JPS60218422A - Improvement of fatigue strength of structural parts for power transmission - Google Patents

Abstract

PURPOSE:To improve remarkably the fatigue strength of structural parts for power transmission and to enable easy working even when the parts have a complex shape by subjecting the parts tempered at a low temp. after carburization and hardening to shot peening under specified conditions. CONSTITUTION:Structural parts for power transmission tempered at 150-200 deg.C low temp. after carburization and hardening are subjected to shot peening under conditions including 0.3-1.0mm. diameter of shot, 5-40min projection time and 35-50m/sec projection speed. Much higher fatigue strength than fatigue strength (10<7> times) attained by a conventional method can be attained by combining carburization and hardening with shot peening and setting the tempering temp. and the shot peening conditions as mentioned above.

Description

【発明の詳細な説明】 産業上の利用分野 本発明は、動力伝達軸、歯車等の動力伝達用構成部品の
疲労強度を著しく高めることのできる処理法に関するも
のである。DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a treatment method that can significantly increase the fatigue strength of power transmission components such as power transmission shafts and gears.

従来技術 従来、機械部品や構造部材の繰返し荷重に対する疲労強
度向上のため、表面層に圧縮残留応力を生ぜしめると同
時に表面層を硬化する方法としては、 ＆Ｌ）　浸炭、窒化、タフトライド処理、高周波焼入れ
等の各種熱処理、 （ｂ）　表面圧延、ショットピーニング等の表面冷間加
工、 （Ｃ）　オース７オーミング等の加工熱処理、が採用さ
れている。Conventional technology Conventionally, in order to improve the fatigue strength of mechanical parts and structural members against repeated loads, methods of generating compressive residual stress in the surface layer and hardening the surface layer at the same time include carburizing, nitriding, tuftride treatment, and induction hardening. (b) Surface cold processing such as surface rolling and shot peening; (C) Processing heat treatment such as aus7 ohming.

しかしながら、オースフォーミングに代表される上記（
Ｃ）の加工熱処理は、強加工を施すため圧延等を行うの
で、動力伝達軸のような複雑な形状のものには加工し難
いという欠点があると共に、Ｃｒ等の含有量の多い高合
金鋼を使用するため高価であるという難点がある。However, the above (as represented by ausforming)
Process heat treatment (C) involves rolling, etc. in order to apply strong working, so it has the disadvantage that it is difficult to process products with complex shapes such as power transmission shafts. The disadvantage is that it is expensive because it uses

一方、前記（α）及び（ｂ）の表面硬化法は、加工の点
では問題はないが、回転曲げ疲労強度（１０’回）が５
０〜９０　ｂｙ　７ｍｍ”程度であり、（Ｃ）ノ加工熱
処理法による場合の１００〜＋＋ｏｋｇ／ｍ−に比べて
低いという問題がある。On the other hand, the surface hardening methods (α) and (b) have no problems in terms of processing, but the rotational bending fatigue strength (10' times) is 5.
There is a problem that it is about 0 to 90 by 7 mm'', which is lower than 100 to ++okg/m- in the case of the processing heat treatment method (C).

発明の目的 従って、本発明の目的は、前記した従来法の欠点を改善
し、複雑な形状の部品にも容易に加工できると共に、動
力伝達軸、歯車等の動力伝達用構成部品などの疲労強度
を著しく高めることのできる処理法を提供することにあ
る。OBJECTS OF THE INVENTION Accordingly, an object of the present invention is to improve the drawbacks of the conventional methods described above, to enable easy processing of parts with complex shapes, and to improve the fatigue strength of power transmission components such as power transmission shafts and gears. The objective is to provide a treatment method that can significantly increase the

発明の構成 本発明に係る動力伝達用構成部品の疲労強度向上法は、
前記目的を達成するため、浸炭焼入後に１５０〜２００
°Ｃの低温で焼戻し処理を施した動力伝達用構成部品に
、ショット径０．３〜１．０ｍｍ、投射時間５〜４０分
、投射速度３５〜５０シ４の条件でショットピーニング
を施すこトラ特徴とするものである。Structure of the Invention The method for improving the fatigue strength of power transmission components according to the present invention is as follows:
In order to achieve the above purpose, after carburizing and quenching, the
Shot peening is applied to power transmission components that have been tempered at a low temperature of °C under the following conditions: shot diameter 0.3 to 1.0 mm, projection time 5 to 40 minutes, and projection speed 35 to 50 cm. This is a characteristic feature.

発明の作用及び態様 本発明に係る動力伝達用構成部品の疲労強度向上法は、
前記（ｇ）の浸炭焼入れ処理と（勾のショットピーニン
グの各方法を組み合わせたものてあｐ１焼戻し温度及び
ショットピーニングの条件を特定範囲に設定することに
よシ、従来得られていた疲労強度（ｉ　ｏ″回ンシも著
しく高い疲労強度を得る方法である。Effects and Modes of the Invention The method for improving fatigue strength of power transmission components according to the present invention is as follows:
By setting the tempering temperature and shot peening conditions within specific ranges, the fatigue strength ( io'' rotation is also a method of obtaining significantly higher fatigue strength.

すなわち、本発明方法の基本構成は、低炭素低合金ｆｉ
ｌ（例えばＳＣＭ４１５）に通常の浸炭焼入れ処理を行
なった後、１５０〜２００°Ｃの低温で焼戻し処理を施
し、次いで室温にてショットピーニングを行ない、浸炭
中に生成した約２０μｍの表面異常層（粒界酸化に伴な
う不完全焼入れ層）の硬さの低下を補ない、表面近傍（
約１５０　ｐｍ　）の硬さ、圧縮残留応力を増加させ、
浸炭焼入れの除虫じた残留オーステナイトを減少させ、
表面からの疲労亀裂の発生を抑制するものである。That is, the basic configuration of the method of the present invention is that low carbon, low alloy fi
1 (for example, SCM415), followed by tempering at a low temperature of 150 to 200°C, followed by shot peening at room temperature to remove the approximately 20 μm abnormal surface layer (for example, SCM415) generated during carburization. It compensates for the decrease in hardness of the incompletely hardened layer (due to grain boundary oxidation), and improves hardness near the surface (
hardness of approximately 150 pm), increasing compressive residual stress,
Reducing residual austenite from carburizing and quenching,
This suppresses the occurrence of fatigue cracks from the surface.

本発明方法のように浸炭した部品にショットピーニング
を施した場合、ショットピーニングの条件により疲労寿
命の増加の程度はかなり異なり、最適条件で行なう必賛
がある。When shot peening is applied to carburized parts as in the method of the present invention, the degree of increase in fatigue life varies considerably depending on the shot peening conditions, and it is essential to carry out shot peening under optimal conditions.

まず、シミツト粒径は、小さすぎると軸方向の圧縮残留
応力の影響層が浅く、従って疲労強度の増加が少なく、
一方、大きすぎると、実用上、動力伝達軸のような複雑
な形状物の応力集中部（例えば各種の溝などンへのピー
ニングが不可能となる。このため、０．３〜ｒ、ｏｍｍ
ｔｓましくは０．６〜Ｑ、ｇｍｍの径のショットを用い
るのが良い。First, if the grain size is too small, the influence layer of compressive residual stress in the axial direction will be shallow, and therefore the increase in fatigue strength will be small.
On the other hand, if it is too large, it is practically impossible to peen stress concentration parts (e.g. various grooves) of complex-shaped objects such as power transmission shafts.
It is preferable to use a shot having a diameter of ts, preferably 0.6 to Q, gmm.

また、ショットの投射時間は、添附第５図から明らかな
ように、５分間の投射時間までは時間が長い方が疲労強
度は向上するが、それ以降紘飽和する傾向にある。この
ため、投射時間は５〜４０分の範囲が好ましい。As for the shot projection time, as is clear from FIG. 5, the longer the shot projection time is, the better the fatigue strength is, but the fatigue strength tends to be saturated after that. For this reason, the projection time is preferably in the range of 5 to 40 minutes.

さらに、ショットの投射速度（遠心式の装置では別車の
回転数に対応）は、小さすぎるとその効果が現われず、
また大きすぎても表面粗さが増したり、表面に微小亀裂
を発生させるため、３５〜５０７ψの範囲が好ましく、
マた最も好ましいのは４５〜５　Ｑ　ｍ／ｚの範囲であ
る。Furthermore, if the shot projection speed (corresponding to the rotation speed of another car in a centrifugal device) is too low, the effect will not be apparent.
Also, if it is too large, the surface roughness will increase and micro-cracks will occur on the surface, so the range of 35 to 507 ψ is preferable.
The most preferred range is from 45 to 5 Q m/z.

実施例 以下、実施例及び比較例を示して本発明について具体的
に説明するが、゛禾発明が下記実施例に限定されるもの
でないことはもとよりである。EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples; however, it goes without saying that the invention is not limited to the following Examples.

比較例 低炭素低合金鋼ＳＣＭ４１５に、常法に従って浸炭焼入
れ・焼戻し処理を施した。すなわち、９３００Ｃで６時
間（０，１３％Ｃへ　含有浸炭性ガスで３．５時間、そ
の後０．２　ＴｏＣＯ，含有浸炭性ガスで２．５′時間
）浸炭を行なった後さらＫ　８５００Ｃで０．５時間（
Ｑ、５　％　ＣＯ雪金含有浸炭性ガス行ない、油焼入れ
をした後、１５０〜２０００Ｃに焼戻しだ。このようＫ
して通常浸炭材ＣＩを得た。Comparative Example Low-carbon, low-alloy steel SCM415 was subjected to carburizing, quenching and tempering according to a conventional method. That is, after carburizing at 9300C for 6 hours (3.5 hours with carburizing gas containing 0.13% C, then 2.5 hours with carburizing gas containing 0.2 ToCO), further carburizing at 8500C with 0. .5 hours (
Q: After quenching with carburizing gas containing 5% CO and oil, tempering at 150-2000C. K like this
A conventional carburized material CI was obtained.

実施例１〜４ 上記比較例と同様に浸炭焼入れ・焼戻し処理を施した通
常浸炭材に、さらに本発明に従って、ショット径を０．
３ｍｍ（実権例１）、０．６ｍｍ　（実施例２）、０．
７ｍ１ｒＬ（実施例３）及びＱ、ｇｍｍ（実施例４）に
変えて、投射速度４６ｍ／ｓ　、投射時間１０分の条件
でショットピーニングを行ない、本発明材Ｐパ実施例Ｉ
）、Ｐ黛（実施例２）、Ｐｓ（実施例３）及びＰ４（実
施例４）を得た。Examples 1 to 4 A normal carburized material that had been subjected to carburizing, quenching and tempering in the same manner as in the comparative example above was further treated with a shot diameter of 0.
3mm (actual example 1), 0.6mm (example 2), 0.
7m1rL (Example 3) and Q, gmm (Example 4), shot peening was performed under the conditions of a projection speed of 46 m/s and a projection time of 10 minutes, and the present invention material P Example I
), P Mayuzumi (Example 2), Ps (Example 3) and P4 (Example 4) were obtained.

上記通常浸炭材ＣＩ及び各本発明材Ｐ、〜への圧縮残留
応力分布を第１図に示す。第１図から、本発明の処理に
よって表面近傍の圧縮残留応力が著しく増加しており、
また加工深さはショットの粒径に影響されることが明ら
かであり、ショットの粒径が大きくなるにつれて圧縮残
留応力の影響層が深くなっている。The compressive residual stress distribution in the above-mentioned conventional carburized material CI and each of the present invention materials P and - is shown in FIG. From Figure 1, the treatment of the present invention significantly increases the compressive residual stress near the surface.
It is also clear that the machining depth is affected by the grain size of the shot, and as the grain size of the shot increases, the layer affected by compressive residual stress becomes deeper.

また、上記本発明材Ｐ雪（ショットピーニング条件：φ
ＱＪ１ｍｍ、４６ｍ／ｌ、ｔｏ分）の表面近傍の硬さ分
布を第２図に、残留オーステナイト量の分布を第３図に
、圧縮残留応力の分布を第４図に示す。なお、第２図に
おける斜線部領域は通常の浸炭処理によって得られる硬
さ分布の範囲を示し、また、第３図及び第４図における
破線は前記通常浸炭材Ｃ宜のデータを示す。In addition, the above-mentioned invention material P snow (shot peening conditions: φ
Figure 2 shows the hardness distribution near the surface of QJ1mm, 46m/l, to minutes), Figure 3 shows the distribution of the amount of retained austenite, and Figure 4 shows the distribution of compressive residual stress. Note that the shaded area in FIG. 2 shows the range of hardness distribution obtained by normal carburizing treatment, and the broken lines in FIGS. 3 and 4 show data for the normal carburized material C.

第２図から明らかなように、浸炭中に生成した約２０μ
ｍ程度までの表面異常層の硬さの低下（斜線部参照）は
、本発明に従ってショットピーニングを施すことによっ
て補なわれ、約１５０ｐｍ程度までの表面近傍において
硬さが増加しており、また表面層に急激な硬さの上昇が
見られる。また、第３図から明らかなように、浸炭焼入
れの際に生じた残留オーステナイト量は、本発明に従っ
てショットピーニングを施すこトニよって減少している
。As is clear from Fig. 2, approximately 20μ was generated during carburizing.
The decrease in hardness of the surface abnormal layer up to about 150 pm (see the shaded area) is compensated for by shot peening according to the present invention, and the hardness increases near the surface up to about 150 pm, and the surface A rapid increase in hardness is observed in the layer. Furthermore, as is clear from FIG. 3, the amount of residual austenite produced during carburizing and quenching is reduced by shot peening according to the present invention.

試験例１ 前記比較例と同様に浸炭焼入れｅ焼戻し処理を施した浸
炭材に、ショット径をＱ、Ｏｍｍ、投射速度を４６７に
／＃に設定し、投射時間を０．５分、１分、３分、５分
及び１０分に変えてショットピーニングを行ない、疲労
強度と投射時間との関係を調べた。その結果を第５図に
示す。第５図から、投射時間５分までは疲労強度は投射
時間に応じて増加しているが、投射時間５分で飽和値に
達している。従って、この試験結果から、浸炭後のショ
ットピーニングは、少なくとも５分の投射時間が必要な
ことがわかる。Test Example 1 The shot diameter was set to Q, Omm, the projection speed was set to 467/#, and the projection time was set to 0.5 minutes, 1 minute, Shot peening was performed for 3 minutes, 5 minutes, and 10 minutes to examine the relationship between fatigue strength and shot time. The results are shown in FIG. From FIG. 5, the fatigue strength increases as the projection time increases until the projection time reaches 5 minutes, but reaches a saturation value at the projection time of 5 minutes. Therefore, from this test result, it can be seen that shot peening after carburization requires a projection time of at least 5 minutes.

試験例２ 上記比較例と同様に浸炭焼入れ・焼戻し処理を施した通
常浸炭材に、ショット径及び投射速度を変えて、投射時
間１０分の条件でショットピーニングを行ない、加工深
さと投射速度との関係を調べた。その結果を第６図に示
す。第６図から、投射速度が大きい程加工深さは深くな
ることがわかる。Test Example 2 A normal carburized material that had been carburized, quenched and tempered in the same manner as the comparative example above was subjected to shot peening for 10 minutes by changing the shot diameter and projection speed. I investigated the relationship. The results are shown in FIG. From FIG. 6, it can be seen that the higher the projection speed, the deeper the machining depth.

試験例３ 上記比較例と同様に浸炭焼入れ・焼戻し処理を施した通
常浸炭材に、ショット径をＱ　、３ｍｍ　。Test Example 3 A normal carburized material was subjected to carburizing, quenching and tempering in the same manner as in the above comparative example, and the shot diameter was set to Q and 3 mm.

Ｑ　、　６　ｍｍ及び０．ｇｍｍに変えて、投射速度４
６ｍ１ｇ、投Ｎ時間１０分の条件でショットピーニング
を行ない、各処理材を得た。これらから得たＪＩＳ２号
試験片をそれぞれ用いて、小野式回転曲げ疲労試験を行
なった。その結果を第７図に示す。なお、第７図中破線
は通常浸炭材Ｃ３についての結果である。第７図から、
本発明の方法によって処理した場合には、疲労強度が著
しく向上する　４゜ことがわかる。Q, 6 mm and 0. Change to gmm, projection speed 4
Shot peening was carried out under the conditions of 6 ml of 1 g and N throwing time of 10 minutes to obtain each treated material. Using the JIS No. 2 test pieces obtained from these, an Ono rotary bending fatigue test was conducted. The results are shown in FIG. Note that the broken line in FIG. 7 is the result for the normal carburized material C3. From Figure 7,
It can be seen that when treated by the method of the present invention, the fatigue strength is significantly improved by 4°.

発明の効果 以上のように、本発明の方法は、浸炭焼入れ後に低温焼
戻し処理を施した動力伝達用構成部品に特定の条件でシ
ョットピーニングを施すものであり、浸炭焼入れによっ
て表面層の炭素濃度が晶く表面硬さも高くなることから
、素材として高価な高合金鋼を使用する必要がなく、ま
た１５０〜２００８Ｃの低温で焼戻し処理を施した後、
室温で特定の条件でショットピーニング１ｌｉｆことか
ら、浸炭中に生成した約２０μｍ程度の表面異常層の硬
さの低下を補ない、約１５０μｍ程度までの表面近傍の
硬さ、圧縮残留応力を増加させ、また浸炭焼入れの際に
生じた残留オーステナイトを減少させ、表面からの疲労
亀裂の発生を抑制でき、それによって顕著な疲労強度の
向上が図れる。また、ショットピーニングを用いるから
複雑な形状のものにも容易に適用することができる。Effects of the Invention As described above, the method of the present invention applies shot peening under specific conditions to power transmission components that have been carburized and quenched and then tempered at a low temperature. Since the crystallized surface hardness increases, there is no need to use expensive high alloy steel as a material, and after tempering at a low temperature of 150 to 2008C,
Since shot peening is carried out for 1 life at room temperature under specific conditions, it compensates for the decrease in hardness of the surface abnormal layer of about 20 μm generated during carburizing, and increases the hardness and compressive residual stress near the surface up to about 150 μm. In addition, it is possible to reduce residual austenite generated during carburizing and quenching, suppress the occurrence of fatigue cracks from the surface, and thereby significantly improve fatigue strength. Furthermore, since shot peening is used, it can be easily applied to objects with complex shapes.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は各種処理材の圧縮残留応力の分布を示すグラフ
、第２図は本発明の方法によって処理した処理材の硬さ
分布を示すグラフ、第３図は残留オーステナイト量の分
布を示すグラフ、第４図は圧縮残留応力の分布を示すグ
ラフ、第５図は投射時間と疲労強度の関係を示すグラフ
、第６図は投射速度と加工深さの関係を示すグラフ、第
７図は各種処理材の回転曲げ疲労試験結果を示すグラフ
である。 第１図 第２図 第３図 第４図 Ｊ　１１１ｔｔう４［ｔｔＰｍ＋ 第５図 喀 第６図 Ｊｌｆ１６”う／）’Ｊ！”　（Ｊ”’）第７図 練工１（しず欠　（ロ）Figure 1 is a graph showing the distribution of compressive residual stress of various treated materials, Figure 2 is a graph showing the hardness distribution of treated materials treated by the method of the present invention, and Figure 3 is a graph showing the distribution of retained austenite amount. , Figure 4 is a graph showing the distribution of compressive residual stress, Figure 5 is a graph showing the relationship between blasting time and fatigue strength, Figure 6 is a graph showing the relationship between blasting speed and machining depth, and Figure 7 is a graph showing the relationship between blasting time and fatigue strength. 2 is a graph showing the results of a rotating bending fatigue test of treated materials. Fig. 1 Fig. 2 Fig. 3 Fig. 4 B)

Claims (1)

【特許請求の範囲】[Claims] 浸炭焼入れ後に１５０〜２００°Ｃの低温で焼戻し処理
を施した動力伝達用構成部品に、ショット径０．３〜＋
、Ｏｍｍ、投射時間５〜４０分、投射速度３５〜５　、
Ｑ　ｍ／ｓの条件でショットピーニングを施すことを特
徴とする動力伝達用構成部品の疲労強度向上法。Shot diameters of 0.3 to +
, Omm, projection time 5-40 minutes, projection speed 35-5,
A method for improving the fatigue strength of power transmission components, characterized by performing shot peening under conditions of Q m/s.