JP6448405B2 - Carbon nitride bearing parts with excellent surface fatigue strength of hydrogen embrittlement type - Google Patents

Carbon nitride bearing parts with excellent surface fatigue strength of hydrogen embrittlement type Download PDF

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JP6448405B2
JP6448405B2 JP2015030396A JP2015030396A JP6448405B2 JP 6448405 B2 JP6448405 B2 JP 6448405B2 JP 2015030396 A JP2015030396 A JP 2015030396A JP 2015030396 A JP2015030396 A JP 2015030396A JP 6448405 B2 JP6448405 B2 JP 6448405B2
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康浩 小竹
康浩 小竹
裕貴 島田
裕貴 島田
木南 俊哉
俊哉 木南
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Daido Steel Co Ltd
Nachi Fujikoshi Corp
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Nachi Fujikoshi Corp
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本発明は、水素脆性型の面疲労剥離による寿命低下を抑制し得る浸炭窒化軸受部品に関する。   The present invention relates to a carbonitrided bearing component capable of suppressing a reduction in life due to surface fatigue peeling of a hydrogen embrittlement type.

近年、自動車や産業機器に用いられる歯車、CVT(Continuously Variable Transmission:連続無段変速機)、軸受部品等の面疲労負荷を受ける部品は高性能化、高速化に伴い使用条件が過酷化している。さらに、CVTのトラクション油をはじめ潤滑油の種類も多様化しており、従来とは異なる剥離形態による早期剥離を生じる問題がある。   In recent years, parts subjected to surface fatigue loads such as gears, CVT (Continuously Variable Transmission), bearing parts, etc. used in automobiles and industrial equipment have become harsher due to higher performance and higher speed. . Furthermore, the types of lubricating oil including CVT traction oil are diversified, and there is a problem in that early peeling due to a peeling form different from the conventional one occurs.

例えば、自動車のオルタネータ用軸受で、従来型の組織変化であるヘルツ応力場に起因した、傾きを有するホワイトバンド(30°バンド、80°バンド)とは異なる粒界に沿った樹木状の白色層の組織変化を伴う早期剥離が生じる場合がある。
これは、高振動、高荷重、急加減速等の厳しい負荷条件下で、油膜厚さが不十分となり一部で金属接触が生じ、潤滑油が分解して転動面に水素が発生し、これが内部に侵入することにより水素脆性剥離が生じたためと考えられている。オルタネータ用軸受では潤滑油を変えることにより、この早期剥離を防止してきた。しかし、単に潤滑油を変えるだけでは水素起因の早期剥離を抑制できなくなりつつあり、水素脆性に優れた材料開発が求められていた。
For example, a bearing for automotive alternator, a tree-like white layer along a grain boundary different from the inclined white band (30 ° band, 80 ° band) due to the Hertzian stress field which is a conventional structural change There is a case where premature exfoliation accompanied by a tissue change occurs.
This is because under severe load conditions such as high vibration, high load, and sudden acceleration / deceleration, the oil film thickness becomes insufficient, metal contact occurs in part, the lubricating oil decomposes, and hydrogen is generated on the rolling surface. This is thought to be due to hydrogen brittle exfoliation caused by entering the inside. Alternator bearings have prevented this early peeling by changing the lubricating oil. However, by simply changing the lubricating oil, it is becoming impossible to suppress the early peeling due to hydrogen, and there has been a demand for the development of a material with excellent hydrogen embrittlement.

本出願人は、下記特許文献1で開示したように、Cr系窒化物であるCrN及びMn系窒化物であるMnSiNの水素トラップを用いた水素脆性型の面疲労強度に優れた浸炭窒化用鋼を開発している。この特許文献1に記載の浸炭窒化用鋼では、粒径300nm未満の微細なCr系窒化物であるCrN及びMn系窒化物であるMnSiNを多数分散析出させ、拡散性水素を良好にトラップすることにより、面疲労強度の向上を図るようにしている。
さらに、下記特許文献2で開示したように、水素脆性剥離寿命を更なる長寿命化するためには、微細な水素トラップサイトを増やす必要がある。すなわち、水素脆性型の転動疲労において長寿命を得るための表層N濃度と表層C濃度の適正条件を各種試験により見出した。具体的には、表層C濃度は窒化に伴うCの拡散により低下してしまうので、通常の浸炭より高めの0.80〜2.00%が適している。一方、表層N濃度が高すぎると粗大な窒化物が生成してしまうので、表層N濃度は0.10〜1.50%が適していることを明らかにした。また、水素トラップとして有効な微細窒化物を増やすためには、単に表層窒素量を高めるだけではなく、化学成分を適正化した上で、生成する窒化物にも工夫が必要であることを各種試験により見出した。すなわち、微細窒化物としてCr系窒化物であるCrNに加えて、同時に生成するMn系窒化物であるMnSiNの生成量を最大化する必要があることを見出した。具体的には、Mn系窒化物であるMnSiNはMnとSiの複合窒化物として生成するため、Si量を0.50〜1.50%、Mn量を0.80〜1.50%添加する必要があることを明らかにした。さらに、その効果を最大化するためには、Si+Mn量を1.8超〜2.50%、Mn+Cr量を3.00〜4.50%とする必要があることを明らかにした。
As disclosed in the following Patent Document 1, the applicant of the present invention is for carbonitriding excellent in surface fatigue strength of a hydrogen embrittlement type using a hydrogen trap of CrN that is Cr-based nitride and MnSiN 2 that is Mn-based nitride. Steel is being developed. In the carbonitriding steel described in Patent Document 1, a large number of CrN nitrides having a particle diameter of less than 300 nm and MnSiN 2 being Mn-based nitrides are dispersed and precipitated to trap diffusible hydrogen well. Thus, the surface fatigue strength is improved.
Furthermore, as disclosed in the following Patent Document 2, in order to further extend the hydrogen brittle exfoliation life, it is necessary to increase the number of fine hydrogen trap sites. That is, appropriate conditions of the surface layer N concentration and the surface layer C concentration for obtaining a long life in rolling fatigue of hydrogen embrittlement type were found by various tests. Specifically, since the surface layer C concentration is lowered by the diffusion of C accompanying nitriding, 0.80 to 2.00% higher than normal carburizing is suitable. On the other hand, when the surface layer N concentration is too high, coarse nitrides are generated, and thus it has been clarified that the surface layer N concentration is suitably 0.10 to 1.50%. In addition, in order to increase the number of fine nitrides that are effective as hydrogen traps, various tests have been conducted not only to increase the surface nitrogen amount but also to optimize the chemical components and to devise the nitrides that are produced. It was found by. That is, it has been found that it is necessary to maximize the amount of MnSiN 2 that is a Mn-based nitride that is simultaneously generated in addition to CrN that is a Cr-based nitride as a fine nitride. Specifically, since MnSiN 2 which is a Mn-based nitride is formed as a composite nitride of Mn and Si, the Si amount is added to 0.50 to 1.50%, and the Mn amount is added to 0.80 to 1.50%. Clarified that there is a need to do. Furthermore, in order to maximize the effect, it has been clarified that the Si + Mn amount needs to be over 1.8 to 2.50% and the Mn + Cr amount needs to be 3.00 to 4.50%.

他方、下記特許文献3には、C量を0.4〜0.8%未満、Cr量を4.0〜8.0%、その他Si,Mn,Moを所定量含み、残部をFe及び不可避不純物とする高クロム系軸受鋼において、浸炭又は浸炭窒化処理を施すことにより、転がり疲労寿命の長寿化を図る技術が開示されている。この技術ではC量及びCr量を高めることで、M系の炭化物又は炭窒化物を生成し、表層を強化して、特に高負荷の下で異物が混入した潤滑環境下の転がり疲労寿命を高めるようにしている。 On the other hand, in Patent Document 3 below, the amount of C is 0.4 to less than 0.8%, the amount of Cr is 4.0 to 8.0%, other predetermined amounts of Si, Mn, and Mo are contained, and the balance is Fe and inevitable. There has been disclosed a technique for prolonging the rolling fatigue life by performing carburizing or carbonitriding treatment on high chromium bearing steel as impurities. By increasing the C content and the Cr content in the art, to generate a M 7 C 3 type carbides or carbonitrides, and strengthen the surface, rolling especially under lubricated environment foreign matter under high load is mixed fatigue The life expectancy is increased.

特開2011−225936号公報JP 2011-225936 A 特開2014−185379号公報JP 2014-185379 A 特公平6−11899号公報Japanese Patent Publication No. 6-11899

しかし、水素原因の早期剥離現象はCVTのプーリ軸受で未だに問題となっている。面疲労負荷を受ける部品の高速回転化と高負荷化、使用条件の過酷化及び潤滑油の多様化等により、軸受部品で発生する環境条件は増加する傾向にある。このため、水素脆性型の面疲労強度をより一層向上させた軸受部品の開発が求められていた。   However, the early peeling phenomenon caused by hydrogen is still a problem in CVT pulley bearings. The environmental conditions generated in bearing parts tend to increase due to high-speed rotation and high load of parts subjected to surface fatigue load, severe use conditions, diversification of lubricating oil, and the like. For this reason, there has been a demand for the development of bearing parts that further improve the surface fatigue strength of the hydrogen embrittlement type.

本発明は以上のような事情を背景としてなされたものであり、その目的は浸炭窒化処理を行うことにより、使用条件によって水素脆性剥離が生じるような場合においても、優れた面疲労強度を有する浸炭窒化軸受部品を提供することにある。   The present invention has been made in the background as described above, and its purpose is to perform carburizing and nitriding, and carburizing having excellent surface fatigue strength even when hydrogen embrittlement delamination occurs depending on use conditions. It is to provide a nitride bearing component.

本発明者らは、水素脆性剥離寿命を更なる長寿命化するためには微細な水素トラップサイトを増やす必要があると考えた。すなわち、微細窒化物としてはCr系窒化物であるCrNに加えて、Mn系窒化物であるMnSiNが同時に生成することとなるが、窒化物量を増加させるためにはCr量の増加によるCrNの増加が有効であることを見出した。これはMnSiNの生成には、CrNの2倍のN量が必要なためである。具体的には、CrNの生成量を増加させるため、Cr量を4.00〜8.00%添加する必要があることを明らかにした。さらに、その効果を高めるためMo量を0.01〜1.00%複合添加することが有効であることを明らかにした。
しかしながら、Cr+Mo量が8.10%を超えると著しく製造性が低下するため、Cr+Mo量を5.00〜8.10%とする必要があることを明らかにした。また、CrNを効果的に活用する一方、MnSiNを生成するMn及びSi量は積極的に添加せず、製造性の観点からMn及びSi量は各々1.00%以下に低減することが望ましいことを明らかにした。
なお、上記特許文献3に記載の技術においても、Cr量を4.00〜8.00%添加し、Mo量を0.01〜1.00%添加するようにしているが、この技術がM系の炭化物又は炭窒化物を積極的に生成するものであるのに対し、本発明はCr系窒化物であるCrNを積極的に生成するものであり、CrNはMに比して微細であるため、より微細な水素トラップを増やすという点で本発明と上記特許文献3の技術思想は相違する。
The present inventors considered that it is necessary to increase the number of fine hydrogen trap sites in order to further extend the hydrogen brittle exfoliation life. That is, the fine nitrides in addition to CrN a Cr-based nitride, although MnSiN 2 is a Mn-based nitride becomes possible to generate simultaneously, in order to increase the nitriding amount is of CrN due to the increase in Cr content We found that the increase was effective. This is because the production of MnSiN 2 requires an amount of N twice that of CrN. Specifically, it has been clarified that it is necessary to add 4.00 to 8.00% of Cr in order to increase the amount of CrN produced. Furthermore, in order to enhance the effect, it has been clarified that it is effective to add Mo in an amount of 0.01 to 1.00%.
However, when the amount of Cr + Mo exceeds 8.10%, the productivity is remarkably lowered. Therefore, it has been clarified that the amount of Cr + Mo needs to be 5.00 to 8.10%. Further, while effectively using CrN, the amount of Mn and Si that generate MnSiN 2 is not actively added, and the amount of Mn and Si is preferably reduced to 1.00% or less from the viewpoint of manufacturability. It revealed that.
In the technique described in Patent Document 3, the Cr amount is added from 4.00 to 8.00%, and the Mo amount is added from 0.01 to 1.00%. to 7 C 3 type of those that actively generate carbides or carbonitrides of the present invention is to produce actively CrN a Cr-based nitride, CrN the M 7 C 3 The technical idea of the present invention is different from that of Patent Document 3 described above in that the number of finer hydrogen traps is increased because it is finer.

以上の知見に基づいた、本発明の水素脆性型の面疲労強度に優れた浸炭窒化軸受部品は、質量%で、C:0.10〜0.50%、Si:0.05〜1.00%、Mn:0.10〜1.00%、P:0.030%以下、S:0.030%以下、Cr:4.00〜8.00%、Mo:0.10〜1.00%、Al:0.050%以下、O:0.0015%以下、N:0.025%以下、Cr+Mo:5.00〜8.10%、残部がFe及び不可避不純物からなる、浸炭窒化処理及び焼入れ焼戻し処理された浸炭窒化軸受部品であって、焼戻し処理後の表層C濃度が質量%で、0.80〜2.00%、表層N濃度が0.05〜1.50%、及び表層C+N濃度が1.10〜3.00%であり、かつ表面硬さがHRC58以上64未満であり、表層に分散析出した窒化物のうち粒径2μm以上の粗大な窒化物の個数が10個/mm以下であって、分散析出した窒化物には粒径300nm以下の微細なCr系窒化物であるCrN及びMn系窒化物であるMnSiN も含まれることを特徴とする。この場合、質量%で、Ni:0.50%未満、Ti:0.10%以下、Nb:0.10%以下、の何れか1種又は2種以上を更に含有している構成とすることもできる。 Based on the above knowledge, the hydrogen embrittlement type carbonitrided bearing component of the present invention having excellent surface fatigue strength is mass%, C: 0.10 to 0.50%, Si: 0.05 to 1.00. %, Mn: 0.10 to 1.00%, P: 0.030% or less, S: 0.030% or less, Cr: 4.00 to 8.00%, Mo: 0.10 to 1.00% , Al: 0.050% or less, O: 0.0015% or less, N: 0.025% or less, Cr + Mo: 5.00 to 8.10%, the balance consisting of Fe and inevitable impurities, carbonitriding and quenching Carbonitrided bearing parts that have been tempered, and the surface layer C concentration after tempering is mass%, 0.80 to 2.00%, the surface layer N concentration is 0.05 to 1.50%, and the surface layer C + N concentration 1.10 to 3.00% and the surface hardness is HRC58 or more and less than 64, The number of out particle size 2μm or more coarse nitrides dispersed precipitated nitrides is not more 10 3 / mm 2 or less, is the particle diameter 300nm or less fine Cr-based nitride in the nitride dispersed precipitated CrN and MnSiN 2 which is a Mn-based nitride are also included . In this case, the composition further includes one or more of Ni: less than 0.50%, Ti: 0.10% or less, and Nb: 0.10% or less. You can also.

本発明の浸炭窒化軸受部品によれば、水素トラップサイトとして有効な微細窒化物を増加させ、さらには粗大な窒化物生成を抑制化することで、水素脆性型の面疲労強度を従来技術に比してより一層向上させることができる。   According to the carbonitrided bearing component of the present invention, the surface fatigue strength of the hydrogen embrittlement type is increased compared to the prior art by increasing the number of fine nitrides effective as hydrogen trap sites and further suppressing the formation of coarse nitrides. Thus, it can be further improved.

水素チャージスラスト転動疲労試験方法の説明図。Explanatory drawing of the hydrogen charge thrust rolling fatigue test method. 2円筒ころがり疲労試験方法の説明図。Explanatory drawing of the 2 cylindrical rolling fatigue test method.

以下、本発明の水素脆性型の面疲労強度に優れた浸炭窒化軸受部品の各化学成分の添加理由及び限定理由について説明する。   Hereinafter, the reason for addition and limitation of each chemical component of the carbonitrided bearing component excellent in surface fatigue strength of the hydrogen embrittlement type of the present invention will be described.

(1)C:0.10〜0.50%
C(鋼材C濃度)は、軸受部品としての例えば転がり軸受の心部硬さを確保するために必要な元素である。所定の熱処理後に必要な心部硬さを確保するためにはC含有量が0.10%以上は必要であるため、C含有量の下限を0.10%に規定した。一方、C含有量が0.50%を超えると、鍛造や旋削加工等の製造性が低下するため、C含有量の上限を0.50%とした。好ましくは0.30〜0.40%未満、さらに好ましくは0.33〜0.38%である。
(1) C: 0.10 to 0.50%
C (steel material C concentration) is an element necessary for securing the core hardness of, for example, a rolling bearing as a bearing component. In order to ensure the required core hardness after a predetermined heat treatment, the C content needs to be 0.10% or more, so the lower limit of the C content is defined as 0.10%. On the other hand, if the C content exceeds 0.50%, the manufacturability such as forging and turning decreases, so the upper limit of the C content is set to 0.50%. Preferably it is 0.30 to less than 0.40%, more preferably 0.33 to 0.38%.

(2)Si:0.05〜1.00%
Siは、浸炭窒化によりMnと複合窒化物(例えばMnSiNなど)を形成して水素トラップサイトとして働き、水素脆性型面疲労強度を改善する。この効果を得るためにはSi含有量が0.05%以上は必要であるため、Si含有量の下限を0.05%に規定した。一方、Si含有量が1.00%を超えると、Cの場合と同様、鍛造や旋削加工等の製造性が低下するため、Si含有量の上限を1.00%とした。好ましくは0.10〜0.50%である。
(2) Si: 0.05 to 1.00%
Si forms a complex nitride (for example, MnSiN 2 or the like) with Mn by carbonitriding and acts as a hydrogen trap site, thereby improving hydrogen embrittlement type surface fatigue strength. In order to obtain this effect, since the Si content is required to be 0.05% or more, the lower limit of the Si content is defined as 0.05%. On the other hand, when the Si content exceeds 1.00%, as in the case of C, manufacturability such as forging and turning decreases, so the upper limit of the Si content is set to 1.00%. Preferably it is 0.10 to 0.50%.

(3)Mn:0.10〜1.00%
Mnは、浸炭窒化によりSiとMn窒化物(例えばMnSiNなど)を形成して水素トラップサイトとして働き、水素脆性型面疲労強度を改善する。この効果を得るためにはMn含有量が0.10%以上は必要であるため、Mn含有量の下限を0.10%に規定した。一方、Mn含有量が1.00%を超えると、Siの場合と同様、鍛造や旋削加工等の製造性が低下するため、Mn含有量の上限を1.00%とした。好ましくは0.20〜0.50%である。
(3) Mn: 0.10 to 1.00%
Mn forms Si and Mn nitride (for example, MnSiN 2 or the like) by carbonitriding to serve as a hydrogen trap site, thereby improving the hydrogen embrittlement type surface fatigue strength. In order to obtain this effect, the Mn content is required to be 0.10% or more, so the lower limit of the Mn content is defined as 0.10%. On the other hand, when the Mn content exceeds 1.00%, as in the case of Si, manufacturability such as forging and turning is lowered, so the upper limit of the Mn content is set to 1.00%. Preferably it is 0.20 to 0.50%.

(4)P:0.030%以下
Pは、鋼のオーステナイト粒界に偏析し、靭性や転動疲労寿命の低下を招く。特に水素脆性型転動疲労の特徴である粒界強度を大きく低下させるため、P含有量の上限を0.030%とした。
(4) P: 0.030% or less P segregates at the austenite grain boundary of the steel and causes a decrease in toughness and rolling fatigue life. In particular, the upper limit of the P content is set to 0.030% in order to greatly reduce the grain boundary strength, which is a characteristic of hydrogen embrittlement type rolling fatigue.

(5)S:0.030%以下
Sは、鋼の熱間加工性を害し、鋼中での非金属介在物を形成して靭性や転動寿命を低下させ、水素脆性型転動疲労強度を低下させるので、可及的に少なくすることが望ましい。このため、S含有量の上限を0.030%とした。一方、Sは切削加工性を向上させる効果も有しているため、好ましくは下限を0.010%とする。
(5) S: 0.030% or less S impairs hot workability of steel, forms non-metallic inclusions in the steel to reduce toughness and rolling life, and hydrogen embrittlement type rolling fatigue strength. It is desirable to reduce it as much as possible. For this reason, the upper limit of the S content is set to 0.030%. On the other hand, since S also has an effect of improving the machinability, the lower limit is preferably set to 0.010%.

(6)Cr:4.00〜8.00%
Crは、本発明において重要な添加元素であり、浸炭窒化により窒化物を形成して水素トラップサイトとして働き、水素脆性型面疲労強度を改善する。また、Crは、焼入れ性の改善や炭化物による硬さの確保、寿命改善のために添加される。高耐水素脆性のための所定の窒化物を得るためには4.00%以上のCr量の添加が必要であるため、Cr含有量の下限を4.00%に規定した。一方、Cr含有量が8.00%を超えると、浸炭性を劣化させ、大型の炭窒化物を生成し、転動疲労寿命の低下を招来するため、Cr含有量の上限を8.00%とした。好ましくは5.00〜7.00%である。
(6) Cr: 4.00 to 8.00%
Cr is an important additive element in the present invention, and forms a nitride by carbonitriding to serve as a hydrogen trap site to improve hydrogen embrittlement type surface fatigue strength. Cr is added to improve hardenability, secure hardness by carbides, and improve life. In order to obtain a predetermined nitride for high hydrogen embrittlement resistance, it is necessary to add a Cr amount of 4.00% or more. Therefore, the lower limit of the Cr content is defined as 4.00%. On the other hand, if the Cr content exceeds 8.00%, the carburizing property is deteriorated, large carbonitrides are formed, and the rolling fatigue life is reduced. Therefore, the upper limit of the Cr content is 8.00%. It was. Preferably it is 5.00 to 7.00%.

(7)Mo:0.10〜1.00%以下
Moは、粒界破壊を抑制することにより、水素脆性型の面疲労強度を向上させる。また、Moは鋼の焼入れ性を改善するとともに、炭化物中に固溶することにより、焼戻し時の硬さの低下を抑制する効果がある。その効果を得るためには0.10%以上のMo量の添加が必要であるため、Mo含有量の下限を0.10%に規定した。一方、Mo含有量が1.00%を超えると、鋼材のコストが上昇する他、鍛造や旋削加工等の製造性が低下するため、Mo含有量の上限を1.00%とした。好ましくは0.20〜0.50%である。
(7) Mo: 0.10 to 1.00% or less Mo improves the surface fatigue strength of the hydrogen embrittlement type by suppressing grain boundary fracture. Further, Mo improves the hardenability of the steel and has the effect of suppressing the decrease in hardness during tempering by dissolving in the carbide. In order to obtain the effect, it is necessary to add an amount of Mo of 0.10% or more, so the lower limit of the Mo content is defined as 0.10%. On the other hand, if the Mo content exceeds 1.00%, the cost of the steel material increases, and the manufacturability such as forging and turning decreases, so the upper limit of the Mo content is set to 1.00%. Preferably it is 0.20 to 0.50%.

(8)Al:0.050%以下
Alは、鋼の製造時の脱酸剤として使用されるが、硬質の非金属介在物を生成し、転動疲労寿命を低下させるため低減することが望ましい。Al含有量が0.050%を超えると、顕著な転動疲労寿命の低下が認められるため、Al含有量の上限を0.050%とした。なお、Al含有量を0.005%未満にすると鋼材のコストが上昇するため、Al含有量の下限を0.005%とすることが好ましい。
(8) Al: 0.050% or less Al is used as a deoxidizer during the production of steel, but it is desirable to reduce it to produce hard non-metallic inclusions and reduce the rolling fatigue life. . When the Al content exceeds 0.050%, a significant decrease in rolling fatigue life is observed, so the upper limit of the Al content was set to 0.050%. In addition, since the cost of steel materials will raise when Al content is made less than 0.005%, it is preferable to make the minimum of Al content into 0.005%.

(9)O:0.0015%以下、N:0.025%以下
O及びNは、鋼中に酸化物、窒化物を形成し、非金属介在物として疲労破壊の起点となり、転動疲労寿命を低下させるため、O含有量の上限を0.0015%とし、N含有量の上限を0.025%とした。
(9) O: 0.0015% or less, N: 0.025% or less O and N form oxides and nitrides in the steel, and serve as starting points for fatigue failure as non-metallic inclusions. Therefore, the upper limit of the O content was 0.0015% and the upper limit of the N content was 0.025%.

(10)Cr+Mo:5.00〜8.10%
CrとMoは、単独添加でも水素脆性型の面疲労強度を改善するが、十分な効果を得るためには、両者を適正に複合添加することが必要である。Cr+Moの含有量が5.00%未満では、水素脆性に対する改善効果を十分に得ることができないため、下限を5.00%とした。一方、Cr+Moの含有量が8.10%を超えると、鍛造や旋削加工等の製造性が低下するため、上限を8.10%とした。好ましくは5.50〜7.50%である。
(10) Cr + Mo: 5.00 to 8.10%
Even if Cr and Mo are added alone, the surface fatigue strength of the hydrogen embrittlement type is improved. However, in order to obtain a sufficient effect, it is necessary to add both appropriately and in combination. When the content of Cr + Mo is less than 5.00%, the improvement effect on hydrogen embrittlement cannot be obtained sufficiently, so the lower limit was made 5.00%. On the other hand, if the content of Cr + Mo exceeds 8.10%, productivity such as forging and turning decreases, so the upper limit was made 8.10%. Preferably it is 5.50-7.50%.

(11)表面硬さ:HRC58以上64未満
焼戻し後の表面硬さと転動疲労寿命には相関が認められ、表面硬さが高いほど転動疲労寿命は長くなる傾向がある。特に、焼戻し処理後の表面硬さがHRC58未満になると急激に転動疲労寿命が低下し、寿命のばらつきも大きくなるため、焼戻し処理後の表面硬さをHRC58以上とした。一方、表面硬さが高くなると水素脆性に対する感受性が高くなり、表面硬さがHRC64以上になると水素脆性型の面疲労強度が著しく低下するため、HRC64未満とした。なお、Hv硬さに換算すると約650Hv以上800Hv未満に相当する。
(11) Surface hardness: HRC 58 or more and less than 64 There is a correlation between the surface hardness after tempering and the rolling fatigue life, and the higher the surface hardness, the longer the rolling fatigue life. In particular, when the surface hardness after the tempering treatment is less than HRC58, the rolling fatigue life is drastically reduced and the variation in the life is increased. Therefore, the surface hardness after the tempering treatment is set to HRC58 or more. On the other hand, when the surface hardness is increased, the sensitivity to hydrogen embrittlement is increased, and when the surface hardness is HRC64 or more, the surface fatigue strength of the hydrogen embrittlement type is significantly decreased. In terms of Hv hardness, this corresponds to about 650 Hv or more and less than 800 Hv.

(12)粒径2μm以上の粗大な窒化物の個数が10個/mm以下
水素脆性型面疲労強度の改善には、微細窒化物を多数析出させることが必要である。すなわち、窒化物のうち水素トラップに有効な窒化物は、粒径300nm以下の微細なCr窒化物(例えばCrN)、及びMnとSiの複合窒化物(例えばMnSiN)である。しかし、表層N濃度や合金元素を高めると、粒径の大きい粗大な窒化物が形成されやすくなり、強度低下の要因となる。粒径2μm以上の粗大な窒化物の個数割合が10個/mmを超えると、著しく水素脆性型面疲労強度が低下するため、粒径2μm以上の粗大な窒化物の個数割合の上限を10個/mmとした。
(12) The number of coarse nitrides having a particle size of 2 μm or more is 10 3 pieces / mm 2 or less. In order to improve the hydrogen embrittlement surface fatigue strength, it is necessary to precipitate a large number of fine nitrides. That is, of the nitrides, nitrides effective for hydrogen trapping are fine Cr nitrides (eg, CrN) having a particle size of 300 nm or less, and composite nitrides of Mn and Si (eg, MnSiN 2 ). However, increasing the surface layer N concentration and the alloy element facilitates the formation of coarse nitrides having a large particle size, which causes a decrease in strength. If the number ratio of coarse nitrides having a particle size of 2 μm or more exceeds 10 3 pieces / mm 2 , the hydrogen embrittlement type surface fatigue strength is remarkably lowered. Therefore, the upper limit of the number ratio of coarse nitrides having a particle size of 2 μm or more is limited. 10 3 pieces / mm 2 .

(13)表層C濃度(表層炭素濃度):0.80〜2.00%
表層Cは、転がり軸受として強度を確保するために必須の元素であり、所定の熱処理後硬さを維持するためには表層C濃度が0.80%以上は必要であるため、表層C濃度の下限を0.80%に規定した。一方、表層C濃度が2.00%を超えると、大型の炭化物が生成し、転動疲労寿命の低下が生じることが判明したため、表層C濃度の上限を2.00%とした。好ましくは1.20〜1.40%である。
(13) Surface layer C concentration (surface layer carbon concentration): 0.80 to 2.00%
The surface layer C is an essential element for securing strength as a rolling bearing, and the surface layer C concentration of 0.80% or more is necessary to maintain the hardness after a predetermined heat treatment. The lower limit was defined as 0.80%. On the other hand, when the surface layer C concentration exceeds 2.00%, it has been found that large carbides are generated and the rolling fatigue life is reduced, so the upper limit of the surface layer C concentration is 2.00%. Preferably it is 1.20 to 1.40%.

(14)表層N濃度(表層窒素濃度):0.05〜1.50%
表層Nは、微細な窒化物を表層に生成することにより水素トラップサイトとして働き、耐水素脆性を改善する。また、鋼の軟化抵抗性を改善することにより転動寿命を向上させる。これらの効果を得るためには表層N濃度が0.05%以上は必要であるため、表層N濃度の下限を0.05%とした。一方、表層N濃度が1.50%を超えると、残留オーステナイトの生成により表面硬さを低下させ、所定の表面硬さが得られなくなるため、表層N濃度の上限を1.50%とした。好ましくは0.60〜0.90%である。
(14) Surface layer N concentration (surface layer nitrogen concentration): 0.05 to 1.50%
The surface layer N works as a hydrogen trap site by generating fine nitride in the surface layer, and improves hydrogen embrittlement resistance. It also improves the rolling life by improving the softening resistance of the steel. In order to obtain these effects, the surface layer N concentration needs to be 0.05% or more, so the lower limit of the surface layer N concentration was set to 0.05%. On the other hand, when the surface layer N concentration exceeds 1.50%, the surface hardness is lowered due to the formation of retained austenite, and a predetermined surface hardness cannot be obtained. Therefore, the upper limit of the surface layer N concentration is set to 1.50%. Preferably it is 0.60 to 0.90%.

(15)表層C+N濃度(表層炭素・窒素濃度):1.10〜3.00%
表層C+N濃度を適正化することで、必要な表層硬さと微細窒化物の析出を両立し、水素脆性面疲労強度を向上させることができる。この効果を得るためには表層C+N濃度が1.10%以上は必要であるため、表層C+N濃度の下限を1.10%に規定した。一方、表層C+N濃度が3.00%を超えると、粗大な炭窒化物が生成し、水素脆性型面疲労強度が低下するため、表層C+N濃度の上限を3.00%に規定した。好ましくは1.80〜2.30%である。
(15) Surface layer C + N concentration (surface layer carbon / nitrogen concentration): 1.10 to 3.00%
By optimizing the surface layer C + N concentration, it is possible to achieve both necessary surface layer hardness and precipitation of fine nitrides and improve hydrogen embrittlement surface fatigue strength. In order to obtain this effect, the surface layer C + N concentration needs to be 1.10% or more, so the lower limit of the surface layer C + N concentration is defined as 1.10%. On the other hand, when the surface layer C + N concentration exceeds 3.00%, coarse carbonitrides are generated and the hydrogen embrittlement surface fatigue strength is lowered. Therefore, the upper limit of the surface layer C + N concentration is defined as 3.00%. Preferably it is 1.80 to 2.30%.

本発明では、更に以下の化学成分の何れか1種又は2種以上を添加することができる。
(16)Ni:0.50%未満
Niは、転動疲労過程での組織変化を抑制し、転動疲労寿命を向上させる。また、Niの添加は靭性および耐食性の改善にも効果がある。一方、Ni含有量が0.50%を超えると、鋼の焼入れ時に多量の残留オーステナイトが生成し、所定の硬さが得られなくなるとともに、鋼材のコストが上昇するため、Ni含有量を0.50%未満とした。
In the present invention, any one or more of the following chemical components can be added.
(16) Ni: Less than 0.50% Ni suppresses structural changes in the rolling fatigue process and improves the rolling fatigue life. Further, the addition of Ni is effective in improving toughness and corrosion resistance. On the other hand, if the Ni content exceeds 0.50%, a large amount of retained austenite is generated during quenching of the steel, and a predetermined hardness cannot be obtained, and the cost of the steel material is increased. Less than 50%.

(17)Ti:0.10%以下
Tiの炭化物は微細であり、水素トラップサイトとして有効に働くことにより、水素脆性型の面疲労強度が改善する。一方、Tiは鋼中に酸化物、窒化物を形成し、非金属介在物として疲労破壊の起点となり、転動疲労寿命を低下させるため、Ti含有量の上限を0.10%とした。
(17) Ti: 0.10% or less Ti carbide is fine and effectively acts as a hydrogen trap site, thereby improving the surface fatigue strength of the hydrogen embrittlement type. On the other hand, Ti forms oxides and nitrides in the steel and serves as a starting point for fatigue failure as a non-metallic inclusion and lowers the rolling fatigue life. Therefore, the upper limit of Ti content is set to 0.10%.

(18)Nb:0.10%以下
Nbの炭化物も微細であり、水素トラップサイトとして有効に働くことにより、水素脆性型の面疲労強度が改善する。また、Nbは結晶粒の粗大化を抑制する。結晶粒が微細化すれば、耐水素脆性の改善に有効となる。一方、Nb含有量が0.10%を超えてもその効果が飽和するため、Nb含有量の上限を0.10%とした。
(18) Nb: 0.10% or less Nb carbide is also fine, and effectively acts as a hydrogen trap site, thereby improving the surface fatigue strength of the hydrogen embrittlement type. Nb suppresses the coarsening of crystal grains. Refinement of crystal grains is effective in improving hydrogen embrittlement resistance. On the other hand, since the effect is saturated even if the Nb content exceeds 0.10%, the upper limit of the Nb content is set to 0.10%.

(19)残部:Fe及び不可避不純物
ここでの不可避不純物(不可避的不純物)は、表1のNiに代表される不純物レベル(表1中に示すNiの欄の「−」表示)を示す。表1において残部はFeである。
(19) Remainder: Fe and inevitable impurities The inevitable impurities here (inevitable impurities) indicate impurity levels represented by Ni in Table 1 (indicated by “-” in the column of Ni shown in Table 1). In Table 1, the balance is Fe.

以下、本発明の実施例について説明する。
表1に示す化学成分の材料を150kgの真空溶解で溶製し、熱間鍛造により直径70mmと直径28mmの棒鋼を製造した。この後、球状化焼なまし処理として850℃に加熱し、4時間保持した後、−15℃/時間で650℃まで冷却した後空冷し、各試験の素材とした。
Examples of the present invention will be described below.
The material of the chemical component shown in Table 1 was melted by vacuum melting of 150 kg, and steel bars having a diameter of 70 mm and a diameter of 28 mm were manufactured by hot forging. Then, as a spheroidizing annealing treatment, it was heated to 850 ° C., held for 4 hours, cooled to 650 ° C. at −15 ° C./hour, and then air-cooled to obtain materials for each test.

その素材から直径25mm、長さ100mmの試験片を削り出し、浸炭窒化処理及び焼入れ焼戻し処理を行った。浸炭窒化処理は、浸炭ガスにアンモニアガスを加えた混合雰囲気中で行い、その後に焼入れ焼戻し処理を行った。   A test piece having a diameter of 25 mm and a length of 100 mm was cut out from the material and subjected to carbonitriding and quenching and tempering. The carbonitriding process was performed in a mixed atmosphere in which ammonia gas was added to the carburizing gas, followed by quenching and tempering.

まず、処理室内に試験片を設置した後、浸炭ガスにアンモニアガスを加えた混合ガスを処理室内へ導入して、930℃にて浸炭窒化処理を行った。その後、引き続き処理室内の温度を850℃まで降下させた状態で均熱処理を行い、試験片を油冷した。   First, after installing a test piece in the processing chamber, a mixed gas obtained by adding ammonia gas to carburizing gas was introduced into the processing chamber, and carbonitriding was performed at 930 ° C. Then, soaking was continued in a state where the temperature in the processing chamber was lowered to 850 ° C., and the test piece was oil-cooled.

次に、850℃で2次焼入れ及び200℃で焼戻し処理を行なった。なお、浸炭窒化処理中の処理室内のカーボンポテンシャルは0.8体積%、アンモニアガス濃度は1.0体積%とした。   Next, secondary quenching at 850 ° C. and tempering treatment at 200 ° C. were performed. The carbon potential in the processing chamber during the carbonitriding process was 0.8% by volume, and the ammonia gas concentration was 1.0% by volume.

浸炭窒化処理及び焼入れ焼戻し処理を行った後、試験片の外周を深さ0.1mmだけ研削し、5点平均でロックウェル硬さ(JIS Z2245に準拠)を求めた。その後、同試験片の縦断面を埋め込んで研磨仕上げし、表層部の表層C濃度と表層N濃度をEPMAで分析した。ここで、表層C濃度と表層N濃度は、最表層から深さ10μmの位置までのC濃度、N濃度の最大値(ピーク値)とした。   After performing the carbonitriding process and the quenching and tempering process, the outer periphery of the test piece was ground by a depth of 0.1 mm, and the Rockwell hardness (conforming to JIS Z2245) was obtained with an average of 5 points. Thereafter, the longitudinal section of the test piece was embedded and polished, and the surface layer C concentration and the surface layer N concentration in the surface layer portion were analyzed by EPMA. Here, the surface layer C concentration and the surface layer N concentration were set to the maximum value (peak value) of the C concentration and N concentration from the outermost layer to a depth of 10 μm.

さらに、走査型電子顕微鏡を用いて、埋め込み研磨した試験片の表層から深さ100μmの位置までに存在する粒径2μm以上の窒化物の個数を測定し、観察領域の面積で除して、粒径2μm以上の粗大な窒化物の個数密度(個/mm)を求めた。 Further, using a scanning electron microscope, the number of nitrides having a particle diameter of 2 μm or more existing from the surface layer of the embedded and polished specimen to a position of 100 μm in depth is measured and divided by the area of the observation region, The number density (pieces / mm 2 ) of coarse nitrides having a diameter of 2 μm or more was determined.

また、上記直径70mmの素材から直径61mm、厚さ6mmのスラスト型転動疲労試験片を粗加工し、各鋼種をそれぞれ前述と同じ浸炭窒化処理条件で浸炭窒化処理及び焼入れ焼戻し処理を行い、試験表面を厚さ5.5mmに研削仕上げし、バフ仕上げして試験片を作製した。同試験片を1L中に1.4gのチオシアン酸アンモニウムを溶解した希硫酸電解液を用い、電流密度0.4mA/cmで20時間の陰極チャージ(水素チャージ)を行った。水素を陰極チャージ後、ペーパー研磨仕上げして転動疲労試験を開始した。 In addition, a 61 mm diameter and 6 mm thick thrust type rolling fatigue test piece is roughly processed from the 70 mm diameter material, and each steel type is subjected to carbonitriding and quenching and tempering under the same carbonitriding conditions as described above. The surface was ground to a thickness of 5.5 mm and buffed to produce a test piece. The test piece was subjected to a cathode charge (hydrogen charge) for 20 hours at a current density of 0.4 mA / cm 2 using a diluted sulfuric acid electrolyte solution in which 1.4 g of ammonium thiocyanate was dissolved in 1 L. After the cathode was charged with hydrogen, the paper was polished and a rolling fatigue test was started.

転動疲労試験は、図1に示されるように、円盤型の試験片13を取り付けた油槽に潤滑油15を注入し、テーブル14を押し上げ、保持器に支持された鋼球12をスラスト軸受11で受けることで所定面圧を負荷し、その状態でモータからの動力を伝達する軸10を回転させるものである。
試験条件は面圧4.9GPaで、潤滑はナフテン系鉱油を用い、負荷速度1800rpmで試験を行った。同一条件で約10点の試験を行い、ワイブル分布の累積破損確率が10%となるL10寿命を求めて評価寿命とした。
In the rolling fatigue test, as shown in FIG. 1, lubricating oil 15 is injected into an oil tank provided with a disk-shaped test piece 13, the table 14 is pushed up, and a steel ball 12 supported by a cage is attached to a thrust bearing 11. In this state, a predetermined surface pressure is applied, and the shaft 10 that transmits power from the motor is rotated in that state.
Test conditions were a surface pressure of 4.9 GPa, lubrication was performed using a naphthenic mineral oil and a load speed of 1800 rpm. Were tested about 10 points under the same conditions, the cumulative failure probability of the Weibull distribution was evaluated life seeking 10% become L 10 life.

また、直径28mmの素材から粗加工後、各鋼種を各々前述と同じ浸炭窒化処理を行い、試験面直径26mmの円筒試験片を作製し、その試験片を用いて2円筒ころがり疲労試験を行った。2円筒ころがり疲労試験は、図2に示されるように、円筒形状の試験片18に対して相手円筒20を所定面圧で押し付け、その状態でモータ22により軸部24を介して試験片18を回転させるとともに、モータ22の回転をギア26,28を介して軸30に伝達して、相手円筒20を回転させるものである。相手円筒20は、SUJ2製の焼入れ焼戻し材からなり、軸方向に曲率半径150mmのクラウニングを有する直径130mmの形状に形成されている。   Further, after roughing from a material having a diameter of 28 mm, each steel type was subjected to the same carbonitriding treatment as described above to produce a cylindrical specimen having a test surface diameter of 26 mm, and a two-cylinder rolling fatigue test was conducted using the specimen. . In the two-cylinder rolling fatigue test, as shown in FIG. 2, the mating cylinder 20 is pressed against the cylindrical test piece 18 with a predetermined surface pressure, and the test piece 18 is pushed by the motor 22 via the shaft portion 24 in this state. While rotating, the rotation of the motor 22 is transmitted to the shaft 30 via the gears 26 and 28 to rotate the counterpart cylinder 20. The counterpart cylinder 20 is made of a quenching and tempering material made of SUJ2, and is formed into a shape with a diameter of 130 mm having a crowning with a curvature radius of 150 mm in the axial direction.

試験は、水素脆性型の早期転動疲労破壊が生じる試験条件(油温90℃、すべり率−60%、面圧3GPa、回転数1500rpm)で行った。同一試験条件でも潤滑油によって水素侵入量が変化し水素脆性剥離に影響するため、より水素脆性剥離が発生しやすい潤滑油を用いた。ここで、すべり率とは、試験片18と相手円筒20の周速の差と、試験片18の周速との比率である。試験は同一条件で4点行い、平均寿命を求めた。表2に試験結果を示す。   The test was performed under test conditions (oil temperature 90 ° C., slip rate −60%, surface pressure 3 GPa, rotation speed 1500 rpm) in which hydrogen brittle type early rolling fatigue failure occurs. Even under the same test conditions, the amount of hydrogen intrusion was changed by the lubricating oil and affected hydrogen brittle exfoliation. Therefore, a lubricating oil that was more likely to cause hydrogen brittle exfoliation was used. Here, the slip ratio is a ratio of the difference between the peripheral speeds of the test piece 18 and the counterpart cylinder 20 and the peripheral speed of the test piece 18. The test was performed at four points under the same conditions, and the average life was obtained. Table 2 shows the test results.

発明例は、いずれも表面硬さHRC58以上64未満であり、表層C濃度は0.80〜2.00質量%の範囲、表層N濃度は0.05〜1.50質量%の範囲、表層C+N濃度は1.10〜3.00質量%の範囲であり、粒径2μm以上の粗大な窒化物を10個/mm以下である。 In all the inventive examples, the surface hardness is HRC58 or more and less than 64, the surface layer C concentration is in the range of 0.80 to 2.00% by mass, the surface layer N concentration is in the range of 0.05 to 1.50% by mass, and the surface layer C + N The concentration is in the range of 1.10 to 3.00% by mass, and 10 3 pieces / mm 2 or less of coarse nitrides having a particle size of 2 μm or more.

発明例の水素チャージ材の転動疲労のL10寿命は、24.05〜30以上×10回と優れる。一方、比較例では、同L10寿命は2.92〜6.77×10回と、いずれも水素脆性型の早期転動疲労破壊が生じて低寿命である。本発明により水素脆性型の転動寿命が改善していることが分かる。 The L 10 life of rolling fatigue of the hydrogen charge material of the inventive example is excellent as 24.05 to 30 × 10 6 times. On the other hand, in the comparative example, the L 10 life and 2.92 to 6.77 × 10 6 times, both of which are low-life cause premature rolling fatigue fracture of hydrogen embrittlement type. It can be seen that the rolling life of the hydrogen brittle type is improved by the present invention.

また、発明例の2円筒試験の平均寿命は、18.1〜20以上×10回と優れる。一方、比較例では、同平均寿命は3.5〜5.7×10回と、いずれも水素脆性により低寿命である。本発明により水素脆性型の転動寿命が1オーダ程度改善していることが分かる。 Moreover, the average life of the two-cylinder test of the invention example is excellent at 18.1 to 20 or more × 10 6 times. On the other hand, in the comparative example, the average life is 3.5 to 5.7 × 10 6 times, both of which are low life due to hydrogen embrittlement. It can be seen that the rolling life of the hydrogen embrittlement type is improved by about one order according to the present invention.

表2の比較例のうち、鋼種No.14,16は化学成分の内Cr量が低いため、鋼種No.15はMo量が低いため、いずれも低寿命となった例である。また、比較例のうち鋼種No.1〜No.3は化学成分は請求範囲内にあるが、以下の理由により低寿命となった例である。   Among the comparative examples in Table 2, steel types Nos. 14 and 16 are examples in which the amount of Cr in the chemical components is low, and since steel type No. 15 has a low amount of Mo, both have a low life. Further, among the comparative examples, steel types No. 1 to No. 3 are examples in which the chemical components are within the scope of claims but have a low life due to the following reasons.

すなわち、比較例の鋼種No.1は浸炭窒化条件が適正でないため、粒径2μm以上の窒化物が10個/mm以上となり低寿命となった。比較例の鋼種No.2は表層C濃度が低く、比較例の鋼種No.3は表層N濃度が低いため、いずれも低寿命となった。 That is, since the carbonitriding condition was not appropriate for the steel type No. 1 in the comparative example, the number of nitrides having a particle size of 2 μm or more was 10 3 pieces / mm 2 or more, and the life was shortened. Steel type No. 2 in the comparative example has a low surface layer C concentration, and steel type No. 3 in the comparative example has a low surface layer N concentration, so that both have a short life.

以上の説明からも明らかなように、水素トラップサイトとして有効な微細窒化物を増加させ、さらには粗大な窒化物生成を抑制化するようにした本発明の浸炭窒化軸受部品によれば、水素脆性型の面疲労強度を従来技術に比してより一層向上させることができる。   As is clear from the above description, according to the carbonitrided bearing component of the present invention that increases the fine nitride effective as a hydrogen trap site and further suppresses the formation of coarse nitride, the hydrogen embrittlement The surface fatigue strength of the mold can be further improved as compared with the prior art.

13、18 試験片 13, 18 Specimen

Claims (2)

質量%で、
C:0.10〜0.50%、
Si:0.05〜1.00%、
Mn:0.10〜1.00%、
P:0.030%以下、
S:0.030%以下、
Cr:4.00〜8.00%、
Mo:0.10〜1.00%、
Al:0.050%以下、
O:0.0015%以下、
N:0.025%以下、
Cr+Mo:5.00〜8.10%、
残部がFe及び不可避不純物からなる、浸炭窒化処理及び焼入れ焼戻し処理された浸炭窒化軸受部品であって、前記焼戻し処理後の表層C濃度が質量%で、0.80〜2.00%、表層N濃度が0.05〜1.50%、及び表層C+N濃度が1.10〜3.00%であり、かつ表面硬さがHRC58以上64未満であり、表層に分散析出した窒化物のうち粒径2μm以上の粗大な窒化物の個数が10個/mm以下であって、前記分散析出した窒化物には粒径300nm以下の微細なCr系窒化物であるCrN及びMn系窒化物であるMnSiN も含まれることを特徴とする水素脆性型の面疲労強度に優れた浸炭窒化軸受部品。
% By mass
C: 0.10 to 0.50%,
Si: 0.05-1.00%,
Mn: 0.10 to 1.00%,
P: 0.030% or less,
S: 0.030% or less,
Cr: 4.00 to 8.00%,
Mo: 0.10 to 1.00%,
Al: 0.050% or less,
O: 0.0015% or less,
N: 0.025% or less,
Cr + Mo: 5.00 to 8.10%,
Carbonitriding bearing parts that have been carbonitrided and quenched and tempered, with the balance being Fe and inevitable impurities, the surface layer C concentration after the tempering treatment being mass%, 0.80 to 2.00%, surface layer N Concentration is 0.05 to 1.50%, surface layer C + N concentration is 1.10 to 3.00%, surface hardness is HRC58 or more and less than 64, and the particle size among the nitrides dispersed and deposited on the surface layer The number of coarse nitrides of 2 μm or more is 10 3 pieces / mm 2 or less, and the dispersed and precipitated nitrides are CrN and Mn nitrides which are fine Cr-based nitrides having a particle size of 300 nm or less. A carbon-nitrided bearing component excellent in surface fatigue strength of a hydrogen embrittlement type characterized by including MnSiN 2 .
請求項1において、質量%で、
Ni:0.50%未満、
Ti:0.10%以下、
Nb:0.10%以下、
の何れか1種又は2種以上を更に含有していることを特徴とする水素脆性型の面疲労強度に優れた浸炭窒化軸受部品。
In claim 1, in mass%,
Ni: less than 0.50%,
Ti: 0.10% or less,
Nb: 0.10% or less,
A carbon-nitrided bearing part excellent in surface fatigue strength of a hydrogen embrittlement type, characterized by further containing any one or more of these.
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