JP2021173402A - Rolling bearing and manufacturing method thereof - Google Patents
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- 238000005096 rolling process Methods 0.000 title claims abstract description 49
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 13
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 47
- 238000012545 processing Methods 0.000 claims abstract description 17
- 238000010791 quenching Methods 0.000 claims abstract description 10
- 230000000171 quenching effect Effects 0.000 claims abstract description 10
- 238000005496 tempering Methods 0.000 claims abstract description 10
- 230000005489 elastic deformation Effects 0.000 claims abstract description 5
- 230000000717 retained effect Effects 0.000 claims description 41
- 238000000034 method Methods 0.000 claims description 28
- 238000003754 machining Methods 0.000 claims description 24
- 238000007373 indentation Methods 0.000 abstract description 12
- 230000000052 comparative effect Effects 0.000 description 14
- 239000000463 material Substances 0.000 description 13
- 238000012360 testing method Methods 0.000 description 13
- 229910000831 Steel Inorganic materials 0.000 description 11
- 239000010959 steel Substances 0.000 description 11
- 229910000734 martensite Inorganic materials 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 5
- 238000005482 strain hardening Methods 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 230000002093 peripheral effect Effects 0.000 description 3
- 238000003672 processing method Methods 0.000 description 3
- 238000005480 shot peening Methods 0.000 description 3
- 230000003068 static effect Effects 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000005255 carburizing Methods 0.000 description 2
- 238000005121 nitriding Methods 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- 229910000760 Hardened steel Inorganic materials 0.000 description 1
- 229910000677 High-carbon steel Inorganic materials 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000007730 finishing process Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- FXNGWBDIVIGISM-UHFFFAOYSA-N methylidynechromium Chemical group [Cr]#[C] FXNGWBDIVIGISM-UHFFFAOYSA-N 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 238000007517 polishing process Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 230000001131 transforming effect Effects 0.000 description 1
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Abstract
Description
本発明は、転がり軸受及びその製造方法に関する。 The present invention relates to rolling bearings and methods for manufacturing the same.
転がり軸受は、静止中に過大な荷重を受けると、外輪軌道輪及び内輪軌道輪と転動体との間にＨｅｒｔｚ接触が生じて、永久変形（ブリネル圧痕）が残ることが知られている。このような圧痕が存在すると、転がり軸受の使用時に音響や振動特性に影響を及ぼす。例えば、工作機械のような高速で回転する用途での転がり軸受では、１μｍ程度の微小な圧痕であっても、異音や振動が生じ、大きな問題となる。このため、転がり軸受を設計する場合には、静的限界荷重（基本静定格荷重）を接触応力で定めており、ＪＩＳ Ｂ １５１９（２００９年）では、例えば、スラスト玉軸受及び自動調心玉軸受を除くラジアル玉軸受の接触応力を、４．２ＧＰａにすることが定められている。 It is known that when an excessive load is applied to a rolling bearing while it is stationary, Hertz contact occurs between the outer ring raceway ring and the inner ring raceway ring and the rolling element, and permanent deformation (Brinell indentation) remains. The presence of such indentations affects acoustic and vibration characteristics when rolling bearings are used. For example, in a rolling bearing for applications that rotate at high speed such as a machine tool, even a minute indentation of about 1 μm causes abnormal noise and vibration, which is a big problem. Therefore, when designing rolling bearings, the static limit load (basic static rated load) is defined by the contact stress. In JIS B 1519 (2009), for example, thrust ball bearings and self-aligning ball bearings are used. It is stipulated that the contact stress of radial ball bearings excluding the above should be 4.2 GPa.
また、自動車などの低燃費化を背景とした転がり軸受の小型化には、過大な荷重に耐えられるような塑性変形抵抗性が必要となる。従来、転がり軸受の塑性変形抵抗性の向上には、転がり軸受の外輪軌道輪及び内輪軌道輪の硬さと残留オーステナイト量とのバランスが重要であり、転がり軸受の軌道輪の硬さを上昇させたり、鋼の軟質な組織である残留オーステナイトを減少させたりすることで永久変形抵抗性を向上させて、耐圧痕性を向上させる取り組みが実施されている。 Further, in order to reduce the size of rolling bearings against the background of low fuel consumption of automobiles and the like, plastic deformation resistance that can withstand an excessive load is required. Conventionally, in order to improve the plastic deformation resistance of rolling bearings, it is important to balance the hardness of the outer ring raceway ring and inner ring raceway ring of the rolling bearing with the amount of retained austenite, and the hardness of the raceway ring of the rolling bearing is increased. Efforts have been made to improve permanent deformation resistance by reducing retained austenite, which is a soft structure of steel, and to improve pressure resistance.
例えば、特許文献１には、高炭素クロム軸受鋼に浸炭窒化処理及び焼戻しを施した技術が記載されている。また、特許文献２には、軸受内外輪の軌道面にサブゼロ処理を施した技術が記載されている。 For example, Patent Document 1 describes a technique in which a high carbon chromium bearing steel is carburized and nitrided and tempered. Further, Patent Document 2 describes a technique in which the raceway surface of the inner and outer rings of the bearing is subjected to subzero treatment.
しかしながら、浸炭窒化処理のような特殊熱処理は、長時間を要するとともに、そのための工程が別途必要にもなり、製造コストが増加する。また、サブゼロ処理は、靱性を低下させる懸念があるとともに、そのための工程が別途必要になり製造コストも増加する。 However, special heat treatment such as carburizing and nitriding requires a long time, and a separate process for that is required, which increases the manufacturing cost. In addition, the sub-zero treatment has a concern of lowering the toughness, and a separate process is required for that purpose, which increases the manufacturing cost.
本発明は、上記の課題に着目してなされたものであり、低コストで耐圧痕性を向上させた転がり軸受及びその製造方法を提供することを目的とする。 The present invention has been made by paying attention to the above problems, and an object of the present invention is to provide a rolling bearing having improved pressure resistance at low cost and a method for manufacturing the same.
上記のように、熱処理及び成分調整のみで転がり軸受の耐圧痕性を向上させようとすると、耐割れ性など他機能の低下を招いたり、生産性の低下を招く。そのため、転がり軸受の機能を損なうことなく課題を解決する必要がある。 As described above, if an attempt is made to improve the pressure resistance of a rolling bearing only by heat treatment and component adjustment, other functions such as crack resistance may be deteriorated, or productivity may be lowered. Therefore, it is necessary to solve the problem without impairing the function of the rolling bearing.
一方、転がり軸受の圧痕の形成は、転動体と軌道輪との接触に伴う軌道面の塑性変形によるものであり、単純な材料の降伏現象として説明できる。材料の強化法は種々の方法があり、熱処理や成分調整の他に、加工硬化という方法が知られている。本発明者らは、熱処理によって最大限に硬化された焼入れ鋼に機械加工を加えることで、転がり軸受の耐圧痕性をより一層高められることを見出した。転がり軸受の機械加工の方法にはバニシング加工やショットピーニング加工など様々な方法が知られており、工業的にも実現されている。転がり軸受にこのような機械加工を実施する場合、加工力が増大するほど得られる耐圧痕性が向上する。加工力の増大に伴って荷重を付与する機構が複雑で大型なものになったり、軌道面を加工するツールの消耗が激しくなったりするため、できるだけ小さな加工力で大きな硬化量を得ることが好ましい。 On the other hand, the formation of indentations in rolling bearings is due to the plastic deformation of the raceway surface due to the contact between the rolling element and the raceway ring, and can be explained as a simple material yielding phenomenon. There are various methods for strengthening materials, and in addition to heat treatment and component adjustment, a method called work hardening is known. The present inventors have found that the pressure resistance of rolling bearings can be further enhanced by machining the hardened steel that has been maximally cured by heat treatment. Various methods such as burnishing and shot peening are known as methods for machining rolling bearings, and they are also industrially realized. When such machining is performed on a rolling bearing, the pressure resistance mark obtained increases as the machining force increases. As the machining force increases, the mechanism for applying the load becomes complicated and large, and the tool for machining the raceway surface becomes heavily consumed. Therefore, it is preferable to obtain a large amount of hardening with the smallest possible machining force. ..
転がり軸受に使用される高炭素鋼を熱処理すると、マルテンサイトと呼ばれる硬い組織の中に残留オーステナイトと呼ばれる軟質の組織が混在した組織となる。軟質な残留オーステナイトは耐圧痕性を低下させる要因であるが、機械加工により大きな応力を加えるとマルテンサイトに変態する性質を持つ。マルテンサイトへの変態は転がり軸受の硬さを大きく向上させることができるという特徴がある。したがって、あらかじめ残留オーステナイトが残存している出発材に機械加工を施すと、大きな加工硬化が得られるとともに、耐圧痕性に有害な残留オーステナイトの量を低減させることができる。 When high carbon steel used for rolling bearings is heat-treated, it becomes a structure in which a soft structure called retained austenite is mixed in a hard structure called martensite. Soft retained austenite is a factor that reduces pressure resistance, but it has the property of transforming into martensite when a large stress is applied by machining. The transformation to martensite is characterized by being able to greatly improve the hardness of rolling bearings. Therefore, if the starting material in which residual austenite remains is machined in advance, a large work hardening can be obtained and the amount of retained austenite harmful to the pressure resistance can be reduced.
本発明はこのような知見に基づくものであり、上記の課題を解決するために下記（１）及び（２）に示す転がり軸受を提供する。 The present invention is based on such findings, and provides the rolling bearings shown in the following (1) and (2) in order to solve the above problems.
（１） 内輪と外輪との間に、複数の転動体を転動自在に保持してなる転がり軸受において、
前記内輪及び前記外輪の少なくとも一方の軌道面における、機械加工の影響を受けておらず、残留オーステナイト量が１０％以上である領域を第１領域とし、
前記転動体と接触する前記軌道面において、残留オーステナイト量が、前記第１領域の残留オーステナイト量より少なく、かつ、硬さが、前記第１領域の硬さより高い領域を第２領域とすることを特徴とする転がり軸受。
(1) In a rolling bearing in which a plurality of rolling elements are rotatably held between an inner ring and an outer ring.
The region of at least one of the raceway surfaces of the inner ring and the outer ring, which is not affected by machining and has a retained austenite amount of 10% or more, is defined as the first region.
In the raceway surface in contact with the rolling element, a region in which the amount of retained austenite is less than the amount of retained austenite in the first region and the hardness is higher than the hardness of the first region is defined as the second region. Rolling bearings that are characteristic.
（２） 前記第２領域が、
（ａ）残留オーステナイト量が、前記第１領域の残留オーステナイト量の７８％以下であり、
（ｂ）硬さが、前記第１領域の硬さよりも１０４％以上であることを特徴とする上記（１）に記載の転がり軸受。
(2) The second region is
(A) The amount of retained austenite is 78% or less of the amount of retained austenite in the first region.
(B) The rolling bearing according to (1) above, wherein the hardness is 104% or more of the hardness of the first region.
また、上記の課題は、本発明に関わる下記の転がり軸受の製造方法により解決される。 Further, the above problem is solved by the following method for manufacturing a rolling bearing according to the present invention.
（３） 上記（１）又は（２）に記載の転がり軸受の製造方法であって、
前記内輪及び外輪に対し、焼入れ焼戻し処理を施した後、
前記内輪及び前記外輪の少なくとも一方の軌道面に対し、弾性変形のみが生じると仮定して算出した、加工治具との最大接触面圧を８．２ＧＰａ以上とした条件で機械加工を施すことを特徴とする転がり軸受の製造方法。
(3) The method for manufacturing a rolling bearing according to (1) or (2) above.
After quenching and tempering the inner ring and outer ring,
Machining is performed on at least one of the raceway surfaces of the inner ring and the outer ring under the condition that the maximum contact surface pressure with the processing jig is 8.2 GPa or more, which is calculated on the assumption that only elastic deformation occurs. A characteristic method for manufacturing rolling bearings.
本発明によれば、例えば、工作機械などの、軌道輪に静的荷重が負荷され、ブリネル圧痕が生じやすい軸受において、軌道輪に発生する１μｍ程度の微小な圧痕形成を抑制できる。また、浸炭窒化処理やサブゼロ処理のような別工程が不要であり、製造コストの増加を招くこともない。 According to the present invention, it is possible to suppress the formation of minute indentations of about 1 μm generated on the raceway wheels in a bearing such as a machine tool in which a static load is applied to the raceway wheels and Brinell indentations are likely to occur. In addition, a separate process such as carburizing nitriding treatment and sub-zero treatment is not required, and the manufacturing cost does not increase.
以下、本発明の実施形態について具体的に説明する。しかしながら、本発明は、以下の実施形態に限定されるものではなく、本発明の要旨を変更しない範囲において適宜変更して適用することができる。 Hereinafter, embodiments of the present invention will be specifically described. However, the present invention is not limited to the following embodiments, and can be appropriately modified and applied without changing the gist of the present invention.
本発明において転がり軸受の種類や構成に制限はなく、例えば図１に示すラジアル玉軸受を挙げることができる。図示されるように、ラジアル玉軸受１は、内周面に外輪軌道面２を有する外輪３と、外周面に内輪軌道面４を有する内輪５と、これら外輪軌道面２と内輪軌道面４との間に設けた、それぞれが転動体である複数個の玉６とを備える。これら各玉６は、円周方向に等間隔に配置された状態で、保持器７により、転動自在に保持されている。
In the present invention, there is no limitation on the type and configuration of the rolling bearing, and examples thereof include the radial ball bearing shown in FIG. As shown in the figure, the radial ball bearing 1 includes an
外輪３、内輪５及び玉６の材質には制限はなく、一般的な軸受用鋼材であるＳＵＪ２やＳＵＪ３などを用いることができる。そのため、鋼材の添加元素を調整することがなく、素材コストを抑えることができる。
The materials of the
上記のラジアル玉軸受１は、まず、環状素材に旋削加工を施して、所定形状の外輪用ブランク材や内輪用ブランク材を作製する。次いで、それぞれのブランク材に焼入れ焼戻し処理を施し、研磨加工によって外輪軌道面２や内輪軌道面４を所定精度に仕上げる。その後で、外輪軌道面２や内輪軌道面４に機械加工を施し、最終的に仕上げ加工を施す。機械加工までの各工程及び仕上げ加工は、常法に従うことができる。
In the radial ball bearing 1 described above, first, an annular material is turned to produce a blank material for an outer ring or a blank material for an inner ring having a predetermined shape. Next, each blank material is subjected to quenching and tempering treatment, and the outer ring raceway surface 2 and the inner
機械加工としては、圧縮応力を付与する加工方法であれば制限はないが、バニシング加工やショットピーニング加工が好ましい。 Machining is not limited as long as it is a processing method that applies compressive stress, but burnishing processing and shot peening processing are preferable.
バニシング加工とは、加工治具である先端が球状で高硬度の部品が設けられた装置を外輪軌道面２や内輪軌道面４に押し当てて、外輪３や内輪５を自身の軸線を中心にして回転させて圧縮応力を付与する加工方法である。また、ショットピーニング加工とは、高硬度で略球状の投射材を外輪軌道面２や内輪軌道面４に噴射する加工方法である。略球状の投射材の大きさや材質、噴射速度などの処理条件を調整し、バニシング加工と同等の品質に調整することができる。
Burnishing is a processing jig in which a device having a spherical tip and a high-hardness component is pressed against an outer ring raceway surface 2 or an inner
この機械加工により、第２領域の残留オーステナイト量を、第１領域の残留オーステナイト量より少なく、具体的には、第１領域の残留オーステナイト量の７８％以下にすることが好ましい。残留オーステナイトは軟質なため、耐圧痕性を低下させる要因であるが、機械加工によりマルテンサイトに変態させて硬さを向上させる。そのため、第２領域の残留オーステナイト量を、第１領域の残留オーステナイト量の７８％以下にすることにより、硬さを向上させ、かつ、軟質な組織である残留オーステナイトを減少させ、十分な耐圧痕性を実現することができる。 By this machining, it is preferable that the amount of retained austenite in the second region is smaller than the amount of retained austenite in the first region, specifically, 78% or less of the amount of retained austenite in the first region. Since retained austenite is soft, it is a factor that lowers pressure resistance, but it is transformed into martensite by machining to improve hardness. Therefore, by reducing the amount of retained austenite in the second region to 78% or less of the amount of retained austenite in the first region, the hardness is improved and the amount of retained austenite, which is a soft structure, is reduced, resulting in sufficient pressure resistance marks. Sex can be realized.
この機械加工により、第２領域の硬さを、第１領域の硬さより高く、具体的には、第１領域の硬さの１０４％以上にすることが好ましい。第２領域の硬さを第１領域の硬さの１０４％以上にすることにより、十分な耐圧痕性を実現することができる。 By this machining, it is preferable that the hardness of the second region is higher than the hardness of the first region, specifically, 104% or more of the hardness of the first region. By setting the hardness of the second region to 104% or more of the hardness of the first region, sufficient pressure resistance marks can be realized.
なお、第２領域よりも更に深く、心部などの機械加工の影響を受けていない上記第１領域は、いわゆる「未加工領域」であり、機械加工の影響を受けている領域は「加工領域」である。この「加工領域」には、上記第２領域も含まれる。 The first region, which is deeper than the second region and is not affected by machining such as the core, is a so-called "unprocessed region", and the region affected by machining is a "machining region". ". The "processing region" also includes the second region.
このような残留オーステナイト量にするには、焼入れ焼戻し処理により、第１領域の残留オーステナイト量を１０％以上、好ましくは１３％以上にし、機械加工する前の残留オーステナイトを多く存在させるのがよい。 In order to obtain such a residual austenite amount, it is preferable to increase the residual austenite amount in the first region to 10% or more, preferably 13% or more by quenching and tempering treatment, and to have a large amount of retained austenite before machining.
また、機械加工において、外輪３や内輪５を製造する際に、外輪３や内輪５に対し、焼入れ焼戻し処理を施した後、弾性変形のみが生じると仮定して算出した、加工治具との最大接触面圧を８．２ＧＰａ以上にすることが好ましい。最大接触面圧が大きいほど、加工域の残留オーステナイトがマルテンサイト変態し、残留オーステナイトが減少する。そのため、最大接触面圧が８．２ＧＰａ未満では、硬さの上昇が少なく、残留オーステナイトが多く存在してしまい十分な耐圧痕性を得にくくなる。なお、最大接触面圧は、９．２ＧＰａ以上であることがより好ましい。
Further, in machining, when the
（予備試験）
本実施例においては、機械加工としてバニシング加工を採用し、その加工条件を検討した。まず、軸受鋼（ＳＵＪ２鋼）を素材として所定形状の軌道輪を作製し、焼入れ焼戻し処理を行った。その後、軌道輪に対して、仕上げ加工を施した後、更に、３種の異なる条件でのバニシング加工を施し、仕様の異なる３種のスラスト玉軸受を作製した。
(Preliminary test)
In this example, burnishing was adopted as machining, and the machining conditions were examined. First, a raceway ring having a predetermined shape was prepared from a bearing steel (SUJ2 steel) and subjected to quenching and tempering treatment. Then, the raceway ring was finished, and then burnished under three different conditions to produce three types of thrust ball bearings having different specifications.
なお、バニシング加工装置において、バニシングツールの先端形状はφ３ｍｍ、すべり率は１００％、周速は１００ｍ/ｍｉｎ、バニシングツールの送り速度は０．０５ｍｍ/ｒｅｖ、バニシングツールの押し込み量は０．３ｍｍである。また、加工時には、ろ過された工作液を供給した。そして、バニシング加工におけるバニシングツールと軌道面との接触面圧を、弾性変形のみが生じると仮定して、最大接触面圧（Ｐ）を算出した。なお、予備試験で作製された各種転がり軸受の最大接触面圧（Ｐ）は、それぞれＰ＝５．８ＧＰａ、Ｐ＝７．３ＧＰａ、Ｐ＝８．２ＧＰａであった。 In the burnishing machine, the tip shape of the burnishing tool is φ3 mm, the slip ratio is 100%, the peripheral speed is 100 m / min, the feed rate of the burnishing tool is 0.05 mm / rev, and the pushing amount of the burnishing tool is 0.3 mm. be. In addition, at the time of processing, a filtered working liquid was supplied. Then, the maximum contact surface pressure (P) was calculated on the assumption that only elastic deformation occurs as the contact surface pressure between the burnishing tool and the raceway surface in the burnishing process. The maximum contact surface pressures (P) of the various rolling bearings produced in the preliminary test were P = 5.8 GPa, P = 7.3 GPa, and P = 8.2 GPa, respectively.
続いて、最大接触面圧（Ｐ）ごとに、軌道輪の軌道面の表面から深さ方向の残留応力をＸ線回折法により測定した結果を表１に示す。なお、深さ２５０μｍ以上の領域を未加工領域（第１領域）とし、当該領域はバニシング加工の影響を受けていない領域である。また、表面（深さ０μｍ）から深さ２５０μｍ未満の領域を加工領域（第２領域）とし、当該領域はバニシング加工の影響を受けている領域である。 Subsequently, Table 1 shows the results of measuring the residual stress in the depth direction from the surface of the raceway surface of the raceway ring by the X-ray diffraction method for each maximum contact surface pressure (P). A region having a depth of 250 μm or more is defined as an unprocessed region (first region), and this region is not affected by burnishing. Further, a region from the surface (depth 0 μm) to a depth of less than 250 μm is defined as a processing region (second region), and this region is a region affected by burnishing.
なお、表面（深さ０μｍ）での残留オーステナイト量が少ないのは、バニシング加工前の研磨加工において残留オーステナイト量が５％程度に減少したためである。 The amount of retained austenite on the surface (depth 0 μm) is small because the amount of retained austenite was reduced to about 5% in the polishing process before the burnishing process.
表１の結果から、バニシング荷重、すなわち最大接触面圧（Ｐ）が大きいほど、加工領域の残留オーステナイトが、加工誘起マルテンサイト変態して減少しており、最大接触面圧が８．２ＧＰａ以上であれば、加工領域（第２領域）である軌道面表層の残留オーステナイト量を少なくとも７８％以下に減少できることがわかる。すなわち、第２領域の残留オーステナイト量を、第１領域の残留オーステナイト量の７８％以下にすることにより、硬さを向上させ、かつ、軟質な組織である残留オーステナイトを減少させ、十分な耐圧痕性を実現することができる。 From the results in Table 1, the larger the burnishing load, that is, the maximum contact surface pressure (P), the more the retained austenite in the processing region is reduced by the processing-induced martensitic transformation, and the maximum contact surface pressure is 8.2 GPa or more. If there is, it can be seen that the amount of retained austenite in the orbital surface surface layer, which is the processing region (second region), can be reduced to at least 78% or less. That is, by reducing the amount of retained austenite in the second region to 78% or less of the amount of retained austenite in the first region, hardness is improved and retained austenite, which is a soft structure, is reduced, resulting in sufficient pressure resistance marks. Sex can be realized.
（実施例１）
軸受鋼を用いて平板形状とし、８４０℃焼入れ１８０℃焼戻しを行い、平面仕上げ加工後にバニシング加工を施して試験片を作製した。バニシング加工における最大接触面圧は、上記した予備試験から８．２ＧＰａ以上あればよいことから、９．２ＧＰａとした。なお、その他の加工条件は、上記と同様とした。
(Example 1)
A test piece was prepared by forming a flat plate shape using bearing steel, quenching at 840 ° C. and tempering at 180 ° C., and performing a vanishing process after a flat surface finishing process. The maximum contact surface pressure in the burnishing process was set to 9.2 GPa because it suffices to be 8.2 GPa or more from the above preliminary test. The other processing conditions were the same as above.
（比較例１）
８４０℃にて焼入れし、３００℃で焼戻しを行った以外は、実施例１と同様にして試験片を作製した。すなわち、実施例１と比較例１とで、焼入れ焼戻し条件を変えることにより、残留オーステナイト量が異なるようにした。
(Comparative Example 1)
A test piece was prepared in the same manner as in Example 1 except that it was quenched at 840 ° C and tempered at 300 ° C. That is, the amount of retained austenite was made different between Example 1 and Comparative Example 1 by changing the quenching and tempering conditions.
（比較例２）
軸受鋼を用いて平板形状とし、８４０℃焼入れ１８０℃焼戻しを行った後、平面仕上げ加工して試験片とした。すなわち、比較例２ではバニシング処理を行っていない。
(Comparative Example 2)
A flat plate shape was formed using bearing steel, and after quenching at 840 ° C and tempering at 180 ° C, a flat surface finish was performed to obtain a test piece. That is, in Comparative Example 2, the burnishing process was not performed.
（比較例３）
８４０℃で焼入れし、３００℃で焼戻しを行った以外は、比較例２と同様にして試験片を作製した。すなわち、比較例３ではバニシング処理を行っていない。
(Comparative Example 3)
A test piece was prepared in the same manner as in Comparative Example 2 except that it was quenched at 840 ° C and tempered at 300 ° C. That is, in Comparative Example 3, the burnishing process was not performed.
表２に、実施例１及び比較例１における、軌道面表面から深さ方向の残留オーステナイト量をＸ線回折により測定した結果を示す。実施例１及び比較例１は、ずぶ焼き処理品であるため、未加工領域の結果から、バニシング加工前の実施例１及び比較例１の軌道面表層（加工領域相当）の残留オーステナイト量は、それぞれ約１３％、約１％である。標準的な熱処理を施した軸受鋼であれば、残留オーステナイト量は１０±５％程度であり、表１（予備試験）で示す３種類のスラスト玉軸受を測定した結果から好ましくは１０％程度有るとよく、表２の実施例１に示すようにさらに好ましくは１３％以上あるとよい。この理由は、後述する表５に示すように、１３％の実施例１の耐圧痕性が、他の実施例と比較しほぼ倍以上に優れているからである。また、実施例１において、バニシング加工領域の残留オーステナイト量が未加工領域に比べて７８％以下に減少しており、軟質な残留オーステナイトが大幅に減少している。 Table 2 shows the results of measuring the amount of retained austenite in the depth direction from the surface of the orbital surface in Example 1 and Comparative Example 1 by X-ray diffraction. Since Examples 1 and Comparative Example 1 are soaking-treated products, the amount of retained austenite in the orbital surface surface layer (corresponding to the processed area) of Example 1 and Comparative Example 1 before the burnishing process is determined from the results of the unprocessed area. They are about 13% and about 1%, respectively. In the case of bearing steel subjected to standard heat treatment, the amount of retained austenite is about 10 ± 5%, which is preferably about 10% from the results of measuring the three types of thrust ball bearings shown in Table 1 (preliminary test). As shown in Example 1 of Table 2, it is more preferably 13% or more. The reason for this is that, as shown in Table 5 described later, the pressure resistance of 13% of Example 1 is almost twice as good as that of other Examples. Further, in Example 1, the amount of retained austenite in the burnishing processed region is reduced to 78% or less as compared with the unprocessed region, and the soft retained austenite is significantly reduced.
続いて、表３及び表４に、実施例１及び比較例１〜３における軌道面表面から深さ方向の硬さの測定結果を示すが、バニシング加工により加工硬化されていることがわかる。実施例１では加工領域の硬さが未加工領域に比べて１０４％以上に増加している。また、実施例１では比較例１に比べて加工領域の加工硬化量が大きい。このことから、残留オーステナイトが多く残存した状態で、バニシング加工を施すことにより、残留オーステナイトの加工誘起マルテンサイト変態量が増加して、硬さが大幅に増加することがわかる。 Subsequently, Tables 3 and 4 show the measurement results of the hardness in the depth direction from the orbital surface surface in Example 1 and Comparative Examples 1 to 3, and it can be seen that the work hardening was performed by the burnishing process. In Example 1, the hardness of the processed region is increased to 104% or more as compared with the unprocessed region. Further, in Example 1, the amount of work hardening in the work area is larger than that in Comparative Example 1. From this, it can be seen that by performing the burnishing process in a state where a large amount of retained austenite remains, the amount of processing-induced martensitic transformation of retained austenite increases and the hardness increases significantly.
更に表５に、実施例１及び比較例１〜３の圧痕試験の結果を示す。圧痕試験では、転がり軸受の軌道輪を模擬した平板形状の試験片と同様、軸受鋼を熱処理して作製された３／８インチの鋼球（転動体）を用いて、実施例１及び比較例１〜３で作製した各試験片に、最大接触面圧がそれぞれ５．０ＧＰａ、５．５ＧＰａ、６．０ＧＰａとなるように荷重を負荷した後、テーラーホブソン社製の３次元表面性状測定機（ＣＣＩ）を用いて、平板形状の試験片の表面に生じた圧痕の深さを測定した。表５の結果から、実施例１が最も圧痕深さが浅く、最も耐圧痕性に優れていることがわかる。 Further, Table 5 shows the results of the indentation test of Example 1 and Comparative Examples 1 to 3. In the indentation test, as in the case of a flat plate-shaped test piece simulating the raceway ring of a rolling bearing, a 3/8 inch steel ball (rolling body) produced by heat-treating the bearing steel was used in Example 1 and Comparative Example. After applying a load to each of the test pieces prepared in Nos. 1 to 3 so that the maximum contact surface pressure is 5.0 GPa, 5.5 GPa, and 6.0 GPa, respectively, a three-dimensional surface property measuring machine manufactured by Taylor Hobson Co., Ltd. ( Using CCI), the depth of indentation generated on the surface of the flat plate-shaped test piece was measured. From the results in Table 5, it can be seen that Example 1 has the shallowest indentation depth and the most excellent pressure indentation.
１ ラジアル玉軸受
２ 外輪軌道面
３ 外輪
４ 内輪軌道面
５ 内輪
６ 玉
７ 保持器
1 Radial ball bearing 2 Outer
Claims (3)
前記内輪及び前記外輪の少なくとも一方の軌道面における、機械加工の影響を受けておらず、残留オーステナイト量が１０％以上である領域を第１領域とし、
前記転動体と接触する前記軌道面において、残留オーステナイト量が、前記第１領域の残留オーステナイト量より少なく、かつ、硬さが、前記第１領域の硬さより高い領域を第２領域とすることを特徴とする転がり軸受。 In a rolling bearing in which a plurality of rolling elements are rotatably held between an inner ring and an outer ring.
The region of at least one of the raceway surfaces of the inner ring and the outer ring, which is not affected by machining and has a retained austenite amount of 10% or more, is defined as the first region.
In the raceway surface in contact with the rolling element, a region in which the amount of retained austenite is less than the amount of retained austenite in the first region and the hardness is higher than the hardness of the first region is defined as the second region. Rolling bearings that are characteristic.
（ａ）残留オーステナイト量が、前記第１領域の残留オーステナイト量の７８％以下であり、
（ｂ）硬さが、前記第１領域の硬さよりも１０４％以上であることを特徴とする請求項１に記載の転がり軸受。 The second region is
(A) The amount of retained austenite is 78% or less of the amount of retained austenite in the first region.
(B) The rolling bearing according to claim 1, wherein the hardness is 104% or more of the hardness of the first region.
前記内輪及び外輪に対し、焼入れ焼戻し処理を施した後、
前記内輪及び前記外輪の少なくとも一方の軌道面に対し、弾性変形のみが生じると仮定して算出した、加工治具との最大接触面圧を８．２ＧＰａ以上とした条件で機械加工を施すことを特徴とする転がり軸受の製造方法。 The method for manufacturing a rolling bearing according to claim 1 or 2.
After quenching and tempering the inner ring and outer ring,
Machining is performed on at least one of the raceway surfaces of the inner ring and the outer ring under the condition that the maximum contact surface pressure with the processing jig is 8.2 GPa or more, which is calculated on the assumption that only elastic deformation occurs. A characteristic method for manufacturing rolling bearings.
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Citations (3)
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| JPH02168022A (en) * | 1988-12-22 | 1990-06-28 | Toyota Motor Corp | Bearing parts |
| JP2004116569A (en) * | 2002-09-24 | 2004-04-15 | Koyo Seiko Co Ltd | Rolling bearing |
| JP2004339575A (en) * | 2003-05-16 | 2004-12-02 | Nsk Ltd | Method for producing parts of rolling device |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH02168022A (en) * | 1988-12-22 | 1990-06-28 | Toyota Motor Corp | Bearing parts |
| JP2004116569A (en) * | 2002-09-24 | 2004-04-15 | Koyo Seiko Co Ltd | Rolling bearing |
| JP2004339575A (en) * | 2003-05-16 | 2004-12-02 | Nsk Ltd | Method for producing parts of rolling device |
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