JP4142841B2

JP4142841B2 - Homogeneous cooling method for gears using ultrasonic waves

Info

Publication number: JP4142841B2
Application number: JP2000109035A
Authority: JP
Inventors: 崇史藤田; 武司三木
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2000-04-11
Filing date: 2000-04-11
Publication date: 2008-09-03
Anticipated expiration: 2020-04-11
Also published as: JP2001294938A

Description

【０００１】
【産業上の利用分野】
本発明は歯車等の部品をバッチ的に熱処理する方法及びその装置に関する。
【０００２】
【従来の技術】
歯車等の部品は、切削加工ないしは冷鍛・熱鍛後に焼入れを行い硬度を増して、製品としている。しかし、この焼入れ過程で熱歪が発生し、部品の精度が損なわれていた。
これを防止する方法としては、焼入れに用いる油の温度を上げ、変態温度を高めることが有効であることが知られてきた。しかしこの方法では、焼き入れ温度の上昇とともに硬度が低下するため、十分な焼き入れ硬度を得るために、鋼材の添加元素を増量する必要があり、コストの上昇を招いている。
【０００３】
一方、超音波を焼入れに用いる技術として、実開平６−３９９５０号公報、特開平８−２５３８１７号公報等があるが、これらは超音波による冷却能の向上をその原理としており、例えば前者ではロールの焼入れ速度の制御により、硬度の制御を行う物であり、歯車等の小品には使用できない。
また後者は、線材連続焼入れに関するものでり、バッチ処理には適さない。
【０００４】
【発明が解決しようとする課題】
本発明は歯車等の小品を熱処理する際に、超音波槽で焼き入れする事により、熱処理歪みを低減し部品の精度を確保する方法を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明は上記のような従来法の欠点を排除しうる焼き入れ法であり、その要旨とするところは、
（１）歯車を、切削加工ないしは冷鍛・熱鍛後に熱処理する際に、水、可溶性物質を溶解した水溶液、油から選ばれる溶媒中で焼き入れするときに、２０ＫＨｚ以上２００ＫＨｚ以下の周波数で１Ｗ／ｌ以上２００Ｗ／ｌ以下の出力の超音波を付与し、歯車歯間の凹部に発生した気泡を離脱させ、歯車歯間の気泡の滞留率（気泡の滞留している歯間数／全歯間数）を低下させて熱伝達係数の不均一性を緩和することを特徴とする超音波を用いた歯車の均質冷却法。
（２）油焼き入れする事を特徴とする前記（１）記載の超音波を用いた歯車の均質冷却法。である。
本発明において、歯車とは歯車だけではなく、等速ジョイント、ボルト、シャフト等の凹凸のある形状の部品も含有するものと定義する。
【０００６】
【発明の実施の形態】
以下、本発明について詳細に説明する。
本発明の根幹をなす技術思想は以下の通りである。
通常、歯車等の凹凸のある形状の部品を焼き入れすると、その形状から凸部は凹部に比べ熱容量が小さいため早く冷却される。また、熱伝達係数も凹部の方が小さくなるため、この傾向は助長される。これにより、焼き入れを行うと、歯車の歯が伸びたような変形が生じる。
【０００７】
さらに、歯車の歯間等の凹部（谷部）では発生した気泡がそこに留まり易いため、気泡の発生した凹部ではより一層熱伝達係数が低下し、不均一な冷却となる。また、この時気泡の滞留はすべての歯間で生じるわけではないので、気泡の滞留している歯間と気泡の滞留していない歯間では熱伝達係数が異なり、変形の不均一性を招いていた。変形が不均一であると、変形しやすい場所に変形が集中するため、変形の最大値は大きくなる。
以上のように、歯車の焼き入れ時の変形は、熱伝達係数の不均一性が大きなウエイトを占めている。
【０００８】
本発明者らは上記の欠点を打破する事を可能とする新しい事実を発見し、それをもとに新たなる焼き入れ方法及び装置を発明した。即ち、図１に示すように高周波焼き入れ等の加熱装置１と加熱した歯車２と、歯車２を急冷する為の槽３とよりなり、槽３は水、可溶性物質を溶解した水溶液、油から選ばれる冷媒となる溶媒４を保持している。そして、槽３の底部或いは側壁等の適宜位置に、超音波振動子５等よりなる超音波付与手段を設けている。
ここで、発明者らは、歯車２等の焼き入れ時に槽３内に超音波を付与すると、歯車２等で凹部に発生した気泡が速やかに焼き入れ素材より離脱し、熱伝達係数の不均一性が緩和されることを見いだした。これによって歯車２等の歪みのばらつきが軽減し、さらに歪み自体も軽減することを見いだした。
【０００９】
以下に本発明の限定理由を述べる。
超音波周波数を２０ＫＨｚ以上とした理由は、それ未満の周波数では気泡の離脱が十分ではないためである。周波数を上げるとともに気泡の離脱は速やかに行われるが、２００ＫＨｚ超の周波数では、気泡の離脱が飽和し、より一層の効果が望めないため、上限を２００ＫＨｚとした。
超音波の出力を１Ｗ／ｌ以上とした理由も、それ未満の周波数では気泡の離脱が十分ではないためである。同様に出力を上げると気泡の離脱は速やかに行われるようになるが、２００Ｗ／ｌ超ではその効果が飽和するので、上限を２００Ｗ／ｌとした。
焼き入れに用いる溶媒は、室温の水、可溶性物質を溶解した水溶液、油であるが、さらなる歪みの低減のため、４０〜２００℃に加熱した油を用いても良い。」
【００１０】
【実施例】
図２は、超音波の周波数および出力が、歯車歯間の気泡の滞留に及ぼす影響を示した説明図である。
横軸は超音波の周波数、縦軸は気泡の滞留率（気泡の滞留している歯間数／全歯間数）、各線は超音波の出力の違いを表している。径１００ｍｍ、厚さ４０ｍｍの歯車を室温の鉱油に焼き入れを行った。本発明を用いれば、気泡の滞留は低く押さえられる。
【００１１】
表１は、本発明および超音波を付与しなかった比較方法を適用して焼き入れした場合の、歯車の変形を表している。歯車の大きさは図２と同じものを使用し，を室温の鉱油に焼き入れを行った。歯車の変形の指針として、歯の伸びの最大値、および最大値最小値の差（ばらつき）を用いた。
【表１】

出力１Ｗ／ｌ未満、周波数２０ＫＨｚ未満では、十分な効果が得られず、２００Ｗ／ｌより上の出力および２００ＫＨｚより上の周波数を用いてもその得られる効果は、２００Ｗ／ｌおよび２００ＫＨｚのものと変わらず効果は頭打ちとなる。
【００１２】
【発明の効果】
本発明により、歯車等の小品を熱処理する際に、熱処理歪みが低減し変形が軽減し，ばらつきも軽減しており、部品の精度を確保することができる。
【図面の簡単な説明】
【図１】本発明に係る超音波焼入装置の概略説明図である。
【図２】本発明において超音波の周波数および出力が、歯車歯間の気泡の滞留に及ぼす影響を示した説明図である。
【符号の説明】
１加熱装置
２歯車
３槽
４溶媒
５超音波振動子[0001]
[Industrial application fields]
The present invention relates to a method and apparatus for batch-treating parts such as gears.
[0002]
[Prior art]
Parts such as gears are hardened by cutting or cold forging / hot forging to increase the hardness, resulting in products. However, thermal distortion occurred during this quenching process, and the accuracy of the parts was impaired.
As a method for preventing this, it has been known that it is effective to raise the temperature of the oil used for quenching and raise the transformation temperature. However, in this method, the hardness decreases as the quenching temperature rises. Therefore, in order to obtain a sufficient quenching hardness, it is necessary to increase the amount of added elements of the steel material, which causes an increase in cost.
[0003]
On the other hand, techniques for using ultrasonic waves for quenching include Japanese Utility Model Laid-Open No. 6-39950, Japanese Patent Laid-Open No. 8-253817, etc., which are based on the principle of improving the cooling ability by ultrasonic waves. The hardness is controlled by controlling the quenching speed, and cannot be used for small items such as gears.
The latter relates to continuous quenching of the wire and is not suitable for batch processing.
[0004]
[Problems to be solved by the invention]
The present invention is in the heat treatment of short pieces such as gears, by quenching in an ultrasonic bath, and an object thereof is to provide a way to ensure the accuracy of reducing heat treatment distortion components.
[0005]
[Means for Solving the Problems]
The present invention is a quenching method that can eliminate the disadvantages of the conventional methods as described above, and the gist thereof is as follows:
(1) When a gear is heat-treated after cutting or cold forging / thermal forging, it is 1 W at a frequency of 20 KHz to 200 KHz when quenching in a solvent selected from water, an aqueous solution in which a soluble substance is dissolved, and oil. / L or more and 200W / L or less of ultrasonic wave is applied , bubbles generated in the recesses between the gear teeth are released, and the retention rate of the bubbles between the gear teeth (the number of teeth where the bubbles are retained / total teeth) homogeneous cooling method of gears using ultrasound, characterized in Rukoto between number) to reduce the by to mitigate non-uniformity of the heat transfer coefficient.
(2) The method for homogeneously cooling a gear using ultrasonic waves according to (1), wherein the oil is quenched. It is.
In the present invention, a gear is defined not only to include a gear, but also to include parts having irregular shapes such as a constant velocity joint, a bolt, and a shaft.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The technical idea forming the basis of the present invention is as follows.
Usually, when a part having an uneven shape, such as a gear, is quenched, the convex portion has a smaller heat capacity than the concave portion due to its shape, and thus cools quickly. In addition, this tendency is promoted because the heat transfer coefficient is smaller in the concave portion. Thereby, when quenching is performed, the gear teeth are deformed.
[0007]
Furthermore, since the bubbles generated in the recesses (valleys) such as between the teeth of the gears are likely to stay there, the heat transfer coefficient is further reduced in the recesses where the bubbles are generated, resulting in uneven cooling. At this time, the retention of bubbles does not occur between all the teeth, so the heat transfer coefficient differs between the teeth where the bubbles stay and between the teeth where the bubbles do not stay, causing non-uniform deformation. It was. If the deformation is not uniform, the deformation concentrates on a place where the deformation is easy to occur, and therefore the maximum value of the deformation becomes large.
As described above, the deformation at the time of quenching of the gears occupies a large weight due to the nonuniformity of the heat transfer coefficient.
[0008]
The present inventors have discovered a new fact that makes it possible to overcome the above-mentioned drawbacks, and based on that, have invented a new quenching method and apparatus. That is, as shown in FIG. 1, it comprises a heating device 1 such as induction hardening, a heated gear 2, and a tank 3 for rapidly cooling the gear 2, and the tank 3 is composed of water, an aqueous solution in which a soluble substance is dissolved, and oil. A solvent 4 is selected as a refrigerant to be selected . Then, an ultrasonic wave applying means including the ultrasonic vibrator 5 is provided at an appropriate position such as the bottom or the side wall of the tank 3.
Here, when the inventors applied ultrasonic waves to the tank 3 during quenching of the gear 2 or the like, bubbles generated in the recesses by the gear 2 or the like quickly detached from the quenched material, and the heat transfer coefficient is not uniform. We found that sex was eased. This reduces variations in the strain, such as gear 2 was found and further strain itself to reduce Turkey.
[0009]
The reasons for limiting the present invention will be described below.
The reason why the ultrasonic frequency is set to 20 KHz or more is that bubbles are not sufficiently detached at a frequency lower than that. While the frequency is increased as the frequency is increased, the bubbles are released quickly. However, at a frequency higher than 200 KHz, the bubbles are saturated and a further effect cannot be expected, so the upper limit is set to 200 KHz.
The reason why the output of the ultrasonic wave is 1 W / l or more is that bubbles are not sufficiently detached at a frequency lower than that. Similarly, when the output is increased, the bubbles are released quickly, but the effect is saturated at over 200 W / l, so the upper limit was set to 200 W / l.
The solvent used for quenching is water at room temperature, an aqueous solution in which a soluble substance is dissolved, or an oil . However, an oil heated to 40 to 200 ° C. may be used to further reduce distortion. "
[0010]
【Example】
FIG. 2 is an explanatory diagram showing the influence of the frequency and output of ultrasonic waves on the retention of bubbles between gear teeth.
The horizontal axis represents the ultrasonic frequency, the vertical axis represents the retention rate of bubbles (the number of interdentations where the bubbles are retained / the total number of interdentations), and each line represents the difference in ultrasonic output. A gear having a diameter of 100 mm and a thickness of 40 mm was quenched into mineral oil at room temperature. By using the present invention, the retention of bubbles can be kept low.
[0011]
Table 1 shows the deformation of the gear when the present invention and the comparative method without applying ultrasonic waves were applied and quenched. The same gear size as in Fig. 2 was used, and was quenched into mineral oil at room temperature. As a guideline for the deformation of the gear, the maximum value of the tooth elongation and the difference (variation) between the maximum value and the minimum value were used.
[Table 1]

If the output is less than 1 W / l and the frequency is less than 20 KHz, a sufficient effect cannot be obtained, and even if the output above 200 W / l and the frequency above 200 KHz are used, the obtained effect is that of 200 W / l and 200 KHz. The effect will end at the same level.
[0012]
【The invention's effect】
According to the present invention, when heat-treating small parts such as gears, heat treatment distortion is reduced, deformation is reduced, and variation is also reduced, so that accuracy of parts can be ensured.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory diagram of an ultrasonic hardening apparatus according to the present invention.
FIG. 2 is an explanatory diagram showing the influence of ultrasonic frequency and output on the retention of bubbles between gear teeth in the present invention.
[Explanation of symbols]
1 Heating device 2 Gear 3 Tank 4 Solvent 5 Ultrasonic vibrator

Claims

When gears are heat-treated after cutting or cold forging / thermal forging, when quenching in a solvent selected from water, aqueous solutions in which soluble materials are dissolved, and oil, 1 W / l or more at a frequency of 20 KHz to 200 KHz Applying ultrasonic waves with an output of 200 W / l or less, bubbles generated in the recesses between the gear teeth are released, and the retention rate of the bubbles between the gear teeth (the number of inter-tooth spaces where the bubbles stay) homogeneous cooling method of gears using ultrasound characterized that you relieve nonuniformity of heat transfer coefficient by reducing the.

The method for homogeneously cooling a gear using ultrasonic waves according to claim 1, wherein oil quenching is performed.