JP3466328B2 - Long life steel for induction hardened bearings - Google Patents
Long life steel for induction hardened bearingsInfo
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- JP3466328B2 JP3466328B2 JP14245495A JP14245495A JP3466328B2 JP 3466328 B2 JP3466328 B2 JP 3466328B2 JP 14245495 A JP14245495 A JP 14245495A JP 14245495 A JP14245495 A JP 14245495A JP 3466328 B2 JP3466328 B2 JP 3466328B2
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- ferrite
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Description
【０００１】[0001]
【産業上の利用分野】本発明は高寿命高周波焼入れ軸受
用鋼材にかかわり、さらに詳しくは、高周波焼入れ工程
で製造され、高負荷下で使用される外輪、内輪、ころ等
の軸受部品用として好適な鋼材に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel material for long-life induction hardening bearings, and more specifically, suitable for bearing parts such as outer rings, inner rings, rollers, etc., which are manufactured in an induction hardening process and are used under high load. Steel materials.
【０００２】[0002]
【従来の技術】近年の自動車エンジンの高出力化および
環境規制対応にともない、軸受部品においても転動疲労
寿命向上の指向が強い。これに対して、これまで鋼の高
清浄化による高寿命化が図られてきた。これは、軸受部
品の転動疲労破壊は非金属介在物が起点となると考えら
れているためである。例えば、日本金属学会報第３２巻
第６号４４１頁から４４３頁には偏心炉底出鋼、ＲＨ真
空脱ガス等の組み合わせにより、酸化物系介在物が低減
し転動疲労寿命が向上することが示されている。しかし
ながら、上記材の高寿命化では必ずしも十分ではなく、
特に高負荷下で使用される場合等において、より一層の
高寿命鋼の開発が強く望まれている。2. Description of the Related Art With the recent trend toward higher output of automobile engines and compliance with environmental regulations, there is a strong tendency to improve rolling contact fatigue life of bearing parts. On the other hand, up to now, the life of the steel has been improved by cleaning the steel highly. This is because it is considered that non-metallic inclusions are the starting point for rolling contact fatigue failure of bearing parts. For example, in the Japan Institute of Metals, Vol. 32, No. 6, pages 441 to 443, oxide-based inclusions are reduced and rolling fatigue life is improved by combining eccentric furnace bottom steel, RH vacuum degassing, etc. It is shown. However, extending the life of the above materials is not always sufficient,
In particular, when used under a high load, the development of further long-life steel is strongly desired.
【０００３】また、特開平６−２６４１８８にはＣ：
０．５〜１．５％、Ｍｏ：０．５超〜２．０％、Ｏ：
０．００２％以下を含有した繰り返し応力負荷によるミ
クロ組織変化遅延特性に優れた軸受鋼が示されている。
しかしながら、本材は経済性の点で好ましくなく、必ず
しも普及していないのが現状である。さらに、軸受部品
は、通常、過共析鋼を球状化焼鈍−焼入れ焼戻しの工程
により製造されているが、低コスト化の指向が強い。In Japanese Patent Laid-Open No. 6-264188, C:
0.5-1.5%, Mo: more than 0.5-2.0%, O:
Bearing steels containing 0.002% or less and having excellent microstructure change retardation characteristics under repeated stress loading are shown.
However, this material is not preferable from the economical point of view and is not always popular. Further, the bearing component is usually manufactured by a process of spheroidizing annealing-quenching and tempering of hyper-eutectoid steel, but there is a strong tendency to reduce costs.
【０００４】[0004]
【発明が解決しようとする課題】本発明の目的は、軸受
部品が低コストで製造可能であり、かつ軸受部品におい
て優れた転動疲労特性を得ることができる高周波焼入れ
軸受用鋼材を提供しようとするものである。SUMMARY OF THE INVENTION An object of the present invention is to provide a steel material for induction hardened bearings, in which bearing parts can be manufactured at low cost and excellent rolling contact fatigue characteristics can be obtained in the bearing parts. To do.
【０００５】[0005]
【課題を解決するための手段】本発明者らは、軸受部品
を低コストで製造するために、従来の過共析鋼の球状化
焼鈍−焼入れ焼戻しに代わる工程として高周波焼入れに
着目した。高周波焼入れ材は、表層に大きな圧縮残留応
力が生成するために高寿命化にも有効である。さらに高
負荷下でも優れた転動疲労特性を得ることができる高周
波焼入れ軸受用鋼材を実現するために、鋭意検討を行い
次の知見を得た。SUMMARY OF THE INVENTION The present inventors have focused on induction hardening as an alternative process to conventional spheroidizing annealing-quenching and tempering of hypereutectoid steel in order to manufacture bearing parts at low cost. The induction-hardened material is effective for extending the life because a large compressive residual stress is generated in the surface layer. Furthermore, in order to realize a steel material for induction hardened bearings that can obtain excellent rolling fatigue characteristics even under high load, earnest studies were conducted and the following findings were obtained.
【０００６】（１）高周波焼入れ材を高負荷下で転動疲
労試験を行った場合、転動疲労過程において、白色組織
・炭化物組織の生成、硬さの低下を伴う材質劣化が起こ
り、こうした局所的な材質劣化部を起点として破壊が起
きる。
（２）転動疲労過程での局所的な材質劣化部生成の主原
因は、硬化層の硬さムラである。特に、高周波加熱前の
組織のフェライト分率が２５％を超え、フェライト結晶
粒径が２０μｍを超えると硬化層で顕著な硬さのムラを
生じ、転動疲労破壊を起こしやすくなる。(1) When an induction hardened material is subjected to a rolling fatigue test under a high load, a white structure / carbide structure is formed and material deterioration accompanied by a decrease in hardness occurs in the rolling fatigue process, and such local deterioration occurs. Destruction occurs from the starting point of the material deterioration. (2) The main cause of the local generation of the material deteriorated portion in the rolling fatigue process is uneven hardness of the hardened layer. In particular, if the ferrite fraction of the structure before high frequency heating exceeds 25% and the ferrite crystal grain size exceeds 20 μm, remarkable hardness unevenness occurs in the hardened layer, and rolling fatigue fracture is likely to occur.
【０００７】（３）また、これらの転動疲労過程での材
質劣化を抑制するには、下記の方法が有効である。
高Ｍｎにより、焼入れ性を確保する。Ｃｒを多量添加
しない。
Ｓｉを増量する。
（４）さらに、局所的な材質劣化部生成を抑制して高寿
命化を図るためには、Ｍｏ添加、非金属介在物の低減、
微細化が有効である。
（５）上記に加えて、さらにＣｒ，Ｎｉ，Ｖ，Ｎｂ，Ｂ
を添加することにより、材質劣化抑制、硬さ低下防止の
硬化はさらに大きくなる。(3) Further, the following method is effective for suppressing the material deterioration in the rolling fatigue process. A high Mn ensures hardenability. Do not add a large amount of Cr. Increase the amount of Si. (4) Further, in order to suppress the local generation of the material-deteriorated portion and achieve a long life, addition of Mo, reduction of non-metallic inclusions,
Miniaturization is effective. (5) In addition to the above, Cr, Ni, V, Nb, B
By adding, the hardening for suppressing the deterioration of the material and preventing the decrease in hardness is further increased.
【０００８】本発明は以上の新規なる知見に基づいてな
されたものであって、その要旨とするところは以下の通
りである。本発明の請求項１〜４の発明は重量比とし
て、Ｃ：０．４５〜０．７０％、Ｓｉ：０．３５〜２．
０％、Ｍｎ：０．９０〜２．０％、Ｓ：０．００１〜
０．０３％、Ａｌ：０．０１０〜０．０７％、Ｎ：０．
００３〜０．０１５％を含有し、さらにまたは、Ｍｏ：
０．０５〜１．２０％を含有し、さらにまたは、Ｃｒ：
０．０３〜０．５０％、Ｎｉ：０．１０〜３．００％、
Ｖ：０．０３〜０．７％、Ｎｂ：０．００５〜０．３
％、Ｂ：０．０００５〜０．００５％の１種または２種
以上を含有し、Ｐ：０．０２５％以下、Ｔｉ：０．００
４０％以下、Ｔ．Ｏ：０．００２０％以下に制限し、残
部が鉄および不可避的不純物からなり、かつ高周波加熱
前のフェライトの組織分率が２５％以下で、フェライト
結晶粒径が２０μｍ以下であることを特徴とする高寿命
高周波焼入れ軸受用鋼材である。The present invention has been made based on the above new findings, and the gist thereof is as follows. The inventions of claims 1 to 4 of the present invention, as a weight ratio, C: 0.45 to 0.70%, Si: 0.35 to 2.
0%, Mn: 0.90 to 2.0%, S: 0.001 to
0.03%, Al: 0.010 to 0.07%, N: 0.
003-0.015%, or Mo:
0.05 to 1.20% and further or Cr:
0.03 to 0.50%, Ni: 0.10 to 3.00%,
V: 0.03-0.7%, Nb: 0.005-0.3
%, B: 0.0005 to 0.005%, 1 or 2 or more, P: 0.025% or less, Ti: 0.00
40% or less, T.I. O: limited to 0.0020% or less, the balance consisting of iron and unavoidable impurities, the structure fraction of ferrite before high-frequency heating is 25% or less, and the ferrite crystal grain size is 20 μm or less. It is a steel material for long-life induction hardening bearings.
【０００９】[0009]
【作用】以下に、本発明を詳細に説明する。本発明の鋼
材の成分含有範囲を上記の如く限定した理由について説
明する。
Ｃ：０．４５〜０．７０％
Ｃは最終製品の軸受部品として必要な転動疲労強度と耐
摩耗性を得るために有効な元素であるが、高周波焼入れ
材の場合、０．４５％未満ではその効果が不十分であ
り、また０．７０％を超えると靱性が劣化しかえって強
度の劣化を招くので、含有量を０．４５〜０．７０％と
した。The present invention will be described in detail below. The reason why the component content range of the steel material of the present invention is limited as described above will be described. C: 0.45 to 0.70% C is an element effective for obtaining rolling fatigue strength and wear resistance required as a bearing component of the final product, but in the case of induction hardened material, less than 0.45% In that case, the effect is insufficient, and if it exceeds 0.70%, the toughness deteriorates and the strength deteriorates, so the content was made 0.45 to 0.70%.
【００１０】Ｓｉ：０．３５〜２．０％
Ｓｉは脱酸元素としておよび転動疲労過程での白色組織
・炭化物組織生成抑制、材質劣化抑制により最終製品の
寿命を増加させることを目的として添加するが、０．３
５％未満ではその効果は不十分であり、一方、２．０％
を超えるとこれらの効果は飽和しむしろ最終製品の靱性
の劣化を招くので、その含有量を０．３５〜２．０％と
した。Si: 0.35-2.0% Si is added as a deoxidizing element and for the purpose of increasing the life of the final product by suppressing the formation of a white structure / carbide structure in the rolling fatigue process and suppressing material deterioration. Yes, but 0.3
If it is less than 5%, its effect is insufficient, while on the other hand, it is 2.0%.
If these values are exceeded, these effects are saturated and rather the toughness of the final product is deteriorated, so the content was made 0.35 to 2.0%.
【００１１】Ｍｎ：０．９０〜２．０％
Ｍｎは転動疲労過程での材質劣化の抑制、焼入れ性
の向上、および鋼中でＭｎＳを形成することによる高
周波焼入れ加熱時のオーステナイト粒の微細化と被削
性の向上を目的として添加する。しかしながら、０．９
０％未満ではこの効果は不十分であり、一方、２．０％
を超えるとこの効果は飽和しむしろ最終製品の靱性の劣
化を招くので、その含有量を０．９０〜２．０％とし
た。[0011] Mn: 0.90 ~2.0% Mn suppression of material deterioration in the rolling fatigue process, the improvement of hardenability and austenite grains fine at the time of induction hardening heat by forming MnS in steel It is added for the purpose of improving the efficiency and machinability. However, 0.9
If it is less than 0 %, this effect is insufficient.
Beyond This effect leads to a deterioration in the toughness of saturated rather the final product was the content thereof from 0.90 to 2.0%.
【００１２】Ｓ：０．００１〜０．０３％
Ｓは鋼中でＭｎＳとして存在し、被削性の向上および組
織の微細化に寄与するが、０．００１％未満ではその効
果は不十分である。一方、０．０３％を超えるとその効
果は飽和し、むしろ転動疲労特性の劣化を招く。以上の
理由から、Ｓの含有量を０．００１〜０．０３％とし
た。S: 0.001 to 0.03% S exists as MnS in steel and contributes to improvement of machinability and refinement of structure, but if less than 0.001%, its effect is insufficient. is there. On the other hand, if it exceeds 0.03%, the effect is saturated, and rather the rolling fatigue characteristics are deteriorated. For the above reason, the content of S is set to 0.001 to 0.03%.
【００１３】Ａｌ：０．０１０〜０．０７％
Ａｌは脱酸元素および結晶粒微細化元素として添加する
が、０．０１０％未満ではその効果は不十分であり、一
方、０．０７％を超えるとその効果は飽和し、むしろ靱
性を劣化させるので、その含有量を０．０１０〜０．０
７％とした。Al: 0.010 to 0.07% Al is added as a deoxidizing element and a grain refinement element, but if it is less than 0.010%, its effect is insufficient, while 0.07% is added. If it exceeds, the effect is saturated and the toughness is rather deteriorated, so the content is set to 0.010 to 0.0.
It was set to 7%.
【００１４】Ｎ：０．００３〜０．０１５％
ＮはＡｌＮの析出挙動を通じて、オーステナイト粒の微
細化に寄与するが、０．００３％未満ではその効果は不
十分であり、一方、０．０１５％超では、その効果は飽
和しむしろ靱性の劣化を招くので、その含有量をＮ：
０．００３〜０．０１５％とした。N: 0.003 to 0.015% N contributes to the refinement of austenite grains through the precipitation behavior of AlN, but if it is less than 0.003%, its effect is insufficient, while 0.015%. If the content exceeds%, the effect is saturated and rather the toughness is deteriorated, so the content is N:
It was set to 0.003 to 0.015%.
【００１５】Ｐ：０．０２５％以下
Ｐは鋼中で粒界偏析や中心偏析を起こし、最終製品の強
度劣化の原因となる。特にＰが０．０２５％を超えると
強度の劣化が顕著となるため、０．０２５％を上限とし
た。P: 0.025% or less P causes grain boundary segregation or center segregation in the steel and causes strength deterioration of the final product. In particular, when P exceeds 0.025%, the deterioration of strength becomes remarkable, so 0.025% was made the upper limit.
【００１６】Ｔｉ：０．００４０％以下
Ｔｉは硬質析出物ＴｉＮを生成し、これが白色組織・炭
化物組織組成、材質劣化の引き金となり、つまり転動疲
労破壊の起点となり、最終製品の転動寿命劣化の原因と
なる。特にＴｉが０．００４０％を超えると寿命の劣化
が顕著となるため、０．００４０％を上限とした。Ti: 0.0040% or less Ti forms a hard precipitate TiN, which triggers a white structure / carbide structure composition and material deterioration, that is, a starting point of rolling fatigue fracture, which deteriorates the rolling life of the final product. Cause of. Especially when Ti exceeds 0.0040%, the deterioration of the life becomes remarkable, so 0.0040% was made the upper limit.
【００１７】Ｔ．Ｏ：０．００２０％以下
本発明においてＴ．Ｏ含有量とは、鋼中の溶存酸素含有
量と酸化物（主にアルミナ）を形成している酸素含有量
の和であるが、Ｔ．Ｏ含有量は酸化物を形成している酸
素含有量にほぼ一致する。従って、Ｔ．Ｏ含有量が高い
ほど酸化物系介在物が多いことになる。酸化物系介在物
は転動疲労過程で、白色組織・炭化物組織生成、材質劣
化の引き金となり、転動疲労寿命劣化の原因となる。特
にＯが０．００２％を超えるとこの現象が顕著になるた
め、０．００２％を上限とした。なお、非金属介在物を
微細化して、より一層高寿命化を図るためには、本出願
人が先に特願平５−２０２４１６にて提案しているＭｇ
の適正量添加が有効である。T. O: 0.0020% or less T.O. The O content is the sum of the dissolved oxygen content in steel and the oxygen content forming oxides (mainly alumina). The O content substantially matches the oxygen content forming the oxide. Therefore, T. The higher the O content, the more oxide inclusions. Oxide inclusions cause white structure / carbide structure formation and material deterioration in the rolling fatigue process, which causes deterioration of rolling fatigue life. Especially when O exceeds 0.002%, this phenomenon becomes remarkable, so 0.002% was made the upper limit. Incidentally, in order to further miniaturize the non-metallic inclusions and achieve a longer life, the present applicant has previously proposed Mg in Japanese Patent Application No. 5-202416.
It is effective to add an appropriate amount of.
【００１８】本発明では、請求項１〜４について、さら
にＴ．Ｍｇ：０．０００５〜０．０３００％を含有し、
鋼中に含有される酸化物が、個数比として次式を満足す
る鋼材としてもよい。
（ＭｇＯ・Ａｌ2 Ｏ3 個数＋ＭｇＯ個数）／全酸化物系
介在物個数≧０．８０In the present invention, according to claims 1 to 4, the method of T. Mg: contains 0.0005 to 0.0300%,
The oxide contained in the steel may be a steel material that satisfies the following formula in terms of the number ratio. (MgO · Al 2 O 3 number + MgO number) / Number of all oxide inclusions ≧ 0.80
【００１９】次に、本発明では、「高周波加熱前のフェ
ライトの組織分率が２５％以下で、フェライト結晶粒径
が２０μｍ以下」とする。高周波焼入れは急速加熱であ
るため、高周波加熱前の組織のフェライト分率が大きく
またそれが粗大であると、フェライトの部分は、オース
テナイト化後、炭素の拡散が不十分で炭素濃度が添加炭
素濃度よりも低くなり、焼入れ後、その位置での硬さが
小さくなる。そのため、この位置で局所的な材質劣化を
起こし、転動疲労き裂の発生起点となりやすい。以上の
現象は、フェライトの組織分率が２５％を超えるか、ま
たはフェライト結晶粒径が２０μｍを超えると特に顕著
になる。以上の理由でフェライトの組織分率を２５％以
下で、フェライト結晶粒径を２０μｍ以下とした。Next, according to the present invention, "the structure fraction of ferrite before high frequency heating is 25% or less and the ferrite crystal grain size is 20 μm or less". Since induction hardening is rapid heating, if the ferrite fraction of the structure before induction heating is large and it is coarse, the ferrite part will not have sufficient carbon diffusion after austenitization and the carbon concentration will be The hardness at that position becomes smaller after quenching. Therefore, local deterioration of the material occurs at this position, which easily becomes the starting point of rolling fatigue crack initiation. The above phenomenon becomes particularly remarkable when the structure fraction of ferrite exceeds 25% or the ferrite crystal grain size exceeds 20 μm. For the above reason, the structure fraction of ferrite is 25% or less, and the ferrite crystal grain size is 20 μm or less.
【００２０】なお、より高寿命化を図るためには、フェ
ライトの組織分率を１５％以下とするか、またはさらに
フェライト結晶粒径を１５μｍ以下とするのが望まし
い。また、本発明の高周波焼入れ軸受用鋼材では、フェ
ライト以外の残りの組織を特に限定するものではなく、
その種類がパーライト、上部ベイナイト、下部ベイナイ
ト、中間段階組織、マルテンサイト、あるいはこれらの
混合組織のいずれでもよい。In order to achieve a longer life, it is desirable that the structure fraction of ferrite be 15% or less, or that the ferrite crystal grain size be 15 μm or less. Further, in the steel material for induction hardened bearings of the present invention, the remaining structure other than ferrite is not particularly limited,
The type thereof may be pearlite, upper bainite, lower bainite, intermediate stage structure, martensite, or a mixed structure thereof.
【００２１】次に、請求項２の発明の鋼材では、転動疲
労過程での硬さ低下防止、白色組織・炭化物組織生成抑
制を目的としてＭｏを含有させることができる。
Ｍｏ：０．０５〜１．２０％
Ｍｏは高周波焼入れ性の向上および転動疲労過程での白
色組織・炭化物組織生成抑制、材質劣化抑制による最終
製品の寿命を増加させることを目的として添加するが、
Ｍｏ：０．０５％未満ではこの効果は不十分であり、一
方、Ｍｏ：１．２％を超えるとこの効果は飽和しむしろ
最終製品の靱性の劣化を招くので、その含有量をＭｏ：
０．０５〜１．２０％とした。Next, in the steel material according to the second aspect of the present invention, Mo can be contained for the purpose of preventing hardness reduction during rolling fatigue process and suppressing white structure / carbide structure formation. Mo: 0.05 to 1.20% Mo is added for the purpose of improving induction hardenability, suppressing white structure / carbide structure generation during rolling fatigue process, and increasing the life of the final product by suppressing material deterioration. ,
If the Mo content is less than 0.05%, this effect is insufficient. On the other hand, if the Mo content exceeds 1.2%, this effect is saturated and rather the toughness of the final product is deteriorated.
It was set to 0.05 to 1.20%.
【００２２】次に、請求項３，４の発明の鋼材では、高
周波焼入れ性の向上および転動疲労過程での材質劣化抑
制、白色組織・炭化物組織生成抑制を目的としてＣｒ，
Ｎｉ，Ｖ，Ｎｂ，Ｂの１種または２種以上を含有させる
ことができる。
Ｃｒ：０．０３〜０．５０％
Ｎｉ：０．１０〜３．００％
Ｖ ：０．０３〜０．７％
Ｎｂ：０．００５〜０．３％
Ｂ ：０．０００５〜０．００５％Next, in the steel materials of the third and fourth aspects of the invention, in order to improve the induction hardenability, suppress the deterioration of the material in the rolling fatigue process, and suppress the formation of white structure / carbide structure,
One kind or two kinds or more of Ni, V, Nb and B can be contained. Cr: 0.03 to 0.50% Ni: 0.10 to 3.00% V: 0.03 to 0.7% Nb: 0.005 to 0.3% B: 0.0005 to 0.005%
【００２３】これらの元素はいずれも焼入れ性を向上
し、転動過程での転位密度の低下を抑制することによ
り、または繰り返し過程でセメンタイトの生成を抑制す
ることにより、繰り返し軟化防止に有効である。この効
果はＣｒ：０．０３％未満、Ｎｉ：０．１０％未満、
Ｖ：０．０３％未満、Ｎｂ：０．００５％未満、Ｂ：
０．０００５％未満では不十分であり、一方、Ｃｒ：
０．５０％、Ｎｉ：３．００％、Ｖ：０．７％、Ｎｂ：
０．３％、Ｂ：０．００５％を超えるとこの効果は飽和
し、むしろ高周波焼入れ時の炭化物の溶解不良、最終製
品の靱性の劣化等の弊害を招くので、その含有量を上記
の範囲に限定した。All of these elements are effective in preventing repeated softening by improving the hardenability and suppressing the decrease of dislocation density in the rolling process or suppressing the formation of cementite in the repeating process. . This effect is Cr: less than 0.03%, Ni: less than 0.10%,
V: less than 0.03%, Nb: less than 0.005%, B:
If it is less than 0.0005%, it is insufficient, while Cr:
0.50%, Ni: 3.00%, V: 0.7%, Nb:
When 0.3% and B: 0.005% are exceeded, this effect is saturated, and rather causes adverse effects such as poor dissolution of carbide during induction hardening and deterioration of toughness of the final product. Limited to.
【００２４】ここで、本発明の高周波焼入れ軸受用鋼材
において、「高周波加熱前のフェライトの組織分率が２
５％以下で、フェライト結晶粒径が２０μｍ以下」とす
るには、本発明規定の化学成分範囲において、熱間圧延
における仕上げ圧延温度を通常より低くし、仕上げ圧延
後の冷却速度を通常より速くする必要がある。具体的に
は鋼の化学成分組成、熱間圧延鋼材寸法によって異なる
が、例えば、鋼材素材の熱間圧延による製造を仕上げ温
度：７５０〜９００℃、仕上げ圧延後７００〜５００℃
の温度範囲の平均冷却速度：０．１〜１．７℃／秒の条
件とするのが好ましい。また、本発明では、本発明の要
件を満足すれば、熱間圧延後、高周波焼入れの前に焼
準、焼鈍、熱間鍛造等の加工熱処理を必要に応じて行う
ことができる。また、本発明では高周波焼入れ工程によ
り製造される軸受け部品用の鋼材を対象としているが、
高周波焼入れ条件、焼戻しの有無、焼戻しを行う場合は
その条件は、特に限定するものではない。Here, the steel material for induction hardened bearings of the present invention
"In the case where the ferrite fraction before high frequency heating is 2
5% or less and ferrite crystal grain size is 20 μm or less ”
Hot rolling within the chemical composition range specified in the present invention.
The finish rolling temperature in the
The subsequent cooling rate needs to be faster than usual. Specifically
Depends on the chemical composition of the steel and the dimensions of the hot rolled steel
However, for example, in the manufacturing of steel material by hot rolling, finishing temperature: 750 to 900 ° C., after finishing rolling 700 to 500 ° C.
Average cooling rate in the temperature range of 0.1 to 1.7 ° C./sec is preferable. Further, in the present invention, if the requirements of the present invention are satisfied, it is possible to perform thermomechanical processing such as normalizing, annealing, hot forging, etc. after hot rolling and before induction hardening, if necessary. Further, in the present invention, the steel material for bearing parts manufactured by the induction hardening process is targeted,
Induction hardening conditions, presence or absence of tempering, and conditions for tempering are not particularly limited.
【００２５】[0025]
【実施例】以下に、本発明の効果を実施例により、さら
に具体的に示す。表１，２の組成を有する鋼材を直径６
５ｍｍφの棒鋼に圧延した。その後熱間鍛造のシミュレ
ーションとして９５０℃加熱−放冷した。この棒鋼か
ら、光学顕微鏡観察試験片を採取し、５％ナイタール液
で腐食して２００倍、４００倍で観察しフェライト分率
およびフェライト結晶粒径を求めた。表１，２にフェラ
イト分率、フェライト結晶粒径を併せて示す。EXAMPLES The effects of the present invention will be more specifically described below with reference to examples. A steel material having the composition shown in Tables 1 and 2 has a diameter of 6
It was rolled into a 5 mmφ steel bar. Then, as a simulation of hot forging, 950 ° C. was heated and allowed to cool. An optical microscope observation test piece was taken from this steel bar, corroded with a 5% nital solution and observed at 200 times and 400 times to determine the ferrite fraction and the ferrite crystal grain size. Tables 1 and 2 also show the ferrite fraction and the ferrite crystal grain size.
【００２６】[0026]
【表１】 [Table 1]
【００２７】[0027]
【表２】 [Table 2]
【００２８】これらの材料から、転動疲労試験片を採取
・作成し、周波数１００ｋＨｚ、硬化層深さ２〜３ｍｍ
の条件で高周波焼入れを行い、１６０℃で焼戻し処理を
行った。転動疲労寿命の評価は、円筒型転動疲労試験片
による点接触型転動疲労試験機（ヘルツ最大接触応力６
００ｋｇｆ／ｍｍ2 ）を用いた。疲労寿命の尺度とし
て、通常、「試験結果をワイブル確率紙にプロットして
得られる累積破損確率１０％における疲労破壊までの応
力繰り返し数」がＬ10寿命として用いられる。Rolling fatigue test pieces were sampled and prepared from these materials, and the frequency was 100 kHz and the hardened layer depth was 2 to 3 mm.
Induction hardening was performed under the conditions of and tempering treatment was performed at 160 ° C. The evaluation of rolling contact fatigue life is performed by a point contact type rolling contact fatigue tester (Hertz maximum contact stress 6
00 kgf / mm 2 ) was used. As a measure of the fatigue life, usually, "the number of repeated stresses of the test results to fatigue failure in a cumulative failure probability of 10% obtained by plotting the Weibull probability paper" is used as the L 10 life.
【００２９】表３，４に比較鋼材２５のＬ10寿命を１と
した時の各鋼材のＬ10寿命の相対値を示した。また、１
０8 回転動疲労後の試験片について、白色帯組織および
炭化物組織の有無を調べ、その結果を表３，４に併せて
示した。さらに、転動疲労過程での材質劣化挙動を評価
するために、１０8 回転動疲労後の試験片の転動面から
深さ０．２ｍｍの位置で、フェライト（２１１）面のＸ
線回折ピークの半価幅の減少量を評価した。Ｘ線発生源
としては、Ｃｒ管球を使用した。また、同位置での転動
疲労試験に伴う硬さの低下量も評価した。Tables 3 and 4 show the relative values of the L 10 lives of the respective steel materials when the L 10 life of the comparative steel material 25 is 1. Also, 1
0 for 8 rotational movement fatigue test piece after, check for white zone tissue and the carbide structure was shown together results in Tables 3 and 4. Further, in order to evaluate the material deterioration behavior in the rolling fatigue process, the X-axis of the ferrite (211) surface was located at a depth of 0.2 mm from the rolling surface of the test piece after 10 8 rotation fatigue.
The reduction amount of the half width of the line diffraction peak was evaluated. A Cr tube was used as the X-ray source. Further, the amount of decrease in hardness due to the rolling fatigue test at the same position was also evaluated.
【００３０】[0030]
【表３】 [Table 3]
【００３１】[0031]
【表４】 [Table 4]
【００３２】表３，４に示した通り、本発明鋼材ではい
ずれも白色帯組織・炭化物組織の生成が抑制され、また
転動疲労過程での半価幅の減少量、硬さの低下量も小さ
い。これにより、本発明鋼材は、従来鋼材の比較鋼材２
５に比べて約２〜６倍と極めて良好な疲労特性が得られ
た。As shown in Tables 3 and 4, in each of the steel materials of the present invention, the formation of white band structure / carbide structure was suppressed, and the reduction amount of full width at half maximum and the reduction amount of hardness in the rolling fatigue process were also reduced. small. As a result, the steel material of the present invention is the comparative steel material 2 of the conventional steel material.
Compared with No. 5, about 2 to 6 times, very good fatigue characteristics were obtained.
【００３３】一方、比較鋼材２６はＣの含有量が本発明
の範囲を下回った場合であり、比較鋼材２７はＳｉの含
有量が本発明の範囲を下回った場合であり、また比較鋼
材２８〜３２は高周波加熱前のフェライト分率またはフ
ェライト結晶粒径のいずれかまたは両者が本発明の範囲
を上回った場合であり、いずれも転動疲労特性は、比較
鋼材２５に比べて１．６倍以下であり、本発明鋼に比較
して転動疲労特性は顕著に劣っている。比較鋼材の「転
動疲労後の半価幅の減少量」、「転動疲労後の硬さ低下
量」は、本発明鋼材に比較して、相対的に大きい。つま
り、本発明鋼材では、転動疲労過程での材質劣化が抑制
されたことにより、優れた転動疲労寿命が得られている
ことが明らかである。On the other hand, the comparative steel material 26 is the case where the C content is below the range of the present invention, the comparative steel material 27 is the case where the Si content is below the range of the present invention, and the comparative steel materials 28 to No. 32 is a case where either or both of the ferrite fraction before the high frequency heating and the ferrite crystal grain size exceeds the range of the present invention, and the rolling fatigue characteristics are 1.6 times or less than those of the comparative steel material 25 in all cases. And the rolling fatigue properties are significantly inferior to those of the steel of the present invention. The “amount of decrease in half-width after rolling fatigue” and “amount of decrease in hardness after rolling fatigue” of the comparative steel materials are relatively large as compared with the steel materials of the present invention. In other words, it is clear that the steel material of the present invention has an excellent rolling fatigue life because the material deterioration in the rolling fatigue process is suppressed.
【００３４】[0034]
【発明の効果】以上述べたごとく、本発明の高周波焼入
れ軸受用鋼材を用いることにより、軸受部品の転動疲労
過程での白色組織・炭化物組織生成の抑制、材質劣化の
防止が実現でき、軸受部品が低コストで製造可能であ
り、かつ軸受部品として高負荷下での転動疲労寿命が飛
躍的に向上し得る軸受用鋼材の提供が可能となり、産業
上の効果は極めて顕著なるものがある。As described above, by using the steel material for induction hardened bearings of the present invention, it is possible to suppress the formation of a white structure / carbide structure in the rolling fatigue process of bearing parts and prevent the deterioration of the material. It becomes possible to provide bearing steel materials that can be manufactured at low cost and whose rolling contact fatigue life under high load can be dramatically improved as bearing parts, and the industrial effect is extremely remarkable. .
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭60−169544（ＪＰ，Ａ) 特開 平４−254547（ＪＰ，Ａ) 特開 平７−118732（ＪＰ，Ａ) 特開 昭63−100157（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) C22C 38/00 - 38/60 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-60-169544 (JP, A) JP-A-4-254547 (JP, A) JP-A-7-118732 (JP, A) JP-A-63- 100157 (JP, A) (58) Fields surveyed (Int.Cl. 7 , DB name) C22C 38/00-38/60
Claims (4)
Ｔ．Ｏ：０．００２０％以下に制限し、残部が鉄および
不可避的不純物からなり、かつ高周波加熱前のフェライ
トの組織分率が２５％以下で、フェライト結晶粒径が２
０μｍ以下であることを特徴とする高寿命高周波焼入れ
軸受用鋼材。1. As a weight ratio, C: 0.45 to 0.70% Si: 0.35 to 2.0% Mn: 0.90 to 2.0% S: 0.001 to 0.03% Al : 0.010-0.07% N: 0.003-0.015% is contained, P: 0.025% or less, Ti: 0.0040% or less,
T. O: limited to 0.0020% or less, the balance consisting of iron and unavoidable impurities, the structure fraction of ferrite before high frequency heating is 25% or less, and the ferrite crystal grain size is 2
A long-life induction hardened bearing steel material having a diameter of 0 μm or less.
Ｔ．Ｏ：０．００２０％以下に制限し、残部が鉄および
不可避的不純物からなり、かつ高周波加熱前のフェライ
トの組織分率が２５％以下で、フェライト結晶粒径が２
０μｍ以下であることを特徴とする高寿命高周波焼入れ
軸受用鋼材。2. As a weight ratio, C: 0.45 to 0.70% Si: 0.35 to 2.0% Mn: 0.90 to 2.0% Mo: 0.05 to 1.20% S : 0.001 to 0.03% Al: 0.010 to 0.07% N: 0.003 to 0.015% P: 0.025% or less, Ti: 0.0040% or less,
T. O: limited to 0.0020% or less, the balance consisting of iron and unavoidable impurities, the structure fraction of ferrite before high frequency heating is 25% or less, and the ferrite crystal grain size is 2
A long-life induction hardened bearing steel material having a diameter of 0 μm or less.
Ｔ．Ｏ：０．００２０％以下に制限し、残部が鉄および
不可避的不純物からなり、かつ高周波加熱前のフェライ
トの組織分率が２５％以下で、フェライト結晶粒径が２
０μｍ以下であることを特徴とする高寿命高周波焼入れ
軸受用鋼材。3. As a weight ratio, C: 0.45 to 0.70% Si: 0.35 to 2.0% Mn: 0.90 to 2.0% S: 0.001 to 0.03% Al : 0.010 to 0.07% N: 0.003 to 0.015%, and further Cr: 0.03 to 0.50% Ni: 0.10 to 3.00% V: 0.03. -0.7% Nb: 0.005-0.3% B: 0.0005-0.005% containing 1 type or 2 types or more, P: 0.025% or less, Ti: 0.0040% Less than,
T. O: limited to 0.0020% or less, the balance consisting of iron and unavoidable impurities, the structure fraction of ferrite before high frequency heating is 25% or less, and the ferrite crystal grain size is 2
A long-life induction hardened bearing steel material having a diameter of 0 μm or less.
Ｔ．Ｏ：０．００２０％以下に制限し、残部が鉄および
不可避的不純物からなり、かつ高周波加熱前のフェライ
トの組織分率が２５％以下で、フェライト結晶粒径が２
０μｍ以下であることを特徴とする高寿命高周波焼入れ
軸受用鋼材。4. As a weight ratio, C: 0.45 to 0.70% Si: 0.35 to 2.0% Mn: 0.90 to 2.0% Mo: 0.05 to 1.20% S : 0.001 to 0.03% Al: 0.010 to 0.07% N: 0.003 to 0.015% Further, Cr: 0.03 to 0.50% Ni: 0.10. .About.3.00% V: 0.03 to 0.7% Nb: 0.005 to 0.3% B: 0.0005 to 0.005% One or more types are contained, and P: 0. 025% or less, Ti: 0.0040% or less,
T. O: limited to 0.0020% or less, the balance consisting of iron and unavoidable impurities, the structure fraction of ferrite before high frequency heating is 25% or less, and the ferrite crystal grain size is 2
A long-life induction hardened bearing steel material having a diameter of 0 μm or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14245495A JP3466328B2 (en) | 1995-05-18 | 1995-05-18 | Long life steel for induction hardened bearings |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14245495A JP3466328B2 (en) | 1995-05-18 | 1995-05-18 | Long life steel for induction hardened bearings |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08311615A JPH08311615A (en) | 1996-11-26 |
| JP3466328B2 true JP3466328B2 (en) | 2003-11-10 |
Family
ID=15315696
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP14245495A Expired - Fee Related JP3466328B2 (en) | 1995-05-18 | 1995-05-18 | Long life steel for induction hardened bearings |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3466328B2 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1113973C (en) | 1999-01-28 | 2003-07-09 | 住友金属工业株式会社 | Machine structural steel product |
| JP2002115030A (en) * | 2000-10-06 | 2002-04-19 | Ntn Corp | Rolling bearing for spindle of machine tool |
| JP3815354B2 (en) * | 2002-03-25 | 2006-08-30 | Ｊｆｅスチール株式会社 | Bearing member with excellent rolling fatigue characteristics and workability in high-frequency heat-treated parts |
| EP1961831A1 (en) | 2003-01-17 | 2008-08-27 | JFE Steel Corporation | High-strength steel product excelling in fatigue strength and process for producing the same |
| JP4507731B2 (en) * | 2003-09-29 | 2010-07-21 | Ｊｆｅスチール株式会社 | Steel materials and steel products excellent in machinability and fatigue characteristics and methods for producing them |
| JP3974115B2 (en) | 2004-03-10 | 2007-09-12 | Ｎｔｎ株式会社 | Wheel bearing device |
| WO2012073488A1 (en) * | 2010-11-29 | 2012-06-07 | Ｊｆｅスチール株式会社 | Bearing steel exhibiting excellent machinability after spheroidizing annealing and excellent resistance to hydrogen fatigue after quenching/tempering |
-
1995
- 1995-05-18 JP JP14245495A patent/JP3466328B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH08311615A (en) | 1996-11-26 |
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