JPH08165556A - Production of pitting resisting soft-nitrided gear - Google Patents
Production of pitting resisting soft-nitrided gearInfo
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- JPH08165556A JPH08165556A JP30927294A JP30927294A JPH08165556A JP H08165556 A JPH08165556 A JP H08165556A JP 30927294 A JP30927294 A JP 30927294A JP 30927294 A JP30927294 A JP 30927294A JP H08165556 A JPH08165556 A JP H08165556A
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、耐ピッチング性に優れ
た高強度軟窒化歯車の製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-strength soft nitrided gear having excellent pitting resistance.
【０００２】[0002]
【従来の技術】一般に、高面圧下で使用される高強度歯
車は、表面の耐摩耗性、耐折損性、耐疲労性等を高める
ため、肌焼鋼に表面硬化処理を施したものが使用されて
いる。そのなかで、窒化および軟窒化処理は、浸炭・高
周波焼入に比べ、処理後の熱処理歪が少なく寸法精度の
高い歯車の製造が可能となる。2. Description of the Related Art Generally, high-strength gears used under high surface pressure are made of case-hardening steel that has undergone a surface hardening treatment in order to improve the wear resistance, breakage resistance, fatigue resistance, etc. of the surface. Has been done. Among them, the nitriding and soft nitriding treatments can produce a gear with less heat treatment distortion after the treatment and higher dimensional accuracy than carburizing and induction hardening.
【０００３】しかし、窒化処理は、熱処理歪の問題はな
いものの、通常、処理時間が50〜100 hrと著しく長く、
処理後も表面の脆い化合物層 (ポーラス層) を除去する
必要があるなど、製造上に問題があった。However, although the nitriding treatment does not have a problem of heat treatment distortion, it usually takes a remarkably long treatment time of 50 to 100 hr.
Even after the treatment, there was a problem in production such as the need to remove the brittle compound layer (porous layer) on the surface.
【０００４】これに対して、軟窒化処理は、一般に500
〜600 ℃の温度域でＮとＣを同時に侵入・拡散させて、
表面硬化をはかる処理であり、窒化処理に比べて処理時
間が約半分ですみ、特にＲＸガス（ＣＯ：23vol%、Ｈ2:
30vol%、Ｎ2:47vol%) とＮＨ3 ガス等を雰囲気ガスとし
て処理を行うガス軟窒化処理は多量生産および安定操業
が可能なことから、熱処理歪の少ない歯車用表面処理法
として急速に普及しつつある。On the other hand, the soft nitriding treatment is generally performed at 500
N and C are simultaneously penetrated and diffused in the temperature range of ~ 600 ℃,
This is a surface hardening treatment, and the treatment time is about half that of nitriding treatment. In particular, RX gas (CO: 23vol%, H 2 :
The gas soft nitriding treatment, which uses 30 vol%, N 2 : 47 vol%) and NH 3 gas as the atmosphere gas, can be mass-produced and stably operated, and is rapidly popularized as a surface treatment method for gears with less heat treatment distortion. I am doing it.
【０００５】しかし、現在、ガス軟窒化処理が用いられ
ている歯車用炭素鋼や低合金鋼は、歯車高強度化の動向
に対し、十分な表面硬さおよび硬化深さが得られておら
ず、また、歯車実働時に最表面の化合物層が剥離する問
題 (耐ピッチング性の低下)が生じてきている。However, at present, carbon steel for gears and low alloy steels for which gas soft nitriding treatment is used have not been able to obtain sufficient surface hardness and hardening depth in response to the trend toward higher strength of gears. In addition, there is a problem that the compound layer on the outermost surface is peeled off during the actual operation of the gear (decrease in pitting resistance).
【０００６】このような問題を解決するために特開昭59
−16950 号公報の開示する発明では、Al、Cr、Ｖ等の化
学組成を制限することによって表面硬さ・硬化深さの向
上を図っているが、歯車接触部で生じるピッチング特性
に関しては充分でない。[0006] In order to solve such a problem
In the invention disclosed in Japanese Patent Publication No. 16950, the surface hardness / hardening depth is improved by limiting the chemical composition of Al, Cr, V, etc., but the pitching characteristics generated at the gear contact portion are not sufficient. .
【０００７】また、特開昭63−93821 号公報開示の発明
では、軟窒化処理品のポーラス層をショットピーニング
により除去し、耐疲労性向上を図ることを提案している
が、耐ピッチング性に関しては充分でなく、耐ピッチン
グ性に優れた軟窒化処理歯車の開発が望まれていた。Further, in the invention disclosed in Japanese Patent Laid-Open No. 63-93821, it has been proposed to remove the porous layer of the soft nitriding product by shot peening to improve fatigue resistance. However, the development of soft nitriding gears with excellent pitting resistance has been desired.
【０００８】[0008]
【発明が解決しようとする課題】本発明の目的は、以上
のような問題を解決し、軟窒化特性に優れ、耐ピッチン
グ性に優れる高強度軟窒化歯車の製造方法を提供するこ
とである。また本発明の具体的な目的は、歯車歯面の耐
ピッチング性の向上を発揮でき、疲労強度の上昇、表面
硬さの増加、硬化深さの深化が得られる軟窒化歯車の製
造方法を提供することである。SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a method for producing a high-strength soft-nitrided gear having excellent soft-nitriding characteristics and excellent pitting resistance. Further, a specific object of the present invention is to provide a method for producing a soft-nitrided gear that can exhibit improvement in pitting resistance of gear tooth surfaces, increase fatigue strength, increase surface hardness, and deepen hardening depth. It is to be.
【０００９】[0009]
【課題を解決するための手段】本発明者らは、かかる目
的を達成すべく、種々検討を重ね、次のような知見を得
た。Means for Solving the Problems The inventors of the present invention have made various studies in order to achieve such an object, and have obtained the following findings.
【００１０】軟窒化特性向上策 Cr、Ｖ、Alを最適添加することで、表面硬さおよび硬化
深さを向上させ、軟窒化処理時間の短縮に効果がある。 Measures for improving soft nitriding characteristics By optimally adding Cr, V, and Al, the surface hardness and the hardening depth are improved, and it is effective in shortening the soft nitriding treatment time.
【００１１】耐ピッチング性向上策 ガス軟窒化時のガス組成および処理温度に制限を加え、
歯車接触部である化合物層の組成を単層化することが有
効である。また、表層のポーラス層の厚さを制限するこ
とが有効である。 Measures for improving pitting resistance : The gas composition and treatment temperature during gas nitrocarburizing are limited,
It is effective to make the composition of the compound layer, which is the gear contact portion, into a single layer. Further, it is effective to limit the thickness of the surface porous layer.
【００１２】かくして本発明によれば、軟窒化特性に優
れ、耐ピッチング性に優れる軟窒化歯車を得ることがで
き、本発明の要旨とするところは、重量％で、Ｃ：0.15
〜0.50％、 Si：1.20％以下、 Mn：0.60〜1.30
％、Cr：0.70〜1.50％、 Mo：０〜0.50％、 Al：
0.02〜0.10％、Ｎ： 0.006〜0.020 ％、Ｖ：0.05〜0.20
％、残部Feおよび不可避的不純物の組成を有する鋼から
なる歯車に、ＲＸ／ＮＨ3 ＝0.5 〜1.5 のガス容積組成
比、かつ550 〜650 ℃の処理温度でガス軟窒化処理を施
し、その後ポーラス層厚さを10μm 以下にすることを特
徴とする、耐ピッチング性に優れる高強度軟窒化歯車の
製造方法である。Thus, according to the present invention, a soft nitrided gear having excellent soft nitriding characteristics and excellent pitting resistance can be obtained. The gist of the present invention is to provide C: 0.15% by weight.
~ 0.50%, Si: 1.20% or less, Mn: 0.60 to 1.30
%, Cr: 0.70 to 1.50%, Mo: 0 to 0.50%, Al:
0.02 to 0.10%, N: 0.006 to 0.020%, V: 0.05 to 0.20
%, The balance Fe and inevitable impurities, the gears made of steel are subjected to gas soft nitriding at a gas volume composition ratio of RX / NH 3 = 0.5 to 1.5 and a processing temperature of 550 to 650 ° C., and then porous. A method for producing a high-strength soft nitrided gear having excellent pitting resistance, which is characterized in that the layer thickness is 10 μm or less.
【００１３】本発明の実施態様によれば、前記組成が、
重量％で、さらにＳ： 0.005〜0.060 ％、Pb：0.02〜0.
20％、およびCa：0.0050〜0.010 ％から成る群から選ん
だ１種または２種以上を含有していてもよい。According to an embodiment of the present invention, the composition comprises
% By weight, S: 0.005 to 0.060%, Pb: 0.02 to 0.
One or two or more selected from the group consisting of 20% and Ca: 0.0050 to 0.010% may be contained.
【００１４】[0014]
【作用】次に、本発明において製造条件を上述のように
限定した理由についてその作用とともに詳述する。な
お、本明細書において、「％」はとくに断りがない限
り、「重量％」である。Next, the reason for limiting the manufacturing conditions in the present invention as described above will be described in detail together with its operation. In the present specification, “%” is “% by weight” unless otherwise specified.
【００１５】Ｃ：0.15〜0.50％ Ｃは焼入性を確保して所定の芯部硬さを確保するために
必要な元素であり、このためには0.15％以上含有する必
要が有るが、0.50％を超える場合には、焼入性増大によ
り靱性が低下するとともに切削性が大幅に低下する。よ
って、Ｃ含有量を0.15〜0.50％とした。好ましくは、0.
15〜0.35％である。C: 0.15 to 0.50% C is an element necessary to secure hardenability and a predetermined core hardness, and for this purpose, it is necessary to contain 0.15% or more, but 0.50 If it exceeds 0.1%, the toughness is lowered due to the increase in the hardenability and the machinability is greatly lowered. Therefore, the C content is set to 0.15 to 0.50%. Preferably, 0.
15 to 0.35%.
【００１６】Si：1.20％以下 Siは脱酸剤として添加されるが、固溶強化を示し、1.20
％を超えると靱性および切削性を悪化させるので、1.20
％以下とした。好ましくは、0.50％以下である。Si: 1.20% or less Although Si is added as a deoxidizing agent, it shows solid solution strengthening and is 1.20%.
%, It deteriorates toughness and machinability, so 1.20
% Or less. Preferably, it is 0.50% or less.
【００１７】Mn：0.60〜1.30％ Mnは脱酸剤として不可欠であり、また芯部強度を確保す
る上で有効な元素であり、芯部硬さ確保のためには他元
素の関連において0.60％以上必要である。また、1.30％
を超えると加工性および切削性を害するので、0.60〜1.
30％の範囲とした。好ましくは、0.70〜1.10％である。Mn: 0.60 to 1.30% Mn is indispensable as a deoxidizing agent and is an element effective in securing core strength. In order to secure core hardness, 0.60% in relation to other elements. The above is necessary. Also, 1.30%
If it exceeds 1.0, workability and machinability will be impaired, so 0.60 to 1.
The range was 30%. It is preferably 0.70 to 1.10%.
【００１８】Cr：0.70〜1.50％ Crは芯部強度を向上させる他、軟窒化性に関しては、多
く添加すればするほど表面硬さ・硬化深さを上昇させる
元素であるが、0.70％未満では軟窒化性と芯部強度の向
上効果を得ることができず、また1.50％を超えると、表
面に強固な軟窒化層を形成するため、逆に硬化深さは減
少する。よって、0.70〜1.50％の範囲とした。好ましく
は、0.80〜1.20％である。Cr: 0.70 to 1.50% Cr improves the strength of the core and, with regard to soft nitriding, is an element that increases the surface hardness and the hardening depth as more is added, but if less than 0.70% The effect of improving the soft nitriding property and the strength of the core part cannot be obtained, and when it exceeds 1.50%, a strong soft nitriding layer is formed on the surface, so that the hardening depth conversely decreases. Therefore, the range is 0.70 to 1.50%. Preferably, it is 0.80 to 1.20%.
【００１９】Mo：０〜0.50％ Moは良好な焼入性を確保すると同時に靱性を向上させる
のに有効な任意添加元素であるが、0.50％を超えると効
果が飽和するため、０〜0.50％とした。好ましくは、0.
35％以下である。Mo: 0 to 0.50% Mo is an optional additive element that is effective in securing good hardenability and at the same time improving toughness, but if it exceeds 0.50%, the effect is saturated, so 0 to 0.50%. And Preferably, 0.
35% or less.
【００２０】Al：0.02〜0.10％ Alは溶製時に脱酸剤として用いられ、軟窒化に際して侵
入してきたＮと結合して表面硬さを高め、かつ硬化深さ
を深めるのに有効な元素である。そのような効果を発揮
するには0.02％以上の含有が必要で、また0.10％を超え
ると表面に強固な軟窒化層を形成するため、逆に硬化深
さは減少する。よって、0.02〜0.10％の範囲とした。好
ましくは、0.03〜0.07％である。Al: 0.02 to 0.10% Al is used as a deoxidizing agent during melting, and is an element effective in increasing the surface hardness by combining with N invading during soft nitriding and deepening the hardening depth. is there. In order to exert such an effect, the content of 0.02% or more is required, and if it exceeds 0.10%, a strong soft nitriding layer is formed on the surface, so that the hardening depth decreases. Therefore, the range is 0.02 to 0.10%. It is preferably 0.03 to 0.07%.
【００２１】Ｎ： 0.006〜0.020 ％ Ｎは結晶粒度を微細化させ、芯部の靱性を向上させる。
このためには、0.006％以上の含有が必要となる。また
0.02％を超えるとＶ窒化物の生成が顕著になり靱性が逆
に劣化し始める。よって、 0.006〜0.020 ％の範囲とし
た。好ましくは、0.006 〜0.015 ％である。N: 0.006 to 0.020% N refines the grain size and improves the toughness of the core.
For this purpose, the content of 0.006% or more is required. Also
If it exceeds 0.02%, the formation of V-nitride becomes remarkable and the toughness starts to deteriorate. Therefore, the range is 0.006 to 0.020%. Preferably, it is 0.006 to 0.015%.
【００２２】Ｖ：0.05〜0.20％ Ｖは焼入れ性を向上させると共に、軟窒化時にＮとＣと
結合し微細なＶ炭窒化物を析出することにより、表面硬
さおよび硬化深さを向上させる。特に硬化深さ増加に対
する寄与が大きいことから、耐疲労性等にきわめて効果
が大きい。そのような効果を発揮させるには、0.05％以
上必要となるが、0.20％超になると含有Ｎと結合して粗
大なＶ窒化物が析出し芯部靱性悪化となる。よって、0.
05〜0.20％の範囲とした。V: 0.05 to 0.20% V improves the hardenability and also improves the surface hardness and the hardening depth by combining with N and C and precipitating fine V carbonitride during soft nitriding. In particular, since it greatly contributes to the increase in the hardening depth, it is extremely effective in fatigue resistance and the like. In order to exert such an effect, 0.05% or more is necessary, but if it exceeds 0.20%, it is combined with the contained N and coarse V nitrides are precipitated to deteriorate the core toughness. Therefore, 0.
The range was from 05 to 0.20%.
【００２３】本発明に係る軟窒化鋼は、以上の元素を必
須成分とするものであるが、必要に応じて、快削成分と
して、Ｓ、Pb、Caよりなる群から選ばれる１種以上を含
有するものであってもよい。The nitrocarburized steel according to the present invention contains the above elements as essential components, but if necessary, one or more selected from the group consisting of S, Pb and Ca may be used as a free-cutting component. It may be contained.
【００２４】Ｓ： 0.005〜0.060 ％、Pb：0.02〜0.20
％、Ca：0.0050〜0.010 ％ Ｓ、Pb、Caはいずれも被削性を向上させるための元素で
ある。更なる被削性の向上を行うには、これらの元素は
少なくとも１種、それぞれＳ： 0.005％、Pb：0.02％、
Ca：0.0050％以上の添加が必要である。しかし、上記の
各上限を超えて添加しても被削性の顕著な向上効果は認
められず、かえって靱性を低下させることになるから、
Ｓ： 0.005〜0.060 ％、Pb：0.02〜0.20％、Ca：0.0050
〜0.010％の少なくとも１種とした。S: 0.005-0.060%, Pb: 0.02-0.20
%, Ca: 0.0050 to 0.010% S, Pb, and Ca are all elements for improving machinability. In order to further improve machinability, at least one of these elements, S: 0.005%, Pb: 0.02%,
Ca: It is necessary to add 0.0050% or more. However, no significant improvement in machinability is observed even if added in excess of the above respective upper limits, rather reducing toughness.
S: 0.005 to 0.060%, Pb: 0.02 to 0.20%, Ca: 0.0050
.About.0.010% of at least one kind.
【００２５】図１は、本発明にかかる軟窒化歯車の表面
部の金属組織の模式的説明図であり、図中、最表層から
順に、ポーラス層10、化合物層12、そして拡散層13から
成り、芯部へと続いている。FIG. 1 is a schematic explanatory view of the metallographic structure of the surface portion of a soft nitrided gear according to the present invention. In the figure, a porous layer 10, a compound layer 12 and a diffusion layer 13 are arranged in this order from the outermost layer. , Continues to the core.
【００２６】なお、従来の窒化層も一般には、図１に示
したように、表層近傍に化合物層12(ポーラス層10と緻
密層からなる) が存在し、その内部が拡散層13と呼ばれ
るマトリックスに窒素が固溶した層となる。生成される
化合物層の最表層であるポーラス層10は通常酸化物を含
有していると言われ、化合物層12の厚さの1/3 以下であ
ることが耐剥離特性の観点からは望ましいとされ、これ
が現場的な良品判定基準とされている。A conventional nitride layer generally has a compound layer 12 (consisting of a porous layer 10 and a dense layer) near the surface layer as shown in FIG. 1, and the inside thereof is a matrix called a diffusion layer 13. A layer in which nitrogen is solid-solved is formed. It is said that the porous layer 10 which is the outermost layer of the produced compound layer usually contains an oxide, and it is desirable that it is 1/3 or less of the thickness of the compound layer 12 from the viewpoint of peel resistance. This is the on-site standard for non-defective products.
【００２７】図１に示すように、軟窒化処理後の化合物
層・拡散層の形態 (第１図) は耐ピッチング性に影響を
及ぼす。特に、化合物層の制御は非常に重要となる。軟
窒化処理により、ξ (Fe2 Ｎ) 、ε (Fe2-3 Ｎ) 、γ'
(Fe4 Ｎ) 、Fe3 Ｃの化合物層を生じるが、これらが混
在すると、組織の境界において応力が発生し、耐ピッチ
ング性が低下する。As shown in FIG. 1, the morphology (FIG. 1) of the compound layer / diffusion layer after the soft nitriding treatment affects the pitting resistance. Especially, control of the compound layer is very important. By soft nitriding treatment, ξ (Fe 2 N), ε (Fe 2-3 N), γ '
Although a compound layer of (Fe 4 N) and Fe 3 C is produced, when these are mixed, stress is generated at the boundary of the structure and the pitting resistance is deteriorated.
【００２８】そこで、強固なε層を単一形成させること
で、化合物層および耐ピッチング性の強化を図ることが
でき、このε層の形成は処理時のガス組成比および処理
温度の調整で可能となることを見出した。そこで、本鋼
を用いた場合、以下の制限を持たなければならない。Therefore, by forming a single strong ε layer, it is possible to enhance the compound layer and pitting resistance, and this ε layer can be formed by adjusting the gas composition ratio and the treatment temperature during the treatment. I found that. Therefore, when the present steel is used, it must have the following restrictions.
【００２９】ＲＸ／ＮＨ3 ＝0.5 〜1.5 のガス容積組成
比 ガス容積組成比が0.5 未満では、非常に脆いξ層やγ'
層が形成され、また、1.5 を超えると化合物中にFe3 Ｃ
が混在することから、ガス組成をＲＸ／ＮＨ3＝0.5 〜
1.5 とした。好ましくは 0.7〜1.3 である。なお、ＲＸ
ガスとしては特に制限されない。Gas volume composition ratio of RX / NH 3 = 0.5 to 1.5 When the gas volume composition ratio is less than 0.5, a very brittle ξ layer and γ '
A layer is formed, and when it exceeds 1.5, Fe 3 C is contained in the compound.
Gas composition is RX / NH 3 = 0.5-
It was set to 1.5. It is preferably 0.7 to 1.3. In addition, RX
The gas is not particularly limited.
【００３０】550 〜650 ℃の処理温度 処理温度が550 ℃未満になると窒化速度の低下による窒
化特性の悪化となる。また、650 ℃を超えると化合物中
にFe3 Ｃが混在することから、処理温度を550〜650 ℃
とした。Treatment temperature of 550 to 650 ° C. If the treatment temperature is less than 550 ° C., the nitriding rate is lowered and the nitriding characteristics are deteriorated. Further, since the Fe 3 C is mixed in the compound when the temperature exceeds 650 ° C, the treatment temperature is 550 to 650 ° C.
And
【００３１】ポーラス層厚さを10μm 以下 ポーラス層厚さの制御は耐ピッチング性・耐摩耗性・耐
疲労性等を向上させるのに必須な因子である。特に10μ
m を超えると、ポーラス層先端部は鋭角で空洞が多く脆
弱になり、揺動部に用いた場合、ポーラス層内部に存在
する長いマイクロクラックの先端への応力負荷が増大
し、急速に内部に亀裂の伝播が進行し、耐ピッチング性
が低下することから、10μm 以下とした。Porous layer thickness is 10 μm or less Control of the porous layer thickness is an essential factor for improving pitting resistance, abrasion resistance, fatigue resistance and the like. Especially 10μ
When it exceeds m, the tip of the porous layer becomes sharp and fragile with many cavities, and when used in the oscillating part, the stress load on the tip of the long microcracks existing inside the porous layer increases and the inside of the porous layer rapidly increases. Since the propagation of cracks progresses and the pitting resistance deteriorates, the thickness was made 10 μm or less.
【００３２】また、接触体同士の摩擦抵抗の増加による
潤滑状態の悪化を考慮し、特に耐ピッチング性が要求さ
れる場合は、１〜５μm が望ましい。なお、ポーラス層
の厚さは窒化処理温度を変更することで変えることがで
きるが、一旦形成されたポーラス層を研摩して除去する
ことで10μm 以下としてもよい。次に、実施例によって
本発明の作用効果をさらに具体的に詳述する。Further, considering the deterioration of the lubrication state due to the increase of the frictional resistance between the contact bodies, it is preferably 1 to 5 μm particularly when the pitting resistance is required. The thickness of the porous layer can be changed by changing the nitriding temperature, but it may be 10 μm or less by polishing and removing the once formed porous layer. Next, the working effects of the present invention will be described in more detail with reference to Examples.
【００３３】[0033]
実施例１ 本例は、本発明方法で製造された鋼の軟窒化特性をみる
のである。表１に示す化学成分を有する鋼を溶製後、各
々160 mm角の鋼片とし、この鋼片を1100℃に加熱し、仕
上温度950 ℃の熱間鍛造を施して直径30mmの丸棒とした
後、放冷した。Example 1 This example looks at the nitrocarburizing properties of the steel produced by the method of the present invention. After smelting steels having the chemical composition shown in Table 1, each was made into a 160 mm square piece, which was heated to 1100 ° C and hot-forged at a finishing temperature of 950 ° C to form a round bar with a diameter of 30 mm. After that, it was left to cool.
【００３４】950 ℃で焼きならし後、歯車作製時の基礎
特性を調査することから、直径20mmの試験片、ＪＩＳ４
号引張試験片およびＪＩＳ２号回転曲げ疲労試験片をそ
れぞれ採取し、処理条件570 ℃×３hr→ＯＣ (油冷) 、
ＲＸ／ＮＨ3 ＝１のガス軟窒化処理を施した。After normalizing at 950.degree. C., the basic characteristics of gears were investigated, so that a test piece with a diameter of 20 mm, JIS4
No. 10 tensile test piece and JIS No. 2 rotating bending fatigue test piece were collected and treated under the treatment conditions of 570 ° C x 3 hrs → OC (oil cooling),
A gas soft nitriding treatment of RX / NH 3 = 1 was performed.
【００３５】これらの試験片を用い、断面調査、引張試
験および疲労試験を行った。試験後の測定結果を表２に
示す。これらの結果からも分かるように、表２において
目標値を示し歯車製造での必要特性を示しているが、本
発明例では表面硬さ、硬化深さ、引張強度、伸びおよび
疲労強度すべてにおいて特性を満足している。Using these test pieces, cross-section investigation, tensile test and fatigue test were conducted. The measurement results after the test are shown in Table 2. As can be seen from these results, the target values are shown in Table 2 and the necessary characteristics in gear manufacturing are shown. In the present invention example, the characteristics are all in terms of surface hardness, hardening depth, tensile strength, elongation and fatigue strength. Are satisfied.
【００３６】一方、供試鋼 No.11〜27と従来鋼No.28 、
29の比較鋼のうち、Ｃ、Mn、Crが規定より少ない鋼 ( N
o.11、14、16) は、引張強度が大きく低下し、目標をは
ずれている。On the other hand, test steel Nos. 11 to 27 and conventional steel No. 28,
Of the 29 comparative steels, the steel with less C, Mn, and Cr than specified (N
Nos. 11, 14, 16) had a large decrease in tensile strength, which was outside the target.
【００３７】Ｃ、Si、Mn、Cr、Mo、Ｖ、Ｎが規定より多
い鋼 ( No.12、13、15、17、18、20、24、25、26、27)
およびＮが規定より少ない鋼 ( No.23) は強度は満足す
るものの、伸びが大きく低下し、目標をはずれている。Steel containing more than C, Si, Mn, Cr, Mo, V and N than specified (No. 12, 13, 15, 17, 18, 20, 24, 25, 26, 27)
The steel (No. 23) with N and less than the specified value satisfies the strength, but the elongation is greatly reduced, which is outside the target.
【００３８】Cr 、Ｖ、Alが規定より少ない鋼 ( No.1
6、19、21、26) やCr、Alが規定より多い鋼 ( No.17、2
2、27) さらに従来鋼 ( No.28、29) では、表面硬さ、
硬化深さともに低く、目標に達していない。以上のよう
に、本発明の範囲を外れる組成を有するものは、いずれ
も目標とする特性を得ることができない。Steel containing less Cr, V, and Al than specified (No. 1
(6, 19, 21, 26) and steel with more Cr and Al than specified (No. 17, 2)
(2, 27) Furthermore, in the conventional steel (No. 28, 29), the surface hardness,
The curing depth is low and the target has not been reached. As described above, any of those having a composition outside the scope of the present invention cannot obtain the target characteristics.
【００３９】[0039]
【表１】 [Table 1]
【００４０】[0040]
【表２】 [Table 2]
【００４１】実施例２ 本例では、処理条件の影響を見る。直径50mmの丸棒を素
材とした表１に示す供試鋼の No.２、９を、熱間鍛造、
焼ならし、機械加工により外径：120 mm、モジュール：
2.0 、歯数：56、歯幅：20mm、歯たけ：4.6 mmの歯車を
作製し、これらを試験品としてガス軟窒化処理を施し
た。Example 2 In this example, the effect of processing conditions is examined. Hot forging of No. 2 and 9 of the sample steel shown in Table 1 using a round bar with a diameter of 50 mm as a material
Normalized and machined, outer diameter: 120 mm, module:
Gears with 2.0, number of teeth: 56, tooth width: 20 mm, and tooth depth: 4.6 mm were produced, and these were subjected to gas nitrocarburizing treatment as test products.
【００４２】ガス軟窒化処理はガス組成比、処理温度を
変えた表３の条件で実施し、歯車疲労試験をおこなっ
た。評価は、トルク：40Kgf 、回転速度：1000RPM 、油
温：80℃の条件下で歯車を回転させ、107 回転時の歯面
１枚 (接触面積：52 mm2) 当たりのピッチング面積測定
により行った。なお、ピッチング面積ゼロをもって合格
とする。The gas soft nitriding treatment was carried out under the conditions of Table 3 in which the gas composition ratio and the treatment temperature were changed, and a gear fatigue test was conducted. The evaluation was performed by rotating the gear under the conditions of torque: 40Kgf, rotation speed: 1000RPM, oil temperature: 80 ° C, and measuring the pitching area per tooth surface (contact area: 52 mm 2 ) at 10 7 rotations. It was A zero pitching area is acceptable.
【００４３】表４に測定結果を示す。ガス組成・処理温
度が満足するものは、化合物層がε単層になり、ポーラ
ス層が10μm を超える条件を除いてピッチングも発生は
していない。ガス組成が0.5 未満となると、化合物層は
複合化し、ピッチングも多数発生する。また、処理温度
が550 ℃未満となると、硬化深さが十分でなく評価完了
までに破損し、評価不能となる。以上のように、本発明
の条件を外れると目標とする特性を得ることができな
い。Table 4 shows the measurement results. When the gas composition and the treatment temperature were satisfied, the compound layer was a single ε layer and no pitting occurred except when the porous layer exceeded 10 μm. When the gas composition is less than 0.5, the compound layer becomes complex and a lot of pitting occurs. If the treatment temperature is less than 550 ° C, the curing depth is not sufficient and damage occurs before the evaluation is completed, making evaluation impossible. As described above, if the conditions of the present invention are not satisfied, the target characteristics cannot be obtained.
【００４４】[0044]
【表３】 [Table 3]
【００４５】実施例３ 本例は、ポーラス層の影響を見る。実施例２で処理条件
が規格内でポーラス層が10μm を超える歯車について、
ショットピーニングにてポーラス層厚さを10μm 以下に
調整した歯車で、実施例２と同様に歯車疲労試験をおこ
ない、評価を行った。表５に測定結果を示す。ポーラス
層を10μm 以下に調整した歯車のピッチングは皆無とな
り、耐ピッチング性のさらなる向上が図れている。Example 3 This example looks at the effect of the porous layer. Regarding the gear in which the treatment condition is within the standard and the porous layer exceeds 10 μm in Example 2,
A gear fatigue test was conducted in the same manner as in Example 2 using a gear whose porous layer thickness was adjusted to 10 μm or less by shot peening, and evaluated. Table 5 shows the measurement results. Gears with a porous layer adjusted to 10 μm or less have no pitching, further improving pitching resistance.
【００４６】[0046]
【表４】 [Table 4]
【００４７】[0047]
【表５】 [Table 5]
【００４８】[0048]
【発明の効果】本発明は高強度が要求される歯車を製造
するに際し、熱処理条件の調整・ポーラス層の厚さ調整
をおこなうことにより、軟窒化鋼として従来鋼にない優
れたピッチング特性を保有することで、歯車の高強度化
・軽量化が可能となるものである。EFFECT OF THE INVENTION The present invention possesses excellent pitting characteristics that conventional steels do not have as soft nitriding steel by adjusting the heat treatment conditions and adjusting the thickness of the porous layer when manufacturing gears that require high strength. By doing so, it is possible to increase the strength and weight of the gear.
【図１】最表面層の金属組織の模式的説明図である。FIG. 1 is a schematic explanatory view of a metal structure of an outermost surface layer.
Claims (2)
〜1.30％、 Cr：0.70〜1.50％、 Mo：０〜0.50％、 Al：0.02
〜0.10％、 Ｎ：0.006 〜0.020 ％、Ｖ：0.05〜0.20％、 残部Feおよび不可避的不純物の組成を有する鋼からなる
歯車に、ＲＸ／ＮＨ3 ＝0.5 〜1.5 のガス容積組成比、
かつ550 〜650 ℃の処理温度でガス軟窒化処理を施し、
その後ポーラス層厚さを10μm 以下にすることを特徴と
する、耐ピッチング性に優れる高強度軟窒化歯車の製造
方法。1. By weight%, C: 0.15 to 0.50%, Si: 1.20% or less, Mn: 0.60
~ 1.30%, Cr: 0.70 ~ 1.50%, Mo: 0 ~ 0.50%, Al: 0.02
.About.0.10%, N: 0.006 to 0.020%, V: 0.05 to 0.20%, and a gas volume composition ratio of RX / NH 3 = 0.5 to 1.5 on a gear made of steel having a composition of balance Fe and inevitable impurities,
And the gas soft nitriding treatment is performed at the treatment temperature of 550-650 ℃,
Thereafter, the porous layer thickness is set to 10 μm or less, and a method for producing a high-strength soft nitrided gear having excellent pitting resistance.
05〜0.060 ％、Pb：0.02〜0.20％、およびCa：0.0050〜
0.010 ％から成る群から選んだ１種または２種以上を含
有する、請求項１記載の高強度軟窒化歯車の製造方法。2. The composition, in% by weight, further comprising S: 0.0
05-0.060%, Pb: 0.02-0.20%, and Ca: 0.0050-
The method for producing a high-strength soft nitrided gear according to claim 1, containing one or more selected from the group consisting of 0.010%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30927294A JP3430685B2 (en) | 1994-12-13 | 1994-12-13 | Pitching resistant nitrocarburized gear |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30927294A JP3430685B2 (en) | 1994-12-13 | 1994-12-13 | Pitching resistant nitrocarburized gear |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08165556A true JPH08165556A (en) | 1996-06-25 |
| JP3430685B2 JP3430685B2 (en) | 2003-07-28 |
Family
ID=17991002
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP30927294A Expired - Lifetime JP3430685B2 (en) | 1994-12-13 | 1994-12-13 | Pitching resistant nitrocarburized gear |
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| Country | Link |
|---|---|
| JP (1) | JP3430685B2 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006131922A (en) * | 2004-11-02 | 2006-05-25 | Mazda Motor Corp | Method for manufacturing gear made of steel |
| WO2016153009A1 (en) * | 2015-03-25 | 2016-09-29 | 新日鐵住金株式会社 | Nitrided or soft nitrided part with excellent wear resistance and pitting resistance, and nitriding and soft nitriding methods |
| WO2018071175A1 (en) * | 2016-10-13 | 2018-04-19 | Caterpillar Inc. | Nitrided track pin for track chain assembly of machine |
| US10272960B2 (en) | 2015-11-05 | 2019-04-30 | Caterpillar Inc. | Nitrided track pin for track chain assembly of machine |
-
1994
- 1994-12-13 JP JP30927294A patent/JP3430685B2/en not_active Expired - Lifetime
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006131922A (en) * | 2004-11-02 | 2006-05-25 | Mazda Motor Corp | Method for manufacturing gear made of steel |
| WO2016153009A1 (en) * | 2015-03-25 | 2016-09-29 | 新日鐵住金株式会社 | Nitrided or soft nitrided part with excellent wear resistance and pitting resistance, and nitriding and soft nitriding methods |
| CN107406959A (en) * | 2015-03-25 | 2017-11-28 | 新日铁住金株式会社 | Wearability and the nitrogen treatment part and tufftride processing component and nitridation treatment method, soft-nitriding treatment method having superior pitting corrosion resistance |
| JPWO2016153009A1 (en) * | 2015-03-25 | 2017-12-28 | 新日鐵住金株式会社 | Nitriding / soft nitriding parts and nitriding / soft nitriding methods with excellent wear resistance and pitting resistance |
| CN107406959B (en) * | 2015-03-25 | 2020-02-04 | 日本制铁株式会社 | Nitrided component and soft nitrided component having excellent wear resistance and pitting resistance, and nitriding method and soft nitriding method |
| US10570496B2 (en) | 2015-03-25 | 2020-02-25 | Nippon Steel Corporation | Nitrided or soft nitrided part with excellent wear resistance and pitting resistance, and nitriding and soft nitriding method |
| US10272960B2 (en) | 2015-11-05 | 2019-04-30 | Caterpillar Inc. | Nitrided track pin for track chain assembly of machine |
| WO2018071175A1 (en) * | 2016-10-13 | 2018-04-19 | Caterpillar Inc. | Nitrided track pin for track chain assembly of machine |
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| Publication number | Publication date |
|---|---|
| JP3430685B2 (en) | 2003-07-28 |
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