JPH07316720A - Non-heat treated steel having high durability ratio and high strength, and its production - Google Patents
Non-heat treated steel having high durability ratio and high strength, and its productionInfo
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- JPH07316720A JPH07316720A JP11267994A JP11267994A JPH07316720A JP H07316720 A JPH07316720 A JP H07316720A JP 11267994 A JP11267994 A JP 11267994A JP 11267994 A JP11267994 A JP 11267994A JP H07316720 A JPH07316720 A JP H07316720A
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- Prior art keywords
- steel
- strength
- heat treated
- toughness
- treated steel
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、非調質のままで高い引
張強度、高い衝撃値を有し、かつ優れた疲労強度を有す
る高耐久比高強度非調質鋼とその製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high durability non-heat treated steel having a high tensile strength, a high impact value and an excellent fatigue strength in a non-heat treated state and a method for producing the same.
【０００２】[0002]
【従来の技術】従来、コネクティングロッド、クランク
軸、ナックル等の自動車用鍛造部品には、機械構造用炭
素鋼あるいは合金鋼を用い、熱間鍛造により部品形状に
成形後、高い疲労強度を付与するため調質処理 (焼入焼
戻し処理) が行われていた。しかしながら、コスト、省
力化、熱処理変形等の問題から調質処理を省略し、鍛造
まま (非調質) で高い疲労強度が得られる鋼の開発が望
まれている。2. Description of the Related Art Conventionally, carbon steel or alloy steel for machine structure is used for forging parts for automobiles such as connecting rods, crankshafts, knuckles, etc., and high fatigue strength is given after forming into parts shape by hot forging. Therefore, heat treatment (quenching and tempering) was performed. However, due to problems such as cost, labor saving, and heat treatment deformation, it is desired to develop a steel that can obtain high fatigue strength without forging (non-tempering) by omitting the tempering process.
【０００３】このような背景から、特開平４−202741号
公報、特開平４−199931号公報では「疲労強度の優れた
熱間鍛造品」と題する発明が提案されている。これら
は、非調質のままで優れた疲労強度を有する熱間鍛造品
の化学成分および熱処理条件を規定することで、フェラ
イト・パーライト組織の非調質鋼での疲労強度の改善を
図ろうとするものである。From this background, Japanese Patent Laid-Open Nos. 4-202741 and 4-199931 propose an invention entitled "Hot forged product having excellent fatigue strength". These are intended to improve the fatigue strength of non-heat treated steels with a ferrite-pearlite structure by defining the chemical composition and heat treatment conditions of hot forged products that have excellent fatigue strength while maintaining their non-heat treated properties. It is a thing.
【０００４】しかし、フェライト・パーライト組織では
安定した高強度、高靱性を得ることができない。そこ
で、安定した高強度、高靱性を有し、高い疲労強度が得
られる鋼が望まれている。However, the ferrite / pearlite structure cannot provide stable high strength and high toughness. Therefore, steel having stable high strength and high toughness and high fatigue strength is desired.
【０００５】[0005]
【発明が解決しようとする課題】ここに、本発明の目的
は、化学成分を最適化することにより鍛造ままで、より
高い引張強度、高い衝撃値および高い耐久比 (疲労強度
／引張強度) を有する鋼およびその製造方法を提供する
ことである。The object of the present invention is to improve the tensile strength, the high impact value and the high durability ratio (fatigue strength / tensile strength) of the as-forged material by optimizing the chemical composition. To provide a steel having the same and a manufacturing method thereof.
【０００６】本発明の具体的な目的は、化学成分を最適
化することにより鍛造ままで、900N/mm2以上の引張強
度、uE+20 50 J/cm2以上の高い衝撃値および0.50以上の
高い耐久比 (疲労強度／引張強度) を有する鋼およびそ
の製造方法を提供することである。[0006] A specific object of the present invention is, as-forged by optimizing the chemical composition, tensile strength of 900 N / mm 2 or more, high impact value of uE +20 50 J / cm 2 or more and 0.50 or more. (EN) A steel having a high durability ratio (fatigue strength / tensile strength) and a method for producing the same.
【０００７】[0007]
【課題を解決するための手段】一般に、自動車用鍛造部
品には、疲労強度のみならず、被削性も要求される。被
削性は強度に依存するものの金属組織に強く依存し、フ
ェライト・パーライト組織では被削性がよく、フェライ
ト・パーライト組織の非調質鋼での疲労強度の改善が試
みられている。しかし、非調質鋼において、さらなる高
強度・高靱性を得るためには組織をベイナイト組織にし
なければならない。そこで、ベイナイト組織の非調質鋼
にて疲労強度の改善を試みた。Generally, forged parts for automobiles are required to have not only fatigue strength but also machinability. The machinability depends on the strength but strongly depends on the metal structure, and the ferrite-pearlite structure has good machinability, and attempts have been made to improve the fatigue strength of the non-heat treated steel of the ferrite-pearlite structure. However, in non-heat treated steel, the structure must be bainite to obtain higher strength and toughness. Therefore, we tried to improve the fatigue strength of non-heat treated steel with bainite structure.
【０００８】ベイナイト組織の疲労強度を高めるにはマ
イクロアロイの添加により、炭窒化物を析出させ強化す
る必要がある。そこで、本発明の完成に先立ち、疲労強
度に及ぼす添加元素の影響を調査し、化学成分の最適化
をはかった。In order to increase the fatigue strength of the bainite structure, it is necessary to precipitate and strengthen carbonitrides by adding a microalloy. Therefore, prior to the completion of the present invention, the influence of additional elements on the fatigue strength was investigated to optimize the chemical composition.
【０００９】よって、本発明は、重量％で、Ｃ：0.10〜
0.20％、 Si：0.05〜1.50％、 Mn：0.50〜2.50
％、Cr：0.50〜2.50％、 Mo：0.05〜0.50％、
Ｖ：0.005 〜0.200 ％、sol.Al：0.005 〜0.050 ％、さ
らに、必要に応じて、Nb：0.005 〜0.080 ％、Ti：0.00
5 〜0.050 ％、およびＢ：0.0001〜0.0030％のうち１種
または２種以上、および／または、Pb：0.005 〜0.50
％、Ca：0.0001〜0.0500％、Se：0.001 〜0.500 ％、T
e：0.005 〜0.050 ％、Bi：0.40％以下、およびＳ：0.0
05 〜0.150 ％のうち１種または２種以上を含み、残部F
eおよび不可避不純物から成る鋼組成を有し、初析フェ
ライトの面積率が10％以下であるベイナイト組織から成
ることを特徴とする高耐久比高強度非調質鋼である。[0009] Therefore, the present invention, in% by weight, C: 0.10 ~
0.20%, Si: 0.05 to 1.50%, Mn: 0.50 to 2.50
%, Cr: 0.50 to 2.50%, Mo: 0.05 to 0.50%,
V: 0.005 to 0.200%, sol.Al: 0.005 to 0.050%, and if necessary, Nb: 0.005 to 0.080%, Ti: 0.00
5 to 0.050%, and B: 0.0001 to 0.0030%, one or more kinds, and / or Pb: 0.005 to 0.50.
%, Ca: 0.0001 to 0.0500%, Se: 0.001 to 0.500%, T
e: 0.005 to 0.050%, Bi: 0.40% or less, and S: 0.0
05 to 0.150%, containing 1 or 2 or more, balance F
A high durability high strength non-heat treated steel characterized by having a steel composition consisting of e and inevitable impurities and having a bainite structure in which the area ratio of proeutectoid ferrite is 10% or less.
【００１０】別の面からは、本発明は、上記鋼組成を有
する鋼材を、950 ℃以上1250℃以下に加熱した後、熱間
鍛造により750 ℃以上の仕上温度で所定形状に成形する
ことを特徴とする高耐久比高強度非調質鋼の製造方法で
ある。From another aspect, the present invention provides that a steel material having the above steel composition is heated to a temperature of 950 ° C. or higher and 1250 ° C. or lower, and then hot forged into a predetermined shape at a finishing temperature of 750 ° C. or higher. It is a method for producing a high-strength non-heat treated steel having a high durability ratio.
【００１１】[0011]
【作用】本発明において、鋼組成および加工処理条件を
規定した理由について説明する。 Ｃ：0.10〜0.20％ Ｃは強度を高めるのに必要な元素であり、0.10％以上含
有しないと所定の強度を満足させることはできない。一
方、Ｃを0.20％超含有させると、強度上昇効果は得られ
るが、逆に著しい靱性の劣化を招くので、0.10〜0.20％
とした。The reason for defining the steel composition and the processing conditions in the present invention will be described. C: 0.10 to 0.20% C is an element necessary for increasing the strength, and if 0.10% or more is not contained, the predetermined strength cannot be satisfied. On the other hand, if C is contained in an amount of more than 0.20%, a strength increasing effect can be obtained, but on the contrary, it causes remarkable deterioration of toughness, so 0.10 to 0.20%
And
【００１２】Si：0.05〜1.50％ Siは固溶強化元素であり、耐久比を向上するのに効果的
な合金元素である。かかる効果を得るためには少なくと
も0.05％を添加する。しかしながら、過剰な添加はその
効果が飽和するとともに鍛造時に表面の脱炭を促すた
め、1.50％以下とする。好ましくは、0.25〜1.25％であ
る。下限としては0.30％がより好ましい。Si: 0.05 to 1.50% Si is a solid solution strengthening element and is an alloying element effective in improving the durability ratio. To obtain such effect, at least 0.05% is added. However, excessive addition saturates the effect and promotes decarburization of the surface during forging, so it is made 1.50% or less. It is preferably 0.25 to 1.25%. The lower limit is more preferably 0.30%.
【００１３】Mn：0.50〜2.50％ Mnは焼入性を向上させて、熱間鍛造後の鋼材の金属組織
をベイナイト組織とするのに効果を発揮させる元素であ
るが、そのためには0.50％以上を含有させる。一方、2.
50％を越えて含有させても、その効果は飽和するばかり
か、製造コストを上昇させるため、0.50〜2.50％、好ま
しくは1.50〜2.20％とした。Mn: 0.50 to 2.50% Mn is an element that improves the hardenability and exerts an effect of making the metal structure of the steel material after hot forging into a bainite structure. Is included. On the other hand, 2.
Even if the content exceeds 50%, not only the effect is saturated but also the manufacturing cost is increased, so the content was made 0.50 to 2.50%, preferably 1.50 to 2.20%.
【００１４】Cr：0.50〜2.50％ Crは固溶強化元素であり、耐久比を向上するのに効果的
な合金元素である。その効果を十分に発揮させるために
は0.50％以上を含有させる。一方、2.50％を越えて含有
すると靱性は低下させる。従って、0.50〜2.50％をCrの
成分範囲とした。好ましくは1.0 〜2.0 ％である。Cr: 0.50 to 2.50% Cr is a solid solution strengthening element and is an alloying element effective for improving the durability ratio. In order to bring out the effect sufficiently, 0.50% or more is contained. On the other hand, if the content exceeds 2.50%, the toughness decreases. Therefore, 0.50 to 2.50% is set as the Cr component range. It is preferably 1.0 to 2.0%.
【００１５】Mo：0.05〜0.50％ Moは鋼に所定の焼入性を付与し、静的強度、靱性を向上
させるのに有効な元素である。その効果を十分に発揮さ
せるためには0.05％以上の含有が必要である。一方、0.
50％を越えて含有しても、その効果は飽和し、経済性を
損なうので0.05〜0.50％とした。好ましくは、0.10〜0.
40％である。Mo: 0.05 to 0.50% Mo is an element effective for imparting a predetermined hardenability to steel and improving static strength and toughness. To fully bring out the effect, the content of 0.05% or more is required. On the other hand, 0.
Even if the content exceeds 50%, the effect is saturated and the economy is impaired, so the content was made 0.05 to 0.50%. Preferably 0.10-0.
40%.
【００１６】Ｖ：0.005 〜0.200 ％ Ｖは析出強化元素であり、耐久比を向上するのに効果的
な合金元素である。その効果を十分に発揮させるために
は0.005 ％以上を含有させる。一方、0.200 ％を越えて
含有させても、析出強化量は飽和するので、0.005 〜0.
200 ％とする。好ましくは、0.05〜0.20％である。V: 0.005 to 0.200% V is a precipitation strengthening element, which is an alloying element effective for improving the durability ratio. To fully bring out the effect, 0.005% or more is contained. On the other hand, even if the content exceeds 0.200%, the precipitation strengthening amount saturates, so 0.005 to 0.
200% Preferably, it is 0.05 to 0.20%.
【００１７】sol.Al：0.005 〜0.050 ％ sol.AlはSi、Mn同様、鋼の脱酸に必要な元素である。ま
た、Al窒化物を生成し、結晶粒を微細化する効果があ
る。しかし、同時に、Ｂ添加による強度および靱性の向
上を図るためには、Tiに加え、sol.Alを添加し、Ｎを固
定する必要がある。それに必要な最低限の含有量は0.00
5 ％である。しかし、sol.Alは0.050 ％を越えて含有す
ると巨大なAl酸化物が生成し、疲労強度を低下させる。
さらに、結晶粒が粗大化し、靱性が低下する。従って、
0.005 〜0.050 ％とした。好ましくは、0.02〜0.04％で
ある。本発明の対象となる鋼組成には、必要に応じさら
に強度・靱性を改善するために、Nb、Ti、Ｂの少なくと
も１種を追加配合する。Sol.Al: 0.005 to 0.050% sol.Al is an element necessary for deoxidizing steel, like Si and Mn. It also has the effect of producing Al nitrides and refining the crystal grains. However, at the same time, in order to improve the strength and toughness by adding B, it is necessary to add sol.Al in addition to Ti and fix N. The minimum content required for that is 0.00
5%. However, if the content of sol.Al exceeds 0.050%, a huge Al oxide is generated and the fatigue strength is reduced.
In addition, the crystal grains become coarse and the toughness decreases. Therefore,
It was set to 0.005 to 0.050%. It is preferably 0.02 to 0.04%. If necessary, at least one of Nb, Ti and B is additionally compounded in the steel composition to be the subject of the present invention in order to further improve strength and toughness.
【００１８】Nb：0.005 〜0.080 ％ Nbは熱間鍛造後の組織を均一微細なベイナイト組織に
し、ベイナイトの強度、靱性を向上させる。その効果を
十分に発揮させるためには0.005 ％以上の含有が必要で
ある。一方、0.080 ％を越えて含有しても、その効果は
飽和し、経済性を損なうので、0.005 〜0.080 ％とす
る。Nb: 0.005-0.080% Nb improves the strength and toughness of bainite by making the structure after hot forging into a uniform fine bainite structure. In order to fully bring out the effect, the content of 0.005% or more is required. On the other hand, if the content exceeds 0.080%, the effect is saturated and the economic efficiency is impaired, so 0.005 to 0.080% is set.
【００１９】Ti：0.005 〜0.050 ％ TiはTiＮとして窒化物を生成させ、結晶粒を微細化する
効果がある。また、Ｂ添加による強度・靱性の向上を図
るためにはTiを添加し、窒化物を生成させＮを固定する
必要がある。それに必要な最低限のTi含有量は0.005 ％
である。一方、0.050 ％を越えて含有させると巨大なTi
窒化物が生成し、靱性を低下させるので0.005 〜0.050
％とした。Ti: 0.005 to 0.050% Ti has the effect of forming nitrides as TiN and refining the crystal grains. Further, in order to improve the strength and toughness by adding B, it is necessary to add Ti to form a nitride and fix N. The minimum required Ti content is 0.005%
Is. On the other hand, if the content exceeds 0.050%, a large Ti
Nitride is formed, which lowers toughness, so 0.005 to 0.050
%.
【００２０】Ｂ：0.0001〜0.0030％ Ｂは焼入性を向上させると同時に靱性を向上させる効果
がある。その効果を十分に発揮させるためには0.0001％
以上含有する必要がある。一方、0.0030％を越えて含有
すると、結晶粒が粗大化し、靱性が低下するので0.0001
〜0.0030％を成分範囲とした。かかる追加成分のうち、
Nb単独添加、またはTi＋Ｂの同時添加がさらに好まし
い。B: 0.0001 to 0.0030% B has the effect of improving hardenability and at the same time improving toughness. 0.0001% to fully bring out the effect
It is necessary to contain the above. On the other hand, if the content exceeds 0.0030%, the crystal grains become coarse and the toughness decreases.
〜0.0030% was made the component range. Of such additional ingredients,
More preferable is the addition of Nb alone or the simultaneous addition of Ti + B.
【００２１】次に、本発明の対象となる鋼組成として
は、必要に応じさらに切削性を改善するために、Pb、C
a、Se、Te、BiおよびＳから成る群から選んだ少なくと
も１種をさらに配合してもよい。Next, as a steel composition to be the subject of the present invention, in order to further improve the machinability, if necessary, Pb, C
You may further mix | blend at least 1 sort (s) selected from the group which consists of a, Se, Te, Bi, and S.
【００２２】Pb：0.005 〜0.50％ Pbは切削性を向上させる元素である。その効果を十分に
発揮させるためには少なくとも0.005 ％以上の含有が必
要である。一方、0.50％を越えて含有させると疲労特性
が著しく低下する。従って、0.005 〜0.50％とした。Pb: 0.005-0.50% Pb is an element that improves the machinability. In order to fully bring out the effect, it is necessary to contain at least 0.005%. On the other hand, if the content of Ni exceeds 0.50%, the fatigue properties are significantly deteriorated. Therefore, it is set to 0.005 to 0.50%.
【００２３】Ca：0.0001〜0.0500％ CaはPb同様、切削性を向上させる元素であるが、その効
果を十分に発揮させるためには、少なくとも0.0001％含
有させることが必要である。一方、0.050 ％を越えて含
有させると靱性が著しく低下する。従って、0.0001〜0.
0500％とした。Ca: 0.0001 to 0.0500% Like Pb, Ca is an element that improves the machinability, but in order to fully exert its effect, it is necessary to contain at least 0.0001%. On the other hand, if the content exceeds 0.050%, the toughness is remarkably reduced. Therefore, 0.0001-0.
It was set to 0500%.
【００２４】Se：0.010 〜0.500 ％ Seも切削性を向上させる元素である。その効果を十分に
発揮させるためには少なくとも0.010 ％含有させること
が必要である。一方、0.500 ％を越えて含有させると靱
性が低下する。従って、0.010 〜0.500 ％とした。Se: 0.010 to 0.500% Se is also an element that improves machinability. In order to fully exert its effect, it is necessary to contain at least 0.010%. On the other hand, if the content exceeds 0.500%, the toughness decreases. Therefore, it is set to 0.010 to 0.500%.
【００２５】Te：0.005 〜0.050 ％ Teも切削性を向上させる元素である。その効果を十分に
発揮させるためには少なくとも0.005 ％含有させること
が必要である。一方、0.050 ％を越えて含有させると靱
性が低下する。従って、0.005 〜0.050 ％とした。Te: 0.005 to 0.050% Te is also an element that improves machinability. In order to fully bring out the effect, it is necessary to contain at least 0.005%. On the other hand, if the content exceeds 0.050%, the toughness decreases. Therefore, it is set to 0.005 to 0.050%.
【００２６】Bi：0.40％以下 BiもTe、Se同様、切削性を向上させる元素である。しか
し、0.40％を超えて添加すると、靱性を低下させる。従
って、上限を0.40％とする。Bi: 0.40% or less Bi, like Te and Se, is an element that improves machinability. However, if added over 0.40%, the toughness decreases. Therefore, the upper limit is 0.40%.
【００２７】Ｓ：0.005 〜0.150 ％ ＳはMnＳとして被削性を向上させる働きがあると同時に
結晶粒を微細化、靱性を向上させる働きがあり、0.005
％以上、好ましくは0.03％以上含有させる。一方、0.15
0 ％を越えて含有させると巨大なMnＳが生成し、疲労特
性を低下させる。従って、0.005 〜0.150 ％、好ましく
は0.03〜0.150 ％とした。S: 0.005 to 0.150% S has the function of improving machinability as MnS and at the same time having the function of refining crystal grains and improving toughness.
% Or more, preferably 0.03% or more. On the other hand, 0.15
If it is contained in excess of 0%, huge MnS will be formed and the fatigue characteristics will be deteriorated. Therefore, it is set to 0.005 to 0.150%, preferably 0.03 to 0.150%.
【００２８】本発明によれば、かかる鋼組成を有する鋼
は、初析フェライトの面積率が10％以下であるベイナイ
ト組織として使用するが、これはベイナイト組織とする
ことで、従来のフェライト・パーライト組織に比較し
て、安定して高強度、高靱性、そして高い疲労強度を得
ようとするためである。しかも、初析フェライトの面積
率を10％以下に制限することで、高強度・高靱性の一層
の改善を図るのである。According to the present invention, a steel having such a steel composition is used as a bainite structure in which the area ratio of proeutectoid ferrite is 10% or less. This is because it is intended to stably obtain high strength, high toughness, and high fatigue strength as compared with the structure. Moreover, by limiting the area ratio of proeutectoid ferrite to 10% or less, it is possible to further improve high strength and high toughness.
【００２９】本発明にかかる鋼は、一般に熱間鍛造など
の成形手段によって所定形状に成形されて使用に供され
るが、その際の熱間鍛造は、一般に本発明にかかる鋼は
棒鋼の形態で用いられることが多いため、例えばプレス
による型鍛造などによって行う。しかし、特定のものに
制限されることはない。The steel according to the present invention is generally used by being formed into a predetermined shape by a forming means such as hot forging, and the hot forging at that time is generally performed in the form of steel bar according to the present invention. In many cases, it is performed by die forging with a press, for example. However, it is not limited to a particular one.
【００３０】ここで、本発明にかかる前述の鋼組成を用
いることで、所定形状に成形するとともに、初析フェラ
イトの面積率が10％以下であるベイナイト組織を実現す
る加工熱処理条件について説明する。The heat treatment conditions for forming a predetermined shape and realizing a bainite structure having an area ratio of proeutectoid ferrite of 10% or less by using the above-described steel composition according to the present invention will be described.
【００３１】加熱温度：950 〜1250℃ 950℃未満の加熱だと、添加元素が鋼中に十分に固溶せ
ず所定の強度・靱性が得られない。一方、1250℃超の加
熱になると、添加元素が飽和状態となり、種々の添加元
素の効果が得られない。従って、950 〜1250℃に限定す
る。好適加熱温度は、1100〜1200℃である。Heating temperature: 950 to 1250 ° C. If heating is performed at less than 950 ° C., the additive element does not sufficiently form a solid solution in the steel and predetermined strength and toughness cannot be obtained. On the other hand, if the heating temperature is higher than 1250 ° C., the additive element becomes saturated and the effects of various additive elements cannot be obtained. Therefore, it is limited to 950 to 1250 ° C. A suitable heating temperature is 1100-1200 ° C.
【００３２】仕上温度：750 ℃以上 加熱後、熱間鍛造によって所定の形状に成形するが、そ
の際、所定の強度・靱性を得るため初析フェライトの面
積率が10％以下であるベイナイト組織にする必要があ
る。そのためには、前述の鋼組成の場合には、750 ℃以
上の仕上温度にする必要がある。750 ℃未満になると、
初析フェライトの面積率が10％超となり、強度が著しく
低下する。従って、750 ℃以上とする。好ましくは、85
0 ℃以上である。換言すれば、ベイナイト組織中の初析
フェライト量は仕上温度を変えることで調節できる。前
述のように、鍛造その他による成形手段、条件は特定の
ものに制限されない。成形完了後は、そのまま空冷する
ことでベイナイト組織が得られ、初析フェライト＋ベイ
ナイト組織により、980 N/mm2 以上という高強度、uE
+20 50 J/cm2以上という高靱性、そして耐久性 0.5以上
という高い疲労強度が実現されるのである。Finishing temperature: After heating at 750 ° C. or higher, hot forging is performed to form a predetermined shape. At that time, in order to obtain predetermined strength and toughness, a bainite structure having an area ratio of proeutectoid ferrite of 10% or less is obtained. There is a need to. For that purpose, in the case of the above-mentioned steel composition, it is necessary to set the finishing temperature to 750 ° C or higher. Below 750 ° C,
The area ratio of proeutectoid ferrite exceeds 10%, resulting in a significant decrease in strength. Therefore, the temperature should be 750 ℃ or higher. Preferably 85
It is 0 ° C or higher. In other words, the amount of pro-eutectoid ferrite in the bainite structure can be adjusted by changing the finishing temperature. As described above, the forging and other forming means and conditions are not limited to particular ones. After forming is completed, a bainite structure can be obtained by air-cooling as it is. Due to the pro-eutectoid ferrite + bainite structure, high strength of 980 N / mm 2 or more, uE
High toughness of +20 50 J / cm 2 or more and high fatigue strength of 0.5 or more are realized.
【００３３】[0033]
【実施例】表１および表２に示す各化学成分の鋼を大気
溶製し、得られた鋳片を950 ℃以上1250℃以下に加熱し
た後、熱間鍛造プレスによる熱間鍛造により750 ℃以上
の仕上温度で直径30mm丸棒に成形し、放冷して初析フェ
ライトの面積率が10％以下のベイナイト組織とした。[Examples] Steels having the chemical compositions shown in Tables 1 and 2 were melted in the air, the obtained slabs were heated to 950 ° C or higher and 1250 ° C or lower, and then hot forged by a hot forging press at 750 ° C. A rod having a diameter of 30 mm was formed at the above finishing temperature and allowed to cool to obtain a bainite structure having an area ratio of proeutectoid ferrite of 10% or less.
【００３４】図１は、供試材No.15 について仕上温度だ
けを種々変更してそのときの初析フェライト面積率(%)
を調べた結果を示すグラフである。仕上温度750 ℃以上
とすることによって初析フェライト面積率10％以下を実
現できることが分かる。FIG. 1 shows the pro-eutectoid ferrite area ratio (%) of the test material No. 15 with various finishing temperatures changed.
It is a graph which shows the result of having investigated. It can be seen that an area ratio of proeutectoid ferrite of 10% or less can be achieved by setting the finishing temperature to 750 ° C or higher.
【００３５】次いで、それらのシミュレーション熱間鍛
造材の中心部からJIS ４号の引張試験片とＲ／２部から
JIS ３号シャルピー試験片を製作して機械的性質を調査
した。また、疲労試験は平行部直径８mmの小野式回転曲
げ試験片を採取し繰り返し速度50Hzにて疲労試験を行っ
た。Then, from the center of these simulated hot forged materials, from the JIS 4 tensile test piece and from the R / 2 part.
A JIS No. 3 Charpy test piece was manufactured to investigate the mechanical properties. In the fatigue test, an Ono-type rotary bending test piece having a parallel part diameter of 8 mm was sampled and the fatigue test was performed at a repetition rate of 50 Hz.
【００３６】なお、疲労限度は破断繰り返し数107 とな
る応力振幅と定義した。表３および表４にこれらの試験
結果を熱間鍛造条件とともに示す。表３および表４にま
とめて示す結果から明らかなように、本発明にかかる鋼
は引張強度、衝撃値が共に優れており、高強度、高靱性
を有している。さらに、本発明の目的である疲労強度も
高い。耐久比は0.5 以上であった。The fatigue limit was defined as the stress amplitude at which the number of repeated fractures was 10 7 . Tables 3 and 4 show the results of these tests together with hot forging conditions. As is clear from the results collectively shown in Tables 3 and 4, the steel according to the present invention is excellent in both tensile strength and impact value, and has high strength and high toughness. Further, the fatigue strength, which is the object of the present invention, is high. The durability ratio was 0.5 or more.
【００３７】一方、比較例として挙げた鋼組成の中で
Ｃ、Mn、Cr、Ｂ、Ti、sol.Alが本発明の規定値よりも高
目に外れたものは衝撃特性が劣り、低目に外れたものは
強度が低下してしまう。また、Si、Cr、Ｖが同じく規定
値よりも低目に外れたものは疲労特性が劣る。十分な引
張強度を有し、十分な疲労強度を得たことを知るための
パラメーター。同じ引張強度レベルで、疲労強度の大小
をはかるため耐久比 (疲労強度／引張強度) が必要であ
る。On the other hand, among the steel compositions given as comparative examples, those in which C, Mn, Cr, B, Ti, and sol.Al deviate higher than the specified values of the present invention have poor impact properties and low If it is outside the range, the strength will decrease. Further, if the contents of Si, Cr and V are also lower than the specified values, the fatigue properties are inferior. A parameter for knowing that sufficient tensile strength is obtained and sufficient fatigue strength is obtained. At the same tensile strength level, the durability ratio (fatigue strength / tensile strength) is required to measure the magnitude of fatigue strength.
【００３８】[0038]
【表１】 [Table 1]
【００３９】[0039]
【表２】 [Table 2]
【００４０】[0040]
【表３】 [Table 3]
【００４１】[0041]
【表４】 [Table 4]
【００４２】次に、鋼No.20 を基本組成として、これに
各快削元素を添加したときの工具寿命を評価した。結果
は一般的傾向として図２〜図４にグラフで示す。いずれ
の快削元素であっても快削性の改善がみられる。なお、
切削試験条件は次の通りであった。Next, using Steel No. 20 as the basic composition, the tool life when each free-cutting element was added thereto was evaluated. The results are shown graphically in Figures 2-4 as a general trend. An improvement in free-cutting property is observed with any of the free-cutting elements. In addition,
The cutting test conditions were as follows.
【００４３】試験条件: 工具：Ｐ20、切込み＝2.0 mm、切削速度Ｖ＝100m/min、
乾式 Vb＝0.2 mm：フランク摩耗が0.2 mmに達するまでの切削
時間Test conditions: Tool: P20, depth of cut = 2.0 mm, cutting speed V = 100 m / min,
Dry type Vb = 0.2 mm: Cutting time until flank wear reaches 0.2 mm
【００４４】[0044]
【発明の効果】以上詳述したように、本発明によれば、
非調質鋼として高強度、高靱性を有し、高い耐久比を実
現できるクランク軸、コネクティングロッド、ナックル
などの熱間鍛造部品が容易に製造でき、実用上からの本
発明の意義は極めて高い。As described in detail above, according to the present invention,
As a non-heat treated steel, it has high strength and high toughness, and can easily manufacture hot forged parts such as crankshafts, connecting rods, knuckles, etc. that can realize a high durability ratio, and the significance of the present invention is extremely high in practical use. .
【図１】仕上温度と初析フェライト量との関係を示すグ
ラフである。FIG. 1 is a graph showing the relationship between finishing temperature and the amount of pro-eutectoid ferrite.
【図２】Ｓ含有量と工具寿命との関係を示すグラフであ
る。FIG. 2 is a graph showing the relationship between S content and tool life.
【図３】Bi、Pb、Seの各含有量と工具寿命との関係を示
すグラフである。FIG. 3 is a graph showing the relationship between the Bi, Pb, and Se contents and the tool life.
【図４】Ca、Teの各含有量と工具寿命との関係を示すグ
ラフである。FIG. 4 is a graph showing the relationship between the Ca and Te contents and the tool life.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 外山 和男 大阪市中央区北浜４丁目５番33号 住友金 属工業株式会社内 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Sotoyama 5-33 Kitahama, Chuo-ku, Osaka Sumitomo Metal Industries Co., Ltd.
Claims (4)
05〜1.50％、 Mn：0.50〜2.50％、 Cr：0.50〜2.50％、 Mo：0.05〜0.50％、 Ｖ：0.
005 〜0.200 ％、 sol.Al：0.005 〜0.050 ％、 残部Feおよび不可避不純物から成る鋼組成を有し、初析
フェライトの面積率が10％以下であるベイナイト組織か
ら成ることを特徴とする高耐久比高強度非調質鋼。1. C: 0.10 to 0.20% by weight, Si: 0.
05 to 1.50%, Mn: 0.50 to 2.50%, Cr: 0.50 to 2.50%, Mo: 0.05 to 0.50%, V: 0.
005 to 0.200%, sol.Al: 0.005 to 0.050%, steel composition with balance Fe and unavoidable impurities, and high durability characterized by a bainite structure with an area ratio of proeutectoid ferrite of 10% or less. High-strength non-heat treated steel.
005 〜0.080 ％、Ti：0.005 〜0.050 ％、およびＢ：0.
0001〜0.0030％のうち１種または２種以上、を含有する
請求項１記載の高耐久比高強度非調質鋼。2. The steel composition further comprises Nb: 0.
005 to 0.080%, Ti: 0.005 to 0.050%, and B: 0.
The high durability high strength non-heat treated steel according to claim 1, containing one or more of 0001 to 0.0030%.
0 〜0.500 ％、Te：0.005 〜0.050 ％、Bi：0.40％以
下、およびＳ：0.005 〜0.150 ％のうち１種または２種
以上を含有する請求項１または２記載の高耐久比高強度
非調質鋼。3. The steel composition further comprises, by weight%, Pb: 0.005-0.50%, Ca: 0.0001-0.0500%, Se: 0.01
High durability ratio high strength non-conditioning according to claim 1 or 2, containing 0 to 0.500%, Te: 0.005 to 0.050%, Bi: 0.40% or less, and S: 0.005 to 0.150%. Quality steel.
組成を有する鋼材を、950 ℃以上1250℃以下に加熱した
後、熱間鍛造により750 ℃以上の仕上温度で所定形状に
成形することを特徴とする高耐久比高強度非調質鋼の製
造方法。4. A steel material having the steel composition according to any one of claims 1 to 3 is heated to 950 ° C. or higher and 1250 ° C. or lower, and then hot forged into a predetermined shape at a finishing temperature of 750 ° C. or higher. A method for producing a high durability non-heat treated high strength steel characterized by the above.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11267994A JP2888135B2 (en) | 1994-05-26 | 1994-05-26 | High durability high strength non-heat treated steel and its manufacturing method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11267994A JP2888135B2 (en) | 1994-05-26 | 1994-05-26 | High durability high strength non-heat treated steel and its manufacturing method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07316720A true JPH07316720A (en) | 1995-12-05 |
| JP2888135B2 JP2888135B2 (en) | 1999-05-10 |
Family
ID=14592766
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP11267994A Expired - Fee Related JP2888135B2 (en) | 1994-05-26 | 1994-05-26 | High durability high strength non-heat treated steel and its manufacturing method |
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| Country | Link |
|---|---|
| JP (1) | JP2888135B2 (en) |
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| JP2010242170A (en) * | 2009-04-06 | 2010-10-28 | Nippon Steel Corp | High strength hot forging non-heat treated steel excellent in toughness and method for manufacturing the same |
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| JP2010242170A (en) * | 2009-04-06 | 2010-10-28 | Nippon Steel Corp | High strength hot forging non-heat treated steel excellent in toughness and method for manufacturing the same |
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| CN115679089A (en) * | 2022-10-27 | 2023-02-03 | 北京科技大学 | Forging and cooling control process for regulating microstructure of low-carbon bainite non-quenched and tempered steel for front axle |
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