JP5776322B2 - Rolling bearing - Google Patents
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Description
この発明は転がり軸受に関する。 The present invention relates to a rolling bearing.
自動車、農業機械、建設機械、鉄鋼機械等のトランスミッションやエンジンで用いられる転がり軸受は、潤滑油中に金属の切粉、削り屑、バリ、摩耗粉等の異物が混入した条件下（以下、「異物混入潤滑下」と記す。）で使用されることが多いため、軌道輪や転動体に異物による早期剥離が生じて、大幅に寿命が低下する場合がある。
このような異物混入潤滑下における早期剥離は、軌道輪と転動体との間に異物が噛み込むことで、転がり面（軌道輪の軌道面および転動体の転動面）に形成された圧痕のエッジ部（以下、「圧痕縁」と記す。）に、応力集中が生じることが原因であると言われている。
Rolling bearings used in transmissions and engines of automobiles, agricultural machinery, construction machinery, steel machinery, etc. are under conditions where foreign matters such as metal chips, shavings, burrs, and abrasion powder are mixed in the lubricating oil (hereinafter referred to as “ In many cases, it is used as "under lubrication mixed with foreign matter."), And there is a case where the raceway or rolling element is prematurely peeled off by foreign matter, resulting in a significant decrease in service life.
Such early separation under foreign matter lubrication is due to the indentation formed on the rolling surface (the raceway surface of the raceway and the rolling surface of the rolling element) by the foreign matter biting between the raceway and the rolling element. It is said that the cause is stress concentration at the edge portion (hereinafter referred to as “indentation edge”).
そこで、本出願人は、異物混入潤滑下で転がり面に圧痕が形成された場合であっても、圧痕縁への応力集中を緩和するために、特許文献１において、内外輪のうち少なくとも一つの軌道面をなす表層部と、転動体の転動面をなす表層部の残留オーステナイト量を２０体積％以上４５体積％以下とし、さらに、転動体の転動面をなす表層部の炭窒化物の含有率を体積比で５％以上１５％以下とすることを提案している。
Therefore, in order to alleviate the stress concentration on the indentation edge even in the case where the indentation is formed on the rolling surface under the contamination with foreign matters, the applicant of the present application disclosed in
ところで、近年、異物混入潤滑下で生じる早期剥離は、上述した圧痕縁への応力集中だけでなく、軌道輪と転動体との転がり面に作用する接線力が原因となっていることが分かってきている。接線力に影響を及ぼす要因としては、転がり面のすべり速度や面圧の他に、転がり面の表面形状や表面粗さ等が挙げられる。すなわち、異物混入潤滑下において早期剥離を生じ難くするためには、転がり面に形成された圧痕縁への応力集中を抑制するとともに、転がり面に作用する接線力を小さくする必要がある。
しかし、圧痕縁への応力集中を抑制するために、転がり面をなす表層部の残留オーステナイト量を多くすることは、表層部の硬さが低下して耐疲労特性の低下につながる。
By the way, in recent years, it has been found that the early peeling that occurs under the contamination with foreign matter is caused not only by the stress concentration on the indentation edge described above but also by the tangential force acting on the rolling surface of the race and the rolling element. ing. Factors affecting the tangential force include the surface shape and surface roughness of the rolling surface in addition to the sliding speed and surface pressure of the rolling surface. That is, in order to make it difficult for early peeling to occur under lubrication mixed with foreign matter, it is necessary to suppress stress concentration on the indentation edge formed on the rolling surface and to reduce the tangential force acting on the rolling surface.
However, increasing the amount of retained austenite in the surface layer portion that forms the rolling surface in order to suppress stress concentration on the indentation edge decreases the hardness of the surface layer portion, leading to a decrease in fatigue resistance.
そこで、本出願人は、特許文献２において、転がり表面層（転がり面の表層部）の残留オーステナイト量と表面硬さとの最適な関係を提案している。また、炭化物形成元素を添加した鋼に浸炭または浸炭窒化を施して、微細な炭化物を多量に析出させることで、残留オーステナイト量が多いことにより生じる硬さの低下を補うことを提案している。
具体的には、軌道輪および転動体の少なくとも一つを、転がり表面層の残留オーステナイト量（γR vol ％）が２０〜４５vol ％、且つ、平均粒径０．５〜１．５μｍの微細炭化物又は炭窒化物の分散強化により、前記転がり表面硬さ（Ｈｖ）が前記残留オーステナイト量（γR vol ％）に対し、−４．７×（γR vol ％）＋９２０≦Ｈｖ≦−４．７×（γR vol ％）＋１０２０を満たすものとすることが記載されている。これにより、異物混入潤滑下ばかりでなくクリーンな潤滑下でも、従来品よりも寿命の長い転がり軸受が得られるとしている。
Therefore, the present applicant has proposed an optimal relationship between the amount of retained austenite of the rolling surface layer (the surface layer portion of the rolling surface) and the surface hardness in
Specifically, at least one of the raceway and the rolling element is a fine carbide having an amount of retained austenite (γ R vol%) of the rolling surface layer of 20 to 45 vol% and an average particle size of 0.5 to 1.5 μm. Alternatively, the rolling surface hardness (Hv) is −4.7 × (γ R vol%) + 920 ≦ Hv ≦ −4.7 with respect to the retained austenite amount (γ R vol%) due to dispersion strengthening of carbonitride. It is described that x (γ R vol%) + 1020 is satisfied. As a result, it is said that a rolling bearing having a longer life than that of the conventional product can be obtained not only under foreign matter lubrication but also under clean lubrication.
しかし、特許文献２の提案は、軌道輪および転動体の転がり表面層の残留オーステナイト量が２０〜４５体積％である場合に適用されるものであって、２０体積％未満の場合には適用されない。また、特許文献２の提案には、残留オーステナイト量増大と高硬度化に伴い、コストが高くなるという問題点がある。
この発明の課題は、軌道輪および転動体の転がり表面層の残留オーステナイト量が２０体積％未満の場合に適用できる、残留オーステナイト量と表面硬さとの最適な関係を提案し、コストの低い方法で、転がり軸受の剥離寿命（異物混入潤滑下での寿命）を長くすることである。
However, the proposal of
The object of the present invention is to propose an optimum relationship between the amount of retained austenite and the surface hardness, which can be applied when the amount of retained austenite in the rolling surface layer of the races and rolling elements is less than 20% by volume, and is a low-cost method. This is to increase the peeling life (life under lubrication with foreign matter) of the rolling bearing.
上記課題を解決するために、この発明の転がり軸受は、内輪、外輪、および転動体を有する転がり軸受であって、下記の構成(a) 〜(c) (k) を有することを特徴とする。
(a) 転動体は、炭素の含有率が０．８０質量％以上１．２０質量％以下で、炭素以外の元素の含有率はＪＩＳ Ｇ４８０５で規定されている高炭素クロム軸受鋼と同じである軸受鋼からなる。
(b) 転動体の転動面の表層部（表面から深さ５０μｍまでの範囲）の残留オーステナイト量（γRb）が２０体積％未満である。
(c) 転動体の転動面の表層部（表面から深さ５０μｍまでの範囲）のビッカース硬さ（Ｈｖb ）と残留オーステナイト量（γRb：体積％）との関係が下記の(1) 式を満たす。
５．６γRb＋７７０≦Ｈｖb ≦５．６γRb＋８７０‥‥(1)
(k) 転動体の転動面の表層部のビッカース硬さ（Ｈｖ b ）が８３２以上９４３以下である。
この発明の転がり軸受は、内輪および外輪のうちの少なくとも一方が、下記の構成(d) 〜(f) を有することが好ましい。
In order to solve the above problems, a rolling bearing of the present invention is a rolling bearing having an inner ring, an outer ring, and rolling elements, and has the following configurations (a) to (c) (k): .
(a) The rolling element has a carbon content of 0.80% by mass or more and 1.20% by mass or less, and the content of elements other than carbon is the same as the high carbon chromium bearing steel defined in JIS G4805. Made of bearing steel.
(b) The amount of retained austenite (γ Rb ) in the surface layer portion (range from the surface to a depth of 50 μm) of the rolling surface of the rolling element is less than 20% by volume.
(c) The relationship between the Vickers hardness (Hv b ) of the surface layer portion (range from the surface to a depth of 50 μm) of the rolling element and the amount of retained austenite (γ Rb : volume%) is the following (1) Satisfy the formula.
5.6γ Rb + 770 ≦ Hv b ≦ 5.6γ Rb +870 (1)
(k) The Vickers hardness (Hv b ) of the surface layer portion of the rolling surface of the rolling element is 832 or more and 943 or less.
In the rolling bearing of the present invention, it is preferable that at least one of the inner ring and the outer ring has the following configurations (d) to (f).
(d) 炭素の含有率が０．８０質量％以上１．２０質量％以下で、炭素以外の元素の含有率はＪＩＳ Ｇ４８０５で規定されている高炭素クロム軸受鋼と同じである軸受鋼からなる。
(e) 軌道面の表層部（表面から深さ５０μｍまでの範囲）の残留オーステナイト量（γRr）が２０体積％未満である。
(f) 軌道面の表層部（表面から深さ５０μｍまでの範囲）のビッカース硬さ（Ｈｖr ）と残留オーステナイト量（γRr：体積％）との関係が下記の(2) 式を満たす。
５．６γRr＋６５０≦Ｈｖr ≦５．６γRr＋７５０‥‥(2)
(d) A bearing steel having a carbon content of 0.80% by mass or more and 1.20% by mass or less and the content of elements other than carbon being the same as the high carbon chromium bearing steel defined in JIS G4805. .
(e) The amount of retained austenite (γ Rr ) in the surface layer portion (range from the surface to a depth of 50 μm) of the raceway surface is less than 20% by volume.
(f) The relationship between the Vickers hardness (Hv r ) of the surface layer portion (range from the surface to a depth of 50 μm) and the retained austenite amount (γ Rr : volume%) satisfies the following formula (2).
5.6γ Rr + 650 ≦ Hv r ≦ 5.6γ Rr +750 (2)
前記構成(a) および(b) を有する転動体のうち前記構成(c) を有する（前記(1) 式を満たす）転動体は、前記構成(c) を有さない（前記(1) 式を満たさない）転動体と比較して降伏強度が高くなるため、表面性状安定性が高い。これにより、この発明の転がり軸受は、転動体の軌道輪との間に作用する接線力が小さくなるため、前記構成(c) を有さない転動体を備えた転がり軸受と比較して、軌道輪の剥離寿命が長くなる。 Of the rolling elements having the configurations (a) and (b), the rolling element having the configuration (c) (satisfying the formula (1)) does not have the configuration (c) (the formula (1) Since the yield strength is higher than that of the rolling element, the surface property stability is high. As a result, the rolling bearing of the present invention has a smaller tangential force acting between the rolling elements and the raceway, and therefore, compared with a rolling bearing having a rolling element that does not have the configuration (c), Increases the peeling life of the ring.
特に、転動体が玉である玉軸受の場合は、以下の理由で軌道輪の剥離寿命の延長効果が大きい。一般に、剥離現象は周速の速い駆動側に比べて、周速の遅い従動側で生じやすいことが知られている。玉軸受の場合、剥離が生じる荷重負荷圏のHertz 面圧が高い接触域中央部において、軌道輪が従動側であるため、軌道輪に剥離が生じやすいことになる。したがって、転動体（玉）の表面性状安定性を向上させることで得られる、軌道輪の内部起点型剥離防止効果が高くなる。 In particular, in the case of a ball bearing in which the rolling element is a ball, the effect of extending the peeling life of the bearing ring is great for the following reasons. In general, it is known that the peeling phenomenon is more likely to occur on the driven side having a lower peripheral speed than on the drive side having a higher peripheral speed. In the case of a ball bearing, since the raceway is on the driven side in the center of the contact area where the Hertz surface pressure of the load-bearing zone where the separation occurs is high, the raceway tends to peel off. Therefore, the effect of preventing the internal starting type peeling of the raceway, which is obtained by improving the surface property stability of the rolling elements (balls), is enhanced.
前記構成(b) に関し、転動体の転動面の表層部が硬くても、残留オーステナイト量が 多すぎると局部的に柔らかい部分ができて表面性状安定性が低くなるため、この発明の転がり軸受では、転動体の転動面の表層部の残留オーステナイト量を２０体積％未満としている。また、前記構成(a) の軸受鋼を用いた場合、浸炭や浸炭窒化等の特殊な熱処理や表面処理を行わずに、ずぶ焼入れと焼戻しによる低コストの熱処理で達成できる表層部の残留オーステナイト量は２０体積％未満である。つまり、前記構成(b) を有することで転 動体の熱処理コストが低くなる。 Regarding the configuration (b), even if the surface layer portion of the rolling surface of the rolling element is hard, if the amount of retained austenite is too large, a locally soft portion is formed and the surface property stability is lowered. Then, the amount of retained austenite in the surface layer portion of the rolling surface of the rolling element is less than 20% by volume. In addition, when the bearing steel having the structure (a) is used, the amount of retained austenite in the surface layer portion that can be achieved by low-cost heat treatment by continuous quenching and tempering without performing special heat treatment or surface treatment such as carburizing or carbonitriding. Is less than 20% by volume. That is, the heat treatment cost of the rolling element is reduced by having the configuration (b).
この発明の転がり軸受は、内輪および外輪のうちの少なくとも一方（軌道輪）が前記構成(d) 〜(f) をさらに有する（軌道輪が前記(2) 式を満たす）ことで、前記構成(d) および(e) を有するが前記構成(f) を有さない（軌道輪が前記(2) 式を満たさない）転がり軸受と比較して、軌道面の表面性状安定性が良好になって、圧痕縁への応力集中が低減される。よって、軌道輪の剥離寿命をさらに延長することができる。
前記構成(e) に関し、前記構成(d) の軸受鋼を用いた場合、浸炭や浸炭窒化等の特殊な熱処理や表面処理を行わずに、ずぶ焼入れと焼戻しによる低コストの熱処理で達成できる表層部の残留オーステナイト量は２０体積％未満である。つまり、前記構成(e) を有することで軌道輪の熱処理コストが低くなる。
In the rolling bearing of the present invention, at least one of the inner ring and the outer ring (the race ring) further includes the configurations (d) to (f) (the race ring satisfies the formula (2)). Compared with a rolling bearing having d) and (e) but not having the configuration (f) (the bearing ring does not satisfy the above formula (2)), the surface property stability of the raceway surface is improved. , Stress concentration on the indentation edge is reduced. Therefore, the peeling life of the bearing ring can be further extended.
With respect to the structure (e), when the bearing steel of the structure (d) is used, a surface layer that can be achieved by low-cost heat treatment by continuous quenching and tempering without performing special heat treatment or surface treatment such as carburizing or carbonitriding. The amount of retained austenite in the part is less than 20% by volume. In other words, the heat treatment cost of the bearing ring is reduced by having the configuration (e).
［前記(1) 式について］
上述のように、前記構成(a) および(b) を有する転動体のうち前記構成(c) を有する（前記(1) 式を満たす）転動体は、前記構成(c) を有さない（前記(1) 式を満たさない）転動体と比較して降伏強度が高くなるため、表面性状安定性が高い。これについて以下に説明する。
先ず、軸受稼働中の転動体表面性状悪化の抑制に降伏応力が関係している理由について述べる。転動体の表面性状安定性には、転動体表面の降伏強度が大きく関係していると考えられる。線傷、圧痕などが形成されるということは、局部的に降伏点以上の応力が作用し、塑性変形したということである。即ち、降伏強度が上がると、作用する応力が降伏強度以上になる確率が小さくなるため、線傷や圧痕は発生しにくくなり、その大きさや深さも小さくなる。
[About Equation (1) above]
As described above, among the rolling elements having the configurations (a) and (b), the rolling element having the configuration (c) (satisfying the expression (1)) does not have the configuration (c) ( Since the yield strength is higher than that of a rolling element that does not satisfy the formula (1), the surface property stability is high. This will be described below.
First, the reason why the yield stress is related to the suppression of deterioration of the rolling element surface properties during operation of the bearing will be described. It is considered that the yield strength of the rolling element surface is largely related to the surface texture stability of the rolling element. The formation of flaws, indentations, etc. means that the stress above the yield point acts locally and plastically deforms. That is, when the yield strength increases, the probability that the applied stress becomes greater than or equal to the yield strength decreases, so that it becomes difficult for line flaws and indentations to occur, and the size and depth thereof also decrease.
図１に応力−歪み曲線の模式図を示す。ａ，ｂは、引張応力が同じ（σBa＝σBb）で降伏応力が異なる（σYa＞σYb）曲線を示している。線傷形成時にσc の応力が発生すると仮定すると、曲線ａの場合はσYa＞σc なので弾性変形し、線傷は形成されない。これに対し、曲線ｂの場合はσYb＜σc となるため、歪みεb だけ塑性変形し、線傷が形成される。即ち、引張応力は同じでも、降伏応力が高い曲線ａの方が線傷や圧痕が少なく、表面性状の悪化も抑制されると考えられる。 FIG. 1 shows a schematic diagram of a stress-strain curve. “a” and “b” indicate curves with the same tensile stress (σ Ba = σ Bb ) and different yield stresses (σ Ya > σ Yb ). Assuming that a stress of σ c is generated at the time of forming the flaw, in the case of the curve a, σ Ya > σ c and elastically deforms, so that no flaw is formed. On the other hand, in the case of the curve b, since σ Yb <σ c , plastic deformation is caused by the strain ε b , and a line flaw is formed. That is, even if the tensile stress is the same, the curve a having a higher yield stress has less flaws and indentations, and the deterioration of the surface properties is also suppressed.
次に、前記(1) 式を満たす転動体は、前記(1) 式を満たさない転動体と比較して降伏強度が高くなる（表面性状安定性が高くなる）理由について述べる。
硬さと降伏応力の関係は一般的に知られており、硬さが高いほど降伏応力は大きくなる。しかし、硬さを高くするために、焼入れ温度を高くし過ぎたり、焼戻し温度を低くし過ぎたりすると、残留オーステナイト量が著しく増加し、局部的に降伏応力も低下するため、表面性状安定性が悪くなる。
Next, the reason why the rolling element satisfying the equation (1) has higher yield strength (higher surface property stability) than the rolling element not satisfying the equation (1) will be described.
The relationship between hardness and yield stress is generally known, and the higher the hardness, the greater the yield stress. However, if the quenching temperature is set too high or the tempering temperature is set too low in order to increase the hardness, the amount of retained austenite increases remarkably, and the yield stress decreases locally. Deteriorate.
具体的に、表１に示すように、表層部の硬さ（Ｈｖb ）と残留オーステナイト量（γRb）を変化させたNo.1〜１２の玉（呼び番号６２０６用の玉）を用意し、試験軸受（呼び番号６２０６の玉軸受）を組み立てて、転動体の表層部の硬さ（Ｈｖb ）と残留オーステナイト量（γRb）が表面性状安定性に及ぼす影響を調査した。
試験条件は、荷重：６２２３Ｎ、回転速度：３０００min -1、異物混入潤滑：潤滑油ＶＧ６８に異物（硬さ：Ｈｖ８７０、サイズ：７４〜１４７μｍ）を０．０５ｇ混入であり、この玉軸受を１時間稼働させた前後の玉の表面粗さ（Ｒａ）を測定し、その差（ΔＲａ：試験により上昇した量）を算出した。その結果も表１に示す。
Specifically, as shown in Table 1, No. 1-12 balls (balls for nominal number 6206) in which the hardness (Hv b ) of the surface layer and the amount of retained austenite (γ Rb ) were changed were prepared. Then, a test bearing (ball bearing of nominal number 6206) was assembled, and the effects of the hardness (Hv b ) and the retained austenite amount (γ Rb ) on the surface property of the rolling element were investigated.
Test conditions are load: 6223N, rotational speed: 3000 min −1 , foreign matter mixed lubrication: lubricating oil VG68 containing 0.05 g of foreign matter (hardness: Hv870, size: 74 to 147 μm), and this ball bearing is used for 1 hour. The surface roughness (Ra) of the balls before and after being operated was measured, and the difference (ΔRa: amount increased by the test) was calculated. The results are also shown in Table 1.
また、No.1〜１２の玉の表層部の硬さ（Ｈｖb ）と残留オーステナイト量（γRb）との関係を図２にグラフで示し、(1) 式を満たす範囲を破線で囲って範囲Ａとした。また、範囲Ａに入るNo.1〜７のΔＲａは０．０１４〜０．０３２であるのに対して、範囲Ａから外れるNo. ８〜１２のΔＲａは０．０５２〜０．０５８と大きかった。ΔＲａが大きいほど表面性状安定性は低くなるため、前記(1) 式を満たす玉（転動体）は、前記(1) 式を満たさない玉（転動体）と比較して表面性状安定性が高くなることが分かる。また、「Ｈｖb ＞５．６γRb＋８７０」となると、靭性が低下し、玉（転動体）が割れやすくなることが問題となる。 Moreover, the relationship between the hardness (Hv b ) of the surface layer of No. 1 to No. 12 balls and the retained austenite amount (γ Rb ) is shown in a graph in FIG. 2, and the range satisfying the formula (1) is enclosed by a broken line. Range A. In addition, ΔRa of No. 1 to 7 entering the range A was 0.014 to 0.032, whereas ΔRa of No. 8 to 12 outside the range A was as large as 0.052 to 0.058. . Since the surface property stability decreases as ΔRa increases, the ball (rolling element) that satisfies the above equation (1) has a higher surface property stability than the ball (rolling member) that does not satisfy the above equation (1). I understand that Further, when “Hv b > 5.6γ Rb +870”, the toughness is lowered and the ball (rolling element) is easily broken.
［前記(2) 式について］
上述のように、この発明の転がり軸受を構成する内輪および外輪のうちの少なくとも一方（軌道輪）が前記(2) 式を満たすことで、前記(2) 式を満たさない内輪および外輪を有する転がり軸受と比較して、軌道面の表面性状安定性が良好になって、圧痕縁への応力集中が低減される。
前記(2) 式は、Ｈｖr ≧５．６γRr＋６５０且つＨｖr ≦５．６γRr＋７５０である。軌道面の表層部の硬さ（Ｈｖr ）が、残留オーステナイト量（γRr）との関係で５．６γRr＋６５０より小さいと耐疲労特性が低下し、５．６γRr＋７５０より大きいと靭性が低下して剥離や割れが生じ易くなる。
[About Equation (2) above]
As described above, at least one of the inner ring and the outer ring (track ring) constituting the rolling bearing of the present invention satisfies the above expression (2), so that the rolling ring has an inner ring and an outer ring that do not satisfy the above expression (2). Compared with the bearing, the surface property stability of the raceway surface becomes better, and the stress concentration on the indentation edge is reduced.
The equation (2) satisfies Hv r ≧ 5.6γ Rr +650 and Hv r ≦ 5.6γ Rr +750. When the hardness (Hv r ) of the surface layer of the raceway surface is smaller than 5.6γ Rr +650 in relation to the retained austenite amount (γ Rr ), the fatigue resistance is lowered, and when it is larger than 5.6γ Rr +750, the toughness is increased. It will fall and it will become easy to produce peeling and a crack.
［前記(1) 式と(2) 式の関係について］
５．６γRb＋７７０≦Ｈｖb ≦５．６γRb＋８７０‥‥(1)
５．６γRr＋６５０≦Ｈｖr ≦５．６γRr＋７５０‥‥(2)
転動面の表層部に関する(1) 式と軌道面の表層部に関する(2) 式を比較すると、転動面の硬さＨｖb が軌道面の硬さＨｖr よりも高く設定されている。これにより、軌道輪より転動体の方が高い表面性状安定性を得られる。このように、剥離が生じやすい従動側となる軌道輪よりも駆動側となる転動体の表面性状の悪化を抑制して接線力を低減することで、軌道輪の剥離寿命を向上できる効果が高くなる。
(1) 式を満たす転動体と(2) 式を満たす軌道輪を組み合わせて転がり軸受を組み立てる場合、ΔＨｖ（＝Ｈｖb −Ｈｖr ）を５０以上１５０以下とすることが好ましい。
[Relationship between the above equations (1) and (2)]
5.6γ Rb + 770 ≦ Hv b ≦ 5.6γ Rb +870 (1)
5.6γ Rr + 650 ≦ Hv r ≦ 5.6γ Rr +750 (2)
Compared surface layer of the rolling surface about (1) regarding the surface layer portion of the formula and the raceway surface (2), hardness Hv b of the rolling surface is set higher than the hardness Hv r raceway surface. As a result, the surface texture stability of the rolling element is higher than that of the raceway. In this way, the effect of improving the peeling life of the bearing ring is high by reducing the tangential force by suppressing the deterioration of the surface property of the rolling element on the driving side rather than the bearing ring on the driven side where peeling easily occurs. Become.
When a rolling bearing is assembled by combining rolling elements that satisfy the equation (1) and raceway rings that satisfy the equation (2), ΔHv (= Hv b −Hv r ) is preferably set to 50 or more and 150 or less.
［構成(a) および(d) について］
転動体、内輪、外輪を構成する軸受鋼として、炭素の含有率が０．８０質量％以上１．２０質量％以下で、炭素以外の元素の含有率はＪＩＳ Ｇ４８０５で規定されている高炭素クロム軸受鋼と同じであるものを使用する。その理由を以下に述べる。
炭素（Ｃ）はマトリックスに固溶してマルテンサイトを強化する元素であり、焼入れ焼戻し後の強度確保と疲労寿命を向上させるために不可欠である。一般に、炭素の含有量が０．８０質量％未満では、こうした効果が得られにくい。一方で、炭素の含有量が１．２２質量％を超えると、鋳造時に巨大炭化物が生成しやすく、加工性が悪くなることや、巨大炭化物が起点となって早期剥離することが懸念される。
転動体、内輪、外輪を構成する軸受鋼として、ＪＩＳ Ｇ４８０５で規定されている高炭素クロム軸受鋼（ＳＵＪ２やＳＵＪ３）に相当する鋼を使用することが好ましい。
[Configuration (a) and (d)]
As a bearing steel constituting rolling elements, inner rings and outer rings, the carbon content is 0.80% by mass or more and 1.20% by mass or less, and the content of elements other than carbon is specified in JIS G4805. Use the same bearing steel. The reason is described below.
Carbon (C) is an element that solid-dissolves in the matrix and strengthens martensite, and is indispensable for ensuring the strength and improving the fatigue life after quenching and tempering. Generally, when the carbon content is less than 0.80% by mass, such an effect is hardly obtained. On the other hand, if the carbon content exceeds 1.22% by mass, there is a concern that giant carbides are likely to be generated during casting, resulting in poor processability and early peeling due to the giant carbides.
It is preferable to use steel corresponding to high carbon chromium bearing steel (SUJ2 or SUJ3) defined in JIS G4805 as the bearing steel constituting the rolling elements, the inner ring, and the outer ring.
［製造方法について］
一般に、高炭素鋼の硬さを高める方法には、熱処理の焼入れ温度を高くして固溶炭素量を増加させる方法と、焼戻し温度を低くして歪み（転位）の開放の緩和を抑制する方法がある。これらの方法を夫々単独で行うよりも、焼入れ温度の上昇と焼戻し温度の低下を組合せることで、転動体の硬さを大幅に高くすることができる。
転動体表層部の硬さを高くする方法としては、ボールピーニング処理（以下、ＢＰとも記す）後に表面から５０μｍ以上７０μｍ以下の深さ部分を研磨で除去する方法が挙げられる。
[Production method]
In general, there are two methods for increasing the hardness of high carbon steel: a method in which the quenching temperature of heat treatment is increased to increase the amount of dissolved carbon, and a method in which the tempering temperature is decreased to suppress the release of strain (dislocation). There is. The hardness of the rolling elements can be significantly increased by combining the increase in the quenching temperature and the decrease in the tempering temperature, rather than performing these methods individually.
As a method of increasing the hardness of the rolling element surface layer portion, a method of removing a depth portion of 50 μm or more and 70 μm or less from the surface by ball polishing after ball peening treatment (hereinafter also referred to as BP) can be mentioned.
鋼球に作用する圧縮残留応力が大きいほど硬さが高くなることが知られている。鋼球に圧縮残留応力を付与させる方法として、特公平１−１２８１２号公報に記載の空気噴射法ピーニングなどが存在するが、一般的には熱処理後、ＢＰを施す手法が用いられる。付与させる圧縮残留応力を大きくするには、ＢＰの処理時間を長くすることや、重量を少なくすることが効果的である。しかし、鋼球はＢＰが施されることによって、内部に最大圧縮残留応力が発生する場合が多い。 It is known that the hardness increases as the compressive residual stress acting on the steel ball increases. As a method for imparting compressive residual stress to a steel ball, there is an air injection peening described in JP-B-1-12812. Generally, a method of applying BP after heat treatment is used. In order to increase the compressive residual stress to be applied, it is effective to increase the BP processing time and to reduce the weight. However, in many cases, the maximum compressive residual stress is generated inside the steel ball by applying BP.
従って、転動体の表層部は圧縮残留応力が低いため、表面性状安定性を向上させるには効果的でない。つまり、転動体の表面性状安定性を向上させ、軌道輪の内部起点型剥離寿命を延長させるには、転動体の表層部に最大の残留圧縮応力を作用させればよい。そこで、ＢＰの後に、表面から５０μｍ以上７０μｍ以下の深さ部分を研磨によって除去する。即ち、ＢＰで生じた表面付近の圧縮残留応力の低い部分を研磨で除去することにより、転動体表面に高い圧縮残留応力を作用させ、硬さを高くすることができる。 Therefore, since the surface layer portion of the rolling element has a low compressive residual stress, it is not effective in improving the surface property stability. That is, in order to improve the surface property stability of the rolling element and extend the internal origin type peeling life of the raceway, the maximum residual compressive stress may be applied to the surface layer portion of the rolling element. Therefore, after BP, a depth portion of 50 μm or more and 70 μm or less from the surface is removed by polishing. That is, by removing a portion having a low compressive residual stress near the surface generated by BP by polishing, a high compressive residual stress can be applied to the surface of the rolling element to increase the hardness.
この発明の転がり軸受によれば、転動面の表層部の残留オーステナイト量が２０体積％未満である転動体を用い、前記表層部の残留オーステナイト量とビッカース硬さとの関係を最適にすることで、コストの低い方法で、転がり軸受の剥離寿命（異物混入潤滑下での寿命）を長くすることができる。 According to the rolling bearing of the present invention, by using a rolling element in which the amount of retained austenite in the surface layer portion of the rolling surface is less than 20% by volume, the relationship between the amount of retained austenite in the surface layer portion and Vickers hardness is optimized. By using a low cost method, it is possible to extend the peeling life (life under lubrication with foreign matter) of the rolling bearing.
以下、この発明の実施形態について説明する。
この実施形態の転がり軸受は、図３に示すように、内輪１、外輪２、玉（転動体）３、および鉄鋼製で波形の保持器４で構成されている。内輪１と外輪２は、ＳＵＪ２（高炭素クロム軸受鋼）からなる素材を内輪１および外輪２の形状に加工した後、ずぶ焼入れと焼戻しからなる熱処理がなされたものである。玉３は、ＳＵＪ２（高炭素クロム軸受鋼）からなる素材を玉３の形状に加工した後、ずぶ焼入れと焼戻しからなる熱処理を行い、さらにＢＰと研磨処理が施されたものである。
Embodiments of the present invention will be described below.
As shown in FIG. 3, the rolling bearing of this embodiment includes an
熱処理は、内輪１、外輪２、および玉３ともに、８２０〜８９０℃（通常のずぶ焼入れの加熱温度８００〜８５０℃より２０〜４０℃高い温度）に保持した後、油冷却する「ずぶ焼入れ」を行った後、１３０〜２１０℃（通常の焼戻し温度１５０〜１７０℃より２０〜４０℃低い温度）で焼戻しを行った。
玉３のＢＰは、処理対象となる玉をバレル形の容器に入れて容器を回転させることで玉同士を衝突させる方法により、容器の回転速度：３０〜６０ｍｉｎ-1、処理時間：３０分〜９０分の条件で行った。
In the heat treatment, the
The BP of the ball 3 is a method in which the balls to be processed are put into a barrel-shaped container and the balls are collided by rotating the container, whereby the rotation speed of the container: 30 to 60 min −1 , the processing time: 30 minutes to The test was performed for 90 minutes.
研磨処理は、加圧機構を備えた２枚の溝付き特殊鋳物盤の間にＢＰ後の玉３を順次流し入れ、圧力を加えながら特殊鋳物盤を回転させる方法により、ＢＰ後の玉３の表層部（表面から５０〜７０μｍの深さまでの部分）を除去した。
具体的には、呼び番号６２０６の玉軸受用の玉として、表２に示すように、表層部の硬さ（Ｈｖb ）と残留オーステナイト量（γRb）を変化させたもの（１６種類）を用意した。また、呼び番号６２０６の玉軸受用の内輪および外輪として、表２に示すように、表層部の硬さ（Ｈｖr ）と残留オーステナイト量（γRr）を変化させたもの（３種類）を用意した。
The surface of the ball 3 after BP is polished by a method in which the ball 3 after BP is sequentially poured between two special casting machines with grooves provided with a pressure mechanism and the special casting machine is rotated while applying pressure. Part (part from the surface to a depth of 50 to 70 μm) was removed.
Specifically, as shown in Table 2, as balls for the ball bearing of the reference number 6206, the surface layer hardness (Hv b ) and the amount of retained austenite (γ Rb ) were changed (16 types). Prepared. Also, as the inner ring and outer ring for the ball bearing of nominal number 6206, as shown in Table 2, those with varying surface layer hardness (Hv r ) and retained austenite amount (γ Rr ) are prepared (three types) did.
７７０≦Ｈｖb −５．６γRb≦８７０であれば前記(1) 式を満たし、６５０≦Ｈｖr −５．６γRr≦７５０であれば前記(2) 式を満たすため、各サンプルで「Ｈｖb −５．６γRb」と「Ｈｖr −５．６γRr」を算出した。この算出値も表２に示す。
これらの内輪１、外輪２、および玉３を組み合わせて呼び番号６２０６の玉軸受を組み立て、異物混入潤滑下での転がり寿命を調べる試験を行った。試験条件は、荷重：６２２３Ｎ、回転速度：３０００min -1、異物混入潤滑：潤滑油ＶＧ６８に異物（硬さ：Ｈｖ８７０、サイズ：７４〜１４７μｍ）を０．０５ｇ混入とした。
If 770 ≦ Hv b −5.6γ Rb ≦ 870, the above equation (1) is satisfied, and if 650 ≦ Hv r −5.6γ Rr ≦ 750, the above equation (2) is satisfied. b -5.6γ Rb "and was calculated" Hv r -5.6γ Rr ". This calculated value is also shown in Table 2.
These
また、同じサンプルを１０体用意して試験を行い、Ｌ１０寿命を調べた。得られた各寿命値から、最も寿命が短かったサンプルNo. １７を「１」とした寿命比を算出した。その結果も表２に示す。また、図４のグラフに、各サンプルの玉の表層部の硬さ（Ｈｖb ）と残留オーステナイト量（γRb）との関係「○」「●」、内輪および外輪の軌道面の表層部の硬さ（Ｈｖr ）と残留オーステナイト量（γRr）との関係「△」「▲」をプロットした。さらに、図５のグラフに、寿命比と玉の表層部の硬さ（Ｈｖb ）との関係をプロットした。 In addition, 10 samples were prepared and tested, and the L10 life was examined. From each of the obtained life values, a life ratio was calculated with Sample No. 17 having the shortest life as “1”. The results are also shown in Table 2. In addition, in the graph of FIG. 4, the relationship between the hardness (Hv b ) of the surface of the ball of each sample and the retained austenite amount (γ Rb ), “○”, “●”, the surface layer of the raceway surface of the inner ring and the outer ring The relationship between the hardness (Hv r ) and the amount of retained austenite (γ Rr ) “Δ” and “▲” was plotted. Furthermore, the relationship between the life ratio and the hardness (Hv b ) of the surface layer of the ball was plotted on the graph of FIG.
図５のグラフにおいて、曲線Ａは、表２のNo. １〜８の結果を示すプロット（▲）をつないだ線であり、曲線Ｂは、表２のNo. ９〜１６の結果を示すプロット（●）をつないだ線である。「△」は表２のNo. １６〜２４の結果を示すプロットであり、「○」は表２のNo. ２５〜３２の結果を示すプロットである。
表２のNo. １〜８は、玉の表層部の硬さ（Ｈｖb ）と残留オーステナイト量（γRb）との関係が(1) 式を満たすが、軌道面の表層部の硬さ（Ｈｖr ）と残留オーステナイト量（γRr）との関係が(2) 式を満たさない。表２のNo. ９〜１６は、玉の表層部の硬さ（Ｈｖb ）と残留オーステナイト量（γRb）との関係が(1) 式を満たし、軌道面の表層部の硬さ（Ｈｖr ）と残留オーステナイト量（γRr）との関係も(2) 式を満たす。
In the graph of FIG. 5, the curve A is a line connecting plots (▲) indicating the results of Nos. 1 to 8 in Table 2, and the curve B is a plot indicating the results of Nos. 9 to 16 in Table 2. It is a line connecting (●). “Δ” is a plot showing the results of Nos. 16 to 24 in Table 2, and “◯” is a plot showing the results of Nos. 25 to 32 in Table 2.
Nos. 1 to 8 in Table 2 show that the relationship between the hardness (Hv b ) of the ball surface layer and the amount of retained austenite (γ Rb ) satisfies the formula (1), but the hardness of the surface layer of the raceway surface ( Hv r ) and the amount of retained austenite (γ Rr ) do not satisfy equation (2). Nos. 9 to 16 in Table 2 show that the relationship between the hardness (Hv b ) of the surface layer of the ball and the amount of retained austenite (γ Rb ) satisfies the equation (1), and the hardness of the surface layer of the raceway surface (Hv The relationship between r ) and the amount of retained austenite (γ Rr ) also satisfies equation (2).
表２のNo. １６〜２４は、玉の表層部の硬さ（Ｈｖb ）と残留オーステナイト量（γRb）との関係が(1) 式を満たさず、軌道面の表層部の硬さ（Ｈｖr ）と残留オーステナイト量（γRr）との関係も(2) 式を満たさない。表２のNo. ２５〜３２は、玉の表層部の硬さ（Ｈｖb ）と残留オーステナイト量（γRb）との関係が(1) 式を満たさず、軌道面の表層部の硬さ（Ｈｖr ）と残留オーステナイト量（γRr）との関係が(2) 式を満たす。
この結果から、(1) 式を満たす玉（図４のプロット●と▲）を有する玉軸受（図５のプロット●と▲）は、(1) 式を満たさない玉（図４のプロット○と△）を有する玉軸受（図５のプロット○と△）と比較して、異物混入潤滑下での剥離寿命が長くできることが分かる。具体的に、No. １〜１６の玉軸受は、No. １７の３．４〜７．０倍の寿命が得られた。
Nos. 16 to 24 in Table 2 show that the relationship between the hardness (Hv b ) of the ball surface layer and the retained austenite amount (γ Rb ) does not satisfy the formula (1), and the hardness of the surface layer of the raceway surface ( The relationship between Hv r ) and the amount of retained austenite (γ Rr ) does not satisfy equation (2). Nos. 25 to 32 in Table 2 indicate that the relationship between the hardness (Hv b ) of the surface layer of the ball and the amount of retained austenite (γ Rb ) does not satisfy the formula (1), and the hardness of the surface layer of the raceway surface ( Hv r ) and the amount of retained austenite (γ Rr ) satisfy equation (2).
From this result, ball bearings (plots ● and ▲ in FIG. 5) having balls satisfying equation (1) (plots ● and ▲ in FIG. 4) It can be seen that, compared with ball bearings having (Δ) (plots ◯ and Δ in FIG. 5), the peeling life can be increased under lubrication mixed with foreign matter. Specifically, the ball bearings No. 1 to 16 had a life of 3.4 to 7.0 times that of No. 17.
また、(1) 式を満たす玉と(2) 式を満たす内輪および外輪を有する玉軸受No. ９〜１６（図５の曲線Ｂ）は、(1) 式を満たす玉と(2) 式を満たさない内輪および外輪を有する玉軸受No. １〜８（図５の曲線Ａ）と比較して、異物混入潤滑下での剥離寿命が長くできることが分かる。
すなわち、転動面の表層部の硬さと残留オーステナイト量との関係を最適化する（(1) 式を満たす転動体を用いる）ことで、転動体の表面性状安定性が高くなり、転動体と軌道輪との間に作用する接線力が低減され、軌道輪の表面起点型剥離寿命が延長できることが分かる。さらに、軌道面の表層部の硬さと残留オーステナイト量との関係を最適化し（(2) 式を満たす軌道輪を用い）、この軌道輪と(1) 式を満たす転動体とで転がり軸受を組み立てることで、転がり軸受の剥離寿命がさらに延長できることが分かる。
In addition, ball bearings Nos. 9 to 16 (curve B in FIG. 5) having a ball satisfying the expression (1) and an inner ring and an outer ring satisfying the expression (2) are expressed as follows. It can be seen that, compared with ball bearings Nos. 1 to 8 (curve A in FIG. 5) having an inner ring and an outer ring that are not satisfied, the peel life under lubrication with foreign matter can be increased.
In other words, by optimizing the relationship between the hardness of the surface layer of the rolling surface and the amount of retained austenite (using a rolling element that satisfies equation (1)), the surface property stability of the rolling element is increased, It can be seen that the tangential force acting between the bearing rings is reduced and the surface-origin peeling life of the bearing rings can be extended. Furthermore, the relationship between the hardness of the surface layer of the raceway and the amount of retained austenite is optimized (using a raceway that satisfies equation (2)), and a rolling bearing is assembled with this raceway and rolling elements that satisfy equation (1). This shows that the peeling life of the rolling bearing can be further extended.
［追加説明］
この発明の転がり軸受は、さらに以下の構成(g) 〜(j) を有することが好ましい。
(g) 前記転動体の表層部（表面から深さ５０μｍまでの範囲）の炭化物面積率が１％以上５％以下であること。
(h) 前記転動体の表層部の残留圧縮応力（σR ）が５００ＭPa以上１４００ＭPa以下であること。
(i) 内輪および外輪のうちの少なくとも一方が、極値統計により推定した面積Ｓ＝３００００ｍｍ2 中の酸化物系最大介在物寸法√areamax と表面硬さ（ＨＲＣ）とがＨＲＣ≧０．２×√areamax ＋５４を満たすこと。
(j) 転動体は、熱処理後の転動体に対してボールピーニング処理を施した後、表面から深さ５０μｍ以上７０μｍ以下までの部分を研磨で除去する方法により得られたものであること。
[Additional explanation]
The rolling bearing of the present invention preferably further has the following configurations (g) to (j).
(g) The carbide area ratio of the surface layer portion (range from the surface to a depth of 50 μm) of the rolling element is 1% or more and 5% or less.
(h) Residual compressive stress (σ R ) of the surface layer portion of the rolling element is 500 MPa or more and 1400 MPa or less.
(i) When at least one of the inner ring and the outer ring has an oxide-based maximum inclusion size √area max and surface hardness (HRC) in the area S = 30000 mm 2 estimated by extreme value statistics, HRC ≧ 0.2 X√area max +54 must be satisfied.
(j) The rolling element is obtained by a method in which a part from the surface to a depth of 50 μm to 70 μm is removed by polishing after performing a ball peening treatment on the rolling element after the heat treatment.
転動体の表層部の炭化物面積率を１％以上５％以下とすることが好ましい理由について、以下に述べる。
高炭素軸受鋼の場合、焼入れ処理によってマトリックスに固溶する炭素量が多いほど、炭素の固溶強化によって降伏応力が高くなる。一般に、マトリックスの固溶炭素量を正確に測定することは困難である。しかし、精錬時の炭素含有量（ベースカーボン量）が既知ならば、炭化物の面積率から固溶炭素量を推定することができると考えられる。即ち、焼入れ後の炭化物面積率が低いほど、マトリックスに固溶している炭素量が多いことを意味し、降伏応力が高く、表面性状安定性が高いことを示している。従って、炭素の固溶量ではなく、炭化物の面積率を規定した。
The reason why the carbide area ratio of the surface layer portion of the rolling element is preferably 1% or more and 5% or less will be described below.
In the case of high carbon bearing steel, the more the amount of carbon dissolved in the matrix by the quenching process, the higher the yield stress due to solid solution strengthening of carbon. In general, it is difficult to accurately measure the amount of dissolved carbon in the matrix. However, if the carbon content (base carbon amount) at the time of refining is known, it is considered that the amount of solute carbon can be estimated from the area ratio of carbides. That is, it means that the lower the carbide area ratio after quenching, the more carbon is dissolved in the matrix, and the higher the yield stress and the higher the surface property stability. Therefore, not the amount of carbon solid solution but the area ratio of carbide was specified.
転動体の表層部の残留圧縮応力（σR ）を５００ＭＰａ以上１４００ＭＰａ以下とすることが好ましい理由を、以下に述べる。
転動体の表層部の残留圧縮応力が低いと、変形抵抗が小さくなるため、降伏応力は小さくなり、軸受稼働中に表面性状が悪化しやすくなる。転動体の表層部の残留圧縮応力が５００ＭＰａより小さくなると塑性変形抵抗が小さくなり、表面性状が悪化していることが分かる。一方、加工によって付与する圧縮残留応力が高すぎる（例えば１４００ＭＰａを超える）と、既に繰返し疲労を受けている状態になり、転がり疲労が進行しやすくなる。
The reason why the residual compressive stress (σ R ) of the surface layer portion of the rolling element is preferably 500 MPa or more and 1400 MPa or less will be described below.
When the residual compressive stress in the surface layer portion of the rolling element is low, the deformation resistance is small, so the yield stress is small, and the surface properties are likely to deteriorate during the operation of the bearing. It can be seen that when the residual compressive stress in the surface layer portion of the rolling element is smaller than 500 MPa, the plastic deformation resistance is decreased and the surface properties are deteriorated. On the other hand, when the compressive residual stress applied by processing is too high (for example, exceeding 1400 MPa), it will be in the state which has already received repeated fatigue | exhaustion and rolling fatigue will advance easily.
内輪および外輪のうちの少なくとも一方が、極値統計により推定した面積Ｓ＝３００００ｍｍ2 中の酸化物系最大介在物寸法√areamax と表面硬さ（ＨＲＣ）とがＨＲＣ≧０．２×√areamax ＋５４を満たすこと（構成(i) ）が好ましい理由を、以下に述べる。
軌道輪の硬さを高めて強度を向上させ、内部き裂の発生・進展を抑制させることで内部起点型剥離寿命を延長できる。しかし、材料中に含まれる酸化物系介在物が大きい場合には、顕著な寿命延長効果は得られない。構成(i) の範囲内では、酸化物系介在物の微細化による応力集中の低減及び内部強度の向上によるき裂の発生・進展の抑制効果によって、内部起点型剥離寿命が延長できる。
At least one of the inner ring and the outer ring has an oxide-based maximum inclusion size √area max and surface hardness (HRC) in an area S = 30000 mm 2 estimated by extreme value statistics, and HRC ≧ 0.2 × √area The reason why it is preferable to satisfy max + 54 (configuration (i)) will be described below.
By increasing the hardness of the bearing ring to improve the strength and suppressing the generation and propagation of internal cracks, it is possible to extend the internal origin-type peel life. However, when the oxide inclusions contained in the material are large, a significant life extension effect cannot be obtained. Within the range of the configuration (i), the internal origin-type peel life can be extended due to the effect of reducing the stress concentration due to the refinement of oxide inclusions and the suppression of crack initiation / propagation by improving the internal strength.
１ 内輪
２ 外輪
３ 玉（転動体）
４ 保持器
1
4 Cage
Claims (2)
転動体は、炭素の含有率が０．８０質量％以上１．２０質量％以下で、炭素以外の元素の含有率はＪＩＳ Ｇ４８０５で規定されている高炭素クロム軸受鋼と同じである軸受鋼からなり、
転動体の転動面の表層部の残留オーステナイト量（γRb）が２０体積％未満であり、
転動体の転動面の表層部のビッカース硬さ（Ｈｖ b ）が８３２以上９４３以下であり、
転動体の転動面の表層部のビッカース硬さ（Ｈｖb ）と残留オーステナイト量（γRb：体積％）との関係が下記の(1) 式を満たすことを特徴とする転がり軸受。
５．６γRb＋７７０≦Ｈｖb ≦５．６γRb＋８７０‥‥(1) A rolling bearing having an inner ring, an outer ring, and rolling elements,
The rolling element has a carbon content of 0.80% by mass or more and 1.20% by mass or less, and the content of elements other than carbon is the same as the high carbon chromium bearing steel defined in JIS G4805. Become
The amount of retained austenite (γ Rb ) in the surface layer portion of the rolling surface of the rolling element is less than 20% by volume,
Vickers hardness (Hv b ) of the surface layer portion of the rolling surface of the rolling element is 832 or more and 943 or less,
A rolling bearing characterized in that the relationship between the Vickers hardness (Hv b ) of the surface layer portion of the rolling surface of the rolling element and the amount of retained austenite (γ Rb : volume%) satisfies the following formula (1).
5.6γ Rb + 770 ≦ Hv b ≦ 5.6γ Rb +870 (1)
炭素の含有率が０．８０質量％以上１．２０質量％以下で、炭素以外の元素の含有率はＪＩＳ Ｇ４８０５で規定されている高炭素クロム軸受鋼と同じである軸受鋼からなり、
軌道面の表層部の残留オーステナイト量（γRr）が２０体積％未満であり、
軌道面の表層部のビッカース硬さ（Ｈｖr ）と残留オーステナイト量（γRr：体積％）との関係が下記の(2) 式を満たすことを特徴とする請求項１記載の転がり軸受。
５．６γRr＋６５０≦Ｈｖr ≦５．６γRr＋７５０‥‥(2) At least one of the inner ring and the outer ring is
The carbon content is 0.80% by mass or more and 1.20% by mass or less, and the content of elements other than carbon is the same as the high carbon chromium bearing steel defined in JIS G4805,
The amount of retained austenite (γ Rr ) in the surface layer of the raceway surface is less than 20% by volume,
The rolling bearing according to claim 1, wherein the relationship between the Vickers hardness (Hv r ) of the surface layer portion of the raceway surface and the retained austenite amount (γ Rr : volume%) satisfies the following expression (2).
5.6γ Rr + 650 ≦ Hv r ≦ 5.6γ Rr +750 (2)
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