JPH07188895A - Manufacture of parts for machine structure use - Google Patents

Manufacture of parts for machine structure use

Info

Publication number
JPH07188895A
JPH07188895A JP33869693A JP33869693A JPH07188895A JP H07188895 A JPH07188895 A JP H07188895A JP 33869693 A JP33869693 A JP 33869693A JP 33869693 A JP33869693 A JP 33869693A JP H07188895 A JPH07188895 A JP H07188895A
Authority
JP
Japan
Prior art keywords
steel
amount
machine structural
carbide
retained austenite
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Withdrawn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
JP33869693A
Other languages
Japanese (ja)
Inventor
Morifumi Nakamura
守文 中村
Toyofumi Hasegawa
豊文 長谷川
Yoshitake Matsushima
義武 松島
Satoshi Abe
安部  聡
Masayoshi Ogura
真義 小倉
Yoichi Watanabe
陽一 渡辺
Takashi Matsumoto
隆 松本
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kobe Steel Ltd
Nissan Motor Co Ltd
Original Assignee
Kobe Steel Ltd
Nissan Motor Co Ltd
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 Kobe Steel Ltd, Nissan Motor Co Ltd filed Critical Kobe Steel Ltd
Priority to JP33869693A priority Critical patent/JPH07188895A/en
Publication of JPH07188895A publication Critical patent/JPH07188895A/en
Withdrawn legal-status Critical Current

Links

Abstract

PURPOSE:To secure high fatigue strength by executing carburizing treatment for satisfying specified properties after forming steel for machine structural use having characteristic components. CONSTITUTION:The componential composition of the steel for machine structural use consists of 0.1-0.40wt.% C, 0.05-2wt.% Si, 0.4-2wt.% Mn, 0.005-0.03wt.% S, 0.005-0.05wt.% Al, 0.005-0.03wt.% N, 0.05-1wt.%. Mo, 0.1-1wt.%. V and the balance Fe with inevitable impurities. After forming the steel for machine structural use into a prescribed shape, the carbon content (C) and nitrogen content (N) of the surface are controlled to the level expressed by the inequality I and inequality II, respectively. R* satisfies the formula III and the parentheses show the wt.% of each element in steel. By executing carburization or carbo- nitriding treatment so as to satisfy them, the carbide of <=1mum in the outer-layer part is defined as 0.5-10% in the rate of area and the amount of residual austenite in the outer-layer part is defined as 15-50%. In this way, the pitting life is remarkably improved.

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、耐ピッチング性と耐疲
労特性に優れた機械構造用部品の製造方法に関し、詳細
には特定条件下に浸炭焼入れ・焼戻し処理あるいは浸炭
窒化焼入れ・焼戻し処理を行うことによって、機械構造
用部品の表層部に適量の残留オーステナイトを生成せし
め、ピッチング寿命を大幅に向上し得る様にした機械構
造用部品の製造方法に関するものである。本発明は、歯
車、摺動部品、軸類等、特に高面圧で使用され、かつ曲
げ疲労強度の必要な機械構造用部品を製造するのに好適
な方法である。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a machine structural component having excellent pitting resistance and fatigue resistance, and more specifically, it is subjected to carburizing and tempering treatment or carbonitriding and quenching treatment and tempering treatment under specific conditions. The present invention relates to a method for producing a machine structural component, which is capable of generating an appropriate amount of retained austenite in the surface layer portion of the mechanical structural component to significantly improve the pitching life. INDUSTRIAL APPLICABILITY The present invention is a method suitable for producing gears, sliding parts, shafts and the like, particularly machine structural parts that are used under high surface pressure and that require bending fatigue strength.

【0002】[0002]

【従来の技術】機械構造用部品は、例えば自動車,建設
機械および産業機械等における動力伝達部品として広く
使用されており、該部品は、高速回転によって高い曲げ
応力と接触応力が付加されるので、優れた耐疲労性や耐
摩耗性が要求される。この様な機械構造用部品に用いら
れる鋼材としては、これまでJIS G4104,G4105お
よびG4103等に夫々規定されているCr肌焼鋼,Cr−
Mo肌焼鋼およびNi−Cr−Mo肌焼鋼等が用いられ
ており、これらの鋼材を成形加工した後、浸炭焼入れ・
焼戻し処理を施してきた。しかしながら、近年、自動車
の高出力化や部品の小型軽量化の動きに対応して、トラ
ンスミッション用歯車の負荷応力はますます増大する傾
向にあり、上述した様な従来の機械構造用鋼材および表
面硬化処理法ではこうした高面圧化の傾向に対応しきれ
ず、接触面の剥離減少、すなわち耐ピッチング性が不足
するという問題が生じている。
2. Description of the Related Art Mechanical structural components are widely used as power transmission components in, for example, automobiles, construction machinery and industrial machinery. Since the components are subjected to high bending stress and contact stress due to high speed rotation, Excellent fatigue resistance and wear resistance are required. Steel materials used for such machine structural parts include Cr case-hardening steel and Cr-, which have been stipulated in JIS G4104, G4105 and G4103, respectively.
Mo case-hardening steel and Ni-Cr-Mo case-hardening steel are used, and after carving and hardening these steel materials,
It has been tempered. However, in recent years, the load stress of transmission gears has been increasing more and more in response to the trend toward higher output of automobiles and smaller and lighter parts. The treatment method cannot cope with such a tendency of increasing the surface pressure, resulting in a problem that the peeling of the contact surface is reduced, that is, the pitting resistance is insufficient.

【0003】そこで、耐ピッチング性を向上させる目的
で、特開昭59−232252号公報に記載されている
様にCr等の炭化物形成元素を添加することにより、浸
炭部に高硬度の微細な球状炭化物を析出させる方法が開
示されている。しかしながら、この方法では浸炭時に炭
化物が微細分散しにくい;1μm以上の炭化物が析出さ
れるので球状化焼きなまし処理が必要となり、曲げ疲労
強度が低くなる等の問題がある。
Therefore, for the purpose of improving the pitting resistance, by adding a carbide-forming element such as Cr as described in JP-A-59-232252, a high hardness fine spherical particle is formed in the carburized portion. A method of precipitating carbides is disclosed. However, according to this method, it is difficult to finely disperse the carbide during carburization; since the carbide having a size of 1 μm or more is deposited, spheroidizing annealing treatment is required, and there is a problem that the bending fatigue strength becomes low.

【0004】[0004]

【発明が解決しようとする課題】本発明はこの様な事情
に着目してなされたものであって、その目的は、高い疲
労強度を確保すると共に耐ピッチング性を大幅に向上さ
せることができる機械構造用部品の製造方法を提供する
ことにある。
SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object thereof is a machine capable of ensuring high fatigue strength and greatly improving pitting resistance. It is to provide a method for manufacturing a structural component.

【0005】[0005]

【課題を解決するための手段】上記目的を達成し得た本
発明の機械構造用部品の製造方法は、重量%でC:0.1
〜0.40%,Si:0.05〜2%、Mn:0.4 〜2%,S:
0.005 〜0.03%,Al:0.005 〜0.05%,N:0.005 〜
0.03%,Mo:0.05〜1%,V:0.1 〜1%を夫々含有
し、残部鉄および不可避不純物からなる機械構造用鋼
を、所定形状に成形加工後、表面の炭素量[C]と窒素
量[N]が下記(1) および(2) : 0.6 %≦[C]≦1.3 % …(1) 1.14−0.15R*≦[C]+[N]≦1.55−0.15R* …(2) 但し、R*=[Mo]+1.5 [Mn]+1.5 [Cr]−
[Si]であり、[ ]は鋼中に存在する各元素の重量
%を示す。を満足する様に前記浸炭処理あるいは浸炭窒
化処理を施すことによって、表層部に1μm以下の炭化
物を面積率で0.5〜10%、かつ表層部の残留オース
テナイト量を15〜50%とするものである。好適な実
施態様では、上記機械構造用鋼は、更にCr:0.2 〜3
%およびNi:0.2 〜2 %よりなる群から選択される少
なくとも1種を含有するものであってもよい。
The method of manufacturing a machine structural component of the present invention, which has achieved the above object, is C: 0.1% by weight.
~ 0.40%, Si: 0.05-2%, Mn: 0.4-2%, S:
0.005-0.03%, Al: 0.005-0.05%, N: 0.005-
Mechanical structural steel containing 0.03%, Mo: 0.05 to 1%, V: 0.1 to 1%, and the balance of iron and unavoidable impurities was formed into a predetermined shape, and then the surface carbon content [C] and nitrogen The amount [N] is the following (1) and (2): 0.6% ≤ [C] ≤ 1.3% (1) 1.14-0.15R * ≤ [C] + [N] ≤ 1.55-0.15R * (2) However, R * = [Mo] +1.5 [Mn] +1.5 [Cr]-
[Si], and [] indicates the weight% of each element present in the steel. By performing the carburizing treatment or carbonitriding treatment so as to satisfy the above condition, the surface layer portion has a carbide of 1 μm or less in an area ratio of 0.5 to 10%, and the residual austenite amount of the surface layer portion is 15 to 50%. Is. In a preferred embodiment, the mechanical structural steel further comprises Cr: 0.2-3.
% And Ni: at least one selected from the group consisting of 0.2 to 2% may be contained.

【0006】更に好適な実施態様では、上記機械構造用
鋼はいずれも、更にNb:0.01〜0.5 %,Ti:0.01〜
0.05%,W:0.01〜1.5 %およびB:0.0003〜0.010 %
よりなる群から選択される少なくとも1種を含有するも
のであってもよい。一層好適な実施態様では、上記機械
構造用鋼はいずれも、更にPb:0.09%以下,Ca:0.
0005〜0.003 %,Zr:0.01〜0.05%,Te:0.005 〜
0.1 %,Sb:0.005 〜0.1 %およびSe:0.005 〜0.
1 %よりなる群から選択される少なくとも1種を含有す
るものであってもよい。
In a further preferred embodiment, each of the above-mentioned steels for machine structure further comprises Nb: 0.01-0.5%, Ti: 0.01-
0.05%, W: 0.01 to 1.5% and B: 0.0003 to 0.010%
It may contain at least one selected from the group consisting of: In a more preferred embodiment, each of the above-mentioned steels for machine structural use further contains Pb: 0.09% or less, Ca: 0.
0005 to 0.003%, Zr: 0.01 to 0.05%, Te: 0.005 to
0.1%, Sb: 0.005 to 0.1% and Se: 0.005 to 0.
It may contain at least one selected from the group consisting of 1%.

【0007】[0007]

【作用】本発明者らは、ピッチング寿命を向上させるに
は表層部に炭化物を微細分散させ、残留オーステナイト
量を適正量に調整することが有効であること;ただし、
曲げ疲労強度を低下させないためには炭化物を1μm以
下に微細化させると共に残留オーステナイト量の上限を
規定することが必要であることを見出し、これらを満足
させるための、機械構造用鋼の化学組成と該鋼の浸炭処
理条件あるいは浸炭窒化処理条件を究明した。即ち、本
発明は、浸炭処理時あるいは浸炭窒化処理時の表面の炭
素量(以後、[C]と略記する)、および該[C]と窒
素量(以後、[N]と略記する)の合計を、合金元素量
によって規定される特定範囲内に制御することにより、
表層部に1μm以下の微細な炭化物の生成を促し、かつ
表層部の残留オーステナイト量を適正量としたものであ
る。
The present inventors have found that it is effective to finely disperse the carbide in the surface layer portion and adjust the amount of retained austenite to an appropriate amount in order to improve the pitching life.
It was found that it is necessary to refine the carbide to 1 μm or less and to specify the upper limit of the amount of retained austenite so as not to reduce the bending fatigue strength, and to satisfy these, the chemical composition of the steel for mechanical structure and The conditions for carburizing or carbonitriding the steel were investigated. That is, in the present invention, the amount of carbon on the surface during carburizing or carbonitriding (hereinafter abbreviated as [C]), and the sum of the amount of [C] and nitrogen (hereinafter abbreviated as [N]). By controlling within a specific range defined by the amount of alloying elements,
It promotes the formation of fine carbides of 1 μm or less in the surface layer portion and sets the amount of retained austenite in the surface layer portion to an appropriate amount.

【0008】本発明に用いられる機械構造用鋼における
化学成分限定理由は下記の通りである。 C:0.1 〜0.40% Cは浸炭焼入れあるいは浸炭窒化焼入れした部品に所望
の芯部硬さを付与するのに必須の元素である。0.1 %未
満では芯部硬さが不足し、0.40%を超えると冷間加工性
や被削性が低下すると共に芯部の靭性劣化を招く。 Si:0.05〜2% Siは粒界炭化物の生成を抑制して疲労強度の低下を防
ぐのに有効な元素であり、この作用を有効に発揮させる
には0.05%以上の添加が必要であるが、2%を超えて過
剰に添加すると、浸炭時の炭素の浸入を妨げたり、冷間
加工性や被削性が低下する。
The reasons for limiting the chemical composition in the mechanical structural steel used in the present invention are as follows. C: 0.1 to 0.40% C is an essential element for imparting a desired core hardness to a carburized or carbonitrided part. If it is less than 0.1%, the hardness of the core is insufficient, and if it exceeds 0.40%, the cold workability and machinability are deteriorated and the toughness of the core is deteriorated. Si: 0.05 to 2% Si is an element that is effective in suppressing the formation of grain boundary carbides and preventing a decrease in fatigue strength, and it is necessary to add 0.05% or more to effectively exhibit this effect. If added in excess of 2%, carbon infiltration during carburization is hindered and cold workability and machinability deteriorate.

【0009】Mn:0.4 〜2% Mnは残留オーステナイトの生成を促進すると共に、鋼
材の脱酸に必要な元素である。0.4 %未満では脱酸が不
十分となり、鋼材の内部品質が劣化すると共に、浸炭層
部の焼入れ性が確保できず、不完全焼入れ層ができるの
で疲労強度の低下をまねく。一方、2%を超えて添加す
ると鋼材硬さが増加し、鍛造性や被削性も劣化する。 S:0.005 〜0.03% Sは鋼中において硫化物系介在物(MnS)として含有
されており、被削性に有効な元素であり、この作用を有
効に発揮させるには、0.005 %以上の添加が必要であ
る。しかしながら、0.03%を超えると靱性が低下すると
共に、MnSが破壊の起点となってピッチング寿命を低
下させる。
Mn: 0.4 to 2% Mn is an element which promotes the formation of retained austenite and is necessary for deoxidizing steel materials. If it is less than 0.4%, deoxidation becomes insufficient, the internal quality of the steel material deteriorates, the hardenability of the carburized layer cannot be secured, and an incompletely hardened layer is formed, resulting in a decrease in fatigue strength. On the other hand, if added in excess of 2%, the hardness of the steel material increases and the forgeability and machinability deteriorate. S: 0.005-0.03% S is contained in the steel as sulfide inclusions (MnS) and is an effective element for machinability. To effectively exhibit this effect, 0.005% or more is added. is necessary. However, if it exceeds 0.03%, the toughness deteriorates, and MnS becomes a starting point of fracture to shorten the pitting life.

【0010】Al:0.005 〜0.05% Alは脱酸と結晶粒の微細化(浸炭時にAlNが生成
し、焼入れ後の結晶粒が微細になる)に有効な元素であ
り、0.005 %未満ではこのような効果は得られない。し
かしながら0.05%を超えて過剰に添加すると、結晶粒が
凝集し結晶粒の成長を招く。 N:0.005 〜0.03% NはAlと結合してAlNを生成し、オーステナイト結
晶粒を微細化させる元素であり、その結果ピッチング寿
命が向上する。0.005 %未満ではこのような効果は得ら
れない。しかしながら0.03%当たりで上記効果が飽和す
る。
Al: 0.005 to 0.05% Al is an element effective for deoxidation and refining of crystal grains (AlN is generated during carburization and crystal grains become fine after quenching). No effect can be obtained. However, if added in excess of 0.05%, the crystal grains agglomerate and the crystal grains grow. N: 0.005 to 0.03% N is an element that combines with Al to generate AlN and refines austenite crystal grains, and as a result, the pitching life is improved. If it is less than 0.005%, such an effect cannot be obtained. However, about 0.03%, the above effect is saturated.

【0011】Mo:0.05〜1% Moは、浸炭層の焼入性を大幅に向上させて不完全焼入
れ層の生成を抑制すると共に、MC型のV系炭化物にお
けるVの一部と置換して炭化物の析出量を増し、浸炭表
層部の高硬度を確保するのに有用な元素である。このよ
うな効果を得るには、0.05%以上の添加が必要である
が、1%を超えて過剰に添加すると、冷間加工性や被削
性が劣化する。 V:0.1 〜1% Vは鋼中のCやNと結合して微細な炭窒化物を表面硬化
処理層に析出し、硬度の向上および耐ピッチング性の向
上に有用な元素であり、この作用を有効に発揮させるに
は、0.1 %以上の添加が必要であるが、1%を超えると
フェライトが多量に生成し、芯部硬さが低下し、静的強
度や疲労強度も低下する。
Mo: 0.05-1% Mo significantly improves the hardenability of the carburized layer to suppress the formation of an incompletely hardened layer, and replaces a part of V in MC type V-based carbide. It is an element useful for increasing the precipitation amount of carbide and ensuring high hardness of the carburized surface layer. To obtain such an effect, it is necessary to add 0.05% or more, but if added in excess of 1%, cold workability and machinability deteriorate. V: 0.1 to 1% V is an element useful for improving hardness and pitting resistance by combining fine carbonitrides in the surface-hardened layer by combining with C and N in steel. However, if it exceeds 1%, a large amount of ferrite is produced, the core hardness is lowered, and the static strength and fatigue strength are also lowered.

【0012】本発明に用いられる機械構造用鋼は、以上
の元素を基本成分とし、残部鉄および不可避不純物から
なるものであるが、必要によりCr,Ni,Nb,T
i,W,B,Pb,Ca,Zr,Te,Sb,Seを含
有してもよい。これらの元素の限定理由は下記の通りで
ある。
The mechanical structural steel used in the present invention contains the above elements as basic components and the balance iron and unavoidable impurities. If necessary, Cr, Ni, Nb, T
You may contain i, W, B, Pb, Ca, Zr, Te, Sb, Se. The reasons for limiting these elements are as follows.

【0013】Cr:0.2 〜3% Crは焼入性や浸炭性を向上させるのに有効な元素であ
り、この作用を有効に発揮させるには、0.2 %以上の添
加が必要である。しかしながら3%を超えて添加する
と、炭化物が網目状に多量に析出して曲げ疲労強度が低
下し、焼入れによって焼割れが発生しやすくなる。 Ni:0.2 〜2% Niは浸炭層の靭性を向上させると共に、浸炭層および
芯部の焼入れ性の確保に有効な元素であり、この作用を
有効に発揮させるには、0.2 %以上の添加が必要であ
る。しかしながら、2%を超えて過剰に添加すると、残
留オーステナイト量が多量に生成し過ぎる。
Cr: 0.2 to 3% Cr is an element effective for improving the hardenability and carburizing property, and 0.2% or more is required to effectively exert this effect. However, if added in excess of 3%, a large amount of carbide precipitates in a mesh-like form, the bending fatigue strength decreases, and quench cracking easily occurs due to quenching. Ni: 0.2 to 2% Ni is an element that is effective in improving the toughness of the carburized layer and ensuring the hardenability of the carburized layer and the core. To effectively exhibit this effect, 0.2% or more is added. is necessary. However, if it is added in excess of 2%, the amount of retained austenite is excessively generated.

【0014】Nb:0.01〜0.5 %,Ti:0.01〜0.05% NbとTiは鋼中のCやNと結合して炭窒化物を生成
し、結晶粒度を微細化して靭性を増大させるのに有用な
元素である。この作用を有効に発揮させるには、Nbお
よびTiを上記範囲内にする必要がある。 W:0.01〜1.5 % Wは、炭化物を生成し、表面硬さをや芯部硬さを高める
のに有効な元素である。この作用を有効に発揮させるに
は、0.01%以上の添加が必要がある。しかしながら、1.
5 %を超えると鋼材硬さが大きくなり、鍛造性や被削性
に悪影響を及ぼす。 B:0.0003〜0.010 % Bは、焼入れ性を向上させるのに有効な元素であるが、
0.0003%未満では、この効果を得ることはできず、0.01
0%を超えると効果が飽和するので上記範囲内にする必
要がある。
Nb: 0.01 to 0.5%, Ti: 0.01 to 0.05% Nb and Ti combine with C and N in steel to form carbonitrides, which are useful for refining the grain size and increasing the toughness. Is an element. In order to exert this effect effectively, it is necessary to set Nb and Ti within the above range. W: 0.01 to 1.5% W is an element that is effective in forming carbides and increasing the surface hardness and core hardness. To exert this effect effectively, it is necessary to add 0.01% or more. However, 1.
If it exceeds 5%, the hardness of the steel material increases, which adversely affects the forgeability and machinability. B: 0.0003 to 0.010% B is an element effective in improving hardenability,
If it is less than 0.0003%, this effect cannot be obtained.
If it exceeds 0%, the effect will be saturated, so it must be within the above range.

【0015】Pb:0.09%以下,Ca:0.0005〜0.003
%,Zr:0.01〜0.05%,Te:0.005 〜0.1 %,S
b:0.005 〜0.1 %,Se:0.005 〜0.1 % これらの元素はいずれも被削性を向上させるのに有効な
元素である。
Pb: 0.09% or less, Ca: 0.0005 to 0.003
%, Zr: 0.01 to 0.05%, Te: 0.005 to 0.1%, S
b: 0.005 to 0.1%, Se: 0.005 to 0.1% All of these elements are effective elements for improving machinability.

【0016】Pbについては、0.09%を超えて過剰に添
加すると、摩擦熱によってPbが溶融して表面破壊の起
点となってピッチング寿命を低下させる。CaはAl2
3 の周囲にCaOとして生成してピッチング寿命を劣
化させずに被削性を向上させる。この作用を有効に発揮
させるには、0.0005%以上の添加が必要であるが、0.00
3 %当たりでその効果が飽和に達する。Zrも熱間圧延
時にMnSの変形を抑制してMnSの粒状化に寄与する
ことができるので、ピッチング寿命を劣化させずに被削
性の向上を図ることができる。この作用を有効に発揮さ
せるには0.01%以上の添加が必要であるが、0.05%を超
えるとZrO2 等の非金属介在物が多量に生成し、却っ
て耐ピッチング性が劣化する。Te,Sb,Seについ
ては、上記の様な作用を有効に発揮させるにはいずれも
0.005 %以上の添加が必要である。しかしながら0.1 %
を超えて過剰に添加しても従量的な効果促進が得られ
ず、却って大型の介在物を生成して表面破壊の起点とな
ってピッチング寿命を低下させる。
If Pb is excessively added in excess of 0.09%, frictional heat causes Pb to melt and become a starting point of surface destruction, thereby reducing the pitching life. Ca is Al 2
It is generated as CaO around O 3 to improve machinability without deteriorating the pitching life. To exert this effect effectively, 0.0005% or more must be added.
The effect reaches saturation at around 3%. Since Zr can also suppress the deformation of MnS during hot rolling and contribute to the granulation of MnS, it is possible to improve the machinability without deteriorating the pitching life. In order to exert this effect effectively, it is necessary to add 0.01% or more, but if it exceeds 0.05%, a large amount of non-metallic inclusions such as ZrO 2 are generated, and the pitting resistance deteriorates. Regarding Te, Sb, and Se, in order to effectively exhibit the above-mentioned action,
It is necessary to add 0.005% or more. However 0.1%
If it is added in excess, the amount of promotion of the effect is not obtained, but rather large inclusions are generated, which becomes the starting point of surface destruction and reduces the pitching life.

【0017】上記機械構造用鋼を所望形状に成形加工し
た後は、[C]が上記(1) を満足する様に、そして
[C]と[N]の合計が上記(2) を満足する様に浸炭処
理あるいは浸炭窒化処理を施す。ここで、[C]自体の
範囲を規定した理由は下記の通りである。即ち、浸炭層
の強度を確保するためには[C]が0.6 %以上であるこ
とが必要であるが、[C]が1.3 %を超えるとM3 C型
の炭化物が析出して1μm以上に容易に成長するため好
ましくない。
After the above machine structural steel is formed into a desired shape, [C] satisfies the above (1), and the sum of [C] and [N] satisfies the above (2). Carburizing or carbonitriding is performed in the same manner. Here, the reason for defining the range of [C] itself is as follows. That is, in order to secure the strength of the carburized layer, it is necessary that [C] is 0.6% or more, but when [C] exceeds 1.3%, M 3 C-type carbides are precipitated to reach 1 μm or more. It is not preferable because it grows easily.

【0018】[C]の範囲を上述した様に規定したうえ
で、さらに[C]+[N]の合計範囲を上記(2) の様に
規定した理由は下記の通りである。即ち、上記各元素の
添加量が所定の範囲内にあっても、R*値(R*=[M
o]+1.5 [Mn]+1.5 [Cr]−[Si])が適切
な範囲内でないと希望する物性の機械構造用部品は得ら
れない。R*値は、鋼の化学成分の変動による残留オー
ステナイト量の変化を求めるための式であり、残留オー
ステナイト量を適正値にするために[C]と[N]の合
計量は上記(2) を満足することが必要である。
The reason for defining the range of [C] as described above and further defining the total range of [C] + [N] as described in (2) above is as follows. That is, even if the added amount of each element is within the predetermined range, the R * value (R * = [M
If [o] +1.5 [Mn] +1.5 [Cr]-[Si]) is not within an appropriate range, a mechanical structural component having desired physical properties cannot be obtained. The R * value is an expression for obtaining the change in the retained austenite amount due to the change in the chemical composition of steel, and the total amount of [C] and [N] is the above (2) in order to make the retained austenite amount an appropriate value. It is necessary to satisfy.

【0019】[C]自体の範囲を規定した理由は下記の
通りである。即ち、浸炭層の強度を確保するためには
[C]が0.6 %以上であることが必要であるが、[C]
が1.3%を超えるとM3 C型の炭化物が析出して1μm
以上に容易に成長するため好ましくない。
The reason for defining the range of [C] itself is as follows. That is, in order to secure the strength of the carburized layer, it is necessary that [C] is 0.6% or more.
When the content exceeds 1.3%, M 3 C type carbides precipitate and 1 μm
It is not preferable because it grows easily.

【0020】上記浸炭法としては特に限定されず、通常
の固体浸炭法、液体浸炭法およびガス浸炭法が用いられ
るが、好ましくはガス浸炭法やプラズマ浸炭法、あるい
は両者を併用した方法が用いられる。プラズマ法による
浸炭窒化処理は、以下の様な利点を有する。 (1)高温処理が可能で浸炭速度が大きくなるため、短
時間で浸炭処理を行うことが可能である。 (2)真空中で処理するため、表面に粒界酸化による不
完全焼入れ層が形成されず、部品の耐ピッチング性、耐
衝撃性、曲げ疲労強度がさらに向上する。 (3)従来のガス浸炭法による窒化処理ではアンモニア
を用いているが、プラズマ法の場合は窒素ガスを用いる
ことが可能である。 さらに上記浸炭法の後に窒化処理を行うことにより、以
下の様な利点が得られる。 (1)残留オーステナイト量を適正量生成することがで
きる。 (2)窒素を表面近傍に拡散させることによりオーステ
ナイトに対するCの固溶限界が増大するため、M3 C型
化合物を形成していたCrが再固溶し、炭化物生成層の
マトリックスの焼入れ性が向上する。これに伴って、表
面および表面近傍の硬度が増加し、耐ピッチング性がさ
らに向上する。
The above carburizing method is not particularly limited, and a usual solid carburizing method, a liquid carburizing method and a gas carburizing method can be used, but a gas carburizing method, a plasma carburizing method, or a combination of both methods is preferably used. . Carbonitriding by the plasma method has the following advantages. (1) Since high-temperature treatment is possible and the carburizing speed is high, it is possible to perform carburizing treatment in a short time. (2) Since the treatment is performed in vacuum, an incompletely hardened layer due to grain boundary oxidation is not formed on the surface, and the pitting resistance, impact resistance, and bending fatigue strength of the component are further improved. (3) Ammonia is used in the nitriding treatment by the conventional gas carburizing method, but nitrogen gas can be used in the plasma method. Further, by performing the nitriding treatment after the carburizing method, the following advantages can be obtained. (1) An appropriate amount of retained austenite can be generated. (2) Since the solid solution limit of C with respect to austenite is increased by diffusing nitrogen into the vicinity of the surface, the Cr forming the M 3 C type compound is re-dissolved and the hardenability of the matrix of the carbide forming layer is improved. improves. Along with this, the hardness of the surface and the vicinity of the surface are increased, and the pitting resistance is further improved.

【0021】焼入れ法としては鋼材のA1 変態点以上か
ら焼入れるか、あるいはA1 点変態以下に冷却後再度A
1 点以上に加熱してから焼入れをすることが好ましい。
この様な処理を施すことによって、表層部に1μm以下
の炭化物を面積率で0.5〜10%、かつ表層部の残留
オーステナイト量を15〜50%とすることができる。
直径1μm以下の微細炭化物が面積率で0.5%未満で
は、残留オーステナイト量を適正量生成させても耐ピッ
チング性が低下し、一方10%を超えると曲げ疲労強度
が低下する。残留オーステナイト量が15%未満ではピ
ッチング寿命が低下し、一方残留オーステナイトが50
%を超えると表面硬さが低くなり、曲げ疲労強度が低下
する。
[0021] or a quenching method Ru quenching from above the A 1 transformation point of the steel material, or again after cooling below A 1 point modification A
It is preferable to quench the material after heating it to one or more points.
By performing such a treatment, it is possible to make the surface layer portion have a carbide of 1 μm or less in an area ratio of 0.5 to 10% and the amount of retained austenite in the surface layer portion to be 15 to 50%.
If the area ratio of fine carbides having a diameter of 1 μm or less is less than 0.5%, the pitting resistance is lowered even if an appropriate amount of retained austenite is generated, while if it exceeds 10%, the bending fatigue strength is lowered. If the amount of retained austenite is less than 15%, the pitting life is reduced, while the amount of retained austenite is 50%.
%, The surface hardness becomes low and the bending fatigue strength becomes low.

【0022】以下実施例を用いて本発明を更に詳細に説
明するが、下記実施例は本発明を限定する性質のもので
はなく、前・後記の趣旨に逸脱しない範囲で適宜設計変
更することはいずれも本発明の技術的範囲に含まれるも
のである。
The present invention will be described in more detail with reference to the following examples. However, the following examples are not intended to limit the present invention, and appropriate design changes may be made without departing from the spirit of the preceding and following description. Both are included in the technical scope of the present invention.

【0023】[0023]

【実施例】【Example】

実施例1 表1に本発明に用いられる鋼(No.1〜21)の化学組成
およびR*値を、表2に比較例に用いられる鋼(No.22
〜31)の化学組成およびR*値を示す。なお、No.2〜
25およびNo.27〜31は、焼入性や浸炭性を良くす
るためにCrを積極的に添加したものであり、他の鋼種
についてはCrが不可避的に混入したものである。この
うち、No.9およびNo.17は上記作用をより有効に発
揮させるためにCrの他にNiを積極的に添加したもの
である。図1に示す様に、本発明に用いられる鋼はいず
れも、[C]と[N]の合計が上記(2) を満足するもの
である。図中、○は本発明に用いられる鋼を示し、●は
比較例に用いられる鋼を示す。
Example 1 Table 1 shows the chemical compositions and R * values of the steels (No. 1 to 21) used in the present invention, and Table 2 shows the steels (No. 22) used in the comparative examples.
The chemical composition and R * value of (-31) are shown. In addition, No. 2
Nos. 25 and Nos. 27 to 31 are those in which Cr is positively added in order to improve hardenability and carburization, and Cr is inevitably mixed in other steel types. Of these, No. 9 and No. 17 are those in which Ni is positively added in addition to Cr in order to more effectively exert the above-mentioned action. As shown in FIG. 1, in all of the steels used in the present invention, the sum of [C] and [N] satisfies the above (2). In the figure, ◯ indicates the steel used in the present invention, and ● indicates the steel used in the comparative example.

【0024】[0024]

【表1】 [Table 1]

【0025】[0025]

【表2】 [Table 2]

【0026】これらの鋼を小型炉にて溶製し、熱間鍛造
後焼ならし処理して試験片を加工した。各種試験片形状
に機械加工した後、表面の炭素量が0.9 %になる様に、
900℃で8 時間浸炭処理してから油焼入れし、さらに160
℃で2時間保持の条件で焼戻した。
These steels were melted in a small furnace, hot forged and then subjected to normalizing treatment to process test pieces. After machining into various test piece shapes, make sure that the carbon content on the surface is 0.9%.
Carburize at 900 ° C for 8 hours, then oil quench, then 160
It tempered on condition of hold | maintaining at 2 degreeC for 2 hours.

【0027】得られた試験片を用いて、表面から約5μ
m の位置での硬さ測定と、表面から約25μm での残量オ
ーステナイト量の測定を行った。回転曲げ疲労試験は切
り欠き付き疲労試験片(形状係数:2.0 )を用いて、回
転数が3600rpm.の条件で107回での曲げ疲労強度を求め
た。またピッチング寿命試験は、回転数1800rpm.,すべ
り率40%,面圧5067MPa の試験条件によって、50%の破
損確率でピッチングが発生するまでの繰り返し回数で評
価した。炭化物の測定は、浸炭層の最表面から0.1 mm内
部を走査型電子顕微鏡と画像解析装置を用いて倍率7000
倍で炭化物の面積率と平均粒径を測定した。その結果
を、表3および表4に示す。
Using the obtained test piece, about 5 μm from the surface
The hardness was measured at the position of m and the residual austenite amount was measured at about 25 μm from the surface. In the rotating bending fatigue test, a fatigue test piece with a notch (shape factor: 2.0) was used to determine the bending fatigue strength at 10 7 times under the condition of a rotation speed of 3600 rpm. In addition, the pitching life test was evaluated by the number of repetitions until pitching occurred with a damage probability of 50% under the test conditions of a rotation speed of 1800 rpm., A slip ratio of 40%, and a surface pressure of 5067 MPa. Carbide is measured at a magnification of 7,000 from the outermost surface of the carburized layer using a scanning electron microscope and an image analyzer within 0.1 mm.
The area ratio and average particle size of the carbides were measured by doubling. The results are shown in Tables 3 and 4.

【0028】[0028]

【表3】 [Table 3]

【0029】[0029]

【表4】 [Table 4]

【0030】表3および表4から次の様に考察できる。
本発明に用いられるNo.1〜21の鋼はいずれも表層部に
1μm以下の微細な炭化物が分散し、かつ15〜50%
の残留オーステナイトが生成しており、曲げ疲労強度は
400 〜460 N/mm2と高く、ピッチング寿命も6.2 〜9.7
×106 と長く優れている。これに対し比較例に用いられ
るNo.22〜31の鋼は、本発明で規定する機械構造用鋼の
化学組成の要件を欠くものであり、次に示す様な不都合
が生じている。
The following can be considered from Tables 3 and 4.
In the steels No. 1 to 21 used in the present invention, fine carbides of 1 μm or less are dispersed in the surface layer portion, and 15 to 50%.
Bending fatigue strength is
High 400 to 460 N / mm 2, and pitching life 6.2 to 9.7
It is long and excellent at × 10 6 . On the other hand, the steel Nos. 22 to 31 used in the comparative examples lack the requirements for the chemical composition of the mechanical structural steel specified in the present invention, and have the following inconveniences.

【0031】(1)No.22はVが無添加である鋼を用い
ているため、1μm以下の微細な炭化物が析出していな
い。 (2)No.23はSiが上限を外れた鋼を用いており、残
留オーステナイト量が少ない。 (3)No.24は、Mnが上限を外れた鋼を用いており、
残留オーステナイト量が多過ぎる。 (4)No.25 はNiが上限を外れた鋼を用いており、残
留オーステナイト量が多過ぎる。 (5)No.26 はCrが上限を外れた鋼を用いており、残
留オーステナイト量が多過ぎると共に10μm以上の炭
化物が多量に析出する。 (6)No.27 はMoが下限を外れ、かつVが無添加であ
る鋼を用いており、1μm以下の微細な炭化物が析出せ
ずに10μm以上の炭化物が多量に析出する。 (7)No.28 はMoが上限を外れた場合であり、曲げ疲
労強度とピッチング寿命の向上効果が飽和している。 (8)No.29 はVが上限を外れた場合であり、炭化物量
が多過ぎて曲げ疲労強度が低い。 (9)No.30 はMoが下限を外れた場合であり、表層に
浸炭異常層ができて曲げ疲労強度が低下している。 (10)No.31 はCが下限を外れた場合であり、芯部硬
さが低下すると共に曲げ疲労強度が低下している。
(1) Since No. 22 uses steel with no V added, fine carbides of 1 μm or less are not deposited. (2) No. 23 uses steel in which Si exceeds the upper limit, and the amount of retained austenite is small. (3) No. 24 uses steel whose Mn is out of the upper limit,
Too much retained austenite. (4) No. 25 uses a steel whose Ni content is out of the upper limit, and the amount of retained austenite is too large. (5) No. 26 uses steel in which the amount of Cr is out of the upper limit. The amount of retained austenite is too large, and a large amount of carbides of 10 μm or more precipitates. (6) No. 27 uses steel in which Mo is out of the lower limit and V is not added, and a large amount of carbides of 10 μm or more is deposited without depositing fine carbides of 1 μm or less. (7) No. 28 is the case where Mo exceeds the upper limit, and the effect of improving bending fatigue strength and pitting life is saturated. (8) No. 29 is a case where V is out of the upper limit, and the bending fatigue strength is low because the amount of carbide is too large. (9) No. 30 is the case where Mo is out of the lower limit, and an abnormal carburizing layer is formed on the surface layer, and the bending fatigue strength is reduced. (10) No. 31 is the case where C is below the lower limit, and the core hardness is lowered and the bending fatigue strength is lowered.

【0032】実施例2 本発明に用いられるNo.2の鋼と、比較例に用いられる
No.22〜27の鋼を使用して、浸炭条件あるいは浸炭窒化
条件を変動させたこと以外は実施例1と同様にして上記
試験を行った。その結果を表5に併記する。
Example 2 An example except that the No. 2 steel used in the present invention and the No. 22-27 steels used in the comparative examples were used and the carburizing conditions or carbonitriding conditions were changed. The above test was conducted in the same manner as in 1. The results are also shown in Table 5.

【0033】[0033]

【表5】 [Table 5]

【0034】表5から次の様に考察できる。(a)は、
No.2における[C]+[N]の要件(0.8〜1.
2)を満たさないため、残留オーステナイト量が少な
く、かつ[C]が減少するため浸炭層の硬さが低くな
る。(b)〜(d)は本発明の範囲内であり、曲げ疲労
強度および耐ピッチング性に優れる。(e)および
(f)は、No.2における[C]+[N]の要件(0.
8〜1.2)の上限を外れているため、残留オーステナ
イト量が多過ぎる。(g)は[C]が多過ぎるため、1
0μm以上の粗大な炭化物が多量に析出する。また、
[C]+[N]の要件(0.8〜1.2)の上限を外れ
ているため、残留オーステナイト量が多過ぎる。
From Table 5, the following can be considered. (A) is
No. 2 requirement of [C] + [N] (0.8 to 1.
Since 2) is not satisfied, the amount of retained austenite is small and [C] is reduced, so that the hardness of the carburized layer becomes low. (B) to (d) are within the scope of the present invention and are excellent in bending fatigue strength and pitting resistance. (E) and (f) are requirements of [C] + [N] in No. 2 (0.
Since it is outside the upper limit of 8 to 1.2), the amount of retained austenite is too large. (G) has too much [C], so 1
A large amount of coarse carbide of 0 μm or more is deposited. Also,
Since the upper limit of the requirement of [C] + [N] (0.8 to 1.2) is exceeded, the amount of retained austenite is too large.

【0035】(h)はVが無添加のため、[C]+
[N]の量を増加させても、微細な炭化物の析出は見ら
れなかった。(i)は[C]+[N]の量を増やすこと
により残留オーステナイト量を増加させたが、表層部に
浸炭異常層が生成した。(j)〜(l)は[C]+
[N]の量を少なくすることにより残留オーステナイト
量を減少させたものの依然として多過ぎる傾向にあり、
また[C]が減少したため、浸炭層の硬さが低下した。
(m)はVが無添加でMoが少ないため、微細な炭化物
が析出しない。
In (h), since V is not added, [C] +
Even if the amount of [N] was increased, fine carbide precipitation was not observed. In (i), the amount of retained austenite was increased by increasing the amount of [C] + [N], but a carburized abnormal layer was formed in the surface layer portion. (J) to (l) are [C] +
Although the amount of retained austenite was reduced by decreasing the amount of [N], it still tends to be too large.
Further, since the [C] was reduced, the hardness of the carburized layer was reduced.
In (m), since V is not added and Mo is small, fine carbide does not precipitate.

【0036】[0036]

【発明の効果】本発明の製造方法は以上の様に構成され
ており、高い疲労強度を確保することができると共にピ
ッチング寿命を大幅に向上することができる機械構造用
部品を製造することができる。
The manufacturing method of the present invention is configured as described above, and it is possible to manufacture a machine structural component that can secure a high fatigue strength and can significantly improve the pitching life. .

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

【図1】浸炭処理時あるいは浸炭窒化処理後の表面の炭
素量[C]と窒素量[N]の合計と、R*値との関係を
示すグラフである。
FIG. 1 is a graph showing the relationship between the R * value and the total amount of carbon [C] and nitrogen [N] on the surface during carburizing or after carbonitriding.

───────────────────────────────────────────────────── フロントページの続き (72)発明者 松島 義武 兵庫県神戸市灘区灘浜東町2番地 株式会 社神戸製鋼所神戸製鉄所内 (72)発明者 安部 聡 兵庫県神戸市灘区灘浜東町2番地 株式会 社神戸製鋼所神戸製鉄所内 (72)発明者 小倉 真義 神奈川県横浜市神奈川区宝町2番地 日産 自動車株式会社内 (72)発明者 渡辺 陽一 神奈川県横浜市神奈川区宝町2番地 日産 自動車株式会社内 (72)発明者 松本 隆 神奈川県横浜市神奈川区宝町2番地 日産 自動車株式会社内 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoshitake Matsushima, 2 Nadahama Higashi-cho, Nada-ku, Kobe-shi, Hyogo Stock Company Kobe Steel Works, Kobe Steel Works (72) Inventor Satoshi Abe 2 Nada-hama-higashi, Nada-ku, Kobe, Hyogo Prefecture Stock Company Kobe Steel Works Kobe Steel Works (72) Inventor Masayoshi Ogura 2 Takara-cho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Yoichi Watanabe 2 Takara-cho, Kanagawa-ku, Yokohama, Nissan Nissan Motor Co., Ltd. (72) Inventor Takashi Matsumoto 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd.

Claims (4)

【特許請求の範囲】[Claims] 【請求項1】 重量%でC:0.1 〜0.40%,Si:0.05
〜2%、Mn:0.4〜2%,S:0.005 〜0.03%,A
l:0.005 〜0.05%,N:0.005 〜0.03%,Mo:0.05
〜1%,V:0.1 〜1%を夫々含有し、残部鉄および不
可避不純物からなる機械構造用鋼を、所定形状に成形加
工後、表面の炭素量[C]と窒素量[N]が下記(1) お
よび(2) : 0.6 %≦[C]≦1.3 % …(1) 1.14−0.15R*≦[C]+[N]≦1.55−0.15R* …(2) 但し、R*=[Mo]+1.5 [Mn]+1.5 [Cr]−
[Si]であり、 [ ]は鋼中に存在する各元素の重量%を示す。を満足
する様に前記浸炭処理あるいは浸炭窒化処理を施すこと
によって、表層部に1μm以下の炭化物を面積率で0.
5〜10%、かつ表層部の残留オーステナイト量を15
〜50%とすることを特徴とする機械構造用部品の製造
方法。
1. C: 0.1 to 0.40% by weight, Si: 0.05
~ 2%, Mn: 0.4 to 2%, S: 0.005 to 0.03%, A
1: 0.005 to 0.05%, N: 0.005 to 0.03%, Mo: 0.05
~ 1%, V: 0.1 ~ 1%, respectively, the mechanical structure steel consisting of the balance iron and unavoidable impurities after forming into a predetermined shape, the surface carbon amount [C] and nitrogen amount [N] (1) and (2): 0.6% ≦ [C] ≦ 1.3% (1) 1.14-0.15R * ≦ [C] + [N] ≦ 1.55-0.15R * (2) where R * = [ Mo] +1.5 [Mn] +1.5 [Cr]-
[Si], and [] indicates the weight% of each element present in the steel. By carrying out the carburizing treatment or carbonitriding treatment so as to satisfy the above condition, carbide having a surface area of 1 μm or less in area ratio of 0.
5-10%, and the amount of retained austenite in the surface layer is 15
A method for manufacturing a machine structural component, wherein the content is set to 50%.
【請求項2】 前記機械構造用鋼が、更にCr:0.2 〜
3%およびNi:0.2 〜2%よりなる群から選択される
少なくとも1種を含有するものである請求項1に記載の
機械構造用部品の製造方法。
2. The machine structural steel further comprises Cr: 0.2-
The method for producing a machine structural component according to claim 1, which contains at least one selected from the group consisting of 3% and Ni: 0.2 to 2%.
【請求項3】 前記機械構造用鋼が、更にNb:0.01〜
0.5 %,Ti:0.01〜0.05%,W:0.01〜1.5 %および
B:0.0003〜0.010 %よりなる群から選択される少なく
とも1種を含有するものである請求項1または2に記載
の機械構造用部品の製造方法。
3. The machine structural steel further comprises Nb: 0.01-
The mechanical structure according to claim 1 or 2, which contains at least one selected from the group consisting of 0.5%, Ti: 0.01 to 0.05%, W: 0.01 to 1.5% and B: 0.0003 to 0.010%. Manufacturing method of parts.
【請求項4】 前記機械構造用鋼が、更にPb:0.09%
以下,Ca:0.0005〜0.003 %,Zr:0.01〜0.05%,
Te:0.005 〜0.1 %,Sb:0.005 〜0.1%およびS
e:0.005 〜0.1 %よりなる群から選択される少なくと
も1種を含有するものである請求項1〜3のいずれかに
記載の機械構造用部品の製造方法。
4. The mechanical structural steel further comprises Pb: 0.09%.
Below, Ca: 0.0005 to 0.003%, Zr: 0.01 to 0.05%,
Te: 0.005-0.1%, Sb: 0.005-0.1% and S
e: The method for producing a machine structural part according to any one of claims 1 to 3, which contains at least one selected from the group consisting of 0.005 to 0.1%.
JP33869693A 1993-12-28 1993-12-28 Manufacture of parts for machine structure use Withdrawn JPH07188895A (en)

Priority Applications (1)

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Application Number Priority Date Filing Date Title
JP33869693A JPH07188895A (en) 1993-12-28 1993-12-28 Manufacture of parts for machine structure use

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JPH07188895A true JPH07188895A (en) 1995-07-25

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JP2005090680A (en) * 2003-09-19 2005-04-07 Koyo Seiko Co Ltd Rolling bearing part and method of manufacturing the same
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002121645A (en) * 2000-10-17 2002-04-26 Nkk Bars & Shapes Co Ltd Steel for gear having excellent dedendum bending fatigue characteristic and facial pressure fatigue characteristic and gear
JP4504550B2 (en) * 2000-10-17 2010-07-14 Jfe条鋼株式会社 Steel for gears and gears with excellent root bending fatigue and surface fatigue properties
JP2005090680A (en) * 2003-09-19 2005-04-07 Koyo Seiko Co Ltd Rolling bearing part and method of manufacturing the same
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JP2007246941A (en) * 2006-03-13 2007-09-27 Sanyo Special Steel Co Ltd Component for high facial pressure and its production method
JP2009242918A (en) * 2008-03-31 2009-10-22 Jfe Steel Corp Component for machine structure having excellent rolling fatigue property, and method for producing the same
KR20190008915A (en) 2016-05-31 2019-01-25 제이에프이 스틸 가부시키가이샤 Progressive steel and its manufacturing method and manufacturing method of gear parts
US11174543B2 (en) 2016-05-31 2021-11-16 Jfe Steel Corporation Case hardening steel, method of producing case hardening steel, and method of producing gear part
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