JPH07138696A - Steel parts excellent in fatigue strength - Google Patents

Steel parts excellent in fatigue strength

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Publication number
JPH07138696A
JPH07138696A JP28272693A JP28272693A JPH07138696A JP H07138696 A JPH07138696 A JP H07138696A JP 28272693 A JP28272693 A JP 28272693A JP 28272693 A JP28272693 A JP 28272693A JP H07138696 A JPH07138696 A JP H07138696A
Authority
JP
Japan
Prior art keywords
less
steel
austenite
nitriding
amount
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
JP28272693A
Other languages
Japanese (ja)
Inventor
Nobuhiro Murai
暢宏 村井
Original Assignee
Sumitomo Metal Ind Ltd
住友金属工業株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sumitomo Metal Ind Ltd, 住友金属工業株式会社 filed Critical Sumitomo Metal Ind Ltd
Priority to JP28272693A priority Critical patent/JPH07138696A/en
Publication of JPH07138696A publication Critical patent/JPH07138696A/en
Withdrawn legal-status Critical Current

Links

Abstract

PURPOSE:To remarkably improve the rolling fatigue life of parts for machine structural use, such as gear, joint, and bearing, requiring weight reduction. CONSTITUTION:The parts have a base material composition consisting of, by weight ratio, 0.05-0.40% C, <=2.0% Si, 0.30-2.0% Mn, <=0.05% P, <=0.05% S, <=2.0% Cr, 0.01-0.10% sol.Al, 0.0030-0.020% N, 0-0.2% Ni, 0-1.0% Mo, 0-0.50% V, 0-. 10% Nb, and the balance Fe with inevitable impurities. Further, C and N in the surface part are incorporated by the amounts satisfying, by weight ratio, 0.05%<=C<=1.0% and 0.8%<N<=-1.325C(%)+2.5%. Moreover, the structure is composed essentially of martensite and austenite. By this method, the steel parts excellent in fatigue strength can be obtained.

Description

【発明の詳細な説明】Detailed Description of the Invention

【0001】[0001]

【産業上の利用分野】本発明は、疲労強度、特に転動疲
労寿命で表示される疲労強度に優れた鋼部品に関する。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel part having excellent fatigue strength, particularly fatigue strength indicated by rolling fatigue life.

【0002】[0002]

【従来の技術】一般に、軸受や継手、歯車等、高い面圧
が繰り返し負荷される機械構造用部品のなかで、その多
くは転動疲労寿命により部品全体の寿命が支配されてい
る。近年の自動車等の燃費規制が厳しくなり、これらの
部品にも軽量化が模索されているが、小型化により負荷
が厳しくなるため、材質面での寿命改善が特に強く望ま
れている。
2. Description of the Related Art Generally, among mechanical structural parts such as bearings, joints, and gears, which are repeatedly subjected to high surface pressure, the life of the entire parts is governed by the rolling contact fatigue life. In recent years, regulations on fuel consumption of automobiles have become stricter, and weight reduction is being sought for these parts as well. However, since the load becomes stricter due to miniaturization, it is strongly desired to improve the service life in terms of materials.

【0003】一般に、転動疲労寿命は鋼の表面硬度が高
いほど向上することが知られており、上記のような部品
には浸炭鋼や軸受鋼が使用されている。しかし、これら
の鋼では最近の寿命向上のニーズに対し充分に対応でき
ない。
It is generally known that the rolling fatigue life increases as the surface hardness of steel increases, and carburized steel and bearing steel are used for the above parts. However, these steels cannot sufficiently meet the recent needs for life improvement.

【0004】従来の浸炭処理に窒化処理を組合せた浸炭
窒化処理は、疲労強度、つまり転動疲労寿命の向上に有
効である。この処理は従来の浸炭処理でのガス雰囲気中
にアンモニアを添加するものであるが、鋼の表面部にC
に加えNを濃縮させることにより転動疲労寿命が向上す
ることが知られている。
Carbonitriding, which is a combination of conventional carburizing and nitriding, is effective for improving fatigue strength, that is, rolling fatigue life. This treatment is to add ammonia to the gas atmosphere in the conventional carburizing treatment.
It is known that the rolling fatigue life is improved by concentrating N in addition to the above.

【0005】しかしながら、浸炭窒化処理ではNの浸透
量に限界がある。浸炭窒化処理は、850 ℃程度に加熱す
ることで鋼のオーステナイト領域で実施するが、この領
域で行う限りNの表面濃度が 0.8%に到達すると処理中
にボイドが発生し、機械的性質を劣化させる。したがっ
て、浸炭窒化で得られる表面部のN量は通常0.2 %程度
であり、最大でも 0.8%である。
However, there is a limit to the amount of N permeated in carbonitriding. Carbonitriding is performed in the austenite region of steel by heating it to approximately 850 ° C. As long as it is performed in this region, when the surface concentration of N reaches 0.8%, voids are generated during the treatment and mechanical properties deteriorate. Let Therefore, the N content in the surface portion obtained by carbonitriding is usually about 0.2%, and 0.8% at the maximum.

【0006】一方、高濃度のNを得るための処理として
窒化処理がある。窒化処理は 550℃程度に加熱すること
で鋼のフェライト領域で実施し、浸炭窒化と同様にして
処理するが、処理雰囲気としてはアンモニア雰囲気を用
いる。この場合、表面部には窒素化合物 (Fe4N, Fe
2-3N) が生成し、表面の窒素濃度は数%に達する。
On the other hand, there is a nitriding treatment as a treatment for obtaining a high concentration of N. The nitriding treatment is performed in the ferrite region of the steel by heating it to about 550 ° C, and the treatment is performed in the same manner as carbonitriding, but an ammonia atmosphere is used as the treatment atmosphere. In this case, nitrogen compounds (Fe 4 N, Fe
2-3 N) is produced and the surface nitrogen concentration reaches several%.

【0007】しかし、このような窒化処理によって得た
窒化鋼は窒素化合物の生成により表面硬度は非常に高く
なるが、そのとき得られる窒素化合物が脆いため転動疲
労寿命は向上しない。
However, the nitrided steel obtained by such a nitriding treatment has a very high surface hardness due to the formation of a nitrogen compound, but the nitrogen compound obtained at that time is brittle, so that the rolling fatigue life is not improved.

【0008】また、このような窒化処理の場合、浸炭窒
化に比べ高い窒素濃度が得られるので、転動疲労寿命を
改善すべく窒化鋼を再加熱焼入れする方法もある。しか
しながら、この窒化焼入れによっても表面部には焼入れ
後、依然として化合物層が粗大に残留し、転動疲労寿命
は大幅には向上しない。
Further, in the case of such nitriding treatment, a higher nitrogen concentration can be obtained as compared with carbonitriding, so there is also a method of reheating and quenching nitrided steel in order to improve rolling fatigue life. However, even with this nitriding quenching, the compound layer still remains coarse after quenching on the surface portion, and the rolling fatigue life is not significantly improved.

【0009】[0009]

【発明が解決しようとする課題】本発明の第一の目的
は、従来の浸炭窒化の問題点である表面部のボイド生成
を防止し、かつ窒化焼入れの問題点である粗大窒素化合
物の生成を低減し、転動疲労寿命を従来になく向上させ
得る技術を開発することである。本発明の具体的な目的
は、軽量化をはかる機械構造部品の疲労強度、特に転動
疲労寿命を大幅に改善できる材料を提供することであ
る。
SUMMARY OF THE INVENTION The first object of the present invention is to prevent the formation of voids on the surface, which is a problem of conventional carbonitriding, and to prevent the formation of coarse nitrogen compounds, which is a problem of nitriding and quenching. To develop a technology that can reduce the rolling fatigue life and improve rolling fatigue life like never before. It is a specific object of the present invention to provide a material that can significantly improve the fatigue strength of a mechanical structural component that is lightweight, especially the rolling fatigue life.

【0010】[0010]

【課題を解決するための手段】そこで、本発明者らは、
かかる目的を達成すべく、従来の問題点を整理、検討し
た結果、次のような点に着目した。 従来の浸炭窒化では表面部の窒素量は 0.8%が限界で
ある。それ以上に窒素量を増大させるために雰囲気のN
ポテンシャルを増大しても、ボイドが発生し、窒素量は
増加しない。
Therefore, the present inventors have
In order to achieve this purpose, as a result of sorting out and examining the conventional problems, the following points have been noted. With conventional carbonitriding, the amount of nitrogen on the surface is limited to 0.8%. N in the atmosphere to increase the nitrogen content more than that
Even if the potential is increased, voids are generated and the amount of nitrogen does not increase.

【0011】一方、鉄−窒素の平衡状態図からは、鉄
のオーステナイト領域ではNは最大2〜3%固溶し、N
量が固溶限を越えるとFe2-3Nが生成することが一般的に
知られている。 したがって、理論的にはオーステナイト領域でも 0.8
%以上の窒素量を固溶させることは可能である。
On the other hand, from the iron-nitrogen equilibrium diagram, in the austenite region of iron, N is dissolved at a maximum of 2 to 3%.
It is generally known that Fe 2-3 N is produced when the amount exceeds the solid solubility limit. Therefore, theoretically, even in the austenite region, 0.8
It is possible to form a solid solution with a nitrogen content of not less than%.

【0012】このような着想をもとに詳細な調査、研究
を実施した結果、次のような事実を見い出し、本発明を
完成した。 (1) フェライト領域で窒化処理し、再加熱焼入すること
によって、表面部には浸炭窒化で限界とされる窒素量す
なわち、0.8 %を越える窒素を固溶させることが出来
る。しかし、通常の窒化処理ではオ−ステナイト領域で
のNの固溶限以上の表面窒素量となるため、再加熱焼入
しても粗大な窒化物が混在する。この窒化物は加熱温度
を上昇させてもほとんど消失することがない。
As a result of conducting a detailed investigation and research based on such an idea, the following facts were found and the present invention was completed. (1) By nitriding in the ferrite region and reheating and quenching, nitrogen that is the limit of carbonitriding, that is, more than 0.8%, can be solid-dissolved on the surface. However, since the amount of surface nitrogen in the austenite region is more than the solid solution limit of N in the normal nitriding treatment, coarse nitrides are mixed even if reheat-quenched. This nitride hardly disappears even if the heating temperature is raised.

【0013】(2) しかし、フェライト領域での窒化処理
の際、表面部のN量をある範囲に制御すれば、再加熱に
より窒化物を容易に固溶させうる。この範囲はN≦−1.
325C(%) +2.5 %であり、再加熱時のNの固溶限は固溶
C量の増加とともに低下するが、従来の浸炭窒化の場合
よりもはるかに高いN量を得ることができる。また、こ
のときのC、N量の範囲内で浸炭も併せて行うことがで
きる。 (3) このような高窒素含有量で残留窒化物が存在しない
状態から焼入れしたものは転動疲労寿命が著しく向上す
る。
(2) However, in the nitriding treatment in the ferrite region, if the N content in the surface portion is controlled within a certain range, the nitride can be easily dissolved by reheating. This range is N ≦ −1.
325C (%) + 2.5%, the solid solution limit of N at the time of reheating decreases with an increase in the amount of solid solution C, but a much higher N content than in the case of conventional carbonitriding can be obtained. . In addition, carburizing can also be performed within the range of C and N amounts at this time. (3) Rolling fatigue life is significantly improved when the steel is quenched from such a high nitrogen content that there is no residual nitride.

【0014】ここに、本発明は、最も広義には、母材の
成分が重量比で、 C: 0.05 〜0.40%、 Si: 2.0 %以下、 Mn: 0.30 〜 2.0%、 P: 0.05%以下、 S: 0.05%以下、 Cr: 2.0 %以下、 sol.Al: 0.01〜0.10%、 N: 0.0030〜0.020 %、 Ni: 0 〜2.0 %、 Mo: 0 〜1.0 %、 V: 0 〜0.50%、 Nb: 0 〜0.10%、 残部Feおよび不可避的不純物 から成り、表面部がC、Nを重量比で 0.05%≦C≦1.0 %、かつ、0.8 %<N≦−1.325C(%)
+2.5 % を満足する量だけ含有する、マルテンサイトとオーステ
ナイトを主体とする組織から構成されることを特徴とす
る疲労強度に優れた鋼部品である。
In the broadest sense of the present invention, the components of the base material are, by weight ratio, C: 0.05 to 0.40%, Si: 2.0% or less, Mn: 0.30 to 2.0%, P: 0.05% or less, S: 0.05% or less, Cr: 2.0% or less, sol.Al: 0.01 to 0.10%, N: 0.0030 to 0.020%, Ni: 0 to 2.0%, Mo: 0 to 1.0%, V: 0 to 0.50%, Nb : 0 to 0.10%, balance Fe and unavoidable impurities, and the surface portion contains C and N in a weight ratio of 0.05% ≤ C ≤ 1.0% and 0.8% <N ≤ -1.325C (%).
It is a steel part with excellent fatigue strength characterized by being composed of a structure mainly containing martensite and austenite, which is contained in an amount that satisfies + 2.5%.

【0015】ここに、本発明の好適態様によれば、本発
明は、母材の成分が重量比で、 C: 0.05〜0.40%、 Si:2.0 %以下、Mn: 0.30〜2.0
%、P: 0.05%以下、 S: 0.05%以下、 Cr:2.0 %以下、sol.Al: 0.01〜0.
10%、 N: 0.0030〜0.020 % を含み、表面部がC、Nを重量比で 0.05%≦C≦1.0 %、かつ、0.8 %<N≦−1.325C(%)
+2.5 % を満足する量だけ含有する、マルテンサイトとオーステ
ナイトを主体とする組織から構成されることを特徴とす
る疲労強度に優れた鋼部品である。
Here, according to a preferred embodiment of the present invention, in the present invention, the weight ratio of the components of the base material is C: 0.05 to 0.40%, Si: 2.0% or less, Mn: 0.30 to 2.0.
%, P: 0.05% or less, S: 0.05% or less, Cr: 2.0% or less, sol.Al: 0.01 to 0.
10%, N: 0.0030 to 0.020%, the surface portion contains C and N in a weight ratio of 0.05% ≤ C ≤ 1.0%, and 0.8% <N ≤ -1.325C (%).
It is a steel part with excellent fatigue strength characterized by being composed of a structure mainly containing martensite and austenite, which is contained in an amount that satisfies + 2.5%.

【0016】さらに、本発明の好適態様によれば、本発
明は、母材の成分が重量比で、 C: 0.05〜0.40%、 Si: 2.0%以下、Mn: 0.30〜2.0
%、P: 0.05%以下、 S: 0.05%以下、 Cr: 2.0%以下、sol.Al: 0.01〜0.
10%、 N: 0.0030〜0.020 % さらに、 Ni: 2.0 %以下、 Mo: 1.0 %以下のうち一種または二
種 を含み、表面部がC、Nを重量比で 0.05%≦C≦1.0 %、かつ、0.8 %<N≦−1.325C(%)
+2.5 % を満足する量だけ含有する、マルテンサイトとオーステ
ナイトを主体とする組織から構成されることを特徴とす
る疲労強度に優れた鋼部品である。
Further, according to a preferred embodiment of the present invention, in the present invention, the weight ratio of the components of the base material is C: 0.05 to 0.40%, Si: 2.0% or less, Mn: 0.30 to 2.0.
%, P: 0.05% or less, S: 0.05% or less, Cr: 2.0% or less, sol.Al: 0.01 to 0.
10%, N: 0.0030 to 0.020%, Ni: 2.0% or less, Mo: 1.0% or less, including one or two kinds, and the surface portion contains C and N in a weight ratio of 0.05% ≤ C ≤ 1.0%, and , 0.8% <N ≤ -1.325C (%)
It is a steel part with excellent fatigue strength characterized by being composed of a structure mainly containing martensite and austenite, which is contained in an amount that satisfies + 2.5%.

【0017】さらに別の好適態様によれば、本発明は、
母材の成分が重量比で、 C: 0.05〜0.40%、 Si:2.0 %以下、Mn: 0.30〜2.0
%、P: 0.05%以下、 S: 0.05%以下、 Cr:2.0 %以下、sol.Al: 0.01〜0.
10%、 N: 0.0030〜0.020 % さらに、 V:0.01 〜0.50%、Nb: 0.01〜0.10%のうち一種または
二種 を含み、表面部がC、Nを重量比で 0.05%≦C≦1.0 %、かつ、0.8 %<N≦−1.325C(%)
+2.5 % を満足する量だけ含有する、マルテンサイトとオーステ
ナイトを主体とする組織から構成されることを特徴とす
る疲労強度に優れた鋼部品である。
According to another preferred embodiment, the present invention provides
The weight ratio of the base material components is C: 0.05 to 0.40%, Si: 2.0% or less, Mn: 0.30 to 2.0
%, P: 0.05% or less, S: 0.05% or less, Cr: 2.0% or less, sol.Al: 0.01 to 0.
10%, N: 0.0030 to 0.020%, V: 0.01 to 0.50%, Nb: 0.01 to 0.10%, including one or two kinds, and the surface portion contains C and N in a weight ratio of 0.05% ≤ C ≤ 1.0%. And 0.8% <N ≤ -1.325C (%)
It is a steel part with excellent fatigue strength characterized by being composed of a structure mainly containing martensite and austenite, which is contained in an amount that satisfies + 2.5%.

【0018】なおさらに別の好適態様によれば、本発明
は、母材の成分が重量比で、 C: 0.05〜0.40%、 Si:2.0 %以下、Mn: 0.30〜2.0
%、P: 0.05%以下、 S: 0.05%以下、 Cr:2.0 %以下、sol.Al: 0.01〜0.
10%、 N: 0.0030〜0.020 % さらに、 Ni: 2.0 %以下、Mo: 1.0 %以下のうちの一種または二
種、および V: 0.01〜0.50%、Nb: 0.01〜0.10%のうち一種または
二種、 を含み、表面部がC、Nを重量比で 0.05%≦C≦1.0 %、かつ、0.8 %<N≦−1.325C(%)
+2.5 % を満足する量だけ含有するマルテンサイトとオーステナ
イトを主体とする組織から構成されることを特徴とする
疲労強度に優れた鋼部品である。ここに、本発明にかか
る上記鋼部品としては、特に制限はされないが、軸受、
継手、歯車等が例示される。
According to still another preferred embodiment, in the present invention, the components of the base material are C: 0.05 to 0.40%, Si: 2.0% or less, and Mn: 0.30 to 2.0 by weight ratio.
%, P: 0.05% or less, S: 0.05% or less, Cr: 2.0% or less, sol.Al: 0.01 to 0.
10%, N: 0.0030 to 0.020%, Ni: 2.0% or less, Mo: 1.0% or less, one or two, and V: 0.01 to 0.50%, Nb: 0.01 to 0.10%, one or two. , And the surface portion contains C and N in a weight ratio of 0.05% ≤ C ≤ 1.0% and 0.8% <N ≤ -1.325C (%).
It is a steel part with excellent fatigue strength characterized by being composed of a structure mainly composed of martensite and austenite that is contained in an amount that satisfies + 2.5%. Here, the steel part according to the present invention is not particularly limited, but a bearing,
Examples include joints and gears.

【0019】[0019]

【作用】このように、本発明によれば、従来の浸炭窒化
の限界であった 0.8%の表面窒素量を越えた窒素量を鋼
の表面部に確保しつつ、しかも従来の窒化焼入れで表面
に残留する粗大化合物が存在していない鋼部品が得ら
れ、転動疲労寿命を従来になく向上させることができ
る。
As described above, according to the present invention, it is possible to secure a nitrogen amount on the surface of the steel which exceeds the surface nitrogen amount of 0.8%, which was the limit of the conventional carbonitriding, and to perform the surface treatment by the conventional nitriding and quenching. It is possible to obtain a steel part in which there is no residual coarse compound, and it is possible to improve rolling fatigue life as never before.

【0020】ところで、本発明に関連する発明として、
特開昭64−83625 号公報の開示する発明がある。この従
来発明は、0.95〜1.1 %Cの高炭素鋼の焼入れ加熱の
際、加熱雰囲気にアンモニアを添加することを特徴とし
ている。すでに説明したとおり、焼入れのためにオース
テナイト領域に加熱してその際にアンモニアを添加して
も、ボイド発生のため表面の窒素含有量には限界があ
り、本発明が目的とする0.8 %超の窒素量を得ることが
できない。従って、特開昭64−83625 号公報の開示に従
って焼入れを実施したとしても、本発明と同等品を製作
することはできない。
By the way, as an invention related to the present invention,
There is an invention disclosed in JP-A-64-83625. This conventional invention is characterized by adding ammonia to the heating atmosphere during quenching and heating of high carbon steel of 0.95 to 1.1% C. As already explained, even if heating to the austenite region for quenching and adding ammonia at that time, there is a limit to the nitrogen content on the surface due to the generation of voids, and there is a limit of more than 0.8%, which is the object of the present invention. Cannot get nitrogen content. Therefore, even if quenching is performed according to the disclosure of Japanese Patent Laid-Open No. 64-83625, it is not possible to manufacture a product equivalent to the present invention.

【0021】したがって、本発明の作用はオーステナイ
ト領域またはフェライト領域での窒化処理によってN富
化を図り、加熱焼入れに際して粗大窒化物の生成、残留
を抑制することで疲労強度の大幅な改善を可能とするの
である。
Therefore, the function of the present invention is to increase the N content by nitriding treatment in the austenite region or the ferrite region, and to suppress the formation and retention of coarse nitrides during heating and quenching, thereby enabling a great improvement in fatigue strength. To do.

【0022】次に、本発明において上記のように鋼組成
が限定された理由についてその作用とともに説明する。
なお、本明細書において特にことわりがない限り、
「%」は「重量%」である。
Next, the reason why the steel composition is limited as described above in the present invention will be explained together with its action.
In this specification, unless otherwise specified,
"%" Is "% by weight".

【0023】C: 0.05〜0.40% 本発明では部品表面部のN濃度あるいはN濃度とC濃度
を上昇させるため、表面部の靱性は低い。従って部品全
体の靱性確保のためには、表面部の靱性低下を母材で補
う必要がある。Cは鋼の強度を向上させると同時に靱性
を低下させる作用がある。0.40%を越えて添加すると母
材の靱性が著しく低下する。また、0.05%未満の添加で
あると、母材の強度が低下する。好ましくは0.15〜0.25
%である。
C: 0.05 to 0.40% In the present invention, the toughness of the surface portion is low because the N concentration or the N concentration and the C concentration in the surface portion of the component is increased. Therefore, in order to secure the toughness of the entire component, it is necessary to make up for the deterioration of the toughness of the surface portion with the base material. C has the effect of improving the strength of the steel and at the same time reducing the toughness. If added in excess of 0.40%, the toughness of the base material will be significantly reduced. Further, if the addition amount is less than 0.05%, the strength of the base material decreases. Preferably 0.15 to 0.25
%.

【0024】Si: 2.0 %以下 Siは溶製時に脱酸材としての作用があるが、添加量が増
すと冷間鍛造性、被削性、靱性を劣化させる作用もある
ので上限を 2.0%とした。好ましくは1.5 %以下であ
る。さらに好ましくは0.15〜0.35%である。
Si: 2.0% or less Si acts as a deoxidizer during melting, but if the addition amount increases, it also has the effect of deteriorating cold forgeability, machinability, and toughness, so the upper limit is 2.0%. did. It is preferably 1.5% or less. More preferably, it is 0.15 to 0.35%.

【0025】Mn: 0.30〜2.0 % Mnは溶製時の脱酸材としての作用と鋼の焼入れ性上昇の
作用がある。本発明では、C、N固溶オーステナイトの
焼入れにより、表層部をマルテンサイトとオーステナイ
ト主体の組織にすることを特徴とするので、焼入れ性の
確保が不可欠である。0.30%未満では充分な焼入れ性を
確保できない。2.0 %を越えて添加すると母材の被削性
が著しく低下する。好ましくは0.4 〜1.5 %である。さ
らに好ましくは0.6 〜1.2 %である。
Mn: 0.30 to 2.0% Mn has an action as a deoxidizing agent during melting and an action to increase hardenability of steel. Since the present invention is characterized in that the surface layer portion has a structure mainly composed of martensite and austenite by quenching of C and N solid solution austenite, it is essential to secure hardenability. If it is less than 0.30%, sufficient hardenability cannot be secured. If added in excess of 2.0%, the machinability of the base material will be significantly reduced. It is preferably 0.4 to 1.5%. It is more preferably 0.6 to 1.2%.

【0026】P: 0.05%以下、S: 0.05%以下 P、Sは硬化層の靱性を劣化させる作用があり、上限を
それぞれ0.05%とした。好ましくは、P≦0.03%、S≦
0.03%である。
P: 0.05% or less, S: 0.05% or less P and S have an action of deteriorating the toughness of the hardened layer, and the upper limits are set to 0.05%. Preferably, P ≦ 0.03%, S ≦
It is 0.03%.

【0027】Cr: 2.0 %以下 CrはMnと同様に鋼の焼入れ性を上昇させる作用がある。
また、Crは添加量が増えると浸炭、窒化時に炭化物、窒
化物を生成させる作用もある。2.0 %を越えると炭化
物、窒化物の生成が著しくなり、表面部の靱性を低下さ
せる。好ましくは0.5 〜1.5 %である。
Cr: 2.0% or less Cr, like Mn, has the effect of increasing the hardenability of steel.
Further, Cr has an action of forming carbides and nitrides at the time of carburizing and nitriding when the added amount increases. If it exceeds 2.0%, carbides and nitrides are remarkably formed and the toughness of the surface portion is lowered. It is preferably 0.5 to 1.5%.

【0028】sol.Al : 0.01 〜0.10% Alは母材中のNと反応しAlN を生成させ、特に浸炭処理
をする場合のオーステナイト粒粗大化を抑制する作用が
ある。オーステナイト粒粗大化の抑制は母材の歪増大、
靱性劣化を抑制し、構造用部品として健全なものとす
る。0.01%未満ではAlN 量が不足し、粒粗大化の抑制効
果はない。また、0.10%を越えて添加しても効果は飽和
する。好ましくは0.01〜0.05%である。
Sol.Al: 0.01 to 0.10% Al has an action of reacting with N in the base material to generate AlN, and particularly suppressing coarsening of austenite grains in the case of carburizing. Suppression of austenite grain coarsening increases strain of base metal,
It suppresses deterioration of toughness and makes it sound as a structural part. If it is less than 0.01%, the amount of AlN is insufficient, and there is no effect of suppressing grain coarsening. Moreover, the effect is saturated even if added over 0.10%. It is preferably 0.01 to 0.05%.

【0029】N: 0.0030〜0.020 % NはAlと反応しAlN を生成させ、浸炭時のオーステナイ
ト粒粗大化を抑制する作用がある。0.01%未満ではAlN
量が不足し、粒粗大化の抑制効果はない。また、0.020
%を越えて添加しても効果は飽和する。好ましくは0.00
80〜0.0180%である。
N: 0.0030 to 0.020% N reacts with Al to form AlN, which has an action of suppressing coarsening of austenite grains during carburization. AlN below 0.01%
The amount is insufficient, and there is no effect of suppressing grain coarsening. Also, 0.020
The effect is saturated even if added in excess of%. Preferably 0.00
80 to 0.0180%.

【0030】本発明においても次に述べるNi、Mo、V、
Nbは、必要によって添加することができ、Ni、Moの場合
には硬化層基地の靱性向上に効果があり、一方V、Nbは
炭窒化物を生成させ、母材を細粒化させ、細粒化を通し
て鋼全体の靱性を向上させる作用が見られる。以下、こ
れらの点について詳述する。
Also in the present invention, Ni, Mo, V, and
Nb can be added if necessary, and in the case of Ni and Mo, it has an effect of improving the toughness of the hardened layer matrix, while V and Nb generate carbonitrides and make the base material fine-grained. It has an effect of improving the toughness of the entire steel through graining. Hereinafter, these points will be described in detail.

【0031】Ni: 2.0 %以下 Niは硬化層の靱性を向上させる効果がある。2.0 %を越
えて添加すると母材の被削性を劣化させる。好ましくは
0.5 〜1.5 %である。
Ni: 2.0% or less Ni has the effect of improving the toughness of the hardened layer. Addition of more than 2.0% deteriorates the machinability of the base material. Preferably
It is 0.5 to 1.5%.

【0032】Mo: 1.0 %以下 MoはNiと同様硬化層の靱性を向上させる効果がある。ま
た、MoはCrと同様、添加量が増えると浸炭、窒化時に炭
化物、窒化物を生成させる作用もある。1.0 %を越える
と炭化物、窒化物の生成が著しくなり、表面部の靱性を
逆に低下させる。好ましくは0.8 %以下である。
Mo: 1.0% or less Mo, like Ni, has the effect of improving the toughness of the hardened layer. Further, Mo, like Cr, has an action of forming carbides and nitrides during carburization and nitriding when the addition amount increases. If it exceeds 1.0%, carbides and nitrides are remarkably formed, and the toughness of the surface portion is decreased. It is preferably 0.8% or less.

【0033】V: 0.01〜0.50% Vは母材中のC、Nと反応し炭窒化物を生成させ、母材
を細粒化させる作用がある。0.01%未満では細粒化効果
はないが、0.50%を越えて添加すると浸炭、窒化時に炭
化物、窒化物の生成が著しくなり、表面部の靱性を低下
させる。好ましくはV: 0.05〜0.30%である。
V: 0.01 to 0.50% V has the action of reacting with C and N in the base material to form carbonitrides and making the base material finer. If it is less than 0.01%, there is no grain refining effect, but if it is added in excess of 0.50%, carbides and nitrides are remarkably generated during carburization and nitriding, and the toughness of the surface portion is reduced. V: 0.05 to 0.30% is preferable.

【0034】Nb: 0.01〜0.10% Nbは母材中のC、Nと反応し炭窒化物を生成させ、母材
を細粒化させる作用がある。0.01%未満では細粒化効果
はない。また、0.10%を越えて添加しても効果は飽和す
る。好ましくはNb:0.02 〜0.04%である。
Nb: 0.01 to 0.10% Nb has the function of reacting with C and N in the base material to form carbonitrides and making the base material finer. If it is less than 0.01%, there is no grain refining effect. Moreover, the effect is saturated even if added over 0.10%. Nb: 0.02 to 0.04% is preferable.

【0035】以上のような鋼組成を有する母材は、本発
明によれば、鍛造、圧延などの適宜加工手段でもって所
定形状に成形され、次いで得られた鋼部品の表層部はN
またはCおよびNが、例えばガス浸炭、窒化処理によっ
て富化される。ここに、本発明に言う表面部とは通常の
窒化処理または浸炭窒化処理によってNまたはCおよび
N富化が見られる深さ領域のことを言い、通常は表面か
ら深さ200 μm 程度の表面層である。
According to the present invention, the base material having the above steel composition is formed into a predetermined shape by an appropriate processing means such as forging and rolling, and then the surface layer portion of the obtained steel part is N-shaped.
Alternatively, C and N are enriched by, for example, gas carburizing and nitriding. Here, the surface portion referred to in the present invention means a depth region where N or C and N enrichment are observed by a normal nitriding treatment or carbonitriding treatment, and usually a surface layer having a depth of about 200 μm from the surface. Is.

【0036】本発明によれば、そのような表面部に見ら
れるCおよびNは、次の式を満足する量だけ含有され
る。ただし、CおよびNの各量は重量比で示す。 0.05%≦C≦1.0 % ・・・・(1) 0.8 %<N≦−1.325C(%)+2.5 % ・・・・(2) 式(1) が満足されない場合、つまり浸炭が行われる場合
であってC含有量が1.0 %を超えて過剰量浸炭が行われ
る場合、疲労強度の改善が十分でなくなる。
According to the present invention, C and N found in such a surface portion are contained in an amount satisfying the following equation. However, the amounts of C and N are shown by weight ratio. 0.05% ≦ C ≦ 1.0% ・ ・ ・ ・ (1) 0.8% <N ≦ −1.325C (%) + 2.5% ・ ・ ・ ・ (2) When the formula (1) is not satisfied, that is, carburization is performed. In this case, when the C content exceeds 1.0% and the excess amount of carburization is performed, the fatigue strength is not sufficiently improved.

【0037】また、式(2) が満足されない場合、つまり
窒化が行われない場合、または過剰量の窒化が行われる
場合には、疲労強度の改善が十分でなく、特に過剰量の
Nが存在する場合、焼入れに際して粗大窒化物の残留は
避けられない。
Further, when the formula (2) is not satisfied, that is, when nitriding is not performed, or when an excessive amount of nitriding is performed, the fatigue strength is not sufficiently improved, and particularly, an excessive amount of N exists. If so, residual coarse nitrides are unavoidable during quenching.

【0038】浸炭窒化処理に続いては、加熱焼入れに伴
ってマルテンサイトが生成すると共にオーステナイトが
一部残留し、最終的にはマルテンサイトとオーステナイ
トを主体とした組織を形成する。両相の割合、つまり残
留オーステナイトの量等は特に制限はないが、好ましく
は30〜50(vol%)である。
Following the carbonitriding treatment, martensite is generated with heating and quenching, and austenite partially remains, and finally a structure mainly composed of martensite and austenite is formed. The ratio of both phases, that is, the amount of retained austenite and the like is not particularly limited, but is preferably 30 to 50 (vol%).

【0039】なお、その他の相としては、ベイナイト等
は許容されるが、通常は20(vol%)以下に制限するのが好
ましい。換言すれば、本発明によれば表面部は焼入れ
(必要により焼戻しを行う) 組織である。
Although bainite and the like are acceptable as other phases, it is usually preferable to limit the content to 20 (vol%) or less. In other words, according to the invention the surface part is hardened
(Tempered if necessary) This is a structure.

【0040】このように、本発明の特徴は浸炭窒化ある
いは窒化単独により表面部のC、N濃度を制御し、再加
熱焼入れにより表面部の組織の主体をマルテンサイトと
オーステナイト、つまり焼入れ組織にすることである。
マルテンサイトとオーステナイトを主体とする組織とし
たのは粗大な炭化物や窒化物が基地中に存在すると疲労
強度を低下させるからである。
As described above, the characteristic feature of the present invention is to control the C and N concentrations in the surface portion by carbonitriding or nitriding alone, and the main constituent of the surface portion structure is martensite and austenite, that is, a quenched structure, by reheating and quenching. That is.
The reason why the structure mainly composed of martensite and austenite is used is that the presence of coarse carbides and nitrides in the matrix lowers the fatigue strength.

【0041】粗大に存在して疲労強度を劣化させる炭化
物、窒化物は、浸炭時あるいは窒化時に生成してその後
の再加熱により解け残るFe3CとFe4N, Fe2-3Nである。鋼
の成分によっても異なるが、表面部の炭素量が浸炭によ
り 1.0%を越えると粗大なFe3Cが生成しやすくなる。従
って、表面部でのCの上限は 1.0%とした。特に浸炭を
実施しない場合は表面部のC量は母材の炭素量となるの
でCの下限は0.05%となる。
The carbides and nitrides which are coarsely present and deteriorate the fatigue strength are Fe 3 C, Fe 4 N and Fe 2-3 N which are formed during carburization or nitriding and remain unsolved by subsequent reheating. Although it depends on the steel composition, if the carbon content of the surface exceeds 1.0% due to carburization, coarse Fe 3 C is likely to be generated. Therefore, the upper limit of C at the surface portion is set to 1.0%. Especially when carburization is not carried out, the amount of C on the surface becomes the amount of carbon of the base material, so the lower limit of C is 0.05%.

【0042】Fe4N, Fe2-3Nは窒化の際表面部に層状に生
成され、表面部のN量が−1.325C+2.5 %を越えると再
加熱によっても解け残る。従って、Nの上限は−1.325C
+2.5 %とした。また、本発明は従来の浸炭窒化では得
られないN量を含む組織が特徴であるので、0.8 %超と
N量は従来品の限界値を越える量とした。
Fe 4 N and Fe 2-3 N are formed in layers on the surface during nitriding, and when the amount of N on the surface exceeds -1.325 C + 2.5%, they are unsolved by reheating. Therefore, the upper limit of N is -1.325C
It was set to + 2.5%. Further, since the present invention is characterized by the structure containing the amount of N that cannot be obtained by the conventional carbonitriding, the amount of N exceeds 0.8%, which exceeds the limit value of the conventional product.

【0043】本発明にかかる鋼部品の製造に際して用い
られる浸炭処理および窒化処理の方法は特に制限なく、
ガス浸炭、ガス窒化、イオン浸炭、イオン窒化、軟窒化
等を例示できるが、前述の式(1) 、(2) のC、N含有量
が実現できるものであればいずれであってもよい。処理
条件としては次のものを挙げることができる。
The carburizing and nitriding methods used in the production of the steel part according to the present invention are not particularly limited.
Examples thereof include gas carburizing, gas nitriding, ion carburizing, ion nitriding, and soft nitriding, but any one can be used as long as the C and N contents of the above formulas (1) and (2) can be realized. The following can be mentioned as processing conditions.

【0044】窒化処理条件: 雰囲気 : 15 %NH3 処理温度 : 550℃ 処理時間 : 10 〜100 H 浸炭処理条件: 雰囲気 : 炭素ポテンシャル0.8 % 処理温度 : 930 ℃ 処理時間 : 2〜10H。Nitriding treatment conditions: Atmosphere: 15% NH 3 Treatment temperature: 550 ° C Treatment time: 10 to 100 H Carburizing treatment conditions: Atmosphere: Carbon potential 0.8% Treatment temperature: 930 ° C Treatment time: 2 to 10H.

【0045】このようにフェライト領域で、N:0.8%超
に窒化処理がされるが、この後は室温にまで冷却してか
ら再加熱するか、あるいは必要により窒化処理後室温ま
で冷却せずにオーステナイト領域に加熱してから冷却
(焼入れ) する。かかる熱処理により表層部 (0〜200
μm) にいわゆる焼きが入り、マルテンサイトが生成
し、一部残留するオーステナイトとともにマルテンサイ
トとオーステナイトとを主体とする組織とする。なお、
焼入れに続いて必要に応じ焼戻し処理を行ってもよい。
焼戻し処理は硬化層の靱性向上の点で有効である。
As described above, in the ferrite region, nitriding treatment is performed with N: more than 0.8%. After that, after cooling to room temperature and then reheating, or if necessary, without nitriding treatment and cooling to room temperature. Heating in the austenite region and then cooling
(Quench) By this heat treatment, the surface layer (0 to 200
(μm) is so-called baked, martensite is formed, and the structure is mainly composed of martensite and austenite together with a part of residual austenite. In addition,
Subsequent to quenching, a tempering process may be performed if necessary.
The tempering treatment is effective in improving the toughness of the hardened layer.

【0046】[0046]

【実施例】【Example】

(実施例1)表1に本例で使用した鋼の成分を示す。ま
ず、供試鋼No.2、3を熱間鍛造で直径20mmの丸棒にして
から、10mm×10mm×60mmの試験片を製作した。次に、各
試験片に表2に示す条件A〜Cの熱処理を施し、表面部
の組織観察とC、N分析をEPMAにより行った。条件Aに
ついては供試鋼No.2、No. 3 を適用し、条件B、Cにつ
いては鋼No. 3 を適用した。
(Example 1) Table 1 shows the components of the steel used in this example. First, the test steel Nos. 2 and 3 were hot forged into a round bar having a diameter of 20 mm, and then a test piece of 10 mm × 10 mm × 60 mm was manufactured. Next, each test piece was heat-treated under the conditions A to C shown in Table 2, and the structure of the surface portion was observed and the C and N analyzes were performed by EPMA. Steels Nos. 2 and 3 were used for condition A, and steel No. 3 was applied for conditions B and C.

【0047】図1に表面部のC、N含有量と組織との関
係を破線のグラフで示す。ここに、表面部は、表面から
深さ200 μm の領域を言う。図中、△は供試鋼No.2、▽
は供試鋼No.3、○は供試鋼No.3についてCを1.0 %まで
富化した例を、□は同じくC=1.41%にまで富化した例
を示す。黒く塗りつぶしてあるのは粗大炭化物窒化物が
残留していたことを示す。
FIG. 1 shows the relationship between the C and N contents of the surface and the structure by a broken line graph. Here, the surface portion means a region having a depth of 200 μm from the surface. In the figure, △ is the sample steel No. 2, ▽
Indicates an example in which C is enriched to 1.0% in the sample steel No. 3 and ○ is in an example, and □ is an example in which C is 1.41% in the same manner. Filled in black indicates that coarse carbide nitride remained.

【0048】かかる表面部の組織はいずれもマルテンサ
イトとオーステナイトを主体とする組織であった。これ
らの結果から分かるように、N>−1.325C+2.5 %の
領域ではFe4NあるいはFe2-3Nが残留する。また、浸炭で
のCポテンシャルが高い場合も炭化物が残留する。
All the structures of the surface portion were structures mainly composed of martensite and austenite. As can be seen from these results, Fe 4 N or Fe 2-3 N remains in the region of N> -1.325C + 2.5%. Further, when the C potential in carburization is high, the carbide remains.

【0049】(実施例2)本例では、表1の供試鋼No.1〜
14を熱間鍛造で直径20mmの丸棒鋼とし、焼準処理の後、
直径12mm×100 mmの棒状試験片を製作し、各鋼の試験片
に図2に示す熱処理〜を施した。本発明例の場合、
表面部の組織はマルテンサイトとオーステナイトを主体
とする組織であった。次に、表面研磨 (約50μm)、切断
をすることにより、疲労試験用の試験片を製作し、転動
疲労試験に供した。
Example 2 In this example, sample steel Nos. 1 to 1 in Table 1 were used.
14 was hot forged into a round steel bar with a diameter of 20 mm, and after normalizing treatment,
A rod-shaped test piece having a diameter of 12 mm × 100 mm was produced, and the heat treatments shown in FIG. In the case of the example of the present invention,
The structure of the surface portion was mainly composed of martensite and austenite. Next, surface grinding (about 50 μm) and cutting were performed to fabricate a test piece for a fatigue test, and the test piece was subjected to a rolling fatigue test.

【0050】図3(a) 、(b) に試験装置とそれを使った
試験要領を示す。このときの疲労試験では上部駆動輪10
を介して試験片20に面圧600kg/mm2 を負荷し、一方標準
鋼球30を介して側部案内輪40および下部案内輪50によ
り、試験片30への面圧負荷回数を46,000回/minとした。
潤滑油としてタービン油を使用した。累積破損の確率が
50%となるときの寿命 (L50) を求めた。
3 (a) and 3 (b) show a test apparatus and a test procedure using the test apparatus. In the fatigue test at this time, the upper drive wheel 10
The surface pressure of 600 kg / mm 2 is applied to the test piece 20 via the meanwhile, while the surface pressure load on the test piece 30 is 46,000 times by the side guide wheel 40 and the lower guide wheel 50 via the standard steel ball 30. It was min.
Turbine oil was used as the lubricating oil. The cumulative damage probability
The life (L 50 ) when 50% was reached was obtained.

【0051】表3にこのときの疲労試験結果と試験片の
最表面部のC、N量を示す。それによれば、本発明例で
は従来の浸炭窒化法では得ることができないN量を得る
ことができ、しかもNとCの含有量の調整により粗大な
窒化物、炭化物の残留がないため、転動疲労寿命がL50
=4.0 ×107 以上と向上することが分かる。
Table 3 shows the fatigue test results and the C and N contents of the outermost surface of the test piece at this time. According to this, in the example of the present invention, it is possible to obtain the amount of N which cannot be obtained by the conventional carbonitriding method, and moreover, by adjusting the contents of N and C, no coarse nitrides or carbides remain, so that rolling Fatigue life is L 50
It can be seen that the value is improved to 4.0 × 10 7 or more.

【0052】[0052]

【表1】 [Table 1]

【0053】[0053]

【表2】 [Table 2]

【0054】[0054]

【表3】 [Table 3]

【0055】[0055]

【発明の効果】以上、説明してきたように、本発明によ
れば、浸炭窒化鋼のボイド発生、窒化焼入れ鋼の粗大窒
化物残留という問題点を解決し、転動疲労寿命を向上さ
せた機械構造用部品が得られ、部品の軽量化、高強度化
という今日的技術要請に応じることができるという優れ
た実際上の効果があり、本発明の意義は大きい。
As described above, according to the present invention, a machine which solves the problems of void generation in carbonitrided steel and residual coarse nitride in nitriding and hardened steel and has improved rolling fatigue life The present invention is of great significance because it has an excellent practical effect that structural parts can be obtained, and that today's technical requirements such as weight reduction and high strength of parts can be met.

【図面の簡単な説明】[Brief description of drawings]

【図1】実施例1での結果である表面部のC、N量と組
織の関係を示す線図である。
FIG. 1 is a diagram showing the relationship between the amounts of C and N in the surface portion and the structure, which is the result of Example 1.

【図2】実施例2における熱処理条件の説明図である。FIG. 2 is an explanatory diagram of heat treatment conditions in Example 2.

【図3】図3(a) 、(b) は、実施例2にて実施した転動
疲労試験装置のそれぞれ側面図および1部省略した正面
図である。
3 (a) and 3 (b) are a side view and a front view with a part omitted, respectively, of a rolling fatigue test apparatus implemented in Example 2. FIG.

Claims (1)

【特許請求の範囲】[Claims] 【請求項1】 母材の成分が重量比で、 C: 0.05〜0.40%、 Si: 2.0 %以下、 Mn: 0.30〜 2.0%、 P: 0.05%以下、 S: 0.05%以下、 Cr: 2.0 %以下、 sol.Al: 0.01〜0.10%、N: 0.0030〜0.020 %、 Ni: 0 〜2.0 %、 Mo: 0 〜1.0 %、 V: 0 〜0.50%、 Nb: 0 〜0.10%、 残部Feおよび不可避的不純物 から成り、表面部のC、Nが重量比で 0.05%≦C≦1.0 %、かつ、0.8 %<N≦−1.325C(%)
+2.5 % を満足する量だけ含有される、マルテンサイトとオース
テナイトを主体とする組織から構成されることを特徴と
する疲労強度に優れた鋼部品。
1. The weight ratio of the components of the base material is C: 0.05 to 0.40%, Si: 2.0% or less, Mn: 0.30 to 2.0%, P: 0.05% or less, S: 0.05% or less, Cr: 2.0%. Below, sol.Al: 0.01 to 0.10%, N: 0.0030 to 0.020%, Ni: 0 to 2.0%, Mo: 0 to 1.0%, V: 0 to 0.50%, Nb: 0 to 0.10%, balance Fe and unavoidable Of C, N on the surface is 0.05% ≤ C ≤ 1.0% and 0.8% <N ≤ -1.325C (%)
Steel parts with excellent fatigue strength, characterized by being composed of a structure mainly composed of martensite and austenite, which is contained in an amount satisfying + 2.5%.
JP28272693A 1993-11-11 1993-11-11 Steel parts excellent in fatigue strength Withdrawn JPH07138696A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP28272693A JPH07138696A (en) 1993-11-11 1993-11-11 Steel parts excellent in fatigue strength

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP28272693A JPH07138696A (en) 1993-11-11 1993-11-11 Steel parts excellent in fatigue strength

Publications (1)

Publication Number Publication Date
JPH07138696A true JPH07138696A (en) 1995-05-30

Family

ID=17656249

Family Applications (1)

Application Number Title Priority Date Filing Date
JP28272693A Withdrawn JPH07138696A (en) 1993-11-11 1993-11-11 Steel parts excellent in fatigue strength

Country Status (1)

Country Link
JP (1) JPH07138696A (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006328457A (en) * 2005-05-25 2006-12-07 Sumitomo Metal Ind Ltd Steel for soft nitriding, and soft-nitrided component
JP2007046088A (en) * 2005-08-09 2007-02-22 Yuki Koshuha:Kk Nitrided quenched part, and method for producing the same
JP2009030134A (en) * 2007-07-30 2009-02-12 Sumitomo Metal Ind Ltd Semifinished product for nitrided gear, and nitrided gear
US8142576B2 (en) 2006-02-27 2012-03-27 Aisin Seiki Kabushiki Kaisha Clutch member and process for manufacturing the same
JP2013112827A (en) * 2011-11-25 2013-06-10 Jfe Bars & Shapes Corp Gear excellent in pitching resistance and manufacturing method therefor

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006328457A (en) * 2005-05-25 2006-12-07 Sumitomo Metal Ind Ltd Steel for soft nitriding, and soft-nitrided component
JP4526440B2 (en) * 2005-05-25 2010-08-18 住友金属工業株式会社 Soft nitriding steel and soft nitriding parts
JP2007046088A (en) * 2005-08-09 2007-02-22 Yuki Koshuha:Kk Nitrided quenched part, and method for producing the same
US8142576B2 (en) 2006-02-27 2012-03-27 Aisin Seiki Kabushiki Kaisha Clutch member and process for manufacturing the same
JP2009030134A (en) * 2007-07-30 2009-02-12 Sumitomo Metal Ind Ltd Semifinished product for nitrided gear, and nitrided gear
JP2013112827A (en) * 2011-11-25 2013-06-10 Jfe Bars & Shapes Corp Gear excellent in pitching resistance and manufacturing method therefor

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