JP3169464B2 - Heat treatment method for mechanical structural parts with high fatigue strength - Google Patents
Heat treatment method for mechanical structural parts with high fatigue strengthInfo
- Publication number
- JP3169464B2 JP3169464B2 JP01391593A JP1391593A JP3169464B2 JP 3169464 B2 JP3169464 B2 JP 3169464B2 JP 01391593 A JP01391593 A JP 01391593A JP 1391593 A JP1391593 A JP 1391593A JP 3169464 B2 JP3169464 B2 JP 3169464B2
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- heat treatment
- strength
- fatigue strength
- high fatigue
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Description
【０００１】[0001]
【産業上の利用分野】本発明は高疲労強度を有する機械
構造部品の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 method for heat treating mechanical structural parts having high fatigue strength.
【０００２】[0002]
【従来の技術】高強度高靱性を必要とする自動車用部
品、機械構造用部品等には、所定の形状に熱間鍛造後、
調質処理としてオフラインでの焼入れ・焼戻しが施され
ている。近年、地球環境保護のため、自動車の低燃費化
が求められるようになってきているが、自動車の低燃費
化を達成するための有効な方法の一つは車両軽量化であ
り、部品の降伏強度、疲労強度向上による小型化が指向
されている。2. Description of the Related Art Parts for automobiles and parts for machine structures that require high strength and high toughness are subjected to hot forging into a predetermined shape.
Off-line quenching / tempering is performed as a refining process. In recent years, there has been an increasing demand for low fuel consumption of automobiles in order to protect the global environment. One of the effective methods for achieving low fuel consumption of automobiles is to reduce the weight of vehicles and to surrender parts. Miniaturization by improving strength and fatigue strength is aimed at.
【０００３】機械部品の高疲労限度比化、高降伏比化を
図るためには焼入れ・焼戻しによる調質処理が最も有効
である。例えば、特開昭５５−１０４４５６号公報のよ
うにＢを添加し焼入れ性を良好にして疲労特性等の機械
的性質の向上を図ろうとしたものや、特公昭５３−２３
２４１号公報に見られるように、強靱化を図るために加
熱温度を１０５０〜１３００℃とし、焼戻し温度を５０
０℃以上Ａc1点以下と規定しているものがある。[0003] The tempering treatment by quenching and tempering is most effective for achieving a high fatigue limit ratio and a high yield ratio of mechanical parts. For example, as disclosed in JP-A-55-104456, B is added to improve the hardenability to improve mechanical properties such as fatigue properties, and Japanese Patent Publication No. 53-23.
As can be seen in JP-A-241, the heating temperature is set at 1050 to 1300 ° C. and the tempering temperature is set at 50 to increase the toughness.
Some are specified as 0 ° C. or higher and A c1 point or lower.
【０００４】[0004]
【発明が解決しようとする課題】部品の疲労強度を向上
させるためには調質処理が必要であるが、「鋼の熱処
理、改訂５版Ｐ１８９」に見られるように通常の調質鋼
の疲労限度比（疲労強度／引張強度）は０．３５〜０．
５程度であり、また特開昭５５−１０４４５６号公報の
ようにＢ添加による焼入れ性向上でも十分な疲労強度を
得ることはできず、疲労強度を向上させるためには焼戻
し温度を下げて引張強度を上げるしか方法はないのが現
状である。引張強度上昇に伴い被削性も低下することに
なるので、被削性という点からは、疲労強度向上のため
に引張強度を必要以上に上げるのは好ましくない。また
疲労強度向上のために析出強化を活用するには焼戻しの
条件設定が非常に重要であるが、特公昭５３−２３２４
１号公報のように高温加熱・高温焼戻を行うと、引張強
度、疲労強度等の機械的性質が低下するだけで、疲労特
性向上には何等寄与するところはない。In order to improve the fatigue strength of a part, it is necessary to perform a refining treatment. However, as shown in "Heat treatment of steel, 5th revised edition P189", the fatigue of a normal refining steel The limit ratio (fatigue strength / tensile strength) is 0.35 to 0.5.
However, sufficient fatigue strength cannot be obtained even by improving the hardenability by adding B as disclosed in Japanese Patent Application Laid-Open No. 55-104456. At present, there is no other way but to raise. Since the machinability also decreases as the tensile strength increases, it is not preferable to increase the tensile strength more than necessary in order to improve the fatigue strength from the viewpoint of machinability. In order to utilize precipitation strengthening to improve fatigue strength, setting of tempering conditions is very important.
When high-temperature heating and high-temperature tempering are performed as in Japanese Patent Publication No. 1 only, mechanical properties such as tensile strength and fatigue strength are reduced, and there is no contribution to improvement in fatigue properties.
【０００５】本発明の目的は、引張強度を必要以上に上
げることなく、つまり被削性を低下させずに高疲労強度
を有する機械構造部品の熱処理方法を提供することであ
る。An object of the present invention is to provide a heat treatment method for mechanical structural parts having high fatigue strength without increasing the tensile strength more than necessary, that is, without reducing the machinability.
【０００６】[0006]
【課題を解決するための手段】本発明者らは、高強度高
靱性かつ被削性に優れた機械構造部品の降伏強度および
疲労強度の向上手法を提供するために、鋭意検討を行な
い、降伏比０．８５以上、疲労限度比０．５１以上を得
るためには、焼入れ性を低下させずに、フリーの転位を
消滅させ、析出物でマトリックスを均一に強化しなけれ
ばならないという結論に達した。そのためには次の４点
が必須である。 特定量のＶを含有した鋼であること。 Ｖの炭窒化物を十分に固溶させるために必要なオース
テナイト化温度以上での加熱を行うこと。 加熱後、２０℃／秒以上の冷却速度で焼入れを行うこ
とにより、オーステナイトをマルテンサイト変態させる
こと。 フリーの転位を消滅させ、更にマトリックスを微細分
散させた析出物により均一に強化するため、６５０℃〜
Ａc1変態点の温度範囲で焼戻しを行うこと。Means for Solving the Problems In order to provide a method for improving the yield strength and fatigue strength of a mechanical structural component having high strength, high toughness, and excellent machinability, the present inventors have conducted intensive studies and studied the yield In order to obtain a ratio of 0.85 or more and a fatigue limit ratio of 0.51 or more, it was concluded that free dislocations should be eliminated and the matrix should be uniformly strengthened by precipitates without reducing hardenability. did. For that purpose, the following four points are essential. Steel containing a specific amount of V. Heating at a temperature equal to or higher than the austenitizing temperature necessary for sufficiently dissolving the carbonitride of V. After heating, austenite is transformed into martensite by quenching at a cooling rate of 20 ° C./sec or more. 650 ° C. to eliminate free dislocations and further strengthen the matrix more uniformly with finely dispersed precipitates
Tempering in the temperature range of the A c1 transformation point.
【０００７】また、低温靱性を必要とする場合には、特
定量のＴｉ、Ｎｂを添加し、さらに大型部品などの焼入
れの際に十分な焼入れ性を確保する必要がある場合に
は、ある特定量のＢを添加し、Ｎ量を特定値以下に抑え
る。本発明は以上の新規なる知見に基づいてなされたも
のであって、その要旨とするところは下記のとおりであ
る。[0007] When low temperature toughness is required, a specific amount of Ti or Nb is added, and when it is necessary to ensure sufficient hardenability when quenching a large part or the like, a certain amount is required. The amount of B is added to keep the amount of N below a specified value. The present invention has been made based on the above-described novel findings, and the gist thereof is as follows.
【０００８】（１）重量比として、 Ｃ：０．２０〜０．５０％未満、 Ｓｉ：０．１５〜２．００％、 Ｍｎ：０．５５〜２．００％、 Ｓ：０．０１〜０．１０％、 Ｐ：０．０３５％以下、 Ａｌ：０．０１５〜０．０５％、 Ｎ：０．０２０％以下、 Ｖ：０．０５〜０．５０％ を含有し、残部が鉄および不可避的不純物からなる成分
の鋼を焼き入れ焼戻しするに際して、１０００℃以上１
３００℃以下のオーステナイト化温度範囲に加熱し、そ
の温度から２０℃／秒以上の冷却速度で焼入れを行う工
程と、その後６５０℃以上Ａc1変態点未満の温度範囲で
焼戻しを行う工程を特徴とする引張強度が８０〜１３０
kgf ／mm2 でかつ降伏比が０．８５以上、疲労限度比が
０．５１以上である高疲労強度を有する機械構造部品の
熱処理方法。(1) As a weight ratio, C: 0.20 to less than 0.50% , Si: 0.15 to 2.00%, Mn: 0.55 to 2.00%, S: 0.01 to 0.10%, P: 0.035% or less, Al: 0.015 to 0.05%, N: 0.020% or less, V: 0.05 to 0.50%, the balance being iron and in tempering quench the components of the steel consisting of unavoidable impurities, 1000 ° C. or higher 1
It is characterized by a step of heating to an austenitizing temperature range of 300 ° C. or less and quenching from that temperature at a cooling rate of 20 ° C./second or more, and a step of thereafter tempering at a temperature range of 650 ° C. or more and less than the A c1 transformation point. 80-130 tensile strength
A heat treatment method for a machine structural part having high fatigue strength, which has a kgf / mm 2 , a yield ratio of 0.85 or more, and a fatigue limit ratio of 0.51 or more.
【０００９】（２）成分が更に、 Ｔｉ：０．００５〜０．０５０％ Ｎｂ：０．０１〜０．１０％ のうち一種または二種を含有する（１）記載の低温靱性
の優れた高疲労強度を有する機械構造部品の熱処理方
法。The component (2) further contains one or two of Ti: 0.005 to 0.050% and Nb: 0.01 to 0.10%. Heat treatment method for mechanical structural parts having fatigue strength.
【００１０】（３）成分が更に、 Ｔｉ：０．００５〜０．０５０％、 Ｂ：０．０００３〜０．００５％ を含有する（１）記載の高疲労強度を有する機械構造部
品の熱処理方法。(3) The method for heat treating mechanical structural parts having high fatigue strength according to (1), wherein the component further contains: 0.005 to 0.050% Ti: 0.0003 to 0.005% B: .
【００１１】（４）成分が更に、 Ｃｒ：０．１０〜１．２０％未満、 Ｍｏ：０．０５〜１．００％、 Ｎｉ：０．１０〜３．６０％、 のうち一種または二種以上を含有する（１）、（２）、
又は（３）記載の高疲労強度を有する機械構造部品の熱
処理方法。The component (4) further includes one or two of the following: Cr: 0.10 to less than 1.20% ; Mo: 0.05 to 1.00%; Ni: 0.10 to 3.60%. Containing the above (1), (2),
Or the heat treatment method for a mechanical structural part having high fatigue strength according to (3).
【００１２】以下に、本発明を詳細に説明する。まず、
Ｃは機械部品としての最終製品の強度を増加させるのに
有効な元素であるが、０．２０％未満では最終製品の強
度が不足し、また０．５０％以上ではむしろ最終製品の
靭性の劣化を招くので、含有量を０．２０〜０．５０％
未満とした。Hereinafter, the present invention will be described in detail. First,
C is an element effective for increasing the strength of the final product as a mechanical part, but if it is less than 0.20%, the strength of the final product is insufficient, and if it is more than 0.50%, the toughness of the final product is rather deteriorated. Content, 0.20 to 0.50%
Less than .
【００１３】次に、Ｓｉは脱酸元素として、また固溶体
硬化および焼戻し軟化抵抗による最終製品の強度を増加
させることを目的として添加するが、０．１５％未満で
はこれらの効果は不十分であり、一方、２．００％を超
えるとこれらの効果は飽和しむしろ最終製品の靱性の劣
化を招くので、その含有量を０．１５〜２．００％とし
た。Next, Si is added as a deoxidizing element and for the purpose of increasing the strength of the final product due to solid solution hardening and tempering softening resistance. However, if it is less than 0.15%, these effects are insufficient. On the other hand, if it exceeds 2.00%, these effects are not saturated but rather deteriorate the toughness of the final product, so the content was made 0.15 to 2.00%.
【００１４】Ｍｎは焼入れ性の向上により、最終製品の
強度を増加させるのに有効な元素であり、また鋼中でＳ
とＭｎＳを形成することにより被削性の向上に寄与する
が、０．５５％未満ではこの効果は不十分であり、一
方、２．００％を超えるとこの効果は飽和しむしろ最終
製品の靱性の劣化を招くので、その含有量を０．５５〜
２．００％とした。Mn is an element effective for increasing the strength of the final product by improving the hardenability.
And MnS contribute to the improvement of machinability, but if it is less than 0.55%, this effect is insufficient, while if it exceeds 2.00%, this effect is saturated, and the toughness of the final product is rather increased. Of 0.55 to 0.55%.
2.00%.
【００１５】一方、Ｐは鋼中で粒界偏析や中心偏析を起
こし、靱性劣化の原因となる。特にＰが０．０３５％を
超えると靱性の劣化が顕著となるため、０．０３５％以
下とした。また、Ｓは鋼中でＭｎＳとして存在し、被削
性の向上および組織の微細化に寄与するが、０．０１％
未満ではその効果は不十分である。一方、０．１０％を
超えるとその効果は飽和し、むしろ靱性の劣化および異
方性の増加を招く。以上の理由から、Ｓの含有量を０．
０１〜０．１０％とした。On the other hand, P causes grain boundary segregation and center segregation in steel, which causes deterioration of toughness. In particular, when P exceeds 0.035%, the toughness deteriorates remarkably. Therefore, the P content is set to 0.035% or less. S exists as MnS in steel and contributes to improvement of machinability and refining of the structure.
If less, the effect is insufficient. On the other hand, when the content exceeds 0.10%, the effect is saturated, and rather, the toughness is deteriorated and the anisotropy is increased. For the above reasons, the content of S is set to 0.
It was made 0.1 to 0.10%.
【００１６】次に、Ａｌは脱酸元素および結晶粒微細化
元素として添加するが、０．０１５％未満ではその効果
は不十分であり、一方、０．０５％を超えるとその効果
は飽和し、むしろ靱性を劣化させるので、その含有量を
０．０１５〜０．０５％とした。ＮはＶ、Ｃと共に焼戻
し時のＶ（ＣＶ）形成による析出強化に寄与し、更にＴ
ｉ、Ｎｂを添加する場合には、ＴｉＮ、ＮｂＮの形成に
より加熱時のγ粒の粗大化防止に寄与する。Ｎ含有量
０．０２０％超では粗大窒化物が形成されてしまい靱性
を低下させるので、Ｎ含有量の上限を０．０２０％とし
た。また焼入れ性確保のためのＢを添加する場合には、
ＢＮ形成によるＢの効果消滅防止のため望ましくはＮ含
有量０．００６％以下がよい。Next, Al is added as a deoxidizing element and a crystal grain refining element. If its content is less than 0.015%, its effect is insufficient, while if it exceeds 0.05%, its effect is saturated. However, since the toughness is rather deteriorated, the content is set to 0.015 to 0.05%. N contributes to precipitation strengthening by V (CV) formation during tempering together with V and C, and further contributes to T
When i and Nb are added, formation of TiN and NbN contributes to prevention of coarsening of γ grains during heating. If the N content exceeds 0.020%, coarse nitrides are formed and the toughness is reduced. Therefore, the upper limit of the N content is set to 0.020%. Also, when adding B for ensuring hardenability,
To prevent the effect of B from disappearing due to BN formation, the N content is desirably 0.006% or less.
【００１７】更に本発明に置いてはＴｉ、Ｎｂの一種ま
たは二種を必要に応じて添加する。これはＴｉＮまたは
ＮｂＮによる加熱時のオーステナイト粒粗大化防止によ
る低温靱性の確保のためである。Ｔｉ含有量０．００５
％未満ではオーステナイト粒の粗大化防止に必要なＴｉ
Ｎは形成されず、またＮｂ含有量０．０１％未満でもオ
ーステナイト粒の粗大化防止に必要なＮｂＮは形成され
ない。Ｔｉ含有量０．０５０％超では粗大ＴｉＮが形成
され、またＮｂ含有量０．１０％超でも粗大ＮｂＮが形
成され、靱性の低下につながる。このためＴｉ含有量を
０．００５〜０．０５０％、Ｎｂ含有量０．０１％〜
０．１０％とした。またＢ添加の場合には、Ｎ固定のた
めに必須元素としてＴｉを上記の量添加する。Further, in the present invention, one or two of Ti and Nb are added as required. This is to secure low-temperature toughness by preventing austenite grain coarsening during heating by TiN or NbN. Ti content 0.005
%, Ti required to prevent austenite grain coarsening
N is not formed, and even if the Nb content is less than 0.01%, NbN necessary for preventing austenite grains from being coarsened is not formed. If the Ti content exceeds 0.050%, coarse TiN is formed, and if the Nb content exceeds 0.10%, coarse NbN is formed, leading to a decrease in toughness. Therefore, the Ti content is set to 0.005 to 0.050%, and the Nb content is set to 0.01% to
0.10%. In addition, in the case of adding B, the above amount of Ti is added as an essential element for fixing N.
【００１８】Ｂは焼入れ性を向上させるために添加する
元素で、０．０００３％未満では焼入れ性の向上は期待
できず、また０．００５％超ではこの効果は飽和し、コ
スト高になるばかりでなく、逆に焼入れ性の低下にもつ
ながるのでＢ添加量は０．０００３〜０．００５％とし
た。さらに本発明においては、析出強化の目的で、Ｖを
必須元素として含有させる。しかしながら、Ｖ含有量が
０．０５％未満ではその効果は不十分であり、一方Ｖ含
有量０．５０％超ではその効果は飽和し、むしろ靱性を
劣化させるので、この含有量をＶ：０．０５〜０．５０
％とした。B is an element added for improving the hardenability. If the amount is less than 0.0003%, no improvement in the hardenability can be expected, and if it exceeds 0.005%, this effect is saturated and the cost is increased. However, on the contrary, the quenching property is also reduced, so the B addition amount is set to 0.0003 to 0.005%. Further, in the present invention, V is contained as an essential element for the purpose of strengthening precipitation. However, if the V content is less than 0.05%, the effect is insufficient, while if the V content is more than 0.50%, the effect is saturated and the toughness is rather deteriorated. .05-0.50
%.
【００１９】ＣｒはＭｏ、Ｎｉと共に必要に応じて添加
することで、焼入れ性の向上により最終製品の強度を増
加させるのに有効な元素である。含有量０．１０％未満
ではその効果はなく、また１．２０％以上では硬度が高
くなりすぎ、靭性の低下を招き、また経済性の点で好ま
しくないためその含有量を０．１０〜１．２０％未満と
した。Cr is an element effective for increasing the strength of the final product by improving the hardenability by adding Cr and Mo as necessary. Rather its effect at a content less than 0.10%, also too high a hardness 1.20% or more, leading to reduction in toughness and 0.10 the content not preferable from the viewpoint of economy 1 And less than 20% .
【００２０】ＭｏもＣｒ同様、必要に応じて添加するこ
とにより、焼入れ性の向上により最終製品の強度を増加
させるのに有効な元素であるが、含有量０．０５％未満
ではその効果はなく、また１．００％超では硬さの増加
を招き、また経済性の点で好ましくないためその含有量
を０．０５〜１．００％とした。更にＮｉも必要に応じ
て添加することにより、最終製品の強度、靱性を向上さ
せるのに有効な元素であるが、含有量０．１０％未満で
はその効果はなく、また３．６０％超では強度、靱性の
向上は飽和し、また経済上の点で好ましくないのでその
含有量を０．１０〜３．６０％とした。Like Cr, Mo is an element effective for increasing the strength of the final product by improving the hardenability by adding it as necessary. However, if the content is less than 0.05%, the effect is lost. If it exceeds 1.00%, the hardness is increased, and it is not preferable in terms of economy, so its content is set to 0.05 to 1.00%. Further, Ni is an element effective in improving the strength and toughness of the final product by adding Ni as needed. However, if the content is less than 0.10%, the effect is not obtained. Since the improvement in strength and toughness is saturated and is not economically preferable, the content is set to 0.10 to 3.60%.
【００２１】なお、被削性向上のため０．３％までのＰ
ｂ、０．００５％までのＣａの添加を行っても、本発明
の効果は何等損なわれない。次に、本発明において、加
熱条件を限定した理由について述べる。まず、加熱温度
の下限を１０００℃としたのは、１０００℃未満の加熱
温度では、Ｖの炭窒化物が十分にオーステナイト中に固
溶しないために焼戻し時の析出効果に効かなくなるため
で、また加熱温度の上限を１３００℃としたのは、１３
００℃超の加熱温度ではオーステナイト粒が急に粗大化
し始めるためである。この加熱温度はＶ添加量に合わせ
て昇降させるのがよく、望ましくは（４８０×√Ｖ％＋
９２５±３５）℃とするのがよい。これをこのまま直ち
に２０℃／秒以上の冷却速度で急冷するが、２０℃／秒
以上の冷却速度で焼入れを行うのは、オーステナイトに
マルテンサイト変態を起こさせるためであり、これ未満
の冷却速度ではベイナイト等が混入するためである。冷
却速度２０℃／秒以上が得られるのであれば、焼入れ溶
媒は水、油等任意のものでよい。In order to improve the machinability, the content of P up to 0.3%
b, Even if Ca is added up to 0.005%, the effect of the present invention is not impaired at all. Next, the reason for limiting the heating conditions in the present invention will be described. First, the reason why the lower limit of the heating temperature is set to 1000 ° C. is that at a heating temperature lower than 1000 ° C., the carbonitride of V does not sufficiently form a solid solution in austenite, so that the precipitation effect during tempering is not effective. The upper limit of the heating temperature was set to 1300 ° C.
This is because austenite grains suddenly start to coarsen at a heating temperature exceeding 00 ° C. The heating temperature is preferably raised and lowered in accordance with the amount of V added, and is preferably (480 × ΔV% +
925 ± 35) it is preferable to the ℃. This is immediately quenched at a cooling rate of 20 ° C./sec or more, but the quenching is performed at a cooling rate of 20 ° C./sec or more to cause austenite to undergo martensitic transformation. This is because bainite and the like are mixed. As long as a cooling rate of 20 ° C./sec or more can be obtained, any quenching solvent such as water and oil may be used.
【００２２】次に、焼入れ後、６５０℃〜Ａc1変態点の
温度範囲で焼戻しを行うのは、疲労亀裂伝播の原因とな
るフリーの転位を消滅させるためと、Ｖの炭窒化物をよ
り多く析出させ、マトリックスを微細分散させた析出物
により均一に強化するためである。焼戻し温度が６５０
℃未満であると、フリーの転位の消滅は十分でなく、Ｖ
の炭窒化物の析出量も少なく、また、Ａc1変態点超であ
ると焼戻しマルテンサイトがオーステナイト変態を起こ
してしまうためで、焼戻しは６５０℃〜Ａc1変態点の温
度範囲で行う。焼戻しの時間は望ましくは０．３〜２時
間がよい。Next, after quenching, tempering in the temperature range of 650 ° C. to the A c1 transformation point is intended to eliminate free dislocations that cause fatigue crack propagation and to increase the amount of V carbonitride. This is for precipitating and uniformly strengthening the matrix by finely dispersing the precipitate. Tempering temperature is 650
If the temperature is lower than 0 ° C., disappearance of free dislocations is not sufficient, and V
The precipitation amount of carbonitride is small, and if it exceeds the A c1 transformation point, the tempered martensite undergoes austenite transformation. Therefore, the tempering is performed in a temperature range from 650 ° C. to the A c1 transformation point. The tempering time is desirably 0.3 to 2 hours.
【００２３】以下に、本発明の効果を実施例により、さ
らに具体的に示す。Hereinafter, the effects of the present invention will be more specifically described with reference to examples.
【００２４】[0024]
【実施例】表１，２，３および４に示す化学成分の鋼を
高周波炉にて溶製し、１５０kgのインゴットに鋳造し
た。これをφ４０mmの棒鋼に圧延し、その圧延材を熱間
鍛造−放冷後、表７に示す条件で再加熱・焼入れ焼戻し
を行った。EXAMPLES Steels having the chemical compositions shown in Tables 1, 2, 3, and 4 were melted in a high-frequency furnace and cast into 150 kg ingots. This was rolled into a bar of φ40 mm, and the rolled material was hot forged and allowed to cool, and then reheated, quenched and tempered under the conditions shown in Table 7.
【００２５】[0025]
【表１】 [Table 1]
【００２６】[0026]
【表２】 [Table 2]
【００２７】[0027]
【表３】 [Table 3]
【００２８】[0028]
【表４】 [Table 4]
【００２９】また、比較例は表５に示す条件で熱処理を
行った。それらの焼入れ−焼戻し後の材料の中央部より
ＪＩＳ１４号引張試験片、ＪＩＳ３号衝撃試験片、ＪＩ
Ｓ１号回転曲げ試験片、およびドリル穴あけ試験片を採
取し、引張強度、−５０℃シャルピー衝撃値、疲労強
度、および被削性を求めた。被削性の評価にはＶL1000
を使用した。送り速度０．３３mm／ｓのドリル（材質：
ＳＫＨ５１−φ１０mm）の周速を種々変化させ、各速度
においてドリルが切削不能になる総穴深さを求め、周速
−ドリル寿命曲線を作成し、ドリル寿命が１０００mmと
なる最大速度をＶ L1000 と規定し、被削性の評価基準と
した。表６，８，９および１０に各鋼材の材質特性の本
発明と比較例を対比して示す。In Comparative Example, heat treatment was performed under the conditions shown in Table 5.
went. From the center of the material after quenching and tempering
JIS No. 14 tensile test piece, JIS No. 3 impact test piece, JI
S1 rotary bending test piece and drilling test piece were collected.
, Tensile strength, -50 ° C Charpy impact value, fatigue strength
The degree and machinability were determined. V for evaluation of machinabilityL1000
It was used. Drill with feed rate of 0.33 mm / s (Material:
SKH51-φ10mm)
The total hole depth at which the drill cannot be cut at
-Draw a drill life curve and make the drill life 1000 mm
Maximum speed V L1000And the evaluation criteria for machinability
did. Tables 6, 8, 9, and 10 show the material properties of each steel material.
The invention and a comparative example are shown in comparison.
【００３０】[0030]
【表５】 [Table 5]
【００３１】[0031]
【表６】 [Table 6]
【００３２】[0032]
【表７】 [Table 7]
【００３３】[0033]
【表８】 [Table 8]
【００３４】[0034]
【表９】 [Table 9]
【００３５】[0035]
【表１０】 [Table 10]
【００３６】表６に示すように、比較例において本発明
の成分から外れた鋼Ｎｏ．１〜５とＮｏ．１２で熱処理
Ｎｏ．Ｉ、IVの焼入れ・焼戻しを行ったものは降伏比、
疲労限度比共に本発明の下限値に達しなかった。また本
発明鋼Ｎｏ．６で本発明の範囲からはずれた焼入れ焼戻
し温度の熱処理Ｎｏ．IIで行ったもの、本発明鋼Ｎｏ．
９で本発明の下限値におよばなかった焼戻し温度のＮ
ｏ．III で行ったもの、本発明鋼Ｎｏ．１７で本発明の
上限値以上の焼戻し温度のＮｏ．Ｖで行ったものもまた
降伏比、疲労限度比共に本発明の下限値に達しなかっ
た。As shown in Table 6, in the comparative examples, steel Nos. Nos. 1 to 5 and Nos. In heat treatment No. 12 , After quenching and tempering of I and IV, yield ratio,
Both the fatigue limit ratios did not reach the lower limit of the present invention. The steel No. of the present invention. In No. 6, heat treatment No. 6 having a quenching and tempering temperature outside the range of the present invention. II, the steel No. of the present invention.
9, the N of the tempering temperature which did not reach the lower limit of the present invention.
o. III, the steel of the present invention No. No. 17 of the tempering temperature of the upper limit or more of the present invention. The test performed at V also did not reach the lower limit of the present invention in both the yield ratio and the fatigue limit ratio.
【００３７】これに比べ、表８、９および１０に示して
いる鋼Ｎｏ．７〜５４による熱処理Ｎｏ．VII 〜XIの本
発明では、例えば、第１発明の鋼Ｎｏ．１１、熱処理Ｎ
ｏ．VIIIの降伏比０．９６、疲労限度比０．５５や、第
２発明の鋼Ｎｏ．１８、熱処理Ｎｏ．IXの降伏比０．９
５、疲労限度比０．５６や、鋼Ｎｏ．２２、熱処理Ｎ
ｏ．IXの降伏比０．９５、疲労限度比０．５６や、第３
発明の鋼Ｎｏ．２７、熱処理Ｎｏ．Ｘの降伏比０．９
６、疲労限度比０．５５や、鋼Ｎｏ．３１、熱処理Ｎ
ｏ．IXの降伏比０．９２、疲労限度比０．５８や、第４
発明の鋼Ｎｏ．４０、熱処理Ｎｏ．IXの降伏比０．９
５、疲労限度比０．５６や、鋼Ｎｏ．４７、熱処理Ｎ
ｏ．VII の降伏比０．９０、疲労限度比０．５８のよう
に降伏比、疲労限度比共に高い。On the other hand, in comparison with the steel No. shown in Tables 8, 9 and 10, No. 7 to No. 54 . In the present invention of Nos. VII to XI, for example , steel No. 1 of the first invention is used. 11, heat treatment N
o. VIII yield ratio of 0.96, fatigue limit ratio of 0.55, and steel No. 2 of the second invention. 18, heat treatment no. IX yield ratio 0.9
No. 5, fatigue limit ratio 0.56, steel No. 22, heat treatment N
o. IX yield ratio 0.95, fatigue limit ratio 0.56,
Inventive steel No. 27, heat treatment no. X yield ratio 0.9
6, fatigue limit ratio 0.55 and steel No. 31, heat treatment N
o. IX yield ratio 0.92, fatigue limit ratio 0.58 ,
The steel No. of the invention. No. 40, heat treatment no. IX yield ratio 0.9
No. 5, fatigue limit ratio 0.56, steel No. 47, heat treatment N
o. Both the yield ratio and the fatigue limit ratio are high, such as the VII yield ratio of 0.90 and the fatigue limit ratio of 0.58.
【００３８】このように本発明法によると引張強度８
０．４〜１２６．５kgf ／mm2 で降伏強度７３．７〜１
１７．６kgf ／mm2 、降伏比０．９０〜０．９６、疲労
強度４２．６〜６９．１kgf ／mm2 、疲労限度比０．５
２〜０．５９を得ることができ、比較例より高い降伏
比、優れた耐久性を有することがわかる。As described above, according to the method of the present invention, the tensile strength of 8
Yield strength of 73.7 to 1 at 0.4 to 126.5 kgf / mm2
17.6 kgf / mm 2 , yield ratio 0.90 to 0.96, fatigue strength 42.6 to 69.1 kgf / mm 2 , fatigue limit ratio 0.5
2 to 0.59 can be obtained, which indicates that the sample has a higher yield ratio and superior durability than the comparative example.
【００３９】[0039]
【発明の効果】以上述べたごとく、本発明法を用いれ
ば、高疲労強度を有する機械構造部品の熱処理が可能で
あり、機械構造部品の軽量化が可能となり、産業上の効
果は極めて顕著なるものがある。As described above, when the method of the present invention is used, heat treatment of a machine structural part having high fatigue strength can be performed, the weight of the machine structural part can be reduced, and the industrial effect is extremely remarkable. There is something.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 子安 善郎 北海道室蘭市仲町12番地 新日本製鐵株 式会社室蘭製鐵所内 (72)発明者 安田 茂 愛知県豊田市トヨタ町１番地 トヨタ自 動車株式会社内 (56)参考文献 特開 平１−259124（ＪＰ，Ａ) 特開 平２−50917（ＪＰ，Ａ) 特開 平２−50911（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) C21D 6/00 C22C 38/00 - 38/60 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yoshiro Koyasu 12 Nakamachi, Muroran City, Hokkaido Nippon Steel Corporation Muroran Works (72) Inventor Shigeru Yasuda 1st Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Vehicle Stock In-company (56) References JP-A-1-259124 (JP, A) JP-A-2-50917 (JP, A) JP-A-2-50911 (JP, A) (58) Fields investigated (Int. . 7, DB name) C21D 6/00 C22C 38/00 - 38/60
Claims (4)
の鋼を焼き入れ焼戻しするに際して、１０００℃以上１
３００℃以下のオーステナイト化温度範囲に加熱し、そ
の温度から２０℃／秒以上の冷却速度で焼入れを行う工
程と、その後６５０℃以上Ａc1変態点未満の温度範囲で
焼戻しを行う工程を特徴とする引張強度が８０〜１３０
kgf ／mm2 でかつ降伏比が０．８５以上、疲労限度比が
０．５１以上である高疲労強度を有する機械構造部品の
熱処理方法。C .: 0.20 to less than 0.50% , Si: 0.15 to 2.00%, Mn: 0.55 to 2.00%, S: 0.01 to 0 as weight ratios. .10%, P: 0.035% or less, Al: 0.015 to 0.05%, N: 0.020% or less, V: 0.05 to 0.50%, the balance being iron and inevitable 1000 ° C or higher when quenching and tempering steel with a component consisting of chemical impurities
It is characterized by a step of heating to an austenitizing temperature range of 300 ° C. or less and quenching from that temperature at a cooling rate of 20 ° C./second or more, and a step of thereafter tempering at a temperature range of 650 ° C. or more and less than the A c1 transformation point. 80-130 tensile strength
A heat treatment method for a machine structural part having high fatigue strength, which has a kgf / mm 2 , a yield ratio of 0.85 or more, and a fatigue limit ratio of 0.51 or more.
性の優れた高疲労強度を有する機械構造部品の熱処理方
法。2. The high fatigue excellent in low temperature toughness according to claim 1, wherein the component further contains one or two of Ti: 0.005 to 0.050% and Nb: 0.01 to 0.10%. A heat treatment method for mechanical structural parts having strength.
部品の熱処理方法。3. The method for heat treating a machine structural component having high fatigue strength according to claim 1, wherein the component further contains: Ti: 0.005 to 0.050%, and B: 0.0003 to 0.005%.
は３記載の高疲労強度を有する機械構造部品の熱処理方
法。4. The composition further comprises one or more of Cr: 0.10 to less than 1.20% , Mo: 0.05 to 1.00%, Ni: 0.10 to 3.60%. The method for heat treating a mechanically structured component having high fatigue strength according to claim 1, containing:
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP01391593A JP3169464B2 (en) | 1993-01-29 | 1993-01-29 | Heat treatment method for mechanical structural parts with high fatigue strength |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP01391593A JP3169464B2 (en) | 1993-01-29 | 1993-01-29 | Heat treatment method for mechanical structural parts with high fatigue strength |
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| Publication Number | Publication Date |
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| JPH06228633A JPH06228633A (en) | 1994-08-16 |
| JP3169464B2 true JP3169464B2 (en) | 2001-05-28 |
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