらに、本発明に係る環状部材の熱処理方法においては、ウェイトの荷重で前記複数のピンの内端部を押圧して、前記ピンの外端部に前記環状部材の内周面を押圧させるとともに、下記式で定義される矯正指数Ｋを２３．５〜１３８．２として、前記環状部材の加熱及び冷却を行うことが好ましい。
【００１５】
【数２】

【００１６】
さらに、本発明に係る環状部材の熱処理方法においては、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が好ましい。
【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、本発明に係る環状部材の熱処理方法を用いる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が収縮した際に前記環状部材の内周面の全面が前記第一保持治具の外周面に接触するような大きさであることを特徴とする。
【００１９】
このような環状部材の熱処理装置においては、前記環状部材を転がり軸受の外輪とし、該外輪の軌道溝を前記ピンの外端部で押圧するようにしてもよい。
さらに、このような環状部材の熱処理装置においては、前記環状部材と接触する部分をセラミック材で構成してもよい。
【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、上記のような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、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、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]
BACKGROUND OF THE INVENTION
  The present invention is a method for heat treatment of an annular member.To the lawIn particular, a method of quenching or tempering a steel annular member used for a bearing ring of a rolling bearing while suppressing deformation.To the lawRelated.
[0002]
[Prior art]
Conventionally, quenching of an annular member has been performed by, for example, holding it at an austenitizing temperature of 800 to 850 ° C. in an electric furnace, and then immersing it in oil or the like to quench it. However, since the annular member has insufficient rigidity, distortion occurs at the time of quenching, and the roundness and flatness are likely to decrease.
[0003]
Therefore, when performing quenching as described above, the annular member heated to the austenitizing temperature is attached to the mold, and the inner peripheral surface or the outer peripheral surface of the annular member is cooled while being held by the mold, Deformation during quenching was suppressed. This utilizes the shrinkage phenomenon during quenching cooling and the expansion phenomenon due to martensitic transformation.
[0004]
Japanese Laid-Open Patent Publication No. 2000-96131 discloses a method of induction hardening while suppressing workpiece distortion by using a workpiece support having the following configuration.
That is, the work support includes a plurality of radially movable heads arranged radially on the base member, and springs provided at the center of the base member to urge the movable heads radially outward. The slide ring and the link transmit the urging force of the spring to the movable head. And distortion of a workpiece | work is suppressed by carrying out induction hardening, pressing the inner surface of a workpiece | work outward in the circumferential direction several places with a movable head.
[0005]
[Patent Document 1]
JP 2000-96131 A
[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, for example, a large annular member having an outer diameter exceeding 400 mm. was difficult.
In other words, in the conventional method as described above, a device for mounting the heated annular member to the mold, a facility for transporting the heated annular member from the heating furnace to the device, and the like are required. There was a problem that the equipment was very expensive.
[0007]
Further, the conventional method as described above can be applied to a relatively thick annular member. For example, the thickness ratio ((outer diameter−inner diameter) / outer diameter × 100) is less than 10%. In the case of a thin annular member, it was 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 transported to the mold, and sufficient hardness cannot be obtained by quenching. It was.
[0008]
For this reason, a large and thin annular member was subjected to normal quenching (quenching without using the mold) in order to reduce the degree of deformation by heat treatment and to secure heat capacity, taking a lot of grinding allowance. Later, it was formed by turning and grinding. In other words, an annular member having a size larger than that of the final product is quenched and processed to the final product size by turning and grinding. Therefore, there is a problem that the processing cost is high.
[0009]
On the other hand, the method described in Japanese Patent Application Laid-Open No. 2000-96131 focuses only on the fact that this method improves the roundness when applied to quenching of the bearing raceway. As a result, it is difficult to improve the roundness because no consideration is given to the suppression of the collapse or the like.
In addition, the temperature of the contact portion between the track ring and the movable head may not be sufficiently increased and the hardness may be insufficient. Therefore, since there is a possibility of adversely affecting the rolling life, this method is not suitable for a component that places importance on hardness such as a bearing ring.
[0010]
Furthermore, the coolant does not spread sufficiently to the contact portion, and there is a possibility that the cooling will be delayed as compared with the other portions, so that the deformation becomes large. This is a problem specific to bearing steel, i.e. the method is not suitable for bearing races.
Furthermore, although the bearing race was partially quenched by induction hardening, it has never been performed conventionally due to its difficulty.
[0011]
  Therefore, the present invention solves such problems of the prior art, and even with a large-diameter and thin-walled annular member, sufficient hardness is ensured, deformation is low, and quenching or tempering is performed at low cost. Heat treatment methodThe lawThe issue is to provide.
[0012]
[Means for Solving the Problems]
  In order to solve the above problems, the present invention has the following configuration. That is, the present invention relates toRingThe heat treatment method of the shaped member is a heat treatment method of quenching or tempering while suppressing deformation of the steel annular member, and a cylindrical first holding jig is inserted through the center hole of the annular member, When 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 greater than 0 before the heat treatment and the annular member contractsThe entire inner peripheral surface of the annular member contacts the outer peripheral surface of the first holding jig.In addition, the plurality of pins are arranged radially inside the annular member, the radial position of the outer end portion of the pin is adjusted according to the inner diameter of the annular member, and the outer end of the pin The annular member is heated and cooled while pressing the inner peripheral surface of the annular member with a portion.
[0013]
  In such a heat treatment method of the annular member according to the present invention,The first gap before the heat treatment is set to exceed 0% and not more than 0.11% of the inner diameter of the annular member.Is preferred. In the heat treatment method for an annular member according to the present invention, the annular member may be an outer ring of a rolling bearing, and the raceway groove of the outer ring may be pressed by the outer end portion of the pin.
[0014]
  further,In the heat treatment method of the annular member according to the present invention,Pressing two spaced apart locations in the width direction of the raceway groove with the outer ends of the pinsIs preferred.
  further,In the heat treatment method of the annular member according to the present invention,The inner end portions of the plurality of pins are pressed with a weight load to press the inner peripheral surface of the annular member against the outer end portions of the pins, and the correction index K defined by the following formula is 23.5 to Heating and cooling the annular member as 138.2Is preferred.
[0015]
[Expression 2]

[0016]
  further,In the heat treatment method of the annular member according to the present invention,In a second holding jig having two holding surfaces facing each other, the annular member is sandwiched between the holding surfaces from both sides in a direction perpendicular to the radial direction, and between the annular member and the holding surface. The size of the second gap is set to 6% or less of the width in the direction perpendicular to the radial direction of the annular member before heat treatment, and the annular member is heated and cooled.Is preferred.
[0017]
With such a configuration, even a large-diameter and thin-walled annular member can be quenched or tempered at low cost while ensuring sufficient hardness and suppressing deformation.
The size of the first gap is greater than 0% and not more than 0.11% 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. The width is preferably 6% or less of the width in the vertical direction. If at least one of the size of the first gap and the size of the second gap is out of the above ranges, it may be difficult to sufficiently suppress deformation of the annular member during quenching or tempering. .
[0018]
  Also,The method for heat treating an annular member according to the present invention is used.The heat treatment device for the annular member is a heat treatment device for quenching or tempering while suppressing deformation of the steel annular member, and a cylindrical first holding jig inserted through the center hole of the annular member, and a radial shape And a plurality of pins that press the inner peripheral surface of the annular member at its outer end, and a pin that adjusts the radial position of the outer end of the pin for each pin according to the inner diameter of the annular member Position adjusting means, 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 a value greater than 0 and before the heat treatment, Annular memberWhen the ring contracts, the entire inner peripheral surface of the annular member comes into contact with the outer peripheral surface of the first holding jig.It is characterized by such a size.
[0019]
  In such an annular member heat treatment apparatus, the annular member may be an outer ring of a rolling bearing, and the raceway groove of the outer ring may be pressed by the outer end portion of the pin.
  further,In such an annular member heat treatment apparatus,The portion in contact with the annular member is made of a ceramic material.May be.
[0020]
In the heat treatment method and heat treatment apparatus for an annular member of 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 an 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 collapse, the dimension is such that 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]
Moreover, 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 so high. Therefore, the manufacturing cost of the member can be kept low. Further, even if the pin or the like is worn, it can be dealt with by adjusting the radial position of the outer end without replacement.
[0022]
  Furthermore, if a high-frequency heating device is used as a heat source, cooling is performed using a water-based coolant, and cooling is performed as it is in the same state as when heating (ring member mounted on a holding jig), heat treatment is performed. The apparatus can be miniaturized.
  further,As aboveSince the annular member is mounted before the heat treatment, the apparatus for mounting the heated annular member on the mold, the facility for conveying the heated annular member from the heating furnace to the mounting apparatus, and the like are unnecessary. . Therefore, the heat treatment apparatus is simple and small overall. Further, since quenching is performed immediately after heating, there is no temperature drop during conveyance, and thus sufficient hardness is ensured and deformation can be suppressed. Accordingly, the machining allowance after the heat treatment can be reduced, so that the grinding cost can be suppressed.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
  Heat treatment method for annular member according to the present inventionLegalEmbodiments 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 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 the respective directions in FIG. 1 for convenience of description unless otherwise specified.
[0024]
First, the annular member 1 to be quenched will be described. This annular member 1 is made of SUJ2, and is used as a bearing ring (outer ring) of a rolling bearing. Therefore, the cross section perpendicular to the circumferential direction has a substantially rectangular shape, and the track groove is continuously provided on the inner circumferential 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 the direction perpendicular to the radial direction) is 26 mm. In the following, the quenching method will be described by 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 of being mounted on the holding jig 10. The holding jig 10 includes a substantially columnar columnar member 11 and a disk-shaped member 12, and the columnar member 11 includes a large-diameter columnar base portion 11a and the base portion. A small-diameter annular convex portion 11b provided at one end of 11a and a rod-like portion 11c similarly provided at one end of the base portion 11a are provided. These base part 11 a, convex part 11 b, and rod-like part 11 c are all arranged concentrically with the axis of the holding jig 10.
[0026]
In addition, a plurality of holes are provided radially at substantially intermediate 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 in the holes. It is inserted as possible. The pin 32 is made of a material that is not easily subjected to high-frequency induction by an induction heating coil 33 described later. For example, austenitic stainless steel is preferable, and a ceramic material is more preferable.
[0027]
In addition, since the end part (hereinafter referred to as the outer end) of the pin 32 facing outward in the radial direction comes into contact with the raceway groove of the annular member 1, heating unevenness and cooling unevenness at the time of heating and cooling are prevented. In order to suppress and reduce the contact area as much as possible, the spherical surface has a smaller diameter than the curved surface constituting the raceway groove. However, when the annular member 1 is an inner ring, there is no raceway groove on the inner peripheral surface of the inner ring, and the size of the spherical surface is not particularly limited.
[0028]
Note that 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). Two holding jigs having respective functions may be used. The holding jig 10 is preferably made of a non-magnetic material, but mild steel or the like may be used.
[0029]
On the other hand, one end of the connecting member 40 is connected to the end portion (hereinafter referred to as the inner end) of the pin 32 facing inward in the radial direction, and the connecting member 40 rotates in the vertical direction around the connecting portion. It is possible. The other end of the connecting member 40 is connected to a weight 50 through which the rod-like portion 11c is inserted, and the connecting member 40 is rotatable in the vertical direction 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. 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 retract 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 advancement and retraction. The length of each connecting member 40 is adjusted according to the inner diameter of the annular member 1 and further adjusted so that the outer ends of all the pins 32 are concentric with the axis of the holding jig 10. The connecting member 40 isTheThis corresponds to the position adjustment means.
[0031]
Since the weight 50 having such a link mechanism and having the rod-shaped portion 11c inserted therein is movable in the vertical direction along the rod-shaped portion 11c, the weight 50 is moved radially outward when the weight 50 moves downward. When the weight 50 moves upward and the weight 50 moves upward, a radially inward force acts on the pin 32.
[0032]
In order to reduce the frictional resistance against the movement of the weight 50, a slide bearing or a rolling bearing may be interposed between the weight 50 and the rod-shaped portion 11c. Furthermore, in the present embodiment, the downward movement of the weight 50 is caused by gravity acting on the weight 50 itself, but may be moved by an actuator such as an air cylinder. In the present embodiment, a weight 50 of 98 to 2940 N is used.
[0033]
When the weight 50 is moved downward, the pin 32 is slidingly guided in the hole provided in the convex portion 11 b and moved radially outward, and the spherical surface of the outer end of the pin 32 is brought into contact with the raceway surface of the annular member 1. Fitted together. As described above, in the first embodiment, the pin 32 is brought into contact with the raceway groove of the annular member 1 by using the link mechanism by the connecting member 40. Since the annular member 1 is pressed radially outward by the link mechanism and concentrically with the axis of the convex portion 11b, the annular member 1 and induction heating which will be described later are used during expansion due to heating and contraction due to cooling. Eccentricity with the coil 33 is prevented.
[0034]
At this time, the appropriate number of pins 32 differs depending on the outer diameter of the annular member 1, but in the radially arranged pins 32, the distance C between the outer ends of adjacent pins 32 is 250 mm or less. It is preferable to do. If the distance C exceeds 250 mm, the effect of suppressing 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 deformation of the annular member 1 and the ease of manufacturing the holding jig 10, six to eight pins may be used.
[0035]
Moreover, since the radial position of the outer end portion of the pin 32 can be adjusted according to the inner diameter of the annular member 1 by adjusting the length of the connecting member 40, the accuracy of the members constituting the link mechanism and the pin 32 is as follows. It doesn't have to be very accurate. Therefore, the manufacturing cost of the heat treatment apparatus can be kept low. Further, specific parts of the members constituting the link mechanism and the tip of the pin 32 are likely to be worn, but even if wear occurs, the radial position of the outer end portion of the pin 32 can be replaced without replacing them. This can be dealt with by adjusting.
[0036]
Next, a method for attaching the annular member 1 to the holding jig 10 will be described.
Initially, the weight 50 is fixed to the upper portion 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. It has become.
The convex portion 11b of the holding jig 10 is inserted into the center hole of the annular member 1, and a disk-like member 12 having a hole at the center (that is, annular) is attached to the upper end of the convex portion 11b. Then, the movement of the annular member 1 in the radial direction is restricted by the outer peripheral surface 21 of the convex portion 11b. Further, since the annular member 1 is sandwiched from above and below by the upper end surface 22 of the base portion 11a and the lower surface 23 of the disk-like member 12 positioned radially outward of the convex portion 11b, the movement in the vertical direction is restricted. Is done. In addition, since the upper end surface 22 of the base part 11a and the lower surface 23 of the disk-shaped member 12 located in the radial direction outer side of the convex part 11b correspond to the holding surface which is a constituent element of the present invention, The

surfaces

22 and 23 may be referred to as holding surfaces.
[0037]
At this time, the radial clearance (first clearance C1) between the inner peripheral surface of the annular member 1 (excluding the raceway groove portion) and the outer peripheral surface 21 (cylindrical surface) of the convex portion 11b is the inner diameter of the annular member 1. D exceeds 0% and is 0.11% or less. The vertical gap (second gap C2) between the upper and lower flat surfaces 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, the second gap C <b> 2 is formed between the upper plane of the annular member 1 and the holding surface 23.
[0038]
Next, a procedure for quenching the annular member 1 will be described.
As described above, the induction heating coil 33 of the heater is arranged circumferentially with an appropriate gap on the outer side in the radial direction of the annular member 1 mounted on the holding jig 10. Thus, the heater can be heated while monitoring the temperature of the annular member 1.
[0039]
A cooling jacket 34 is arranged on the lower side of the induction heating coil 33 in a circumferential shape. 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. Furthermore, the holding jig 10 is fixed to a rotary table (not shown), and can be heated while rotating the annular member 1. When heated in a stationary state, if the axial center of the annular member 1 and the induction heating coil 33 do not coincide with each other, heating unevenness occurs and hardness unevenness or deformation is likely to occur. However, the annular member 1 is rotated. However, even if the axial centers of the annular member 1 and the induction heating coil 33 do not coincide somewhat, the annular member 1 is heated uniformly.
[0040]
In addition, 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 close, 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, the induction heating coil 33 performs induction heating to a desired temperature (900 to 1100 ° C.). In that case, heating is stopped when the set temperature is reached, and then the temperature is soaked 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 portion 11a. However, the annular member 1 and the holding jig 10 are the same iron-based material. Since the temperature becomes higher than 800 ° C., the frictional resistance between them increases. Further, when the diameter of the annular member 1 is increased, the distance of sliding on the upper end surface 22 is increased, so that the frictional resistance may adversely affect the roundness of the annular member 1. For this reason, it is preferable that the part where the holding surface 22 of the base part 11a is located is comprised with the ceramic material which reduces frictional resistance and has heat resistance, or coat | covers with a ceramic material or graphite. It is also effective to reduce the contact area by providing irregularities on the holding surface 22.
[0042]
When the entire annular member 1 is heated uniformly, the holding jig 10 is moved downward until the cooling jacket 34 is positioned radially outward of the annular member 1. And cooling water is injected from the cooling jacket 34 (50-100 L / min), the annular member 1 is rapidly cooled, and it quenches.
The annular member 1 made of high carbon steel such as bearing steel is susceptible to cracking due to overcooling when the whole is uniformly cooled. Therefore, as a countermeasure against burning cracks, the annular member 1 is cooled only from the radially outer side of the annular member 1. It is important to do. The disk-shaped member 12 is provided to cover the upper side 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 to prevent the cooling water from reaching. At this time, it is necessary to provide a gap 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 to remove the radially outward force acting on the annular member 1.
After quenching, tempering was performed as follows. First, the holding jig 10 was moved upward so that the heater was positioned radially outward of the annular member 1 again. Then, the heater was energized and heated to 250 to 300 ° C. At that time, when the set temperature was reached, the heater was turned off, and after that, it was soaked by heat diffusion and gradually cooled (air cooled). Tempering may be performed in an atmospheric furnace. It is also effective to correct warpage and roundness at that time.
[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 position relative to the induction heating coil 33 varies depending on the position of the annular member 1 on the circumference, causing uneven heating, As a result, the annular member 1 may be defective such as deformation, cracking, and unevenness in hardness. However, since all the pins 32 move uniformly outward in the radial direction and press the annular member 1, the annular member 1 is uniformly expanded to prevent the above problems from occurring.
[0045]
Further, during cooling, the annular member 1 contracts and contacts the holding jig 10 (the outer peripheral surface 21 of the convex portion 11 b) on almost the entire inner peripheral surface of the annular member 1, so that the annular member 1 has the shape of the holding jig 10. 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 is separated 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]
In addition, the method using the holding jig 10 as in the present embodiment simultaneously suppresses the 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, the annular member 1 can be quenched with high productivity. In addition, the deformation suppression of the annular member 1 in the present embodiment is not due to the position but due to the constant pressure of the weight 50, which is the reason for improving the quenching productivity.
[0047]
Further, since the annular member 1 is mounted on the holding jig 10 in advance and quenching is performed, the apparatus for mounting the heated annular member on the mold as in the prior art, or the heated annular member is conveyed from the heating furnace to the apparatus. No equipment is required to do this. Therefore, the equipment for quenching is not so huge and can be simplified.
Furthermore, since it can harden immediately without conveying after heating, sufficient hardness is ensured by quenching without temperature drop due to conveyance, and deformation can be suppressed to a small extent. Therefore, since the grinding allowance after quenching can be reduced, the processing cost can be kept low, and the annular member can be manufactured at a low cost.
[0048]
Next, the annular member 1 having various inner diameters D was quenched as described above, and the relationship between the size of the first gap C1 and the effect of suppressing 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 indicates the ratio of the size of the first gap C1 to the inner diameter D of the annular member 1, the inner diameter of the annular member 1 at room temperature being D, and the outside of the convex portion 11b of the holding jig 10 at room temperature. It is a value calculated by (D−d) / D × 100 (%), where d is the diameter. The size of the second gap C2 was unified to 1% of the width h of the annular member 1.
[0049]
From the graph of FIG. 3, when the size of the first gap C1 is more than 0% and not more than 0.11% of the inner diameter D of the annular member 1, the roundness of the annular member 1 after quenching is excellent, and deformation It can be seen that the suppression effect is high. And it is understood that the effect of suppressing deformation is higher when it is 0.07% or less, and the effect of suppressing deformation is extremely high when it is 0.03% or less. The reason why the first gap C1 exceeds 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 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 are described. To do.
The annular member 1 has three types of outer diameters of 450, 600, and 960 mm, and the number of pins 32 is either 6, 8, or 12, and the weight 50 is variously changed between 98 to 2940 N and quenched. The size of the first gap C1 is unified to 0.05% of the inner diameter D of the annular member 1, and the size of the second gap C2 is unified to 1% of the width h of the annular member 1.
[0051]
The result is shown in the graph of FIG. The horizontal axis of this graph is a parameter unique to the present invention called the correction index K. This correction index K is based on the thin annular member having an outer diameter of 400 mm, and is calculated from the above formula.
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 of exceeding and 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 straightening index K is less than 23.5, the roundness increases because the load applied to the annular member by the pin is small, so that the residual stress applied by the pre-processing is released during the austenite transformation. It is thought that this is because it is not possible to suppress the deformation and the transformation that occurs during the martensitic transformation cannot be suppressed.
[0053]
In addition, when the correction index K exceeds 138.2, the roundness increases because the load applied to the annular member by the pin is too large for the rigidity of the annular member, and thus plastic deformation occurs during the austenite transformation. The reason is that it is deformed into a polygonal shape because it cannot be uniformly shrunk during the quenching process.
If the outer end portion of the pin 32 is planar as in the modification shown in FIG. 5, the outer end of each pin 32 comes into contact with the upper and lower two locations in the width direction of the raceway groove of the annular member 1. It will be. If it does so, the curvature of the annular member 1 can be suppressed more effectively compared with the case where the track groove of the annular member 1 and the pin 32 contact at one place.
[0054]
[Second Embodiment]
Below, the hardening method different from 1st embodiment is demonstrated. However, since the method of the second embodiment is almost the same as the first embodiment except that the mechanism for transmitting the load due to the weight to the annular member is different, only the different parts will be described, and the description of the same parts will not be given. Omitted.
[0055]
FIG. 6 is a front view for explaining a method of quenching by mounting an annular member on a holding jig, and a part thereof is broken away. In the following description, terms indicating directions such as “up” and “down” mean the respective directions in FIG. 6 for convenience of description unless otherwise specified. In FIG. 6, the same or corresponding parts as those in FIG.
[0056]
The structure of the annular member 1 is the same as that of the first embodiment described above, 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 convex portion 11b so as to advance and retract in the radial direction. ing. In FIG. 6, the outer end of the pin 32 that contacts the raceway groove of the annular member 1 is planar. However, as in the first embodiment, the spherical surface has a smaller diameter than the curved surface constituting the raceway groove of the annular member 1. It is good.
[0057]
The inner end of the pin 32 is in contact with a conical surface 51 a of the substantially conical slide ring 51. The slide ring 51 is mounted on the rod-like portion 11c so that the weight 50 is placed and the apex of the cone is directed downward so as to be movable in the vertical direction. Therefore, when the slide ring 51 is moved downward, the inner end of the pin 32 is pushed by the conical surface 51a, and is guided by sliding into 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 from each other, so that the pin 32 moves radially inward by the urging force of the spring 52 attached to the pin 32. Become.
[0058]
The pin 32 is provided with a pin length adjusting unit 60 having a structure substantially similar to that of the connecting member 40 described in the first embodiment. Then, by adjusting the length of the pin 32 by the pin length adjusting unit 60, the radial position of the outer end portion of the pin 32 can be adjusted according to the inner diameter of the annular member 1. This pin length adjustment unit 60TheThis corresponds to the position adjustment means.
[0059]
As described above, in the second embodiment, the track groove of the annular member 1 is used by using a mechanism that converts the vertical displacement by the slide ring 51 into the horizontal displacement instead of the link mechanism by the connecting member 40 of the first embodiment. The pin 32 is in contact with this. Since the annular member 1 is pressed radially outward by the conversion mechanism concentrically with the axis of the convex portion 11b, the annular member 1 and a high-frequency induction to be described later at the time of expansion due to heating, contraction due to cooling, or the like. Eccentricity with the heating coil 33 is prevented.
[0060]
Since the method for mounting the annular member 1 on the holding jig 10 and the procedure for quenching the annular member 1 are the same as those in the first embodiment, a detailed description thereof is omitted, but the radial direction outward of the annular member 1 is omitted. A high frequency induction heating coil 33 of the heater is disposed, and heating is performed by this 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 disposed below the high frequency induction heating coil 33 to cool the annular member 1. For these reasons, the annular member 1 is subjected to quenching processing such as quenching and tempering.
[0061]
The mechanism in which deformation is suppressed when heat treatment is performed as described above and the effect when heat treatment is performed as described above are the same as in the first embodiment, but the deformation of the annular member 1 is suppressed to a perfect circle. 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 circular shape. To that end, the horizontality of the holding surface 22, the verticality of the rod-shaped portion 11 c, the accuracy of the conical surface 51 a and the like need to be high precision, but these members are manufactured by machining so that the necessary precision is achieved. 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. It is necessary to design a heat treatment apparatus in consideration of these, but in the case of a mechanism that converts vertical displacement into horizontal displacement as in this embodiment, each member may be processed with high accuracy. This is very advantageous for ensuring the accuracy and maintaining the heat treatment equipment.
[0063]
The area of the contact portion between the outer end of the pin 32 and the annular member 1 is preferably 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 difficult to equalize. If it does so, a low-hardness part will arise in the internal peripheral surface of the annular member 1, and there exists a possibility that a deformation | transformation may arise in the annular member 1. In addition, 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 heat treatment, it is preferable to take the following measures. That is, the portion of the annular member 1 that makes contact with the lower holding surface 22 is reduced, the holding surface 22 is made of a high melting point material such as ceramic or carbon material, or a lubricant made of ceramic or carbon material is used. For example, it is applied to the holding surface 22.
[0065]
In the present embodiment, means for constituting the holding surface 22 with ceramic is adopted, and a member 55 made of ceramic is embedded in a portion where the holding surface 22 of the base portion 11a is located as shown in FIG. Yes.
Furthermore, when quenching high carbon steel such as bearing steel, it is important to cool only from the outer diameter side of the annular member 1 as a countermeasure against quenching cracks. Considering 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]
Furthermore, when the spring 52 is attached to the pin 32 as shown in FIG. 6, the annular member 1 can be easily detached from the holding jig 10.
Furthermore, if the pin 32 is provided by adjusting the position in the vertical direction so that the outer end of the pin 32 is positioned at the center of the raceway groove of the annular member 1, it is easy to prevent the annular member 1 from warping.
[0067]
Furthermore, since the bearing steel has an Mf point below room temperature, it is necessary to cool it sufficiently. 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 show examples of the present invention, and the present invention is not limited to the embodiments.
[0068]
For example, in each of the embodiments described above, the annular member 1 is made of SUJ2, but may be made of other materials as long as it is hardened by quenching.
Moreover, in each said embodiment, although the quenching method was demonstrated exemplifying the annular member used as a bearing ring of a rolling bearing, the heat processing method of this invention is applicable not only to this but to various annular members. Of course.
[0069]
【The invention's effect】
As described above, the heat treatment method of the annular member of the present inventionTo the lawTherefore, if heat treatment is performed, even a large-diameter and thin-walled annular member is less deformed 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 for explaining the first embodiment of the heat treatment method for an annular member according to the present invention.
FIG. 3 is a graph showing the correlation between the ratio of the size of the first gap to the inner diameter of the annular member and the roundness of the annular member.
FIG. 4 is a graph showing the correlation between the correction index K and the roundness of the annular member.
FIG. 5 is a partial cross-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 second embodiment of the heat treatment method for an annular member according to the present invention.
[Explanation of symbols]
1 Ring member
10 Holding jig
11 Cylindrical member
11a base
11b Convex part
11c Bar-shaped part
12 Disc-shaped member
21 Outer peripheral surface of convex part
22, 23 Holding surface
40 connecting members
60 Pin length adjuster
C1 first gap
C2 second gap
D Inner diameter of annular member
d Outer diameter of convex part
h Ring member width
t Distance between holding surfaces

Claims

A heat treatment method for 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 heat treated. Before, the value is larger than 0 and when the annular member contracts , the entire inner peripheral surface of the annular member is in contact with the outer peripheral surface of the first holding jig ,
A plurality of pins are arranged radially inside the annular member, and after adjusting the radial position of the outer end portion of the pin according to the inner diameter of the annular member,
While pressing the inner ends of the plurality of pins with the weight load and pressing the inner peripheral surface of the annular member with the outer ends of the pins, the correction index K defined by the following formula is 23.5 to The method for heat-treating the annular member is characterized by heating and cooling the annular member as 138.2 .
Weight load (N) / Number of pins (pieces)
Correction index K (N / mm ^1/3 ) = ────────────────────
(Outer diameter of annular member (mm) / 400) ^1/3

A heat treatment method for 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 heat treated. Previously, the value is larger than 0, and when the annular member contracts, the entire inner peripheral surface of the annular member is in contact with the outer peripheral surface of the first holding jig,
In a second holding jig having two holding surfaces facing each other, the annular member is sandwiched between the holding surfaces from both sides in a direction perpendicular to the radial direction, and between the annular member and the holding surface. The size of the second gap is 6% or less of the width in the direction perpendicular to the radial direction of the annular member before the heat treatment,
A plurality of pins are arranged radially inside the annular member, and after adjusting the radial position of the outer end portion of the pin according to the inner diameter of the annular member,
A method for heat-treating an annular member, wherein the annular member is heated and cooled while pressing an inner peripheral surface of the annular member with an outer end portion of the pin.

In a second holding jig having two holding surfaces facing each other, the annular member is sandwiched between the holding surfaces from both sides in a direction perpendicular to the radial direction, and between the annular member and the holding surface. The size of the second gap is set to 6% or less of the width in the direction perpendicular to the radial direction of the annular member before heat treatment, and the annular member is heated and cooled. A heat treatment method for an annular member.

The method for heat treatment of an annular member according to any one of claims 1 to 3, wherein the first gap before the heat treatment is set to exceed 0% and not more than 0.11% of the inner diameter of the annular member.

5. The heat treatment method for an annular member according to claim 1, 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.

6. The method for heat-treating an annular member according to claim 1, wherein two locations separated in the width direction of the raceway groove are pressed by outer end portions of the pins.