JP3104449B2 - Heat treatment of carburized gears - Google Patents
Heat treatment of carburized gearsInfo
- Publication number
- JP3104449B2 JP3104449B2 JP05005115A JP511593A JP3104449B2 JP 3104449 B2 JP3104449 B2 JP 3104449B2 JP 05005115 A JP05005115 A JP 05005115A JP 511593 A JP511593 A JP 511593A JP 3104449 B2 JP3104449 B2 JP 3104449B2
- Authority
- JP
- Japan
- Prior art keywords
- gear
- heat treatment
- heating
- carburized
- steel
- 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.)
- Expired - Fee Related
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Description
【０００１】[0001]
【産業上の利用分野】この発明は、浸炭歯車の熱処理法
に関し、とくに耐ピッティング性や歯元疲労強度などの
歯車特性の有利な向上を、生産能率の向上に併せて実現
しようとするものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment method for carburized gears, and more particularly to an advantageous improvement of gear characteristics such as pitting resistance and tooth root fatigue strength, together with an improvement in production efficiency. It is.
【０００２】[0002]
【従来の技術】自動車や建設機械用の歯車としては、高
強度のみならず、とくに耐ピッティング性が必要とされ
るため、従来から浸炭処理を施して表面硬度を向上させ
た浸炭歯車が用いられている。ここに、浸炭歯車の耐ピ
ッティング性を向上させるためには、表面に炭化物を析
出させ、さらにこの炭化物を微細かつ粒状化させる必要
がある。そのため、例えば特開平２-34766号公報に開示
の方法では、図１（ａ）に示すように、浸炭処理後、焼
入れ前に少なくとも１回、Ａ1 変態点を挟んでその上下
に昇降温する加熱冷却処理を施すことにより、析出セメ
ンタイトの球状化を図っている。2. Description of the Related Art Car gears for automobiles and construction machines require not only high strength but also especially pitting resistance. Therefore, conventionally, carburized gears having been subjected to carburizing treatment to improve surface hardness have been used. Have been. Here, in order to improve the pitting resistance of the carburized gear, it is necessary to precipitate carbide on the surface and to further finely and granulate the carbide. Therefore, in the method disclosed in Japanese Unexamined Patent Publication No. 2-34766, as shown in FIG. 1 (a), after the carburizing treatment, at least once before quenching, and heating and cooling above and below across the A 1 transformation point By performing the heating and cooling treatment, the precipitated cementite is made spherical.
【０００３】また特開平２−159360号公報には、高濃度
浸炭により表面にFeやCrの炭化物を析出させて硬度の上
昇を図る一方、焼入性向上元素であるCrが炭化物になる
ことに起因して生じる生地の焼入性の低下については、
その後に浸窒処理を施し、Ｎの拡散によりCrを再固溶さ
せることによって、その弊害を回避する方法が開示され
ている。Japanese Patent Application Laid-Open No. 2-159360 discloses that while increasing the hardness by depositing carbides of Fe and Cr on the surface by high-concentration carburization, Cr, which is an element for improving hardenability, becomes carbide. The decrease in hardenability of the dough caused by
After that, a method is disclosed in which a nitriding treatment is performed and Cr is dissolved again by diffusion of N to avoid the adverse effect.
【０００４】[0004]
【発明が解決しようとする課題】しかしながら、上記の
方法では、析出物の球状化処理や浸窒処理に30分〜２時
間もの時間を要することから、生産性が阻害されるとい
う問題があった。とくに浸窒処理を付加する方法には、
NH3ガスの使用による環境の悪化や、 NH3ガスコントロ
ールの困難さに起因した品質のバラツキなども問題とさ
れる。また、上記の各方法では、耐ピッティング性は改
善されるものの、歯元疲労強度が依然として低いところ
にも問題を残していた。この発明は、上記の問題を有利
に解決するもので、生産性を阻害することなしに、耐ピ
ッティング性はいうまでもなく、歯元疲労強度を効果的
に向上させ得る、浸炭歯車の新規な熱処理法を提案する
ことを目的とする。However, in the above-mentioned method, the spheroidizing treatment and the nitriding treatment of the precipitate require 30 minutes to 2 hours, so that the productivity is impaired. . In particular, the method of adding nitriding is
It is also considered that the use of NH 3 gas deteriorates the environment, and that the quality of the NH 3 gas varies due to difficulties in controlling the gas. Further, in each of the above methods, although the pitting resistance is improved, a problem still remains where the root fatigue strength is still low. The present invention advantageously solves the above-described problems, and provides a new carburized gear that can effectively improve the root fatigue strength, not to mention pitting resistance, without impairing productivity. The purpose is to propose a suitable heat treatment method.
【０００５】[0005]
【課題を解決するための手段】さて発明者らは、上記の
目的を達成すべく鋭意研究を重ねた結果、焼入れ直前の
表面Ｃポテンシャルを調整すると共に、その後に高周波
誘導加熱を加熱手段として活用した熱処理を施すことに
よって、所期した目的が有利に達成されることの知見を
得た。この発明は、上記の知見に立脚するものである。Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have adjusted the surface C potential immediately before quenching, and subsequently utilized high-frequency induction heating as a heating means. It has been found that the intended purpose can be advantageously achieved by performing the heat treatment described above. The present invention is based on the above findings.
【０００６】すなわちこの発明は、所定の形状に仕上げ
た歯車に、焼入れ直前における表面Ｃポテンシャルが
0.9％以上となる浸炭処理を施した後、焼入れし、つい
で高周波誘導加熱によって該歯車の表層部のみ 850〜10
00℃に再加熱後、急冷することを特徴とする浸炭歯車の
熱処理法である。この発明において、耐ピッティングや
歯元疲労強度の一層の向上のためには、歯車素材中に、
Ｖを0.05wt％（以下単に％で示す）以上含有させること
が好ましい。That is, according to the present invention, a surface C potential immediately before quenching is applied to a gear finished in a predetermined shape.
After carburizing to 0.9% or more, it is quenched, and then the high-frequency induction heating is applied to only the surface layer of the gear.
This is a heat treatment method for carburized gears, which is characterized by rapidly cooling after reheating to 00 ° C. In the present invention, in order to further improve pitting resistance and tooth root fatigue strength, in the gear material,
It is preferable to contain V in an amount of 0.05 wt% or more (hereinafter simply indicated by%).
【０００７】[0007]
【作用】この発明によれば、高周波焼入れという短時間
の処理で析出炭化物の球状化を実現できるので、十分な
耐ピッティング性が得られるのはいうまでもなく、処理
時間を大幅に短縮でき、しかも高周波加熱後再焼入れさ
れるのは歯車の表層部のみであるので、歯元の残留圧縮
応力が大きくなり、その結果、歯元疲労強度も向上す
る。According to the present invention, it is possible to realize the spheroidization of the precipitated carbide by a short-time treatment of induction hardening, so that it is needless to say that sufficient pitting resistance can be obtained, and that the treatment time can be greatly reduced. Moreover, since only the surface layer of the gear is requenched after high-frequency heating, the residual compressive stress at the root becomes large, and as a result, the root fatigue strength is also improved.
【０００８】以下、熱処理条件を、上記の範囲に限定し
た理由について説明する。まず、焼入れ直前における歯
車表面のＣポテンシャルは 0.9％以上とする必要があ
る。というのは、Ｃポテンシャルが 0.9％に満たない
と、焼入れ前の炭化物量が不足し、その後の高周波加熱
によってほとんど固溶してしまう結果、硬度不足とな
り、満足いく耐ピッティング性が得られないからであ
る。浸炭処理後の冷却は、常温まで行っても一向にかま
わないけれども、 500〜700 ℃以下までの放冷または強
制ガス冷却でも良い。というのは、引き続く高周波加熱
前に Ac1変態点（ 500〜700 ℃）以下に冷却されていれ
ば、炭化物の球状化が生ずるからである。Hereinafter, the reason why the heat treatment conditions are limited to the above range will be described. First, the C potential on the gear surface immediately before quenching must be 0.9% or more. If the C potential is less than 0.9%, the amount of carbide before quenching will be insufficient, and the solid solution will be hardly formed by high frequency heating after that, resulting in insufficient hardness, and satisfactory pitting resistance will not be obtained. Because. The cooling after the carburizing treatment may be carried out to normal temperature, but may be cooling to 500 to 700 ° C or lower or forced gas cooling. This is because carbides are spheroidized if cooled below the Ac 1 transformation point (500 to 700 ° C.) before the subsequent high-frequency heating.
【０００９】次に、高周波加熱処理については、加熱温
度が 850℃に満たないと、オーステナイト化が不十分と
なって十分な焼入れが望めず、一方、1000℃を超える
と、浸炭後に析出した炭化物のほとんどが固溶してかえ
って硬度が低下し、耐ピッティング性の劣化を招くだけ
でなく、硬化層の結晶粒が粗大化して歯元疲労強度が低
下するので、高周波加熱温度は 850〜1000℃とする必要
がある。Next, in the high-frequency heating treatment, if the heating temperature is lower than 850 ° C., the austenitization becomes insufficient and sufficient quenching cannot be expected. Most of the solid solution dissolves and lowers the hardness, causing not only the deterioration of pitting resistance but also the coarsening of the crystal grains of the hardened layer and the reduction of the tooth root fatigue strength. ° C.
【００１０】ここに、この発明に従って高周波加熱を行
う場合、所定の加熱温度まで一気に昇温しても良いが、
500〜750 ℃までは〜20 kHz程度で加熱し、その後所定
温度までは〜300 kHz 程度で高速加熱する２段階加熱と
することが、炭化物の球状化を必要とする表面部のみ加
熱し、他に熱影響を及ぼさない点で一層好ましい。な
お、単純加熱及び２段階加熱いずれであっても、所要時
間は３〜５秒程度にすぎないので、従来に較べると、冷
却−再加熱処理は大幅に短縮される。また、かような高
周波加熱−冷却処理は、一回の処理で十分ではあるが、
複数回の繰り返し処理を禁止するものではない。Here, when high-frequency heating is performed according to the present invention, the temperature may be raised to a predetermined heating temperature at a stretch.
Heating at about 20 kHz up to 500-750 ° C and then high-speed heating up to about 300 kHz up to a predetermined temperature should be a two-step heating, in which only the surface portion that requires carbide spheroidization is heated. Is more preferable in that it does not affect the heat. In addition, since the required time is only about 3 to 5 seconds in both the simple heating and the two-stage heating, the cooling-reheating treatment is significantly shortened as compared with the related art. In addition, such a high-frequency heating-cooling process is sufficient by one process,
It does not prohibit multiple repetitions.
【００１１】また、この発明では、歯車素材中に、Ｖを
少量含有させることが有利である。というのは、Ｖを含
有させた場合には、高周波焼入れ後の炭化物がより微細
となり、また結晶粒も微細化されるので、耐ピッティン
グ性及び歯元疲労強度ともに一層向上するからである。
ここに上記の効果を得るためには少なくとも0.05％のＶ
の添加が必要であるので、この発明では、冷間鍛造用鋼
素材中に含有させるべきＶ量につき、0.05％以上に限定
した。しかしながら、あまりに多量のＶ添加は、切削性
低下の不利を招くので、0.5％以下程度とするこのが好
ましい。Further, in the present invention, it is advantageous to include a small amount of V in the gear material. This is because when V is contained, the carbide after induction hardening becomes finer and the crystal grains become finer, so that both pitting resistance and root fatigue strength are further improved.
Here, in order to obtain the above effect, at least 0.05% of V
In the present invention, the amount of V to be contained in the steel material for cold forging is limited to 0.05% or more. However, an excessively large amount of V causes a disadvantage of lowering the machinability.
【００１２】さらにこの発明における歯車用鋼素材とし
ては、機械構造用鋼であればいずれもが適合するが、と
くに好適な鋼種は次のとおりである。 ・Cr鋼：SCr 415, SCr 420など。 ・Cr−Mo鋼：SCM 415, SCM 420, SCM 421 など。 ・Ni−Cr鋼：SNC 415, SNC 815など。 ・Ni−Cr−Mo鋼：SNCM 220, SNCM 415, SNCM 420など。Further, as the steel material for gears in the present invention, any steel for machine structure is suitable, and particularly preferred steel types are as follows.・ Cr steel: SCr 415, SCr 420, etc.・ Cr-Mo steel: SCM415, SCM420, SCM421 etc.・ Ni-Cr steel: SNC 415, SNC 815, etc.・ Ni-Cr-Mo steel: SNCM 220, SNCM 415, SNCM 420, etc.
【００１３】[0013]
【実施例】表１に成分組成を示す供試鋼（鋼：SCM42
0、鋼：Ｖ添加鋼）をそれぞれ、表２に示す歯車諸元
に従って機械加工したのち、図１（ａ）〜（ｃ）に示す
履歴になる熱処理を施した。このとき、高周波焼入れ処
理については、図２（ａ），（ｂ）の条件で行った。な
お、表２に示した歯車諸元のうち、（ａ）はピッティン
グ試験用、（ｂ）は歯元疲労試験用である。[Example] Test steel (Steel: SCM42) whose component composition is shown in Table 1
0, steel: V-added steel) were machined according to the gear specifications shown in Table 2, and then subjected to a heat treatment having a history shown in FIGS. 1 (a) to 1 (c). At this time, the induction hardening was performed under the conditions shown in FIGS. 2 (a) and 2 (b). In the gear specifications shown in Table 2, (a) is for a pitting test, and (b) is for a tooth root fatigue test.
【００１４】[0014]
【表１】 [Table 1]
【００１５】[0015]
【表２】 [Table 2]
【００１６】表３に、得られた製品の表面硬度、組織、
平均結晶粒径、歯元残留応力及びピッティング寿命につ
いて調べた結果を示す。Table 3 shows the surface hardness, structure,
The results of examining the average crystal grain size, root residual stress, and pitting life are shown.
【表３】 [Table 3]
【００１７】同表より明らかなように、この発明に従っ
て高周波加熱・焼入れ処理を施したものは、析出炭化物
が効果的に球状化され、優れた耐ピッティング性が得ら
れるだけでなく、歯元疲労強度にも優れている。とくに
Ｖ添加鋼（No.7）は、ピッティング寿命が大幅に延長さ
れている。また、この発明に従った場合には、従来法に
比較して、処理時間を１時間以上も短縮することができ
た。As is apparent from the table, the steel subjected to the high-frequency heating and quenching treatment according to the present invention not only has an effective spheroidization of the precipitated carbides, provides excellent pitting resistance, but also has an excellent tooth root. Excellent fatigue strength. In particular, the V-added steel (No. 7) has a significantly extended pitting life. Further, according to the present invention, the processing time could be reduced by one hour or more as compared with the conventional method.
【００１８】次に図３に、得られた製品の繰り返し数と
歯元応力との関係について調べた結果を示す。同図より
明らかなように、この発明に従い熱処理を施した歯車
（No.6, 7)はいずれも、従来材や比較材に較べて、歯元
応力の劣化程度が著しく小さく、寿命の大幅な延長が達
成されている。Next, FIG. 3 shows the results of an investigation on the relationship between the number of repetitions of the obtained product and the root stress. As can be seen from the figure, the gears (Nos. 6 and 7) heat-treated according to the present invention have significantly smaller tooth root stress degradation compared to the conventional and comparative materials, and have a significantly longer life. Extension has been achieved.
【００１９】[0019]
【発明の効果】かくしてこの発明によれば、生産性を低
下させることなしに、耐ピッティング性及び歯元疲労強
度を併せて向上させることができる。As described above, according to the present invention, the pitting resistance and the root fatigue strength can be improved together without lowering the productivity.
【図１】熱処理条件を示す模式図である。FIG. 1 is a schematic diagram showing heat treatment conditions.
【図２】高周波加熱条件を示す模式図である。FIG. 2 is a schematic diagram showing high-frequency heating conditions.
【図３】浸炭歯車の繰り返し数と歯元応力との関係を示
すグラフである。FIG. 3 is a graph showing the relationship between the number of repetitions of a carburized gear and the root stress.
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.7，ＤＢ名) C21D 9/00 - 9/44 C21D 9/50 C21D 1/10 ──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. 7 , DB name) C21D 9/00-9/44 C21D 9/50 C21D 1/10
Claims (2)
前における表面Ｃポテンシャルが 0.9％以上となる浸炭
処理を施した後、焼入れし、ついで高周波誘導加熱によ
って該歯車の表層部のみ 850〜1000℃に再加熱後、急冷
することを特徴とする浸炭歯車の熱処理法。A gear finished in a predetermined shape is subjected to a carburizing treatment so that the surface C potential immediately before quenching becomes 0.9% or more, then quenched, and then the surface layer portion of the gear is subjected to 850 to 1000 by high frequency induction heating. A heat treatment method for carburized gears, characterized by quenching after reheating to ℃.
るものである請求項１記載の浸炭歯車の熱処理法。2. The heat treatment method for a carburized gear according to claim 1, wherein the gear material contains V at 0.05% by weight or more.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP05005115A JP3104449B2 (en) | 1993-01-14 | 1993-01-14 | Heat treatment of carburized gears |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP05005115A JP3104449B2 (en) | 1993-01-14 | 1993-01-14 | Heat treatment of carburized gears |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH06212271A JPH06212271A (en) | 1994-08-02 |
| JP3104449B2 true JP3104449B2 (en) | 2000-10-30 |
Family
ID=11602341
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP05005115A Expired - Fee Related JP3104449B2 (en) | 1993-01-14 | 1993-01-14 | Heat treatment of carburized gears |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3104449B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10774413B2 (en) | 2015-11-11 | 2020-09-15 | Honeywell International Inc. | Low pressure induction carburization |
-
1993
- 1993-01-14 JP JP05005115A patent/JP3104449B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH06212271A (en) | 1994-08-02 |
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