JPH08253842A - Steel for induction hardening shaft parts excellent in twisting fatigue strength - Google Patents
Steel for induction hardening shaft parts excellent in twisting fatigue strengthInfo
- Publication number
- JPH08253842A JPH08253842A JP8344795A JP8344795A JPH08253842A JP H08253842 A JPH08253842 A JP H08253842A JP 8344795 A JP8344795 A JP 8344795A JP 8344795 A JP8344795 A JP 8344795A JP H08253842 A JPH08253842 A JP H08253842A
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- steel
- ferrite
- fatigue strength
- induction hardening
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は高周波焼入れ軸部品用鋼
材に係り、さらに詳しくは、図１の（ａ）〜（ｃ）に示
したスプライン部を有するシャフト、フランジ付シャフ
ト、外筒付シャフト等の自動車の動力伝達系を構成する
軸部品用として好適な、優れた捩り疲労強度を有する鋼
材に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel material for induction hardened shaft parts, and more particularly to a shaft having a spline portion shown in FIGS. 1A to 1C, a shaft with a flange, and a shaft with an outer cylinder. The present invention relates to a steel material having excellent torsional fatigue strength, which is suitable as a shaft component constituting a power transmission system of an automobile.
【０００２】[0002]
【従来の技術】自動車の動力伝達系を構成する軸部品
は、通常中炭素鋼を所定の部品に成形加工し、高周波焼
入れ−焼戻しを施して製造されているが、近年の自動車
エンジンの高出力化および環境規制対応に伴い高捩り強
度化の指向が強い。これに対して、特開平５−１７９４
００号公報にはＣ：０．３８〜０．４５％、Ｓｉ：０．
３５％以下、Ｍｎ：１．０超〜１．５％、Ｂ：０．００
０５〜０．０３５％、Ｔｉ：０．０１〜０．０５％、Ａ
ｌ：０．０１〜０．０６％、Ｎ：０．０１０％以下でフ
ェライト結晶粒度番号６以上の細粒組織を有する直接切
削−高周波焼入れ用鋼材が示されている。該発明材では
静的捩り強度については言及されているものの、捩り疲
労強度については全く配慮されていない。2. Description of the Related Art A shaft component constituting a power transmission system of an automobile is usually manufactured by forming a medium carbon steel into a predetermined component and subjecting it to induction hardening-tempering. There is a strong tendency toward higher torsional strength in line with the trend toward compliance and environmental regulations. On the other hand, JP-A-5-1794
In the No. 00 publication, C: 0.38 to 0.45%, Si: 0.
35% or less, Mn: more than 1.0 to 1.5%, B: 0.00
05-0.035%, Ti: 0.01-0.05%, A
It shows a steel material for direct cutting-induction hardening, which has a fine grain structure with a ferrite grain size number of 6 or more with l: 0.01 to 0.06% and N: 0.010% or less. Although the invention material mentions the static torsional strength, no consideration is given to the torsional fatigue strength.
【０００３】また、日本鉄鋼協会講演論文集「材料とプ
ロセス」第７巻第３号第７７１頁、第１図には、Ｓ５３
Ｃ鋼（代表的な成分系０．５３Ｃ−０．２５Ｓｉ−０．
８Ｍｎ）をベースに捩り疲労強度に及ぼす合金元素の影
響を検討し、Ｂ、Ｓｉ、Ｍｏが有効であることが示され
ている。しかしながら、高周波焼入れ用軸部品用鋼とし
ていかなる鋼材が適しているかについては全く開示され
ていない。In addition, the Iron and Steel Institute of Japan "Materials and Processes" Vol. 7, No. 3, page 771, FIG. 1 shows S53.
C steel (typical composition 0.53C-0.25Si-0.
The effect of alloying elements on the torsional fatigue strength based on (8Mn) was examined and it was shown that B, Si and Mo are effective. However, there is no disclosure what kind of steel material is suitable as a steel for shaft parts for induction hardening.
【０００４】[0004]
【発明が解決しようとする課題】本発明の目的は、捩り
疲労強度の優れた高周波焼入れ軸部品用鋼材を提供しよ
うとするものである。DISCLOSURE OF THE INVENTION An object of the present invention is to provide a steel material for induction hardened shaft parts which is excellent in torsional fatigue strength.
【０００５】[0005]
【課題を解決するための手段】本発明者らは、高周波焼
入れにより優れた捩り疲労強度を有する軸部品を実現す
るために、鋭意検討を行い次の知見を得た。 （１）高周波焼入れ材の捩り疲労破壊は、次の過程で起
きる。 Ａ）表面または硬化層と芯部の境界で亀裂が発生する。 Ｂ）軸方向に平行な面または垂直な面で亀裂が初期伝播
する。 Ｃ）軸方向に４５度の面で粒界割れを伴って脆性破壊を
起こし、最終破壊を起こす。 （２）表面硬化層で硬さのムラがあれば、早期に疲労亀
裂が発生する。高周波焼入れ前の組織のフェライト分率
が３５％を超え、フェライト結晶粒径が２０μｍを超え
ると硬化層で顕著な硬さのムラを生じ、早期に疲労亀裂
が発生しやすい。Means for Solving the Problems The inventors of the present invention have made extensive studies in order to realize a shaft component having excellent torsional fatigue strength by induction hardening, and have obtained the following findings. (1) Torsional fatigue fracture of induction hardened material occurs in the following process. A) Cracks occur on the surface or at the boundary between the hardened layer and the core. B) The crack initially propagates in a plane parallel to the axial direction or a plane perpendicular to the axial direction. C) Brittle fracture occurs along with grain boundary cracks at a surface of 45 degrees in the axial direction, and final fracture occurs. (2) If the surface hardened layer has uneven hardness, fatigue cracks occur early. If the ferrite fraction of the structure before induction hardening exceeds 35% and the ferrite crystal grain size exceeds 20 μm, remarkable hardness unevenness occurs in the hardened layer, and fatigue cracking is likely to occur early.
【０００６】（３）次に、硬化層は捩り疲労過程で材質
劣化を起こす。つまり、捩り疲労過程では、表面圧縮残
留応力の減衰、硬さの低下が起きる。疲労過程でこのよ
うな材質劣化を起こしやすい材料ほど疲労亀裂の発生が
早期に起きる。捩り疲労過程でのこうした材質劣化を抑
制するには、下記の方法が有効である。 高Ｍｎにより焼入れ性を確保する。Ｃｒを多量添加
しない。 Ｍｏを添加する。 Ｓｉを増量する。 （４）上記捩り疲労破壊過程はＣ）の欄で述べた、軸方
向に４５度の面で粒界割れを伴う脆性破壊を抑制するた
めには、次の方法による粒界強化が有効である。 Ｔｉ−Ｂ添加。 Ｐ，Ｃｕ，Ｏ量の低減。 （５）捩り疲労は破壊の亀裂が表面で発生する場合に比
べて、硬化層と芯部の境界で発生する場合には、捩り疲
労強度は低下する。これを抑制するためには、Ｎｂ，Ｖ
添加により析出強化を図ることが有効である。(3) Next, the hardened layer undergoes material deterioration during the torsional fatigue process. That is, in the torsional fatigue process, the surface compressive residual stress is attenuated and the hardness is decreased. The material that is more prone to such material deterioration in the fatigue process causes the fatigue crack to occur earlier. The following method is effective for suppressing such material deterioration in the torsional fatigue process. A high Mn ensures hardenability. Do not add a large amount of Cr. Mo is added. Increase the amount of Si. (4) In the torsional fatigue fracture process, grain boundary strengthening by the following method is effective for suppressing the brittle fracture accompanied by grain boundary cracks in the plane of 45 degrees in the axial direction described in the section C). . Add Ti-B. Reduction of P, Cu, O amount. (5) When torsional fatigue occurs at the boundary between the hardened layer and the core, the torsional fatigue strength is lower than when fracture cracks occur at the surface. To suppress this, Nb, V
It is effective to promote precipitation strengthening by addition.
【０００７】本発明は以上の新規なる知見に基づいてな
されたものであり、本発明の要旨は以下の通りである。
重量比として、Ｃ：０．３５〜０．６５％、Ｓｉ：０．
３５〜２．５％、Ｍｎ：１．０〜１．８％、Ｍｏ：０．
０５〜０．８％、Ｓ：０．０１〜０．１５％、Ａｌ：
０．０１５〜０．０５％、Ｔｉ：０．００５〜０．０５
％、Ｂ：０．０００５〜０．００５％、Ｎ：０．００２
〜０．０１％、を含有し、Ｐ：０．０２０％以下、Ｃ
ｕ：０．０５％以下、Ｏ：０．００２０％以下に制限
し、またはさらに、Ｎｂ：０．０１〜０．２５％、Ｖ：
０．０３〜０．５％の１種または２種を含有し、または
さらに、Ｃｒ：０．０５〜０．５％、Ｎｉ：０．１〜
３．５％の１種または２種を含有し、残部が鉄および不
可避的不純物からなり、かつフェライトの組織分率が３
５％以下で、フェライト結晶粒径が２０μｍ以下である
ことを特徴とする捩り疲労強度の優れた高周波焼入れ軸
部品用鋼材である。The present invention was made based on the above new findings, and the gist of the present invention is as follows.
As a weight ratio, C: 0.35 to 0.65%, Si: 0.
35-2.5%, Mn: 1.0-1.8%, Mo: 0.
05-0.8%, S: 0.01-0.15%, Al:
0.015-0.05%, Ti: 0.005-0.05
%, B: 0.0005 to 0.005%, N: 0.002
To 0.01%, P: 0.020% or less, C
u: 0.05% or less, O: 0.0020% or less, or Nb: 0.01 to 0.25%, V:
0.03 to 0.5% of 1 type or 2 types, or Cr: 0.05 to 0.5%, Ni: 0.1 to 0.1%
It contains 3.5% of 1 type or 2 types, the balance is iron and unavoidable impurities, and the ferrite has a structural fraction of 3
It is a steel material for induction hardened shaft parts with excellent torsional fatigue strength, which is characterized by having a ferrite crystal grain size of 5% or less and 20 μm or less.
【０００８】[0008]
【作用】以下に、本発明を詳細に説明する。本発明の成
分含有範囲を上記の如く限定した理由について説明す
る。まず、Ｃは高周波焼入れ硬化層の硬さを増加させる
のに有効な元素であるが、０．３５％未満では硬さが不
十分であり、また０．６５％を超えるとオーステナイト
粒界への炭化物析出が顕著になって粒界強度を劣化さ
せ、脆性破壊強度の低下を招くとともに、焼き割れが発
生しやすくなるため、含有量を０．３５〜０．６５％に
定めた。次に、Ｓｉは捩り疲労過程での材質劣化の抑
制、オーステナイト粒界への炭化物析出抑制による粒
界強化を目的とし、および脱酸元素として添加する。
しかしながら、０．３５％未満ではその効果は不十分で
あり、一方、２．５％を超える過剰添加は、むしろ粒界
脆性を招くので、その含有量を０．３５〜２．５％とし
た。The present invention will be described in detail below. The reason why the component content range of the present invention is limited as described above will be described. First, C is an element effective in increasing the hardness of the induction hardening layer, but if the content is less than 0.35%, the hardness is insufficient, and if it exceeds 0.65%, the austenite grain boundary is formed. Since the precipitation of carbides becomes remarkable, the grain boundary strength is deteriorated, brittle fracture strength is reduced, and quench cracking is likely to occur, the content is set to 0.35 to 0.65%. Next, Si is added as a deoxidizing element for the purpose of suppressing material deterioration in the torsional fatigue process, strengthening the grain boundary by suppressing the precipitation of carbide in the austenite grain boundary.
However, if it is less than 0.35%, its effect is insufficient, while excessive addition exceeding 2.5% causes rather grain boundary brittleness, so its content was made 0.35 to 2.5%. .
【０００９】Ｍｎは捩り疲労過程での材質劣化の抑
制、焼入れ性の向上、および鋼中でＭｎＳを形成する
ことによる高周波焼入れ加熱時のオーステナイト粒の
微細化と被削性の向上を目的として添加する。しかし
ながら、１．０％未満ではこの効果は不十分である。一
方、Ｍｎはオーステナイト粒界に粒界偏析を起こし、粒
界強度を低下させて捩り応力下での脆性破壊を起こし易
くし、そのため強度を低下させる。特にこの傾向は１．
８％を超えると顕著になる。以上の理由から、Ｍｎの含
有量を１．０〜１．８％とした。Ｍｏは捩り疲労過程
での材質劣化の抑制、オーステナイト粒界に粒界偏析
を起こすことによる粒界強度増加、および焼入れ性の
向上を狙いとして添加する。しかしながら、０．０５％
未満ではこの効果は不十分であり、一方、０．８％を超
える過剰添加は、効果が飽和し経済性の観点から望まし
くないので、その含有量を０．０５〜０．８％とした。Mn is added for the purpose of suppressing material deterioration in the torsional fatigue process, improving hardenability, and refining austenite grains during induction hardening heating by forming MnS in steel and improving machinability. To do. However, if it is less than 1.0%, this effect is insufficient. On the other hand, Mn causes grain boundary segregation at the austenite grain boundaries, lowers the grain boundary strength, and easily causes brittle fracture under torsional stress, which lowers the strength. Especially this tendency is 1.
It becomes remarkable when it exceeds 8%. For the above reasons, the Mn content is set to 1.0 to 1.8%. Mo is added for the purpose of suppressing material deterioration in the torsional fatigue process, increasing grain boundary strength by causing grain boundary segregation in austenite grain boundaries, and improving hardenability. However, 0.05%
If it is less than 0.1%, this effect is insufficient. On the other hand, if over 0.8% is added excessively, the effect is saturated and it is not desirable from the economical point of view, so the content was made 0.05 to 0.8%.
【００１０】また、Ｓは鋼中でＭｎＳを形成、これによ
る高周波焼入れ加熱時のオーステナイト粒の微細化およ
び被削性の向上を目的として添加するが、０．０１％以
下ではその効果は不十分である。一方、０．１５％を超
えるとその効果は飽和し、むしろ粒界偏析を起こし粒界
脆化を招く。以上の理由から、Ｓの含有量を０．０１超
〜０．１５％とした。Ａｌは、Ｎと結合してＡｌＮを
形成することによる高周波焼入れ加熱時のオーテスナイ
ト粒の微細化を目的とし、および脱酸元素として添加
するが、０．１５％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。Further, S forms MnS in steel and is added for the purpose of refining austenite grains during induction hardening heating and improving machinability, but if 0.01% or less, the effect is insufficient. Is. On the other hand, if it exceeds 0.15%, the effect is saturated and rather grain boundary segregation occurs to cause grain boundary embrittlement. For the above reason, the content of S is set to more than 0.01 to 0.15%. Al is added as a deoxidizing element for the purpose of refining austenite grains at the time of induction hardening heating by combining with N to form AlN, and if less than 0.15%, the effect is insufficient. ,
On the other hand, if it exceeds 0.05%, the effect is saturated and rather the toughness is deteriorated, so the content is 0.015 to 0.
It was set to 05%.
【００１１】Ｔｉもやはり鋼中でＮと結合してＴｉＮと
なるが、これによる高周波焼入れ加熱時のオーステナ
イト粒の微細化、および固溶Ｎの完全固定によるＢＮ
析出防止、つまり固溶Ｂの確保を目的として添加する。
しかしながら、、０．００５％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０．０
０５〜０．０５％とした。Ｂは固溶状態でオーステナイ
ト粒界に粒界偏析し、Ｐ，Ｃｕ等の粒界不純物を粒界か
ら追い出すことにより粒界強度を増加させることを狙い
として添加する。しかしながら、、０．０００５％未満
ではその効果は不十分であり、一方０．００５％を超え
る過剰添加は、むしろ粒界脆化を招くので、その含有量
を０．０００５〜０．００５％とした。Ti is also combined with N in steel to form TiN. Due to this, the austenite grains are refined during induction hardening and heating, and the solid solution N is completely fixed.
It is added for the purpose of preventing precipitation, that is, securing solid solution B.
However, if it is less than 0.005%, the effect is insufficient, while if it exceeds 0.05%, the effect is saturated and rather the toughness is deteriorated, so its content is 0.0.
It was set to 05 to 0.05%. B is added as a solid solution in order to increase the grain boundary strength by segregating to the austenite grain boundaries at the grain boundaries and expelling grain boundary impurities such as P and Cu from the grain boundaries. However, if the content is less than 0.0005%, the effect is insufficient, while excessive addition exceeding 0.005% causes rather grain boundary embrittlement, so the content is set to 0.0005 to 0.005%. did.
【００１２】さらに、ＮはＡｌＮ等の炭窒化物析出によ
る高周波加熱時のオーステナイト粒の微細化を目的とし
て添加するが、０．００２％未満ではその効果は不十分
であり、一方０．０１％超では、その効果は飽和し、む
しろＢＮを析出して固溶Ｂの低減を引き起こすので、そ
の含有量を０．００２〜０．０１％とした。一方、Ｐは
オーステナイト粒界に粒界偏析を起こし、粒界強度を低
下させて捩り応力下での脆性破壊を起こし易くし、その
ため強度を低下させる。特にＰが０．０２０％を超える
と強度低下が顕著となるため、０．０２０％を上限とし
た。なお、より粒界強化を図る場合には、０．０１５％
以下が望ましい。また、ＣｕもＰと同様オーステナイト
粒界に粒界偏析を起こし、強度低下の原因となる。特に
Ｃｕが０．０５％を超えると強度低下が顕著となるた
め、０．０５％を上限とした。さらに、Ｏは粒界偏析を
起こし粒界脆化を起こすとともに、鋼中で硬い酸化物系
介在物を形成し、捩り応力下での脆性破壊を起こし易く
し、強度低下の原因となる。特にＯが０．００２０％を
超えると強度低下が顕著となるため、０．００２０％を
上限とした。Further, N is added for the purpose of refining austenite grains during high frequency heating by precipitation of carbonitrides such as AlN, but if less than 0.002%, its effect is insufficient, while 0.01%. If it exceeds the above range, the effect is saturated and rather BN is precipitated to cause a decrease in the solid solution B, so the content is made 0.002 to 0.01%. On the other hand, P causes grain boundary segregation at the austenite grain boundaries, lowers the grain boundary strength, and easily causes brittle fracture under torsional stress, and thus lowers the strength. In particular, when P exceeds 0.020%, the strength is significantly reduced, so 0.020% is made the upper limit. When strengthening the grain boundaries, 0.015%
The following is desirable. Further, Cu causes grain boundary segregation at the austenite grain boundaries, which is a cause of strength reduction, like P. In particular, if the Cu content exceeds 0.05%, the strength is significantly reduced, so the upper limit was made 0.05%. Further, O causes grain boundary segregation to cause grain boundary embrittlement, forms hard oxide inclusions in steel, and easily causes brittle fracture under torsional stress, which causes strength reduction. In particular, when O exceeds 0.0020%, the strength is markedly reduced, so 0.0020% was made the upper limit.
【００１３】次に、本発明では、「フェライトの組織分
率が３５％以下で、フェライト結晶粒径が２０μｍ以
下」とする。高周波焼入れは急速加熱であるため、高周
波焼入れ前の組織のフェライト分率が大きくまたそれが
粗大であると、フェライトの部分はオーステナイト化
後、炭素の拡散が不十分で炭素濃度が添加炭素濃度より
も低くなり、焼入れ後、その位置での硬さが小さくな
る。そのため、この位置が疲労亀裂の発生起点となり易
い。以上の現象は、フェライトの組織分率が３５％を超
えるか、またはフェライト結晶粒径が２０μｍを超える
と特に顕著になる。以上の理由でフェライトの組織分率
を３５％以下で、フェライト結晶粒径を２０μｍ以下と
した。なお、より高捩り疲労強度を図るためには、フェ
ライトの組織分率を２５％以下とするか、またはさらに
フェライト結晶粒径を１５μｍ以下とするのが望まし
い。また、本発明の高周波焼入れ軸部品用鋼材では、フ
ェライト以外の残りの組織を特に限定するものではな
く、その種類がパーライト、上部ベイナイト、下部ベイ
ナイト、中間段階組織、マルテンサイト、あるいはこれ
らの混合組織のいずれでもよい。Next, in the present invention, "the structure fraction of ferrite is 35% or less and the ferrite crystal grain size is 20 μm or less". Since induction hardening is rapid heating, if the ferrite fraction of the structure before induction hardening is large and it is coarse, the ferrite part after austenitization has insufficient carbon diffusion and the carbon concentration is higher than the added carbon concentration. Becomes lower, and the hardness at that position becomes smaller after quenching. Therefore, this position easily becomes a starting point of fatigue crack generation. The above phenomenon becomes particularly remarkable when the structure fraction of ferrite exceeds 35% or when the ferrite crystal grain size exceeds 20 μm. For the above reasons, the structure fraction of ferrite is 35% or less, and the ferrite crystal grain size is 20 μm or less. In order to achieve a higher torsional fatigue strength, it is desirable that the structure fraction of ferrite be 25% or less, or that the ferrite crystal grain size be 15 μm or less. Further, in the steel material for induction hardened shaft parts of the present invention, the remaining structure other than ferrite is not particularly limited, and its type is pearlite, upper bainite, lower bainite, intermediate stage structure, martensite, or a mixed structure thereof. Any of
【００１４】第２の発明は、高周波焼入れ後の芯部硬さ
を析出硬化により増加させ、硬化層と芯部の境界での捩
り疲労亀裂の発生を抑制するとともに、高周波加熱時の
オーステナイト粒を一層微細化し、粒界破壊防止による
高強度化を図った軸部品用鋼材である。Ｎｂ，Ｖは鋼中
で炭窒化物を形成し、析出硬化により高周波焼入れ後の
芯部硬さを増加させるとともに、高周波加熱時のオース
テナイト粒を微細化させる効果を有する。しかしなが
ら、、Ｎｂ含有量が０．０１％未満、Ｖ含有量が０．０
３％未満ではその効果は不十分であり、一方、Ｎｂ：
０．２５％超、Ｖ：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、これらの含有量をＮ
ｂ：０．０１〜０．２５％、Ｖ：０．０３〜０．５％と
した。In a second aspect of the present invention, the hardness of the core portion after induction hardening is increased by precipitation hardening to suppress the occurrence of torsional fatigue cracks at the boundary between the hardened layer and the core portion, and to reduce austenite grains during induction heating. It is a steel material for shaft parts that has been further refined to achieve higher strength by preventing grain boundary fracture. Nb and V form carbonitrides in the steel, and have the effect of increasing the hardness of the core after induction hardening by precipitation hardening and making the austenite grains fine during induction heating. However, the Nb content is less than 0.01% and the V content is 0.0
If it is less than 3%, the effect is insufficient, while Nb:
If the content is more than 0.25% and V: more than 0.50%, the effect is saturated and rather the toughness is deteriorated.
b: 0.01 to 0.25%, V: 0.03 to 0.5%.
【００１５】第３の発明は、Ｃｒ、Ｎｉ添加により、
捩り疲労過程での硬さの以下の抑制、および焼入れ性
の向上を図った軸部品用鋼材である。なお、Ｎｉには、
粒界近傍の靱性を改善し、脆性破壊を抑制する効果も有
する。ただし、Ｃｒ：０．０５％未満、Ｎｉ：０．１％
未満ではこの効果は不十分である。一方、Ｃｒ：０．５
％超では高周波焼入れ前の組織中のセメンタイトが安定
化し、高周波焼入れ加熱時にセメンタイトの溶解が困難
になり、高周波焼入れ後の効果層の硬さが不十分とな
る。また、３．５％を超えるＮｉの多量添加は、効果が
飽和し経済性の観点から好ましくない。以上の理由か
ら、Ｃｒ：０．０５％〜０．５％、Ｎｉ：０．１〜３．
５％とした。A third aspect of the present invention is that by adding Cr and Ni,
It is a steel material for shaft parts, which is intended to suppress the hardness below in the torsional fatigue process and to improve hardenability. In addition, in Ni,
It also has the effect of improving the toughness near the grain boundaries and suppressing brittle fracture. However, Cr: less than 0.05%, Ni: 0.1%
If it is less than, this effect is insufficient. On the other hand, Cr: 0.5
If it exceeds%, the cementite in the structure before induction hardening is stabilized, it becomes difficult to dissolve the cementite during heating by induction hardening, and the hardness of the effect layer after induction hardening becomes insufficient. Further, the addition of a large amount of Ni exceeding 3.5% saturates the effect and is not preferable from the economical viewpoint. For the above reasons, Cr: 0.05% to 0.5%, Ni: 0.1 to 3.
It was set to 5%.
【００１６】ここで、本発明の高周波焼入れ軸部品用鋼
材では、製造条件は特に限定せず、本発明の要件を満足
すればいずれの条件でもよい。例えば、鋼材素材の熱間
圧延による製造を仕上げ温度；７５０〜９００℃、仕上
げ圧延後７００〜５００℃の温度範囲の平均冷却速度；
０．１〜１．７℃／秒の条件で行う方法が挙げられる
が、本発明では特に限定するものではない。また、本発
明では、本発明の要件を満足すれば熱間圧延後、高周波
焼入れの前に焼準、焼鈍、熱間鍛造等の加工熱処理を必
要に応じて行うことができる。In the steel material for induction hardened shaft parts of the present invention, the manufacturing conditions are not particularly limited, and any condition may be satisfied as long as the requirements of the present invention are satisfied. For example, the finishing temperature in the production of the steel material by hot rolling; the average cooling rate in the temperature range of 750 to 900 ° C. and 700 to 500 ° C. after the finish rolling;
The method may be performed under the condition of 0.1 to 1.7 ° C./second, but the present invention is not particularly limited thereto. Further, in the present invention, if the requirements of the present invention are satisfied, it is possible to perform thermomechanical treatment such as normalizing, annealing, and hot forging after hot rolling and before induction hardening, if necessary.
【００１７】[0017]
【実施例】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。表１，２の組成を有する鋼材を３４ｍ
ｍφの棒鋼に圧延した。この棒鋼から、光学顕微鏡観察
試験片を採取し、５％ナイタール液で腐食して２００
倍、４００倍で観察しフェライト分率およびフェライト
結晶粒径を求めた。表１，２にフェライト分率、フェラ
イト結晶粒径を示す。また、比較鋼材２３，２４，２５
の材料については圧延後８５０度×１時間加熱し、８５
０〜５００℃の温度範囲を１．２℃／秒の冷却速度で冷
却した。本材料に新規に２３Ｍ，２４Ｍ，２５Ｍと記号
を付し、フェライト分率およびフェライト結晶粒径を測
定した。その結果を表３に示す。これらの材料から、平
行部直径２０ｍｍの静的捩り試験片、捩り疲労試験片を
採取した。EXAMPLES The effects of the present invention will be more specifically described below with reference to examples. 34m steel material having the composition of Tables 1 and 2
Rolled to mφ steel bar. An optical microscope observation test piece was taken from this steel bar and corroded with a 5% Nital solution to give 200
Double observation and 400 times observation were performed to determine the ferrite fraction and the ferrite crystal grain size. Tables 1 and 2 show the ferrite fraction and the ferrite crystal grain size. In addition, comparative steel materials 23, 24, 25
For the material of, after rolling, heat at 850 ° C for 1 hour, and
The temperature range of 0 to 500 ° C was cooled at a cooling rate of 1.2 ° C / sec. This material was newly labeled with 23M, 24M, and 25M, and the ferrite fraction and the ferrite crystal grain size were measured. Table 3 shows the results. From these materials, a static torsion test piece and a torsion fatigue test piece having a parallel part diameter of 20 mm were collected.
【００１８】[0018]
【表１】 [Table 1]
【００１９】[0019]
【表２】 [Table 2]
【００２０】[0020]
【表３】 [Table 3]
【００２１】静的捩り試験片、捩り疲労試験片について
周波数８．５ｋＨｚで高周波焼入れを行い、その後１７
０℃×１時間の条件で焼戻しを行った。いずれも有効硬
化層深さは約５ｍｍである。その後、静的捩り試験、捩
り疲労試験を行った。捩り疲労特性は５×１０5 サイク
ルでの時間強度で評価した。表４，５に各供試材の静的
捩り強度、捩り疲労強度を示す。また、捩り疲労過程で
の材質劣化挙動を評価するために、応力振幅７００ＭＰ
ａで１×１０4 サイクル疲労試験を行った試験片につい
て、表面での圧縮残留応力の減衰量およびフェライ
ト（２１１）面のＸ線回折ピークの単価幅の減衰量を評
価した。Ｘ線回折ピークの半価幅の減衰量は、疲労過程
での正味の硬さの低下量を評価するために用いた。Ｘ線
発生源としては、Ｃｒ管球を使用した。表４，５のＮ
ｏ．１〜２５Ｍは本発明鋼材であるが、本発明鋼材で
は、いずれも優れた静的捩り強度、捩り疲労強度を有し
ている。特に捩り疲労強度は、０．４％Ｃ鋼で概ね６０
０ＭＰａ以上、０．５％Ｃ鋼で概ね７００ＭＰａ以上と
優れた特性が得られている。The static torsion test piece and the torsion fatigue test piece were induction hardened at a frequency of 8.5 kHz, and then 17
Tempering was performed under the condition of 0 ° C. × 1 hour. In each case, the effective hardened layer depth is about 5 mm. Then, a static torsion test and a torsion fatigue test were conducted. The torsional fatigue property was evaluated by the time strength at 5 × 10 5 cycles. Tables 4 and 5 show the static torsional strength and torsional fatigue strength of each test material. In addition, in order to evaluate the material deterioration behavior in the torsional fatigue process, the stress amplitude 700MP
With respect to the test piece subjected to the 1 × 10 4 cycle fatigue test in a, the attenuation amount of the compressive residual stress on the surface and the attenuation amount of the unit price width of the X-ray diffraction peak of the ferrite (211) plane were evaluated. The attenuation of the full width at half maximum of the X-ray diffraction peak was used to evaluate the net decrease in hardness during the fatigue process. A Cr tube was used as the X-ray source. N in Tables 4 and 5
o. 1 to 25 M are steel materials of the present invention, but the steel materials of the present invention all have excellent static torsional strength and torsional fatigue strength. Especially, the torsional fatigue strength is about 60 for 0.4% C steel.
Excellent properties such as 0 MPa or more and 0.5% C steel of approximately 700 MPa or more are obtained.
【００２２】[0022]
【表４】 [Table 4]
【００２３】[0023]
【表５】 [Table 5]
【００２４】一方、比較鋼材２３，２４，２５はフェラ
イト分率またはフェライト結晶粒径のいずれか、または
両者が本発明の範囲を上回った場合であり、比較鋼材２
６，２７，２８はＳｉ，Ｍｏ，Ｂの含有量が本発明の範
囲を下回った場合であり、比較鋼材２９，３０はＰ，Ｃ
ｒの含有量が本発明の範囲を上回った場合であり、比較
鋼材３１はＳｉ，Ｍｎ，Ｍｏ，Ｔｉ，Ｂの含有量が本発
明の範囲を下回り、フェライト分率、フェライト結晶粒
径が本発明の範囲を上回った場合であり、いずれも同一
炭素量の本発明鋼材に比較して、静的捩り強度、捩り疲
労強度が劣っている。特に捩り疲労強度は、０．４％Ｃ
鋼で、いずれも６００ＭＰａ未満、０．５％Ｃ鋼で７０
０ＭＰａ未満であり、本発明鋼材に比較して顕著に劣っ
ている。比較鋼材の「疲労過程での残留応力減衰量」
「疲労過程での半価幅の減少量」は、同一炭素量の本発
明鋼に比較して相対的に大きい。つまり、本発明鋼材で
は、捩り疲労過程での材質劣化が抑制されたことによ
り、優れた捩り疲労強度が得られていることが明らかで
ある。On the other hand, the comparative steel materials 23, 24, and 25 are cases in which either the ferrite fraction or the ferrite crystal grain size, or both exceeds the range of the present invention.
6, 27 and 28 are cases where the contents of Si, Mo and B are below the range of the present invention, and the comparative steel materials 29 and 30 are P and C.
In the case where the content of r exceeds the range of the present invention, the comparative steel material 31 has the content of Si, Mn, Mo, Ti, B below the range of the present invention, and the ferrite fraction and the ferrite crystal grain size are the same. This is the case where the range of the invention is exceeded, and in both cases, the static torsional strength and torsional fatigue strength are inferior to the steel materials of the present invention having the same carbon content. Especially torsional fatigue strength is 0.4% C
Steel, less than 600 MPa, 0.5% C steel 70
It is less than 0 MPa, which is significantly inferior to the steel material of the present invention. "Residual stress attenuation during fatigue process" of comparative steels
The “amount of decrease in half-value width in the fatigue process” is relatively large as compared with the steel of the present invention having the same carbon content. In other words, it is clear that the steel material of the present invention has excellent torsional fatigue strength due to the suppression of material deterioration in the torsional fatigue process.
【００２５】[0025]
【発明の効果】以上述べたごとく、本発明の高周波焼入
れ軸部品用鋼材を用いれば、捩り疲労強度の優れた高周
波焼入れ軸部品の製造が可能となり、産業上の効果は極
めて顕著なるものがある。As described above, by using the steel material for induction hardened shaft parts of the present invention, it is possible to manufacture an induction hardened shaft part having excellent torsional fatigue strength, and the industrial effect is extremely remarkable. .
【図１】（ａ）はセレーション部を有するシャフ、
（ｂ）はフランジ付シャフト、（ｃ）は外筒付シャフト
を示した図FIG. 1A is a shuff having a serrated portion,
(B) shows a shaft with a flange, (c) shows a shaft with an outer cylinder
１０ シャフト １１，１２ セレーション ２０，２１ シャフト ２２ フランジ ３０，３１，３２ シャフト ３３ 外筒部 10 Shaft 11,12 Serration 20,21 Shaft 22 Flange 30,31,32 Shaft 33 Outer cylinder part
Claims (3)
可避的不純物からなり、かつフェライトの組織分率が３
５％以下で、フェライト結晶粒径が２０μｍ以下である
ことを特徴とする捩り疲労強度の優れた高周波焼入れ軸
部品用鋼材。1. As a weight ratio, C: 0.35 to 0.65% Si: 0.35 to 2.5% Mn: 1.0 to 1.8% Mo: 0.05 to 0.8% S : 0.01 to 0.15% Al: 0.015 to 0.05% Ti: 0.005 to 0.05% B: 0.0005 to 0.005% N: 0.002 to 0.01% Contained, P: 0.020% or less, Cu: 0.05% or less, O: 0.0020% or less, the balance consisting of iron and unavoidable impurities, and a ferrite microstructure fraction of 3
A steel material for an induction-hardened shaft component having excellent torsional fatigue strength, which is characterized by having a ferrite crystal grain size of 20 μm or less at 5% or less.
が３５％以下で、フェライト結晶粒径が２０μｍ以下で
あることを特徴とする捩り疲労強度の優れた高周波焼入
れ軸部品用鋼材。2. A ferrite structure containing, in addition to the components of claim 1, one or two of Nb: 0.01 to 0.25% V: 0.03 to 0.5%. A steel material for induction-hardened shaft parts having excellent torsional fatigue strength, characterized by having a fraction of 35% or less and a ferrite crystal grain size of 20 μm or less.
えて、 Ｃｒ：０．０５〜０．５％ Ｎｉ：０．１〜３．５％ の１種または２種を含有し、かつフェライトの組織分率
が３５％以下で、フェライト結晶粒径が２０μｍ以下で
あることを特徴とする捩り疲労強度の優れた高周波焼入
れ軸部品用鋼材。3. In addition to the component according to claim 1 or 2, it contains one or two of Cr: 0.05 to 0.5% Ni: 0.1 to 3.5%, and A steel material for induction hardened shaft parts having excellent torsional fatigue strength, characterized in that the ferrite has a structural fraction of 35% or less and a ferrite crystal grain size of 20 μm or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP08344795A JP3432944B2 (en) | 1995-03-16 | 1995-03-16 | Steel material for induction hardened shaft parts with excellent torsional fatigue strength |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP08344795A JP3432944B2 (en) | 1995-03-16 | 1995-03-16 | Steel material for induction hardened shaft parts with excellent torsional fatigue strength |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08253842A true JPH08253842A (en) | 1996-10-01 |
| JP3432944B2 JP3432944B2 (en) | 2003-08-04 |
Family
ID=13802701
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP08344795A Expired - Fee Related JP3432944B2 (en) | 1995-03-16 | 1995-03-16 | Steel material for induction hardened shaft parts with excellent torsional fatigue strength |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3432944B2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1069198A1 (en) * | 1999-01-28 | 2001-01-17 | Sumitomo Metal Industries, Ltd. | Machine structural steel product |
| EP1584700A1 (en) * | 2003-01-17 | 2005-10-12 | JFE Steel Corporation | High-strength steel product excelling in fatigue strength and process for producing the same |
| JP2006045678A (en) * | 2003-01-17 | 2006-02-16 | Jfe Steel Kk | Steel product having excellent fatigue property after induction hardening, and production method therefor |
| WO2006110100A1 (en) * | 2005-04-12 | 2006-10-19 | Scania Cv Ab (Publ) | Boron steel grade for induction hardening and shaft |
| US7740722B2 (en) | 2003-01-23 | 2010-06-22 | Jtekt Corporation | Steel for use in high strength pinion shaft and manufacturing method thereof |
-
1995
- 1995-03-16 JP JP08344795A patent/JP3432944B2/en not_active Expired - Fee Related
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1069198A1 (en) * | 1999-01-28 | 2001-01-17 | Sumitomo Metal Industries, Ltd. | Machine structural steel product |
| EP1069198A4 (en) * | 1999-01-28 | 2002-02-06 | Sumitomo Metal Ind | Machine structural steel product |
| US6475305B1 (en) | 1999-01-28 | 2002-11-05 | Sumitomo Metal Industries, Ltd. | Machine structural steel product |
| EP1584700A1 (en) * | 2003-01-17 | 2005-10-12 | JFE Steel Corporation | High-strength steel product excelling in fatigue strength and process for producing the same |
| JP2006045678A (en) * | 2003-01-17 | 2006-02-16 | Jfe Steel Kk | Steel product having excellent fatigue property after induction hardening, and production method therefor |
| EP1584700A4 (en) * | 2003-01-17 | 2007-03-28 | Jfe Steel Corp | High-strength steel product excelling in fatigue strength and process for producing the same |
| EP1961831A1 (en) * | 2003-01-17 | 2008-08-27 | JFE Steel Corporation | High-strength steel product excelling in fatigue strength and process for producing the same |
| JP4517983B2 (en) * | 2003-01-17 | 2010-08-04 | Ｊｆｅスチール株式会社 | Steel material excellent in fatigue characteristics after induction hardening and method for producing the same |
| US7740722B2 (en) | 2003-01-23 | 2010-06-22 | Jtekt Corporation | Steel for use in high strength pinion shaft and manufacturing method thereof |
| WO2006110100A1 (en) * | 2005-04-12 | 2006-10-19 | Scania Cv Ab (Publ) | Boron steel grade for induction hardening and shaft |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3432944B2 (en) | 2003-08-04 |
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