JP2549038B2 - Method for carburizing heat treatment of high-strength gear with small strain and its gear - Google Patents
Method for carburizing heat treatment of high-strength gear with small strain and its gearInfo
- Publication number
- JP2549038B2 JP2549038B2 JP3236603A JP23660391A JP2549038B2 JP 2549038 B2 JP2549038 B2 JP 2549038B2 JP 3236603 A JP3236603 A JP 3236603A JP 23660391 A JP23660391 A JP 23660391A JP 2549038 B2 JP2549038 B2 JP 2549038B2
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- less
- tooth
- gear
- carburizing
- carburized
- Prior art date
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、浸炭熱処理方法、特に
疲労強度が高く、焼入れ時の歪が少なく、騒音の少ない
自動車トランスミッション用ギアを製造することのでき
る歯車の浸炭熱処理方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carburizing heat treatment method, and more particularly to a carburizing heat treatment method for gears, which is capable of producing a gear for an automobile transmission having high fatigue strength, low distortion during quenching and low noise. .
【０００２】[0002]
【従来の技術】一般に、自動車用歯車の素材には、耐疲
労強度および表面の耐摩耗性を高めるために肌焼鋼が使
用されている。この場合、肌焼鋼は歯車等の所定形状に
機械加工された後、表面硬化のために浸炭焼入れ処理を
施される。すなわち、炭素含有量の比較的低い低合金鋼
の表面に炭素を浸透させ、次に焼入れ、焼戻しを施して
歯表面をマルテンサイトにすることで硬化させ、かつ歯
車の靱性を確保する意味から、歯車芯部を一部マルテン
サイトあるいはベイナイトを含んだフェライト・パーラ
イト組織にする。ただし、歯車芯部とは図１（Ｂ）の網
掛で示す歯車の中央部である。このように歯表面と歯車
芯部の組織差を利用することは、耐疲労強度および靱性
を得るための基本原理であり、また浸炭焼入れ法におい
て冷却速度の質量効果を利用することにより十分達成さ
れていることは周知の事実である。2. Description of the Related Art Generally, case hardening steel is used as a material for automobile gears in order to enhance fatigue resistance and surface wear resistance. In this case, the case-hardened steel is machined into a predetermined shape such as a gear and then carburized and quenched for surface hardening. That is, carbon is infiltrated into the surface of a low alloy steel having a relatively low carbon content, and then quenching and tempering are performed to harden the tooth surface to martensite, and from the meaning of securing the toughness of the gear, The gear core has a ferrite / pearlite structure that partially contains martensite or bainite. However, the gear core is the center of the gear shown by the mesh in FIG. Utilizing the difference in structure between the tooth surface and the gear core is a basic principle for obtaining fatigue strength and toughness, and is sufficiently achieved by utilizing the mass effect of the cooling rate in the carburizing and quenching method. It is a well-known fact.
【０００３】しかしながら、歯車芯部は質量効果により
一部マルテンサイトあるいはベイナイトを含んだフェラ
イト・パーライト組織になるものの、歯内部（図１
（Ａ）の斜線部で示される歯の浸炭層より内側の部分）
は芯部より冷速が速いため、焼入れ組織であるマルテン
サイトと一部ベイナイトの混在組織になる。この時、マ
ルテンサイト生成による変態応力（オーステナイトから
マルテンサイト組織に変化するときに生じる体積膨張に
起因する応力）が発生するため、熱処理変形の発生が避
けられず、歯車精度を維持することができない。特に、
自動車トランスミッション用ギアは、騒音の発生に対し
て最も厳しい制限があるにも拘らず、小さくかつ肉厚が
薄いため、歯内部の組織はマルテンサイトとベイナイト
組織になり、このことが歯車騒音の最大の原因になって
いる。However, although the gear core part has a ferrite-pearlite structure containing a part of martensite or bainite due to the mass effect, the inside of the tooth (see FIG. 1).
(A portion inside the carburized layer of the tooth shown by the hatched portion in (A))
Has a faster cooling rate than the core, and therefore has a mixed structure of martensite, which is a quenched structure, and part of bainite. At this time, transformation stress due to martensite formation (stress due to volume expansion that occurs when changing from austenite to martensite structure) occurs, so heat treatment deformation cannot be avoided and gear precision cannot be maintained. . In particular,
Despite the strictest restrictions on noise generation, automotive transmission gears are small and thin, resulting in martensite and bainite microstructures inside the teeth, which results in maximum gear noise. Is causing
【０００４】そこで従来は、焼入れ歪に対して歯車研削
を追加することにより、精度を向上させる方法が用いら
れている。また、イオン窒化、ガス軟窒化やタフトライ
ドなどの低温で行う窒化処理等も検討されている。さら
に、２次焼入れ法を用いて、２次焼入れ温度をＡ3 点以
下にし、非浸炭部をマルテンサイトとフェライトの混合
組織にする方法（内藤武志：浸炭焼入れの実際、日刊工
業新聞社、Ｐ．１６１）、あるいは特開昭５５−６４５
６号公報では、等温焼きなまし処理によりフェライト・
パーライト組織にした後、軟窒化処理により表面のみ硬
化する方法が開示されている。Therefore, conventionally, a method of improving accuracy by adding gear grinding to quenching distortion has been used. In addition, nitriding treatments performed at low temperatures such as ion nitriding, gas soft nitriding, and tuftride are being studied. Furthermore, the secondary quenching method is used to set the secondary quenching temperature to A 3 point or less and the non-carburized portion has a mixed structure of martensite and ferrite (Takeshi Naito: Carburizing and quenching practice, Nikkan Kogyo Shimbun, P. 161), or JP-A-55-645.
In the publication No. 6, ferrite is annealed by isothermal annealing treatment.
A method is disclosed in which only the surface is hardened by soft nitriding after forming a pearlite structure.
【０００５】[0005]
【発明が解決しようとする課題】しかし、機械切削では
浸炭層を部分的に削り取ることから、製造工程数が増加
するほか、複雑な形状部品には適用しがたく、また表面
硬さや残留応力にムラを生ずることとなり、品質上の問
題があった。一方、イオン窒化、ガス軟窒化、タフトラ
イドおよび特開昭５５−６４５６号公報の方法では、焼
入れ硬化層が薄く、また内部硬度が低いため、十分な疲
労強度が得られず、また２次焼入れ法でも内部硬度が低
いため、同様に十分な疲労強度が得られないという問題
を有している。However, since the carburized layer is partially shaved off in mechanical cutting, the number of manufacturing steps increases, and it is difficult to apply to parts with complicated shapes, and it is difficult to apply surface hardness and residual stress. There was unevenness, and there was a quality problem. On the other hand, in the methods of ion nitriding, gas nitrocarburizing, tufftride and JP-A-55-6456, since the quench hardened layer is thin and the internal hardness is low, sufficient fatigue strength cannot be obtained, and the secondary quenching method is also used. However, since the internal hardness is low, it also has a problem that sufficient fatigue strength cannot be obtained.
【０００６】すなわち、従来の機械加工法では経済性と
歯車自身の品質を犠牲にしたものであり、材料側からの
取組みも、歯内部のマルテンサイト化防止により歪は軽
減できるものの、歯車本来の特性である高疲労強度を犠
牲にしたものであり、歪を軽減しつつ高強度化を達成で
きる有効な方法が望まれている。That is, the conventional machining method sacrifices economy and the quality of the gear itself, and even when the material is used, distortion can be reduced by preventing martensite formation inside the tooth, but the original gear It is a sacrifice of high fatigue strength, which is a characteristic, and an effective method that can achieve high strength while reducing strain is desired.
【０００７】[0007]
【課題を解決するための手段】本発明者らは、このよう
な実情に対処して、高強度でかつ熱処理歪みの小さい、
歯車の浸炭熱処理方法を開発するために多くの研究を行
ってきた結果、以下の知見を得たものである。 浸炭焼入れ法における熱処理歪の低減と疲労強度の向
上には、歯内部を所定の体積分率のマルテンサイトと、
残りを高硬度のフェライト・パーライト組織とすること
が有効である。SUMMARY OF THE INVENTION The present inventors have dealt with such an actual situation and have high strength and small heat treatment distortion.
As a result of many studies to develop a carburizing heat treatment method for gears, the following findings were obtained. In order to reduce heat treatment strain and improve fatigue strength in the carburizing and quenching method, the inside of the tooth is martensite with a predetermined volume fraction,
It is effective to make the rest a high hardness ferrite-pearlite structure.
【０００８】前記組織は歯内部（非浸炭部）のＡｒ1
変態点以上Ａｒ3 変態点以下の温度域に保持した後、焼
入れすることにより達成できる。 高硬度のフェライト・パーライト組織は、炭窒化物の
析出硬化および微細化効果により達成できる。 前記組織の歯車において、表層の内部酸化層および不
完全焼入れ層の生成抑制が、疲労強度向上に有効であ
る。The tissue is Ar 1 inside the tooth (non-carburized portion).
This can be achieved by holding the material in a temperature range not lower than the transformation point and not higher than the Ar 3 transformation point and then quenching. A high hardness ferrite / pearlite structure can be achieved by the precipitation hardening and refinement effects of carbonitrides. In the gear having the above structure, suppressing the formation of the internal oxide layer and the incompletely hardened layer on the surface layer is effective for improving the fatigue strength.
【０００９】そこで、こうした知見に基づいて、具体的
な達成手段を明らかにするため、さらに研究検討を重
ね、特定の化学組成の肌焼鋼より製造された歯車に浸炭
処理を施した直後に、特定の温度範囲に所定時間保持
し、その後、焼入れ・焼戻しを行うことにより、表面硬
さを低下させずに、歯内部の組織を所定量のマルテンサ
イトと高硬度のフェライト・パーライト組織にし、騒音
の発生源となる歯の焼入れ時の歪を大幅に低減できると
ともに、疲労強度の高い全く新しい歯車の浸炭熱処理方
法を完成させた。[0009] Therefore, based on these findings, further research and studies have been carried out in order to clarify the concrete means for achieving it, and immediately after carburizing the gear manufactured from case hardening steel of a specific chemical composition, By holding in a specific temperature range for a certain period of time and then quenching and tempering, the internal structure of the tooth is made into a predetermined amount of martensite and a high hardness ferrite / pearlite structure without reducing the surface hardness, and noise is reduced. We have completed a completely new carburizing heat treatment method for gears, which is capable of significantly reducing the strain at the time of quenching of the teeth, which is the source of heat generation, and has high fatigue strength.
【００１０】すなわち、本発明の要旨とするところは下
記のとおりである。 （１） 重量％で、Ｃ：０．１％以上０．３％未満、Ｓ
ｉ：０．１５％未満、Ｍｎ：０．３０％以上１．５０％
未満、Ｃｒ：０．３０％以上１．５０％未満、Ｍｏ：
０．１０％以上１．００％未満を含むとともに、Ｖ：
０．０５％以上０．２０％以下、Ｎｂ：０．０２％以上
０．２０％以下、Ｔｉ：０．０１％以上０．２０％以下
の１種以上を含有し、残部Ｆｅおよび不純物よりなる鋼
を素材とした歯車に、浸炭処理を施した後に、歯内部
（非浸炭部）のＡｒ1 変態点以上でＡｒ 3 変態点以下の
温度域に５分以上２時間未満保持して、歯表面をオース
テナイトの状態に保ちつつ、油あるいは塩浴中で焼入れ
し、１３０〜２００℃の焼戻しを行うことを特徴とする
歪の小さい高強度歯車の浸炭熱処理方法。That is, the gist of the present invention is as follows.
It is as described in the note. (1) In% by weight, C: 0.1% or more and less than 0.3%, S
i: less than 0.15%, Mn: 0.30% or more and 1.50%
Less than, Cr: 0.30% or more and less than 1.50%, Mo:
In addition to including 0.10% or more and less than 1.00%, V:
0.05% or more and 0.20% or less, Nb: 0.02% or more
0.20% or less, Ti: 0.01% or more and 0.20% or less
Steel containing at least one of the above and the balance Fe and impurities
After carburizing the gear made of
Ar (non-carburized part)1Ar above the transformation point 3Below the transformation point
Hold in the temperature range for 5 minutes or more and less than 2 hours to ausate the tooth surface
Quench in oil or salt bath while maintaining tenite state
And tempering is performed at 130 to 200 ° C.
Carburizing heat treatment method for high strength gears with low distortion.
【００１１】ただし、歯内部とは図１（Ａ）の斜線部で
示される歯の浸炭層より内側である。 （２） 重量％で、Ｃ：０．１％以上０．３％未満、Ｓ
ｉ：０．１５％未満、Ｍｎ：０．３０％以上１．５０％
未満、Ｃｒ：０．３０％以上１．５０％未満、Ｍｏ：
０．１０％以上１．００％未満を含むとともに、Ｖ：
０．０５％以上０．２０％以下、Ｎｂ：０．０２％以上
０．２０％以下、Ｔｉ：０．０１％以上０．２０％以下
の１種以上を含有し、残部Ｆｅおよび不純物よりなる鋼
を素材とした歯車に、浸炭処理を施した後に、歯表面部
（浸炭部）のＡｒ1 変態点以下の温度域まで徐冷し、再
度歯表面部（浸炭部）のＡｃ3 変態点以上に加熱した
後、歯内部（非浸炭部）のＡｒ1 変態点以上でＡｒ3変
態点以下の温度域に５分以上２時間未満保持して、歯表
面をオ−ステナイトの状態に保ちつつ、油あるいは塩浴
中で焼入れし、１３０〜２００℃の焼戻しを行うことを
特徴とする歪の小さい高強度歯車の浸炭熱処理方法。However, the inside of the tooth is the inside of the carburized layer of the tooth shown by the shaded portion in FIG. 1 (A). (2) Weight%, C: 0.1% or more and less than 0.3%, S
i: less than 0.15%, Mn: 0.30% or more and 1.50%
Less than, Cr: 0.30% or more and less than 1.50%, Mo:
In addition to including 0.10% or more and less than 1.00%, V:
0.05% or more and 0.20% or less, Nb: 0.02% or more and 0.20% or less, Ti: 0.01% or more and 0.20% or less, and at least one of Fe and impurities. After carburizing a gear made of steel, it is annealed to a temperature range below the Ar 1 transformation point of the tooth surface (carburized portion) and again above the Ac 3 transformation point of the tooth surface (carburized portion). After being heated to, the temperature inside the tooth (non-carburized portion) is kept at a temperature range not lower than Ar 1 transformation point and not higher than Ar 3 transformation point for 5 minutes or more and less than 2 hours to keep the tooth surface in an austenite state. A method for carburizing heat treatment of a high-strength gear with small strain, which comprises quenching in an oil or salt bath and tempering at 130 to 200 ° C.
【００１２】ただし、歯内部とは図１（Ａ）の斜線部で
示される歯の浸炭層より内側である。 （３） 前項１または２記載の製造方法で得られる歯内
部が３０％以上５０％未満のマルテンサイトと残りがフ
ェライト−パーライトである歪の小さい高強度の歯車。However, the inside of the tooth is the inside of the carburized layer of the tooth shown by the shaded portion in FIG. 1 (A). (3) A high-strength gear with small strain, which has a martensite content of 30% or more and less than 50% in the tooth and the remainder being ferrite-pearlite, which is obtained by the manufacturing method according to the above 1 or 2.
【００１３】以下に本発明について説明する。最初に、
本発明の浸炭熱処理方法が適用できる合金鋼の化学成分
について述べる。本発明における合金鋼は、浸炭後の焼
入れ時に、歯内部の組織をマルテンサイトとフェライト
・パーライトとの混合組織にすることにより焼入れ歪を
低減することができ、しかも歯車としての剛性や靱性等
を維持するのに十分な内部硬さでなければならない。一
方、この合金鋼は浸炭されるため、浸炭処理により悪影
響を受けない化学成分でなければならない。The present invention will be described below. At first,
The chemical composition of alloy steel to which the carburizing heat treatment method of the present invention can be applied will be described. The alloy steel in the present invention can reduce the quenching strain by making the internal structure of the tooth a mixed structure of martensite and ferrite / pearlite at the time of quenching after carburizing, and further, the rigidity and toughness as a gear can be obtained. It must have sufficient internal hardness to maintain. On the other hand, since this alloy steel is carburized, it must have a chemical composition that is not adversely affected by the carburizing treatment.
【００１４】まずＣは自動車用歯車として必要な強度、
特に芯部強度を確保するために添加する元素であるが、
０．１％未満ではこのような効果が十分に得られず、
０．３％以上では靱性が低下して脆くなり、浸炭用鋼と
して使用が困難となるので、その含有量は０．１％以上
０．３％未満とした。Ｓｉは浸炭用鋼の粒界酸化に著し
く悪影響を及ぼす元素であり、含有量は０．１５％以上
では浸炭層に顕著な粒界酸化が形成され、浸炭用鋼の材
質特性が劣化するため、その含有量は０．１５％未満と
した。First, C is the strength required for automobile gears,
In particular, it is an element added to secure the core strength,
If it is less than 0.1%, such an effect cannot be sufficiently obtained,
If the content is 0.3% or more, the toughness decreases and the material becomes brittle, making it difficult to use as a carburizing steel. Therefore, the content is set to 0.1% or more and less than 0.3%. Si is an element that significantly affects the intergranular oxidation of carburizing steel, and if the content is 0.15% or more, remarkable intergranular oxidation is formed in the carburized layer and the material properties of the carburizing steel deteriorate. The content was less than 0.15%.
【００１５】Ｍｎは鋼に強度、靱性、焼入れ性を与える
のに必要な元素であるが、１．５０％以上では熱間圧延
後の冷却においてベイナイトやマルテンサイトの硬質な
組織になり、その後の切削等の二次加工には適さなくな
るために１．５０％未満とする。しかし、Ｍｎの添加量
が０．３０％未満では焼入れ性向上の効果が十分でない
ので、その含有量は０．３０％以上とする。Mn is an element necessary for imparting strength, toughness and hardenability to steel, but if it is 1.50% or more, it becomes a hard structure of bainite or martensite in cooling after hot rolling, and thereafter. It is less than 1.50% because it is not suitable for secondary processing such as cutting. However, if the addition amount of Mn is less than 0.30%, the effect of improving the hardenability is not sufficient, so the content is made 0.30% or more.
【００１６】Ｃｒは鋼の粒界酸化に著しい悪影響を及ぼ
す元素であり、また二相域の温度幅を狭くし、焼入れ時
の制御性を悪くする。１．５０％以上では顕著に粒界酸
化層を形成するとともに、焼入れ性を阻害するため１．
５０％未満とする。しかし、Ｃｒの添加量が０．３０％
未満では焼入れ性向上の効果が十分でないので、その含
有量は０．３０％以上とする。[0016] Cr is an element that has a significant adverse effect on the grain boundary oxidation of steel, and also narrows the temperature range in the two-phase region and deteriorates controllability during quenching. If it is 1.50% or more, a grain boundary oxide layer is formed remarkably and hardenability is hindered.
It is less than 50%. However, the amount of Cr added is 0.30%
If the amount is less than this, the effect of improving hardenability is not sufficient, so the content is made 0.30% or more.
【００１７】Ｍｏは粒界酸化層を形成することなしに鋼
の耐摩耗性、焼入れ性、機械的特性を向上し、特に歯内
部の硬度上昇に有用な元素であり、０．１０％未満では
その効果が十分でなく、１．０％以上では靱性を劣化さ
せるため、０．１０％以上１．０％未満とする。Ｖ、Ｔ
ｉおよびＮｂは炭窒化物を生成し、歯内部組織であるフ
ェライト・パーライトの硬度上昇をもたらすとともに、
浸炭結晶粒を微細化する効果のある元素であり、その効
果を得るには１種以上の元素をＶで０．０５％以上、Ｎ
ｂで０．０２％以上およびＴｉで０．０１％以上の含有
が必要である。しかし、Ｖ、ＮｂおよびＴｉをそれぞれ
で０．２０％を超えて含有しても効果は飽和するため、
これらの元素の上限を０．２０％とする。Mo is an element that improves the wear resistance, hardenability and mechanical properties of steel without forming an intergranular oxide layer, and is particularly useful for increasing the hardness inside the tooth. The effect is not sufficient, and if it is 1.0% or more, the toughness is deteriorated, so the content is made 0.10% or more and less than 1.0%. V, T
i and Nb generate carbonitrides, which increases the hardness of ferrite / pearlite, which is the internal structure of teeth, and
It is an element that has an effect of refining carburized crystal grains, and in order to obtain the effect, one or more elements are added in an amount of 0.05% or more by V, N
It is necessary that the content of b is 0.02% or more and the content of Ti is 0.01% or more. However, since the effect is saturated even if V, Nb, and Ti are contained in excess of 0.20%, respectively,
The upper limit of these elements is 0.20%.
【００１８】上記成分のほか、以下に示す元素を添加す
ることにより、よりいっそう特性の向上が可能である。
ＣａはＭｎＳの延伸抑制のために必要な元素であり、歯
車の疲労における異方性を軽減する。ＭｎＳの延伸抑制
効果を与えるために、Ｃａを０．００１０％以上含有さ
せる。しかし、０．０１０％を超えて含有させても、そ
の効果は飽和して経済性を損うため上限を０．０１０％
とする。The characteristics can be further improved by adding the following elements in addition to the above components.
Ca is an element necessary for suppressing the stretching of MnS and reduces anisotropy in fatigue of gears. To give the effect of suppressing the stretching of MnS, Ca is contained in an amount of 0.0010% or more. However, even if the content exceeds 0.010%, the effect is saturated and the economy is impaired, so the upper limit is 0.010%.
And
【００１９】また、Ｎｉは鋼に所定の焼入れ性を与え、
強度および靱性を向上させるのに必要な元素である。本
発明では、前述のＳｉ、Ｍｎ、ＣｒおよびＭｏ含有量に
関する限定のもとで、従来鋼と同等あるいはそれ以上の
焼入れ性を与えるために、任意に添加することができ
る。しかし、１．００％を超えて含有させても、その効
果は飽和して経済性を損うため上限を１．００％とす
る。Further, Ni gives the steel a predetermined hardenability,
It is an element necessary for improving strength and toughness. In the present invention, in order to provide hardenability equivalent to or higher than that of conventional steel, it may be optionally added under the above-mentioned restrictions on the contents of Si, Mn, Cr and Mo. However, even if the content exceeds 1.00%, the effect is saturated and the economy is impaired, so the upper limit is made 1.00%.
【００２０】浸炭法としては、ガス浸炭法または液体浸
炭法が好ましく、また浸炭深さは表層硬さおよび残留応
力の観点から０．５mm以上であることが好ましい。表面
炭素量が共析以上、Ａcm以下のカーボンポテンシャルに
て、８５０〜９８０℃の温度で浸炭処理することにより
浸炭部のＡ3 変態点（＝Ａ1 ）は７００〜７４０℃に下
がる。The carburizing method is preferably a gas carburizing method or a liquid carburizing method, and the carburizing depth is preferably 0.5 mm or more from the viewpoint of surface hardness and residual stress. By carrying out carburizing at a temperature of 850 to 980 ° C. with a carbon potential of the surface carbon content of not less than eutectoid and not more than A cm, the A 3 transformation point (= A 1 ) of the carburized part is lowered to 700 to 740 ° C.
【００２１】次に浸炭後炉冷等により７００〜８２０℃
（浸炭部のＡｒ3 変態点以上、歯内部のＡｒ1 変態点以
上およびＡｒ3 変態点以下）に冷却した後一定時間保持
することにより、非浸炭部の歯内部は一部オーステナイ
ト状態のまま残りはフェライト・パーライト組織なる。
一方、歯表層の浸炭部はオーステナイト状態を維持す
る。この場合、歯内部のオーステナイト量を体積分率で
３０％以上、５０％未満になるように、７００〜８２０
℃の間で冷却保持温度を調整する。また、保持時間は温
度の均一性および熱処理コストより、５分以上２時間未
満とする（それ以上保持時間を長くしても、品質上のメ
リットはなく、また不経済である）。Next, after carburizing, the temperature is 700 to 820 ° C. by cooling the furnace.
After cooling to (Ar 3 transformation point of carburized part or more, Ar 1 transformation point of tooth interior or more and Ar 3 transformation point or less) and holding for a certain period of time, part of the tooth inside the non-carburized portion remains austenite Is a ferrite-pearlite structure.
On the other hand, the carburized portion of the tooth surface layer maintains the austenitic state. In this case, the amount of austenite in the tooth should be 700 to 820 so that the volume fraction is 30% or more and less than 50%.
Adjust the cooling hold temperature between ℃. Further, the holding time is set to 5 minutes or more and less than 2 hours in view of the uniformity of temperature and the heat treatment cost (even if the holding time is longer than that, there is no merit in quality and it is uneconomical).
【００２２】歯内部のマルテンサイト量は、歯の歪と歯
内部の硬度を決める重要な因子であり、焼入れ前のオー
ステナイト量に依存する。マルテンサイト量は体積分率
で３０％未満では硬度が低く、十分な疲労特性が得られ
ず、５０％以上では歪が大きすぎるため、３０％以上５
０％未満とする。浸炭部の結晶粒を細粒化する、より好
ましい条件としては、浸炭後歯表面部（浸炭部）のＡｒ
1 変態点以下の温度域まで徐冷し、次に歯表面部のＡｃ
3 変態点以上に再加熱する。この時、浸炭部のオーステ
ナイト粒の細粒化が図られる。次に歯内部のＡｒ1 変態
点以上でＡｒ3 変態点以下に一定時間保持することによ
り、歯表層の浸炭部はオーステナイトのまま、非浸炭部
の歯内部は一部オーステナイトで、残りは微細なフェラ
イト・パーライト組織になる。この場合、歯内部のオー
ステナイト量を体積分率で３０〜５０％になるように、
７００〜８２０℃の間で冷却保持温度を調整する。また
保持時間は温度の均一性および熱処理コストより、５分
以上２時間未満が好ましい。The amount of martensite inside the tooth is an important factor that determines the strain of the tooth and the hardness inside the tooth, and depends on the amount of austenite before hardening. When the volume fraction of martensite is less than 30% by volume, the hardness is low and sufficient fatigue characteristics cannot be obtained, and when it is 50% or more, the strain is too large.
Less than 0%. More preferable conditions for refining the crystal grains of the carburized portion are Ar of the tooth surface portion (carburized portion) after carburization.
Gradually cool to a temperature range below 1 transformation point, and then Ac of the tooth surface
Reheat above 3 transformation points. At this time, the austenite grains in the carburized portion are refined. Next, by keeping the temperature above the Ar 1 transformation point inside the tooth and below the Ar 3 transformation point for a certain period of time, the carburized portion of the tooth surface layer remains austenite, the tooth inside the non-carburized portion is partially austenite, and the rest is fine. It has a ferrite / pearlite structure. In this case, the amount of austenite inside the tooth should be 30 to 50% in terms of volume fraction,
Adjust the cooling hold temperature between 700-820 ° C. The holding time is preferably 5 minutes or more and less than 2 hours in view of the temperature uniformity and the heat treatment cost.
【００２３】以上のように、歯表面をオーステナイト状
態に保ちつつ、歯内部のオーステナイト量を体積分率で
３０％以上５０％未満になるようにし、残りを高強度化
されたフェライトとパーライトにし、しかる後に油ある
いは塩浴中で焼入れすることにより、歯表層の浸炭部は
全てマルテンサイトにでき、歯内部は体積分率で３０％
以上５０％未満のみがマルテンサイトとなり、既に変態
を終了しているフェライト・パーライトはそのまま維持
できる。その後、浸炭部の内部応力の除去および強さ、
ねばさを増すために、１３０〜２００℃の焼戻し処理を
行う。As described above, while maintaining the tooth surface in an austenite state, the amount of austenite inside the tooth is adjusted to 30% or more and less than 50% in volume fraction, and the rest is made to be ferrite and pearlite with high strength, Then, by quenching in an oil or salt bath, the carburized part of the tooth surface layer can be made entirely martensite, and the tooth interior has a volume fraction of 30%.
Only the above and less than 50% become martensite, and the ferrite / pearlite that has already completed the transformation can be maintained as it is. After that, removal of internal stress and strength of carburized part,
In order to increase the stickiness, a tempering treatment at 130 to 200 ° C. is performed.
【００２４】以下に実施例を挙げてさらに説明する。Hereinafter, the present invention will be further described with reference to examples.
【００２５】[0025]
【実施例】表１、表２（表１のつづき）示す化学成分の
鋼を溶製し、１６２mm角ビレットに分塊圧延した後、熱
間圧延にて５０mmφ棒鋼に仕上げた。次に得られた棒鋼
を熱間鍛造および焼ならしし、その後機械加工により、
外径８７mm、モジュール３、歯数２７、歯幅２０mmの歯
車を製作し、これらを試料として浸炭処理を施した。ま
ず、試料をカーボンポテンシャル：０．９％、温度：９
３０℃で浸炭した後、No. １は歯内部のＡｒ3 変態点超
の８４０℃、No. ２は歯内部のＡｒ1 変態点未満（歯表
面部のＡｒ3 変態点未満）の７００℃まで炉冷し、３０
分保持後、No. ３からNo. １５は炉中で表１に示す歯内
部のＡｒ1 変態点以上Ａｒ3 変態点以下の温度に３０分
保持後、No. １６からNo.２３は浸炭後歯表面部のＡｒ
1 変態点以下の５００℃まで０．５℃／ｓで冷却し、再
度歯表面部（浸炭部）のＡｃ3 変態点以上に加熱した
後、歯内部のＡｒ1 変態点以上でＡｒ3 変態点以下の温
度に３０分保持後、全てのNo.の試料を１７０℃の油浴
中で冷却した。次いで、１８０℃、１時間の焼戻しを行
った。なお、焼入れ前のオーステナイト量は、同一条件
で水焼入れし、得られたマルテンサイトの量より求め、
また一歯曲げ疲労強度は油圧サーボ式引張圧縮疲労試験
により測定し、さらに歪量はＪＩＳ Ｂ１７０２により
歯形誤差を測定し、併せて表３、表４（表３のつづき）
および表５に示した。EXAMPLES Steels having the chemical compositions shown in Tables 1 and 2 (continued from Table 1) were melted, slab-rolled into 162 mm square billets, and then hot rolled into 50 mmφ steel bars. Next, hot forging and normalizing the obtained steel bar, followed by machining,
A gear having an outer diameter of 87 mm, a module 3, 27 teeth, and a tooth width of 20 mm was manufactured, and carburized as a sample. First, the sample is carbon potential: 0.9%, temperature: 9
After carburizing at 30 ° C, No. 1 is up to 840 ° C above the Ar 3 transformation point inside the tooth, and No. 2 is up to 700 ° C below the Ar 1 transformation point inside the tooth (below the Ar 3 transformation point inside the tooth surface). Furnace cooled, 30
After holding for 30 minutes, No. 3 to No. 15 were held in the furnace at the temperature of Ar 1 transformation point or more and Ar 3 transformation point or less shown in Table 1 for 30 minutes, and No. 16 to No. 23 were carburized. Ar of tooth surface
After cooling to 500 ° C below 1 transformation point at 0.5 ° C / s and heating again to above the Ac 3 transformation point of the tooth surface (carburized portion), the Ar 3 transformation point above the Ar 1 transformation point inside the tooth After being kept at the following temperatures for 30 minutes, all No. samples were cooled in a 170 ° C. oil bath. Then, it was tempered at 180 ° C. for 1 hour. Incidentally, the amount of austenite before quenching, water quenching under the same conditions, determined from the amount of martensite obtained,
The one-tooth bending fatigue strength was measured by a hydraulic servo tension / compression fatigue test, and the amount of strain was measured by measuring the tooth profile error in accordance with JIS B1702. In addition, Table 3 and Table 4 (continued from Table 3)
And shown in Table 5.
【００２６】表に示すように、歯内部のＡｒ3 変態点超
で焼入れしたNo. １は歯内部がマルテンサイトとなり、
歯形歪量も多く、また歯内部のＡｒ1 変態点未満（歯表
面のＡｒ3 変態点未満）で焼入れしたNo. ２では歯内部
はマルテンサイトのないフェライト・パーライト組織に
はなるものの、歯表面もベイナイトとパーライト組織と
なり、歯車として必要な表面硬さを得ることができな
い。さらに、歯内部（非浸炭部）のＡｒ1 変態点以上Ａ
ｒ3 変態点以下の温度で焼入れしているものの歯内部の
マルテンサイト量が７０％と多いNo. ３は、歯形歪量が
多く、またマルテンサイト量が２０％と少ないNo. ４は
歯内部硬度が低く、実用には適さない。さらに、No. ５
は本発明範囲のマルテンサイト量を有するものの、本発
明の化学成分範囲外のため、内部酸化層が深く、また不
完全焼入れ層が発生し、疲労強度が低い。As shown in the table, No. 1 hardened above the Ar 3 transformation point inside the tooth became martensite inside the tooth,
There is a large amount of tooth profile distortion, and No. 2 hardened below the Ar 1 transformation point inside the tooth (below the Ar 3 transformation point on the tooth surface) has a ferrite-pearlite structure with no martensite inside the tooth, but the tooth surface Also has a bainite and pearlite structure, and cannot obtain the surface hardness required for a gear. In addition, above the Ar 1 transformation point inside the tooth (non-carburized part) A
No. 3, which has a large martensite content of 70% in the tooth but is hardened at a temperature below the r 3 transformation point, has a large amount of tooth profile distortion, and No. 4, which has a small martensite content of 20%, has a tooth interior of the tooth. Hardness is low and not suitable for practical use. Furthermore, No. 5
Has an amount of martensite within the range of the present invention, but has a deep internal oxide layer and an incompletely hardened layer due to being out of the chemical composition range of the present invention, resulting in low fatigue strength.
【００２７】これに対して本発明の範囲内にあるNo. ６
〜２３では何れも歯内部は３０％以上５０％未満のマル
テンサイトと、残りがフェライト・パーライト組織にな
り、歯内部硬度も十分であり、歯形歪量も著しく低減で
き、また内部酸化層と不完全焼入れ層の抑制により、疲
労強度も高いことが明らかである。On the other hand, No. 6 within the scope of the present invention
In each of No. 23 to 23, the inside of the tooth has a martensite content of 30% or more and less than 50% and the rest is a ferrite / pearlite structure, the tooth internal hardness is sufficient, the tooth profile distortion amount can be significantly reduced, and the internal oxide layer and the It is clear that the fatigue strength is high due to the suppression of the completely hardened layer.
【００２８】[0028]
【表１】 [Table 1]
【００２９】[0029]
【表２】 [Table 2]
【００３０】[0030]
【表３】 [Table 3]
【００３１】[0031]
【表４】 [Table 4]
【００３２】[0032]
【表５】 [Table 5]
【００３３】[0033]
【発明の効果】本発明に従い、浸炭焼入れにより製造さ
れる自動車用歯車の浸炭後の焼入れ温度を制御すること
により、歯内部のマルテンサイトの量を調整し、残りを
高硬度のフェライト・パーライト組織にし、歯車として
疲労強度が高く、歯車の歪を著しく低減し、騒音の少な
い自動車トランスミッション用ギアを提供することがで
きるので、産業上の効果は極めて顕著なものがある。Industrial Applicability According to the present invention, the amount of martensite inside the tooth is adjusted by controlling the quenching temperature after carburizing of the gear for automobiles manufactured by carburizing and quenching, and the remainder is a high hardness ferrite / pearlite structure. In addition, since a gear having high fatigue strength, a significant reduction in gear distortion, and a low-noise gear for an automobile transmission can be provided, the industrial effect is extremely remarkable.
【図１】（Ａ）は歯車の歯内部、（Ｂ）は歯車芯部の説
明図である。FIG. 1A is an explanatory diagram of a tooth inside of a gear, and FIG. 1B is an explanatory diagram of a gear core portion.
Claims (3)
満、Ｓｉ：０．１５％未満、Ｍｎ：０．３０％以上１．
５０％未満、Ｃｒ：０．３０％以上１．５０％未満、Ｍ
ｏ：０．１０％以上１．００％未満を含むとともに、
Ｖ：０．０５％以上０．２０％以下、Ｎｂ：０．０２％
以上０．２０％以下、Ｔｉ：０．０１％以上０．２０％
以下の１種以上を含有し、残部Ｆｅおよび不純物よりな
る鋼を素材とした歯車に、浸炭処理を施した後に、歯内
部（非浸炭部）のＡｒ1 変態点以上でＡｒ3 変態点以下
の温度域に５分以上２時間未満保持して、歯表面をオー
ステナイトの状態に保ちつつ、油あるいは塩浴中で焼入
れし、１３０〜２００℃の焼戻しを行うことを特徴とす
る歪の小さい高強度歯車の浸炭熱処理方法。ただし、歯
内部とは図１（Ａ）の斜線部で示される歯の浸炭層より
内側である。1. By weight%, C: 0.1% or more and less than 0.3%, Si: less than 0.15%, Mn: 0.30% or more 1.
Less than 50%, Cr: 0.30% or more and less than 1.50%, M
o: Including 0.10% or more and less than 1.00%,
V: 0.05% or more and 0.20% or less, Nb: 0.02%
Or more and 0.20% or less, Ti: 0.01% or more and 0.20%
After carburizing a gear made of steel that contains one or more of the following, with the balance Fe and impurities, after the carburizing treatment, the tooth inside (non-carburized portion) of Ar 1 transformation point or more and Ar 3 transformation point or less High strength with little distortion, characterized by holding in the temperature range for 5 minutes or more and less than 2 hours, quenching in an oil or salt bath while maintaining the tooth surface in an austenite state, and tempering at 130 to 200 ° C. Gear carburizing heat treatment method. However, the inside of the tooth is the inside of the carburized layer of the tooth shown by the hatched portion in FIG.
満、Ｓｉ：０．１５％未満、Ｍｎ：０．３０％以上１．
５０％未満、Ｃｒ：０．３０％以上１．５０％未満、Ｍ
ｏ：０．１０％以上１．００％未満を含むとともに、
Ｖ：０．０５％以上０．２０％以下、Ｎｂ：０．０２％
以上０．２０％以下、Ｔｉ：０．０１％以上０．２０％
以下の１種以上を含有し、残部Ｆｅおよび不純物よりな
る鋼を素材とした歯車に、浸炭処理を施した後に、歯表
面部（浸炭部）のＡｒ1 変態点以下の温度域まで徐冷
し、再度歯表面部（浸炭部）のＡｃ3 変態点以上に加熱
した後、歯内部（非浸炭部）のＡｒ1 変態点以上でＡｒ
3 変態点以下の温度域に５分以上２時間未満保持して、
歯表面をオ−ステナイトの状態に保ちつつ、油あるいは
塩浴中で焼入れし、１３０〜２００℃の焼戻しを行うこ
とを特徴とする歪の小さい高強度歯車の浸炭熱処理方
法。ただし、歯内部とは図１（Ａ）の斜線部で示される
歯の浸炭層より内側である。2. In% by weight, C: 0.1% or more and less than 0.3%, Si: less than 0.15%, Mn: 0.30% or more 1.
Less than 50%, Cr: 0.30% or more and less than 1.50%, M
o: Including 0.10% or more and less than 1.00%,
V: 0.05% or more and 0.20% or less, Nb: 0.02%
Or more and 0.20% or less, Ti: 0.01% or more and 0.20%
After carburizing a gear made of steel containing one or more of the following, with the balance Fe and impurities, the gear is gradually cooled to a temperature range below the Ar 1 transformation point of the tooth surface (carburized portion). , Again after heating to the Ac 3 transformation point of the tooth surface (carburized portion) or higher, and then Ar at the Ar 1 transformation point or higher of the tooth interior (non-carburized portion)
Hold in the temperature range below 3 transformation points for 5 minutes or more and less than 2 hours,
A carburizing heat treatment method for a high-strength gear with small strain, which comprises quenching in an oil or salt bath and tempering at 130 to 200 ° C. while maintaining the tooth surface in an austenite state. However, the inside of the tooth is the inside of the carburized layer of the tooth shown by the hatched portion in FIG.
れる歯内部が３０％以上５０％未満のマルテンサイトと
残りがフェライト−パーライトである歪の小さい高強度
の歯車。ただし、歯内部とは図１（Ａ）の斜線部で示さ
れる歯の浸炭層より内側である。3. A high-strength gear with small strain, which has a martensite content of 30% or more and less than 50% and a balance of ferrite-pearlite in the tooth obtained by the manufacturing method according to claim 1. However, the inside of the tooth is the inside of the carburized layer of the tooth shown by the hatched portion in FIG.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3236603A JP2549038B2 (en) | 1991-09-17 | 1991-09-17 | Method for carburizing heat treatment of high-strength gear with small strain and its gear |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3236603A JP2549038B2 (en) | 1991-09-17 | 1991-09-17 | Method for carburizing heat treatment of high-strength gear with small strain and its gear |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0570924A JPH0570924A (en) | 1993-03-23 |
| JP2549038B2 true JP2549038B2 (en) | 1996-10-30 |
Family
ID=17003091
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3236603A Expired - Fee Related JP2549038B2 (en) | 1991-09-17 | 1991-09-17 | Method for carburizing heat treatment of high-strength gear with small strain and its gear |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2549038B2 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5746842A (en) * | 1995-09-29 | 1998-05-05 | Toa Steel Co., Ltd. | Steel gear |
| KR20030022427A (en) * | 2001-08-10 | 2003-03-17 | 현대자동차주식회사 | A High Strength Alloy Steel of Chrome-Molybdene for a Transmission |
| KR101617985B1 (en) | 2012-01-26 | 2016-05-03 | 신닛테츠스미킨 카부시키카이샤 | Case hardening steel material with little heat-treatment strain |
| CN104711401B (en) * | 2015-02-09 | 2017-12-05 | 中车戚墅堰机车车辆工艺研究所有限公司 | Large heavy-load gear carburization quenching method |
| CN104806725A (en) * | 2015-03-13 | 2015-07-29 | 常州大学 | Computing method for flexible gear minimum teeth number of wave generator external harmonic gear mechanism |
| CN114779601A (en) * | 2022-05-06 | 2022-07-22 | 江苏沙龙机电科技有限公司 | Wear-resistant mechanical timer transmission assembly and production process thereof |
-
1991
- 1991-09-17 JP JP3236603A patent/JP2549038B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0570924A (en) | 1993-03-23 |
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