JPH06172867A - Production of gear excellent in impact fatigue life - Google Patents
Production of gear excellent in impact fatigue lifeInfo
- Publication number
- JPH06172867A JPH06172867A JP32341492A JP32341492A JPH06172867A JP H06172867 A JPH06172867 A JP H06172867A JP 32341492 A JP32341492 A JP 32341492A JP 32341492 A JP32341492 A JP 32341492A JP H06172867 A JPH06172867 A JP H06172867A
- Authority
- JP
- Japan
- Prior art keywords
- steel
- gear
- less
- fatigue life
- temperature
- 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.)
- Pending
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/32—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for gear wheels, worm wheels, or the like
Abstract
Description
【０００１】[0001]
【産業上の利用分野】この発明は自動車、土木建築用機
械、その他各種の産業機械の重要部品である歯車、特に
衝撃疲労寿命に優れた歯車、の製造に関するものであ
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of gears, which are important parts of automobiles, civil engineering and construction machinery, and various other industrial machinery, in particular gears having an excellent impact fatigue life.
【０００２】[0002]
【従来の技術】従来、自動車、土木建築用機械、あるい
は各種機械に使用される歯車やシャフト類で高強度を必
要とする機械部品は、肌焼鋼 (JIS で機械構造用合金鋼
として定められているSCr420、SCM420、SNCM420 など)
を素材とし、これらを所定の形状に機械加工した後、浸
炭処理と焼入れ・焼戻し処理を施して製造されている。2. Description of the Related Art Conventionally, gears and shafts used for automobiles, civil engineering and construction machinery, or various machines require mechanical strength to be hardened steel (JIS is defined as alloy steel for machine structure). SCr420, SCM420, SNCM420, etc.)
It is manufactured by carburizing and quenching / tempering after machining these into a predetermined shape.
【０００３】しかし、上記肌焼鋼を素材として製造され
た歯車等を最近の高出力エンジンに使用すると、歯元疲
労、歯面疲労、曲げ疲労などによる疲労破壊を生じるこ
とがあり、疲労寿命の優れた肌焼鋼の開発が強く望まれ
ている。例えば、ショットピーニング加工を施すことに
より、歯元疲労強度をある程度まで改善することができ
るが、更に一層疲労寿命が優れた肌焼鋼の開発が望まれ
ている。However, when a gear or the like manufactured from the above case hardening steel is used in a recent high-power engine, fatigue fracture may occur due to tooth root fatigue, tooth surface fatigue, bending fatigue, etc. Development of excellent case hardening steel is strongly desired. For example, it is possible to improve the root fatigue strength to some extent by performing shot peening, but there is a demand for the development of a case-hardening steel that has even better fatigue life.
【０００４】また、最近は、自動車、土木建築用機械等
に使用される歯車では、例えば急発進、急ブレーキな
ど、使用条件が過酷である場合に、歯車に衝撃が加わ
り、衝撃疲労破壊が起きるという問題がクローズアップ
されてきた。衝撃疲労は、通常の歯元疲労とは異なり、
低サイクル疲労であり、ショットピーニングの効果が現
れない領域である。Recently, in gears used in automobiles, civil engineering and construction machines, etc., when the operating conditions are severe such as sudden start and sudden braking, impact is applied to the gears, causing impact fatigue fracture. That problem has been highlighted. Impact fatigue is different from normal root fatigue,
It is a low-cycle fatigue region where the effect of shot peening does not appear.
【０００５】[0005]
【発明が解決しようとする課題】この発明の目的は、素
材鋼中の化学成分を厳密に制御することと共に、歯車へ
の製造プロセスを改善することによって、従来の歯車で
は到底達することのできなかった、優れた耐疲労特性を
有する歯車を製造する方法を提供することにある。DISCLOSURE OF THE INVENTION The object of the present invention cannot be reached by conventional gears by strictly controlling the chemical composition in the raw steel and improving the manufacturing process for gears. Another object of the present invention is to provide a method of manufacturing a gear having excellent fatigue resistance.
【０００６】[0006]
【課題を解決するための手段】本発明の要旨は、下記
(1) の素材鋼を使用し、(2) のプロセスで加工、熱処理
をすることを特徴とする衝撃疲労寿命に優れた歯車の製
造方法、にある。The summary of the present invention is as follows.
A method for manufacturing a gear having an excellent impact fatigue life, characterized by using the material steel of (1) and processing and heat treating in the process of (2).
【０００７】(1) 素材鋼：重量％で、Ｃ: 0.10〜0.30
％、 Si: 0.15％以下、 Mn: 0.60％以下、Cr: 0.90
％以下、 Mo: 0.30〜2.00％、 Nb:0.010〜0.100
％、を含み、残部がFeおよび不可避的不純物からなる
鋼、または、上記の成分に加えて更に、Cu: 1.00 ％以
下、 Ni: 3.50％以下、 Al:0.010〜0.100 ％、Ti:
0.010〜0.100 ％、Ｖ: 0.01〜0.30％、Ｂ: 0.0003〜0.0
050％ の６種の成分の中の１種以上を含み、残部がFeおよび不
可避的不純物からなる鋼。(1) Material steel:% by weight, C: 0.10 to 0.30
%, Si: 0.15% or less, Mn: 0.60% or less, Cr: 0.90
% Or less, Mo: 0.30 to 2.00%, Nb: 0.010 to 0.100
%, Steel with the balance being Fe and inevitable impurities, or in addition to the above components, Cu: 1.00% or less, Ni: 3.50% or less, Al: 0.010 to 0.100%, Ti:
0.010 to 0.100%, V: 0.01 to 0.30%, B: 0.0003 to 0.0
Steel containing 050% of one or more of the six components with the balance Fe and inevitable impurities.
【０００８】(2) 加工、熱処理のプロセス:上記の素材
鋼に浸炭処理を施した後、高周波誘導加熱によって 750
〜850 ℃の温度範囲に加熱し、この温度範囲で 0.1〜2.
0 分間保持した後ただちに歯車に鍛造し、次いで焼入れ
および焼戻し処理を施す。(2) Processing and heat treatment process: After the above steel material is carburized, it is heated to 750 by high frequency induction heating.
Heat to a temperature range of ~ 850 ° C and 0.1 ~ 2 in this temperature range.
After holding for 0 minutes, the gear is immediately forged, followed by quenching and tempering.
【０００９】[0009]
【作用】この発明の方法で用いる素材鋼は、先に本発明
者が提案 (特開平２−125842号公報参照) した耐疲労特
性に優れた浸炭肌焼鋼である。この鋼は、次のような本
発明者の知見を基にして開発されたものである。The material steel used in the method of the present invention is a carburized case-hardening steel excellent in fatigue resistance, which was previously proposed by the present inventor (see Japanese Patent Application Laid-Open No. 2-125842). This steel was developed based on the following knowledge of the present inventor.
【００１０】 疲労破壊が、浸炭処理中に発生する浸
炭異常層 (オーステナイト粒界の酸化、不完全焼入組
織）に起因しているので、この浸炭異常層を抑制する必
要があること、 そのためには肌焼鋼中のSi、MnおよびCr含有量を適
正範囲内に調整し、かつ、適正量のNbを添加することが
有効であること、 Si、MnおよびCrの低減は、主にオーステナイト粒界
の酸化防止に有効であり、Nbは浸炭層中のオーステナイ
トの焼入性を向上させて、不完全焼入層の生成を防止す
ることができること。Since fatigue failure is caused by an abnormal carburizing layer (oxidation of austenite grain boundaries, incomplete quenching structure) generated during carburizing treatment, it is necessary to suppress this abnormal carburizing layer. Is effective to adjust the Si, Mn and Cr contents in the case-hardening steel to within the proper range and to add an appropriate amount of Nb.The reduction of Si, Mn and Cr is mainly due to the austenite grain. It is effective in preventing the oxidation of the field, and Nb can improve the hardenability of austenite in the carburized layer and prevent the formation of an incompletely hardened layer.
【００１１】上記の新しい肌焼鋼で製造した歯車は、従
来の肌焼鋼によって製造したものよりも優れた歯面疲労
強度と歯元疲労強度を持つ。しかし、前述のように、用
途によっては、優れた歯面疲労強度および歯元疲労強度
とともに高い衝撃疲労強度を併せ持つことが必要とされ
る。そこで、本発明者は、この衝撃疲労強度の向上を目
的として研究を進めた結果、これは浸炭部のオーステナ
イト結晶粒の大きさに著しく影響されることを知った。Gears made of the above-mentioned new case-hardening steel have superior tooth surface fatigue strength and root fatigue strength to those made of conventional case-hardening steel. However, as described above, depending on the application, it is necessary to have both excellent tooth surface fatigue strength and tooth root fatigue strength as well as high impact fatigue strength. Then, the present inventor has conducted research for the purpose of improving the impact fatigue strength, and as a result, has found that this is significantly affected by the size of austenite crystal grains in the carburized portion.
【００１２】本発明は、歯面疲労強度と歯元疲労強度の
向上のために化学組成を厳密に制御した素材鋼を使用し
て、浸炭処理中に発生する浸炭異常層を防止し、更に、
浸炭処理後、高周波誘導加熱によって急速に昇温し、比
較的低温の温度範囲において歯車に鍛造してオーステナ
イト結晶粒を微細化し、次いで焼入れ、焼戻し処理を行
うことを特徴とするもので、これによって、衝撃疲労寿
命を含めて総合的に優れた耐疲労特性を有する歯車の製
造を可能としたものである。The present invention uses a material steel whose chemical composition is strictly controlled to improve the tooth surface fatigue strength and the tooth root fatigue strength, and prevents the abnormal carburizing layer generated during the carburizing treatment.
After carburizing, the temperature is rapidly raised by high-frequency induction heating, the austenite crystal grains are refined by forging into a gear in a relatively low temperature range, and then quenching and tempering are performed. It is possible to manufacture a gear having comprehensively excellent fatigue resistance including impact fatigue life.
【００１３】以下に素材鋼の化学組成およびその加工、
熱処理の条件を前記のように特定した理由を作用効果と
ともに説明する。なお、合金成分の含有量の「％」は、
すべて「重量％」である。The chemical composition of the material steel and its processing are as follows:
The reason why the heat treatment condition is specified as described above will be explained together with the function and effect. In addition, "%" of the content of the alloy component is
All are "% by weight".
【００１４】(1) 素材鋼の化学組成について、 Ｃ：0.10〜0.30％ Ｃは鋼に所定の静的強度を付与するのに必要な元素であ
るが、その反面、靭性を低下させる。特に浸炭処理を施
す肌焼鋼では、静的強度と靭性のバランスが必要であっ
て、最低限の静的強度を得るには0.10％以上のＣが必要
である。しかし、Ｃが0.30％を超えると鋼の靭性が急激
に低下するため上限を0.30％とする。(1) Regarding the chemical composition of the raw material steel, C: 0.10 to 0.30% C is an element necessary for imparting a predetermined static strength to the steel, but on the other hand, it lowers the toughness. Particularly in case hardening steel to be carburized, a balance between static strength and toughness is required, and 0.10% or more of C is required to obtain the minimum static strength. However, if C exceeds 0.30%, the toughness of the steel sharply decreases, so the upper limit is made 0.30%.
【００１５】Si：0.15％以下 Siは鋼の脱酸に必要であると共に、所定の静的強度を付
与するのに必要な元素である。しかし、Siは酸素との結
合力が強いために、浸炭処理を施す肌焼鋼では浸炭処理
時に粒界にSiの酸化物が生成して粒界脆化を生じ、歯車
においては歯元疲労強度、歯面疲労強度、曲げ疲労強度
等を低下させる。特に0.15％を超えるとSi酸化物の生成
が著しく、本発明の目的とする疲労寿命を向上させるた
めには、後述するMn、CrおよびNb含有量の限定に加え、
Siを0.15％以下に制限することが不可欠の要件である。Si: 0.15% or less Si is an element necessary for deoxidizing steel and imparting a predetermined static strength. However, since Si has a strong binding force with oxygen, in case-hardening steel that is subjected to carburizing, oxides of Si are generated at the grain boundaries during carburizing, causing intergranular embrittlement. , Tooth surface fatigue strength, bending fatigue strength, etc. are reduced. In particular, when the content of Si oxide exceeds 0.15%, the formation of Si oxide is remarkable, and in order to improve the fatigue life aimed at by the present invention, in addition to the Mn, Cr and Nb contents described below,
Limiting Si to 0.15% or less is an essential requirement.
【００１６】Mn：0.60％以下 MnはSiと同様に鋼の脱酸に必要な元素であり、また鋼の
焼入性を向上させるのに有効である。しかし、酸素との
結合力が強いために浸炭処理時に粒界にMn酸化物を生成
し、特に0.60％を超えるとMn酸化物の生成が著しい。従
って、本発明の目的である疲労寿命の向上を実現させる
ためには、前述のSiおよび後述するCr、Nb含有量の限定
に加え、Mn含有量を0.60％以下に制限する必要がある。Mn: 0.60% or less Mn is an element necessary for deoxidizing steel similarly to Si, and is effective for improving the hardenability of steel. However, Mn oxide is generated at the grain boundary during carburizing treatment because of its strong bonding force with oxygen, and especially when Mn oxide exceeds 0.60%. Therefore, in order to realize the improvement of the fatigue life, which is the object of the present invention, it is necessary to limit the Mn content to 0.60% or less in addition to the above-mentioned Si and Cr and Nb contents described later.
【００１７】Cr：0.90％以下 Crは鋼に焼入性を付与するのに有効な元素である。ま
た、浸炭性を向上させるために肌焼鋼には添加されるこ
とが多い。しかし、前記のSi、Mnと同じように、酸素と
の結合力が強いため浸炭処理の際に粒界にCr酸化物を生
じ、粒界を脆化して疲労強度を低下させる。特に0.90％
を超えるとCr酸化物の生成が著しくなる。Cr: 0.90% or less Cr is an element effective for imparting hardenability to steel. Further, it is often added to case-hardening steel in order to improve the carburizing property. However, like Si and Mn described above, since the bond strength with oxygen is strong, Cr oxide is generated at the grain boundary during the carburizing treatment, and the grain boundary is embrittled to reduce the fatigue strength. Especially 0.90%
If it exceeds, the formation of Cr oxide becomes remarkable.
【００１８】この発明の目的とする疲労寿命を向上させ
るには、前述のSi、Mnおよび後述するNb含有量の限定に
加えて、Cr含有量を0.90％以下に制限する必要がある。
なお、衝撃疲労強度を特に重視する場合には、Crは 0.1
0 ％以下に抑えるのが望ましい。In order to improve the fatigue life, which is the object of the present invention, it is necessary to limit the Cr content to 0.90% or less in addition to the above-mentioned limitation of the Si, Mn and Nb contents described later.
If impact fatigue strength is emphasized, Cr is 0.1
It is desirable to keep it below 0%.
【００１９】Mo：0.30〜2.00％ Moは鋼に所定の焼入性を与え、静的強度および靭性を向
上させるのに必要である。本発明では、前述のSi、Mnお
よびCr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性を与えるために、Moを0.30％以上
含有させる。しかし、2.00％を超えて含有させてもその
効果は飽和して経済性を損なうため、上限を2.00％とす
る。Mo: 0.30 to 2.00% Mo is necessary for imparting a predetermined hardenability to steel and improving static strength and toughness. In the present invention, Mo is contained in an amount of 0.30% or more in order to provide the hardenability equal to or higher than that of the conventional steel under the above-mentioned limitation on the Si, Mn and Cr contents. However, even if the content exceeds 2.00%, the effect is saturated and the economy is impaired, so the upper limit is made 2.00%.
【００２０】Nb： 0.010〜0.100 ％ Nbは、浸炭異常層、特に表面の不完全焼入層の生成を防
止するのに重要な元素である。前述のSi、MnおよびCr含
有量の限定に加えて、Nbを含有させることにより浸炭異
常層の発生を効果的に抑制することができる。その効果
を発揮させるためには 0.010％以上含有させることが必
要である。しかし、Nbが0.100 ％を超えると、鋼の結晶
粒が粗大化して靭性が劣化し、また機械加工時の切削性
が損なわれる。Nb: 0.010 to 0.100% Nb is an important element for preventing the formation of an abnormal carburized layer, especially an incompletely hardened layer on the surface. In addition to the above-mentioned limitation of Si, Mn, and Cr contents, the inclusion of Nb can effectively suppress the occurrence of an abnormal carburized layer. In order to exert its effect, it is necessary to contain 0.010% or more. However, when Nb exceeds 0.100%, the crystal grains of the steel become coarse, the toughness deteriorates, and the machinability during machining is impaired.
【００２１】本発明方法で素材として使用する肌焼鋼の
一つは、以上で述べたＣ、Si、Mn、Cr、Mo、Nbを所定量
含有し残部がFeと不可避的な不純物からなるものであ
る。One of the case-hardening steels used as a raw material in the method of the present invention is one containing a predetermined amount of C, Si, Mn, Cr, Mo and Nb described above, and the balance being Fe and inevitable impurities. Is.
【００２２】素材鋼のもう一つは、上記の成分に加えて
更に下記の成分の１種以上を適正量含有する肌焼鋼であ
る。Another type of base steel is case-hardening steel containing an appropriate amount of one or more of the following components in addition to the above components.
【００２３】Cu：1.00％以下 Cuは鋼の焼入性と静的強度を上昇させるのに有効な元素
である。その効果を発揮させるためには適宜添加すれば
よいが、1.00％を超えて含有させると熱間加工性が低下
する。また静的強度も低下するので1.00％を上限とす
る。Cu: 1.00% or less Cu is an element effective in increasing the hardenability and static strength of steel. In order to exert the effect, it may be added as appropriate, but if it is contained in excess of 1.00%, the hot workability is deteriorated. In addition, the static strength also decreases, so 1.00% is the upper limit.
【００２４】Ni：3.50％以下 NiはCuと同様に、鋼に所定の焼入性を付与し、静的強度
を上昇させるのに有効な元素である。またNiは鋼の靭性
を向上させるので、所定の焼入性と靭性を確保するため
任意に添加することができる。更にNiは、前述のＣ、S
i、Mn、Cr、Mo、Nb含有量の限定範囲内で浸炭部の焼入
性を向上させることができる。特に大型歯車の場合に
は、不完全焼入層の生成を防止して疲労寿命を向上させ
ることができる。しかし、3.50％を超えて含有させて
も、その効果は飽和し経済性を損なうので3.50％を上限
とする。Ni: 3.50% or less Like Cu, Ni is an element effective for imparting a predetermined hardenability to steel and increasing the static strength. Further, Ni improves the toughness of steel, so Ni can be optionally added to ensure the predetermined hardenability and toughness. Furthermore, Ni is the above-mentioned C, S
The hardenability of the carburized part can be improved within the limited range of the i, Mn, Cr, Mo, and Nb contents. Particularly in the case of a large gear, the fatigue life can be improved by preventing the formation of an incompletely hardened layer. However, if the content exceeds 3.50%, the effect is saturated and the economy is impaired, so 3.50% is made the upper limit.
【００２５】Ｖ：0.01〜0.30％ Ｖは鋼中で炭窒化物を析出させ、鋼の高温強度を高める
のに有効な元素である。例えば、高出力エンジンの歯車
として使用する場合、その熱間静的強度を発揮させるた
めには0.01％以上含有させることが必要である。しか
し、0.30％を超えて含有させると熱間加工性が低下する
ので0.30％を上限とする。V: 0.01 to 0.30% V is an element effective for precipitating carbonitrides in the steel and increasing the high temperature strength of the steel. For example, when it is used as a gear of a high-power engine, it is necessary to contain 0.01% or more in order to exert its hot static strength. However, if the content exceeds 0.30%, the hot workability deteriorates, so the upper limit is 0.30%.
【００２６】Al ：0.010 〜0.100 ％ Al は鋼の結晶粒を微細化して靭性を向上させる効果を
有する。その効果を発揮させるためには 0.010％以上含
有させることが必要である。しかし、Alの含有量が 0.1
00％を超えると鋼の清浄度が悪化して切削性を損わせ、
また鋼の結晶粒を粗大化させて靭性を低下させるので
0.100％を上限とする。Al: 0.010 to 0.100% Al has the effect of refining the crystal grains of the steel and improving the toughness. In order to exert its effect, it is necessary to contain 0.010% or more. However, the Al content is 0.1
If it exceeds 00%, the cleanliness of the steel deteriorates and the machinability is impaired.
Also, since the crystal grains of steel are coarsened and the toughness is reduced,
The upper limit is 0.100%.
【００２７】Ti： 0.010〜0.100 ％ TiはAlと同様に鋼の結晶粒を微細化して鋼の靭性を向上
させる。その効果を充分に発揮させるためには、0.010
％以上含有させることが必要である。一方、0.100 ％を
超えて含有させると鋼の清浄度が低下して切削性が悪く
なると共に、鋼の結晶粒を粗大化して靭性を低下させる
ので 0.100％を上限とする。Ti: 0.010 to 0.100% Ti, like Al, refines the crystal grains of the steel and improves the toughness of the steel. In order to fully bring out the effect, 0.010
% Or more is necessary. On the other hand, if the content exceeds 0.100%, the cleanliness of the steel decreases and the machinability deteriorates, and the crystal grains of the steel coarsen to decrease the toughness, so 0.100% is made the upper limit.
【００２８】Ｂ：0.0003〜0.0050％ Ｂは鋼の焼入性を向上させ、静的強度を上昇させるのに
有効な元素であり、その効果を発揮させるためには、0.
0003％以上の含有が必要である。しかし、含有量が0.00
50％を超えると鋼の結晶粒を粗大化させ靭性を低下させ
るので0.0050％を上限とする。B: 0.0003 to 0.0050% B is an element effective for improving the hardenability of steel and increasing the static strength.
It is necessary to contain at least 0003%. However, the content is 0.00
If it exceeds 50%, the crystal grains of the steel will be coarsened and the toughness will be reduced, so 0.0050% is made the upper limit.
【００２９】(2) 加工、熱処理について、図１は、本発
明方法におけるヒートパターンを示す図である。以下、
この図を参照しながら説明する。(2) Regarding processing and heat treatment, FIG. 1 is a diagram showing a heat pattern in the method of the present invention. Less than,
Description will be given with reference to this figure.
【００３０】浸炭処理:前述の素材鋼は、連続鋳造また
はインゴットに鋳造し、熱間圧延、更に必要に応じて冷
間伸線して線材 (または棒鋼) となし、これを所定の寸
法に切断して浸炭する。浸炭は、通常の条件で、例えば
ガス浸炭を行えばよい。Carburizing treatment: The above-mentioned raw material steel is continuously cast or cast into an ingot, hot-rolled, and if necessary, cold-drawn to form a wire rod (or steel bar), which is cut to a predetermined size. And carburize. Carburization may be carried out under normal conditions, for example, gas carburization.
【００３１】鍛造の前に浸炭処理を施すのは、浸炭温度
が通常 900〜930 ℃であるため、鍛造後に浸炭処理を施
すと鍛造によって微細化した結晶粒が再び粗大化してし
まうからである。The reason why the carburizing treatment is carried out before the forging is that the carburizing temperature is usually 900 to 930 ° C., so that if the carburizing treatment is carried out after the forging, the crystal grains refined by the forging again become coarse.
【００３２】(ロ)加熱および鍛造:本発明の方法では、図
１に〜として示すように、高周波誘導加熱によって
750〜850 ℃の範囲に素材を加熱し、この温度域で0.1
〜2.0 分保持したのち、ただちに鍛造を行う。以下、こ
の温度を鍛造温度という。(B) Heating and forging: In the method of the present invention, as shown in FIG.
The material is heated in the range of 750 to 850 ℃ and 0.1
Hold for ~ 2.0 minutes and then forge immediately. Hereinafter, this temperature is referred to as a forging temperature.
【００３３】鍛造温度までの加熱方法を高周波誘導加熱
としたのは、急速昇温と短時間加熱(保持) とによって
結晶粒の粗大化を防止するためである。実施例に示すよ
うに、高周波誘導加熱の条件が鋼の組織、衝撃疲労寿命
などに及ぼす影響を調査し、この結果に基づいて適切な
高周波誘導加熱条件を定めた。The reason why the heating method up to the forging temperature is high-frequency induction heating is to prevent coarsening of crystal grains by rapid heating and short-time heating (holding). As shown in the examples, the influence of the conditions of high frequency induction heating on the structure of steel, impact fatigue life, etc. was investigated, and appropriate high frequency induction heating conditions were determined based on these results.
【００３４】高周波誘導加熱の温度、即ち、鍛造温度を
750〜850 ℃に限定したのは次の理由による。即ち、75
0 ℃より低温ではオーステナイト粒が再結晶せず、結晶
粒の微細化ができない。また、750 ℃より低温では変形
抵抗が大きいために鍛造の際に割れが発生し易い。一
方、850 ℃を超えると結晶粒が粗大化し、本発明の目的
である結晶粒微細化による衝撃疲労寿命の向上効果がな
くなる。従って、高周波誘導加熱温度、即ち鍛造加熱温
度は 750〜850 ℃とする。The temperature of high frequency induction heating, that is, the forging temperature,
The reason for limiting the temperature to 750 to 850 ℃ is as follows. That is, 75
At temperatures lower than 0 ° C, the austenite grains do not recrystallize, and the crystal grains cannot be refined. Further, at a temperature lower than 750 ° C, cracking is likely to occur during forging because of high deformation resistance. On the other hand, when the temperature exceeds 850 ° C., the crystal grains become coarse, and the effect of improving the impact fatigue life due to the grain refinement, which is the object of the present invention, is lost. Therefore, the high frequency induction heating temperature, that is, the forging heating temperature is set to 750 to 850 ° C.
【００３５】上記の温度範囲における保持時間を 0.1〜
2.0 分としたのは、炭化物を固溶させるには最低でも
0.1分間は必要であるし、一方、この温度域での保持時
間が２.0分を超えると脱炭が生じ、浸炭処理した効果が
低下するからである。The holding time in the above temperature range is 0.1 to
2.0 minutes is the minimum for solid solution of carbides.
This is because 0.1 minute is required, and on the other hand, if the holding time in this temperature range exceeds 2.0 minutes, decarburization occurs and the effect of carburizing treatment decreases.
【００３６】(ハ)焼入れ、焼戻しについて:図１に及び
で示すように、鍛造終了後に焼入れと焼戻しの熱処理
を施す。(C) Regarding quenching and tempering: As shown by and in FIG. 1, after the forging, heat treatments of quenching and tempering are performed.
【００３７】この熱処理は、例えば、60〜90℃の油中へ
の焼入れと 150〜250 ℃で１〜２時間加熱する焼戻しで
ある。焼戻し後の冷却は空冷、水冷のいずれでもよい。
なお、鍛造後に、一旦室温まで冷却してから高周波誘導
加熱で再加熱して焼入れを行ってもよいが、その場合
も、加熱温度は 750〜850 ℃の範囲とする。This heat treatment is, for example, quenching in oil at 60 to 90 ° C. and tempering at 150 to 250 ° C. for 1 to 2 hours. Cooling after tempering may be air cooling or water cooling.
After forging, the material may be once cooled to room temperature and then reheated by high-frequency induction heating for quenching, but in that case as well, the heating temperature is in the range of 750 to 850 ° C.
【００３８】[0038]
【実施例】溶解能力 150kgの真空溶解炉で、表１および
表２に示す各種の組成の肌焼鋼を溶製してインゴットと
した。表１に示すのは本発明方法の素材鋼に相当するも
の、表２に示すのは、成分の種類または含有量が前記の
範囲を外れた比較のための素材鋼である。Example A case ingot of various compositions shown in Table 1 and Table 2 was melted in a vacuum melting furnace having a melting capacity of 150 kg to prepare an ingot. Table 1 shows the steel corresponding to the raw steel of the method of the present invention, and Table 2 shows the raw steel for comparison in which the kinds or contents of the components are out of the above ranges.
【００３９】上記のインゴットを1250℃で１時間加熱
し、30mm角に熱間鍛伸したものを28mm角に機械加工し、
長さ 200mmに切断して図２に示すヒートパターンで浸炭
処理を施した。即ち、カーボンポテンシャルが 0.9の雰
囲気中で 925℃×２時間の均熱を行い、その後、焼割れ
防止と残留オーステナイト抑制のために浸炭炉内で 850
℃まで徐冷し、１時間保持する拡散処理を行った。The above ingot was heated at 1250 ° C. for 1 hour, hot forged into a 30 mm square and machined into a 28 mm square,
It was cut to a length of 200 mm and carburized in the heat pattern shown in FIG. That is, soaking is performed at 925 ℃ for 2 hours in an atmosphere with a carbon potential of 0.9, and then in a carburizing furnace to prevent quench cracking and suppress retained austenite.
Diffusion treatment was performed by gradually cooling to 0 ° C. and holding for 1 hour.
【００４０】上記浸炭処理後の試料を１kHz 、30 kＷの
高周波電流により、750 〜900 ℃の範囲内で50℃のピッ
チで変えた温度に加熱し、各々の温度で 0.5分間の保持
を行った後、図３に示す形状の試験片に型鍛造し、直ち
に直接水焼入れをし、引き続いて 170℃で１時間の焼戻
しをした。The sample after the above carburizing treatment was heated by a high frequency current of 1 kHz and 30 kW to a temperature changed in the range of 750 to 900 ° C. at a pitch of 50 ° C. and held at each temperature for 0.5 minutes. Then, the test piece having the shape shown in FIG. 3 was die-forged, immediately water-quenched, and subsequently tempered at 170 ° C. for 1 hour.
【００４１】このようにして作製した試験片を用いて、
落錘型衝撃試験機により衝撃疲労試験を実施した。ま
た、オーステナイト粒度もこの試験片で測定した。衝撃
疲労試験は、試験片の一方を固定し、他端に負荷エネル
ギー (４ kＮ−ｍ )を繰り返し与え、割れが発生するま
での繰り返し数を求める試験である。Using the test piece thus produced,
An impact fatigue test was conducted using a falling weight impact tester. The austenite grain size was also measured on this test piece. The impact fatigue test is a test in which one of the test pieces is fixed and load energy (4 kN-m) is repeatedly applied to the other end to obtain the number of repetitions until cracking occurs.
【００４２】オーステナイト結晶は、粒度番号で10以
上、衝撃疲労寿命は50回以上の場合をここでは目標達成
と評価した。試験結果を表３〜表５に示す。Here, the case where the grain size number of the austenite crystal is 10 or more and the impact fatigue life is 50 times or more is evaluated as achieving the target here. The test results are shown in Tables 3 to 5.
【００４３】表３は、表１に示した本発明で定めた組成
の素材鋼を用いた場合の鍛造温度ごとのオーステナイト
結晶番号と衝撃疲労寿命である。Table 3 shows the austenite crystal number and impact fatigue life for each forging temperature when the raw steel having the composition defined in the present invention shown in Table 1 is used.
【００４４】本発明で定める高周波誘導加熱温度（即
ち、鍛造温度）と加熱時間に準拠して作製された試験片
では、オーステナイト粒度は、その目標値である粒度番
号10以上の細粒であり、衝撃疲労寿命も目標の50回以上
を満足するものであった。In the test piece produced according to the high frequency induction heating temperature (ie, forging temperature) and heating time defined in the present invention, the austenite grain size is a fine grain having a grain size number 10 or more, which is the target value, The impact fatigue life also satisfied the target of 50 times or more.
【００４５】素材鋼の化学組成が本発明で定める範囲で
あっても、鍛造温度を規定の上限を超える 900℃とした
ものは粒度番号は全て10未満で、衝撃疲労寿命も全て50
回を下回った成績であった。Even if the chemical composition of the raw material steel is within the range defined by the present invention, the grain size number is all less than 10 and the impact fatigue life is all 50 when the forging temperature is 900 ° C. which exceeds the specified upper limit.
The result was less than the number of times.
【００４６】表４は、表２の比較鋼を素材とした場合の
試験結果である。 750〜900 ℃の全域の鍛造温度におい
て、オーステナイト粒度、衝撃疲労寿命の値が目標値を
満足しないものが多かった。特に鍛造加熱温度が 800℃
を超える場合は、衝撃疲労寿命は全部が目標値を下回っ
た。Table 4 shows the test results when the comparative steel of Table 2 was used as the material. At the forging temperatures in the entire range of 750 to 900 ℃, the values of austenite grain size and impact fatigue life often did not satisfy the target values. Especially forging heating temperature is 800 ℃
When the value exceeds, the impact fatigue life was entirely below the target value.
【００４７】表５は、鍛造温度を 850℃とした場合の試
料の表面からの脱炭の深さを保持時間ごとに調査した結
果である。脱炭深さは、0.010 mmならば実用上問題がな
いと言える。表５から、鍛造温度として最も高い 850℃
の温度でも、保持時間が 2.0分以下であれば脱炭は特に
問題にならないことが分かる。ただし、保持時間が0.05
分のように短いものでは未固溶炭化物の存在が認めら
れ、これによって疲労強度、特に衝撃疲労寿命の低下が
予想される。Table 5 shows the results of examining the depth of decarburization from the surface of the sample for each holding time when the forging temperature was 850 ° C. If the decarburization depth is 0.010 mm, it can be said that there is no practical problem. From Table 5, the highest forging temperature is 850 ℃
It can be seen that decarburization does not become a problem even if the holding time is 2.0 minutes or less even at the temperature. However, the retention time is 0.05
The presence of undissolved carbides is recognized in the short ones, and it is expected that the fatigue strength, in particular, the impact fatigue life will be shortened.
【００４８】なお、鍛造温度を 750℃および 800℃とし
た場合についても脱炭深さを測定したが、これらの場合
には 2.5分までの保持時間で、まったく脱炭は認められ
なかった。The decarburization depth was also measured when the forging temperature was 750 ° C. and 800 ° C., but in these cases, decarburization was not observed at all for a holding time of 2.5 minutes.
【００４９】上記の実施例の結果からも、素材鋼の化学
組成を適切に選び、かつ鍛造温度およびその温度での保
持時間を本発明に定める範囲にすることによって、はじ
めてオーステナイト粒が微細となり、高い衝撃疲労寿命
が得られることが明らかである。Also from the results of the above examples, by appropriately selecting the chemical composition of the raw material steel and setting the forging temperature and the holding time at that temperature within the range defined in the present invention, the austenite grains become fine, and It is clear that a high impact fatigue life can be obtained.
【００５０】[0050]
【表１】 [Table 1]
【００５１】[0051]
【表２】 [Table 2]
【００５２】[0052]
【表３】 [Table 3]
【００５３】[0053]
【表４】 [Table 4]
【００５４】[0054]
【表５】 [Table 5]
【００５５】[0055]
【発明の効果】本発明の製造方法によって造られた歯車
は、衝撃疲労寿命をはじめとする耐疲労特性に優れたも
のであるから、自動車、土木建築用機械、その他各種機
械において、特に高負荷の厳しい条件で使用するのに好
適である。The gears produced by the manufacturing method of the present invention are excellent in fatigue resistance including impact fatigue life, and therefore have a particularly high load in automobiles, civil engineering construction machines and other various machines. It is suitable for use under severe conditions.
【図１】本発明方法のヒートパターンの一例を示す図で
ある。FIG. 1 is a diagram showing an example of a heat pattern of the method of the present invention.
【図２】実施例で行った浸炭処理のヒートパターンを示
す図である。FIG. 2 is a diagram showing a heat pattern of a carburizing process performed in an example.
【図３】実施例で用いた衝撃疲労試験の試験片形状を示
す側面図(a) と正面図(b) で、単位はmmである。FIG. 3 is a side view (a) and a front view (b) showing the shape of a test piece of the impact fatigue test used in the examples, and the unit is mm.
Claims (2)
以下、Mn: 0.60％以下、Cr: 0.90％以下、Mo: 0.30〜2.
00％、Nb:0.010〜0.100 ％を含み、残部がFeおよび不可
避的不純物からなる鋼に浸炭処理を施した後、高周波誘
導加熱によって 750〜850 ℃の温度範囲に加熱し、この
温度範囲で 0.1〜2.0 分間保持した後ただちに歯車に鍛
造し、次いで焼入れおよび焼戻し処理をすることを特徴
とする衝撃疲労寿命に優れた歯車の製造方法。1. By weight%, C: 0.10 to 0.30%, Si: 0.15%
Below, Mn: 0.60% or less, Cr: 0.90% or less, Mo: 0.30 to 2.
Steel containing 00% and Nb: 0.010 to 0.100%, the balance of which is Fe and unavoidable impurities, is carburized and then heated to a temperature range of 750 to 850 ° C by high frequency induction heating. A method for producing a gear having an excellent impact fatigue life, which is characterized by holding for ~ 2.0 minutes, forging the gear immediately, and then quenching and tempering the gear.
以下、Mn: 0.60％以下、Cr: 0.90％以下、Mo: 0.30〜2.
00％、Nb:0.010〜0.100 ％と、更にCu: 1.00％以下、N
i:3.50 ％以下、Al:0.010〜0.100 ％、Ti:0.010〜0.100
％、Ｖ: 0.01〜0.30％およびＢ: 0.0003〜0.0050％の
中の１種以上を含み、残部がFeおよび不可避的不純物か
らなる鋼に浸炭処理を施した後、高周波誘導加熱によっ
て 750〜850 ℃の温度範囲に加熱し、この温度範囲で
0.1〜2.0 分間保持した後ただちに歯車に鍛造し、次い
で焼入れおよび焼戻し処理をすることを特徴とする衝撃
疲労寿命に優れた歯車の製造方法。2. C: 0.10 to 0.30%, Si: 0.15% by weight
Below, Mn: 0.60% or less, Cr: 0.90% or less, Mo: 0.30 to 2.
00%, Nb: 0.010 to 0.100%, Cu: 1.00% or less, N
i: 3.50% or less, Al: 0.010 to 0.100%, Ti: 0.010 to 0.100
%, V: 0.01 to 0.30% and B: 0.0003 to 0.0050%, the balance of which is Fe and unavoidable impurities, and the balance of the steel is carburized, and then 750 to 850 ℃ by high frequency induction heating. Heating to this temperature range and in this temperature range
A method for producing a gear having an excellent impact fatigue life, which comprises holding for 0.1 to 2.0 minutes, forging the gear immediately, and then quenching and tempering the gear.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32341492A JPH06172867A (en) | 1992-12-02 | 1992-12-02 | Production of gear excellent in impact fatigue life |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32341492A JPH06172867A (en) | 1992-12-02 | 1992-12-02 | Production of gear excellent in impact fatigue life |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH06172867A true JPH06172867A (en) | 1994-06-21 |
Family
ID=18154436
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP32341492A Pending JPH06172867A (en) | 1992-12-02 | 1992-12-02 | Production of gear excellent in impact fatigue life |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH06172867A (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008179849A (en) * | 2007-01-24 | 2008-08-07 | Jfe Bars & Shapes Corp | Steel for gear having superior impact fatigue resistance, and gear using the same |
| JP2008297618A (en) * | 2007-06-02 | 2008-12-11 | Sanyo Special Steel Co Ltd | Method for manufacturing carburized steel part excellent in indentation resistance |
| US7507303B2 (en) * | 2004-09-08 | 2009-03-24 | Arvinmeritor Technology, Llc | Carbonitrided low manganese carbon steel alloy driveline component |
| US20110120596A1 (en) * | 2009-10-14 | 2011-05-26 | Armin Zuber | Manufacturing process of a structural component for a motor vehicle, plate bar for hot forming and structural component |
| CN102226252A (en) * | 2011-06-10 | 2011-10-26 | 钢铁研究总院 | High-toughness carburized bearing steel with ultra-long contact fatigue life and preparation method thereof |
| CN102226253A (en) * | 2011-06-10 | 2011-10-26 | 钢铁研究总院 | Carburized bearing steel for high-speed railways and preparation method thereof |
| WO2016158375A1 (en) * | 2015-03-27 | 2016-10-06 | 株式会社神戸製鋼所 | Steel for carbonitriding and carbonitrided component |
| CN106435397A (en) * | 2016-11-09 | 2017-02-22 | 安徽千禧精密轴承制造有限公司 | Carburized bearing roller processing technology |
| CN114959465A (en) * | 2022-05-17 | 2022-08-30 | 石家庄钢铁有限责任公司 | Steel for fine-grain gear and production method thereof |
| CN115386798A (en) * | 2022-08-31 | 2022-11-25 | 马鞍山钢铁股份有限公司 | Ultra-low silicon Nb microalloyed gear steel and manufacturing method thereof |
| CN115418567A (en) * | 2022-08-31 | 2022-12-02 | 马鞍山钢铁股份有限公司 | Nb-Ti-B microalloyed high temperature resistant low internal oxidation carburized gear steel and manufacturing method thereof |
| CN115505841A (en) * | 2022-08-31 | 2022-12-23 | 马鞍山钢铁股份有限公司 | Fatigue-carburization-resistant gear steel with excellent tail end hardenability and manufacturing method thereof |
-
1992
- 1992-12-02 JP JP32341492A patent/JPH06172867A/en active Pending
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